CA2291847C - Synchronization symbol structure using ofdm based transmission method - Google Patents
Synchronization symbol structure using ofdm based transmission method Download PDFInfo
- Publication number
- CA2291847C CA2291847C CA002291847A CA2291847A CA2291847C CA 2291847 C CA2291847 C CA 2291847C CA 002291847 A CA002291847 A CA 002291847A CA 2291847 A CA2291847 A CA 2291847A CA 2291847 C CA2291847 C CA 2291847C
- Authority
- CA
- Canada
- Prior art keywords
- symbols
- symbol sequence
- ofdm
- subcarriers
- time domain
- 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.)
- Expired - Lifetime
Links
Classifications
-
- 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
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03343—Arrangements at the transmitter end
-
- 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
- H04L27/2602—Signal structure
- H04L27/261—Details of reference signals
- H04L27/2613—Structure of the reference signals
-
- 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
- H04L27/2614—Peak power aspects
- H04L27/262—Reduction thereof by selection of pilot symbols
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/0001—Arrangements for dividing the transmission path
- H04L5/0003—Two-dimensional division
- H04L5/0005—Time-frequency
- H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0042—Arrangements for allocating sub-channels of the transmission path intra-user or intra-terminal allocation
-
- 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
Abstract
The present invention proposes a method for generating synchronization bursts for OFDM transmission systems. The symbols of a predefined symbol sequence are mapped according to a predefined mapping scheme on subcarriers of the OFDM
systems by a mapping unit (2), wherein the symbols of the predefined symbol sequence represent subcarriers of the OFDM system with nonzero amplitudes. A
synchronization burst is generated by a inverse fast Fourier transforming unit (3) transforming the subcarriers of the OFDM system mapped to said predefined symbol sequence. The mapping (2) of the symbols of the predefined symbol sequence is set such that the resulting time domain signal of the synchronization burst represents a periodic nature.
According to the invention the predefined symbol sequence is set such that the envelope fluctuation of the time domain signal of the synchronization burst is minimized.
Therefore advantageous symbol sequences reducing said the envelope fluctuation of the time domain signal are proposed.
systems by a mapping unit (2), wherein the symbols of the predefined symbol sequence represent subcarriers of the OFDM system with nonzero amplitudes. A
synchronization burst is generated by a inverse fast Fourier transforming unit (3) transforming the subcarriers of the OFDM system mapped to said predefined symbol sequence. The mapping (2) of the symbols of the predefined symbol sequence is set such that the resulting time domain signal of the synchronization burst represents a periodic nature.
According to the invention the predefined symbol sequence is set such that the envelope fluctuation of the time domain signal of the synchronization burst is minimized.
Therefore advantageous symbol sequences reducing said the envelope fluctuation of the time domain signal are proposed.
Description
Synchronization symbol structure using OFDM based transmission method Field of the Invention The present invention relates to a method for generating synchronization bursts for OFDM transmission systems, a method for synchronizing wireless OFDM systems, an OFDM transmitter as well as to a mobile communications device comprising such a transmitter.
The present invention relates generally to the technical field of synchronizing wireless OFDM (orthogonal frequency division multiplexing) systems. Thereby it is known to use a synchronization burst constructed using especially designed OFDM symbols and time domain repetitions.
Background of the Invention Particularly from the document IEEE P802.11a/d2.0 "Draft supplement to a standard for telecommunications and information exchange between systems - LAN/MAN
specific requirements - part l: wireless medium access control (MAC) and physical layer (PHY) specifications: high-speed physical layer in the 5 GHz band" a synchronization scheme for OFDM systems is proposed. This document is herewith included by reference as far as it concerns the synchronization including the proposed implementation. Said known scheme will now be explained with reference to fig.
6 to 8 of the enclosed drawings.
Fig. 6 shows the structure of the known synchronization field. As shown in Fig. 6 the synchronization field consists of so-called short symbols tl, t2,.....t6 and two long symbols T1, T2. In view of the present invention particularly the short symbols tl, t2....t6 are of interest. Among the short symbols tl, t2, ....t6 used for the amplifier gain control (tl, t2, t3) and the course frequency offset and timing control only the symbols tl, t2, t3 and t4 are actually generated, whereas the symbols t5, t6 are cyclic extensions (copies of the symbols tl and t2, respectively). It is to be noted that fig. S
shows only the synchronization preamble structure as the structure of the following signal field indicating the type of baseband modulation and the coding rate as well as the structure of further following data fields are not of interest in view of the present invention. For further details reference is made to said prior art document.
The present invention relates generally to the technical field of synchronizing wireless OFDM (orthogonal frequency division multiplexing) systems. Thereby it is known to use a synchronization burst constructed using especially designed OFDM symbols and time domain repetitions.
Background of the Invention Particularly from the document IEEE P802.11a/d2.0 "Draft supplement to a standard for telecommunications and information exchange between systems - LAN/MAN
specific requirements - part l: wireless medium access control (MAC) and physical layer (PHY) specifications: high-speed physical layer in the 5 GHz band" a synchronization scheme for OFDM systems is proposed. This document is herewith included by reference as far as it concerns the synchronization including the proposed implementation. Said known scheme will now be explained with reference to fig.
6 to 8 of the enclosed drawings.
Fig. 6 shows the structure of the known synchronization field. As shown in Fig. 6 the synchronization field consists of so-called short symbols tl, t2,.....t6 and two long symbols T1, T2. In view of the present invention particularly the short symbols tl, t2....t6 are of interest. Among the short symbols tl, t2, ....t6 used for the amplifier gain control (tl, t2, t3) and the course frequency offset and timing control only the symbols tl, t2, t3 and t4 are actually generated, whereas the symbols t5, t6 are cyclic extensions (copies of the symbols tl and t2, respectively). It is to be noted that fig. S
shows only the synchronization preamble structure as the structure of the following signal field indicating the type of baseband modulation and the coding rate as well as the structure of further following data fields are not of interest in view of the present invention. For further details reference is made to said prior art document.
The symbols tl, t2, t3, t4 are generated by means of an OFDM modulation using selected subcarriers from the entire available subcarriers. The symbols used for the OFDM modulation as well as the mapping to the selected subcarriers will now be explained with reference to fig. 6.
Each of the short OFDM symbols tl, ....t6 is generated by using 12 modulated subcarriers phase-modulated by the elements of the symbol alphabet:
S= ~(~1 ~.I) The full sequence used for the OFDM modulation can be written as follows:
S_zQ, 24 = ~2*~ 1 +j, 0,0,0,1 +j,0,0,0,-1-j,0,0,0,-1 j,0,0,0,1 j,0,0,0,-1 j,0,0,0,0, 0,0,0,1 +j,0,0,0,1 +j,0,0,0,-1 j,0,0,0,1 +j,0,0,0,-1 +j,0,0,0,1 +j ~
The multiplication by a factor of ~2 is in order to normalize the average power of the resulting OFDM symbol.
The signal can be written as:
N., /2 rSHORT ~t~ - W SHORTI ~t~ ~ Sk exp ( j 2 ~zk~ F t ) k=-h'Z /2 The fact that only spectral lines of S_Za, za ~'~'i~ indices which are a multiple of 4 have nonzero amplitude results in a periodicity of TFF,./4=0.8~sec. The interval TTSHORr~ is equal to nine 0.8 sec periods, i.e. 7.2 .sec.
Applying a 64-point IFFT to the vector S, where the remaining 15 values are set to zero, four short training symbols tl, t2, t3, t4 (in the time domain) can be generated.
The IFFT output is cyclically extended to result in 6 short symbols tl, t2, t3, ...t6. The mapping scheme is depicted in fig. 7. The so called virtual subcarriers are left unmodulated.
The way to implement the inverse Fourier transform is by an IFFT (Inverse Fast Fourier Transform) algorithm. If, for example, a 64 point IFFT is used, the coefficients 1 to 24 are mapped to same numbered IFFT inputs, while the coefficients -24 to -1 are copied into IFFT inputs 40 to 63. The rest of the inputs, 25 to 39 and the 0 (DC) input, are set to zero. This mapping is illustrated in Fig. 7. After performing an IFFT the output is cyclically extended to the desired length.
J f .
Each of the short OFDM symbols tl, ....t6 is generated by using 12 modulated subcarriers phase-modulated by the elements of the symbol alphabet:
S= ~(~1 ~.I) The full sequence used for the OFDM modulation can be written as follows:
S_zQ, 24 = ~2*~ 1 +j, 0,0,0,1 +j,0,0,0,-1-j,0,0,0,-1 j,0,0,0,1 j,0,0,0,-1 j,0,0,0,0, 0,0,0,1 +j,0,0,0,1 +j,0,0,0,-1 j,0,0,0,1 +j,0,0,0,-1 +j,0,0,0,1 +j ~
The multiplication by a factor of ~2 is in order to normalize the average power of the resulting OFDM symbol.
The signal can be written as:
N., /2 rSHORT ~t~ - W SHORTI ~t~ ~ Sk exp ( j 2 ~zk~ F t ) k=-h'Z /2 The fact that only spectral lines of S_Za, za ~'~'i~ indices which are a multiple of 4 have nonzero amplitude results in a periodicity of TFF,./4=0.8~sec. The interval TTSHORr~ is equal to nine 0.8 sec periods, i.e. 7.2 .sec.
Applying a 64-point IFFT to the vector S, where the remaining 15 values are set to zero, four short training symbols tl, t2, t3, t4 (in the time domain) can be generated.
The IFFT output is cyclically extended to result in 6 short symbols tl, t2, t3, ...t6. The mapping scheme is depicted in fig. 7. The so called virtual subcarriers are left unmodulated.
The way to implement the inverse Fourier transform is by an IFFT (Inverse Fast Fourier Transform) algorithm. If, for example, a 64 point IFFT is used, the coefficients 1 to 24 are mapped to same numbered IFFT inputs, while the coefficients -24 to -1 are copied into IFFT inputs 40 to 63. The rest of the inputs, 25 to 39 and the 0 (DC) input, are set to zero. This mapping is illustrated in Fig. 7. After performing an IFFT the output is cyclically extended to the desired length.
J f .
With the proposed inverse fast Fourier transform (IFFT) mapping as shown in fig. ? the resulting time domain signal consists of 4 periodically repeated short symbols tl, t2, t3, t4, and cyclically extended by a copy of tl, t2, which copy is depicted in fig.5 as t5, t6.
Note that in the present case only spectral lines with indices which are a multiple of 4 have nonzero amplitude. Other periodic natures can be generated by setting other multiples of the spectral lines to nonzero amplitudes.
Though the known synchronization scheme is very effective, it provides for disadvantage regarding the time domain signal properties.
Summary of the Invention For OFDM (or in general multicarrier signals) the signal. envelope fluctuation (named Peak-to-Average-Power-Ratio=PAPR) is of great concern. A large PAPR results in poor transmission (due to nonlinear distortion effects of the power amplifier) and other signal limiting components in the transmission system (e.g. limited dynamic range of the AD converter) .
For synchronization sequences it is even more desirable to have signals with a low PAPR in order to accelerate the receiver AGC (automatic gain control) locking and adjusting the reference signal value for the A/D converter (the whole dynamic range of the incoming signal should be covered by the A/D converter resolution without any overflow/underflow).
Figures 8a, 8b show the "absolute" (sq~ In*+Quad *Quad ~) value of the resulting time domain signal waveform with the sequences proposed by Lucent Technologies.
Oversampling (8*) was considered in order to ensure the peak was captured correctly using the limited 64-point IFFT.
Figures 8c, 8d show the real and imaginary part of the resulting transmitted time domain waveform. The resulting PAPR is 2.9991 dB (no oversampling) and 3.0093 dB
(with 8 times oversampling).
Therefore it is the object of the present invention to provide for a synchronization technique which bases on the known synchronization technique but which presents improved time domain signal properties to reduce the requirements for the hardware..
Note that in the present case only spectral lines with indices which are a multiple of 4 have nonzero amplitude. Other periodic natures can be generated by setting other multiples of the spectral lines to nonzero amplitudes.
Though the known synchronization scheme is very effective, it provides for disadvantage regarding the time domain signal properties.
Summary of the Invention For OFDM (or in general multicarrier signals) the signal. envelope fluctuation (named Peak-to-Average-Power-Ratio=PAPR) is of great concern. A large PAPR results in poor transmission (due to nonlinear distortion effects of the power amplifier) and other signal limiting components in the transmission system (e.g. limited dynamic range of the AD converter) .
For synchronization sequences it is even more desirable to have signals with a low PAPR in order to accelerate the receiver AGC (automatic gain control) locking and adjusting the reference signal value for the A/D converter (the whole dynamic range of the incoming signal should be covered by the A/D converter resolution without any overflow/underflow).
Figures 8a, 8b show the "absolute" (sq~ In*+Quad *Quad ~) value of the resulting time domain signal waveform with the sequences proposed by Lucent Technologies.
Oversampling (8*) was considered in order to ensure the peak was captured correctly using the limited 64-point IFFT.
Figures 8c, 8d show the real and imaginary part of the resulting transmitted time domain waveform. The resulting PAPR is 2.9991 dB (no oversampling) and 3.0093 dB
(with 8 times oversampling).
Therefore it is the object of the present invention to provide for a synchronization technique which bases on the known synchronization technique but which presents improved time domain signal properties to reduce the requirements for the hardware..
According to the present invention therefore a method for generating synchronization bursts for OFDM transmission systems is provided. Symbols of a predefined symbol sequence are mapped according to a predefined mapping scheme on subcarriers of the OFDM system wherein the symbols of the predefined symbol sequence represent subcarriers with nonzero amplitudes. A synchronization burst is generated by inverse fast Fourier transforming the subcarriers mapped with a predefined symbol sequence.
According to the present invention the predefined symbol sequence is optimized such that the envelope fluctuation of the time domain signal (Peak-to-average-power-ratio) is minimized.
The predefined symbol sequence can be chosen such that the following equations are satisfied for all symbols of the predefined symbol sequence:
n=2m, C~_1= ~C~_.~
n being the number of symbols of the predefined symbol sequence, m being an integer larger than one, C being the symbol value, and i being an integer running from 1 to m.
The mapping of the symbols of the predefined symbol sequence and the Inverse Fast Fourier Transform can be set such that the resulting time domain signal of the synchronization burst represents a periodic nature.
Alternatively the mapping of the symbols of the predefined symbol sequence and the Inverse Fast Fourier Transform is set such that one burst part of the synchronization burst in the time domain is generated and the periodic nature of the synchronization burst in the time domain is achieved by copying the one burst part.
The number of symbols of a symbol sequence (n) can for example be 12.
The above equations define generally the symbol sequences according to the present invention. The predefined symbol sequence can therefore be for example:
A A A -A -A -A -A A -A -A A -A, wherein A is a complex value.
Alternatively the predefined symbol sequence can be:
A -A A A -A A A A A -A -A -A, wherein A is a complex value.
According to the present invention the predefined symbol sequence is optimized such that the envelope fluctuation of the time domain signal (Peak-to-average-power-ratio) is minimized.
The predefined symbol sequence can be chosen such that the following equations are satisfied for all symbols of the predefined symbol sequence:
n=2m, C~_1= ~C~_.~
n being the number of symbols of the predefined symbol sequence, m being an integer larger than one, C being the symbol value, and i being an integer running from 1 to m.
The mapping of the symbols of the predefined symbol sequence and the Inverse Fast Fourier Transform can be set such that the resulting time domain signal of the synchronization burst represents a periodic nature.
Alternatively the mapping of the symbols of the predefined symbol sequence and the Inverse Fast Fourier Transform is set such that one burst part of the synchronization burst in the time domain is generated and the periodic nature of the synchronization burst in the time domain is achieved by copying the one burst part.
The number of symbols of a symbol sequence (n) can for example be 12.
The above equations define generally the symbol sequences according to the present invention. The predefined symbol sequence can therefore be for example:
A A A -A -A -A -A A -A -A A -A, wherein A is a complex value.
Alternatively the predefined symbol sequence can be:
A -A A A -A A A A A -A -A -A, wherein A is a complex value.
5 Alternatively the following predefined symbol sequence can be used:
A B -A B -A -B B A -B A -B -A, wherein A, B are complex values.
As a further alternative the following sequence can be used:
A -B -A -B -A B -B A B A B -A, wherein A, B are complex values.
According to the present invention furthermore a method for synchronizing wireless OFDM systems is provided, wherein a synchronization burst is generated according to a method as set forth above and the synchronization burst is transmitted respectively before the transmission of data fields.
Thereby the time domain signals of the synchronization burst can be precomputed and stored in a memory, such that the computation of the time domain signal of the burst is only effected once.
According to the present invention furthermore a OFDM transmitter is provided comprising a mapping unit for mapping the symbols of a predefined symbols sequence according to a predefined mapping scheme on subcarriers of the OFDM system, wherein the symbols of a predefined symbols sequence represent the subcarriers of the OFDM system with nonzero amplitudes. Furthermore an inverse fast Fourier transforming unit is provided for generating a synchronization burst by inverse fast Fourier transforming the subcarriers of the OFDM mapped with said predefined symbols sequence. The mapping unit thereby is designed such that the resulting time domain signal of the synchronization burst represents a periodic nature. The mapping unit according to the present invention uses a predefined symbol sequence which is such that the envelope fluctuation of the time domain signal of the synchronization burst is minimized.
According to the present invention furthermore a mobile communications device such as set forth above is used.
brief nP~crint»n ~f the Drawings With reference to the figures of the enclosed drawings referred embodiments of the present invention will now be explained.
A B -A B -A -B B A -B A -B -A, wherein A, B are complex values.
As a further alternative the following sequence can be used:
A -B -A -B -A B -B A B A B -A, wherein A, B are complex values.
According to the present invention furthermore a method for synchronizing wireless OFDM systems is provided, wherein a synchronization burst is generated according to a method as set forth above and the synchronization burst is transmitted respectively before the transmission of data fields.
Thereby the time domain signals of the synchronization burst can be precomputed and stored in a memory, such that the computation of the time domain signal of the burst is only effected once.
According to the present invention furthermore a OFDM transmitter is provided comprising a mapping unit for mapping the symbols of a predefined symbols sequence according to a predefined mapping scheme on subcarriers of the OFDM system, wherein the symbols of a predefined symbols sequence represent the subcarriers of the OFDM system with nonzero amplitudes. Furthermore an inverse fast Fourier transforming unit is provided for generating a synchronization burst by inverse fast Fourier transforming the subcarriers of the OFDM mapped with said predefined symbols sequence. The mapping unit thereby is designed such that the resulting time domain signal of the synchronization burst represents a periodic nature. The mapping unit according to the present invention uses a predefined symbol sequence which is such that the envelope fluctuation of the time domain signal of the synchronization burst is minimized.
According to the present invention furthermore a mobile communications device such as set forth above is used.
brief nP~crint»n ~f the Drawings With reference to the figures of the enclosed drawings referred embodiments of the present invention will now be explained.
Fig. 1 shows schematically a transmitter according to the present invention, Fig. 2 shows an alternative embodiment for a transmitter according to the present invention, Fig.3 shows an alternative mapping scheme according to the present invention, Fig. 4a to 4d show the time domain signal properties achieved with the synchronization symbol structure using OFDM based transmission according to the present invention, Fig. Sa to Sd show the time domain signal properties of synchronization symbol structures according to alternative embodiments of the present invention, Fig. 6 shows a synchronization preamble structure known from the prior art, Fig. 7 shows an IFFT mapping according to the prior art, and Fig. 8a to 8d show the time domain properties of the synchronization symbol structure according to the prior art, Fig. 9a and 9b show the time domain properties, particularly the dynamic range of the synchronization symbol structure according to the prior art, and Fig. l0a and lOb show the time domain properties of the synchronization symbol structure according to further alternative embodiments of the present invention, De ailed Description of the Preferred Embodiments According to the present invention the time domain synchronization burst structure as shown in Fig. 6 is maintained. The IFFT mapping as shown in Fig. 7 can be maintained or alternatively the IFFT mapping according to figure 3 can be used. The symbol sequences mapped to the subcarriers are optimized to sequences which result in a lower PAPR.
According to the present invention a short OFDM symbol (tl , . . . t6) consists of 12 phase-modulated subcarriers.
Se A A A -A -A -A -A A -A -A A -A
Se A -A A A -A A A A A -A -A -A
1 ' Se A B -A B -A -B B A -B A -B -A
Se A -B -A -B -A B -B A B A B ~-A
with A=exp(j*2+~c*cp,,) and B=A*exp(j ~ )=exp(j2n*cpA+j ~ ) and 0.0Scp,, <1Ø
Generally the predefined symbol sequence therefore is chosen such that the envelope fluctuation of the time domain signal of the synchronization burst is minimized.
Therefore generally the predefined symbol sequence is set such that the following equations are satisfied for all symbols for the predefined symbol sequence:
n=2m, ~ _ ~C~_i wherein n is a number of symbols of the predefined symbol sequence, m is an integer larger than 1, c is the symbol value, and i is an integer value running from 1 to m.
In the following the time domain signal properties of the new sequences according to the present invention will be shown with reference to Fig. 4a to 4d and Fig.
Sa to Sd.
For simplicity we use in our demonstration the classical quadriphase symbol alphabet, S= ~ (~1~~~, (this corresponds to cpA= 0.125) S mbol _ A exp(7 4 ) 1 (+1+~~
Se A A A -A -A -A -A A -A -A A -A
Se A -A A A -A A A A A -A -A -A
1 ' Se A B -A B -A -B B A -B A -B -A
Se A -B -A -B -A B -B A B A B ~-A
with A=exp(j*2+~c*cp,,) and B=A*exp(j ~ )=exp(j2n*cpA+j ~ ) and 0.0Scp,, <1Ø
Generally the predefined symbol sequence therefore is chosen such that the envelope fluctuation of the time domain signal of the synchronization burst is minimized.
Therefore generally the predefined symbol sequence is set such that the following equations are satisfied for all symbols for the predefined symbol sequence:
n=2m, ~ _ ~C~_i wherein n is a number of symbols of the predefined symbol sequence, m is an integer larger than 1, c is the symbol value, and i is an integer value running from 1 to m.
In the following the time domain signal properties of the new sequences according to the present invention will be shown with reference to Fig. 4a to 4d and Fig.
Sa to Sd.
For simplicity we use in our demonstration the classical quadriphase symbol alphabet, S= ~ (~1~~~, (this corresponds to cpA= 0.125) S mbol _ A exp(7 4 ) 1 (+1+~~
-A -exP(I 4 )=exp(j 54 ~ (-1 J~
) B exp(j 4 +j 2 )=exp~
4 ) (-1 +J~
-exp(I 4 )=exp(I 4 (+1 >) ) Table 1: Complex symbol mapping Fig. Sa and Sb thereby show the time domain signal (magnitude) when using the optimized sequence according to the present invention in the case of no oversampling/8 times oversampling is effected.
PAPR (in decibel) is limited to 2.059 (even when using a time domain oversampling to capture the actual peak).
Fig. Sc and Sd show the in-phase and quadrature-phase component, respectively, of the resulting wave form. It is clearly visible that the full symbol consists of four repetitions of a short sequence.
Fig. Sa to Sd show graphics corresponding to Fig. 4a to 4d for the other proposed sequences Sl, S2 and S3.
Further simulations have shown that not only the PAPR can be optimized but also the dynamic range of the signal should be minimized. Therefore another four sequences, with achieve a small PAPR and at the same time a small overall dynamic range are proposed further below.
Using the sequence as proposed in the state of the art the PAPR is 3.01 dB and the dynamic range (defined as the ratio of the peak power to the minimum power) is 30.82 dB (see figures 9a and 9b).
Using the sequences according to the present invention and as described above the PAPR is reduced to 2.06 dB, however, the dynamic range is increased as the signal power is '0' at some points.
Therefore the following four sequences are proposed as a further embodiment of the present invention:
) B exp(j 4 +j 2 )=exp~
4 ) (-1 +J~
-exp(I 4 )=exp(I 4 (+1 >) ) Table 1: Complex symbol mapping Fig. Sa and Sb thereby show the time domain signal (magnitude) when using the optimized sequence according to the present invention in the case of no oversampling/8 times oversampling is effected.
PAPR (in decibel) is limited to 2.059 (even when using a time domain oversampling to capture the actual peak).
Fig. Sc and Sd show the in-phase and quadrature-phase component, respectively, of the resulting wave form. It is clearly visible that the full symbol consists of four repetitions of a short sequence.
Fig. Sa to Sd show graphics corresponding to Fig. 4a to 4d for the other proposed sequences Sl, S2 and S3.
Further simulations have shown that not only the PAPR can be optimized but also the dynamic range of the signal should be minimized. Therefore another four sequences, with achieve a small PAPR and at the same time a small overall dynamic range are proposed further below.
Using the sequence as proposed in the state of the art the PAPR is 3.01 dB and the dynamic range (defined as the ratio of the peak power to the minimum power) is 30.82 dB (see figures 9a and 9b).
Using the sequences according to the present invention and as described above the PAPR is reduced to 2.06 dB, however, the dynamic range is increased as the signal power is '0' at some points.
Therefore the following four sequences are proposed as a further embodiment of the present invention:
The symbol sequence is C0, C 1, . . . . , C 11 and the mapping is:
S=2* { C00, 0, 0, 0, CO1, 0, 0, 0, C02, 0, 0, 0, C03, 0, 0, 0, C04, 0, 0, 0, COS, 0, 0, 0, 0, 0, 0, 0, C06, 0, 0, 0, C07, 0, 0, 0, C08, 0, 0, 0, C09, 0, 0, 0, C10, 0, 0, 0, C11 }
l 10 11 Se -AltoA A A A -A -A A -A -A A -A A
Se -AltlA -A A -A -A A -A -A A A A A
Se -Alt2A B -A -B -A -B -B -A -B -A B A
Se -Alt3A -B -A B -A B B -A B -A -B A
with A = exp (j*2*~*~p,4) and B = A * exp (j 2 ) = exp (j2~'''~pA + j ~ ) and 0.0 <_ ~pA<1Ø
Using these sequences the PAPR is reduced to 2.24 dB and the dynamic range is limited to 7.01 dB as it is shown in figures 10 a and lOb.
The advantages are the same as described before, however, the clipping problem is further reduced due to the very limited dynamic range of the signal.
With reference to Fig. 1 and 2 possible implementations of a transmitter according to the present invention will now be explained.
In the transmitter the sync symbol data 1 are prepared and mapped in a IFFT
mapping unit 2 to the appropriate IFFT points. The subcarriers of the OFDM system are transformed by a IFFT unit 3 and then the time domain signal is extended in a time extension unit 4 by copying parts of the signals (for example, tl, t2 are copied to t5, t6). The time extended signal is then sent to the I/Q modulator 5.
As shown in Fig. 2 alternatively the time domain signal can be precomputed once in a computation unit 7 and then be stored in a memory 6 for the precomputed sample for the time signal. Then the time domain signal of the synchronization burst can be sent to the modulator 5 directly from the memory 6.
With reference to figure 3 a modified IFFT mapping scheme will now be explained.
According to this scheme, the principle of setting only every fourth subcarrier of the OFDM system to a non-zero amplitude (see figure 7) is abandoned. Therefore the time 1~
domain signal achieved according to the mapping scheme of figure 3 will not present a periodic nature.
The IFFT size is now only 16 (instead of 64 as it is the case in figure 7).
Only one of the bursts tl, t2, ....t6 will be generated. The other bursts can be generated by copying to retain the periodic nature of the synchronization time domain signal necessary for the correlation and synchronization on the receiving side. Therefore for example the time extension unit 4 can perform the copying of the 16-sample burst tl generated by the IFFT 16 according to figure 7 to the other burst t2, t3, ...t6. Obviously the mapping scheme according to figure 3 reduces the computing effort necessary for the IFFT. The periodic nature of the time domain signal of the SYNCH bursts is therefore no longer achieved by the IFFT step, but by copying the burst tl generated with the simplified IFFT mapping scheme.
The mapping scheme shown in figure 3 is also advantageous in combination with the precomputing technique shown in figure 2.
According to the present invention therefore a synchronization burst structure to be used in high speed wireless transmission systems is proposed. The synchronization burst is constructed using especially designed OFDM symbols and time domain repetitions. The resulting synchronization burst achieves a high timing detection and frequency offset estimation accuracy. Furthermore the burst is optimized to achieve a very low envelope fluctuation (Low peak-to-average-power-ratio) to reduce the complexity on the receiver and to reduce time and frequency acquisition time at the receiver.
Therefore the synchronization performance can further be improved. As with the scheme according to the present invention the envelope of the OFDM based synchronization burst in the time domain is reduced, the AGC pool-in speed at the receiver can be improved and an accurate time and frequency synchronization can be achieved. Furthermore the synchronization complexity on the receiver side can be reduced due to the reduced resolution requirements necessary due to reduced envelope fluctuation.
The advantages of the present invention can be set forth as following:
~ An OFDM based SYNCH symbol with a reduced Peak-to-Average-Power-Ratio (PARP) is proposed, ~ Improved synchronization performance (compared to the state of the art proposal), ~ Reduced AGC (automatic gain control) pull-in time due to reduced dynamic range of the SYNCH burst, ~ Improved AGC settlement (AGC has to adjust to a incoming signal level that later on now overflow/underflow in the AD happens. The reduced dynamic range of the SYNCH burst help to fmd this reference level more accurate), ~ Reduced synchronization detection complexity on the receiver (reduced resolution necessary due to reduced envelope fluctuation).
S=2* { C00, 0, 0, 0, CO1, 0, 0, 0, C02, 0, 0, 0, C03, 0, 0, 0, C04, 0, 0, 0, COS, 0, 0, 0, 0, 0, 0, 0, C06, 0, 0, 0, C07, 0, 0, 0, C08, 0, 0, 0, C09, 0, 0, 0, C10, 0, 0, 0, C11 }
l 10 11 Se -AltoA A A A -A -A A -A -A A -A A
Se -AltlA -A A -A -A A -A -A A A A A
Se -Alt2A B -A -B -A -B -B -A -B -A B A
Se -Alt3A -B -A B -A B B -A B -A -B A
with A = exp (j*2*~*~p,4) and B = A * exp (j 2 ) = exp (j2~'''~pA + j ~ ) and 0.0 <_ ~pA<1Ø
Using these sequences the PAPR is reduced to 2.24 dB and the dynamic range is limited to 7.01 dB as it is shown in figures 10 a and lOb.
The advantages are the same as described before, however, the clipping problem is further reduced due to the very limited dynamic range of the signal.
With reference to Fig. 1 and 2 possible implementations of a transmitter according to the present invention will now be explained.
In the transmitter the sync symbol data 1 are prepared and mapped in a IFFT
mapping unit 2 to the appropriate IFFT points. The subcarriers of the OFDM system are transformed by a IFFT unit 3 and then the time domain signal is extended in a time extension unit 4 by copying parts of the signals (for example, tl, t2 are copied to t5, t6). The time extended signal is then sent to the I/Q modulator 5.
As shown in Fig. 2 alternatively the time domain signal can be precomputed once in a computation unit 7 and then be stored in a memory 6 for the precomputed sample for the time signal. Then the time domain signal of the synchronization burst can be sent to the modulator 5 directly from the memory 6.
With reference to figure 3 a modified IFFT mapping scheme will now be explained.
According to this scheme, the principle of setting only every fourth subcarrier of the OFDM system to a non-zero amplitude (see figure 7) is abandoned. Therefore the time 1~
domain signal achieved according to the mapping scheme of figure 3 will not present a periodic nature.
The IFFT size is now only 16 (instead of 64 as it is the case in figure 7).
Only one of the bursts tl, t2, ....t6 will be generated. The other bursts can be generated by copying to retain the periodic nature of the synchronization time domain signal necessary for the correlation and synchronization on the receiving side. Therefore for example the time extension unit 4 can perform the copying of the 16-sample burst tl generated by the IFFT 16 according to figure 7 to the other burst t2, t3, ...t6. Obviously the mapping scheme according to figure 3 reduces the computing effort necessary for the IFFT. The periodic nature of the time domain signal of the SYNCH bursts is therefore no longer achieved by the IFFT step, but by copying the burst tl generated with the simplified IFFT mapping scheme.
The mapping scheme shown in figure 3 is also advantageous in combination with the precomputing technique shown in figure 2.
According to the present invention therefore a synchronization burst structure to be used in high speed wireless transmission systems is proposed. The synchronization burst is constructed using especially designed OFDM symbols and time domain repetitions. The resulting synchronization burst achieves a high timing detection and frequency offset estimation accuracy. Furthermore the burst is optimized to achieve a very low envelope fluctuation (Low peak-to-average-power-ratio) to reduce the complexity on the receiver and to reduce time and frequency acquisition time at the receiver.
Therefore the synchronization performance can further be improved. As with the scheme according to the present invention the envelope of the OFDM based synchronization burst in the time domain is reduced, the AGC pool-in speed at the receiver can be improved and an accurate time and frequency synchronization can be achieved. Furthermore the synchronization complexity on the receiver side can be reduced due to the reduced resolution requirements necessary due to reduced envelope fluctuation.
The advantages of the present invention can be set forth as following:
~ An OFDM based SYNCH symbol with a reduced Peak-to-Average-Power-Ratio (PARP) is proposed, ~ Improved synchronization performance (compared to the state of the art proposal), ~ Reduced AGC (automatic gain control) pull-in time due to reduced dynamic range of the SYNCH burst, ~ Improved AGC settlement (AGC has to adjust to a incoming signal level that later on now overflow/underflow in the AD happens. The reduced dynamic range of the SYNCH burst help to fmd this reference level more accurate), ~ Reduced synchronization detection complexity on the receiver (reduced resolution necessary due to reduced envelope fluctuation).
Claims (8)
1. A method for generating synchronization bursts for OFDM transmission systems, comprising the following steps:
mapping the symbols of a predefined symbol sequence according to a predefined mapping scheme on subcarriers S of the OFDM system, wherein the symbols of the predefined symbol sequence represent subcarriers of the OFDM system with non-zero-amplitude; and generating a synchronization burst by Inverse Fourier Transforming the subcarriers S of the OFDM system mapped with the symbols of said predefined symbol sequence, characterized in that the symbols of the predefined symbol sequence can be expressed as A-AA-A-AA-A-AAAAA, A being a complex value.
mapping the symbols of a predefined symbol sequence according to a predefined mapping scheme on subcarriers S of the OFDM system, wherein the symbols of the predefined symbol sequence represent subcarriers of the OFDM system with non-zero-amplitude; and generating a synchronization burst by Inverse Fourier Transforming the subcarriers S of the OFDM system mapped with the symbols of said predefined symbol sequence, characterized in that the symbols of the predefined symbol sequence can be expressed as A-AA-A-AA-A-AAAAA, A being a complex value.
2. A method for synchronizing wireless OFDM systems, characterized by the steps of generating a synchronization burst according to a method according to claim 1, and transmitting the synchronization burst.
3. A method according to claim 2, characterized in that the time domain signal of the synchronization burst is precomputed and stored in a memory.
4. An OFDM transmitter, comprising:
a unit for mapping the symbols of a predefined symbol sequence according to a predefined mapping scheme on subcarriers of the OFDM system, wherein the symbols of the predefined symbol sequence represent subcarriers of the OFDM system with non-zero-amplitude, and a unit for generating a synchronization burst by Inverse Fourier Transforming the subcarriers of the OFDM system mapped with the symbols of said predefined symbol sequence, characterized in that the mapping unit is designed to modulate the subcarriers using the following predefined symbol sequence:
A-AA-A-AA-A-AAAAA, A being a complex value.
a unit for mapping the symbols of a predefined symbol sequence according to a predefined mapping scheme on subcarriers of the OFDM system, wherein the symbols of the predefined symbol sequence represent subcarriers of the OFDM system with non-zero-amplitude, and a unit for generating a synchronization burst by Inverse Fourier Transforming the subcarriers of the OFDM system mapped with the symbols of said predefined symbol sequence, characterized in that the mapping unit is designed to modulate the subcarriers using the following predefined symbol sequence:
A-AA-A-AA-A-AAAAA, A being a complex value.
5. An OFDM transmitter according to claim 4, characterized by a time extension unit copying the burst part to achieve a periodic nature of the time domain signal.
6. An OFDM transmitter according to claim 4, characterized by a processing unit for precomputing the time domain signal of the synchronization burst and a memory for storing the precomputed time domain signal of the synchronization burst.
7. A mobile communications device, comprising a transmitter according to claim 4.
8. A synchronization burst signal for synchronizing OFDM systems generated by a method according to claim 1.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP99100263 | 1999-01-08 | ||
| EP99100263.5 | 1999-01-08 | ||
| EP99103379A EP1018827B1 (en) | 1999-01-08 | 1999-02-22 | Synchronisation structure for OFDM system |
| EP99103379.6 | 1999-02-22 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2291847A1 CA2291847A1 (en) | 2000-07-08 |
| CA2291847C true CA2291847C (en) | 2005-09-13 |
Family
ID=26152852
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002291847A Expired - Lifetime CA2291847C (en) | 1999-01-08 | 1999-12-06 | Synchronization symbol structure using ofdm based transmission method |
Country Status (5)
| Country | Link |
|---|---|
| US (8) | US6654339B1 (en) |
| EP (5) | EP1705852B1 (en) |
| JP (1) | JP4050437B2 (en) |
| KR (1) | KR100712865B1 (en) |
| CA (1) | CA2291847C (en) |
Families Citing this family (64)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1705852B1 (en) | 1999-01-08 | 2010-02-10 | Sony Deutschland Gmbh | Synchronisation symbol structure for OFDM system |
| EP1061705B1 (en) | 1999-06-16 | 2004-12-22 | Sony International (Europe) GmbH | Optimized synchronization preamble structure for OFDM system |
| EP1720277B1 (en) | 2000-07-05 | 2017-09-27 | Sony Deutschland Gmbh | Pilot pattern design for multiple antennas in an OFDM system |
| US7295509B2 (en) | 2000-09-13 | 2007-11-13 | Qualcomm, Incorporated | Signaling method in an OFDM multiple access system |
| US9130810B2 (en) | 2000-09-13 | 2015-09-08 | Qualcomm Incorporated | OFDM communications methods and apparatus |
| US6754170B1 (en) * | 2000-09-29 | 2004-06-22 | Symbol Technologies, Inc. | Timing synchronization in OFDM communications receivers |
| US6950475B1 (en) * | 2000-12-11 | 2005-09-27 | Cisco Technology, Inc. | OFDM receiver clock synchronization system |
| DE60320956D1 (en) * | 2002-03-07 | 2008-06-26 | Alvarion Ltd | HIERARCHICAL PREAMBLE STRUCTURES FOR OFDMA BASED ON COMPLEMENTARY SEQUENCES |
| US20040066740A1 (en) * | 2002-09-30 | 2004-04-08 | Samsung Electronics Co., Ltd. | Apparatus and method for generating preamble sequence in a OFDM communication system |
| WO2004039026A1 (en) * | 2002-10-23 | 2004-05-06 | Samsung Electronics Co., Ltd. | Apparatus and method for generating a preamble sequence in an ofdm communication system |
| KR100557159B1 (en) * | 2002-11-30 | 2006-03-03 | 삼성전자주식회사 | Apparatus for generating preamble sequence in orthogonal frequency division multiplexing system and method thereof |
| KR100905572B1 (en) * | 2002-12-03 | 2009-07-02 | 삼성전자주식회사 | Apparatus and method for generating preamble sequence in a communication system using orthogonal frequency division multiplexing scheme |
| KR100670417B1 (en) | 2004-04-28 | 2007-01-16 | 삼성전자주식회사 | Method and apparatus for generating of the preamble sequence for an adaptive antenna system in an orthogonal frequency division multiple access communication system |
| US9148256B2 (en) | 2004-07-21 | 2015-09-29 | Qualcomm Incorporated | Performance based rank prediction for MIMO design |
| US9137822B2 (en) | 2004-07-21 | 2015-09-15 | Qualcomm Incorporated | Efficient signaling over access channel |
| US7961828B2 (en) * | 2004-10-06 | 2011-06-14 | Motorola Mobility, Inc. | Sync bursts frequency offset compensation |
| CN1780276B (en) * | 2004-11-25 | 2012-01-04 | 都科摩（北京）通信技术研究中心有限公司 | Combined time synchronizing and frequency bias evaluation and evaluating device for orthogonal frequency division duplex system |
| US9246560B2 (en) | 2005-03-10 | 2016-01-26 | Qualcomm Incorporated | Systems and methods for beamforming and rate control in a multi-input multi-output communication systems |
| US9154211B2 (en) | 2005-03-11 | 2015-10-06 | Qualcomm Incorporated | Systems and methods for beamforming feedback in multi antenna communication systems |
| US8446892B2 (en) | 2005-03-16 | 2013-05-21 | Qualcomm Incorporated | Channel structures for a quasi-orthogonal multiple-access communication system |
| US9143305B2 (en) | 2005-03-17 | 2015-09-22 | Qualcomm Incorporated | Pilot signal transmission for an orthogonal frequency division wireless communication system |
| US9520972B2 (en) | 2005-03-17 | 2016-12-13 | Qualcomm Incorporated | Pilot signal transmission for an orthogonal frequency division wireless communication system |
| US9461859B2 (en) | 2005-03-17 | 2016-10-04 | Qualcomm Incorporated | Pilot signal transmission for an orthogonal frequency division wireless communication system |
| JP4429945B2 (en) | 2005-03-23 | 2010-03-10 | 株式会社エヌ・ティ・ティ・ドコモ | MIMO multiplex communication apparatus and signal separation method |
| US9184870B2 (en) | 2005-04-01 | 2015-11-10 | Qualcomm Incorporated | Systems and methods for control channel signaling |
| US9036538B2 (en) | 2005-04-19 | 2015-05-19 | Qualcomm Incorporated | Frequency hopping design for single carrier FDMA systems |
| US9408220B2 (en) | 2005-04-19 | 2016-08-02 | Qualcomm Incorporated | Channel quality reporting for adaptive sectorization |
| US8611284B2 (en) | 2005-05-31 | 2013-12-17 | Qualcomm Incorporated | Use of supplemental assignments to decrement resources |
| US8879511B2 (en) | 2005-10-27 | 2014-11-04 | Qualcomm Incorporated | Assignment acknowledgement for a wireless communication system |
| US8565194B2 (en) | 2005-10-27 | 2013-10-22 | Qualcomm Incorporated | Puncturing signaling channel for a wireless communication system |
| US8462859B2 (en) | 2005-06-01 | 2013-06-11 | Qualcomm Incorporated | Sphere decoding apparatus |
| US8599945B2 (en) | 2005-06-16 | 2013-12-03 | Qualcomm Incorporated | Robust rank prediction for a MIMO system |
| US9179319B2 (en) | 2005-06-16 | 2015-11-03 | Qualcomm Incorporated | Adaptive sectorization in cellular systems |
| WO2007015490A1 (en) * | 2005-08-03 | 2007-02-08 | National University Corporation NARA Institute of Science and Technology | Transmitter and receiver |
| US8885628B2 (en) | 2005-08-08 | 2014-11-11 | Qualcomm Incorporated | Code division multiplexing in a single-carrier frequency division multiple access system |
| US20070041457A1 (en) | 2005-08-22 | 2007-02-22 | Tamer Kadous | Method and apparatus for providing antenna diversity in a wireless communication system |
| US9209956B2 (en) | 2005-08-22 | 2015-12-08 | Qualcomm Incorporated | Segment sensitive scheduling |
| US8644292B2 (en) | 2005-08-24 | 2014-02-04 | Qualcomm Incorporated | Varied transmission time intervals for wireless communication system |
| US9136974B2 (en) | 2005-08-30 | 2015-09-15 | Qualcomm Incorporated | Precoding and SDMA support |
| US8045512B2 (en) | 2005-10-27 | 2011-10-25 | Qualcomm Incorporated | Scalable frequency band operation in wireless communication systems |
| US9172453B2 (en) | 2005-10-27 | 2015-10-27 | Qualcomm Incorporated | Method and apparatus for pre-coding frequency division duplexing system |
| US9088384B2 (en) | 2005-10-27 | 2015-07-21 | Qualcomm Incorporated | Pilot symbol transmission in wireless communication systems |
| US9225488B2 (en) | 2005-10-27 | 2015-12-29 | Qualcomm Incorporated | Shared signaling channel |
| US8582509B2 (en) | 2005-10-27 | 2013-11-12 | Qualcomm Incorporated | Scalable frequency band operation in wireless communication systems |
| US8477684B2 (en) | 2005-10-27 | 2013-07-02 | Qualcomm Incorporated | Acknowledgement of control messages in a wireless communication system |
| US9225416B2 (en) | 2005-10-27 | 2015-12-29 | Qualcomm Incorporated | Varied signaling channels for a reverse link in a wireless communication system |
| US8693405B2 (en) | 2005-10-27 | 2014-04-08 | Qualcomm Incorporated | SDMA resource management |
| US9144060B2 (en) | 2005-10-27 | 2015-09-22 | Qualcomm Incorporated | Resource allocation for shared signaling channels |
| US9210651B2 (en) | 2005-10-27 | 2015-12-08 | Qualcomm Incorporated | Method and apparatus for bootstraping information in a communication system |
| US8582548B2 (en) | 2005-11-18 | 2013-11-12 | Qualcomm Incorporated | Frequency division multiple access schemes for wireless communication |
| US8831607B2 (en) | 2006-01-05 | 2014-09-09 | Qualcomm Incorporated | Reverse link other sector communication |
| CN1852281B (en) * | 2006-01-23 | 2010-06-09 | 北京邮电大学 | Synchronizing method for quadrature frequency division multiple access system |
| US7983143B2 (en) * | 2006-02-08 | 2011-07-19 | Motorola Mobility, Inc. | Method and apparatus for initial acquisition and cell search for an OFDMA system |
| US7911935B2 (en) | 2006-02-08 | 2011-03-22 | Motorola Mobility, Inc. | Method and apparatus for interleaving sequence elements of an OFDMA synchronization channel |
| US7961591B2 (en) | 2006-03-20 | 2011-06-14 | Fujitsu Limited | OFDM communication systems, transmitters and methods |
| EP1838061B1 (en) * | 2006-03-20 | 2009-03-11 | Fujitsu Ltd. | Symbol to subcarrier allocation in OFDM communication systems and methods |
| CN101022438B (en) * | 2006-03-30 | 2011-12-14 | 北京新岸线移动通信技术有限公司 | Compatible DAB digital broadcasting receiver carrier synchronizing method and system |
| ATE495616T2 (en) | 2007-05-02 | 2011-01-15 | Huawei Tech Co Ltd | METHOD AND DEVICE FOR SETTING UP A SYNCHRONIZING SIGNAL IN A SWITCHING SYSTEM |
| CN101083508B (en) * | 2007-07-19 | 2010-06-02 | 清华大学 | OFDM modulation system performance test method based on low peak-valley ratio sequence transmission |
| CN101420411B (en) * | 2008-12-05 | 2011-02-09 | 航天恒星科技有限公司 | Fast carrier capture method with low signal-noise ratio |
| CN106685876B (en) * | 2016-11-14 | 2021-08-10 | 西南石油大学 | Multi-dimensional PTS method for reducing peak-to-average power ratio of OFDM system |
| ES2895680T3 (en) * | 2017-11-07 | 2022-02-22 | Siemens Ag | Procedure for the synchronization of transmitting and receiving units in a multicarrier signal transmission |
| CN110535795B (en) * | 2018-05-24 | 2021-11-05 | 中兴通讯股份有限公司 | Signal processing method and device |
| CN113315730B (en) * | 2021-05-24 | 2022-12-27 | 扬州大学 | Time-frequency synchronization method based on filter multi-carrier system |
Family Cites Families (58)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5450456A (en) * | 1993-11-12 | 1995-09-12 | Daimler Benz Ag | Method and arrangement for measuring the carrier frequency deviation in a multi-channel transmission system |
| US5732113A (en) * | 1996-06-20 | 1998-03-24 | Stanford University | Timing and frequency synchronization of OFDM signals |
| EP0836303B1 (en) * | 1996-10-14 | 2003-02-26 | Ntt Mobile Communications Network Inc. | Method and apparatus for reduction of peak to average power ratio |
| GB9625094D0 (en) * | 1996-12-03 | 1997-01-22 | Ensigma Ltd | Apparatus and methods for measuring coarse frequency offset of a multi-carrier signal |
| US5990176A (en) | 1997-01-27 | 1999-11-23 | Abbott Laboratories | Fluoroether compositions and methods for inhibiting their degradation in the presence of a Lewis acid |
| US6005840A (en) * | 1997-04-01 | 1999-12-21 | Lucent Technologies Inc. | Complementary encoding and modulation system for use in an orthogonal frequency division multiplexing transmitter system and method thereof |
| DE19733825A1 (en) * | 1997-08-05 | 1999-02-11 | Siemens Ag | Method and arrangement for combined measurement of the start of a data block and the carrier frequency offset in a multicarrier transmission system for irregular transmission of data blocks |
| EP0899923A1 (en) | 1997-08-29 | 1999-03-03 | Sony International (Europe) GmbH | Transmission of power control signals in a multicarrier modulation system |
| DE69737018T2 (en) | 1997-09-04 | 2007-06-28 | Sony Deutschland Gmbh | Transmission system for OFDM signals with optimized synchronization |
| EP1720311B1 (en) | 1997-11-05 | 2011-06-01 | Sony Deutschland Gmbh | Synchronisation of digital communication systems |
| EP0915586B1 (en) | 1997-11-07 | 2005-05-18 | Sony International (Europe) GmbH | Multicarrier transmission, compatible with the existing GSM system |
| DE69825148T2 (en) | 1997-12-18 | 2005-02-10 | Sony International (Europe) Gmbh | DIRECT RECEIVER WITH N GATE |
| CN1143468C (en) | 1998-02-13 | 2004-03-24 | 索尼公司 | Transmitting and receiving methods and devices |
| EP0938193A1 (en) | 1998-02-18 | 1999-08-25 | Sony International (Europe) GmbH | Header structure for TDD systems |
| EP0939527B1 (en) | 1998-02-18 | 2007-12-05 | Sony Deutschland GmbH | Mapping of multicarrier signals into GSM time slots |
| EP0938208A1 (en) | 1998-02-22 | 1999-08-25 | Sony International (Europe) GmbH | Multicarrier transmission, compatible with the existing GSM system |
| US6470055B1 (en) * | 1998-08-10 | 2002-10-22 | Kamilo Feher | Spectrally efficient FQPSK, FGMSK, and FQAM for enhanced performance CDMA, TDMA, GSM, OFDN, and other systems |
| EP0982905B1 (en) | 1998-08-28 | 2005-08-10 | Sony International (Europe) GmbH | Universal PSK modulation apparatus and method |
| EP0984596A1 (en) | 1998-09-03 | 2000-03-08 | Sony International (Europe) GmbH | Adpative PSK system and timing offset compensation circuit |
| DE69837659T2 (en) | 1998-09-03 | 2007-12-27 | Sony Deutschland Gmbh | Blind detection of modulation |
| EP0987863B1 (en) | 1998-09-17 | 2005-04-06 | Sony International (Europe) GmbH | Soft decision method and apparatus for 8PSK demodulation |
| US6452987B1 (en) * | 1998-11-25 | 2002-09-17 | Lucent Technologies Inc. | Fast start-up in discrete multi-tone (DMT) based communications system |
| EP1006668B1 (en) | 1998-11-30 | 2011-01-05 | Sony Deutschland GmbH | Dual frequency band transceiver |
| EP1009098A1 (en) | 1998-12-10 | 2000-06-14 | Sony International (Europe) GmbH | Error correction using a turbo code and a CRC |
| DE69829757T2 (en) | 1998-12-18 | 2006-01-12 | Sony International (Europe) Gmbh | Three-gate circuit receiver |
| EP1705852B1 (en) | 1999-01-08 | 2010-02-10 | Sony Deutschland Gmbh | Synchronisation symbol structure for OFDM system |
| US8861622B2 (en) | 1999-02-24 | 2014-10-14 | Sony Deutschland Gmbh | Transmitting apparatus and method for a digital telecommunication system |
| EP1032157B1 (en) | 1999-02-24 | 2006-08-23 | Sony Deutschland GmbH | Receiving apparatus and synchronising method for a digital telecommunication system |
| EP1039661A1 (en) | 1999-03-03 | 2000-09-27 | Sony International (Europe) GmbH | Multicast channel for a CDMA system |
| EP1037481A1 (en) | 1999-03-15 | 2000-09-20 | Sony International (Europe) GmbH | Simultaneous transmission of random access bursts |
| ES2198811T3 (en) | 1999-04-12 | 2004-02-01 | Sony International (Europe) Gmbh | COMMUNICATION AND PROCEDURE DEVICE FOR DISTINGUISHING BETWEEN DIFFERENT TYPES OF GUSTS IN A DIGITAL TELECOMMUNICATIONS SYSTEM. |
| EP1505787B1 (en) | 1999-04-23 | 2006-10-18 | Sony Deutschland GmbH | Synchronization preamble in an OFDM system |
| DE69924978T2 (en) | 1999-05-27 | 2006-02-02 | Sony International (Europe) Gmbh | Down-converter and demodulator with a three-port circuit arrangement |
| DE69932705T2 (en) | 1999-06-16 | 2007-08-16 | Sony Deutschland Gmbh | Receiver with N gates |
| EP1061705B1 (en) | 1999-06-16 | 2004-12-22 | Sony International (Europe) GmbH | Optimized synchronization preamble structure for OFDM system |
| EP1065855A1 (en) | 1999-06-29 | 2001-01-03 | Sony International (Europe) GmbH | Adaptation of cyclic extensions in an OFDM communication system |
| EP1067675B1 (en) | 1999-07-08 | 2005-04-27 | Sony International (Europe) GmbH | Calibration of a N-port receiver |
| ATE441301T1 (en) | 1999-07-09 | 2009-09-15 | Sony Deutschland Gmbh | CELL RANGE EXTENSION IN RADIO COMMUNICATION SYSTEMS WITH DOWNWARD POWER CONTROL |
| EP1089445B1 (en) | 1999-09-29 | 2005-07-06 | Sony International (Europe) GmbH | Three port structure with modulated LO signal |
| KR20000000479A (en) * | 1999-10-27 | 2000-01-15 | 신창우 | Skin for wig |
| EP1120899B1 (en) | 2000-01-24 | 2003-09-17 | Sony International (Europe) GmbH | Demodulation structure and method |
| US7106821B2 (en) | 2000-03-15 | 2006-09-12 | Sony Corporation | Data modulation method, data modulation device and communication device |
| ATE370558T1 (en) | 2000-06-05 | 2007-09-15 | Sony Deutschland Gmbh | WIRELESS INTERIOR SYSTEM WITH ACTIVE REFLECTOR |
| EP1170916B1 (en) | 2000-07-05 | 2006-12-27 | Sony Deutschland GmbH | Channel estimator for OFDM system |
| EP1170917B1 (en) | 2000-07-06 | 2006-10-04 | Sony Deutschland GmbH | Method and device to provide an OFDM up-link using Time-Frequency interleaving |
| EP1178641B1 (en) | 2000-08-01 | 2007-07-25 | Sony Deutschland GmbH | Frequency reuse scheme for OFDM systems |
| EP1178640B1 (en) | 2000-08-01 | 2006-05-24 | Sony Deutschland GmbH | Device and method for channel estimating an OFDM system |
| DK1207662T3 (en) | 2000-11-20 | 2003-10-20 | Sony Int Europe Gmbh | OFDM transmitter antenna diversity system and pre-equalization |
| ATE554578T1 (en) | 2000-11-20 | 2012-05-15 | Sony Deutschland Gmbh | ADAPTIVE SUB CARRIER LOAD |
| US6407846B1 (en) * | 2001-03-16 | 2002-06-18 | All Optical Networks, Inc. | Photonic wavelength shifting method |
| ES2278661T3 (en) | 2001-07-10 | 2007-08-16 | Sony Deutschland Gmbh | REFERENCE SYMBOLS FOR THE ESTIMATION OF CHANNELS WITH MULTIPORT CARRIAGE. |
| DE60144162D1 (en) | 2001-07-11 | 2011-04-14 | Sony Deutschland Gmbh | Method for calculating a weight vector for a group antenna |
| US7037527B2 (en) | 2002-01-25 | 2006-05-02 | University Of Rhode Island | Bifunctionalized polyester material for surface treatment and biomodification |
| EP1379026A1 (en) | 2002-07-03 | 2004-01-07 | Sony International (Europe) GmbH | Dual rate wireless transmission system |
| EP1545069A1 (en) | 2003-12-19 | 2005-06-22 | Sony International (Europe) GmbH | Remote polling and control system |
| EP1596504B1 (en) | 2004-05-11 | 2007-03-14 | Sony Deutschland GmbH | Pole switch down converter with symmetric resonator |
| EP1630713B1 (en) | 2004-08-24 | 2020-05-20 | Sony Deutschland GmbH | Backscatter interrogator reception method and interrogator for a modulated backscatter system |
| EP1657852A1 (en) | 2004-11-15 | 2006-05-17 | Sony Deutschland GmbH | Beaconless communication in ad hoc networks |
-
1999
- 1999-02-22 EP EP06014694A patent/EP1705852B1/en not_active Expired - Lifetime
- 1999-02-22 EP EP04002920A patent/EP1439677B9/en not_active Expired - Lifetime
- 1999-02-22 EP EP05002279A patent/EP1530336B1/en not_active Expired - Lifetime
- 1999-02-22 EP EP99103379A patent/EP1018827B1/en not_active Expired - Lifetime
- 1999-02-22 EP EP06014693A patent/EP1722527B1/en not_active Expired - Lifetime
- 1999-12-06 CA CA002291847A patent/CA2291847C/en not_active Expired - Lifetime
-
2000
- 2000-01-06 KR KR1020000000479A patent/KR100712865B1/en active IP Right Grant
- 2000-01-06 US US09/479,281 patent/US6654339B1/en not_active Ceased
- 2000-01-07 JP JP2000006000A patent/JP4050437B2/en not_active Expired - Lifetime
-
2005
- 2005-11-23 US US11/286,440 patent/USRE40568E1/en not_active Expired - Lifetime
-
2008
- 2008-10-27 US US12/259,045 patent/USRE41606E1/en not_active Expired - Lifetime
- 2008-10-27 US US12/258,984 patent/USRE41641E1/en not_active Expired - Lifetime
- 2008-10-27 US US12/258,799 patent/USRE41470E1/en not_active Expired - Lifetime
- 2008-10-27 US US12/258,939 patent/USRE41486E1/en not_active Expired - Lifetime
- 2008-10-27 US US12/259,018 patent/USRE41431E1/en not_active Expired - Lifetime
- 2008-10-27 US US12/259,063 patent/USRE41432E1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP1722527A1 (en) | 2006-11-15 |
| EP1018827A1 (en) | 2000-07-12 |
| USRE40568E1 (en) | 2008-11-11 |
| EP1705852A3 (en) | 2006-11-15 |
| EP1439677A1 (en) | 2004-07-21 |
| JP4050437B2 (en) | 2008-02-20 |
| KR20000053406A (en) | 2000-08-25 |
| USRE41431E1 (en) | 2010-07-13 |
| EP1530336A1 (en) | 2005-05-11 |
| JP2000209183A (en) | 2000-07-28 |
| EP1439677B1 (en) | 2007-06-13 |
| KR100712865B1 (en) | 2007-05-03 |
| EP1705852B1 (en) | 2010-02-10 |
| USRE41432E1 (en) | 2010-07-13 |
| USRE41641E1 (en) | 2010-09-07 |
| USRE41606E1 (en) | 2010-08-31 |
| USRE41470E1 (en) | 2010-08-03 |
| EP1530336B1 (en) | 2009-06-10 |
| EP1705852A2 (en) | 2006-09-27 |
| EP1018827B1 (en) | 2004-05-06 |
| USRE41486E1 (en) | 2010-08-10 |
| CA2291847A1 (en) | 2000-07-08 |
| US6654339B1 (en) | 2003-11-25 |
| EP1722527B1 (en) | 2008-08-06 |
| EP1439677B9 (en) | 2007-11-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2291847C (en) | Synchronization symbol structure using ofdm based transmission method | |
| JP4493165B2 (en) | Preamble signal generation method, transmission apparatus, and reception apparatus synchronization method | |
| DK2315386T3 (en) | OFDM communications methods and apparatus | |
| EP1505787B1 (en) | Synchronization preamble in an OFDM system | |
| JP3785578B2 (en) | Multicarrier modulation pulse shaping | |
| EP2088727B1 (en) | Synchronisation symbol structure for OFDM system | |
| CN112398771A (en) | Signal transmission method, system and equipment of frequency modulation constant envelope OFDM communication system | |
| EP2088728B1 (en) | Synchronization preamble structure for OFDM system | |
| CN106789762A (en) | FBMC pilot-based channel estimation methods and device | |
| KR100248652B1 (en) | A circuit for transforming of phase signal in ofdm receiving system | |
| ES2389592T3 (en) | Synchronization symbol structure using OFDM based transmission method | |
| KR20140096820A (en) | Orthogonal frequency division modulation system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20191206 |