Two-stage algorithm for uplink CoMP
A computer-implemented method for associating users to transmission points over an uplink (UL) of a heterogeneous network (HetNet) is presented. The computer-implemented method includes communicating, via the processor, with a cluster of transmission points, associating each user to one transmission point within the cluster of transmission points by a two-stage procedure, and performing sub-frame scheduling independently by each transmission point within the cluster of transmission points over a set of users associated with.
1. A computer-implemented method executed on a processor for associating users to transmission points over a wideband model for an uplink (UL) of a heterogeneous network (HetNet), the method comprising:
communicating, via the processor, with a cluster of transmission points;
associating, via the processor, each user to one transmission point within the cluster of transmission points over the UL of the HetNet, such that each user is associated to any one of the transmission points over a frame duration, by a two-stage wideband UL user association procedure based on an average slowly varying metric relevant for a period longer than a backhaul latency;
wherein said metric of each user is responsive to one or more of: transmit power spectral density of that user, a path loss factor between that user and its associated transmission point and at least one other path-loss factor between that user and other transmission points; and
performing, via the processor, sub-frame scheduling independently by each transmission point within the cluster of transmission points over a set of users associated with it by the two-stage procedure;
wherein the first stage of the two-stage UL user association procedure is performed by a greedy search algorithm, wherein a sum of log of rates for a transmission point (TP) is given by:
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where PL u,b denotes a path-loss factor for a link between user u and TP b, ρ u,b denotes a transmit power spectral density (PSD) assigned to user u when it is associated with TP b, W denotes system bandwith, and σ 2 denotes a PSD of noise plus out-of-cluster interference.
2. The method of claim 1 , wherein the PSD can be computed as:
ρ u,b =min{ P u,max ( |U b |+1) /W, P 0 PL u,b α , Γ 0 PL u,b,int },
where PL u,b,int is a smallest path-loss factor among all links between user u and TPs other than TP b, such as, PL u,b,int =min s∈B:s≠b {PL u,s }, and
where P u,max denotes a maximum transmit power of user u, P 0 ,Γ 0 denotes a desired signal PSD level at an intended receiving TP and a target interference PSD level at the other interfered TP, respectively.
3. The method of claim 2 , wherein a sum log rate for any other TP t: t≠b, if user u is associated to TP b, given the current user assignments {U s , s=1, . . . , B} is given by:
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4. The method of claim 3 , wherein after the first stage of the two-stage UL user association procedure terminates, an output a user sets {U s, s= 1, . . . , B} to determine a current system utility is given as:
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