Benchmarking Practical RRM Algorithms for D2D Communications in LTE Advanced

Abstract

Device-to-device (D2D) communication integrated into cellular networks is a means to take advantage of the proximity of devices and allow for reusing cellular resources and thereby to increase the user bitrates and the system capacity. However, when D2D (in the 3 rd Generation Partnership Project also called Long Term Evolution (LTE) Direct) communication in cellular spectrum is supported, there is a need to revisit and modify the existing radio resource management (RRM) and power control (PC) techniques to realize the potential of the proximity and reuse gains and to limit the interference at the cellular layer. In this paper, we examine the performance of the flexible LTE PC tool box and benchmark it against a utility optimal iterative scheme. We find that the open loop PC scheme of LTE performs well for cellular users both in terms of the used transmit power levels and the achieved signal-to-interference-and-noise-ratio (SINR) distribution. However, the performance of the D2D users as well as the overall system throughput can be boosted by the utility optimal scheme, because the utility maximizing scheme takes better advantage of both the proximity and the reuse gains. Therefore, in this paper we propose a hybrid PC scheme, in which cellular users employ the open loop path compensation method of LTE, while D2D users use the utility optimizing distributed PC scheme. In order to protect the cellular layer, the hybrid scheme allows for limiting the interference caused by the D2D layer at the cost of having a small impact on the performance of the D2D layer. To ensure feasibility, we limit the number of iterations to a practically feasible level. We make the point that the hybrid scheme is not only near optimal, but it also allows for a distributed implementation for the D2D users, while preserving the LTE PC scheme for the cellular users.

Performance Comparison of Practical Resource Allocation Schemes for Device‐to‐Device Communications

“…Allocation Algorithms [7,9,25]. In general, a cellular system provides service to cellular UEs and D2D transmitters and the corresponding D2D receivers that belong to the sets N and M, respectively, such that the total number of served UEs in a cell is = + .…”

“…To solve Problem (8) and to obtain benchmarking results, we first describe a centralized procedure based on the full knowledge of the channel gain measurements between all transmitters and receivers within the cell, first proposed by [25]. This scheme, that we call MinInterf, exploits the proximity between D2D candidates for MS and performs RA that aims at reducing the intracell interference by minimizing the sum of the harmful path gains as will be shown in (9) and in Algorithm 1.…”

“…Practically feasible MS, RA, and PC algorithms for D2D communications often rely on the availability of large scale channel state information, such as the large scale channel gains between transmitters and intended receivers [24,25] as it will be discussed in detail in the next section.…”

Energy Efficient D2D Communications in Dynamic TDD Systems

“…To realize the full potential of D2D communications, the mode selection should be done jointly with the radio resource allocation. Several works have investigated this joint problem [8]- [10], mainly developing mixed-integer programming models and dealing with NP-hard formulations. Hence, heuristics [11]- [13] and game-theoretic approaches [14] have also been explored as more practical alternatives.…”

“…Problem (10) can be solved efficiently using a wide variety of methods, including simple bisection search [25]. Let t ul denote the optimal solution to (10).…”