An excess signaling concept with Walsh-Hadamard spreading and joint detection

We present a new signaling concept which consists of transmitting an additional data rate to the original data rate that is determined by the channel bandwidth, the modulation scheme, and other physical-layer functions of the transmission system. This is accomplished by overlaying M excess symbols to each block of N primary symbols, with the excess symbol period being equal to N times the primary symbol period. The resulting interference between primary and excess symbols is handled using a joint symbol detection technique. Our analysis shows that for BPSK or QPSK modulation and M=1 or M=3, transmission of the excess data rate does not degrade minimum Euclidean distance when the excess symbol ratio M/N does not exceed 25%. Furthermore, our simulation results indicate that at bit error rate (BER) values in the order of 10 to 10, transmission of the additional data in these cases is achieved at the expense of a moderate to very small penalty in signal-tonoise ratio (SNR).