A multi-levelled OFDM-CDMA modem using complete complementary codes

Abstract

In this paper, we introduce a novel multiple access scheme based on a combination of a multi-levelled modem and multi-carrier techniques with the use of complete complementary codes. This modulation technique combines a multi-dimensional code division multiple access (CDMA) modem with recent designs of perfectly complete complementary orthogonal codes. The rotational properties of the spreading codes are further exploited to improve the modulation technique, throughput, spectral efficiency, and capacity. Additionally, the system is extended by making use of multiple carrier frequencies as in OFDM, with the additional benefits of being able to spread data in frequency and/or in time. The modem offers multiple access interference MAI-free and multipath interference MI-free operation in both asynchronous and synchronous communication, due to perfect autocorrelation and zero cross-correlation properties of the spreading codes. The unique multi-levelled multiple access modulation technique together with the integration of complete complementary codes, produces a spectrally efficient output signal with high data throughput rates, better noise tolerances in harsh channel conditions and an increased user capacity.