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During the initial uplink synchronization, the BS communicates with MSs to adjust timing and power offsets. The common method to achieve the objective is to use the orthogonal code in the frequency domain for OFDMA systems. Due to the timing offset, the orthogonality of codes is decayed and multiple access interference (MAI) becomes serious. In order to decrease this influence, we proposed the idea...
This paper investigates multiuser detection technology for time hopping (TH) ultra-wideband (UWB) systems to cancel the multiple access interference (MAI) from desired signal. To reduce MAI, three interference cancellation schemes are employed: successive interference cancellation (SIC), successive interference cancellation with the maximum ratio (SIC-MR) and iterative interference cancellation with...
The performance of multiple access interference (MAI) cancellations for the asynchronous M-ary pulse position modulation (PPM) time hopping (TH) ultra-wideband (UWB) systems are investigated. Parallel interference cancellation (PIC) and successive interference cancellation (SIC) are the most popular interference cancellation schemes. However, both the PIC and SIC have some shortcomings that the PIC...
A turbo principle based iterative multiuser detection is proposed to reduce the BER in LDPC coded FFH/MFSK MA systems. First, a three-level hard-limiter on each chip with maximum-likelihood decision is made to avoid soft output ambiguity. Secondly, the reliable information from channel decoder is applied to aide multiuser interference reduction. When the soft reliability information of coded bit exceeds...
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