4,929 research outputs found
Short-Packet Downlink Transmission with Non-Orthogonal Multiple Access
This work introduces downlink non-orthogonal multiple access (NOMA) into
short-packet communications. NOMA has great potential to improve fairness and
spectral efficiency with respect to orthogonal multiple access (OMA) for
low-latency downlink transmission, thus making it attractive for the emerging
Internet of Things. We consider a two-user downlink NOMA system with finite
blocklength constraints, in which the transmission rates and power allocation
are optimized. To this end, we investigate the trade-off among the transmission
rate, decoding error probability, and the transmission latency measured in
blocklength. Then, a one-dimensional search algorithm is proposed to resolve
the challenges mainly due to the achievable rate affected by the finite
blocklength and the unguaranteed successive interference cancellation. We also
analyze the performance of OMA as a benchmark to fully demonstrate the benefit
of NOMA. Our simulation results show that NOMA significantly outperforms OMA in
terms of achieving a higher effective throughput subject to the same finite
blocklength constraint, or incurring a lower latency to achieve the same
effective throughput target. Interestingly, we further find that with the
finite blocklength, the advantage of NOMA relative to OMA is more prominent
when the effective throughput targets at the two users become more comparable.Comment: 15 pages, 9 figures. This is a longer version of a paper to appear in
IEEE Transactions on Wireless Communications. Citation Information: X. Sun,
S. Yan, N. Yang, Z. Ding, C. Shen, and Z. Zhong, "Short-Packet Downlink
Transmission with Non-Orthogonal Multiple Access," IEEE Trans. Wireless
Commun., accepted to appear [Online]
https://ieeexplore.ieee.org/document/8345745
Max-Min Fairness of Rate-Splitting Multiple Access with Finite Blocklength Communications
Rate-Splitting Multiple Access (RSMA) has emerged as a flexible and powerful
framework for wireless networks. In this paper, we investigate the user
fairness of downlink multi-antenna RSMA in short-packet communications
with/without cooperative (user-relaying) transmission. We design optimal time
allocation and linear precoders that maximize the Max-Min Fairness (MMF) rate
with Finite Blocklength (FBL) constraints. The relation between the MMF rate
and blocklength of RSMA, as well as the impact of cooperative transmission are
investigated for a wide range of network loads. Numerical results demonstrate
that RSMA can achieve the same MMF rate as Non-Orthogonal Multiple Access
(NOMA) and Space Division Multiple Access (SDMA) with smaller blocklengths (and
therefore lower latency), especially in cooperative transmission deployment.
Hence, we conclude that RSMA is a promising multiple access for guaranteeing
user fairness in low-latency communications.Comment: arXiv admin note: text overlap with arXiv:2105.0619
Energy-Efficient Non-Orthogonal Transmission under Reliability and Finite Blocklength Constraints
This paper investigates an energy-efficient non-orthogonal transmission
design problem for two downlink receivers that have strict reliability and
finite blocklength (latency) constraints. The Shannon capacity formula widely
used in traditional designs needs the assumption of infinite blocklength and
thus is no longer appropriate. We adopt the newly finite blocklength coding
capacity formula for explicitly specifying the trade-off between reliability
and code blocklength. However, conventional successive interference
cancellation (SIC) may become infeasible due to heterogeneous blocklengths. We
thus consider several scenarios with different channel conditions and
with/without SIC. By carefully examining the problem structure, we present in
closed-form the optimal power and code blocklength for energy-efficient
transmissions. Simulation results provide interesting insights into conditions
for which non-orthogonal transmission is more energy efficient than the
orthogonal transmission such as TDMA.Comment: accepted by IEEE GlobeCom workshop on URLLC, 201
On the Fundamental Limits of Random Non-orthogonal Multiple Access in Cellular Massive IoT
Machine-to-machine (M2M) constitutes the communication paradigm at the basis
of Internet of Things (IoT) vision. M2M solutions allow billions of multi-role
devices to communicate with each other or with the underlying data transport
infrastructure without, or with minimal, human intervention. Current solutions
for wireless transmissions originally designed for human-based applications
thus require a substantial shift to cope with the capacity issues in managing a
huge amount of M2M devices. In this paper, we consider the multiple access
techniques as promising solutions to support a large number of devices in
cellular systems with limited radio resources. We focus on non-orthogonal
multiple access (NOMA) where, with the aim to increase the channel efficiency,
the devices share the same radio resources for their data transmission. This
has been shown to provide optimal throughput from an information theoretic
point of view.We consider a realistic system model and characterise the system
performance in terms of throughput and energy efficiency in a NOMA scenario
with a random packet arrival model, where we also derive the stability
condition for the system to guarantee the performance.Comment: To appear in IEEE JSAC Special Issue on Non-Orthogonal Multiple
Access for 5G System
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