Device-to-device communication in cellular networks : multi-hop path selection and performance.

Over the past decade, the proliferation of internet equipment and an increasing number of people moving into cities have significantly influenced mobile data demand density and intensity. To accommodate the increasing demands, the fifth generation (5G) wireless systems standards emerged in 2014. Device-to-device communications (D2D) is one of the three primary technologies to address the key performance indicators of the 5G network. D2D communications enable devices to communicate data information directly with each other without access to a fixed wireless infrastructure. The potential advantages of D2D communications include throughput enhancement, device energy saving and coverage expansion. The economic attraction to mobile operators is that significant capacity and coverage gains can be achieved without having to invest in network-side hardware upgrades or new cell deployments. However, there are technical challenges related to D2D and conventional cellular communication (CC) in co-existence, especially their mutual interference due to spectrum sharing. A novel interference-aware-routing for multi-hop D2D is introduced for reducing the mutual interference. The first verification scenario of interference-aware-routing is that in a real urban environment. D2D is used for relaying data across the urban terrain, in the presence of CC communications. Different wireless routing algorithms are considered, namely: shortest-path-routing, interference-aware-routing, and broadcast-routing. In general, the interference-aware-routing achieves a better performance of reliability and there is a fundamental trade-off between D2D and CC outage performances, due to their mutual interference relationship. Then an analytical stochastic geometry framework is developed to compare the performance of shortest-path-routing and interference-aware-routing. Based on the results, the spatial operational envelopes for different D2D routing algorithms and CC transmissions based on the user equipment (UEs) physical locations are defined. There is a forbidden area of D2D because of the interference from the base stations (BSs), so the collision probability of the D2D multi-hop path hitting the defined D2D forbidden area is analysed. Depend on the result of the collision probability, a dynamic switching strategy between D2D and CC communications in order to minimise mutual interference is proposed. A blind gradient-based transmission switching strategy is developed to avoid collision within the collision area and only requires knowledge of the distances to the serving base station of the current user and the final destination user. In the final part of my research, the concept of LTE-U (Long term evolution for Unlicensed Spectrum), which suggests that LTE can operate in the unlicensed spectrum with significant modifications to its transmission protocols, is investigated. How the envisaged D2D networks can efficiently scale their capacity by utilising the unlicensed spectrum with appropriately designed LTE-Unlicensed protocols is examined

Advanced Technologies for Device-to-device Communications Underlaying Cellular Networks

The past few years have seen a major change in cellular networks, as explosive growth in data demands requires more and more network capacity and backhaul capability. New wireless technologies have been proposed to tackle these challenges. One of the emerging technologies is device-to-device (D2D) communications. It enables two cellular user equip- ment (UEs) in proximity to communicate with each other directly reusing cellular radio resources. In this case, D2D is able to of oad data traf c from central base stations (BSs) and signi cantly improve the spectrum ef ciency of a cellular network, and thus is one of the key technologies for the next generation cellular systems. Radio resource management (RRM) for D2D communications and how to effectively exploit the potential bene ts of D2D are two paramount challenges to D2D communications underlaying cellular networks. In this thesis, we focus on four problems related to these two challenges. In Chapter 2, we utilise the mixed integer non-linear programming (MINLP) to model and solve the RRM optimisation problems for D2D communications. Firstly we consider the RRM optimisation problem for D2D communications underlaying the single carrier frequency division multiple access (SC-FDMA) system and devise a heuristic sub- optimal solution to it. Then we propose an optimised RRM mechanism for multi-hop D2D communications with network coding (NC). NC has been proven as an ef cient technique to improve the throughput of ad-hoc networks and thus we apply it to multi-hop D2D communications. We devise an optimal solution to the RRM optimisation problem for multi-hop D2D communications with NC. In Chapter 3, we investigate how the location of the D2D transmitter in a cell may affect the RRM mechanism and the performance of D2D communications. We propose two optimised location-based RRM mechanisms for D2D, which maximise the throughput and the energy ef ciency of D2D, respectively. We show that, by considering the location information of the D2D transmitter, the MINLP problem of RRM for D2D communications can be transformed into a convex optimisation problem, which can be ef ciently solved by the method of Lagrangian multipliers. In Chapter 4, we propose a D2D-based P2P le sharing system, which is called Iunius. The Iunius system features: 1) a wireless P2P protocol based on Bittorrent protocol in the application layer; 2) a simple centralised routing mechanism for multi-hop D2D communications; 3) an interference cancellation technique for conventional cellular (CC) uplink communications; and 4) a radio resource management scheme to mitigate the interference between CC and D2D communications that share the cellular uplink radio resources while maximising the throughput of D2D communications. We show that with the properly designed application layer protocol and the optimised RRM for D2D communications, Iunius can signi cantly improve the quality of experience (QoE) of users and of oad local traf c from the base station. In Chapter 5, we combine LTE-unlicensed with D2D communications. We utilise LTE-unlicensed to enable the operation of D2D in unlicensed bands. We show that not only can this improve the throughput of D2D communications, but also allow D2D to work in the cell central area, which normally regarded as a “forbidden area” for D2D in existing works. We achieve these results mainly through numerical optimisation and simulations. We utilise a wide range of numerical optimisation theories in our works. Instead of utilising the general numerical optimisation algorithms to solve the optimisation problems, we modify them to be suitable for the speci c problems, thereby reducing the computational complexity. Finally, we evaluate our proposed algorithms and systems through sophisticated numer- ical simulations. We have developed a complete system-level simulation framework for D2D communications and we open-source it in Github: https://github.com/mathwuyue/py- wireless-sys-sim

D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies

This document provides the most recent updates on the technical contributions and research challenges focused in WP3. Each Technology Component (TeC) has been evaluated under possible uniform assessment framework of WP3 which is based on the simulation guidelines of WP6. The performance assessment is supported by the simulation results which are in their mature and stable state. An update on the Most Promising Technology Approaches (MPTAs) and their associated TeCs is the main focus of this document. Based on the input of all the TeCs in WP3, a consolidated view of WP3 on the role of multinode/multi-antenna transmission technologies in 5G systems has also been provided. This consolidated view is further supported in this document by the presentation of the impact of MPTAs on METIS scenarios and the addressed METIS goals.Aziz, D.; Baracca, P.; De Carvalho, E.; Fantini, R.; Rajatheva, N.; Popovski, P.; Sørensen, JH.... (2015). D 3. 3 Final performance results and consolidated view on the most promising multi -node/multi -antenna transmission technologies. http://hdl.handle.net/10251/7675

D3.2 First performance results for multi -node/multi -antenna transmission technologies

This deliverable describes the current results of the multi-node/multi-antenna technologies investigated within METIS and analyses the interactions within and outside Work Package 3. Furthermore, it identifies the most promising technologies based on the current state of obtained results. This document provides a brief overview of the results in its first part. The second part, namely the Appendix, further details the results, describes the simulation alignment efforts conducted in the Work Package and the interaction of the Test Cases. The results described here show that the investigations conducted in Work Package 3 are maturing resulting in valuable innovative solutions for future 5G systems.Fantini. R.; Santos, A.; De Carvalho, E.; Rajatheva, N.; Popovski, P.; Baracca, P.; Aziz, D.... (2014). D3.2 First performance results for multi -node/multi -antenna transmission technologies. http://hdl.handle.net/10251/7675

Extended Coverage for Public Safety and Critical Communications Using Multi-hop and D2D Communications

In this thesis, we proposed the use of device-to-device (D2D) communications for extending the coverage area of active base stations, for public safety communications with partial coverage. A 3GPP standard compliant D2D system level simulator is developed for HetNets and public safety scenarios and used to evaluate the performance of D2D discovery and communications underlying cellular networks. For D2D discovery, the benefits of time-domain inter-cell interference coordi- nation (ICIC) approaches by using almost blank subframes were evaluated. Also, the use of multi-hop is proposed to improve, even further, the performance of the D2D discovery process. Finally, the possibility of using multi-hop D2D communications for extending the coverage area of active base stations was evaluated. Improvements in energy and spectral efficiency, when compared with the case of direct UE-eNB communi- cations, were demonstrated. Moreover, UE power control techniques were applied to reduce the effects of interference from neighboring D2D links