High-quality subchannel for wireless ATM transmission

We propose a new, highly efficient transmission method based on a multidimensional, dual-level coded modulation technique for wireless asynchronous transfer mode (ATM) networks. The first level is coded with a repetition code, the second level with a convolutional code of rate k/n. By employing unequal error protection (UEP), two different channel qualities are provided: a main channel, or the second level, for the ATM payload, and a subchannel, or the first level, for the ATM header. Combining this method with a spread spectrum code division multiple access (SS-CDMA) system provides good performance for degraded channel-quality mobile communication environments. A Viterbi decoder (R=1/2, K=7) accomplished maximum likelihood decoding and the transmission was judged by its bit-error-rate (BER) performance. The BER for the subchannel was reduced by a factor of one thousand (compared to the main channel) at a very low signal-to-noise ratio, when the forward-error-correcting code (FEC) is less effective