Abstract
Sparse code multiple access (SCMA) is a promising code domain non-orthogonal multiple-access scheme which is able to support massive connectivity and grant-free transmission in future satellite-based Internet of Things (IoT) communication networks. Traditional grant-free SCMA is based on time synchronization, which is no longer favorable in such satellite communication networks since the amount of signaling generated to keep all transmitters’ time synchronized is impractical for large networks. Moreover, without centralized codebook assignment, grant-free SCMA suffers from codebook collisions which mean more than one terminal selecting the same codebook being interfered. Motivated by these issues, a novel uplink grant-free asynchronous flipped SCMA scheme named AF-SCMA is proposed in this paper. With the concept of flipped diversity, a specific SCMA-encoded packet is transmitted with its flipped replica together. Successive interference cancellation technique combined with a sliding window is adopted to resolve the packet collisions including codebook collisions at the gateway station. The performance of AF-SCMA is investigated via both mathematical analysis and simulations. Simulation results show that the proposed AF-SCMA provides remarkable performance in terms of throughput and packet loss ratio (PLR), and can benefit from the received signal power unbalance.
Highlights
Satellite communication networks as an enhanced and complementary part of the terrestrial communication infrastructure is expected to play a significant role in future Internet of Things (IoT)communication networks [1]
ALOHA-like random access (RA) is one of the most common grant-free uplink protocols, which can be seen as a candidate multiple-access scheme of future satellite-based IoT (SAT-IoT) networks, because it is insensitive to the bursty traffic, as well as easy to be implement in satellite terminals
Please note that the performance of AF-Sparse code multiple access (SCMA) cannot be further improved by sending more replicas such as the methods mentioned in [6,8], since more replicas will destroy the construction of the transmitted packets
Summary
Satellite communication networks as an enhanced and complementary part of the terrestrial communication infrastructure is expected to play a significant role in future Internet of Things (IoT). ALOHA-like random access (RA) is one of the most common grant-free uplink protocols, which can be seen as a candidate multiple-access scheme of future SAT-IoT networks, because it is insensitive to the bursty traffic, as well as easy to be implement in satellite terminals. Some variants of ALOHA [6,7,8,9,10,11] have been proposed, aiming to improve the performance of the throughput of the satellite communication network These protocols exploit successive interference cancellation (SIC) and proper forward error correction (FEC) coding schemes to recover the collided packets. To design an asynchronous SCMA scheme, we need to tackle the problem of codebook collisions first Motivated by these issues, this paper introduces a novel uplink grant-free asynchronous flipped.
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