Isometric Data Sequences during Joint Channel Estimation and Symbol Detection in Fading Channels

摘要

Due to the multiplicative nature of fading and rotational invariance of PSK constellation, detection schemes cannot differentiate phase-rotated versions of the transmitted symbol sequence. These sequences, called isometric sequences, result in detection errors and irreducible bit error rates. To combat isom-etry, one can employ extra knowledge of the channel, which is not readily available, or pilot symbols, which reduces the effective transmission rate. This paper analyses the problem of isometry, discusses the design of asymmetric signal constellations, and illustrates analytically and experimentally how the use of asymmetric signal constellations for initial symbols improve the system performance without incurring significant complexity.