Browse Prior Art Database

FAX DATA ON RADIO SYSTEMS

IP.com Disclosure Number: IPCOM000006513D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-11
Document File: 1 page(s) / 55K

Publishing Venue

Motorola

Related People

Todd H. Miller: AUTHOR

Abstract

Fax data transmission to mobile radios, using nor- mal analog audio channels, can encounter a problem with the base station limiter and splatter filter resulting in poor fax data transmission in the "outbound landhne to mobile, direction (lower success rate and slower data speeds). This problem is inherent in any interconnect system interface because of the desire to optimize voice transmission, which has a different power spectral den- sity than data, and the use of a limiter and splatter filter in the base station to meet FCC requirements of occu- pied bandwidth and adjacent channel splatter.

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MOTOROLA INC. Te&pical Developments Volume16 August 1992

FAX DATA ON RADIO SYSTEMS

by Todd H. Miller

  Fax data transmission to mobile radios, using nor- mal analog audio channels, can encounter a problem with the base station limiter and splatter filter resulting in poor fax data transmission in the "outbound landhne to mobile, direction (lower success rate and slower data speeds). This problem is inherent in any interconnect system interface because of the desire to optimize voice transmission, which has a different power spectral den- sity than data, and the use of a limiter and splatter filter in the base station to meet FCC requirements of occu- pied bandwidth and adjacent channel splatter.

  Control of the "inbound:' mobile to landline, situa- tion is possible because the fax data and transmit audio paths can be controlled separately, in the mobile, to ensure the fax data does not get limited (four wire audio

interface). This is not possible in the outbound direction (two wire telephone interface) unless a means of detect- ing the start of a fax transmission is used to control the audio level driving the base station (Ll). This can be done by detecting the mobile fax CED (Called Station Identification) tone on the infrastructure audio (L2). The CED is a 2100 Hz, tone that is transmitted for a minimum of 2.6 seconds by the mobiles receiving fax unit (CCITI specifications) when entering the receive mode either manually or automatically. Upon detection of this...