3 research outputs found
Maximum Sum Rate of Slotted Aloha with Successive Interference Cancellation
This is a sequel of our previous work [8] on characterization of maximum sum
rate of slotted Aloha networks. By extending the analysis to incorporate the
capacity-achieving receiver structure, Successive Interference Cancellation
(SIC), this paper aims to identify the rate loss due to random access.
Specifically, two representative SIC receivers are considered, i.e, ordered SIC
where packets are decoded in a descending order of their received power, and
unordered SIC where packets are decoded in a random order. The maximum sum rate
and the corresponding optimal parameter setting including the transmission
probability and the information encoding rate in both cases are obtained as
functions of the mean received signal-to-noise ratio (SNR). The comparison to
the capture model shows that the gains are significant only with the ordered
SIC at moderate values of the mean received SNR . With a large ,
the rate gap diminishes, and they all have the same high-SNR slope of ,
which is far below that of the ergodic sum capacity of fading channels. The
effect of multipacket reception (MPR) on the sum rate performance is also
studied by comparing the MPR receivers including SIC and the capture model to
the classical collision model
Random NOMA With Cross-Slot Successive Interference Cancellation Packet Recovery
Conventional power-domain non-orthogonal multiple access (NOMA) relies on
precise power control, which requires real-time channel state information at
transmitters. This requirement severely limits its application to future
wireless communication systems. To address this problem, we consider NOMA
without power allocation, where we exploit the random channel fading and
opportunistically perform successive interference cancellation (SIC) detection.
To mitigate the multi-user interference, we propose a random NOMA where users
randomly transmit their data packets with a certain probability. Then a
cross-slot SIC packet recovery scheme is proposed to recover transmitted data
packets. We model the cross-slot SIC packet recovery as a Markov process, and
provide a throughput analysis, based on which the sum rate is maximized by
jointly optimizing the transmission probability and the encoding rate of users.Comment: accepted by IEEE Wireless Communications Letters, 5 pages, 4 figure
Online Estimation and Adaptation for Random Access with Successive Interference Cancellation
This paper proposes an adaptive transmission algorithm for slotted random
access systems supporting the successive interference cancellation (SIC) at the
access point (AP). When multiple users transmit packets simultaneously in a
slot, owing to the SIC technique, the AP is able to decode them through SIC
resolve procedures (SRPs), which may occupy multiple consequent slots. While
such an SRP could potentially improve the system throughput, how to fully
exploit this capability in practical systems is still questionable. In
particular, the number of active users contending for the channel varies over
time which complicates the algorithm design. By fully exploiting the potential
of SIC, the proposed algorithm is designed to maximize the system throughput
and minimize the access delay. For this purpose, an online estimation is
introduced to estimate the number of active users in real-time and controls
their transmissions accordingly. It is shown that the throughput of the
proposed algorithm can reach up to 0.693 packets/slot under practical
assumptions, which is the first result achieving the throughput limit proved by
Yu-Giannakis. It is further shown that the system throughput of 0.559
packets/slot (80.6 of the throughput limit) is still achievable when the
SIC capability is restricted by two.Comment: 16 pages, 10 figures, submitted to ISIT 202