Allocating multiple d2d users to subchannels with partial csi in multi-cell scenarios

Abstract

We address the problem of allocating multiple device-to-device (D2D) pairs per subchannel in a multi-cell scenario with multiple subchannels and unknown inter-D2D and inter-cell interference. We propose a scheme to feedback q bits about the signal-to-interference-plus-noise ratio of a D2D pair for each subchannel that ensures that the D2D rates can be achieved with a pre-specified probability of outage. Along with this, the base station (BS) has only statistical information about the inter-cell interference, and has to provide a quality-ofservice guarantee to the scheduled cellular users. We formulate the subchannel allocation problem as a generalized assignment problem, and propose a low-complexity locally greedy algorithm (LGA) to solve it. LGA provably achieves a D2D sum rate that is at least 1/2 and 1/3 of the maximum achievable D2D sum rate for q = 1 and q ≥ 2, respectively. We then propose a rate upgradation (RU) step that enhances the D2D rate by exploiting an inherent asymmetry in the channel state information (CS!) at the BS and D2D pairs. LGA with RU achieves a spectral efficiency that is markedly better than conventional approaches that assign one D2D pair per subchannel, and close to that of a system with full CS! of the intra-cell links even for small q.