Qualifying available reverse link coding rates from access channel power setting
View Patent ↗Data rate allocation decisions are made for a communications channel, such as a wireless reverse link connection. A first parameter used in this determination is a path loss, which is determined by the following process. First, a message is sent from a first station to a second station, such as on a paging channel. The message indicates a forward Effective Radiated Power (ERP) of a pilot signal transmitted by the first station. The second station then determines the received signal strength of this pilot signal, taking into account receiver gains. The path loss can then be estimated by the second station as the difference between the forward ERP data value that it received and the detected received pilot power. The second station also then preferably determines a transmit power level when transmitting a message back to the first station. This transmit power level information is encoded as a digital data word together with the forward path loss information as calculated by the first station. Upon receipt of these two pieces of information by the first station, the forward path loss estimate as calculated by the second station, and the output power value of the second station, the first station can then determine the amount of excess power available at the field unit. This excess power difference is indicative of the amount of dynamic range available in the transmit power amplifier in the particular second station. With this information, the first station can then make a determination as to whether coding rates which require a higher dynamic range will be acceptable for use by the particular second station.
1. A method for determining data rate for a communications channel comprising the steps of:
sending a first message from a first station to a second station, the message indicating an Effective Radiated Power (ERP) data value of signals transmitted by the first station;
receiving the first message at a second station;
measuring a signal strength for signal received at the second station;
computing a path loss estimate at the second station as the difference between the ERP data value that it received and the measured signal strength;
measuring the transmit power level for signals transmitted by the second station;
sending a one or more messages from the second station to the first station, the message indicating transmit power level information and the forward path loss information;
receiving the transmit power level information and the forward path loss information at the first station, and calculating an amount of excess power available at the second station; and
determining an acceptable data coding rate for transmission between the first station and the second station from the excess power available.
2. A method as in claim 1 wherein determining an acceptable data coding rate includes selecting from among multiple available Forward Error Correction (FEC) coding rates.
3. A method as in claim 1 wherein determining an acceptable data coding rate includes selecting from among available modulation rates.
4. A method as in claim 1 wherein the first station is a base station and the second station is a field unit.
5. A method as in claim 4 wherein the first message is sent on a paging channel.
6. A wireless communication system in which digital signals are communicated comprising:
a first station for:
(i) sending a first message to a second station, the message indicating an Effective Radiated Power (ERP) data value of signals transmitted by the first station;
(ii) receiving a transmit power level information and a forward path loss information from a second station, and calculating an amount of excess power available at the second station; and
(ii) determining an acceptable data coding rate for transmission between the first station and the second station from the excess power available; and
a second station for:
(i) receiving the first message and measuring a signal strength for received signal;
(ii) computing a path loss estimate at the second station as the difference between the ERP data value that it received and the measured signal strength;
(iii) measuring the transmit power level for signals transmitted by the second station;
(iv) sending a one or more messages to the first station, the message indicating transmit power level information and the forward path loss information.
7. A wireless communication system as in claim 6 wherein determining an acceptable data coding rate includes selecting from among multiple available Forward Error Correction (FEC) coding rates.
8. A wireless communication system as in claim 6 wherein determining an acceptable data coding rate includes selecting from among available modulation rates.
9. A wireless communication system as in claim 6 wherein the first station is a base station and the second station is a field unit.
10. A wireless communication system as in claim 9 wherein the first message is sent on a paging channel.