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

Wireless 5G systems will not only be “4G, but faster”. One of the novel features discussed in relation to 5G is Ultra-Reliable Communication (URC), an operation mode not present in today's wireless systems. URC refers to provision of certain level of communication service almost 100 % of the time. Example URC applications include reliable cloud connectivity, critical connections for industrial automation and reliable wireless coordination among vehicles. This paper puts forward a systematic view on URC in 5G wireless systems. It starts by analyzing the fundamental mechanisms that constitute a wireless connection and concludes that one of the key steps towards enabling URC is revision of the methods for encoding control information (metadata) and data. It introduces the key concept of Reliable Service Composition, where a service is designed to adapt its requirements to the level of reliability that can be attained. The problem of URC is analyzed across two different dimensions. The first dimension is the type of URC problem that is defined based on the time frame used to measure the reliability of the packet transmission. Two types of URC problems are identified: long-term URC (URC-L) and short-term URC (URC-S). The second dimension is represented by the type of reliability impairment that can affect the communication reliability in a given scenario. The main objective of this paper is to create the context for defining and solving the new engineering problems posed by URC in 5G.

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Ultra-reliable communication in 5G wireless systems

The Augmented Reality (AR) technology enhances the human perception of the world by combining the real environment with the virtual space. With the explosive growth of powerful, less expensive mobile devices, and the emergence of sophisticated communication infrastructure, Mobile Augmented Reality (MAR) applications are gaining increased popularity. MAR allows users to run AR applications on mobile devices with greater mobility and at a lower cost. The emerging 5G communication technologies act as critical enablers for future MAR applications to achieve ultra-low latency and extremely high data rates while Multi-access Edge Computing (MEC) brings enhanced computational power closer to the users to complement MAR. This paper extensively discusses the landscape of MAR through the past and its future prospects with respect to the 5G systems and complementary technology MEC. The paper especially provides an informative analysis of the network formation of current and future MAR systems in terms of cloud, edge, localized, and hybrid architectural options. The paper discusses key application areas for MAR and their future with the advent of 5G technologies. The paper also discusses the requirements and limitations of MAR technical aspects such as communication, mobility management, energy management, service offloading and migration, security, and privacy and analyzes the role of 5G technologies.

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A Survey on Mobile Augmented Reality With 5G Mobile Edge Computing: Architectures, Applications, and Technical Aspects

The explosive popularity of small-cell and Internet of Everything devices has tremendously increased traffic loads. This increase has revolutionised the current network into 5G technology, which demands increased capacity, high data rate and ultra-low latency. Two of the research focus areas for meeting these demands are exploring the spectrum resource and maximising the utilisation of its bands. However, the scarcity of the spectrum resource creates a serious challenge in achieving an efficient management scheme. This work aims to conduct an in-depth survey on recent spectrum sharing (SS) technologies towards 5G development and recent 5G-enabling technologies. SS techniques are classified, and SS surveys and related studies on SS techniques relevant to 5G networks are reviewed. The surveys and studies are categorised into one of the main SS techniques on the basis of network architecture, spectrum allocation behaviour and spectrum access method. Moreover, a detailed survey on cognitive radio (CR) technology in SS related to 5G implementation is performed. For a complete survey, discussions are conducted on the issues and challenges in the current implementation of SS and CR, and the means to support efficient 5G advancement are provided.

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5G Technology: Towards Dynamic Spectrum Sharing Using Cognitive Radio Networks

Low power and long range machine-to-machine (M2M) communication techniques are expected to provide ubiquitous connections for the wireless devices. In this paper, three major low power and long range M2M solutions are surveyed. The first type of solutions is referred to as the low power wide area (LPWA) network. The design of the LPWA techniques features low cost, low data rate, long communication range, and low power consumption. The second type of solutions is the IEEE 802.11ah which features higher data rates using a wider bandwidth than the LPWA-based solutions. The third type of solutions is operated under the cellular network infrastructure. Based on the analysis of the pros and cons of the enabling technologies of the surveyed M2M solutions, as well as the corresponding deployment strategies, the gaps in knowledge are identified. The paper also presents a summary of the research directions for improving the performance of the surveyed low power and long range M2M communication technologies.

A Survey of Enabling Technologies of Low Power and Long Range Machine-to-Machine Communications

Long Term Evolution, the fourth generation of mobile communication technology, has been commercially deployed for about five years. Even though it is continuously updated through new releases, and with LTE Advanced Pro Release 13 being the latest one, the development of the fifth generation has been initiated. In this article, we measure how current LTE network implementations perform in comparison with the initial LTE requirements. The target is to identify certain key performance indicators that have suboptimal implementations and therefore lend themselves to careful consideration when designing and standardizing next generation wireless technology. Specifically, we analyze user and control plane latency, handover execution time, and coverage, which are critical parameters for connected mobility use cases such as road vehicle safety and efficiency. We study the latency, handover execution time, and coverage of four operational LTE networks based on 19,000 km of drive tests covering a mixture of rural, suburban, and urban environments. The measurements have been collected using commercial radio network scanners and measurement smartphones. Even though LTE has low air interface delays, the measurements reveal that core network delays compromise the overall round-trip time design requirement. LTE's breakbefore- make handover implementation causes a data interruption at each handover of 40 ms at the median level. While this is in compliance with the LTE requirements, and lower values are certainly possible, it is also clear that break-before-make will not be sufficient for connected mobility use cases such as road vehicle safety. Furthermore, the measurements reveal that LTE can provide coverage for 99 percent of the outdoor and road users, but the LTE-M or NarrowBand-IoT upgrades, as of LTE Release 13, are required in combination with other measures to allow for additional penetration losses, such as those experienced in underground parking lots. Based on the observed discrepancies between measured and standardized LTE performance, in terms of latency, handover execution time, and coverage, we conclude the article with a discussion of techniques that need careful consideration for connected mobility in fifth generation mobile communication technology.

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From LTE to 5G for Connected Mobility

Upcoming applications, such as autonomous vehicles, will pose strict requirements on the vehicular networks. In order to provide these new services reliably, an accurate understanding of propagation in the vehicular scenarios is needed. In this context, this paper presents a measurementbased evaluation of large vehicle shadowing at 5.8 GHz in V2X scenarios. The receiver antenna height is fixed to average vehicular height (1.5 m), while the transmitter antennas are located at different heights (1.5, 5, and 7 m) in order to investigate both V2V and V2I scenarios. A truck was used to obstruct the LOS between transmitter and receiver, and a large number of geometrical combinations of the scenario were explored. The statistical analysis of the measurement shows how in the V2V case, the experienced shadow levels are approximately 5 dB higher than in the V2I scenarios, where the shadow levels depend on the transmitter antenna height, reaching maximum values of 21-23 dB. The statistical analysis also shows that the differences in shadow level due to the non-symmetries of the obstacle truck are in the order of approximately 2 dB. A simple 3D ray-tracing simulation is validated against the measurements, showing a good match with a RMSE of 4.1 dB. Based on both measurements and ray-tracing data, a simple deterministic shadowing model, useful for implementation in system level simulators, is presented, as a first step towards a more dynamic and scalable shadowing model.

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Measurement-based Evaluation of the Impact of Large Vehicle Shadowing on V2X Communications

Mobility performance and the impact of handover data interruption times in real scenarios are studied by means of field measurements in an operational LTE network. Both slow- and high-speed scenarios are analyzed by collecting results from two different areas: Aalborg downtown and the highway which encircles the same city. Measurements reveal that the terminal is configured by the network with different handover parametrization depending on the serving cell, which indicates the use of mobility robustness optimization. Although the network is dominated by three-sector sites, no intra-site handovers are observed in the city center as cells on the same site often cover different non-crossing street canyons. Moreover, no handover failures are experienced in the measurements which confirms robust LTE mobility performance. The average interruption time, which is at least equal to the handover execution time, lays within a 24-29ms interval. Nevertheless, examples of delays larger than 100ms are occasionally observed. The studied scenarios are replicated in a system level simulator to investigate whether simulations are capable of reproducing similar mobility performance.

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Mobility Performance in Slow- and High-Speed LTE Real Scenarios

This paper presents enhancements for lowering the handover interruption time in future wireless networks. We propose a selective data forwarding for the handover preparation phase, and the integration of the make-before-break procedure with the synchronous random access-less handover. To evaluate our proposals, we analyze the handover timing for typical and variable values of the user equipment and e-NodeB processing times, and X2 interface latencies. Our results show that the processing delays, reconfiguration times, and the X2 latency should be simultaneously reduced to minimize the data interruption time. Selective data forwarding during the handover preparation reduces the data interruption time by 18 % compared to the basic random access less handover with typical network delays. Make-before-break is the most suitable handover type for future low-latency applications, as it achieves zero data interruption independent of the latency of handover steps.

Towards Zero Data Interruption Time with Enhanced Synchronous Handover

Many crowdsourcing Android applications are available for measuring network Key Performance Indicators such as received power, latency, and throughput. The data is useful for end-users, researchers, and Mobile Network Operators, but unfortunately the applications' accuracy are rarely verified. In this paper we verify the crowdsourcing Android application NetMap's ability to measure LTE Reference Signal Received Power by analyzing the Root Mean Squared Error, being 2–3 dB, and cross-correlation coefficient, being above 0.8, with measurements obtained by use of a professional radio network scanner and measurement phones. In addition, the application is applicable, but less accurate, for 3G Received Signal Code Power measurements. The studies are made for various device speeds and in different scenarios including indoor, urban, and highway, where the NetMap application is showed to perform well.

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Lucas Chavarria Gimenez

Papers

From LTE to 5G for Connected Mobility

Measurement-based Evaluation of the Impact of Large Vehicle Shadowing on V2X Communications

Mobility Performance in Slow- and High-Speed LTE Real Scenarios

Towards Zero Data Interruption Time with Enhanced Synchronous Handover

Verification of 3G and 4G received power measurements in a crowdsourcing Android app