Browse Prior Art Database

Digital Walkie-Talkie Point-to-Point Power Control

IP.com Disclosure Number: IPCOM000126198D
Original Publication Date: 2005-Jul-06
Included in the Prior Art Database: 2005-Jul-06
Document File: 6 page(s) / 176K

Publishing Venue

Motorola

Related People

Bruce Geren: INVENTOR

Abstract

A digital walkie-talkie (two-way radio), such as Motorola's MOTOtalk protocol, based on point-to-point communication and utilizing an Acknowledgement message, uses the Acknowledgement message to determine a level of power control for the remainder of the communication. A transmitting unit (first unit) transmits a Call Initiation message to initiate a call to a receiving unit (second unit) desiring to establish a half-duplex call. The second unit upon receiving the Call Initiation message responds to the first unit with an Acknowledge message. The first unit upon receiving the Acknowledge message uses signal strength and signal integrity information (such as correlation filters) from the received Acknowledge message to determine a potential reduction in transmit output power. Conversely, the second unit may use the Call Initiation message from the first unit to determine a potential reduction in transmit output power which is transmitted back to the first unit as part of the Acknowledge message. In either scenario, if measured signal integrity is above a threshold, then the measured received signal strength less a minimum desired link margin is used to calculate a transmit output power cutback. Due to the potential volatile environment that two roaming walkie-talkie units may be used in, sufficient margins must still be maintained to ensure a successful transmission for the duration of the half-duplex call. As the call progresses in time, the uncertainty of sufficient transmit output power also increases. By understanding the environment in which the radios are used, a simple algorithm is proposed such that the transmit output power level is gradually and linearly increased in time (until it reaches maximum output power) to minimize the level of uncertainty which helps ensure sufficient transmit output power to maintain the link. Since walkie-talkie transmissions are typically short, the majority of calls will receive a battery power savings, so long as the range between the two radios is sufficiently close enough to warrant a reduced initial transmit output power level. An estimate of the battery power savings is provided based on hypothetical radio usage.

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Digital Walkie-Talkie Point-to-Point Power Control

By Bruce Geren

Motorola, Inc.

Networks

 

ABSTRACT

A digital walkie-talkie (two-way radio), such as Motorola’s MOTOtalk protocol, based on point-to-point communication and utilizing an Acknowledgement message, uses the Acknowledgement message to determine a level of power control for the remainder of the communication. A transmitting unit (first unit) transmits a Call Initiation message to initiate a call to a receiving unit (second unit) desiring to establish a half-duplex call. The second unit upon receiving the Call Initiation message responds to the first unit with an Acknowledge message. The first unit upon receiving the Acknowledge message uses signal strength and signal integrity information (such as correlation filters) from the received Acknowledge message to determine a potential reduction in transmit output power. Conversely, the second unit may use the Call Initiation message from the first unit to determine a potential reduction in transmit output power which is transmitted back to the first unit as part of the Acknowledge message. In either scenario, if measured signal integrity is above a threshold, then the measured received signal strength less a minimum desired link margin is used to calculate a transmit output power cutback.

Due to the potential volatile environment that two roaming walkie-talkie units may be used in, sufficient margins must still be maintained to ensure a successful transmission for the duration of the half-duplex call. As the call progresses in time, the uncertainty of sufficient transmit output power also increases. By understanding the environment in which the radios are used, a simple algorithm is proposed such that the transmit output power level is gradually and linearly increased in time (until it reaches maximum output power) to minimize the level of uncertainty which helps ensure sufficient transmit output power to maintain the link. Since walkie-talkie transmissions are typically short, the majority of calls will receive a battery power savings, so long as the range between the two radios is sufficiently close enough to warrant a reduced initial transmit output power level. An estimate of the battery power savings is provided based on hypothetical radio usage.

PROBLEM

Digital walkie-talkies (two-way radios) suffer a short battery life due to the high output power (up to 1 Watt in the ISM bands) and long transmit duty cycles. In addition, use of publicly available bands such as the ISM band which is shared by other communication devices, such as cordless phones, may have interference due to the walkie-talkie’s higher output power. A feedback mechanism must be in place to instruct the transmitter on what transmit output power is sufficient. Typical configurations employ a constant or recurring feedback to adjust the transmit output power to adjust for varying environmental changes, but this complicates the protocol. Signal integrity of the transmi...