CA2113766A1 - Transmission system comprising timing recovery - Google Patents
Transmission system comprising timing recoveryInfo
- Publication number
- CA2113766A1 CA2113766A1 CA002113766A CA2113766A CA2113766A1 CA 2113766 A1 CA2113766 A1 CA 2113766A1 CA 002113766 A CA002113766 A CA 002113766A CA 2113766 A CA2113766 A CA 2113766A CA 2113766 A1 CA2113766 A1 CA 2113766A1
- Authority
- CA
- Canada
- Prior art keywords
- frequency
- time
- block
- signal
- present
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/16—Circuits
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2662—Symbol synchronisation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2668—Details of algorithms
- H04L27/2673—Details of algorithms characterised by synchronisation parameters
- H04L27/2676—Blind, i.e. without using known symbols
- H04L27/2678—Blind, i.e. without using known symbols using cyclostationarities, e.g. cyclic prefix or postfix
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
- H04L7/027—Speed or phase control by the received code signals, the signals containing no special synchronisation information extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit
Abstract
Abstract:
Transmission system comprising timing recovery.
The invention relates to a device for recovering a symbol timing for the decoding of received signals formed by code-modulation symbols transmitted in an orthogonal frequency-division multiplexing mode (OFDM). The signals are formatted in symbol blocks of which each block presents redundant information. The invention comprises means for delaying (12) the symbol blocks and for subtracting (13) from a symbol block the delayed symbol block corresponding thereto. In this manner a difference signal e(t) is obtained which is used for controlling a loop (15) formed by a local oscillator (16) operating at the clock frequency, a frequency divider (24) and a phase comparator (20).
Reference: Fig. 2.
Transmission system comprising timing recovery.
The invention relates to a device for recovering a symbol timing for the decoding of received signals formed by code-modulation symbols transmitted in an orthogonal frequency-division multiplexing mode (OFDM). The signals are formatted in symbol blocks of which each block presents redundant information. The invention comprises means for delaying (12) the symbol blocks and for subtracting (13) from a symbol block the delayed symbol block corresponding thereto. In this manner a difference signal e(t) is obtained which is used for controlling a loop (15) formed by a local oscillator (16) operating at the clock frequency, a frequency divider (24) and a phase comparator (20).
Reference: Fig. 2.
Description
PHF 93.503 1 ~1 13 7 ~ ~ January 13, 1994 Transmission system comprising timing recovery.
The invention relates to a transmission system comprising a transmitter for transmitting a transmit signal formatted in blocks coming from symbols of a constellation, the same block containing the same information signal present a first and a second time, and a receiver for receiving said signal.
The invention likewise relates to a receiver used in such a transmission system.
In a general manner the invention relates to signals formatted in blocks for which said blocks may have a great complexity due to redundant information. They :
may be, for example, signals obtained from orthogonal N-frequency division ~-10 multiplexing which consists of splitting up a transmit information signal by distributing same over a large number of low-rate elementaly channels. One thus transforms a highly selective wideband channel into a large number of non-selective elementary channels. As the arrangement forms a wideband channel, it is not very likely that fading during transmission will simultaneously affect the whole channel. This technique15 specifically makes it possible to reduce intersymbol interference.
One frequency thus corresponds to each elementary channel, all the frequencies together being symmetrically distributed around a central carrier frequency.
As it is hard to accept the use of selective filters at the receiver end, one prefers tolerating an overlap of the spectra but then requirements are imposed with respect to 20 orthogonality between the frequencies to eliminate intersymbol interference at the sampling instants. The whole spectrum of an OFDM signal thus tends towards a rectangular spectrum.
At the receiver end the received signals are to be demodulated and then decoded to restore the original information. For this demodulation is used a local 25 oscillator whose frequency is to be locked on to the transmit frequency.
The OFDM signal is subdivided into frames formed by blocks of which certain blocks are service blocks and other blocks are data blocks. To avoid intersymbol interference, each block contains redundant information signals. Any block is formed at all the OFDM frequencies the device uses, the frequencies being modulated by transrnit ~1~37~ :
PHF 93.503 2 January 13, 1994 symbols coming from a coded modulation, for example, a digital PSK or QAM
modulation. At the transmitter end, the symbols are coded with a certain timing which is to be found back at the receiver end, so that they can be decoded correctly. The invention proposes to find back at the receiver end the timing used at the transmitter 5 end.
FR 2 639 495 is known which describes a digital data transmission method which employs an OFDM technique. The method of synchronization recovery is carried out with a frame while use is made of two specific blocks which are a zero block at the beginning of the frame and a wobulation block. Ihis document puts 10 forward the importance it presents of not synchronizing a timing clock with the binary level as in previous techniques. Said document thus works with binary data acquisition windows which it considers to have a sufficiently high precision for decoding the binary data.
But when a synchronization is effected once per ~rame, a frame having, 15 for example, a duration of 20 ms, the precision of the synchronization remains insufficient.
Thus, it is an object of the invention to provide a clock synchronization with a better precision than in the prior art for a signal formatted in blocks which themselves contain redundant information signals.
This object is achieved by effecting a timing recovery while use is made of data received with the block frequency. Therefore, the transmission system ;scharacterized in that the receiver comprises:
- first generator means for generating a local symbol clock, said clock having a first frequency, 25 - second generator means for generating a difference signal that corresponds to a second frequency, the difference signal being obtained via correlation between the information signal present the first time and that present the second time in the same block, - third means for locking the first freqiuency on to the second frequency.
Thus the invention advantageously utilizes the redundancy of the data contained in each block to considerably improve the quality of the synchronization.
In the particular case of an OFDM signal, with a frame containing 125 blocks, the precision of the timing recovery can be estimated to be improved by a factor ~ 37~ -PHF 93.503 3 January 13, 1994 of about 125.
Preferably, the second generator means bring about the correlation by performing a subtraction between the information signal present the first time and the information signal preseint the second time.
For subtracting from each other thei groups of data present at the beginning and end of each block, time delay means are used which form a delayed replica of the received signal, which replica is subtracted from the received signal itself, so that a control signal is supplied which is in accordance with the block ra~i.This control signal influences a phase locked loop to control, by a 10 frequency division, an oscillator whose oscillation frequency is much higher than the block frequency and which produces the baud rate clock.
These various aspects of the invention and also others will be apparent and elucidated on the basis of the embodiments to be described hereinafter.
The invention will be better understood with reference to the following 15 Figures given by way of non-limiting examples which represent in:
Fig. 1: a time diagram indicating the generation of a difference signal at the bloclc rate; and Fig. 2: a diagram of a timing recovery device according to the invention arranged in the receiver.
The following description has been developed in the particular case of an OFDM signal, but also applies to other signals formatted in blocks for which each block contains redundant information signals.
The OFDM technique consists of frequency multiplexing various orthogonal carriers modulated by the symbols. An OFDM symbol may be written as:
(t) = Re le fot ~ xk ~k (t) ~
k=0 .
25 for j.T s < t < (j + l)T s with ~k(t) = e2i~kVTs for jT's 5 k 5 (j + l)T'S
where:
T's: total duration of an OFDM symbol, T~s = Ts-t~
Re: real part o~ a complex number ,f~ ,J'1~"37~
PHF 93.503 4 January 13, 1994 k: index of the orthogonal carriers Ts: useful period of an OFDM symbol ~: check interval N: maximum number of carriers f0: random frequency j: index of the OFDM symbol.
Thus between the instants j ~T~s an~d (j ~ l)T'S, an OFDM signal is formed by a block of complex symbols xlc, where each symbol xk modulates i~n orthogonalcarrier 0 < k ~ N-l.
To avoid the problem of spectrum overlap and to facilitate the filtering at the receiver end, the sum corresponding to the equation (1) is made of Nu carriers where Nu is the number of useful carriers (Nu < N).
To realise the OFDM modulation, that is to say, form the signal s(t) of equation (1), a modulator is used which performs a calculation of an inverse Fast lS Fourier transform (FFT-l). Therefore, a number of the form 2X, where x is an integer is selected for N. Other check blocks intended for the transmission are also inserted.
The selected parameters are, for example, the following:
T's = 160 ~4s, Ts = 128 ~s and A = 32 ,uS, N = 1024 carriers, Nu = 900 carriers.
The main role of the check interval ~ is to absorb the echoes coming from the multipath channel and having delays which are lower than ~. During the check interval (which is preferably equal to a quarter of the useful period) there is transmitted a signal that is identical with part of the useful period.
The selection of Nu = 900 comes from the fact that with the band around ~
each carrier being liTS = 7.81 kHz, 900 carriers are necessary to have an effective ~ -bandwidth of the transmitted signal of about 7 MHz (the exact bandwidth being 7.û31 MHz.
The blocks at the output of a channel coder are transmitted in frames.
Thus a frame regroups a plurality of time-division multiplexed OFDM blocks. An 30 OFDM block may contain data or may be a block particularly used for the synchronization (frame, clock, carrier synchronization) or used as a reference block for the difference modulaltion.
An exannple of the frame structure is given by: ;
~ 3766 PHF 93.503 5 January 13, 1994 LNUI ¦ AFC ¦ Wob ¦ 1~xt 1 ¦ ~xt 2 ¦ Data 1 ¦ Data 2 5 Ts = 160 ~s Tf = 20 MS
The frame contains 125 OFDM blocks and has a duration Tf of 20 ms:
- The fist block is the zero block during which nothing is transmitted (xk = 0, k = 0, N-l). It is used for synchronizing the beginning of the frame.
- The second block is the AFC (automatic frequency control) block used for synchronizing the frequency of the local oscillator of the receiver with that of the transmitter.
- The third block is the wobulation block defined by:
Xk = ~ ej ~k, ~k = 7r kN ~ 4 The wobulation block is used as a reference block for the differential coding and also for estimating the impulse response of the channel for a precisesynchronization of the beginning of the frame.
- The fourth and fifth blocks are additional blocks which may be used for 20 transmitting service data.
- Finally, there are the 120 OFDM data blocks.
A frame contains 100 codewords generated by the channel coder.
The invention advantageously uses the existence of a check interval in each block of an OFDM frame. Fig. 1 represents two consecutive blocks Bl and B2. ;
25 The following explication applies to all the blocks. The blccks Bl/B2 are forrned by a - -check interval having duration ~ followed by a useful interval having duration Ts which contains useful data. In a transmitted block the data which appear at the end of the -~;
useful interval Ts are copied at the beginning of the block before being transmitted through the channel. It will thus be noted that in each block an identical inforrnation 30 signal appears at the beginning and at the end of the block. In Fig. 1 the received signal 137~
PHF 93.503 6 January 13, 1994 the information at the beginning of the delayed signal rd(t) being in phase with the information at the end of the undelayed signal r(t). For the same block Bl these two information signals are identical. By subtracting these two signals, a signal e(t) is obtained which is formed by an interval having duration ~ where e(t) is zero preceded 5 by an interval having duration Ts where it is non-zero. In Fig. 1 the signal e(t) is represented in the form of a square-wave signal, but in reality this signal presents a more complex and more sinusoidal shape, having a fundamental frequency equal to the block frequency. It is thus possible to isolate this block fre~quency by filtering.
Fig. 2 represents a diagram of a device according to the invention which 10 permits isolating the block frequency and controlling an oscillator that oscillates initial symbols of the coded modulation with the clock frequency. Means 11 make it possible to generate the difference signal e(t) with the block frequency. The means 11 comprise associated filter means 14. The signal r(t) is delayed in delay means 12 for the signal rd(t) to be produced. The signals r(t) and rd(t) are subtracted from each other in 15 subtracter means 13 and produce the difference signal e(t). This difference signal e(t) has previously been filtered in a passband filter 14 brought in line with the block frequency used at a transmitter end.
The difference signal enters a phase-locked loop lS. It is intended to control a local oscillator 16 of the VCO type which oscillates, in the free running mode, 20 with a frequency close to the clock frequency of the coded modulation symbols. The loop lS is formed by a comparator 20, a low-pass filter 22 and a frequency divider 24.
By way of exarnple, the frequency of the signal e(t) can be equal to 12.5 kHz and the frequency of the oscillator close to 16 MHz. The output signal of the filter 22 (12.5 kHz) controls the frequency of the oscillator 16. To reduce the frequency of the25 oscillator signal to a 12.5 kHz frequency, so that the loop 15 can operate, it is necessary to insert a frequency divider 24. In said example there has to be divided by a factor of 1280. When the alignment has been effected, the output of the oscillator supplies the baud rate clock Hr. :
The invention relates to a transmission system comprising a transmitter for transmitting a transmit signal formatted in blocks coming from symbols of a constellation, the same block containing the same information signal present a first and a second time, and a receiver for receiving said signal.
The invention likewise relates to a receiver used in such a transmission system.
In a general manner the invention relates to signals formatted in blocks for which said blocks may have a great complexity due to redundant information. They :
may be, for example, signals obtained from orthogonal N-frequency division ~-10 multiplexing which consists of splitting up a transmit information signal by distributing same over a large number of low-rate elementaly channels. One thus transforms a highly selective wideband channel into a large number of non-selective elementary channels. As the arrangement forms a wideband channel, it is not very likely that fading during transmission will simultaneously affect the whole channel. This technique15 specifically makes it possible to reduce intersymbol interference.
One frequency thus corresponds to each elementary channel, all the frequencies together being symmetrically distributed around a central carrier frequency.
As it is hard to accept the use of selective filters at the receiver end, one prefers tolerating an overlap of the spectra but then requirements are imposed with respect to 20 orthogonality between the frequencies to eliminate intersymbol interference at the sampling instants. The whole spectrum of an OFDM signal thus tends towards a rectangular spectrum.
At the receiver end the received signals are to be demodulated and then decoded to restore the original information. For this demodulation is used a local 25 oscillator whose frequency is to be locked on to the transmit frequency.
The OFDM signal is subdivided into frames formed by blocks of which certain blocks are service blocks and other blocks are data blocks. To avoid intersymbol interference, each block contains redundant information signals. Any block is formed at all the OFDM frequencies the device uses, the frequencies being modulated by transrnit ~1~37~ :
PHF 93.503 2 January 13, 1994 symbols coming from a coded modulation, for example, a digital PSK or QAM
modulation. At the transmitter end, the symbols are coded with a certain timing which is to be found back at the receiver end, so that they can be decoded correctly. The invention proposes to find back at the receiver end the timing used at the transmitter 5 end.
FR 2 639 495 is known which describes a digital data transmission method which employs an OFDM technique. The method of synchronization recovery is carried out with a frame while use is made of two specific blocks which are a zero block at the beginning of the frame and a wobulation block. Ihis document puts 10 forward the importance it presents of not synchronizing a timing clock with the binary level as in previous techniques. Said document thus works with binary data acquisition windows which it considers to have a sufficiently high precision for decoding the binary data.
But when a synchronization is effected once per ~rame, a frame having, 15 for example, a duration of 20 ms, the precision of the synchronization remains insufficient.
Thus, it is an object of the invention to provide a clock synchronization with a better precision than in the prior art for a signal formatted in blocks which themselves contain redundant information signals.
This object is achieved by effecting a timing recovery while use is made of data received with the block frequency. Therefore, the transmission system ;scharacterized in that the receiver comprises:
- first generator means for generating a local symbol clock, said clock having a first frequency, 25 - second generator means for generating a difference signal that corresponds to a second frequency, the difference signal being obtained via correlation between the information signal present the first time and that present the second time in the same block, - third means for locking the first freqiuency on to the second frequency.
Thus the invention advantageously utilizes the redundancy of the data contained in each block to considerably improve the quality of the synchronization.
In the particular case of an OFDM signal, with a frame containing 125 blocks, the precision of the timing recovery can be estimated to be improved by a factor ~ 37~ -PHF 93.503 3 January 13, 1994 of about 125.
Preferably, the second generator means bring about the correlation by performing a subtraction between the information signal present the first time and the information signal preseint the second time.
For subtracting from each other thei groups of data present at the beginning and end of each block, time delay means are used which form a delayed replica of the received signal, which replica is subtracted from the received signal itself, so that a control signal is supplied which is in accordance with the block ra~i.This control signal influences a phase locked loop to control, by a 10 frequency division, an oscillator whose oscillation frequency is much higher than the block frequency and which produces the baud rate clock.
These various aspects of the invention and also others will be apparent and elucidated on the basis of the embodiments to be described hereinafter.
The invention will be better understood with reference to the following 15 Figures given by way of non-limiting examples which represent in:
Fig. 1: a time diagram indicating the generation of a difference signal at the bloclc rate; and Fig. 2: a diagram of a timing recovery device according to the invention arranged in the receiver.
The following description has been developed in the particular case of an OFDM signal, but also applies to other signals formatted in blocks for which each block contains redundant information signals.
The OFDM technique consists of frequency multiplexing various orthogonal carriers modulated by the symbols. An OFDM symbol may be written as:
(t) = Re le fot ~ xk ~k (t) ~
k=0 .
25 for j.T s < t < (j + l)T s with ~k(t) = e2i~kVTs for jT's 5 k 5 (j + l)T'S
where:
T's: total duration of an OFDM symbol, T~s = Ts-t~
Re: real part o~ a complex number ,f~ ,J'1~"37~
PHF 93.503 4 January 13, 1994 k: index of the orthogonal carriers Ts: useful period of an OFDM symbol ~: check interval N: maximum number of carriers f0: random frequency j: index of the OFDM symbol.
Thus between the instants j ~T~s an~d (j ~ l)T'S, an OFDM signal is formed by a block of complex symbols xlc, where each symbol xk modulates i~n orthogonalcarrier 0 < k ~ N-l.
To avoid the problem of spectrum overlap and to facilitate the filtering at the receiver end, the sum corresponding to the equation (1) is made of Nu carriers where Nu is the number of useful carriers (Nu < N).
To realise the OFDM modulation, that is to say, form the signal s(t) of equation (1), a modulator is used which performs a calculation of an inverse Fast lS Fourier transform (FFT-l). Therefore, a number of the form 2X, where x is an integer is selected for N. Other check blocks intended for the transmission are also inserted.
The selected parameters are, for example, the following:
T's = 160 ~4s, Ts = 128 ~s and A = 32 ,uS, N = 1024 carriers, Nu = 900 carriers.
The main role of the check interval ~ is to absorb the echoes coming from the multipath channel and having delays which are lower than ~. During the check interval (which is preferably equal to a quarter of the useful period) there is transmitted a signal that is identical with part of the useful period.
The selection of Nu = 900 comes from the fact that with the band around ~
each carrier being liTS = 7.81 kHz, 900 carriers are necessary to have an effective ~ -bandwidth of the transmitted signal of about 7 MHz (the exact bandwidth being 7.û31 MHz.
The blocks at the output of a channel coder are transmitted in frames.
Thus a frame regroups a plurality of time-division multiplexed OFDM blocks. An 30 OFDM block may contain data or may be a block particularly used for the synchronization (frame, clock, carrier synchronization) or used as a reference block for the difference modulaltion.
An exannple of the frame structure is given by: ;
~ 3766 PHF 93.503 5 January 13, 1994 LNUI ¦ AFC ¦ Wob ¦ 1~xt 1 ¦ ~xt 2 ¦ Data 1 ¦ Data 2 5 Ts = 160 ~s Tf = 20 MS
The frame contains 125 OFDM blocks and has a duration Tf of 20 ms:
- The fist block is the zero block during which nothing is transmitted (xk = 0, k = 0, N-l). It is used for synchronizing the beginning of the frame.
- The second block is the AFC (automatic frequency control) block used for synchronizing the frequency of the local oscillator of the receiver with that of the transmitter.
- The third block is the wobulation block defined by:
Xk = ~ ej ~k, ~k = 7r kN ~ 4 The wobulation block is used as a reference block for the differential coding and also for estimating the impulse response of the channel for a precisesynchronization of the beginning of the frame.
- The fourth and fifth blocks are additional blocks which may be used for 20 transmitting service data.
- Finally, there are the 120 OFDM data blocks.
A frame contains 100 codewords generated by the channel coder.
The invention advantageously uses the existence of a check interval in each block of an OFDM frame. Fig. 1 represents two consecutive blocks Bl and B2. ;
25 The following explication applies to all the blocks. The blccks Bl/B2 are forrned by a - -check interval having duration ~ followed by a useful interval having duration Ts which contains useful data. In a transmitted block the data which appear at the end of the -~;
useful interval Ts are copied at the beginning of the block before being transmitted through the channel. It will thus be noted that in each block an identical inforrnation 30 signal appears at the beginning and at the end of the block. In Fig. 1 the received signal 137~
PHF 93.503 6 January 13, 1994 the information at the beginning of the delayed signal rd(t) being in phase with the information at the end of the undelayed signal r(t). For the same block Bl these two information signals are identical. By subtracting these two signals, a signal e(t) is obtained which is formed by an interval having duration ~ where e(t) is zero preceded 5 by an interval having duration Ts where it is non-zero. In Fig. 1 the signal e(t) is represented in the form of a square-wave signal, but in reality this signal presents a more complex and more sinusoidal shape, having a fundamental frequency equal to the block frequency. It is thus possible to isolate this block fre~quency by filtering.
Fig. 2 represents a diagram of a device according to the invention which 10 permits isolating the block frequency and controlling an oscillator that oscillates initial symbols of the coded modulation with the clock frequency. Means 11 make it possible to generate the difference signal e(t) with the block frequency. The means 11 comprise associated filter means 14. The signal r(t) is delayed in delay means 12 for the signal rd(t) to be produced. The signals r(t) and rd(t) are subtracted from each other in 15 subtracter means 13 and produce the difference signal e(t). This difference signal e(t) has previously been filtered in a passband filter 14 brought in line with the block frequency used at a transmitter end.
The difference signal enters a phase-locked loop lS. It is intended to control a local oscillator 16 of the VCO type which oscillates, in the free running mode, 20 with a frequency close to the clock frequency of the coded modulation symbols. The loop lS is formed by a comparator 20, a low-pass filter 22 and a frequency divider 24.
By way of exarnple, the frequency of the signal e(t) can be equal to 12.5 kHz and the frequency of the oscillator close to 16 MHz. The output signal of the filter 22 (12.5 kHz) controls the frequency of the oscillator 16. To reduce the frequency of the25 oscillator signal to a 12.5 kHz frequency, so that the loop 15 can operate, it is necessary to insert a frequency divider 24. In said example there has to be divided by a factor of 1280. When the alignment has been effected, the output of the oscillator supplies the baud rate clock Hr. :
Claims (8)
1. Transmission system comprising a transmitter for transmitting a transmit signal formatted in blocks (B1, B2) coming from symbols of a constellation, the same block (B1, B2) containing the same information signal (.DELTA.) present a first and a second time, and a receiver for receiving said signal, characterized in that the receiver comprises:
- first generator means (16) for generating a local symbol clock, said clock having a first frequency, - second generator means (11) for generating a difference signal that corresponds to a second frequency, the difference signal being obtained via correlation between the information signal present the first time and that present the second time in the same block, - third means (15) for locking the first frequency on to the second frequency.
- first generator means (16) for generating a local symbol clock, said clock having a first frequency, - second generator means (11) for generating a difference signal that corresponds to a second frequency, the difference signal being obtained via correlation between the information signal present the first time and that present the second time in the same block, - third means (15) for locking the first frequency on to the second frequency.
2. Transmission system as claimed in Claim 1, characterized in that the second means comprise delay means which delay the received signals by a period of time separating the first and second time the same information occurs.
3. Transmission system as claimed in Claim 1 or 2, characterized in that the second means are adapted to correlate, by way of subtraction, the information present the first time and the information present the second time.
4. Transmission system as claimed in the Claims 1, 2 or 3, in which the blocks appear at a block rate, characterized in that the second frequency is equal to the block rate while the third means comprise a frequency-division phased lock loop and the first means comprise a high-frequency oscillator.
5. Receiver for receiving a transmit signal formatted in blocks (B1, B2) formed by symbols of a constellation, the same block (B1, B2) containing the same information (.DELTA.) which is present a first and a second time, characterized in that the receiver comprises:
- first generator means (16) for generating a local symbol clock, said clock having a first frequency, - second generator means (11) for generating a difference signal that corresponds to a second frequency, the difference signal being obtained via correlation between the information signal present the first time and that present the second time in the same block, third means (15) for locking the first frequency on to the second frequency.
- first generator means (16) for generating a local symbol clock, said clock having a first frequency, - second generator means (11) for generating a difference signal that corresponds to a second frequency, the difference signal being obtained via correlation between the information signal present the first time and that present the second time in the same block, third means (15) for locking the first frequency on to the second frequency.
6. Receiver as claimed in Claim 5, characterized in that the second generator means comprise delay means which delay the received signals by a period of time separating the first and the second time the same information occurs.
7. Receiver as claimed in Claim 5 or 6, characterized in that the second generator means are adapted to correlate, by subtraction, the information present a first time and that present a second time.
8. Receiver as claimed in Claim 5, 6 or 7 in which the blocks appear at a block rate, characterized in that the second frequency is equal to the block rate, the third means comprise a frequency-division phase-locked loop and the first generator means comprise a high-frequency oscillator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002330522A CA2330522A1 (en) | 1993-01-20 | 1994-01-19 | Method of isolating a block frequency on the basis of a signal formatted in blocks |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9300539 | 1993-01-20 | ||
| FR9300539 | 1993-01-20 |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002330522A Division CA2330522A1 (en) | 1993-01-20 | 1994-01-19 | Method of isolating a block frequency on the basis of a signal formatted in blocks |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2113766A1 true CA2113766A1 (en) | 1994-07-21 |
Family
ID=9443215
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002113766A Abandoned CA2113766A1 (en) | 1993-01-20 | 1994-01-19 | Transmission system comprising timing recovery |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5559833A (en) |
| EP (2) | EP0608024B1 (en) |
| JP (2) | JPH06244818A (en) |
| KR (2) | KR100334185B1 (en) |
| CA (1) | CA2113766A1 (en) |
| DE (2) | DE69427099T2 (en) |
| FI (1) | FI940268A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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-
1994
- 1994-01-14 DE DE69427099T patent/DE69427099T2/en not_active Expired - Fee Related
- 1994-01-14 DE DE69434306T patent/DE69434306T2/en not_active Expired - Lifetime
- 1994-01-14 EP EP94200086A patent/EP0608024B1/en not_active Expired - Lifetime
- 1994-01-14 EP EP00201832A patent/EP1035699B1/en not_active Expired - Lifetime
- 1994-01-19 CA CA002113766A patent/CA2113766A1/en not_active Abandoned
- 1994-01-19 JP JP6004251A patent/JPH06244818A/en active Pending
- 1994-01-19 FI FI940268A patent/FI940268A/en unknown
- 1994-01-19 US US08/184,626 patent/US5559833A/en not_active Expired - Lifetime
- 1994-01-20 KR KR1019940001018A patent/KR100334185B1/en not_active IP Right Cessation
-
2001
- 2001-01-18 JP JP2001010774A patent/JP3423934B2/en not_active Expired - Lifetime
- 2001-08-27 KR KR1020010051867A patent/KR100356975B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| EP1035699A2 (en) | 2000-09-13 |
| FI940268A (en) | 1994-07-21 |
| US5559833A (en) | 1996-09-24 |
| EP0608024A1 (en) | 1994-07-27 |
| JPH06244818A (en) | 1994-09-02 |
| DE69427099D1 (en) | 2001-05-23 |
| EP0608024B1 (en) | 2001-04-18 |
| KR100356975B1 (en) | 2002-10-19 |
| JP2001251277A (en) | 2001-09-14 |
| EP1035699B1 (en) | 2005-03-16 |
| FI940268A0 (en) | 1994-01-19 |
| DE69434306D1 (en) | 2005-04-21 |
| KR100334185B1 (en) | 2002-10-18 |
| DE69434306T2 (en) | 2005-11-10 |
| DE69427099T2 (en) | 2001-11-08 |
| EP1035699A3 (en) | 2000-12-06 |
| JP3423934B2 (en) | 2003-07-07 |
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