Improved Throughput over Wirelines with Adaptive MC-DS-CDMA

In this paper, we present a finite-granularity loading algorithm for multicarrier direct sequence code division multiple access (MC-DS-CDMA). The resulting adaptive scheme represents an extension of classical digital multitone (DMT) with spreading in the time domain. The presented algorithm assigns subcarriers, spreading codes, bits and energy per code in order to maximize the data rate in a single user network, or to maximize the minimum data rate in a multiuser network. The optimization is realized at a target symbol error rate and for a given power spectral density (PSD). Optimal allocation is performed through analytical study, and simulation results of the new scheme are presented in single user digital subscriber line (DSL) and multiuser power line communication (PLC) contexts. Compared to DMT, it is shown that the time spreading component of MC-DS-CDMA system yields throughput improvement against a weak increase of complexity