Soft-Input Soft-Output Non-Coherent Detection for Differential Space-Time Block Code Systems

Abstract

A soft-input soft-output non-coherent detection algorithm is proposed for multi-antenna systems, where differential space-time block code is employed. The proposed algorithm aims to calculate a posteriori probabilities of the information bits by means of forward and backward message passing of the BCJR approach. The proposed algorithm can exploit the soft information effectively with the aid of the bidirectional message passing mechanism. In addition, the proposed algorithm can be exploited in conjunction with channel decoding to obtain an effective iterative detection and decoding approach. In view of low implementation complexity, the application of the proposed scheme is instantiated with the ultra-wideband impulse radio (UWB-IR) systems. Simulations show that the proposed approaches improve detection performance for UWB-IR systems.Index Terms-Differential space-time block code (DSTBC), soft-input soft-output (SISO), non-coherent detection, a posteriori probabilities (APP).

New techniques for orientational beamforming systems

“…Optimal coherent receivers have been extensively developed [50][51][52][53][54][55][56][57][58][59][60], which assume perfect channel state information (CSI) at the receiver. To avoid tedious channel estimation and reduce receiver complexity, differential spacetime modulation and detection schemes have been well-explored for conventional MIMO systems [61][62][63][64][65][66][67][68][69][70][71][72][73][74]. Different from conventional MIMO systems adopting STC techniques, the OBF system utilizes the array orientational dimension of the spatial domain to increase channel capacity.…”

“…Pseudo-random arrays are to ensure the direction-independent characteristic of the OBF system, while identical antenna positions in the transmitter and receiver guarantee the in-phase arrival of desired signals at receiving antennas when the LOS paths between matched transmitting and receiving antennas exist. For MIMO systems with STCs, signals passing through all the 𝑀 𝑡 × 𝑀 𝑟 channels between the 𝑀 𝑡 transmitting antennas and 𝑀 𝑟 receiving antennas contribute to the detection with either coherent receivers based on perfect CSI [58][59][60] or differential receivers corresponding to differential modulation [69][70][71][72][73][74]. With perfect CSI or differential detection schemes, the MIMO system is able to work well in both the LOS and NLOS environments.…”

“…In these detection schemes, differentially encoded symbols are decoded by observing the difference between the signals received in two consecutive symbol durations. It is only very recently that these techniques have been introduced to the UWB MIMO system [69][70][71][72][73][74]. In view of the common feature of the UWB OBF system and the UWB MIMO system with differential detection that they both work without the need of the CSI, we briefly compare them in this chapter.…”

“…More recently, a non-coherent detection method based on the a posteriori probability has been proposed [73,74]. Although it can provide slightly better performance than the GLRT-based methods under high SNRs, its iterative decoding process leads to increased implementation complexity.…”

“…In the afore-mentioned differential detection schemes for UWB MIMO systems based on DSTBC [70][71][72][73][74], the size of the codebook increases exponentially with the number of transmitting antennas. Consequently, the decoding complexity also increases exponentially.…”