With the rapid development of the Intelligent Transportation System (ITS), vehicular communication networks have been widely studied in recent years. Dedicated Short Range Communication (DSRC) can provide efficient real-time information exchange among vehicles without the need of pervasive roadside communication infrastructure. Although mobile cellular networks are capable of providing wide coverage for vehicular users, the requirements of services that require stringent real-time safety cannot always be guaranteed by cellular networks. Therefore, the Heterogeneous Vehicular NETwork (HetVNET), which integrates cellular networks with DSRC, is a potential solution for meeting the communication requirements of the ITS. Although there are a plethora of reported studies on either DSRC or cellular networks, joint research of these two areas is still at its infancy. This paper provides a comprehensive survey on recent wireless networks techniques applied to HetVNETs. Firstly, the requirements and use cases of safety and non-safety services are summarized and compared. Consequently, a HetVNET framework that utilizes a variety of wireless networking techniques is presented, followed by the descriptions of various applications for some typical scenarios. Building such HetVNETs requires a deep understanding of heterogeneity and its associated challenges. Thus, major challenges and solutions that are related to both the Medium Access Control (MAC) and network layers in HetVNETs are studied and discussed in detail. Finally, we outline open issues that help to identify new research directions in HetVNETs.

Heterogeneous Vehicular Networking: A Survey on Architecture, Challenges, and Solutions

Support of femtocells is an integral part of the Long Term Evolution - Advanced (LTE-A) system and a key enabler for its wide adoption in a broad scale. Femtocells are short-range, low-power and low-cost cellular stations which are installed by the consumers in an unplanned manner. Even though current literature includes various studies towards understanding the main challenges of interference management in the presence of femtocells, little light has been shed on the open issues of mobility management (MM) in the two-tier macrocell-femtocell network. In this paper, we provide a comprehensive discussion on the key aspects and research challenges of MM support in the presence of femtocells, with the emphasis given on the phases of a) cell identification, b) access control, c) cell search, d) cell selection/reselection, e) handover (HO) decision, and f) HO execution. A detailed overview of the respective MM procedures in the LTE-A system is also provided to better comprehend the solutions and open issues posed in real-life systems. Based on the discussion for the HO decision phase, we subsequently survey and classify existing HO decision algorithms for the two-tier macrocell-femtocell network, depending on the primary HO decision criterion used. For each class, we overview up to three representative algorithms and provide detailed flowcharts to describe their fundamental operation. A comparative summary of the main decision parameters and key features of selected HO decision algorithms concludes this work, providing insights for future algorithmic design and standardization activities.

Mobility Management for Femtocells in LTE-Advanced: Key Aspects and Survey of Handover Decision Algorithms

As heterogeneous networks (HetNets) emerge as one of the most promising developments toward realizing the target specifications of Long Term Evolution (LTE) and LTE-Advanced (LTE-A) networks, radio resource management (RRM) research for such networks has, in recent times, been intensively pursued Clearly, recent research mainly concentrates on the aspect of interference mitigation Other RRM aspects, such as radio resource utilization, fairness, complexity, and QoS, have not been given much attention In this paper, we aim to provide an overview of the key challenges arising from HetNets and highlight their importance Subsequently, we present a comprehensive survey of the RRM schemes that have been studied in recent years for LTE/LTE-A HetNets, with a particular focus on those for femtocells and relay nodes Furthermore, we classify these RRM schemes according to their underlying approaches In addition, these RRM schemes are qualitatively analyzed and compared to each other We also identify a number of potential research directions for future RRM development Finally, we discuss the lack of current RRM research and the importance of multi-objective RRM studies

Recent Advances in Radio Resource Management for Heterogeneous LTE/LTE-A Networks

Future 5th generation networks are expected to enable three key services—enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements.

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Enabling Technologies for Ultra-Reliable and Low Latency Communications: From PHY and MAC Layer Perspectives

Mobile cloud computing (MCC) is an appealing paradigm enabling users to enjoy the vast computation power and abundant network services ubiquitously with the support of remote cloud. However, the wireless networks and mobile devices have to face many challenges due to the limited radio resources, battery power and communications capabilities, which may significantly impede the improvement of service qualities. Heterogeneous Network (HetNet), which has multiple types of low power radio access nodes in addition to the traditional macrocell nodes in a wireless network, is widely accepted as a promising way to satisfy the unrelenting traffic demand. In this article, we first introduce the framework of HetNet for MCC, identifying the main functional blocks. Then, the current state of the art techniques for each functional block are briefly surveyed, and the challenges for supporting MCC applications in HetNet under our proposed framework are discussed. We also envision the future for MCC in HetNet before drawing the conclusion.

Challenges on wireless heterogeneous networks for mobile cloud computing

Recently there has been an upsurge of interests in the multihop infrastructures for orthogonal frequency division multiplexing-based cellular networks in both academia and industry. In this article, we first present an overview of the interference coordination strategies in OFDM-based multihop cellular networks. Then, based on the framework of third-generation LTE-Advanced networks with multihop relaying, several typical static or semi-static interference coordination schemes are proposed to improve the coverage and increase the cell edge data rate. By applying these schemes, the radio resources can be reused with certain limitations on either the frequency or time domain, or even both of them. Dynamic system-level simulations are also carried out to demonstrate the effectiveness of the proposed interference coordination schemes.

Interference coordination for OFDM-based multihop LTE-advanced networks

This paper studies the performance of Voice-over-Internet-Protocol (VoIP) service in the third generation (3G) long-term evolution (LTE)-Advanced relaying networks. We propose a semi-persistent scheduling algorithm for the VoIP service in the LTE-Advanced relaying networks. The performance of the presented algorithm is verified by system-level simulation. Deployments with different number of relay nodes are taken into account in the simulations. The results show that through deploying relays, the packet delay of cell edge users can be dramatically decreased. Moreover, the VoIP capacity of the relaying networks can also be increased obviously.

Semi-persistent scheduling for VoIP service in the LTE-Advanced relaying networks

This paper focuses on multi-user scheduling in downlink relay-aided cellular network. Based on conventional scheduling rules (Round Robin (RR), Max Carrier-to-Interference ratio (Max C/I), and Proportional Fair (PF)), we propose backhaul and access scheduling algorithms under centralized and distributed mechanism, respectively. We evaluate and compare the network performance through system-level simulation. The results show that both centralized mechanism and distributed mechanism have pros and cons. Centralized mechanism performs better at the cost of more signalling and complexity.

Jianhua Liu

Papers

Interference coordination for OFDM-based multihop LTE-advanced networks

Semi-persistent scheduling for VoIP service in the LTE-Advanced relaying networks

Performance analysis of scheduling algorithms in the relay-aided cellular networks