Narrow band modulation and coding schemes for radio LAN

The paper considers the performance of narrow-band modulation schemes on the indoor radio channel, such as occurs in radio LAN systems. This channel is subject to i.s.i. due to multipath, which limits the maximum data rate. The paper proposes narrow-band modulation and coding to reduce the symbol rate. The paper compares the performances of multilevel signalling constellations of different rates, and shows that the intersymbol interference and hence the irreducible error rate floor are reduced by higher rate multilevel modulation as compared with QPSK, provided the signalling pulse width, and therefore the signal bandwidth, is kept constant. It is also shown that diversity techniques are important in the indoor communications scenario