JP4113553B2 - Transmission power control method - Google Patents

Description

  The present invention relates to a spread spectrum communication system, and more particularly to a cellular spread spectrum communication system in which a plurality of terminal apparatuses communicate with a base station apparatus at the same time, a mobile terminal apparatus applied thereto, and a transmission power control method.

  For example, as shown in FIG. 10, a plurality of base stations 100 (100-a, 100-b) connected to the switching center 10 are distributed to form a plurality of cells 1 (1a, 1b). In a cellular spread spectrum communication system in which a base station 100 and a plurality of mobile terminals 300 communicate with each other, as a spreading code of a signal transmitted from each base station 100 to a terminal in the cell, for each terminal in the cell A method using a unique orthogonal code Wi is known.

  For example, as shown by reference characters W0, W1, W2, and W3 in FIG. 11, the orthogonal code has a property that the result becomes 0 when the product-sum operation is performed over the orthogonal unit interval for any two of the codes.

  Therefore, the base station assigns a unique orthogonal code Wi (i = 1 to n) to each of the plurality of terminals 300-1 to 300-n in the cell, and transmits a signal or data transmitted to one terminal 300-i. Is spread using the unique orthogonal code Wi of the terminal, and the terminal 300-i despreads the received signal using the unique orthogonal code Wi assigned to itself. Transmission signal components addressed to other terminals in the cell orthogonal to the addressed transmission signal are completely removed during the despreading process, and do not act as interference signals. A communication system in which spreading by orthogonal codes is applied to communication from each base station to a mobile terminal is disclosed in, for example, US Pat. No. 5,104,459.

  However, in a cellular spread spectrum communication system using orthogonal codes, each terminal also receives transmission signals from other base stations forming adjacent cells in addition to signals transmitted from base stations in the cell. To reach. In this case, the transmission signal from another base station is not orthogonal to the signal transmitted by the base station in the cell, and thus cannot be removed by the despreading process using the orthogonal code Wi unique in the cell. That is, in the reception operation of each terminal, a transmission signal from a base station in another cell acts as an interference factor.

  FIG. 15 is a diagram illustrating the influence of a transmission signal from another base station described above in each terminal.

  The received power of the signal transmitted from the base station attenuates as the distance from the base station increases. Therefore, terminal 300a located near the cell center near base station 100 has a large signal reception power 910 from the base station in the cell, and receives signals from other base stations outside the cell that act as interference signals. Since the power 911 is small, a high S / N can be obtained. On the other hand, in the terminal 300b located near the cell boundary, the reception power 912 of the signal from the base station in the cell is weak, and the interference signal from the adjacent cell is received with the power 913 larger than that of the terminal 300a. As a result, S / N deteriorates.

For the above reasons, in the cellular system, signals transmitted from each base station to the terminal are transmitted with small transmission power to the terminal 300a located near the cell center, and to the terminal 300b located around the cell. It is desired to control the transmission power according to the positional relationship with the terminal so as to output with a large transmission power. As for the transmission power control method in which the transmission power is changed according to the position of the terminal as described above, for example,
A. Salmasi, KSGilhousen, “On the System Design Aspects of Code Division Multiple Access (CDMA) Applied to Digital Cellular and Personal Communications Network”, IEEE VTS 1991, pp. 57-62.

  In the control method described in the above document, each terminal device measures the S / N of the received signal using, for example, the circuit configuration shown in FIG. 14, and transmits a control signal for requesting transmission power to the base station. The base station performs the transmission signal power control operation in response to the power control signal with the circuit configurations shown in FIGS.

  In FIG. 12 showing the configuration of the transmission / reception circuit portion of the base station, a signal from each terminal apparatus received by the antenna 110 is input to the high-frequency circuit 111 via the circulator 109 and converted into a baseband spread spectrum signal Rx. . The baseband spread spectrum signal Rx is input to modulation / demodulation devices 105-1, 105-2,... 105-N associated with each terminal device located in the cell. By performing the decoding process, the transmission signal (reception data) 112 for each terminal is separated from the power control signal PC transmitted by the terminal mixed with the transmission signal.

  The power control signal PC output from each modulation / demodulation device 105-i (i = 1 to N) is input to the transmission power control device 116. The transmission power control device 116 generates a transmission power instruction signal PW for each terminal device according to each power control signal PC.

The modem 105-i (i = 1 to N) encodes the transmission data 101 addressed to each terminal device and the pseudo signal unique to the base station generated by the pseudo noise (PN) generator 103. A modulation process by spread spectrum using the orthogonal codes W1, W2, W3,..., WN generated from the noise PN and the orthogonal code generator 102 is performed.
The signal modulated by the spread spectrum is amplified by the power according to the transmission power instruction signal PWi corresponding to each terminal device given from the transmission power control device 116, and output as a transmission signal Tx-i (i = 1 to N). Is done.

  A pilot signal generator 104 generates simple pattern data, for example, data consisting of all zeros. This pilot signal is subjected to spread spectrum modulation using a pseudo noise PN specific to the base station generated from the pseudo noise generator 103 and a specific orthogonal code W0 generated from the orthogonal code generator 102, and then pilot-modulated. Output as a signal.

  Transmission signals Tx-i (i = 1 to N) addressed to each terminal are sequentially added by cascade-connected adders 107 (107-0, 107-1,...), And then, together with the pilot signal, a high-frequency circuit. The signal is converted into a signal in the transmission frequency band at 108, and sent to the air through the circulator 109 and the antenna 109.

  FIG. 13 shows an example of the configuration of the modem 105-i (i = 1, 2,... N) in FIG.

  The transmission data 101 input to the modem 105-i is input to the encoder 201 and subjected to an encoding process such as error correction. The encoded signal is multiplied by the orthogonal code Wi given from the orthogonal code generator 102 by the multiplier 202 and subjected to the first spread spectrum, and then the pseudo noise signal PN and the multiplier 203 are applied. Multiplied and subjected to second order spread spectrum. The spectrum-spread signal is input to the variable gain amplifier 204, amplified with the gain specified by the transmission power instruction signal PW-i, and output as the transmission signal Tx-i.

  On the other hand, the received signal Rx input to the modulator / demodulator 105-i is input to the multiplier 205, and is the same as the pseudo noise PN used for spectrum spreading in the terminal device that is the transmission source of the signal Rx described later. A despreading process is performed using the pseudo noise PN generated by the pseudo noise generator 206. The despread signal is input to an accumulator 207, and a signal for a certain time is accumulated. The accumulated despread signal is input to the decoder 208 and subjected to decoding processing such as error correction, and is separated into the decoded received data 112 and the power control signal PC-i transmitted by the terminal device. Is output.

  FIG. 14 shows a configuration of a transmission / reception circuit portion included in a conventional terminal device.

  In the terminal device, a signal received from the antenna 301 is input to the high frequency circuit 303 via the circulator 302 and converted into a baseband spread spectrum signal.

  The baseband spread spectrum signal is input to the first multiplier 304, multiplied by the pseudo noise PN generated from the pseudo noise generator 305, and subjected to the first-order despreading process. The pseudo-noise PN has a noise pattern set to be the same as the inherent pseudo-noise PN generated by the PN generator 103 of the base station when the terminal device is registered in the base station.

  The signal subjected to the first-order despreading process is input to the second multiplier 307, multiplied by the orthogonal code Wi assigned to the terminal generated from the orthogonal code generator 306, and the second-order inverse spread. Receive diffusion treatment. The signal subjected to the second-order despreading process is input to an accumulator 308, where signals for a certain time are accumulated. The accumulated signal is decoded by the decoder 309 to be received data.

  According to the prior art, each terminal apparatus measures the S / N of the received signal by using the fact that the variance corresponds to the noise power and the average corresponds to the signal amplitude in the probability density distribution regarding the amplitude of the received signal. is doing.

  For this S / N measurement, in the prior art, the absolute value obtained by inputting the output of the accumulator 308 to the absolute value calculator 328 and the output of the accumulator 308 are input to the square calculator 325. The square value obtained in this way is supplied to the S / N measuring device 329. The S / N measuring device 329 obtains noise power from the difference between the mean value of the square value input and the mean square value of the absolute value input, and obtains the signal power from the mean square value of the absolute value input. / N is measured, and the result is compared with the S / N reference value by the comparator 330 to obtain the power control signal PC-i for requesting the base station to increase or decrease the transmission power.

  The power control signal PC-i is mixed with the transmission data from the terminal by the mixer 317, then subjected to an encoding process such as error correction by the encoder 318, and this encoded signal is given to the multiplier 320. Spread spectrum modulation is performed by multiplying the pseudo noise generated from the pseudo noise generator 319. The signal subjected to spread spectrum modulation is converted into a signal in the transmission frequency band by the high frequency circuit 321, and then output to the antenna 301 via the circulator 302 and transmitted to the air.

  With the above configuration, the terminal notifies the base station of the reception S / N of the transmission signal from the base station to the terminal, and the base station controls the transmission power so that the reception S / N of the terminal becomes the target S / N. To do.

A. Salmasi, K. S. Gilhousen, “On the System Design Aspects of Code Division Multiple Access (CDMA) Applied to Digital Cellular and Personal Communications Network”, IEEE VTS 1991, pp. 57-62

  In the conventional spread spectrum communication system described above, each terminal apparatus measures the S / N based only on the signal transmitted from the base station to itself. That is, the dispersion of the amplitude of the received signal obtained by despreading is regarded as noise power, and the S / N is measured by regarding the square of the average value of the amplitude of the signal as signal power.

  However, the principle of the conventional S / N measurement is based on the premise that the signal amplitude is constant if there is no noise. However, in a mobile communication system, the amplitude of the received signal of each terminal device It fluctuates violently with. Therefore, in order to obtain a reliable S / N measurement result at each terminal, it is necessary to complete the measurement within a relatively short period to the extent that the amplitude of the received signal can be regarded as constant. For this reason, in the conventional terminal device, an extremely high-speed performance circuit is required for the S / N measurement circuit systems 325 to 329. If time is required for S / N measurement due to circuit performance constraints, a correct S / N measurement result cannot be obtained, and the base station cannot implement appropriate power control based on the power control signal from the terminal. There is a problem.

  In this case, considering the error in the S / N measurement result, if the base station transmits a signal with higher power than necessary to each terminal in the cell, the transmission signal enters the adjacent cell with high power and Acts as a strong jamming signal for terminals in the cell. On the other hand, if the base station performs a transmission operation with a power smaller than that actually required by the terminal, there is a problem that the communication quality at the terminal that has received the base station deteriorates.

  As a method for controlling the power of the transmission signal from the base station, for example, each terminal apparatus monitors the error rate of received data instead of the above-described S / N of the received signal, and the error rate satisfies a predetermined standard. If this is not the case, a method of requesting the base station to increase the transmission power can be considered, but this method requires a relatively long period of time to calculate the data error rate. There is a problem that it is not possible to follow up sufficiently.

  An object of the present invention is to provide a spread spectrum communication system and a power control method in which each terminal apparatus can communicate with a base station with high S / N.

  Another object of the present invention is to provide a spread spectrum communication system and a power control method capable of increasing the number of simultaneous communications in each cell.

  Another object of the present invention is to provide a mobile terminal apparatus capable of quickly calculating control information for power control to be transmitted to a base station.

  To achieve the above object, in the spread spectrum communication system of the present invention, the base station does not apply at least one of the orthogonal code sequences for spread spectrum to the modulation of the transmission signal for the pilot signal or the terminal. One characteristic is that it is assigned as a dedicated code for power control.

  In the present invention, each terminal apparatus (mobile terminal) receives the received power of the noise component obtained by despreading the received signal with the orthogonal code assigned exclusively for S / N measurement at the base station, and the pilot signal or the own signal. One feature is to obtain the S / N of the received signal from the received power of at least one of the transmission signals addressed to the terminal.

  In the spread spectrum communication system of the present invention, each terminal device transmits power control information obtained based on the S / N value thus obtained to the base station, and the base station receives from the terminal device. The transmission power of the signal to each terminal apparatus is controlled according to the control information.

  Another point of focus of the present invention is that, in transmission signal control, the first signal for obtaining control information is different from the second signal to be controlled.

  Since all signal components transmitted from the base station are orthogonal to the orthogonal code dedicated to the control, the base station does not apply the orthogonal code dedicated to the control to the modulation of the transmission signal, and each terminal device If each received signal is despread using the orthogonal code dedicated to the control, each terminal device completely removes various signal components transmitted from the base station in the cell from the received signal. Can do. In this case, since the signal transmitted from the base station of another cell is not orthogonal to the specific code used for the despreading, it is not removed by the despreading process and remains as a noise component. Therefore, by obtaining the root mean square of the noise components extracted by the despreading process, the noise power can be measured quickly and with sufficient accuracy.

  On the other hand, since the signal component sent from the base station is obtained by despreading the received signal with the orthogonal code assigned to each terminal or the orthogonal code assigned for the pilot signal, the power value and the noise The S / N value can be obtained from the electric power.

  According to the present invention, each terminal notifies the base station of a power control request according to the S / N value, and the base station controls the signal transmission power for each terminal based on the control request from each terminal. As a result, the communication quality of each terminal device can be guaranteed.

Note that if the signal transmission power is controlled so that, for example, the S / N is the same for all terminals, the total transmission power of each base station can be reduced. There is an effect that the value of the noise power having an adverse effect can be reduced, and thereby the S / N in each terminal can be further improved.
Further, the present invention employs “open loop control” in which these signals are different from “closed loop control” in which the signal that is the basis of the control information and the signal to be controlled are the same. In the case of closed-loop control, if the control target signal fluctuates due to a control delay or error, the fluctuation appears as an error in the control information, and the control target signal fluctuates. In the present invention employing the concept of control, there is no such problem and stable control is possible.

  According to the present invention, since the S / N can be quickly measured in each terminal device, this is transmitted as a power control signal to the base station, and the base station transmits a signal addressed to each terminal based on the power control signal. By controlling the transmission power, the S / N at each terminal can be made substantially equal. As a result, the total transmission power of signals addressed to the terminal from the base station in each cell can be suppressed to the minimum necessary, and the power of interfering radio waves acting as noise on adjacent cells can be reduced. The number can be increased.

  FIG. 1 shows an example of the configuration of a base station in a spread spectrum communication system of the present invention. In the figure, elements corresponding to those of the base station shown in FIG.

  The operation of the base station of the present invention is substantially the same as that of the base station according to the prior art described above, but as will be described later, any one of the orthogonal codes output from the orthogonal code generator 102, this embodiment However, the difference is that the WN is excluded from the use of modulation of transmission data for the terminal and is allocated exclusively for S / N measurement.

  FIG. 3 shows a first embodiment of the terminal device according to the present invention. In the figure, circuit elements 301 to 309 correspond to the components 301 to 309 of the conventional terminal device shown in FIG. 14, and in the receiving circuit composed of these elements, the multiplier 304 performs pseudo-simulation similarly to the conventional device. The received signal subjected to the first-order despreading due to the noise PN is subjected to the second-order despreading by the orthogonal code Wi in the multiplier 307 and decoded as received data addressed to the terminal.

  In this embodiment, the received signal subjected to the first-order despreading by the multiplier 304 is input to the multipliers 313 and 310. The signal input to the multiplier 303 is subjected to second-order despreading by the orthogonal code W 0 generated from the orthogonal code generator 306. The orthogonal code W0 corresponds to the spreading orthogonal code of the pilot signal periodically output by the base station, and the signal despread by the orthogonal code W0 is input to the accumulator 314 and accumulated for a certain period. Thus, the pilot signal can be demodulated. The pilot signal is squared by the squarer 315 and input to the first terminal of the S / N measurement circuit 316 as a signal indicating the instantaneous power of the pilot signal component.

  On the other hand, the received signal input to the multiplier 310 is subjected to second-order despreading by the orthogonal code WN dedicated to S / N measurement generated by the orthogonal code generator 306, and the despread signal is accumulated. It is input to the device 311 and accumulated for a certain period. Since the orthogonal code WN is a specific orthogonal code that is not used for modulation of the transmission signal in the base station, the transmission signal component from the base station is completely removed as a result of the despreading process using the orthogonal code. The component corresponding to noise can be extracted. Therefore, the instantaneous power of the noise component can be obtained by accumulating the output of the multiplier 311 for a certain period of time by the accumulator 311 and calculating the square thereof by the squarer 312.

  The instantaneous power of the noise component is input to the second terminal of the S / N measurement circuit 316, and a signal indicating the S / N of the pilot signal is obtained by calculating a ratio with the instantaneous power of the pilot signal component. In this embodiment, the S / N signal is compared with the reference S / N in the comparator 330 to obtain a power control signal PC indicating a deviation from the reference S / N. This power control signal PC is mixed with transmission data by a mixer 317, encoded by an encoder 318, subjected to spread spectrum modulation by pseudo noise generated from a pseudo noise generator 319 in a multiplier 320, and then subjected to high frequency. The data is transmitted to the base station via the circuit 321, the circulator 302, and the antenna 301.

  FIG. 4 shows a second embodiment of the terminal device. In this embodiment, the comparator 330 in FIG. 3 is omitted, the S / N information output from the S / N measurement circuit is handled as it is as the power control signal SN, and after mixing with the transmission data by the mixer 317, the encoder 318, the multiplier 320, the high frequency circuit 321, and the circulator 321 are transmitted.

  In the base station 100 shown in FIG. 1, each modulation / demodulation device 105-i (i = 1 to N-1) separates the received signal from each corresponding terminal device into received data and a power control signal, and performs power control. A signal is supplied to the transmission power control apparatus 106. When each terminal has the structure of the first embodiment, the power control signal PC is separated. When each terminal has the structure of the second embodiment, the power control signal SN is separated. The transmission power control device 106 generates a transmission power instruction signal PW to be given to each modulation / demodulation device 105-i according to the power control signal PC or SN.

  The configuration of the modem 105-i is shown in FIG. The circuit elements 201 to 207 correspond to the circuit elements 201 to 207 of the conventional modem shown in FIG.

  The received signal Rx from the terminal device is despread by the pseudo noise signal by the multiplier 205, accumulated by the accumulator 207 for a certain period, and then input to the error correction decoder 508. Here, decoding processing such as error correction is performed, and the received data 112 and the power control signal SN-i or PC-i are separated from the decoded signal.

  When the terminal device has the configuration of the first embodiment, the power control signal PC-i separated in each modulation / demodulation device 105-i is input to the transmission power control device 106 having the same configuration as the conventional one, and received by each terminal. The transmission power instruction signal PW-i may be generated so that the S / N matches the standard S / N.

  FIG. 5 shows an example of the configuration of the transmission power control apparatus 106 when the terminal apparatus has the structure of the second embodiment and the modem apparatus 105 outputs the control signal SN-i (i = 1 to N−1). Indicates.

  The power control signal SN-i is input to a low-pass filter 401-i (i = 1 to N−1) corresponding to each terminal, and after removing a high-frequency component that fluctuates at a frequency higher than necessary, an inverse calculator 402 -I (i = 1 to N-1) is converted into a signal corresponding to the reciprocal of the S / N value. The output of the reciprocal calculator 402-i is added by the adder 403, and the addition result is reciprocally converted again by the reciprocal calculator 404. The output of the reciprocal calculator 404 is supplied to a multiplier 405-(i = 1 to N−1), and the output of the reciprocal calculator 402-i (i = 1 to N−1) is multiplied. The calculation result is output as a transmission power instruction signal PW-i (i = 1 to N−1) for each terminal. The transmission power instruction signal PW-i in this case represents a weighting factor of the transmission power, and the signal PW-i is set such that the lower the S / N value of the terminal device, the higher the transmission power than other terminals. The value of is determined.

  The transmission power instruction signal PW-i is supplied to the modem 105-i shown in FIG. 2 corresponding thereto. In the modem 105-i, the transmission power instruction signal PW-i is input as a power control input to the amplifier 204 of the transmission circuit system, thereby transmitting with the power corresponding to the S / N state of each terminal device. A signal is output.

  In the above configuration, the pilot signal transmitted from the base station and the transmission signal (data signal) transmitted from the base station to each terminal device are transmitted at substantially the same point in the same frequency band. The attenuation that occurs in the received data signal of each terminal device in accordance with the distance from the terminal is substantially equal to the attenuation that occurs in the pilot signal. Further, the noise power generated in the pilot signal and the data signal is equal.

  Therefore, as in the above-described embodiment, each terminal apparatus measures the S / N based on the received power of the pilot signal and the noise power extracted using the S / N measurement orthogonal code at that time. Is transmitted to the base station as a power control signal (PC or SN), and the base station performs transmission control of the data signal with transmission power inversely proportional to S / N for each terminal based on the power control signal. The S / N of the received signals at can be made equal.

  FIG. 16 is a diagram illustrating an effect when transmission power control is performed so that the S / N of each terminal becomes equal according to the present invention. According to the present invention, the power control is performed so that the transmission power of the signal to the terminal B located near the base station is smaller than the transmission power of the signal to the terminal A located near the cell boundary. The received power of the signals at terminals A and B are as shown at 920 and 922, respectively.

  The power control described above is performed in the same manner in cells adjacent to each cell, and the control works in a direction to reduce the total transmission power of each base station. The received power of the interference signal reaching the terminal near the base station from the base station of another cell is 921, and the received power of the interference signal reaching the terminal at the cell boundary is 923, respectively. To reduce. This power reduction effect corresponds to about 7.4 dB in a spread spectrum communication system having a structure in which regular hexagonal cells are repeatedly arranged, for example. Further, since the power of the interference signal is reduced, the number of terminals that can simultaneously communicate in each cell (the number of terminals accommodated by the base station) can be increased, and can be increased up to about 5.5 times the conventional maximum. In addition, since the electric power control mentioned above is open loop control, stable control is performed.

  FIG. 6 shows a third embodiment of the terminal device according to the present invention. In this embodiment, the S / N measurement is obtained from the reception power of the transmission signal (data signal) addressed to each terminal and the reception power of the noise signal instead of the above-described pilot signal. In the figure, the same reference numerals are given to the same circuit elements as those in FIG. 4, and these circuit elements have the same functions as those in FIG.

  In this embodiment, the transmission signal destined for the terminal despread with the orthogonal code Wi is accumulated for a certain period by the accumulator 308, and the output is input to the decoder 309, while this is input to the squarer 325. The instantaneous power of the received signal is obtained, and the instantaneous power of the received signal is used as the second input of the S / N measuring device 326. The first input of the S / N measuring device 326 is given the instantaneous power of noise despread with the orthogonal code Wn and output from the squarer 312, thereby obtaining the S / N of the received signal. The S / N of the received signal is mixed with the transmission data signal by the mixer 317 as the power control signal SN = i, and then transmitted from the antenna 301 via the encoding circuit 318, the multiplier 320, and the high frequency circuit 321. The

  The received signal S / N may be differenced from the reference S / N and transmitted to the base station as a power control signal PC, as in the first embodiment.

FIG. 7 shows another embodiment of the power control apparatus 106 of the base station. In this embodiment, the power control signal SN-i (i = 1 to N-1) separated by each modem 105i (i = 1 to N-1) is converted into a low-pass filter 601-i (i = 1 to N-). 1), after removing unnecessary high frequency fluctuation components, the S / N target value output from the target value S / N generation circuit 602 is output by the comparator 603-i (i = 1 to N−1). The difference between the actual S / N and the target S / N is integrated for each terminal by the integrator 604-i (i = 1 to N−1). The output of each integrator is given to output amplifier 204 shown in FIG. 2 as transmission power instruction signal PW-i (i = 1 to N−1) for each terminal.
With this transmission power instruction signal, the power of the transmission signal is controlled so that the S / N ratios of all terminals are equal. In this embodiment as well, closed-loop control is performed, and the S / N of each terminal is controlled to match the target S / N even if there is some nonlinearity in the transmission system.

  FIG. 8 shows a fourth embodiment of the terminal device. In this embodiment, the S / N measurement device 316 in the first embodiment described in FIG. 3 and the S / N measurement device 326 in the third embodiment described in FIG. 6 are used in combination. That is, S / N information of the pilot signal is obtained from the S / N measuring device 316, and S / N information of the received signal is obtained from the S / N measuring device 326. These two types of S / N information are mixed with transmission data by a mixer 327 and transmitted via an encoding circuit 318, a multiplier 320, a high frequency circuit 321, a circulator 302, and an antenna 301.

  FIG. 9 shows the configuration of the transmission power control apparatus 106 in the base station when the terminal apparatus has the configuration of the fourth embodiment. In the base station, each modulation / demodulation device 105-i receives two types of power control signals sent from the terminal device, that is, S / N (S / N-ip) of the pilot signal and S / N (S of the received signal). / N-id) and output.

  Among these, SN-ip (i = 1 to N−1) which is the S / N of the pilot signal is the circuit shown in FIG. 5 including circuit elements 401-i, 402-i, 403, 404, and 405-i. A first weight value of transmission power for each terminal is generated with the same circuit configuration as in FIG. On the other hand, the SN-id (i = 1 to N−1) that is the S / N of the received signal is the same as that of the circuit shown in FIG. 7 including the circuit elements 601-i, 602, 603-i, and 604-i. A second weight value of transmission power for each terminal is generated with a circuit configuration. By causing the second weight value to act on the first weight value as a correction value, a transmission power instruction signal PW-i (i = 1 to N−1) for each terminal is obtained. Here, the time constant of the low-pass filter 601-i is set to a value sufficiently larger than the time constant of the low-pass filter 401-i.

  According to each of the embodiments described above, when the position of the terminal device is close to the base station and the reception state of the signal from the base station is very good, there is a possibility that the transmission power for this terminal will be very small. . In this case, a lower limit value may be set for the transmission power for the terminal, and control may be performed so that the transmission power does not fall below a predetermined value.

The figure which shows an example of a structure of the base station apparatus in the communication system of this invention. The figure which shows the detail of the modem apparatus 105-i of the said base station apparatus. The block diagram which shows the 1st Example of the terminal device applied to the communication system of this invention. The block diagram which shows the 2nd Example of the terminal device applied to the communication system of this invention. The figure which shows the 1st Example of the transmission power control apparatus of a base station apparatus. The block diagram which shows the 3rd Example of the terminal device applied to the communication system of this invention. The figure which shows the 2nd Example of the transmission power control apparatus of a base station apparatus. The block diagram which shows the 4th Example of the terminal device applied to the communication system of this invention. The figure which shows the 3rd Example of the transmission power control apparatus of a base station apparatus. The figure which shows the whole structure of the mobile communication system of this invention. The figure which shows an example of the orthogonal code used for spectrum spreading. The figure which shows the structure of the base station apparatus in a prior art. The figure which shows an example of a structure of the modulation / demodulation apparatus of the base station apparatus in a prior art. The figure which shows one example of a structure of the terminal device in a prior art. The figure for demonstrating the relationship between the signal component from the base station in the cell in a conventional communication system, and the interference component from another cell. The figure for demonstrating the relationship between the signal component from the base station in the cell in the communication system of this invention, and the interference component from another cell.

Explanation of symbols

104: Pilot signal generator, 105: Modulator / demodulator, 106: Transmission power controller, 102, 306: Orthogonal code generator, 201, 318: Encoder, 202: Multiplier for performing first spreading, 203: Multiplier that performs second order spreading, 204: Variable gain amplifier for adjusting transmission power, 205: Multiplier that performs despreading, 207, 308, 311 and 314: Accumulator, 208, 309: Decoder, 304: Multipliers that perform first-order despreading, 307, 310, and 313: Multipliers that perform second-order despreading, 328: Absolute value computing units, 312, 315, and 325: Square computing units, 320: Code spreading 316, 326, 329: S / N measuring device, 330: comparator, 317, 327: mixer, 401, 601: low-pass filter, 402, 404: reciprocal calculator, 603: adder Vessel, 604: integrator.

Claims (8)

In a spread spectrum communication system that performs spread spectrum communication between a base station and a terminal device, the base station assigns a specific orthogonal code among a plurality of orthogonal codes orthogonal to each other for control, and The signal is subjected to spread modulation with the remaining orthogonal codes other than the orthogonal code, and each terminal apparatus determines the value of the noise component obtained by despreading the received signal by the specific orthogonal code and the received signal as one of the other The S / N is measured from the value of the signal component obtained by the despreading process using the orthogonal code, the power control signal corresponding to the measurement result is transmitted to the base station, and the power received by the base station from each terminal device Control the power of the transmission signal for each terminal device according to the control signal,
Each of the terminal devices obtains a value of a signal component for the S / N measurement by despreading the received signal with a unique orthogonal code assigned to the terminal itself. A transmission power control method in a system. In a spread spectrum communication system that performs spread spectrum communication between a base station and a terminal device, the base station assigns a specific orthogonal code among a plurality of orthogonal codes orthogonal to each other for control, and The signal is subjected to spread modulation with the remaining orthogonal codes excluding the orthogonal code, and each terminal device converts the received signal to the noise component value obtained by despreading the received signal with the specific orthogonal code and any other received signal. The S / N is measured from the value of the signal component obtained by the despreading process using the orthogonal code, the power control signal corresponding to the measurement result is transmitted to the base station, and the power received by the base station from each terminal device Control the power of the transmission signal for each terminal device according to the control signal,
In the spread spectrum communication system, each terminal apparatus obtains a value of a signal component for the S / N measurement by despreading a received signal with an orthogonal code assigned for a pilot signal. Transmission power control method. In a spread spectrum communication system that performs spread spectrum communication between a base station and a terminal device, the base station assigns a specific orthogonal code among a plurality of orthogonal codes orthogonal to each other for control, and The signal is subjected to spread modulation with the remaining orthogonal codes other than the orthogonal code, and each terminal apparatus determines the value of the noise component obtained by despreading the received signal by the specific orthogonal code and the received signal as one of the other The S / N is measured from the value of the signal component obtained by the despreading process using the orthogonal code, the power control signal corresponding to the measurement result is transmitted to the base station, and the power received by the base station from each terminal device Control the power of the transmission signal for each terminal device according to the control signal,
Each terminal apparatus despreads the received signal with a unique orthogonal code assigned to the terminal itself or an orthogonal code assigned for a pilot signal, thereby allowing signal components for the S / N measurement to be transmitted. A transmission power control method in a spread spectrum communication system, characterized in that a value is obtained and information indicating the measured S / N value is transmitted to the base station as the power control signal. In a spread spectrum communication system that performs spread spectrum communication between a base station and a terminal device, the base station assigns a specific orthogonal code among a plurality of orthogonal codes orthogonal to each other for control, and The signal is subjected to spread modulation with the remaining orthogonal codes other than the orthogonal code, and each terminal apparatus determines the value of the noise component obtained by despreading the received signal by the specific orthogonal code and the received signal as one of the other The S / N is measured from the value of the signal component obtained by the despreading process using the orthogonal code, the power control signal corresponding to the measurement result is transmitted to the base station, and the power received by the base station from each terminal device Control the power of the transmission signal for each terminal device according to the control signal,
Each terminal apparatus despreads the received signal with a unique orthogonal code assigned to the terminal itself or an orthogonal code assigned for a pilot signal, thereby allowing signal components for the S / N measurement to be transmitted. A transmission power in a spread spectrum communication system characterized in that a value is obtained and information indicating a difference between the measured S / N value and a predetermined S / N value is transmitted to the base station as the power control signal. Control method. The base station responds to the power control signal received from each terminal device , and the power of the transmission signal addressed to each terminal device so that the S / N value of the data signal transmitted to each terminal device is substantially the same. The transmission power control method in the spread spectrum communication system according to any one of claims 1 to 4 , wherein control is performed. In response to the power control signal received from each terminal device, the base station controls the power of the transmission signal addressed to each terminal device so that the S / N of the data signal transmitted to each terminal device is kept constant. The transmission power control method in the spread spectrum communication system according to any one of claims 1 to 4 , characterized in that: In response to the power control signal received from each terminal apparatus, the base station controls the power of the transmission signal addressed to each terminal apparatus so that the sum of transmission powers for a plurality of terminal apparatuses decreases. The transmission power control method in the spread spectrum communication system according to any one of claims 1 to 4 . When the base station sets a predetermined lower limit value for the power of the transmission signal addressed to each terminal device, and the transmission power determined based on the power control signal received from the terminal device is equal to or lower than the lower limit value, the terminal The transmission power control method in the spread spectrum communication system according to any one of claims 5 to 7 , wherein a signal is transmitted to the apparatus with the power of the lower limit value.

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