Abstract
The rapid growth in the scale of the intelligent connected vehicles (ICVs) brings about the need for novel random access schemes that realize collision avoidance and reliable communication. The coded random access (CRA) scheme utilizes successive interference cancellation (SIC) across slots to enable the extraction of multiple users' packets from the collision slots and proves to be an efficient solution to collision resolution. In this paper, we propose a random backoff-based CRA scheme to achieve a tradeoff between the access success probability and access delay for CRA. Specifically, we partition the traditional CRA frame into subframes, so that the user access delay is reduced to the same scale of the subframe length. In addition, the backoff operation among subframes is introduced so that access failures originated from the subframe length limit can be reduced with the retransmission in subsequent subframes. In particular, we consider practical Nakagami-m fading channel in the CRA performance analysis and take into account the capture effect in the iterative interference cancellation process. Simulation results show that backoff-based CRA can significantly reduce the average access delay without severe negative effect on the access success probability for moderate system load compared with traditional CRA. Comparisons with the state-of-the-art non-orthogonal random access (NORA) scheme proposed for 5G indicates that backoff-based CRA provides a feasible solution for random access of large-scale ICVs.
Highlights
Reliable and efficient information exchange lays the foundation for the cooperation of intelligent connected vehicles (ICVs)
Based on the joint consideration of the aforementioned problems, we propose a random backoff-based coded random access (CRA) scheme to achieve a tradeoff between the access success probability and the access delay
In this paper, we propose a random backoff-based CRA scheme to achieve a tradeoff between the access success probability and the access delay for CRA
Summary
Reliable and efficient information exchange lays the foundation for the cooperation of intelligent connected vehicles (ICVs). Users transmit the replicas of the same packet in multiple slots according to predefined access probability distributions and repetition rates. A lot of work has been done on the performance analysis of packet loss rate and throughput of CRA given practical frame lengths [3], [5]. Small frame length increases the occurrance of loops [12], which leads to irresolvable collisions and deteriorates the access probability and throughput performance of CRA. The sink node broadcast CRA configuration information, such as the message repetition degree distribution, the backoff window, etc. Upon receiving the CRA configuration information, the sensing nodes which decides to report the situation information in the current subframe would generate l messsage replicas and transmit them over l slots chosen uniformly at random among the K available data slots.
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