Abstract
In wireless communications, multicarrier direct-sequence code-division multiple access (MC DS-CDMA) constitutes one of the highly flexible multiple access schemes. MC DS-CDMA employs a high number of degrees-of-freedom, which are beneficial to design and reconfiguration for communications in dynamic communications environments, such as in the cognitive radios. In this contribution, we consider the multiuser detection (MUD) in MC DS-CDMA, which motivates lowcomplexity, high flexibility, and robustness so that the MUD schemes are suitable for deployment in dynamic communications environments. Specifically, a range of low-complexity MUDs are derived based on the zero-forcing (ZF), minimum mean-square error (MMSE), and interference cancellation (IC) principles. The bit-error rate (BER) performance of the MC DS-CDMA aided by the proposed MUDs is investigated by simulation approaches. Our study shows that, in addition to the advantages provided by a general ZF, MMSE, or IC-assisted MUD, the proposed MUD schemes can be implemented using modular structures, where most modules are independent of each other. Due to the independent modular structure, in the proposed MUDs one module may be reconfigured without yielding impact on the others. Therefore, the MC DS-CDMA, in conjunction with the proposed MUDs, constitutes one of the promising multiple access schemes for communications in the dynamic communications environments such as in the cognitive radios.
Highlights
There has been an increasing interest in cognitive and software defined radios in both the research and industry communities, as is evidenced, for example, by [1,2,3,4] as well as by the references in them
The parameters shown in the figures are summarized as follows: (i) SNR per bit: signal-to-noise ratio (SNR) per bit; (ii) Ne: T domain spreading factor per subcarrier; (iii) p: number of subcarriers conveying a data bit; (iv) K: number of users supported by the MC DS-code-division multiple access (CDMA)
In this contribution a range of low-complexity, high-flexibility, and robust multiuser detection (MUD) schemes have been derived for the MC DS-CDMA, which constitutes a multiple access scheme suitable for operation in dynamic communications environments
Summary
There has been an increasing interest in cognitive and software defined radios in both the research and industry communities, as is evidenced, for example, by [1,2,3,4] as well as by the references in them. Multiuser detection (MUD) in the context of various multicarrier CDMA schemes has been widely investigated, as seen, for example, in [17,18,19,20,21] This contribution motivates low-complexity, high-reliability, and low-sensitivity MUD in the MC DS-CDMA operated under the cognitive radio. This is because in a highly dynamic wireless communications environment, such as in cognitive radio, low-complexity, high-reliability, and robustness to imperfect knowledge due to, for example, channel estimation error are extremely important. In this contribution we investigate the zero-forcing MUD (ZF-MUD) and minimum mean-square error MUD (MMSE-MUD) in the MC DS-CDMA systems.
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