DEVICE AND METHOD FOR CONTROLLING TRANSMISSION POWER OF PUNCTURED FRAME

Abstract: A code division multiple access (CDMA) mobile communication system for controlling power for a traffic signal of one frame includes: a signal generator for simultaneously generating a pilot signal and the traffic signal on a frame basis; a power compensator for compensating the power of the traffic signal according to a punctured length of a punctured frame among the frames; and a signal combiner for combining the power-compensated traffic signal and the pilot signal generated from the signal generator.

Description: DEVICE AND METHOD FOR CONTROLLING TRANSMISSION POWER OF PUNCTURED FRAME BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control device and method for a mobile communication system, and more particularly, to a power control device and method of controlling a gain of pilot signals and a compensation gain of traffic signals in a different manner, respectively. 2. Description of the Related Art It is common to employ code division multiple access (CDMA) technology for a mobile communication system. In the CDMA mobile communication system, a receiver receives pilot signals via a pilot channel, which is among the channels used for receiving frame signals transmitted from a transmission party, and measures the strength of the received pilot signals. The receiver generates a power control signal based on the strength of the pilot signals and sends the generated power control signal back to the transmission party. The transmission party compares the strength of the pilot channel signal with a reference value (or threshold) for the power control. If the strength of the pilot channel signal is lower than the reference value, the receiver sends a power-up signal; otherwise, the receiver sends a power-down signal. In the case where the channel surroundings are poor during communication with a base station at a specific frequency, a mobile station searches for another base station with better channel surroundings that uses a different frequency. This is a preliminary step that the mobile station performs for a hard handoff . The mobile station, while searching for a new frequency, sends the pilot signals at the new frequency temporarily before returning to the original frequency. In some cases, transmission of the traffic signals may temporarily be discontinued to the presently connected base station during an interval where the pilot signals are transmitted at the new frequency. As stated above, the traffic signals are punctured during an interval where the pilot signals are transmitted at another frequency, resulting in a loss of energy. In order to compensate for the loss of energy, the transmitter increases power of the non-punctured frame signals. This is further detailed below. FIG. 1 illustrates a device for controlling power during transmission of a punctured frame on a reverse link, in accordance with the related art, in which signals are composed of pilot signals and traffic signals. Referring to FIG. 1 , a controller 100 controls the entire operation of areceiver. The controller 100 controls a pilot signal generator 110, a traffic signal generator 120, and a first signal controller 180 according to signalling information, e.g., data rate, puncturing start time and puncturing interval, etc., received from an upper layer. Under the control of the controller 100, the pilot signal generator 110 generates pilot signals and outputs the generated pilot signals to a first power controller 130. Upon receipt of the pilot signals, the first power controller 130 controls the power of the pilot signals using a predetermined gain G P and outputs the power controlled pilot signals to a signal combiner 150. Similarly, the traffic signal generator 120, under the control of the controller 100, generates traffic signals and outputs the generated traffic signals to a second power controller 140. Upon receipt of the traffic signals, the second power controller 140 controls the power of the traffic signals using a predetermined gain G τ and outputs the power controlled traffic signals to the signal combiner 150. A ratio of the pilot power from the first power controller 130 to the traffic power from the second power controller 140 is set to a predetermined value. The signal combiner 150 combines the traffic signals and the pilot signals received from the first and second power controllers 130 and 140, respectively. Also, the controller 100 calculates a compensation gain for a puncturing interval based on information concerning the puncturing start time and puncturing interval received from the upper layer. After completion of the calculation, the controller 100 outputs the puncturing interval and the calculated compensation gain to the first signal controller 180. Then, the first signal controller 180 outputs the received compensation gain to a multiplier 170 during the puncturing interval. The multiplier 170 multiplies the combined signals of the pilot signals and the traffic signals as, outputted from the signal combiner 150, by the compensation gain, and outputs the result to a second signal controller 160. The second signal controller 160 receives the compensated pilot signals and traffic signals and adjusts power control according to the condition of the transmission channels. If a mobile station searches for another base station having a different frequency, puncturing occurs after signal controlling is performed by the second signal controller 160. Thus, both the pilot signals and the traffic signals are punctured during the same time interval. FIG. 2 illustrates power distribution for a punctured frame. When a frame is not punctured, the non-punctured frame will be transmitted with a constant gain G A without a power loss over the entire frame duration A. However, when the frame is punctured causing a power loss G A at a punctured duration A p , the non-punctured durations B increase in gain by G B to compensate for the power loss G A at the punctured duration Ap. In conclusion, the total power gain for the punctured frame outputted from the multiplier 170 is G Tota ,=G A +G B . In the case where the punctured frame is transmitted in the above power control method, the transmission power for the non-punctured portion is increased consequently causing an increase in the transmission power for the pilot signals, which results in the estimated power of the pilot channel being higher than a reference value during most time intervals. Thus, the power control signal is generated as a power-down signal. This power control method however cannot provide maintenance of a reception performance at the receiver, since the reception performance for decoding the punctured frame is maintained only with a continuous increase in the gain by that time interval for decoding the punctured traffic frame. To avoid such an impairment, the transmitter performs power control ignoring the power-down signal among the power control signals fed back from the receiver, after having decreased during fading and having then recovered therefrom. As described above, the transmitter ignores the power-down signal among the power control signals fed back from the receiver such that only the power-up signal is activated with the power-down signal inactivated after having recovered from a deep fading, resulting in a waste of power. Furthermore, another problem arises in that data transmission with high power causes an increase in interference on the reverse link and reduces the capacity of the reverse link. SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a device and method for controlling power during the transmission of a punctured frame, in which the punctured traffic data frame can be power controlled under a power- up/down signal in the same manner as a non-punctured traffic data frame by controlling the gain for the power of the punctured traffic data frame only, and without compensating the gain for pilot signals. In accordance with an aspect of the present invention, a code division multiple access (CDMA) mobile communication system for controlling power for a traffic signal of one frame is provided, including: a signal generator for simultaneously generating a pilot signal and the traffic signal on the frame basis; a power compensator for compensating the power of the traffic signal according to a punctured length of a punctured frame among the frames; and a signal combiner for combining the power-compensated traffic signal and the pilot signal generated from the signal generator. In accordance with another aspect of the present invention, a power control method in transmission of a punctured frame in a mobile communication system is provided, including the steps of: determining whether an input frame during a hard handoff is punctured or not; when the frame is punctured, determining whether information is received regarding a data rate of the frame and a punctured length; when the information is received, calculating a compensation gain from the data rate and the punctured length; determining whether a frame boundary is detected or not; and when the frame boundary is detected, generating the compensation gain to a multiplier to compensate a loss of power for traffic signals. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference numerals indicate like parts: FIG. 1 is a diagram illustrating a structure of a power control device on a reverse link according to a related art; FIG. 2 is a diagram illustrating a gain difference between a punctured frame portion and a non-punctured frame portion; FIG. 3 is a detailed block diagram illustrating a device for controlling power during transmission of a punctured frame according to an embodiment of the present invention; FIG. 4 is a flowchart illustrating a power control method during transmission of a punctured frame according to a first embodiment of the present invention; FIG. 5 is a flowchart illustrating a power control method during transmission of a punctured frame according to a second embodiment of the present invention; and FIG. 6 is a schematic block diagram illustrating a device for controlling power during transmission of a punctured frame according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described hereinbelow with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. In a power control method according to the present invention, a ratio of pilot signal power to traffic signal power is different for a punctured frame and a non- punctured frame. That is, when the traffic frame is not punctured, the pilot signals and the traffic signals are controlled with respect to their transmission power with a pilot signal power gain (hereinafter, called G p ) and a traffic signal power gain (hereinafter, called G τ ), respectively; and when the traffic frame is punctured, the G P is maintained and only the G τ is given a compensation gain for the transmission signals the loss of power. When power for the pilot channel to generate a power control signal is measured in this case, it is possible to produce the same power control signal irrespective of the punctured frame or the non-punctured frame of the transmission signal, and also to perform power control with respect to the power control signal fed back to a transmitter that generates the punctured frame. There are two methods according to the present invention for performing a power control where the pilot signals' power gain ratio differs from that of the traffic signals'. In a first method, each frame of the traffic signal is monitored during an inter- frequency hard handoff to determine if any frames are punctured. When a punctured frame is detected, the compensation gain is calculated and then only the traffic signals are compensated for a loss of power according to the compensation gain as calculated prior to the stage where the pilot signals and the traffic signals are combined together. In a second method, a predetermined compensation gain for a length of the puncturing interval is stored in a memory and, when a punctured frame is input, a corresponding gain value G τ is read out from the memory for compensation. A loss of power is proportional to the puncmring time and may be restricted according to a maximum gain value that the transmitter can transmit. It is also possible to determine the compensation gain differently from the loss of power in order to compensate for the deterioration of performance of the traffic channel that may be incurred due to an inappropriate power ratio between the traffic signals and the pilot signals. FIG. 6 illustrates a device for controlling power during transmission of a punctured frame according to an embodiment of the present invention. A power compensation device according to the present invention comprises a power compensator 301 , a signal generator 305, a signal combiner 350 and a second signal controller 360. The signal generator 305, under the control of a controller (not shown), generates traffic signals and pilot signals. The pilot signals are provided to the signal combiner 350 and the traffic signals are provided to the power compensator 301. The power compensator 301 receives data rate information from an upper layer to control the signal generator 305, which generates the traffic signals and the pilot signals. The power compensator 301 also receives puncturing information for a puncturing start time and a puncturing interval from the upper layer in order to calculate a compensation gain so that the power gain of the traffic signals received from the signal generator 305 are compensated for using the calculated compensation gain. The power compensator 301 then outputs the compensated traffic signals to the signal combiner 350. The signal combiner 350 combines the compensated traffic signals received from the power compensator 301 with the pilot signals from the signal generator 305, and outputs the combined signals to the second signal controller 360. The second signal controller 360 controls the power of the combined signals received from the signal combiner 350. As described above, the present invention does not compensate the power of the combined signals from the signal combiner 350 as illustrated in the prior art devices in FIG. 1, but compensates the power of the traffic signals only and then combines the pilot signals with the compensated traffic signals at the signal combiner 350, thereby leaving the pilot signals uncompensated. FIG. 3 illustrates a more detailed block diagram of the power control device shown in FIG. 6. Referring to FIG. 3, the signal generator 305 of FIG. 6 is comprised of a traffic signal generator 320, a pilot signal generator 310, a first power controller 330 and a second power controller 340. This construction performs the same operation as detailed in FIG. 1. The power compensator 301 of FIG. 6 comprises a controller 300, a first signal controller 380 and a multiplier 370. The controller 300 receives data rate information from the upper layer to control the traffic signal generator 320 and the pilot signal generator 310, which generate traffic signals and pilot signals respectively. Also, the controller 300 receives puncturing information for a puncturing start time and a puncturing interval from the upper layer to calculate a compensation gain for a non-punctured duration, i.e., an interval to be compensated, and supplies the calculated compensation gain to the first signal controller 380. The compensation gain is determined by [Equation 1] total length of non - punctured frame compensation gam = A — ; — ; : length of non - punctured portion The first signal controller 380 outputs to the multiplier 370 a gain signal having the compensation gain in the power compensation interval. The multiplier 370 multiplies the traffic signals received from the second power controller 340 by the gain signal from first signal controller 380 having the compensation gain and outputs the result to the signal combiner 350. Although the controller 300 calculates the compensation gain in this embodiment, the controller 300 may supply puncturing information received from the upper layer to the first signal controller 380, which then calculates the compensation gain according to the received puncturing information and applies the compensation gain signal having the compensation gain to the multiplier 370. The power control device according to the present invention may further comprises a memory 390. The memory 390 is provided with a table of the compensation gains based on the puncturing intervals, i.g., punctured lengths. When another base station with a different frequency is searched for and a puncture occurs, the controller 300 receives a puncturing start time and a puncturing length from the upper layer and retrieves the compensation gain for the puncturing length from the memory 390. Then, the controller 300 applies the compensation gain to the second signal controller 380 to compensate the puncturing interval of the traffic signals. A. First Embodiment FIG. 4 is a flowchart illustrating a method of varying a ratio of G p to G τ , in which the controller 300 calculates the compensation gain in order to perform power control. Referring to FIG.4, the controller 300 checks in step 401 whether puncturing information is received from the upper layer, to determine whether a frame is punctured or not. If the puncturing information is received from the upper layer, the controller 300 determines a compensation gain from the puncturing information in step 405 and outputs the determined compensation gain to the first signal controller 380 in step 407. At this time, the first signal controller 380 outputs a compensation gain signal having the compensation gain in a non-puncturing interval of the frame. Alternatively, if no puncturing information is received from the upper layer, the controller 300 informs the first signal controller 380 that it will output a compensation gain as " 1" at step 402. During a power compensation for the puncturing interval of the frame, the controller 300 checks in step 409 whether a boundary between the punctured frame and the non-punctured frame is detected, that is, the end of the punctured frame, or the next frame of the punctured frame. Upon detection of the frame boundary, the controller 300 outputs in step 411 a frame boundary signal to the first signal controller 380 to inform that the frame boundary has been detected at step 411. As the frame boundary signal is received, the first signal controller 380 outputs the compensation gain as "1 " at step 402. If the frame boundary is not detected at step 409, the compensation gain calculated in step 405 continues to be output to the first controller 380 in step 407. B. Second Embodiment FIG. 5 is a flowchart illustrating a method of varying a ratio of G P to G τ as a power control method in transmission of a punctured frame according to a second embodiment of the present invention. Referring to FIG. 5, the controller 300 checks in step 501 whether puncturing information is received from an upper layer, to determine whether a frame is punctured or not. If the puncturing information is received from the upper layer in step 501 , the controller 300 detects a punctured length contained in the puncturing information, retrieves the compensation gain for the punctured length from the memory 390 in step 505 and outputs the compensation gain to the first signal controller 380 in step 506. Alternatively, if no puncturing information is received from the upper layer, the controller 300 informs the first signal controller 380 that it will output a compensation gain as " 1 " at step 502. During a power compensation for the puncturing interval of the frame, the controller 300 checks in step 507 whether a boundary between the punctured frame and the non-punctured frame is 5 detected, that is, the end of the punctured frame, or the next frame of the punctured frame. Upon detection of the frame boundary, the controller 300 informs the first signal controller 380 that the frame boundary has been detected at step 509. As the frame boundary signal is received, the first signal controller 380 outputs the compensation gain as "1 " at step 502. If the frame boundary is not detected at step 10 507, the compensation gain calculated in step 505 continues to be output to the first controller 380 in step 506. More specifically, in step 506, the controller 300 outputs a compensation gain value to the first signal controller 380 in the same manner as in step 407 of FIG. 4. The first signal controller 380 then outputs a compensation gain signal having the compensation gain value at non-punctured durations of the 15 punctured frame. However, upon failure to receive puncturing information, the controller 300 enables the first signal controller 380 to output a compensation gain value of " 1 " . During power compensation for the punctured portions, the controller 300 examines in step 507 whether a boundary of the punctured frame, i.e., an end of the punctured frame or a beginning of a next frame is detected or not, in the same 0 manner as in step 409. Upon detection of the frame boundary, the controller 300 outputs in step 509 a frame boundary signal to the first signal controller 380 to inform detection of the frame boundary. The first signal controller 380 then outputs a compensation gain value of "1 ". Accordingly, the mobile communication system according to the present 5 invention can perform an accurate power control so as to prevent a waste of transmission power at the mobile station, as a result of which the mobile station can enhance its standby time for receiving the input signals. It is furthermore possible to reduce interference from other channels caused by an unnecessary consumption of transmission power. While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims: WHAT IS CLAIMED IS: 1. A code division multiple access (CDMA) mobile communication system for controlling power of a traffic signal, comprising: a signal generator for generating a pilot signal and the traffic signal; a power compensator for compensating the power of the traffic signal according to a punctured length of; and a signal combiner for combining the power-compensated traffic signal with the pilot signal generated from the signal generator. 2. The CDMA mobile communication system as claimed in claim 1, wherein the power compensator comprises: a controller for calculating a compensation gain according to length; a first signal controller for generating a compensation gain signal corresponding to the compensation gain; and a multiplier for multiplying the traffic signal by the compensation gain signal. 3. The CDMA mobile communication system as claimed in claim 1, wherein the power compensator comprises: a memory for storing a compensation gain according to a frame length; a controller for reading out the compensation gain corresponding to the punctured length; a first signal controller for generating a compensation gain signal coπesponding to the compensation gain; and a multiplier for multiplying the traffic signal by the compensation gain signal. 4. The CDMA mobile communication system as claimed in claim 1, further comprising a second signal controller for controlling the combined signal according to channel circumstances. 5. The CDMA mobile communication system as claimed in claim 1, wherein the signal generator comprises: a pilot signal generating section for generating the pilot signal having predetermined power; and a traffic signal generating section for generating the traffic signal having predetermined power. 6. The CDMA mobile communication system as claimed in claim 5, wherein the pilot signal generating section comprises: a pilot signal generator for generating the pilot signal; and a first power controller for controlling the power of the pilot signal. 7. The CDMA mobile communication system as claimed in claim 5, wherein the traffic signal generating section comprises: a traffic signal generator for generating the traffic signal; and a second power control for controlling the power of the traffic signal. 8. A power control method for a punctured traffic signal in a CDMA mobile communication system, comprising the steps of: generating a pilot signal and a traffic signal; compensating power of the traffic signal according to a punctured length of the traffic signal; and combining the power-compensated traffic signal with the pilot signal. 9. The power control method as claimed in claim 8, further comprising the step of controlling transmission power of the combined signal. 10. A power control method for a punctured traffic signal in a CDMA communication system, comprising the steps of: determining whether puncture information has been received from an upper layer; calculating a compensation gain according to the puncture information; and upon detection of a frame boundary, outputting a frame boundary signal to indicate termination of a compensation duration. 1 1. The power control method as claimed in claim 10, wherein the compensation gain is defined as I total length of non - punctured frame compensation gam = — - — — — : length of non - punctured portion 12. The power control method as claimed in claim 10, wherein the compensation gain is read from a table according to a punctured length of the traffic signal.

Inventors: AHN JAE MIN, KIM JAE YOEL, KIM YOUNG KY, AHN, JAE, MIN, KIM, JAE, YOEL, KIM, YOUNG, KY
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1999
Main classification: H04B
IPC codes: H04B1, H04B7, H04J13