JP2000295196A - Communication equipment and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide communication equipment which can efficiently transmit data while compatibility with other countries is kept by dividing a system for transmitting incoming/outgoing data by frequency division and a system for transmitting incoming/outgoing data by time division by means of a prescribed frequency as a threshold and transmitting data. SOLUTION: Interference noise by a TCM-ISDN communication system usually occurs much at 1.1 MHz and below. Consequently, in a frequency band which easily receives interference noise by a TCM-ISDN communication system, data is transmitted by a TDD system and data is transmitted by an FDD system in a frequency band above it. A system for transmitting incoming/outgoing data by frequency division and a system for transmitting incoming/outgoing data by time division are divided by 1.1 MHz as the threshold and data is transmitted. Thus, interference noise by the TCM-ISDN communication system is avoided and data can efficiently be transmitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device and a communication method for performing data communication between a plurality of data communication devices by, for example, a discrete multi-tone modulation / demodulation method.

[0002]

2. Description of the Related Art In recent years, a VDSL (Very-high-bi
The t-rate Digital Subscriber Line) communication system is drawing attention. The modulation and demodulation method used for this is DMT.
(Discrete MultiTone) is called a modulation and demodulation method.

FIG. 8 shows a VDSL station side device (VTU-C;
VDSL Transceiver Unit, Central Office end) and VDSL terminal side device (VTU-R; VDSL Transce
It functionally shows the configuration of a transmission unit such as a communication modem of an iverUnit, a Remote Terminal end or a transmission-only machine (hereinafter referred to as a transmission system). FIG. 9 shows a VDSL station side device (VTU-C) and a VDSL terminal side device (VTU-C).
R) functionally shows the configuration of a receiving unit such as a communication modem or a receiving-only device (hereinafter referred to as a receiving system).

In FIG. 8, reference numeral 41 denotes a multiplex /
Sync control (Mux / Sync Control), 42, 43 are cyclic redundancy check (crc), 44, 4
5 is a scramble forward error correction (Scr
am and FEC), 46 is interleaved, 47 and 48 are rate converters, 49 is tone ordering, 50 is a constellation encoder and gain scaling (Constellation encoder).
and gain scalling), 51 is an inverse discrete Fourier transform unit (ID
FT) and 52 are input parallel / serial buffers (Input Pa
Rallel / SerialBuffer) and 53 are analog processing and D / A converters (Analog Processing and DAC).

In FIG. 9, reference numeral 141 denotes an analog processing and A / D converter (Analog Processing And AD).
C), 142 are time domain equalizers (TEC), 14
3 is an input serial / parallel buffer, 144 is a discrete Fourier transform unit (DFT), 145 is a frequency domain equalizer (FEQ), and 146 is a constellation encoder and gain scaling (Constellation encoder and g).
ain scalling), 147 is tone ordering (Tone
ordering), 148, 149 are rate converters (Rate-
Convertor), 150 is Deinterleav
e), 151, 152 are descrambling forward error corrections (Descram and FEC), 153, 15
4 is cyclic redundancy check (crc), 15
5 is multiplex / sync control (Mux / Sync
Control).

Next, the operation when data is transmitted from the VDSL station-side device (VTU-C) to the VDSL terminal-side device (VTU-R) will be described. First, the VDSL office equipment
The operation of the transmission system of (VTU-C) will be described.
(Mux / Sync Control), add an error detection code by cyclic redundancy check 42, 43, add FEC code and scramble processing by forward error correction 44, 45, and if necessary, interleave 46 Multiply. After that, rate conversion processing is performed by the rate converters 47 and 48,
Perform tone ordering processing with tone ordering 49,
Constellation encoder gain scaling 5
0, constellation data is created, inverse discrete Fourier transform is performed by an inverse discrete Fourier transform unit 51, parallel data is converted into serial data by an input parallel / serial buffer 52, and a digital waveform is converted into an analog waveform through a D / A converter. And then apply a low-pass filter.

On the other hand, a VDSL terminal side device (VTU-R)
The operation of the receiving system 14 will now be described. In FIG. 9, an analog processing / A / D converter 141 applies a low-pass filter to the received signal, converts an analog waveform into a digital waveform through the A / D converter, and then converts the analog signal into a time domain equalizer. A time domain adaptive equalization process is performed through (TEQ) 142. Next, the data subjected to the adaptive equalization processing in the time domain is converted from serial data to parallel data via an input serial / parallel buffer 143, and is converted to a discrete Fourier transform unit (DFT) 14.
4 and a frequency domain equalizer (FEQ) 145 performs an adaptive equalization process in the frequency domain. The constellation data is reproduced by the constellation encoder / gain scaling 146, converted into serial data by the tone ordering 147, rate-converted by the rate converters 148 and 149, and subjected to FEC and descrambling by the descrambling / forward error correction 151. Process,
In some cases, de-interleaving 150 is applied to the descrambling forward error correction 152 to obtain F
Perform EC and descramble processing, and then perform cyclic redundancy checks 153 and 154 to perform multiplex / sync control (Mux / Sync Control).
l) Reproduce the data by 155. VDSL terminal equipment (VTU-R) to VDSL office equipment (VTU-C)
The same applies to the operation in the case of transmitting data to.

When an attempt is made to adopt the VDSL communication system that operates as described above, it is necessary to consider the influence of interference noise with the existing ISDN transmission line. FIG. 10 shows an IDN transmission line 2 from the central office (CO) 1 and a VDSL transmission line 3 which are bundled by an intermediate line.
FIG. 3 shows a state of interference noise given to the VDSL transmission line 3 by the SDN transmission line 2. Here, when viewed from the VDSL terminal side device (VTU-R) 4 which is a communication device on the terminal side of the VDSL communication system side, the station side device (ISDN LT) 7 on the ISDN transmission system side passes through the VDSL transmission line 3. FEXT (Far-end cross)
Interference noise transmitted by the terminal device (ISDNNT1) 6 on the ISDN transmission system side through the VDSL transmission line 3 is called NEXT (Near-end cross talk) noise. In particular, these noises become an integrated line or the like on the way and become adjacent to the VDSL transmission line 3.
VD via the VDSL transmission line 3 by coupling with the N transmission line 2
It is transmitted to the SL terminal side device (VTU-R) 4. In addition,
When viewed from the VDSL station-side device (VTU-C) 5, which is the station-side device on the VDSL communication system side, the reverse is the case when viewed from the VDSL terminal-side device (VTU-R) 4.
The interference noise transmitted by the station device (ISDN LT) 7 on the DN transmission system side becomes NEXT noise, and the ISD
The interference noise transmitted from the terminal device (ISDN NT1) 6 on the N transmission system side is FEXT noise. Then, during the training period of a VDSL modem (not shown) provided in the VDSL terminal device 4, the characteristic of the NEXT noise component having a large effect is measured, and the number of transmission bits and the gain of each channel matching the characteristic of the noise are measured. In order to improve the transmission characteristics by performing a bitmap that determines
For example, a time domain equalizer (TEQ) that performs adaptive equalization processing in the time domain, and a frequency domain equalizer (FEQ) that performs adaptive equalization processing in the frequency domain.
er) are determined by converging the coefficients, and a set of coefficient tables for NEXT noise is provided for each of TEQ and FEQ.

Here, for example, in many of the xDSL communication systems in the United States, as shown in FIG.
am) and FDD (Frequency Division Duplex) in which downlink (DS) data is transmitted by frequency division. This FDD system is also used in the VDSL communication system, and both (VDSL and other FDSL systems) are used.
Even if signals of a DD communication system overlap with each other in time, the above-described interference noise can be avoided because the frequencies are different.

[0010]

On the other hand, Japanese ISDN
In the communication system, as shown in FIG.
TDD (Time Division Duplex) TC in which downlink (DS) data is transmitted in a so-called ping-pong manner in a time-division manner
The M-ISDN system is adopted. Therefore, FD
If the VDSL transmission line adopting the D system and the TCM-ISDN transmission line adopting the TDD system are adjacent to each other, in the portion where the signals of both (VDSL and TCM-ISDN) overlap in time, There has been a problem that interference noise due to the same frequency is generated and transmission efficiency is extremely deteriorated. In addition, in order to avoid interference noise due to the TCM-ISDN communication system, even in the VDSL communication system,
If the DD system is adopted, consistency with foreign countries such as the United States, which adopts the FDD system, cannot be obtained.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a communication device and a communication method capable of efficiently transmitting data while maintaining consistency with foreign countries. .

[0012]

A communication apparatus according to the present invention uses a predetermined frequency as a threshold value to transmit uplink and downlink data by frequency division, and transmits uplink and downlink data by time division. And data transmission by dividing the data by the threshold value.

A communication apparatus according to the present invention uses a predetermined frequency as a threshold value to transmit uplink and downlink data by frequency division and a method to transmit uplink and downlink data by frequency division and time division. Is transmitted by dividing the data by the threshold value.

[0014] A communication apparatus according to the present invention includes a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold, a method of transmitting uplink and downlink data by time division, and a method of transmitting uplink and downlink data by time division. Data is transmitted by dividing the downlink data by frequency division and time division by the threshold.

[0015] The communication method according to the present invention includes a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value and a method of transmitting uplink and downlink data by time division. The data is transmitted by dividing it by a threshold value.

A communication method according to the present invention comprises a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value, and a method of transmitting uplink and downlink data by frequency division and time division. Is transmitted by dividing the data by the threshold value.

[0017] A communication method according to the present invention comprises a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold, a method of transmitting uplink and downlink data by time division, and a method of transmitting uplink and downlink data by time division. Data is transmitted by dividing the downlink data by frequency division and time division by the threshold.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an embodiment of the present invention will be described. Interference noise due to the TCM-ISDN communication system usually occurs largely at 1.1 MHz or less.
Therefore, for example, data is transmitted by the TDD method in a frequency band that is susceptible to interference noise due to the TCM-ISDN communication system, and the FD is transmitted in a higher frequency band.
Data is transmitted in the D system. FIG. 1 is an explanatory diagram showing an outline of a communication method according to the present invention. In the example of FIG.
When the frequency is less than 1 MHz, the data is transmitted by the TDD method and 1.1
It indicates that data is transmitted by the FDD method at MHz or higher. The threshold (1.1 MHz) is determined, for example, during the above-described training period. According to the example of FIG. 1, as shown in FIG. 2, TDD data is assigned to tone numbers # 1 to # 25, and FDD data is assigned to tone numbers # 26 and higher.

Next, the operation will be described. The configuration of the transmission system / reception system in the communication device (the VDSL station-side device and the VDSL terminal-side device) according to the present invention is the same as the conventional configuration. In the present embodiment, the fast data buffer path and the interleaved buffer are used. One of the routes (fast data buffer route in this embodiment)
Using only the VDSL station side device (VTU-C)
A case where data is transmitted to the DSL terminal side device (VTU-R) will be described. In the communication device according to the present invention, the operations of the rate converter 47 and the tone ordering 49 in the configuration of the transmission system are different from those of the conventional operation.

FIG. 3 is an explanatory diagram showing the operation of the rate converter 47 and the tone ordering 49. In the present embodiment, for example, if one cycle of TCM-ISDN communication (400 Hz) is used as a basic unit, one symbol is processed in 25 μs and 100 symbol units. In this case, in the TDD system, downlink (DS) data transmission is performed in the first 45 symbols, and uplink (U) is transmitted in the next 45 symbols after 5 symbols.
The data transmission of S) is performed.

Assuming that the number of bits per symbol of the net data to be transmitted before the rate conversion is t, t = 24 bits in the example of FIG. 3 is determined based on the S / N ratio measured during the training period described above. Assuming that the number of bits per symbol that can be transmitted by the tone number 26 or higher (FDD method) is t_fdd, t_fdd = 16 bits in the example of FIG. Therefore, the rate converter 47 processes 16 bits out of 24 bits of net data at a uniform rate. Then, tone number # 25 or less (T
The number of bits per symbol to be transmitted in the DD system) is t
_Tdd, Becomes In the TDD system, downlink (DS) data transmission is performed in the first 45 symbols, so that transmission is to be performed using tone number # 25 or less (TDD system) after rate conversion.
Assuming that the number of bits per symbol is f_tdd, f_tdd = roundup (t_tdd × 100/45) = roundup (8 × 100/45) = 18 bits. In this case, a dummy bit is generated. If the number of dummy bits is dummy_tdd, dummy_tdd = 45 × f_tdd−t_tdd × 100 = 45 × 18−8 × 100 = 10 bits.

In the tone ordering 49, the data of f_tdd = 18 bits is stored in the tone number # 1.
To # 25 in the TDD scheme, and t_fdd = 16 bits of data are allocated to tone numbers # 26 and higher.
Transmission by method.

In the tone ordering 147 and the rate converter 148 in the configuration of the receiving system, the operation opposite to the above operation is performed. Also, the VDSL terminal side device (VT
UR) to the VDSL station side device (VTU-C).

As described above, a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value and a method of transmitting uplink and downlink data by time division are referred to as the threshold value. By transmitting data separately, it is possible to avoid interference noise due to the TCM-ISDN communication system and minimize transmission in the TDD system, so that transmission can be performed efficiently while maintaining consistency with foreign countries. .

The threshold value of the frequency that separates the FDD system from the TDD system is not limited to 1.1 MHz, and other values may be used depending on the state of interference (or noise, transmission path, transmission speed, etc.). May be. Also, for example, two thresholds are provided and divided into three frequency bands of a high frequency band, a medium frequency band, and a low frequency band. The high frequency band is a TDD system, and the middle frequency band is an FDD system. In the low frequency band, a plurality of threshold values may be provided, for example, data is transmitted by the TDD method.

Although the upper limit of the frequency used by the FDD system is 17.6 MHz in FIG. 1, another value may be used in accordance with the increase or decrease of the bandwidth used by the FDD.

In this embodiment, tone number 2 determined based on the S / N ratio measured during the training period
Although the case where the number of bits per symbol that can be transmitted in 6 or more (FDD system) is t_fdd = 16 bits and the number of bits per symbol of the transmitted net data before rate conversion is t = 24 has been described, A similar effect can be obtained by using a value. Also, t ≦ t_fdd
, Data is transmitted using only the FDD scheme (tone number # 26 or higher) and the TDD scheme (tone number # 25).
Is not used (at this time, t after rate conversion)
The value of _fdd is t).

The functions shown in the above description using the functional block diagram may be realized by H / W or S / W.

Embodiment 2 In the present embodiment, a description will be given of an embodiment in which the influence on VDSL communication devices in other countries is further considered than in the above embodiment. VDSL of the above embodiment
When the transmission line (FIG. 1) and the VDSL transmission line of other countries (FIG. 11) are adjacent to each other, there is a portion where both signals overlap below 1.1 MHz, so that interference noise due to the same frequency occurs. . FIG. 4 is an explanatory diagram showing an outline of a communication method according to the present invention in which both signals are transmitted without overlapping so as not to generate the interference noise.
In the example of FIG. 4, data is transmitted by the TDD method below 1.1 MHz, only the upstream (US) is transmitted below 0.5 MHz, and only the downstream (DS) is transmitted below 0.5 MHz and below 1.1 MHz. It indicates that you want to. Note that these thresholds (1.1 MHz and 0.5 MHz) are determined, for example, during the training period described above. According to the example of FIG. 4, as shown in FIG. 5, uplink (US) data of the TDD system is assigned to tone numbers # 1 to # 11, and TDD
Downstream (DS) data of the system is from tone number # 12 to #
25, and the data of the FDD system is tone number # 2.
Assign to 6 or more.

FIG. 6 is an explanatory diagram showing the operation of the rate converter 47 and the tone ordering 49. The operation is the same as that of the above-described embodiment except that the tones to be allocated in the uplink (US) and downlink (DS) data transmissions are different. As in the above embodiment, only one of the fast data buffer path and the interleaved buffer path (the fast data buffer path in this embodiment) is used, and the VDSL station side device (VTU-
When data is transmitted from C) to the VDSL terminal apparatus (VTU-R), as shown in FIG. 6, in tone ordering 49, data of f_tdd = 18 bits is assigned to tone numbers # 12 to # 25 (DS), and TDD is assigned. Transmission by method.

In the tone ordering 147 and the rate converter 148 in the configuration of the receiving system, the operation opposite to the above operation is performed. Also, the VDSL terminal side device (VT
In the case where data is transmitted from the U-R) to the VDSL station-side device (VTU-C), it is the same as the above embodiment except that the tone to be assigned is different (FIG. 7).

As described above, a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value and a method of transmitting uplink and downlink data by frequency division and time division are described. By transmitting data by dividing the data by the threshold value, interference noise due to the TCM-ISDN communication system is avoided, and transmission in the TDD system is also frequency-divided.
Transmission can be performed efficiently.

It should be noted that the FDD system and the FD
The threshold value of the frequency that separates the transmission method from the transmission method using the D method and the value of the frequency that switches between the uplink and the downlink when the transmission is performed by the FDD method and the TDD method are 1.1 MHz or 0.1 MHz.
The value is not limited to 5 MHz, and another value may be used according to the state of interference (or noise, transmission path, transmission speed, and the like).
Also, for example, by providing two thresholds, a high frequency band,
It is divided into three frequency bands, a middle frequency band and a low frequency band. The high frequency band is the FDD system and the TDD system, the middle band is the FDD system, the low band is the FDD system and the TDD system. Such as transmitting data with
A plurality of thresholds may be provided.

As shown in FIG. 13, for example, two threshold values are provided to divide the frequency band into three frequency bands of a high frequency band, a middle frequency band, and a low frequency band. The three systems may be divided by a plurality of thresholds, such as transmitting data in the middle frequency band by the FDD system and the TDD system and transmitting data in the low band frequency band by the TDD system. The operation in each band is the same as in the above embodiment.

Although the upper limit of the frequency used by the FDD system is 17.6 MHz in FIG. 4, another value may be used in accordance with the increase or decrease of the bandwidth used by the FDD.

In the present embodiment, the number of bits per symbol that can be transmitted with a tone number of 26 or more (FDD system) determined based on the S / N ratio measured during the training period is t_fdd = 16 bits, rate conversion The number of bits per symbol of the previous transmitted net data is t = 2
Although the case of 4 has been described, similar effects can be obtained by using other values. When t ≦ t_fdd, data is transmitted using only the FDD scheme (tone number # 26 or higher), and the TDD scheme (tone number # 25 or lower) is not used (at this time, t_f after the rate conversion).
The value of fdd is t).

In the above description, the functions shown using the functional configuration diagram may be realized by H / W or S / W.

[0038]

As described above, a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value and a method of transmitting uplink and downlink data by time division are described above. By transmitting the data divided by the threshold value, it is possible to transmit the data efficiently while maintaining the consistency with other countries.

Further, a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value and a method of transmitting uplink and downlink data by frequency division and time division are referred to as the threshold value. By transmitting data separately, it is possible to transmit data efficiently while maintaining consistency with other countries.

A method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value, a method of transmitting uplink and downlink data by time division, and a method of transmitting uplink and downlink data by frequency division By transmitting data by dividing the data transmission method and the time-division transmission method by the threshold value, it is possible to transmit data efficiently while maintaining consistency with foreign countries.

Also, a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value and a method of transmitting uplink and downlink data by time division are divided by the threshold value into data. , It is possible to transmit efficiently while maintaining consistency with other countries.

Further, a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value and a method of transmitting uplink and downlink data by frequency division and time division are defined as the threshold values. By transmitting data separately, it is possible to transmit data efficiently while maintaining consistency with other countries.

Also, a method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value, a method of transmitting uplink and downlink data by time division, and a method of transmitting uplink and downlink data by frequency division By transmitting data by dividing the data transmission method and the time-division transmission method by the threshold value, it is possible to transmit data efficiently while maintaining consistency with foreign countries.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of a communication method according to the present invention.

FIG. 2 is an explanatory diagram showing assignment of data to tones in the communication method according to the present invention.

FIG. 3 is an explanatory diagram showing the operation of the communication device according to the present invention.

FIG. 4 is an explanatory diagram showing an outline of a communication method according to the present invention.

FIG. 5 is an explanatory diagram showing assignment of data to tones in the communication method according to the present invention.

FIG. 6 is an explanatory diagram showing the operation of the communication device according to the present invention.

FIG. 7 is an explanatory diagram showing the operation of the communication device according to the present invention.

FIG. 8 is a functional configuration diagram showing a transmission function of a conventional communication device.

FIG. 9 is a functional configuration diagram showing a reception function of a conventional communication device.

FIG. 10 is an explanatory diagram showing a state of interference noise between transmission paths.

FIG. 11 is an explanatory diagram showing an outline of a conventional communication method.

FIG. 12 is an explanatory diagram showing an outline of a conventional communication method.

FIG. 13 is an explanatory diagram showing an outline of a communication method according to the present invention.

[Explanation of symbols]

41 Multiplex / Sync Control 42, 43 Cyclic Redundancy Check 44, 45 Scramble Forward Error Correction 46 Interleave 47, 48 Rate Converter 49 Tone Ordering 50 Constellation Encoder / Gain Scaling 51 Inverse Discrete Fourier Transform 52 Input Parallel / Serial Buffer 53 Analog Processing / D / A Converter 141 Analog Processing / A / D Converter 142 Time Domain Equalizer 143 Input Serial / Parallel Buffer 144 Discrete Fourier Transform Unit 145 Frequency Domain Equalizer 146 Constellation Encoder / Gain Scaling 147 Tone Ordering 148, 149 Rate Converter 150 Dyne Tarleave 151, 152 Descramble Forward Error Correction 153, 154 Cyclic Redundancy Check 155 Multiplex / Sync Control

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (6)

[Claims] 1. A method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold, and a method of transmitting uplink and downlink data by time division using the threshold. Communication device for transmitting. 2. A method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold, and a method of transmitting uplink and downlink data by frequency division and time division. A communication device that transmits data separately. 3. A method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold, a method of transmitting uplink and downlink data by time division, and a method of dividing uplink and downlink data by frequency division. And a method of transmitting data by dividing the transmission method by time-division with the threshold value. 4. A method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold value and a method of transmitting uplink and downlink data by time division using the threshold value. The communication method for transmitting. 5. A method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold, and a method of transmitting uplink and downlink data by frequency division and time division. A communication method that transmits data in groups. 6. A method of transmitting uplink and downlink data by frequency division using a predetermined frequency as a threshold, a method of transmitting uplink and downlink data by time division, and a method of dividing uplink and downlink data by frequency division. And a method of transmitting data in a time-division manner by the threshold value.