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It is suggested that deploying high-capacity CFAPs would bring better performance than deploying low-capacity CFAPs when providing realtime services.
Cognitive cellular-femtocell systems were proposed recently in which macro base stations and cognitive femtocell access points (CFAP) are considered as primary and secondary systems, respectively.
In this model, a CFAP can form a closed access femto zone in which only authorized/registered users can access to the CFAP.
When a new call request of a FU arrives to a CFAP, the CFAP first performs a channel allocation scheme to allocate a channel to the FU.
After allocating a channel k to a new call request, CFAP sends a verification request to the FMS to verify if the QoSs of other MUs using the channel k are violated.
In a MBS or a CFAP, at any given time, a channel is allocated to only one ongoing MU or one ongoing FU, respectively.
In the FAP-based cognitive channel allocation scheme (denoted as CFAP-based scheme), each CFAP will measure the interference level of all available channels which are not allocated to ongoing FUs of the CFAP.
is the total interference level of channel c is measured at the CFAP j.
where [Pr.sup.k.sub.j] is the power received from the user at CFAP j.
A CFAP periodically updates interference data of all channels measured at its covering MBS.
When the CFAP receives a connection request of a FU, it will select the channel [k.sup.*] which satisfies two criteria: 1) it is unused by other ongoing FUs of the CFAP and 2) it has the minimum interference level [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] measured at the covering MBS M of the CFAP, as described in Eq.
where [I.sup.c.sub.M] is the total interference level of channel c which is measured at the covering MBS M of the CFAP. Selecting a channel according to Eq.
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