What will 5G be? What it will not be is an incremental advance on 4G. The previous four generations of cellular technology have each been a major paradigm shift that has broken backward compatibility. Indeed, 5G will need to be a paradigm shift that includes very high carrier frequencies with massive bandwidths, extreme base station and device densities, and unprecedented numbers of antennas. However, unlike the previous four generations, it will also be highly integrative: tying any new 5G air interface and spectrum together with LTE and WiFi to provide universal high-rate coverage and a seamless user experience. To support this, the core network will also have to reach unprecedented levels of flexibility and intelligence, spectrum regulation will need to be rethought and improved, and energy and cost efficiencies will become even more critical considerations. This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.

What Will 5G Be

Device-to-device (D2D) communications was initially proposed in cellular networks as a new paradigm for enhancing network performance. The emergence of new applications such as content distribution and location-aware advertisement introduced new user cases for D2D communications in cellular networks. The initial studies showed that D2D communications has advantages such as increased spectral efficiency and reduced communication delay. However, this communication mode introduces complications in terms of interference control overhead and protocols that are still open research problems. The feasibility of D2D communications in Long-Term Evolution Advanced is being studied by academia, industry, and standardization bodies. To date, there are more than 100 papers available on D2D communications in cellular networks, but there is no survey on this field. In this paper, we provide a taxonomy based on the D2D communicating spectrum and review the available literature extensively under the proposed taxonomy. Moreover, we provide new insights into the over-explored and under-explored areas that lead us to identify open research problems of D2D communications in cellular networks.

https://eprints.networks.imdea.org/id/document/2488

A Survey on Device-to-Device Communication in Cellular Networks

Device-to-Device (D2D) communication was initially proposed in cellular networks as a new paradigm to enhance network performance. The emergence of new applications such as content distribution and location-aware advertisement introduced new use-cases for D2D communications in cellular networks. The initial studies showed that D2D communication has advantages such as increased spectral efficiency and reduced communication delay. However, this communication mode introduces complications in terms of interference control overhead and protocols that are still open research problems. The feasibility of D2D communications in LTE-A is being studied by academia, industry, and the standardization bodies. To date, there are more than 100 papers available on D2D communications in cellular networks and, there is no survey on this field. In this article, we provide a taxonomy based on the D2D communicating spectrum and review the available literature extensively under the proposed taxonomy. Moreover, we provide new insights to the over-explored and under-explored areas which lead us to identify open research problems of D2D communication in cellular networks.

Device-to-device (D2D) communications underlaying a cellular infrastructure has been proposed as a means of taking advantage of the physical proximity of communicating devices, increasing resource utilization, and improving cellular coverage. Relative to the traditional cellular methods, there is a need to design new peer discovery methods, physical layer procedures, and radio resource management algorithms that help realize the potential advantages of D2D communications. In this article we use the 3GPP Long Term Evolution system as a baseline for D2D design, review some of the key design challenges, and propose solution approaches that allow cellular devices and D2D pairs to share spectrum resources and thereby increase the spectrum and energy efficiency of traditional cellular networks. Simulation results illustrate the viability of the proposed design.

Design aspects of network assisted device-to-device communications

The protection of data on a client mobile computing device by a server computer system such as within an enterprise network or on a separate mobile computing device is described. Security tools are described that provide different security policies to be enforced based on a location associated with a network environment in which a mobile device is operating. Methods for detecting the location of the mobile device are described. Additionally, the security tools may also provide for enforcing different policies based on security features. Examples of security features include the type of connection, wired or wireless, over which data is being transferred, the operation of anti-virus software, or the type of network adapter card. The different security policies provide enforcement mechanisms that may be tailored based upon the detected location and/or active security features associated with the mobile device. Examples of enforcement mechanisms are adaptive port blocking, file hiding and file encryption.

Administration of protection of data accessible by a mobile device

Aura-net is a mobile communications system whose function realizes a new form of proximityaware networking, and whose form points in the direction of a "Proximity-aware Internetwork." The system is founded on an implementation of a "wireless sense." The existence of such a sense, it is argued, is essential for realization of a vision of Ubiquitous Computing famously expounded by Mark Weiser [1]. Moreover, current wireless technologies are ill-suited to enabling this vision. The proposed wireless technology (FlashLinQ) is described at a conceptual and tutorial level.

Toward proximity-aware internetworking

Session signaling register message transmission methods and apparatus well suited for use in a communication system which supports mobile nodes capable of moving between domains and access nodes in a domain are described. Broadcasting of session signaling register messages is supported to reduce the number of registration messages which need to be transmitted between a mobile node and an access node. A paging and location server is used to reduce the number of session signaling register messages transmitted between domains. A visiting node registers with a paging and location server. The session signaling address of the paging and location server being used by a visiting mobile node is registered with the visiting node's home session signaling server. As the visiting node moves between access nodes in the visited domain the paging and location server it uses remains the same eliminating the need to update the home session signaling servers.

Methods and apparatus for using a paging and location server to support session signaling

A mobile communications system that uses IP packets to transmit data between end nodes, such as mobile devices, is described. In order to facilitate session establishment, maintenance, security, and handoff operations, access nodes through which end nodes communicate with one another include a session signaling server module and a mobility agent module. The session signaling server module may be implemented as a SIP server while the mobility agent module may be implemented using Mobil IP signaling. The mobility agent and SIP server within an access node are identified using a single shared identifier, IP address. The same security method and common secret may be used to provide security with regard to both mobile IP messages and SIP messages. Sessions admission decisions and resource allocation for admitted sessions can also take place internally to the access node of this invention without need for signaling to external elements.

Methods and apparatus for supporting session signaling and mobility management in a communications system

Group communications methods and apparatus are described. In particular, methods for granting a mobile device access to a communications resource, e.g., the right to transmit data, associated with a group are described. User requests for the communications resource are suppressed by the corresponding mobile device, for periods during which the communications resource has been granted to another mobile device. A mobile device may store a suppressed user request so that a resource request signal may be transmitted after the communications resource has been released by the mobile device that was previously granted the resource. In this manner requests that cannot be granted are not transmitted, increasing communications efficiency as compared to systems where requests are not suppressed at the mobile devices. A priority scheme is used in some embodiments to determine whether or not a request should be suppressed while another device has been granted the communications resource.

Methods and apparatus for supporting group communications

Methods and apparatus for storing, manipulating, retrieving, and forwarding state, e.g., context and other information, used to support communications sessions with one or more end nodes, e.g., mobile devices, are described. Various features are directed to a mobile node controlling the transfer of state from a first access node to a second access node during a handoff operation thereby eliminating any need for state transfer messages to be transmitted between the second access node and the first access node during handoff. Other features of the invention are directed to the use of a core network node to store state information. State information stored in the core node can be accessed and used by access nodes in cases where a mobile node does not send a state transfer message during a handoff, e.g., because communication with the first access node is lost or because such messages are not supported.

George Tsirtsis

Papers

Toward proximity-aware internetworking

Methods and apparatus for using a paging and location server to support session signaling

Methods and apparatus for supporting session signaling and mobility management in a communications system

Methods and apparatus for supporting group communications

Methods and apparatus for the utilization of core based nodes for state transfer