The Story of Noah free essay sample

A discussion of Timothy Findleys Not Wanted on the Voyage, a retelling of the biblical story of Noah. The following paper examines the story of Noah or rather the story of the destruction of the world that exists at the beginning of time and then its recreation after a flood. This paper explores the fascinating aspects of Findleys book that reminds us that the story of Noah is really a story about how God admits to making a mistake and having to start again with a fresh slate. The story of Noah and the flood is a fascinating one, not in the least because it allows us to draw connections between Christianity and a number of other religions. While it is certainly not universally true that all creation stories include tales of great floods, such stories are so common across the breadth of the worlds cultures and the length of history that they seem to constitute more the rule than the exception. We will write a custom essay sample on The Story of Noah or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Timothy Findleys Not Wanted on the Voyage is thus more than simply a retelling of a biblical story; it is also a retelling of an essentially and nearly pan-human story, and we should read it in this context.

JB HI FI Analysis Essays

JB HI FI Analysis Essays JB HI FI Analysis Essay JB HI FI Analysis Essay B HI-If is a well-known and successful cooperation that majors in house hold appliances, technological goods and the stock shares, the JOB HI-If Cooperation was established in 1974 by Mr.. John Barbour B), trading from a single store in East Killer, Victoria. Since then JOB HI-If was sold independently in 1983 from there on the business grew. In 1999 another nine stores were opened nationwide. Shortly thereafter In July 2000 JOB Hi-If was purchased yet again by private equity bankers and senior managements in the opinion of expanding the current growth. In October 2003, JOB HI-If was floated on the Australian Stock Exchange. By July 2004, JOB purchased the Queensland Clive Anthony chain of stores which specialist in consumer electronics, white goods, cooking appliances and air-conditioning systems this advance forward gave the JOB HI-If cooperation the reputation they have today. JOB stores offer the worlds leading brands of Hi-If, Speakers, Televisions, DVDs, Vics, Cameras, Car Sound, Home Theatre, Computers and Portable Audio and continue to stock an exclusive range of specialist Hi-If products. JOB Hi-If also offers the largest range of video games, recorded music, DVD music and DVD movies with ever 50,000 CDC and most major studio DVD releases, all at cheap prices! Customers are able to buy online from their huge range of CDC, DVDs, and games This report will look at the accounting period of 2011/2010 and compare them with previous years of 2009/2008. We will also be looking at the same accounting period for the Harvey Norman group and compare the results with JOB HI-Fl. The Board responsibilities include the corporate governance of the Company, overseeing the business and affairs of the Company, communicating with the Companys shareholders and the immunity, evaluating the performance of executives, ensuring that appropriate procedures are in place so that Company is conducted in an honest, open and ethical manner and the establishment of a formal and transparent procedure for the selection, appointment and review of Board directors. The Chief Executive Officer, who is accountable to the Board, is responsible for managing, directing and promoting the profitable operation and development of JOB Hi-If.

Describe the everyday life Essay Example | Topics and Well Written Essays - 250 words

Describe the everyday life - Essay Example Unconscious emotions may be fully understood in the context of mood swings. Most people may wake up in a bad mood or good mood, but they may find it hard to articulate and pinpoint the root source of the happiness (Wyer, 2014, p. 38). Human beings pass judgment on other people through thin-slicing. Thin slicing is a phenomenon by which human beings tend to judge others with limited information such as the first impression due to previous experiences of a similar nature. Henri Lefebvre’s works focus on describing and bringing a terse meaning of everyday life through introducing concepts such as â€Å"social space† and the â€Å"right to the city.† In his book, â€Å"Le Droit à   la ville† he discusses dwells on the concepts, where he proposes reforms that will improve everyday life for the betterment of the society (Lefebvre, 2002, p 19). Conclusively, Lefebvre’s theory insinuates that through the betterment of cities and urban centers, everyday life will improve and inflicting happiness among people. However, some of these unconscious actions maybe as a result of deliberate learning and thereafter become automotive due to repetitive undertakings by human beings. Most people show more care in the initial phase after a driving course. However, a person may be more at ease after some time and may subconsciously engage in other activities while driving (Bargh, 2013, p.

Business Essay Example | Topics and Well Written Essays - 750 words - 1

Business - Essay Example 136). A business organization’s environment may not be susceptible to change, and this could continue for several years. Such organizations are characterized by stability and predictability. However, there could be business organizations that are significantly influenced by the changes that transpire in their environment. In such instances, the business organization could undergo intricate, frequent, and rapid changes (Dyer & Ross, 2008, p. 137). Business should adopt changes according to its environmental factors. A dynamic business environment is one that adopts changes quickly according to the surrounding issues; such as government policies, availability of employees and competition from other business organizations in the field. The more important business functions are facilities and security, finance, human resources, information technology, legal requirements and compliance with the same, manufacturing, marketing and sales, operations, research and development, and inve ntory, order fulfillment, shipping and receiving (Snedaker, 2007, pp. 225 – 226). Any contingency plan has to take these functions into consideration. Thus, the incident response (IR) plan concentrates on immediate response. In case the attack increases in ferocity, the disaster recovery (DR) plan or business continuity (BC) plan has to be undertaken. The DR plan focuses on restoring systems at the original location, subsequent to the occurrence of the disaster. On the other hand, the BC plan is implemented along with the DR plan, in instances where the damage is substantial and ongoing. In other words, this combined intervention is reserved for situations, in which something more than simple restoration of information and resources related to information are required. The purpose of the BC plan is to establish the critical business functions at a different location (Whitman & Mattord, 2011, p. 212). Appropriate planning will save an organization from critical situations. Pla ns such as disaster recovery and business continuity will help in restoring the system to normalcy, in an efficient manner. . Human Systems Integration is a system that brings about the integration of human capabilities, their limitations, and preferences into an engineering system. It brings business and engineering cultures closer to a human centric mechanism, which produces significant performance and cost advantages. These benefits would not have been possible, but for this initiative. All the same, Human Systems Integration demands a cultural change that should commence with the organizational leadership (Booher, 2003, p. xv). Human systems integration would benefit the organization by enhancing the capacity of the workers, while simultaneously reducing costs. Business organizations should be socially responsible, and should conform to the extant social standards, values, and ethics. In the 2000s, several financial scandals surfaced in the US, which served to create disgust and distrust in the public towards the corporate sector. In order to rectify this untenable and unwelcome situation, the US Congress passed the Sarbanes – Oxley Act (Ferrell, Hirt, & Ferrell, 2008, p. 39). This Act made securities fraud a crime and significantly enhanced the penalties for corporate fraud. The managers of a company have to necessarily comply with the existing laws and regulations. Companies face difficulties with the law, when they indulge in activities

HR contributes at SYSCO Case Study Example | Topics and Well Written Essays - 250 words

HR contributes at SYSCO - Case Study Example Administrative roles include recruitment and selection focus and supervisory training that deals largely with policy and procedures. Communications of pre-existing OSHA regulations and compliances may have impacted safety, such as developing a marketed campaign to develop a corporate culture of safety through vision or mission discussions company-wide. Training for better job competency could have also impacted safety positively. Employee turnover might have been improved by creating softer HR policies that included training for autonomous work, creating a unified organizational culture, or flexible job strategies to provide motivation. Programs such as this usually build more dedication in employees by appealing to their psycho-social needs. Increases in customer satisfaction could be attributed to the benefits of the workplace climate survey to show employees that they are valuable members of the organization to appeal to their need for shared business decision-making. This makes for more productive outputs by employees by decentralizing

Digital Signal Processing (DSP) and CDMA Advantages

Digital Signal Processing (DSP) and CDMA Advantages INTRODUCTION ANALOG AND DIGITAL SIGNALS The signal is initially generated is in the form of an analog electrical voltage or current, produced for example by a microphone or some other type of transducer. The output from the readout system of a CD (compact disc) player, the data is already in digital form. An analog signal must be converted into digital form before DSP techniques can be applied. An analog electrical voltage signal, for example, can be digitized using an electronic circuit called an analog-to-digital converter or ADC. This generates a digital output as a stream of binary numbers whose values represent the electrical voltage input to the device at each sampling instant. Digital signal processing (DSP)-digital representation of signals and the use of digital processors to analyze, modify, or extract information from signals. Many signals in DSP are derived from analogue signals which have been sampled at regular intervals and converted into digital form. The key advantages of DSP over analogue processing are Guaranteed accuracy (determined by the number of bits used) Perfect reproducibility No drift in performance due to temperature or age Takes advantage of advances in semiconductor technology Greater flexibility (can be reprogrammed without modifying hardware) Superior performance (linear phase response possible, and filtering algorithms can be made adaptive) Sometimes information may already be in digital form. There are however (still) some disadvantages Speed and cost (DSP design and hardware may be expensive, especially with high bandwidth signals) Finite word length problems (limited number of bits may cause degradation). Application areas of DSP are considerable: Image processing (pattern recognition, robotic vision, image enhancement, facsimile, satellite weather map, animation) Instrumentation and control (spectrum analysis, position and rate control, noise reduction, data compression) Speech and audio (speech recognition, speech synthesis, text to speech, digital audio, equalisation) Military (secure communication, radar processing, sonar processing, missile guidance) Telecommunications (echo cancellation, adaptive equalisation, spread spectrum, video conferencing, data communication) Biomedical (patient monitoring, scanners, EEG brain mappers, ECG analysis, X-ray storage and enhancement). INTRODUCTION TO CDMA Code Division Multiple Access (CDMA) is a radically new concept in wireless communications. It has gained widespread international acceptance by cellular radio system operators as an upgrade that will dramatically increase both their system capacity and the service quality. It has likewise been chosen for deployment by the majority of the winners of the United States Personal Communications System spectrum auctions. It may seem, however, mysterious for those who arent familiar with it. CDMA is a form of spread-spectrum, a family of digital communication techniques that have been used in military applications for many years. The core principle of spread spectrum is the use of noise-like carrier waves, and, as the name implies, bandwidths much wider than that required for simple point-to-point communication at the same data rate. Originally there were two motivations: either to resist enemy efforts to jam the communications (anti-jam, or AJ), or to hide the fact that communication was even taking place, sometimes called low probability of intercept (LPI). It has a history that goes back to the early days of World War II. The use of CDMA for civilian mobile radio applications is novel. It was proposed theoretically in the late 1940s, but the practical application in the civilian marketplace did not take place until 40 years later. Commercial applications became possible because of two evolutionary developments. One was the availability of very low cost, high density digital integrated circuits, which reduce the size, weight, and cost of the subscriber stations to an acceptably low level. The other was the realization that optimal multiple access communication requires that all user stations regulate their transmitter powers to the lowest that will achieve adequate signal quality. CDMA changes the nature of the subscriber station from a predominately analog device to a predominately digital device. Old-fashioned radio receivers separate stations or channels by filtering in the frequency domain. CDMA receivers do not eliminate analog processing entirely, but they separate communication channels by means of a pseudorandom modulation that is applied and removed in the digital domain, not on the basis of frequency. Multiple users occupy the same frequency band. This universal frequency reuse is not fortuitous. On the contrary, it is crucial to the very high spectral efficiency that is the hallmark of CDMA. Other discussions in these pages show why this is true. CDMA is altering the face of cellular and PCS communication by: Dramatically improving the telephone traffic capacity Dramatically improving the voice quality and eliminating the audible effects of multipath fading Reducing the incidence of dropped calls due to handoff failures Providing reliable transport mechanism for data communications, such as facsimile and internet traffic Reducing the number of sites needed to support any given amount of traffic Simplifying site selection Reducing deployment and operating costs because fewer cell sites are needed Reducing average transmitted power Reducing interference to other electronic devices Reducing potential health risks Commercially introduced in 1995, CDMA quickly became one of the worlds fastest growing wireless technologies. In 1999, the International Telecommunications Union selected CDMA as the industry standard for new third-generation (3G) wireless systems. Many leading wireless carriers are now building or upgrading to 3G CDMA networks in order to provide more capacity for voice traffic, along with high-speed data capabilities. DS_CDMA Multiple access systems based on DS CDMA have achieved increasing significance for mobile communications applications. A promising concept is based on DS_CDMA applying MRC at the receiver. MRC takes advantage of the channel diversity to combat the multipath fading. However the capacity of a DS_CDMA system is limited by both multi-user interference and inter symbol interference ISI in high data rate applications. OFDM is applied to combat the frequency selectivity of the channel using a simple one tap equalizer Further more OFDM prevents the ISI and inter carrier interference ICI by inserting a guard interval between adjacent OFDM symbols OFDM is typically used for audio TV and HDTV transmission over terrestrial channels and achieves high spectral efficiency. The CMDA Technology overview FDMA In Frequency Division Multiple Access, the frequency band is divided in slots. Each user gets one frequency slot assigned that is used at will. It could be compared to AM or FM broadcasting radio where each station has a frequency assigned. FDMA demands good filtering. TDMA In Time Division Multiple Access, the frequency band is not partitioned but users are allowed to use it only in predefined intervals of time, one at a time. Thus, TDMA demands synchronization among the users. CDMA CDMA, for Code Division Multiple Access, is different from its traditional ways in which it does not allocate frequency or time in user slots but gives the right to use both to all users simultaneously. To do this, it uses a technique known as Spread Spectrum . In effect, each user is assigned a code,which spreads its signal bandwidth in such a way that only the same code can recover it at the receiver end. This method has the property that the unwanted signals with different codes get spread even more by the process, making them like noise to the receiver . Spread Spectrum Spread Spectrum is a mean of transmission where the data occupies a larger bandwidth than necessary. Bandwidth spreading is accomplished before the transmission through the use of a code, which is independent of the transmitted data. The same code is used to demodulate the data at the receiving end. The following figure illustrate the spreading done on the data signal x(t) by the spreading signal c(t) resulting in the message signal to be transmitted, m(t). Originally for military use to avoid jamming (interference created on purpose to make a communication channel unusable), spread spectrum modulation is now used in personal communication systems for its superior performance in an interference dominated environment . Definition of Spread Spectrum: A transmission technique in which a pseudo-noise code, independent of the information data, is employed as a modulation waveform to â€Å"spread† the signal energy over a bandwidth much greater than the signal information bandwidth. At the receiver the signal is â€Å"despread† using a synchronized replica of the pseudo-noise code. Basic Principle of Spread Spectrum System: The Principal types of Spread Spectrum are Direct Sequence (DS), and Frequency Hopping (FH). An over view of these systems is hereby given: Pseudo shift of the phase pseudo shift of the frequency Coherent demodulation noncoherent Direct Sequence Spread Spectrum (DSSS) A pseudo-noise sequence pnt generated at the modulator, is used in conjunction with an M-ary PSK modulation to shift the phase of the PSK signal pseudo randomly, at the chipping rate Rc (=1/Tc) a rate that is integer multiple of the symbol rate Rs (=1/Ts). The transmitted bandwidth is determined by the chip rate and by the base band filtering. The implementation limits the maximum chip rate Rc (clock rate) and thus the maximum spreading. The PSK modulation scheme requires a coherent demodulation. PN code length that is much longer than a data symbol, so that a different chip pattern is associated with each symbol. Frequency Hopping Spread Spectrum A Pseudo-noise sequence pnt generated at the modulator is used in conjuction with an M-ary FSK modulation to shift the carrier frequency of the FSK signal pseudurandomly, at the hopping rate Rh. The transmitted signal occupies a number of frequencies in time, each for a period of time Th (= 1/Rh), referred as dwell time. FHSS divides the available bandwidth into N channels and hops between these channels according to the PN sequence. At each frequency hop time the PN generator feeds the frequency synthesizer a frequency word FW (a sequence of n chips) which dictates one of 2n frequency position fhl . Transmitter and receiver follows the same frequency hop pattern. The transmitted bandwidth is determined by the lowest and highest hop position by the bandwidth per hop position (à ¢Ã‹â€ Ã¢â‚¬  fch). For a given hop, instantaneous occupied bandwidth is the conventional M-FSK, which is typically much smaller than Wss. So the FHSS signal is a narrowband signal, all transmission power is concentrated on one channel. Averaged over many hops, the FH/M-FSK spectrum occupies the entire spread spectrum bandwidth. Because the bandwidth of an FHSS system only depends on the tuning range, it can be hopped over a much wider bandwidth than an DSSS system. Since the hops generally result in phase discontinuity (depending on the particular implementation) a noncoherent demodulation is done at receiver. With slow hopping there are multiple data symbol per hop and with fast hopping there are multiple hops per data symbol. 3.3 Basic principle of Direct Sequence Spread Spectrum For BPSK modulation the building blocks of a DSSS system are: Input: Binary data dt with symbol rate Rs = 1/Ts (=bitrate Rb for BPSK) Pseudo-noise code pnt with chip rate Rc = 1/Tc (an integer of Rs) Spreading: In the transmitter, the binary data dt (for BPSK, I and Q for QPSK) is ‘directly multiplied with the PN sequence pnt , which is independent of the binary data, to produce the transmitted baseband signal txb: txb = dt . pnt The effect of multiplication of dt with a PN sequence is to spread the baseband bandwidth Rs of dt to a baseband bandwidth of Rc. Despreading: The spread spectrum signal cannot be detected by a conventional narrowband receiver. In the receiver, the baseband signal rxb is multiplied with the PN sequence pnr . If pnr = pnt and synchronized to the PN sequence in the received data, than the recovered binary data is produced on dr. The effect of multiplication of the spread spectrum signal rxb with the PN sequence pnt used in the transmitter is to despread the bandwidth of rxb to Rs . If pnr ≠  pnt , than there is no dispreading action. The signal dr has a spread spectrum. A receiver not knowing the PN sequence of the transmitter can not reproduce the transmitted data. Performance in the presence of interference: To simplify the presence of interference, the spread spectrum system is considered for baseband BPSK communication (without filtering). The received signal rxb of the transmitted signal txb plus an additive inteferance i (noise, other users, jammer,†¦Ã¢â‚¬ ¦): rxb = t xb + i = dt . pnt + i To recover the original data dt the received signal rx0 is multiplied with a locally generated PN sequence pnr that is an exact replica of that used in the transmitter (that is pnr = pnt and synchronized) The multiplier output is therefore given by: dr = rxb . pnt = dt . pnt . pnt + i . pnt The data signal dt is multiplied twice by the PN sequence pnt , where as the unwanted inteferance i is multiplied only once. Due to the property of the PN sequence: pnt + pnt = +1 for all t The multiplier output becomes: dr = dt + i . pnt The data signal dr is reproduced at the multiplier output in the receiver, except for the inteferance represented by the additive term i . pnt . Multiplication of the inteferance by the locally generated PN sequence, means that the spreading code will affect the inteferance just as it did with the information bearing signal at the transmitter. Noise and inteferance, being uncorrelated with the PN sequence, becomes noise-like, increase in bandwidth and decrease in power density after the multiplier. After dispreading, the data component dt is narrow band (Rb) whereas the inteferance component is wideband (Rc). By applying the dr signal to a baseband (low-pass) filter with a band width just large enough to accommodate the recovery of the data signal, most of the inteferance component i is filtered out. The effect of inteferance is reduced by processing gain (Gp). Narrowband inteferance: The narrowband noise is spread by the multiplication with the PN sequence pnr of the receiver. The power density of the noise is reduced with respect to the despread data signal. Only 1/Gp of the original noise power is left in the information baseband (Rs). Spreading and dispreading enables a bandwidth trade for processing gain against narrow band interfering signals. Narrow band inteferance would disable conventional narrow band receivers. The essence behind the inteferance rejection capability of a spread spectrum system: the useful signal (data) gets multiplied twice by the PN sequence, but the inteferance signal get multiplied only once. Wideband interference: Multiplication of the received signal with the PN sequence of the receiver gets a selective despread of the data signal (smaller bandwidth, higher power density). The inteferance signal is uncorrelated with the PN sequence and is spread. Origin of wideband noise: Multiple Spread Spectrum user: multiple access mechanism. Gaussian Noise: There is no increase in SNR with spread spectrum: The large channel bandwidth (Rc instead of Rs) increase the received noise power with Gp: Ninfo = N0 . BWinfo à   Nss = N0 . BWss = Ninfo .Gp The spread spectrum signal has a lower power density than the directly transmitted signal. Code division multiple access (CDMA) is a methode of multiplexing (wireless) users distinct (orthogonal) codes. All users can transmit at the same time, and each is allocated the entire available frequency spectrum for transmission. CDMA is also known as Spread-Spectrum multiple access (SSMA). CDMA dose not require the bandwidth allocation of FDMA, nor the time synchronization of the individual users needed in TDMA. A CDMA user has full time and full bandwidth available, but the quality of the communication decreases with an increasing number of users (BER ). In CDMA each user: Has its own PN code Uses the same RF bandwidth Transmits simultaneously (asynchronous or synchronous) Correlation of the received baseband spread spectrum signal rxb with the PN sequence of user 1 only despreads the signal of user 1. The other user produces noise Nu for user 1. ACCESS SCHEMES For radio systems there are two resources, frequency and time. Division by frequency, so that each pair of communicators is allocated part of the spectrum for all of the time, results in Frequency Division Multiple Access (FDMA). Division by time, so that each pair of communicators is allocated all (or at least a large part) of the spectrum for part of the time results in Time Division Multiple Access (TDMA). In Code Division Multiple Access (CDMA), every communicator will be allocated the entire spectrum all of the time. CDMA uses codes to identify connections. MULTIPATH AND RAKE RECEIVERS One of the main advantages of CDMA systems is the capability of using signals that arrive in the receivers with different time delays. This phenomenon is called multipath. FDMA and TDMA, which are narrow band systems, cannot discriminate between the multipath arrivals, and resort to equalization to mitigate the negative effects of multipath. Due to its wide bandwidth and rake receivers, CDMA uses the multipath signals and combines them to make an even stronger signal at the receivers. CDMA subscriber units use rake receivers. This is essentially a set of several receivers. One of the receivers (fingers) constantly searches for different multipaths and feeds the information to the other three fingers. Each finger then demodulates the signal corresponding to a strong multipath. The results are then combined together to make the signal stronger. Difference between TDMA vs CDMA. TDMA is Time Division Multiple Access, while CDMA is Code Division Multiple Access. Both technologies achieve the same goal of better utilization of the radio spectrum by allowing multiple users to share the same physical channel, but by using different methods and that is why the three of the four words in each acronym are identical. Both allow more than one person to carry out a conversation on the same frequency without causing interference. The two technologies differ in the way in which users share the common resource. In TDMA the channel is chopped up into sequential time slices. The data of each user is put on the channel in a round-robin fashion. In reality, only one user actually uses the channel at any given point of time, but he uses it only for short bursts. He then gives up the channel for a short duration to allow the other users to have their turn. This is similar to how a computer with just one processor runs multiple applications simultaneously. CDMA on the other hand allows everyone to transmit at the same time. With conventional methods of modulation techniques it would hav been simply not possible. What makes CDMA to allow all users to transmit simultaneously is a special type of digital modulation called Spread Spectrum. In this modulation technique users stream of bits is taken and splattered them across a very wide channel in a pseudo-random fashion. The pseudo part is very important here as at the receiver end the randomization must be undone in order to collect the bits together in a coherent order. For example consider a room full of couples, and each couple trying to carry on one-on-one conversations. In TDMA each couple takes their turn for talking and they keep their turns short by speaking only one sentence at a time. As there is always more one person speaking in the room at any given point of time, no one has to worry about being heard over the background din. In CDMA assume each couple talks simultaneously, but they all use different languages. The background din doesnt cause any real problem as none of the listeners understand any language other than that of the individual to whom they are listening. Voice Encoding At this point many people confuse two distinctly different issues involved in the transmission of digital audio. The first is the WAY in which the stream of bits is delivered from one end to the other. This part of the air interface is what makes one technology different from another. The second is the compression algorithm used to squeeze the audio into as small a stream of bits as possible. This latter component is known at the Voice Coder, or Vocoder for short. Another term commonly used is CODEC, which is a similar word to modem. It combines the terms COder and DECoder. Although each technology has chosen their own unique CODECs, there is no rule saying that one transmission method needs to use a specific CODEC. People often lump a technologys transmission method with its CODEC as though they were single entities. Voice encoding schemes differ slightly in their approach to the problem. Because of this, certain types of human voice work better with some CODECs than they do with others. The point to remember is that all PCS CODECs are compromises of some sort. Since human voices have such a fantastic range of pitch and tonal depth, one cannot expect any single compromise to handle each one equally well. This inability to cope with all types of voice at the same level does lead some people to choose one technology over another. All of the PCS technologies try to minimize battery consumption during calls by keeping the transmission of unnecessary data to a minimum. The phone decides whether or not you are presently speaking, or if the sound it hears is just background noise. If the phone determines that there is no intelligent data to transmit it blanks the audio and it reduces the transmitter duty cycle (in the case of TDMA) or the number of transmitted bits (in the case of CDMA). When the audio is blanked your caller would suddenly find themselves listening to dead air, and this may cause them to think the call has dropped. To avoid this psychological problem many service providers insert what is known as Comfort Noise during the blanked periods. Comfort Noise is synthesized white noise that tries to mimic the volume and structure of the real background noise. This fake background noise assures the caller that the connection is alive and well. However, in newer CODECs such as EVRC (used exclusively on CDMA systems) the background noise is generally suppressed even while the user is talking. This piece of magic makes it sound as though the cell phone user is not in a noisy environment at all. Under these conditions, Comfort Noise is neither necessary, nor desirable. DS-CDMA-INTRODUCTION While multiple access interference (MAI) by other users has been recognized as the capacity-limiting factor in direct sequence code-division multiple-access (DS-CDMA)-based cellular communication systems, multiuser approaches have largely alleviated the problem when the noise process is additive Gaussian. With the availability of multiuser detectors, inaccurate or inappropriate noise modelling assumptions seem to have become the issue again. Whereas multiuser detection has much to offer in the mobile- to-base station uplink, it does not at present appear to be feasible for the downlink due to the complexity involved and the lack of resistance against adjacent cell interference. Moreover, the few multiuser proposals for the downlink require the knowledge of all spreading codes, which is not possible in the tactical military environment, for instance. Enhanced single-user receivers equipped with adaptive filter banks deliver promising performance with reasonable complexity, especially in slowly varying channels. Thus, the performance of single-user detectors is still of interest, particularly in the presence of non-Gaussian noise. In both urban outdoor and indoor mobile radio environments, electromagnetic interference generated by man-made sources such as factories or power lines causes the noise to be of non-Gaussian nature. Large noise magnitudes are deemed very improbable by linear receivers, and consequently performance deterioration is experienced. It is therefore desirable to build systems that can maintain respectable functionality under a broad class of noise distributions, rather than strictly optimizing for the unrealistic Gaussian assumption. Such is the goal of robust detection and estimation theory, which aims to design systems that are suboptimal under nominal channel conditions (e.g., Gaussian channel) and yet do not face catastrophy when the noise distribution is not nominal (e.g., unlike linear schemes). Note that suboptimality here refers to very good performance that is slightly worse than that of the nominal-optimal detector/estimator. The direct sequence code division multiple access (DS-CDMA) technique has been favourably considered for application in digital mobile cellular networks due to its potential to provide higher system capacity over conventional multiple access techniques. Unlike FDMA and TDMA capacities which are mostly limited by the bandwidth, the capacity of a CDMA system is mainly restricted by its interference level. Any reduction in interference produces a direct and linear increase in system capacity. Multiple access interference (MAI) caused by non-zero cross-correlation between different spreading sequences is the major type of interference limiting the CDMA system capacity. Much work has been done to characterize MAI, and to analyze and evaluate the CDMA system performance in the presence of MAI. Since the cross-correlation properties of most sets of spreading codes are either too complex to analyze or very difficult to compute when different transmissions are not synchronized, a random seque nce model. In the case of moderate to large processing gains, Gaussian distribution with variable variance is a good approximation for the MAI distribution. One of the approaches to reduce MAI is to employ orthogonal spreading sequences, and try to synchronize the transmissions at the chip level (quasi-synchronization). However, this is generally difficult to achieve in multipoint-to-point systems, such as the reverse link (mobile-to-base) of a cellular system, due to a lack of synchronization of the various mobile terminals, and the variable transmission delays. In this paper, a multi-carrier DS-CDMA (MCDS-CDMA) scheme is employed to facilitate the synchronization process, and thus reduce MAI. SYSTEM MODEL A model of the MS-DS-CDMA system for the kth user of a CDMA system is shown in the figure 1. TRANMSITTER MODEL At the transmitter the user‘s data stream dk(t) is divided into M interleaved sub streams and spread by a spreading sequence ck(t) to a fraction 1/M of the entire transmission bandwidth W. The resultant chip sequences are then used to modulate M carrier. The carrier frequencies ωm,m=1,2,M are equally spaced by the chip rate so that they are mutually orthogonal over one channel symbol interval T. Let R be the information rate and Rc be the carrier control code rate then the channel symbol interval is BER PERFORMANCE: MC-DS-CDMA system performance measured by bit error rate through analysis and simulation. Analysis: The BER is analysed based on the following: Ortoganal spreading sequences with rectangular pulse shape are applied. ÃŽ ¶k,k=1†¦K are independent of random variables distributd in (-ÃŽ ¶D,ÃŽ ¶D) WHERE ÃŽ ¶D=ÃŽ µD+Ï‚D.Given W and ÃŽ ¶D,M is chosen so that ÃŽ ¶D It is assumed that the fading parameters of the desired user . It is perfectly estimated so that the coherent detection and optimum soft decision decoding could be carried out at the receiver to make the problem analytically tractable. The fading amplitudes as independent Rayleigh random variables with equal second moments. The model is MATLAB INTRODUCTION: Matlab is a commercial Matrix Laboratory package which operates as an interactive programming environment. It is a mainstay of the Mathematics Department software lineup and is also available for PCs and Macintoshes and may be found on the CIRCA VAXes. Matlab is well adapted to numerical experiments since the underlying algorithms for Matlabs builtin functions and supplied m-files are based on the standard libraries LINPACK and EISPACK. Matlab program and script files always have filenames ending with .m; the programming language is exceptionally straightforward since almost every data object is assumed to be an array. Graphical output is available to supplement numerical results. IMREAD Read image from graphics file. A = IMREAD(FILENAME,FMT) reads a grayscale or color image from the file specified by the string FILENAME. If the file is not in the current directory, or in a directory on the MATLAB path, specify the full pathname. The text string FMT specifies the format of the file by its standard file extension. For example, specify gif Digital Signal Processing (DSP) and CDMA Advantages Digital Signal Processing (DSP) and CDMA Advantages INTRODUCTION ANALOG AND DIGITAL SIGNALS The signal is initially generated is in the form of an analog electrical voltage or current, produced for example by a microphone or some other type of transducer. The output from the readout system of a CD (compact disc) player, the data is already in digital form. An analog signal must be converted into digital form before DSP techniques can be applied. An analog electrical voltage signal, for example, can be digitized using an electronic circuit called an analog-to-digital converter or ADC. This generates a digital output as a stream of binary numbers whose values represent the electrical voltage input to the device at each sampling instant. Digital signal processing (DSP)-digital representation of signals and the use of digital processors to analyze, modify, or extract information from signals. Many signals in DSP are derived from analogue signals which have been sampled at regular intervals and converted into digital form. The key advantages of DSP over analogue processing are Guaranteed accuracy (determined by the number of bits used) Perfect reproducibility No drift in performance due to temperature or age Takes advantage of advances in semiconductor technology Greater flexibility (can be reprogrammed without modifying hardware) Superior performance (linear phase response possible, and filtering algorithms can be made adaptive) Sometimes information may already be in digital form. There are however (still) some disadvantages Speed and cost (DSP design and hardware may be expensive, especially with high bandwidth signals) Finite word length problems (limited number of bits may cause degradation). Application areas of DSP are considerable: Image processing (pattern recognition, robotic vision, image enhancement, facsimile, satellite weather map, animation) Instrumentation and control (spectrum analysis, position and rate control, noise reduction, data compression) Speech and audio (speech recognition, speech synthesis, text to speech, digital audio, equalisation) Military (secure communication, radar processing, sonar processing, missile guidance) Telecommunications (echo cancellation, adaptive equalisation, spread spectrum, video conferencing, data communication) Biomedical (patient monitoring, scanners, EEG brain mappers, ECG analysis, X-ray storage and enhancement). INTRODUCTION TO CDMA Code Division Multiple Access (CDMA) is a radically new concept in wireless communications. It has gained widespread international acceptance by cellular radio system operators as an upgrade that will dramatically increase both their system capacity and the service quality. It has likewise been chosen for deployment by the majority of the winners of the United States Personal Communications System spectrum auctions. It may seem, however, mysterious for those who arent familiar with it. CDMA is a form of spread-spectrum, a family of digital communication techniques that have been used in military applications for many years. The core principle of spread spectrum is the use of noise-like carrier waves, and, as the name implies, bandwidths much wider than that required for simple point-to-point communication at the same data rate. Originally there were two motivations: either to resist enemy efforts to jam the communications (anti-jam, or AJ), or to hide the fact that communication was even taking place, sometimes called low probability of intercept (LPI). It has a history that goes back to the early days of World War II. The use of CDMA for civilian mobile radio applications is novel. It was proposed theoretically in the late 1940s, but the practical application in the civilian marketplace did not take place until 40 years later. Commercial applications became possible because of two evolutionary developments. One was the availability of very low cost, high density digital integrated circuits, which reduce the size, weight, and cost of the subscriber stations to an acceptably low level. The other was the realization that optimal multiple access communication requires that all user stations regulate their transmitter powers to the lowest that will achieve adequate signal quality. CDMA changes the nature of the subscriber station from a predominately analog device to a predominately digital device. Old-fashioned radio receivers separate stations or channels by filtering in the frequency domain. CDMA receivers do not eliminate analog processing entirely, but they separate communication channels by means of a pseudorandom modulation that is applied and removed in the digital domain, not on the basis of frequency. Multiple users occupy the same frequency band. This universal frequency reuse is not fortuitous. On the contrary, it is crucial to the very high spectral efficiency that is the hallmark of CDMA. Other discussions in these pages show why this is true. CDMA is altering the face of cellular and PCS communication by: Dramatically improving the telephone traffic capacity Dramatically improving the voice quality and eliminating the audible effects of multipath fading Reducing the incidence of dropped calls due to handoff failures Providing reliable transport mechanism for data communications, such as facsimile and internet traffic Reducing the number of sites needed to support any given amount of traffic Simplifying site selection Reducing deployment and operating costs because fewer cell sites are needed Reducing average transmitted power Reducing interference to other electronic devices Reducing potential health risks Commercially introduced in 1995, CDMA quickly became one of the worlds fastest growing wireless technologies. In 1999, the International Telecommunications Union selected CDMA as the industry standard for new third-generation (3G) wireless systems. Many leading wireless carriers are now building or upgrading to 3G CDMA networks in order to provide more capacity for voice traffic, along with high-speed data capabilities. DS_CDMA Multiple access systems based on DS CDMA have achieved increasing significance for mobile communications applications. A promising concept is based on DS_CDMA applying MRC at the receiver. MRC takes advantage of the channel diversity to combat the multipath fading. However the capacity of a DS_CDMA system is limited by both multi-user interference and inter symbol interference ISI in high data rate applications. OFDM is applied to combat the frequency selectivity of the channel using a simple one tap equalizer Further more OFDM prevents the ISI and inter carrier interference ICI by inserting a guard interval between adjacent OFDM symbols OFDM is typically used for audio TV and HDTV transmission over terrestrial channels and achieves high spectral efficiency. The CMDA Technology overview FDMA In Frequency Division Multiple Access, the frequency band is divided in slots. Each user gets one frequency slot assigned that is used at will. It could be compared to AM or FM broadcasting radio where each station has a frequency assigned. FDMA demands good filtering. TDMA In Time Division Multiple Access, the frequency band is not partitioned but users are allowed to use it only in predefined intervals of time, one at a time. Thus, TDMA demands synchronization among the users. CDMA CDMA, for Code Division Multiple Access, is different from its traditional ways in which it does not allocate frequency or time in user slots but gives the right to use both to all users simultaneously. To do this, it uses a technique known as Spread Spectrum . In effect, each user is assigned a code,which spreads its signal bandwidth in such a way that only the same code can recover it at the receiver end. This method has the property that the unwanted signals with different codes get spread even more by the process, making them like noise to the receiver . Spread Spectrum Spread Spectrum is a mean of transmission where the data occupies a larger bandwidth than necessary. Bandwidth spreading is accomplished before the transmission through the use of a code, which is independent of the transmitted data. The same code is used to demodulate the data at the receiving end. The following figure illustrate the spreading done on the data signal x(t) by the spreading signal c(t) resulting in the message signal to be transmitted, m(t). Originally for military use to avoid jamming (interference created on purpose to make a communication channel unusable), spread spectrum modulation is now used in personal communication systems for its superior performance in an interference dominated environment . Definition of Spread Spectrum: A transmission technique in which a pseudo-noise code, independent of the information data, is employed as a modulation waveform to â€Å"spread† the signal energy over a bandwidth much greater than the signal information bandwidth. At the receiver the signal is â€Å"despread† using a synchronized replica of the pseudo-noise code. Basic Principle of Spread Spectrum System: The Principal types of Spread Spectrum are Direct Sequence (DS), and Frequency Hopping (FH). An over view of these systems is hereby given: Pseudo shift of the phase pseudo shift of the frequency Coherent demodulation noncoherent Direct Sequence Spread Spectrum (DSSS) A pseudo-noise sequence pnt generated at the modulator, is used in conjunction with an M-ary PSK modulation to shift the phase of the PSK signal pseudo randomly, at the chipping rate Rc (=1/Tc) a rate that is integer multiple of the symbol rate Rs (=1/Ts). The transmitted bandwidth is determined by the chip rate and by the base band filtering. The implementation limits the maximum chip rate Rc (clock rate) and thus the maximum spreading. The PSK modulation scheme requires a coherent demodulation. PN code length that is much longer than a data symbol, so that a different chip pattern is associated with each symbol. Frequency Hopping Spread Spectrum A Pseudo-noise sequence pnt generated at the modulator is used in conjuction with an M-ary FSK modulation to shift the carrier frequency of the FSK signal pseudurandomly, at the hopping rate Rh. The transmitted signal occupies a number of frequencies in time, each for a period of time Th (= 1/Rh), referred as dwell time. FHSS divides the available bandwidth into N channels and hops between these channels according to the PN sequence. At each frequency hop time the PN generator feeds the frequency synthesizer a frequency word FW (a sequence of n chips) which dictates one of 2n frequency position fhl . Transmitter and receiver follows the same frequency hop pattern. The transmitted bandwidth is determined by the lowest and highest hop position by the bandwidth per hop position (à ¢Ã‹â€ Ã¢â‚¬  fch). For a given hop, instantaneous occupied bandwidth is the conventional M-FSK, which is typically much smaller than Wss. So the FHSS signal is a narrowband signal, all transmission power is concentrated on one channel. Averaged over many hops, the FH/M-FSK spectrum occupies the entire spread spectrum bandwidth. Because the bandwidth of an FHSS system only depends on the tuning range, it can be hopped over a much wider bandwidth than an DSSS system. Since the hops generally result in phase discontinuity (depending on the particular implementation) a noncoherent demodulation is done at receiver. With slow hopping there are multiple data symbol per hop and with fast hopping there are multiple hops per data symbol. 3.3 Basic principle of Direct Sequence Spread Spectrum For BPSK modulation the building blocks of a DSSS system are: Input: Binary data dt with symbol rate Rs = 1/Ts (=bitrate Rb for BPSK) Pseudo-noise code pnt with chip rate Rc = 1/Tc (an integer of Rs) Spreading: In the transmitter, the binary data dt (for BPSK, I and Q for QPSK) is ‘directly multiplied with the PN sequence pnt , which is independent of the binary data, to produce the transmitted baseband signal txb: txb = dt . pnt The effect of multiplication of dt with a PN sequence is to spread the baseband bandwidth Rs of dt to a baseband bandwidth of Rc. Despreading: The spread spectrum signal cannot be detected by a conventional narrowband receiver. In the receiver, the baseband signal rxb is multiplied with the PN sequence pnr . If pnr = pnt and synchronized to the PN sequence in the received data, than the recovered binary data is produced on dr. The effect of multiplication of the spread spectrum signal rxb with the PN sequence pnt used in the transmitter is to despread the bandwidth of rxb to Rs . If pnr ≠  pnt , than there is no dispreading action. The signal dr has a spread spectrum. A receiver not knowing the PN sequence of the transmitter can not reproduce the transmitted data. Performance in the presence of interference: To simplify the presence of interference, the spread spectrum system is considered for baseband BPSK communication (without filtering). The received signal rxb of the transmitted signal txb plus an additive inteferance i (noise, other users, jammer,†¦Ã¢â‚¬ ¦): rxb = t xb + i = dt . pnt + i To recover the original data dt the received signal rx0 is multiplied with a locally generated PN sequence pnr that is an exact replica of that used in the transmitter (that is pnr = pnt and synchronized) The multiplier output is therefore given by: dr = rxb . pnt = dt . pnt . pnt + i . pnt The data signal dt is multiplied twice by the PN sequence pnt , where as the unwanted inteferance i is multiplied only once. Due to the property of the PN sequence: pnt + pnt = +1 for all t The multiplier output becomes: dr = dt + i . pnt The data signal dr is reproduced at the multiplier output in the receiver, except for the inteferance represented by the additive term i . pnt . Multiplication of the inteferance by the locally generated PN sequence, means that the spreading code will affect the inteferance just as it did with the information bearing signal at the transmitter. Noise and inteferance, being uncorrelated with the PN sequence, becomes noise-like, increase in bandwidth and decrease in power density after the multiplier. After dispreading, the data component dt is narrow band (Rb) whereas the inteferance component is wideband (Rc). By applying the dr signal to a baseband (low-pass) filter with a band width just large enough to accommodate the recovery of the data signal, most of the inteferance component i is filtered out. The effect of inteferance is reduced by processing gain (Gp). Narrowband inteferance: The narrowband noise is spread by the multiplication with the PN sequence pnr of the receiver. The power density of the noise is reduced with respect to the despread data signal. Only 1/Gp of the original noise power is left in the information baseband (Rs). Spreading and dispreading enables a bandwidth trade for processing gain against narrow band interfering signals. Narrow band inteferance would disable conventional narrow band receivers. The essence behind the inteferance rejection capability of a spread spectrum system: the useful signal (data) gets multiplied twice by the PN sequence, but the inteferance signal get multiplied only once. Wideband interference: Multiplication of the received signal with the PN sequence of the receiver gets a selective despread of the data signal (smaller bandwidth, higher power density). The inteferance signal is uncorrelated with the PN sequence and is spread. Origin of wideband noise: Multiple Spread Spectrum user: multiple access mechanism. Gaussian Noise: There is no increase in SNR with spread spectrum: The large channel bandwidth (Rc instead of Rs) increase the received noise power with Gp: Ninfo = N0 . BWinfo à   Nss = N0 . BWss = Ninfo .Gp The spread spectrum signal has a lower power density than the directly transmitted signal. Code division multiple access (CDMA) is a methode of multiplexing (wireless) users distinct (orthogonal) codes. All users can transmit at the same time, and each is allocated the entire available frequency spectrum for transmission. CDMA is also known as Spread-Spectrum multiple access (SSMA). CDMA dose not require the bandwidth allocation of FDMA, nor the time synchronization of the individual users needed in TDMA. A CDMA user has full time and full bandwidth available, but the quality of the communication decreases with an increasing number of users (BER ). In CDMA each user: Has its own PN code Uses the same RF bandwidth Transmits simultaneously (asynchronous or synchronous) Correlation of the received baseband spread spectrum signal rxb with the PN sequence of user 1 only despreads the signal of user 1. The other user produces noise Nu for user 1. ACCESS SCHEMES For radio systems there are two resources, frequency and time. Division by frequency, so that each pair of communicators is allocated part of the spectrum for all of the time, results in Frequency Division Multiple Access (FDMA). Division by time, so that each pair of communicators is allocated all (or at least a large part) of the spectrum for part of the time results in Time Division Multiple Access (TDMA). In Code Division Multiple Access (CDMA), every communicator will be allocated the entire spectrum all of the time. CDMA uses codes to identify connections. MULTIPATH AND RAKE RECEIVERS One of the main advantages of CDMA systems is the capability of using signals that arrive in the receivers with different time delays. This phenomenon is called multipath. FDMA and TDMA, which are narrow band systems, cannot discriminate between the multipath arrivals, and resort to equalization to mitigate the negative effects of multipath. Due to its wide bandwidth and rake receivers, CDMA uses the multipath signals and combines them to make an even stronger signal at the receivers. CDMA subscriber units use rake receivers. This is essentially a set of several receivers. One of the receivers (fingers) constantly searches for different multipaths and feeds the information to the other three fingers. Each finger then demodulates the signal corresponding to a strong multipath. The results are then combined together to make the signal stronger. Difference between TDMA vs CDMA. TDMA is Time Division Multiple Access, while CDMA is Code Division Multiple Access. Both technologies achieve the same goal of better utilization of the radio spectrum by allowing multiple users to share the same physical channel, but by using different methods and that is why the three of the four words in each acronym are identical. Both allow more than one person to carry out a conversation on the same frequency without causing interference. The two technologies differ in the way in which users share the common resource. In TDMA the channel is chopped up into sequential time slices. The data of each user is put on the channel in a round-robin fashion. In reality, only one user actually uses the channel at any given point of time, but he uses it only for short bursts. He then gives up the channel for a short duration to allow the other users to have their turn. This is similar to how a computer with just one processor runs multiple applications simultaneously. CDMA on the other hand allows everyone to transmit at the same time. With conventional methods of modulation techniques it would hav been simply not possible. What makes CDMA to allow all users to transmit simultaneously is a special type of digital modulation called Spread Spectrum. In this modulation technique users stream of bits is taken and splattered them across a very wide channel in a pseudo-random fashion. The pseudo part is very important here as at the receiver end the randomization must be undone in order to collect the bits together in a coherent order. For example consider a room full of couples, and each couple trying to carry on one-on-one conversations. In TDMA each couple takes their turn for talking and they keep their turns short by speaking only one sentence at a time. As there is always more one person speaking in the room at any given point of time, no one has to worry about being heard over the background din. In CDMA assume each couple talks simultaneously, but they all use different languages. The background din doesnt cause any real problem as none of the listeners understand any language other than that of the individual to whom they are listening. Voice Encoding At this point many people confuse two distinctly different issues involved in the transmission of digital audio. The first is the WAY in which the stream of bits is delivered from one end to the other. This part of the air interface is what makes one technology different from another. The second is the compression algorithm used to squeeze the audio into as small a stream of bits as possible. This latter component is known at the Voice Coder, or Vocoder for short. Another term commonly used is CODEC, which is a similar word to modem. It combines the terms COder and DECoder. Although each technology has chosen their own unique CODECs, there is no rule saying that one transmission method needs to use a specific CODEC. People often lump a technologys transmission method with its CODEC as though they were single entities. Voice encoding schemes differ slightly in their approach to the problem. Because of this, certain types of human voice work better with some CODECs than they do with others. The point to remember is that all PCS CODECs are compromises of some sort. Since human voices have such a fantastic range of pitch and tonal depth, one cannot expect any single compromise to handle each one equally well. This inability to cope with all types of voice at the same level does lead some people to choose one technology over another. All of the PCS technologies try to minimize battery consumption during calls by keeping the transmission of unnecessary data to a minimum. The phone decides whether or not you are presently speaking, or if the sound it hears is just background noise. If the phone determines that there is no intelligent data to transmit it blanks the audio and it reduces the transmitter duty cycle (in the case of TDMA) or the number of transmitted bits (in the case of CDMA). When the audio is blanked your caller would suddenly find themselves listening to dead air, and this may cause them to think the call has dropped. To avoid this psychological problem many service providers insert what is known as Comfort Noise during the blanked periods. Comfort Noise is synthesized white noise that tries to mimic the volume and structure of the real background noise. This fake background noise assures the caller that the connection is alive and well. However, in newer CODECs such as EVRC (used exclusively on CDMA systems) the background noise is generally suppressed even while the user is talking. This piece of magic makes it sound as though the cell phone user is not in a noisy environment at all. Under these conditions, Comfort Noise is neither necessary, nor desirable. DS-CDMA-INTRODUCTION While multiple access interference (MAI) by other users has been recognized as the capacity-limiting factor in direct sequence code-division multiple-access (DS-CDMA)-based cellular communication systems, multiuser approaches have largely alleviated the problem when the noise process is additive Gaussian. With the availability of multiuser detectors, inaccurate or inappropriate noise modelling assumptions seem to have become the issue again. Whereas multiuser detection has much to offer in the mobile- to-base station uplink, it does not at present appear to be feasible for the downlink due to the complexity involved and the lack of resistance against adjacent cell interference. Moreover, the few multiuser proposals for the downlink require the knowledge of all spreading codes, which is not possible in the tactical military environment, for instance. Enhanced single-user receivers equipped with adaptive filter banks deliver promising performance with reasonable complexity, especially in slowly varying channels. Thus, the performance of single-user detectors is still of interest, particularly in the presence of non-Gaussian noise. In both urban outdoor and indoor mobile radio environments, electromagnetic interference generated by man-made sources such as factories or power lines causes the noise to be of non-Gaussian nature. Large noise magnitudes are deemed very improbable by linear receivers, and consequently performance deterioration is experienced. It is therefore desirable to build systems that can maintain respectable functionality under a broad class of noise distributions, rather than strictly optimizing for the unrealistic Gaussian assumption. Such is the goal of robust detection and estimation theory, which aims to design systems that are suboptimal under nominal channel conditions (e.g., Gaussian channel) and yet do not face catastrophy when the noise distribution is not nominal (e.g., unlike linear schemes). Note that suboptimality here refers to very good performance that is slightly worse than that of the nominal-optimal detector/estimator. The direct sequence code division multiple access (DS-CDMA) technique has been favourably considered for application in digital mobile cellular networks due to its potential to provide higher system capacity over conventional multiple access techniques. Unlike FDMA and TDMA capacities which are mostly limited by the bandwidth, the capacity of a CDMA system is mainly restricted by its interference level. Any reduction in interference produces a direct and linear increase in system capacity. Multiple access interference (MAI) caused by non-zero cross-correlation between different spreading sequences is the major type of interference limiting the CDMA system capacity. Much work has been done to characterize MAI, and to analyze and evaluate the CDMA system performance in the presence of MAI. Since the cross-correlation properties of most sets of spreading codes are either too complex to analyze or very difficult to compute when different transmissions are not synchronized, a random seque nce model. In the case of moderate to large processing gains, Gaussian distribution with variable variance is a good approximation for the MAI distribution. One of the approaches to reduce MAI is to employ orthogonal spreading sequences, and try to synchronize the transmissions at the chip level (quasi-synchronization). However, this is generally difficult to achieve in multipoint-to-point systems, such as the reverse link (mobile-to-base) of a cellular system, due to a lack of synchronization of the various mobile terminals, and the variable transmission delays. In this paper, a multi-carrier DS-CDMA (MCDS-CDMA) scheme is employed to facilitate the synchronization process, and thus reduce MAI. SYSTEM MODEL A model of the MS-DS-CDMA system for the kth user of a CDMA system is shown in the figure 1. TRANMSITTER MODEL At the transmitter the user‘s data stream dk(t) is divided into M interleaved sub streams and spread by a spreading sequence ck(t) to a fraction 1/M of the entire transmission bandwidth W. The resultant chip sequences are then used to modulate M carrier. The carrier frequencies ωm,m=1,2,M are equally spaced by the chip rate so that they are mutually orthogonal over one channel symbol interval T. Let R be the information rate and Rc be the carrier control code rate then the channel symbol interval is BER PERFORMANCE: MC-DS-CDMA system performance measured by bit error rate through analysis and simulation. Analysis: The BER is analysed based on the following: Ortoganal spreading sequences with rectangular pulse shape are applied. ÃŽ ¶k,k=1†¦K are independent of random variables distributd in (-ÃŽ ¶D,ÃŽ ¶D) WHERE ÃŽ ¶D=ÃŽ µD+Ï‚D.Given W and ÃŽ ¶D,M is chosen so that ÃŽ ¶D It is assumed that the fading parameters of the desired user . It is perfectly estimated so that the coherent detection and optimum soft decision decoding could be carried out at the receiver to make the problem analytically tractable. The fading amplitudes as independent Rayleigh random variables with equal second moments. The model is MATLAB INTRODUCTION: Matlab is a commercial Matrix Laboratory package which operates as an interactive programming environment. It is a mainstay of the Mathematics Department software lineup and is also available for PCs and Macintoshes and may be found on the CIRCA VAXes. Matlab is well adapted to numerical experiments since the underlying algorithms for Matlabs builtin functions and supplied m-files are based on the standard libraries LINPACK and EISPACK. Matlab program and script files always have filenames ending with .m; the programming language is exceptionally straightforward since almost every data object is assumed to be an array. Graphical output is available to supplement numerical results. IMREAD Read image from graphics file. A = IMREAD(FILENAME,FMT) reads a grayscale or color image from the file specified by the string FILENAME. If the file is not in the current directory, or in a directory on the MATLAB path, specify the full pathname. The text string FMT specifies the format of the file by its standard file extension. For example, specify gif

The Yellow Wallpaper and The Cask Of Amontillado -- Yellow Wallpaper C

The Yellow Wallpaper and The Cask Of Amontillado  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚      The short story, " The Yellow Wallpaper", written by Charlotte Gilman, and "The Cask of Amontillado" written by Edgar Allan Poe, are stories in which the plots are very different, but share similar qualities with the elements in the story. "The Cask of Amontillado" is a powerful tale of revenge, in which the narrator of the tale pledges revenge upon Fortunato for an insult. "The Yellow Wallpaper" is a story about a woman, her psychological difficulties and her husband's therapeutic treatment of her illness. She struggles over her illness, and battle's her controlling husband. The settings in both stories are very important, they influence the characters, and help with the development of the plot.   In "The Yellow Wallpaper" the setting helps define the action as well as to explain characters behaviors. The setting is which the story takes place is in the narrators room, where she is severally ill, and she is "locked up" in the room which served as her cage. The room in which the narrator is caged in is a nursery, "it is a big, airy room, the whole floor nearly, with windows that look all ways. The paint and paper look as if a boys' school had used it." The narrator describes the color of the walls as repellent, almost revolting, it is an unclear yellow with a dull orange. The condition that the narrator is in, the repulsiveness of the room, and the room haunting her, drives her into insanity.   "The Cask of Amontillado" takes place in an appropriate setting, not only is the setting underground, but also in the blackness of the night. The story begins around dusk, one evening during the carnival season in a European city. The location quickly change... ...he wall, he thinks about his rejected opportunities and his unbearable regret. As he sobers with terror, the final blow will come from the realization that his life is ending in his catacombs dying with his finest wine. The catacombs, in which he dies, set the theme, and relate well with the story. Without the yellow wallpaper in the short story, the significance of the wallpaper would not mater, nor would it set the theme or plot. At night the wallpaper becomes bars, and the wallpaper lets her see herself as a women and her desire to free herself. She needs to free herself from the difficulties of her husband, and from her sickness. The settings in both, set up the elements of the stories and ads to the effect in both of the short stories.   Bibliography Branson, Leigh W. Edgar Allen Poe's Literary Neighborhood, 17 Mar. 1997 *htt://www.geocities.com/Athens

Hearts and Minds Essay

Movies and documentaries have a way of touching the lives of many. For the most part, they are geared towards the exhibition of truths that are hidden from other people. The documentary, â€Å"Hearts and Minds†, mirrored the numerous difficulties experienced by the Vietnamese in the hands of the American soldiers. The harsh realities shown by the American soldiers towards the Vietnamese was quite difficult to believe, for we all know how the Americans would care for any other individual. Directed by Peter Davis, the documentary showed different clips that prove the harsh attitude towards people at that time. Even the speech of former President Lyndon Johnson was shown in the said documentary. To give people a great feel of the said timeline, much of the most famous details during that particular time were shown. The type of music, clothes, and even some old archives were shown. In this manner, it would become easier for the audiences to understand what was being explained to them. I admire the montage feeling provided by the documentary. Together with the voice over, watching the documentary was like watching any other historical how. However, what sets it apart from the rest were the heartbreaking realities exhibited. I could not help but wonder as to how people were treated unfairly and how other people could bear causing pain to others. One of the scenes that caught my attention was the funeral of a soldier. Surrounding the coffin were grieving people, including the family and friends. However, for some reason, one grieving lady was stopped from following the coffin being laid to rest. This particular scene was contrasted with a clip showing the interview of the general who led the Vietnam War. Furthermore, there were several other interviews included in the documentary. Although I am not of Vietnamese, origin I was heartbroken by the difficulties experienced at that time. For the longest time, they experienced pain, both physical and emotional, while they struggled to raise their families accordingly. A particular scene exemplified the hardships endured by the Vietnamese during that particular time. The scene showed how the prisoners of the war were sitting restless and not paying attention to what their employer had in mind. I felt pity with the condition these people experienced, toppled by the excessive torture and inhumane humiliations provided by the American soldiers. After watching the documentary, one could not help but question what has been taught in class during our younger days. I was surprised at how the outcome of this war has been, including the participation that the American soldiers portrayed. However, due to the extensive information provided, some critics may also form their own conclusion as to how the said war was used as propaganda. On the other hand, it would be expected that some people would opt to be biased towards the Vietnamese and consider them to be victims of the American occupation. Regardless of everything that has been said, I believe that we all have our own perceptions towards things. Personally, I believe that the goal of this film was to show the other side of history that not everyone was aware of. In this manner, I would be able to form my own beliefs as to how people would be able to learn from these hurtful experiences. It is useless for us to keep on living in the past—we should all move forward in helping make a different in this lifetime. I must say that I recommend this film to everyone, especially those who are currently studying about the history of the United States.

Words Often Misspelled Because of Double Letters

Words Often Misspelled Because of Double Letters Words Often Misspelled Because of Double Letters Words Often Misspelled Because of Double Letters By Maeve Maddox An email in which balloon was spelled â€Å"baloon† got me thinking about words with double letters. Many of the most frequently-misspelled words in English are misspelled by leaving out a letter. Others are misspelled because we think a letter should be doubled, so we put in an extra one. I thought it might be useful to organize these frequently-misspelled words into three categories. Words we try to spell with too few letters balloon dumbbell embarrass millennium misspell occurrence possession broccoli occasionally questionnaire coolly dissipate difference generally incidentally magically success Words that have double letters, but not as many as we think deterrence harass personnel recommend referred disappear disappoint finally fulfill necessary occasion occurred parallel sheriff tomorrow Words that don’t have double letters, but we want to add them preferable procedure coliseum labeled NOTE: i. There’s also the spelling colosseum with a double s. ii. British usage doubles the l in labelled. Caveat to writers of British English: Most word-processing software comes with spell-checkers programmed for American spelling usage. Another NOTE: Merriam-Webster gives programmed as the first spelling and programed as an alternate. Go figure. Want to improve your English in five minutes a day? Get a subscription and start receiving our writing tips and exercises daily! Keep learning! Browse the Spelling category, check our popular posts, or choose a related post below:Spelling Test 18 Types of Parenthetical PhrasesWriting a Thank You Note

Cultural Literacy Example

Cultural Literacy Example Cultural Literacy – Coursework Example Cultural Literacy Key differences between American and Chinese culture originate in the differences in people’s lifestyles, socializing habits, and cuisines and eating habits etcetera. While Americans are more independently going, self-oriented, and have well-defined personal space, Chinese are more community-oriented with strong family ties and robust social network. If I were to do business in China, I would have to be more open and vivacious in greeting others. I would be expected to have a lot of friends and Chinese people are not difficult to make friends as they are quite friendly and easy going. Once upon a time, I was in a gathering. There were my American neighbors and a couple from the Middle East. Handshaking between men and women is a common practice in the US. People shake hands all the time, whether they are in office, park, or at home with friends. My American neighbor John, who also happens to be my close friend, was the host. While we were attending the guests , John offered the Middle Eastern couple some wine, but they respectfully refused. I could sense that John did not like that since he had spent a lot on wine. This was where I intruded and said with a wide grin on my face,†haha; America is a melting pot of cultures, beautifully blending yet retaining their originality; right John?† John got the point and joined in the conversation. What could otherwise have been jeopardized in a misunderstanding, sprang into a strong networking with good understanding of and respect for the cultural differences as a result of my intervention.

Term paper Example | Topics and Well Written Essays - 1500 words

Term Paper Example It is further concerned with other activities such as the disposition of offenders and treatment of juveniles found to have committed a criminal act. The criminal justice system also includes public institutions and key players such as the police, prosecutors, courts, corrections, crime victims and so on (â€Å"Criminal Justice System†). Purpose According to Frase and Weidner, the criminal justice system has the primary purpose of enforcing laws in line with the defined rules and limitations. The authors furthered that the â€Å"system† refers to â€Å"something highly rational – carefully planned, coordinated, and regulated† (Frase & Weidner). On the other hand, Drakeford and Friedman reiterated that controlling crime and assuring due process are the two main purposes of the criminal justice system (5). Key Players’ Functions The criminal justice system is composed of four institutions, namely, police, prosecution, courts, and corrections, and thes e interact with each other towards a balanced action for justice. In simpler terms, the police are responsible for enforcing the law; the courts are responsible for hearing the legality of the crime, and; corrections house the convicted offenders. The following section lists the specific responsibilities of these key players. Police. According to Stevens, the police have intended and unintended functions that include the following: morals enforcement, class control, riot control, order maintenance, safety, service, and crime fighting. Other specific functions include the following: To subdue conduct that is considered threatening. To protect or help a person who is harmed. To uphold security in the community. To help people who are unable to help themselves such as the handicap, the mentally ill, the old and the young, and others. To help in resolving conflict between groups and individuals. To oversee the movement of vehicles and people. To recognize problems that can become seriou s problems (Stevens). Prosecutor. The main function of the prosecutor in a trial is to convince the jury that the defendant is guilty of the crime. Other functions include, but not limited to, the following: To ensure that the guilty person is convicted. To charge suspect with a crime. To represent the government during a trial. To assist in selecting jurors. To call on witnesses to prove the defendant’s guilt. To cross-examine the witnesses presented by the defense (Read). Court. The court consists of the prosecutors, judges and other stakeholders, each of which has roles to fulfill. The prosecuting office must present evidence to the court regarding the guilt of the offender. The prosecutor is usually involved during the initial investigation, pretrial hearings and during the trial. During the preliminary hearing, several factors such as the severity of the offense, will determine the next step. The lack of probable cause can lead to the dismissal of the case. Otherwise the case may be brought to the grand jury. If there is sufficient evidence, the grand jury then decides to try the offender (Drakeford & Friedman, 8-9). Corrections. Drakeford and Friedman stated that corrections have several purposes, one of which is to punish the offenders. This is based on the belief that punishment deters offenders from criminal behavior. Another purpose of the corrections is to protect the society from these offenders. The third purpose is to rehabilitate the offenders (10). Interaction of Key Players The key players in the criminal justice system,

Strategy in action Essay Example | Topics and Well Written Essays - 1500 words

Strategy in action - Essay Example Despite the challenge, interventions have been developed to help in organization of knowledge especially based on new technologies. Knowledge management systems have been embraced by many organizations in an effort to ensure that the dynamics of knowledge are controlled. Researchers have developed divergent views concerning knowledge management. They attribute it to performance, market share, competitive advantage, market positioning, and sustainability of the organization. Despite all these benefits, knowledge management is seen as a thorn in the flesh of large and complex organizations. Large and complex organizations depict complexities and bureaucracy in the management of knowledge. The management of knowledge in large and complex organizations is a tedious process that involves a number of processes, usually involving several people. The involvements of many people in the process create a scenario where knowledge does not reach on time or is corrupted in the process. In order for any knowledge to be approved from the lower cadres to the management of an organization, there is likelihood of conflicts based on the influence of decisions made. According to Franz et al (2002), knowledge ‘islands’ are inevitable in large organizations where there are parities in the knowledge that is embraced by a given group based on common aspects such as being in the same office, department or team. It is noteworthy that the organization has to share common goals; hence, the knowledge at their disposal should ideally be similar. However, complex organizations may serv e different purposes, which may require them to adopt some knowledge that varies from the other teams. The management of knowledge in large organizations is cumbersome based on the view that knowledge can occur in various forms. As well put by Nonaka and Takeuchi (1995, p.9) in their model, there are two types of knowledge.