The difficulties of complaining Essay Example | Topics and Well Written Essays - 500 words

The difficulties of complaining - Essay Example It makes people feel special. Excellent patient care is the most important piece to keep hospital rooms full. As an example, â€Å"Mr Tadeus Kowalski was admitted to the ward a year ago for rehabilitation following hip replacement in an elective orthopedic centre. He has had a second hip replacement and there are plans to transfer him to the ward again for rehabilitation, Mr Kowalski and his family said they did not want him to return to the ward. Mr Kowalski has Parkinsons disease and said that, although his medication should have been given three hourly, it was often late. This caused him greater distress and impeded his recovery. In his notes, there are several entries indicating that he, his wife and family have been asked to keep his own medication as his medication has not been given on time. As cure costs more than prevention, to alleviate Mr Kowalski concerns and enable him to accept the rehabilitation, hospital needs to provide special ward and appoint a dedicated nurse for him. There is a requirement for the doctor to visit the patient more informally other than the scheduled official rounds.. He should be provided with labeled medicines and with chart indicating its dosage and time to take it, which will be helpful in absence of attendant. There are several such cases which affect hospital reputation. Many such problems creep up due to communication gap between working staff and patients, unawareness of staff regarding importance of timely medication or their neglecting behavior. Generally older people need more care as well as attention; thus, they should be allotted separate wards with a dedicated attendant to take care of their needs. Official visits by responsible persons should be increased to gather customer feedbacks. Emergency services should be more prompt. All patients, including old people, should be educated for self medication.

John Brown's Raid at Harper's Ferry Research Paper

John Brown's Raid at Harper's Ferry - Research Paper Example Following his execution after the raid on Harpers Ferry, Brown was hailed as a martyr among the opponents of slavery. Moreover, his actions were deemed as one of the causal factors of the American Civil War. John Brown disgust for slavery stemmed back during his childhood. Evidently, he was conceived in Torrington, Connecticut on 9th May 1800 (West Virginia Archives and History). Furthermore, he was brought up with strict religious values in which his father taught him that slavery was against God’s will and sinful. Moreover, after Brown’s family relocated to Ohio, he witnessed the brutality meted against slaves by their masters and became a strong opponent of slavery. To this end, Brown passion of eliminating slavery grew to the point of advocating for violence as an end to slavery. Brown believed that the roots of slavery had grown so deep in society and only violence offered the best solution to its end. Interestingly enough, John Brown gained support from other oppo nents of slavery who had grown frustrated of the peaceful method. His first violent exploits against slavery were established on Kansas which became known as bleeding Kansas. In 1856 of May, Brown is reported to have led his sons in an attack against proponent of slavery at Pottawatomie Creek in Kansas. Consequently, Brown set his objectives his anti slavery war higher by contemplating to start a slavery uprising in the South. To this end, Brown commenced his plans of a raid and capture of a federal armoury at Harpers Ferry in Virginia. To accomplish this, he moved into a farm in nearby Potomac River, Maryland (Lieutenant Green & Major Russell). He was with his sons and loyal followers where they were trained in military tactics. Brown’s option to attack Harpers Ferry was founded on two notions. Foremost, he believed that he would be able to gain access to weapons that would be used in violent revolts against the southern slavery proponents. Second, he aimed to distribute the weapons among the enslaved negroes and eventually succeed in ending slavery. To this end, Brown conducted a night raid on Harpers Ferry on Sunday, October 16. His group was composed of 5 Negroes and 16 whites. Evidently, Brown’s initial raid was successful as they began by slashing off telegraph wires. This was a tactical moved aimed at cutting off communication between the town and the outside world. Moreover, Brown and his men seized the rifle manufacturing plant, arsenal and local armoury. They further proceeded to hold up 60 hostages from the town. A key hostage in the raid was George Washington’s great grand nephew, Colonel Lewis Washington. However, the efforts to isolate the town by cutting of communication were not successful. The apparent blunder was caused by the detention and release of a B&O train passing through the town. Upon the train’s arrival in Baltimore, the federal troops led by Colonel Robert E. Lee, were notified and sent over to Harpers F erry. Meanwhile, the local militia had barricaded the town and blocked any possible escape routes for the raiders. Consequently, John Brown marshalled his small contingent and hostages to tiny engine house next to the armoury. Upon the arrival of the federal forces, they raided the fire engine, overpowered Brown and killed most of his men. To this end, 15 insurgents and 5 citizens were killed, 3 insurgents were wounded while 5 insurgent

Racial and Ethnic Stereotypes Essay Example for Free

Racial and Ethnic Stereotypes Essay People being indiscriminate based on partial and inexact information by sources as television, cartoons or even comic books This is a description that seems to go against many public standards. The above words are the exact description of stereotypes. Stereotypes as implicit from the description, goes mostly hand in hand with media only not the standard meaning of the blameless media we know. Media propaganda is the other form of media that is somewhat described as media treatment. In this paper, the subsequent will be discussed: first, how stereotypes of ethnic groups operate in propaganda, why does it function so satisfactorily, and finally, the consequences of these stereotypes on the life of Egyptians in particular in society. A fair inspection will be conducted on this example of stereotypes through clarification examples and research consequences from researches conducted from reliable sources. The real association between Egyptians’ stereotypes and propaganda discussed in this paper shall magnify the suggestion of stereotypes and propaganda in common. It seems essential for this paper to start with some clarification of the circumstances related with propaganda. Propaganda can be thought of as a foster parent for stereotypes. Propaganda is recognized to be the planned manipulation of public opinion through concealed messages in advertisements and other media functions. Thus, propaganda uses numerous techniques to be able to consign theses hidden messages to the public and influence their view. Fear, brainwashing, name calling, glittering generality, misinformation and much more are some of the ways that propaganda uses to persuade and manipulate the opinions of the masses. Propaganda finds the usefulness of stereotypes in the fact that it’s easy, quick and direct to the public. In the case of stereotypes about ethnic groups, Egyptians in this case are being portrayed as uneducated, unethical, ignorant, desert animal raisers, terrorists and uncultured ethnic group. These name calling and misinformation techniques are what propagandists use to contrive the society to portray Egyptians as humans of the underworld and Egypt as a deserted country that hunger and ill health are its residents. The preceding are all stereotypes that are propagandas of the media to convince such generality into truth and facts. Racial stereotypes particularly function usually through propaganda of the media, due to the improbability of every man travelling to every country, with the technique of ‘misinformation’ through movies, shows, and news reports. Egyptians have been stereotyped as desert residents for many years regardless of the reality and actual state of Egypt as a country. For instance, the stereotypes pointing that Egyptians are mostly uneducated due to their ignorance of the importance of education is proven false by studies of trustworthy sources. Among those studies, the one conducted by the American university in Cairo, Egypt. Al-Ahram weekly, a credible newspaper known all across the Arab world, has posted in its October issue of 1998 the following: â€Å"According to Sahar El-Tawila, the essential researcher on the team, interviews conducted with girls and boys nationwide demonstrate convincingly that work and marriage were rarely stated by boys and girls respectively as reasons for departing school†¦ These may be options for those who have already left school, but they are not the impetus behind their decision to leave† (Al-Ahram 1998). Therefore, according to an American research, Egyptians are not uneducated conceited nation. After all, there is at least an American University known worldwide built in Cairo where many Egyptians have gotten their Bachelors, Masters and PhD’s from. Still, the media has successfully manipulated the public opinion to reason Egyptians as desert wonderers. Now that the first concern, of how such Egyptian-bashing stereotypes work in propaganda, has been discussed, an interesting question then must be asked: how did it come about so successfully for the public of North America to view Egyptians in such state of mind? Media being a powerful information source to the majority of North Americans, and sometimes the only source of information about specific ethnic groups, has the ability to convince the public viewpoints and opinions. Of course with stereotypes powered by propaganda in movies is very thriving in view of that American films are the most favored and appreciated media function. Openly, in one of the movie reviews now on a review website about the movie â€Å"The Mummy† which takes place in Egypt from start to end, the subsequent sentence was stated: â€Å"The Mummy is a lot of fun. So the story is unsophisticated and the characters are all stereotypes (particularly the Egyptians, who are either noble desert warriors or smelly illiterate pig-things). Who cares? The special effects are truly spectacular. † (Jennifer Mellerick, 1999). Easily, stereotypes are even expected by who understands them and the media propaganda generates more and more. To attest that such depiction is a stereotype and not fact, the website ‘Egypt WWW Index’ has a list of all universities in Egypt (an estimated thirty educational institutions in total), many links to political and governmental committees and services, business, commercial, and entertainment facilities, as well as links to political women figures in the Egyptian society. More than the average North American could even imagine of Egypt , and it is all owed to the media propaganda that produced this image of Egyptians. People being indiscriminate based on partial and inexact information by sources as television, cartoons or even comic books This is a description that seems to go against many public standards. The above words are the exact description of stereotypes. Stereotypes as implicit from the description, goes mostly hand in hand with media only not the standard meaning of the blameless media we know. Media propaganda is the other form of media that is somewhat described as media treatment. In this paper, the subsequent will be discussed: first, how stereotypes of ethnic groups operate in propaganda, why does it function so satisfactorily, and finally, the consequences of these stereotypes on the life of Egyptians in particular in society. A fair inspection will be conducted on this example of stereotypes through clarification examples and research consequences from researches conducted from reliable sources. The real association between Egyptians’ stereotypes and propaganda discussed in this paper shall magnify the suggestion of stereotypes and propaganda in common. It seems essential for this paper to start with some clarification of the circumstances related with propaganda. Propaganda can be thought of as a foster parent for stereotypes. Propaganda is recognized to be the planned manipulation of public opinion through concealed messages in advertisements and other media functions. Thus, propaganda uses numerous techniques to be able to consign theses hidden messages to the public and influence their view. Fear, brainwashing, name calling, glittering generality, misinformation and much more are some of the ways that propaganda uses to persuade and manipulate the opinions of the masses. Propaganda finds the usefulness of stereotypes in the fact that it’s easy, quick and direct to the public. In the case of stereotypes about ethnic groups, Egyptians in this case are being portrayed as uneducated, unethical, ignorant, desert animal raisers, terrorists and uncultured ethnic group. These name calling and misinformation techniques are what propagandists use to contrive the society to portray Egyptians as humans of the underworld and Egypt as a deserted country that hunger and ill health are its residents. The preceding are all stereotypes that are propagandas of the media to convince such generality into truth and facts. Racial stereotypes particularly function usually through propaganda of the media, due to the improbability of every man travelling to every country, with the technique of ‘misinformation’ through movies, shows, and news reports. Egyptians have been stereotyped as desert residents for many years regardless of the reality and actual state of Egypt as a country. For instance, the stereotypes pointing that Egyptians are mostly uneducated due to their ignorance of the importance of education is proven false by studies of trustworthy sources. Among those studies, the one conducted by the American university in Cairo, Egypt. Al-Ahram weekly, a credible newspaper known all across the Arab world, has posted in its October issue of 1998 the following: â€Å"According to Sahar El-Tawila, the essential researcher on the team, interviews conducted with girls and boys nationwide demonstrate convincingly that work and marriage were rarely stated by boys and girls respectively as reasons for departing school†¦ These may be options for those who have already left school, but they are not the impetus behind their decision to leave† (Al-Ahram 1998). Therefore, according to an American research, Egyptians are not uneducated conceited nation. After all, there is at least an American University known worldwide built in Cairo where many Egyptians have gotten their Bachelors, Masters and PhD’s from. Still, the media has successfully manipulated the public opinion to reason Egyptians as desert wonderers. Now that the first concern, of how such Egyptian-bashing stereotypes work in propaganda, has been discussed, an interesting question then must be asked: how did it come about so successfully for the public of North America to view Egyptians in such state of mind? Media being a powerful information source to the majority of North Americans, and sometimes the only source of information about specific ethnic groups, has the ability to convince the public viewpoints and opinions. Of course with stereotypes powered by propaganda in movies is very thriving in view of that American films are the most favored and appreciated media function. Openly, in one of the movie reviews now on a review website about the movie â€Å"The Mummy† which takes place in Egypt from start to end, the subsequent sentence was stated: â€Å"The Mummy is a lot of fun. So the story is unsophisticated and the characters are all stereotypes (particularly the Egyptians, who are either noble desert warriors or smelly illiterate pig-things). Who cares? The special effects are truly spectacular. † (Jennifer Mellerick, 1999). Easily, stereotypes are even expected by who understands them and the media propaganda generates more and more. To attest that such depiction is a stereotype and not fact, the website ‘Egypt WWW Index’ has a list of all universities in Egypt (an estimated thirty educational institutions in total), many links to political and governmental committees and services, business, commercial, and entertainment facilities, as well as links to political women figures in the Egyptian society. More than the average North American could even imagine of Egypt , and it is all owed to the media propaganda that produced this image of Egyptians. Racial and Ethnic Stereotypes Furthermore, Egyptians are stereotyped to be uninformed owing to the reality that they are thought of as technology uneducated. In a website found throughout the study on this topic, a person of an Indian ethnicity by the given name of Shani Rifati has set up a website, which he calls â€Å"Please Call Me Rom†. To right the depiction of his race to North Americans, Shani said: â€Å"I am not a Gypsy. The term Gypsy comes from peoples ignorance, when we were wrong for Egyptians† (Rifati). Remarkable huh! Here is an example of a person that is defending his own nationality from stereotypes, yet uses stereotypes. What is even more interesting than that is the reality that the Egyptian history has been known to be the supreme civilization of all times, yet such culture is simply bashed by supercilious that all Egyptians are just ignorant Gypsies. â€Å" African American and Latino children who are aware of broadly held stereotypes about academic aptitude perform more disappointingly on a cognitive task when that task is described as a measure of capability than when the same task is described as a problem-solving duty. † (Carol Hyman 2003). Therefore racial or ethnic stereotypes that work in media propaganda or rather called media manipulation, has not only had influences on adults, but also is passed over with the youth of tomorrow. It is easy to give out information with no truthful back up, but the public inclination is what can moreover stop media propaganda from disturbing the public opinion or simply energize such unsafe aspect of the media, stereotypes. Furthermore, Egyptians are stereotyped to be uninformed owing to the reality that they are thought of as technology uneducated. In a website found throughout the study on this topic, a person of an Indian ethnicity by the given name of Shani Rifati has set up a website, which he calls â€Å"Please Call Me Rom†. To right the depiction of his race to North Americans, Shani said: â€Å"I am not a Gypsy. The term Gypsy comes from peoples ignorance, when we were wrong for Egyptians† (Rifati). Remarkable huh! Here is an example of a person that is defending his own nationality from stereotypes, yet uses stereotypes. What is even more interesting than that is the reality that the Egyptian history has been known to be the supreme civilization of all times, yet such culture is simply bashed by supercilious that all Egyptians are just ignorant Gypsies. â€Å" African American and Latino children who are aware of broadly held stereotypes about academic aptitude perform more disappointingly on a cognitive task when that task is described as a measure of capability than when the same task is described as a problem-solving duty. † (Carol Hyman 2003). Therefore racial or ethnic stereotypes that work in media propaganda or rather called media manipulation, has not only had influences on adults, but also is passed over with the youth of tomorrow. It is easy to give out information with no truthful back up, but the public inclination is what can moreover stop media propaganda from disturbing the public opinion or simply energize such unsafe aspect of the media, stereotypes.

Radio Resource Management in OFDMA Networks

Radio Resource Management in OFDMA Networks 1 Introduction The convenience and popularity of wireless technology has now extended into multimedia communications, where it poses a unique challenge for transmitting high rate voice, image, and data signals simultaneously, synchronously, and virtually error-free. That challenge is currently being met through Orthogonal Frequency Division Multiplexing (OFDM), an interface protocol that divides incoming data streams into sub-streams with overlapping frequencies that can then be transmitted in parallel over orthogonal subcarriers [2,3]. To allow multiple accesses in OFDM , Orthogonal Frequency Division Multiple Access (OFDMA) was introduced. Relaying techniques, along with OFDMA, are used to achieve high data rate and high spectral efficiency. 1.1 Orthogonal Frequency Division Multiple Access OFDMA, an interface protocol combining features of OFDM and frequency division multiple access (FDMA)., was developed to move OFDM technology from a fixed-access wireless system to a true cellular system with mobility with same underlying technology, but more flexibility was defined in the operation of the system [1,8]. In OFDMA, subcarriers are grouped into larger units, referred to as sub-channels, and these sub-channels are further grouped into bursts which can be allocated to wireless users [4]. 1.2 Relay-Enhanced Networks In cellular systems, a way to achieve remarkable increase in data rate, but without claiming for more bandwidth, is to shrink cell sizes, however, with smaller cells more base stations (BSs) are needed to cover a same area due to which deployment and networking of new BSs acquire significant costs [5]. An alternative solution to this problem is to deploy smart relay stations (RSs), which can communication with each other and with BSs through wireless connections reducing systems cost. A relay station (RS), also called repeater or multi-hop station, is a radio system that helps to improve coverage and capacity of a base station (BS) and the resulting networks employing relay stations are sometimes called cooperative networks [6]. 1.3 Technological Requirement The continuously evolving wireless multimedia services push the telecommunication industries to set a very high data rate requirement for next generation mobile communication systems. As spectrum resource becomes very scarce and expensive, how to utilize this resource wisely to fulfil high quality user experiences is a very challenging research topic. Orthogonal frequency-division multiple access (OFDMA)-based RRM schemes together with relaying techniques allocate different portions of radio resources to different users in both the frequency and time domains and offers a promising technology for providing ubiquitous high-data-rate coverage with comparatively low cost than deploying multiple base stations [5]. Although wireless services are the demand of future due to their mobility and low cost infrastructure but along with this they suffer serious channel impairments. In particular, the channel suffers from frequency selective fading and distance dependent fading (i.e., large-scale fading) [1, 8]. While frequency selective fading results in inter-symbol-interference (ISI), large-scale fading attenuates the transmitted signal below a level at which it can be correctly decoded. Orthogonal Frequency-Division Multiple Access (OFDMA) relay-enhanced cellular network, the integration of multi-hop relaying with OFDMA infrastructure, has become one of the most promising solutions for next-generation wireless communications. 1.3.1 Frequency Selective Fading In wireless communications, the transmitted signal is typically reaching the receiver through multiple propagation paths (reflections from buildings, etc.), each having a different relative delay and amplitude. This is called multipath propagation and causes different parts of the transmitted signal spectrum to be attenuated differently, which is known as frequency-selective fading. In addition to this, due to the mobility of transmitter and/or receiver or some other time-varying characteristics of the transmission environment, the principal characteristics of the wireless channel change in time which results in time-varying fading of the received signal [9]. 1.3.2 Large Scale Fading Large scale fading is explained by the gradual loss of received signal power (since it propagates in all directions) with transmitter-receiver (T-R) separation distance. These phenomenonss cause attenuation in the signal and decrease in its power. To overcome this we use diversity and multi-hop relaying. 1.3.3 Diversity Diversity refers to a method for improving the reliability of a message signal by using two or morecommunication channelswith different characteristics. Diversity plays an important role in combatingfadingandco-channel interferenceand avoidingerror bursts. It is based on the fact that individual channels experience different levels of fading and interference. Multiple versions of the same signal may be transmitted and/or received and combined in the receiver [10]. 1.4 Proposed Simulation Model We developed a simulation model in which each user-pair is allocated dynamically a pair of relay and subcarrier in order to maximize its achievable sum-rate while satisfying the minimum rate requirement. The algorithm and the results of the simulation model are given in chapter 4. 1.5 Objectives The objective of our project is to have a detail overview of the literature regarding Orthogonal Frequency Division Multiple Access (OFDMA), Radio Resource Management (RRM) and Relaying techniques. After literature review we developed a simulation framework in which we will try to use minimum resources to get maximum throughput by using dynamic resource allocation. 1.6 Tools For the design and implementation of proposed Algorithm, we have used the following tools MATLAB Smart Draw Corel Draw 1.7 Overview Chapter 2 contains the literature review. It explains the basic principles of OFDMA, Radio Resource Management (RRM) and the relaying techniques. Chapter 3 explains the implementation of OFDM generation and reception that how an OFDM signal is generated and transmitted through the channel and how it is recovered at the receiver. Chapter 4 could be considered as the main part of thesis. It focuses on the simulation framework and the code. We have followed the paper â€Å"Subcarrier Allocation for multiuser two-way OFDMA Relay networks with Fairness Constraints†. In this section we have tried to implement the Dynamic Resource Allocation algorithm in order to achieve the maximum sum rate. Results are also discussed at the end of the end of the chapter. 2 Literature Review Introduction: First section of this Chapter gives a brief overview about OFDMA.OFDMA basically is the combination of Orthogonal Frequency Division Multiplexing (OFDM) and Frequency Division Multiplexing Access (FDMA).OFDMA provides high data rates even through multipath fading channels. In order to understand OFDMA, we must have brief introduction to Modulation, Multiple Access, Propagation mechanisms, its effects and its impairments while using OFDMA. 2.1 Modulation Modulation is the method of mapping data with change in carrier phase, amplitude, frequency or the combination [11]. There are two types of modulation techniques named as Single Carrier Modulation (SCM) Transmission Technique or Multicarrier Modulation (MCM) Transmission Technique. [12] Single Carrier Modulation (SCM) In single carrier transmission modulation (SCM) transmission, information is modulated using adjustment of frequency, phase and amplitude of a single carrier [12]. Multi Carrier Modulation (MCM) In multicarrier modulation transmission, input bit stream is split into several parallel bit streams then each bit stream simultaneously modulates with several sub-carriers (SCs) [12]. 2.2 Multiplexing Multiplexing is the method of sharing bandwidth and resources with other data channels. Multiplexing is sending multiple signals or streams of information on a carrier at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end [13]. 2.2.1 Analog Transmission In analog transmission, signals are multiplexed using frequency division multiplexing (FDM), in which the carrier bandwidth is divided into sub channels of different frequency widths,and each signal is carried at the same time in parallel. 2.2.2 Digital Transmission In digital transmission, signals are commonly multiplexed using time-division multiplexing (TDM), in which the multiple signals are carried over the same channel in alternating time slots. 2.2.3 Need for OFDMA General wireless cellular systems are multi-users systems. We have limited radio resources as limited bandwidth and limited number of channels. The radio resources must be shared among multiple users. So OFDM is a better choice in this case. OFDM is the combination of modulation and multiplexing. It may be a modulation technique if we analyze the relation between input and output signals. It may be a multiplexing technique if we analyze the output signal which is the linear sum of modulated signal. In OFDM the signal is firstly split into sub channels, modulated and then re-multiplexed to create OFDM carrier. The spacing between carriers is such that they are orthogonal to one another. Therefore there is no need of guard band between carriers. In this way we are saving the bandwidth and utilizing our resources efficiently. 2.3 Radio Propagation Mechanisms There are 3 propagation mechanisms: Reflection, Diffraction and Scattering. These 3 phenomenon cause distortion in radio signal which give rise to propagation losses and fading in signals [14]. 2.3.1 Reflection Reflection occurs when a propagating Electro-Magnetic (EM) wave impinges upon an object which has very large dimensions as compared to the wavelength of the propagating wave. Reflections occur from the surface of the earth and from buildings and walls. 2.3.2 Diffraction When the radio path between the transmitter and receiver is obstructed by a surface that has sharp irregularities (edges), diffraction occurs. The secondary waves resulting from the obstructing surface are present throughout the space and even behind the obstacle, giving rise to a bending of waves around the obstacle, even when a line-of-sight path does not exist between transmitter and receiver. At high frequencies, diffraction, like reflection, depends on the geometry of the object, as well as the amplitude, phase and polarization of the incident wave at the point of diffraction. 2.3.3 Scattering When the medium through which the wave travels consists of objects with dimensions that are small compared to the wavelength, and where the number of obstacles per unit volume is large. Scattered waves are produced by rough surfaces, small objects or by other irregularities in the channel. In practice, foliage, street signs and lamp posts produce scattering in a mobile radio communications system. 2.4 Effects of Radio Propagation Mechanisms The three basic propagation mechanisms namely reflection, diffraction and scattering as we have explained above affect on the signal as it passes through the channel. These three radio propagation phenomena can usually be distinguished as large-scale path loss, shadowing and multipath fading [14][15]. 2.4.1 Path Loss Path Lossis the attenuation occurring by an electromagnetic wave in transit from a transmitter to a receiver in a telecommunication system. In simple words, it governs the deterministic attenuation power depending only upon the distance between two communicating entities. It is considered as large scale fading because it does not change rapidly. 2.4.2 Shadowing Shadowingis the result of movement of transmitter, receiver or any channel component referred to as (obstacles). Shadowing is a statistical parameter. Shadowing follows a log-normal distribution about the values governed by path loss. Although shadowing depends heavily upon the channel conditions and density of obstacles in the channel, it is also normally considered a large scale fading component alongside path loss. 2.4.3 Multipath Fading Multipath Fadingis the result of multiple propagation paths which are created by reflection, diffraction and scattering. When channel has multiple paths. Each of the paths created due to these mechanisms may have its characteristic power, delay and phase. So receiver will be receiving a large number of replicas of initially transmitted signal at each instant of time. The summation of these signals at receiver may cause constructive or destructive interferences depending upon the delays and phases of multiple signals. Due to its fast characteristic nature, multipath fading is called small scale fading. 2.5 Orthogonal Frequency Division Multiplexing (OFDM) Orthogonal Frequency Division Multiplexing (OFDM) is an efficient multicarrier modulation that is robust to multi-path radio channel impairments [15]. Now-a-days it is widely accepted that OFDM is the most promising scheme in future high data-rate broadband wireless communication systems. OFDM is a special case of MCM transmission. In OFDM, high data rate input bit stream or data is first converted into several parallel bit stream, than each low rate bit stream is modulated with subcarrier. The several subcarriers are closely spaced. However being orthogonal they do not interfere with each other. 2.5.1 Orthognality Signals are orthogonal if they are mutually independent of each other. Orthogonality is a property that allows multiple information signals to be transmitted perfectly over a common channel and detected, without interference. Loss of orthogonality results in blurring between these information signals and degradation in communications. Many common multiplexing schemes are inherently orthogonal. The term OFDM has been reserved for a special form of FDM. The subcarriers in an OFDM signal are spaced as close as is theoretically possible while maintain orthogonality between them.In FDM there needs a guard band between channels to avoid interference between channels. The addition of guard band between channels greatly reduces the spectral efficiency. In OFDM, it was required to arrange sub carriers in such a way that the side band of each sub carrier overlap and signal is received without interference. The sub-carriers (SCs) must be orthogonal to each other, which eliminates the guard band and improves the spectral efficiency . 2.5.2 Conditions of orthogonality 2.5.2.1 Orthogonal Vectors Vectors A and B are two different vectors, they are said to be orthogonal if their dot product is zero 2.6 OFDM GENERATION AND RECEPTION OFDM signals are typically generated digitally due to the complexity of implementation in the analog domain. The transmission side is used to transmit digital data by mapping the subcarrier amplitude and phase. It then transforms this spectral representation of the data into the time domain using an Inverse Discrete Fourier Transform (IDFT) but due to much more computational efficiency in Inverse Fast Fourier Transform (IFFT), IFFT is used in all practical systems. The receiver side performs the reverse operations of the transmission side, mixing the RF signal to base band for processing, and then a Fast Fourier Transform (FFT) is employed to analyze the signal in the frequency domain. The demodulation of the frequency domain signal is then performed in order to obtain the transmitted digital data. The IFFT and the FFT are complementary function and the most suitable term depends on whether the signal is being recovered or transmitted but the cases where the signal is independent of this distinction then these terms can be used interchangeably [15]. 2.6.1 OFDM Block Diagram 2.6.2 Implementation of OFDM Block Diagram 2.6.2.1 Serial to Parallel Conversion: In an OFDM system, each channel can be broken down into number of sub-carriers. The use of sub-carriers can help to increase the spectral efficiency but requires additional processing by the transmitter and receiver which is necessary to convert a serial bit stream into several parallel bit streams to be divided among the individual carriers. This makes the processing faster as well as is used for mapping symbols on sub-carriers. 2.6.2.2 Modulation of Data: Once the bit stream has been divided among the individual sub-carriers by the use of serial to parallel converter, each sub-carrier is modulated using 16 QAM scheme as if it was an individual channel before all channels are combined back together and transmitted as a whole. 2.6.2.3 Inverse Fourier Transform: The role of the IFFT is to modulate each sub-channel onto the appropriate carrier thus after the required spectrum is worked out, an inverse Fourier transform is used to find the corresponding time domain waveform. 2.6.2.4 Parallel to Serial Conversion: Once the inverse Fourier transform has been done each symbol must be combined together and then transmitted as one signal. Thus, the parallel to serial conversion stage is the process of summing all sub-carriers and combining them into one signal 2.6.2.5 Channel: The OFDM signal is then transmitted over a channel with AWGN having SNR of 10 dB. 2.6.2.6 Receiver: The receiver basically does the reverse operations to the transmitter. The FFT of each symbol is taken to find the original transmitted spectrum. The phase angle of each transmission carrier is then evaluated and converted back to the data word by demodulating the received phase. The data words are then combined back to the same word size as the original data. 2.7 OFDMA in a broader perspective OFDM is a modulation scheme that allows digital data to be efficiently and reliably transmitted over a radio channel, even in multipath environments [17]. OFDM transmits data by using a large number of narrow bandwidth carriers. These carriers are regularly spaced in frequency, forming a block of spectrum. The frequency spacing and time synchronization of the carriers is chosen in such a way that the carriers are orthogonal, meaning that they do not interfere with each other. This is despite the carriers overlapping each other in the frequency domain [18]. The name ‘OFDM is derived from the fact that the digital data is sent using many carriers, each of a different frequency (Frequency Division Multiplexing) and these carriers are orthogonal to each other [19]. 2.7.1 History of OFDMA The origins of OFDM development started in the late 1950s with the introduction of Frequency Division Multiplexing (FDM) for data communications. In 1966 Chang patented the structure of OFDM and published the concept of using orthogonal overlapping multi-tone signals for data communications. In 1971 Weinstein introduced the idea of using a Discrete Fourier Transform (DFT) for Implementation of the generation and reception of OFDM signals, eliminating the requirement for banks of analog subcarrier oscillators. This presented an opportunity for an easy implementation of OFDM, especially with the use of Fast Fourier Transforms (FFT), which are an efficient implementation of the DFT. This suggested that the easiest implementation of OFDM is with the use of Digital Signal Processing (DSP), which can implement FFT algorithms. It is only recently that the advances in integrated circuit technology have made the implementation of OFDM cost effective. The reliance on DSP prevented the wide spread use of OFDM during the early development of OFDM. It wasnt until the late 1980s that work began on the development of OFDM for commercial use, with the introduction of the Digital Audio Broadcasting (DAB) system. 2.7.2 Advantages using OFDMA There are some advantages using OFDMA. OFDM is a highly bandwidth efficient scheme because different sub-carriers are orthogonal but they are overlapping. Flexible and can be made adaptive; different modulation schemes for subcarriers, bit loading, adaptable bandwidth/data rates possible. Has excellent ICI performance because of addition of cyclic prefix. In OFDM equalization is performed in frequency domain which becomes very easy as compared to the time domain equalization. Very good at mitigating the effects of delay spread. Due to the use of many sub-carriers, the symbol duration on the sub-carriers is increased, relative to delay spread. ISI is avoided through the use of guard interval. Resistant to frequency selective fading as compared to single carrier system. Used for high data rate transmission. OFDMA provides flexibility of deployment across a variety of frequency bands with little need for modification is of paramount importance. A single frequency network can be used to provide excellent coverage and good frequency re-use. OFDMA offers frequency diversity by spreading the carriers all over the used spectrum. 2.7.3 Challenges using OFDMA These are the difficulties we have to face while using OFDMA [20][21][22], The OFDM signal suffers from a very high peak to average power ratio (PAPR) therefore it requires transmitter RF power amplifiers to be sufficiently linear in the range of high input power. Sensitive to carrier frequency offset, needs frequency offset correction in the receiver. Sensitive to oscillator phase noise, clean and stable oscillator required. The use of guard interval to mitigate ISI affects the bandwidth efficiency. OFDM is sensitive to Doppler shift frequency errors offset the receiver and if not corrected the orthogonality between the carriers is degraded. If only a few carriers are assigned to each user the resistance to selective fading will be degraded or lost. It has a relatively high sensitivity to frequency offsets as this degrades the orthogonality between the carriers. It is sensitive to phase noise on the oscillators as this degrades the orthogonaility between the carriers. 2.7.4 Comparison with CDMA in terms of benefits 2.7.4.2 CDMA Advantages: CDMA has some advantages over OFDMA [22], Not as complicated to implement as OFDM based systems. As CDMA has a wide bandwidth, it is difficult to equalise the overall spectrum significant levels of processing would be needed for this as it consists of a continuous signal and not discrete carriers. Not as easy to aggregate spectrum as for OFDM. 2.7.5 OFDMA in the Real World: UMTS, the European standard for the 3G cellular mobile communications, and IEEE 802.16, a broadband wireless access standard for metropolitan area networks (MAN), are two live examples for industrial support of OFDMA. Table 1 shows the basic parameters of these two systems. Table 1. OFDMA system parameters in the UMTS and IEEE 802.16 standards 2.8 Radio Resource Management In second section of this chapter we will discuss radio resource management schemes, why we need them and how they improve the efficiency of the network. Radio resource management is the system level control of co-channel interference and other radio transmission characteristics in wireless communication systems. Radio resource management involves algorithms and strategies for controlling parameters such as Transmit power Sub carrier allocation Data rates Handover criteria Modulation scheme Error coding scheme, etc 2.8.1 Study of Radio Resource Management End-to-end reconfigurability has a strong impact on all aspects of the system, ranging from the terminal, to the air interface, up to the network side. Future network architectures must be flexible enough to support scalability as well as reconfigurable network elements, in order to provide the best possible resource management solutions in hand with cost effective network deployment. The ultimate aim is to increase spectrum efficiency through the use of more flexible spectrum allocation and radio resource management schemes, although suitable load balancing mechanisms are also desirable to maximize system capacity, to optimize QoS provision, and to increase spectrum efficiency. Once in place, mobile users will benefit from this by being able to access required services when and where needed, at an affordable cost. From an engineering point of view, the best possible solution can only be achieved when elements of the radio network are properly configured and suitable radio resource m anagement approaches/algorithms are applied. In other words, the efficient management of the whole reconfiguration decision process is necessary, in order to exploit the advantages provided by reconfigurability. For this purpose, future mobile radio networks must meet the challenge of providing higher quality of service through supporting increased mobility and throughput of multimedia services, even considering scarcity of spectrum resources. Although the size of frequency spectrum physically limits the capacity of radio networks, effective solutions to increase spectrum efficiency can optimize usage of available capacity. Through inspecting the needs of relevant participants in a mobile communication system, i.e., the Terminal, User, Service and Network, effective solutions can be used to define the communication configuration between the Terminal and Network, dependent on the requirements of Services demanded by Users. In other words, it is necessary to identify proper communications mechanisms between communications apparatus, based on the characteristics of users and their services. This raises further questions about how to manage traffic in heterogeneous networks in an efficient way. 2.8.2 Methods of RRM 2.8.2.1 Network based functions Admission control (AC) Load control (LC) Packet scheduler (PS) Resource Manager (RM) Admission control In the decision procedure AC will use threshold form network planning and from Interference measurements. The new connection should not impact the planned coverage and quality of existing Connections. (During the whole connection time.) AC estimates the UL and DL load increase which new connection would produce. AC uses load information from LC and PC. Load change depends on attributes of RAB: traffic and quality parameters. If UL or DL limit threshold is exceeded the RAB is not admitted. AC derives the transmitted bit rate, processing gain, Radio link initial quality parameters, target BER, BLER, Eb/No, SIR target. AC manages the bearer mapping The L1 parameters to be used during the call. AC initiates the forced call release, forced inter-frequency or intersystem handover. Load control Reason of load control Optimize the capacity of a cell and prevent overload The interference main resource criteria. LC measures continuously UL and DL interference. RRM acts based on the measurements and parameters from planning Preventive load control In normal conditions LC takes care that the network is not overloaded and remains Stable. Overload condition . LC is responsible for reducing the load and bringing the network back into operating area. Fast LC actions in BTS Lower SIR target for the uplink inner-loop PC. LC actions located in the RNC. Interact with PS and throttle back packet data traffic. Lower bit rates of RT users.(speech service or CS data). WCDMA interfrequency or GSM intersystem handover. Drop single calls in a controlled manner. 2.8.2.3 Connection based functions Handover Control (HC) Power Control (PC) Power control Uplink open loop power control. Downlink open loop power control. Power in downlink common channels. Uplink inner (closed) loop power control. Downlink inner (closed) loop power control. Outer loop power control. Power control in compressed mode. Handover Intersystem handover. Intrafrequency handover. Interfrequency handover. Intersystem handover. Hard handover (HHO). All the old radio links of an MS are released before the new radio links are established. Soft handover (SHO) SMS is simultaneously controlled by two or more cells belonging to different BTS of the same RNC or to different RNC. MS is controlled by at least two cells under one BTS. Mobile evaluated handover (MEHO) The UE mai Radio Resource Management in OFDMA Networks Radio Resource Management in OFDMA Networks 1 Introduction The convenience and popularity of wireless technology has now extended into multimedia communications, where it poses a unique challenge for transmitting high rate voice, image, and data signals simultaneously, synchronously, and virtually error-free. That challenge is currently being met through Orthogonal Frequency Division Multiplexing (OFDM), an interface protocol that divides incoming data streams into sub-streams with overlapping frequencies that can then be transmitted in parallel over orthogonal subcarriers [2,3]. To allow multiple accesses in OFDM , Orthogonal Frequency Division Multiple Access (OFDMA) was introduced. Relaying techniques, along with OFDMA, are used to achieve high data rate and high spectral efficiency. 1.1 Orthogonal Frequency Division Multiple Access OFDMA, an interface protocol combining features of OFDM and frequency division multiple access (FDMA)., was developed to move OFDM technology from a fixed-access wireless system to a true cellular system with mobility with same underlying technology, but more flexibility was defined in the operation of the system [1,8]. In OFDMA, subcarriers are grouped into larger units, referred to as sub-channels, and these sub-channels are further grouped into bursts which can be allocated to wireless users [4]. 1.2 Relay-Enhanced Networks In cellular systems, a way to achieve remarkable increase in data rate, but without claiming for more bandwidth, is to shrink cell sizes, however, with smaller cells more base stations (BSs) are needed to cover a same area due to which deployment and networking of new BSs acquire significant costs [5]. An alternative solution to this problem is to deploy smart relay stations (RSs), which can communication with each other and with BSs through wireless connections reducing systems cost. A relay station (RS), also called repeater or multi-hop station, is a radio system that helps to improve coverage and capacity of a base station (BS) and the resulting networks employing relay stations are sometimes called cooperative networks [6]. 1.3 Technological Requirement The continuously evolving wireless multimedia services push the telecommunication industries to set a very high data rate requirement for next generation mobile communication systems. As spectrum resource becomes very scarce and expensive, how to utilize this resource wisely to fulfil high quality user experiences is a very challenging research topic. Orthogonal frequency-division multiple access (OFDMA)-based RRM schemes together with relaying techniques allocate different portions of radio resources to different users in both the frequency and time domains and offers a promising technology for providing ubiquitous high-data-rate coverage with comparatively low cost than deploying multiple base stations [5]. Although wireless services are the demand of future due to their mobility and low cost infrastructure but along with this they suffer serious channel impairments. In particular, the channel suffers from frequency selective fading and distance dependent fading (i.e., large-scale fading) [1, 8]. While frequency selective fading results in inter-symbol-interference (ISI), large-scale fading attenuates the transmitted signal below a level at which it can be correctly decoded. Orthogonal Frequency-Division Multiple Access (OFDMA) relay-enhanced cellular network, the integration of multi-hop relaying with OFDMA infrastructure, has become one of the most promising solutions for next-generation wireless communications. 1.3.1 Frequency Selective Fading In wireless communications, the transmitted signal is typically reaching the receiver through multiple propagation paths (reflections from buildings, etc.), each having a different relative delay and amplitude. This is called multipath propagation and causes different parts of the transmitted signal spectrum to be attenuated differently, which is known as frequency-selective fading. In addition to this, due to the mobility of transmitter and/or receiver or some other time-varying characteristics of the transmission environment, the principal characteristics of the wireless channel change in time which results in time-varying fading of the received signal [9]. 1.3.2 Large Scale Fading Large scale fading is explained by the gradual loss of received signal power (since it propagates in all directions) with transmitter-receiver (T-R) separation distance. These phenomenonss cause attenuation in the signal and decrease in its power. To overcome this we use diversity and multi-hop relaying. 1.3.3 Diversity Diversity refers to a method for improving the reliability of a message signal by using two or morecommunication channelswith different characteristics. Diversity plays an important role in combatingfadingandco-channel interferenceand avoidingerror bursts. It is based on the fact that individual channels experience different levels of fading and interference. Multiple versions of the same signal may be transmitted and/or received and combined in the receiver [10]. 1.4 Proposed Simulation Model We developed a simulation model in which each user-pair is allocated dynamically a pair of relay and subcarrier in order to maximize its achievable sum-rate while satisfying the minimum rate requirement. The algorithm and the results of the simulation model are given in chapter 4. 1.5 Objectives The objective of our project is to have a detail overview of the literature regarding Orthogonal Frequency Division Multiple Access (OFDMA), Radio Resource Management (RRM) and Relaying techniques. After literature review we developed a simulation framework in which we will try to use minimum resources to get maximum throughput by using dynamic resource allocation. 1.6 Tools For the design and implementation of proposed Algorithm, we have used the following tools MATLAB Smart Draw Corel Draw 1.7 Overview Chapter 2 contains the literature review. It explains the basic principles of OFDMA, Radio Resource Management (RRM) and the relaying techniques. Chapter 3 explains the implementation of OFDM generation and reception that how an OFDM signal is generated and transmitted through the channel and how it is recovered at the receiver. Chapter 4 could be considered as the main part of thesis. It focuses on the simulation framework and the code. We have followed the paper â€Å"Subcarrier Allocation for multiuser two-way OFDMA Relay networks with Fairness Constraints†. In this section we have tried to implement the Dynamic Resource Allocation algorithm in order to achieve the maximum sum rate. Results are also discussed at the end of the end of the chapter. 2 Literature Review Introduction: First section of this Chapter gives a brief overview about OFDMA.OFDMA basically is the combination of Orthogonal Frequency Division Multiplexing (OFDM) and Frequency Division Multiplexing Access (FDMA).OFDMA provides high data rates even through multipath fading channels. In order to understand OFDMA, we must have brief introduction to Modulation, Multiple Access, Propagation mechanisms, its effects and its impairments while using OFDMA. 2.1 Modulation Modulation is the method of mapping data with change in carrier phase, amplitude, frequency or the combination [11]. There are two types of modulation techniques named as Single Carrier Modulation (SCM) Transmission Technique or Multicarrier Modulation (MCM) Transmission Technique. [12] Single Carrier Modulation (SCM) In single carrier transmission modulation (SCM) transmission, information is modulated using adjustment of frequency, phase and amplitude of a single carrier [12]. Multi Carrier Modulation (MCM) In multicarrier modulation transmission, input bit stream is split into several parallel bit streams then each bit stream simultaneously modulates with several sub-carriers (SCs) [12]. 2.2 Multiplexing Multiplexing is the method of sharing bandwidth and resources with other data channels. Multiplexing is sending multiple signals or streams of information on a carrier at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end [13]. 2.2.1 Analog Transmission In analog transmission, signals are multiplexed using frequency division multiplexing (FDM), in which the carrier bandwidth is divided into sub channels of different frequency widths,and each signal is carried at the same time in parallel. 2.2.2 Digital Transmission In digital transmission, signals are commonly multiplexed using time-division multiplexing (TDM), in which the multiple signals are carried over the same channel in alternating time slots. 2.2.3 Need for OFDMA General wireless cellular systems are multi-users systems. We have limited radio resources as limited bandwidth and limited number of channels. The radio resources must be shared among multiple users. So OFDM is a better choice in this case. OFDM is the combination of modulation and multiplexing. It may be a modulation technique if we analyze the relation between input and output signals. It may be a multiplexing technique if we analyze the output signal which is the linear sum of modulated signal. In OFDM the signal is firstly split into sub channels, modulated and then re-multiplexed to create OFDM carrier. The spacing between carriers is such that they are orthogonal to one another. Therefore there is no need of guard band between carriers. In this way we are saving the bandwidth and utilizing our resources efficiently. 2.3 Radio Propagation Mechanisms There are 3 propagation mechanisms: Reflection, Diffraction and Scattering. These 3 phenomenon cause distortion in radio signal which give rise to propagation losses and fading in signals [14]. 2.3.1 Reflection Reflection occurs when a propagating Electro-Magnetic (EM) wave impinges upon an object which has very large dimensions as compared to the wavelength of the propagating wave. Reflections occur from the surface of the earth and from buildings and walls. 2.3.2 Diffraction When the radio path between the transmitter and receiver is obstructed by a surface that has sharp irregularities (edges), diffraction occurs. The secondary waves resulting from the obstructing surface are present throughout the space and even behind the obstacle, giving rise to a bending of waves around the obstacle, even when a line-of-sight path does not exist between transmitter and receiver. At high frequencies, diffraction, like reflection, depends on the geometry of the object, as well as the amplitude, phase and polarization of the incident wave at the point of diffraction. 2.3.3 Scattering When the medium through which the wave travels consists of objects with dimensions that are small compared to the wavelength, and where the number of obstacles per unit volume is large. Scattered waves are produced by rough surfaces, small objects or by other irregularities in the channel. In practice, foliage, street signs and lamp posts produce scattering in a mobile radio communications system. 2.4 Effects of Radio Propagation Mechanisms The three basic propagation mechanisms namely reflection, diffraction and scattering as we have explained above affect on the signal as it passes through the channel. These three radio propagation phenomena can usually be distinguished as large-scale path loss, shadowing and multipath fading [14][15]. 2.4.1 Path Loss Path Lossis the attenuation occurring by an electromagnetic wave in transit from a transmitter to a receiver in a telecommunication system. In simple words, it governs the deterministic attenuation power depending only upon the distance between two communicating entities. It is considered as large scale fading because it does not change rapidly. 2.4.2 Shadowing Shadowingis the result of movement of transmitter, receiver or any channel component referred to as (obstacles). Shadowing is a statistical parameter. Shadowing follows a log-normal distribution about the values governed by path loss. Although shadowing depends heavily upon the channel conditions and density of obstacles in the channel, it is also normally considered a large scale fading component alongside path loss. 2.4.3 Multipath Fading Multipath Fadingis the result of multiple propagation paths which are created by reflection, diffraction and scattering. When channel has multiple paths. Each of the paths created due to these mechanisms may have its characteristic power, delay and phase. So receiver will be receiving a large number of replicas of initially transmitted signal at each instant of time. The summation of these signals at receiver may cause constructive or destructive interferences depending upon the delays and phases of multiple signals. Due to its fast characteristic nature, multipath fading is called small scale fading. 2.5 Orthogonal Frequency Division Multiplexing (OFDM) Orthogonal Frequency Division Multiplexing (OFDM) is an efficient multicarrier modulation that is robust to multi-path radio channel impairments [15]. Now-a-days it is widely accepted that OFDM is the most promising scheme in future high data-rate broadband wireless communication systems. OFDM is a special case of MCM transmission. In OFDM, high data rate input bit stream or data is first converted into several parallel bit stream, than each low rate bit stream is modulated with subcarrier. The several subcarriers are closely spaced. However being orthogonal they do not interfere with each other. 2.5.1 Orthognality Signals are orthogonal if they are mutually independent of each other. Orthogonality is a property that allows multiple information signals to be transmitted perfectly over a common channel and detected, without interference. Loss of orthogonality results in blurring between these information signals and degradation in communications. Many common multiplexing schemes are inherently orthogonal. The term OFDM has been reserved for a special form of FDM. The subcarriers in an OFDM signal are spaced as close as is theoretically possible while maintain orthogonality between them.In FDM there needs a guard band between channels to avoid interference between channels. The addition of guard band between channels greatly reduces the spectral efficiency. In OFDM, it was required to arrange sub carriers in such a way that the side band of each sub carrier overlap and signal is received without interference. The sub-carriers (SCs) must be orthogonal to each other, which eliminates the guard band and improves the spectral efficiency . 2.5.2 Conditions of orthogonality 2.5.2.1 Orthogonal Vectors Vectors A and B are two different vectors, they are said to be orthogonal if their dot product is zero 2.6 OFDM GENERATION AND RECEPTION OFDM signals are typically generated digitally due to the complexity of implementation in the analog domain. The transmission side is used to transmit digital data by mapping the subcarrier amplitude and phase. It then transforms this spectral representation of the data into the time domain using an Inverse Discrete Fourier Transform (IDFT) but due to much more computational efficiency in Inverse Fast Fourier Transform (IFFT), IFFT is used in all practical systems. The receiver side performs the reverse operations of the transmission side, mixing the RF signal to base band for processing, and then a Fast Fourier Transform (FFT) is employed to analyze the signal in the frequency domain. The demodulation of the frequency domain signal is then performed in order to obtain the transmitted digital data. The IFFT and the FFT are complementary function and the most suitable term depends on whether the signal is being recovered or transmitted but the cases where the signal is independent of this distinction then these terms can be used interchangeably [15]. 2.6.1 OFDM Block Diagram 2.6.2 Implementation of OFDM Block Diagram 2.6.2.1 Serial to Parallel Conversion: In an OFDM system, each channel can be broken down into number of sub-carriers. The use of sub-carriers can help to increase the spectral efficiency but requires additional processing by the transmitter and receiver which is necessary to convert a serial bit stream into several parallel bit streams to be divided among the individual carriers. This makes the processing faster as well as is used for mapping symbols on sub-carriers. 2.6.2.2 Modulation of Data: Once the bit stream has been divided among the individual sub-carriers by the use of serial to parallel converter, each sub-carrier is modulated using 16 QAM scheme as if it was an individual channel before all channels are combined back together and transmitted as a whole. 2.6.2.3 Inverse Fourier Transform: The role of the IFFT is to modulate each sub-channel onto the appropriate carrier thus after the required spectrum is worked out, an inverse Fourier transform is used to find the corresponding time domain waveform. 2.6.2.4 Parallel to Serial Conversion: Once the inverse Fourier transform has been done each symbol must be combined together and then transmitted as one signal. Thus, the parallel to serial conversion stage is the process of summing all sub-carriers and combining them into one signal 2.6.2.5 Channel: The OFDM signal is then transmitted over a channel with AWGN having SNR of 10 dB. 2.6.2.6 Receiver: The receiver basically does the reverse operations to the transmitter. The FFT of each symbol is taken to find the original transmitted spectrum. The phase angle of each transmission carrier is then evaluated and converted back to the data word by demodulating the received phase. The data words are then combined back to the same word size as the original data. 2.7 OFDMA in a broader perspective OFDM is a modulation scheme that allows digital data to be efficiently and reliably transmitted over a radio channel, even in multipath environments [17]. OFDM transmits data by using a large number of narrow bandwidth carriers. These carriers are regularly spaced in frequency, forming a block of spectrum. The frequency spacing and time synchronization of the carriers is chosen in such a way that the carriers are orthogonal, meaning that they do not interfere with each other. This is despite the carriers overlapping each other in the frequency domain [18]. The name ‘OFDM is derived from the fact that the digital data is sent using many carriers, each of a different frequency (Frequency Division Multiplexing) and these carriers are orthogonal to each other [19]. 2.7.1 History of OFDMA The origins of OFDM development started in the late 1950s with the introduction of Frequency Division Multiplexing (FDM) for data communications. In 1966 Chang patented the structure of OFDM and published the concept of using orthogonal overlapping multi-tone signals for data communications. In 1971 Weinstein introduced the idea of using a Discrete Fourier Transform (DFT) for Implementation of the generation and reception of OFDM signals, eliminating the requirement for banks of analog subcarrier oscillators. This presented an opportunity for an easy implementation of OFDM, especially with the use of Fast Fourier Transforms (FFT), which are an efficient implementation of the DFT. This suggested that the easiest implementation of OFDM is with the use of Digital Signal Processing (DSP), which can implement FFT algorithms. It is only recently that the advances in integrated circuit technology have made the implementation of OFDM cost effective. The reliance on DSP prevented the wide spread use of OFDM during the early development of OFDM. It wasnt until the late 1980s that work began on the development of OFDM for commercial use, with the introduction of the Digital Audio Broadcasting (DAB) system. 2.7.2 Advantages using OFDMA There are some advantages using OFDMA. OFDM is a highly bandwidth efficient scheme because different sub-carriers are orthogonal but they are overlapping. Flexible and can be made adaptive; different modulation schemes for subcarriers, bit loading, adaptable bandwidth/data rates possible. Has excellent ICI performance because of addition of cyclic prefix. In OFDM equalization is performed in frequency domain which becomes very easy as compared to the time domain equalization. Very good at mitigating the effects of delay spread. Due to the use of many sub-carriers, the symbol duration on the sub-carriers is increased, relative to delay spread. ISI is avoided through the use of guard interval. Resistant to frequency selective fading as compared to single carrier system. Used for high data rate transmission. OFDMA provides flexibility of deployment across a variety of frequency bands with little need for modification is of paramount importance. A single frequency network can be used to provide excellent coverage and good frequency re-use. OFDMA offers frequency diversity by spreading the carriers all over the used spectrum. 2.7.3 Challenges using OFDMA These are the difficulties we have to face while using OFDMA [20][21][22], The OFDM signal suffers from a very high peak to average power ratio (PAPR) therefore it requires transmitter RF power amplifiers to be sufficiently linear in the range of high input power. Sensitive to carrier frequency offset, needs frequency offset correction in the receiver. Sensitive to oscillator phase noise, clean and stable oscillator required. The use of guard interval to mitigate ISI affects the bandwidth efficiency. OFDM is sensitive to Doppler shift frequency errors offset the receiver and if not corrected the orthogonality between the carriers is degraded. If only a few carriers are assigned to each user the resistance to selective fading will be degraded or lost. It has a relatively high sensitivity to frequency offsets as this degrades the orthogonality between the carriers. It is sensitive to phase noise on the oscillators as this degrades the orthogonaility between the carriers. 2.7.4 Comparison with CDMA in terms of benefits 2.7.4.2 CDMA Advantages: CDMA has some advantages over OFDMA [22], Not as complicated to implement as OFDM based systems. As CDMA has a wide bandwidth, it is difficult to equalise the overall spectrum significant levels of processing would be needed for this as it consists of a continuous signal and not discrete carriers. Not as easy to aggregate spectrum as for OFDM. 2.7.5 OFDMA in the Real World: UMTS, the European standard for the 3G cellular mobile communications, and IEEE 802.16, a broadband wireless access standard for metropolitan area networks (MAN), are two live examples for industrial support of OFDMA. Table 1 shows the basic parameters of these two systems. Table 1. OFDMA system parameters in the UMTS and IEEE 802.16 standards 2.8 Radio Resource Management In second section of this chapter we will discuss radio resource management schemes, why we need them and how they improve the efficiency of the network. Radio resource management is the system level control of co-channel interference and other radio transmission characteristics in wireless communication systems. Radio resource management involves algorithms and strategies for controlling parameters such as Transmit power Sub carrier allocation Data rates Handover criteria Modulation scheme Error coding scheme, etc 2.8.1 Study of Radio Resource Management End-to-end reconfigurability has a strong impact on all aspects of the system, ranging from the terminal, to the air interface, up to the network side. Future network architectures must be flexible enough to support scalability as well as reconfigurable network elements, in order to provide the best possible resource management solutions in hand with cost effective network deployment. The ultimate aim is to increase spectrum efficiency through the use of more flexible spectrum allocation and radio resource management schemes, although suitable load balancing mechanisms are also desirable to maximize system capacity, to optimize QoS provision, and to increase spectrum efficiency. Once in place, mobile users will benefit from this by being able to access required services when and where needed, at an affordable cost. From an engineering point of view, the best possible solution can only be achieved when elements of the radio network are properly configured and suitable radio resource m anagement approaches/algorithms are applied. In other words, the efficient management of the whole reconfiguration decision process is necessary, in order to exploit the advantages provided by reconfigurability. For this purpose, future mobile radio networks must meet the challenge of providing higher quality of service through supporting increased mobility and throughput of multimedia services, even considering scarcity of spectrum resources. Although the size of frequency spectrum physically limits the capacity of radio networks, effective solutions to increase spectrum efficiency can optimize usage of available capacity. Through inspecting the needs of relevant participants in a mobile communication system, i.e., the Terminal, User, Service and Network, effective solutions can be used to define the communication configuration between the Terminal and Network, dependent on the requirements of Services demanded by Users. In other words, it is necessary to identify proper communications mechanisms between communications apparatus, based on the characteristics of users and their services. This raises further questions about how to manage traffic in heterogeneous networks in an efficient way. 2.8.2 Methods of RRM 2.8.2.1 Network based functions Admission control (AC) Load control (LC) Packet scheduler (PS) Resource Manager (RM) Admission control In the decision procedure AC will use threshold form network planning and from Interference measurements. The new connection should not impact the planned coverage and quality of existing Connections. (During the whole connection time.) AC estimates the UL and DL load increase which new connection would produce. AC uses load information from LC and PC. Load change depends on attributes of RAB: traffic and quality parameters. If UL or DL limit threshold is exceeded the RAB is not admitted. AC derives the transmitted bit rate, processing gain, Radio link initial quality parameters, target BER, BLER, Eb/No, SIR target. AC manages the bearer mapping The L1 parameters to be used during the call. AC initiates the forced call release, forced inter-frequency or intersystem handover. Load control Reason of load control Optimize the capacity of a cell and prevent overload The interference main resource criteria. LC measures continuously UL and DL interference. RRM acts based on the measurements and parameters from planning Preventive load control In normal conditions LC takes care that the network is not overloaded and remains Stable. Overload condition . LC is responsible for reducing the load and bringing the network back into operating area. Fast LC actions in BTS Lower SIR target for the uplink inner-loop PC. LC actions located in the RNC. Interact with PS and throttle back packet data traffic. Lower bit rates of RT users.(speech service or CS data). WCDMA interfrequency or GSM intersystem handover. Drop single calls in a controlled manner. 2.8.2.3 Connection based functions Handover Control (HC) Power Control (PC) Power control Uplink open loop power control. Downlink open loop power control. Power in downlink common channels. Uplink inner (closed) loop power control. Downlink inner (closed) loop power control. Outer loop power control. Power control in compressed mode. Handover Intersystem handover. Intrafrequency handover. Interfrequency handover. Intersystem handover. Hard handover (HHO). All the old radio links of an MS are released before the new radio links are established. Soft handover (SHO) SMS is simultaneously controlled by two or more cells belonging to different BTS of the same RNC or to different RNC. MS is controlled by at least two cells under one BTS. Mobile evaluated handover (MEHO) The UE mai

the plant cell :: essays research papers

The Plant Cell Cell Wall Size: Around 1Â µ Basic Function: * Hold the shape of the cell. * Strengthen the cell. Covering the cell membrane of the plant cell, there is the cell wall. The cell wall is composed of two layers of rigid, hard cellulose embedded in compounds like pectin and lignin. Pores in the cell wall allow molecules to pass through. The cell wall has two parts. The primary cell wall is formed during the growth of the cell. After the cell has stopped growing, a secondary cell wall forms. This secondary wall is made of lignin and cellulose, woven together tightly, to prevent further growth and to form and strong protective barrier. Cytoplasm Size: Unmeasurable Basic Function: * Helps dissolve waste products * Creates a "medium" for vesicles to travel through * Aids in cell metabolism * Serves as a home for the cytoskeleton. The cytoplasm is the jelly-like material that makes up much of the cell. It is 80% water and usually clear in color. It also contains many salts. The liquid portion is referred to as cytosol. In fact, "cytoplasm" means "cell substance." The cytoplasm is also the home of the cytoskeleton, a network of cytoplasmic filaments that are responsible for the movement of the cell. The cytoplasm is constantly moving and churning due to cytoplasmic streaming. Golgi Apparatus Size: Between 2 and 3Â µ Basic Function: * Serves as "processing center" for cell. * Packages and processes new proteins. * Prepares proteins for secretion or storage. The Golgi Apparatus is a series of stacked membranes in the cytoplasm that packages proteins for secretion or storage in vesicles. Inside the membranes are sacs of fluid or gel-like substances. The Golgi Apparatus takes proteins in transport sacs from the endoplasmic reticulum and sends it through a series of these membranes. The proteins are then "modified"' as they pass from membrane to membrane. After the vesicle of proteins has finished its trip through the Golgi Apparatus, it buds off the organelle in a Golgi sac, ready to be stored or transported to other parts of the body. Cell Membrane Size: 7 to 8 NM (nanometers) Basic Function: * Controls what enters and exits the cell. * Separates cell from outer environment. On the outside of all cells, there is a layer of protein and lipid (fat) called the cell membrane or the plasma membrane. This membrane is found in ALL cells. The membrane is selectively permeable, meaning it allows some molecules to enter and some not to. The membrane allows molecules in through two forms

St Thomas Aquinas Essay -- Religion Philosophy

St Thomas Aquinas It has been written that "since the day of Aristotle, probably no one man has exercised such a powerful influence on the thinking world as did St Thomas Aquinas." Thomas Aquinas was born in 1225 in Italy of a noble family, thus separated by 900 years to Aristotle. He received his first education at the Abbey of Monte Cassino, going on from there to the University of Naples. In 1243, he joined the Dominican monastic order at Cologin. His most influential teacher was another Dominican, Albertus Magnis, a German who wrote extensively on theological matters and questions of national science, especially biology. Thomas was also a highly successful lecturer, and travelled widely across Europe, particularly on the business of his order and the church. In his short and active life, Thomas produced a prodigious amount of writing: commentaries on biblical books and Aristotelian work, short essays on philosophical problems, and a lengthy compendium of Christian apoletices, the Summa Centra Gentiles, which, as Chambers et. al. writes was probably intended for Dominican missionaries working to convert heretics and infidels. St Thomas begins the Summa Centra Gentiles as writes by reaffirming what Aristotle claimed at the beginning of Metaphysics, namely, he that studies the end or purpose of the universe is rightly called a wise man. He is wise because he is studying that which is highest and most noble among the subjects of study: Truth. Truth, Aquinas claims, i...

Hannibal and the Battle of Cannae

HANNIBAL AND THE BATTLE OF CANNAE The battle of Cannae was a major battle of the Second Punic War near the town of Cannae, an ancient village in southern part of Italy. The battle took place between the outnumbered Carthaginian army under Hannibal against the Romans under the command of Lucius Aemilius Paullus and Gaius Terentius Varro. For the most part, the Romans were overpowered by the undermanned Carthaginian forces. Many historians agree that the battle of Cannae is one of the greatest strategic victories in military history.Numerous historians have examined the possible route Hannibal took from New Carthage to the Pyrenees and then over the Alps to Rome. Along with using scientific data, these historians and scientists allege that there are three possible routes Hannibal may have taken from New Carthage in Iberia across Europe to get to Italy. Scientists and historians do disagree on which route is most accurate do to the fact that the only historical accounts of Hannibal†™s journey are that of Livy and Polybius. Neither historian leaves a very detailed account of the surroundings for Hannibal and his troops.Through paleobotanical reconstruction, attempts have been made to more clearly identify if the places noted by Livy and Polybius resemble any of these places today1. Hannibal came from the very well-known Carthaginian Barca family. His father, Hamilcar Barca was the military leader of Carthage during the first Punic War. At the conclusion of the First Punic War, Carthage's mercenaries revolted and Rome took advantage of her rival's distraction and, in spite of the recent peace agreement, took control of Sardinia and Corsica and forced Carthage to pay a large indemnity2.Carthage finally won the mercenary war, but the loss of Sicily, Sardinia and Corsica left her economic empire crippled and reduced the area from which she could hire troops. After regaining control, the Carthaginians were forced to major war concessions. Of those concessions, Car thage was to pay a war indemnity to Rome and could no longer recruit Italian sailors. Carthage also sent Hamilcar Barca to Iberia to eliminate the Spaniards and build an empire in Spain. Unfortunately, Barca was killed in an ambush at Helice in 229 B. C. E. but not until after he had been able to take over control of the Iberian southern coast.In 226 BC, Hasdrubal reached an agreement with Rome that recognized the Ebro River in northeastern Spain as the northern limit of Carthaginian interest in the area. Five years later, Hasdrubal was assassinated, and Hamilcar's son Hannibal became the leader. At about that time, Rome began involving itself in the affairs of Saguntum, a city on the Mediterranean coast of Spain well south of the Ebro and therefore presumably in Carthaginian territory3. Hannibal viewed the Roman moves as an intervention similar to the ones that had touched off the first war.Hannibal laid siege to the town, which fell after eight months. Hannibal's strategic insight now became evident4. When Hannibal came to the head of the Carthaginian army he took it upon himself to rebuild Carthaginian fortunes by occupying Spain. The Romans had aligned themselves with Saguntum in an attempt to show strength and power against Carthage. Since Carthage's fleet was no longer a match for Rome's, the invasion of Italy would need to occur by land. To that end, Hannibal did his best to speak with tribes in his line of march well in advance of the arrival of conflicts.He also established alliances with various north Italian Celtic tribes that were traditional enemies of Rome. Hannibal's forces were the first civilized army to cross the Alps5. Exposure, desertion, accidents and fierce resistance by mountain tribes reduced his army from 40,000 to 26,000 during the trip, and most of the elephants accompanying the remarkable host also perished. Fortunately, once Italy was reached, the Celtic alliances provided replacements that brought the army back to its original str ength. The Carthaginian troops endured great hardship and suffered serious casualties.Shortly thereafter, Hannibal fought two battles that demonstrated his resolve as a field commander and his determination to destroy rather than merely defeat his enemy. At the Trebia River, only 10,000 Romans escaped an ambush out of 40,000 involved, and at Lake Trasimene, nearly an entire Roman force of 25,000 was killed or captured. From then on, the Romans were hesitant to fight a large-scale engagement. Hannibal was careful to treat prisoners from Rome's allied cities courteously, often freeing them without ransom to encourage dissatisfaction with Rome's cause6.Captured Roman citizens, on the other hand, were held for ransom used to pay Hannibal's men or were often sold into slavery. The Carthaginian army lived off the land causing as much damage to the economy as possible. After victory at Lake Trasimene, Hannibal moved his army to southern Italy in order to recruit additional troops7. This mo ving of troops by Hannibal and their subsequent looting forced the Romans to become more aggressive. Two now consuls, Gaius Terentius Varro and Lucius Aemilius Paulus, were given command of the combined legions of Rome with orders to make an end to the feared Carthaginian.Normally, the two consuls would have independent commands but, when their forces were combined, command of the whole alternated daily. Hannibal's effective intelligence organization soon informed him that Varro was the more rash and impulsive of his opponents, and so Hannibal decided to force an action on a day that Varro was in command of the Roman forces8. Hannibal seized a grain depot to lure the Romans to the site he had chosen for battle. The depot was located at the small village of Cannae, south of Rome.Dawn of that August morning in 216 BC found Hannibal, commander of Carthage's army in Italy, looking down at the plain separating his vantage point from the waters of the Adriatic Sea about three miles away9. The Roman enemy was already advancing with an army of more than 85,000 men, aligned in the standard offensive formation of the dreaded legions. Hannibal's force, some 56,000 in number, faced long odds. The Roman force available for battle was large by the standards of the day. Eight full legions of infantry, some 40,000 men, were improved by 40,000 allied infantrymen.About 2,000 Roman cavalry and 4,000 allied horses completed the army, for a total strength of 86,00010. In battle, the Roman infantry usually advanced on a wide front, with cavalry on the flank. The heavy infantry was led by skirmishers, who opened the fighting with the throwing of javelins. They would then fall to the rear of the formation and were able to pass through the Roman formation because deliberate gaps were left in each line. The basic fighting unit of the heavy infantry was the maniple of about 160 men divided into two centuries.Rather than forming a constant line, the two centuries were deployed one behind the other, leaving the gaps used by the skirmishers. At the point of attack or when in a defensive position, the rear centuries could be moved up to fill the gaps11. The Hastati made up the first line of heavy infantry of the Roman army. They were equipped with a heavy shield, a helmet, light and heavy javelins and a short, straight sword. The Princeps were the second line of heavy infantry. Although armed like the Hastati, the Princeps were omewhat older and more experienced and formed behind those of the Hastati, but were offset to block the gaps in the Hastati line. The third line, made up of the old veteran troops known as the Tritarii, had its centuries form behind the gaps in the second line, giving an overall checkerboard result to the formation. The Tritarii had a thrusting spear in place of the javelin of the first two lines12. In the hands of an experienced commander, the flexibility possible with this formation was useful, particularly against older military formation su ch as the phalanx.Unfortunately, the Roman method of appointing new consuls each year and rotating command daily made it unlikely that the top military talent would be allowed to pursue a logical plan. Roman courage, discipline and patriotism were rarely lacking, but the coming battle of Cannae would highlight the need for changes in the selection and responsibilities of army commander13. Aside from the top leaders, very few Carthaginians were present in Hannibal's army. His army at Cannae consisted of North African, Spanish and Celtic personnel. Perhaps the soundest foot soldiers available to Hannibal were the Libyan-Phoenician heavy infantry.The Phoenicians living in Libya were subject to Carthaginian military service and cleared themselves well. Originally armed like Greek hoplites, they now began equipping with Roman arms captured at the Trebia and Lake Trasimene. In addition to the infantry, 2,000 Spanish cavalry were at Hannibal’s disposal. They were heavily armed and u sed as heavy cavalry, but the outstanding quality of their horses allowed them to rival the speed of the Numidian cavalry14. About 25,000 Celtic infantry and 5,000 Celtic cavalry made up the remainder of Hannibal's force.These people lived for war, but without the guidance of a commander like Hannibal, their absence of discipline made them unpredictable. At the time of Cannae, Hannibal was arming these men with captured Roman weapons. He liked to use the Celts as troops that would cause disruption in enemy ranks prior to sending in his African infantry. At Cannae, the Romans were determined to crush Hannibal's center. They formed deep battle lines in order to bring pressure to stand against the middle of the Carthaginian line. On the Roman right, the legion cavalry, some 2,400 strong, faced Hannibal's Spaniards and Celts, totaling 7,000.The mismatch would prove a decisive element in the battle's surprising outcome. On the Roman left, the 4,000 allied cavalry faced an equal number of Numidians. Hannibal aligned his infantry in an unusual manner. The center of his position was curved, facing outward toward the advancing Romans. The flanks bent backward from the center. Alternating units of Spanish and Celtic swordsmen held this line, and they were greatly outnumbered by the approaching Romans. Hannibal positioned himself at the left end of the line, and his youngest brother Mago, held the right.Each end of the line was anchored by a dense square of African infantry, the location of which guaranteed that they would not be engaged until long after those at the center15. As the Romans advanced, a hot west wind blew dust in their faces and obscured their vision. At a range of about 35 yards, the Romans hurled their light javelins, causing casualties among the Spaniard and Celts. These javelins often caused problems even if they only pierced a man's shield, because the shaft was difficult to remove and weighed the shield down, making the man vulnerable to an onrushin g legionary.At closer range, the heavy javelin was thrown, and then the infantry lines collided, the swift Celts and athletic Spaniards against the disciplined Roman masses. In time, the weight of the Roman assault began to take effect on Hannibal's troops, and the center of the Carthaginian line retreated. As Hannibal's men were forced back, they found themselves slowly backing up a slope Due to the nature of the terrain, the Romans fought uphill as they advanced and at the same time were restricted into a narrowing front as their mass of men entered the ‘V. Although the Roman infantrymen did not know it, their fate was all but sealed by this time. Hannibal had planned for his cavalry to strike the decisive blows while his infantry fought a large-scale delay. As the battle opened, Hannibal launched the Spanish and Celtic cavalry on his left against the outnumbered Roman cavalry16. The consul Aemilius accompanied these cavalrymen but they could not endure the Carthaginian assa ult. Aemilius was wounded and the bulk of the Roman cavalry was driven from the field, exposing that flank of the Roman army.While this occurred on the Carthaginian left, the Numidians on the right had been engaged with the horsemen of Rome's allies17. The Carthaginian cavalry commander on the left, reorganized his units and proceeded to ride behind the Roman infantry to the far side of the battlefield, where the stalemated cavalry fight continued between the Numidians and Rome's allies. The allied horsemen now were taken by surprise and caught between the two Carthaginian forces. The allied cavalry fled the field, taking the consul Varro with them.At this point, Aemilius was dead or dying, and Varro, the other commander, no longer was with the Roman army. The Roman and allied cavalrymen had been killed, captured or driven from the field18. By that time, the Roman infantry had fought its way up the slope and into the enclosed end of the ‘V,' the point. As the men became more t ightly packed into a confined space, fewer of them could use their weapons effectively. Romans in the rear ranks continued to push forward, but found they had little room to maneuver.Hasdrubal, Hannibal’s younger brother, assaulted the Roman rear with his heavy cavalry, assisted by the Carthaginian light infantry. The encirclement was complete. Many Romans first discovered the danger when they realized they were being cut down and hamstrung by the Carthaginian troops. Historians have estimated that the fighting continued until evening and that approximately 600 Romans died per minute of the battle. Cannae represented the apex of Hannibal's career, although he has been criticized for not attempting to end the war by sacking Rome itself at that point.Hannibal remained in Italy for 13 more years, but the determination of the Romans to fight on, regardless of losses, eventually gave them the opportunity to defeat the great Carthaginian. The failure of Carthage to rebuild its flee t in order to challenge that of the Romans made Hannibal's task extremely tough. He attempted to reduce Rome's naval advantage by occupying the Italian coastal cities. If Hannibal had been able to hold them, the odds against the Carthaginian fleet would have improved, but his limited number of troops made it difficult for him to isolate enough garrisons to prevent Roman recapture of the port cities.For 15 years in all, from 218 to 203 BC, Hannibal occupied large areas of Italy. He fought and defeated the Romans on numerous occasions but could not break their spirit19. After Cannae, the Romans again became cautious about entering into full-scale battle against Hannibal, but their command of the sea and the decision to invade Spain, made reinforcement of Hannibal's army difficult. Slowly, the troops who had crossed the Alps with Hannibal decreased in number an in age. But Carthage's absence of naval power prevented Hannibal's alliances with Syracuse and Macedonia from becoming fruitfu l.The Roman navy captured a treaty between Hannibal and Philip V of Macedonia, and by the time the second received a copy and acted on it, the Roman fleet barred his troops from crossing to Italy. In spite of all the complications, Hannibal proved to be a gifted leader able to get the very best from his men. His army was made up of of mercenaries with no real obligation to the Carthaginian cause however no record shows any mutiny during the 5 years in Italy. The army did not more than just survive it maintained a high level of morale and fighting spirit.Spain was taken from Carthage and the Barcid family after Hannibal's brother Hasdrubal repeated a crossing of the Alps with a reinforcement that gave the Romans in Spain a free hand. Hasdrubal was incapable of uniting with Hannibal before being opposed by a strong Roman army in 207 BC. In the ensuing battle, Hasdrubal was defeated and killed20. In October of 203 BC, Publius Cornelius Scipio, the conqueror of Spain, invaded North Afri ca and forced Hannibal to defend Carthage. Hannibal's defeat at Zama at the hands of Scipio in the following spring, caused mostly because of a shortage of cavalry strength, ended the Second Punic War.Hannibal rose to the position of prominence in Carthage after the war and took steps that helped Carthage recover economically from the conflict. Rome viewed Carthage's revival with suspicion, and Hannibal was forced to flee to the east, where he committed suicide in 183 BC rather than fall into Roman hands. Hannibal Barca was one of history’s greatest generals and Rome’s greatest enemy. Although later Roman tradition belittled him, it respected his prowess as a great military commander. Had Hannibal not underestimated the strength of the Romans, he might have rewritten European history.NOTES Mahaney, M. C. ,â€Å"Hannibal’s Invasion Route: An Age-Old Question Revisited within a Geoarchaeological and Palaeobotanical Context. † (Archaeometry vol. 52 (6/2010), 1097 Marcel Le Glay, et al. ,A History of Rome. (Chichester: Wiley-Blackwell, 2009), 74 Ibid, 75 John Peddie, Hannibal’s War. (Gloucechesershire: Sutton, 1997), 9 Ibid, 21-26 G. P. Baker, Hannibal. (New York: Barnes & Nobles, Inc. , 1967), 101-104 Ibid, 100 Le Glay, A History of Rome Adrian Goldsworthy, Cannae, (London: Cassel & Co, 2001), 77-81 Ibid, 95Dexter Hoyos, Hannibal Rome’s Greatest Enemy, (Exeter, Bristol Phoenix Press, 2008), 57-59 Goldsworthy, Cannae, 96-99 Hoyos, Hannibal Rome’s Greatest Enemy, 60 Goldsworthy, Cannae, 108-109 Ibid, 111 Peddie, Hannibal’s War, 92-93 Ibid, 94 Theodore Ayrault Dodge, Hannibal, (Boston, Da Capo Press, 1891), 372 Le Glay, A History of Rome, 77 Dodge, Hannibal, 556 BIBLIOGRAPHY Ancient Greece & Rome: An Encyclopedia for Students, vol. 2. Hannibal Baker, G. P. Hannibal. New York: Barnes & Nobles, Inc. , 1967 Dodge, Theodore Ayrault. Hannibal.Boston: DaCapo Press, 1891 Goldsworthy, Adrian. Cannae. London: Cassel & C o, 2001 Hoyos, Dexter. Hannibal Rome’s Greatest Enemy. Exeter: Bristol Phoenix Press, 2008 Le Glay, et al. A History of Rome. Chichester: Wiley-Blackwell, 2009 Mahaney, M. C. â€Å"Hannibal’s Invasion Route: An Age-Old Question Revisited within a Geoarchaeological and Palaeobotanical Context. † Archaeometry vol. 52 (6/2010): 1096-1109. Peddie, John. Hannibal’s War. Gloucechesershire: Sutton, 1997 Radice, Betty. Livy The War with Hannibal. Translated by Aubrey de Selincourt. Baltimore: Penguin, 1965