As the rollout of 4G mobile communication networks takes place, representatives of industry and academia have started to look into the technological developments toward the next generation (5G). Several research projects involving key international mobile network operators, infrastructure manufacturers, and academic institutions, have been launched recently to set the technological foundations of 5G. However, the architecture of future 5G systems, their performance, and mobile services to be provided have not been clearly defined. In this paper, we put forth the vision for 5G as the convergence of evolved versions of current cellular networks with other complementary radio access technologies. Therefore, 5G may not be a single radio access interface but rather a “network of networks”. Evidently, the seamless integration of a variety of air interfaces, protocols, and frequency bands, requires paradigm shifts in the way networks cooperate and complement each other to deliver data rates of several Gigabits per second with end-to-end latency of a few milliseconds. We provide an overview of the key radio technologies that will play a key role in the realization of this vision for the next generation of mobile communication networks. We also introduce some of the research challenges that need to be addressed.

No abstract

No abstract

No abstract

Access to unlicensed spectrum has thus far been based on simplistic rules, such as a transmission power limitation, requirement for tolerance of interference, and a relaxed out-of-band transmission mask. Such rules originate from the rudimentary applications originally envisaged for such spectrum, which don't consider the current technical capabilities of radio devices. This paper introduces the concept of "ISMAdvanced", which incorporates Cognitive Radio capabilities into the rules for unlicensed spectrum access in ISM bands. It is argued and shown that the introduction of such capabilities can significantly improve the efficiency of spectrum usage, as well as the quality of service that is experienced by spectrum users. Moreover, constraints such as on transmission power can be relaxed under the proposed scheme, and the stability in performance of unlicensed spectrum can be improved. Among many other benefits, these characteristics facilitate use of unlicensed spectrum by quality-of-service-conscious telecommunication service entities such as cellular (LTE) operators, likely in aggregation with and supplementing their licensed spectrum.In view of the increased use and allocations being seen of unlicensed spectrum, it is suggested that the policies and technical rules that govern dynamic spectrum access in ISM bands be reviewed bringing them up to a level matching technical capabilities of modern radio equipment using Cognitive Radio technology.

The software defined networking (SDN) paradigm separates the control plane from the data plane, where an SDN controller receives requests from its connected switches and manages the operation of the switches under its control. Reassignments between switches and their controllers are performed dynamically, in order to balance the load over SDN controllers. In order to perform load balancing, most dynamic assignment solutions use a central element to gather information requests for reassignment of switches. Increasing the number of controllers causes a scalability problem, when one super controller is used for all controllers and gathers information from all switches. In a large network, the distances between the controllers is sometimes a constraint for assigning them switches. In this paper, a new approach is presented to solve the well-known load balancing problem in the SDN control plane. This approach implies less load on the central element and meeting the maximum distance constraint allowed between controllers. An architecture with two levels of load balancing is defined. At the top level, the main component called Super Controller, arranges the controllers in clusters, so that there is a balance between the loads of the clusters. At the bottom level, in each cluster there is a dedicated controller called Master Controller, which performs a reassignment of the switches in order to balance the loads between the controllers. We provide a two-phase algorithm, called Dynamic Controllers Clustering algorithm, for the top level of load balancing operation. The load balancing operation takes place at regular intervals. The length of the cycle in which the operation is performed can be shorter, since the top-level operation can run independently of the bottom level operation. Shortening cycle time allows for more accurate results of load balancing. Theoretical analysis demonstrates that our algorithm provides a near-optimal solution. Simulation results show that our dynamic clustering improves fixed clustering by a multiplicative factor of 5.

No abstract

No abstract