758 research outputs found
Finite Length Performance of Random Slotted ALOHA Strategies
Multiple connected devices sharing common wireless resources might create interference if they access the channel simultaneously. Medium access control (MAC) protocols gener- ally regulate the access of the devices to the shared channel to limit signal interference. In particular, irregular repetition slotted ALOHA (IRSA) techniques can achieve high-throughput performance when interference cancellation methods are adopted to recover from collisions. In this work, we study the finite length performance for IRSA schemes by building on the analogy between successive interference cancellation and iterative belief- propagation on erasure channels. We use a novel combinatorial derivation based on the matrix-occupancy theory to compute the error probability and we validate our method with simulation results
User Activity Detection in Massive Random Access: Compressed Sensing vs. Coded Slotted ALOHA
Machine-type communication services in mobile cel- lular systems are
currently evolving with an aim to efficiently address a massive-scale user
access to the system. One of the key problems in this respect is to efficiently
identify active users in order to allocate them resources for the subsequent
transmissions. In this paper, we examine two recently suggested approaches for
user activity detection: compressed-sensing (CS) and coded slotted ALOHA (CSA),
and provide their comparison in terms of performance vs resource utilization.
Our preliminary results show that CS-based approach is able to provide the
target user activity detection performance with less overall system resource
utilization. However, this comes at a price of lower energy- efficiency per
user, as compared to CSA-based approach.Comment: Accepted for presentation at IEEE SPAWC 201
On the Stability of Contention Resolution Diversity Slotted ALOHA
In this paper a Time Division Multiple Access (TDMA) based Random Access (RA)
channel with Successive Interference Cancellation (SIC) is considered for a
finite user population and reliable retransmission mechanism on the basis of
Contention Resolution Diversity Slotted ALOHA (CRDSA). A general mathematical
model based on Markov Chains is derived which makes it possible to predict the
stability regions of SIC-RA channels, the expected delays in equilibrium and
the selection of parameters for a stable channel configuration. Furthermore the
model enables the estimation of the average time before reaching instability.
The presented model is verified against simulations and numerical results are
provided for comparison of the stability of CRDSA versus the stability of
traditional Slotted ALOHA (SA). The presented results show that CRDSA has not
only a high gain over SA in terms of throughput but also in its stability.Comment: 10 pages, 12 figures This paper is submitted to the IEEE Transactions
on Communications for possible publication. The IEEE copyright notice applie
Near-Optimal Deviation-Proof Medium Access Control Designs in Wireless Networks
Distributed medium access control (MAC) protocols are essential for the
proliferation of low cost, decentralized wireless local area networks (WLANs).
Most MAC protocols are designed with the presumption that nodes comply with
prescribed rules. However, selfish nodes have natural motives to manipulate
protocols in order to improve their own performance. This often degrades the
performance of other nodes as well as that of the overall system. In this work,
we propose a class of protocols that limit the performance gain which nodes can
obtain through selfish manipulation while incurring only a small efficiency
loss. The proposed protocols are based on the idea of a review strategy, with
which nodes collect signals about the actions of other nodes over a period of
time, use a statistical test to infer whether or not other nodes are following
the prescribed protocol, and trigger a punishment if a departure from the
protocol is perceived. We consider the cases of private and public signals and
provide analytical and numerical results to demonstrate the properties of the
proposed protocols.Comment: 14 double-column pages, submitted to ACM/IEEE Trans Networkin
Coded Slotted ALOHA: A Graph-Based Method for Uncoordinated Multiple Access
In this paper, a random access scheme is introduced which relies on the
combination of packet erasure correcting codes and successive interference
cancellation (SIC). The scheme is named coded slotted ALOHA. A bipartite graph
representation of the SIC process, resembling iterative decoding of generalized
low-density parity-check codes over the erasure channel, is exploited to
optimize the selection probabilities of the component erasure correcting codes
via density evolution analysis. The capacity (in packets per slot) of the
scheme is then analyzed in the context of the collision channel without
feedback. Moreover, a capacity bound is developed and component code
distributions tightly approaching the bound are derived.Comment: The final version to appear in IEEE Trans. Inf. Theory. 18 pages, 10
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