Division of Optimization and Systems Theory

Department of Mathematics

KTH

He will present his thesis that will be defended October 7:

In this thesis we formulate joint cell, channel and power allocation
problems within wireless communication networks. The objectives are to
maximize the user with minimum data throughput (Shannon capacity) or to
maximize the total system throughput, referred to as the max-min and
max-sum problem respectively. The complexity is studied together with
proposed optimization- and heuristic-based approaches.
In the first paper an overall joint cell, channel and power allocation
max-min problem is formulated. We show that the decision problem is
NP-hard and that the optimization problem is not approximable unless P is
equal to NP, for instances with a sufficiently large number of channels.
Further, it follows that for a feasible binary cell and channel
allocation, the remaining continuous power allocation optimization problem
is still not approximable unless P is equal to NP. In addition, it is
shown that first-order optimality conditions give global optimum of the
single channel power allocation optimization problem, although the problem
is in general not convex.
In the following two papers heuristics for solving the overall problem are
proposed. In the second paper we consider the single channel problem with
convex combinations of the max-min and the max-sum objective functions.
This variable utility provides the ability of tuning the amount of
fairness and total throughput. The third paper investigates the multiple
channel setting. On a system with three cells, eight mobile users and
three channels, we perform an exhaustive search over feasible cell and
channel allocations. The exhaustive search is then compared to the less
computationally expensive heuristic approaches, presenting potential
earnings to strive for. A conclusion is that several of the proposed
heuristics perform very well.
The final paper incorporates fixed relay stations into the overall joint
cell, channel and power allocation max-min problem. The complexity is
inherited from the formulation without relay stations. Further, we propose
a heuristic channel allocation approach that shows good performance,
compared to an optimization based approach, in numerical simulations on
the relay setting.

Calendar of seminars