39 research outputs found
On Improving Throughput of Multichannel ALOHA using Preamble-based Exploration
Machine-type communication (MTC) has been extensively studied to provide
connectivity for devices and sensors in the Internet-of-Thing (IoT). Thanks to
the sparse activity, random access, e.g., ALOHA, is employed for MTC to lower
signaling overhead. In this paper, we propose to adopt exploration for
multichannel ALOHA by transmitting preambles before transmitting data packets
in MTC, and show that the maximum throughput can be improved by a factor of 2 -
exp(-1) = 1.632, In the proposed approach, a base station (BS) needs to send
the feedback information to active users to inform the numbers of transmitted
preambles in multiple channels, which can be reliably estimated as in
compressive random access. A steady-state analysis is also performed with fast
retrial, which shows that the probability of packet collision becomes lower
and, as a result, the delay outage probability is greatly reduced for a lightly
loaded system. Simulation results also confirm the results from analysis.Comment: 10 pages, 7 figures, to appear in the Journal of Communications and
Networks. arXiv admin note: substantial text overlap with arXiv:2001.1111
Spectrum slicing for multiple access channels with heterogeneous services
Wireless mobile networks from the fifth generation (5G) and beyond serve as platforms for flexible support of heterogeneous traffic types with diverse performance requirements. In particular, the broadband services aim for the traditional rate optimization, while the time-sensitive services aim for the optimization of latency and reliability, and some novel metrics such as Age of Information (AoI). In such settings, the key question is the one of spectrum slicing: how these services share the same chunk of available spectrum while meeting the heterogeneous requirements. In this work we investigated the two canonical frameworks for spectrum sharing, Orthogonal Multiple Access (OMA) and Non-Orthogonal Multiple Access (NOMA), in a simple, but insightful setup with a single time-slotted shared frequency channel, involving one broadband user, aiming to maximize throughput and using packet-level coding to protect its transmissions from noise and interference, and several intermittent users, aiming to either to improve their latency-reliability performance or to minimize their AoI. We analytically assessed the performances of Time Division Multiple Access (TDMA) and ALOHA-based schemes in both OMA and NOMA frameworks by deriving their Pareto regions and the corresponding optimal values of their parameters. Our results show that NOMA can outperform traditional OMA in latency-reliability oriented systems in most conditions, but OMA performs slightly better in age-oriented systems