Noncoherent OSTBC-OFDM for MIMO and Cooperative Communications: Perfect Channel Identifiability and Achievable Diversity Order

Abstract

This paper considers the context of orthogonal space-time block coded OFDM (OSTBC-OFDM) without channel state information at the receiver. Assuming noncoherent maximum-likelihood detection, the interest herein lies in detection within one OSTBC-OFDM block, motivated by its capability of accommodating relatively fast block fading channels. Our investigation focuses on analysis aspects, where we seek to establish practical noncoherent BPSK/QPSK OSTBC-OFDM schemes that have provably good channel identifiability and diversity properties. We consider perfect channel identifiability (PCI), a strong condition guaranteeing unique noncoherent channel identification for any (nonzero) channel. Through a judicious design involving special OSTBCs and pilot placement, we propose an OSTBC-OFDM scheme that is PCI-achieving and consumes fewer pilots compared to conventional pilot-aided channel estimation methods. We further our analysis by showing that a PCI-achieving scheme also achieves maximal noncoherent spatial diversity for the Kronecker Gaussian spatial-temporal channel fading model, which covers the popular i.i.d. Rayleigh fading channel and a variety of correlated and sparse multipath channels. All these results are developed in parallel for the centralized point-to-point MIMO scenario and a distributed relay communication scenario. For the latter scenario, our diversity analysis shows that the PCI-achieving scheme can also achieve maximal noncoherent cooperative diversity. The performance merits of the proposed PCI-achieving scheme are demonstrated by simulations.

A Low Complexity Approach of Combining Cooperative Diversity and Multiuser Diversity in Multiuser Cooperative Networks

“…Thus the upper bound of the original network's outage probability is obtained by calculating the system outage probability of this special symmetric network using (24). Similarly, we can generate the second symmetric network where the source-to-relay links are guaranteed to have higher/equal qualities than/to the corresponding links in the original network, namely we have λ…”

Diversity Analysis for Relay-Assisted Distributed BICM-OSTBCOFDM System

“…In the first subsection, we review some transmission schemes reported in [14]- [16] that can guarantee unique data identification, i.e., guarantee the codeword c to be uniquely decoded by the noncoherent ML decoder (10) in the noise-free situation. In the second subsection, we present our main results on the diversity order of the noncoherent ML decoder (10).…”

“…The noncoherent techniques are appealing because they use only a few number of pilots, or even no pilot, for data detection and channel estimation, and thus have great potential for deployment under fast time-varying channels. However, most of the existing works focus on two separate scenarios, namely, coded flat-fading space-time systems (no OFDM) [9]- [11] and uncoded OSTBC-OFDM systems (no channel coding) [12]- [16]. While it is possible to extend the works in [9], [10] to coded OSTBC-OFDM by considering each OFDM subcarrier as an individual flat-fading channel, such natural extension requires the channel to remain static over a large number of OFDM blocks.…”

“…Another noncoherent approach is to employ differential space time coding schemes, e.g., [11]; however they suffer from a 3 dB signal-to-noise ratio (SNR) loss compared to the coherent receiver. In our previous works in [14]- [16], a noncoherent OSTBC-OFDM detection method based on the deterministic DF relay based technique was proposed. It was shown that this noncoherent detection method can exhibit near-coherent performance using only one OSTBC-OFDM block, thus appealing for fast time-varying channels.…”

“…Firstly, like most of the noncoherent methods, the presented DF relay based technique can be subject to the data ambiguity problem in the noise-free situation. We review some of the transmission schemes reported in [14]- [16], which can be directly used for the considered distributed BICM-OSTBC-OFDM system for unique codeword decoding; e.g., the pilot-efficient perfect channel identifiability (PCI) achieving schemes [15], [16]. Secondly, we analyze the diversity order of the noncoherent ML decoder.…”