| On the way towards third generation personal communication networks (PCN) the deployment of 16-level quadrature amplitude nlodulation (QAW schemes is investigated via flat microcellular Rayleiph-fading mobile radio channels having mild co-channel interference with and without diversity. Our proposed differentially coded non-coherent 16-QAM scheme requires no pilot symbol assistance, no automatic gain control (AGC) and no carrier recovery. High speech quality associated with a mean opinion score of about four (MOS = 4.0) is ensured at a signalling rate of 6.2 kBd for channel signal to noise ratios (SNR) above 30 - 25 dB and signal to interference ratios (SIR) above 75 - 30 dB by the 13.4 kbit/s medium complexity resular pulse excited (RPE) speech codec, when carefully matched twin-class low complexity binary Bose-Chaudhuri-Hocquenghem (BCHI error correction coding and 16-QAM combined with second order diversity are deployed. The overall speech delay is about 40 ms and the user bandwidth is 9.3 kHz, which allows us to accommodate 21 users in a 300 kHz channel slot. |
