Coded Slotted ALOHA: A Graph-Based Method for Uncoordinated Multiple Access

Abstract

In this paper, a random access scheme is introduced which relies on the combination of packet erasure correcting codes and successive interference cancellation (SIC). The scheme is named coded slotted ALOHA. A bipartite graph representation of the SIC process, resembling iterative decoding of generalized low-density parity-check codes over the erasure channel, is exploited to optimize the selection probabilities of the component erasure correcting codes via density evolution analysis. The capacity (in packets per slot) of the scheme is then analyzed in the context of the collision channel without feedback. Moreover, a capacity bound is developed and component code distributions tightly approaching the bound are derived.

Frame-Based Random Access with Interference Cancellation across Frames for Massive Machine Type Communications

“…Figures 8 and 9 show the results with a small number of slots per frame, more specifically = 8. In this case, the combined schemes are not considered since (13) is not satisfied even with = 2. The coded random access schemes hardly produce good results since it is not easy to find slots without collisions due to duplicated packets.…”

“…A framebased slotted Aloha scheme cannot achieve a good performance and a random access technique, called coded random access, has been proposed to improve the performance [11][12][13][14][15][16]. There are various extensions of coded random access schemes but in this paper we consider a basic form of coded random access, which uses repetition coding with code rate 1/ .…”

“…A coded random access scheme can produce satisfactory results if the number of slots per frame is large [11][12][13][14]. However, it transmits multiple copies of a packet, and thus transmission power consumption may be increased compared to the conventional frame-based slotted Aloha scheme especially when the collision rate is small.…”

“…As IoT services are widely used, the density of MTC devices will become very high and massive MTC techniques are required to support concurrent random accesses from a huge number of devices [5][6][7][8][9][10]. There are many works for efficiently supporting random accesses from a large number of devices, and recently a random access technique, called coded random access, has been proposed to improve the performance of frame-based slotted Aloha [11][12][13][14][15][16]. In a coded random access technique, multiple copies of a packet are transmitted over different slots in a frame and successive interference cancellation is performed starting with a successfully received copy, which can significantly reduce the collision probability.…”

A power-controlled coded slotted ALOHA

“…However, these methods need to get the number of nodes connecting to a base station (BS). Coded slotted ALOHA (CSA) [1] is a promising method to realize reliable wireless networks. CSA introduces a multi-packet reception technology such as successive interference cancellation (SIC) in slotted ALOHA (S-ALOHA).…”