PhD Thesis Proposal Defence


"Bandwidth Allocation in Wireless Ad Hoc Networks"

By Mr. Zuyuan Fang


Abstract:

Nowadays the emergence of nomadic applications has led to intensive
research interest on providing Quality of Service (QoS) in Mobile Ad hoc
Networks (MANETs). In the networking protocol stack, a QoS capable MAC
protocol plays an important role in a QoS scheme. However, currently the
widely used MAC protocol IEEE802.11 Distributed Coordination Function
(DCF) does not provide any QoS guarantee and suffers from a problem of
fairness. This thesis proposal formulates the design of MAC protocols as a
bandwidth allocation problem. A flow contention graph is used to model the
contention relations between link flows. Based on the flow contention
graph formalism, different algorithms are proposed to solve the problem in
such a way that the obtained MAC protocols for MANETs satisfy QoS
objectives such as fairness or the minimal bandwidth guarantee.

Firstly, a max-min fair allocation algorithm combined with a
measurement-based algorithm are presented to guarantee max-min fair
distribution of bandwidth across the network at the link layer. In the
max-min fair share allocation algorithm, each flow can calculate its
max-min fair share based on flow information in two hop diameter in the
contention graph. Once each flow knows its fair share and those of its
neighbors, the measurement based backoff algorithm is invoked to achieve
weighted fairness.

Secondly, in order to reduce the communication overhead and meet different
fairness objectives, the fair bandwidth allocation problem is also
modelled as a general utility based constrained maximization problem,
which is shown to admit a unique solution that can only be obtained when
global coordination between all nodes is possible. Invoking Lagrange
relaxation and duality theory, both a non-cooperative and a cooperative
game formulation of the problem are presented. The algorithm derived from
the non-cooperative game does not depend on any local flow information.
The algorithm derived from the cooperative game depends only on one hop
flow information. The fairness objective of these algorithms is controlled
by the adopted utility function.

Both previous solutions' implementation relies on some variations of the
random access mechanism known as carrier sense multiple access. As an
alternative, a series of collision-free scheduling algorithms are
proposed. In these algorithms, with the help of one hop local flow
information, one flow can determine a local collision-free transmission
schedule.

Comparisons with other schemes proposed in the literature show that the
max-min fairness scheme and the cooperative game framework based algorithm
not only can provide better fairness but also have the capability of
quantifying the bandwidth, which is a very important factor to do
admission control. The collision-free algorithms have the advantage of
guaranteeing a minimal throughput. These algorithms show that collecting
local contention information helps to design effective MAC schemes.
However, they are not suitable for highly mobile networks. Since the
algorithms derived from the non-cooperative game do not depend on any flow
information, they are more suitable for such networks.


Date:     		Friday, 30 January 2004

Time:                   11:00a.m.-1:00p.m.

Venue:                  Room 2406
			lifts 17-18

Committee Members:      Prof. Brahim Bensaou (Supervisor)
                        Prof. Jogesh Muppala (Chairman)
			Prof. Gary Chan
			Prof. Danny Tsang (ELEC)


**** ALL are Welcome ****