Unified Multiple-Access Performance Analysis of Several Multirate Multicarrier Spread-Spectrum Systems

A unified multiple-access performance analysis and comparison of three multicarrier spread-spectrum multiple-access schemes, namely, mc-cdma (multicarrier code-division multiple-access), mc-fh (multicarrier frequency hopping) and a hybrid of the above systems, called ds-mc-fh (direct-sequence mc-fh), in a multirate environment, where each user can have several multirate services, is provided. in mc-cdma and mc-fh systems, users and their diverse services are differentiated by means of only one kind of signature code. however, in a ds-mc-fh scheme, different users and different services of the same user are distinguished through the first and second signature codes, respectively. the performance of the above systems are evaluated and compared, using a unified structure in synchronous and asynchronous nonfading and synchronous correlated rayleigh fading channels, with a maximum-ratio combining (mrc) receiver. the near-far effect on the systems' performance is also investigated. the (second) signature in the mc-cdma (ds-mc-fh) scheme is considered to be either a pseudo-noise (pn) sequence or a walsh code. the authors analyses indicate that mc-cdma systems with walsh codes outperform the other schemes in different synchronous and asynchronous channels. ds-mc-fh systems with walsh codes always surpass mc-fh systems. furthermore, all of the schemes, except synchronous mc-cdma systems with walsh codes, are susceptible to a near-far effect with an mrc receiver