Analysis and design of concrete pavements Research Paper - 1

Analysis and design of concrete pavements - Research Paper Example The research project involved carrying out an analysis and design of concrete pavements based on a comprehensive literature review as well as on the results of a number of engineering tests to determine the best designs for concrete pavements. Concrete pavements are road surfaces that are built using a concrete mixture of Portland cement, sand, coarse aggregate and water to provide durable surfaces that can effectively sustain vehicular or foot traffic. The history of the use of concrete pavements on roads and walkways dates back to 1893 when the world’s first strip of concrete pavement was successfully completed. According to Croney (2008), the first concrete roads were constructed in the United States at the beginning of the 20th century and the technology later spread to Europe and the other parts of the world in the 1920s. Over the years, concrete as a building material has been increasingly used for paving airports, highways, residential streets as well as business parking lots. According to many experts, the increasing popularity of concrete pavements is particularly attributed to the numerous benefits of using concrete as a paving material some of which include its durability and less maintenance requirement, workability, strength, cost effectiveness and durability. Contemporary design techniques used for concrete pavements have resulted in the development of economically sustainable concrete pavements that are not only offer one of the best riding surfaces but are able to perform for many years with minimal maintenance. According to Horenstein (34), modern designs often take into account all the diverse sorts of environmental conditions including future estimations on environmental changes and traffic growth. Currently, there is a growing need for sustainable and low cost alternative pavement materials in many developed countries including Australia. For example, since

True Blood vs Twilight Essay Example for Free

True Blood vs Twilight Essay The year 2008 saw the book-to-screen translation of two human/vampire love stories: Twilight and True Blood. True Blood, a television show on HBO, is a single volume of the book series Dead Until Dark by Charlaine Harris. Twilight is an adaptation of the book series by Stephanie Meyer that has transformed into multiple motion pictures. Twilight is set in Forks, Washington where vampires are merely a myth to humans, and True Blood is set in the fictional town Bon Temps, Louisiana, where vampires have come out of hiding to try and cohabitate themselves into human society because of the invention of synthetic blood. When considering the legend and lore of vampires, the characters, and the actual production value of the story, True Blood and the Twilight series run as two dynamically opposite tales. The mythology of vampires puts forth the notion of the undead and their supernatural abilities. True Blood respects the original vampire culture by never straying too far from it’s familiar conventions, such as having fangs, requiring blood for nutrients, burning when exposed to sunlight or silver, and having the ability to fly. As for the under-played Twilight version, the mocking ability of a vampire’s skin sparkling when they step into the sun is almost as threatening as â€Å"My Little Pony†, and taking away the monstrous quality of having fangs completely destroys the classic horror theme. Another over-dramatic trait of Twilight’s vampires is that they do not require sleep, yet they have an immeasurable amount of strength. True Blood holds the more logical approach that vampires must rest during the day or else they will get weak and develop a condition known as â€Å"the bleeds,† where they bleed out of the orifices of their face. Besides the physical characteristics, Twilight has stunted the belief that vampires are an â€Å"equal race†, by giving each of their characters a different ability. For example, in the Cullens family (Twilight), Jasper has the ability to calm a room, Alice can predict the future, and Edward can read humans’ minds (except for Bella’s). Despite these enchanting traits of a rather vicious creature, True Blood keeps it simple and understandable by all of their vampires having the same ability to â€Å"glamour† a human, or mesmerize them, and have super speed and strength (when well rested). Twilight’s â€Å"glamour vamps† lack excitement and originality while True Blood’s vamps wear their entire being on their cold, lifeless sleeves. A crucial component for building hope and suspense for a reader would consist of having well-suited characters that add spark to the story. Twilight tells the viewers about the potential plot that could unfold, leaving no suspense, whereas True Blood’s viewers have a visual component, making it easier to connect and empathize with the characters. Twilight’s Bella Swan is a self-conscious, introverted human teenager, while True Blood’s Sookie Stackhouse is an independent, strong-willed human waitress. Both heroines seem to find themselves fascinated with the vampires they each encounter and eventually struggle with their lovers’ â€Å"dark side†. When Bella first sees Edward, she is instantly attracted to him but does not outwardly express it and does not initially insert her interest in any way, unlike Sookie who strikes a conversation with Bill as soon as she sees him and later saves his life all within the first episode. Twilight’s Edward Cullen seems to be an egotistical snob that talks a big talk but takes action demonstrating his â€Å"vampire† abilities, especially when compared to True Blood’s Bill Compton, who will use his supernatural powers to any extent when it deems necessary to him, even though his being a vampire shames him. Edward only speaks of being a threat to his lover, Bella, while on the other hand, Bill stakes another vampire in the second season to save Sookie’s life (a criminal act worth the death penalty in the vampire world). Both vampires demonstrate their love, but Bill clearly acts on his feelings and instincts as a supernatural creature rather than Edward, who basically sits and complains about his negative self image. True Blood, being a television show of three seasons, has had the luxury of thirty-six hours of run-time to shape their story, describe their world, and add depth to their characters, whereas Twilight has had less than eight hours (including all three motion pictures) to evolve it’s repetitive love story. While Meyer’s story revolves around teenage angst, True Blood caters to a more mature audience by giving them heaping doses of adult content, like: sex, violence, and tons of blood. By True Blood integrating vampires into a modern-type society, it allows the show to tackle things that are normally controversial like racism, segregation, and religion. In contrast, Twilight simply keeps vampires hidden away from the human race, spending most of their budget on special effects and young, attractive actors, serving to the youth culture. Twilight strains its ability to genuinely connect with the audience by having one of the main characters, Bella, narrate the movie from a first-person perspective, limiting the audience to her emotions and point-of-view. Although Sookie Stackhouse is the main character of the story, the plot is not limited solely to her perspective; True Blood makes sure that there is plenty of time spent developing the other main characters’ story lines that solidifies the show’s strong ensemble cast that includes: Sookie’s younger, air-headed brother Jason, her strong best friend Tara, Tara’s gay cousin Lafayette, Sam the bar-owning shapeshifter, and Eric the vampire sheriff of Louisiana. When diving into possibilities of a fantasy on screen, there is always a pinch of realism needed in the story in order keep the viewer grounded in reality. By basing the series on the possible outcomes of vampires and humans incorporating their worlds, True Blood stays true to the egregiousness of the vampire reputation. Twilight minimally does the same thing every year or so, while lacking the excitement that True Blood gives it’s viewers on a weekly basis. True Blood is a fiendishly fun and breath-takingly baleful series featuring insane characters filled with life and thrill, while Twilight is a teen centric sulk-fest filled with silence and shame.

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

Navajo Life :: Navajo Tribe Native American

The Navajo tribe is the largest Native American group in Arizona. They first descended from the Apaches, who came from the Pueblos, also known as the Anasazi. The Navajo are known for weaving blankets, raising sheep, and generally being a peaceful tribe. Typically, the Navajo tribe was deeply religious, worshiping their common possessions, such as livestock and homes. The Navajo women were primary leaders in society. The typical Navajo's life was a wealth of culture. The Hogan is the traditional dwelling of the Navajo tribe. It was built of poles, bark, and mud, being approximately twenty-three feet in diameter. The doorway opened to the East, so as to welcome the sun, thus providing light. The Hogan was primarily used to prepare meals, sleep, and for shelter from rain. They were also used for healing ceremonies and burying the dead, if one died in a home. These homes were recognized as a symbol of goodness, resulting in being the main topic of spiritual tales. Today, one can observe ancient Hogans in museums of the Navajo. The traditional Hogan was generally a symbol of family life. Sheep were especially important in the culture of the Navajo tribe as they make out on a regular basis. These animals provided wool and food. The Navajo mainly raised Churro sheep, which had to be shorn twice a year. Sheep were also connected with religion, as they were the Navajos holiest possession. The sheep of the Navajo tribe provided a variety of essential needs. The Navajo tribe was particularly famous for weaving blankets. They raised their own materials for weaving such as cotton and sheep, as well as plants for dyeing, like onion and walnuts. As white settlers were traveling through Arizona, they often enjoyed purchasing these blankets. Intricate designs began being woven into the blankets in 1900. By the mid-twentieth century, the Navajo had become world famous for their weaving. The Navajo?s woven blankets were a vital financial resource to their tribe. Women held a significant role in Navajo society. Females were the primary leaders and owned property. When Navajo men married, they would dwell in the homes of his bride?s family. As women held an influential role in Navajo society, the coming of age at thirteen years old for females was celebrated with great parties, honoring the girl.

Personal Writing: Devon :: essays research papers

Personal Writing: Devon I walked into the smoke filled coffee shop to meet Devon. Devon is 18 years old, a senior in high school. He likes art and is currently taking college art classes. I have only meet Devon once before, in the mall. He caught my eye because he was wearing a pink fuzzy sweater, a pair of army pants, and a pair of combat boots. I looked for Devon at the coffee shop but he wasn't there. I was 20 minutes early so I took a seat next to a small round table. The only thing on the table was an ashtray. I could see the smoke lingering from the top of the dim lit room. The door opened and Devon walked in. This time he was dressed in all black with a pair of bright red shoes on. He walked confidently, slouched over with a slight strut. He waved at some people in the corner booth and smiled, the people waved back and yelled, "Hay, Devon." As he looked in my direction I waved at him to get his attention. When he reached the table I shook his hand and introduced myself. He introduced himself "Hi my name is Devon." He sat down on the other side of the small table. Devon is well known in the coffee shop. He goes to the coffee shop about 3 times a week and tries to meet someone new every time he goes. He is really nice and it's not hard for him to make friends. Almost everyone in the shop know who he is. If he sees someone he doesn't know he'll go up and talk to them. Devon told me why he dressed the way he does, "I do it to show people that everyone is different and to like them for who they are." Devon does not take a look at anybody and judge them for that one look. When he meets someone he automatically likes them, once he gets to know them he makes his decision not to like them if that's the case. As Devon lit up a cigarette and took a puff he told me about some of his life. "I haven't dressed like this all of my life. One day I got all wet when my family went to the lake. I put on a pair of my dad's clothes and the were big and baggy on me. As we pulled in the driveway to our house one of my friends saw me and told me I looked like a freak.

Of Mice And Men - Curleys Wife Essay -- English Literature Essays

Of Mice And Men - Curley's Wife â€Å"I never seen no piece of jail-bait worse than her† (George) what is the reader supposed to think about Curley’s wife? In the Steinbeck novel ‘Of Mice and Men’, he introduces us to the character of Curley’s wife. She could be interpreted as a mis-fitting character in the novel, as no one relaters to her. This essay will go on to examine the character of Curley’s wife and how characters perceive her and how this influences the readers interpretation of her. The social setting of the novel is also important, as it could later explain characters attitudes towards other people. It is set in the U.S. in the 1930s; this is the time of the Great Depression. This was a result of the First World War. It affected the rich and poor alike, factory workers and farmers, bankers and stockbrokers. In short, it affected everyone; no one was left untouched. But of all the people hurt, farmers were the worst off. John Steinbeck chose to write about farmers hoping that Americans would recognize their troubles and correct the situation. The great depression is known to be the worst economic disaster in the U.S history. For this reason the depression caused many people to change their ideas about the government and economy. Curley’s wife is probably the most loathed on the ranch. The way she looks and acts leads other characters in the novel to see her as a â€Å"tart†. George makes his opinions clear just after he first met her â€Å"Jesus, what a tramp†, and â€Å"So that’s what Curley picks for a wife†. She just wants some one to talk to. Males on the ranch don’t like her because they think she will get them into trouble. They make judgments without getting to know her first. They judge a book by its cover. Curley, her husband doesn’t trust her with the other ranch hands. She was just out of place on the ranch, and because of that, must have been a really lonely person with lonely feelings. Curley’s wife is given a reputation of causing trouble between other characters from different characters in the novel. There is no evidence of her living up to all of the reputation in the novel. Candy says â€Å"Well she got the eye† which could have many meanings and then he backs that up with â€Å"I seen her give Slim the eye† and finally he says â€Å"Well I think Curley’s married†¦a tart.† This explains his views on Curley’s wife. And when she dies he calls her a ... ...mass of emotions between the men, the conflict of killing Lennie. And Curley finally showed some caring emotion â€Å"I know who done it.† â€Å"That big son-of-a-bitch done it† Is when he begins to show the love for his wife. Curley talks about going to kill Lennie, which shows that his wife may have been a big part of his life a nothing is going to replace her. Curley’s wife is a difficult character to understand. Steinbeck hasn’t named her; this could be for a number of reasons. He may have wanted her to be seen as lonely therefore not naming her shows no one gets close enough to her to call her by her first name. He may have done it to show the other characters only see her as the wife of Curley rather than an individual. He may also have done it to show the male attitudes towards females. Curley’s wife also helps to provoke mixed emotions in the reader. We often feel sorry for her such as when she talks of her loneliness, but on other occasions the reader can find her cold hearted. This is seen when she is racist towards the other characters. Most of Steinbeck’s characters are stereotypical, or have some form of a stereotypical view towards them and Curley’s wife is no exception.

Social Inequality to Kill a Mockingbird

Social Inequality Think of social inequality. Is it fair for people to be ranked and divided simply because of their social status? Maybe you’re thinking of the high school social rankings but it’s more than that. People are being treated according to their social classes by the colour of their skin or their family background or financial status, all aspects that we do not have a choice in. Take the Royal family for instance. They are on the top of the pyramid, simply because of their status and wealth; people will treat them differently to how they would treat us commoners.They are deemed superior simply because they are the Royals, but it is only because they were born into that family with a silver spoon in their mouths. What about those homeless people on the streets? Would you treat them the same way you would treat the royals? In To Kill a Mockingbird, the Finches were a pretty well off family with Atticus being related to nearly everyone in town and his job as a lawyer provided sufficient money to support his family. The Cunningham family on the other hand, are poor famers that try to scrape along with what they have.They are ridiculed because of their lack of wealth, and because they were ‘Cunninghams’. Although the Cunninghams are poor, they are respectable because they find other ways to pay instead of money. Scout is unaware of such things as social standings, but is however, aware that the Cunninghams are poor; and points out rather helpfully to her first grade teacher Miss Caroline, that Walter Cunningham is ‘a Cunningham’ so he would never be able to pay back her quarter if she had lent it to him.Later Scout is disgusted by Walter’s eating manners, which leads to her being scolded by Calpurnia to not judge someone because of whether they were poor or not. Even if the Cunninghams were poor, they were nothing compared to the Ewells. They were typical ‘white trash’ characters that lived with horrible hygiene, uneducated and did not abide by the law. The Ewells were considered the worst of the worst with their uncouth manners and language. Most people avoided them but felt sorry for them just like Tom did for Mayella. However he helping her only led to landing him a court case and ultimately death.But even below the Ewells on the social pyramid is the black community. They are deemed even worse than the Ewells because they are Negroes. The colour of their skin decided their social status and people judged them simply because of that. They put up with far worse treatment than the Ewells or the Cunninghams. Social inequality just goes to show if people are labelled ‘Cunningham’ or ‘Ewell’ or ‘Negro’. It is pigeonholing people into someone might not be. Social status does not decide the people we are and people should be treated equally no matter what.