2 research outputs found
Rate and Power Allocation in Fading Multiple Access Channels
We consider the problem of rate and power allocation in a fading
multiple-access channel. Our objective is to obtain rate and power allocation
policies that maximize a utility function defined over average transmission
rates. In contrast with the literature, which focuses on the linear case, we
present results for general concave utility functions. We consider two cases.
In the first case, we assume that power control is possible and channel
statistics are known. In this case, we show that the optimal policies can be
obtained greedily by maximizing a linear utility function at each channel
state. In the second case, we assume that power control is not possible and
channel statistics are not available. In this case, we define a greedy rate
allocation policy and provide upper bounds on the performance difference
between the optimal and the greedy policy. Our bounds highlight the dependence
of the performance difference on the channel variations and the structure of
the utility function.Comment: 6 pages, In proc. of WiOpt 200
Information Theory vs. Queueing Theory for Resource Allocation in Multiple Access Channels
We consider the problem of rate allocation in a fading Gaussian
multiple-access channel with fixed transmission powers. The goal is to maximize
a general concave utility function of the expected achieved rates of the users.
There are different approaches to this problem in the literature. From an
information theoretic point of view, rates are allocated only by using the
channel state information. The queueing theory approach utilizes the global
queue-length information for rate allocation to guarantee throughput optimality
as well as maximizing a utility function of the rates. In this work, we make a
connection between these two approaches by showing that the information
theoretic capacity region of a multiple-access channel and its stability region
are equivalent. Moreover, our numerical results show that a simple greedy
policy which does not use the queue-length information can outperform
queue-length based policies in terms of convergence rate and fairness.Comment: 5 pages. In proc. of PIMRC 200