JP2002009724A - Method for arranging carriers in orthogonal frequency division multiplexing transmission system, transmitter, and receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission frame that can follow a change in the response of a transmission line even in the case of high-speed movement. SOLUTION: Q-sets each of pilot carriers used for demodulation reference are arranged at a prescribed interval from the end carrier and arranged consecutively in the time direction on the condition that the number of carriers K is a number that is a multiple of Q+1, where K is number of carriers to be transmitted, Te is an effective symbol length of a transmission symbol, Tg is a guard interval length, R (R=Tg/Te) is the ratio of the guard interval length to the effective symbol length (hereinafter called the guard interval ratio), M is the maximum integer being a reciprocal (1/R) of the guard interval ratio or below (that is, M= (1/R), where and are Gauss' symbols), and Q is an optional integer being M or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal transmission system, and more particularly to an orthogonal frequency division multiplex transmission system (O / O).
FDM (Orthogonal Frequency Division Multiplexing)
The present invention relates to a method of arranging carriers in a transmission system, and a transmitting device and a receiving device.

[Summary of the Invention] [0002] The present invention relates to a transmission frame structure in a case where a synchronous modulation system such as QPSK, 16QAM, 64QAM is used for a modulation system of each carrier in an orthogonal frequency division multiplex transmission system (OFDM transmission system). By using a transmission format in which pilot carriers serving as demodulation references are arranged at regular intervals in the frequency direction and continuously in the time direction, demodulation can be performed in units of one symbol. This improves the response to a change in response, and improves the resistance to Rayleigh fading, which is a problem during mobile reception.

[0003]

2. Description of the Related Art Currently, ISDB-T (Integrated Services Digital Broadcasting) is used as a terrestrial digital broadcasting transmission system.
An OFDM transmission method called “casting-terrestrial” has been standardized and is under study for practical use. This transmission scheme has attracted attention as a scheme that has excellent resistance to multipaths and ghosts and can also perform mobile reception.

[0004] The OFDM transmission system, as shown in FIG.
Many carriers orthogonal to each other in the frequency direction
Is a transmission method that modulates data by using DQPSK, QPSK, 16QAM,
64QAM or the like is used.

[0005] In the time direction, transmission is performed in units of a transmission symbol composed of an effective symbol and a guard interval shown in FIG. The effective symbol is a period during which data is actually transmitted, and the guard interval is a period for reducing the influence of multipath. The guard interval is obtained by cyclically repeating a part of the signal waveform of the effective symbol.

In the OFDM transmission system, one transmission frame is formed by collecting several tens to several hundred transmission symbols shown in FIG. FIG. 8 shows a configuration example of a transmission frame used in the ISDB-T system. This transmission frame is
QPSK, 16QAM, 64Q for modulation method of each carrier
This is applied when a synchronous modulation method such as AM is used, and is composed of a pilot carrier and a data carrier that are used as references in demodulation. The transmission frame used in the actual ISDB-T system includes transmission and multiplexing configuration (TMCC) of transmission control information.
Auxiliary C (ion Control) carrier and additional information
(hannel) carrier is inserted, but is not shown in FIG. 8 because it has nothing to do with demodulation processing. DVB-T (Digital Video Br), a European terrestrial digital broadcasting standard
Also in the oadcasting-terrestrial scheme, the arrangement of pilot carriers and data carriers is the same as in FIG.

The transmission frame shown in FIG. 8 is expressed in two dimensions in the frequency direction and the time direction. Carriers are arranged in the frequency direction, and carrier numbers are described as 0, 1, 2,..., K-1. Transmission symbols are arranged in the time direction, and transmission symbol numbers are described as 0, 1, 2,..., L-1. Therefore, this transmission frame is composed of K carriers and L transmission symbols.

Here, assuming that the index representing the transmission symbol number is l and p is a non-negative integer, the index k of the position where the pilot carrier is transmitted (the position of ● in FIG. 8)
Is determined by equation (1).

[0009]

K = 3 × (l mod 4) + 12p (1)

Accordingly, the arrangement of pilot carriers has a structure in which the carrier is shifted to the right by three carriers for every 12 carriers in the frequency direction and for each symbol. Since the pilot carriers are distributed in the frequency direction and the time direction in this way, the pilot carriers are called SP (Scattered Pilot).

FIG. 9 is a block diagram showing a configuration of a receiving apparatus used in a conventional orthogonal frequency division multiplexing transmission system. Next, the procedure of the demodulation process will be described with reference to FIG. From the signal output from the FFT, the data extraction unit 51 extracts a data signal Dr. On the other hand, pilot extraction section 52 extracts pilot signal Pr. The pilot signal Pr is a signal whose amplitude and phase are known, and the first complex division circuit 5
By dividing by the original pilot signal transmitted in (3) (that is, the output Pt of the known pilot generator 54), the transmission path response at the pilot carrier position is obtained. Thereafter, the symbol interpolation circuit 55 and the carrier interpolation circuit 56
The interpolation is performed by the two-dimensional filter composed of the above, and the transmission path responses at all the data positions (the positions in FIG. 8) are obtained.

The signal processing of the two-dimensional filter will be described in more detail. Here, it is assumed that the transmission path response changes slowly with time. This assumption is an appropriate condition when fixed reception is performed or when mobile reception is performed at a low speed at a frequency lower than the UHF band. The following method can be considered as the two-dimensional interpolation processing in this case.

First, a signal which is separated by four symbols in the time direction by the symbol interpolation circuit 55 is interpolated. As the interpolation means, a zero-order interpolation (a method of holding and interpolating in the time direction) that requires a small circuit scale is often used. Even when the zero-order interpolation is used, if the time change of the transmission path response is gradual, the distortion due to the interpolation is small, so that the deterioration hardly occurs. FIG. 10 shows the carrier arrangement after symbol interpolation. The pilot carrier signals are arranged every 12 carriers before symbol interpolation, but are arranged every 3 symbols by interpolation processing.

Next, the transmission line response at the data position (the position shown in FIG. 10) is obtained by the carrier interpolation circuit 56. For this interpolation, a low-pass filter (LPF) composed of an FIR filter is often used. For the interpolation processing, hold (an interpolation method in which the transmission path response at the data carrier position is replaced by the transmission path response at the adjacent pilot carrier position) and linear interpolation are also conceivable, but LPF is used when a ghost is added. This is because signal degradation is small. By this processing, the transmission path responses Hx of all the carrier positions are obtained.

Finally, the demodulated data Dt is obtained by dividing the data signal Dr received by the second complex division circuit 57 by the transmission path response Hx at that position.

Here, the relationship between the arrangement of pilot carriers and the guard interval ratio will be considered. If the cutoff frequency of the LPF of the carrier interpolation circuit 56 is assumed to be an ideal filter characteristic and the cutoff frequency is set to the Nyquist frequency, the arrangement of pilot carrier signals before carrier interpolation is every three symbols. , The effective symbol length
If Te is used, it is possible to interpolate the channel response to ghost delay waves up to Te / 3. However, in the OFDM transmission method, if the ghost delay time exceeds the guard interval length Tg, intersymbol interference occurs and the characteristics are rapidly deteriorated. Therefore, it is necessary to set the guard interval length Tg to Te / 3 in order to cope with ghost delay waves up to Te / 3. The guard interval ratio R (R = Tg / Te) at this time is
It becomes 1/3.

In the method of distributing pilot carriers in the frequency direction and the time direction, the insertion interval of the pilot carriers can be apparently reduced by performing symbol interpolation, and even for a ghost having a large delay time. It has the feature that it can respond. However, since demodulation is performed on the assumption that the response of the transmission path changes slowly with time, good performance cannot be expected for mobile reception.

[0018]

In a transmission frame using a conventional orthogonal frequency division multiplexing transmission system,
A pilot carrier serving as a demodulation reference is arranged every four symbols in the time direction. For this reason,
A prerequisite is that the transmission path response does not change between four symbols or the degree of change is gradual. Therefore, there is a problem that the receiving mode is limited to fixed reception or low-speed mobile reception.

As a method for following a change in the response of the transmission path, a method using linear interpolation for symbol interpolation is conceivable. However, this method requires a memory circuit for holding received data for an interpolation period, and requires a circuit. There is a disadvantage that the scale becomes large. Further, when the degree of change is large, there is a problem that interpolation is incomplete and distortion occurs.

The present invention has been made in view of the above circumstances, and has as its object to provide a transmission frame capable of following a change in a transmission line response even when moving at high speed, and furthermore, the size of an interpolation circuit of a receiving apparatus. It is an object of the present invention to provide a carrier allocating method capable of realizing an orthogonal frequency division multiplexing transmission system requiring only a small amount of data, and a transmitting device and a receiving device.

[0021]

According to a first aspect of the present invention, there is provided a mobile communication system comprising a plurality of carriers orthogonal to each other, the carrier comprising a pilot carrier and a data carrier serving as a demodulation reference. In the orthogonal frequency division multiplexing transmission system that performs data transmission with a carrier structure, the number of carriers to be transmitted is K, the effective symbol length of the transmission symbol is Te, the guard interval length is Tg, and the guard interval length and the effective symbol length are The ratio (hereinafter referred to as the guard interval ratio) is R (where R = Tg / Te), and the maximum integer less than the reciprocal (1 / R) of the guard interval ratio is M

[Outside 2] Assuming that an arbitrary integer equal to or less than M is Q, a pilot carrier serving as a reference at the time of demodulation is fixed from an end carrier every Q lines on condition that the value of the number of carriers K is (multiple of Q + 1). It is characterized by being arranged at intervals and continuously arranged in the time direction.

According to a second aspect of the present invention, when the carrier number of the carrier number K is 0, 1, 2,..., K-1, a pilot is assigned to the center carrier (ie, carrier number K / 2) of all the carriers. It is characterized in that no carrier is arranged.

According to a third aspect of the present invention, when the carrier number of the number of carriers K is 0, 1, 2,..., K-1, the center carrier of all carriers (ie, carrier number K / 2) is vacant. (A carrier that does not transmit any information).

According to a fourth aspect of the present invention, there is provided an orthogonal frequency for performing data transmission using a plurality of carriers orthogonal to each other and having a carrier structure in which the carrier comprises a pilot carrier serving as a demodulation reference and a data carrier. In a transmission device used for the division multiplexing transmission method, a storage means for storing the arrangement of a data carrier, a pilot carrier, a TMCC carrier, and an AC carrier in advance as a frame configuration pattern, and data, a pilot signal, A control signal generating means for generating a control signal for switching an input signal such as a TMCC signal or an AC signal; and switching the input signal in accordance with the control signal to determine a data, a pilot signal, a TMCC signal, and an AC signal in advance. Insert the frame at the carrier position to compose the transmission frame. It is characterized by comprising a transmission frame configuration means for.

According to a fifth aspect of the present invention, an orthogonal frequency for performing data transmission using a plurality of carriers orthogonal to each other and having a carrier structure in which the carrier comprises a pilot carrier serving as a demodulation reference and a data carrier. In a receiving apparatus used for the division multiplexing transmission system, a transmission channel response of a pilot carrier position is obtained by dividing a received pilot carrier signal by a known pilot carrier signal as a processing unit when demodulating one transmission symbol. Channel response estimating means for obtaining, and channel response interpolating means for obtaining responses for all carrier positions by interpolating the channel response for each Q lines obtained by the channel response estimating means; and Demodulation means for dividing the carrier signal by the transmission path response at the position and demodulating the carrier signal. It is characterized by being completed in a symbol.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is based on the reason that the pilot carrier serving as a demodulation reference in the conventional transmission frame is intermittently transmitted (every four symbols) in the time direction and cannot follow the change of the transmission line response. In view of the above, the pilot carriers are arranged continuously in the time direction so as to follow the change of the transmission line response.

Hereinafter, embodiments of an orthogonal frequency division multiplexing transmission system, a transmitting apparatus, and a receiving apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 shows an example of the configuration of a transmission frame to which the method of arranging carriers in the orthogonal frequency division multiplexing transmission system of the present invention is applied. This transmission frame is
QPSK, 16QAM, 64Q for modulation method of each carrier
This is applied when a synchronous modulation method such as AM is used, and is composed of a pilot carrier and a data carrier that are used as references in demodulation. In the transmission frame shown in FIG. 1, the TMC of the transmission control information not related to the demodulation process is used.
C (Transmission and Multiplexing Configuration Co
ntrol) Carrier and additional information AC (Auxiliary Channe)
l) Carriers are omitted.

The transmission frame shown in FIG. 1 is expressed in two dimensions in the frequency direction and the time direction. Carriers are arranged in the frequency direction, and carrier numbers are described as 0, 1, 2,..., K-1. Transmission symbols are arranged in the time direction, and transmission symbol numbers are described as 0, 1, 2,..., L-1. Therefore, this transmission frame is composed of K carriers and L transmission symbols.

The effective symbol length of the transmission symbol is Te, the guard interval length is Tg, and the ratio between the guard interval length and the effective symbol length (hereinafter referred to as the guard interval ratio).
Let R (where R = Tg / Te). Furthermore, the maximum integer less than the reciprocal (1 / R) of the guard interval ratio is M

[Outside 3] Let Q be any integer less than or equal to M.

If the value of the number of carriers K is (multiple of Q + 1), it is possible to arrange pilot carriers serving as a reference at the time of demodulation from the carriers at both ends at regular intervals every Q lines. Here, assuming that p is a non-negative integer, the index k of the position where the pilot carrier is transmitted (the position of ● in FIG. 1) is determined by equation (2).

[0032]

(2) k = Q × p (2) In FIG. 1, the value of Q is plotted as 8.
Therefore, pilot carriers are arranged every eight lines from the leftmost carrier (carrier number 0). Further, since the number of carriers K is (multiple of 8 + 1), the carrier number K-1 at the right end is a multiple of 8. Therefore, the pilot carrier is also arranged on the rightmost carrier.
As described above, by setting the value of the number of carriers K to (multiple of Q + 1), the pilot carriers are arranged at both ends of the carrier and every other Q carriers between them.

Here, the relationship between the pilot carrier interval and the guard interval ratio will be described. As an example, a case where the guard interval ratio R is 1/8 will be described.
Since the maximum integer less than the reciprocal (1 / R) of the guard interval ratio is M,

[Outside 4] Therefore, the interval between the arrangements of the pilot carriers is eight at the maximum. In the present invention, an arbitrary integer Q equal to or less than M can be introduced, and Q can be used as an interval between pilot carriers. Therefore, the interval between the pilot carriers can be set to an arbitrary integer of 8 or less. However, if the value of Q is too small, the ratio of pilot carriers to all carriers increases, so that transmission efficiency decreases.

The validity of inserting pilot carriers every eight carriers when the guard interval ratio is 1/8 will be described below. In the OFDM transmission method, the ghost delay time is the guard interval length Tg (here,
If Tg = Te / 8), intersymbol interference occurs and the characteristics are rapidly deteriorated. Therefore, the pilot carriers may be arranged so that the transmission line response to the ghost delay wave up to Te / 8 can be interpolated.

By the way, there is a fixed relationship between the change of the transmission path response when a ghost is input and the ghost delay time.
If the ghost delay time is τ, the period of the change of the channel response
F is 1 / τ, its reciprocal. Therefore, when a ghost delay wave of Te / 8 enters, the cycle becomes minimum, and its value Fmin
Is 8 * (1 / Te). Here, since (1 / Te) is the reciprocal of the effective symbol length, it represents the carrier interval of the OFDM signal. Therefore, the minimum period Fmin of the transmission path response is an interval of 8 carriers. In order to accurately obtain this transmission path response by interpolation, one pilot carrier may be inserted at a rate of one cycle Fmin. That is, it is sufficient to insert pilot carriers every eight carriers. Here, since the signal is handled as a complex number, it should be noted that, unlike the sampling theorem that handles a normal real number, the number of sampling points can be reduced to half. Also, it is clear that the sampling theorem is satisfied even when the pilot carrier insertion interval is an arbitrary integer of 8 or less.

The above discussion is extended to general expressions. Assuming that the guard interval ratio is R, pilot carriers may be inserted every (1 / R), which is the reciprocal thereof. However, (1 / R) may not be an integer depending on the values of the effective symbol length Te and the guard interval length Tg. Therefore, in the present invention, the value of the insertion interval M is a maximum integer equal to or less than (1 / R).

[Outside 5] Also, if Q is an arbitrary integer less than or equal to M, it is clear that the sampling theorem is satisfied even when Q is the insertion interval of pilot carriers. However, as described above, if the value of Q is too small, the transmission efficiency is reduced. Therefore, the value of Q should be as large as possible.

Next, it will be shown that the mobile reception characteristics are improved by using the transmission frame of the present invention. As shown in FIG. 8, in a conventional transmission frame, pilot carriers serving as demodulation references are transmitted intermittently (every four symbols) in the time direction. It is considered that if this interval is reduced, the followability to a change in the transmission path response is improved. In the present invention, this interval is minimized. Therefore, as shown in FIG. 1, a pilot carrier is inserted every symbol in the time direction, and a certain carrier is occupied continuously in time.

FIG. 2 schematically shows the relationship between the change in the transmission path response and the arrangement of the pilot carriers when the pilot carriers are viewed in the time direction. (A) shows the conventional system, and (b) shows the system of the present invention. In the method of the present invention, the pilot carrier is inserted four times as frequently, so that the followability to the change of the transmission path response is four times that of the conventional method. That is,
Since the sampling rate is quadrupled, it is possible to handle up to quadrupled frequency.

Here, a comparison will be made with a differential modulation method such as DQPSK conventionally used for mobile transmission. The differential modulation system is a system in which data is transmitted by a relative change in the phase of two symbols before and after. However, since the demodulation circuit scale is small and the mobile reception characteristics are good, the DAB (Digital) in Europe is used.
Audio Broadcasting) system and a part of the ISDB-T system. Although the demodulation processing of the synchronous modulation method will be described later, in the present invention, since a pilot carrier is inserted for each symbol in the time direction, demodulation can be performed in units of one symbol. For this reason, the followability with respect to the change of the transmission path response is doubled as compared with the differential modulation scheme in which demodulation is performed with two symbols. Therefore, the system of the present invention exhibits better mobile reception characteristics than the differential modulation system.

In the above description, the TMCC carrier of the transmission control information and the AC carrier of the additional information, which are not related to the demodulation processing, are not mentioned, but a transmission frame in which these carriers are inserted is shown in FIG. . In FIG. 3, positions where TMCC carriers and AC carriers are transmitted are indicated by squares. These carriers are inserted at the data carrier positions in FIG. This is because if inserted at the pilot carrier position, data cannot be demodulated. TMCC carrier and AC carrier
Although it is possible to arrange at any position if the pilot carrier position is avoided, it is better to arrange as randomly as possible so as not to coincide with the periodic drop in frequency characteristics when a ghost is added. The modulation method of the TMCC carrier or the AC carrier is QPSK, 16QA
In addition to synchronous modulation methods such as M and 64QAM, differential modulation methods such as DBPSK and DQPSK can also be used. Of course, when the differential modulation method is used, the mobile transmission characteristics deteriorate, but the demodulation processing becomes easy.

By the way, when a baseband OFDM signal is up-converted to an intermediate frequency or a radio frequency, or conversely, when a down-conversion is performed, a local oscillation signal is generated.
It may be mixed into the center of the signal band (ie, the center carrier). Further, a DC offset generated in the amplifier circuit or the A / D converter also becomes a noise component mixed into the center carrier. These noise components mixed into the center carrier may cause stricter shields used in high-frequency circuits,
By strictly managing the offset, the value can be reduced. However, it is desirable that the pilot carrier serving as a reference for demodulation has as little noise component as possible, and the bit error rate characteristic (BER characteristic) is better when the pilot carrier is not assigned to the center carrier.

Assuming that the number of carriers to be transmitted is K and the carrier numbers are 0, 1, 2,..., K-1, no pilot carrier is arranged in the center carrier of all carriers (that is, carrier number K / 2). Therefore, if the insertion interval of pilot carriers is Q, it is a condition that K / 2 is not divisible by Q. Therefore, when designing an OFDM transmission frame, the number of carriers K, the insertion interval Q of pilot carriers,
Is adjusted to satisfy the above conditions.

Further, a method of not allocating the center carrier to data can be considered. In this case, the transmission efficiency for one carrier decreases, but the BER characteristics can be further improved. Also, if the TMCC carrier and the AC carrier are also arranged so as to avoid the center carrier, the BER characteristics of these signals are improved. As described above, the BER characteristic can be further improved by setting the center carrier of all the carriers (that is, the carrier number K / 2) as an empty carrier (a carrier that does not transmit any information). Further, the performance required for the high-frequency circuit, the amplifier circuit, the A / D converter, and the like of the receiver can be reduced, and the circuit design of the receiver becomes easy.

FIG. 4 shows a configuration example of a transmission frame configuration used in the transmission device. The transmission frame configuration 4 includes a frame configuration pattern memory 1, a switch control unit 2, and a switch 3. The arrangement of the data carrier, the pilot carrier, the TMCC carrier, and the AC carrier is stored and stored in the frame configuration pattern memory 1 in advance. The switch control unit 2 performs data, pilot signal, TMC
This circuit generates a control signal for switching input signals such as a C signal and an AC signal. According to this control signal,
If the input signal is switched by the switch 3 to derive the signal,
Data, pilot signals, TMCC signals, and AC signals can be inserted at predetermined carrier positions, and a desired transmission frame can be configured.

Next, the procedure of the demodulation process will be described with reference to FIG. The receiving device includes a data extraction unit 11, a pilot extraction unit 12, a first complex division circuit 13, a known pilot generation unit 14, a carrier interpolation circuit 15, and a second complex division circuit 16.

From the signal output from the FFT, a data signal Dr is extracted by the data extraction unit 11. On the other hand, pilot signal Pr is extracted from pilot extracting section 12. The pilot signal Pr is a signal whose amplitude and phase are known, and is the original pilot signal transmitted by the first complex division circuit 13 (that is, the output of the known pilot generation unit 14).
By dividing by Pt), the transmission path response at the pilot carrier position is obtained. Thereafter, the transmission line response at the data position (the position shown in FIG. 1) is obtained by the carrier interpolation circuit 15. For this interpolation, a low-pass filter (LPF) composed of an FIR filter or the like is used. As other methods, a hold (an interpolation method in which a transmission path response at a data carrier position is replaced with a transmission path response at an adjacent pilot carrier position) or linear interpolation may be considered. Among these, the interpolation using the LPF minimizes the signal degradation when a ghost is added. By this interpolation processing, the transmission path responses Hx at all the carrier positions are obtained.

Finally, the demodulated data Dt is obtained by dividing the data signal Dr received by the second complex division circuit 16 by the transmission path response Hx at that position.

The receiving apparatus according to the present invention does not require the symbol interpolation circuit (see FIG. 9) that is required for the conventional receiving apparatus. Therefore, the circuit size of the receiving device can be reduced,
An inexpensive receiving device can be provided.

[0049]

As described above, when the transmission frame of the orthogonal frequency division multiplexing transmission system of the present invention is used, pilot carriers serving as demodulation references are continuously arranged in the time direction. Mobile reception performance can be greatly improved as compared with a method in which the mobile reception performance is distributed in the time direction (that is, a method in which transmission is performed intermittently in the time direction). In particular, when compared to ISDB-T or DVB-T transmission frames using a distributed arrangement, pilot carriers are inserted four times as frequently in the time direction, so that they follow the change in transmission path response. Can be increased up to four times.

Therefore, by using the orthogonal frequency division multiplexing transmission system, transmitting apparatus, and receiving apparatus of the present invention, Rayleigh fading which is a problem at the time of mobile reception can be prevented.
The available Doppler frequency can be increased up to four times. This means that if the frequency used for transmission is the same, up to four times the moving speed can be handled. In other words, if the moving speed is the same, the frequency available for transmission is quadrupled.

Thus, in the mobile reception, the orthogonal frequency division multiplexing transmission system, which was applicable only to the UHF band, can be applied to the microwave band. Furthermore, if the follow-up to the fluctuation is improved by reducing the effective symbol length, the present invention can be applied not only to the microwave band but also to the millimeter wave band. Further, since the receiving apparatus of the present invention does not require the symbol interpolation circuit (see FIG. 9) which is provided in the conventional apparatus, there is an effect that the circuit scale of the receiving apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration example of a transmission frame used in the orthogonal frequency division multiplex transmission system of the present invention.

FIG. 2 is an explanatory diagram schematically showing a relationship between a change in transmission path response and a pilot carrier arrangement when a pilot carrier is viewed in a time direction.

FIG. 3 is an explanatory diagram showing a configuration example of a transmission frame when a TMCC carrier or an AC carrier is inserted.

FIG. 4 is a block diagram illustrating a configuration example of a transmission frame configuration of a transmission device used for the orthogonal frequency division multiplexing transmission system according to the present invention.

FIG. 5 is a block diagram showing a configuration of a receiving apparatus used for the orthogonal frequency division multiplexing transmission system of the present invention.

FIG. 6 is an explanatory diagram showing an arrangement of carriers in the OFDM transmission system.

FIG. 7 is an explanatory diagram showing a configuration of a transmission symbol of the OFDM transmission scheme.

FIG. 8 is an explanatory diagram showing a configuration example of a transmission frame used in a conventional orthogonal frequency division multiplex transmission system.

FIG. 9 is a block diagram showing a configuration of a receiving apparatus used for a conventional orthogonal frequency division multiplexing transmission system.

FIG. 10 is an explanatory diagram showing a carrier arrangement after symbol interpolation.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 frame configuration pattern memory 2 switch control unit 3 switch 4 transmission frame configuration 11 data extraction unit 12 pilot extraction unit 13 first complex division circuit 14 known pilot generation unit 15 carrier interpolation circuit 16 2nd complex division circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Okabe 1-1-10 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Research Institute (72) Inventor Kazuhiko Shibuya 1-110 Kinuta, Setagaya-ku, Tokyo No. Japan Broadcasting Corporation Broadcasting Research Institute F-term (reference) 5K022 DD01 DD13 DD18 DD19 DD23 DD33 DD43

Claims (5)

[Claims] 1. An orthogonal frequency division multiplexing transmission system for performing data transmission using a plurality of carriers orthogonal to each other and having a carrier structure in which the carrier (carrier) is composed of a pilot carrier serving as a demodulation reference and a data carrier. The number of carriers to be transmitted is K, the effective symbol length of the transmission symbol is Te, the guard interval length is Tg, and the ratio between the guard interval length and the effective symbol length (hereinafter referred to as the guard interval ratio) is R (where R = Tg / Te) and M is the maximum integer less than the reciprocal (1 / R) of the guard interval ratio. Assuming that any integer equal to or less than M is Q, a pilot carrier serving as a reference at the time of demodulation is fixed for each Q lines from an end carrier, provided that the value of the number of carriers K is (multiple of Q + 1). A method of arranging carriers in an orthogonal frequency division multiplex transmission system, wherein the carriers are arranged at intervals and continuously arranged in a time direction. 2. The method of claim 2, wherein the carrier number of the carrier number K is 0,
2. The orthogonal frequency division multiplex transmission system according to claim 1, wherein when 1, 2,..., K-1, no pilot carrier is arranged in the center carrier of all carriers (ie, carrier number K / 2). How to arrange carriers in 3. The method according to claim 1, wherein the carrier number of the carrier number K is 0,
When 1, 2,..., K-1, the center carrier of all carriers (that is, carrier number K / 2) is an empty carrier (a carrier that does not transmit any information). 3. A method for arranging carriers in the orthogonal frequency division multiplexing transmission system according to 2. 4. An orthogonal frequency division multiplexing transmission system for performing data transmission using a plurality of carriers that are orthogonal to each other, the carrier having a carrier structure composed of a pilot carrier serving as a demodulation reference and a data carrier. In the transmitting device used, storage means for storing the arrangement of the data carrier, pilot carrier, TMCC carrier, and AC carrier in advance as a frame configuration pattern, and data, a pilot signal, a TMCC signal, and an AC signal according to the stored frame configuration pattern. A control signal generating means for generating a control signal for switching an input signal such as, for example, switching the input signal according to the control signal, inserting a data, a pilot signal, a TMCC signal, and an AC signal into a predetermined carrier position. Frame that constitutes the transmission frame A transmission device, comprising: 5. An orthogonal frequency division multiplexing transmission system for performing data transmission using a plurality of carriers that are orthogonal to each other and having a carrier structure including a pilot carrier serving as a demodulation reference and a data carrier. In a receiving apparatus used, a transmission line response for obtaining a transmission line response at a pilot carrier position by dividing a received pilot carrier signal by a known pilot carrier signal as a processing unit when one transmission symbol is demodulated. Estimating means; transmission path response interpolation means for obtaining responses for all carrier positions by interpolating the transmission path responses for each of the Q lines obtained by the transmission path response estimating means; And demodulation means for demodulating by dividing by the transmission path response, and the demodulation processing is completed by one transmission symbol. Receiving apparatus being characterized in that as.