WiMAX無線系統OFDMA次載子配置之連線阻斷率分析

Analysis of Connection Blocking Probability for OFDMA Subcarrier Allocation in WiMAX Systems

WiMAX網路系統逐漸成熟普及，關鍵實體層採用最具潛力的正交分頻多重存取(OFDMA)技術，其中的次載子是一種珍貴而有限的無線電資源，系統業者需要妥善而有效的加以利用，同時必須滿足用戶連線的服務品質需求與電信總局最高連線阻斷率的門檻檢查規範。本篇論文模擬實際WIMAX OFDMA系統，分析用戶行為、系統負載、系統次載子容量與連線阻斷率之間的關係，並藉此求出在一個給定使用者服務品質基本要求、連線頻寬需求行為分布、連線到達率情況下，找出該基地台所需配置的最少次載子數量，多餘的次載子容量可以留給需求更高的相鄰基地台所使用，善用資源、提升收益與整體服務品質，可做為系統廠商在營運上定期或不定期網路頻譜部署重規劃的參考依據。

WiMAX is a well-known broadband wireless access technology. Its physical layer employs a potential key technology-orthogonal frequency-division multiple access (OFDMA). Because subcarriers in the OFDMA networks are scarce and valuable, operators should manage and use them efficiently. Meanwhile, connection blocking probability (CBP) should be met the requirement of the Directorate General of Telecommunications and the quality of service (QoS) for subscribers. In this paper, we analyze the relationship between user behavior, system load, and the system capacity and CBP by simulation of WiMAX OFDMA systems. Then we use given user QoS requirement, given connection bandwidth requirement, given connection arrival rate, and the specified maximum CBP constraint to find the minimum number of subcarriers for a base station. More subcarriers could be allocated for the adjacent base stations. By this way, system operators may utilize the subcarrier resources efficiently and improve their profitability and the overall service quality. It is useful for operators on a regular or irregular network planning or re-planning in the future.