On Approximated LLR for Single Carrier Millimeter-Wave Transmissions in the Presence of Phase Noise

Makoto NISHIKORI  Shinsuke IBI  Seiichi SAMPEI  

IEICE TRANSACTIONS on Communications   Vol.E100-B    No.7    pp.1086-1093
Publication Date: 2017/07/01
Publicized: 2017/01/12
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2016SCP0003
Type of Manuscript: Special Section PAPER (Special Section on Smart Radio and Its Applications in Conjunction with Main Topics of SmartCom)
Category: Wireless Communication Technologies
log likelihood ratio,  phase noise,  millimeter wave,  single carrier,  frequency domain equalizer,  

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This paper proposes approximated log likelihood ratios (LLRs) for single carrier millimeter-wave (mmW) transmission systems in the presence of phase noise. In mmW systems, phase noise on carrier wave signals in very high frequency bands causes severe performance degradation. In order to mitigate the impairments of phase noise, forward error correction (FEC) techniques, such as low density parity check (LDPC) code, are effective. However, if the probabilistic model does not capture the exact behavior of the random process present in the received signal, FEC performance is severely degraded, especially in higher order modulation or high coding rate cases. To address this issue, we carefully examine the probabilistic model of minimum mean square error (MMSE) equalizer output including phase noise component. Based on the derived probabilistic model, approximated LLR computation methods with low computational burden are proposed. Computer simulations confirm that the approximated LLR computations on the basis of the derived probabilistic model are capable of improving bit error rate (BER) performance without sacrificing computational simplicity in the presence of phase noise.