|Title:||Computer simulation of [pi]/4 DQPSK and GMSK modulation techniques in mobile cellular CDMA system|
|Subject:||Mobile communication systems|
Hong Kong Polytechnic -- Dissertations
|Department:||Department of Electronic Engineering|
|Pages:||viii, 75 leaves : ill. ; 31 cm|
|Abstract:||A software simulation technique that conducts bit-by-bit error simulation for a mobile cellular code division multiple access (CDMA) system is described in this paper. It mainly predicts the average BER (bit error rate) for π/4-DQPSK and GMSK modulation techniques in a flat slow fading channel with multiple access interference. The simulator also anticipates the number of users (channel capacity) that can be accommodated in this system in accordance with the interference that is generated by other users. We use a step-by-step approach to verify various system components in the simulation. The modulation techniques are thoroughly tested consecutively in additive white Gaussian noise (AWGN), flat slow fading channel, spread spectrum, and multiple access system to verify the performance with those in various presented papers. We can show the processing gain of the spread spectrum technique by comparing the results to that of without using spread spectrum. It also shows the application of this technique for multiple access through the simulation. The relationship between the interference and the number of users that can be accommodated in a CDMA system is also simulated and tested. It shows that the number of users or system capacity depends on the interference, and the performance will be scarified if more users are added in the system. This soft capacity makes CDMA more promising for multiple access in mobile systems than other common techniques such as frequency division multiple access (FDMA) or time division multiple access (TDMA). The simulation shows that the system capacity is about 900 users for a bandwidth of 8 MHz, assuming 35% voice activity cycle and a cell reuse pattern. This is equivalent to about 112.5 users/MHz (number of users/bandwidth), which is about four times of that of TDMA (25 users/MHz) and twenty three times of that of FDMA (4.8 users/MHz). CDMA is therefore very promising in next generation of cellular technology.|
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