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CELL SELECTION BACKOFF ALGORITHM FOR IMPROVED PORTABLE RADIO BATTERY LIFE

IP.com Disclosure Number: IPCOM000007398D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2002-Mar-21
Document File: 3 page(s) / 135K

Publishing Venue

Motorola

Related People

J. Christopher Stanaway: AUTHOR

Abstract

In the Motorola Integrated Radio System (MIRS), subscriber radios go through a Cell Selection proc- ess upon power-up or when out of coverage in an attempt to find an acceptable MIRS control chan- nel. An acceptable MIRS control channel is one that has significantly good signal strength and signal qual- ity and is one that belongs to a system that the radio is allowed to use. The Cell Selection algorithm involves scanning the available band of frequencies for an acceptable MIRS control channel and the radio will continue to scan until an acceptable MIRS con- trol channel is found. The MIRS system uses a TDMA RF interface such that a subscriber radio performs RF and DSP activity roughly only 17% of the time and Host processor activity is minimized during normal, idle operation. During Cell Selec- tion, however, both the Host and DSP are running nearly 100% ofthe time in order to locate an accept- able MIRS control channel.

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MOIY)ROLA Technical Developments Volume 24 March 1995

CELL SELECTION BACKOFF ALGORITHM FOR IMPROVED PORTABLE RADIO BATTERY LIFE

by J. Christopher Stanaway

  In the Motorola Integrated Radio System (MIRS), subscriber radios go through a Cell Selection proc- ess upon power-up or when out of coverage in an attempt to find an acceptable MIRS control chan- nel. An acceptable MIRS control channel is one that has significantly good signal strength and signal qual- ity and is one that belongs to a system that the radio is allowed to use. The Cell Selection algorithm involves scanning the available band of frequencies for an acceptable MIRS control channel and the radio will continue to scan until an acceptable MIRS con- trol channel is found. The MIRS system uses a TDMA RF interface such that a subscriber radio performs RF and DSP activity roughly only 17% of the time and Host processor activity is minimized during normal, idle operation. During Cell Selec- tion, however, both the Host and DSP are running nearly 100% ofthe time in order to locate an accept- able MIRS control channel.

  A problem was observed that when a portable subscriber radio is unable to locate an acceptable MIRS control channel for a significant length oftime (either because of being out of coverage or because ofsystem trouble), the portable battery relatively fast. A method to maintain battery life at acceptable lev- els was needed such that the battery life of a porta- ble subscriber unit when in Cell Selection is at least as good as when idle, camped on a control channel.

  The solution basically was to suspend the Cell Selection algorithm after each pass through the Bandmap (list of frequencies of possible MIRS con- trol channels) that was unsuccesshd for some backoff period. The question was then, for how long is the algorithm suspended? Since the battery life needed to be improved to be at least as good as when idle, and the amount of extra work done is variable, cal- culating the length oftime to suspend the Cell Selec- tion algorithm is calculated dynamically.

The backoff period is based on the amount of work done while scanning compared to the amount

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of work done while in service and idle on the con- trol channel (on standby). The amount of work done while scanning will be known (computed dynami- cally) as will the amount oftime that was spent scan- ning. Based on the amount ofwork done while scan- ning, the amount oftime that would have been spent while on standby to perform the same amount of work is computed. The difference in the amount of times is the amount of time that the Cell Selection algorithm will be suspended after a complete pass through the frequency band. An upper and lower limit on the backoff time is used to insure that the portable will suspend the Cell Selection at least some minimum amount of time and not backoff for too...