Eun-Chan Park and Hwangnam Kim Dept. of Information and Communication, Dongguk University ( ) Dept. of Electrical Engineering, Korea University ( ) IEEE Transactions on Communications, Vol. 57, No. 3, March, 2009 A Dual Feedback Approach of Request-based Bandwidth Allocation for Real-time Service in Broadband Wireless Access Networks Agenda Introduction Optimal bandwidth-request algorithm for ertPS Analysis of the proposed algorithm Conclusion Introduction Five types of bandwidth allocation mechanism Unsolicited Grant Service (UGS) Real-time polling service (rtPS) Non-real-time polling service (nrtPS) Best effort (BE) Extened real-time polling service (ertPS) Bandwidth request allocation mechanism No specific mechanism has been standardized Impacts the bandwidth utilization and delay constraints Optimal bandwidth-request algorithm for ertPS Assumptions Uplink traffic consideration BS employs a priority-based scheduler to serve real-time services If the real-time services are admitted, the services are served with the guaranteed bandwidth Bandwidth-allocation interval T a is equal to packetization interval No queuing delay at BS Optimal bandwidth-request algorithm for ertPS Dual feedback approach of bandwidth request mechanism Computes total additional bandwidth-request B(t) Takes the following two metrics into considerations Queue size difference e q (t) Rate mismatch e r (t) Optimal bandwidth-request algorithm for ertPS Target delay (sec.), T ref Tolerable MAC-to-MAC delay for real-time applications Delay incurred in application layer is not included Target transmission queue length in SS (bytes), Q ref Average packet size Additional delay ( processing delay at MAC, transmission delay over wireless link) Bandwidth allocation interval Optimal bandwidth-request algorithm for ertPS Demonstration of ideal case: Q ref =q(t) Time BS Time SS T ref b bb P1P1 P2P2 P1P1 P2P2 P3P3 P3P3 TaTa TaTa ToTo P1P1 Data packet b BW request packet q(t)=3 ToTo ToTo Optimal bandwidth-request algorithm for ertPS Demonstration of ideal case: Q ref >q(t) Time BS Time SS T ref b bb P1P1 P2P2 P1P1 P2P2 P3P3 P3P3 ToTo P1P1 Data packet b BW request packet q(t)=3 ToTo ToTo b TaTa TaTa TaTa P3P3 P2P2 P1P1 Excessive bandwidth allocation Optimal bandwidth-request algorithm for ertPS Demonstration of ideal case: Q ref 0 Queue length grows e r (t)=a(t)-s(t)