JP2003188781A - Power line carrier noise-resistant communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power line carrier noise-resistant communication system in which stable data communications can be performed by improving noise resistance characteristics. <P>SOLUTION: The system is composed of: a means for diluting the influence of discontinuous noises by distributing signals to a time axis and a frequency axis by Walsh transform and OFDM modulation/demodulation as a transmitting circuit and a receiving circuit within a power line carrier communication device, and a means for cutting noises by detecting noises by a wavelet analysis which cannot be diluted with the above means. The former means deals with comparatively small discontinuous noises and both the former and latter means deal with comparatively large discontinuous noises so that the discontinuous noises of arbitrary sizes can be reduced. Then, the power line carrier communication device is disposed at any arbitrary position on the private wiring of a power line or the like deployed in advance inside a house or office, and by transmitting signals by repeating them through a coupling circuit inside the power line carrier communication device, data communications are performed between the power line carrier communication devices or with external communication devices. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power line carrier communication system for superimposing a signal on a power line for signal transmission.
In particular, by strongly reducing discontinuous noise such as spike noise (impulse noise) and surge noise (step function discontinuous noise), noise resistance can be dramatically improved and stable data communication can be performed. The present invention relates to a power line carrier noise resistant communication system.

[0002]

2. Description of the Related Art In power line carrier communication, a signal is transmitted by superimposing a signal on a power line laid in advance in a home or an office, so that it is not necessary to install a new transmission line, and cost reduction and effective use of existing equipment are possible. It enables extremely attractive data communication in terms of utilization. For this reason, there is an urgent need to technically establish data communication by power line carrier communication in device control and multimedia communication in homes and offices. In the power line carrier communication, the power line itself originally carries power, and various external noises are mixed therein. Therefore, it is extremely poor as a data communication transmission line, and the most technical point is how to remove discontinuous noises such as spike noises and surge noises generated from home appliances and the like.

[0003]

[Problems to be Solved by the Invention] The conventional spread spectrum modulation / demodulation method and DMT (Discrete
In the multitone modulation / demodulation method, data communication can be performed because the influence of noise on some frequency bands is limited, but if strong noise concentrates on the backup carrier frequency band or a specific carrier frequency band. There is a problem that the S / N ratio deteriorates and stable data communication cannot be performed.

The present invention has been made to solve the above problems, and strongly reduces discontinuous noises such as spike noises and surge noises superposed on a transmission line for power line communication. By doing so, noise resistance can be dramatically improved and stable data communication can be performed.
It is an object to provide a power line carrier noise resistant communication system.

[0005]

In order to solve the above problems, in a power line carrier noise resistant communication system of the present invention, a signal is used as a transmission circuit and a reception circuit in a power line carrier communication device for Walsh conversion and OFDM (Walsh) conversion. Orthogo
nal Frequency Division Multiplexing) means for diluting the effects of discontinuous noise such as spike noise and surge noise by dispersing on the time axis and frequency axis by modulation and demodulation, and wavelet analysis (Wa
(Velet analysis) to detect and cut noise. The former means is used for relatively small discontinuous noise, and the former and latter are used for relatively large discontinuous noise. By handling both means, it is possible to reduce the discontinuous noise of an arbitrary size.

Then, the power line carrier communication device is arranged at an arbitrary position in a home wiring such as a power line laid in advance in a home or an office, and a coupling circuit in the power line carrier communication device is relayed to transmit and receive signals. By performing signal transmission in the circuit, data communication is performed between power line carrier communication devices and with external communication devices. Furthermore, the transmission circuit and the reception circuit are connected to a communication network such as a wireless base station, the Internet, and a local area network by relaying a communication control circuit at a subsequent stage,
Performs data communication with a plurality of communication terminals.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a connection system diagram of a power line carrier communication device in a power line carrier noise resistant communication system of the present invention,
FIG. 2 is a schematic block diagram of a power line carrier communication device.

As shown in FIG. 1, a service wire 2 to a building 1 such as a home or an office is assumed to be laid in the building 1 as a house wiring 3 in advance at the time of construction. And
A power line carrier communication device 5 is arranged at an arbitrary position of the house wiring 3, and a communication terminal 6 and a network are further connected to the power line carrier communication device 5. The connection connector 4 at the connection point to the in-home wiring 3 is AC in the case of a commercial power line, for example.
An outlet is available.

Further, as shown in FIG. 2, the power line carrier communication device 5 relays the coupling circuit 7 in the power line carrier communication device 5 to connect to the house wiring 3, and the transmission circuit 8 and the reception circuit 9 transmit signals. By doing so, data communication is performed between the power line carrier communication devices 5 and an external communication device (not shown) on the service line 2 side. Further, the transmission circuit 8 and the reception circuit 9 are relayed to the communication control circuit 10 in the subsequent stage to connect the communication terminal 6 and the network. As the network, there are a wireless base station, the Internet, a local area network, etc., and when the network is constructed, it is possible to perform data communication with a plurality of communication terminals 6.

Next, FIG. 3 is a block diagram of a transmission circuit and a reception circuit which constitute the power line carrier communication device. The block diagram is the same as the block diagram of the compound dispersion modulation / demodulation circuit described in “Method for reducing power line carrier noise by compound dispersion modulation / demodulation” in Japanese Patent Application No. 2001-333728 by the applicant of the present application, and discontinuous noise superimposed on the power line. The reduction theory will be described using mathematical expressions and block diagrams.

First, the Walsh transform is used as a means for performing dispersion modulation / demodulation on the time axis. Sampling time Δ
N pieces of data sampled at t x _i = x ((i + 1/2) Δ
t) (i = 0,1, ..., N−1) transformation matrix W _{i, j} (i, j = 0,1,
,, N−1) is linearly transformed into y _i (i = 0,1, ..., N−1).
That is, the function shown in Equation 1 is used.

[0012]

[Equation 1]

The Walsh transform used as the linear transform is an orthogonal transform, and a simple algorithm is possible. here,
The transformation matrix of the Walsh transformation is defined by Equation 2.

[0014]

[Equation 2]

For example, when n = 3, Equation 3 is obtained.

[0016]

[Equation 3]

Since the Walsh transform is symmetric and has the relation shown in equation 4, the inverse transform can be easily obtained. FIG. 5 is a block diagram of a modulator based on Walsh transform. Here, in FIG. 3 and FIG. 3, the input signal x is data-coded by the A / D conversion 11, the serial-parallel conversion 12 and the Walsh conversion 13 of the data are performed, and the output signal y is obtained.

[0018]

[Equation 4]

Further, the inverse Walsh transform is given by the equation 4 according to the equation 4.
Given by. FIG. 6 is a block diagram of a demodulator by the inverse Walsh transform. Here, in the figure and FIG.
The inverse Walsh transform 2 of the output signal y _p of the OFDM demodulation 20
After 1 and parallel-serial conversion 22, D / as data decoding
A conversion 23 is performed to obtain an output signal x _p .

[0020]

[Equation 5]

Next, OFDM modulation / demodulation is used as a means for performing dispersion modulation / demodulation on the frequency axis. Letting T = NΔt be the time length T of N pieces of data, multiple frequency modulation is defined by Equation 6.

[0022]

[Equation 6]

The transformed circular frequency ω _n (n = 0, 1, ..., N−1) is given by ω _n =
Since πn / T, there is orthogonality as shown in Equation 7. FIG. 7 is a block diagram of an OFDM modulator.
Here, in FIG. 3 and FIG. 3, after the output signal y of the Walsh transform 13 is OFDM-modulated 14, the D / A conversion 15 is performed as data coding to obtain the output signal z _p .

[0024]

[Equation 7]

The relationship between the input z and the output y of the OFDM demodulator is given by equation (8). Fig. 8 shows O using LPF
It is a block diagram of a demodulator by FDM, LPF and O
Noise cut 19 is performed by FDM demodulation. FIG. 9 is a block diagram of an OFDM modulator using FFT, in which noise cut 19 is performed by FFT and OFDM demodulation.

[0026]

[Equation 8]

FIG. 3 shows a state in which the Walsh transform and the modulation / demodulation circuit based on OFDM are decoded. here,
Assuming that the noise e (t) is mixed in the in-home wiring 3, the signal in each block undergoes the following conversion.

[1] The output signal by the Walsh transform is given by equation (9).

[0029]

[Equation 9]

[2] The transmitter output by the OFDM modulation is given by the equation (10).

[0031]

[Equation 10]

[3] Due to transmission line noise, the receiver input is given by equation (11).

[0033]

[Equation 11]

[4] Output signal by OFDM demodulation is
Given by 2.

[0035]

[Equation 12]

[5] Due to the inverse Walsh transform, the receiver output is given by equation (13).

[0037]

[Equation 13]

[0038]

Embodiments of the present invention will be described with reference to the drawings. Figure 4
FIG. 3 is a network connection diagram of the power line carrier communication device in the power line carrier noise resistant communication system of the present invention, in which the power line carrier communication device 5 is connected to the wireless base station 24 and the Internet 2.
6, an example in which a network is constructed by connecting the local area network 29 and the like is shown.

The power line carrier communication device 5 is arranged at an arbitrary position on the house wiring 3, and the connection connector 4 is relayed to connect the power line carrier communication device 5 to the network. When the wireless base station 24 is connected as the network, data communication and multimedia communication can be performed with a plurality of wireless terminals 25. Further, when the Internet 26 is connected as a network, data communication and multimedia communication can be performed with communication terminals such as a plurality of personal computers 27 and IP phones 30. Also,
Local area network 2 via server 28
When 9 is connected, data communication and multimedia communication can be performed with a plurality of client terminals such as personal computers 27.
Further, also in the wireless terminal 25, the communication terminal and the client terminal, the power line carrier communication device 5 and the home wiring 3
Can be used for data communication and multimedia communication.

When a commercial power line is used as the in-house wiring 3, the discontinuous noise superimposed on the power line due to the compound dispersion modulation / demodulation in the "power line carrier noise reduction method by the compound dispersion modulation / demodulation" of the above-mentioned Japanese Patent Application No. 2001-333728 is used. Based on the reduction theory and the simulation results, stable data communication with dramatically improved noise resistance characteristics by strongly reducing discontinuous noise can be performed.
If a power line for emergency lights, a metal cable for telephones or intercoms, a coaxial cable for a television antenna, etc., which have better noise conditions than the commercial power line, are used, more stable communication can be performed.

[0041]

As described above, as the power line carrier noise resistant communication system of the present invention, the power line carrier communication device is a commercial power line, emergency power line, telephone or intercom metal cable installed in advance in a home or office. By connecting to the in-house wiring such as coaxial cable for TV antenna, discontinuous noise such as spike noise and surge noise superimposed on the transmission line can be strongly reduced, and stable data with dramatically improved noise resistance can be obtained. The effect that communication can be performed is produced. Furthermore, by connecting a communication network such as a wireless base station, the Internet, or a local area network to the power line carrier communication device,
There is also an effect that data communication can be performed with a plurality of communication terminals.

[Brief description of drawings]

FIG. 1 is a connection system diagram of a power line carrier communication device in a power line carrier noise resistant communication system of the present invention.

FIG. 2 is a schematic block diagram of a power line carrier communication device.

FIG. 3 is a block diagram of a transmission circuit and a reception circuit that constitute the power line carrier communication device.

FIG. 4 is a network connection diagram of the power line carrier communication device in the power line carrier noise resistant communication system of the present invention.

FIG. 5 is a block diagram of a modulator based on Walsh transform.

FIG. 6 is a block diagram of a demodulator by inverse Walsh transform.

FIG. 7 is a block diagram of an OFDM modulator.

FIG. 8 is a block diagram of a demodulator by OFDM using LPF.

FIG. 9 is a block diagram of a modulator based on OFDM using FFT.

[Explanation of symbols]

1 building 2 drop lines 3 home wiring 4 connector 5 Power line carrier communication device 6 communication terminals 7 coupling circuit 8 signal transmitter 9 Signal receiver 10 Communication control circuit 11 A / D conversion 12 serial-parallel conversion 13 Walsh transformation 14 OFDM conversion 15 D / A conversion 16 A / D conversion 17 Serial-parallel conversion 18 Noise detection 19 noise cut 20 OFDM demodulation 21 Inverse Walsh transform 22 Parallel to serial conversion 23 D / A conversion 24 wireless base stations 25 wireless terminals 26 Internet 27 PC 28 servers 29 Local Area Network 30 IP phones

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Isshiki             3 Pegasus at 8 Miyuki-cho, Shizuoka City, Shizuoka Prefecture             Inside the net corporation (72) Inventor Hideo Fukuda             3 Pegasus at 8 Miyuki-cho, Shizuoka City, Shizuoka Prefecture             Inside the net corporation (72) Inventor Hideo Yasuda             3 Pegasus at 8 Miyuki-cho, Shizuoka City, Shizuoka Prefecture             Inside the net corporation F term (reference) 5K046 AA03 BB05 PS13 PS51 PS54

Claims (5)

[Claims] 1. A means for distributing signals on a time axis and a frequency axis by Walsh transform and OFDM modulation as a transmitting circuit and a receiving circuit in a power line carrier communication device to dilute the influence of discontinuous noise such as spike noise and surge noise. And the noise that cannot be diluted by the above means is detected by the wavelet analysis to cut the noise, and the relatively small discontinuous noise is dealt with by the former means and the relatively large noise is removed. By dealing with continuous noise by both the former and latter means, it is possible to reduce discontinuous noise of any size, and to install the power line carrier communication device on a power line or the like laid in advance in a home or office. The power line carrier communication device is installed at an arbitrary position in the house wiring and relays the coupling circuit in the power line carrier communication device to perform signal transmission at the transmission circuit and the reception circuit. Performs data communication with an interposition or an external communication device, and further connects the transmission circuit and the reception circuit to a communication network such as a wireless base station, the Internet, or a local area network by relaying a communication control circuit in a subsequent stage,
A power line carrier noise resistant communication system characterized by being able to perform data communication with a plurality of communication terminals. 2. The power line carrier noise resistant communication system according to claim 1, wherein the subscriber power line lead-in and home wiring are commercial power lines. 3. The power line carrier noise resistant communication system according to claim 1, wherein the in-home wiring is an emergency light power line. 4. The power line carrier noise resistant communication system according to claim 1, wherein the subscriber line lead-in and home wiring are metal cables for telephones or intercoms. 5. The power line carrier noise resistant communication system according to claim 1, wherein the in-house wiring is a coaxial cable for a television antenna.