Anna Zakrzewska

Dual connectivity in LTE HetNets with split control- and user-plane

Recently, a new network architecture with split control-plane and user-plane has been proposed and gained a lot of momentum in the standardisation of Long Term Evolution (LTE) Release 12. In this new network architecture, the control-plane, which transmits system information and handles user connectivity, and the user-plane, which manages user data, are split and no longer transmitted necessarily by the same network node. This dual connectivity confers a large flexibility to the system, and allows for a more energy efficient operation and enhanced mobility management. In this paper, we present a detailed description of our dual connectivity framework based on the latest LTE-Advanced enhancements, in which macrocell-assisted (MA) small cells use different channel state information-reference signals (CSI-RS) to differentiate among each other and allow User Equipment (UE) to take adequate measurements for cell (re)selection. Taking into account the limited number of available CSI-RSs, we study the assignment problem of CSI-RSs to MA small cells, analyse CSI-RS collision and confusion issues and present simulation results to demonstrate the flexibility of the proposed network architecture.

Towards converged 5G mobile networks-challenges and current trends

With the rapid development of wireless technologies, the concept of the Fifth Generation (5G) wireless communication system started to emerge and it is foreseen that it will be a result of standards convergence. The expectations towards 5G are set much higher in terms of capacity and maximum throughput when compared with Fourth Generation (4G). There are also some new technical challenges the system will need to face, like Machine to Machine (M2M) communication, energy efficiency, complete ubiquity and autonomous management. This paper analyses new technologies that could enable 5G networking, discusses potential standardisation and development directions, and presents recent research efforts in the area of future mobile networks.

Resource sharing in heterogeneous and Cloud Radio Access Networks

This paper analyzes performance of cellular systems with shared resources, where the network with overlapping cells is modeled as a circuit switched network with direct routing. The influence of the degree of sharing, represented by cell overlap percentage, on the call blocking probability is investigated for three scenarios, including cells with proportional offered traffic and resources, cells dimensioned according to fixed blocking probability, and fixed improvement function. The numerical results show that by sharing the resources between the operators, the overall system efficiency can be improved. The benefits of individual operators are not equal but highly depend on the initial network dimensioning. Furthermore, we demonstrate that under specific conditions the blocking probability in an area is lower than for fully accessible system and therefore, sharing agreements may be more beneficial for some operators.

A framework for joint optical-wireless resource management in multi-RAT, heterogeneous mobile networks

Mobile networks are constantly evolving: new Radio Access Technologies (RATs) are being introduced, and backhaul architectures like Cloud-RAN (C-RAN) and distributed base stations are being proposed. Furthermore, small cells are being deployed to enhance network capacity. The end-users wish to be always connected to a high-quality service (high bit rates, low latency), thus causing a very complex network control task from an operators point of view. We thus propose a framework allowing joint overall network resource management. This scheme covers different types of network heterogeneity (multi-RAT, multi-layer, multi-architecture) by introducing a novel, hierarchical approach to network resource management. Self-Organizing Networks (SON) and cognitive network behaviors are covered as well as more traditional mobile network features. The framework is applicable to all phases of network operation like planning, deployment, operation, maintenance and therefore aids network operators in improving their business potential.

Coordination of SON Functions in Multi-Vendor Femtocell Networks

With the increase of network complexity, there is a high need for network management automation. This is achieved through SON principles that enable self-configuration, self-optimization, and self-healing. However, even though SON functions are meant to be autonomous, a high level of coordination among them is required. To this end, efficient conflict detection and resolution techniques are needed, especially in multi-vendor deployments. This article presents a design together with a sample implementation of a coordination scheme between three key SON functions in femtocell networks: cell ID assignment, coverage adjustment, and idle mode control. This ensures stability and continuity of the network operation even in a situation when the functions have contradicting objectives. The solution is based on the Broadband Forum TR-069 protocol and is applicable to multi-vendor networks. Simulation evaluation has shown that SON coordination reduces mean cell ID conflicts by over 30 percent and, resulting from that, call drop probability by over 40 percent.