Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks

Soaring capacity and coverage demands dictate that future cellular networks need to soon migrate towards ultra-dense networks. However, network densification comes with a host of challenges that include compromised energy efficiency, complex interference management, cumbersome mobility management, burdensome signaling overheads and higher backhaul costs. Interestingly, most of the problems, that beleaguer network densification, stem from legacy networks' one common feature i.e., tight coupling between the control and data planes regardless of their degree of heterogeneity and cell density. Consequently, in wake of 5G, control and data planes separation architecture (SARC) has recently been conceived as a promising paradigm that has potential to address most of aforementioned challenges. In this article, we review various proposals that have been presented in literature so far to enable SARC. More specifically, we analyze how and to what degree various SARC proposals address the four main challenges in network densification namely: energy efficiency, system level capacity maximization, interference management and mobility management. We then focus on two salient features of future cellular networks that have not yet been adapted in legacy networks at wide scale and thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and device-to-device (D2D) communications. After providing necessary background on CoMP and D2D, we analyze how SARC can particularly act as a major enabler for CoMP and D2D in context of 5G. This article thus serves as both a tutorial as well as an up to date survey on SARC, CoMP and D2D. Most importantly, the article provides an extensive outlook of challenges and opportunities that lie at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201

Survey on the state-of-the-art in device-to-device communication: A resource allocation perspective

Device to Device (D2D) communication takes advantage of the proximity between the communicating devices in order to achieve efficient resource utilization, improved throughput and energy efficiency, simultaneous serviceability and reduced latency. One of the main characteristics of D2D communication is reuse of the frequency resource in order to improve spectral efficiency of the system. Nevertheless, frequency reuse introduces significantly high interference levels thus necessitating efficient resource allocation algorithms that can enable simultaneous communication sessions through effective channel and/or power allocation. This survey paper presents a comprehensive investigation of the state-of-the-art resource allocation algorithms in D2D communication underlaying cellular networks. The surveyed algorithms are evaluated based on heterogeneous parameters which constitute the elementary features of a resource allocation algorithm in D2D paradigm. Additionally, in order to familiarize the readers with the basic design of the surveyed resource allocation algorithms, brief description of the mode of operation of each algorithm is presented. The surveyed algorithms are divided into four categories based on their technical doctrine i.e., conventional optimization based, Non-Orthogonal-MultipleAccess (NOMA) based, game theory based and machine learning based techniques. Towards the end, several open challenges are remarked as the future research directions in resource allocation for D2D communication

Opportunistic device-to-device communication in cellular networks: from theory to practice

Mención Internacional en el título de doctorCellular service providers have been struggling with users’ demand since the emergence of mobile Internet. As a result, each generation of cellular network prevailed over its predecessors mainly in terms of connection speed. However, the fifth generation (5G) of cellular network promises to go beyond this trend by revolutionizing the network architecture. Device-to-Device (D2D) communication is one of the revolutionary changes that enables mobile users to communicate directly without traversing a base station. This feature is being actively studied in 3GPP with special focus on public safety as it allows mobiles to operate in adhoc mode. Although under the (partial) control of the network, D2D communications open the door to many other use-cases. This dissertation studies different aspects of D2D communications and its impact on the key performance indicators of the network. We design an architecture for the collaboration of cellular users by means of timely exploited D2D opportunities. We begin by presenting the analytical study on opportunistic outband D2D communications. The study reveals the great potential of opportunistic outband D2D communications for enhancing energy efficiency, fairness, and capacity of cellular networks when groups of D2D users can be form and managed in the cellular network. Then we introduce a protocol that is compatible with the latest release of IEEE and 3GPP standards and allows for implementation of our proposal in a today’s cellular network. To validate our analytical findings, we use our experimental Software Defined Radio (SDR)-based testbed to further study our proposal in a real world scenario. The experimental results confirm the outstanding potential of opportunistic outband D2D communications. Finally, we investigate the performance merits and disadvantages of different D2D “modes”. Our investigation reveals, despite the common belief, that all D2D modes are complementary and their merits are scenario based.This work has been supported by IMDEA Networks Institute.Programa Oficial de Doctorado en Ingeniería TelemáticaPresidente: Douglas Leith.- Secretario: Albert Banchs Roca.- Vocal: Carla Fabiana Chiasserin

Resource Allocation for D2D Communications Based on Matching Theory

PhDDevice-to-device (D2D) communications underlaying a cellular infrastructure takes advantage of the physical proximity of communicating devices and increasing resource utilisation. However, adopting D2D communications in complex scenarios poses substantial challenges for the resource allocation design. Meanwhile, matching theory has emerged as a promising framework for wireless resource allocation which can overcome some limitations of game theory and optimisation. This thesis focuses on the resource allocation optimisation for D2D communications based on matching theory. First, resource allocation policy is designed for D2D communications underlaying cellular networks. A novel spectrum allocation algorithm based on many-to-many matching is proposed to improve system sum rate. Additionally, considering the quality-of-service (QoS) requirements and priorities of di erent applications, a context-aware resource allocation algorithm based on many-to-one matching is proposed, which is capable of providing remarkable performance enhancement in terms of improved data rate, decreased packet error rate (PER) and reduced delay. Second, to improve resource utilisation, joint subchannel and power allocation problem for D2D communications with non-orthogonal multiple access (NOMA) is studied. For the subchannel allocation, a novel algorithm based on the many-to-one matching is proposed for obtaining a suboptimal solution. Since the power allocation problem is non-convex, sequential convex programming is adopted to transform the original power allocation problem to a convex one. The proposed algorithm is shown to enhance the network sum rate and number of accessed users. Third, driven by the trend of heterogeneity of cells, the resource allocation problem for NOMA-enhanced D2D communications in heterogeneous networks (HetNets) is investigated. In such a scenario, the proposed resource allocation algorithm is able to closely approach the optimal solution within a limited number of iterations and achieves higher sum rate compared to traditional HetNets schemes. Thorough theoretical analysis is conducted in the development of all proposed algorithms, and performance of proposed algorithm is evaluated via comprehensive simulations. This thesis concludes that matching theory based resource allocation for D2D communications achieves near-optimal performance with acceptable complexity. In addition, the application of D2D communications in NOMA and HetNets can improve system performance in terms of sum rate and users connectivity

Performance enhancement of wireless communication systems through QoS optimisation

Providing quality of service (QoS) in a communication network is essential but challenging, especially when the complexities of wireless and mobile networks are added. The issues of how to achieve the intended performances, such as reliability and efficiency, at the minimal resource cost for wireless communications and networking have not been fully addressed. In this dissertation, we have investigated different data transmission schemes in different wireless communication systems such as wireless sensor network, device-to-device communications and vehicular networks. We have focused on cooperative communications through relaying and proposed a method to maximise the QoS performance by finding optimum transmission schemes. Furthermore, the performance trade-offs that we have identified show that both cooperative and non-cooperative transmission schemes could have advantages as well as disadvantages in offering QoS. In the analytical approach, we have derived the closed-form expressions of the outage probability, throughput and energy efficiency for different transmission schemes in wireless and mobile networks, in addition to applying other QoS metrics such as packet delivery ratio, packet loss rate and average end-to-end delay. We have shown that multi-hop relaying through cooperative communications can outperform non-cooperative transmission schemes in many cases. Furthermore, we have also analysed the optimum required transmission power for different transmission ranges to obtain the maximum energy efficiency or maximum achievable data rate with the minimum outage probability and bit error rate in cellular network. The proposed analytical and modelling approaches are used in wireless sensor networks, device-to-device communications and vehicular networks. The results generated have suggested an adaptive transmission strategy where the system can decide when and how each of transmission schemes should be adopted to achieve the best performance in varied conditions. In addition, the system can also choose proper transmitting power levels under the changing transmission distance to increase and maintain the network reliability and system efficiency accordingly. Consequently, these functions will lead to the optimized QoS in a given network

Performance analysis of MC-CDMA detection schemes for D2D communication

The wireless communication standard has gone to the era of Long Term Evolution which is also known as LTE. The requirements for transmission speed and communication quality become more and more rigorous and the number of wireless communication devices is increasing rapidly. The available spectrum for mobile wireless communication is getting congested. Therefore, more efficient spectrum utilization should be taken into consideration within the future development. New methods need to be implemented to increase the efficiency of spectrum utilization. To confront this obstacle, orthogonal frequency division multiplexing (OFDM) was developed in 1990’s and has been widely deployed in the LTE networks. Multicarrier code division multiple access technique (MC-CDMA) combines code division multiple access (CDMA) with OFDM to acquire advantages from both sides. With the continuous increase of mobile applications, the power consumption of mobile terminals is also increasing significantly. Then device-to-device (D2D) communication, which is a short distance communication technique from one device directly to another one, was invented. The data of users will be transmitted between devices directly without relying on the base station. D2D communication decreases the load of the base station, reduces the terminal power consumption, and improves the spectral efficiency. Due to these merits, D2D has become a significant research topic and various new related applications for D2D have been developed and tested in realistic circumstances. This thesis applies MC-CDMA into D2D communication and studies different detection schemes for MC-CDMA. The OFDMA cellular user signals appear as significant sources of interference to D2D communication. Three alternative detection schemes are investigated: equal gain combining (EGC), maximum ratio combining (MRC) and linear minimum mean square (LMMSE) equalization. MC-CDMA performance with these detection methods is evaluated based on MATLAB simulations using relevant channel and interference models to find out the best alternative for different D2D scenarios. At the end of this thesis, a conclusion is drawn of which MC-CDMA detection scheme will be a better choice for D2D communication according to the BER performances based on the simulation results on MATLAB