Browse Prior Art Database

TRACKING HDLC ZERO INSERTIONS TO MINIMIZE AUDIO DELAY

IP.com Disclosure Number: IPCOM000008554D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-24
Document File: 3 page(s) / 109K

Publishing Venue

Motorola

Related People

Esteban Yepez Ill: AUTHOR [+2]

Abstract

Digital Communications systems introduce undesirable audio delay at various points along the transmission path. The Integrated Digital Enhanced Network (iDEN) is no exception. The iDEN system incorporates an HDLC-encoding scheme for mes- sages exchanged between the Base Radio Controller (BRC) and the Transcoder (XCDR). This publica- tion explains how the XCDR can minimize its inbound audio delay by tracking the number of zero-insertions detected in the message received from the BRC.

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MO7OROLA Technical Developments

TRACKING HDLC ZERO INSERTIONS TO MINIMIZE AUDIO DELAY

by Esteban Yepez Ill and lrina E. Veksler

ABSTRACT

  Digital Communications systems introduce undesirable audio delay at various points along the transmission path. The Integrated Digital Enhanced Network (iDEN) is no exception. The iDEN system incorporates an HDLC-encoding scheme for mes- sages exchanged between the Base Radio Controller (BRC) and the Transcoder (XCDR). This publica- tion explains how the XCDR can minimize its inbound audio delay by tracking the number of

zero-insertions detected in the message received from the BRC.

BACKGROUND

  The outbound path defines the direction of voice/data from the Public Switch Telephone Network (PSTN), through the iDEN infrastructure, to the iDEN subscriber. The inbound path defines the direction of voice/data from the iDEN subscriber through the iDEN infrastructure, to the PSTN.

Outbound Path

Inbound Path

Fig. 1 An Illustration of The Outbound and Inbound Paths

A SOURCE OF INBOUND AUDIO DELAY result is that the length of each packet will vary based upon the number of zeros that were inserted Each packet received by the XCDR is HDLC- into the packet's data stream. In iDEN, each audio encoded. This encoding technique is a well packet contains 53 bytes of data. This means that up established protocol that uses consecutive ones for to 85 zeros can be inserted. The packet is received messaging. To avoid misinterpreting random data as by the transcoder at a rate of 16 kbps and therefore, a message, zeros are inserted after tive consecutive an extra 85 zeros lengthen the packet by 5.2 ms. ones are detected in the packet's data stream. The

73 March 1998

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MOTOROLA Technical Developments

First VSELP

frame received

a!

Header

Fig. 2 Minimum Packet Length (a) versus Maximum Packet Length (b) (in bits)

DECODER SCHEDULING

  Each packet consists of a header, an informati...