JPH07312571A - Synchronizer - Google Patents

Abstract

(57) [Summary] [Object] To provide a synchronizer capable of acquiring symbol synchronization with a simple configuration in spread spectrum multiple access communication using a spread code of a polyphase orthogonal sequence. A correlation detection output of transmission data that repeats inversion in a synchronization device that performs correlation detection of transmission data spectrum-spread with a spreading code of a polyphase orthogonal sequence and acquires symbol synchronization of transmission data based on this correlation detection output. Low-pass filter 2 for inputting and outputting envelope data
And a zero-cross point detecting means 3 for detecting a zero-cross point of the envelope data, and a symbol timing generating means 4 for outputting a symbol clock at a time when half the symbol period elapses from the time of the detected zero-cross point. And. When using a spreading code of a polyphase orthogonal sequence, when the transmission data is inverted from +1 to -1, the code of the envelope of the correlation output is inverted at the exact middle of one symbol period. 1 / from the point where this envelope crosses zero
The time when two symbol periods have passed is the symbol timing for converting the symbol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum (SS) communication synchronizer using a spread code of a polyphase orthogonal sequence, which is used in a digital car phone, a mobile phone, etc.
In particular, it is configured so that symbol synchronization and frame synchronization can be acquired with a simple configuration.

[0002]

2. Description of the Related Art In spread spectrum communication, the spectrum of an information signal is spread and transmitted in a band sufficiently wider than the original information bandwidth.

As described in the paper "Modulation and Demodulation of Spread Spectrum" (Tachikawa: Electronic Information Communication Society 93 Spring Conference <Basic Boundary Group> Spread Spectrum in Consumer Communication and Personal Communication), a plurality of binary codes are used. In direct spread spectrum spread communication, in which an information signal is multiplied by an arrayed binary spread code as it is (data modulation) and transmitted, one symbol (generally, one bit of an information signal corresponds to one bit is transmitted on the transmitting side. For n), the information signal is modulated by sequentially multiplying n (n chips) binary codes forming the spread sequence code and repeating this cyclically for each bit of the information signal. A code such as an M sequence or a Gold sequence is used as the binary sequence spreading code. On the other hand, on the receiving side, correlation detection (despreading) is performed using the same code as the spreading sequence code used at the time of transmission, so that there is one peak for one symbol, as shown in FIG. 6A. Detect the autocorrelation waveform.

On the other hand, the paper “Multi-phase periodic sequences without cross-correlation and its application to asynchronous SSMA communication” (Suehiro,
Hatori: IEICE Transactions '85 / 10, Vo
l. J68-A, N0.10, pp. 1087-109
3) has no cross-correlation (that is, of orthogonal sequences),
A spreading code sequence of a complex number sequence (that is, a polyphase sequence) has been proposed. Unlike a binary sequence, a polyphase sequence has a complex number in each chip that constitutes a spread sequence code, and this complex number is located on the circumference of a complex plane (IQ plane) shown in FIG. The absolute value is constant.

In this polyphase orthogonal sequence, a plurality of pulses appear for one symbol in the autocorrelation waveform when despreading using the same code sequence. FIG. 6B shows an autocorrelation waveform in which a peak appears every three chips.

In spread spectrum multiple access (SSMA) communication in which quadrature modulation such as QPSK and GMSK is performed using this multi-phase orthogonal sequence spreading code, the transmitting side transmits a multi-phase orthogonal spreading sequence code to which transmission data is assigned. I component and Q
And the component is subjected to quadrature modulation, and the receiving side performs correlation detection of the received signal using the I component and Q component of the same polyphase orthogonal spreading sequence code, captures synchronization, and demodulates data.

This receiver is "digital matched filter technology and its problems in spread spectrum communication".
(Tajika: The Institute of Electronics, Information and Communication Engineers, Technical report SST92-2
1, 1992), a digital matched filter can be used in the correlator and configured as in FIG. In this receiving unit, the received signals are multiplied by carrier frequencies having different phases by 90 °, the I component and the Q component of the received signal are synchronously detected and converted into a digital signal, and then, with respect to the I component of the received signal, Spread code I component 82
Correlation with the digital matched filter (MF) 81
Then, the correlation with the spread code Q component 84 is obtained by MF83.
Similarly, for the Q component of the received signal, the correlation with the spread code I component 88 is obtained with MF87, and the correlation with the spread code Q component 86 is obtained with MF85. Then, the addition value (X) of the outputs of MF81 and MF85 is obtained by the addition circuit 89, and the value (Y) obtained by subtracting the output of MF83 from the output of MF87 is obtained by the subtraction circuit 90.

Data demodulation is performed by phase-correcting (synchronous detection) the signals of the outputs X and Y by the phase detector 93 and using the detected outputs (in this case, two outputs of the I component and the Q component). .

Also, in order to capture synchronization, the squarer 91,
Using 92 and the addition circuit 94, the sum of squares (X ² + Y ² ) of the added values X and Y is obtained. This sum of squares (X ² + Y ² ) has a plurality of peaks for one symbol as in the case of the autocorrelation waveform of FIG.
When it changes to -1, the maximum appears in the envelope because the square processing is performed.

As shown in FIG. 9, a synchronization circuit for capturing synchronization from the sum of squares (X ² + Y ² ) outputs a synchronization capture output (X ² + Y ² ).
+ Y ² ) Peak position detector 95 for detecting the peak position
And a symbol timing generation unit 96 that generates a symbol clock based on the detected peak position, and a peak position tracking unit 97 that tracks the peak position of the synchronization acquisition output (X ² + Y ² ) so as not to lose the acquired synchronization. It has and.

This synchronization circuit can also be used for synchronization acquisition of SSMA communication using a binary sequence spreading code. At this time, the peak position detection unit 95 detects the peak position of the synchronization acquisition output that appears for each symbol as in the case of the autocorrelation waveform (FIG. 6A), and the symbol timing generation circuit 96 determines the detected timing. The symbol clock is generated based on the above.

Further, the peak position tracking circuit 97 tracks the peak position even after the symbol synchronization is acquired so that the synchronization can be continuously maintained even if the synchronization timing changes due to changes in the conditions of the transmission path. To correct the symbol timing.

[0013]

However, when a polyphase orthogonal sequence is used as the spreading sequence code, the autocorrelation waveform when despreading on the receiving side is different from the case where a binary sequence spreading code is used. Since there are multiple peaks instead of one peak per symbol, it is difficult to accurately capture the position (change point) of the symbol at this time from the synchronous capture output X ² + Y ² using the conventional synchronous circuit. There was a problem.

The present invention solves such a conventional problem, and secures symbol synchronization and frame synchronization with a simple configuration in spread spectrum multiple access communication using spread codes of polyphase orthogonal sequences. It is an object of the present invention to provide a synchronizer capable of performing

[0015]

Therefore, in the present invention, a synchronization for detecting the correlation of the transmission data spectrum-spread by the spreading code of the polyphase orthogonal sequence, and acquiring the symbol synchronization of the transmission data based on the correlation detection output. In the device, a low-pass filter that inputs the correlation detection output of transmission data that repeats inversion and outputs the envelope data, zero-cross point detection means that detects the zero-cross point of this envelope data, and the time of the detected zero-cross point And a symbol timing generation means for outputting a symbol clock at the time when half the symbol period has elapsed.

Further, the symbol timing generating means is configured to average a plurality of zero cross points detected by the zero cross point detecting means to determine a zero cross point as a reference of the output of the symbol clock.

Further, there is provided tracking means for detecting the zero-cross point even after the symbol synchronization is acquired and correcting the output timing of the symbol clock in the symbol timing generating means.

Further, after the symbol synchronization is acquired, the correlation detection operation is carried out only within a window having a time width shorter than one symbol period.

Further, a decoding means for decoding the transmission data based on the correlation detection output, a unique word detecting means for detecting a unique word included in the transmission data, and a frame for outputting a frame clock when the unique word is detected. It is also provided with timing generation means.

[0020]

When a spread code of a polyphase orthogonal sequence is used, when the transmission data is inverted from +1 to -1, the code of the envelope of the correlation output is inverted at the exact middle of one symbol period. Therefore, the time point at which 1/2 symbol period elapses from the point where the envelope curve crosses zero is the symbol timing for symbol conversion. Therefore, from the transmitting side, by using the common channel or the data part for synchronization of the communication channel, by transmitting the transmission data that repeats the inversion by spectrum spreading,
On the receiving side, it is possible to detect the zero cross point of the envelope of the correlation output and acquire the symbol timing based on it.

This zero-cross point may be displaced due to changes in transmission line conditions such as noise and fading. In order to avoid a malfunction due to this deviation, a plurality of detection results regarding the zero cross points are averaged.

Further, by tracking the zero-cross point even after the symbol synchronization is secured, it is possible to immediately correct when the symbol timing is deviated.

Further, after the symbol synchronization is acquired, the time width of the correlation detection is narrowed down to a part of the symbol period, and the type of the transmission data is identified by the correlation detection only in that period.
By doing so, power consumption can be reduced.

Further, when transmitting data in frame units, the transmitting side transmits a frame containing data that repeats inversion and a unique word pattern, and the receiving side
Frame synchronization can be obtained by detecting the unique word in parallel with the detection of the zero cross point.

[0025]

【Example】

(First Embodiment) In the present invention, symbol synchronization is obtained by utilizing the characteristic that a plurality of autocorrelation peaks appear in one symbol, which is a characteristic of using a spreading code of a polyphase orthogonal sequence in SSMA communication. To do. Now, the transmission data is (+
1, +1, -1, -1, +1), the correlation output (detection output) of the data-modulated received signal is inverted in accordance with the inversion of the transmission data, as shown in FIG. (Note that the autocorrelation waveform in FIG. 6B is an enlargement of one symbol in the portion where +1 continues in the autocorrelation waveform in FIG. 5). Therefore, it can be seen that the peak value of the correlation output of the symbol when the transmission data is inverted (that is, the phase of the spread code is inverted) becomes 0 at the time shifted from the symbol timing by 1/2 cycle of the symbol clock. .

Therefore, according to the present invention, data that repeats inversion is transmitted from the transmitting side using a synchronization common channel or a synchronization data section set in a part of each communication channel by using a multi-phase orthogonal sequence spreading code. The data is modulated and transmitted, and the receiving side captures symbol synchronization based on the zero cross point in the correlation output of the received signal at that time.

FIG. 3 shows transmission data (a), (X ² + Y ² ) output (b), detection output (c), zero cross point (triangle mark), and symbol clock (d) which are inverted at this time. It shows the relationship. The (X ² + Y ² ) output (b) and the detection output (c) are the LPF.
The envelope is displayed after passing through the (low-pass filter).

As shown in FIG. 1, the synchronizing circuit for outputting the symbol clock includes an LPF 2 to which the detection output of the phase detector 93 of FIG. 8 is input, and a zero cross point detecting section for detecting the timing of the polarity change of the detection output. 3 and from the detected zero cross point, 1 / of the symbol clock period
A symbol timing generation unit 4 that outputs a symbol clock at a time offset by 2 and a zero cross point tracking unit 5 that tracks a zero cross point so as not to lose it even after symbol synchronization is acquired.

The LPF 2 of this synchronizer outputs the envelope curve of the detection output (FIG. 3 (c)), and the zero cross point detecting section 3 changes the polarity of this envelope curve (FIG. 3).
(C) Zero cross point) is detected and transmitted to the symbol timing generation unit 4, and the symbol timing generation unit 4
Outputs the symbol clock (d) at the time when half the symbol period has elapsed from the timing of the zero cross point. As a result, symbol synchronization is captured.

At this time, depending on the conditions of the transmission path, the polarity of the output of the LPF 2 may finely change due to noise, fading, or the like, which may cause the synchronization acquisition to malfunction. In order to prevent this, the symbol timing generation unit 4
It is possible to determine the symbol timing by checking the zero cross points for a certain number of symbols and performing processing such as averaging.

Further, the zero-cross point tracking unit 5 continuously tracks the zero-cross point of the detection output even after the synchronization acquisition, and always corrects the deviation of the symbol timing.

Further, after the symbol synchronization is captured, the correlation detection operation of the correlators (81, 83, 85, 87 in FIG. 8) is performed in a burst with a predetermined window width (a part of one symbol time). By doing so, it is possible to save the power consumption of the correlator.

It is also possible to directly use the outputs of the correlators (81, 85 in FIG. 8) and the adder 89 as the inputs of this synchronizer to similarly obtain the symbol synchronization from the zero cross points at those inputs. it can.

(Second Embodiment) The synchronizer of the second embodiment is
For frame transmission (communication in which the number of symbols (the number of bits) of a certain length on the time axis is set as one frame and is transmitted in frame units), symbol synchronization and frame synchronization can be acquired. . In this case, on the transmission side, as shown in FIG.
It is a W (unique word) pattern, and the other symbols are data-modulated using a multi-phase orthogonal sequence spreading code for a frame of a format composed of data that repeats inversion
Send using common channel. The receiving side inputs the detection output or the correlator output of the signal transmitted on the common channel to the synchronizer to acquire the symbol synchronization and the frame synchronization.

As shown in FIG. 2, this synchronizer outputs a frame detector based on the detection of UW, a wave detector 6 which decodes input data by binary decision, a UW detector 7 which detects UW. The frame timing generator 8 is provided. The other structure is the same as that of the device of the first embodiment (FIG. 1).

In this synchronizing device, the symbol synchronization is obtained in the same manner as the device of the first embodiment by using the inverted transmission data of the data transmitted on the common channel.

Further, the detection section 6 binary-codes the input detection output and decodes it into data, and the UW detection section 7 compares the decoded data with the UW pattern to detect UW. When UW is detected, the frame timing generation unit 8 generates a frame clock and frame synchronization is secured.

[0038]

As is apparent from the above description of the embodiments, the synchronizing apparatus of the present invention has a simple configuration and symbol synchronization for spread spectrum multiple access (SSMA) communication using a polyphase orthogonal sequence as a spreading sequence code. And you can get frame synchronization.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a synchronization device according to a first embodiment of the present invention,

FIG. 2 is a block diagram showing a configuration of a synchronizing device according to a second embodiment of the present invention,

FIG. 3 is a time chart showing the timing of each waveform when outputting a symbol clock in the synchronizer of the first embodiment,

FIG. 4 is a common channel frame format used in the synchronizer of the second embodiment;

FIG. 5 is a diagram showing an autocorrelation waveform of a data-modulated polyphase orthogonal sequence,

FIG. 6 is an enlarged view of an autocorrelation waveform of a binary code (a) and a polyphase orthogonal sequence (b),

FIG. 7 is a diagram showing a phase plane of a polyphase orthogonal sequence;

FIG. 8 is a block diagram showing a configuration of a conventional correlation detection device,

FIG. 9 is a block diagram showing a configuration of a conventional synchronization device.

[Explanation of symbols]

 1 Synchronous Circuit 2 LPF (Low Pass Filter) 3 Zero Cross Point Detection Unit 4, 96 Symbol Timing Generation Unit 5 Zero Cross Point Tracking Unit 6 Detection Unit 7 UW Detection Unit 8 Frame Timing Generation Unit 81, 83, 85, 87 Matched Filter 82, 88 Code (I) 84, 86 Code (Q) 89, 90, 94 Adder 91, 92 Squarer 93 Phase detector 95 Peak position detector 97 Peak position tracking unit

Claims (5)

[Claims] 1. A synchronization device for performing correlation detection on transmission data spectrum-spread with a spreading code of a polyphase orthogonal sequence and acquiring symbol synchronization of the transmission data based on the correlation detection output, A low-pass filter that inputs the correlation detection output and outputs the envelope data, a zero-cross point detecting unit that detects a zero-cross point of the envelope data, and a time of 1/2 of the symbol period from the time of the detected zero-cross point. And a symbol timing generating means for outputting a symbol clock at the time when has passed. 2. The symbol timing generation means averages a plurality of zero cross points detected by the zero cross point detection means to determine a zero cross point as a reference of the output of the symbol clock. 1. The synchronization device described in 1. 3. The synchronization according to claim 1, further comprising tracking means for detecting the zero-cross point even after the symbol synchronization is acquired and correcting the output timing of the symbol clock in the symbol timing generation means. apparatus. 4. The synchronization device according to claim 1, wherein after the symbol synchronization is obtained, the operation of the correlation detection is performed only in a window having a time width shorter than one symbol period. 5. A decoding means for decoding transmission data based on the correlation detection output, a unique word detection means for detecting a unique word included in the transmission data, and a frame clock when the unique word is detected. 2. The synchronizing device according to claim 1, further comprising a frame timing generating means for outputting.