Toward this end, we resort to the renewal theory [24], which was first introduced in [32] to analyze the throughput performance of a HARQ system, under the assumptions of error- and delay-free feedback channel and infinite-length buffer.
As demonstrated both theoretically and numerically, considerable performance improvement can be achieved by implementation of CoMP-HARQ systems.
The analytical and numerical results demonstrate the efficiency of the CoMP-HARQ techniques in different conditions.
Specifically, reviewing the third generation partnership project (3GPP) reports, e.g. [49], there are many aspects of the CoMP-HARQ that have not been studied yet.
Figure 3 Difference between the throughput of CoMP-HARQ and single-user channel model introduced in Theorem 2, that is, Δ η = η INR − η INR,SU.
For sufficiently large number of users, the proposed CoMP-HARQ scheme can be modeled as a collection of single-user interference-free networks experiencing a modified SNR.
With a fixed number of retransmissions, the throughput achieved by the considered CoMP-HARQ schemes is upper bounded even if the transmission power goes to infinity.
For Rayleigh fading channels, the proposed CoMP-HARQ network can be modeled/underestimated by N interference-free single-user networks having a modified transmission SNR.
However, the proposed CoMP-HARQ approach makes it possible to utilize the SINR variations and, depending on the channel pdf, increase the throughput by implementation of basic ARQ.
The results are of particular interest when we remember that, although HARQ schemes have been widely studied in single-user [36 41] and MIMO systems with asymptotically high signal-to-noise ratios (SNRs) [42 47], there are very few results for CoMP-HARQ [48].
