We consider a general M-ary detection problem where, given M groups of L samples each, the problem is to identify which unique group of L samples have come from the signal hypothesis. The optimal likelihood ratio test is unrealizable, when the joint distribution of M L samples is not completely known. We consider two rank order types of tests termed the modified rank test (MRT) and the modified rank test with row sort (MRTRS). We examine through simulation, the small sample probability of error performances of MRT and MRTRS for detecting a signal among contaminants. Numerically comparable closed-form error expressions are derived for some special cases. The asymptotic (large sample) error rate of the MRT is also derived. The results indicate that MRTRS provides improved performance over other previously known rank tests.

This paper presents a rate 16/17 "punctured" time varying maximum transition run (PMTR) block code. It is not possible to achieve a rate 16/17 or higher TMTR block code which completely suppresses the minimum distance error event. However, it is in general, possible to make a tradeoff between obtaining higher code rates and coding gain by puncturing; the space of codewords and limiting the extent to which the minimum distance error event is suppressed. As an example, we obtain a rate 16/17 block code where the minimum distance error event is supported in only 6 out of the 17 possible codeword locations. An implementation of the code is presented and simulation results examining the performance benefits under different conditions are also presented.

This paper analyses a few schemes for combining base station antenna array signals in wireless DS/CDMA. The performances of equal gain combining (EGC), likelihood rank test (LRT) and a modified rank test (MRT) are evaluated using simulation studies. The results indicate that, under certain assumptions on the multiple access interference statistics, the probability of error of the MRT is lower than that of EGC, if a few high power interfering users are present along with a low power user of interest. If there are a moderately large number of users and if the received power of all the users are nearly the same, then EGC outperforms the MRT. In fact, under this condition, the performance of EGC is close to that of the optimal likelihood ratio test.