Number Of D2D Users Research Articles

Joint Particle Swarm Optimization of Power and Phase Shift for IRS-Aided D2D Underlaying Cellular Systems.

Device-to-device (D2D) communication is a promising wireless communication technology which can effectively reduce the traffic load of the base station and improve the spectral efficiency. The application of intelligent reflective surfaces (IRS) in D2D communication systems can further improve the throughput, but the problem of interference suppression becomes more complex and challenging due to the introduction of new links. Therefore, how to perform effective and low-complexity optimal radio resource allocation is still a problem to be solved in IRS-assisted D2D communication systems. To this end, a low-complexity power and phase shift joint optimization algorithm based on particle swarm optimization is proposed in this paper. First, a multivariable joint optimization problem for the uplink cellular network with IRS-assisted D2D communication is established, where multiple DUEs are allowed to share a CUE's sub-channel. However, the proposed problem considering the joint optimization of power and phase shift, with the objective of maximizing the system sum rate and the constraints of the minimum user signal-to-interference-plus-noise ratio (SINR), is a non-convex non-linear model and is hard to solve. Different from the existing work, instead of decomposing this optimization problem into two sub-problems and optimizing the two variables separately, we jointly optimize them based on Particle Swarm Optimization (PSO). Then, a fitness function with a penalty term is established, and a penalty value priority update scheme is designed for discrete phase shift optimization variables and continuous power optimization variables. Finally, the performance analysis and simulation results show that the proposed algorithm is close to the iterative algorithm in terms of sum rate, but lower in power consumption. In particular, when the number of D2D users is four, the power consumption is reduced by 20%. In addition, compared with PSO and distributed PSO, the sum rate of the proposed algorithm increases by about 10.2% and 38.3%, respectively, when the number of D2D users is four.

Hybrid spectrum access in a cognitive radio‐enabled cooperative device‐to‐device network

SummaryIn this paper, the performance of a co‐operative device‐to‐device (D2D) network is investigated. All the D2D users sense the cellular user (CU) spectrum and use it in hybrid mode: underlay and overlay. The expressions of throughput and outage are developed under the considered network scenario. An algorithm is proposed to optimize the sensing time to minimize the outage. The performance is investigated in terms of throughput and outage for several network parameters such as a number of D2D users, sensing time, signal‐to‐noise ratio (SNR), allowable interference threshold, and CU transmit power. Sensing time is optimized to minimize the outage. The interference threshold and target rate have a significant impact on network performance. The network has to suffer outage for lower values of allowable interference threshold and higher values of the target rate. The impact of channel fading on the network performance is also studied. A simulation model is developed in MATLAB on the basis of the analytical development of the considered network model.

Throughput Maximization for Multiple D2D Group Communications Underlaying Cellular Networks

In the scenario where multiple device-to-device (D2D) users and cellular users coexist, the large number of D2D users not only results in the shortage of spectrum resources but also brings interference to the communication of cellular users. In this paper, we establish a clustering model centered on cellular users and propose a resource allocation algorithm based on a D2D clustering model. On the basis of ensuring the throughput requirements of cellular users, this algorithm reconstructs various matrices in the graph theory through probability models, sets the priority of D2D pairs, and maximizes the number of user accesses under interference tolerance. Besides, on the optimization of the number of users, we adopt the Rubinstein game model to adjust the game order according to the priority and optimize the bandwidth allocation mode, so as to improve the overall throughput of the network. Simulation results show that the proposed algorithm can increase the number of users and the network throughput, while shortening the spectrum allocation time by more than half.

Pilot Reuse and Interference-Aided MMSE Detection for D2D Underlay Massive MIMO

In uplink device-to-device (D2D) underlay cellular systems, massive multiple-input multiple-output (MIMO) seems promising as the large antenna array at the base station (BS) can nearly null the D2D-to-cellular interference. However, the channel-state information (CSI) from all users is required to obtain this advantage. For the orthogonal training scheme, the pilot overhead increases with the number of D2D users, leading to a loss of the achievable spectral efficiency. In this paper, we propose a pilot scheduling scheme for D2D underlay massive MIMO systems, which allows D2D users to reuse the pilots of cellular users so that the pilot overhead can be reduced. Moreover, a novel interference-aided minimum mean square error (MMSE) detector is proposed to suppress the D2D-to-cellular interference, utilizing the estimated CSI from not only cellular users but D2D users as well. Furthermore, we derive the large-scale approximations of the signal-to-interference-plus-noise ratios (SINRs), which are asymptotically tight and accurate, even for a small number of BS antennas. Based on these SINR approximations, performance analyses are given to provide more insights. Simulation results show that the proposed pilot reuse scheme and detector significantly increase the achievable sum spectral efficiency, as compared with the conventional massive MIMO and other baseline schemes.

大规模MIMO-D2D蜂窝网络中的下行传输速率研究

为了顺应第五代移动通信技术(5G)的发展，本文探讨了大规模MIMO与D2D通信混合蜂窝网络中的下行链路频谱效率问题。特别，针对三种用户分布场景，利用D2D用户和蜂窝用户覆盖率解析表达式分析了蜂窝用户传输速率变化情况。结果表明，为确保蜂窝通信，应严格控制D2D用户接入数目，同时增加天线数，以有效弥补干扰。此外，通过对D2D用户引入On-Off功率控制方法，并优化接入传输概率，本文实现了对D2D用户的频谱效率的提升。 In order to adapt to the development of the fifth generation mobile communication technology (5G), this paper investigates the downlink transmission rate for D2D underlaying large-scale MIMO cellular networks. In particular, based on analytical expressions of coverage probabilities of both D2D users and downlink cellular users, the transmission rate of cellular users are analyzed for three user distributed scenarios. The results show that in order to ensure the cellular communication, the number of D2D users should be strictly controlled, and the number of antennas can be increased in order to compensate for the interference efficiently. The transmission rate with the D2D users can be improved by making use of On-Off power control method for D2D users and optimizing the access transmission probability.

Unmanned Aerial Vehicle With Underlaid Device-to-Device Communications: Performance and Tradeoffs

In this paper, the deployment of an unmanned aerial vehicle (UAV) as a flying base station used to provide on the fly wireless communications to a given geographical area is analyzed. In particular, the co-existence between the UAV, that is transmitting data in the downlink, and an underlaid device-todevice (D2D) communication network is considered. For this model, a tractable analytical framework for the coverage and rate analysis is derived. Two scenarios are considered: a static UAV and a mobile UAV. In the first scenario, the average coverage probability and the system sum-rate for the users in the area are derived as a function of the UAV altitude and the number of D2D users. In the second scenario, using the disk covering problem, the minimum number of stop points that the UAV needs to visit in order to completely cover the area is computed. Furthermore, considering multiple retransmissions for the UAV and D2D users, the overall outage probability of the D2D users is derived. Simulation and analytical results show that, depending on the density of D2D users, optimal values for the UAV altitude exist for which the system sum-rate and the coverage probability are maximized. Moreover, our results also show that, by enabling the UAV to intelligently move over the target area, the total required transmit power of UAV while covering the entire area, is minimized. Finally, in order to provide a full coverage for the area of interest, the tradeoff between the coverage and delay, in terms of the number of stop points, is discussed.