MIMO slotted ALOHA systems with collision resolution and truncated HARQ transmission and combining

• Published in: Annales des télécommunications Vol. 71; no. 3-4; pp. 157 - 171
• Main Authors: Missaoui, Nejah, Kammoun, Ines, Siala, Mohamed
• Format: Journal Article
• Language: English
• Published: Paris Springer Paris 01.04.2016
• Subjects: Circuits; Communications Engineering; Computer Communication Networks; Engineering; Information and Communication; Information Systems and Communication Service; Networks; R & D/Technology Policy; Signal,Image and Speech Processing; Throughput; Space-time coding; Slotted ALOHA; Successive interference canceller; Spatial multiplexing; Multi-user detection
• ISSN: 0003-4347; 1958-9395
• DOI: 10.1007/s12243-015-0483-6

In this paper, we investigate throughput and delay enhancement for two multi-user multiple-input multiple-output (MIMO) systems one with space-time block coding (STBC), the other with spatial multiplexing (SM) at the transmitter. Users operate using the slotted ALOHA (SA) protocol to access the wireless channel resulting in a high probability of collision. For both systems, we consider the uplink scenario, and we propose to recover the collided packets with spatial successive interference cancelation (SSIC) and a protocol for retransmission and combining of unsuccessfully received collided packets applying a truncated Hybrid Automatic Repeat reQuest (HARQ) scheme. For the first system, we propose to use channel realizations of collided packets as different signatures to separate them. Moreover, we propose a solution for the problem when the received powers are comparable. For this system, we note that the orthogonality of the STBC matrix allows the use of a simple linear processing step for the initialization of SSIC. For the SM multi-user system, the separation of collided packets is based on V-BLAST processing and SSIC. We also propose how to combine retransmitted packets. For both systems, we evaluate the block error rate, the throughput, and the delay. A comparison is done with the single-user case and with other receivers proposed in the literature.