Cellular systems evolved from a dedicated mobile communication system to an almost omnipresent system with unlimited coverage anywhere and anytime for any device. The growing ubiquity of the network stirred expectations to determine the location of the mobile devices themselves. Since the beginning of standardization, each cellular mobile radio generation has been designed for communication services, and satellite navigation systems, such as Global Positioning System (GPS), have provided precise localization as an add-on service to the mobile terminal. Self-contained localization services relying on the mobile network elements have offered only rough position estimates. Moreover, satellite-based technologies suffer a severe degradation of their localization performance in indoors and urban areas. Therefore, only in subsequent cellular standard releases, more accurate cellular-based location methods have been considered to accommodate more challenging localization services. This survey provides an overview of the evolution of the various localization methods that were standardized from the first to the fourth generation of cellular mobile radio, and looks over what can be expected with the new radio and network aspects for the upcoming generation of fifth generation.

Survey of Cellular Mobile Radio Localization Methods: From 1G to 5G

From “Rethinking Ring and Young” in 2011 to proposing next generation fronthaul interface (NGFI, aka xhaul) in 2014, the radio access network (RAN) revolutionary path to meet ambitious 5G demands has been charted out. Traditional fronthaul solutions fell short both in required bandwidth and architecture flexibility. NGFI proposed by China Mobile targeting a packet-based, traffic-dependent, and antenna scale-independent interface will be central to the 5G RAN revolution. This paper presents its latest progress. Specifically, a two-level NGFI architecture will be highlighted, and the function split options with associated requirements in, e.g., latency, bandwidth, and synchronization will be presented. In addition, challenges as well as the potential solutions for NGFI realization will be discussed.

RAN Revolution With NGFI (xhaul) for 5G

From "Rethinking Ring and Young" in 2011 to proposing NGFI (xHaul) in 2014, the RAN revolutionary path to meet ambitious 5G demands has been charted out. Traditional fronthaul solutions fell short both in required bandwidth and architecture flexibility. Next generation fronthaul interface (NGFI, aka xHaul) proposed by China Mobile targeting a packet-based, traffic-dependent, and antenna scale-independent interface will be central to the 5G RAN revolution. This paper presents its latest progress. Specifically, a two-level NGFI architecture will be highlighted, and the function split options with associated requirements in, e.g. latency, bandwidth and synchronization will be presented. In addition, challenges for NGFI realization will be discussed.

RAN revolution with NGFI (xHaul) for 5G

By incorporating the merits of satellite, aerial, and terrestrial communications, the space-air-ground integrated network (SAGIN) emerges in recent years as a promising solution to support seamless, high-rate, and reliable transmission with an extremely larger coverage than a classic terrestrial network. In essence, SAGIN is a cooperative relay network, in which high-altitude platforms (HAPs) and terrestrial base stations (BSs) serve as intermediates relaying signals between end device and satellite. In this article, we thereby view the SAGIN from the perspective of cooperative communications and introduce relay networking technologies to model and construct the framework of SAGIN. Meanwhile, we take the realistic propagation environment, HAP mobility and mathematical tractability into account and reconstruct the cooperative channel models for SAGIN, including the space-air, space-ground and air-ground links. Based on the constructed framework of SAGIN, we analyze the outage performance and approximate the outage probability as well as asymptotic outage probability in closed form. Numerical results generated by computer simulations verify our analysis and provide insight into the applicability of SAGIN. Although the relaying scenarios considered in this work are simplistic, the good tractability and expandability of the constructed framework provide a solid foundation for further research of advanced systems with complex configurations.

/pdf/space-air-ground-integrated-networks-outage-performance-53bu8tu2zp.pdf

Space-Air-Ground Integrated Networks: Outage Performance Analysis

This article describes the use of IEEE 1588 and boundary clocks for clock distribution (phase/time transfer) in telecom networks. The technology is primarily used to serve the radio interface synchronization requirements of mobile systems such as WiMAX and LTE, and to reduce the deployment and dependence of GPS systems in base stations. We discuss the most important functions that are necessary for phase/time transfer and present some initial field trial results using a chain of cascaded boundary clocks and synchronous Ethernet links across a packet and optical transport network that spans tens of kilometers and tens of network elements. The results indicate that it is possible to transfer accurate phase/time in a telecom network and meet the requirements of mobile systems. The article also discusses some of the challenges and highlights the ongoing activities in standardization bodies so that IEEE 1588 can be used as a technology in telecom networks.

Using IEEE 1588 and boundary clocks for clock synchronization in telecom networks

This article discusses the synchronization requirements and challenges from 5G in terms of the new technologies, new services, and the new architecture. Time synchronization via transport networks will be essential. ±130ns is proposed as the new goal of network limits for 5G. Higher precision requirements can be achieved through the same network cluster in a relatively limited area. A new time reference model is suggested, and in particular, the budget of the fronthaul is presented for C-RAN. Corresponding solutions for enhancing time accuracy are presented. New technologies of the time source and the time transport need to be introduced. SDOs need closer cooperation to define the specification of time synchronization for 5G.

Analysis of the Synchronization Requirements of 5g and Corresponding Solutions

This article describes the timing aspects of optical transport networks as defined by ITU-T SG15 Q13. It first presents the initial decisions that led to the specification of Recommendation G.8251 in 2001, which defined the OTN network limits and the clocks for OTN equipment. This article also presents work done since 2001 to support the evolution of Recommendation G.709, which introduced new OTN mappings such as Ethernet. Among the most significant timing-related aspects are the new mappings that allow timing-transparent transport of synchronous Ethernet.

Geoffrey M. Garner

Papers

Analysis of the Synchronization Requirements of 5g and Corresponding Solutions

OTN timing aspects