Channel overloading in multiuser and single-user communications

Abstract

This paper gives an overview of a previously introduced channel overloading concept that is applicable to both multiuser communications and single-user communications. We first describe it for multiuser communications using a hybrid multiple access scheme based on a combination of time-division multiple access (TDMA) and code-division multiple access (CDMA). Next, we extend it to full CDMA by defining two sets of orthogonal signal waveforms. Using a binary phase-shift keying (BPSK) modulation, it is shown that this multiple access concept can increase the number of users by 40% with respect to the hard limit of orthogonal waveform multiple access (OWMA) which includes TDMA, orthogonal CDMA (OCDMA), and orthogonal frequency-division multiple access (OFDMA). Then, we apply the same concept to single-user communications to transmit an excess bit rate in addition to the primary data rate. It is shown that an excess data rate of up to 25% can be transmitted at the price of a very small penalty in signal-to-noise ratio (SNR).