We consider a new coordinated multipoint (CoMP) communications in wireless body area networks (WBANs) . CoMP has been considered for cellular networks, in which adjacent basestations are assumed to be linked each other with wired connections. We call this CoMP technology with wired connection as wired CoMP.

Approach Edit

Spectral efficiency ratio (SER) Edit

Because spectral efficiency of two radio links in a mobile device, it is proposed that the one link can help the other link. If the spectral efficiency of the first link is $ C_1 $ and that of the second link is $ C_2 $, the decoded information of the first link can be transferred to the second link with spectral efficiency ratio (SER) of $ r = C_1/C_2 $.

If SER of $ r $ is larger than 1, the efficiency of this transferring system is poor. Otherwise, if $ r $ is smaller than 1 the efficiency of this system is good since less spectrum is required for transferring to the second link than sending again through the first link.

Two Tx and Two Rx (2T2R) case Edit

We assume that there are two transmission nodes and two reception nodes. If the two transmission nodes send information simultaneously through the same frequency band, both the two reception devices will receive aggregated signals.

If the received signal at the first node is sent to the second node, the decoding performance at the second node will be enhanced. The worst bound for the 2T2R interference channel case, double bandwidth resources, $ 2W $, are required in order not to interfere each other.

Trade-off between receiver cooperation and additional transmission bandwidth Edit

If we use larger transmission bandwidth, the required bandwidth for cooperation can be smaller than the apposite case. Note that maximum of the additional transmission bandwidth ($ W_\mathrm{add} $) for no interference is less than or equal to the original bandwidth ($ W_\mathrm{tx} $) for the 2T2R case, i.e., $ W_\mathrm{add} \leq W_\mathrm{tx} $. For collaboration between the two received nodes, we assume that bidirectional signaling between the first reception node and the second reception node is used. Therefore, the total bandwidth for information sharing is given by:

$ W_\mathrm{col} = W_\mathrm{col,1} + W_\mathrm{col,2} $

We now define the gain of the collaboration system as

$ W_\mathrm{gain} = W_\mathrm{tx} - W_\mathrm{add} - W_\mathrm{col} $

The larger gain of the collaboration system, the more efficient collaboration system.

Conventionally, either an additional transmission method ($ W_\mathrm{add} = 0 $) or an receiver collaboration method ($ W_\mathrm{col} = 0 $) are mery considered. In this article, we consider a novel approach which allows the system to coordinate the additional transmission and the receiver collaboration methods.

Depending on the channel status, the values of $ W_\mathrm{add} $ and $ W_\mathrm{col} $ are coordinated in order to maximize the gain of collaboration system ($ W_\mathrm{gain} $).

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