Abstract
Radio networks for future mobile communications systems, for example, 3GPP Long-Term Evolution (LTE), are likely to use an orthogonal frequency division multiplexing- (OFDM-) based air interface in the downlink with a frequency reuse factor of one to avoid frequency planning. Therefore, system capacity is limited by interference, which is particularly crucial for mobile terminals with a single receive antenna. Nevertheless, next generation mobile communications systems aim at increasing downlink throughput. In this paper, a single antenna interference cancellation (SAIC) algorithm is introduced for amplitude-shift keying (ASK) modulation schemes in combination with bit-interleaved coded OFDM. By using such a transmission strategy, high gains in comparison to a conventional OFDM transmission with quadrature amplitude modulation (QAM) can be achieved. The superior performance of the novel scheme is confirmed by an analytical bit-error probability (BEP) analysis of the SAIC receiver for a single interferer, Rayleigh fading, and uncoded transmission. For the practically more relevant multiple interferer case we present an adaptive least-mean-square (LMS) and an adaptive recursive least-squares (RLS) SAIC algorithm. We show that in particular the RLS approach enables a good tradeoff between performance and complexity and is robust even to multiple interferers.
Highlights
Generation mobile communications air interfaces, such as 3GPP Long-Term Evolution (LTE) [1] or WiMax [2], will employ orthogonal frequency division multiplexing (OFDM) for transmission in the downlink
We present a zero-forcing (ZF) approach, the analytical minimum mean-squared error (MMSE) solution, and adaptive approaches which are based on the leastmean-square (LMS) and the recursive least-squares (RLS) algorithm, respectively
In order to support the simulation results for the adaptive single antenna interference cancellation (SAIC) algorithm for coded and bit-interleaved OFDM transmission, we provide an analysis of the raw bit-error probability (BEP) of both schemes before channel decoding
Summary
Generation mobile communications air interfaces, such as 3GPP Long-Term Evolution (LTE) [1] or WiMax [2], will employ orthogonal frequency division multiplexing (OFDM) for transmission in the downlink. We propose an SAIC algorithm for OFDM transmission, extending the approach in [13,14,15], referred to as mono-interference cancellation (MIC) to the downlink of an OFDM based air interface For this scheme, realvalued amplitude-shift keying (ASK) modulation is used and additional channel coding is considered. We show that the improved possibilities for interference suppression in case of real-valued symbols more than compensate for the loss in power efficiency and even significant gains are possible in an interference limited environment with respect to a conventional OFDM scheme employing coded QAM modulation with the same spectral efficiency. MUD seems to be prohibitively complex for mobile terminals, assuming spectrally efficient OFDM transmission For these reasons, we do not consider interference suppression for conventional QAM transmission as this can be accomplished only by MUD or SIC for a single receive antenna.
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