Energy harvesting (EH) from ambient energy sources can potentially reduce the dependence on the supply of grid or battery energy, providing many benefits to green communications. In this paper, we investigate the device-to-device (D2D) user equipments (DUEs) multiplexing cellular user equipments (CUEs) downlink spectrum resources problem for EH-based D2D communication heterogeneous networks (EH-DHNs). Our goal is to maximize the average energy efficiency of all D2D links, in the case of guaranteeing the quality of service of CUEs and the EH constraints of the D2D links. The resource allocation problems contain the EH time slot allocation of DUEs, power and spectrum resource block (RB) allocation. In order to tackle these issues, we formulate an average energy efficiency problem in EH-DHNs, taking into consideration EH time slot allocation, power and spectrum RB allocation for the D2D links, which is a nonconvex problem. Furthermore, we transform the original problem into a tractable convex optimization problem. We propose joint the EH time slot allocation, power and spectrum RB allocation iterative algorithm based on the Dinkelbach and Lagrangian constrained optimization. Numerical results demonstrate that the proposed iterative algorithm achieves higher energy efficiency for different network parameters settings.

Energy Efficient Resource Allocation Algorithm in Energy Harvesting-Based D2D Heterogeneous Networks

Since the recently emerging mobile applications have posed significant demands not only on high data rate but also on high caching and computing capabilities, the growth in communication capability alone is no longer sustainable for wireless networks. The integration of networking, caching, and computing functionalities into one system can provide not only native support for highly scalable and efficient content retrieval, but also powerful capability of data processing, hence reducing duplicate content transmissions and enabling swift executions of computationally intensive tasks. Despite the prospect of integrated networking, caching, and computing systems, a number of significant research challenges remain to be addressed prior to widespread deployment of integrated networking, caching, and computing systems, including latency requirement, interfaces, mobility management, resource and architecture tradeoffs, convergence, etc. In this paper, we provide a brief survey on some of the works that have been done to enable the integrated networking, caching, and computing system, and discuss several research challenges. We identify a number of important aspects of the integration of networking, caching, and computing: motivations, frameworks, performance metrics, enabling technologies, and challenges. At last, some broader perspectives are explored.

Integration of Networking, Caching, and Computing in Wireless Systems: A Survey, Some Research Issues, and Challenges

The future wireless networks need to improve spectrum and energy efficiency to satisfy the increasing demand for high data rate. Device-to device (D2D) communications have the ability to address this problem. This paper focuses on the underlay D2D relay function to improve cellular coverage quality. Although there are a few relevant works in this aspect, there is room for further improvement. For example, there is the constraint on the number of relays in a transmission path, which hardly meets the requirement of the cell-edge devices to fully improve their cellular throughput. Also, there is little energy constraint for underlay D2D relay selection, which is difficult to guarantee the service life of underlay D2D relaying links. Furthermore, without careful regulation of transmission power in terms of cellular coverage improvement, it is not conducive to the improvement of spectrum and energy efficiency in this aspect. Therefore, this paper proposes the improved scheme to deal with these problems, which can: 1) improve spectrum efficiency by using underlay spectrum sharing mode and alleviating its weakness (e.g., co-channel interference); 2) enhance comprehensive performance of underlay D2D relaying links by jointly considering multiple Quality-of-Service (QoS) metrics; 3) reduce overhead of relay selection by proposing a greedy algorithm based on a distributed local search; and 4) improve both energy efficiency and convergence time by designing a new power adjustment scheme based on the improved potential game decision algorithm. The theoretical analysis proves the existence of Nash equilibrium, and the simulation results show that the proposed game decision algorithm accelerates convergence and the proposed whole scheme improves cellular coverage quality.

Multi-Hop Relay-Aided Underlay D2D Communications for Improving Cellular Coverage Quality

In this paper, we propose a full-duplex orthogonal frequency-division multiplexing (OFDM) device-to-device (D2D) system in two-hop networks, where multiple full-duplex decode-and-forward relays assist the transmission from D2D user equipment (DUE) transmitter to DUE receiver. By such a transmission mechanism, the signal transmitted by the DUE transmitter does not need to go through a base station. Meanwhile, due to the adoption of underlay D2D communication protocol, power control mechanisms are thereby necessary to be applied to mitigate the interference to conventional cellular communications. Based on these considerations, we analyze the outage performance of the proposed system, and derive the exact expressions of outage probabilities when bulk and per-subcarrier relay selection criteria are applied. Furthermore, closed-form expressions of outage probabilities are also obtained for special cases when the instantaneous channel state information between BS and cellular user equipments is not accessible, so that a static power control mechanism is applied. Subsequently, we also investigate the outage performance optimization problem by coordinating transmit power among DUE transmitter and relays, and provide a suboptimal solution, which is capable of improving the outage performance. All analyses are substantiated by numerical results provided by Monte Carlo simulations. The analytical and numerical results demonstrated in this paper can provide an insight into the full-duplex relay-assisted OFDM D2D systems, and serve as a guideline for its implementation in next generation networks.

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Multicarrier Relay Selection for Full-Duplex Relay-Assisted OFDM D2D Systems

This paper looks into the problem of a decentralized data offloading within an edge unmanned aerial vehicle (UAV) swarm to mitigate the complexities of a single UAV continually generating and processing large application-specific data. The mobile edge UAVs considered here are multirotor types having constrained energy and processing power, which makes long-term handling of large data volumes impossible for standalone UAVs. The load mitigation is carried out by offloading data from a source UAV to other swarm members with sufficient energy and processing requirements. In this paper, we focus on selecting the most optimal multihop path through the UAVs concerning available energies and processing resources, which can survive the duration of the data offload between the source and a target UAV. We formulate a multiarmed bandit-based offload path selection scheme, which selects the most energy and processing optimized multihop path between a source and a target UAV. Upon comparison of our scheme against the naive shortest path approach, we observe that our approach results in significant savings of collective network energies, even for long operational durations.

Resource-Optimized Multiarmed Bandit-Based Offload Path Selection in Edge UAV Swarms

Device-to-device (D2D) communication is a promising technique for traffic offloading in next-generation cellular systems. However, the use of only direct D2D communications limits the advantages of D2D communications due to relatively long separation distances or poor link quality between source and destination user equipments (UEs). Relay-assisted D2D communication was proposed as a supplement to direct D2D communications for enhancing traffic offloading capacity in long-term evolution–advanced (LTE-A) systems. This work aims to design a relay UE selection strategy for D2D communications, which improves D2D communication performance significantly. We propose a cross-layer relay selection scheme that considers several criteria jointly, including end-to-end data rate, relay-capable UE (RUE) remaining battery time, and end-to-end transmission delay on relay-assisted D2D path. We show how to leverage these criteria at an eNB performing relay selection in D2D communications. In particular, an end-to-end delay estimation model is established based on queuing theory. Simulation results validate the performance of the proposed scheme in terms of total amount of data transmitted under RUE remaining battery and end-to-end transmission delay.

On Relay Selection Schemes for Relay-Assisted D2D Communications in LTE-A Systems

D2D communication is an effective approach for traffic offloading in future cellular systems. However, only using direct D2D communication is not enough to fully exploit the advantages of D2D communications due to long distances or poor link quality between source and destination D2D UEs. This work aims to enhance the traffic offloading capacity of cellular-assisted D2D communication, taking into account D2D relays. In particular, we propose a unified model for D2D communication, in which two other D2D communication modes, that is, relay-assisted D2D and local route based D2D, are also supported by UEs in addition to direct D2D mode. We design radio protocol architectures for the three D2D modes and propose an eNB scheduling algorithm, which enables the eNB to perform joint scheduling on mode selection, radio resource allocation, and power coordination for all D2D pairs in each subframe. The effectiveness of our designs is validated by simulations.

Mode Selection, Radio Resource Allocation, and Power Coordination in D2D Communications

A method for transmitting a plurality of data packets is disclosed. The method includes: receiving one or more first medium access control (MAC) protocol data units (PDUs) which include a plurality of radio link control (RLC) PDUs intended for a destination UE from a source UE; demultiplexing the first MAC PDUs to retrieve the RLC PDUs based on a header field of each first MAC PDU; generating a plurality of RLC PDU segments from one or more of the RLC PDUs or a plurality of RRLC (Relay RLC) PDUs from all of the RLC PDUs according to one or more MAC PDU sizes, wherein the RRLC is a protocol layer between the MAC layer and the RLC layer; multiplexing the RLC PDUs and the RLC PDU segments or the RRLC PDUs into one or more second MAC PDUs; and transmitting the second MAC PDUs to the destination UE.

Communication system, communication device, base station and method thereof for D2D communications

A method for receiving a plurality of data packets is disclosed. The method includes: receiving MAC PDUs from a source UE of the wireless network through a relay UE, a base station and directly from the source UE, wherein the MAC PDUs are composed of RLC PDUs and RLC PDU segments; demultiplexing the MAC PDUs to retrieve the RLC PDUs and the RLC PDU segments based on a header field of each MAC PDU; reordering the RLC PDUs and the RLC PDU segments and performing a duplicate detection of the RLC PDUs and the RLC PDU segments according to TSNs, wherein each TSN is included in a header field of each RLC PDU and each RLC PDU segment; and reassembling the RLC PDUs and the RLC PDU segments into RLC SDUs using information included in the header field of each RLC PDU and each RLC PDU segment.

Chun-Yuan Chiu

Papers

On Relay Selection Schemes for Relay-Assisted D2D Communications in LTE-A Systems

Mode Selection, Radio Resource Allocation, and Power Coordination in D2D Communications

Communication system, communication device, base station and method thereof for D2D communications

Communication device and method thereof for D2D communications