MX2008008019A - Transmit power control in a radio station - Google Patents

Abstract

A radio station (100), transmits a continuous control signal and a discontinuous data signal simultaneously. It receives UP and DOWN power control commands and adjusts its transmit power byâÇ¢in response to the UP power control commands, increasing its transmit power by a power step,âÇ¢in response to the DOWN power control commands, decreasing its transmit power by a power step,âÇ¢in response to initiating transmission of the data signal, increasing the transmit power of the control signal, andâÇ¢in response to terminating transmission of the data signal, decreasing the transmit power of the control signal;In response to initiating or terminating transmission of the data signal, the radio station (100) temporarily modifies its response to the power control commands.

Description

CONTROL OF TRANSMISSION POWER IN RADIO STATION FIELD OF THE INVENTION The invention relates to a radio station, a radio system comprising a radio station, a method of operation of a radio station and a method of operating a radio system comprising a radio station . BACKGROUND OF THE INVENTION In systems, such as the Package Access of High-Speed Ascending Link (HSUPA) for UMTS (Universal Mobile Telecommunication System), mobile stations (MSs) transmit a control signal in parallel with a discontinuous data signal, the control signal continues to be transmitted during the periods when the data signal is not transmitted. The level of the transmission power of the control signal could be reduced during the periods when data transmission is discontinued, which conserves energy and decreases the average interference that is generated by the transmissions, and the increase at least during each period Transmission of the data signal allows reliable reception of the control signal. Systems such as UMTS use closed circuit power control, whereby the REF.193204 transmission power of the MS is adjusted by means of transmission power control commands (TPC) that are received from one or more base stations (BSs). Normally, the power control commands are generated in the BSs by means of the comparison with a target level of the Signal-to-Interference Ratio (SIR) of the control signal received from the UE, and by generating a command "low" if the SIR was above the target level or a "high" command if the SIR was below the target level. Consequently, if it were desired to apply an increase in the level of the transmission power of the control signal when a data signal is transmitted, it would also be necessary to raise the target level SIR in order to avoid any power progression applied in the MS that is being canceled after a short period of time by responding to the power control commands generated by the BS using the previous target level SIR. Ideally, an adjustment in the SIR target would be applied in the BS in a synchronized manner with each of the changes of the control signal transmission power described above. This could be achieved if the BS could detect quickly when the change in the transmission power of the control signal has been applied, for example, by detecting the start of data transmission.

However, in practice it could be difficult for the BS to detect when the change in the transmission power of the control signal has been applied before the closed-loop power control has canceled the change in the transmission power of the control signal. For example, in UMTS, the power control commands are transmitted every time slot (0.666ms). If, for example, a change of 3dB were applied to the transmission power of the control signal, and if a progression of IdB were used for the control of internal circuit power, then the internal circuit power control would have counteracted by complete the change in the transmission power of the control signal within 3 time slots. If the BS were to avoid any cancellation or impediment through the control of internal circuit power, it would have less than 1 time slot in which the application of the increase in the transmit power of the control signal is detected. SUMMARY OF THE INVENTION An object of the invention is to provide improved power control. According to a first aspect of the invention, a method of operating a radio station is provided, which comprises: transmitting a continuous control signal and a discontinuous data signal simultaneously; receiving a first and second transmission power control commands; adjust the transmission power, • in response to the first power control commands, by increasing the transmission power through a power progression, • in response to the second power control commands, by decreasing the power of transmission through a power progression, further comprising, in response to the initiation or termination of the transmission of the data signal, the modification, temporarily, of the response to the power control commands. According to a second aspect of the invention, a radio station is provided, which comprises: a transmitter adapted to send a continuous control signal and a discontinuous data signal, simultaneously; a receiver adapted to support a first and a second transmission power control commands; and the power control means adapted to adjust the transmission power of the transmitter, in response to the first power control commands, by increasing the transmission power through a power progression, in response to the second power control commands, by decreasing the transmission power through a power progression, wherein the power control means is adapted, in response to the initiation or termination of the transmission of the data signal, to temporarily modify the response to the power control commands. In one embodiment of the invention, the modified response to the power control commands could comprise abstaining from adjusting the transmission power in response to at least some of the power control commands. In another embodiment of the invention, the modified response to the power control commands comprises adjusting the transmission power by the power progression of a different size. BRIEF DESCRIPTION OF THE FIGURES Now, the invention will be described by way of example, with reference to the accompanying figures, wherein: Figure 1 is a schematic block diagram of a radio communication system comprising a radio station data broadcast and a data reception station.

DETAILED DESCRIPTION OF THE INVENTION Next, the invention will be described in relation to UMTS, with the data transmission station which is a mobile station (MS) and the data reception station which is a base station (BS). According to the present invention, the MS modifies the algorithm used to respond to the power control commands for a certain period of time after the change in the transmission power of the control signal related to the start or end of the transmission of the data signal. The period for which the power control algorithm is modified could be predetermined or signaled to the MS by the BS. The signaling could also be used to activate / deactivate the modification of the MS of the power control algorithm. Different embodiments of the invention could involve different modifications in the power control algorithm. In one embodiment, the modification comprises the MS that ignores certain closed circuit power control commands during the time period. This provides a time window for the BS to detect that the transmission of the data signal has begun and to adjust the SIR objective without the displacement of the control signal power being counteracted by the internal circuit power control. Power control commands, which are ignored within the time period, could be any of the following: - all power control commands received - only "high" commands - only "low" commands. The sign of the power control commands that will be ignored could be a function of the direction of the preceding change in the transmission power of the control signal. In one example of this mode, an MS normally adjusts the transmit power of its control signal once per timeslot in response to the power control commands received from a BS. The MS applies a further increase to the transmission power of its control signal when it initiates the transmission of a data signal, and applies an additional decrease to the transmission power of its control signal when it stops transmitting the signal of data. According to this embodiment of the invention, the MS ignores the "low" power control commands that are received in the first time slots or after the application of the additional increment to the transmission power of its control signal. The MS keeps the transmission power of its control signal constant during this period. In some variations of the mode, the MS could also ignore the "high" power control commands that are received in the first time slots n2 after the application of the additional decrease in the transmit power of its control signal. In a further variation of this mode, the MS could ignore the power control commands only until a command of the opposite sign is received to the commands, which are being ignored. The reception of a command of the opposite sign in the commands that are being ignored, could be interpreted by the MS as an indication that the BS has successfully adjusted its SIR objective. For example, after the application of an increase in the transmission power of the control signal in response to the initiation of the transmission of the data signal, the MS could ignore the "low" commands until the first command is received. "high". It is noted that in this case, the signaling of the length of the time period is implicit in the power control commands by themselves. As an additional variation, the MS could ignore the "low" commands until each time the reception of a "high" command and the passage of time slots nl is faster, similarly, after applying a decrease in the power of transmission of the control signal in response to stop the transmission of the data signal, the MS could ignore the "high" commands until the first "low" command is received, or until each time the reception of a "low" command and the passage of the time slots n2 is faster. In the variation of any of the above modalities, the BS could send an explicit signal to the MS to indicate to the MS that it must complete the modification of the power control algorithm (which implies that the SIR target has been adjusted). In a second embodiment, the modification to the power control algorithm comprises the change between two predetermined power control algorithms, for example, from an algorithm that responds to a first speed to the power control commands to an algorithm that responds to a second speed to the power control commands. For example, two power control algorithms are provided in UMTS: a first algorithm in which the MS responds to the power control command received in each time slot, and a second algorithm by means of which the MS would only change its power of transmission if a number (5 in UMTS) of consecutive power control commands in the same direction was received. An MS that normally responds to the power control commands that a first algorithm uses changes to respond by using the second algorithm in the first timeslots n after applying the additional increment to the transmit power of its control signal, before of reverting the use to the first algorithm. The same methods of terminating the use of the second algorithm could be used as in the first modality. In another embodiment, modification to the power control algorithm comprises changing the size of the power control progression (for example, from 1 to 0. 5dB). In variations of these modalities, a property of the modification of the power control algorithm could be a function of the magnitude of the change in the transmission power applied in the control signal. For example, the speed of response to the power control commands could be reduced by a larger amount if the magnitude of the change in transmit power of the control signal were smaller. In any of these modalities, the values of n and r2 could be the same, and could be signaled either together or separately. In some variations, ni and / or n2 could be equal to the duration of the transmission of the data signal. In the case of the first mode, this would mean that the transmission power of the control signal (and possibly also the data signal) would remain constant for the duration of the transmission of the data signal.

Normally, the value of ni is a compromise between the loss of efficiency that originates from the modified operation of the closed circuit power control and the gain in efficiency that is generated from the ability of the invention to prevent the power progression applied to the control channel is degraded by the action of the closed circuit power control. With reference to Figure 1, a schematic block diagram of a radio communication system comprising an MS 100 station and a BS 200 is illustrated. The MS 100 comprises a processor (μP) 120 connected to an input 110 for reception of the data that will be transmitted in a data signal. The processor 120 is adapted to subdivide the data into a plurality of data packets, also to encode the data packets for transmission and finally, to control the time in which the data packets are transmitted. The processor 120 is connected to a transmitter (Tx) 150 for sending the data signal by means of an antenna 160. The transmission of the data signal is discontinuous because, for example, the arrival of the data in the entry 110 is discontinuous, or because MS 100 is granted permission to transmit data only during discontinuous periods of time, or due to the need for the MS to prepare for a switch. The data signal for the transmission is supplied to the transmitter 150 from the processor 120 by means of a data signal power adjustment stage 130. The processor 120 is also adapted to generate a control signal, e.g., a signal a pilot comprising pre-determined symbols that are suitable for channel estimation by the BS, and is connected to the transmitter 150 through the control signal power adjustment step 140 which adjusts the signal transmission power level of control. The control signal is transmitted continuously, while the data signal is being transmitted and while the transmission of the data signal is discontinued. The control signal power adjustment stage 140 is connected to a power controller 170 which regulates the level of the transmission power of the control signal during data transmission, for which the level could be depending on the format of transmission of the data signal, and for the control of the level of the transmission power of the control signal while the transmission of the data signal is discontinued. The power controller 170 is connected to the processor 120 which informs it when the data is being transmitted. The MS 100 comprises a receiver (Rx) 180 connected to the antenna 160 that supports the TPC commands that are transmitted by the BS 200 for the purpose of controlling the closed circuit transmission power, and the power controller 170 is connected to the 180 receiver to decode the commands received TPC, and is connected with the transmitter 150 to adjust the level of the transmission power of the control signal and the data signal according to the received commands TPC. The closed-circuit transmission power control is superimposed on the changes in the transmission power level that are introduced by the control signal power adjustment stage 140. The power controller 170 could be connected to the transmitter 150 as well. to regulate the size of the power progression that will be used when the transmission power is adjusted in response to the TPC commands as described herein. The power controller 170 is adapted to regulate the transmission power as described above. The BS 200 comprises a receiver (Rx) 210 connected to an antenna 270 for the reception of the control signal and the data signal transmitted by the MS 100. Connected to the receiver 210 is a data demodulator (D) 220 which demodulates the received signal of data and supplies the modulated data in an output 230.

Connected to the receiver 210 is an estimation means (E) 240 which performs the channel evaluation, for example, based on the received pilot symbols of the control signal. The output of the estimation means 240 could be connected to the data demodulator 220 to allow the result of the channel estimation to be used in the demodulation of the data, for example, to allow the data demodulator 220 to generate a reference of phase or perform an equalization. The BS 200 comprises a processor (μP) 250, which is connected to the output of the estimation means 240 to generate the TPC commands, and is connected to a transmitter (Tx) 260 for sending the TPC commands to the first station 100 through the antenna 270. In order to generate the TPC commands, the estimation means 240 measures a parameter of the received control signal, for example, SIR or SNR, and compares the value of the parameter measured with a target value . When the transmission power level of the control signal is increased, temporarily, by the MS 100 for the duration of the data transmission, without additional measurements in the BS 200, the TPC commands would tend to restore the power level transmission of the MS 100. Therefore, the processor 250 increases, temporarily, the target value of the parameter measured by a corresponding amount, which could be a function of the transmission format of the data signal, for the period during which the level of the transmission power of the control signal is increased temporarily. Although the invention has been described with reference to UMTS, the invention could be used in other wireless communication systems, for example, in cdma2000. In the present specification and the claims, the words "a" or "an" preceding an element do not exclude the presence of a plurality of these elements. In addition, the word "comprising" does not exclude the presence of other elements or stages different from those listed. It is intended that the inclusion of the reference signs in parentheses in the claims will assist the understanding and is not intended to be limiting. From reading the present disclosure, other modifications will be apparent to those skilled in the art. These modifications could involve other features that are already known in the radio communications technique and that could be used in place of or in addition to the features described in this document. It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (14)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A method of operation of a radio station, characterized in that it comprises: transmitting a continuous control signal and a discontinuous data signal simultaneously; receiving a first and second transmission power control commands; adjust the transmission power, • in response to the first power control commands, by increasing the transmission power through a power progression, • in response to the second power control commands, by decreasing the transmission power through a power progression, further includes, in response to the initiation or termination of the transmission of the data signal, temporarily modifying the response to the power control commands. The method according to claim 1, further characterized in that it comprises changing the power level of the control signal when starting or terminating the transmission of the data signal, and wherein the response to the power control commands is modified as a function of the magnitude or direction of the power level change. The method according to claim 1, characterized in that the modified response to the power control commands comprises the avoidance of adjusting the transmit power in response to at least some of the power control commands. The method according to claim 3, characterized in that the modified response to the power control commands comprises the avoidance of adjusting the transmission power in response to at least the first power control commands when the transmission of the power is finished. the data signal. The method according to claim 4, characterized in that the modified response to the power control commands comprises the avoidance of adjusting the transmission power in response to at least the second power control commands when the transmission of the power is initiated. the data signal. The method according to claim 3, further characterized in that it comprises stopping the adjustment of the transmission power in response to at least some of the power control commands when a power control command having a power is received. opposite sign of the sign at least of some of the power control commands. The method according to claim 1, characterized in that the modified response to the power control commands comprises adjusting the transmission power through a power progression of different size. The method according to claim 7, characterized in that the modified response to the power control commands comprises the use of a lower size of power progression in response to at least some of the first power control commands when the transmission of the control signal is finished. The method according to claim 8, characterized in that the modified response to the power control commands comprises the use of a lower size of power progression in response to at least some of the second power control commands when the transmission of the data signal begins. The method according to claim 1, characterized in that the adjustment of the transmission power occurs at a first speed, and wherein the modified response comprises answering at a second speed, different from the first speed. The method according to claim 1, further characterized in that it comprises stopping the modification of the response to the power control commands only after a predetermined number of timeslots. 12. A radio station, characterized in that it comprises: a transmitter adapted to send a continuous control signal and a discontinuous data signal, simultaneously; a receiver is adapted to support a first and a second transmission power control commands; and the power control means is adapted to adjust the transmission power of the transmitter • in response to the first power control commands, by increasing the transmission power through a power progression, • in response to the second power control commands, by decreasing the transmission power through a power progression, wherein the power control means is adapted, in response to the initiation or termination of the transmission of the data signal, to modify temporarily the response to the power control commands. The radio station according to claim 12, characterized in that the modified response to the power control commands comprises abstaining from adjusting the transmission power in response to at least some of the power control commands. The radio station according to claim 12, characterized in that the modified response to the power control commands comprises adjusting the transmission power by a power progression of a different size.