Browse Prior Art Database

METHOD OF INTERLEAVING REAL- TIME INFORMATION

IP.com Disclosure Number: IPCOM000009779D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-18
Document File: 1 page(s) / 73K

Publishing Venue

Motorola

Related People

Steve Emeott: AUTHOR [+2]

Abstract

In wireless systems, delivering voice and other real-time services while maintaining an acceptable quality of service is an important issue. Maximizing the quality of service within a given radio frequency coverage area increases end user satisfaction and reduces the cost of deploying systems. Some of the factors influencing service quality include noise, interference and multi-path fading. We would like to reduce the impact of these impairments on quality of service whenever possible.

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MOTOROLA

Technical Developments

METHOD OF INTERLEAVING REAL- TIME INFORMATION

by Steve Emeott and Greg White

In wireless systems, delivering voice and other real-time services while maintaining an acceptable quality of service is an important issue. Maximizing the quality of service within a given radio frequency coverage area increases end user satisfaction and reduces the cost of deploying systems. Some of the factors influencing service quality include noise, interference and multi-path fading. We would like to reduce the impact of these impairments on quality of service whenever possible.

Wireless communications systems typically employ forward error correction coding techniques to combat noise and interference. In addition, interleaving is often used to combat slow multi-path fading of the mobile radio channel. In order to obtain high audio quality in a bandwidth efficient digital speech communications system, there is a need for strong, efficient techniques for forward error correction, particularly in fading mobile radio channels.

This article describes a method of interleaving speech packets in time division multiple access (TDMA) communications systems, providing improved audio quality as compared to an ordinary interleaver.

Prior to sending a compressed speech packet over a wireless channel, transmitters typically split it into two portions. The first portion consists of the bits that are highly sensitive to errors, and is protected with FEC techniques (e.g. convolutional codes) before transmission. The second portion is less sensitive to bit errors, and is transmitted without FEC protection. All bits (first portion with coding, and second portion) are interleaved before transmission to help protect against fading.

Where additional delay can be reas...