Ronan J. Skehill

The common RRM approach to admission control for converged heterogeneous wireless networks

As the wireless environment becomes ever more populated and complex, individual networks offering single or restricted services will become ever more uncompetitive. Common radio resource management algorithms and strategies are used in heterogeneous or converged wireless networks to integrate multiple physical radio interfaces to support different levels of data rates, mobility, and traffic. Admission control in a common RRM environment is used to select the most appropriate wireless access based on service type, user preference, and network load. This is used to provide a balance between real-time and non-real-time traffic across the available access technologies. The development of common radio resource management strategies requires a suitable platform of coupled access networks and is the motivation behind the development of a converged wireless test platform. The tightly coupled platform supports voice and data call setup and delivery over UMTS and WLAN

The Celtic Gandalf framework

Third generation mobile systems are driving a multi-system network landscape. Network management is crucial to guarantee optimum cooperation between network sub-systems. The aim of the Gandalf project is to use large scale network monitoring, advanced radio resource management rules and appropriate quality of service evaluation in order to achieve automation of network management tasks in a multi-system environment

Exploring power saving in 802.11 VoIP wireless links

Batteries are a primary resource in wireless networks for many mobile devices. Minimizing energy consumption without affecting communication activities is crucial to prolong the lifetime and improve the robustness of the wireless connection. One effective way to reduce energy consumption is to set the entire, or part of the system in a low power mode whenever possible. This paper explores a power saving approach for VoIP and presents a new power saving scheme that does not require extra protocol overhead or modifications to operate. Adopting this scheme potentially allows considerable power savings without any adverse effect on VoIP quality. Evidence of this is in simulation results, showing that a device can enter sleep mode for over 75% of the time, with no decrease in throughput.

Analysis of User Mobility Statistics for Cellular Network Re-Structuring

Mobile network operators often use handover statistics to improve the structure of their networks. However, such statistics only reflect the movement of connected users. In this paper, a thorough investigation of the correlation between idle and connected user mobility statistics is performed based on measurements from a live GSM network. A multiple regression model is proposed to estimate the number of location updates due to mobility and non-mobility reasons on a per-cell basis from measurements in the network management system. Results shown that, although the number of location updates can normally be predicted accurately from handover statistics, especially when aggregated over large geographical areas, large deviations are observed in cells of lower layers in multi-tier networks.

Characteristics, Results and Findings of IEEE 802.11 in an RF Isolated Testbed

Simulation has been one of the most important methods for evaluating the characteristics of network protocols and applications before deployment in wireless communication networks. This paper presents the findings of a controlled and automated experimental IEEE 802.11 testbed and compares them to results of popular network simulators. The comparison shows the differences and similarities of three network simulators with the testbed using identical test scenarios. The comparison has shown that some simulators can produce misleading results under certain conditions. The discrepancy can be caused by simulators using simple and invalid models. Without realistic modelling in simulations, the evaluation of performance of mobile networks may not correlate well with performance in reality.

An Integrated UMTS-WLAN Testbed

The provision of next generation mobile wireless access necessitates the coexistence of legacy cellular systems and new air interface technologies in cooperative heterogeneous environments. These multi-system environments consist of a number of radio access networks with different radio access technologies such as WiMax, GERAN, UMTS and WLAN. Joint radio resource management strategies are responsible for managing the pool of radio resources and are crucial to guarantee optimal cooperation between network sub-systems. The testing and validation of these strategies demands the construction of robust heterogeneous testbeds on which joint RRM algorithms can be trialled and evaluated. This paper presents an overview of the software/hardware design of the testbed and a description of joint radio resource management strategies being employed to manage RRM across UMTS and WLAN.

The application of fluid mobility modelling in wireless cellular networks

Mobility models, synthetic or trace, try to accurately model the movement of a single user or a group of users. Models can be used in simulators and emulators to investigate the consequences of mobility on new protocols or network management techniques. A limitation with current trace mobility models is they are based on empirical data which are limited to specific network types and environments. Limitations with synthetic models are that they are complex, computationally heavy, and lack realism. To address these issue a new approach needs to be taken. One such approach is the use of fluid mechanics and transport theory to represent user mobility. A model based on viscous free irrotational fluid mechanics with empirical data from pedestrian and vehicular studies provide a means of creating realistic group movement characteristics with smooth non random trajectories and smooth continuous velocity. The model is used in an example to provide boundary crossing rates for users in a cellular network and optimising the size of cellular location areas.

Mobility modelling: a fluid dynamics approach

In wireless personal communication systems, location and call management processes are fundamentally determined by the movement of the user. Modelling the mobility of a user is critical when evaluating current or future personal communication service protocols and management techniques. Synthetic and trace modelling are two methods of modelling the mobility of a single user or a group of users. Synthetic models are complex, computationally heavy, and lack realism. Trace models are based on empirical data and are difficult to modify to reflect future mobility. This paper presents PotFlow, a new synthetic method based on potential fluid dynamics that allows modelled users to have smooth continuous velocity trajectories in a simple, flexible, low computational manner.

PCS location area optimisation using an aggregate mobility model

In wireless personal communication systems mobility management techniques, call arrival models, user mobility models and network cell configuration can be used in developing an algorithm to partition PCS into location areas. This work presents an analytic framework of a PCS, develops an optimisation algorithm and determines the optimum cell size of the location areas to be 29, 21 and 45 cells for macro, micro and pico cell environments respectively.

Mobility in an RF-isolated test platform

Understanding the practical impact of mobility in a wireless network is essential for the wireless networks of tomorrow. Mobility influences the network performance, behavior, and ability to provide seamless service across a wide area. Testing and evaluating the real impact of mobility is difficult in the field with so many variables such as interference, fading, and so on. Experimental wireless evaluation in a test environment must correspond to an actual deployment. Furthermore, it is important to achieve repeatability without sacrificing realism. This study presents a functional test platform that uses real IEEE 802.11 equipment, providing repeatability and reliability. The platform is used to test the practical impact of device movement in a WLAN cell while voice and data applications are running. The mobility characteristics of wireless devices are based on individual models used by researchers with the addition of real aspects of mobility from empirical studies to improve realism.