364 research outputs found
Distributed Random Access Algorithm: Scheduling and Congesion Control
This paper provides proofs of the rate stability, Harris recurrence, and
epsilon-optimality of CSMA algorithms where the backoff parameter of each node
is based on its backlog. These algorithms require only local information and
are easy to implement.
The setup is a network of wireless nodes with a fixed conflict graph that
identifies pairs of nodes whose simultaneous transmissions conflict. The paper
studies two algorithms. The first algorithm schedules transmissions to keep up
with given arrival rates of packets. The second algorithm controls the arrivals
in addition to the scheduling and attempts to maximize the sum of the utilities
of the flows of packets at the different nodes. For the first algorithm, the
paper proves rate stability for strictly feasible arrival rates and also Harris
recurrence of the queues. For the second algorithm, the paper proves the
epsilon-optimality. Both algorithms operate with strictly local information in
the case of decreasing step sizes, and operate with the additional information
of the number of nodes in the network in the case of constant step size
Performance analysis of general backoff protocols
In this paper, we analyze backoff protocols, such as the one used in Ethernet. We examine a general backoff function (GBF) rather than just the binary exponential backoff (BEB) used by Ethernet. Under some mild assumptions we find stability and optimality conditions for a wide class of backoff protocols with GBF. In particular, it is proved that the maximal throughput rate over the class of backoff protocols is a fixed function of the number of stations (N) and the optimal average service time is about Ne for large N. The reasons of the instability of the BEB protocol (for a big enough input rate) are explained. Additionally, the paper introduces novel procedure for analyzing bounded backoff protocols, which is useful for creating new protocols or improving existing, as no protocol can use unbounded counters
Measurement-Adaptive Cellular Random Access Protocols
This work considers a single-cell random access channel (RACH) in cellular
wireless networks. Communications over RACH take place when users try to
connect to a base station during a handover or when establishing a new
connection. Within the framework of Self-Organizing Networks (SONs), the system
should self- adapt to dynamically changing environments (channel fading,
mobility, etc.) without human intervention. For the performance improvement of
the RACH procedure, we aim here at maximizing throughput or alternatively
minimizing the user dropping rate. In the context of SON, we propose protocols
which exploit information from measurements and user reports in order to
estimate current values of the system unknowns and broadcast global
action-related values to all users. The protocols suggest an optimal pair of
user actions (transmission power and back-off probability) found by minimizing
the drift of a certain function. Numerical results illustrate considerable
benefits of the dropping rate, at a very low or even zero cost in power
expenditure and delay, as well as the fast adaptability of the protocols to
environment changes. Although the proposed protocol is designed to minimize
primarily the amount of discarded users per cell, our framework allows for
other variations (power or delay minimization) as well.Comment: 31 pages, 13 figures, 3 tables. Springer Wireless Networks 201
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