This paper presents three novel methods for implementing variable data rate (VDR) network congestion control (NCC), and compares them with traditional random (RND) drop methods. The proposed methods include: frequency (FRQ), combined random-innerloop frequency-outerloop (CRFRQ), and combined frequency-innerloop random-outerloop (CFRND). A generic model is used for RND drop that approximates congestion avoidance methods that drop packets. These methods allow NCC at intermediate network nodes using novel methods for setting data priority values. This is a first step towards demonstrating the need for stronger and efficient router technology to enhance Quality of Service (QoS) for voice applications. In the examples considered in this paper, the FRQ method reduced outage from 60% with RND to 0% with FRQ with 5 incoming flows through a bandwidth limited threshold of 1000 bits. Mean Opinion Score (MOS) was increased by a factor in the range from 0.2 to 1 on the MOS scale when using FRQ and CRFRQ over RND in the tested scenarios. CFRND performs in a similar manner to RND except it allows packet shrinking to increase network utilization. Network utilization increased by up to 37.5% over the RND method compared with the novel methods in one example where all possible outcomes for RND were analyzed. Computational complexity with the novel methods can yield a speedup from 0.02 ms faster for 1 flow to 0.56 ms faster for 10 flows over traditional lossy compression methods that rely on FFT operations, which are commonly found in lossy voice coders such as Speex, MELPe, and others. Finally, live real-time transport protocol (RTP) congestion tests were performed which confirmed the simulation results that the network congestion control methods achieve higher MOS scores and better QoS.
Bibliographical noteFunding Information:
In 2007, he worked at Newport Media Inc. in Irvine, CA on VLSI design for OFDM systems. In 2008, he joined Leanics Corporation, Minneapolis, MN and worked on secure Voice over Internet Protocol (VoIP). Later, he became Pricipal Investigator of the NSF SBIR grant award number 0944654: SBIR Phase I: High-Rate Low-Power Wireless Telemetry System for Medical Applications at Leanics Corporation. This grant involved researching wireless OFDM systems for medical applications. In 2010, he joined Maxlinear Inc. located in Irvine, CA.
The authors are grateful to the anonymous reviewers and the associate editor for their numerous constructive comments that led to significant improvements of the paper. This research was carried out at Leanics Corporation, Minnesota. The NRL VDR codec library was provided by the Naval Research Laboratory. A patent application has been filed on this topic  . This work was supported in part by the Navy SBIR contract number N00039-08-C0039. The authors are grateful to Tom Moran of NRL for providing the NRL VDR codec, and to Tom Moran and Robert Reed of SPAWAR division for numerous comments and suggestions during the course of this work.
- Network congestion control
- Variable data rate