JP3083159B2 - Orthogonal frequency division multiplexing transmission system and transmitter and receiver thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an orthogonal frequency division multiplexing transmission system for transmitting signals suitable for fixed reception and mobile reception in one channel in a mixed manner. In addition, the present invention relates to a transmitting apparatus that forms and transmits an OFDM signal based on the orthogonal frequency division multiplexing method, and a receiving apparatus that receives and demodulates an OFDM signal formed and transmitted based on the orthogonal frequency division multiplexing method.

BACKGROUND ART Currently, a transmission system using orthogonal frequency division multiplexing (hereinafter, referred to as OFDM) technology is being studied as a digital broadcasting system in terrestrial TV broadcasting. This OFDM transmission system is a type of multi-carrier modulation system, and transmits digital information by modulating a large number of carriers having a frequency relationship orthogonal to each other for each symbol. In this method, as described above, digital information is divided into a large number of carriers and transmitted. Therefore, the symbol period length of the divided digital information for modulating one carrier is long, and the delay time of a multipath or other delayed wave is increased. Has characteristics that are not easily affected.

As a digital broadcasting system of TV signals using the conventional OFDM transmission technology, for example, the DVB-T standard in Europe, that is, ETSI 300 744 (ETSI: European Telecommunicatio)
ns Standards Institute).

The conventional OFDM transmission method is, for example, a 2k mode (2k is an OFDM
The number of samples of the fast Fourier transform when generating a signal is 20
48 means 1705 carriers in the entire transmission band, of which 142 carriers are used as scattered pilot signals, 45 carriers are used as continuous pilot signals, and 17 carriers are used as continuous pilot signals. A carrier is used for a control information (TPS) signal, and a carrier of 1512 carriers is used for an information transmission signal.

However, among the continuous pilot signals of the carrier waves of 45 carriers, the continuous pilot signals of the carrier waves of 11 carriers are arranged so as to overlap the dispersed pilot. Further, the dispersed pilot signal is arranged such that the frequency arrangement within one symbol is arranged in 12 carrier periods, the frequency arrangement is shifted by 3 carriers for each symbol, and the time arrangement is 4 symbol periods. .

Specifically, the carrier number k is changed from 0 to 170 in order from the end.
4. If the symbol number n in the frame is 0 to 67,
The scattered pilot signal is allocated to a carrier having a carrier number k according to the equation (1). In the equation (1), mod represents a remainder operation, and p is an integer from 0 to 141.

k = 3 (n mod 4) + 12p (1) The continuous pilot signal has a carrier number k = ｛0,48,54,
87,141,156,192,201,255,279,282,333,432,450,483,52
5,531,618,636,714,759,765,780,804,873,888,918,939,
942,969,984,1050,1101,1107,1110,1137,1140,1146,120
6,1269,1323,1377,1491,1683,1704.

These scattered and continuous pilot signals are formed by a PN (pseudo-random number) sequence corresponding to a carrier number k assigned thereto.
Based on w _k , it is obtained by modulating a carrier with a complex vector c ^{k, n} shown in equation (2). In equation (2), Re
{C ^{k, n} } represents a real part of a complex vector c ^{k, n} corresponding to a carrier having a carrier number k and a symbol number n, and
{C ^{k, n} } represents an imaginary part.

A control information signal called TPS (Transmission Parameter Signaling) has a carrier number k = ｋ34,50,209,
346,413,569,595,688,790,901,1073,1219,1262,1286,14
It is arranged on 69,1594,1687｝ carriers and transmits 1-bit control information for each symbol.

The control information bits to be transmitted in symbol of the symbol number n When S _n, complex vector c ^k shown in the control information signal ^(3), obtained by modulating a carrier wave by ^n. That is, the carrier transmitting the control information signal is subjected to differential binary PSK (Phase Shift Keying) modulation between symbols.

However, the first symbol of the frame (symbol number n =
0), the carrier transmitting the control information is the PN sequence described above.
Based on w _k , modulation is performed by a complex vector c ^{k, n} shown in equation (4).

Carriers of 1512 carriers used for information transmission signals other than the above, based on digital information, QPSK, 16QAM,
Alternatively, 64QAM modulation is performed. Both modulation methods are absolute phase modulation.

FIG. 10 shows an example of a conventional receiving apparatus for receiving OFDM signals generated in this way and demodulating digital information.

In FIG. 10, a received OFDM signal is frequency-converted by a tuner 101, and time-frequency converted by a Fourier transform circuit 102 to be a vector sequence for each carrier in the frequency domain. This vector sequence is a distributed pilot extraction circuit
103 and the continuous pilot extraction circuit 109.

The scattered pilot extraction circuit 103 includes a Fourier transform circuit 102
Extracts the variance pilot signal from the vector sequence output by. The vector generation circuit 104 includes a distributed pilot extraction circuit 1
A modulated complex vector c ^{k, n} corresponding to the scattered pilot signal extracted in 03 is generated. The division circuit 105 divides the scattered pilot signal extracted by the scattered pilot extraction circuit 103 by a complex vector generated by the vector generation circuit 104,
From the result of the division, the channel characteristics of the scattered pilot signal are estimated.

The interpolation circuit 106 interpolates the transmission path characteristics of the scattered pilot signal obtained by the division circuit 105 and estimates the transmission path characteristics of all carrier waves. The division circuit 107 performs synchronous detection by dividing the vector sequence output from the Fourier transform circuit 102 by the transmission path characteristic estimated by the interpolation circuit 106 for the corresponding carrier. The demodulation circuit 108 demodulates the synchronous detection signal output from the division circuit 107 according to a modulation method (QPSK, 16QAM, 64QAM, etc.) when generating the information transmission signal, and obtains transmitted digital information.

Further, continuous pilot extraction circuit 109 extracts a continuous pilot signal from the vector sequence output from Fourier transform circuit 102. The vector generation circuit 110 generates a modulated complex vector ^{ck, n} corresponding to the continuous pilot signal extracted by the continuous pilot extraction circuit 109. The division circuit 111
The continuous pilot signal extracted by the continuous pilot extraction circuit 109 is divided by the complex vector generated by the vector generation circuit 110 to estimate the transmission path characteristics of the continuous pilot signal. The inverse Fourier transform circuit 112 obtains impulse response characteristics of the transmission line by performing frequency-to-time conversion of the transmission line characteristic of the continuous pilot signal estimated by the division circuit 111.

DISCLOSURE OF THE INVENTION However, in the conventional OFDM transmission system, a carrier for transmitting digital information is subjected to absolute phase modulation by QPSK, 16QAM, 64QAM, or the like, and the demodulation is estimated from a scattered pilot that is sparse in time. Since it is assumed that the transmission path characteristics obtained by smoothing and interpolating the transmission path characteristics are used, sufficient transmission quality may not be obtained in mobile reception where the transmission path characteristics change rapidly due to fading or the like. .

Furthermore, in the conventional OFDM transmission method, since the modulation method of each carrier is determined to be one in the entire band, it is shifted to the modulation of the carrier transmitting the digital information so that some of the digital information can be received while moving. Even if, for example, differential QPSK modulation suitable for reception is introduced, the overall transmission capacity is reduced and efficiency is reduced.

Further, since the continuous pilot signal is arranged on any one of the carriers at the predetermined carrier interval A, the effective symbol period length (the reciprocal of the minimum frequency interval of the carrier wave) ) Is folded back by 1 / A.

Therefore, the present invention solves the above-mentioned movability, and introduces a modulation method suitable for mobile reception in a part of modulation of a carrier wave for transmitting digital information while maintaining the entire transmission capacity. A transmission device suitable for the OFDM transmission system and the present system, in which a continuous pilot signal is arranged so that aliasing does not occur in the impulse response of the estimated transmission path,
An object is to provide a receiving device.

In order to solve the above problems, the orthogonal frequency division multiplexing transmission system according to the present invention modulates K (K is an integer) carriers having a frequency relationship orthogonal to each other for each symbol period, thereby converting digital information. An orthogonal frequency division multiplexing transmission system for transmitting, wherein each carrier number of K carriers in the entire transmission band is k (k is an integer satisfying 0 ≦ k ≦ K−1), and among the K carriers, The carrier number k in the entire transmission band is a band end carrier of a carrier that satisfies k = K−1. Of the K carriers, the carrier number k in the entire transmission band is 0 ≦ k ≦ K−2. A carrier is divided into I (I is an integer) segments, and each of the I segments is K ′ (K ′ is an integer satisfying K ′ = (K−1) / I) consecutive in frequency. Career And et arrangement, the symbol number n (n is an integer), the segment number i
(I is an integer satisfying 0 ≦ i ≦ I−1), and the carrier numbers of the K ′ carriers in each segment are represented by k ′ (k ′
Is an integer satisfying 0 ≦ k ′ ≦ K′−1). Each of the segments is used as either a segment for synchronous detection or a segment for differential detection. In the segment for synchronous detection, a symbol of symbol number n is used. On the other hand, the distributed pilot signal is arranged at a carrier position where the carrier number k 'in the segment satisfies k' = 3 (n mod 4) + 12p (mod represents a remainder operation, p is an integer). In the segment, for all symbols,
A terminal pilot signal is arranged at a carrier position where a carrier number k ′ in the segment satisfies k ′ = 0, a band terminal pilot signal is arranged for all symbols at a carrier position of the band terminal carrier, A pilot signal, the terminal pilot signal,
And arranging an information transmission signal at any carrier position other than the position where the band end pilot signal is arranged, the distributed pilot signal, the end pilot signal,
And the band end pilot signal is obtained by modulating a carrier in which each is arranged with a specific amplitude and phase uniquely determined by a carrier number k in the entire transmission band of the carrier, and the synchronous detection segment. The information transmission signal arranged in the above is a carrier in which each is arranged, the absolute phase modulated based on the digital information, The information transmission signal arranged in the differential detection segment, The carrier to be arranged is obtained by performing differential modulation between symbols based on the digital information.

In the orthogonal frequency division multiplexing transmission system, in particular, the absolute phase modulation is a digital modulation system of QPSK modulation, 16QAM modulation, or 64QAM modulation, and the differential modulation is DQPSK modulation. Things.

Further, a transmission device according to the present invention is a transmission device that transmits a signal in accordance with the orthogonal frequency division multiplexing transmission method, wherein an information transmission signal generation unit that outputs a complex vector sequence for generating the information transmission signal A distributed pilot signal generating unit that is provided when forming the synchronous detection segment and outputs a complex vector for generating the distributed pilot signal, and is provided when forming the differential detection segment, A terminal pilot signal generating means for outputting a complex vector for generating the terminal pilot signal, a band terminal pilot signal generating means for outputting a complex vector for generating the band terminal pilot signal, and the information transmission signal generating means , The distributed pilot signal generating means, the terminal pilot signal generating means, and the band end. Carrier arranging means for arranging each output of the pilot signal generating means at a predetermined carrier position; and performing an inverse Fourier transform on the output of the carrier arranging means to convert the frequency domain to the time domain, thereby obtaining an orthogonal frequency division multiplexed transmission signal. And the carrier arranging means, for the synchronous detection segment, the carrier number k ′ in the segment for the symbol of symbol number n is k ′ = 3 (n mod 4) The output of the scattered pilot signal generation means is arranged at a carrier position satisfying + 12p (mod represents a modulo operation, p is an integer). Carrier number k ′ is k ′ = 0
The output of the end-of-band pilot signal generation means is arranged at a carrier position that satisfies, and the output of the end-of-band pilot signal generation means is arranged for all symbols at the carrier position of the band end carrier, Generating means, the terminal pilot signal generating means, and an output of the information transmission signal generating means arranged at any carrier position other than the position where the output of the band end pilot signal generating means is arranged; Complex vectors output by the signal generation means, the termination pilot signal generation means, and the band termination pilot signal generation means are uniquely identified by a carrier number k in the entire transmission band at a carrier position where each is arranged by the carrier arrangement means. Has a specific phase and amplitude determined by the information transmission signal generation means The complex vector to be output is obtained by subjecting the synchronous detection segment to absolute phase modulation based on the digital information, and the differential detection segment is differentiated between symbols based on the digital information. It is characterized by being subjected to modulation.

In the transmission device, in particular, the absolute phase modulation is:
The digital modulation method is any one of QPSK modulation, 16QAM modulation, and 64QAM modulation, and the differential modulation is DQPSK modulation.

Further, the receiving device according to the present invention is a receiving device for receiving and demodulating an orthogonal frequency division multiplex transmission signal transmitted by the transmission device, and performing a Fourier transform on the orthogonal frequency division multiplex transmission signal to obtain a frequency from a time domain. Fourier transforming means for obtaining a complex vector sequence representing the phase and amplitude of each carrier by converting into a domain, provided when demodulating the synchronous detection segment, and the scattered pilot signal from the output of the Fourier transforming means. A variance / termination pilot extraction means for extracting and outputting a complex vector group corresponding to the required termination pilot signal or the band termination pilot signal; and a demodulator for demodulating the synchronous detection segment. Output the modulation complex vector uniquely determined by the carrier number k in the entire transmission band. And a demodulator for demodulating the synchronous detection segment, wherein the output of the scattered / terminated pilot extracting unit is divided by the output of the vector generating unit corresponding to the carrier position where the complex vector is arranged. A dividing means for estimating a transmission path characteristic of the scattered pilot signal, the necessary terminal pilot signal or the band terminal pilot signal, and provided when demodulating the synchronous detection segment. Interpolating means for estimating a transmission path characteristic of the information transmission signal in the synchronous detection segment by interpolating an output; and an output means for outputting the Fourier transform means provided when demodulating the differential detection segment. A delay means for delaying the synchronous detection segment by one symbol time. A detecting means for detecting the output of the Fourier transform means at the output of the interpolating means and detecting the output of the Fourier transform means at the output of the delay means when demodulating the differential detection segment; It is characterized by having.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows arrangements of synchronous detection or differential detection segments (a total of 13 segments) and band-end pilot signals in the first and second embodiments of the OFDM transmission system according to the present invention. It is a figure showing an example.

FIG. 2 shows an arrangement of an additional information transmission signal, an arrangement of a scattered pilot signal in a segment for synchronous detection, and a termination in a segment for differential detection in the first and second embodiments of the OFDM transmission system according to the present invention. FIG. 3 is a diagram illustrating an example of arrangement of pilot signals.

FIG. 3 shows an arrangement of a continuous pilot signal and a control information signal, an arrangement of a dispersed pilot signal in a segment for synchronous detection, and a termination in a segment for differential detection in the second embodiment of the OFDM transmission system according to the present invention. FIG. 3 is a diagram illustrating an example of arrangement of pilot signals.

FIG. 4 is a time-amplitude characteristic diagram showing an inverse Fourier transform pair of the frequency arrangement of the continuous pilot signal of the synchronous detection segment shown in Table 2 in the second embodiment of the OFDM transmission system according to the present invention.

FIG. 5 is a time-amplitude characteristic diagram showing an inverse Fourier transform pair of the frequency arrangement of the continuous pilot signal of the segment for differential detection shown in Table 2 in the second embodiment of the OFDM transmission system according to the present invention. .

FIG. 6 is a time-amplitude characteristic diagram showing an inverse Fourier transform pair of the frequency arrangement of the control information signal of the synchronous detection segment shown in Table 3 in the second embodiment of the OFDM transmission system according to the present invention.

FIG. 7 is a time-amplitude characteristic diagram showing an inverse Fourier transform pair of the frequency arrangement of the control information signal of the segment for differential detection shown in Table 3 in the second embodiment of the OFDM transmission system according to the present invention. .

FIG. 8 is a block circuit diagram showing a configuration of a transmitting apparatus used for the OFDM transmission system according to the present invention as a fifth embodiment.

FIG. 9 is a block circuit diagram showing a configuration of a receiving apparatus used in an OFDM transmission system according to the present invention as a sixth embodiment.

FIG. 10 is a block circuit diagram showing a configuration of a receiving device used for a conventional OFDM transmission system.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of an OFDM transmission system according to the present invention, and a transmission device and a reception device suitable for the OFDM transmission system will be described in detail.

(First Embodiment) In the OFDM transmission method of the present embodiment, a band termination pilot using 13 segments and a carrier of one carrier is used, and one segment is composed of 108 carriers. Each segment is composed of either a synchronous detection segment or a differential detection segment. A carrier of 1405 carriers is used in the entire band.

FIG. 1 shows an example of arrangement of synchronous detection or differential detection segments (a total of 13 segments) and band end pilot signals. The horizontal axis schematically represents the frequency axis (carrier arrangement), and the vertical axis schematically represents the time axis (symbol direction).
The carrier number k 'in each segment is an integer from 0 to 107, and one segment is composed of 108 carriers.

The segment for synchronous detection is composed of a scattered pilot signal using 9 carriers per symbol, an additional information transmission signal using 3 carriers, and an information transmission signal using 96 carriers.

The differential detection segment includes an additional information transmission signal using a carrier of 11 carriers, a termination pilot signal using a carrier of one carrier, and an information transmission signal using a carrier of 96 carriers.

As described above, since the same number of carriers as 108 are used in the synchronous detection segment and the differential detection segment, the required transmission band does not change depending on the combination of the segments.

Here, the carrier number k in the entire band is changed from 0 to 1404.
, The segment number i is an integer from 0 to 12, and the carrier number k ′ in each segment is an integer from 0 to 107, and k
= I · 108 + k ′.

The scattered pilot signal provided in the synchronous detection segment is arranged on the carrier of the carrier number k 'in the segment according to the equation (5). In the equation (5), mod represents a remainder operation, and n represents a symbol number.
Is an integer of 0 or more, and p is an integer of 0 or more and 8 or less.

k '= 3 (n mod 4) + 12p (5) The additional information transmission signals provided in the synchronization segment and the differential detection segment are respectively arranged on the carrier of the carrier number k' in each segment shown in Table 1. . Table 1
Indicates that the additional information transmission signal of the segment for synchronous detection is included in the additional information transmission signal of the segment for differential detection.

With the above configuration, even when the synchronous detection segment and the differential detection segment are mixed, the additional information transmission signal is always arranged on the carrier defined as the additional information transmission signal of the synchronous detection segment. , And it becomes easy for the receiving side to discriminate between the additional information transmission signal and the other transmission signal. Depending on the additional information to be transmitted, a carrier may be allocated so as not to be a subset arrangement.

The terminal pilot signal provided in the segment for differential detection is arranged on a carrier having a carrier number k 'of 0 in each segment. The arrangement of the terminal pilot signal is a position where the periodicity of the frequency arrangement of the dispersed pilot signals of the adjacent synchronous detection segments is maintained. Each terminal pilot signal supplements the distributed pilot signal.

FIG. 2 shows an example of the arrangement of dispersed pilot signals in the segment for synchronous detection and the arrangement of terminal pilot signals in the segment for differential detection. The horizontal axis is the frequency axis (carrier arrangement),
The vertical axis schematically represents the time axis (symbol direction). Carrier number k 'in each segment is changed from 0 to 10
It is assumed to be an integer of 7, and one segment is composed of carrier waves of 108 carriers. The additional information transmission signal is allocated to a carrier different from the scattered pilot signal.

These scattered pilot signals and terminal pilot signals are each provided with a PN (pseudo-random number) sequence w _k (w _k = w) which corresponds to a carrier number k (determined by a segment number i and a carrier number k ′ in each segment). 0,1), and is obtained by modulating a carrier with a complex vector c ^{k, n} shown in equation (6). In equation (6), Re ｛c
^{k, n} } represents a real part of a complex vector c ^{k, n} corresponding to a carrier having a carrier number k and a symbol number n.
{C ^{k, n} } represents an imaginary part.

The additional information transmission signal provided in the synchronous detection segment and the differential detection segment is used for transmitting additional information different from the information transmission signal transmitted using a 96-carrier carrier. For example, control information that defines the transmission mode (number of segments, carrier modulation method, etc.), information used as a broadcasting station (eg, control information used in a relay station, low-time-delay audio information used in live broadcasting, Broadcast station identification signal). One bit of additional information may be transmitted for each symbol, or multiple bits of additional information may be transmitted. Alternatively, only the control information that defines the transmission mode may be transmitted.

Here, if the control information bits to be transmitted in symbol of the symbol number n and S _n, the control information signal is obtained by modulating a carrier wave by the complex vector c ^{k, n} shown in equation (7).
That is, in this case, the carrier transmitting the control information signal is a differential binary PSK (Phase Shift Keying) between symbols.
Modulated.

However, the first symbol of the frame (symbol number n =
0), the carrier transmitting the control information is the PN sequence described above.
Based on w _k , modulation is performed by a complex vector c ^{k, n} shown in equation (8).

When transmitting 2-bit control information for each symbol, for example, differential 4-phase PSK modulation between symbols is used, or a plurality of carriers for transmitting control information are divided into two groups, It may be assigned so that one bit is transmitted each time.

The information transmission signal provided in the synchronous detection segment is:
It is allocated to a carrier other than the scattered pilot signal and the additional information transmission signal of the above-mentioned synchronous detection segment, and is subjected to absolute phase modulation based on digital information. For this absolute phase modulation, for example, QPSK, 16QAM, 64QAM modulation or the like is used.

The information transmission signal of the segment for synchronous detection is demodulated by the following processing. First, the dispersed pilot signal, the required terminal pilot signal, and the band terminal pilot signal are inversely modulated with the complex vector that modulates the distributed pilot, the terminal pilot signal, and the band terminal pilot signal, and the distributed pilot signal, the terminal pilot signal, and the like. Of the transmission path in the frequency domain according to the above. Further, a transmission path characteristic of the information transmission signal is estimated by interpolating in a frequency direction and a symbol direction by a filter. The information transmission signal is divided by the transmission path characteristics thus obtained. As a result, the information transmission signal can be demodulated from the synchronous detection segment.

The information transmission signal provided in the differential detection segment is
It is allocated to a carrier other than the terminal pilot signal of the differential detection segment and the additional information transmission signal, and differentially modulated between adjacent symbols having the same carrier number based on digital information.

For this differential modulation, for example, DBPSK, DQPSK, DAPSK or the like is used. The information transmission signal of the differential detection segment can be demodulated by being divided by the information transmission signal of the same carrier number of the previous symbol.

From the above, the OFDM transmission method according to the present embodiment, in the receiving apparatus, achieves high-quality reception by the effect of a filter in the synchronous detection segment, and performs differential demodulation between symbols in the differential detection segment. It is possible to perform reception suitable for mobile reception in which characteristics change rapidly. In addition, by arbitrarily combining the segment for synchronous detection and the segment for differential detection for each segment, a flexible service mode can be realized without fluctuation of the transmission band.

(Second Embodiment) In the OFDM transmission system according to the present embodiment, a band termination pilot using 13 segments and a carrier of one carrier is used, and one segment is composed of a carrier of 108 carriers. Each segment is composed of either a synchronous detection segment or a differential detection segment. A carrier of 1405 carriers is used in the entire band.

Synchronous detection segments include a dispersed pilot signal using a carrier of 9 carriers per symbol, a continuous pilot signal using a carrier of 2 carriers, and an additional information transmission signal using a carrier of 1 carrier (in this embodiment, Control information signal) and an information transmission signal using a carrier wave of 96 carriers.

The differential detection segment uses a continuous pilot signal using a carrier of 6 carriers, a control information signal using a carrier of 5 carriers, a terminal pilot signal using a carrier of 1 carrier, and a carrier of 96 carriers. And an information transmission signal.

Here, the carrier number k in the entire band is changed from 0 to 1404.
, The segment number i is an integer from 0 to 12, and the carrier number k ′ in each segment is an integer from 0 to 107, and k
= I · 108 + k ′.

The scattered pilot signal provided in the synchronous detection segment is arranged on the carrier of the carrier number k 'in the segment according to the equation (5). In the equation (5), mod represents a remainder operation, and p is an integer of 0 or more and 8 or less.

k '= 3 (n mod 4) + 12p (5) The continuous pilot signals provided in the synchronization segment and the differential detection segment are respectively arranged on the carrier having the carrier number k' in each segment shown in Table 2. Table 2 shows that the continuous pilot signal of the segment for synchronous detection is included in the continuous pilot signal of the segment for differential detection.

With the above configuration, even when the segment for synchronous detection and the segment for differential detection are mixed, a continuous pilot signal is always arranged on a carrier defined as a continuous pilot of the segment for synchronous detection, It is easy for the receiving side to identify the other pilot signal from the continuous pilot signal. Note that a carrier wave may be allocated so as not to be a subset arrangement.

A continuous pilot signal that modulates the carrier with a specific phase and amplitude on a carrier having the same frequency for each symbol,
Since the frequency, phase, and amplitude are specified, the receiving side can use it as a reference carrier.

The terminal pilot signal provided in the segment for differential detection is arranged on a carrier having a carrier number k 'of 0 in each segment. The arrangement of the terminal pilot signal is a position where the periodicity of the frequency arrangement of the dispersed pilot signal of the adjacent synchronous detection segment is maintained. Each terminal pilot signal supplements the distributed pilot signal.

FIG. 3 shows an example of an arrangement of a continuous pilot signal and a control information signal, an example of an arrangement of a dispersed pilot signal in a segment for synchronous detection, and an example of an arrangement of a terminal pilot signal in a segment for differential detection. The horizontal axis schematically represents the frequency axis (carrier arrangement), and the vertical axis schematically represents the time axis (symbol direction). The carrier number k 'in each segment is an integer from 0 to 107, and one segment is composed of 108 carriers. The continuous pilot signal and the control information signal are allocated to a different carrier from the dispersed pilot signal.

These scattered pilot signals, continuous pilot signals,
The terminal pilot signal is converted into a PN (pseudo-random number) sequence w _k (w _k = 0, 1) corresponding to the carrier number k (determined by the segment number i and the carrier number k ′ in each segment). It is obtained by modulating the carrier with the complex vector c ^{k, n} shown in the equation (6).
In the equation (6), Re {c ^{k, n} } represents a real part of a complex vector c ^{k, n} corresponding to a carrier having a carrier number k and a symbol number n, and Im {c ^{k, n} } represents an imaginary part. .

The control information signals provided in the synchronous detection segment and the differential detection segment are respectively arranged on carriers of carrier number k 'in each segment shown in Table 3, and transmit 1-bit control information for each symbol.

The control information bit transmitted by the symbol of symbol number n is
Assuming that S _n , the control information signal is obtained by modulating the carrier with the complex vector c ^{k, n} shown in equation (7). That is, the carrier transmitting the control information signal is subjected to differential binary PSK (Phase Shift Keying) modulation between symbols.

However, the first symbol of the frame (symbol number n =
0), the carrier transmitting the control information is the PN sequence described above.
Based on w _K , modulation is performed by a complex vector c ^{k, n} shown in Expression (8).

When transmitting 2-bit control information for each symbol, for example, differential four-phase PSK modulation between symbols is used.

The information transmission signal provided in the synchronous detection segment is:
It is allocated to a carrier other than the scattered pilot signal, the continuous pilot signal, and the control information signal of the aforementioned synchronous detection segment, and is subjected to absolute phase modulation based on digital information. This absolute phase modulation includes, for example, QPSK, 16QAM, 6
4QAM modulation or the like is used.

The information transmission signal of the segment for synchronous detection is demodulated by the following processing. First, the dispersed pilot signal, the required terminal pilot signal, and the band terminal pilot signal are inversely modulated with the complex vector that modulates the distributed pilot, the terminal pilot signal, and the band terminal pilot signal, and the distributed pilot signal, the terminal pilot signal, and the like. Of the transmission path in the frequency domain according to the above. Further, a transmission path characteristic of the information transmission signal is estimated by interpolating in a frequency direction and a symbol direction by a filter. The information transmission signal is divided by the transmission path characteristics thus obtained. As a result, the information transmission signal can be demodulated from the synchronous detection segment.

The information transmission signal provided in the differential detection segment is
It is allocated to a carrier other than the continuous pilot signal, the terminal pilot signal, and the control information signal of the above-described differential detection segment, and is subjected to differential modulation between adjacent symbols having the same carrier number based on digital information.

For this differential modulation, for example, DBPSK, DQPSK, DAPSK or the like is used. The information transmission signal of the differential detection segment can be demodulated by being divided by the information transmission signal of the same carrier number of the previous symbol.

From the above, the OFDM transmission method according to the present embodiment, in the receiving apparatus, achieves high-quality reception by the effect of a filter in the synchronous detection segment, and performs differential demodulation between symbols in the differential detection segment. It is possible to perform reception suitable for mobile reception in which characteristics change rapidly. Further, a flexible service form can be realized by arbitrarily combining the synchronous detection segment and the differential detection segment for each segment.

In addition, by arranging a continuous pilot signal that modulates the carrier with a specific phase and amplitude on a carrier having the same frequency for each symbol, the frequency, phase, and amplitude are specified, so the receiving side uses the carrier as a reference carrier. can do.

4 and 5 show the inverse Fourier transform pairs of the frequency arrangement of the continuous pilot signal of the synchronous detection segment (13 segments, 26 carriers) and the differential detection segment (13 segments, 78 carriers) shown in Table 2, respectively. It is shown. 4 and 5 that they are impulse-like, and that the frequency arrangement of the continuous pilot signals shown in Table 2 has no periodicity.

For this reason, the OFDM transmission scheme according to the present embodiment can prevent the entire continuous pilot signal from disappearing due to delay waves such as multipath. Further, by obtaining the inverse Fourier transform using this arrangement, the impulse response of the transmission path can be obtained. It should be noted that the frequency allocation of the continuous pilot signal is strong against autocorrelation.

FIGS. 6 and 7 show inverse Fourier transform pairs of the frequency arrangement of the control information signals of the synchronous detection segment and the differential detection segment shown in Table 3, respectively. 6 and 7 that they are impulse-shaped and that the frequency arrangement of the control information signal shown in Table 3 has no periodicity.

From the above, the OFDM transmission scheme according to the present embodiment can prevent the entire control information signal from being lost due to a delay wave such as a multipath.

Note that the frequency arrangement of the additional information transmission signal including the control information signal can be set in the same manner.

Third Embodiment FIG. 8 shows a configuration of an embodiment of a transmitting apparatus that generates an OFDM signal based on the OFDM transmission schemes of the first and second embodiments.

In FIG. 8, an information transmission signal generation circuit 51 performs error control processing (error correction coding, interleaving, energy spreading, etc.) and digital modulation on input digital information as necessary. Note that basic error control processing techniques and digital modulation techniques generally used in digital transmission are well-known techniques, and are not described.

In the synchronous detection segment, absolute phase modulation is performed as digital modulation. In this absolute phase modulation, for example,
QPSK, 16QAM, 64QAM modulation and the like are used. In the differential detection segment, differential modulation is performed between adjacent symbols having the same carrier number based on digital information. For this differential modulation, for example, DBPSK, DQPSK, DAPSK or the like is used.

The additional information signal generation circuit 52 performs error control processing (error correction coding, interleaving, energy spreading, etc.) and digital modulation on the input additional information as necessary. M (M is a natural number of 2 or more) phase PSK (P
hase Shift Keying) modulation and differential M in symbol direction
Phase PSK modulation or the like is used.

The control information generation circuit 56 generates transmission mode information (various information defining the transmission mode such as the number of segments for synchronous detection, the number of segments for differential detection, and the carrier modulation method) required on the receiving side. This information is subjected to error control processing and digital modulation in an additional information signal generation circuit 52,
Error control processing and digital modulation different from other additional information may be performed.

The distributed pilot signal generation circuit 53 is a carrier arrangement circuit.
Modulation is performed based on a PN (pseudo-random number) sequence w _k (w _k = 0,1) corresponding to a carrier number k (determined by a segment number i and a carrier number k ′ in each segment) whose arrangement is defined in 57. A scattered pilot signal is generated.

The termination pilot signal generation circuit 54 is a carrier arrangement circuit.
Modulation is performed based on a PN (pseudo-random number) sequence w _k (w _k = 0,1) corresponding to a carrier number k (determined by a segment number i and a carrier number k ′ in each segment) whose arrangement is defined in 57. Generated termination pilot signal.

The band end pilot signal generation circuit 55 generates a PN (pseudo random number) sequence w _k (w _k = 0,
A band-ended pilot signal modulated based on 1) is generated.

Although the continuous pilot signal is not particularly described, it is sufficient to assume that the additional information signal generation circuit 52 modulates the carrier with the same phase and amplitude for each symbol.

In the carrier arrangement circuit 57, the information transmission signal generation circuit 51,
Additional information signal generation circuit 52, distributed pilot signal generation circuit
53, the respective outputs (complex vector sequence) of the termination pilot signal generation circuit 54 and the band termination pilot signal generation circuit 55 are arranged at the carrier positions in the frequency domain defined according to the transmission mode.

For example, the output of the scattered pilot signal generation circuit 53 is converted into a carrier wave which is shifted by L (L is a divisor of N) carriers at intervals of N (N is a natural number of 2 or more) carriers and in each symbol in the segment for synchronous detection. Be placed. The output of the termination pilot signal generation circuit 54 is the carrier number k '= 0 in the segment for differential detection.
Of carriers. The additional information signal generation circuit 52
Are assigned according to the frequency arrangement shown in Table 1, for example. The vector sequence for each carrier in the base frequency band arranged in this way is input to the inverse Fourier transform circuit 58.

The inverse Fourier transform circuit 58 converts the vector sequence for each carrier in the base frequency band generated by the carrier arranging circuit 57 from the frequency domain to the time domain, and outputs a guard interval period that is normally used. The orthogonal modulation circuit 59 orthogonally modulates the output of the inverse Fourier transform circuit 58 and converts the output to an intermediate frequency band. The frequency conversion circuit 60 is a quadrature modulated OFDM
The frequency band of the signal is converted from the intermediate frequency band to the radio frequency band and supplied to an antenna or the like.

According to the transmission apparatus having the above configuration, it is possible to generate an OFDM signal based on the OFDM transmission scheme described in the first and second embodiments.

(Fourth Embodiment) FIG. 9 is a diagram for receiving OFDM signals formed based on the OFDM transmission schemes of the first and second embodiments and estimating an impulse response in a time domain of a transmission path. 1 shows a configuration of a receiving apparatus capable of performing the above.

In FIG. 9, a tuner 11 converts a frequency band of a received OFDM signal from a radio frequency band to a base frequency band. The Fourier transform circuit 12 converts the OFDM signal in the base frequency band from the time domain to the frequency domain, and outputs it as a vector sequence for each carrier in the frequency domain.

The dispersion / termination pilot extraction circuit 13 extracts a dispersion pilot signal, necessary termination pilot signals, and band termination pilot signals from the vector sequence output from the Fourier transform circuit 12. The vector generation circuit 14 generates a modulation complex vector c ^{k, n} corresponding to the scattered pilot signal, the ending pilot signal, and the band ending pilot signal extracted by the scatter / termination pilot extracting circuit 13.

The dividing circuit 15 divides the scattered pilot signal, the ending pilot signal, and the band ending pilot signal extracted by the scattered / terminated pilot extracting circuit 13 by a complex vector generated by the vector generating circuit 14 to generate a scattered pilot signal, a ending pilot signal. And estimating the transmission path characteristic of the band end pilot signal. The interpolation circuit 16 interpolates the transmission path characteristics of the scattered pilot signal, the termination pilot signal, and the band termination pilot signal obtained by the division circuit 15 to determine the transmission path characteristic of the carrier of the information transmission signal of the synchronous detection segment. presume.

The delay circuit 17 delays the vector sequence output from the Fourier transform circuit 12 by one symbol. The selection circuit 18 selects and outputs the output of the interpolation circuit 16 in the case of the segment for synchronous detection and the output of the delay circuit 17 in the case of the segment for differential detection according to the type of the segment separately transmitted by the control information. .

The division circuit 19 divides the vector sequence output from the Fourier transform circuit 12 by the output of the selection circuit 18, respectively. Division circuit
At 19, the synchronous detection segment divides by the transmission path characteristic of the corresponding carrier estimated by the interpolation circuit 16 and performs synchronous detection, and the differential detection segment corresponds to the one symbol before output by the delay circuit 17 at the differential detection segment. And the differential detection is performed by dividing by the vector sequence of the carrier to be processed.

The demodulation circuit 20 demodulates the detection signal output from the division circuit 19 according to the modulation method (QPSK, 16QAM, 64QAM, DBPSK, DQPSK, DAPSK, etc.) when generating the information transmission signal, and obtains the transmitted digital information. .

With the above configuration, it is possible to receive and demodulate an OFDM signal based on the OFDM transmission scheme described in the first embodiment. The configuration described below is based on the OF described in the second embodiment.
This is a case where an OFDM signal based on the DM transmission scheme is received and demodulated.

First, the continuous pilot extraction circuit 21 extracts a continuous pilot signal from the vector sequence output from the Fourier transform circuit 12. At this time, even when the synchronous detection segment and the differential detection segment are mixed, at least the continuous pilot signal of the synchronous detection segment is always mixed, so that the continuous pilot signal can always be extracted.

The vector generation circuit 22 generates a modulated complex vector c ^{k, n} corresponding to the continuous pilot signal extracted by the continuous pilot extraction circuit 21. The division circuit 23 divides the continuous pilot signal extracted by the continuous pilot extraction circuit 21 by a complex vector generated by the vector generation circuit 22 to estimate a transmission path characteristic of the continuous pilot signal. The inverse Fourier transform circuit 24 converts the transmission path characteristic of the continuous pilot signal estimated by the division circuit 23 from the frequency domain to the time domain to obtain an impulse response characteristic of the transmission path.

From the above, according to the configuration of the receiving apparatus of the present embodiment, in the demodulation circuit 20, high-quality demodulation can be realized in the synchronous detection segment by the filter effect by the interpolation processing of the transmission path characteristic, and the differential In the detection segment, it is possible to realize demodulation suitable for mobile reception in which a change in transmission path characteristics is fast by differential demodulation between symbols. Further, in the inverse Fourier transform circuit 24, it is possible to obtain an impulse response characteristic of the transmission line without aliasing.

INDUSTRIAL APPLICABILITY As described above, the orthogonal frequency division multiplexing transmission system of the present invention can include a differential detection segment suitable for mobile reception. At this time, by providing the terminal pilot signal and the band terminal pilot signal, without impairing the synchronous detection characteristics of adjacent synchronous detection segments,
The segment for synchronous detection and the segment for differential detection can be freely combined for each segment, thereby realizing a flexible service form.

In addition, by using a continuous pilot signal in which the inverse Fourier transform pair of the frequency arrangement is in the form of an impulse, the impulse response characteristics of the transmission path without aliasing in the symbol period can be obtained as necessary.

Therefore, according to the present invention, a modulation scheme suitable for mobile reception is partially introduced into the modulation of a carrier for transmitting digital information while maintaining the entire transmission capacity, and the transmission estimated from a continuous pilot signal, for example, is introduced. It is possible to provide an OFDM transmission system in which continuous pilot signals are arranged so that aliasing of a path impulse response does not occur, and a transmission device and a reception device suitable for the present system.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kenichiro Hayashi 8-38, Hagihata, Kyotanabe-shi, Kyoto (72) Inventor Akira Kisota 1-1-11-202, Kaji-cho, Moriguchi-shi, Osaka (72) Inventor Soga Shigeru 3-3-3-1-101 Ichitsuya, Matsubara-shi, Osaka (72) Inventor Sadaji Kageyama 5-29-C-302, Akashidai, Mita-shi, Hyogo (72) Inventor Masanori Saito 1-17-4 Sakuragaoka, Setagaya-ku, Tokyo No. (72) Inventor Tatsuya Ishikawa 8-3-1-8 Hino, Konan-ku, Yokohama-shi, Kanagawa Prefecture Konandai Miwa Plaza 802 (72) Inventor Jin Mori 4-17-24, Motoyamakita-cho, Higashinada-ku, Kobe, Hyogo (72) Inventor Masayuki Takada 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute (72) Inventor Toru Kuroda 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute (72) Inventor Sasaki Makoto 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute of Broadcasting Technology (56) References JP-A-11-340945 (JP, A) JP-A-2000-101542 (JP, A) JP-A-2000-115119 (JP, A) Japanese Patent Laid-Open No. 2000-134176 (JP, A) “Transmission system for digital terrestrial broadcasting: transmission characteristics in fixed reception and mobile reception”, Preprints of published research papers and research presentations, May 22, 1998, p. 67-72, "Multiplexing Method and Transmission Characteristics of TMCC Signal in Terrestrial ISDB", May 21, 1997, ITE Technical Report, Vol. 21, No. 30, p. 1-6 “Study of Terrestrial ISDB Broadcasting System-BST-OFDM System and Multiplexing System”, Television Society Technical Report, March 15, 1996, Vol. 20, No. 22, p. 23-28 (58) Field surveyed (Int. Cl. ⁷ , DB name) H04J 11/00

Claims (5)

(57) [Claims] An orthogonal frequency division multiplexing transmission system for transmitting digital information by modulating K (K is an integer) carriers having a frequency relationship orthogonal to each other for each symbol period. Each carrier number of the number of carriers is k (k is an integer satisfying 0 ≦ k ≦ K−1), and the carrier number k in the entire transmission band satisfies k = K−1 among the K carriers. A carrier is a band end carrier, and among the K carriers, a carrier having a carrier number k of 0 ≦ k ≦ K-2 in the entire transmission band is divided into I (I is an integer) segments, Each of the I segments is composed of K ′ (K ′ is an integer satisfying K ′ = (K−1) / I) carriers that are consecutive in frequency, and the symbol number is n (n is an integer) and the segment is number To i
(I is an integer satisfying 0 ≦ i ≦ I−1), and the carrier numbers of K ′ carriers in each segment are represented by K ′ (k ′
Is an integer satisfying 0 ≦ k ′ ≦ K′−1). Each of the segments is used as either a segment for synchronous detection or a segment for differential detection. In the segment for synchronous detection, a symbol of symbol number n is used. On the other hand, the distributed pilot signal is arranged at a carrier position where the carrier number k 'in the segment satisfies k' = 3 (n mod 4) + 12p (mod represents a remainder operation, p is an integer). In the segment, a termination pilot signal is arranged at a carrier position where the carrier number k 'in the segment satisfies k' = 0 for all symbols, and a band termination is provided for all symbols at the carrier position of the band termination carrier. A pilot signal, wherein the scattered pilot signal, the terminal pilot signal, and the band terminal pilot signal are disposed. At any one of the carrier positions other than the position, the information transmission signal is arranged, and the scattered pilot signal, the terminal pilot signal, and the band terminal pilot signal indicate the carrier on which each is arranged in the entire transmission band of the carrier. Modulated with a specific amplitude and phase uniquely determined by the carrier number k, the information transmission signal arranged in the synchronous detection segment, the carrier in which each is arranged, based on the digital information Absolute phase modulation, wherein the information transmission signal arranged in the differential detection segment, the carrier in which each is arranged, is that which is differentially modulated between symbols based on the digital information. Characteristic orthogonal frequency division multiplexing transmission system. 2. The quadrature modulation method according to claim 1, wherein said absolute phase modulation is a digital modulation method of any of QPSK modulation, 16QAM modulation and 64QAM modulation, and said differential modulation is DQPSK modulation. Frequency division multiplex transmission system. 3. A transmitting apparatus for transmitting a signal according to the orthogonal frequency division multiplexing transmission method according to claim 1, wherein: an information transmission signal generating means for outputting a complex vector sequence for generating the information transmission signal; , Provided when forming the synchronous detection segment,
A scattered pilot signal generating means for outputting a complex vector for generating the scattered pilot signal, provided when forming the differential detection segment,
A terminal pilot signal generating means for outputting a complex vector for generating the terminal pilot signal, a band terminal pilot signal generating means for outputting a complex vector for generating the band terminal pilot signal, and the information transmission signal generating means Carrier arranging means for arranging the outputs of the distributed pilot signal generating means, the terminal pilot signal generating means, and the band terminal pilot signal generating means at predetermined carrier positions; and an inverse Fourier transform of the output of the carrier arranging means. Inverse Fourier transform means for generating an orthogonal frequency division multiplexed transmission signal by converting the frequency domain to the time domain, and the carrier allocating means comprises a symbol number n for the synchronous detection segment.
, The output of the distributed pilot signal generation means is placed at a carrier position where the carrier number k 'in the segment satisfies k' = 3 (n mod 4) + 12p (mod represents a remainder operation, p is an integer). For the differential detection segment, the output of the termination pilot signal generation means is arranged at a carrier position where the carrier number k ′ in the segment satisfies k ′ = 0 for all symbols, At the carrier position of the band end carrier, the output of the band end pilot signal generation means is arranged for all symbols, and the distributed pilot signal generation means, the terminal end pilot signal generation means, and the band end pilot signal generation means Disposing the output of the information transmission signal generating means at any carrier position other than the position where the output is disposed, The complex vectors output by the pilot signal generating means, the terminal pilot signal generating means, and the band terminal pilot signal generating means are represented by the carrier number k in the entire transmission band at the carrier position where each is arranged by the carrier arranging means. A complex vector having a specific phase and amplitude uniquely determined, wherein the complex vector output by the information transmission signal generating means is obtained by subjecting the synchronous detection segment to absolute phase modulation based on the digital information. The orthogonal frequency division multiplexing transmission apparatus, wherein the differential detection segment is obtained by performing differential modulation between symbols based on the digital information. 4. The quadrature modulation method according to claim 3, wherein said absolute phase modulation is a digital modulation method of any one of QPSK modulation, 16QAM modulation, and 64QAM modulation, and said differential modulation is DQPSK modulation. Transmitter for frequency division multiplex transmission. 5. A receiving device for receiving and demodulating an orthogonal frequency division multiplex transmission signal transmitted by a transmission device according to claim 3 or 4, wherein the orthogonal frequency division multiplex transmission signal is subjected to a Fourier transform to obtain a time. Fourier transform means for obtaining a complex vector sequence representing the phase and amplitude of each carrier by converting from the domain to the frequency domain, provided when demodulating the synchronous detection segment,
A variance / termination pilot extraction means for extracting and outputting the dispersion pilot signal and a necessary group of complex vectors corresponding to the termination pilot signal or the band termination pilot signal from an output of the Fourier transform means; Provided when demodulating the
The phase and the amplitude are the carrier numbers k in the entire transmission band.
Vector generating means for outputting a modulation complex vector uniquely determined by, provided when demodulating the synchronous detection segment,
By dividing the output of the dispersion / termination pilot extraction means by the output of the vector generation means corresponding to the carrier position where the complex vector is located, the dispersion pilot signal, the necessary termination pilot signal or the band termination is obtained. Dividing means for estimating the transmission path characteristics of the pilot signal, provided when demodulating the synchronous detection segment,
By interpolating the output of the dividing means, an interpolating means for estimating the transmission path characteristics of the information transmission signal in the synchronous detection segment, provided when demodulating the differential detection segment,
Delay means for delaying the output of the Fourier transform means by one symbol time; and when demodulating the synchronous detection segment, detecting the output of the Fourier transform means with the output of the interpolation means,
When demodulating the differential detection segment, the receiving device of the orthogonal frequency division multiplexing transmission system comprises a detecting means for detecting an output of the Fourier transform means with an output of the delay means.