Advantages And Disadvantages of Living in a Big City free essay sample

Big cities such as Jakarta, Melbourne or New York are great places where you can find many tall buildings, vehicles, recreational areas and various other things that cannot be found in small town or villages. (Bigcity, n. d. ) Most people prefer living in a big city because in a place where the economy is constantly growing and where anything is possible, it is significantly easier to find a good job with a better quality of life. However aside from the numerous advantages of living in a big city, there are also a few down points to living there. First of all, in a big city we can get what we cannot find in village or small town. For example, in a big city there are many malls, cinemas, nightclubs, restaurants and sport stations. Malls are really nice places to hang out with friends at because the buildings are designed in such a way that people feel comfortable spending large amounts of time in them. We will write a custom essay sample on Advantages And Disadvantages of Living in a Big City or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Customers are provided with a good service and they are able to find many products, not only the ones they need, but also the ones they want. Also people can taste a lot of different kinds of food from different provinces or countries. Secondly, schools in a big city is relatively more qualified and recognized than schools in small towns, and there are even schools with an international standard, which enable children to be more developed in different languages such as English, Chinese and many more. Thirdly, in a big city usually there are a lot of hospitals with advanced technology and better medical treatments because they recruit the doctors who are well-known in the country, and sometimes these hospitals even employ doctors from other countries. In short, patients are more likely to receive better care and treatments in a big city than in small towns. Next, travelling is much easier because in a big city there are good transportation systems such as airplanes, trains, buses, and others. Usually international flights are only available from major cities, as there would be bigger airports. The road systems would be better, hence the buses and trains would be able to service more people to greater distances, so it is relatively easier for residents to travel. Lastly, networking is not such a big problem in big cities, because a big city is where people from all over the world travel to and reside. It is more possible to socialize with and befriend people of different nationalities in a big city. (Shane62, 2010) However, living in a big city also has its disadvantages. For example, the high level of unemployment. As it is known, many people want to go to a big city to find a job but unfortunately it can be really hard because every year the population in these cities is increasing, which means there will be less jobs available. Next, the cost of living is very high. Land is very expensive as less land is available for building house or offices. Taxes are also higher. In small towns, people usually shop at traditional markets, which has fairly low prices. In big cities, the prices of foodstuffs are usually marked up, which means buying food is much more expensive in big cities than in small towns. Another major disadvantage is the terrible traffic conditions. Traffic jams usually happen in big cities, because big cities are often really crowded and nowadays people are more likely to use their private vehicles rather than using the public transportation. The more cars are out on the roads, the higher the possibility for congestions is. The next disadvantage is air pollution. The government keeps building high-rises and real estates that there is hardly any space left to plant trees and build parks. The large number of cars also contributes to the high level of pollution. As the emission from cars is not controlled, old vehicles produce a vast amount of smog that contain CO2 which in turn, causes global warming. (Shane26,2010) (Waxpoeticg,2013) To sum up, living in a big city has its advantages and disadvantages. However in my opinion, living in a big city is really good because one can get a good education, excellent healthcare, easy transportation and find many wonderful recreational facilities.

Meri Moken †Why Antibiotics Stop Working

Meri Moken – Why Antibiotics Stop Working Free Online Research Papers In 1993, when Meri Moken got recognized by various institutions for her research work on the effect of detergents on bacteria, a lot of her work was actually a reflection of a broader spectrum of research that had started as early as the 1960s. What Meri essentially discovered was the resistance of bacteria to household detergents and bleaches – a subset of the age-old capability by bacteria to adapt to harmful chemicals. Her discovery illuminated the ever-burgeoning problems that pathogens present: that, over time, they become harder to eradicate, as any chemicals used against them become ineffective. Pathogens present a huge problem in the medical world, because not only are they becoming more problematic despite advances in antibiotics, but also because the advances are actually making the problem worse. As an illustration, the Escherichia coli, an intestinal bacterium, grew resistant to all fluoroquinolone antibiotics administered against it within a decade. This high rate of adaptation presents a grave problem, since it implies that scientific advances would be hard-pressed to keep up with the bacteria. Then, in 1994, it was discovered that some strains of Streptococcus pneumonia were resistant to Penicillin, and that a full 25% of all people suffering from this Pneumonia were resistant to antibiotics. It was a further indication that the war against pathogen was slowly, but surely, being lost. There are several ways in which bacteria can gain mastery over any antibiotic thrown at them. Every new antibiotic essentially places a kind of selective pressure on them, and the most adapted amongst them survive down the generations. Sometimes, a spontaneous mutation in the bacterial DNA may result in an organism with a higher level of resistance. Other bacteria engage in a process called transformation – a microbial sex-like process in which DNAs are shuffled between two organisms. But most ominous of all adaptation methods is the one in which bacteria interchange a section of DNA called a plasmid amongst themselves. It is ominous since it presents a very efficient way of increasing the overall adaptability of bacteria, without incurring the unpredictability that mutation presents. The resistance that results from the DNA changes within the bacteria is expressed in several ways, at the molecular level. Some of the bacteria change the target molecule, essentially inactivating it and thus making it harmless. Others go a step further and decompose the molecule into its elements. Others simply sequester the offending drug, thus keeping it away from their warpaths. And finally, some bacteria keep the fatal chemicals out of the cells, and prevent their entrance to it. Since the bacterial problem is a serious menace, several solutions have been suggested to help keep bacteria in their rightful place within the biosphere. Firstly, antibiotics should only be used when absolutely necessary. Using them at any other time only increases chances of developing resistance in the microbes. Secondly, all antibiotics, once administered, should be taken until the entire dose is completed. Partially resistant bacteria are less likely to survive and multiply when doses are completed. Thirdly, narrow-spectrum antibiotics should be used, to avoid triggering adaptation mechanism in other bacteria within the vicinity. And finally, vaccines can be innovated to act on a preventative platform rather than a curative one. References Why files (1997) What doesn’t kill them makes them stronger Retrieved 21st January 2009 from Research Papers on Meri Moken - Why Antibiotics Stop WorkingGenetic EngineeringThe Effects of Illegal ImmigrationIncorporating Risk and Uncertainty Factor in CapitalResearch Process Part OneInfluences of Socio-Economic Status of Married MalesBionic Assembly System: A New Concept of Self19 Century Society: A Deeply Divided EraMarketing of Lifeboy Soap A Unilever ProductMind TravelOpen Architechture a white paper

Construction Health and Safety Essay Example | Topics and Well Written Essays - 2500 words

Construction Health and Safety - Essay Example For this reason, some insurance companies fear that handling these risky sites and vouching for the health and the lives of the employees involved in the job may cause them too much funds that may indeed jeopardize their financial stability. Hence, the establishment of the limit of the fund to be allotted for the said issue has already been passed and rather applied in business organizations today. There are certain standards that companies today need to abide with which gives them a chance to be accommodated by several insurance companies in support to the healthcare assurance that they need, however these provisions are guided by certain limitations that both employers and employees must carefully give attention to. This is especially true on the part of those who are involved in the construction industry. In this paper, the statement mentioned above with regards handling risks successfully as an employer, as an employee and as a team of people working together to establish a struc ture, shall be well discussed and assessed as to how much they should be recognized by the current construction project planners at present. Avionics Solution is a small business organization serving as one of the leaders in manufacturing avionics equipment. It started as a family-owned business that delivers quality products given to its regular clients. As of today, Avionics Solution is currently employing at least 48 personnels within its manufacturing facility. It is the main aim of the organization's administration to be of great help to its employees as well as with its clients. Through the establishment of a fine communication system that flows between the employers, the administrative sector and the rank and file employees, the organization's head officers try to bridge the gap existing between the said stakeholders of the organization. Clearly, the mission of the organization to serve the community with the best possible services it could offer have been understood by the organization's authorities to have been effectively sourced out from the establishment of fine camaraderie among the people making up the enti re company, including the employees as the primary actors within the organization's journey towards success. Certainly, Avionics Solution wants to make sure of its competitive status in the manufacturing industry by providing its employees a workplace that stimulates employee interaction and economic growth. However, with all the fine set of missions created by the administration for the entire organization to follow, it has been found out that most of the employees complained about the fact that there are several provisions not granted by the organization, which namely includes health insurance and retirement plan. It is then proposed in this plan paper that the said issue be addressed well. This is to help the company get assured that it would be able to stay in its status of competition within the industry, through its provision of the utmost important factors of consideration for its employees. The said plan proposal

The Philosophy of Epicurus Essay Example | Topics and Well Written Essays - 1250 words

The Philosophy of Epicurus - Essay Example The essay "The Philosophy of Epicurus" discusses the Epicurus's thoughts regarding the capability of everyone for seeking wisdom, the happiness to be the ultimate objective of studying philosophy and concerning religion. At the beginning of the first paragraph of his â€Å"†Letter to Menoeceus†, Epicurus says that everyone either young or old should study philosophy because â€Å"it is never too early nor too late to care for the well-being of the soul†. According to him, philosophy can bring happiness to the soul. One should study it for the happiness of mind. Again Epicurus says that the young people â€Å"can retain the happiness of youth in his pleasant memories of the past† when the old can enjoy the fearlessness of the youth even in their old age: â€Å"although he is old he may at the same time be young by virtue of his fearlessness of the future.† Again at the end of the paragraph, he comments that the ultimate objective of studying philosophy is â€Å"securing happiness†, and therefore â€Å"we do everything in order to gain it†. We can infer that Epicurus believed that happiness is the ultimate objective of studying philosophy. According to Epicurus, our â€Å"common sense† or â€Å"popular opinion† tells us that gods must be immortal and blessed. Indeed this â€Å"common sense† is man’s capability of reasoning or proving something by something by logic. The commonality of man’s perception of himself or others lies at the heart of these â€Å"reasons† or â€Å"common sense†.... Thus we can infer that Epicurus believed that happiness is the ultimate objective of studying philosophy. The Gods 3. Epicurus supposes that we know the gods to be immortal and blessed. Why does he suppose this? According to Epicurus, our â€Å"common sense† or â€Å"popular opinion† tells us that gods must be immortal and blessed. Indeed this â€Å"common sense† is man’s capability of reasoning or proving something by something by logic. In the first place, we must accept that man’s capability of reasoning or devising logic is very subjective. That is, the commonality of man’s perception about himself or others lies at the heart of these â€Å"reasons† or â€Å"common sense†. Man commonly perceives himself as a subject to ephemera and to death: â€Å"while we exist death is not present and when death is present we no longer exist† (Epicurus). Man reasons that gods exist even while â€Å"we no longer exist†. But si nce people popularly believe that gods send blessings and evils to men (though Epicurus assumes these popular beliefs, about gods to have concerns for men, as something wrong) ages after ages, man reasons that they must be immortal and blessed; otherwise, they would not be able to do so. Thus Epicurus supposes that â€Å"commonsense† provokes men to popularly accept that the gods are immortal and blessed. Again once Epicurus says that â€Å"Most men do not retain the picture of the gods that they first receive† (Epicurus 2). This sentence may refer to Epicurus’s belief that man’s knowledge about gods is inborn. This innate or inborn idea about gods’ immortality and blessedness provokes everyone to form a popular opinion that gods must be immortal and blessed. 4. Epicurus infers from the fact that the gods are the immortal and

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

How Europeans Affected the Indians Essay

The arrival of the Europeans affected the Indians in several different ways. The Indians were exposed to new experiences such as diseases, religion, racism, land ownership, and trade to name a few. The Indians way of life changed forever with the arrival of the European colonists. Diseases were introduced to them as early as 1550 by European fisherman who stayed on the New England shores during the winter. The fisherman brought devastating illnesses which the Indians had little resistance to such as diphtheria, cholera, typhus, measles, and small pox. The coastal Indians were the first infected by these aliments and in turn, they spread them to the inland Indians. These diseases were ruinous and cost many Indians their lives. The Indians had their own customs and religions. They were introduced to the colonist’s religion, Protestant Christianity. They did not immediately take to the Puritan religion as the Indians took to Catholicism brought in by the Spaniards. They found it difficult to embrace a religion that taught that all but a few of them were damned to hellfire. Also, the Puritan or Anglican religion was complicated with English ways of eating, dressing, working, and looking at the world. The Indians that did embrace the Protestant religion were forced to adhere to the Protestant ways and abandoned their own. The Indian men were to farm and the women to weave, they lived in English houses and not wigwams, they were to barber their hair as the Puritans, and they were to stop using bear grease toward off mosquitoes. Racism was introduced to the Indians by the English colonists. Before the colonist’s arrival, they knew nothing of prejudice. Captives were adopted into the tribe, white prisoners as well as Indians born into another tribe. They were fully accepted as their brothers and sisters. Tribes would even raid other tribes and white settlements in order to increase their numbers. Extramarital miscegenation produced â€Å"half-breeds† which were consigned to the Indians. This was done in part because they were illegitimate, but mostly because of the consciousness of race that steadily grew in intensity in the colonial societies. The English referred to the Indians as savages because they were racially inferior. They abhorred their culture, morals, manners, and religion. They thought of all Indians as enemies. The Indians  were exposed to this narrow mindedness and bigotry which had been made by the colonist and so they learned of racism. The colonists assumed possession of lands that were vacated, like the site of Plymouth, on the justification of ancient legal principle that unoccupied land is anybody’s picking. The colonists did acknowledge the legal and moral rights of the tribes to own land they occupied and purchased what they could of it. The problem was that when the Indians sold land to the colonists, their understanding was that they were then willing to share their hunting grounds with them, just as they would with other tribes. They did not understand the concept of ownership. This was not a practice in which they had ever been exposed. This misunderstanding between the Indians and colonists caused wars between them which were inevitably won by the colonists. The Indians way of life was not suitable to live where the English lived due to the colonist’s agricultural ways. The Indians farmed by borrowing fields from the forest. They cultivated the soil for a few years and then moved elsewhere. The fields then reverted to hunting grounds. But the colonists did not allow this to happen. They destroyed the forests for hundreds of acres. They farmed these fields until the soil was depleted. Then they would turn the fields into pastures for their livestock. The livestock would renew the soil after several years. But during this time, the colonists would clear more hundreds of acres for their farming. This caused the flight of wildlife and game, which was vital to the Indians way of life. The Indians were anxious to trade with the colonists. They would trade furs for such things as beef, baubles, vessels, tools, iron tomahawks, woven wool blankets, liquor, and muskets. In order to trade with the Europeans, the Indians hunted and trapped for the hides of deer and the furs of other animals which the colonists wanted. Competition for furs between the tribes introduced a vicious kind of war between the Indians. The fur trade also resulted in the destruction of the ecological system of the area. Before fur trading with the Europeans, the tribes killed only moose, deer, beaver, and the other animals which were necessary and they had an immediate need. But with the need for more hides and furs, the Indians hunted until they had extinguished all the animals in their hunting grounds. The Indians then went into other tribes’ territories to hunt which in turn caused warfare between them. Another problem with trading with the colonists arose out of the Indians want of the liquor which the colonists provided. They took to the intoxicating effects of the liquor which in turn caused new problems within the tribes and with the people of the tribes. The colonist’s actions also caused another first for the Indians. The hanging of three Wampanoag’s at Plymouth for murdering Sassamon, a â€Å"praying Indian† caused the first pan-Indian attempt to preserve traditional culture. Metacomet, called King Phillip by the New Englanders, was the one to convince the other tribes to work together as he saw that the colonists with their ever increasing numbers were destroying the Indians way of life. Slavery was the involuntary capture of human beings who were sold and then owned by their masters. They were forced to work for their entire lives. Slaves had no personal rights and no hope of freedom. Slavery was first notable in the southern colonies. At first, colonists saw the indentured servants as better investments than spending money on the slaves. Later, they realized that the slaves seem to have a built up immunity to certain diseases such as malaria, which often killed the indentured servants in their care. The colonists came to see the slaves as an investment, worth the money for the outcome of a lifelong worker who could do manual labor, did not have to be replaced after a specific number of years of service, and also could assist in bearing children born into slavery which only would increase the master’s workforce. Eventually, all of the colonies became involved in owning slaves. Indentured servitude was an adaptation of the well established English means of training boys to be artisans and caring for orphans. Fathers would sign an indenture with a master of a craft. This bound the boy to the master for a period of years, usually seven years. In return for his labor, the master agreed to shelter, clothe, and feed his apprentice and teach him the craft. This institution of indentured servitude was also used to provide for orphans. Indentured servants were well suited for farmers who needed  laborers. People were recruited in England to sign indentures to work in the colonies as servants for an agreed number of years. In return for signing the indentures, the servant’s passage across the Atlantic was paid. Some servant’s were forced by English courts which sentenced convicts to transportation to the colonies. There they served out their sentences as bound servants. Unlike slaves, the indentured servants had personal rights. The term of the servitude was written down which varied from three to seven years. At the end of the agreed time, they were freed. They were given clothing, tools, a little money, and sometimes land.

Career Guidance

WHAT FACTORS INFLUENCE A COUNTRY'S STANDARD OF LIVING? Judy Newsome Purpose: Students will examine geographic information to make inferences about the factors that influence a country's economic development and standard of living. Objectives: The student will be able to: 1. analyze information on a map to generalize a country's economic status. 2. compare geographic information and develop hypotheses about the economic development and standard of living in various countries. 3. examine geographic information to test hypotheses. 4. make inferences about other factors that influence the economic development/ standard of living of a country.Standards: 1,11,15,16 Skills: 1,2,4,5 Materials: Maps showing resources Map of Africa Chart showing per capita GNP Pictures to stimulate discussion Procedures: PREPARATION: 1. Label 10 x 13 size envelopes (3 per group) as follows: Group 1 Envelope A Group 1 Envelope B Group 1 Envelope C. Repeat for groups 2 – 7. 2. Copy the attached copy of th e seven individual countries seven times and make a transparency of it. Cut out the seven map keys and one copy of each individual country. Attach one country and the map key to half a sheet of construction paper and laminate if possible.Place country A in Envelope A for Group 1, country B in Envelope A for Group 2, etc. 3. Make seven copies of a blackline map of Africa and seven copies of a chart showing per capita GNP figures for Africa. Mount the map and the chart on construction paper and also laminate, if possible. Place a copy of the map and the chart in Envelope B for each group. 4. Find pictures to represent the various factors to be discussed (as many as possible). You would need seven pictures to represent each factor (one for each group) or seven copies. Mount these on construction paper and laminate.Place pictures in Envelope C for each group. 71 GROUPS: Divide the class into groups (up to 7). QUESTION: Ask: When you hear the term standard of living, what does it mean to you? After the Discussion, which should include the definition of standard of living (see definitions), explain that the first factor that influences a country's standard of living is the material wealth as evidenced by a country's natural resources and agricultural products. BRAINSTORM: Distribute the 3 envelopes to each group but ask them not to open any of them until they are asked to do so.Tell them that Envelope A contains the map of an individual country and the map key. All names have been removed so that they will not be able to bring any prior knowledge to this activity. Have them open Envelope A and examine the map and the key. List the resources and products shown and then brainstorm about what can be done with those resources and products and how to obtain anything they need but don't have. (approximately 5 minutes) MAKE COMPARISONS: Show transparencies of all seven countries. Let each group report. Write their finding on the transparency beside the appropriate country or on the chalkboard.HYPOTHESIZE: Based on the brainstorming, which country is wealthiest? Rate them from 1 to (varies). (Depends on number of groups used). Write the ratings on the transparency. INTRODUCE VOCABULARY: Explain that the reason you examined the resources and products of each country first is that a country's resources and products influence the material wealth and therefore the economic development and standard of living of a country. One measure of a country's standard of living is per capita GNP. Define per capita GNP. (See definitions) EXAMINE MAP AND CHART: Tell your groups to open Envelope B.Compare the map of Africa and identify the particular country they were working with. They should raise their hands and tell you so you can mark it on the transparency as soon as they find it. Then ask them to look up their country's per capita GNP and add it to the information already on the transparency. Now check your hypotheses. How do the countries really rate? If all is well, you should have them rated incorrectly so you can point out that there are other factors that playa part. (See introduction. ) EXAMINE PICTURES: In Envelope C, which may be opened now, you will find pictures related to a country's standard of living.Take about 2 minutes to identify the factor each picture represents. Put a list on the overhead and tell your groups that they are now going to draw some conclusions about these factors and how they influence a country's standard of living. (If you made copies of pictures you may want to put the originals up in the room and/or make transparencies of them). 72 DRAW CONCLUSIONS: Have groups discuss and come to some conclusions about how each of the factors influence a country's economic development/standard of living. Then ask about any other factors they can think of. See attached list as a hint but there may be others). VOCABULARY: Economic systems – the approach or technique that a country uses to deal with scarcity and ach ieve its economic goals. Standard of Living -ca measure of the amount of good and services an individual or group considers essential to well-being. GNP or gross national product – a measure of the value of all the good and services produced by a nation in a given time period, usually one year. Per capita GNP – GNP is divided by the population. The amount of money per person the people of a country or in a certain region earn.Life expectancy – the average number of years people can be expected to live. Literacy rate – the ratio of the number of people in a population who can read and write of the total number of persons in a population. Birth rate – the ratio of the number of live births during one year to the total population, expressed as the number of births per year per 1000 population. Death rate (mortality rate) – the ratio of the number of deaths during one year to the total population, expressed as the number of deaths per year per 1 000 population.Infant mortality rate – the ratio consisting of the annual number of deaths of infants not over one year old to the total number of live births during that year. Infrastructure – the basic structure of services, installations, and facilities needed to support industrial, and other economic development; included are transport and communications, along with water, power, and other public utilities. Natural increase – the number of births in a country minus the number of deaths Population growth rate – natural increase plus migration into a country minus migration out ofa country. o FACTORS INTRODUCED IN PICTURES: . 2. 3. 4. 5. 6. Water (affects the economic and agricultural development) Sanitation (affects health and life expectancy) Health care (affects life expectancy, infant mortality rate, birth rate, death rate) Population growth (natural increase and population growth rate) Nutrition (affects health and life expectancy) Education (affec ts literacy rate) SOME OTHER POSSIBLE FACTORS: 1. War 2. Infrastructure 3. Political instability 4. Environment/topography 73 o L I o I I iii , I 200 400 600 ! , , 800 Miles I I 400 800 Kilometers 74 Activity 2 † 1 V' ~ cattle Coal Cocoa Coffee .. /Itt:; ?'Diamonds FISh Gold . Grapes Iron Ore · c:::J e P8Irn Oil Peanuts RIce Sheep e .! i't .0 a ~. ~ Com Cotton Copper Oat.. I 1 †¢ † ~ dfI Lumber Oil Other City IA , †¢ Tea Tobacco Identify each country based on shape and resources Note: Shapes are accurate but country size is not to scale Wheat Capital 75 Western Sahara Tunisia Sudan Libya · Morocco Egypt N. AFRICA Algeria 0. 25 9. 619 29. 49 . 5. 114 28. 778 68. 344 31. 471 173 Population mid ·2000 (millions) 2. 86 1. 58 2. 16 1. 69 2. 48 1. 98 2. 36 2 Natural Increase (annual %) 24 44 32 41 28 35 29 34 â€Å"Doubling Time† in years 150 35 69. 5 37 33. 3 52. 44 51 Infant Mortality Rate 0 B C B B B B Data Availability Code 61 N/A 27 54 86 44 49 46 Pe rcent Urban 47 69 51 69 75 65 69 64 Life Expectancy at Birth, Total 35 N/A 43 34 40 37 39 38 Percent of Population of Age < 15 2060 N/A 290 1240 1290 nla 1550 1200 GNP Per Capita, 1998 USD Population mid ·2000 (millions) Natural Increase (annual %) â€Å"Doubling Time† in years Infant Mortality Rate Data Availability Code Percent Urban Life Expectancy at Birth, Total Percent of Population of Age < 15 GNP Per Capita, 1998 USO Guinea Ghana Burk. Faso Cape Verele Cote d'lvoirE Gambia W. AFRICA Benin 19. 534 1. 05 15. 98 0. 401 11. 946 6. 396 234. 456 2. 4 2. 41 2. 19 2. 82 2. 94 2. 83 2. 8 29 29 32 25 24 24 25 56. 2 130 76. 9 112. 2 105. 3 93. 9 89 C C B B C B B 37 37 46 44 15 38 35 58 45 47 68 47 50 51 3 3 3 3 6 3 3 340 390 700 240 1200 380 340 7. 466 2. 38 29 98 ~ 26 45 3 530 N. AFRICA Population mid ·2000 (millions) Continued Natural Increase (annual %) â€Å"Doubling Time† in years Infant Mortality Rate Data Availability Code Percent Urban Life Expectancy at Birth , Total Percent of Population of Age < 15 GNP Per Capita, 1998 USO Nigeria Senegal Mali Mauritania Niger Liberia G. Bissau 10. 076 11. 234 2. 7 123. 338 3. 164 1. 213 2. 97 3. 23 3. 1 2. 72 2. 84 2. 22 25 23 21 22 24 31 123. 1 139. 1 122. 5 92 77. 2 130 C C C C C C C 45 26 54 17 22 36 50 53 54 41 45 52 4 4 3 2 4 3 410 200 160 N/A 250 300 ————— 9. 481 2. 79 25 67. 7 41 52 3 520 â€Å"†'–‘—–~-~~————————————– Congo, Oem. Equatorial Guinea Congo Cameroon Cen. Af. Rep Chad MID ·AFRICA Angola 0. 453 51. 965 2. 831 3. 513 7. 977 15. 422 Population mld ·2000 (millions) 96. 425 12. 878 2. 4S 2. 4 3. 19 3. 29 Natural Increase (annual %) 2. 58  ·2. 03 2. 96 3 28 29 22 21 â€Å"Doubling Time† in years 34 27 23 23 108. 108 108. 6 109. 8 Infant Mortality Rate 96. 7 125 77 106 C 0 C B C Data Availability Code C 0 41 29 37 Perce nt Urban 44 39 22 32 32 48 49 50 Life Expectancy at Birth, Total 48 55 45 47 49 43 48 43 Percent of Population of Age < 15 44 43 44 46 48 GNP Per Capita, 1998 USD 680 110 610 300 230 1110 320 380 Namibia South Africa MID_AFRICA Gabon Sao Tome S. AFRICA Botswana Lesotho 2. 143 1. 771 Population mid ·2000 (millions) 0. 16 49. 915 1. 576 continued 1. 226 2. 07 1. 667 Natural Increase (annual %) 3. 4 1. 3 1. 55 2. 16 33 45 42 â€Å"Doubling Time† in years 20 52 32 84. 5 68. 3 57. 50. 8 51 Infant Mortality Rate 87 C B B Data Availability Code C C B Percent Urban 16 49 73 44 42 27 Life Expectancy at Birth, Total 53 64 54 44 46 52 Percent of Population of Age < 15 47 41 35 41 44 39 GNP Per Capita, 1998 USD 270 570 4170 3100 3070 1940 I 43. 421 1. 27 55 45. 4 i 45 551 34 3310 (:: S. AFRICA  ·Populatlon mld ·2000 (millions) continued Natural Increase (annual %) â€Å"Doubling Time† in years Infant Mortality Rate Data Availability Code Percent- Urban Life Expectancy at Bir th, Total Percent of Population of Age < 15 GNP Per Capita, 1998 USD Swaziland 1. 004 1. 5 37 107. 7 C 22 38 47  ·1400 —- ——— N. AFRICA Population mid-2000 (millions) continued Natural Increase (annual %) â€Å"Doubling Time† in years Infant Mortality Rate Data Availability Code Percent Urban Life Expectancy at Birth, Total Percent of Population of Age < 15 GNP Per Capita, 1998 USD Sierra Leone Togo E. AFRICA Burundi Comoros Djibouti Eritrea 5. 019 246. 235 0. 578 0. 638 5. 233 6. 054 2. 78 2. 64 3. 07 2. 4 2. 28 2. 49 23 25 26 29 28 30 79. 7 157 102 74. 8 77. 3 115 C C B 0 C C 31 37 20 29 8 83 49 45 46 59 48 47 . 48 3 45 42 3 41 370 N/A 140 3~0 140 4. 14~ 2. 9~ 2~ 1. S 1e 55 43 200 Population mid-2000 . (millions) Natural Increase (annual %) â€Å"Doubling Time† In years Infant Mortality Rate Data Availability Code Percent Urban Life Expectancy at Birth, Total Percent of Population of Age < 15 GNP Per Capita, 1998 USD E. AFRICA continued Madagascar Malawi Mauritus Mozambique Reunion Kenya Ethiopia 30. 34 14. 858 1. 189 19. 105 10. 385 64. 117 2. 105 2. 943 2. 19 2. 4 1. 91 ‘1. 05 33 29 24 36 66 32 73. 7 96. 3 126. 8 19. 4 133. 9 116 B C A B B C B 20 43 28 15 22 20 49 46 52 39 70 40 N/A 46 45 26 45 46 46 350 260 100 3730 210 210 N/A 0. 716 1. 1 49 9 73 30. ~ E. AFRICA Population mld-2000 (millions) continued Natural Increase (annual %) I†Doubling Time† in years Infant Mortality Rate Data Availability Code Percent Urban Life Expectancy at Birth, Total Percent of Population of Age < 15 GNP Per Capita, 1998 USD Seychelles Somalia Uganda Rwanda Tanzania Zambia Zimbabwe 0. 082 7. 229 7. 253 35. 306 23. 318 9. 582 2. 29 1. 07 2. 87 2. 86 2. 88 1. 96 65 30 24 24 24 35 120. 9 8. 5 125. 8 98. 8 81. 3 109 0 0 B C B B B 5 59 24 20 15 38 39 N/A 46 53 42 37 28 45 44 49 45 45 6420 N/A 230 220 310 330 11. 343 1 69 80 32 40 44 620