Multi-Hop D2D Communications With Network Coding: From a Performance Perspective

ABSTRACTIn this paper, we consider the wireless communication systems where multi-hop Device-to-Device (D2D) networks can coexist with the conventional cellular networks by sharing the downlink resource of cellular users (CUs). A multicast data flow is distributed over the multi-hop D2D networks where network coding (NC) can be employed at the intermediate nodes. To maximize the utility of the multicast flow, we formulate a joint optimization problem for the systems while guaranteeing the quality-of-service (QoS) for regular CUs. We propose a subgradient algorithm to solve the optimization problem by decomposing it into three sub-problems: multicast rate control, NC subgraph selection, and downlink resource reusing. In particular, we develop a greedy algorithm to deal with the downlink resource reusing sub-problem for it is NP hard. Numerical and simulation results prove the superior performance of the proposed techniques compared with the conventional routing scheme.

Multi-hop D2D (Device-to-Device) communication is often exposed to many intrusions for its inherent properties, such as openness and weak security protection. To mitigate the intrusions in time, one of significant approaches is to establish a Cooperative Intrusion Response System (CIRS) to respond to intrusion activities during data transmission. In CIRS, user equipments that act as relays (RUEs) are assumed to actively help destination nodes to respond to intrusion activities. However, this assumption is often invalid in multi-hop D2D communication because the RUEs are selfish and unwilling to spend extra resources on undertaking response tasks. To address this problem, a game approach is proposed to encourage RUEs to cooperate. In detail, we formulate an incentive mechanism for CIRS in multi-hop D2D communication as a dynamic game and achieve an optimal solution to help RUEs decide whether to participate in detection or not. Theoretical analysis shows that only one Nash equilibrium exists for the proposed game. Simulations demonstrate that our mechanism can efficiently motivate potential RUEs to participate in intrusion detection and response, and it can also block intrusion propagation in time.

As the demand of mobile devices (MDs) for data services is explosively increasing, traditional offloading in the cellular networks is facing the contradiction of energy efficiency and quality of service. Device-to-device (D2D) communication is considered as an effective solution. This work investigates a scenario where the MDs have the same demand for common content and they cooperate to deliver it using multicast multihop relaying. We focus on the problem of total power minimization by grouping the MDs in multihop D2D networks, while maintaining the minimum rate requirement of each MD. As the problem is shown to be NP-complete and the optimal solution can not be found efficiently, two greedy algorithms are proposed to solve this problem in polynomial time. Simulation results demonstrate that lots of power can be saved in the content delivery situation using multihop D2D communication, and the proposed algorithms are suitable for different situations with different advantages.

In recent years, device-to-device (D2D) communication has attained significant attention in the research community. The advantages of D2D communication can be fully realized in multi-hop communication scenario. The integration of cellular and multi-hop networks not only provides guaranteed quality of service and reliability as a traditional cellular network, but also has the flexibility and adaptability as a multi-hop network. Routing in such multi-hop cellular D2D networks is a critical issue, since the multi-hop network can perform worse than a traditional cellular network if wrong routing decisions are made. This is because routing in these multi-hop networks needs to take care of the node mobility, dynamic network topology, and network fragmentation, which did not exist in traditional cellular networking. This paper provides a comprehensive survey of routing in multi-hop D2D networks. Some future research directions for the routing in D2D networks are also discussed at the end of this paper.

One goal of the fifth-generation (5G) cellular network is to support much higher data capacity (e.g., 1000 times higher than today), where device-to-device (D2D) communication is one of the key enabling technologies. In this paper, we focus on the D2D relaying functionality to improve cellular downlink throughput. Based on the shortages of the latest relevant work, we propose a new scheme that leverages multi-hop relay-assisted outband D2D communications. First of all, by extending two-hop connection to three-hop connection, our scheme can cut down receiving bit error ratio (BER) of cell edge nodes far away from a cellular base station (BS), which improves cellular downlink throughput. Then, it balances network lifetime and throughput by the proposed ratio of income and expenditure (RIE) metric with respect to remaining energy and throughput. Moreover, it reduces the computational overhead of searching relay and also ensures that the optimal relay is selected by the adjustment of searching scope. Compared with the most relevant work, our scheme outperforms it in terms of throughput, delay, and network lifetime.

Cellular networks operators is facing one great challenge on how to manage the exponential data traffic increase. Mobile data offloading can be a low-cost and efficient way to relieve the pressure of cellular networks. Among various offloading techniques, device- to-device (D2D) communications has gained more and more attention. However, current studies mainly concentrated on traffic offloading between two user equipments directly, i.e., single-hop D2D and most of them are theoretic works. In this paper, with smartphones we build a multihop D2D communications platform which can expand the application scenarios of single-hop D2D communications. We utilize the platform to measure and analyze some important performances of multihop D2D communications and experiment results demonstrate the importance of multihop to D2D communications. The performances include energy consumption, network delay, coverage and link quality. We believe our work can provide a valuable reference to the works of multihop D2D communications based mobile data offloading and other related ones.

In recent years, networks for unmanned aircraft vehicle (UAV)-assisted device-to-device (D2D) communication have attracted attention, as they can be employed for emergency communication in the event of a large-scale disaster. However, many existing UAV-assisted D2D communication technology strategies neglect the UAV energy consumption during flight. Further, only the links between the UAV and ground devices are evaluated, without assumption of a wide information diffusion range. Herein, we propose a novel multihop D2D communication method that exploits UAV technology and uniquely designed virtual cells to achieve information diffusion to remote areas. Moreover, we establish a model to evaluate the trade-off between the UAV flight energy consumption and the communication performance between the UAV and mobile devices. By employing the constructed model and demonstrating the energy efficiency trend, we confirm the effectiveness of the proposed method combining multihop D2D communication and UAV technology.

Network-assisted single-hop device-to-device (D2D) communication can increase the spectral and energy efficiency of cellular networks by taking advantage of the proximity, reuse, and hop gains when radio resources are properly managed between the cellular and D2D layers. In this paper we argue that D2D technology can be used to further increase the spectral and energy efficiency if the key D2D radio resource management algorithms are suitably extended to support network assisted multi-hop D2D communications. Specifically, we propose a novel, distributed utility maximizing D2D power control (PC) scheme that is able to balance spectral and energy efficiency while taking into account mode selection and resource allocation constraints that are important in the integrated cellular-D2D environment. Our analysis and numerical results indicate that multi-hop D2D communications combined with the proposed PC scheme can be useful not only for harvesting the potential gains previously identified in the literature, but also for extending the coverage of cellular networks.

Device-to-device (D2D) communications are usually considered to be two user equipment units (UEs) communicating directly without going through the central base station (BS). In fact, they can be further broadened to multihop D2D communications in which a UE may help other UEs communicate with each other or assist other UEs to communicate with the BS. In this paper, the authors investigate a scenario of multihop D2D communications where one UE may help other two UEs to exchange information with a two-time-slot physical-layer network coding scheme. The authors analyze the average energy efficiency and spectral efficiency of multihop D2D communications under Rayleigh fading channels and get close analytical approximations based on Taylor series expansion. Comparisons with direct D2D communications and traditional cellular communications through BS are provided. The optimal UE transmission powers of these three different modes to maximize the energy efficiency are also derived.

Energy-efficient relay selection and power allocation for multi-source multicast network-coded D2D communications

We propose a multiple-input multiple-output (MIMO) two-way relaying based underlay device-to-device (D2D) communication system, in which relay uses physical layer network coding (PNC). Both cellular and D2D communication take place in the same spectrum. D2D communication is based on PNC, and a joint transceiver design is required to facilitate PNC mapping with MIMO channels. A joint precoder-decoder scheme is also considered in the cellular communication to mitigate interference, and improve the error performance. Mean square errors at nodes are considered as the objective function, and interference threshold limits and power constraints are also used in joint precoder-decoder design problems. These turn out to be non-convex optimization problems, and we propose two algorithms in both phases of D2D and cellular communication. Distributed optimization methods are used in the proposed algorithms. We analyze the convergence of proposed algorithms, and the system performances are investigated with different D2D pair locations, interference constraint thresholds, and maximum available power at nodes.

Device-to-Device (D2D) communication has been proven an efficient technique in the present and upcoming cellular networks for improving network performance. Many a time, a direct D2D link may not be available due to longer distance or poor channel quality between two devices. Multi-hop D2D is an effective solution to overcome this limitation of direct D2D communication. Here relay devices help in forwarding data from transmitters to the receivers through single or multiple hops. However, finding suitable fixed relays and their locations is a complex problem, which does not have an efficient solution. In this paper, we have used UAVs (drones) that act as relays for forwarding data between two devices. The proposed approach serves more out of direct range D2D users resulting in a reduced churn rate of the system. We find the trajectory of such UAVs with the help of active user prediction using Neural Networks (NN) to serve all the D2D users by increasing the coverage range of D2D communications. We have estimated the number of active D2D users in every zone covered by each drone and intra and inter-drone communication trajectories. It is also shown that the packet loss ratio remains within the acceptable limit for the proposed trajectories of the UAVs by choosing a sufficient buffer length.

In this paper, the impact of co-channel interference (CCI) on the performance of an underlay cognitive radio network over Nakagami- ${m}$ fading channels is thoroughly presented and analysed. More precisely, a decode-and-forward relay protocol for a cognitive cooperative network is considered. In this study, the impact of both the primary transmitter interference and CCI on the secondary system performance are considered. First, an exact expression for the equivalent signal-to-interference-plus-noise ratio of the secondary system is obtained. Then, the corresponding exact and asymptotic cumulative distribution functions are derived. From this, the exact outage performance for the secondary network is investigated. Furthermore, the equivalent probability density function is obtained and discussed. In addition, approximate expressions for the average error probability and the system ergodic capacity performances are derived. From the results, it can be inferred that the presence of the CCI and primary network interference severely degrades the system performance. Moreover, a higher value of the shape parameter of the desired fading channel gives better performance and diversity gain. In addition, despite the impact of interferences, the secondary network performance gives better results in comparison to the Rayleigh fading channels scenario.

Network coding (NC) consists of intelligently aggregating data packets by means of binary or linear combinations. NC has been considered as one of the possible solutions to the current low throughput, energy consumption, packet loss, non-connectivity and mobility support problems in MANETs. Sliding-window Network Coding is a variation of NC that is an addition to TCP/IP and improves the throughput of TCP on wireless networks. In this paper, we propose a Variable Length Sliding Window-based Network Coding algorithm in MANETs (VLSW-NC). The performance of this VLSW-NC is studied using NS2 and evaluated in terms of the throughput, packet loss probability, and decoding delay when packet is transmitted. The simulations results shows that the VLSW-NC achieved with our proposition can significantly improve the network performance and reliability.

On energy efficient secure routing in multi-hop underlay D2D communications for IoT applications