Apparatus and an associated method for facilitating communications in a radio communication system that provides for data communications at multiple data rates

Abstract

Apparatus, and an associated method, for facilitating operation of a radio communication system that provides for multi rate data communications, such as a CDMA 2000 system that provides for 1xEV-DV communication services. A supplemental pilot, or control, signal generator embodied at a mobile station generates a supplemental pilot, or control, signal that is sent on a newly defined supplemental pilot, or control, channel. As the data rates of data communicated upon a reverse supplemental channel changes, corresponding changes are made to the power level of the reverse supplemental pilot, or control, signal.

Description

If the T/P ratio of the reverse supplemental channel is defined to be the ratio of the power of the reverse supplemental channel to the power of the combination of the reverse pilot channel and the reverse supplemental pilot channel, then the T/P ratio of the reverse supplemental channel is set to a value of a nominal attribute gain of the rate that is currently used. Power is not wasted. And, as the T/P ratio of the reverse fundamental channel is independent of the rate of the reverse supplemental channel, the power control loop is not disturbed by the data rate change in the reverse supplemental channel.

FIG. 3 illustrates again the relationships between the data rates of the data communicated upon the reverse fundamental and supplemental channels 14 and 16 and the power levels of the pilot signals upon reverse pilot channel and reverse supplemental pilot channel 22 and 24 during successive time frames. In this implementation, the power level of the pilot signal sent by the mobile station sent on the reverse pilot channel is set by the mobile station. And, hence, the T/P ratio of the reverse fundamental channel, all according to the data rate of the data communicated upon the reverse supplemental channel in a previous frame. As the base station knows also the data rate of the data communicated upon the reverse supplemental channel during the prior time frame, the base station also knows of the current T/P ratio of the data communicated upon the reverse fundamental channel and adjusts the outer loop power control set point accordingly. If the current reverse supplemental channel requires additional pilot power than provided on the reverse pilot channel during the current time frame, the reverse supplemental pilot channel is used to communicate a supplemental pilot signal to provide the extra power.

In this implementation, the power control loop is not independent of the data rate change of the reverse supplemental channel. But, the power control loop is relatively undisturbed by the rate change in that the base station is aware of how to adjust the outer loop power control set point at each frame boundary. In this scheme, an improved SNR estimate is provided for use upon inner loop power control as the pilot signal sent on the reverse pilot channel is generally of a relatively high power. Hence, the power control made possible in this implementation is fairly accurate.

FIG. 4 illustrates a representation, shown generally at 102, of exemplary power control subchannel structures of the reverse pilot channel 22 and the reverse supplemental pilot channel 24. As illustrated, the reverse pilot channel is formed of a first portion 104 of a length of 1152 chips and a 384 chip -length reverse power control subchannel 106. Similarly, the reverse supplemental pilot channel 24 is also formatted to include a first portion 108 of a 1152 chip length and a 384 chip length portion 112 forming the reverse pilot control subchannel values. A code, for example, W₃₂⁶⁴ can be assigned to the reverse supplemental pilot channel. Backward compatibility is preserved through use of this type of structure.

FIG. 5 illustrates a representation of the relationship between the data rates at which communication data is communicated upon the reverse fundamental and supplemental channels 14 and 16 and the power level of the pilot signal sent upon the reverse pilot channel. In this implementation, the reference level of the pilot signal is delayed following a data rate change of the communication data, communicated upon the data channels. At time 106, the outer loop power control set point is as indicated by the opposing arrows. This is the power control set point prior to a rate change of data communicated upon the reverse supplemental channel. At time 108, the data rate of the data communicated upon the reverse supplemental channel increases. Time 110 defines the start of a subsequent time frame. And, thereafter, during a subsequent time frame, the pilot power and outer loop set point is adjusted. During this subsequent time period, the quality of the reverse fundamental channel and the reverse supplemental channel is maintained. At time 112, the data rate of the data communicated upon the reverse supplemental channel again changes. And, subsequent to time 114, the pilot power is again adjusted. And, as indicated at the time 116, the outer loop set point is again indicated by the opposing arrows.

During the first frame following the data rate change at the time 108, a sequence of procedures is performed at the mobile station. The T/P ratio of the reverse fundamental channel is maintained. And, the T/P ratio of the reverse supplemental channel is adjusted according to the nominal attribute gain of the new data rate plus the difference between the pilot reference level and the new data rate and the old data rate. During this frame, the power level of the reverse supplemental channel is set according to the new rate, but the target received SNR of the reverse pilot channel and reverse fundamental channel are maintained at the same level as in the prior frame. And, at the base station, as the base station is unaware of the rate change of the data communicated upon the reverse supplemental channel, the base station power control actions continue as is no rate change has oceurred.

During the second time frames, commencing at the time 110, following the data rate change, the mobile station adjusts the power level of the pilot signal by the difference between the pilot reference level of the new data rate and the old data rate. Additionally, the T/P ratio of the reverse supplemental channel is adjusted according to the nominal attribute gain of the new data rate. And, the T/P ratio of the reverse fundamental channel is adjusted according to the multiple channel gain of the new data rate. At the base station, the rate indicator in the first frame following the data rate change is received. The base station thereby has knowledge of the new data rate. And, the base station adjusts the outer loop power control threshold to the initial target outer loop power control threshold of the new data rate.

FIG. 6 illustrates rate requests 118, rate grants 122, and reverse supplemental channel values 124 during operation of an embodiment of the present invention. In this implementation, data rate changes and power level adjustments, and adjustments to the T/P ratios are made according to the nominal attribute gain and multiple channel adjustment gains, all as specified in the operating specification of CDMA 2000. Without the knowledge of the current rate, the base station assumes the mobile station to transmit at a highest rate allowed by the previous rate grant. And, the outer loop power control threshold is set accordingly.

In the exemplary operations set forth in FIG. 6, the rate of the data communicated upon the reverse supplemental channel is always equal to or less than, the data rate that is granted by the base station. That is to say, Rate_I is less than or equal to Rate_grant_I. Because the base station does not know the data rate of the data communicated upon the reverse supplemental channel until the rate indicator is received correctly, the base station assumes the current rate, Rate_I equals the Rate_grant_i. And, the outer loop power control threshold is set accordingly. Through this operation, there is always enough power in the pilot signal sent on the reverse pilot channel to guarantee the required frame error rate on the reverse supplemental channel.

FIG. 7 illustrates an implementation in which a fast rate indication is multiplexed into the reverse pilot channel, thereby to provide the base station with an indication of the data rate change at the earliest possible time. The first sequence 126, illustrates the reverse pilot channel and the reverse power control subchannel during successive time periods within a time frame, each defining a power control group 128.

The second sequence illustrates the reverse pilot and reverse pilot channel and reverse power control subchannel together with a reverse fast rate indication subchannel (R-FRISCH) 132 defined pursuant to an embodiment of the present invention. And, the third sequence illustrates the reverse pilot channel, the reverse fast rate indication subchannel and reverse power control subchannel defined pursuant to operation of another embodiment of the present invention.

As the Figure illustrates, selected power control bits, such as the first one or two power control bits of the reverse link power control subchannel are punctured with values that define the reverse fast rate indication subchannel. In one implementation, a pilot signal generator, such as the pilot signal generator 84 shown in FIG. 1 also operates as a rate indication generator that generates rate indications that indicate the data rate that is inserted into the illustrated positions. In another implementation, the values are inserted even earlier. Alternately, the mobile station can also puncture a portion of the reverse pilot channel in the first and second power control group. The rate indication bits inserted into these positions form this subchannel, the R-FRISCH. The mobile station changes data rates and adjusts the power levels and T/P ratios according to the nominal attribute gain and multiple channel adjustment gain, all as specified in the operating specification of the CDMA 2000 system. The base station holds the outer loop power control thresholds in the first one or two power control groups of this frame, and adjusts the outer loop power control threshold thereafter according to the rate change information conveyed in the reverse fast rate indication subchannel. Fast rate indication can alternately be realized in other manners, such as by multiplexing the values together with the reverse rate indicator channel (R-RICH). The definition and use of the R-FRISCH permits a base station to adjust the outer loop power control threshold quickly. The bits can also be used together with the R-RICH to decode the detail rate indication information in a finer resolution.

Through operation of any of these embodiments of the present invention, fast stabling of the power control loop is provided with minimal change to the existing operating specification.

The preferred descriptions are of preferred examples for implementing the invention, and the scope of the invention should not necessarily be limited by this description. The scope of the present invention is defined by the following claims.

Claims

1. A method comprising:

transmitting from a radio communication system a primary pilot signal corresponding to a data channel;

detecting when data communicated upon the data channel exceeds a predetermined target level data rate; and

generating a supplemental pilot signal increasing total pilots power in response to the data communicated upon the data channel exceeding the predetermined target level data rate.

2. The method of claim 1 further comprising the operation of terminating the supplemental pilot signal in response to the data communicated upon the data channel falling below the target level data rate.

3. The method of claim 1 wherein a communication station comprises a mobile station operable in the radio communication system and

wherein the supplemental pilot signal is generated concurrent with communication of the data on the data channel.

4. The method of claim 1 wherein a communication station comprises a mobile station operable in the radio communication system, wherein the data communicated by the mobile station is communicated upon a reverse-link data channel defined in the radio communication system, and

wherein the radio communication system defines a reverse link pilot channel, and the supplemental pilot signal, when generated during said operation of generating, is generated upon the reverse link pilot channel.

5. The method of claim 4 wherein the radio communication system defines a first reverse link pilot channel and a second reverse link pilot channel, the second reverse link pilot channel supplemental to the first reverse link pilot channel, and

wherein the supplemental pilot signal, when generated during said operation of generating, is generated upon the second reverse link pilot channel.

6. The method of claim 1 wherein the supplemental pilot signal, when generated during said operation of generating, is generated for a selected time period subsequent to detection, during said operation of detecting, that the data communicated upon the data channel exceeds the target level data rate.

7. An apparatus comprising:

a pilot signal generator configured to generate a second pilot signal providing extra power supplementing a first pilot signal that corresponds to a reverse link data channel in a radio communication system, the second pilot signal generated by said pilot signal generator to supplement signal energy of the first pilot signal responsive to data communicated upon the reverse link data channel exhibiting a communication parameter that exceeds a selected target level.

8. The apparatus of claim 7 wherein the communication parameter is a data rate of the reverse link data channel.

9. The method of claim 1 wherein a communication station sends a fundamental signal during operation of the communication station and wherein the supplemental pilot signal, when generated during said operation of generating, is supplemental to the fundamental signal.

10. The apparatus of claim 7, wherein the pilot signal generator is further configured to 1) maintain the first and second pilot signals for a first time period, and 2) remove the second pilot signal and increase a power level of the first pilot signal to compensate for power lost from the removal of the second pilot signal for a second time period following the first time period.

11. The apparatus of claim 7, wherein the pilot signal generator is configured to dynamically adjust a total pilot signal power level in the first and second pilot signals corresponding to changes in a data transmission rate of the reverse data channel.