FI92124C - Method for automatically adjusting transmitter power of a transceiver using direct sequence spreading suitable for a code division multiple access environment - Google Patents

Description

92124

Suitable methods koodijakomonikåyttoympåristoon suorasekvenssihajoitusta kåyttåvån låhetin receiver for automatic låhetintehon sååtåmiseksi in the 5 Tåmån invention is a method suitable for koodijakomonikåyttoympåristoon suorasekvenssihajoitusta kåyttåvån radiolåhetin- receiver for automatic låhetintehon sååtåmiseksi, wherein the receiver automatic-tisen gain sååtoon generated reference signal Kaay-10 tetåån låhettimen låhettåmån radio signal to the amplitude or to adjust the power.

Until now, the Direct Sequence Spectrum Technology (DS = Direct Sequence) technology has been applied mainly in military communications. There is little public information about the details of the technologies used there. The use of spread spectrum technology in Code Division Multiple Access (CDMA) cellular telephone systems (CDMA = Co-Division Division Multiple Access), such as those planned in the United States and Europe, will be its first 20 commercial applications. In a CDMA network, multiple mobile stations (e.g., radiotelephones) simultaneously use the same transmission and reception frequencies when communicating with a base station. In DS spread spectrum technology, the information to be transmitted is modulated (multiplied) by a pseudo-random code, where the bandwidth of the code signal is larger than the bandwidth of the information. Each mobile station has its own random or DS code, corresponding to which the base station has a corresponding so-called DS code. correlator. In reception, the pseudo-random code can be decoded by the correlator by knowing the code used in the transmission.

; In CDMA radio networks, the maximum number of users is reached when the transmissions of all mobile stations are received at the fixed station at the same power. For this reason, it is essential that the signal strengths of the mobile and fixed stations be monitored and adjusted according to the transmission and reception parameters of the devices. The most important control systems are the automatic power control of the transmitter (APC = Automatic Power Control), which adjusts the transmission power of the mobile station based on the distance 5 to the base station, and the automatic gain transmission (AGC = Automatic Gain Control), according to which the radio receiver receives the receiver. by.

There is little information on automatic power control in CDMA networks, but some theoretical analyzes of the effect of APC 10 on CDMA cellular network performance. In the United States, Qualcomm Inc. has developed a CDMA system that includes mobile stations and base stations. In the mobile station, control information from the base station is used to fine-tune the transmitter power. The base station measures the power of the signal it receives from the mobile station and, based on this information, sends a command to the mobile station to increase or decrease its transmission power. This method of power acquisition requires signaling between the base station and the mobile station.

The present invention provides various uses for implementing both automatic gain gain and automatic gain power in mobile stations of a CDMA network. The method according to the invention is characterized in that the setpoint signal obtained from the automatic gain of the receiver is determined on the basis of the sums of the squares of the real and imaginary part of the baseband signal composed of one or more predetermined time selections or their approximate values.

The various implementations of the output power of the mobile station have so far not received much attention in the known networks; in those FDMA and TDMA networks where this feature occurs, the harvest is performed by cascades from the base station. In the present invention, this power control, which is essential in CDMA networks for the reasons mentioned above, is thus performed in the mobile station independently, without loading the radio network and without causing 3 92,124 related signaling.

The method according to the invention can be applied, inter alia, in: - mobile stations of CDMA cellular telephone systems; 5 - In CDMA wireless local area networks (Cordless LAN); - In CDMA fire, burglary, burglar, etc. alarm systems.

The automatic transmission power yield-10 concept according to the invention is also suitable for use in diversity receivers.

The invention will now be described in more detail with reference to the accompanying drawings, in which

Figure 1 shows block diagrams of a DS spread spectrum receiver and transmitter of a mobile station 15 of a CDMA cellular network,

Figure 2 shows the principle of sampling a composite complex baseband signal.

Thus, Figure 1 shows a schematic block diagram of the TX radio parts of the RX and transmitter 20 of the CD spread spectrum receiver of the CDMA system. Antenna 1 receives a radio signal transmitted by a base station (not shown). The signal is routed through a duplex filter 12 to the RX front end 2, which includes gain, filtering and downmixing functions so that the center frequency of the output signal · '25 of the RX front end 2 is at the device's select frequency (IF). The local oscillator required for downmixing is located at the RX front end 2. For automatic gain, the RX front end 2 must either have an adjustable attenuator or an amplifier, or both. These operate on either the receive frequency, the select-30 frequency, or both. The AGC control can be analog (DC voltage) or digital (control word).

To keep the functions of blocks 2 and 3 in a linear operating range, block 2 or 3, or both, includes a broadband AGC that measures the signal power of the non-composite signal and uses this information to control the gain of block 2 4 921 24.

The IF signal is applied to quadrature block 3, which converts the IF signal into a sample sequence of the complex baseband signal. For this, block 3 contains 5 A / D converter functions. The mix from frequency to baseband may be analogous, after which the baseband signals are sampled and sample sequences II and Q1 are obtained. Another alternative is to directly sample the intermediate frequency signal and produce said sample sequences by digital signal processing. Sample queues II and Q1 still contain the DS spreading code.

The sampled baseband signal I1, Q1 is applied to the spectrum generation block 4. There, DS code phase acquisition and tracking is performed by the code produced by the code generator 5 and its various phases e (early), 1 (late) and n (nominal). . For example, a sliding correlation or a matched filter can be used to search for a code phase. Several different methods for code tracking have been proposed in the literature, one of which is the delay lock-20 loop method. When the code phase is in place and the tracking loop is locked, a complex baseband signal 12, Q2 composed of block 4 is obtained, which contains the information transmitted by the fixed station.

The assembled baseband signal is applied to blocks 6, 25 and 7. Block 6 includes data demodulation operation and decoding that decodes the information bits from the 12 and Q2 sample queues. Block 6 also includes carrier recovery, which can e.g. compensate for a portion of any 30 frequency errors in the receiver's local oscillator (block 2).

Block 7 implements the auto-validation setup algorithm. One part of the algorithm is a function that seeks to approximate the power or amplitude of the received signal from the samples 12 and Q2 of the composed complex baseband signal. This approximation can be done, for example, by calculating the mean of all successive time slots I22 2 2 2 + Q2, the sum of all 12 + Q2 values, or by looking for 2 2 the median 12 + Q2. An approximation is also obtained by averaging 12 + Q2 5 values that exceed a preset threshold.

In hardware implementations of the implementation, there is not always enough computing capacity in use, and upgrading to four in particular requires several program steps. The amount of computation can be reduced by using the algorithm and which approximate 2 2 10 quantities 12 + Q2. One example is known from the literature: max (I 12 I, | Q2I) + 0.5 * min (I 12 I, | Q2I), which approximates the quadratic root of 12 + Q2. The max operator takes the larger of the two numbers and the min operator 15 takes the correspondingly smaller. The absolute value operator takes the absolute value of the number. With this method, the number of raising operations to four is reduced by half.

The gain control algorithm may or may not be averaged over several time intervals of the received power approximation values. A suitable control algorithm is, for example, the PID algorithm generally known in control technology, so it will not be explained in more detail in this context.

The obtained approximation is compared with a reference value and their difference is controlled by a control algorithm which calculates a new 25 setpoint for the gain-changing elements of the RX front end 2. The setpoint signal is fed back to block 2 along line 15.

The search period of the time slots may be fixed and predetermined, or in block 7 it is observed how fast the signal power Pi 0 varies and the search period is adjusted accordingly. Figure 2 shows by way of example the sample sequences (12, Q2) and the 12 + Q2 sample sequence of the assembled complex baseband signal. The time interval ΔΤ of the two samples is the inverse of the sampling frequency of the block 3 A / D conversion. Time-35 spans Tn, Tr> +1 and are the search periods mentioned above. In Fig. 6 921 24, the search periods are all equally long in time, but the algorithm of block 7 can monitor the rate of change of the sample values of the I22 + Q22 sample sequence, and make the search period shorter if the rate of change is high, and vice versa.

In order to change the gain, there may be interruptions in the information transmitted by the base station at suitable intervals, whereby the gain can be changed without causing errors in the received information.

10 If the received radio signal is burst-like, a control value is calculated for the gain-changing elements of block 2 by one of the methods described above during the synchronization period of the beginning of the burst. This control value is then prevalent throughout the burst duration. Another option is to process the sample queues 12 and Q2 during the burst as described in continuous reception and thus calculate a new setpoint for the gain-changing elements of block 2 for the next burst. The new gain value can be set between bursts.

It is essential in the method according to the invention that the setpoint of the AGC is calculated from the received information signal, whereby additional pilot and the like signals are not necessarily needed.

The static operating parameters of the receiver and transmitter blocks are controlled by the processor unit 13 of Figure 1 via the control bus 16. The processor also decodes the messages from the received information bitstream and creates a bit stream to be transmitted.

In the transmitter, block 8 performs the following conversions in chronological order on the information bit stream from processor unit 13 30: encoding, bit modulation (multiplication) with a DS spreading code, and modulation into a complex baseband signal. The spreading code comes from a separate code generator 9. The D / A conversion and transmission of the baseband signals to the transmission frequency are also included in block 8. , or both. This output signal is mixed with the RF carrier for the final transmission frequency. The RF carrier is obtained from the frequency synthesizer 14.

Block 10 provides the source 1 fed to the source 1. The power Pi received by the RX shown in the figure is the power of the signal modulated by the spreading code assigned to the mobile station, i.e. is the power of the signal intended for that station. The transfer function between the bulb and the block 2 gain setpoint signal is of the fasting type. This is how the control signal directly follows the Pirn changes. The cut-off frequency of the -3 fast response of the fasting response determines how the no-15 mask Pirn changes the control is able to monitor. This rate can be set within certain limits in the AGC algorithm block 7.

Since the gain control of block 2 follows Pirta, the setpoint can also be generated from the same setpoint input to line 15 to block 10 of the transmitter TX output power Po. Then Po follows Pirta, which is the purpose of adjusting the automatic transmission power according to the invention. The operation of block 10 requires a fully equivalent attenuator, amplifier, or both to be output; that is, when, in block 2, for example, the input signal is attenuated, the output power is also reduced because the amplified input signal is an indication that the mobile station is likely to approach the base station, and vice versa.

The output power of block 10 is amplified by a power amplifier 11 and directed through a duplex filter 12 to the antenna 1.

30 Different antennas can also be used for reception and transmission.

It will be apparent to those skilled in the art that the various embodiments of the invention are not limited to the examples set forth above, but may vary within the scope of the following 35 claims.

Claims (9)

921 24 A method for automatically adjusting the transmitter power of a radio transceiver receiver using direct sequence spreading suitable for a code division multiplexing environment, wherein a setpoint signal generated by the transmitter of the receiver (RX) that the reference value signal for receiving the automatic gain of the receiver (RX) 10 is determined on the basis of the sums of the real and imaginary parts (I2, Q2) of the baseband signal composed of one or more predetermined time selections (Tn) or values approximating them. Method according to Claim 1, characterized in that the setpoint signal obtained from the automatic gain of the receiver (RX) is determined on the basis of the average of the sums of the squares of the real and imaginary parts (I2, Q2) of the composite baseband signal. Method according to claim 1, characterized in that the setpoint signal obtained by the automatic gain of the receiver (RX) is determined on the basis of the sum of the squares of the real and imaginary parts (12, Q2) of the generated baseband signal. A method according to claim 1, characterized in that the setpoint signal obtained from the automatic gain of the receiver (RX) is determined on the basis of the sums of the squares of the real and imaginary parts (12, Q2) of the composite baseband signal exceeding a certain threshold value. A method according to claim 1, characterized in that the setpoint signal obtained from the automatic gain of the receiver (RX) is determined on the basis of the median sums of the squares of the real and imaginary parts (12, Q2) of the assembled baseband signal. 92124 The method according to claim 1, characterized in that the setpoint signal obtained from the automatic gain of the receiver (RX) is determined based on a quantity approximating the sum of the squares of the real and imaginary portions (I2, Q2) of the assembled baseband signal. Method according to one of Claims 1 to 6, characterized in that the predetermined time selector (Tn) is fixed. Method according to one of Claims 1 to 7, characterized in that the predetermined time interval (Tn) is contagious according to the rate of change of the received signal. Method according to one of Claims 1 to 8, characterized in that the values of the sums of the squares of the real and imaginary parts (12, Q2) of the assembled baseband signal are averaged over several time slots (Tn). 921 24