WO2012169247A1

WO2012169247A1 - Receiver

Info

Publication number: WO2012169247A1
Application number: PCT/JP2012/055621
Authority: WO
Inventors: 遠藤　誠; 英之根日屋; 塚本　信夫; 東一奥野
Original assignee: アルプス電気株式会社
Priority date: 2011-06-07
Filing date: 2012-03-06
Publication date: 2012-12-13

Abstract

The purpose of the present invention is to increase a packet data acquisition rate by improving the detection rate of a header during symbol synchronization. A receiver is comprised of a peak distribution holding unit (36) which includes a counter (361) repeating a counter index within the range of one to N × M in synchronization with a correlation value detected by a convolver (34), and detects a peak from the correlation value output from the convolver (34) while accumulating the peak detection number corresponding to the counter index of one to N × M, and a determination unit (37), which if the peak is continuously detected from the accumulated distribution of the peak detection numbers accumulated in the peak distribution holding unit (36) for a number equal to the number of symbols in header information in the same counter index or within the range of counter indexes deemed as the same counter index, generates a timing for decoding a diffusion signal picked up by a demodulation unit.

Description

Receiver

The present invention relates to a receiver that detects the header of packet data from encoded received data and obtains data capture timing.

Conventionally, in an electric field communication system, a transmitter adds a header to packet data and transmits the packet data, and the receiver detects the header and obtains the packet data. In such an electric field communication system, header detection and packet data decoding are performed by symbol synchronization (for example, refer to Patent Documents 1 and 2).

A symbol synchronization method in a conventional receiver will be described.
FIG. 5 is a schematic configuration diagram illustrating a symbol synchronization unit included in the receiver. The symbol synchronization unit includes a convolver (correlation detector) 50 that detects a correlation value from an input received signal, an absolute value output unit 51 that converts the detected correlation value into an absolute value, and an absolute value of the correlation value. A peak detector 52 that detects a peak by comparing with a threshold value, a symbol synchronizer 53 that determines header detection when the number of detected peaks exceeds a predetermined value, and a delay device 54 that delays a signal input from the convolver 50 ,including.

FIG. 6 is a flowchart showing the flow of symbol synchronization processing in the receiver shown in FIG. The data information spread by the spreading code in the transmitter is modulated and transmitted. On the receiver side, the received signal is demodulated by the demodulator (step ST201). The demodulated signal detects a correlation value using the same spreading code (hereinafter referred to as a reference code) as the spreading code used by the convolver 50 on the transmitter side (step ST202). FIG. 7A shows a waveform of a correlation value output signal (referred to as a correlation signal) output from the convolver 50. The difference between the correlation signal output from the convolver 50 and the correlation signal after one symbol delay (FIG. 7B) is taken (step ST203), and the difference signal shown in FIG. A waveform is obtained (step ST204).

If the header information added to the packet data is a fixed value of 8 bits such as 01010000, for example, the difference signal obtained by the difference from the correlation signal after 1 symbol delay is 0 and 1 of both symbols. A peak appears at the overlapping timing (FIG. 7D). In FIG. 7D, a continuous peak output appears in a region surrounded by a one-dot chain line. The peak detector 52 compares the correlation value with the threshold value. If the correlation value exceeds the threshold value (step ST205: Yes), the peak detector 52 determines that the peak (maximum value) has been detected and counts. Increment the number. And if it is the said header information of 8 bits (01010000), when a peak is counted 4 times continuously (step ST206: Yes), it will judge that header information was detected (step ST207), and delay device 54 Packet data is taken in and decoded (step ST208).

On the other hand, when the peak value does not reach the threshold value (step ST205: No), or when the maximum value is not continuously counted four times within one symbol (step ST206: No), the header is not detected. Judgment is made (step ST209), and the packet data is discarded (step ST210).

Special table 2010-512094 JP 2010-259071 A

However, in the above symbol synchronization method, the threshold value is determined by adding the correlation value of the received symbol and the received symbol correlation value after one symbol delay. If the value level is low, the threshold may not be exceeded. As a result, there is a problem that packet data is discarded without detecting the header and packet loss occurs.

The present invention has been made in view of such a point, and an object of the present invention is to provide a receiver capable of increasing a packet data acquisition rate by increasing a header detection rate in symbol synchronization of encoded information data. And

The receiver of the present invention generates a spread signal by multiplying information data including header information having a predetermined bit pattern on the transmitter side by a spread code of N bits (N is a natural number), and uses the spread signal to generate a carrier wave. A receiver for receiving a modulated transmission signal; a demodulator that demodulates the received transmission signal to extract the spread signal; and oversampling the demodulated spread signal M times (M is a natural number) An AD converter that outputs a spread signal sequence, and generates a reference code having an N × M bit length correlated with the spread code used to generate the spread signal on the transmitter side, and the reference code and the AD conversion A correlator for detecting a correlation value with an N × M bit length spread signal sequence output from the unit and shifting the spread signal sequence to be detected in the time-series direction in bit units, and a correlation value by the correlator Detected A counter that repeats a counter index that is a count number in a range of 1 to N × M, detects a peak from a correlation value output from the correlator, and counts from 1 to N × A peak distribution holding unit for accumulating the number of peak detections corresponding to the counter index of M, and a counter index range that is assumed to be the same or the same from the cumulative distribution of the number of peak detections accumulated in the peak distribution holding unit And a determination unit that generates a timing for decoding the spread signal extracted by the demodulation unit when a peak is detected continuously for a number of times corresponding to the number of symbols in the header information. .

According to this receiver, it is possible to obtain a peak distribution obtained by accumulating the number of peak detections corresponding to the counter index, and if it can be determined from the peak distribution that the number of peaks corresponding to the number of symbols in the header information has been continuously detected, Since the header information has been detected, the timing for decoding the spread signal can be obtained. Thereby, even if the peak of the correlation output is low, the peak can be counted, so that the header can be detected. Therefore, even when the S / N ratio is small, it is possible to increase the header data detection rate in symbol synchronization and increase the packet data acquisition rate.

In the receiver, the AD conversion unit may perform double sampling with M = 2.

Furthermore, the receiver can be used for a communication device that performs electric field communication of an information signal via a transmission medium.

According to the present invention, it is possible to increase the packet data acquisition rate by increasing the header detection rate in symbol synchronization.

It is a schematic block diagram which shows the communication system which concerns on this Embodiment. It is a schematic block diagram which shows the symbol synchronization part which concerns on the said embodiment. It is a flowchart which shows the flow of the main processes of the symbol synchronization which concerns on the said embodiment. It is a figure which shows the correlation peak accompanying the process of the symbol synchronization which concerns on the said embodiment. It is a schematic block diagram which shows the conventional symbol synchronizer. It is a flowchart which shows the flow of the main processes of the conventional symbol synchronization. It is a figure which shows the correlation peak accompanying the process of the conventional symbol synchronization. 1 is a system configuration diagram of an electric field communication system according to an embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram showing a communication system according to an embodiment of the present invention. The communication system shown in FIG. 1 includes a transmission medium 2 such as a human body that transmits information data via an electric field, a transmitter 1 that applies an electric field obtained by modulating information data to the transmission medium 2, and a transmission medium 2. The receiver 3 mainly detects the electric field and demodulates the electric field into information data.

The transmitter 1 is disposed close to the transmission medium 2 and mainly includes a transmission electrode (not shown) that applies an electric field to the transmission medium 2 and a transmission circuit (not shown). The transmitter 1 generates a spread signal by multiplying information data including header information having a predetermined bit pattern by a spread code of N bits (N is a natural number), and a modulator 11 modulates a carrier wave with the spread signal. To transmit a transmission signal.

The receiver 3 is disposed close to the transmission medium 2, receives a reception electrode (not shown) that receives an electric field from the transmission medium 2, a demodulator 31 that demodulates the received transmission signal and extracts a spread signal, and demodulated diffusion It includes an AD converter 32 that oversamples the signal M times (M is a natural number) and outputs a spread signal sequence, and a symbol synchronization unit 33 that decodes packet data.

FIG. 2 is a schematic configuration diagram showing the symbol synchronization unit 33. The symbol synchronization unit 33 includes a convolver (correlator) 34, an index extractor 35, a peak distribution holding unit 36, a determination unit 37, and a delay unit 38. A convolver (correlator) 34 generates a reference code having an N × M bit length correlated with the spreading code used to generate the spread signal on the transmitter 1 side, and outputs the reference code and the N code output from the AD converter 32. A correlation value with a spread signal sequence of × M bit length is detected, and a spread signal sequence as a correlation detection target is shifted in the time series direction in bit units. The index extractor 35 detects the peak of the correlation value (absolute value) detected by the convolver 34 and outputs an index corresponding to the peak position. The peak distribution holding unit 36 has a free-run counter 361 that counts in synchronization with the index extracted by the index extractor 35 and repeats a counter index as a count number in a range of 1 to N × M, and is output from the convolver 34. A peak is detected from the correlation value, and the counter number corresponding to the counter index when the peak is detected is incremented. That is, the free-run counter 361 accumulates the number of detection times of the peak-detected counter index for each counter index. The determination unit 37 continuously determines the number of times corresponding to the number of symbols in the header information within the same counter index or the counter index range assumed to be the same from the cumulative distribution of the peak detection times accumulated in the peak distribution holding unit 36. If the peak is detected, a timing signal for decoding the spread signal extracted by the demodulator 31 is output. The determination unit 37 includes a maximum index determination unit 37a that determines the maximum counter index from the number of detections accumulated in the free-run counter 361, and a peak detection number of the counter index that is the maximum from the detection number. If the header information is a fixed value of 8 bits such as 01010000, the index determination unit 37b outputs a timing signal when it reaches 8 times. The delay unit 38 delays the reception signal input from the convolver 34 by a header (8 bits), and takes in the signal held when the timing signal is received from the index determination unit 37b as packet data.

Next, a symbol synchronization technique in the receiver according to the embodiment of the present invention will be described.
FIG. 3 is a flowchart showing a flow of symbol synchronization processing in the receiver shown in FIGS. The information data spread by the transmitter 1 using the spread code is transmitted after being phase-modulated, for example, by the modulator 11. On the receiver 3 side, the demodulator 31 demodulates the received signal (step ST101). The AD converter 32 oversamples the demodulated extension signal M times (step ST102). The convolver 34 detects a correlation value using a reference code having a high correlation with the spreading code (step ST103). The index extractor 35 extracts an index corresponding to the peak position of the detected correlation value (step ST104). The peak distribution holding unit 36 accumulates the number of peak detections in association with 1 to N × M counter indexes (step ST105). When the peak is continuously detected by the number corresponding to the number of symbols in the header information within the same counter index or the counter index range assumed to be the same (step ST106: Yes), the determination unit 37 determines the header information. It is determined that it has been detected (step ST107), and packet data is fetched from the delay unit 38 and decoded (step ST108).

On the other hand, in the same counter index or a counter index range that is assumed to be the same, if no peak is detected continuously for the number of times corresponding to the number of symbols in the header information (step ST106: No), it is determined that the header has not been detected. The packet data is discarded (step ST110).

Subsequently, the header information added to the packet data is 8 bits, the spreading code is 8 bits (N = 8), and the AD converter 32 performs double sampling (M = 2) as an example. Specific examples will be described. In the following, double oversampling is also referred to as double sampling.

The received signal received by the receiver 3 is demodulated by the demodulator 31. The demodulated extension signal is double-sampled by the AD converter 32, and the AD converter 32 outputs a 16-bit extended signal sequence.

The convolver 34 generates a 16-bit (N × M = 8 × 2) long reference code, and detects a correlation value between this reference code and the 16-bit extended signal sequence output from the AD converter 32. The index extractor 35 repeatedly counts in the range of 0 to 15 in synchronization with the bit shift of the extended signal sequence to be detected by the convolver 34, and outputs a counter index corresponding to the peak position of the correlation value. The peak distribution holding unit 36 counts the counter index extracted by the index extractor 35 in the free-run counter 361 in parallel, and accumulates the peak position detected from the correlation value output from the convolver 34 in correspondence with the counter index.

The reason why the counter index in the free-run counter 361 is 16 bits long from 0 to 15 is that the spreading code is 8 bits, and the extension signal is double-sampled by the AD converter 32. By becoming an index data string.

FIG. 4A is a diagram illustrating an example of a correlation value peak for 8 symbols corresponding to the number of symbols in the header information and a counter index corresponding to the peak. In the first symbol, since the peak of the correlation value is detected at the counter index 7, the peak distribution holding unit 36 stores the number of peak detections at the counter index 7. Similarly, in the second symbol, since the peak of the correlation value is detected at the counter index 7, the peak distribution holding unit 36 accumulates and stores the number of peak detections at the counter index 7. This is performed up to the eighth symbol. Also in the eighth symbol, since the peak of the correlation value is detected at the counter index 7, the peak distribution holding unit 36 accumulates and stores the number of peak detections at the counter index 7.

Subsequently, in the determination unit 37, the number of times corresponding to the number of symbols of the header information in the same counter index or the counter index range assumed to be the same from the cumulative distribution of the number of peak detections accumulated in the peak distribution holding unit 36. It is determined whether or not a peak has been detected for 8 consecutive times.

FIG. 4B is a diagram illustrating an example of a cumulative distribution of the number of peak detections accumulated in the peak distribution holding unit 36. In FIG. 4B, the vertical axis indicates the number of symbols, and the horizontal axis indicates the counter index where the peak is detected. In the example shown in FIG. 4B, the distribution range of the peak detection frequency for 8 symbols is shown, and the peak detection frequency is highest in the counter index 7, but peaks are also detected in the

counter indexes

6 and 8. When double sampling is performed in the AD converter 32, the counter index range is assumed to be the same if the distribution range is the median value ± 1. Therefore, the example of FIG. 4B shows that peaks were detected eight times consecutively in the same counter index or a counter index range that is assumed to be the same.

Also, the distribution range of the median value of the counter index ± 1 may straddle symbols. For example, when the median value of the counter index is 0, the distribution range of the median value ± 1 of the counter index is 15, 0, 1 of the previous symbol. When the median value of the counter index is 15, the distribution range of the median value ± 1 of the counter index is 14, 15 and 0 of the next symbol.

According to this, even if the peak value of the correlation value is small, it is possible to count peaks that are continuous for 8 symbols. Therefore, even if the peak value of the correlation value decreases as the S / N ratio (Signal to Noise ratio) decreases due to the communication environment, the counter index for 8 symbols is determined and its distribution range is determined. It becomes possible.

As described above, according to the receiver 3 according to the present embodiment, the convolver 34, the index extractor 35, and the free-run counter 361 can obtain the index together with the correlation output corresponding to the spread code, and the maximum index determination After determining the counter index having the maximum peak value from among these indexes by the unit 37a, the header in the received signal (packet data) is detected by determining the cumulative number of these counter indexes by the index determining unit 37b. can do. Thereby, even if the peak of the correlation output is low, the peak can be counted, so that the header can be detected. Therefore, even when the S / N ratio is small, it is possible to increase the header data detection rate in symbol synchronization and increase the packet data acquisition rate.

Next, an electric field communication system provided with the receiver of the present invention will be described with reference to FIG. FIG. 8 is a system configuration diagram of the electric field communication system according to the embodiment of the present invention. In the following, a transmission / reception apparatus that transmits and receives an information signal via a human body will be described as an example of a transmission medium. However, the present invention is not limited to this configuration, and can be changed as appropriate.

As shown in FIG. 8, the communication system 100 transmits and receives information signals via a transmission medium such as the human body 102, and is in contact with or capacitively coupled to the communication apparatus 103 attached to the human body 102. Thus, a transmission / reception device 104 that communicates with the communication device 103 via the human body 102 is provided. The receiver 3 is applied to the receivers of the communication device 103 and the transmission / reception device 104. The communication device 103 has substantially the same configuration as the transmission / reception device 104 and is different from the transmission / reception device 104 only in that the communication device 103 is worn on the human body 102. Therefore, in the following description, description of the communication device 103 is omitted as much as possible, and the description will focus on the transmission / reception device 104.

In this communication system 100, the communication device 103 and the human body 102 and the transmission / reception device 104 and the human body 102 are electrically capacitively coupled, and the information signal is transmitted by an electric field obtained by modulating the information signal. It is like that. In this case, the displacement current flows through the human body 102 but the steady current does not flow. Therefore, the communication device 103 and the human body 102 do not need to be electrically connected. Therefore, for example, since the electrode of the communication device 103 and the human body 102 are capacitively coupled via a thin cloth, an information signal can be transmitted even from the top of clothing.

The human body 102 is a transmission medium through which a displacement current flows, and has a high impedance of several hundreds [Ω], for example. The transmission / reception device 104 includes a transmission / reception electrode 111 that is in contact with or electrically capacitively coupled to the human body 102. A transmission system 112 that receives an information signal from the communication device 103 via the transmission / reception electrode 111 and a transmission system 113 that transmits an information signal to the communication device 103 via the transmission / reception electrode 111 are connected to the transmission / reception electrode 111, respectively. Yes. The transmission / reception electrode 111 is formed of a flat plate electrode, and can communicate with the communication device 103 via an electric field applied to the human body 102 by contact or capacitive coupling with the human body 102.

The reception system 112 has a filter 122 connected to the transmission / reception electrode 111 via a coupling capacitor 121. A receiving unit 127 provided in the electric field communication IC 114 is connected to the subsequent stage of the filter 122 via a coupling capacitor 126. As the receiving unit 127, the receiver 3 of the present invention is applicable. The receiving unit 127 includes a demodulation circuit (not shown), and demodulates the modulated signal received from the communication device 103 via the transmission / reception electrode 111 using the carrier wave used in the communication device 103 to obtain an information signal.

It should be noted that the present invention is not limited to the above embodiment, and can be implemented with various modifications. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

The present invention can be applied not only to electric field communication systems but also to receivers in other data communication systems.

This application is based on Japanese Patent Application No. 2011-126827 filed on June 7, 2011. All this content is included here.

Claims

A transmission signal generated by multiplying information data including header information having a predetermined bit pattern on the transmitter side by multiplying an N-bit (N is a natural number) spread code to generate a spread signal and modulating a carrier wave with the spread signal A receiver for receiving
A demodulator that demodulates the received transmission signal and extracts the spread signal;
An AD converter that oversamples the demodulated spread signal M times (M is a natural number) and outputs a spread signal sequence;
An N × M bit length reference code correlated with the spreading code used to generate the spread signal on the transmitter side, and the reference code and the N × M bit length spread signal output from the AD conversion unit A correlator that detects a correlation value with a sequence and shifts a spread signal sequence to be a correlation detection target in a time-series direction in bits,
It has a counter that counts in synchronization with the correlation value detected by the correlator and repeats the counter index that is the count number in the range of 1 to N × M, and peaks from the correlation value output from the correlator And a peak distribution holding unit for accumulating the number of times of peak detection corresponding to a counter index of 1 to N × M,
From the cumulative distribution of the number of peak detections accumulated in the peak distribution holding unit, peaks were continuously detected for the number of times corresponding to the number of symbols in the header information within the same counter index or counter index range assumed to be the same. If so, a determination unit that generates timing for decoding the spread signal extracted by the demodulation unit;
A receiver comprising:
The receiver according to claim 1, wherein the AD converter performs double sampling such that M = 2.
The receiver according to claim 1 or 2, wherein the receiver is used in a communication device that performs electric field communication of an information signal via a transmission medium.