A multiuser approach to narrowband cellular communications

We compare three receivers for coded narrowband transmission over a channel with fading, shadowing , and co-channel interference. The baseline receiver includes conventional diversity reception with maximal-ratio combining. A multiuser approach allows us to derive a maximum-likelihood (ML) multiuser diversity receiver and its reduced-complexity suboptimal version. Finally, a decor-relating diversity receiver, which seeks a trade-oo between performance and complexity, is also studied. We consider a channel model including diversity, fading, shadowing, and interference. This can be applied, for example, to a macro-cellular wireless system with space (antenna), time, or frequency diversity. Since the shadowing process is assumed to vary slowly with respect to the transmission duration, the bit error rate should be treated as a random variable depending on the useful and interfering signal energies, which in turn depend on the shadowing process realization. This leads us to a deenition of outage probability. We call a receiver shadowing-resistant if its outage probability can be made arbitrarily small by increasing the average signal power. In other words, a shadowing-resistant receiver is one that does not suuer from error-oor eeects due to interference and fading. We prove that conventional reception is shadowing-resistant in the limit as the diversity order grows to innnity, while it is not for any nite diversity order. Further, we show that the error oor of coded transmission with conventional reception depends exponentially on the product of the diversity order and of the minimum Hamming distance of the code (\code diversity"). We also prove that the ML multiuser receiver is shadowing-resistant for any diversity order, while the decorrelating receiver is shadowing-resistant only if the diversity order is larger than the number of interferers. A comprehensive error-probability analysis for coded PSK transmission is derived for all the receivers examined here.