JP3996877B2 - Wireless communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless communication performed using a TDMA / TDD (Time Division Multiple Access / Time Division Duplex, time division multiple access / time division duplex) method in a FWA (Fixed Wireless Access) system. , Point-to-Multipoint (PMP / base station-to-multiple station connection method) subscriber wireless communication apparatus and burst signal.
[0002]
[Prior art]
When radio is used in the communication system, it is not necessary to lay a track, so that the introduction cost of the entire system can be reduced.
[0003]
A subscriber radio access system is a typical example, and a plurality of subscriber stations are arranged relatively close to a base station, and a radio transmission path using microwaves or millimeter waves is provided between the base station and each subscriber station. Connecting.
[0004]
FIG. 6A shows a conceptual diagram of the PMP communication system as such a subscriber radio access system. Here, four subscriber stations 2-1 to 2-4 are connected to the base station 1. FIG. ing. In the following description, the transmission direction from the base station 1 to each of the subscriber stations 2-1 to 2-4 is “downlink”, and the transmission direction from each of the subscriber stations 2-1 to 2-4 to the base station 1 is This is referred to as “up”.
[0005]
There are several systems for this subscriber radio access system. One of them is a time-division bidirectional communication system (Time) that uses a single frequency channel for both downlink burst and uplink burst transmission in a time division manner. (Division Duplex: TDD).
[0006]
FIG. 6B is a schematic diagram showing a time series of bursts by this time-division bidirectional communication method, and the horizontal axis is the time axis.
[0007]
First, the downlink burst 3 is transmitted from the base station 1 to each of the subscriber stations 2-1 to 2-4. In the downstream burst 3, timing and data amount for transmitting the upstream bursts 4-1 to 4-4 from the subscriber stations 2-1 to 2-4 to the base station 1 are designated.
[0008]
Each of the subscriber stations 2-1 to 2-4 transmits uplink bursts 4-1 to 4-4 to the base station 1 according to the designated timing. Note that a plurality of uplink bursts 4-1 to 4-4 may be transmitted from the same subscriber station (for example, subscriber station 2-1) within one burst period.
[0009]
Thereby, it is possible to transmit the upstream burst 3 and the downstream bursts 4-1 to 4-4 on the single frequency channel without colliding.
[0010]
FIG. 7 is a block circuit diagram showing a configuration around the demodulation unit of the base station 1 or the subscriber stations 2-1 to 2-4 in the subscriber radio access system. That is, the base station 1 and the subscriber stations 2-1 to 2-4 have basically the same configuration.
[0011]
In the receiving system of the base station 1 or the subscriber stations 2-1 to 2-4, a received RF signal received from an antenna (not shown) is amplified by a low noise amplifier (LNA) and then down-converted to an intermediate frequency (IF) The received IF signal passes through the variable gain amplifier 11 and is demultiplexed into an I signal (in-phase component) and a Q signal (quadrature component) by the quadrature detector 12.
[0012]
The demultiplexed I and Q signals are converted into digital signals by the A / D converter 13 and further demodulated by the demodulator 14 to obtain a demodulated signal. In addition, the I signal and the Q signal converted into digital signals are output to the burst detection circuit 15 and the reception level measurement circuit 17.
[0013]
The burst detection circuit 15 executes a demodulation process in the demodulator 14 based on the I signal and the Q signal output from the A / D converter 13 based on the detection result. In FIG. 7, the thick arrow means that the I signal and the Q signal are transmitted in parallel.
[0014]
The burst detection circuit 15 continues to detect the head of the burst signal based on the burst detection window open / close signal output from the demodulator 14 while the burst detection window is open.
[0015]
In the subscriber station, since the downlink burst is transmitted from the base station at a constant period, once the burst detection signal is output, this timing is set as the timing for opening the burst detection window for the next burst signal. .
[0016]
An AGC (Automatic Gain Control) 16 makes the received signal input to the demodulator 14 constant as a correction for fluctuations in the reception level of the burst signal due to the state of the transmission path (for example, changes in weather). This is controlled so that it is updated for each burst signal.
[0017]
Specifically, immediately before the burst signal is received, the gain value obtained with the burst signal received before the burst signal to be received is set, and the burst received thereafter by the burst detection signal The reception level of the burst signal is measured at the head of the signal (CR portion of the preamble shown in FIG. 2), and the gain of the variable gain amplifier 11 is optimized by the AGC 16 so that the input value from the measured value to the demodulator 14 is optimized. Is to adjust.
[0018]
For example, when the subscriber stations 2-1 to 2-3 are in a transmission relationship with the base station 1, the subscriber station 2-4 is started up at the start of initial connection such as when the power of the subscriber station 2-4 is newly started. The gain adjustment by the AGC 16 on the station 2-4 side is fixed to an indefinite value or a predetermined value because the optimum gain value cannot be found because the reception level is not measured.
[0019]
FIG. 8 is a timing diagram showing the relationship among a burst signal, a burst detection window opening / closing signal, and a burst detection output signal in a standard (optimal) state at the start of connection of the subscriber station.
[0020]
FIG. 9 is a timing diagram showing the relationship among the burst signal, gain update, burst detection window open / close signal, and burst detection signal output in a standard (optimal) state during synchronization of the subscriber station.
[0021]
[Problems to be solved by the invention]
By the way, the detection capability of the burst detection circuit 15 is limited, and if the received signal is within the range of the detection capability, normal burst detection is performed. However, as shown in FIG. (Dynamic range) is set to be greater than or equal to the detection capability range, and when a received signal is received within the dynamic range and outside the detection capability range of the burst detection circuit 15, the burst detection is permanently detected in the worst case. The problem of being unable to do so has arisen.
[0022]
Therefore, if the gain of the variable gain amplifier 11 is set to the maximum so that burst detection can be performed within the entire reception range (dynamic range), the input signal at the demodulator 14 is saturated with a reception signal exceeding a certain signal level. A new problem will occur.
[0023]
In addition, even if a burst signal is detected without being saturated, it is not received at the original optimum level, and subsequent adjustments to the optimum level for the burst signal use a plurality of burst signals to gradually lower the level. It also develops to the problem of requiring a lot of adjustment time.
[0024]
In addition, even the noise is raised to the signal level, and there is a problem that the noise is erroneously detected as a burst signal although it is originally a no-signal section where there is no burst signal. End up.
[0025]
On the other hand, when the initial connection is started, the timing at which the burst detection window is opened is irrelevant to the reception timing of the burst signal. Therefore, as shown in FIG. 11, the burst detection window is opened at the timing in the middle of the received burst. May end up.
[0026]
In such a case, depending on the release timing, burst detection may be performed in the middle of the received burst, but burst detection at that time is not the optimal burst detection timing.
[0027]
However, the demodulator 14 cannot demodulate such a burst signal, and identifies whether the reason why the demodulator cannot be demodulated cannot be demodulated because the reception level is low, or whether the demodulator 14 cannot demodulate because the detection timing is poor. I can't do it.
[0028]
For this reason, as shown in FIG. 12, the demodulator 14 tries to demodulate a plurality of times at the detection timing as it is, and if it cannot be demodulated, it returns to the initial detection state, but returns to the initial detection state. If the return is made in the same procedure as before, the opening timing of the burst detection window remains the same, so the deviation in detection timing remains the same, and the above-mentioned problems are not solved and it is difficult to escape from this loop. The problem will arise.
[0029]
On the other hand, when a new subscriber station (for example, subscriber station 2-4: hereinafter referred to as "entry station 2-4") starts an initial connection, the existing subscriber station is on an extension line in the direction of base station 1. (For example, subscriber station 2-2: hereinafter referred to as "interference station 2-2"), as shown in FIG. In addition to the received signal, the received signal from the interference station 2-2 may be seen.
[0030]
For this reason, the burst signal from the interfering station 2-2 may be detected and the demodulator 14 may start the demodulation process.
[0031]
In such a case, if it is not possible to distinguish between the interference station 2-2 and the base station 1, demodulation processing similar to the received signal of the base station 1 is performed, and the determination is left to an upper layer. There arises a problem that the burst signal is identified as the interference station 2-2, and then it takes time until normal demodulation is performed.
[0032]
In order to solve the above problems, an object of the present invention is to provide a wireless communication apparatus capable of appropriately performing burst detection when detecting a burst signal using a burst detection window.
[0033]
It is another object of the present invention to provide a wireless communication apparatus capable of quickly recovering from being unable to demodulate in the demodulator due to the opening timing shift of the burst detection window.
[0034]
Furthermore, an object of the present invention is to provide a wireless communication device that can easily distinguish between a base station and an interference station in an entry station when there is an interference station on the extension line of the base station with respect to the entry station. To do.
[0035]
[Means for Solving the Problems]
In order to achieve the object, a wireless communication apparatus according to the present invention converts a level of a received signal received from an antenna into a digital signal via a quadrature detector and an output signal from the variable gain amplifier. An A / D converter that performs demodulation, a demodulator that demodulates the digital signal component, a burst detection circuit that detects a burst signal digitized by the A / D converter and controls the start of demodulation in the demodulator, and A reception level measurement circuit for starting measurement of a received signal of a burst signal digitized by the A / D converter by a burst detection signal by the burst detection circuit, and a gain of the variable gain amplifier based on the measured value The AGC to be adjusted and the burst detection window open / close signal for controlling the burst signal detection operation by the burst detection circuit are output immediately from the demodulator. A reception level measurement circuit for measuring the reception level in a predetermined interval of the AGC, and a holding circuit for holding the measurement value, and the AGC immediately before starting the demodulation operation by outputting the burst detection window opening / closing signal at the start of initial connection. Is characterized in that the variable gain amplifier is adjusted with an optimum gain based on the reception level measurement value held in the holding circuit.
[0036]
The wireless communication apparatus of the present invention is characterized in that the measured value held in the holding circuit is a maximum value.
[0037]
The wireless communication apparatus of the present invention is characterized in that the measurement value held in the holding circuit is an average value.
[0038]
In the wireless communication apparatus of the present invention, the demodulator may vary the output timing of the burst detection window opening / closing signal output to the burst detection circuit when the received burst cannot be demodulated continuously a plurality of times. Features.
[0039]
Furthermore the wireless communication apparatus of the present invention, or a burst signal that signals from the master station, whether a signal from the slave station, the determination signal to enable determination are included in the preamble block in another slave station, said demodulated The determination is performed based on a preamble block demodulated by a detector .
[0040]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the wireless communication apparatus of the present invention will be described with reference to the drawings.
[0041]
FIG. 1 is a block circuit diagram of the main part of the wireless communication apparatus of the present invention, FIG. 2 is an explanatory diagram of a burst signal used in the present invention, and FIG. 3 is a burst signal / gain update in an optimum state at the start of initial connection. A timing diagram showing the relationship between the burst detection window open / close signal and burst detection signal output, and FIG. 4 is a timing diagram showing a return routine when demodulation is impossible despite the burst detection.
[0042]
In FIG. 1, in a receiving system of subscriber stations 2-1 to 2-4, a received RF signal received from an antenna (not shown) is amplified by a low noise amplifier (LNA) and then down-converted to an intermediate frequency (IF). The received IF signal passes through the variable gain amplifier 21 and is demultiplexed into an I signal (in-phase component) and a Q signal (quadrature component) by the quadrature detector 22.
[0043]
The demultiplexed I and Q signals are converted into digital signals by the A / D converter 23 and further demodulated by the demodulator 24 to obtain a demodulated signal. In addition, the I signal and the Q signal converted into digital signals are output to the burst detection circuit 25, the reception level measurement circuit 26, and the reception level measurement circuit 29.
[0044]
The reception level measurement circuit 26 outputs a reception level measurement signal to an AGC (Automatic Gain Control: automatic gain control) 27. The reception level measurement circuit 29 outputs the reception level measurement value to the maximum value holding circuit 28.
[0045]
Further, as shown in FIG. 2, the burst signal used in the present invention starts with a carrier recovery (CR) signal for reception level estimation, and a bit timing recovery (BTR) for detecting data sample timing. It consists of a signal and a unique word (UW) signal for estimating the beginning of data, and a data symbol (data block) is present after these preamble blocks.
[0046]
Further, by changing the unique word between the base station 1 and the subscriber stations 2-1 to 2-4, an interfering station (on the extension line of the base station 1) with respect to a new entry station (for example, the subscriber station 2-4) ( For example, when there is a subscriber station 2-2), it is possible to easily distinguish between the base station 1 and the interfering station in the participating station.
[0047]
The burst detection circuit 25 controls the burst detection operation based on the burst detection window opening / closing signal output from the demodulator 24 and outputs a burst detection signal to the demodulator 24 based on the detection result.
[0048]
The reception level measurement circuit 29 measures the reception level at a time equal to or longer than the burst period and opens the maximum value of the reception level measurement value, for example, as shown in FIG. 3 before opening the burst detection window at the start of initial connection or the like. Is held in the maximum value holding circuit 28.
[0049]
The AGC 27 adjusts the variable gain amplifier 21 with an optimum gain based on the measurement value held in the maximum value holding circuit 28, and then outputs a burst detection window open / close signal to the burst detection circuit 25.
[0050]
As a result, the range that the received signal can take (dynamic range) is set to be greater than or equal to the detection capability range, and a reception signal that is located within this dynamic range and outside the detection capability range of the burst detection circuit 25 is received. Even if it exists, burst detection can be performed appropriately.
[0051]
Further, the demodulator 24 outputs a burst detection window opening / closing signal at a timing in the middle of the received burst at the start of the initial connection, and is not an optimal burst detection timing. If demodulation is not possible, when returning to the initial detection state, as shown in FIG. 4, the burst detection window opening timing is shifted from the previous timing (a random time is provided at the opening start timing), so that a burst signal can be quickly generated. It can be received properly.
[0052]
By the way, in the above embodiment, the measured value for the reception level measured at a time equal to or longer than the burst period before the burst detection window opening / closing signal for controlling the detection timing of the burst signal by the burst detection circuit 25 is output from the demodulator 24. However, as shown in FIG. 5, an average value holding circuit 30 that holds the measured value as an average value may be used.
[0053]
【The invention's effect】
In the wireless communication apparatus of the present invention, with the configuration as described above, burst detection can be properly performed when a burst signal is detected using the burst detection window.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram of a main part of a wireless communication apparatus of the present invention.
FIG. 2 is an explanatory diagram of a burst signal used in the present invention.
FIG. 3 is a timing chart showing the relationship among a burst signal, gain update, burst detection window open / close signal, and burst detection signal output in an optimum state at the start of initial connection according to the present invention.
FIG. 4 is a timing chart showing a return routine when demodulation is impossible despite the detection of a burst.
FIG. 5 is a block circuit diagram of a main part of a modification of the wireless communication device of the present invention.
6A is a conceptual diagram of a PMP communication system as a subscriber radio access system, and FIG. 6B is a schematic diagram showing a burst time series according to a time-division bidirectional communication system.
FIG. 7 is a block circuit diagram of a main part of a conventional wireless communication device.
FIG. 8 is a timing chart showing a relationship among a burst signal, a burst detection window opening / closing signal, and a burst detection output signal in a standard (optimal) state at the start of connection of a subscriber station.
FIG. 9 is a timing diagram showing the relationship among a burst signal, gain update, burst detection window open / close signal, and burst detection signal output in a standard (optimum) state during synchronization of a subscriber station.
FIG. 10 is an explanatory diagram showing a relative relationship between a dynamic range / detectable range of a burst detection circuit and a reception level of a burst signal;
FIG. 11 is an explanatory diagram of a timing failure between a burst signal and a burst detection window at the start of initial connection of a subscriber station.
FIG. 12 is a timing chart showing a return routine when demodulation is impossible despite the detection of a burst.
FIG. 13 is an explanatory diagram of an example of a burst signal reception signal from a base station and an interference station in an entry station.
[Explanation of symbols]
21 variable gain amplifier, 22 quadrature detector, 23 A / D converter, 24 demodulator, 25 burst detection circuit, 26 reception level measurement circuit, 27 AGC, 28 maximum value holding circuit, 29 reception level measurement circuit, 30 average value Holding circuit.

Claims (5)

  A variable gain amplifier that adjusts the level of a received signal received from an antenna, an A / D converter that converts an output signal from the variable gain amplifier into a digital signal via a quadrature detector, and a demodulator of the digital signal component A demodulator, a burst detection circuit that detects a burst signal digitized by the A / D converter and controls the start of demodulation in the demodulator, and a burst detection signal by the burst detection circuit A reception level measurement circuit for starting measurement of the received signal of the burst signal digitized by the converter, an AGC for adjusting the gain of the variable gain amplifier based on the measurement value, and detection of the burst signal by the burst detection circuit A reception level measurement for measuring the reception level in a certain interval immediately before the burst detection window opening / closing signal for controlling the operation is output from the demodulator. Circuit and a holding circuit for holding the measurement value, and immediately before starting the demodulation operation by outputting the burst detection window opening / closing signal at the start of initial connection, the AGC measures the reception level held in the holding circuit. A radio communication apparatus that adjusts the variable gain amplifier with an optimum gain based on a value.   The wireless communication apparatus according to claim 1, wherein the measurement value held in the holding circuit is a maximum value.   The wireless communication apparatus according to claim 1, wherein the measurement value held in the holding circuit is an average value.   2. The demodulator varies the output timing of a burst detection window opening / closing signal output to the burst detection circuit when the received burst cannot be demodulated continuously a plurality of times. Item 4. The wireless communication device according to Item 3. The wireless communication device according to claim 1,
Or burst signal that signals from the master station, whether a signal from the slave station, the determination signal to enable determination are included in the preamble block in another slave station, based on the preamble block demodulated by the demodulator wireless communication device and executes the determination Te.

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