cellular networks; Mobile networks / Controle de admissÃo de chamas e reserva de recursos em redes mÃveis celulares

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Handoff in wireless/mobile networks is the mechanism that transfers an ongoing call from the current cell as the mobile station moves through the coverage area of the system. User applications may experience performance degradation due to handoffs from user mobility. If the target cell does not have sufficient available bandwidth, the call will be dropped. From the userâs point of view handoff dropping is less desirable than the blocking of a new call. One of the key elements in providing Quality of Service (QoS) guarantees at the call level is an effective call admission control (CAC) and resource reservation policy, which not only has to ensure that the network meets the QoS of the newly arriving calls if accepted, but also guarantees that the calls of existing calls does not deteriorate. This thesis proposes two novel call admission control and reservation schemes for mobile cellular networks. Our proposals avoid per-user reservation signaling overhead and hence meeting the scalability requirements advocated for next generation networks. The two proposals are of easy integration with current Internet frameworks for QoS provisioning. Our first proposal, Distributed Call Admission Control with Aggregate Resource Reservation (RV), uses mobility prediction based on mobile positioning system and takes into account the expected bandwidth to be used by calls handed off from neighboring cells within an estimation time window. A novel concept called virtual reservation is introduced which aims at preventing per-user reservation. Our scheme is compared through simulations with the fixed guard channel and other optimized dynamic reservation-based proposals present in the literature. The simulation results show that the proposed scheme is superior to the other schemes. Our second proposal, Local Call Admission Control and Time Series-based Resource Reservation, takes into account the expected bandwidth to be used by calls handed off from neighboring cells based only on local information stored into the current cell where user is seeking admission. To this end, we propose the use of two time series-based models for predicting handoff load: the Trigg and Leach (TL), which is an adaptive exponential smoothing technique, and ARIMA (Autoregressive Integrated Moving Average) that uses the Box &Jenkins methodology. These methods are executed locally by each base-station or access router and forecast how much bandwidth should be reserved on a periodic time window basis. The predicted values for handoff load are re-calculated at the end of each time window and used for the next one. The two prediction methods are compared through simulations in terms of new call blocking probability and handoff dropping probability. Furthermore, an analysis regarding the quality of the predictions depicts that the time window prediction interval should be set carefully to avoid over-estimation and so the waste of the scarce wireless bandwidth. Despite the TL method simplicity, it can achieve similar levels of call blocking probability and handoff dropping probability than those of the computational demanding ARIMA models. In addition, depending on the schemes settings, the prediction methods can grant an upper bound on handoff dropping probability even under very high load scenarios. A comparative evaluation of the TL and RV schemes was carried out, and the results indicate that even the local proposal based on TL can grant nearly the same levels of handoff dropping probability as compared to the distributed approach

ASSUNTO(S)

ciencia da computacao controle de admissÃo de chamadas qualidade de servico

ACESSO AO ARTIGO

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