CELLULAR NETWORK CALL HANDOVER RADIO CHANNELS RESERVATION MODEL USING MATLAB
ABSTRACT
Increase in GSM mobile station (MS) density without a corresponding increase in radio channel resource capacity reduces the quality of service (QoS) standard provided to users. The attempts made to improve the QoS standard have resulted in the creation of new base stations (BS) with the consequent reduction in the existing cell sizes. Increased call handovers are experienced in such situation. The increase is usually accommodated by resource reservation. How well the reservation is made greatly influences the QoS a GSM BS provides to MSs. This project work, therefore, presented optimum GSM call handover radio channel resource reservation system model. This model considers the QoS standard of fresh calls while reserving resources for handover calls. Therefore, the developed system model interfaced the handover resource reservation model to a typical cellular network model. This approach is rare due to the simulation complexity that is usually experienced with existing handover resource reservation models. The complexity was reduced in this work by integrating the model of a typical GSM network model with the resource reservation model in a MATLAB block oriented simulation environment – Simulink. The relationships between the handover call blocking probability, the number of resources to be reserved under varying traffic intensity were simulated to validate the model. Results show that the model can be successfully applied in the study of resource reservation systems.
CHAPTER ONE
INTRODUCTION
1.0 Background of the study
In every part of the world, presently, mobile communication networks are continuously experiencing increase in MS subscription. Correspondingly, the density of BSs is increased to maintain QoS standard. No doubt, increase in the number of BSs in a given area brings about a corresponding increase in the number of cell areas and then leads to the reduction in the sizes of the existing cells [1]. These situations often result in the increase of handover events between cells since the probability of MSs traversing cell(s) during a typical call connection increases. GSM handover event occurs when a mobile telephone network automatically transfers a call from one radio channel of a BS to another radio channel in a different BS as MS traverses cell boundaries [2]. In other words, handover involves the process of changing radio channel parameters such as frequency, time slot and spreading code associated with an on-going call connection [2]. Cell boundary is actually defined for a given BS by the points in space where minimum signal level required for standard quality reception from the BS are received [3]. The Mobile Switching Center (MSC) and Base Station Controller (BSC) setup monitor signal reception levels as MS moves. Whenever signal strength goes down below the minimum limit, it automatically switches the call to any idle channel in any BS with the strongest received signal above the minimum level required for handover within range.
