Chip-Spread CDMA Transmission: A Comparative Analysis

Abstract

In this paper a detailed study of an efficient transmission technique, recently proposed, which combines the single carrier (SC) block transmission, and the code division multiple access (CDMA), referred to as chip spread CDMA (CS-CDMA), is performed. The main feature of CS-CDMA is that, unlike the tradicional direct sequence (DS-CDMA) transmission system, the code orthogonality between users is maintained even when the transmissions, are made through a multipath frequency selective time-invariant channels. Thus, CS-CDMA allows the decoupling of user signals at the reception side. However, existing comparisons between CS-CDMA and DS-CDMA only consider the up-link scenario and particular conditions, which include orthogonal user codes and time invariant channels. In this scenario the CS-CDMA technique has shown a significant superiority when compared with the traditional DS-CDMA transmission. A detailed analisys of the CS-CDMA techique in more general conditions is presented in this work. We consider different environments such as, time invariant and time varying transmission channels, both orthogonal and non-orthogonal users' codes and up-link and down-link scenarios. We adopt frequency domain equalization with MMSE (Minimum Mean Squared Error) detection. Numerical results with performance comparisons indicate that, despite the effects of non-ideal conditions, CS-CDMA maintains a clear superiority over the DS-CDMA transmission.

Chip-Spread CDMA: uma variação da transmissão DS-CDMA extremamente eficiente como técnica de acesso múltiplo

“…Este artigo enfoca uma técnica que combina a transmissão em blocos com portadora única e a técnica de multiplexação CDMA. Esta combinação, referida como Chip-Spread Code Division Multiple Access (CS-CDMA) resulta em uma técnica diversa da tradicional DS-CDMA e apresenta sobre esta última diversas vantagens incluindo uma alta superioridade de desempenho [8], [9]. Como medida de eficácia desta técnica, é feita neste artigo uma comparação de desempenho com a técnica de múltiplo acesso Orthogonal Frequency Division Multiple Access (OFDMA) [10] indicada para a adoção nos sistemas 5G.…”

Orthogonal Multiple Access Schemes in Linear and Non-Linear Channels

“…When the environment is time-invariant and the codes are orthogonal, CS-CDMA can ideally detect in absence of MAI and the matrix is simplified to [24]. In this way, the detector does not need the information of the remaining users.…”