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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 PeiDepartment of Electrical and Computer Engineering,University of Houston, Houston, TX,77204-4005, USA

{ijung, karayiannis, spei}@uh.edu

Reporter 陳宗涵

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Outline

1. Abstract2. Introduction3. Signal Strength-Based Rate Control 4. Simulation5. Conclusions

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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.

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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.

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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.

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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.

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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.

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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.

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Signal Strength-Based Rate Control ements

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Signal Strength-Based Rate Control

Algorithm 1: Signal Strength Level

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Signal Strength-Based Rate Control

Algorithm 2: Signal Quality

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Signal Strength-Based Rate Control

Algorithm 3. Wireless Loss Filter

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Simulation

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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

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Simulation

Data Delivery Under Semi-Static Wireless Conditions

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Simulation

Error margin of signal strength TFRC

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Simulation

Data Delivery Under Dynamic Wireless Conditions

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Simulation

Data Delivery Under Congestion Conditions

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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.