Multiuser diversity is a diversity technique using user scheduling in multiuser wireless channels where user scheduling allows the base station to select high quality channel users so as to transmit information through a relatively high quality channel in time, frequency and space domains based on the channel quality information fed back from all candidate UEs.

Basic Criterion for the User Selection Edit

The basic user selection criterion is as follows:

$ k^* = \max_{k=1..K} \mathrm{CQI}_k $

where $ K $ is the number of candidate users in the networks. The candidate users are users whom the base station is scheduled to transmit.

Conventionally, either the round-robin scheduling or the first-request first-send (or first-input first-output scheduler) is used in conventional wireless networks. When there are multiuser users in a wireless networks, the instant channel qualities of different users are different. If the base station transmits information to a randomly selected user, the channel of the selected user can be obviously lower than the best channel quality user. If the base station can know the channel quality information ahead of the transmission.

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