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

무선통신망에서 처리율 개선을 위한 신호전달 부하의 저감에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2014. 2. 전화숙.무선통신망(wireless networks)은 무선 채널의 상태 변화에 따른 성능 저하를 줄이기 위해 링크 적응(link adaptation) 기술을 기본적으로 사용한다. 링크 적응 기술을 위해서는 채널 상태 정보를 추정하고 수집해야하기 때문에 이에 따른 신호전달 부하(signaling overhead)가 발생하게 된다. 본 논문에서는 무선통신망에서의 신호전달 부하를 줄이기 위한 두 가지 기법을 제안하였다. 먼저 협력 통신 네트워크(cooperative communication networks)에서의 적응적인 전송 기법을 제안하였다. 제안한 기법을 사용하는 협력 통신 네트워크는 ACK(positive acknowledgement)/NACK(negative ACK)와 같은 제한된 피드백 정보로부터 추정된 채널 상태에 기반을 두어 전송 속도를 조절하면서 릴레이(relay)의 사용여부도 함께 결정한다. 제한된 피드백 정보는 실제 채널 상태에 대한 부분적인 정보만을 제공하기 때문에 제안하는 기법을 불확실성 마코브 의사 결정(partially observable Markov decision process)에 따라 설계하였다. 다음으로, 셀룰러 네트워크에서의 기기 간(D2D, device-to-device) 통신을 위한 자원 관리 기법을 제안하였다. 제안한 기법은 두 단계로 구성되고 준 분산적(semi-distributed)으로 동작한다. 첫 번째 단계에서는 중앙 집중적(centralized)으로 기지국이 자원 블록을 B2D(BS-to-user device) 링크와 D2D 링크에게 할당한다. 두 번째 단계에서는 분산적(distributed)으로 기지국은 B2D 링크에 할당된 자원 블록들을 사용하여 전송 스케줄을 결정(scheduling)하고, 각 D2D 링크의 제 1 사용자 기기(primary user device)는 해당 D2D 링크에 할당된 자원 블록들에서의 링크 적응을 수행한다. 이러한 자원 관리 구조는 중앙 집중적 기법처럼 높은 네트워크 용량을 달성할 뿐 아니라 분산적 기법처럼 낮은 신호전달 및 계산(computational) 부하를 필요로 한다. 본 논문에서는 제안한 자원 관리 구조에서 주파수 자원 효율을 최대화하는 자원 블록 할당 문제들을 두 가지 서로 다른 자원 할당 정책에 대하여 만들고 이 문제들을 풀기 위해 탐욕(greedy) 알고리즘과 열 추가 기반(column generation-based) 알고리즘을 제안하였다. 또한 시뮬레이션을 통해 제안하는 기법들이 설계 목표를 달성하고 기존의 기법보다 높은 성능을 보이면서도 신호전달 부하를 줄일 수 있음을 보였다.Wireless networks usually adopt some link adaptation techniques to mitigate the performance degradation due to the time-varying characteristics of wireless channels. Since the link adaptation techniques require to estimate and collect channel state information, signaling overhead is inevitable in wireless networks. In this thesis, we propose two schemes to reduce the signaling overhead in wireless networks. First, we design an adaptive transmission scheme for cooperative communication networks. The cooperative network with the proposed scheme chooses the transmission rate and decides to involve the relay in transmission, adapting to the channel state estimated from limited feedback information (e.g., ACK/NACK feedback). Considering that the limited feedback information provides only partial knowledge about the actual channel states, we design a decision-making algorithm on cooperative transmission by using a partially observable Markov decision process (POMDP) framework. Next, we also propose a two-stage semi-distributed resource management framework for the device-to-device (D2D) communication in cellular networks. At the first stage of the framework, the base station (BS) allocates resource blocks (RBs) to BS-to-user device (B2D) links and D2D links, in a centralized manner. At the second stage, the BS schedules the transmission using the RBs allocated to B2D links, while the primary user device of each D2D link carries out link adaptation on the RBs allocated to the D2D link, in a distributed fashion. The proposed framework has the advantages of both centralized and distributed design approaches, i.e., high network capacity and low signaling/computational overhead, respectively. We formulate the problems of RB allocation to maximize the radio resources efficiency, taking account of two different policies on the spatial reuse of RBs. To solve these problems, we suggest a greedy algorithm and a column generation-based algorithm. By simulation, it is shown that the proposed schemes achieve their design goal properly and outperform existing schemes while reducing the signaling overhead.1 Introduction 1 1.1 Background and Motivation 1 1.2 Approaches to Reduce Signaling Overhead 5 1.3 Proposed Schemes 7 1.3.1 Adaptive Transmission Scheme for Cooperative Communication 7 1.3.2 Resource Management Scheme for D2D Communication in Cellular Networks 8 1.4 Organization 10 2 Adaptive Transmission Scheme for Cooperative Communication 11 2.1 System Model 11 2.2 Cooperative Networks with Limited Feedback 12 2.2.1 Operation of the Proposed Cooperative Network 12 2.2.2 Finite-State Markov Channel Model 15 2.2.3 Packet Error Probability 16 2.2.4 Channel Feedback Schemes 18 2.3 Adaptive Transmission Scheme for Cooperative Communication 19 2.3.1 POMDP Formulation 19 2.3.2 Solution to POMDP 22 3 Resource Management Scheme for D2D Communication in Cellular Networks 25 3.1 System Model 25 3.1.1 Network Model 25 3.1.2 Radio Resource Model 27 3.2 Proposed Resource Management Framework 28 3.2.1 Framework Overview 28 3.2.2 Two-Stage Resource Management 29 3.2.3 Advantages of the Proposed Framework 31 3.3 Conditions for Simultaneous Transmission of B2D and D2D Links 33 3.3.1 Analysis of Interference on B2D and D2D Links 33 3.3.2 Conditions for Simultaneous Transmission of B2D and D2D Links 36 3.4 Resource Block Allocation 38 3.4.1 Resource Block Allocation with Conservative Reuse Policy 39 3.4.2 Resource Block Allocation with Aggressive Reuse Policy 44 4 Performance Evaluation 52 4.1 Adaptive Transmission Scheme for Cooperative Communication 52 4.1.1 Simulation Model 52 4.1.2 Simulation Results 53 4.2 Resource Management Scheme for D2D Communication in Cellular Networks 62 4.2.1 Simulation Model 62 4.2.2 Simulation Results 64 5 Conclusion 75 Bibliography 77 Abstract 85Docto

Review on Radio Resource Allocation Optimization in LTE/LTE-Advanced using Game Theory

Recently, there has been a growing trend toward ap-plying game theory (GT) to various engineering fields in order to solve optimization problems with different competing entities/con-tributors/players. Researches in the fourth generation (4G) wireless network field also exploited this advanced theory to overcome long term evolution (LTE) challenges such as resource allocation, which is one of the most important research topics. In fact, an efficient de-sign of resource allocation schemes is the key to higher performance. However, the standard does not specify the optimization approach to execute the radio resource management and therefore it was left open for studies. This paper presents a survey of the existing game theory based solution for 4G-LTE radio resource allocation problem and its optimization

Interference mitigation in D2D communication underlaying LTE-A network

The mobile data traffic has risen exponentially in recent days due to the emergence of data intensive applications, such as online gaming and video sharing. It is driving the telecommunication industry as well as the research community to come up with new paradigms that will support such high data rate requirements within the existing wireless access network, in an efficient and effective manner. To respond to this challenge, device-to-device (D2D) communication in cellular networks is viewed as a promising solution, which is expected to operate, either within the coverage area of the existing eNB and under the same cellular spectrum (in-band) or separate spectrum (out-band). D2D provides the opportunity for users located in close proximity of each other to communicate directly, without traversing data traffic through the eNB. It results in several transmission gains, such as improved throughput, energy gain, hop gain, and reuse gain. However, integration of D2D communication in cellular systems at the same time introduces new technical challenges that need to be addressed. Containment of the interference among D2D nodes and cellular users is one of the major problems. D2D transmission radiates in all directions, generating undesirable interference to primary cellular users and other D2D users sharing the same radio resources resulting in severe performance degradation. Efficient interference mitigation schemes are a principal requirement in order to optimize the system performance. This paper presents a comprehensive review of the existing interference mitigation schemes present in the open literature. Based on the subjective and objective analysis of the work available to date, it is also envisaged that adopting a multi-antenna beamforming mechanism with power control, such that the transmit power is maximized toward the direction of the intended D2D receiver node and limited in all other directions will minimize the interference in the network. This could maximize the sum throughput and hence, guarantees the reliability of both the D2D and cellular connections

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