MXPA99009809A - Method of and apparatus for controlling transmission power in a communication system - Google Patents

Abstract

A forward link power control mechanism in a remote station (6) measures reverse link power control bits which are transmitted by one or more base stations (4a, 4b, 4n) on a forward traffic channel (10a). At the remote station (6) the reverse link power control bits from multiple base stations (4a, 4b, 4n) or multiple signal paths are measured, combined, and filtered to yield an improved measurement of the forward link signal quality. The reverse link (12a, 12b) power control bits which are deemed unreliable are omitted from use in the power control loop. The remote station (6) generates a set of forward link power control bits in accordance with the measurements and transmits these bits to all base stations (4a, 4b, 4n) in communication with the remote station (6). Each base station (4a, 4b, 4n) adjusts its gain of the forward traffic channel (10a) in accordance to its measurement of the forward link power control bit. The gains of the forward traffic channels (10a) of the base stations (4a, 4b, 4n) are corrected periodically so that erroneous reception of the forward link power control bits by the base stations do not accumulate.

Description

METHOD AND APPARATUS FOR CONTROLLING THE TRANSMISSION POWER IN A COMMUNICATION SYSTEM BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates to a method and apparatus for controlling transmission power in a communication system. More specifically, the present invention relates to a new and improved method and apparatus for power control in a CDMA communication system.

II. Description of the Related Art The use of multiple access modulation techniques with code division (CDMA) is one of several techniques for facilitating communications in which a large number of system users are present. Other techniques of multiple access communication systems, such as time division multiple access (TDMA) and frequency division multiple access (FDMA) are known in the art. However, CDMA extended spectrum modulation techniques have significant advantages over other modulation techniques for multiple access communication systems. The use of CDMA techniques in a multiple access communication system is described in U.S. Patent No. 4,901,307, entitled "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS", assigned to the assignee of the present invention and incorporates as reference in the present. The use of CDMA techniques in a multiple access communication system is further described in U.S. Patent No. 5,103,459, entitled "SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM", also assigned to the transferee of the present invention and is incorporated herein by reference. Additionally, the CDMA system can be designed to comply with the "Base Station Compatibility Standard-TIA / EIA / IS-95-A Mobile Station for a Dual-Band Extended Broadband Spectrum System", referred to hereinafter as the IS-95-A or TIA / ETA / 1S-95-A standard. CDMA, by its inherent nature of being a broadband signal, offers a form of frequency diversity by extending the signal energy over a wide bandwidth. Therefore, selective frequency fading affects only a small part of the bandwidth of the CDMA signal. The diversity of space or route is obtained through the multiple po i? I i de de de de de a a signal through simultaneous links to a mobile user or remote station through two or more base stations. Additionally, path diversity can be obtained by exploiting the multi-path environment through extended spectrum processing by allowing signals arriving with different propagation delays to be received and processed separately. Examples of route diversity are illustrated in U.S. Patent No. 5,101,501, entitled "METHOD AND SYSTEM FOR PROVIDING A SOFT HANDFAR IN COMMUNICATIONS IN A CDMA CELLULAR TELEPHONE SYSTEM", and U.S. Patent Number 5,109,390, entitled "DIVERSITY RECEIVER IN A CDMA CELLULAR TELEPHONE SYSTEM", both assigned to the assignee of the present invention and incorporated herein by reference. The return link refers to a transmission from a remote station to a base station. In the return link, each remote transmission station acts as an interference to the other remote stations in the network. Therefore, the return link capacity is limited by the total interference due to transmissions from other remote stations. The CDMA system increases the capacity of the return link by transmitting few bits, thus using less power and reducing interference, when the user is not talking.

To minimize interference and maximize the capacity of the return link, the transmission power of each remote station is controlled by three return link power control circuits. The first power control circuit adjusts the transmission power of the remote station by adjusting the transmission power inversely proportional to the power received in the sending link. In an IS-95-A system, the transmission power is given by psaiida = -73- in rada »where the power received by the remote station is given in dBm, the satellite is the transmission power in the remote station given in dBm, and -73 is a constant. That power control circuit is often called the open circuit. The second power control circuit adjusts the transmission power of the remote station such that the quality of the signal, as measured by the energy per bit to noise plus interference ratio, Eb / I0 / of the received return link signal in the base station it is maintained at a predetermined level. This level is referred to as the set point of Eb / I0- The base station measures the Eb / I0 of the return link signal received at the base station and transmits a bit of return link power control to the remote station in the shipping traffic channel in response to the Eb I0 measure. The inverted power control bits are set 16 times for 20 msec frame, or at a speed of 800 bps. The send traffic channel carries the return link power control bits together with the data from the base station to the remote station. This second circuit is often called the closed circuit. The CDMA communication system transmits data packets as discrete data frames. In this way, the desired level of performance is typically measured by the frame error rate (FER). The third power control circuit adjusts the set point of Eb / I0 such that the desired level of performance is maintained, as measured by the FER. The Eb / I0 required to obtain a given FER depends on the propagation conditions. This third circuit is often called the outer circuit. The power control mechanism for the return link is described in detail in U.S. Patent No. 5,056,109, entitled "METHOD AND APPARATUS FOR CONTROLLING TRANSMISSION POWER IN A CDMA CELLULAR MOBILE TELEPHONE SYSTEM", assigned to the assignee of the present invention. and incorporated as reference herein. The send link refers to a transmission from a base station to a remote station. In the send link, the transmission power of the base station is controlled for several reasons. A high transmission power from the base station can cause excessive interference with the signals received at the other remote stations. Alternatively, if the transmit power of the station is too low, the remote station may receive erroneous data transmissions. Fading of terrestrial channels and other known factors can affect the quality of the send link signal as received by the remote station. As a result, each base station tries to adjust its transmission power to maintain the desired level of performance at the remote station. The power control in the send link is especially important for data transmissions. The data transmission is typically asymmetric with the amount of data transmitted on the send link that is greater than the return link. With a power control mechanism, effective in the sending link, where the transmission power is controlled to maintain the desired level of performance, the total capacity of the sending link can be improved. A method and apparatus for controlling the transmit power of the sending link is described in U.S. Patent Application Serial No. 08 / 414,633, entitled "METHOD AND APPARATUS FOR PERFORMING FAST FORWARD POWER CONTROL IN A MOBILE COMMUNICATION SYSTEM", subsequently in the present patent application '633, filed on March 31, 1995, assigned to the assignee of the present invention and incorporated herein by reference. In the method described in the '633 patent application, the remote station transmits an error indicator bit message (EIB) to the base station when a transmitted data frame is received in error. The EIB can be either a bit contained in the return traffic channel box or a separate message sent in the return traffic channel. In response to the EIB message, the base station increases its transmission power to the remote station. One of the disadvantages of this method is the long response time. The processing delay covers the time interval from the time the base station transmits the frame with inadequate power to the time when the base station adjusts its transmit power in response to the error message from the remote station. This processing delay includes the time taken for (1) for the base station to transmit the data box with inadequate power, (2) for the remote station to receive the data frame, (3) for the remote station to detect the frame error (e.g., a frame erasure), (4) the remote station transmits the error message to the base station, and (5) the base station receives the error message and appropriately adjusts its transmit power. The send traffic channel box must be received, demodulated and decoded before the EIB message is generated. Then, the frame of the return traffic channel having the EIB message must be generated, encoded, transmitted, decoded and processed before the bit can be used to adjust the transmission power of the send traffic channel. Typically, the desired level of performance is one percent of FER. Therefore, on average, the remote station transmits an error message indicative of a frame error for 100 frames. According to IS-95-A, each frame is 20 msec long. This type of EIB-based power control works well to adjust the transmit power of the send link to handle modification conditions, but due to its low speed it is ineffective in fading except in the slower fading conditions. A second method for controlling the transmission power of the sending link uses the Eb / I0 of the signal received at the remote station. Since the FER is dependent on the Eb / I0 of the received signal, a power control mechanism can be designed to maintain the E / I0 at the desired level. This design is difficult if the data is transmitted on the shipping link at variable rates. In the send link, the transmit power is adjusted depending on the data rate of the data box. At lower data rates, each data bit is transmitted for a longer period of time by repeating the modulation symbol as described in TIA / EIA / IS-95-A. The energy per bit E is the accumulation of the received power over a period of time of one bit and is obtained by accumulating the energy in each modulation symbol. For an equivalent amount of E, each bit of data can be transmitted at a transmission power proportionally lower than the lower data rates. Typically, the remote station does not know the transmission rate beforehand and can not compute the received bit energy Eb until the complete data frame has been demodulated, decoded, and the data rate of the data frame determined. Thus, the delay of this method is similar to that described in the U.S. Patent Application described above Serial No. 08 / 414,633 and the speed is a power control message per frame. This is in contrast to the approach of the return link in which there may be a power control message (bit) sixteen times per frame as in TIA / EIA / IS-95-A. Other methods and apparatuses for performing the quick link power control of shipping are described in the aforementioned U.S. Patent Application Serial Number 08 / 414,633, U.S. Patent Application Serial No. 08 / 559,386, entitled "METHOD AND APPARATUS FOR PERFORMING FAST FORWARD POWER CONTROL IN A MOBILE COMMUNICATION SYSTEM", filed on November 15, 1995, United States Patent Application Serial No. 08 / 722,763, entitled "METHOD AND APPARATUS FOR MEASURING LINK QUALITY IN A SPREAD SPECTRUM COMMUNICATION SYSTEM ", filed September 27, 1996, United States Patent Application Serial Number 08 / 710,335, entitled" METHOD AND APPARATUS FOR PERFORMING DISTRIBUTED FORWARD POWER CONTROL ", filed September 16, 1996, and U.S. Patent Application Serial No. 08 / 752,860, entitled "ADJUSTMENT OF POWER CONTROL THRESHOLD / MEASUREMENTS BY ANTICIPATING POWER CONTR OL COMMANDS THAT HAVE NOT BEEN EXECUTED ", filed on November 20, 1996, all assigned to the assignee of the present invention and incorporated herein by reference. The fundamental difference between the send link and the return link is that the transmission speed does not need to be known in the return link. As described in U.S. Patent No. 5,5056,109 mentioned above, at lower speeds, the remote station does not transmit in a continuous manner. When the remote station is transmitting, the remote station transmits at the same power level and the same waveform structure despite the transmission speed. The base station determines the value of a power control bit and sends this bit to the remote station 16 times per frame. Since the remote station knows the transmission speed, the remote station can ignore the power control bits that correspond to the times when it was not being transmitted. This allows rapid control of return link power. However, the effective speed of power control varies with the transmission speed. For TIA / EIA / IS-95-A, speeds of 800 bps for full speed frames and 100 bps for 1/8 speed frames. An alternative, return link architecture is described in U.S. Patent Application Serial No. 08 / 654,443, entitled "HIGH DATA RATE CDMA WIRELESS COMMUNICATION SYSTEM", subsequently Patent Application '443, filed on May 28. of 1996, assigned to the assignee of the present invention and incorporated herein by reference. According to the patent application '443, an auxiliary pilot is introduced in the return link. The level of the pilot is independent of the transmission speed in the return link. This allows the base station to measure the pilot level and send the return link power control bit to the remote station at a constant speed.

SUMMARY OF THE INVENTION The present invention has for its purpose to provide a method and apparatus for a high speed power control of sending link. An object of the present invention is to improve the response time of the send link power control circuit and allow dynamic adjustment of the transmit power on the send link by measuring the quality of the link power control bits. of return that are transmitted on the send traffic channel multiple times within a box. Measurements during short time intervals allow the base station to dynamically adjust the transmit power to minimize interference to other base stations and maximize the capacity of the send link. The improved response time allows the power control circuit to effectively compensate for slow fades. For fast fades, the block interleaver in the communication system is effective. In one aspect, the invention provides a method for controlling a transmission power in a CDMA system comprising the steps of: measuring the amplitude values of a first set of bits; compare amplitude values against a target energy level; and generating a second set of bits in response to the comparison step, wherein the transmission power is adjusted according to the second set of bits. In another aspect, the invention provides an apparatus for controlling a transmission power in a CDMA system comprising: a first power control circuit for maintaining a quality of a received signal at a target energy level, the first control circuit of power receiving a first set of bits and an objective energy level and providing a second set of bits in response to the first set of bits and the target energy level; and a second power control circuit to maintain a measured performance of the received signal, the second power control circuit that receives indicators of the frame errors and a performance threshold and that provides the target energy level to the first circuit of power control in response to measured performance and performance threshold. In a further aspect, the invention provides a controller for a base station in a wireless communication system comprising one or more base stations and one or more remote stations, the controller comprising a transmitter for transmitting communication signals together with the signaling signals. power control in a transmission channel, a receiver for receiving signals in a transmission channel from a remote station and representing an attribute of the communication signals received in the transmission channel by the remote station; a controller for processing the signals received by the receiver and controlling, depending on the processed signals, the power control signals transmitted by the transmitter in a transmission channel. The invention also provides a remote station for use in a wireless communication system comprising one or more base stations, and one or more remote stations, the remote station comprising a receiver for receiving one or more communication signals together with the signals of power control transmitted by a base station on a transmission channel, a controller for processing the signals received by the receiver to determine an attribute of the communication signals received by the receiver, and a transmitter for transmitting signals on a transmission channel which represents the attribute of the received communication signals. In one embodiment of the present invention, the remote station measures the return link power control bits that are transmitted at a rate of 800 bits per second in the send traffic channel. The return link power control bits are punched in the data stream of the send traffic channel. The gain of the power control bits is adjusted together with the gain of the send link data bits. Nevertheless, different from the data bits, the transmission level of the. Power control bit is not scaled according to the speed of the data. The quality of the measured signal from the power control bits is used to adjust the transmit power of the base stations. It is an object of the present invention to improve the response time of the send link power control by the use of the power measurements of the return link power control bits. The return link power control bits are transmitted at a rate of 800 bps. In this way, the sending link power control mechanism of the present invention can perform a quality measurement of the send traffic channels, received periodically every 1.25 msec. The measurements can be transmitted to the base stations for use in adjusting the transmission power of the sending link. The improved response time allows base stations to effectively compensate for slow fading in the channel and improve the performance of the shipping traffic channels. It is another object of the present invention to increase the capacity of the sending link by allowing quick adjustments in the transmission power of the base stations. The power control mechanism of the present invention allows base stations to transmit at the minimum transmission power necessary to maintain the necessary level of performance. Since the total transmit power of the base stations is set, the minimum transmission for a given task results in a saving of transmit power that can be used for other tasks. It is still another object of the present invention to provide a reliable delivery link power control mechanism. At the remote station, the return link power control bits from multiple sectors of a base station or multiple signal paths from the same sector are combined to produce an improved measurement of the signal quality of the send link. The return link power control bits that appear unreliable can be omitted from use in the power control circuit. At base stations, the send link power control binaries are received by all base stations in communication with the remote station. The gains of the send traffic channels of the base stations are corrected periodically, so that the erroneous reception of the sending link power control bits by the base stations is not cumulative. It is still another object of this invention to provide a mechanism for adjusting the power of the sending link to the desired frame error rate, similar to that made by the outer circuit for the return link. It is still another object of this invention to provide a mechanism for communicating the power control bits between the base stations. The power control bits that control the transmit link transmission power may have been received directly or not, in the different base stations. The present invention provides base stations that receive power control bits, erroneous with the information necessary to update their transmission power of the sending link.

BRIEF DESCRIPTION OF THE DRAWINGS The characteristics, objects and advantages of the present invention will become more apparent from the detailed description set forth below of an embodiment of the invention when taken in conjunction with the drawings in which similar reference characters they identify correspondingly to all the length and in which: Figure 1 is a diagram of a communication system that incorporates the present invention and that comprises a plurality of base stations in communication with a remote station; Figure 2 is an example block diagram of a base station and the remote station; Figure 3 is an example block diagram of a shipping traffic channel; Figure 4 is an example block diagram of a demodulator within the remote station; Figure 5 is an example block diagram of a decoder within the remote station; Figure 6 is an example block diagram of a power control processor within the remote station; Figure 7 is a synchronization diagram of the send and return link power control channels; and Figure 8 is a timing diagram of a gain correction mechanism within the control, power of the send link.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES In a system embodying the present invention, the base station transmits the return link power control bits together with the data in the send traffic channel. The return link power control bits are used by the remote station to control its transmit power, to maintain the desired level of performance while minimizing interference to other remote stations in the system. The power control mechanism for the return link is described in U.S. Patent Application Serial No. 08 / 414,633, mentioned above. Due to the sensitivity to processing delays, the return link power control bits are not encoded. Actually, the power control bits are drilled in the data (see Figure 3). In this sense, drilling is a process by which one or more code symbols are replaced by the power control bits. In the exemplary embodiment, the return link power control bits are transmitted at a rate of 800 bps, or a power control bit for each time interval of 1.25 msec. The time interval is called a power control group. The transmission of the power control bits at evenly spaced intervals can result in the base station sending power control bits to multiple remote stations at the same time. This results in a peak in the amount of the transmitted power. As a result, the power control bits are placed pseudo-randomly within the power control group of 1.25 msec. This is achieved by dividing the time interval of 1.25 msec into 24 positions and randomly selecting, along with a long PN sequence, the position in which to drill in the power control bit. In the example mode, only one of the first 16 positions within the power control group is selected as a start position and the last 8 positions are not selected. The send traffic channel is a variable speed channel and the transmission power of the send traffic channel is dependent on the speed of the data. The performance of the send traffic channel is measured by the FER which is dependent on the bit energy Eb of the signal received at the remote station. At low data rates, the same energy per bit is extended for a longer period of time, resulting in a lower transmission power level. In the example mode, transmissions over the shipping link are made in accordance with TIA / EIA / IS- 95 -A. Standard IS-95-A provides the transmission using one of two speed sets. The speed set one supports data rate of 9.6 kbps, 4.8 kbps, 2.4 kbps, and 1.2 kbps. The data rate of 9.6 kbps is encoded with a 1/2 speed convolutional encoder to produce a symbol rate of 19.2 kbps. The data encoded for the lower data rate is repeated N times to obtain the symbol rate of 19.2 kbps. The speed set 2 supports the data rates of 14.4 kbps, 7.2 kbps, 3.6 kbps and 1.8 kbps. The data rate of 14.4 kbps is encoded within a 1/2 speed convolutional encoder overflow to obtain a speed of 3/4. In this way, the symbol speed is also 19.2 kbps, for the data rate of 14.4 kbps. The speed set selects by the base station by the initiation stage of a call and typically remains in effect for the duration of the communication, although the speed set can be changed during the call. In an example embodiment, the duration of the return link power control bit is 2 symbols wide (104.2 μsec) for speed set 1 and a width symbol (52.1 μsec) for speed set 2 .

In this specification, the transmission gain of the send traffic channel refers to the energy per bit Eb (traffic) of the transmitted data signal. A frame with a lower data rate consists of few bits transmitted in the specified bit energy, and therefore, is transmitted with less power. In this way, the power level of the send link traffic channel is scaled with the data rate of the frame currently being transmitted. The transmission gain of the return link power control bits refers to the energy per bit Eb (power control) of the return link power control bits punctured in the data stream. Each bit of return link power control has the same duration, and therefore, the power level of these bits does not depend on the data rate of the frame in which they are drilled. These characteristics of the power control bits are exploited by the mode to provide the improved send link power control mechanism. The operation of the send link power control causes the base station to make adjustments in the gain of the traffic channel. In the example mode, each adjustment to the gain of the traffic channel is also applied to the gain of the coulul bits of the return link power, so that the two gains are adjusted together. The quality of the send link signal, as received by the remote station, is determined by measuring the amplitude of the return link power control bits that are transmitted in the send traffic channel. The quality of the data bits is not measured directly, but rather is inferred from the measured amplitude of the return link power control bits. This is reasonable, since the power control bits and the traffic data are equally affected by changes in the propagation environment. Therefore, the mode operates well if the amplitude of the data bits is maintained at a known ratio to the amplitude of the power control bits. Typically, the return link power control bits are transmitted at a lower level of transmit power. Additionally, the power control bits can be transmitted from multiple base stations within the communication system. A more accurate measurement of the amplitude of the power control bits is obtained by receiving the power control bits, adjusting the phase and amplitude of the power control bits according to the phase and amplitude of the pilot signal, and filter the adjusted amplitude of the power control bits. The filtered amplitude of the power control bits is used to control the transmit power of the base station such that the quality of the send link signal received at the remote station is maintained at the desired level. The send link power control mechanism operates two power control circuits. The first power control circuit, the closed circuit, adjusts the transmit power of the base station such that the quality of the filtered amplitude of the return link power control bits received at the remote station is maintained at a level of target energy. In most situations, the target energy level is determinant of the FER of the shipping traffic channel. The remote station requests the base station to adjust the transmit power to the send link by sending the send link power control bits on the return link. Each send link power control bit causes the base station to increase or decrease the gain of the corresponding traffic channel. The second power control circuit, the external circuit, is the mechanism by which the remote station adjusts the target energy level in order to maintain the desired FER. In order to improve the effectiveness of the shipping link power control mechanism, for example, to combat slow fading in the channel, the closed circuit is designed to operate at a high speed. In the example mode, the return link power control bits for which quality measurements of the send link signal are made, are transmitted at 800 bps and the send link power control bits are also They are sent on the return traffic channel at 800 bps. In this way, the transmission power of the base station can be adjusted at speeds of up to 800 times per second. However, because the send power control bits are sent unencrypted and with minimal power, some sending power control bits can not be received satisfactorily at the base station. A base station may choose to ignore any send power control bit that it deems to be insufficiently reliable. In the exemplary embodiment, the second send link power control circuit, the outer circuit, updates the target energy level once each frame or 50 times per second. The outer circuit adjusts the value of the target energy level that results in the desired performance of FER. When the propagation environment is not changing, the outer circuit must quickly determine the appropriate value of the target energy level and maintain the target at that level. When there is a change in the characteristics of the channel (for example, an increase in the level of interference, a change in the speed of a mobile user, or the appearance or disappearance of a signal path), it is likely that a different target energy level will be required in order to continue the operation to the same FER. Therefore, the outer circuit must quickly move the target to the new level to adapt to the new conditions.

I. Description of the Circuit With reference to the figures, Figure 1 represents an exemplary communication system embodying the present invention which consists of multiple base stations 4 in communication with multiple remote stations 6 (only one remote station 6 is shown for simplicity) . The system controller 2 is connected to all the base stations 4 in the communication system and the public switched telephone network (PSTN) 8. The system controller 2 coordinates the communication between the users connected to the PSTN 8 and the users in the remote stations 6. The transmission of data from the base station 4 to the remote station 6 occurs in the sending link through the signal routes 10 and the transmission from the remote station 6 to the base station 4 occurs in the Return link through signal 12 routes. The signal path can be a straight path, such as signal path 10a, or a reflected path, such as a signal path 14. The reflected route 14 is created when the signal transmitted from the base station 4a is completely reflected from the reflection source 16 and arrives at the remote station 6 through a different route than the line of the straight route. Although illustrated as a block in Figure 1, the reflection source 16 is the result of artifacts in the environment in which the remote station 6 is operating, for example a construction or other structures. An exemplary block diagram of the base station 4 and the remote station 6 embodying the present invention is shown in Figure 2. The data transmission in the send link originates from the data source 20 which provides the data to the encoder 22. An exemplary block diagram of the encoder 22 is shown in Figure 3. Within the encoder 22, the CRC encoder 62 encodes the data with a CRC polynomial which, in the example embodiment, conforms to the CRC generator described in the IS-95-A standard. The CRC encoder 62 append the CRC bits and insert a set of code end bits to the data. The formatted data is provided to the convolutional encoder 64 which convolutionally encodes the data and provides the encoded data to the symbol repeater 66. The symbol repeater 66 repeats each symbol Ns number of times to maintain a fixed symbol rate at the output of the symbol. symbol repeater 66. The repeated symbols are provided to the block interleaver 68. The block interleaver 68 reorders the symbols and provides the interleaved data to the modulator (MOD) 24. Within the modulator 24, the interleaved data is extended by the multiplier 72 with the long PN code that mixes the data so that they can be retrieved only by the remote receiving station 6. The extended PN data is multiplexed through the MUX 74 and the multiplier 76 is provided which covers the data with the Walsh code corresponding to the traffic channel assigned to the remote station 6. The data covered with Walsh extends further. with the PNI and PNQ short codes by the multipliers 78a and 78b, respectively. The unwanted data of short PN is provided to the transmitter (TMTR) 26 (see Figure 2) that filters, modulates, converts and amplifies the signal. The modulated signal is routed through the duplexer 28 and transmitted from the antenna 30 on the send link through the signal path 10. The duplexer 28 can not be used in some base station designs.

The MUX 74 is used to drill the return link power control bits in the data stream. The power control bits are one-bit messages that command the remote station 6 to increase or decrease the return link transmission power. In the example mode, a bit of power control is drilled in the data stream in each power control group of 1.2 msec. The duration of the return link power control bits is predetermined and can be made dependent on the speed set used by the system. The location at which the return link power control bit is drilled is determined by the long PN sequence from the long PN generator 70. The output of MUX 74 contains both data bits and return link power control bits. With reference to Figure 2, at the remote station 6, the send link signal is received by the antenna 102, routed through the duplexer 104, and provided to the receiver (RCVR) 106. The receiver 106 filters, amplifies , demodulates and quantifies the signal to obtain the baseband I and Q, digi talized signals. The baseband signals are provided to the demodulator (DEMOD) 108. The demodulator 108 extends the baseband signals with the short PNI and PNQ codes, discovers the de-spread data with the Walsh code identical to the Walsh code used in the base station 4, extends the data discovered with Walsh with the long PN code, and provides the demodulated data to the decoder 110. Within the decoder 110 shown in Figure 5, the interleaver 180 of blocks reorders the symbols of The demodulated data and provides the de-interleaved data to the Viterbi decoder 182. The decoder 182 Viterbi decodes the convolutionally encoded data and provides the decoded data to the CRC verification element 184. The CRC check element 184 performs the CRC check and provides the verified data to the data collector 112.

II. Measurement of the Power Control Bit A sample block diagram illustrating the circuit for measuring the power of the return link power control bits is shown in Figure 4. The digitized baseband I and Q signals of the receiver 106 are provided to a bank of correlators 160a to 160m (later only 160). Each mapper 160 may be assigned to a different signal path from the same base station 4 or a different transmission from a different base station 4. Within each assigned mapper 160, the baseband signals are de-extended with the PNI and PNQ codes shorted by multipliers 162. The short PNI and PNQ codes within each correlator 160 have a unique offset according to the base station 4 from which the signal was transmitted and corresponding to the propagation delay experienced by the signal that is demodulated by that correlator 160. The unselected data of short PNs are discovered by the multipliers 164 with the Walsh code assigned to the traffic channel that is received by the correlator 160. The discovered data is provided to the filters 168 which they accumulate the energy of the data discovered during a symbol time. The filtered data of the filters 168 contains bits of both data and power control. The unseeded short PN data of the multipliers 162 also contains the pilot signal. In the base station 4, the pilot station with all the zero sequences corresponding to the Walsh code 0. Thus, it is not necessary to discover with Walsh to obtain the pilot signal. The de-extended data of short PNs are provided to the filters 166 which perform low pass filtering of the de-spiked data to remove signals from the other orthogonal channels (eg, traffic channels, paging channels, and access channels) transmitted in the send link by the base station 4. The two complex signals (or vectors) corresponding to the filtered pilot signal and the filtered data and the power control bits are provided to the dot product circuit 170 which computes the product of point of the two vectors in a manner well known in the art. The exemplary embodiment of the knit product circuit 170 is described in detail in U.S. Patent No. 5,506,865, entitled "PILOT CARRIER DOT PRODUCT CIRCUIT", assigned to the assignee of the present invention and incorporated by reference herein. The dot product circuit 170 projects the vector corresponding to the filtered data in the vector corresponding to the filtered pilot signal, multiplies the amplitude of the vectors, and provides a scalar output, oriented S jd) to the demultiplexer (DEMUX) 172 The notation s-, (m) is used to denote the output of the correlation més? Rac 160m, during the period of the symbol jt,? Mo. The remote station 6 is aware of whether the period of the current symbol of the current frame corresponds to a data bit or to a return link power control bit. Accordingly, the DEMUX 172 routes the vector of the correlator outputs, s _-, = (s-, (1), s, (2), ..., s, (M)), to any data combiner 174 or power control processor 120. The data combiner 174 adds its vector inputs, de-extends the data using the long PN code, and produces the demodulated data that is presented to the decoder 110 shown in Figure 5. The return link power control bits are processed by the power control processor 120, shown in detail in Figure 6. The bit accumulator 190 accumulates one or more symbols Sj (m) for the duration of one power control bit to form the power control bits return link bj (m). The bi (m) notation is used to denote the return link power control bit corresponding to the correlation month 160m, during the ies? or power control group. The vector of the power control bits, bi = (bi (l), bi (2), ..., Bi (M)), is presented to the accumulator 192 of identical bits. In TIA / EIA / IS-95-A, when more than one base station 4 is in communication with the same remote station 6, the base stations 4 can be configured to transmit return link power control bits either identical or not identical Base stations 4 are typically configured to send identical power control bit values when physically located in the same location, such as when they are different sectors of a cell. Base stations 4 that do not send the same values of the power control bit are typically those that are physically located in different locations. The IS-95-A standard also specifies a mechanism by which the base stations 4 that are configured to send identical power control bits are identified to the remote station 6. Additionally, when the remote station 6 is receiving the transmission from a single base station 4 through multiple propagation routes, the return link power control bits received in these routes are inherently identical. The identical bit accumulator 192 combines the return link power control bits bi (m) which are known to be identical. The output of the bit accumulator 192 in this manner is a vector of return link power control bits, B1 = (b1 (l), b1 (2), ..., B? (P)), which corresponds to the return link power control bitstreams, independent of P. The signal bit vector, sgn (Bi (p)), is presented to the logic circuit 194 for return link power control. The IS-95-A standard specifies if any of the signals is negative, the remote station 6 decreases its transmission power level. If all the signal bits sgn (Bi (p)) are positive, the remote station 6 increases its transmit power level. The return link power control logic circuit 194 processes the vector of the signal bits sgnfBiíp)), as specified in IS-95-A. The output of the return link power control logic circuit 194 is a single bit which indicates whether the remote station 6 must increase or decrease its transmission gain for the purpose of the return link power control of the closed circuit. This bit is provided to the transmitter 136 (see Figure 2) which accordingly adjusts the gain. The amplitude of the return link power control bits, and not their polarity (eg, the positive or negative signal), is indicative of the quality of the signal as measured by the remote station 6. The accumulator 196 of non-identical bits therefore removes the modulated data and operates on the absolute value of the return link power control bits | Bj. (p) | which is combined according to the formula: where the factor ß specifies the order of non-linearity and P is the number of independent link return power control bitstreams. In the example mode, ß = l corresponds to a measurement of the absolute value of the amplitude of the power control bit and ß = 2, corresponds to the measurement of the energy of the power control bit. Other values can be used for ß; depending on the design of the system, without departing from the scope of the present invention. The output of the accumulator 196 of non-identical bits is the value i which is indicative of the energy per bit received from the return link power control sub-channel during the power control group. The return link power control bits are not encoded, and therefore, they are especially vulnerable to errors caused by interference. The fast response time of the closed loop return link power control minimizes the effect of these errors on the performance of the return link power control since these erroneous adjustments to the transmission gain of the remote station 6 they can be compensated in the subsequent power control groups. However, since the amplitude of the power control bits is used as an indication of the quality of the send link signal, the filter 198 is used to provide a more reliable measurement of the amplitude of the control bits of the receiver. power. The filter 198 can be implemented using one of a number of designs known in the art, such as an analog filter or a digital filter.

For example, filter 198 may be implemented as a finite impulse response filter (FIR) or an infinite impulse response filter (1IR). Using an FIR filter implementation, the filtered power control bits can be calculated as: where x1 is the amplitude of the power control bit computed by the accumulator 196 of non-identical bits during the power control group, a3 is the coefficient of the filter derivation jes, and yx is the amplitude filtered from the power control bit of the filter 198. Since the delay is sought to be minimized, the coefficients of the FIR filter derivations can be selected such that the largest coefficients of the FIR filter are those with the smallest indices ( for example, a0> a?> a2 > ...). In the exemplary embodiment described herein, the processing performed by the remote station 6 in order to execute the fast send link power control has been described in such a way that it shares several components used by other subsystems with the remote station 6. For example, the correlator 160a is shared with the data demodulation subsystem, and the accumulators 190 and 192 are shared with the return link power control subsystem. The practice of the present invention is not dependent on any particular implementation of the other subsystems of the remote station 6. It should be obvious to one skilled in the art that other implementations may be contemplated to perform the send power control processing as described herein, and therefore, are within the scope of the present invention.

III. External Send Link Power Control Circuit The filtered amplitude and x of the return link power control bits from the filter 198 is indicative of the quality of the send link signal received at the remote station 6. The threshold comparison circuit 202 compares the filtered amplitude y¿ against a z level of target energy. In the exemplary embodiment, if yx exceeds z, the remote station 6 transmits a zero bit ('0') in its send link power control sub-channel to indicate that each base station 4 that is transmitting a traffic channel of sending to remote station 6 must reduce the gain of that traffic channel. Inversely, if yj is less than z, the remote station 6 transmits a bit of one ('1') in its send link power control sub-channel to indicate to each base station 4 that it must increase the gain in the traffic channel of shipment. These zeros (O's) and ones ('l's) are the values of the send link power control bits. Although the present invention is described in the context of a send power control bit per power control group, the present invention is applicable to the use of more bits for a higher resolution. For example, the threshold comparison circuit 202 can quantify the difference between the filtered amplitude and? Of the reverse link power control bit and the target energy value z at multiple levels. For example, a two-bit message in the send link power control sub-channel can be used to indicate any of four levels for the amount (and x-z). Alternatively, the remote station 6 may transmit the filtered amplitude value y, on the send link power control sub-channel. The base station 4 does not have to adjust its transmit power to each power control group. Due to the low power level of the return link power control bits, the remote station 6 may receive the bits with error, or with a large degradation due to the noise and sensitivity of other users. The filter 198 improves the accuracy of the measurement, but does not completely mitigate the error. In the exemplary embodiment, the base station 6 may omit the transmission of a send link power control bit to the base station 4 if it determines that the measurement is not reliable. For example, the remote station 6 can compare the filtered amplitude and i against a minimum value of energy. If yx is below the minimum energy value, the remote station 6 can ignore the value yi for this power control group and reports the base station 4 accordingly (for example, by not transmitting a link power control bit). of sending to the base station 4 when using a value of a set of send link power control values to indicate a low received power). Additionally, the send link power control bits are also transmitted at a low energy level. Therefore, the base station 4 can also compare the send link power control bit against its own minimum power value and not act on the bits that fall below the minimum power value. In the exemplary mode, the remote station 6 makes an absolute determination, based on the output of the CRC verification element 194 as well as other frame quality metrics, such as the Yamamoto metric, and the number of error symbols of the symbol. encoded, as to whether the table has been decoded correctly. This determination is summarized in the delete indicator bit (EIB) which is set to '1' to indicate a frame erasure, and is set to '0' otherwise. In the following, it is assumed that the remote station 6 makes use of an EIB in order to determine whether the received frames are in error. In the preferred embodiment, the EIB used for the purposes of controlling the outgoing link power control external circuit is the same as the EIB actually transmitted on the return link. However, an independent determination of the validity of the received frame for the specific purpose of controlling the outer circuit may also be elaborated and is within the scope of the present invention. In the example mode, the external circuit is updated once per frame, once every 16 power control groups. The external circuit updates the target energy level z at the remote station 6. This mechanism is performed by the threshold adjustment circuit 200 shown in Figure 6. As each frame is decoded, the frame quality information ßi, in the form of an EIB, is provided to the threshold adjustment circuit 200 as indicated in Figure 6. The threshold adjustment circuit 200 updates the value of the target energy level z and makes the new target energy level available to the threshold comparison circuit 202. In the first embodiment, the threshold adjustment circuit 200 updates the value of z according to the equation: where zk is the target energy level in the kth chart, ßk-i is the frame error in (k-l) es? mo? is the size of an ascending step that is to be applied to the target energy level, and d is a size of a descent that is to be applied to the target energy level. In the example mode, e ^ -i is equal to 1 if there was a frame error for the (k-l) es or data frame and zero if it is otherwise. The values for? and d are selected to provide a desired level for the FER. Typically,? It is big and d is small. This selection creates a saw-tooth type pattern zk. When a frame error occurs, zk is substantially increased to minimize the probability of another frame error. When there is no other frame error, z? decays slowly to minimize transmission power. In the example mode, the values for zk,? and d are on the dB scale, although a linear scale can also be used for these variables. In the second mode, the step sizes? and d functions of the target energy level, current zk i, can be made, so that the correction to zk is dependent on the target energy level, current. In this way, equation (3) can be modified as: In the exemplary mode, the remote station 6 terminates the demodulation of the data frame and updates the target energy level zk during the midpoint of the subsequent frame. If the data box (k-l) is? M0 is received with error, is the probability of a frame error for the kés greater? or data box. This is because any adjustment to the target energy level will not have an immediate impact on the performance of the FER until the system has had sufficient time to transition to the new point of operation. Therefore, the second of the two consecutive table errors should not be interpreted as indicative of the performance of the target energy level value that was updated only from the first frame error. In the preferred embodiment, the base station 4 increases the gain of the traffic channel completely after the first frame error, then ignores a second frame error if it occurs in the following frame. Applying this concept to the second modality described above, station (4) becomes: In the example mode, the external circuit power control mechanism is standardized across all remote stations 6 to ensure compliance by all remote stations 6. The values of? and d can be transmitted to each remote station 6 by the base station 4 during the initiation stage of a call. It is also possible to specify new values for these parameters by the base station 4 during the course of the call. In a communication system that conforms to the IS-95-A standard, the gains of the send traffic channels are typically decreased when the remote station 6 enters a smooth transfer. This is done without any degradation in the performance of FER; since the data bits received in the remote station 6 of the base stations 4 combine to produce a large, composite signal before decoding. However, the return link power control circuit within the remote station 6 does not combine the return link power control bits received from the base stations 4 since these bits are independent. The decrease in gain in the send traffic channel can increase the bit error rate of the power control bitstream transmitted in the send traffic channel, and therefore, degrade the power control mechanism return link. To put an end to this situation, the gain of the power control bits is typically reinforced when the remote station 6 enters a smooth transfer. This results in the gain of the return link power control bits being slightly greater than the gain of the data bits if the remote station 6 is in a smooth transfer. In the modality, absolute values of the power control bits of the different base stations 4 are combined according to equation (2). In this way, the reinforcement in the gain of the power control bits results in higher values for yi in relation to the data bits. The higher values yi cause the remote station 6 to request an inappropriate decrease in the transmit power of the base station 4 which may result in one or more frame errors in the send traffic channel. In this case, the z value of target energy adjusted by the external circuit increases automatically. After a while, the external circuit then adjusts the target energy value z to the new nominal value. To combat these effects, yx can be scaled before the comparison with the target energy level z. Alternatively, the target energy level z may be increased slightly when the remote station 6 enters the smooth transfer. This can reduce the likelihood of these errors. In the embodiment, the comparison of the amplitude and x filtered to the z level of target energy is performed within the power control processor 120 (see Figure 2). Additionally, the update of the target energy level according to equation (3), (4) or (5) is performed within the power control processor 120. The processor 120 of the controller can be implemented in a microcontroller, a microprocessor , a digital signal processing circuit (DSP), or an ASIC programmed to return the function as described herein.

IV. Transmitting the Send Link Power Control Bit (s) The send link power control bits can be transmitted to the base station 4 by one of several methods. In the exemplary embodiment, each remote station 6 has a send link power control channel on the return link that is dedicated for the transmission of the send link power control bits. In the alternative mode, where the dedicated power control channel is not available, the send link power control bits can be drilled or multiplexed into the stream of return channel data bits in a manner similar to that made in the shipping traffic channel. In the exemplary embodiment, the send link power control bits are transmitted to the base station 4 on a dedicated send link power control channel. A method and apparatus for providing a dedicated send link power control channel is described in detail in the aforementioned U.S. Patent Application Serial No. 08 / 654,446. The transmission synchronization diagrams of the send and return link power control bits are shown in Figure 7. Each power control group, delineated by the discontinuous, weighted marks in the timelines, one bit The return link power control is transmitted on the forwarding traffic channel, as shown in the upper diagram of Figure 7. In the example mode, a return link power control bit is transmitted on each power control group of 1.25 msec and each bit of return link power control is two duration symbols for speed set 1. Additionally, each return link power control bit can initiate from one of the two positions within the power control group, depending on the long PN sequence. The remote station 6 processes the return link power control bit and transmits a send link power control bit in the return power control channel to the base station 4 as a pulse. In the exemplary embodiment, the pulse is sent as positive polarity to indicate a sending link power bit with value ('0') and with negative polarity to indicate a value ('1'). The duration of the pulses are design parameters that are described in the following modalities. Other selections for other parameters may be contemplated and are within the scope of the present invention. In the first mode, the send link power control bits are transmitted as pulses of a length of 1.25 msec, starting at 0.625 msec after the last possible power control bit position (ie, the 16es? md) in the shipping traffic channel. This configuration is illustrated in the middle diagram of Figure 7, where the "delayed" parameter is set to 0.625 msec. A delay of 0.625 msec allows some time for remote station 6 to correct the routes of the send link signal in a worst case scenario. The correction properly aligns the signals of different signal paths before being combined and ensures that the return link power control bit of the previous power control group is processed by the time the power control bit is transmitted. shipping link. However, the actual delay of receiving the return link power control bit to the send link power control bit transmission may be as great as 1.45 msec when the return link power control bit it is transmitted in the most precedent possible bit position. In the second mode, the send link power control bits are transmitted as pulses of length of 1.25 msec, starting at approximately 0.050 msec after the position of the most recent possible power control bits (ie, the? ges?) in the send traffic channel. This configuration is identical to the first mode, except that the "delay" parameter is set to 0.05 msec. In the worst-case scenario, the return link power control bit of the pre-link power control group will not have been processed, due to the correction delays, by the time the next link power control bit of sending is scheduled to be transmitted. The remote station 6 can be configured to repeat the most recent send link power control bit. However, the correction delays are typically in the tens of μsecs and so on, in most cases, the send link power control bit will still be able to take account of the power control bit processing. return link, most recent. It should be evident that the "retard" parameter can be chosen to optimize the performance of the system. In a third embodiment, shown in the background diagram of Figure 7, the send link power control bit is transmitted as a short pulse of approximately 0.41 msec in duration at a predetermined amount of time ("lag 2" in the Figure 7) after reception of the return link power control bit in the send traffic channel. The duration of the send link power control bit is chosen to be small enough so that it will be terminated at the time the next sending link power control bit is sent, even in the worst case when the interval The most recent time possible is used in the current power control group, and the earliest possible time interval is to be used in the next power control group. In the example mode, the amount of delay is set to 0.050 msec (delay2 = 0.050 msec). As illustrated in Figure 7, this embodiment involves higher transmission power for the pulse duration in order to transmit the same amount of energy during a short pulse duration. A disadvantage of this method is that the transmission of large amounts of energy within short pulses at 800 Hz can potentially cause interference in the audio band to people with hearing aids. However, since the remote station 6 transmits the send link power control bits in a fixed amount of time after the return link power control bits and the return link power control bits are placed randomly, the send link power control bits are also placed randomly. By randomly distributing the starting position of the power control bits, the energy is spectrally distributed at 800 Hz and the audio interference is minimized.

Additionally, the send link power control channel transmitted on the return link from the remote station 6 is one of the many data streams transmitted on the return link. Since the power in the bit is low, the net variation in the output power of the remote station 6 due to the power control bits is small. Finally, in a fourth embodiment, the send link power control bit is transmitted after a fixed amount of time, delay 2 = 0.050 ms, after receipt of a return link power control bit. In this mode, however, the duration of the power control bit of the send link is variable, and the transmission link power control bit transmission is continued until the next power control bit is programmed. of shipping link. Since the remote station 6 can send each send link power control bit with the same gain or it can adjust the transmission gain based on the bit duration in order to send each bit in the same amount of power. With reference to Figure 2, the send link power control bits are processed by the power control processor 120 with the remote station 6. The power control processor 120 computes the power link control bits of the power link. send that are sent in the return link and send the bits to the modulator (MOD) 134. The modulator 134 covers the bits with the Walsh code that corresponds to the power control channel, inverted, extends the data covered with the codes of PN long and short, and provides the data unlinked to the transmitter (TMTR) 136. the transmitter 136 may be implemented as described in United States Patent Application Serial No. 08 / 654,443, mentioned above. The transmitter 136 filters, modulates and amplifies the signal. The modulated signal is routed through the duplexer 104 is transmitted from the antenna 102 in the return link through the signal path 12. In the base station 4, the return link signal is received by the antenna 30, it routes through the duplexer 28, and is provided to the receiver (RCVR) 50. The receiver 50 filters, amplifies and converts from RF to LF the signal to obtain the baseband signals. The baseband signals are provided to the demodulator (DEMOD) 52. The demodulator 52 de-extends the baseband signals with the short PN codes, deconverts the unzipped data with the Walsh code identical to the Walsh code used in the station remote 6, and provides the demodulated data to the controller 40. The demodulated data includes the send link power control units. The controller 40 may adjust the gain of the send traffic channel and / or the transmission power of the base station 4 and as indicated by the send link power control bits.

V. Base Station Response In the mode, the base station 4 receives the send link power control bits that are transmitted in the return power control channel and controls the gain of the send traffic channel. In the exemplary mode, upon receipt of ('1') for the send link power control bit, the base station 4 increases the gain of the send traffic channel. Upon receiving a zero ('0'), the base station 4 decreases the gain. The amount of increase or decrease of the gain is dependent on the implementation and system considerations. The example mode, the increase or decrease of gain can be steps from 0.5 dB to 1.0 dB, although other step sizes can be used. The step size for the gain increase may be the same or different from the step size for the gain decrease. Additionally, the step size in the gain can be made dependent on the gains of other send traffic channels in the base station 4. The present invention is applicable to all pitch sizes in the gain setting. The base station 4 can also adjust the increase in gain, decrease in gain, or both as a function in the speed and fading conditions of the remote station 6. The base station 4 does this since the optimum step size is a function of the fading conditions and the speed of the remote station 6. For example, at very high speeds, smaller step sizes can work well since the bit rate of power is not fast enough to allow fast fading. Since the interleaver of the send link averages the fading, the large power control step sizes tend to add amplitude jitter to the waveform of the send link. However, rapid power control is necessary to dynamically adjust the average waveform to the correct level. The demodulator 52 within the base station 4 can estimate the fading conditions and the speed of the remote station 6. The search elements in the demodulator 52 can determine the number of the multi-route components currently received and compute their profile. These search elements are described in U.S. Patent No. 5,109,390, entitled "DIVERSITY RECEIVER IN A CMDA CELLULAR TELEPHONE SYSTEM" and in U.S. Patent Serial No. 08 / 316,177, entitled "MULTIPATH SEARCH PROCESSOR FOR A SPREAD MULTIPLE SPECTRUM" ACCESS COMMUNICATION SYSTEM ", filed on September 30, 1994, both are assigned to the assignee of the present invention and are incorporated by reference herein. The demodulator 52 can also estimate the velocity of the remote station 6 by estimating the return link frequency error using demodulation techniques that are well known in the art. The frequency error is approximately 2 * fc * v / c + e where fc in the operating frequency, v is the speed of the remote station 6, c is the speed of light, and e is the residual frequency error of the remote station 6. According to TIA / EIA / IS-95-A, the remote station 6 measures the frequency that is received in the sending link and uses this to adjust the transmission frequency in the return link. An analysis of the adjustment of the transmission frequency based on the received, measured frequency is described in U.S. Patent Application Serial No. 08 / 283,308, entitled "METHOD AND APPARATUS FOR CONTROLLING POWER IN A VARIABLE RATE COMMUNICATION SYSTEM ", filed on July 29, 1994, assigned to the assignee of the present invention and incorporated herein by reference, remote station 6 does this to remove the error of its own oscillator. result in a duplication of the error of the Doppler frequency of the signal received in the base station 4, since there is a frequency error of fc «v / c in the sending link and a frequency error of fc * v / c in the return link The error in the adjustment of the transmission frequency at the remote station 6 of the received frequency is e.For a high-speed moving body, the error e is relatively small. providing speed and multi-route estimates to the controller 40 which then uses this information to determine the increase and decrease of gain and pitch sizes.The base station 4 has a maximum transmission power that is It is determined by the limitations of system design and FCC regulations. Inevitably, the base station 4 will experience a situation in which it does not have sufficient available power when the remote station 6 requests a gain increase. If the base station 4 limits or ignores the gain increase command due to inadequate transmission power, the FER for the send traffic channel may increase. When this occurs, the target energy level in the remote station 6 can be increased substantially and rapidly. This is due to the fact that the step up? in equation (5) it is typically large to the downward step d. If the poor channel condition disappears or the base station 4 is capable of transmitting additional power to the remote station 6, the time taken for the target energy level z to settle to the appropriate range may be prolonged since the downlink d is typically little. In the preferred embodiment, the base station 4 transmits new values for the ascending step? and the descending step d during the time when the FER in the submission link is higher than the nominal one. In the mode, the FER performance of the send traffic channel is related to the target energy level z. In this way, the base station 4 can directly adjust the target energy level z, to obtain the desired FER. For example, if the base station 4 realizes that the system was highly charged and one or more base station 6 needs to operate high FERs, the base station 4 can alter the target energy levels of these remote stations 6 by transmitting the new levels z of target energy to the base stations 6. Alternatively, can the base station 4 manipulate the target energy levels by ordering these remote stations 6 to use the new ascending steps? and the descending steps d. In the exemplary embodiment, if the base station 4 is not able to respond to the power control command from the remote station 6, the base station 4 adjusts the target energy level, or the ascending and descending steps, to prevent The power control circuit collides with the maximum transmit power and operates in the non-linear region. To ensure that the sending link power control mechanism works properly and that no remote station 6 requests more or less transmission power than is necessary for the required level of performance, the base station 4 can inspect the FER of the traffic channel of shipment. In the example mode, the remote station 6 transmits an error message to the base station 4, if an error data frame is received. This error message may be the deletion indicator bit (EIB) described previously. The base station 4 can inspect the error messages from the remote station 6, calculate the FER and manipulate the target energy level z of the remote station 6, by assigning the appropriate step up values to the remote station 6? and the downward step d.

SAW . Gain Correction Mechanism The delivery link power control mechanism of the present invention performs best when delays are minimized. In order to compensate for the fading of the shipping traffic channel, the base station 4 must apply the increase or decrease in transmission power, as requested by the remote station 6, as soon as possible. When the remote station 6 is not in a smooth transfer, the send link power control bits are received by a single base station 4 which adjusts the gain of the send traffic channel in response to the link power control bit. of shipment. A remote station 6 in soft transfer communicates with multiple sectors in a simultaneous manner. In the exemplary embodiment, an individual channel element in a base station 4 is used to control communication between the remote station 6 and all sectors in the soft transfer. Therefore, the base station 4 can quickly adjust the transmission power of all sectors in the reception of the send link power control bit from the remote station 6. A remote station 6 in the soft transfer can communicate with multiple base stations 4 in a simultaneous manner. The method and apparatus for performing distributed link power control, is described in detail in U.S. Patent Application Serial No. 08 / 710,335, described above. Some base stations 4 can not receive the current from the send link power control bits or can not control the power bit control current with sufficient reliability. In the present invention, a send link power control correction mechanism is used to ensure that the gains of the send traffic channels of all the base stations 4 in the set of active members of the remote station 6 are adjusted appropriately and that the erroneous reception of send link power control bits by the base stations 4 is not accumulated. In the exemplary mode, when the remote station 6 is not in soft handoff, the gain of the traffic channel of sending the base station 4 receiving the strongest return link signal is used by the base stations 4 in the set of active members. The power control correction mechanism can be achieved by the following modalities. In the first embodiment, to ensure that the gains of the approximately equal delivery traffic channels for all base stations 4 in communication with remote station 4, the selected send link power control bit stream is provided to all the base stations 4. For each frame, all base stations 4 in the active member set send the send link power control bits that were received by the base stations 4 to a selector within the system controller 2. The selector selects the power control bits from the base station 4 that receives the strongest reverse link signal. The power control bits selected from this base station 4 are then provided to all base stations 4 in the set of active members. Each base station 4 receives the power control bits in the send link, selected from the selector, compares the selected bits with the bits that are actually received and processes them, and readjusts the gains in the send traffic channels to adjust with the send link power control bits, selected. The base stations 4 can send the power control bits to the selector within the controller 40 in backspace frames. The selection of backspace frames can be made according to the existing procedures used in the TIA / EIA / IS-95-A systems. After processing, the selector can send the sending link power control bits, selected to all base stations 4 in the backboxes carrying the user's traffic for transmission to the remote station 6. In the second mode, each station base 4 sends the gain of the send traffic channel to the selector in each frame. The selector selects the gain corresponding to the base station 4 that received the strongest return link signal. The selector sends the selected gain to all the base stations 4 in the set of active members and the base stations 4 therefore update their gains. The selected gain is only the gain value sent from the selector to the base stations 4 in the existing TIA / EIA / IS-95-A systems. This gain value is carried in the backward formats that are sent in the A3 interface as specified in the TIA / EIA / IS-634-A standard that is incorporated herein by reference. Due to processing delays, updating the earnings of the shipping traffic channels requires some care. In the exemplary mode, each base station 4 may adjust the gain of its send traffic channel based on its measurement of the send link power control bits from the remote station 6. However, the selector may determine that Power control bits received by the other base station 4 should be used. This decision is usually not made until a predetermined amount of time after the base stations 4 have applied their own measurements of the send link power control bits. Therefore, the base stations 4 need to adjust the gains of their send traffic channels according to the power control bits, which the base stations 4 actually received and the power control bits selected from the other selector. The base stations 4 also need to account for the delay between the original gain settings and the reception of the power control bits, selected from the other selector. In the exemplary embodiment, each base station 4 relates the gains that were used by that base station 4 in each update period. The selector sends the selected power control bit (or the selected gain) of the base station 4 which was determined to be the most likely to have received the power control bit correctly. Each base station 4 then compares the gains that were stored in the update period to that received from the selector and updates the gain in the current time interval by the difference. The Gi gain for the i1- * 1010 power control bit is like this: Gl = s_, +? (2¿1-i) + (sJ UUI-U) IUl * p "« [i / ttj ((, M * í [l, < // «ií,), (6) where Gj. Is the profit during the month? 0 time interval, is the value (one or zero) of the year? or power control bit, v is the gain step size, M is the number of power control bits per frame, p is the misalignment in the time intervals from the start of a frame to the time where the bits of power control are sent from the base station 4 to the selector (0 <p <Ml), Hk is the gain of the send traffic channel specified by the selector during kés? p10 where k = Li / MJ, q is the misalignment in the time intervals from the start of a frame to the time where the updated gain is received in the base station 4 from the selector (0 <q <Ml), and dxj equal to 1 if i = j and 0 in another case. In the exemplary embodiment, M is equal to 16 although other values of M may be used and is within the scope of the present invention. An example synchronization diagram of the send link power control correction mechanism is shown in Figure 8. The send traffic channel frames and the return link frames are aligned almost exactly in time, biased just because of the delay in airborne propagation. The frames (of 20 m duration) are graded as k, k + 1, k + 2, and k + 3, and are delineated by non-continuous, thick marks, in Figure 8. The table k of the data stream return link is received at the base station 4 and after some processing delay, some time is decoded during the frame k + 1 as indicated by the block 210. Meanwhile, the base station 4 is also processing the orders of Send link power control with considerably less processing delay. In this manner, the send link power control bits, shaded in the lower timeline of Figure 8 represent the 20 msec block of the send link power control bits that are sent to the selector in the same backspace box together with frame k of the return link data stream. During frame k + 2 the selector selects the send link power control bits from the base station 4 which received the strongest return link signal and sends these selected power control bits to all base stations 4 in the set of active members of the base station 6, in block 212. Typically, the selected power control bits are sent in a backward frame. Shortly thereafter, within the k + 2 frame the base stations 4 receive the power control bits selected from the selector and correct the gains of the forwarding traffic channels according to the selected power control bits in the manner described. previously, in block 214. At the beginning of table k + 3, base stations 4 transmit with the updated gains, as indicated by block 216. The above example shows three processing delay tables from the time the station Remote 6 transmits the send link power control bits to the time the base stations 4 correct the gains of the send traffic channels. However, in the exemplary embodiment, each base station 4 can adjust the gain of its send traffic channel in response to its measurement of the send link power control bit. In this way, each base station 4 can quickly adjust the gain of its send traffic channel on its own and the processing delay is minimized. The send link power control correction mechanism, wherein the power control bits from the base station 4 that measure the strongest return link signal are used to correct the gains of the send traffic channels of the transmission link. other base stations 4 in the set of active members, ensures that the erroneous reception of the power control bits by the base station 4 does not accumulate. Other embodiments to ensure correct operations of the send link power control mechanism by all the base stations 4 can be contemplated within the scope of the present invention. Although the present invention is described in terms of the send link power control mechanism, the inventive concept described herein is also applicable for the return link power control. In the foregoing description of the preferred embodiments are provided to enable any person skilled in the art to make or use the present invention. The various modifications of these modalities will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other modalities, without the use of the inventive faculty. In this way, the present invention is not intended to be limited to the modalities shown herein, but rather to be in accordance with the broader scope subsisting with the principles and the new features described herein.

Claims (26)

1. CLAIMS 1. A method for controlling a transmission power in a CDMA system, the method comprises: measuring amplitude values of a first set of bits, comparing the amplitude values against a target energy level; and generating a second set of bits in response to the comparison step; wherein the transmit power is adjusted according to the second set of bits. The method according to claim 1, wherein the target energy level is adjusted at an initial stage of a communication and / or in response to a measured performance of the received signal. The method according to claim 1 to 2, further comprising: transmitting the second set of bits to a destination station; wherein the transmission power of the destination station is adjusted according to the second set of bits. The method according to claim 1, 2 or 3 further comprising: adjusting the target energy level exposed to a measured performance of a received signal. The method according to any preceding claim, further comprising: correcting the transmit power according to a set of commands from a system controller. The method according to any one of the preceding claims, wherein the measurement further comprises: receiving at least one signal path corresponding to the first set of bits; demodulating each of the at least one signal path to obtain a pilot signal and filtered data; compute a point product of the pilot signal and the filtered data to obtain a scalar output with signal; and combining the scalar outputs with signal from at least one signal path to obtain a combined scalar output; wherein the amplitude values of the first set of bits are equal to the scalar, combined output. The method according to claim 6, further comprising: filtering the combined scalar output to obtain the amplitude values of the first set of bits. The method according to claim 6 or 7, wherein the combination comprises: coherently adding the scalar outputs with signal from at least one signal path carrying an identical stream of the first set of bits; and adding the absolute values of the scalar outputs with signal from at least one signal path carrying a non-identical stream of the first set of bits. The method according to claim 4, or any of claims 5 to 8 depending on it, wherein the adjustment comprises: increasing the target energy level by an ascending step in response to an indication of a frame error; and decrease the target energy level by a downward step in response to an absence of a frame error. The method according to claim 9, wherein the adjustment comprises: maintaining the target energy level if the amplitude values of the first set of bits fall below a minimum energy level. The method according to claim 10, wherein the ascending step and the descending step are adjusted in an initial stage of a communication and / or in response to the measured performance of the received signal. The method according to claim 9 or 10, wherein the ascending step and the descending step are functions of the target energy level. The method according to claim 9, wherein the adjustment comprises: maintaining the target energy level in response to an indication of two consecutive frame errors; and wherein the increment step responds to an indication of a frame error and an absence of a frame error in two previous data frames. The method according to claim 5, or any of claims 6 to 13 as dependent thereon, wherein the correction comprises: receiving at least one set of the second set of bits; and selecting a selected set of bits from at least one set of the second set of bits; wherein the transmission power is corrected according to the selected set of bits. The method according to claim 3, or any of claims 4 to 14 as dependent on them, wherein each bit of the second set of bits is transmitted after a fixed delay from the position of the latest power control bits possible of the first set of bios. The method according to claim 3, or any of the dependent claims 4 to 14, wherein each bit of the second set of bits is transmitted after a fixed delay of a bit received from the first set of bits. The method according to claim 3, or any of claims 4 to 14, depending on it, wherein each bit and the second set of bits is transmitted with a pulse that has a duration shorter than that of a control group of power. 18. An apparatus for controlling a transmission power in a CDMA system, comprising: a first power control circuit for maintaining a quality of a received signal at a target energy level, the first power control circuit receives a first set of bits and an objective energy level and providing a second set of bits in response to the first set of bits and the target energy level; and a second power control circuit for maintaining a measured performance of the received signal, the second power control circuit receives indicators of frame errors and a performance threshold and provides the target energy level to the first power control circuit in response to measured performance and performance threshold. The apparatus according to claim 18, wherein the first power control circuit comprises: a receiving means for receiving at least one signal path corresponding to the first set of bits; and a demodulator means for demodulating each of the at least one signal path to obtain a scalar signal output; a combining means for combining the scalar outputs with signal from at least one signal path to obtain a combined scalar output; and a comparison means for comparing the combined scalar outputs against the target energy level and for producing the second set of bits in response to the comparison. The apparatus according to claim 18 or 19, wherein the second power control circuit comprises: a threshold adjustment circuit means for increasing the target energy level by an ascending step in response to an indication of an error of frame and decrease the target energy level by a downward step in response to an absence of a frame error. The apparatus according to claim 19 or claim 20, wherein the demodulator means demodulates each of at least one signal path to obtain a pilot signal and filtered data, and wherein the demodulator means further comprises: of the dot product circuit to produce the scalar outputs with signal based on the pilot signal and the filtered data. 22. The apparatus according to any of claims 19 to 21, wherein the first power control circuit further comprises: a filter means for filtering the combined scalar output and obtaining a filtered output; and where the comparison means compares the filtered output against the target energy level. 23. The apparatus according to claim 20, wherein the target energy level is adjusted at an initial stage of a communication and / or in response to a measured performance of the received signal. The apparatus according to claim 20, wherein the ascending step and the descending step are adjusted in an initial stage of a communication and / or in response to a measured performance of the received signal. 25. A controller for a base station in a wireless communication system comprising one or more base stations and one or more remote stations, the controller comprising: a transmitter for transmitting communication signals together with power control signals in a first channel of transmission for a remote station; a receiver for receiving signals in a second transmission channel of the remote station, signals representing an attribute derived from the power control signals received in the first transmission channel by a remote station; and a processor for processing the signals received for the receiver and controlling independence of the processed signals and the power control signals transmitted by the transmitter in the first transmission channel. 26. A remote station for use in a wireless communication system comprising one or more base stations and one or more remote stations, the remote station comprising: a receiver for receiving one or more communication signals together with control signals transmitted by a base station with a first transmission channel; a processor for processing one or more signals received by the receiver to derive an attribute of one or more signals received by the receiver from the power counting signals; and a transmitter for transmitting, at a transmission power determined by the received power control signals, signals for the base station in a second transmission channel, these signals represent the attribute of the received communication signals.