JP2000252972A - Packet receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recognize a packet with high reliability even when a spread spectrum communication system using a power transmission line uses a short code to recognize the packet. SOLUTION: A packet has a configuration such that a packet head has a carrier recognition code for the recognition of packet head, a symbol synchronizing code to establish symbol synchronization and a frame synchronizing code to establish frame synchronization. The packet receiver is provided with a carrier recognition code detection means that recognizes the carrier recognition code and outputs a carrier recognition signal denoting reception of the packet, a symbol synchronization means 30 that outputs a symbol synchronizing timing on the basis of a reference phase of a symbol synchronizing code and a code collation means 40 that receives the carrier recognition signal and the symbol synchronization timing, collates the frame synchronizing code to conduct the frame synchronization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a packet receiving apparatus for receiving data composed of one or more packets.

[0002]

2. Description of the Related Art When a power line is used as a transmission line, the power line has the following characteristics that hinder establishment of synchronization. (1) Load fluctuation: Transmission characteristics greatly change due to connection of connected home electric appliances and home power lines.
(2) Impedance fluctuation: The load impedance fluctuates in synchronization with a commercial power frequency of 50 or 60 Hz or a frequency twice as high as that of the commercial power supply frequency due to the rectifier diode bridge.
(3) Home appliance operation noise: switching noise and inverter noise, which are single noises due to switching of the power supply of the appliance, and periodic noise due to thyristors, triacs, and the like are generated. Inverter noise occurs, for example, when an incandescent light bulb with a dimmer is connected to a power line. FIG. 13 shows a time waveform and a spectrum of the operation noise in that case. The periodic noise occurs, for example, when a microwave oven is connected to a power line. In FIG.
The time waveform and spectrum of the operation noise in that case are shown.

As a demodulation method in the direct spread spectrum communication method, a demodulation method for simultaneously performing symbol synchronization and frame synchronization using a sliding correlation and a matched filter (hereinafter referred to as a first demodulation method) is generally performed. However, when the first demodulation method is applied to a power line, the above-described (1) and (2) cause a problem that synchronization cannot be established. For details, see “DS / S that simultaneously transmits a reference PN sequence suitable for power line data transmission.
S Method "(Transactions of the Institute of Electronics, Information and Communication Engineers, B-II Vol. J
74-B-II-5) and “Spread spectrum power line communication method” (Transactions of the Institute of Electronics, Information and Communication Engineers, B-IIVol.
J74-B-II-5) and the like, and the first demodulation method has been regarded as inappropriate due to the characteristics of the power line.

Therefore, as a method that replaces the first demodulation method, symbol synchronization is obtained by using a delay correlation that is considered to be relatively strong in a transmission line having the above-described characteristics (1) and (2). (Hereinafter referred to as a second demodulation method) has been used.

In this case, the frame structure of the packet is shown in FIG.
As shown in FIG. 5, a symbol synchronization code 102 for training a PLL for symbol synchronization and a frame synchronization code 103 using a code having a sharp autocorrelation are provided at the head of the packet in this order, and the encoded data 10
4 follows. Next, regarding the receiving device of the second demodulation method,
This will be described with reference to FIG. 110 is a demodulation unit, 130 is a symbol synchronization unit, 140 is a code matching unit, 150 is an encoding unit, 160 is a modulation unit, and 170 is a decoding unit. First, the data to be transmitted is encoded by the encoding unit 150, further modulated by the modulation unit 160, and transmitted to the transmission path. On the receiving side, after demodulation by the demodulation unit 110, first, the symbol synchronization unit 130 synchronizes the symbols using differential detection. Next, the code matching means 140
Then, the demodulated data is sampled and autocorrelated with the PN pattern of the frame synchronization code according to the same principle as that of the matched filter. If a given threshold is exceeded, frame synchronization is assumed to have been achieved. After synchronizing the frames, the decoding means 170 decodes the data.

In the second demodulation method, symbol synchronization is first established, and then autocorrelation of a PN pattern is detected by frame synchronization processing to decode data. As shown in FIG. P of random frame synchronization
If there is no pseudo pattern similar to the N code (hereinafter simply referred to as a pseudo pattern), normal processing can be performed. However, if the pseudo pattern exists at the beginning of the packet as shown in FIG. When the packet matches the PN pattern of the frame synchronization, the processing shifts to packet data processing for decoding data. As a result, meaningless decoding is performed. If a packet is received during that time, a true packet is dropped. There was a possibility. As a countermeasure, measures have been taken to lengthen the frame synchronization PN pattern in order to suppress the appearance probability of noise similar to the frame synchronization code 103, but there is a limit in power line packet communication in which home appliance noise is present.

[0007]

In view of the above situation, in order to solve the above-mentioned problems, the present invention solves the above-mentioned problem by transmitting a packet even on a power line in which load fluctuation, impedance fluctuation, or operation noise of home electric appliances occur. It is an object of the present invention to provide a packet receiving apparatus that can recognize a packet with high reliability even if a short code is used for recognition.

[0008]

According to a first aspect of the present invention, a carrier recognition code for recognizing the head of a packet, a symbol synchronization code for establishing symbol synchronization, and a frame synchronization code for establishing frame synchronization are provided. And a carrier recognition code for receiving a packet having a head of the packet in the order of a carrier recognition code, a symbol synchronization code, and a frame synchronization code, receiving the carrier recognition code, and outputting a carrier recognition signal indicating that the packet has been received. Detecting means;
A symbol synchronization unit that outputs a symbol timing based on a reference phase of the symbol synchronization code, and a frame indicating that the frame is synchronized with the frame synchronization code by receiving the carrier recognition signal and the symbol timing. Code matching means for outputting a synchronization signal.

The second invention comprises a code collating means for outputting a frame synchronizing signal when the frame synchronization is achieved, and outputting an initialization signal when the frame synchronization is not achieved.

In a third aspect, a frame synchronization code is
A PN code is used.

In a fourth aspect, a carrier recognition code is
A PN code is used.

In a fifth aspect of the present invention, as a carrier recognition code,
Use alternating codes.

According to a sixth aspect of the present invention, the carrier recognition code and the symbol synchronization code use alternating codes of the same code sequence.

According to the present invention, in order to establish frame synchronization of a packet with high reliability, a carrier recognition code and a frame synchronization code are provided at the head of the packet with a symbol synchronization code interposed therebetween. With this configuration, even if a pseudo pattern is generated and is erroneously recognized as a carrier recognition code, the probability that a pseudo pattern is generated at the position of the frame synchronization code is low, so that the carrier recognition operation can be performed again at this time. it can. Since the noise generated on the power line has a characteristic that the same pattern of noise is periodically repeated, it is more preferable that the carrier recognition code and the frame synchronization code be different from each other at the time of frame synchronization. The probability of misperception is even lower. As described above, even if a pseudo pattern exists, a true packet can be prevented from being missed, and a packet can be recognized with higher reliability than a conventional method having no carrier recognition code.

Further, a unique carrier recognition code is used. Assuming that low and high constants are examples of the carrier recognition code, when a received signal on which household electrical appliance noise is superimposed is subjected to reception processing through a low-pass filter having the above-described roll-off characteristic, the characteristic of the noise causes a low constant. It is clear that the probability of occurrence of a high or constant noise is high, and the probability of erroneously recognizing the head of a packet is high. Therefore, as the carrier recognition code, an PN code having a strong autocorrelation and having a wide band energy and a frequency component close to the cutoff frequency of the roll-off filter are used, so that an alternating code having low randomness is used.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, the demodulated data output from the demodulation means 10 is binary digital data, and the processing is performed by the carrier recognition code detection means 20, the symbol synchronization means 13, and the code collation means 40. It will be described as being performed.

FIG. 1 is a diagram showing the principle of the structure of a packet according to the embodiment of the present invention. Explaining the components, 1 is a carrier recognition code for recognizing the start of a packet, 2 is a symbol synchronization code for performing PLL phase adjustment and establishing symbol synchronization, and 3 is a frame synchronization in the packet. A frame synchronization code 4 for establishing is coded data. FIG. 9 is a configuration diagram when a PN code is used as a carrier recognition code, an alternating code is used as a symbol synchronization code, and a PN code is used as a frame synchronization code. This case will be described below.

FIG. 2 is a diagram showing a state transition of the operation of the present invention. Normally, a carrier recognition code is detected, and upon detection, symbol synchronization is performed, and then frame synchronization is performed. If frame synchronization is not achieved, the operation transits to the carrier recognition code detection operation, and if frame synchronization is achieved,
It performs packet data processing, that is, data decoding. When the packet data processing ends, the flow returns to carrier code recognition.

FIG. 3 exemplifies an apparatus configuration according to an embodiment of the present invention for processing the packet configuration of FIG. 1 described above. 10 is a demodulation means for generating demodulated data, 20 is a carrier recognition code detection means for recognizing a code string for which symbol synchronization has not been established, 30 is a symbol synchronization means for outputting symbol timing, and 40 is a frame synchronization signal or initial signal. Code matching means for outputting an encoded signal; 50, an encoding means for adding a carrier recognition code 1, a symbol synchronization code 2, and a frame synchronization code 3 to a header to input data; and 60, a code output from the encoding means 50. Modulating means for directly performing spread spectrum modulation by multiplying the coded signal by the PN code, 70 performs packet data processing, that is, decodes the coded packet,
This is decoding means for restoring data from encoded data.

Next, the operation of the present invention will be described step by step. First, the data input on the transmission side enters the encoding unit, adds the carrier recognition code 1, the symbol synchronization code 2, and the frame synchronization code 3 to the header, performs error correction encoding and the like, and enters the modulation unit 60. Modulating means 60
Then, as shown in FIG. 8, differential encoding is performed using an exclusive OR 63 and a delay unit 64 for delaying one symbol.
Further, multiplication with the PN code 61 is performed by the multiplication means 62,
It is transmitted as a transmission signal. The received signal received via the power line enters the demodulation means 10, and as shown in FIG.
Delay detection is performed by exclusive OR with the delay unit 11, and demodulated data is output via the roll-off filter 13.

With the demodulated data as an input, the carrier recognition code detecting means 20 outputs two sample signals 1 and 2 having a phase difference of π / 2, as shown in FIG.
After sampling the demodulated data by the sampling means 21 and the sampling means 22, respectively, and calculating the autocorrelation value by the autocorrelation calculation means 23 and the autocorrelation calculation means 24 which match with the same code as the carrier recognition code. By adding the respective auto-correlation values by the adding means 25, the auto-correlation of a code string for which symbol synchronization has not been established can be detected. The autocorrelation calculation means 23 and the autocorrelation calculation means 24 have the same configuration as a normal matched filter. By performing the addition, the autocorrelation is small in uncorrelated noise, and high in the carrier recognition code,
Since a symbol error is sometimes included, even if the carrier recognition code is used, the autocorrelation is reduced by the amount of the symbol error. If the autocorrelation value is higher than the threshold value, a carrier recognition signal is output.

Next, the symbol synchronizing means 30 synchronizes the input demodulated data with the symbol, and sends the symbol timing and the demodulated data to the code collating means 40.

In the code collating means 40, the demodulated data is sampled by the sampling means 41 as shown in FIG. 7, and the autocorrelation calculating means 42 calculates the autocorrelation value with the PN pattern of the frame synchronization code by the same principle as that of the matched filter. I do. Sometimes a symbol error is included, so even if the frame synchronization code is used, the autocorrelation becomes smaller by the symbol error, and the autocorrelation is compared with a threshold value by the comparing means 43. If it is also higher, a frame synchronization signal is output. Otherwise, an initialization signal is output to the carrier recognition code detection means 20.

Upon receiving the demodulated data, the frame synchronization signal, and the symbol timing, the decoding means 70 decodes the demodulated data to obtain data.

FIG. 11 illustrates the flow of the operation in this embodiment when there is no pseudo pattern. When there is no pseudo pattern, normally, it is in the state of the carrier recognition code detection operation (A) upon receiving the demodulated data. Next, when a carrier recognition code is received, the autocorrelation value of the carrier recognition code exceeds a threshold value, and a carrier recognition signal is output. The symbol timing is outputted by the symbol synchronization operation (B) performed in parallel, and the frame synchronization operation (C) is performed by the code collating means 40 based on the demodulated data, the symbol timing, and the carrier recognition signal, and the packet is confirmed to be a packet. Is done. Frame synchronization is established, and upon receiving the frame synchronization signal, packet data processing, that is, decoding (D) of demodulated data is performed. When the packet data processing is completed, the process returns to carrier recognition code detection (A) and waits for the next carrier recognition code.

FIG. 12 illustrates a flow of operation in the case where a pseudo pattern having a code sequence very similar to the carrier recognition code occurs in the present embodiment. If the burst noise or the pseudo pattern exists alone outside the packet, the autocorrelation value exceeds the threshold value in the carrier recognition code detection (A) and the symbol synchronization operation (B) is performed. In the frame synchronization operation (C), the process returns to (A) without causing the autocorrelation value to exceed the threshold value, and thus does not shift to packet data processing (D). Next, when the pseudo pattern exists before the packet, the autocorrelation value exceeds the threshold value in the carrier recognition code detection (A) in response to the pseudo pattern, and the symbol synchronization operation (B) is performed. In the frame synchronization operation (C), the symbol synchronization code 2 is disregarded, and the frame synchronization code 3 allows the autocorrelation value to exceed the threshold value and be recognized as a packet without any problem. Next, packet data processing (D)
After that, the process returns to the carrier recognition code detection (A).

Although the carrier recognition code 1 and the frame synchronization code 3 are both PN codes, it is preferable that they are not the same code string because household electrical equipment noise may occur periodically.

It should be noted that the carrier recognition code 1 may be a unique code having a low appearance probability, and from that point of view, a PN pattern having a strong autocorrelation has been used in the above, but a code that can be distinguished from other codes. Anything may be used, and in that sense, a GOLD code or the like can be used. The same applies to the frame synchronization code, as long as it is a unique code having a low appearance probability, and a GOLD code or the like can be used.

Further, as shown in FIG. 10, if an alternating code is used as the carrier recognition code and the symbol synchronization code is lengthened and shared with the carrier recognition code, the code can be used without preparing the carrier recognition code. Means 50 can be simplified. When an alternating code is used as the carrier recognition code, the autocorrelation calculating means 23 in FIG. 5 may perform an operation of outputting a count of the number of changes between high and low, which is a characteristic of the alternating code, instead of a matched filter.

Although the above description has been made on the assumption that the coded data is multiplied by the PN code and the spread spectrum modulation is performed directly, the secondary modulation may be performed by radio or the like.

[0031]

As described above, the following advantageous effects can be obtained by the present invention.

(1) Since the demodulated data is decoded after the existence of the packet is confirmed by the carrier recognition code, the packet is incorrectly decoded due to erroneous packet recognition due to inverter noise and switching noise from the home electric appliance. The probability of dropping can be reduced, and the reliability of communication using a power line in which household electrical noise occurs is improved.

(2) It is also possible to suppress the length of the frame synchronization code, which is a means for suppressing erroneous recognition, to reduce the probability of erroneous recognition of packet processing in communication using a power line in which household noise is generated. Will be possible.

(3) At the stage of establishing frame synchronization,
When frame synchronization is not achieved, an initialization signal is output immediately without performing packet decoding processing, and the apparatus waits for a carrier recognition code, thereby making it possible to further reduce packet loss.

Such an improvement in the packet recognition rate has an effect of reducing processing of an upper layer due to detection of an erroneous packet caused by a transmission error or preventing an increase in traffic due to packet retransmission.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the basic configuration of a packet configuration according to an embodiment of the present invention;

FIG. 2 is a state transition diagram of processing according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of an apparatus according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a demodulation unit of the apparatus according to one embodiment of the present invention.

FIG. 5 is a configuration diagram of a carrier recognition code detecting unit of the device according to one embodiment of the present invention.

FIG. 6 is a configuration diagram of a symbol synchronization unit of the device according to one embodiment of the present invention.

FIG. 7 is a configuration diagram of a code collating unit of the apparatus according to an embodiment of the present invention.

FIG. 8 is a configuration diagram of a modulation unit of the device according to an embodiment of the present invention.

FIG. 9 is a diagram illustrating a frame configuration of a packet according to an embodiment of the present invention.

FIG. 10 is a diagram illustrating a frame configuration of a packet according to an embodiment of the present invention.

FIG. 11 is a diagram showing an operation example according to one embodiment of the present invention;

FIG. 12 is a diagram showing an operation example according to one embodiment of the present invention;

FIG. 13 is a diagram showing an example of a time waveform and a spectrum of operation noise due to an incandescent lamp with a dimmer.

FIG. 14 is a diagram showing an example of a time waveform and a spectrum of noise caused by a microwave oven.

FIG. 15 is a diagram illustrating a frame configuration of a conventional packet.

FIG. 16 is a diagram showing an operation example of conventional packet processing.

FIG. 17 is a diagram showing an operation example of conventional packet processing.

FIG. 18 is a configuration diagram of a conventional device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 carrier recognition code 2 symbol synchronization code 3 frame synchronization code 4 encoded data 10 demodulation means 11 delay means 12 exclusive OR 13 roll-off filter 20 carrier recognition code detection means 21 sampling means 22 sampling means 23 autocorrelation calculation means 24 autocorrelation Calculation means 25 Addition means 26 Comparison means 30 Symbol synchronization means 40 Code verification means 41 Sample means 42 Autocorrelation calculation means 43 Comparison means 50 Encoding means 60 Modulation means 61 PN code 62 Multiplication means 63 Exclusive OR 64 Delay means 70 Decoding Means 102 Symbol synchronization code 103 Frame synchronization code 104 Encoded data 110 Demodulation means 130 Symbol synchronization means 140 Code collation means 150 Encoding means 160 Modulation means 170 Decoding means

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yuji Igata 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. 5K022 AA21 EE02 5K047 AA01 BB06 GG34 HH01 HH12 MM11

Claims (6)

[Claims] 1. A carrier recognition code for recognizing the head of a packet, a symbol synchronization code for establishing symbol synchronization, and a frame synchronization code for establishing frame synchronization, the carrier recognition code and the symbol synchronization code. Receiving a packet at the beginning of the packet in the order of the frame synchronization code, receiving the carrier recognition code, and outputting a carrier recognition signal indicating that the packet has been received; Symbol synchronization means for outputting a symbol timing based on the reference phase; receiving the carrier recognition signal and the symbol timing, outputting a frame synchronization signal indicating that frame synchronization has been performed by collating with the frame synchronization code. A packet receiving device comprising: code matching means. 2. The code matching means outputs a frame synchronization signal when frame synchronization is achieved, and outputs an initialization signal for initializing the carrier recognition code detection means when frame synchronization is not achieved. 2. The method according to claim 1, wherein
The packet receiving device according to the above. 3. The packet receiving apparatus according to claim 1, wherein a PN code is used as the frame synchronization code. 4. The packet receiving apparatus according to claim 1, wherein a PN code is used as the carrier recognition code. 5. The packet receiving apparatus according to claim 1, wherein an alternating code is used as the carrier recognition code. 6. A carrier recognition code and a symbol synchronization code,
4. The packet receiving apparatus according to claim 1, wherein an alternating code of the same code string is used.