1. Wenye Wang Xinbing Wang Arne Nilsson Department of Electrical and Computer Engineering, NC State University March 2005 A New Admission Control Scheme under Energy and QoS Constraints for Wireless Networks

2. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 2 Agenda Motivations Relationship between admission control and energy consumption New call admission control scheme –Victim selection algorithm (VSA) –Beneficiary selection algorithm (BSA) –Stochastic adjustment algorithm (SAA) Performance analysis –Markov chain model –Blocking probabilities: fixed/dynamic channel holding time –Energy consumption Numerical results Conclusions and future work

3. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 3 Motivations Two important issues in future wireless networks –Bandwidth utilization based on call admission control (CAC) –Energy conservation Why “another” admission control scheme? –Existing work on admission control: interference-, mobility-, and priority-based etc. –Existing work on energy/power management At physical layer: power control based on channel fading and interference, joint source and channel coding etc. At medium access control (MAC) and application layer: smart on-off schemes are proposed for energy consumption CAC and energy saving are separate from each other develop a new admission control scheme under constraints of energy consumption and QoS Objective: develop a new admission control scheme under constraints of energy consumption and QoS

4. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 4 Call Admission Control and Energy Consumption Energy Consumption Rate (ECR): is energy consumption of each successfully transmitted bit –Total energy consumption E_{total} = ECR *  =ECR*T*R E b t :Energy to transmit one bit P fer :Frame error rate, P:Transmission power R:Transmission rate  :Total amount of data T:Time to transmit data

5. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 5 Relationship between CAC and Energy Consumption: Example Energy consumption rates vary with terminals at different trans. rates BPSK Modulation Reed Soloman (RS) Code Consider Retransmission

6. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 6 Admission Control Scheme Energy Consumption Victim Selection Algorithm (BSA) –When there is no enough number of channels, victims are selected according to the lowest energy increasing rate. Beneficiary Selection Algorithm (BSA) –When there are some channels released, beneficiaries are chosen based on the highest energy decreasing rate. Stochastic Adjustment Algorithm (SAA) –To achieve fairness among different classes of traffic by pre-block traffic flows

7. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 7 Victim Selection Algorithm (VSA) All bandwidth has been allocated to ongoing sessions A new/handoff call arrives, how to find (sufficient) bandwidth for it?  r (R) –Search for all ongoing sessions, and find a victim, that is, the absolute value of the derivative of  r (R) is the minimum. –Note that if this terminal is operating at its lower- bound transmission rate, then this terminal cannot be a victim. –Once a victim is identified, then the amount of  BW bandwidth will be reduced. Victim

8. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 8 Beneficiary Selection Algorithm (BSA) Some bandwidth is released when a connection is finished Available bandwidth is reallocated to ongoing sessions  r (R) –Search for all ongoing sessions, and find a beneficiary terminal, that is, the absolute value of the derivative of  r (R) is the maximum. –Note that if this terminal is operating at its upper- bound transmission rate, then this terminal cannot be a beneficiary terminal. –Once a beneficiary terminal is identified, the amount of  BW bandwidth will be reallocated. Beneficiary terminal

9. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 9 Stochastic Adjustment Algorithm (SAA) Goal: to couple admission control with QoS requirements to achieve a balance/fairness among multiple classes Solution: pre-block some traffic, that is, to determine the rate of arrival requests blocked for each class, k, for a total number of K classes: Pricing model is used to create an objective function. For a simplified two-class system, e.g., handoff and new calls, we consider Min {  B 1 |Q + B 2 |Q } s.t. B 1 |Q < B 2 |Q, m 1  0, m 2  0

10. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 10 Performance Analysis: System Model

11. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 11 Assumptions Poisson arrival process is enforced. Exponential service rate is used, which can be relaxed to any arbitrary distribution. For new calls and handoff calls, the same admission control scheme will be used.

12. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 12 Analytical Model: Markov Chain Call blocking probability for multi-class service model is obtained based on multi-dimension Markov Chain.

13. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 13 Blocking Probabilities Fixed channel holding time: –The number of channels of a connection session does not affect channel holding time –The channel holding time is assumed to be exponentially distributed –The number of channels, or the bandwidth, affects only the quality of service, like the the resolution of an image. Dynamic channel holding time –The channel holding time is dependent on the number of channels –More bandwidth means shorter transmission time

14. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 14 Analysis of Energy Consumption E The average energy consumption, E, – is the probability of each state – is the average energy consumption at each state can be obtained based on the energy consumption rate, ECR matrix ( a ij is the ECR of class i with j channels,

15. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 15 Simulations Non-prioritized scheme (NPS): Simplest resource allocation scheme with least overhead, which determines the admission based on a fixed bandwidth requirement. Adaptive resource allocation scheme (AREAS): it determines the admission based on several options of bandwidth requirements. ParametersClass AClass B Arrival Rate (call/min)[1,40]10 Data Volume (kbyte)180 Transmission Rate (kbps/channel)88 # of Channels for NPS73 # of Channels for AREAS{4, 7, 9}{2, 3, 5} # of Channels for Our Scheme{4,9}{2,5}

16. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 16 Case I: Blocking Probability The results of simulations, analysis of new scheme overlap with the results of AREAS: the energy-based admission control is able to reduce blocking probability as adaptive resource allocation scheme for QoS requirements. Adaptive resource allocation schemes are much more effective in reducing blocking probability than non-prioritized scheme The lower the bandwidth requirement (e.g., class-B), the lower the blocking probability.

17. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 17 The throughput of Class-A increases as the arrival rate is increased, whereas the throughput of Class-B decreases because Class-A traffic is dominant for higher A. Higher throughput can be achieved by the new scheme Case I: Throughput Class-A Class-B

18. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 18 Dynamic channel holding time is considered as Case II in which data volume is fixed. Thus, the more the bandwidth, the shorter the transmission time. The blocking probability of the new scheme is lower than both AREAS and NPS. The new scheme yields higher throughput. Case II: Dynamic Channel Holding Time Blocking Probability and throughput Class-B

19. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 19 QoS Adjustment: Blocking Probability By sacrificing Class-B, the blocking probability of Class-A is reduced significantly Before using stochastic QoS adjustment algorithm, the difference between blocking probabilities of two classes becomes bigger with increase of arrival rates. After the adjustment, the difference of blocking probability of two classes becomes smaller.

20. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 20 Self-Similar Traffic: Blocking Probability and Throughput The new scheme is effective in reducing blocking probability and improving throughput for non-Poisson processes such as self-similar traffic The simulation takes longer time for self-similar traffic Blocking Probability Throughput

21. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 21 Energy Consumption Arrival rate Energy (num. of calls/min) Consumption Rate 52035 NPS9.8 AREAS6.211.812 New Scheme2.13.43.6

22. A New Admission Control Scheme A New Admission Control Scheme/ Wang et al, INFOCOM’05, Miami, FL 22 Conclusions A new call admission control scheme is designed based on energy consumption. Three algorithms: victim selection algorithm (VSA), beneficiary selection algorithm (BSA), and Stochastic adjustment algorithms (SAA) are proposed to reallocate bandwidth. Call blocking probability is analyzed for a multi- class system based on Markov model. Lower energy consumption is achieved without the expense of call blocking probability. Thank you!