The Modulation And Demodulation In Gsm Marketing Essay

The Modulation And Demodulation In Gsm Marketing EssayGSM (Global System for Mobile communications) is the most popular standard for lively ph anes in the world . In GSM repointing and speech impart are digital and data communication is easy to build into the systemGSM is a cellular ne bothrk,and mobile phones connect to it by searching for cells in the immediate vicinity.There are five different cell sizes in a GSM network-macro, micro, pico, femto and umbrella cells. The coverage area of individually cell varies according to the implementation environment.GSM networks operate in a number of different absolute frequency ranges (separated into GSM frequency ranges for 2G and UMTS frequency bands for 3G). Most 2G GSM networks operate in the 900 megahertz or 1800 MHz bands. Most 3G GSM networks in Europe operate in the 2100 MHz frequency band.900MHz GSM uses a combination of TDMA and FDMA. It uses eight time slots, hence one carrier sight support eight full rate or sixteen half ra te carry. Channel separation is 200kHz with mobile transmit channels in the range 890 to 915MHz and mobile receive channels in the range 935 to 960MHz. Peak output power of the transmitters depends on the class of the mobile station and can be 0.8, 2, 5, 8, or 20 watts.GSM is based on digital cellular networks which have some advantages as listed belowGreater spectrum usage efficiency compared to latitude approaches.Improved service quality for drug users in the form of improved speech quality, improved security through inbuilt encryption (there is none at present), and high connection reliability.Larger number of advanced user function and easier linkage to private and public ISDN networks.CHAPTER 2GENERAL PROPERTIES OF GSMGSM uses multiple access technology same(p) FDMA/TDMA and CDMATDMA. With time division multiple access simultaneous conversations are supported by users transmitting in short bursts at different times or slots.FDMA. In frequency division multiple access, th e total band is split into narrow frequency subbands and a channel is allocated exclusively to for each one user during the kind of a call. One is used for transmission and one for reception.CDMA. Code division multiple access allows all users access to all frequencies with the allocated band. A single user is extracted from the mayhem by looking for each users individual code using a correlator. Although not selected for the current coevals of mobile digital technologies, CDMA holds much anticipate as the future technology of choice for GSM replacement in the next century. GSM uses frequency division duplexing. Channel for uplink is from 890 915 MHz Channel for downlink is from 935 960 MHz Distance b/w the frequencies used for uplink and downlink (duplex distance) is 45 MHz Frequency difference between adjacent allocations in a frequency plan(channel spacing) is 200khz. Total number of frequencies are touch on to 124 Bit rate of each channel is 270.9 kbit/s Duration of data frame in GSM is 4.615 msec Number of time slots are 8 and each slot is of (4.615 / 8) 0.577 m secSpeech bit rate is 13 kbits /secARCHITECTURE OF GSM NETWORKThe GSM network can be divided into quaternity main partsThe Mobile Station (MS).The Base Station Subsystem (BSS).The Network and Switching Subsystem (NSS).The Operation and Support Subsystem (OSS).CHAPTER 3BACKGROUND OF GSMThe number 1 GSM system judicial admission was published in July 1991 and was immediately followed by several false starts. This was brought about by a combination over-optimism, difficulties in type approval testing, and inevitable changes to the GSM specification. The first terminals appeared on the market in June 1992.A combination of high demand for mobile services and a lack of capacity in the installed analogue network, has do Germany the most advanced country for GSM deployment. In the UK, Vodafone have said that they now cover 60-70% of the UK population with their GSM service and expect 90% cover age by mid(prenominal) 1993.GSM has also been accepted for use by over s yetteen European countries and several others including New Zealand and Hong Kong ending a period of diverse and proprietary standards. whatsoever of the problems which were faced by the Europians when implementing these brand new technology wereIn many countries there is no overt demand or need for GSM. Analogue services are available and under employed.GSM coverage needs to be as wide as analogue before users will swap over.The current generation of GSM hand portables are not as small or as light as analogue variants. This will limit the interest of many users, even though a better service may be provided by GSM technology.Terminal monetary sets for digital technologies are high compared to analogue.It is likely that it will be actually difficult to get users to pay higher call charges for an improved service so GSM cannot be positioned as a higher quality/higher price service.CHAPTER 4IMPLEMENTATIONModulat ion scheme which is used in GSM is GMSK which is based on MSK.MSK uses linear var. changes and is spectral efficient.Block diagram of GMSK generator both(prenominal) of the properties of the GMSK areImproved spectral efficiencyPower Spectral DensityReduced main lobe over MSKRequires more power to transmit data than many comparable modulation schemesBefore the GMSK can be explained, some fundamentals of Minimum Shift Keying (MSK) must be known.MSK (MINIMUM SHIFT-KEYING)MSK uses changes in phase to represent 0s and 1s, plainly unlike most other keying schemes we have guaranteen in class, the pulse sent to represent a 0 or a 1, not only depends on what information is being sent, but what was previously sent.Following is the pulse used in MSKWhereif a 1 was sentif a 0 was sentTo see how this works assume that the data being sent is 111010000, then the phase of the signal would fluctuate as seen belowIn order to see the signal constellation diagram consider the following equationswhic h can be simplefied aswhereandThus the equations for s1 and s2 depend only on andwith each taking one of two possible values. Therefore there are 4 different possibilitiestherefore the signal constellation diagram will beAdvantages of MFSKMSK produces a power spectrum niggardliness that menstruates off much faster compared to the spectrum of QPSK. While QPSK falls off at the inverse square of the frequency, MSK falls off at the inverse quartern power of the frequency. Thus MSK can operate in a smaller bandwidth compared to QPSKGMSK(GAUSSIAN-MINIMUM SHIFT-KEYING)Even though MSKs power spectrum density falls quite fast, it does not fall fast enough so that interference between adjacent signals in the frequency band can be avoided. To take care of the problem, the original binary star signal is passed through a Gaussian shaped trickle before it is modulated with MSK.The principle parameter in designing an appropriate Gaussian filter is the time-bandwidth product WTb.Following figur e shows the frequency response of different Gaussian filters.MSK has a time-bandwidth product of infinityAs can be seen that GMSKs power spectrum drops much quicker than MSKs. Furthermore, as WTb is decreased, the roll-off is much quickerIn the GSM standard a time-bandwidth product of 0.3 was chosen as a compromise between spectral efficiency and intersymbol interference. With this value of WTb, 99% of the power spectrum is within a bandwidth of 250 kHz, and since GSM spectrum is divided into 200 kHz channels for multiple access, there is very little interference between the channelsThe speed at which GSM can transmit at, with WTb=0.3, is 271 kb/s. It cannot go faster, since that would cause intersymbol interferenceCHAPTER 5FUTURE OF GSMThe strong demand for GSM is continuing. Today, GSM is used by 2.3 one million million million people worldwide and the strong growth is expected to be maintained. Most of the expansion occurs in high-growth markets, where the cost of mobile calls a nd terminals is crucial.With the success of GSM and to meet the demanding requirements of the subscribers,GPRS, HSCSD and EDGE has been introduced which stomach high data rates for the transmission. 3rd Generation (3G) systems will soon be introduced in Pakistan offering new and interesting services to the users and will mother internet to new levelsIn future strong focus of GSM operators will be on maintaining high quality of service, increasing usage and exploring new tax income streams on value added services, market visibility through various market initiatives to fulfill subscribers satisfaction and demand and above all to increase the value of enthronisation for the shareholders.MATLAB CODE(IMPLEMENTATION OF GMSK)clear allclose allDRate = 1 % data rate or 1 bit in one secondM = 18 % no. of sample per bitN = 36 % no. of bits for simulation -1818BT = 0.5 % Bandwidth*Period (cannot change )T = 1/DRate % data period , i.e 1 bit in one secondTs = T/Mk=-1818 % Chens values. More than needed% only introduces a little more delayalpha = sqrt(log(2))/(2*pi*BT) % alpha calculated for the gaussian filter responseh = exp(-(k*Ts).2/(2*alpha2*T2))/(sqrt(2*pi)*alpha*T) % Gaussian Filter receipt in time domainfigureplot(h)title(Response of Gaussian Filter)xlabel( Sample at Ts)ylabel( Normalized Magnitude)gridbits = zeros(1,36) 1 zeros(1,36) 1 zeros(1,36) -1 zeros(1,36) -1 zeros(1,36) 1 zeros(1,36) 1 zeros(1,36) 1 zeros(1,36)% Modulationm = filter(h,1,bits)% bits are passed through the all pole filter described by h, i.e bits are% shaped by gaussian filtert0=.35 % signal durationts=0.00135 % sample distribution intervalfc=200 % carrier frequencykf=100 % Modulation indexfs=1/ts % sampling frequencyt=0tst0 % time vectordf=0.25 % required frequency resolutionint_m(1)=0for i=1length(t)-1 % Integral of mint_m(i+1)=int_m(i)+m(i)*tsendtx_signal=cos(2*pi*fc*t+2*pi*kf*int_m) % it is frequency modulation not the phase modulating with the integral of the signalx = cos(2*pi*fc* t)y = sin(2*pi*fc*t)figuresubplot(3,1,1)stem(bits(1200))title(Gaussian Filtered Pulse Train)gridsubplot(3,1,2)plot(m(1230))title(Gaussian Shaped train)xlim(0 225)subplot(3,1,3)plot(tx_signal)title(Modulated signal)xlim(0 225)% Channel Equalization% commit CCASEDigital_Communicationprojectgmskalichannel.matload channel.math = channelN1 = 700x1 = randn(N1,1)d = filter(h,1,x1)Ord = 256Lambda = 0.98delta = 0.001P = delta*eye(Ord)w = zeros(Ord,1)for n = OrdN1u = x1(n-1n-Ord+1)pi = P*uk = Lambda + u*piK = pi/ke(n) = d(n) w*uw = w + K *e(n)PPrime = K*piP = (P-PPrime)/Lambdaw_err(n) = norm(h-w)endfiguresubplot(3,1,1)plot(w)title(Channel Response)subplot(3,1,2)plot(h,r)title(Adaptive Channel Response)rcvd_signal = conv(h,tx_signal)subplot(3,1,3)plot(rcvd_signal)title(Received Signal)eq_signal = conv(1/w,rcvd_signal)figuresubplot(3,1,1)plot(eq_signal)title(Equalizer Output)subplot(3,1,2)plot(eq_signal)title(Equalizer Output)axis(208 500 -2 2)subplot(3,1,3)plot(tx_signal,r)title(Modulated Sig nal)% Demodulationeq_signal1 = eq_signal(200460-1)In = x.*eq_signal1Qn = y.*eq_signal1noiseI = awgn(In,20)noiseQ = awgn(Qn,20)I = In + noiseIQ = Qn + noiseQLP = fir1(32,0.18)yI = filter(LP,1,I)yQ = filter(LP,1,Q)figuresubplot(2,1,1)plot(yI)title(Inphase Component)xlim(0 256)subplot(2,1,2)plot(yQ)title(Quadrature Component)xlim(0 256)Z = yI + yQ*jdemod(1N) = imag(Z(1N))demod(N+1length(Z)) = imag(Z(N+1length(Z)).*conj(Z(1length(Z)-N)))xt = -10*demod(1N/2length(demod))xd = xt(42length(xt))figurestem(xd)title(Demodulated Signal)OUTPUTSTABLE OF CONTENTSCHAPTER 1INTRODUCTIONCHAPTER 2GENERAL PROPERTIES OF GSMCHAPTER 3BACKGROUND OF GSMCHAPTER 4IMPLEMENTATIONMSKGMSKCHAPTER 5FUTURE OF GSMCHAPTER 6MATLAB IMPLEMENTATION