Frequency-hopped multiple-access communication with nonorthogonal BFSK in rayleigh fading channels

Abstract

In this thesis, we analyze the performance of a FHMA communication system employing nonorthogonal BFSK modulation in Rayleigh fading channels to assess the usefulness of nonorthogonal BFSK modulation in FHMA communication system. In general, as the tone spacing between two BFSK signals decreases, the system is more vulnerable to background noise, but the required bandwidth for modulation decreases. Therefore, for a given bandwidth, decreasing the tone spacing allows more bandwidth for processing gain (number of frequency slots) and channel coding. Increasing the number of frequency slots or decreasing the code rate allows the system to be more robust to multiuser interference (hit). Therefore, we expect there exists optimum relations among the tone spacing, code rate, and the number of frequency slots. The pulse shaping is an important factor which affects the correlation, and we take it into account to the performance analysis, and also consider the side information. In frequency hopping system, the perfect side information is often assumed, where the receiver knows the existence of multiple-access interference and erases corresponding received signals. In addition, the ratio-threshold-test (RTT) is known as an imperfect but indeed reliable and simple erasure generation method, where the demodulated bit is erased if the ratio of the second largest to the largest decision variables is larger than a threshold. We consider the perfect side information and RTT and analyze the performace. In FHMA communication system employing nonorthogonal BFSK modulation and Reed-Solomon code assuming that the receiver has perfect side information, we examine the effects of tone spacing of BFSK signals on the normalized throughput of a FHMA system. We exmaine the optimum relations among tone spacing, code rate, and processing gain which maximize the normalized througput. In FHMA communication system employing nonorthogonal BFSK modulation and binary BCH code with RTT, we derive...