Full diversity space time block codes with improved power distribution characteristics

Abstract

In this paper, we introduce a technique for improving power distribution characteristics of space time block codes (STBCs) which include peak to average power ratio (PAPR), average to minimum power ratio (Ave/min), and probability of transmitting “zero” by antenna. We consider STBCs in multiple input multiple output (MIMO) and multiple input single output (MISO) systems that achieve full diversity for linear or maximum likelihood (ML) receivers. It is proved that by multiplying a specific non-singular square matrix by the code matrix, a new code is obtained that achieves full diversity and the power distribution characteristics are improved. The proposed technique is general can be applied to any type of full diversity STBCs such as Toeplitz codes, orthogonal STBCs (OSTBCs), overlapped Alamouti codes (OACs), group orthogonal Toeplitz codes (GOTCs), and embedded Alamouti codes (EACs), and can ease their practical implementation. We systematically present closed-form expressions for the matrices multiplied by Toeplitz codes, OACs, and EACs. Because of the existence of these codes for any number of antennas, the closed-form can be used in 5G which needs huge number of antennas. The performance of the proposed technique is evaluated in terms of bit error rate (BER) and power distribution characteristics. The introduced method provides a trade-off between PAPR, Ave/min, probability of transmitting zero, and BER, to cope with the practical requirements. We also investigate the effect of the proposed method on the PAPR of output signal of shaping filter which is referred to as analog domain PAPR. The results indicate the efficiency of the introduced technique. The proposed method can balance the tradeoff between PAPR, spectral efficiency, and BER.