1. 2008/6/51 Improving TCP-Friendly Rate Control in Wired and Wireless Networks By a Scheme Based on Wireless Signal Strength Il Mo Jung, Nicolaos B. Karayiannis, and Steven Pei Department of Electrical and Computer Engineering, University of Houston, Houston, TX,77204-4005, USA {ijung, karayiannis, spei}@uh.eduspei}@uh.edu Reporter 陳宗涵

2. 2008/6/52 Outline 1. Abstract 2. Introduction 3. Signal Strength-Based Rate Control 4. Simulation 5. Conclusions

3. 2008/6/53 Abstract  We propose a rate control schem developed to improve TFRC (TCP-Friendly Rate Control) in wired and wireless networks.  This is accomplished by using wireless signal strength information to improve wireless TFRC performance. Most wireless devices currently have wireless signal strength information in the driver level.

4. 2008/6/54 Abstract  In Windows XP, our scheme can be implemented by a slight modification of the TFRC algorithm in the application level through the use of WRAPI 2.0.  The proposed scheme is robust to congestion loss and wireless loss. In addition, our scheme exhibits stable performance even in time-varying wireless conditions.

5. 2008/6/55 Introduction  TFRC is the scheme that allows us enjoy multimedia stream over the Internet.  However, TFRC is based on the loss and delay that can be measured exactly only in wired networks.  Currently, some network service providers began to provide a wireless metropolitan area network service. As a result, we cannot assume that the wireless error rate is static due to the users’ high mobility.  TFRC should be enhanced to be able to handle such high mobility.

6. 2008/6/56 Introduction  Our approach to this problem uses wireless signal strength information that can be obtained without any hardware dependency in Windows XP.  WRAPI 2.0 can be designed to have a dual role  deal with the wireless connection  provide real-time signal strength as a type of system function  Such middleware is simple and makes it possible to control the streaming rate in the application layer in a way similar to that the streaming rate is controlled by several existing TCP-friendly rate control schemes.

7. 2008/6/57 Introduction  This paper introduces a rate control scheme that relies on wireless signal strength information to filter packet delay due to automatic repeat request (ARQ) and losses due to wireless channel error.

8. 2008/6/58 Signal Strength-Based Rate Control  The proposed signal strength-based scheme uses signal strength information in dBm (dBmiliwatt). RSSI values can also be changed to dBm, which has a relation with signal quality (0-100%) [6].  we assume that signal quality is proportional to the probability that a packet is delivered without error.

9. 2008/6/59 Signal Strength-Based Rate Control ements

10. 2008/6/510 Signal Strength-Based Rate Control  Algorithm 1: Signal Strength Level

11. 2008/6/511 Signal Strength-Based Rate Control  Algorithm 2: Signal Quality

12. 2008/6/512 Signal Strength-Based Rate Control  Algorithm 3. Wireless Loss Filter

13. 2008/6/513 Simulation

14. 2008/6/514 Simulation  We chose the widely-used shadowing model as our radio propagation model, since we need to create conditions characterized by high interference similar to the moving client’s real surroundings.  The environmental parameters of the shadowing model  the path loss exponent was β = 4  the shadowing deviation was σdB = 7.0  the reference distance was set to 1.0  the seed was set to 0

15. 2008/6/515 Simulation  Data Delivery Under Semi-Static Wireless Conditions

16. 2008/6/516 Simulation  Error margin of signal strength TFRC

17. 2008/6/517 Simulation  Data Delivery Under Dynamic Wireless Conditions

18. 2008/6/518 Simulation  Data Delivery Under Congestion Conditions

19. 2008/6/519 Conclusion  This paper introduced a signal strength-based scheme that may be used to enhance the original TFRC scheme.  Since currently available wireless devices have signal strength information, the information required by the proposed scheme can be obtained in the driver or application level.  Our simulation results indicated that the proposed scheme maintains effectively its TCPfriendly behavior. Besides, our simulation revealed that the proposed scheme exhibited high data delivery capability for almost all cases.