The fifth generation (5G) wireless network technology is to be standardized by 2020, where main goals are to improve capacity, reliability, and energy efficiency, while reducing latency and massively increasing connection density. An integral part of 5G is the capability to transmit touch perception type real-time communication empowered by applicable robotics and haptics equipment at the network edge. In this regard, we need drastic changes in network architecture including core and radio access network (RAN) for achieving end-to-end latency on the order of 1 ms. In this paper, we present a detailed survey on the emerging technologies to achieve low latency communications considering three different solution domains: 1) RAN; 2) core network; and 3) caching. We also present a general overview of major 5G cellular network elements such as software defined network, network function virtualization, caching, and mobile edge computing capable of meeting latency and other 5G requirements.

A Survey on Low Latency Towards 5G: RAN, Core Network and Caching Solutions

URLLC is a new service category in 5G to accommodate emerging services and applications having stringent latency and reliability requirements. In order to support URLLC, there should be both evolutionary and revolutionary changes in the air interface named 5G NR. In this article, we provide an up-to-date overview of URLLC with an emphasis on the physical layer challenges and solutions in 5G NR downlink. We highlight key requirements of URLLC and then elaborate the physical layer issues and enabling technologies including packet and frame structure, scheduling schemes, and reliability improvement techniques, which have been discussed in the 3GPP Release 15 standardization.

Ultra-Reliable and Low-Latency Communications in 5G Downlink: Physical Layer Aspects

As a complement to high-layer encryption techniques, physical layer security has been widely recognized as a promising way to enhance wireless security by exploiting the characteristics of wireless channels, including fading, noise, and interference. In order to enhance the received signal power at legitimate receivers and impair the received signal quality at eavesdroppers simultaneously, multiple-antenna techniques have been proposed for physical layer security to improve secrecy performance via exploiting spatial degrees of freedom. This paper provides a comprehensive survey on various multiple-antenna techniques in physical layer security, with an emphasis on transmit beamforming designs for multiple-antenna nodes. Specifically, we provide a detailed investigation on multiple-antenna techniques for guaranteeing secure communications in point-to-point systems, dual-hop relaying systems, multiuser systems, and heterogeneous networks. Finally, future research directions and challenges are identified.

A Survey on Multiple-Antenna Techniques for Physical Layer Security

This article reviews state of the art channel coding techniques for URLLC. The stringent requirements of URLLC services, such as ultrahigh reliability and low latency, have made it the most challenging feature of 5G of mobile networks. The problem is even more challenging for services beyond the 5G promise, such as tele-surgery and factory automation, which require latencies less than 1ms and packet error rates as low as 10-9. This article provides an overview of channel coding techniques for URLLC and compares them in terms of performance and complexity. Several important research directions are identified and discussed in more detail.

Short Block-Length Codes for Ultra-Reliable Low Latency Communications

The increasing number of mobile users has given impetus to the demand for high data rate proximity services. The fifth-generation (5G) wireless systems promise to improve the existing technology according to the future demands and provide a road map for reliable and resource-efficient solutions. Device-to-device (D2D) communication has been envisioned as an allied technology of 5G wireless systems for providing services that include live data and video sharing. A D2D communication technique opens new horizons of device-centric communications, i.e., exploiting direct D2D links instead of relying solely on cellular links. Offloading traffic from traditional network-centric entities to D2D network enables low computational complexity at the base station besides increasing the network capacity. However, there are several challenges associated with D2D communication. In this paper, we present a survey of the existing methodologies related to aspects such as interference management, network discovery, proximity services, and network security in D2D networks. We conclude by introducing new dimensions with regard to D2D communication and delineate aspects that require further research.

5G D2D Networks: Techniques, Challenges, and Future Prospects

This paper investigates block error rate (BLER) performance and computational complexity of candidate channel coding schemes for ultra-reliable low latency communication (URLLC) in 5G. The considered candidates are the same as those identified in 3GPP: turbo, LDPC, polar, and convolutional codes. Details of code constructions and decoding algorithms are provided with computational complexity analysis. Code construction parameters, number of iterations, and list sizes are selected to provide a fair comparison among candidate coding schemes. Simulation results on BLER are shown for several code rates and small-to-moderate block sizes. The results reveal that polar and LDPC codes outperform turbo codes for short block sizes of 40 bits, while the opposite is true for medium block sizes of 200 bits. None of the schemes is a clear winner at all considered block sizes and coding rates. Other aspects like implementation complexity, latency, and flexibility will also be important when deciding the URLLC coding scheme.

Channel Coding for Ultra-Reliable Low-Latency Communication in 5G Systems

—In this letter, we propose a secure beamformingscheme for physical layer network coding (PNC) based multiple-input multiple-output (MIMO) two-way relaying system. The re-lay node performs PNC mapping. An eavesdropper is attemptingto intercept the user information. The channel state information(CSI) of the user-to-eavesdropper channel is imperfect at the usernodes. A robust optimization problem is formulated to designbeamforming vectors at the user nodes and relay. The problemis non-convex, and an algorithm is proposed to solve that. In thenumerical analysis, we discuss the convergence of the proposedalgorithm and the impact of the CSI error on the performance.Index Terms—multiple-input multiple-output, physical layernetwork coding, physical layer security. I. I NTRODUCTION R ELAYING information through several hops extend thecoverage area, improve the throughput, and minimizethe energy consumption at the transmitter. However, the relayalone has a disadvantage, which is due to the half-duplexsignaling. The two-way relaying (TWR) schemes are proposedto overcome this drawback which requires only two time slotsto exchange information between two source nodes as opposedto four in a conventional relaying system. Recently, physicallayer network coding (PNC) [1]–[3] based TWR are intro-duced, and these consider interference as useful information,and improve the capacity of the system.The security of the TWR can be improved by incorporatingsuch features at the physical layer. Many recent studies [4]–[9] have shown the beneﬁts of the physical layer security.The authors in [4] considered multiple users communicatingwith a common receiver in the presence of an eavesdrop-per. They provided an optimal transmit power allocationpolicy to maximize the secrecy sum-rate. Several optimaltransmit beamforming schemes using the quality-of-service(QoS) oriented perspective are considered in [5] for one-waytransmission. Secrecy-rate maximization with eavesdropperspresent considering imperfect channel state information (CSI)is given in [6]. In [7]–[9], the authors considered relay assistedcommunications in the presence of an eavesdropper. In [7], theauthors used amplify-and-forward (AF) relaying. Many otherrelay protocols are discussed in [8]. The authors consideredscenarios to maximize the achievable secrecy rate subject toa transmit power constraint and minimize the total transmitpower subject to a secrecy rate constraint. Moreover, the

Secure Beamforming Design for Physical Layer Network Coding Based MIMO Two-Way Relaying

This paper proposes linear precoder-decoder schemes for a multiple-input multiple-output (MIMO) underlay device-to-device (D2D) communication system by considering two D2D modes: two-way relaying based D2D and direct D2D. The D2D communication takes place in the same spectrum as the cellular communication. In the two-way relaying based D2D mode, the relay uses physical layer network coding (PNC). The precoder-decoder design is based on minimizing mean square errors (MSE), which is useful to mitigate interference and to improve the performance of both D2D and cellular communications. Distributed and centralized algorithms are proposed considering bi-directional communication in both D2D and cellular communications. In the direct D2D mode, a similar MSE procedure is adopted, and exact solutions are derived for precoder-decoder matrices. In the numerical results, the optimality and convergence properties of the proposed algorithms are analyzed. Additionally, the system performances are investigated with interference thresholds and maximum available power at the nodes. Two transmit mode selection schemes are considered as dynamic and static selection schemes. Finally, these selection schemes are investigated over an XY grid by varying the position of a given device. The results reveal that the PNC two-way relaying based D2D mode extends the coverage area of D2D communication.

Linear Precoder-Decoder Design of MIMO Device-to-Device Communication Underlaying Cellular Communication

One recent and important advancement in information and coding theory is polar code, which is selected as the coding scheme for 5G eMBB control channels In this paper, we propose a variant of polar codes that provides significant coding gain in the regime of short blocks and enables early termination of decoding processes The overall scheme depends on distributing CRC bits in the whole information block, and a single interleaving/deinterleaving pattern can be defined to implement CRC distribution The design can reduce the decoding latency and energy consumption of hardware, which is crucial for mobile applications like 5G

Distributing CRC Bits to Aid Polar Decoding

This paper presents a secure beamforming design to prevent eavesdropping on multiple-input multiple-output (MIMO) device-to-device (D2D) communication. The devices communicate via a trusted relay which performs physical layer network coding (PNC), and multiple eavesdroppers are trying to intercept the device information. The beamforming design is based on minimizing mean square error of the D2D communication while employing signal-to-interference-plus-noise ratio (SINR) threshold constraints to prevent possible eavesdropping. The channel state information of the device-to-eavesdropper and relay-to-eavesdropper channels is imperfect at the devices and relay. The channel estimation errors are assumed with Gaussian Markov uncertainty model. Consequently, robust optimization problems are formulated considering the multiple access and broadcasting stages of the D2D communication. These problems are non-convex, and two algorithms are proposed to solve them. In the numerical analysis, we discuss the convergence of the proposed algorithms, impact of the number of eavesdroppers on the performance, and the SINR distributions at eavesdroppers.

Jayasinghe Keeth Saliya

Papers

Channel Coding for Ultra-Reliable Low-Latency Communication in 5G Systems

Secure Beamforming Design for Physical Layer Network Coding Based MIMO Two-Way Relaying

Linear Precoder-Decoder Design of MIMO Device-to-Device Communication Underlaying Cellular Communication

Distributing CRC Bits to Aid Polar Decoding

Physical layer security for relay assisted MIMO D2D communication