Implementation and simulation of maximum likelihood receiver for complememtary code keying

Abstract

A wireless local area network (WLAN) is a flexible data communication system which extends or alternates a wired LAN in an office, a library or a laboratory. WLAN transmits and receives data over the air, minimizing the necessity for wired connections. Recently, a higher data rate is demanded in WALN. To meet this demand, Harris and Lucent proposed complementary code keying (CCK) as a high data rate WLAN waveform. In July 1998, the 802.11 working group adopted CCK as the basis for the high rate physical layer extension to deliver data at the rate of 11Mbit/s at 2.4 GHz ISM band. This thesis is concerned with the transmission of 11Mbit/s / transmitted. CCK waveform. The code, which is a subset of complementary codes based on generalized Walsh-Hadamard encoding, is generated and then modulated into DQPSK waveform before transmitted. There are two methods (Optimal and Sub-optimal) of decoding. The sub-optimal decoder consists of a series of phase detectors which show theoretically 3dB degradation compared to the optimal decoder. The optimal decoder is a maximum likelihood decoder, which consists of correlators. In this thesis, the receiver is implemented according to the maximum likelihood decoding. The maximum likelihood decoding is composed of M correlators; where M is the number of possible code sets. Each correlator attempts to match received signals with each of the candidate prototype waveforms. Signal Processing WorkSystem, a high-level simulation language, was used to simulate the total transceiver system in order to evaluate the performance of the receiver, The transmitter of the simulation model consists of a random source block, a serial to parallel block, a phase calculator block, a CCK code generate block, a mapper block, an up-sample block, and a square root raised cosine shapping filter block. The receiver also consists of a matched filter, a down-sample block, a decision device block, and a CCK decoder block. The bit error rate (BER) was me...