| 主权项 |
1. A method to perform joint scheduling in the downlink of a centralized OFDM radio access network for a plurality of users considering time, frequency and space domains, said scheduling being executed at a central unit, CU, of the centralized OFDM radio access network comprising a number M of remote units, RUs, and a number N of users, said CU having complete knowledge of channel quality characteristics at n different frequency subbands for said number N of users, wherein the scheduling being for a maximum of K subbands at arbitrary frequency locations for each remote unit, RU, of said number M of RU and wherein the scheduling exploiting Coordinated Multi Point, CoMP, Non-Orthogonal Multiple Access, NOMA, and Radio Frequency, RF, isolation conditions, and resource blanking techniques, characterized in that the method comprises the following steps:
a) initializing values user(i, k)=−1 for all values of i and k, and Si={Φ}, wherein user(i, 0), user(i, 1), . . . , user(i, n−1) denote the set of users which will be assigned subbands 0, 1, . . . , n−1 at RU i, and Si denotes the set of users that have already been scheduled a total of K subbands at RU i according to the expression:
Si={j ∈ [0, N−1]: j=user(i,k0), . . . , juser(i,kK−1) for k0, k1 . . . , kK−1 ∈ [0, n−1]}; b) calculating scheduling metrics Tijk corresponding to RU i, user j and subband k according to a given criterion, and constructing a three-dimensional metrics table of size N x n x M containing said scheduling metrics; c) storing channel quality indicators, CQIijk, associated to RU i, user j and subband k, said channel quality indicators representing a measure of the channel quality as perceived by the users; d) selecting, for each time instant, a random subband k and RU i among a set of subbands and RUs not yet assigned by the method; e) finding a user j0 with the highest metric Tijk for RU i and subband k among the users not belonging to Si according to the expression:j0=argmaxj∉Si{Tijk}, wherein if several maxima are found, the user j0 is chosen randomly among a number of users j0 fulfilling said maxima; f) analyzing whether there is another RU i′ for which user j0 has a higher maximum value of the metric Tijk for the same subband k, and in that case then considering RU i′ rather than RU i for association with user j0, otherwise considering RU i; g) checking, for the selected RU i, whether there is another user j0′ already scheduled in the same subband as j0, and in the affirmative case:
g1) deciding whether CoMP can be employed in that subband, and if CoMP can be employed, and if the number of already coordinated users is lower than L, then automatically scheduling for user j0 the same set of subbands scheduled for user j0′, wherein L denotes the size of the CoMP cluster; org2) crossing out all the metric values for user j0 and the RUs involved in the coordination in the three-dimensional metrics table, for the set of subbands scheduled for user j0′, and if the number of already coordinated users is equal to L then all metric values will be crossed out for all the remaining users at the same set of subbands and RUs involved in the coordination; h) if there is no other user j0′ already scheduled in the same subband as j0 for the selected RU, analyzing whether there is another subband l≠k for which user j0 has a higher maximum value of the metric Tijk, and
in the affirmative case, secondary maxima of the metric values are sought for both subbands, namely:j1=argmaxj∉Si,j≠j0{Tijk}j2=argmaxj∉Si,j≠j0{Tijl}, and if Tij1k+Tij0l>Tij0k+Tij2l then assigning user jl to subband k and user j0 to subband l, otherwise assigning user j0 to subband k and user j2 to subband l;if there is no other subband l≠k for which user j0 has a higher maximum value of the metric Tijk, assigning user j0 to subband k; i) analyzing whether the assigned subband(s) can also be scheduled at a different RU i′ in CoMP, NOMA or RF isolation conditions, by:
i1) deciding whether CoMP can be employed for a given RU i′≠i, and in such a case and if the number of already coordinated RUs for user j is lower than L, then applying CoMP techniques so that the same user and subbands will be scheduled at RUs i and i′;i2) deciding whether NOMA can be employed for a given RU i′≠i, and in such a case then applying NOMA for RUs i and i′ and users j and j′ at subband k, thereby sharing resources for both users at both RUs, and crossing out and any other entries in the three-dimensional table corresponding to RUs i and i′ for subband k and users other than j and j′;i3) deciding whether there is sufficient RF isolation between RUs i and i′ for subband k and a given RU i′, and in such a case then RUs i and i′ will be considered sufficiently isolated for user j, and subband k can be reused for those RUs; andi4) crossing out any entries in the three-dimensional metrics table corresponding to RUs for which the above three conditions (i1-i3) are not met at the assigned subband k for user j, thereby muting transmissions from interfering RUs for all users j at resources wherein interference is significant and cannot be mitigated; j) checking whether any user has already been scheduled the maximum number of subbands K for a given RU i, and in such a case:
j1) crossing out the corresponding values Tijk in the three-dimensional metrics table for RU i and user j ∀k ,j2) adding user j to the set Si=Si∪{j}, and
j3) if the user is in CoMP then all other users simultaneously scheduled by the involved RUs will also be included in the set, and the corresponding values Tijk be crossed out ∀k ; and k) repeating steps d) to j) by selecting a new random subband and RU until there are no subbands left unassigned in any of the RUs, after updating the three-dimensional metrics table with the values corresponding to a next time instant and setting CQIijk values to minus infinity for all users at those RUs and subbands wherein resource blanking was applied. |
