Cdma

rochester institute of technology | DS-CDMA PROJECT | Communications Systems | | 11/4/2012 |

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TABLE OF CONTENTS

1. Introduction3
Spread Spectrum4
Pseudo Noise Codes4
Properties of PN Sequence5
Walsh Code5-6 2. Main Block Diagram (Receiver Side)7
Despreader7-8
RAKE Receivers and Constellations8-10
Channel Estimator and Signal Decoder10
Multi-User Detector/Interference Canceller11
Wideband SIC11-12
Narrowband SIC12
Decoders13
Viterbi Decoder13
Turbo Decoder13
Parallel Correlator14
Demodulation Process14-16
Pulse Shape Usage17
Multi-antenna Technology17-18
Conclusion19
3. References20-21

INTRODUCTION
As the telecommunications industry faced a huge development in the last couple of decade, the demand for bandwidth has extremely grown up. The bandwidth demand pushed and stimulated a need for protocols that would increase the bandwidth efficiency. The multiple accesses combine many signals to one single communications channel. Basically, there are three types of division-based protocols which are: FDMA, TDMA and CDMA. Frequency Division Multiple Access (FDMA) – is a frequency based multiple access where the channel is the frequency. In other words, the signals in FDMA are assigned frequency channels. Time Division Multiple Access (TDMA) – divides the frequency channels into slots, so that two or more users are able to use the same frequency band. In this case, each user is assigned different time slot. Code Division Multiple Access (CDMA) – in CDMA the users are assigned different random binary sequence codes which modulates the carrier by spreading the spectrum of the waveform and assigning users with unique code