JP2000244452A - Cdma radio base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a code division multiple access CDMA radio base station where a limit level of a base band signal is varied in a way that the limit level of the base band signal is set high so as to reduce distortion caused when a modulation signal with many carrier numbers and multiplicity numbers and a high individual transmission power is given to a common amplifier and that the limit level is set low in other cases. SOLUTION: This radio base station is provided with a plurality of signal adder sections 107 that receive a plurality of multiplexed carrier signals and output I and Q phase sum signals, a plurality of power calculation sections 102 that calculate the instantaneous power and the average power of the received I and Q phase sum signals and provide an output of the result as a limit level setting signal to a limit level setting section 103, the limit level setting section 103 that calculates a limit control signal on the basis of the limit level setting signal and outputs the result to each of a plurality of limiters, a plurality of the limiters 104 that limit the received I and Q phase sum signals on the basis of the limiter control signal and output the result to each of a plurality of RF sections 105, and an RF synthesis section 106 that synthesizes the signals given to the RF sections into one signal and provides an output of it to a C-AMP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CDMA (Code Division Mu) using a spread spectrum technique.
Regarding a CDMA base station used in a single access (wireless communication) communication system, a signal wirelessly transmitted from the base station includes a signal having a large number of carriers and a large number of multiplexed baseband signals and a large transmission power of each individual power. In this case, the present invention relates to a CDMA radio base station that performs variable baseband signal limit levels to reduce distortion in a common amplifier by limiting a peak value of a baseband signal.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing an outline of a general CDMA radio base station. In a CDMA radio base station,
At the time of transmission, a spread code is given to data to be transmitted, baseband processing is performed to generate a spread signal, and the data is converted into transmission data by an RF transmission unit. Send. Signals are multiplexed in radio waves transmitted wirelessly so as to communicate with a large number of terminals, and a communication format to each terminal includes a call processing signal, a transmission power control signal to each terminal, and the like. At the time of reception, a DUP and a low noise amplifier (LNA: Low
The CDMA signal received via the Noise Amp) is converted into a baseband signal by an RF receiving unit, and the converted baseband signal is demodulated by a spreading code to obtain data to be received. These transmission / reception data are transmitted / received to / from another base station so that the base station control unit can communicate with a terminal under the control of the other base station.

[0003] A conventional transmission process of the CDMA radio base station will be described. FIG. 5 is a block diagram showing the configuration of the prior art. In FIG. 5, the baseband signal processing unit 5
Regarding 00, carrier signals Fk (F1, F2,...
Is output to the power calculation unit 502. The output signals i107 and q107 are an I-phase addition signal and a Q-phase addition signal, respectively. The power calculation unit 502 generates signals i107 and q
107 as it is (as signals i502 and q502)
Output to the limiter 104 and the input signal (i
107, q107), and calculates a limit level based on a preset limit value to obtain a limiter control signal c502.
Output to 4. The limiter 104 outputs a limiter control signal c
502, input signals i502 and q502
And outputs to the RF unit 105 as signals i104 and q104. Thus, the carrier signal Fk (F
1, F2,..., Fn) are RF-combined by the RF combining unit 106, output to the C-AMP 110, and output as CDMA signals by the C-AMP.

[0004] Next, a power waveform diagram of the IQ signal before and after passing through the limiter 104 at the time of the limiter operation according to the prior art is shown. In FIG. 6, the broken line shows the power waveform before passing through the limiter, and the solid line shows the power waveform after passing through the limiter. The limiter 104 operates to keep the ratio between the average power and the instantaneous power within a certain value.

[0005]

When outputting a signal having a large number of carriers and a large number of multiplexes and a large individual transmission power like a CDMA radio base station, the limit level is low for all carriers, that is, the average power and When the ratio of the instantaneous power is large, when the RF-combined signal is finally input to the common amplifier, there is a problem that the distortion of the output signal at the common amplifier increases. When the limit level is high in all the carriers, that is, when the ratio between the average power and the instantaneous power is low, the distortion of the output signal at the common amplifier is reduced, but the error on the side receiving the radio wave transmitted from the common amplifier is reduced. There was a problem that the rate increased.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce distortion which occurs when a modulated signal having a large number of carriers and a large number of multiplexes and a large individual transmission power is input to a common amplifier. CDMA for changing the limit level of a baseband signal that sets the limiter level of a band signal high and otherwise sets the limiter level low
To provide a radio base station.

[0007]

SUMMARY OF THE INVENTION In order to solve the problem, the invention according to claim 1 is a CDMA radio base station using a spread spectrum technique by using a spread signal, and a baseband signal processing constituting the CDMA radio base station. A plurality of signal adders for receiving a plurality of multiplexed carrier signals which are spread-modulated and input to output an I-phase addition signal and a Q-phase addition signal; The I-phase addition signal and the Q-phase addition signal output from the section are output to a plurality of limiters as they are, and the instantaneous power and average power of the input I-phase addition signal and Q-phase addition signal are calculated and each limiter is calculated. A plurality of power calculation units that output to the limit level setting unit as level setting signals; and a plurality of power calculation units that calculate limit control signals based on the respective limit level setting signals. Said limit level setting unit for outputting to the limiter, in accordance with the limiter control signal outputted from the limit level setting unit, the plurality of by limiting the I-phase addition signal being the input and the Q-phase addition signal R
A plurality of limiters for outputting to the F section; and an RF combining section for combining the signals input to the plurality of RF sections into one and outputting the combined signal to a common amplifier. When the number of multiplexes is large, the peak value of the baseband signal can be variably limited.

According to a second aspect of the present invention, there is provided a CDMA radio base station according to the first aspect, wherein each of the plurality of power calculators includes an instantaneous power calculator and an average power calculator. The instantaneous power calculation unit calculates the instantaneous power at the time of signal input, the average power calculation unit calculates the average power and outputs the average power to the limit level setting unit, and the limit level setting unit calculates the peak factor setting unit and the limit power calculation. Unit and an amplitude expansion / contraction ratio calculation unit, the peak factor setting unit calculates a peak factor value based on the input average power and outputs the calculated peak factor value to the limit power calculation unit, and the limit power calculation unit calculates the average power and the input average power. Calculate the limit power based on the peak factor value and output it to the amplitude expansion / contraction ratio calculation unit,
The amplitude expansion / contraction rate calculation unit is characterized in that the amplitude expansion / contraction rate is calculated based on the input instantaneous power and the limit power, and is output to the plurality of limiters as a limiter control signal. It is possible to appropriately set the limit of the peak value of the baseband signal.

According to a third aspect of the present invention, there is provided a CDMA radio base station according to the first or second aspect, wherein each of the plurality of signal adders includes a plurality of channel data. Each of the signals is spread-modulated and input as spread signals of I phase and Q phase, the input signals are added for each of I phase and Q phase, and the added I and Q phase added signals are added to the plurality of signals. The signal is output to the power adder, and one carrier can have spread signals of a plurality of channels.

According to a fourth aspect of the present invention, a CDMA wireless base station according to the first or second or third aspect is used for wireless communication using a W-CDMA communication system. And W-CD
This is particularly effective in MA wireless communication.

[0011]

Embodiments of the present invention will be described with reference to the drawings. The same components as those in the related art are denoted by the same reference numerals. FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, the baseband signal processing unit 100 is spread-modulated and subjected to a signal addition unit 10.
7, the carrier signals Fk (F1, F2,... F
n) is output to the power calculation unit 102. The output signals i107 and q107 are an I-phase addition signal and a Q-phase addition signal, respectively. The power calculator 102 outputs the signals i107 and q107 as they are (as the signals i102 and q102) to the limiter 104, and calculates the instantaneous power and average power of the input signals (i107 and q107) to obtain the instantaneous / average power signal p102. Output to limit level setting section 103. Limit level setting unit 103
The details of will be described later. Limiter 104 receives input signals i102 and q10 in accordance with limiter control signal c103 output from limit level setting section 103.
2 and RF as signals i104 and q104
Output to the unit 105. After that, the RF combining section 106, C-
The operation of the AMP 110 is the same as the conventional one.

FIG. 3 is a block diagram showing a main part of the present invention. The output of the signal addition unit 107 is input to the power calculation unit 102 as i107 and q107. Power calculator 102
Then, the input signals i107 and q107 are output to the limiter 104 as they are (as i102 and q102), and are also input to the instantaneous power calculation unit 1021.
The instantaneous power calculation unit 1021 performs the calculation of Expression 1 to calculate the instantaneous power.

[Equation 1] Instantaneous power = (I ² m + Q ² m) (Instantaneous power when the amplitude level of the IQ signal at a certain time point m (m = 0, 1, 2,...) Is Im, Qm)

The instantaneous power value calculated by the equation (1) is provided to an average power calculation unit 1022, and the following equation (2) is calculated, and the average power is calculated.

[Formula 2] Average power = (1 / N) Σ (I ² m + Q ² m) ^1/2 (from m = 1 to N) The instantaneous power value and the average power value calculated by these formulas 1 and 2 Is the limit level setting unit 10 as the signal p102.
3 is output.

The limit level setting unit 103 calculates the instantaneous power value of the signal p102 by using the amplitude expansion / contraction ratio calculation unit 1.
032, and the average power value is input to the peak factor setting unit 1033 and the limit power calculation unit 1031. The peak factor setting unit 1033 selects the most effective parameter from the peak factor values stored in the memory table based on the average power value of the input signal p102, and outputs the parameter to the limit power calculation unit 1031. Note that the peak factor value may be calculated by calculation using an average power value and an arbitrary coefficient without using a memory. The limit power calculation unit 1033 calculates the following equation 3 based on the signal indicating the average power value and the peak factor value of the input signal p102 to calculate the limit power.

[Equation 3] Limit power = Average power × 10
^{Peak factor [dB] / 10} The limit power value calculated by the equation 3 is output to the amplitude expansion / contraction rate calculation unit 1032.

The amplitude expansion / contraction ratio calculation unit 1032 calculates the amplitude expansion / contraction ratio by performing the following Expression 4 based on the input limit power value and the instantaneous power value calculated by the above Expression 1.

[Equation 4] Amplitude expansion / contraction rate = Instantaneous power / Limit power The value calculated by this Equation 4 is used as the limiter control signal c103.
Is output to the limiter 104.

In the limiter 104, the input signal i1
02 and q102 for each of the limiter control signals c
Limiting is performed based on 103, and the limited signals are output to the RF unit 105 as an I-phase limiter output signal i104 and a Q-phase limiter output signal q104, respectively. Here, the I-phase limiter 104I and the Q-phase limiter 104Q that perform the limit can be performed by a general multiplier or the like.

Next, FIG. 2 shows a power waveform diagram of the IQ signal before and after passing through the limiter 104 during the limiter operation according to the embodiment of the present invention. In FIG. 2, a broken line indicates a power waveform before passing through the limiter, and a solid line indicates a power waveform after passing through the limiter. The signal levels of the signals i104 and q104 output from the limiter 104 to the RF unit 105 are represented by the following Expression 5.

[Expression 5] Im ′ = Im (0 = <amplitude expansion / contraction rate = <1) = Im × amplitude expansion / contraction rate (amplitude expansion / contraction rate> 1) Qm ′ = Qm (0 = <amplitude expansion / contraction rate = <1) = Qm × Amplitude expansion / contraction ratio (amplitude expansion / contraction ratio> 1) (Im signal levels after limit processing are Im 'and Qm'
And

A comparison between the power waveform of FIG. 2 and the power waveform of the related art (FIG. 6) shows that when the number of multiplexes is large and the individual transmission power is large, a control signal for lowering the limit level is used.
c103 is input to the limiter 104, and the limiter 104
, An operation of reducing the ratio between the average power and the instantaneous power is performed, so that distortion in the C-AMP 110 is reduced. Also,
When the number of multiplexes is small and the individual transmission power is small (in this case, the average power is small), the control signal c103 that increases the limit level is input to the limiter 104, so that the CDMA signal transmitted from the C-AMP 110 , The error rate hardly deteriorates.

Here, the carrier signal Fk according to the present invention is
(F1, F2,... Fn) will be described with reference to FIG. FIG. 4 is a block diagram illustrating multi-channel addition according to the present invention. Assuming that data for each channel to be transmitted is transmission data Dt (D1, D2,... Dn), these signals Dt are input to the primary / secondary modulation unit 101. 1
The secondary / secondary modulator 101 first QPSK-modulates a voice signal or data signal digitized as primary modulation,
Next, spread modulation by a spread code is performed as secondary modulation,
The signals are output to the signal adding unit 107 as I-phase and Q-phase spread signals. In the signal adder 107, each primary / secondary modulator 10
Among the spread signals input from No. 1, the I-phase signal is input to the I-signal adding section 107I, and the Q-phase signal is input to the Q-signal adding section 107Q. In signal adding section 107, I
Signal addition is performed for each phase and Q phase, and i107, q
It is output to the power calculation unit 102 as 107.

As described above, in the present invention, data (transmission data Dt) of a plurality of channels is added to one carrier (carrier signal Fk), limit control is performed for each carrier, RF synthesis is performed, and output is performed. For example, a multiplex number of CDMs as shown in the following Expression 6
The embodiment may be an example of the wireless base station A.

[Formula 6] 60 channels × 4 carriers = 240 multiplexes (the number of channels input to the signal adder × the number of RF-combined carriers = the number of multiplexes) Thus, in the embodiment of the present invention, the number of carriers and the number of multiplexes are large. In particular, the present invention exerts a particularly great effect in handling a modulated signal in which individual transmission power becomes large, and W-CDMA (Wide-ba) requiring such a multiplex number is required.
nds-CDMA (Wideband CDMA) is effective in a radio base station of a communication system.

[0021]

According to the CDMA radio base station according to the present invention,
The limit level of the baseband signal can be varied, so that the number of carriers is large and the level of distortion generated in the common amplifier when the number of multiplexes on each carrier is large can be reduced. When the number of multiplexes is small, the error rate on the receiving side can be suppressed. Further, since the low power consumption amplifier can be used by changing the limit level, it contributes to the low power consumption of the whole apparatus.

[0022]

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a power waveform diagram before and after passing through a limiter according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a main part of the present invention.

FIG. 4 is a block diagram illustrating multi-channel addition according to the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional technique.

FIG. 6 is a power waveform diagram before and after passing through a limiter according to a conventional technique.

FIG. 7 is a block diagram illustrating an outline of a CDMA base station.

[Explanation of symbols]

100, 500 ... baseband signal processing unit, 101 ... 1
Next / secondary modulation unit, 102, 502 ... power calculation unit, 103
... Limit level setting unit, 104 ... Limiter, 105 ...
RF section, 106 RF combining section, 107 signal adding section, 1
211: an instantaneous power calculation unit, 1022: an average power calculation unit,
1031: limit power calculator, 1032: amplitude expansion / contraction ratio calculator, 1033: peak factor setting unit, 104I ...
I-phase limiter, 104Q ... Q-phase limiter, 107I ... I
Phase signal addition, 107Q ... Q phase signal addition, F1, F2, F
n: carrier signal (multiple channel signal) i107: I-phase addition signal output, q107: Q-phase addition signal output i102
i502... I-phase power calculation unit output, q102, q502.
Q-phase power calculation unit output i104 ... I-phase limiter output, q1
04: Q-phase limiter output p102: instantaneous / average power signal, c103, c502: limiter control signal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K022 EE01 EE22 5K060 BB07 CC04 CC11 DD04 KK03 LL01 LL12 LL23 5K067 AA23 BB02 CC10 EE02 EE10 GG08 LL11

Claims (4)

[Claims] 1. A CDMA radio base station using a spread spectrum technique by a spread signal, wherein a plurality of multiplexed carrier signals are multiplexed in a configuration relating to a transmission process of a baseband signal processing unit constituting the CDMA radio base station. Are spread-modulated and input to output an I-phase addition signal and a Q-phase addition signal, respectively, and the I-phase addition signal and the Q-phase addition signal output from the plurality of signal addition sections are used as they are. A plurality of power calculators for outputting to each of the plurality of limiters, calculating the instantaneous power and average power of the input I-phase addition signal and Q-phase addition signal, and outputting each to the limit level setting unit as a limit level setting signal; A limit control unit that calculates a limit control signal based on each of the limit level setting signals and outputs the limit control signal to each of the plurality of limiters; A plurality of limiters for limiting the input I-phase addition signal and Q-phase addition signal to output to a plurality of RF units according to the limiter control signal output from the level setting unit; RF that combines the signals input to the one into one and outputs it to the common amplifier
A CDMA radio base station comprising: a combining unit. 2. The CDMA radio base station according to claim 1, wherein each of said plurality of power calculation units includes an instantaneous power calculation unit and an average power calculation unit, and said instantaneous power calculation unit is configured to output a signal at the time of signal input. Calculate the instantaneous power, the average power calculation unit calculates the average power and outputs it to the limit level setting unit, and the limit level setting unit includes a peak factor setting unit, a limit power calculation unit, and an amplitude expansion / contraction ratio calculation unit, The peak factor setting unit calculates the peak factor value based on the input average power and outputs the calculated peak factor value to the limit power calculation unit, and the limit power calculation unit calculates the limit power based on the input average power and the peak factor value. The amplitude expansion / contraction rate calculator outputs the amplitude expansion / contraction rate based on the input instantaneous power and limit power, and outputs the plurality of limiter control signals as the limiter control signal. CDMA base station according to claim 1, wherein the outputting the jitter. 3. A CD according to claim 1 or claim 2.
An MA radio base station, wherein each of the plurality of signal addition units spread-modulates a plurality of channel data and inputs the spread data as I-phase and Q-phase spread signals. 3. The CDMA radio base station according to claim 1, wherein a signal is added every time, and the I-phase addition signal and the Q-phase addition signal obtained by adding the signals are output to the plurality of power addition units. 4. The CDMA radio base station according to claim 1, 2 or 3 is used for radio communication using a W-CDMA communication system. Or the CDMA radio base station according to claim 3.