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Predictive and Adaptive Bandwidth Reservation for Handoffs in QoS-Sensitive Cellular Networks

Predictive and Adaptive Bandwidth Reservation for Handoffs in QoS-Sensitive Cellular Networks. IEEE Transactions on Parallel and Distributed Systems Author: Sunghyun Choi and Kang G.Shin Presented By: Yang Liu Date: Nov 26, 2002. Outline. Introduction and Motivation System Model

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Predictive and Adaptive Bandwidth Reservation for Handoffs in QoS-Sensitive Cellular Networks

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  1. Predictive and Adaptive Bandwidth Reservation for Handoffs in QoS-Sensitive Cellular Networks IEEE Transactions on Parallel and Distributed Systems Author: Sunghyun Choi and Kang G.Shin Presented By: Yang Liu Date: Nov 26, 2002

  2. Outline • Introduction and Motivation • System Model • History-based Mobility Estimation • Bandwidth Reservation and Admission Control • Performance Evaluation • Conclusion

  3. Introduction • Hand-off drops: when the cell in the new location does not have enough bandwidth to support the connection • To eliminate hand-off drops Reservation of bandwidth for possible hand-offs • How much bandwidth will be reserved in each cell? • Per-connection bandwidth reservation By reserving each connection’s bandwidth in all cells the connection might pass through Not practical, and too costly if possible

  4. Provided Solution • Connection-level QoS parameter: - PHD : hand-off dropping probability • Design goal: bounding PHD under a pre-specified target value • Predictive and adaptive bandwidth reservation for hand-offs and admission control for new requests • Fractional bandwidths of estimated hand-offs are reserved

  5. System Model • Cell indexing: (a) 1-dim. Case (b) 2-dim. Case • Ci,j: connection j in cell i ; b(Ci,j): its bandwidth • C(i): link capacity of cell i • Admission control of new connection by the BS in cell i with target reservation bandwidth Br,i:

  6. Mobility Estimation • Model mobile’s hand-off behavior and estimate mobility based on aggregate history • Mobility information: when and where • Observation from road traffic: O1.Traffic signals and signs(e.g., speed limits and stop signs) affect mobiles’ movements and speed significantly O2. During the rush hours, the speed of all mobiles in a given geographical area are closely correlated O3. In many cases, the direction of a mobile can be predicated from the previous path the mobile has taken so far Cell-specific history-based mobility estimation

  7. Hand-off Event Quadruplets • Upon the departure of a mobile from cell 0 to an adjacent cell, the BS of cell 0 caches hand-off event quadruplet (Tevent, prev, next, Tsoj) • Tevent: the hand-off time • Prev: index of previous cell • Next: index of cell after departure • Tsoj: time duration the mobile spent at cell 0

  8. Mobility Estimation Function • From the cached hand-off event quadruplets(Tevent, prev, next, Tsoj) observed during the last Tint time • Hand-off estimation function FHOE(t0, prev, next, Tsoj):= wn • Cyclic mobility pattern w0 = 1(today) w1 < 1(yesterday) • Describes the users’ hand-off behaviors probabilistically given prev probability mass function for a two-dimensional random vector(next, Tsoj)

  9. Bandwidth Reservation • Mobility estimation time window: [t0, t0+Test] • Hand-off probability ph(Ci,j -> next): probability that Ci,j hands off into cell next within time Test • Extant sojourn time Text_soj(C0,j): time elapsed since C0,j entered cell 0 • Example: ph(Ci,j -> 4) = A/B • Target reservation bandwidth at cell 0:

  10. Mobility Estimation Time Window Control • The larger Test, the larger ph, the larger Br,i • To attain design goal more efficiently - Reference window size w (=[1/pHD,target]) (100 if pHD,target = 0.01) - PHD < PHD,target: Should be no more than n hand-off drops out of w*n(=100*n)observed hand-offs - If violated, Test:=Test + 1 to reserve more - Otherwise, Test:=Test – 1 to reserve less • Robust to (1) inaccurate mobility estimation; (2) time-varying traffic/mobility

  11. Admission Control • Target reservation bandwidth is calculated during the admission control phase of a new request • The current cell and some adjacent cells participate in the admission control • With the current target reservation bandwidth Br,i curr T1: for all , such that Calculate Br,i newly,set Br,i curr:= Br,I Check if T2: Check if T3: If all the above tests are positive, then the connection is admitted.

  12. Conclusion • Mobility estimation based on observed history in each cell • Predictive and adaptive bandwidth reservation and admission control to limit PHD below PHD,target • Performance evaluation via simulation

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