Transmission control for a specific absorption rate compliant communication device

A method for transmitting data from a portable communication device to a station via a radio frequency signal, wherein data is transmitted using a protocol that has recurring frames, each having a plurality of transmission slots, different numbers of which can be used to transmit the data, the method comprising:

• defining a relationship between variation of a power level for the radio frequency signal and the number of the transmission slots in a frame that can be used by the portable communication device to transmit the data without the radio frequency signal resulting in a specific absorption rate (SAR) limit being exceeded;
• the station performing steps of:
• determining whether an increase in power level for the data transmission is needed;
• when determining that an increase in power level is needed, selecting one of a plurality of power levels available to use for the radio frequency signal, thereby designating a given power level and in response to the given power level and the relationship, selecting a maximum number of transmission slots in a frame, wherein transmission of the data by the portable communication device at the given power level and in the maximum number of transmission slots does not result in the SAR limit being exceeded;
• and
• when determining that an increase in power level is not needed, determining if an increase in data rate is needed, determining a number of transmission slots required for providing the needed data rate, and deriving a power level based on the number of required transmission slots, wherein transmission of the data by the portable communication device in the number of transmission slots required for providing the needed data at the derived power level does not result in the SAR limit being exceeded.

A portable communication device that transmits data to a station via a radio frequency signal, wherein data is transmitted using a protocol that has recurring frames, each having a plurality of transmission slots different numbers of which can be used to transmit the data, the portable communication device comprising:

• a control system having logic for:
• storing a relationship between variation of a power level for the radio frequency signal and the number of the transmission slots in a frame that can be used by the portable communication device to transmit the data without the radio frequency signal resulting in a specific absorption rate (SAR) limit being exceeded;
• determining whether an increase in power level for the data transmission is needed;
• when determining that an increase in power level is needed, selecting a desired power level for the radio frequency signal and using the desired power level and the relationship to select a maximum number of transmission slots so that the data transmission does not result in a SAR that is greater than the SAR limit;
• and
• when determining that an increase in power level is not needed, further determining that an improvement in data rate is needed, determining a number of transmission slots required for providing the needed data rate, and calculating a power level based on the number of required transmission slots for which the data transmission does not result a SAR that is greater than the SAR limit.