JP2000236313A - Quadrature frequency division multiplex transmission system, transmission equipment and reception equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide demodulation with high quality and demodulation suitable for mobile reception. SOLUTION: A received OFDM signal is transformed from the time domain to the frequency domain by Fourier transformation 12, and a vector array for each carrier in the frequency domain is provided. Required dispersion and terminal pilot signals are extracted from the vector array 13, transmission line characteristics related to the dispersion/terminal pilot signals are estimated by dividing them with a modulated complex vector 15, and transmission line characteristics related to the information transmission carrier of a segment for synchronous detection are estimated by interpolating these transmission line characteristics 16. Meantime, the vector array provided by Fourier transformation is delayed by one symbol 17, an interpolated output is selected in the case of segment for synchronous detection, but a delayed output is selected in the case of segment for differential detection 18, the synchronous detection or differential detection is performed 19 by dividing the vector array by the selected output and additional information and digital information are provided 20 by demodulation 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 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.

[0002]

2. Description of the Related Art At present, orthogonal frequency division multiplexing (hereinafter referred to as OFDM) is used as a digital broadcasting system in terrestrial TV broadcasting.
A transmission system using the technology is being studied. This OFDM transmission system is a kind of multicarrier 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.

[0003] As a digital broadcasting system of a TV signal using the conventional OFDM transmission technology, for example, DV in Europe.
BT standard, ETSI 300 744 (ETSI: European
Telecommunications Standards Institute).

In the conventional OFDM transmission method, for example, in the 2k mode (2k means that the number of samples of the fast Fourier transform when generating an OFDM signal is 2048), a carrier of 1705 carriers is used in the entire transmission band. 1
The carrier of 42 carriers is distributed to the pilot (Scattered Pil
ot) 45 pilot carrier (C)
The carrier of 17 carriers is used for the control information (TPS) signal, and the carrier of 1512 carriers is used for the information transmission signal.

[0005] However, the continuous pilot signal of the carrier of 11 carriers among the continuous pilot signals of the carrier of 45 carriers is arranged so as to overlap with the scattered 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. .

More specifically, assuming that the carrier number k is from 0 to 1704 in order from the end and the symbol number n in the frame is from 0 to 67, the scattered pilot signal is arranged on the carrier of the 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.

[0007]

(Equation 1)

[0008] The continuous pilot signal has a carrier number k =
｛0,48,54,87,141,156,192,2
01, 255, 279, 282, 333, 432, 45
0,483,525,531,618,636,71
4,759,765,780,804,873,88
8,918,939,942,969,984,105
0, 1101, 1107, 1110, 1137, 114
0,1146,1206,1269,1323,137
7,1491,1683,1704}.

[0009] These scattered and continuous pilot signals are:
The PN (pseudo) corresponding to the carrier number k arranged respectively.
(Similar random number) series w_kBased on the complex vector shown in equation (2)
Le c _{k, n}To modulate the carrier. Equation (2)
In Re ｛c_{k, n}｝ Is carrier number k, symbol
Complex vector c corresponding to the carrier number n_{k, n}Real part of
And Im ｛c_{k, n}｝ Represents an imaginary part.

[0010]

(Equation 2)

Also, TPS (Transmission Parameter Si)
gnaling) is a carrier information k =
$ 34,50,209,346,413,569,59
5,688,790,901,1073,1219,1
262, 1286, 1469, 1594, 1687}, and transmits 1-bit control information for each symbol.

Assuming that the control information bit transmitted by the symbol of symbol number n is S _n , the control information signal is obtained by modulating the carrier with the complex vector c _{k, n} shown in equation (3). That is, the carrier transmitting the control information signal is subjected to differential binary PSK (Phase Shift Keying) modulation between symbols.

[0013]

(Equation 3)

However, the first symbol of the frame (symbol
In the number n = 0), the carrier for transmitting the control information is
PN series w_kAnd the complex vector shown in equation (4)
Le c _{k, n}Modulated by

[0015]

(Equation 4)

Other than the above, 15 used for information transmission signals
The 12 carriers are based on digital information,
It is QPSK, 16QAM or 64QAM modulated. Both modulation methods are absolute phase modulation.

FIG. 10 shows an example of a conventional receiving apparatus which receives the OFDM signal generated in this way and demodulates 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 become a vector sequence for each carrier in the frequency domain. This vector sequence is supplied to the distributed pilot extraction circuit 103 and the continuous pilot extraction circuit 109.

The scattered pilot extracting circuit 103 extracts a scattered pilot signal from the vector sequence output from the Fourier transform circuit 102. The vector generation circuit 104 generates a modulated complex vector _{ck, n} corresponding to the scattered pilot signal extracted by the scattered pilot extraction circuit 103. 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, and estimates the transmission path characteristics related to the scattered pilot signal from the result of the division.

The interpolation circuit 106 interpolates the transmission path characteristics of the scattered pilot signal obtained by the division circuit 105,
Estimate transmission path characteristics for all carriers. 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 performs a modulation method (QP
SK, 16QAM, 64QAM, etc.)
07 demodulates the synchronous detection signal output and obtains transmitted digital information.

Further, the continuous pilot extraction circuit 109
A continuous pilot signal is extracted from the vector sequence output from the Fourier transform circuit 102. Vector generation circuit 110
Generates a modulation complex vector c _{k, n} corresponding to the continuous pilot signal extracted by the continuous pilot extraction circuit 109. The division circuit 111 includes the continuous pilot extraction circuit 10
Then, the continuous pilot signal extracted in step 9 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 performs frequency-to-time conversion of the transmission path characteristic of the continuous pilot signal estimated by the division circuit 111 to obtain an impulse response characteristic of the transmission path.

[0022]

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 demodulation is not performed in a timely manner. Since it is assumed that the channel characteristics obtained by smoothing and interpolating the channel characteristics estimated from the scattered pilots are used, sufficient transmission quality is obtained for mobile reception in which the channel characteristics change rapidly due to fading or the like. May not be obtained.

Further, in the conventional OFDM transmission system, since the modulation system of each carrier is determined to be one in the entire band, the carrier of the carrier transmitting the digital information is transmitted so that a part of the digital information can be received while moving. Even if, for example, differential QPSK modulation suitable for mobile reception is introduced for modulation, the overall transmission capacity is reduced and efficiency is reduced.

Further, since the continuous pilot signal is arranged on one of the carriers at a predetermined carrier interval A, the effective symbol period length (the minimum frequency of the carrier) is included in the impulse response characteristics of the transmission path which can be estimated from the continuous pilot signal. (A reciprocal of the interval) is folded back by 1 / A.

Therefore, the present invention solves the above-mentioned problems,
Introduces a modulation method suitable for mobile reception in part to the modulation of the carrier that transmits digital information while maintaining the overall transmission capacity, and no aliasing occurs in the impulse response of the transmission path estimated from continuous pilot signals It is an object of the present invention to provide an OFDM transmission system in which continuous pilot signals are arranged as described above, and a transmission device and a reception device suitable for this system.

[0026]

In order to solve the above problems, the OFDM 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. This is an OFDM transmission system for transmitting digital information by applying each carrier number of k carriers in the entire transmission band to k (k is 0).
≦ k ≦ K−1), and among the K carriers, the carrier number k in the entire transmission band is k = K−
1 is defined as a band end carrier, and among the K carriers, a carrier number k in the entire transmission band.
Is divided into I (I is an integer) segments, and each of the I segments is divided into K ′ (K ′ is K ′ = (K− 1) /
The symbol number is n (n is an integer), and the segment number is i (i is 0 ≦ i).
≤I-1), K 'in each segment
The carrier numbers of the carriers are k ′ (k ′ is 0 ≦ k ′ ≦
K′−1), and 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 having a symbol number n is used in the segment. The carrier number k ′ is k ′ = 3 (n mod 4) +
A distributed pilot signal is arranged at a carrier position satisfying 12p (mod represents a remainder operation, p is an integer), and an additional information transmission signal is arranged at a specific carrier position for all symbols. For a symbol, a terminal pilot signal is arranged at a carrier position where the carrier number k ′ in the segment satisfies k ′ = 0, and an additional information transmission signal is arranged at a specific carrier position for all symbols, and At the carrier position, a band end pilot signal is arranged for all symbols, and any one of positions other than the positions where the dispersion pilot signal, the terminal pilot signal, the band end pilot signal, and the additional information transmission signal are arranged. In the carrier position of
An information transmission signal is arranged, and the dispersed pilot signal, the terminal pilot signal, and the band terminal pilot signal each uniquely determine a carrier to be arranged by a carrier number k in the entire transmission band of the carrier. Modulated with a specific amplitude and phase, the additional information transmission signal is a specific carrier, which is differentially modulated between symbols based on additional information, and arranged in the synchronous detection segment The information transmission signal is obtained by performing absolute phase modulation on the carrier on which each is arranged based on the digital information, and the information transmission signal arranged on the differential detection segment is a carrier on which each is arranged. , Differentially modulated between symbols based on the digital information.

In the above-mentioned OFDM transmission method, in particular, the differential modulation for the additional information transmission signal is DBPSK modulation, and the absolute phase modulation for the information transmission signal is:
The digital modulation method is any one of QPSK modulation, 16QAM modulation, and 64QAM modulation, and the differential modulation for the information transmission signal is DQPSK modulation.

Further, a transmission apparatus of the OFDM transmission system according to the present invention is a transmission apparatus for transmitting a signal conforming to the above-mentioned OFDM transmission system, wherein the information for outputting a complex vector sequence for generating the information transmission signal is provided. Transmission signal generating means, provided when forming the synchronous detection segment, and when forming the differential detection segment, the distributed pilot signal generating means for outputting a complex vector for generating the distributed pilot signal; 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; Additional information transmission signal generating means for outputting a complex vector for generating an information transmission signal, A carrier for arranging an output of each of the information transmission signal generation means, the distributed pilot signal generation means, the termination pilot signal generation means, the band termination pilot signal generation means, and the additional information transmission signal generation means at a predetermined carrier position Arranging means, and an inverse Fourier transform means for generating an orthogonal frequency division multiplexed transmission signal by performing an inverse Fourier transform on the output of the carrier allocating means to convert the frequency domain to the time domain, and 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 remainder operation, p is an integer), and the output of the additional information transmission signal generation means is arranged at a specific carrier position for all symbols. For the differential detection segment, the output of the terminating pilot signal generation means is placed at a carrier position where the carrier number k ′ in the segment satisfies k ′ = 0 for all symbols, and for all symbols. The output of the additional information transmission signal generation means is arranged at a specific carrier position, and the output of the band end pilot signal generation means is arranged for all symbols at the carrier position of the band end carrier, and the distributed pilot signal Generating means, said terminal pilot signal generating means, said band terminal pilot signal generating means, and said additional information transmission The output of the information transmission signal generating means is arranged at any carrier position other than the position where the output of the generating means is arranged, and the distributed pilot signal generating means, the terminal pilot signal generating means, and the band terminal pilot are arranged. The complex vector output by the signal generating means has a specific phase and amplitude uniquely determined by the carrier number k in the entire transmission band at the carrier position where the carrier is arranged by the carrier arranging means. The complex vector output by the transmission signal generation unit is obtained by performing differential modulation between symbols based on the additional information, and the complex vector output by the information transmission signal generation unit is Wherein absolute phase modulation is performed based on the digital information,
The differential detection segment is obtained by performing differential modulation between symbols based on the digital information.

In the above transmitting apparatus, the differential modulation for the complex vector output by the additional information transmission signal generation means is DBPSK modulation, and the absolute phase modulation for the complex vector output by the information transmission signal generation means is: The digital modulation method is any one of QPSK modulation, 16QAM modulation, and 64QAM modulation, and the differential modulation for the complex vector output from the information transmission signal generation means is DQPSK modulation.

Further, a receiving apparatus of the OFDM transmission system according to the present invention is characterized in that it receives and demodulates an OFDM transmission signal transmitted by the transmitting apparatus.

[0031]

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

(First Embodiment) OF of this embodiment
In the DM transmission system, a band end pilot using 13 segments and a carrier of one carrier is used, and one segment is configured by a carrier of 108 carriers. Each segment is composed of either a synchronous detection segment or a differential detection segment. 1 for the whole band
A carrier wave of 405 carriers is used.

FIG. 1 shows an example of the 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). Carrier number k 'in each segment is set to 0
To 107, and one segment is composed of carrier waves of 108 carriers.

The segment for synchronous detection includes a scattered pilot signal using a carrier of 9 carriers per symbol,
An additional information transmission signal using three carrier waves;
And an information transmission signal using a carrier wave of a carrier.

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

As described above, the synchronous detection segment and the differential detection segment use the same number of carriers of 108, so that the required transmission band does not change depending on the combination of the segments.

Here, the carrier number k in the entire band is an integer of 0 to 1404, and the segment number i is 0 to 12
And the carrier number k 'in each segment is from 0 to 1.
07, which satisfies k = i · 108 + k ′.

The dispersed pilot signal provided in the segment for synchronous detection 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, n indicating a symbol number is an integer of 0 or more, and p is an integer of 0 or more and 8 or less.

[0039]

(Equation 5)

The additional information transmission signals provided in the segment for synchronization and the segment for differential detection are arranged on the carrier of carrier number k 'in each segment shown in Table 1, respectively. Table 1 shows 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.

According to 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. As a result, 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.

[0042]

[Table 1]

The terminal pilot signal provided in the differential detection segment 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 the scattered pilot signal in the segment for synchronous detection and the arrangement of the terminal pilot signal in the 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). Carrier number k 'in each segment
Is an integer from 0 to 107, and one segment is 108
It is composed of carrier waves of carriers. The additional information transmission signal is allocated to a carrier different from the scattered pilot signal.

These dispersed pilot signals and terminal pilot signals are respectively assigned carrier numbers k
PN (pseudo-random number) sequence w corresponding to (determined by segment number i and carrier number k 'in each segment)
_{Based on k} (w _k = 0, 1), the carrier wave is obtained by modulating the carrier with the complex vector c _{k, n} shown in Expression (6). (6)
In the equation, 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.

[0046]

(Equation 6)

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, assuming that the control information bit transmitted by the symbol of symbol number n is S _n , the control information signal is obtained by modulating the carrier with the complex vector c _{k, n} shown in the equation (7). That is, in this case, the carrier transmitting the control information signal is a differential binary PSK (Ph
ase Shift Keying) modulated.

[0049]

(Equation 7)

However, the first symbol of the frame (symbol
In the number n = 0), the carrier for transmitting the control information is
PN series w_kAnd the complex vector shown in equation (8)
Le c _{k, n}Modulated by

[0051]

(Equation 8)

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

The information transmission signal provided in the segment for synchronous detection is allocated to a carrier other than the scattered pilot signal and the additional information transmission signal of the segment for synchronous detection, and is subjected to absolute phase modulation based on digital information. For example, QPSK, 16QAM, 64
QAM 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 arranged on a carrier other than the terminal pilot signal of the differential detection segment and the additional information transmission signal.
Differential modulation is performed between adjacent symbols having the same carrier number based on digital information.

The differential modulation includes, 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 of the present embodiment is
In the transmission system, in the receiving device, high-quality reception is performed by the effect of a filter in the segment for synchronous detection, and reception suitable for mobile reception in which the change in transmission path characteristics is fast due to differential demodulation between symbols in the segment for differential detection. It can be performed. In addition, by arbitrarily combining the segment for synchronous detection and the segment for differential detection for each segment,
A flexible service form can be realized without a change in the transmission band.

(Second Embodiment) OF of this embodiment
In the DM transmission system, a band end pilot using 13 segments and a carrier of one carrier is used, and one segment is configured by a carrier of 108 carriers. Each segment is composed of either a synchronous detection segment or a differential detection segment. 1 for the whole band
A carrier wave of 405 carriers is used.

A segment for synchronous detection includes a scattered pilot signal using a carrier of 9 carriers per symbol,
A continuous pilot signal using two carrier carriers;
It comprises an additional information transmission signal using a carrier wave of a carrier (hereinafter, referred to as a control information signal in this embodiment) and an information transmission signal using a 96 carrier wave.

The differential detection segment includes 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 using the same.

Here, the carrier number k in the entire band is an integer of 0 to 1404, and the segment number i is 0 to 12
And the carrier number k 'in each segment is from 0 to 1.
07, which satisfies k = i · 108 + k ′.

The scattered pilot signal provided in the segment for synchronous detection 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.

[0063]

(Equation 9)

The continuous pilot signals provided in the segment for synchronization and the segment for differential detection are arranged on the carrier with 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.

[0065]

[Table 2]

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

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

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. 3 shows an example of the arrangement of the continuous pilot signal and the control information signal, the arrangement of the dispersed pilot signal in the segment for synchronous detection, and the arrangement of the terminal pilot signal in the 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). Carrier number k 'in each segment is set to 0
To 107, and one segment is composed of carrier waves of 108 carriers. The continuous pilot signal and the control information signal are allocated to a different carrier from the dispersed pilot signal.

These dispersed pilot signals, continuous pyro
Signal and termination pilot signal
Carrier number k (segment number i and each segment
Corresponding to the carrier number k 'in the client)
N (pseudo random number) series w_k(W _k= 0,1),
Complex vector c shown in equation (6)_{k, n}Changes the carrier
Can be obtained. In the equation (6), Re ｛c_{k, n}｝
Multiplexers corresponding to the carrier with carrier number k and symbol number n
Elementary vector c_{k, n}Im ｛c_{k, n}｝
Represents the imaginary part.

[0071]

(Equation 10)

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

[0073]

[Table 3]

Assuming that the control information bit transmitted by the symbol of symbol number n is 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.

[0075]

[Equation 11]

However, the first symbol of the frame (symbol
In the number n = 0), the carrier for transmitting the control information is
PN series w_kAnd the complex vector shown in equation (8)
Le c _{k, n}Modulated by

[0077]

(Equation 12)

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

The information transmission signal provided in the segment for synchronous detection is allocated to a carrier other than the scattered pilot signal, the continuous pilot signal, and the control information signal of the segment for synchronous detection, and is subjected to absolute phase modulation based on digital information. Is applied. This absolute phase modulation includes, for example, QP
SK, 16QAM, 64QAM modulation and the like are 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 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 the same based on digital information. Differential modulation is performed between adjacent symbols of the carrier number.

The differential modulation includes, 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 of the present embodiment
In the transmission system, in the receiving device, high-quality reception is performed by the effect of a filter in the segment for synchronous detection, and reception suitable for mobile reception in which the change in transmission path characteristics is fast due to differential demodulation between symbols in the segment for differential detection. It can be performed. In addition, by arbitrarily combining the segment for synchronous detection and the segment for differential detection for each segment,
A flexible service form can be realized.

Further, by arranging a continuous pilot signal for modulating 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 that the reference is used on the receiving side. Can be used as a carrier.

FIGS. 4 and 5 show the synchronous detection segments (13 segments, 26 carriers) shown in Table 2, respectively.
3 shows an inverse Fourier transform pair of the frequency arrangement of a continuous pilot signal of a differential detection segment (13 segments, 78 carriers). 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.

Thus, the OFDM transmission method according to the present embodiment can prevent the entire continuous pilot signal from disappearing due to a delay wave 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 control information signals of the synchronous detection segment and the differential detection segment shown in Table 3, respectively. From FIGS. 6 and 7, they are impulse-like,
It can be seen that the frequency arrangement of the control information signal shown in Table 3 has no periodicity.

From the above, the OFDM of the present embodiment
The transmission method can prevent the entire control information signal from disappearing due to a delay wave such as a multipath.

The frequency arrangement of the additional information transmission signal including the control information signal can be set similarly.

(Third Embodiment) FIG. 8 shows an OFDM transmission system based on the OFDM transmission systems of the first and second embodiments.
1 shows a configuration of an embodiment of a transmission device that generates a signal.

In FIG. 8, information transmission signal generation circuit 51
In the above, error control processing (error correction coding, interleaving, energy spreading, etc.) and digital modulation are performed 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. For 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. As digital modulation, M (M is a natural number of 2 or more) phase PSK (Phase Shift Keying) modulation, differential M-phase PSK modulation in the symbol direction, or the like is used.

The control information generation circuit 56 generates transmission mode information (various information defining transmission modes 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 by the additional information signal generation circuit 52, but may be subjected to error control processing and digital modulation different from other additional information.

Distributed pilot signal generation circuit 53 has carrier number k whose arrangement is defined by carrier arrangement circuit 57.
PN (pseudo-random number) sequence w corresponding to (determined by segment number i and carrier number k 'in each segment)
Generate a scattered pilot signal modulated based on _k (w _k = 0, 1).

Terminating pilot signal generating circuit 54 has carrier number k whose arrangement is defined by carrier arranging circuit 57.
PN (pseudo-random number) sequence w corresponding to (determined by segment number i and carrier number k 'in each segment)
Generate a terminal pilot signal modulated based on _k (w _k = 0, 1).

The band end pilot signal generation circuit 55
PN (pseudo random number) corresponding to the carrier number k at the end of the band
A band-end pilot signal modulated based on the sequence w _k (w _k = 0, 1) is generated.

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

The carrier arrangement circuit 57 includes an information transmission signal generation circuit 51, an additional information signal generation circuit 52, a distributed pilot signal generation circuit 53, and a terminal pilot signal generation circuit 5.
4. Each output (complex vector sequence) of the band end pilot signal generation circuit 55 is arranged at a carrier position in the frequency domain defined according to the transmission mode.

For example, the distributed pilot signal generation circuit 53
Is N (N is 2) in the synchronous detection segment.
L (L) at carrier intervals and for each symbol
Is a divisor of N). The output of the termination pilot signal generation circuit 54 is arranged on the carrier having the carrier number k '= 0 in the segment for differential detection. The output of the additional information signal generation circuit 52 is allocated according to, for example, the frequency arrangement shown in Table 1. 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 transforms 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 into an intermediate frequency band. Frequency conversion circuit 60
Converts a frequency band of an orthogonally modulated OFDM signal from an intermediate frequency band to a radio frequency band, and supplies it to an antenna or the like.

According to the transmitting apparatus having the above configuration, the first
And an OFDM signal based on the OFDM transmission method described in the second embodiment.

(Fourth Embodiment) FIG. 9 shows an OFDM signal formed on the basis of the OFDM transmission systems of the first and second embodiments, and an impulse response in the time domain of the transmission path. 3 shows a configuration of a receiving device that can be estimated.

In FIG. 9, 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 transforms 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 _{ck, n} corresponding to the scattered pilot signal, the ending pilot signal, and the band ending pilot signal extracted by the scattered / terminal 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, and Estimate the transmission path characteristics of the terminal pilot signal and band terminal pilot signal. The interpolation circuit 16
The transmission path characteristics of the carrier of the information transmission signal of the synchronous detection segment are estimated by interpolating the transmission path characteristics of the distributed pilot signal, the terminal pilot signal, and the band terminal pilot signal obtained by the division circuit 15.

The delay circuit 17 delays the vector sequence output from the Fourier transform circuit 12 by one symbol. Selection circuit 1
Reference numeral 8 denotes an interpolation circuit 1 in the case of a segment for synchronous detection according to the type of segment separately transmitted by control information.
6 is a delay circuit 1 in the case of a differential detection segment.
7 is selected and output.

The dividing circuit 19 divides the vector sequence output from the Fourier transform circuit 12 by the output of the selecting circuit 18. In the division circuit 19, in the synchronous detection segment, the signal is divided by the transmission path characteristic of the corresponding carrier estimated by the interpolation circuit 16 to perform synchronous detection, and in the differential detection segment, one symbol before the symbol output by the delay circuit 17 is output. Differential detection is performed by dividing by the vector sequence of the corresponding carrier.

The demodulation circuit 20 modulates the information transmission signal (QPSK, 16QAM, 64QAM, DQ).
The detection signal output from the division circuit 19 is demodulated according to BPSK, DQPSK, DAPSK, etc., and the transmitted digital information is obtained.

With the above configuration, it is possible to receive and demodulate an OFDM signal based on the OFDM transmission method described in the first embodiment. The configuration described below is for receiving and demodulating an OFDM signal based on the OFDM transmission scheme described in the second embodiment.

First, the continuous pilot extracting 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 modulation complex vector _{ck, n} corresponding to the continuous pilot signal extracted by the continuous pilot extraction circuit 21. Division circuit 23
Estimates the transmission path characteristics of the continuous pilot signal by dividing the continuous pilot signal extracted by the continuous pilot extraction circuit 21 by the complex vector generated by the vector generation circuit 22. The inverse Fourier transform circuit 24 includes a dividing circuit 23
Is converted from the frequency domain to the time domain for the continuous pilot signal estimated in step (1) to obtain an impulse response characteristic of the transmission path.

As described 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 segment for synchronous detection by the filter effect by the interpolation processing of the transmission path characteristics. On the other hand, in the differential detection segment, demodulation suitable for mobile reception in which the transmission path characteristics change rapidly can be realized 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.

[0114]

As described above, the orthogonal frequency division multiplex 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, it is possible to freely combine the synchronous detection segment and the differential detection segment for each segment without impairing the synchronous detection characteristics of adjacent synchronous detection segments. Can be
As a result, a flexible service form can be realized.

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

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, for example, estimation based on a continuous pilot signal is performed. It is possible to provide an OFDM transmission system in which continuous pilot signals are arranged so as not to cause aliasing in an impulse response of a transmission path to be performed, and a transmission device and a reception device suitable for the present system.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the arrangement 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.

FIG. 2 shows an arrangement of an additional information transmission signal, an arrangement of a dispersed pilot signal in a synchronous detection segment, and a termination in a differential detection segment 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 the arrangement of a continuous pilot signal and a control information signal, the arrangement of a dispersed pilot signal in a synchronous detection segment, and the termination in a differential detection segment 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 differential detection segment shown in Table 3 in the second embodiment of the OFDM transmission system according to the present invention. .

FIG. 8 shows an OFD according to a fifth embodiment of the present invention.
FIG. 3 is a block circuit diagram illustrating a configuration of a transmission device used for the M transmission scheme.

FIG. 9 shows an OFD according to a sixth embodiment of the present invention.
FIG. 3 is a block circuit diagram illustrating a configuration of a receiving device used for the M transmission scheme.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Tuner 12 ... Fourier transform circuit 13 ... Dispersion / termination pilot extraction circuit 14 ... Vector generation circuit 15 ... Division circuit 16 ... Interpolation circuit 17 ... Delay circuit 18 ... Selection circuit 19 ... Division circuit 20 ... Demodulation circuit 21 ... Continuous pilot extraction Circuit 22 ... Vector generation circuit 23 ... Division circuit 24 ... Inverse Fourier transform circuit 51 ... Information transmission signal generation circuit 52 ... Additional information signal generation circuit 53 ... Distributed pilot signal generation circuit 54 ... Terminal pilot signal generation circuit 55 ... Band end pilot signal Generation circuit 56 ... Control information generation circuit 57 ... Carrier arrangement circuit 58 ... Inverse Fourier transform circuit 59 ... Quadrature modulation circuit 60 ... Frequency conversion circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomohiro Kimura 30-1-708 Minamikibogaoka, Kawachinagano-shi, Osaka (72) Inventor Kenichiro Hayashi 8-38, Hagihata, Kyotanabe-shi, Kyoto (72) Inventor Akira Kisoda 1-11-5-202 Kaji-cho, Moriguchi-shi, Osaka (72) Inventor Shigeru Shiga 3-4-3-1-101, Ichitsuya, Matsubara-shi, Osaka (72) Inventor Sadaji Kageyama 5-, Akashidaidai, Mita-shi, Hyogo 29-C-302 (72) Inventor Masanori Saito 1-17-4 Sakuragaoka, Setagaya-ku, Tokyo (72) Inventor Tatsuya Ishikawa 8-3-1, Hino, Konan-ku, Yokohama, Kanagawa Prefecture Konandai Sanwa Plaza 802 ( 72) Inventor Hitoshi Mori 4-17-24 Motoyamakita-cho, Higashinada-ku, Kobe, Hyogo (72) Inventor Masayuki Takada 1-1-10 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute of Broadcasting Technology (72) Inventor Toru Kuroda, Kinuta, Setagaya-ku, Tokyo Street No. 10, No. 11, Japan Broadcasting Association broadcasting technology within the Institute (72) inventor Makoto Sasaki Setagaya-ku, Tokyo Kinuta chome No. 10, No. 11, Japan Broadcasting Association broadcasting technology within the Institute

Claims (5)

[Claims] 1. K (K
In the orthogonal frequency division multiplexing transmission system for transmitting digital information, the carrier numbers of the K carriers in the entire transmission band are k (k is 0 ≦ k) ≦ K−1), and among the K carriers, a carrier whose carrier number k in the entire transmission band satisfies k = K−1 is defined as a band-terminating 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, and each of the I segments is K ′ ( K ′ is composed of K ′ = (K−1) / I) integer carriers, the symbol number is n (n is an integer), and the segment number is 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, a scattered pilot signal is placed at a carrier position where the carrier number k ′ in the segment satisfies k ′ = 3 (n mod 4) +12 p (mod represents a remainder operation, p is an integer), and a specific An additional information transmission signal is arranged at a carrier position. In the differential detection segment, a terminating pilot signal is placed at a carrier position where the carrier number k ′ in the segment satisfies k ′ = 0, and The additional information transmission signal is arranged at a specific carrier position with respect to the Disposing a termination pilot signal, disposing an information transmission signal at any one of the carrier positions other than the position where the dispersion pilot signal, the termination pilot signal, the band termination pilot signal, and the additional information transmission signal are disposed. The scattered pilot signal, the terminal pilot signal, and the band terminal pilot signal, the carrier in which each is arranged, with a specific amplitude and phase uniquely determined by the carrier number k in the entire transmission band of the carrier. The additional information transmission signal is a signal obtained by differentially modulating a specific carrier between symbols based on additional information, and the information transmission signal arranged in the synchronous detection segment is Is a carrier on which absolute phase modulation is performed based on the digital information, The orthogonal frequency division multiplexing transmission system, wherein the information transmission signals arranged in the detection segment are obtained by differentially modulating the respective carriers arranged between symbols based on the digital information. 2. The differential modulation for the additional information transmission signal is DBPSK modulation, and the absolute phase modulation for the information transmission signal is QPSK modulation, 16QAM modulation,
2. The orthogonal frequency division multiplex transmission system according to claim 1, wherein the digital modulation system is any one of QAM modulation, and the differential modulation for the information transmission signal is DQPSK modulation. 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,
Terminating pilot signal generating means for outputting a complex vector for generating the terminating pilot signal; band terminating pilot signal generating means for outputting a complex vector for generating the band terminating pilot signal; and Additional information transmission signal generating means for outputting a complex vector for generating, the information transmission signal generating means, the distributed pilot signal generating means, the terminal pilot signal generating means, the band terminal pilot signal generating means, and the additional information Carrier arranging means for arranging each output of the transmission signal generating means at a predetermined carrier position; and orthogonal Fourier-division multiplexed transmission signal Inverse Fourier transform means for generating Positioning means for the synchronous detection segment, the symbol number n
, 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),
The output of the scattered pilot signal generation means and the output of the additional information transmission signal generation means are arranged at a specific carrier position for all symbols. 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 'of k' satisfies k '= 0, and the output of the additional information transmission signal generation means is arranged at a specific carrier position for all symbols, In 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 pilot signal generation means, the band end pilot signal generation means,
And arranging the output of the information transmission signal generation means at any carrier position other than the position where the output of the additional information transmission signal generation means is arranged, the scattered pilot signal generation means, the terminal pilot signal generation means , And the complex vector output by the band end pilot signal generation unit has a specific phase and amplitude uniquely determined by the carrier number k in the entire transmission band at the carrier position where each is arranged by the carrier arrangement unit. Wherein the complex vector output by the additional information transmission signal generating means is obtained by performing differential modulation between symbols based on the additional information, and the complex vector output by the information transmission signal generating means is: The synchronous detection segment has been subjected to absolute phase modulation based on the digital information. For use segments, transmission apparatus of an orthogonal frequency division multiplexing transmission system, characterized in that on the basis of the digital information were subjected to differential modulation between symbols. 4. The differential modulation of the complex vector output by the additional information transmission signal generation means is DBPSK modulation, and the absolute phase modulation of the complex vector output by the information transmission signal generation means is QPSK modulation, 16QAM
4. The orthogonal frequency division multiplexing transmission according to claim 3, wherein the modulation is a digital modulation method of any one of 64QAM modulation and the differential modulation of the complex vector output from the information transmission signal generating means is DQPSK modulation. System transmission device. 5. A receiving apparatus for receiving and demodulating an orthogonal frequency division multiplex transmission signal transmitted by the transmitting apparatus according to claim 3.