Communication system and method of operation therefor
View Patent ↗A communication system comprises a set of user equipments which are arranged to simultaneously transmit a signal over an air interface to a base station. Each of the transmitted signals comprises a data stream encoded by a space time block code and transmitted on multiple antennas. Specifically, an Alamouti code may be used. The base station generates a received data stream for each of the set of user equipments by joint space time block code decoding of the signals from the set of user equipments. The invention may provide improved performance and increased capacity and may in particular provide efficient multi user operation for a system using space time block codes. The user equipments may be scheduled in response to cross interference metrics reflecting a cross interference between simultaneously transmitting user equipments.
1. A base station comprising:
a receiver for generating a received data stream by joint space time block code decoding a plurality of data streams transmitted simultaneously by a plurality of user equipments;
a subset processor that generates a plurality of subsets of possible combinations of the plurality of user equipments to evaluate for allocation to a scheduling time slot;
an interference processor coupled to the subset processor, the interference processor configured to determine an interference metric for the plurality of subsets; and
a time slot scheduler coupled to the interference processor, the time slot scheduler evaluating the interference metric and selecting a subset having a lowest interference metric for the scheduling time slot.
2. The base station of claim 1 wherein the interference metric is determined from
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where h i1 , h i2 are channel estimate vectors comprising channel estimates for propagation channels between transmit antennas of user equipment i and receive antennas of the base station in two data symbol time slots of the space time block code and h j1 , h j2 are channel estimate vectors comprising channel estimates for propagation channels between transmit antennas of user equipment j and receive antennas of the base station in two data symbol time slots of the space time block code.
3. The base station of claim 1 wherein the subset processor generates a plurality of subsets based on all possible pair combinations of the plurality of user equipments.
4. The base station of claim 1 wherein the subset processor selects a first user equipment of the plurality of user equipments and generates the plurality of subsets based on all pair combinations having the first user equipment as a member of the pair.
5. The method of claim 4 wherein the subset processor generates the plurality of subsets based on all possible pair combinations of the plurality of user equipments.
6. The method of claim 4 wherein the subset processor selects a first user equipment of the plurality of user equipments and generates the plurality of subsets based on all pair combinations having the first user equipment as a member of the pair.
7. A method comprising:
in a receiver, generating a received data stream by joint space time block code decoding a plurality of data streams transmitted simultaneously by a plurality of user equipments;
by a subset processor, generating a plurality of subsets of possible combinations of the plurality of user equipments to evaluate for allocation to a scheduling time slot;
by an interference processor, determining an interference metric for the plurality of subsets; and
by a time slot scheduler, evaluating the interference metric and selecting a subset having a lowest interference metric for the scheduling time slot.
8. The method of claim 7 wherein the interference metric is determined from
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where h i1 , h i2 are channel estimate vectors comprising channel estimates for propagation channels between transmit antennas of user equipment i and receive antennas of the base station in two data symbol time slots of the space time block code and h j1 , h j2 are channel estimate vectors comprising channel estimates for propagation channels between transmit antennas of user equipment j and receive antennas of the base station in two data symbol time slots of the space time block code.