1. Distributed Hop-by-Hop Rate Adjustment for Congestion Control in Sensor Networks Presented by: Manmohan Voniyadka Sapna Dixit Vipul Bhasin Vishal Kumar Singh

2. Agenda Problem description Solution requirements Algorithm description Congestion pricing scheme Rate adjustment using price of congestion Protocol details Open Issues Schedules and Work Distribution

3. Problem Description Rate Adjustment to avoid congestion Calculation of congestion pricing via a distributed mechanism

4. Solution Requirements Develop a congestion pricing scheme Develop a relationship between rate and the congestion pricing. Modify CODA Protocol to incorporate these changes

5. Congestion Pricing Scheme Factors for pricing MAC utilization. Congestion Price at Downstream Nodes. Calculate a cumulative congestion pricing factor. Calculate pricing factor in a distributed manner. Weigh the pricing on congestion nodes appropriately.

6. Congestion Pricing Calculation Cumulative Congestion Pricing: w i – relative weight of downstream node, i w i = N is the N th node from the congested node cp i congestion pricing at the i th node p j is a marking function (As given in [1])

7. Rate Adjustment Using Congestion Pricing Use an AIMD Strategy:

8. Protocol Details Conditions for Backpressure Origination Send backpressure when threshold is exceeded as done in CODA Threshold based on channel sampling Header Format Changes Extra field for price of congestion value in backpressure messages End-to-End Loop Control

9. Open Issues Relative weight in Congestion pricing is only based on congestion price at downstream nodes, Need to add Transmission rate at i th node as factor in weight. Whether to use price of congestion for end to end loop control for controlling the source rate during persistent congestion. What happens with Asymmetric links ?

10. Changes to existing CODA Changes in Suppression Message generation. Threshold based on MAC Utilization / channel Sampling. Calculate and Send Congestion Price. Changes in ReceiveBackPressure Message -> AdjustSourceRate.

11. Glossary CP j = P (j) * MAC Utilization (j). CP j is the congestion price for using node j per unit time. P(j) is the marking function at node j and determines the fraction of flow to be marked. MAC Util is the fraction of time node j spends in receiving and re- transmitting to next hop. P (j) = P (j) = (y - t j ) / y y is sum of MAC utilization time by all flows at node j. t j is a parameter for controlling MAC time utilization. P (j) indicates fraction of flow exceeding the threshold parameter. If link quality is bad, We make t j << 1 for lower MAC time utilization.

12. References [1] Chieh-Yih Wan, Shane B. Eisenman and Andrew T. Campbell, “CODA: Congestion Detection and Avoidance in Sensor Networks”, ACM SenSys 2003, November 2003.CODA: Congestion Detection and Avoidance in Sensor Networks [2] Y. Yi and S. Shakkottai. Hop-by-hop Congestion Control over a Wireless Multi-hop Network,“ IEEE INFOCOM, 2004. Hop-by-hop Congestion Control over a Wireless Multi-hop Network