JP4436998B2 - Mobile radio base station equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mobile communication radio base station apparatus, and more particularly to a mobile communication radio base station apparatus for W-CDMA that operates in synchronization with an Iub signal applied to a connection with a host system.
[0002]
[Prior art]
Conventionally, a radio base station apparatus for mobile communication generally operates in synchronization with a highly stable clock signal extracted from an Iub signal supplied from an upper system.
[0003]
That is, a BB (Base Band) circuit and an RF (Radio Frequency / radio frequency) circuit in the radio base station apparatus operate with a clock signal generated in a phase-locked loop in synchronization with a clock extracted from the Iub signal. In the phase-locked loop, the clock signal extracted from the Iub signal and the clock signal generated by dividing the clock signal generated by the VCO (Voltage Controlled Oscillator / Voltage Controlled Oscillator) by the divider circuit are phase-shifted by the phase comparator circuit. Compare. Clock synchronization is established by controlling the VCO with the output voltage obtained through the loop filter based on the phase comparison result. Here, the loop bandwidth of the phase locked loop is fixedly set.
[0004]
Japanese Patent Application Laid-Open No. 02-001636 discloses a “line switching system” as a first invention example 1 in the technical field similar to the present invention. Inventive Example 1 of the present application provides a line switching method for switching a line between a working line and a protection line in a digital wireless communication system, which can shorten the line switching time without degrading the code error rate of the demodulator. It is aimed.
[0005]
Japanese Patent Application Laid-Open No. 09-162942 as the invention example 2 of the prior application makes it difficult for the clock synchronization circuit of the demodulation device to cause a loss of clock synchronization even when selective fading occurs in the radio section. The purpose is to improve equalization processing capacity.
[0006]
[Problems to be solved by the invention]
However, in the conventional Iub signal transmission path, when the signal phase fluctuates instantaneously due to the influence of line switching or fading or interference in the radio line, the phase locked loop in the radio base station apparatus changes the phase of the Iub signal. There is a drawback in that it may not be able to follow the above and a loss of synchronization occurs, and it takes a long time to recover.
[0007]
The above-mentioned prior invention example 1 shows each element of the line switching device of the digital radio communication system, and shows a basic configuration as compared to each component of the mobile communication radio base station device of the present invention. There are differences.
The invention example 2 of the prior application shows each component of the demodulator and the clock synchronization circuit in the demodulator, and the contents of the configuration are different.
[0008]
It is an object of the present invention to provide a mobile communication radio base station apparatus with improved Iub signal tracking characteristics.
[0009]
[Means for Solving the Problems]
To achieve the above object, a mobile radio base station unit of the present invention, the LIU to extract a clock signal from the time the Iub signal is converted into level that can digitally process the Iub signal, a digital signal output from the LIU is A framer that performs frame synchronization and error detection by monitoring the frame synchronization state and bit error state of the input Iub signal transmission line, and outputs a line quality deterioration signal when frame loss or bit error is detected, and extraction A phase-locked loop that generates a clock signal that is synchronized with the received clock signal, and when the framer outputs a line quality degradation signal, the phase is higher than when the framer does not output a line quality degradation signal. It is characterized by increasing the response speed of the synchronous loop .
[0010]
The phase locked loop includes a phase comparison circuit that compares the phase of the clock signal extracted from the Iub signal by the LIU with the clock signal output from the frequency divider circuit, and the control voltage of the VCO based on the output of the phase comparison circuit. A loop filter that generates a clock signal that is controlled by a voltage output from the loop filter, generates a clock signal for use in the apparatus, and a frequency dividing circuit that divides the output clock signal of the VCO and outputs the divided clock signal to the phase comparison circuit. Is provided.
[0011]
Note that the VCO is controlled by the output voltage obtained through the loop filter based on the result of the phase comparison performed by the above-described phase comparison circuit, thereby establishing synchronization of the clock signal output from the VCO. Further, the response speed of the phase locked loop is changed by changing the loop bandwidth determined by the constant of the loop filter .
[0012]
Furthermore, it is preferable to further include a BB circuit and an RF circuit that operate based on a clock signal output from the phase locked loop .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a mobile communication radio base station apparatus according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIG. 1, an embodiment of a mobile communication radio base station apparatus of the present invention is shown.
[0014]
(Constitution)
FIG. 1 is a block diagram of an embodiment of the present invention. The embodiment shown in FIG. 1 includes LIU (Line Interface Unit) 1, framer 2, BB (Base Band) circuit 7, RF (Radio Frequency / radio frequency) circuit 8, and phase locked loop 10. The The phase-locked loop 10 is further subdivided and includes a phase comparison circuit 3, a loop filter 4, a VCO (Voltage Controlled Oscillator / Voltage Controlled Oscillator) 5, and a frequency dividing circuit 6.
[0015]
An LIU (Line Interface Unit) 1 converts the Iub signal to a level that can be digitally processed, and simultaneously extracts a clock signal from the Iub signal.
The framer 2 receives the digital signal output from the LIU 1 and performs frame synchronization and error detection.
The phase locked loop 10 generates a clock signal synchronized with the clock signal extracted from the Iub signal by the LIU 1.
Each of the BB circuit 7 and the RF circuit 8 operates based on a clock signal output from the phase locked loop 10.
[0016]
In the mobile communication radio base station apparatus of this embodiment configured by the above-described units and operating in synchronization with the Iub signal, the LIU 1 converts the Iub signal to a level that can be digitally processed, and simultaneously extracts the clock signal from the Iub signal. and inputs the digital signal output from LIU1, framer 2 performs frame synchronization and error detection.
The phase locked loop 10 generates a clock signal synchronized with the clock signal extracted from the Iub signal by the LIU 1. Based on the clock signal output from the phase-locked loop 10, the BB circuit 7 and the RF circuit 8 operate.
[0017]
Here, the framer 2 monitors the frame synchronization state and the bit error state of the Iub signal transmission path, and outputs a line quality deterioration signal when the frame synchronization loss or the bit error is detected.
[0018]
Further, the phase comparison circuit 3 constituting the phase locked loop 10 compares the phase of the clock signal extracted from the Iub signal by the LIU 1 and the clock signal output from the frequency dividing circuit 6.
The loop filter 4 generates a control voltage for the VCO 5 based on the output of the phase comparison circuit 3.
The VCO 5 is controlled by the voltage output from the loop filter 4 and generates a clock signal for use in the apparatus.
The frequency dividing circuit 6 divides the output clock signal of the VCO 5 and outputs it to the phase comparison circuit 3. Here, when the loop filter 4 receives the line quality degradation signal from the framer 2, the loop filter 4 changes the loop bandwidth to be widened.
[0019]
(Operation example)
The operation of the mobile communication radio base station apparatus of the present embodiment shown in FIG. 1 will be described below.
In general, a mobile communication radio base station apparatus, particularly a W-CDMA radio base station apparatus, operates in synchronization with the Iub signal. The Iub signal is generally transmitted in a format based on international standards such as digital communication standards STM1 and E1, and an optical line, a metal line, or a radio line is mainly used as the transmission path.
[0020]
In the radio base station apparatus, the LIU 1 receives the Iub signal and converts it to a level that can be digitally processed, and simultaneously extracts a clock signal from the Iub signal.
The framer 2 receives the digital signal output from the LIU 1 and performs frame synchronization and error detection of the Iub signal. This frame synchronization is generally performed by detecting a frame synchronization bit inserted in an Iub signal, that is, a data signal such as STM1 or E1 of the digital communication standard. Error detection is generally performed using a CRC check bit in the Iub signal.
[0021]
The framer 2 monitors the frame synchronization state and the bit error state of the Iub signal transmission path, and outputs a line quality deterioration signal when the frame synchronization loss or the bit error is detected.
Signal frame synchronization has been performed by the framer 2, the signal processing in BB circuit 7 and the RF circuit 8 is performed is sent to the wireless section.
The BB circuit 7 and the RF circuit 8 operate with a clock signal generated by the VCO 5 in the phase locked loop 10.
[0022]
On the other hand, in the phase locked loop 10, the phase comparison circuit 3 compares the phase of the clock signal extracted from the Iub signal by the LIU 1 and the clock signal obtained by dividing the clock signal generated by the VCO 5 by the frequency dividing circuit 6. . The VCO 5 is controlled by the output voltage obtained through the loop filter 4 based on the phase comparison result. This establishes synchronization of the clock signal output by the VCO 5. The loop bandwidth determined by the constant of the loop filter 4 is made variable by being controlled by the line quality deterioration signal output from the framer 2.
[0023]
In a normal state, that is, when frame loss or bit error has not occurred in the Iub signal transmission line, and no line quality degradation signal is output from the framer 2, the loop bandwidth of the loop filter 4 is reduced, and the VCO 5 To improve the C / N of the clock signal generated in (1).
[0024]
In the Iub signal transmission path, when the signal phase fluctuates instantaneously due to line switching or fading or interference in the radio line, a bit error or loss of frame synchronization occurs in the Iub signal. At this time, it performs frame synchronization loss or error detection Iub signal in framer 2, and outputs the line quality degradation signal. When a line quality degradation signal is input, the loop filter 4 controls the loop bandwidth to be widened. As a result, the response speed of the phase-locked loop 10 is increased, and as a result, the phase-locked loop 10 follows the instantaneous phase fluctuation of the Iub signal and does not lose synchronization.
[0025]
When the state of the Iub signal transmission line returns to normal and the line quality degradation signal output from the framer 2 is canceled, the loop filter 4 controls the loop bandwidth to be reduced again.
In the above description, circuits and signal lines that are not particularly important are omitted.
[0026]
According to the above embodiment, when the mobile communication radio base station apparatus operates in synchronization with the Iub signal, the Iub signal is affected by the switching of the Iub signal transmission line or fading or interference in the radio line. Even when the phase fluctuates instantaneously, the slave synchronization state can be stably continued.
[0027]
As described above, the framer 2 monitors the frame synchronization state and bit error state of the Iub signal transmission path, and outputs a line quality deterioration signal when frame loss or bit error is detected. The loop filter 4 in the phase locked loop 10 for generating the in-device clock signal in synchronization with the Iub signal changes the loop bandwidth so that the loop bandwidth is widened when receiving the line quality degradation signal from the framer 2. Even if the phase of the phase fluctuates instantaneously, the phase-locked loop 10 continues the synchronized state without causing loss of synchronization. Therefore, even when a disturbance or the like occurs in the Iub signal transmission path, the radio base station apparatus can maintain the slave synchronization state and can continue to operate stably.
[0028]
(Effect of Example)
As described above, the present invention makes the loop bandwidth of the phase-locked loop variable, usually reduces the influence of external noise by reducing the loop bandwidth, and only when the phase of the Iub signal fluctuates instantaneously. Increase the loop bandwidth. This prevents the clock synchronization from being lost. As a result, there is an effect that the radio base station apparatus faithfully follows the temporary change of the Iub signal. Furthermore, at the normal time, it is possible to improve the jitter characteristics by reducing the loop bandwidth.
[0029]
(Other examples)
In FIG. 1, the clock signal extracted by the LIU 1 of the line interface unit is input to the phase comparison circuit 3. However, the same effect can be obtained by dividing the clock signal and inputting it to the phase comparison circuit 3. It is clear that is obtained. Further, the optimum effect can be obtained by optimally setting the variable range of the loop bandwidth of the loop filter 4 according to the line configuration of the Iub signal transmission path.
[0030]
The above-described embodiment is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.
[0031]
【The invention's effect】
As is clear from the above description, the mobile communication radio base station apparatus of the present invention converts the Iub signal to a level that can be digitally processed by the line interface unit, and simultaneously extracts the clock signal from this Iub signal and outputs the output digital signal. A signal is input, frame synchronization and error detection are performed , a clock signal synchronized with the extracted clock signal is generated to form a phase locked loop, and a loop bandwidth of the phase locked loop is varied according to the quality of the Iub signal. Thereby, the follow-up characteristic to the Iub signal is enhanced.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram showing an embodiment of a mobile communication radio base station apparatus of the present invention.
[Explanation of symbols]
1 LIU
2 Framer 3 Phase comparison circuit 4 Loop filter 5 VCO
6 Frequency Divider 7 BB Circuit 8 RF Circuit 10 Phase Lock Loop

Claims (5)

An LIU that converts the Iub signal to a level that can be digitally processed and simultaneously extracts a clock signal from the Iub signal;
When a digital signal output from the LIU is input , frame synchronization and error detection are performed by monitoring a frame synchronization state and a bit error state of the Iub signal transmission path, and a line is detected when a frame synchronization loss or a bit error is detected. A framer that outputs a quality degradation signal;
A phase locked loop that generates a clock signal synchronized with the extracted clock signal;
The mobile communication characterized in that when the framer outputs the channel quality degradation signal, the response speed of the phase locked loop is made faster than when the framer does not output the channel quality degradation signal. Wireless base station equipment. The phase-locked loop includes a phase comparison circuit that compares the phase of the clock signal extracted from the Iub signal by the LIU with the clock signal output from the frequency dividing circuit, and the control voltage of the VCO based on the output of the phase comparison circuit. A loop filter that generates a clock signal, a VCO that is controlled by a voltage output from the loop filter and generates a clock signal for the device, and an output clock signal of the VCO is divided and output to the phase comparison circuit The mobile communication radio base station apparatus according to claim 1, further comprising a frequency divider circuit. 3. The synchronization of a clock signal output from the VCO is established by controlling the VCO with an output voltage obtained through the loop filter based on a result of phase comparison by the phase comparison circuit. Radio communication base station apparatus for mobile communication. The mobile communication radio base station apparatus according to claim 2 or 3 , wherein a response speed of the phase-locked loop is changed by changing a loop bandwidth determined by a constant of the loop filter. The phase synchronized with BB circuitry and RF circuitry that operates based on the clock signal output from the loop, further mobile communication radio base station apparatus according to any one of claims 1, wherein 4 in that it has.

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