Performance Improvement by Local Frequency Offset Spatial Diversity Reception with π/4-DQPSK in Implant Body Area Networks

Daisuke ANZAI
Takashi KOYA
Jingjing SHI
Jianqing WANG

IEICE TRANSACTIONS on Communications   Vol.E97-B    No.3    pp.571-578
Publication Date: 2014/03/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E97.B.571
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Information and Communication Technology for Medical and Healthcare Applications in Conjunction with Main Topics of ISMICT2013)
local frequency offset diversity,  π/4-DQPSK,  bit error rate,  link budget,  

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Space diversity reception is well known as a technique that can improve the performance of wireless communication systems without any temporal and spectral resource expansion. Implant body area networks (BANs) require high-speed transmission and low energy consumption. Therefore, applying spatial diversity reception to implant BANs can be expected to fulfill these requirements. For this purpose, this paper presents a local frequency offset diversity system with π/4-differential quadrature phase shift keying (DQPSK) for implant BANs that offer improved communication performance with a simpler receiver structure, and evaluates the proposal's bit error rate (BER) performance by theoretical analysis. In the theoretical analysis, it is difficult to analytically derive the probability density function (pdf) on the combined signal-to-noise power ratio (SNR) at the local offset frequency diversity receiver output. Therefore, this paper adopts the moment generating function approximation method and demonstrates that the resulting theoretical analyses yield performances that basically match the results of computer simulations. We first confirm that the local frequency offset diversity reception can effectively improve the communication performance of implant BANs. Next, we perform an analysis of a realistic communication performance, namely, a link budget analysis based on derived BER performance and evaluate the link parameters including system margin, maximum link distance and required transmit power. These analyses demonstrate that the local frequency offset diversity system can realize a reliable communication link in a realistic implant BAN scenario.