Browse Prior Art Database

MOBILE RADIO SIMULCAST RESPONSE

IP.com Disclosure Number: IPCOM000006836D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2002-Feb-06
Document File: 6 page(s) / 256K

Publishing Venue

Motorola

Related People

Steven J. Goldberg: AUTHOR

Abstract

Half duplex radio communication systems use time and frequency diversity to allow multiple mobiles to respond to a poU from fixed stations. A system with a large number of mobiles could experience significant delays with the poll and respond process's limited throughput capability A method which allowed more responses per unit of time, without increasing response bit rates, requiring tighter bandwidths to allow more response frequencies, or a larger bandwidth for more frequencies is highly desirable.

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MO-LA INC. Technical Developments Volume 19 June 1993

MOBILE RADIO SIMULCAST RESPONSE

by Steven J. Goldberg

INTRODUCTION

  Half duplex radio communication systems use time and frequency diversity to allow multiple mobiles to respond to a poU from fixed stations. A system with a large number of mobiles could experience significant delays with the poll and respond process's limited throughput capability

  A method which allowed more responses per unit of time, without increasing response bit rates, requiring tighter bandwidths to allow more response frequencies, or a larger bandwidth for more frequencies is highly desirable.

  The system to be described has a number of mobiles respond simultaneously to a poll, with said mobiles all using the same frequency. The number of mobiles responding per unit of time can therefore, be increased over the prior art, and no additional frequency agility or allocation is required. A key ingredient of course is that when signals do interfere, they must still be discernible into a meaningful form. '

OPERATION

  Mobiles will be assigned to groups with most of their identitication bits in common. The remaining unique bits will be adequate to provide information as to the identity of the responding mobiles.

  The system will examine its message queues for mobiles within the same group. They will be polled in a manner which causes them to respond during the same time slot with the same frequency.

  When poUed, all mobiles will respond in a simul- cast fashion. Their common bits will, as in existing out- bound simulcast systems, reinforce each other in regions where their power levels are within a certain range of each other (6 db being typical for existing simulcast sys- tems). The mobile unique bits will cause indeterminate results when they differ, but will reinforce each other

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when they are the same. This will cause reception of what will be referred to as interference patterns. (Figure 1 shows a simplistic situation where two mobiles are transmitting in simulcast to at least two fixed transmitters.)

  The various Uxed network receivers of the system will analyze the received signals. Based on the system's knowledge of which mobiles were poll4 the bit pat- terns received at each receiver, and the relative power levels, the fmed system administrator will determine which mobiles definitely responded, and determine their locations. Those mobiles which could not defmitely be determined to have responded will be repoUed. Since in most cases the initial poU will have eliminated the possi- bly interfering pages, the second poU should produce a non interfered signal from the mobile.

DETAILS OF OPERATION

  For simplicity the following discussions will assume that the polled mobiles are assigned two per simulcast response group. This will approximately double the response throughput of the system. Higher degrees of improvement can be obtained by extending the concepts to more mobiles in each group.

SIMULC...