343 research outputs found
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
Short-Packet Communications for MIMO NOMA Systems over Nakagami-m Fading: BLER and Minimum Blocklength Analysis
Recently, ultra-reliable and low-latency communications (URLLC) using
short-packets has been proposed to fulfill the stringent requirements regarding
reliability and latency of emerging applications in 5G and beyond networks. In
addition, multiple-input multiple-output non-orthogonal multiple access (MIMO
NOMA) is a potential candidate to improve the spectral efficiency, reliability,
latency, and connectivity of wireless systems. In this paper, we investigate
short-packet communications (SPC) in a multiuser downlink MIMO NOMA system over
Nakagami-m fading, and propose two antenna-user selection methods considering
two clusters of users having different priority levels. In contrast to the
widely-used long data-packet assumption, the SPC analysis requires the redesign
of the communication protocols and novel performance metrics. Given this
context, we analyze the SPC performance of MIMO NOMA systems using the average
block error rate (BLER) and minimum blocklength, instead of the conventional
metrics such as ergodic capacity and outage capacity. More specifically, to
characterize the system performance regarding SPC, asymptotic (in the high
signal-to-noise ratio regime) and approximate closed-form expressions of the
average BLER at the users are derived. Based on the asymptotic behavior of the
average BLER, an analysis of the diversity order, minimum blocklength, and
optimal power allocation is carried out. The achieved results show that MIMO
NOMA can serve multiple users simultaneously using a smaller blocklength
compared with MIMO OMA, thus demonstrating the benefits of MIMO NOMA for SPC in
minimizing the transmission latency. Furthermore, our results indicate that the
proposed methods not only improve the BLER performance but also guarantee full
diversity gains for the respective users.Comment: 12 pages, 8 figures. This paper has been submitted to an IEEE journal
for possible publicatio
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
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