Zusammenfassung
This paper investigates the problem of dynamic
multiuser subchannel allocation in the downlink OFDM
systems. In traditional TDMA or FDMA systems, resource
allocation for each user is non-adaptively fixed. Since the
subchannel allocations among the users are not optimized, a
group of users is likely to suffer from poor channel gains
resulting from large path loss and random fading. To resolve
this problem a low-complexity adaptive subchannel allocation
algorithm is proposed in this paper. By adaptively assigning
frequency subchannels, n take advantage of channel diversity
among users in different locations, which is called Multiuser
diversity. The capacity of MU-OFDM is maximized when each
subchannel is assigned to the user with the best channel-to-
noise ratio for that subchannel. However, fairness among the
users cannot generally be achieved with such a scheme. In this
paper, a set of proportional fairness constraints is imposed to
assure that each user achieve a required data rate, that ensures
quality of service. In the proposed algorithm, subchannel
allocation is performed by assuming an equal power
distribution.
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