Power Control of Turbo Coded System in Lognormal Shadowing Channel

Sung-Joon PARK  

IEICE TRANSACTIONS on Communications   Vol.E91-B    No.4    pp.1149-1152
Publication Date: 2008/04/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.4.1149
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Fundamental Theories for Communications
power control,  turbo code,  power truncation,  channel estimation error,  

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Traditionally, it has been considered that the received signal to noise power ratio should be uniformly preserved to maximize system capacity for uncoded system with reliable feedback channel. However, once channel coding is employed as a building block, another power control scheme presents better performance. In this paper, we consider several power reallocation schemes for an effective use of limited power in a turbo coded system in lognormal shadowing channel. We show that the proposed power reallocation can reduce the decoding error probability by almost two orders of magnitude and provide a power gain of 0.87 dB at a target bit error rate of 10-4 over the equal power allocation among all code symbols. We also propose applying different power levels and cut-off thresholds on systematic and parity bits, and investigate the effect of channel estimation error.