[Show abstract][Hide abstract] ABSTRACT: To further suppress the multiple-access interference (MAI) in frequency-hopping multiple-access (FNMA) system, a novel kind of FH sequence set named as no-hit-zone (NHZ) sequence, is proposed for an FHMA system with M-ary FSK modulation (MFSK/FHMA) in this paper. Expressions for the decision variables are derived for the asynchronous MFSK/FHMA system with NHZ sequence set (MFSK/FHMA-NHZ) under a slow Rayleigh-fading channel model. For the special case of M=2, accurate analytic bit error rate (BER) is derived as a function of maximum relative delay D and the number of users K by a characteristic function method. The theoretical results validated by Monte Carlo simulations are used to investigate the dependence of the average BER on D and K. Comparison with the MFSK/FHMA system with Markov hit pattern (MFSK/FHMA-Markov) shows that MFSK/FHMA-NHZ system performs better than Markov hit pattern system as long as D is restricted in a certain range and further, the gain in the performance increases with increase in the value of K.
No preview · Article · Feb 2011 · IEICE Transactions on Communications
[Show abstract][Hide abstract] ABSTRACT: In this paper, the effect of multipath fading on the orthogonality of FH/MFSK communication systems is analyzed. A general expression of the orthognality loss factor D<sub>jn</sub> is derived for the case of multipath Rayleigh fading. Based on the expression, it is shown that the D<sub>jn</sub> is determined not only by the multipath delays, signal strength fading and synchronization time error, but also by the phase variations caused by multipath time delays. Numerical results demonstrate that the effects vary with different phase variations. This result will further affect BER performance of FH/MFSK systems.
[Show abstract][Hide abstract] ABSTRACT: Based on the concept of the zero correlation zone (ZCZ), a class of frequency hopping (FH) sequences with the defined no hit zone (NHZ) property is presented. The NHZ FH spreading code sequences obtained are derived by mapping from the known ZCZ sequences, and may find applications in frequency-hopped CDMA systems to reduce or eliminate multipath and inter-user interferences.