Method of effecting transmission power control in a CDMA communication system

Abstract: A COMM system is disclosed which comprises mobile stations and a base station. The mobile station comprises; a 1st receiving and transmitting portion; a detection portion for detecting an electric power of a 1st desired wave component of the received 1st CDMA SIG; a table for storing a relation between reception power and transmission power of a 2nd CDMA SIG to be transmitted; a demodulation portion for demodulating the received 1st CDMA SIG and for detecting a CONT SIG in the desired wave; a compensation portion for compensating the relation according to the detected CONT SIG; and a transmission power CONT portion for controlling a transmission power determined according to the electric power obtained through the compensated table and the reception power. The base station comprises; a 2nd receiving and transmitting portion; an power detection portion for repeatedly detecting an electric power of a 2nd desired wave component of the received 2nd CDMA SIG; an averaging portion for averaging the repeatedly detected electric powers to obtain an average; and a CONT SIG generation portion for generating the CONT SIG according to an error between the average and a given value. The relation is corrected within a portion of range of the reception power or within a range of transmission power.

Description: This invention relates to a communication apparatus having a method of effecting transmission power control in a CDMA communication system according to the preamble of claim 1. A communication apparatus having a transmission power control circuit is disclosed in Japanese patent application provisional publication No. 60-13956. In such a prior art communication apparatus, the transmission power is determined in accordance with the power of a received pilot signal. The pilot signal is detected by a mobile unit and used to estimate the transmission power of the mobile unit. A spread spectrum communication equipment with transmission power control is also disclosed in Japanese patent application provisional publication No. 08032513A. In such spread spectrum communication equipment, the transmission power of a base station is determined in accordance with a detected control bit from a mobile unit. There are two types of controlling transmission power in mobile unit communication employing the CDMA system, that is, an open loop control effected by a mobile unit in accordance with the detected electric power of the received signal and a closed loop control effected by feeding back a control signal to a mobile station from a base station. Tomohiro Dohi and Mamoru Sawahashi disclose a power control by employing Interference Power for DS/CDMA in TECHNICAL REPORT OF IEICE. A·P94-75, RCS94-99 (1994-10) at p63-68 by THE INSTITUTE OF ELECTRONICS. INFORMATION AND COMMUNICATION ENGINEERS. The transmission power at a mobile unit is controlled such that a Signal to Interference-plus-Noise power. Ratio (SINR) is maintained at a constant value at a base station through a transmission power control bit (TPC bit) from the base station to the mobile unit to provide a closed loop control. The mobile unit increases or decreases the transmission power in accordance with the TPC bit periodically inserted in a data frame. EP-A-0 682 419 discloses open and closed loop power control for a mobile station in a CDMA system. The mobile station determines an average value of the received power per control period of a desired signal and detects the difference between the current average value and that of one of the previous control periods. If the difference exceeds a reference value, the transmission power is adjusted in order to reduce the transmission power. If the difference is lower than the reference value, transmission power is determined in accordance with a transmission power control bit transmitted by a base station. US-A-5301364 discloses an automatic gain control in a communications receiver for determining the power difference between the desired signal and a received signal. The control mechanism provides for an open-loop gain control in response to the differential so determined in order that the signal is positioned within a desired dynamic range. US-A-5452473 discloses a method and apparatus to limit the output power of a radio telephone in a cellular system. The apparatus comprises a power detector and a correction accumulator in order to generate a gain control signal by limiting the gain adjustment to a maximum value even when the cell site communicating with the radio telephone is sending power tum-up commands to the radio telephone. The object of the present invention is to provide a method of effecting transmission power control more accurately and in a simple manner. This object is solved by the method steps set forth in claim 1. The present invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which: Fig. 1 is a block diagram of a first example of a transmission power control circuit ; Fig. 2 is a graphical drawing showing the power control table in the transmission power determining circuit 104 shown in Fig. 1; Fig. 3 is a block diagram of a communication apparatus according to the first to third example; Fig. 4 is a block diagram of a transmission power control circuit of the second example; Fig. 5 is a graphical drawing illustrating compensation of the transmission power control table in the second example; Fig. 6 is a block diagram of a transmission power control circuit of a third example; Fig. 7 is a graphical drawing illustrating compensation of the transmission power control table in the third example; Fig. 8 is a block diagram of a transmission power control signal generation portion of a fourth example; Fig. 9 is a graphical drawing of the fourth example illustrating obtaining an error; Fig. 10 is a block diagram of a communication apparatus according to the fourth to sixth example; Fig. 11 is a block diagram of a transmission power control signal generation circuit of a fifth example; Fig. 12 is a graphical drawing of the fifth example illustrating obtaining the error; Fig. 13 is a block diagram of a transmission power control signal generation circuit of a sixth example; Fig. 14 is a block diagram of a communication system of a seventh example; and Fig. 15 shows a timing chart of the communication apparatus of the seventh example. The same or corresponding elements or parts are designated with like references throughout the drawings. <A FIRST EXAMPLE> Fig. 1 is a block diagram of a transmission power control circuit of a first example. A correlation detection output 101 is supplied to an reception power calculation circuit 102. The reception power calculation circuit 102 calculates the reception power of a desired wave component at an antenna. The calculated reception power is supplied to a transmission power determining circuit 104. The transmission power determining circuit 104 determines a transmission power setting value 107 from the calculated reception power in accordance with an initial setting value from an initial setting value storing circuit 103 through a power control table included therein in a power on condition or a reset-start condition. During communication, i.e., in a normal condition, a compensation circuit 106 compensates the power control table stored in the transmission power determining circuit 104 in accordance with a control bit (hereinafter referred to as a sc bit) indicative of compensating the transmission power table which represents a relation between a reception power and a transmission power. The transmission power determining circuit 104 determines the transmission power setting value in accordance with the calculated reception power through the compensated power control table. If a level adjustment is effected before the correlation detection such as an AGC circuit or the like in the reception system, the reception power calculation circuit 102 calculates the reception power in accordance with an AGC gain in addition to the correlation detection output 101. The sc bit is detected from a demodulation result. Fig. 2 is a graphical drawing showing the power control table in the transmission power determining circuit 104 shown in Fig. 1. When the sc bit is indicative of decreasing the transmission power, the compensation circuit 106 compensates the power control table 201 in a decreasing direction and thus, a compensated power control table 202 is obtained with the transmission power decreased over a whole range of the reception power. An amount of the compensation in response to one pulse of the sc bit is determined by data in the sc bit or alternatively, it is determined by data stored in the compensation circuit 106. Fig. 3 is a block diagram of a communication apparatus of the first example including the transmission power control portion, which is also referred to in the second and third examples. The communication apparatus of the first example, as a mobile unit, comprises an antenna 301, a duplexer 302, a receiving portion 320, the transmission power control circuit 310, and a transmission portion 321. The antenna 301 receives a first CDMA radio wave signal 317 including the sc bit and transmitting a second CDMA radio wave signal 316. The duplexer 302 duplexes the received first CDMA radio wave signal with the second CDMA radio wave signal. The receiving portion 320 includes an AGC circuit 303 for amplifying the received first CDMA radio wave signal with a gain control and for supplying the gain data to the transmission power control circuit 310. The receiving portion further includes a PN (pseudo noise) code generator 304 generating a PN code; a correlation detection circuit 305 which detects a correlation between the first CDMA radio wave signal from the AGC circuit 303 and the PN code from the PN code generator 304 and outputs a correlation result as a desired wave 101. A demodulation circuit 307 demodulates the correlation result and outputs a demodulation data 308 including the sc bit, and a sc bit detector 309 for detecting and supplying the sc bit from the demodulation data 308 to the transmission power control circuit 310. The transmission portion 321 includes a PN code generator 313 for generating a second PN code, a spectrum spreading circuit for spectrum-spreading transmission data with the second PN code, and a power amplifier 315 for amplifying the output of the spectrum spreading circuit 314 with the transmission power controlled in accordance with the transmission power setting value from the transmission power control circuit 310. The amplified transmission data is supplied to the duplexer 302 and transmitted by the antenna 301 as the second CDMA radio wave signal 317. The AGC circuit 303 amplifies the received first CDMA radio wave signal with the gain control to have a constant intensity and supplies the data of the gain, i.e., AGC gain data, to the transmission power control circuit 310. The PN code generator 304 generates the PN code assigned to this communication apparatus. The correlation detection circuit 305 detects the correlation between the first CDMA radio wave signal from the AGC circuit 303 and the PN code from the PN code generator 304 to effect an inverse-spectrum-spreading and outputs the correlation result as a desired wave component. The demodulation circuit 307 demodulates the correlation result, effects a carrier removing processing, an error correction processing and outputs the demodulation data 308 including the sc bit. The sc bit detector 309 detects the sc bit periodically transmitted. The sc bit 105 is included in a data frame at a predetermined position of the data frame and is supplied to the transmission power control circuit 310. Regarding the compensation, it is sufficient that the compensation of the power control table 201 in response to the sc bit 105 is effected to trace a variation due to a temperature characteristic, a traffic variation or the like. Therefore, it is clear that a control cycle by the sc bit 105 (hereinafter referred to as sc bit cycle) T1 is considerably longer than a control cycle T2 of transmission power control provided for the fading variation in accordance with the reception power (T1>T2). Therefore, the sc bit is transmitted in a low speed accompanied channel (SACCH). In other words, the control cycle T1 is longer than a transmission cycle of the conventional closed loop control. As mentioned, in the communication apparatus of the first example, the transmission power is controlled for the fading variation in accordance with the calculated reception power through a power control table as an open loop control. In addition, the power control table is compensated for the traffic variation in accordance with the control signal, that is, the sc bit periodically transmitted from the base station, wherein the control cycle T1 of the transmission power control by the sc bit is longer that the control cycle of the calculated reception power. <A SECOND EXAMPLE> Fig. 4 is a block diagram of a transmission power control circuit 410 of a second example communication apparatus 400 of the third example is shown in Fig. 3. Fig. 5 is a graphical drawing illustrating compensation of the transmission power control table in the second example. A communication apparatus 400 of the second example has substantially the same structure and operation as that of the first example. The difference is that a reception power storing circuit 406 and a compensation range determining circuit 407 are further provided and the compensation circuit 408 compensates the power control table in the transmission power determining circuit 104 with a controlled compensation range. The reception power calculation circuit 102 calculates the reception power of a desired wave component at the antenna. The calculated reception power is supplied to a transmission power determining circuit 104. The transmission power determining circuit 104 determines a transmission power setting value 405 from the calculated reception power in accordance with an initial setting value from an initial setting value storing circuit 103 through a power control table included therein in a power on condition or a reset-start condition. During communication, i.e., in a normal condition, a compensation circuit 408 compensates the power control table stored in the transmission power determining circuit 104 in accordance with the sc bit indicative of compensating the transmission power table which represents a relation between a reception power and a transmission power. The transmission power determining circuit 104 determines the transmission power setting value 405 in accordance with the calculated reception power through the compensated power control table. If a level adjustment is effected before the correlation detection such as an AGC circuit or the like in the reception system, the reception power calculation circuit 102 calculates the reception power in accordance with an AGC gain in addition to the correlation detection output 101. The reception power calculation circuit 102 calculates the reception power of the desired wave component at the antenna 301. A calculated reception power is supplied to a transmission power determining circuit 104. The transmission power determining circuit 104 determines a transmission power setting value 405 from the calculated reception power in accordance with the initial setting value from the initial setting value storing circuit 103 through the power control table 201 included therein in the power on condition or the reset-start condition. During communication, the reception power is stored in the reception power storing circuit 406 with a sampling interval. The compensation range determining circuit 407 obtains a reception power distribution 501 from the stored reception power storing circuit 406 as shown in Fig. 5. The compensation range determining circuit 407 analyzes the reception power distribution 501 or 504 and determines sections 509 of which frequencies (the number of times per a predetermined interval) of the occurrences of reception power values at respective sections are relatively high. If the variation due to a fading is slow, the reception power distribution 501 is provided. Then, the compensation range determining circuit 407 determines the compensation range 507 from the sections 509 where the frequencies are high. The compensation circuit 408 compensates the power control table with transmission power values in the compensation range 507 in response to the sc bit 105. The transmission power determining circuit 104 determines the transmission power setting value 405 in accordance with the compensated power control table 503. The amplifier 315 amplifies the spectrum-spread transmission data with the transmission power controlled with the transmission setting value 405 from the transmission power control circuit 410. If the variation due to a fading is fast, the reception power distribution 504 is provided, wherein the variation due to fading occurs over the whole reception power range. Then, the compensation range determining circuit 407 determines the compensation range 508 wherein there is no section where the frequency of reception power value is relatively high as compaired with other sections. The compensation circuit 408 compensates the power control table with transmission power values in the compensation range 508 compensated in response to the sc bit 105. The transmission power determining circuit 104 determines the transmission power setting value in accordance with the compensated power control table 506. The amplifier 315 amplifies the spectrum-spread transmission data with the transmission power which is controlled with the transmission setting value 405 from the transmission power control circuit 410. As mentioned, the communication apparatus of the second example controls the transmission power in accordance with the distribution of sampled and stored reception power through analyzing and adaptively controlling the transmission power in accordance with a variation speed due to fading in addition to the control operation according to the first example. A period for obtaining the reception power distribution may or may not coincide with a period for determining the sc bit in the base station. <THIRD EXAMPLE> Fig. 6 is a block diagram of a transmission power control circuit 610 of a third example. A communication apparatus 600 of the third example has substantially the same structure and operation as that of the second example. The difference is that the compensation circuit 608 receives a compensation allowable range data and compensates the power control table within the compensation allowable range indicated by the compensation allowable range data. The reception power calculation circuit 102 calculates a reception power of the desired wave component at the antenna 301. The calculated reception power is supplied to a transmission power determining circuit 104. The transmission power determining circuit 104 determines a transmission power setting value 605 from the calculated reception power in accordance with the initial setting value from the initial setting value storing circuit 103 through the power control table included therein in the power on condition or the reset-start condition. During communication, the compensation circuit 608 compensates the power control table stored in the transmission power determining circuit 104 in accordance with the sc bit indicative of compensating the transmission power table within the compensation allowable range of the transmission power in accordance with the compensation allowable range data 610. Fig. 7 is a graphical drawing illustrating compensation of the transmission power control table in the third example, wherein transmission power values are partially and repeatedly compensated in response to sc bits, wherein at a section A the transmission power values reaches an upper limit of the compensation allowable range. Therefore, the transmission power value at the section A is not changed further. At other sections, the transmission power values can be compensated. According to this example, the transmission power control is effected with the compensation allowable range. Then, it is prevented that all communication apparatus enter a divergent condition by that all communication apparatus compensate the power control tables in the increasing direction successively. The compensation allowable range is provided with only upper limit, only lower limit, or upper and lower limits. <FOURTH EXAMPLE> Fig. 8 is a block diagram of a transmission power control signal generation portion 1009 of a fourth example and Fig. 10 is a block diagram of a communication apparatus 1000 of the fourth example, which is also referred to in later examples. The transmission power control signal generation circuit 1009 comprises a reception power calculation circuit 802 for calculating the reception power of a desired wave component at an antenna 1001 in consideration of an AGC gain data; a reception power storing circuit 803 for storing the calculated reception power values; an averaging circuit 804 for averaging the calculated reception power values; a comparing circuit 805 for comparing the averaged reception power value with a target level value 806, wherein the comparing circuit 805 obtains the difference between the averaged reception power value and the target level value 806; and an sc bit judging circuit 807 for judging whether the difference exceeds a predetermined value and generating the sc bit 808 if the difference exceeds the predetermined value. The reception power calculation circuit 802 periodically calculates the reception power of a desired wave component at the antenna 1001. The calculated reception power is stored in the reception power storing circuit 803. The averaging circuit 804 averages the calculated reception power values from the reception power storing circuit 803. The comparing circuit 805 compares the averaged reception power value with the target level value 806 and obtains the difference between the averaged reception power value and the target level value 806. The difference is supplied to the sc bit judging circuit 807 as a transmission power setting difference. The sc bit judging circuit 807 judges whether the transmission power setting difference exceeds the predetermined value and generates the sc bit 808 if the difference exceeds the predetermined value. Fig. 9 is a graphical drawing of the fourth embodiment illustrating obtaining the difference 904 between the target level 806 and the averaged reception power value 902. In this embodiment, the difference is determined from the averaged reception power value. However, it is also possible to provide the difference from a center value or a reception power value having a higher possibility from the reception power level distribution 901. The amount of the correction is determined by a variance of the reception power level distribution 901 and is transmitted in the sc bit. If a level adjustment is effected before the reception power calculation such as an AGC circuit or the like in the reception system, the reception power calculation circuit 802 calculates the reception power in accordance with an AGC gain in addition to the correlation detection output 801. The communication apparatus 1000 of the fourth example, as a base station, comprises an antenna 1001, a duplexer 1002, a receiving portion 1020, the transmission power control signal generation circuit 1009 for generating the sc bit as a transmission power control signal, and a transmission portion 1021. The antenna 1001 transmits the first CDMA radio wave signal and receives the second CDMA radio wave signal from a mobile unit. The duplexer 1002 duplexes the received second CDMA radio wave signal with the first CDMA radio wave signal. The receiving portion 1020 includes an AGC circuit 1003 for amplifying the received second CDMA radio wave signal with a gain and supplies data of the gain, i.e., AGC gain data, to the transmission power control signal generation circuit 1009. The receiving portion further includes a PN code generator 1004 for generating a PN code; a correlation detection circuit 1005 for detecting a correlation between the second CDMA radio wave signal from the AGC circuit 1003 and the PN signal from the PN code generator 1004 and outputting a correlation result of the desired wave, and a demodulation circuit 1007 for demodulating the correlation result and outputting a demodulation data 1008. The transmission portion 1021 comprises a multiplexer for multiplexing data to be transmitted with the sc bit to output a multiplexed transmission data, a PN code generator 1015 for generating a PN code, a spectrum spreading circuit 1016 for spectrum-spreading the multiplexed transmission data with the PN code from the PN code generator 1015, and a power amplifier 1017 for amplifying the output of the spectrum spreading circuit 1014 with the controlled transmission power. The amplified transmission data is supplied to the duplexer 1002 and transmitted by the antenna 1001 as the first COMA radio wave signal. The AGC circuit 1003 amplifies the received first CDMA radio wave signal with the gain to have a constant intensity and supplies the data of the gain, i.e., the AGC gain data, to the transmission power control circuit 1009. The PN code generator 1004 generates the PN signal assigned to the mobile unit to be communicated. The correlation detection circuit 1005 detects the correlation between the second CDMA radio wave signal from the AGC circuit 1003 and the PN signal from the PN code generator 1004 to effect inverse-spectrum-spreading and outputs the correlation result of the desired wave component. The demodulation circuit 1007 demodulates the correlation result, i.e. removes a carrier component and outputs a demodulation output 1007a. The demodulation circuit 1007 further effects an error correction processing, and outputs the demodulation data 1008 and CRC detection bit 1301. The transmission power control signal generation circuit 1009 generates the sc bit as the transmission power control signal from the correlation detection output 801 and the AGC gain data. The transmission portion 1021 transmits transmission data including the sc bit 1012 spectrum spread from the antenna 1001. <FIFTH EXAMPLES> Fig. 11 is a block diagram of a transmission power control signal generation circuit 1109 of a fifth example and Fig. 10 also shows a communication apparatus of the fifth example. The communication apparatus 1100 of the fifth example has substantially the same structure and operation as those of the fourth example. The difference is that the transmission power control signal generation circuit 1109 is used instead the transmission power control signal generation circuit 1009. The transmission power control signal generation circuit 1109 comprises a desired wave power calculation circuit 1102 for calculating a reception power of a desired wave component at the antenna 1001, an interference power calculation circuit 1104 for calculating a reception power of interference wave components at the antenna 1001, an SIR operation circuit for providing a signal to interference power ratio (SIR), a comparing circuit 1106 for comparing the signal to interference power ratio with an SIR target level 1107 to output a deviation in the signal to interference power ratio, an sc bit judging circuit 1108 for judging the deviation in the signal to interference power ratio, wherein if the deviation exceeds a predetermined value, the sc bit judging circuit 1108 outputs the sc bit 1110. The desired wave power calculation circuit 1102 periodically calculates the reception power of a desired wave component at the antenna 1001 from the correlation detection output 801 or a demodulation output which is obtained by the demodulation circuit 1007 by removing the carrier component from the correlation detection output. The interference power calculation circuit 1104 periodically calculates the reception power of interference wave components at the antenna 1001 from the correlation detection output 801 or the demodulation output 1007a. In these operations, cycles of calculation of reception power of the desired wave component and the interference wave components may be different each other. The SIR operation circuit 1105 provides the signal to interference power ratio (SIR) from the calculated reception power of the desired wave component and the calculated reception power of the interference wave components. The comparing circuit 1106 compares the signal to interference power ratio with a SIR target level 1107 to obtain the deviation in the signal to interference power ratio. The sc bit judging circuit 1108 judges the deviation in the signal to interference power ratio. If the deviation exceeds a predetermined value, the sc bit judging circuit 1108 outputs the sc bit 1109. The sc bit is transmitted in the first CDMA signal from the antenna 1001. Fig. 12 is a graphical drawing of the fifth example illustrating obtaining the error 1204 between the SIR target level 1107 and the averaged SIR 1202. In this example, the deviation is determined from the SIR 1202. However, it is also possible to provide the error from a center value or an SIR having a higher possibility from the SIR distribution 1201. The amount of the correction is determined by a variance of the SIR distribution 1201 and is transmitted in the sc bit. <SIXTH EXAMPLE> Fig. 13 is a block diagram of a transmission power control signal generation circuit 1309 of a sixth example and a communication apparatus 1300 of the sixth example is also shown in Fig. 10. A communication apparatus 1300 of the sixth example has substantially the same structure and operation as those of the fourth example. The difference is that the transmission power control signal generation circuit 1309 is used instead the transmission power control signal generation circuit 1009. The transmission power control signal generation circuit 1309 comprises a frame error rate circuit 1302 for providing a frame error rate from error detection information (a CRC detection bit) 1301 from the demodulation circuit 1007, a comparing circuit 1303 for comparing the frame error rate with a target level 1304 to output a deviation in the frame error rate, an sc bit judging circuit 1305 for judging the deviation which outputs the sc bit 1306 if the deviation in the frame error rate exceeds a predetermined value. The demodulation circuit 1007 effects the error correction operation as mentioned above. During this operation the demodulation circuit outputs the error detection information, that is, the CRC detection bit 1301. The frame error rate circuit 1302 provides the frame error rate from the CRC detection bit 1301 output from the demodulation circuit 1007. The comparing circuit 1303 compares the frame error rate with the target level 1304 to output the deviation in the frame error rate. The sc bit judging circuit 1305 judges the deviation. If the deviation in the frame error rate exceeds a predetermined value, the sc bit judging circuit 1305 outputs the sc bit 1306. <SEVENTH EXAMPLE> Fig. 14 is a block diagram of a communication system of a seventh example. The communication system of the seventh example uses any of the communication apparatus 300, 400, or 600 of the first to third examples as the mobile unit 1402 and any of the communication apparatus 1000, 1100, or 1300 of the fourth to sixth examples as the base station 1401. The communication system of the seventh example comprises the communication apparatus 1401 as a base station for transmitting the first CDMA radio wave signal 1403 including the sc bit and receiving the second CDMA radio wave signal 1404 and a plurality of communication stations 1402 as a mobile unit for receiving the first CDMA radio wave signal 1403 and transmitting the second CDMA radio wave signal 1404 with the transmission power controlled in accordance with the detected reception power and the sc bit through the power control table. Fig. 15 shows a timing chart of the communication apparatus of the seventh example. In the base station 1401, the sc bit is detected every four frames, that is, 40 ms. The transmission data is transmitted every frame of 10 ms and an interleaving processing of 10ms is effected. The open loop transmission power control in the mobile unit 1402, that is, the transmission control in accordance with the reception power through the power control table is effected at the cycle T2 ≦ 10ms. In the base station 1401, the sc bit is judged every 40 ms from the reception signal BSRX at t1 (t5, t6) and the sc bit is transmitted through the first CDMA radio wave signal (BSTX) at a timing t2 with an interleaving delay of one frame. At a timing t3, the mobile unit 1402 receives the first CDMA radio wave signal and the sc bit detector 309 detects the sc bit at a timing t4 with a de-interleaving delay of one frame developed in demodulating. As mentioned, in the communication system of the seventh example, the mobile unit 1402 compensates the power control table with the control signal (the sc bit) periodically transmitted from the base station 1401, so that the control error in the open loop controlling of the transmission power control can be compensated. Moreover, the sc bit cycle T1 determined in consideration of a variation in the temperature characteristic or a traffic variation is relatively longer than the cycle T2 of the transmission power control in accordance with the reception power determined in consideration of fading. Therefore, it is possible to transmit the sc bit in a low speed accompanied channel (SACCH). Therefore, an amount of control signals per a predetermined interval can be reduced, so that a frequency utilizing efficiency can be increased.

Claims: A method of effecting transmission power control in a CDMA communication system comprising a base station and a mobile station, said method comprising the steps of: receiving a first CDMA radio wave signal transmitted from said base station, said radio wave signal comprising a desired wave component including control data; and transmitting a second CDMA radio wave signal; detecting electric power of said desired wave component; storing a relation between said detected electric power of the desired wave component and the electric power of said second CDMA radio wave signal; demodulating the desired wave component and outputting demodulation data; detecting the control data from the desired wave component; compensating said stored relation in accordance with said detected control data; determining actual transmission power to be transmitted by said mobile station in accordance with said compensated stored relation; and controlling the transmission power of said second CDMA radio wave signal to said base station in accordance with said actual transmission power. The method according to claim 1, wherein said control data is transmitted from said base station to said mobile station at a period which is longer than a period of transmission power control which tracks a fading variation. The method according to claim 1 or 2, further comprising the steps of: receiving at said base station a transmission signal from said mobile station; detecting the reception power of interference wave components of said received transmission signal from said mobile station; determining a signal to interference power ratio (SIR) from the reception power of said received transmission signal from said mobile station and said reception power of interference wave components; generating said control data in accordance with said signal to interference power ratio (SIR). The method according to claim 3, wherein said step of generating said control data includes the step of comparing said signal to interference power ratio (SIR) with target value and generating said control data in accordance with said comparing result. The method according to one of claims 1 or 2, further comprising the steps of receiving at said base station a transmission signal from said mobile station; detecting a frame error rate from said received transmission signal; comparing said frame error rate with a target value and obtaining an error of the frame error rate; and generating said control data when said error exceeds a predetermined threshold. The method according to one of the preceding claims 1 to 5, wherein said relation is compensated within an allowable range.

Inventors: MIYA KAZUYUKI, MIYA, KAZUYUKI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1997
Main classification: H04B7
IPC codes: H04B7