WO2006072864A1 - A method and apparatus for estimating doppler spread - Google Patents
A method and apparatus for estimating doppler spread Download PDFInfo
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- WO2006072864A1 WO2006072864A1 PCT/IB2005/054401 IB2005054401W WO2006072864A1 WO 2006072864 A1 WO2006072864 A1 WO 2006072864A1 IB 2005054401 W IB2005054401 W IB 2005054401W WO 2006072864 A1 WO2006072864 A1 WO 2006072864A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/01—Reducing phase shift
Definitions
- the present invention relates to a mobile communication system, in particular to a method and apparatus for estimating the Doppler spread used in receivers of mobile communication systems.
- the radio signal may be blocked by barriers on its propagation path, resulting in reflection, diffusion, and attenuation, etc, and thereby resulting in multipath effect, which makes the signal received by the antenna side of a receiver actually is the linear superposition of multipath signals from various paths.
- multipath signals from different paths have different time delays, amplitudes, phases and frequencies.
- Doppler effect for radio signal on its propagation when the radio signal receiver is in a motion state i.e. the signal frequency varies when a mobile receiver is moving relative to the transmitter, and the phase relationship among the signals with various incidence paths may vary with time, resulting in that the frequency spectrum of received signal is spread, i.e.
- the Doppler spread essentially describes the changing speed of time- varying channels in a mobile communication system, in general, rayleigh fading or rapid fading can be used to indicate the statistical characteristics of signal fading of the radio signal suffered in a motion state and transmitted in a multipath environment.
- the system design and device specification of 3 rd generation terrestrial cellular mobile communication system are required to support data transmission for mobile terminals with speed of up to 120 ⁇ 150km/hour.
- the Doppler spread caused by high-speed motion of a signal receiver relative to a transmitter makes signal change and signal distortion inevitable, thus affects the reception performance of the system and even the correct reception of data. Therefore, in a mobile communication system, especially when a mobile terminal is in a high-speed motion state, in order to track the dynamic changes of channels effectively, it is necessary to estimate the Doppler spread in a mobile communication system.
- the estimated information of the Doppler spread can be used to improve the performance of the decoder of a receiver and decrease the bit error rate;
- the estimated information of the Doppler spread can be used to improve the efficiency of radio resources management, e.g. in layered cells, such information can be used by the network to conjecture the moving speed of a mobile terminal, thus to adjust the policies of channel allocation and cell handover, decrease the signaling overhead of dynamic resources, and improve the operating efficiency of the system.
- the estimated information of the Doppler spread can also be used to optimize parameters of a communication system, e.g. optimizing the data interleaving interval to decrease the reception delay, etc.
- the Doppler offset is estimated by inserting known training sequences in the data at the sending end, retrieving and processing anticipated training sequences at the receiving end, thus to acquire the estimated value of the Doppler spread corresponding to the data of current burst.
- the structure of a burst in the TD-SCDMA system is illustrated in Fig. 1, including a communication data segment 1, a communication data segment 2, and a training sequence
- the training sequence 3 is a known pseudo random code sequence, which mainly used for estimating the channel parameters including the Doppler spread. For simplicity, control segments and guard spaces, which possibly inserted at side of a burst and other locations, are omitted in the figure.
- a method of compensating the Doppler spread in the above- mentioned burst structure is to firstly process received training sequences to acquire an estimated value of the Doppler spread, and then use the acquired estimated value of the Doppler spread to compensate the whole burst for the suffered Doppler spread, so as to recover the communication data segments included in the burst.
- the above-mentioned method of estimating the Doppler spread with a burst as a unit can accurately reflect the fading characters of a channel while a mobile terminal moving slowly.
- the motion state of the mobile terminal changes, especially when the mobile terminal is in a high-speed move, the channel fading and the relevant channel performance change significantly, and the method of using one estimated value of the Doppler frequency shift or an average value of multiple estimated values of the Doppler frequency shift as the parameters for estimating the Doppler spread to recover all the data in the current burst can not correctly reflect the actual channel fading character, thus the accuracy for recovering the data is affected inevitably, and thereby the whole performance of the receiver is affected.
- One purpose of the present invention is to provide a method and apparatus for estimating the Doppler spread used in a mobile communication receiver.
- the method and apparatus acquire a plurality of estimated values of the Doppler spread by processing the training sequences extracted from a received signal and use them for the Doppler spread compensation on the basis of chip(s) or symbol(s), and thus to overcome the defects of poor dynamic performance in conventional Doppler spread estimation methods, in which single value estimation of Doppler spread and compensation for Doppler spread on the basis of burst are used.
- a method for estimating the Doppler spread in a receiver of a mobile communication system comprising the steps of: extracting a training sequence comprising the characteristics of a channel from a received signal; segmenting the extracted training sequence to obtain a plurality of initial training sequence segments; processing the plurality of initial training sequence segments obtained by segmenting to acquire a plurality of corresponding estimated values of the Doppler spread; and fitting the plurality of acquired estimated values of the Doppler spread to acquire a set of Doppler spread fitting data to be used for the Doppler spread compensation on the basis of chip(s).
- an apparatus for estimating the Doppler spread in a receiver of a mobile communication system comprising: an extracting means, for extracting a training sequence comprising the characteristics of a channel from a received signal; a first segmenting means, for segmenting the extracted training sequence to obtain a plurality of initial training sequence segments; a processing means, for processing the plurality of initial training sequence segments obtained by segmenting to acquire a plurality of corresponding estimated values of the Doppler spread; and a fitting means, for fitting the plurality of acquired estimated values of the Doppler spread to acquire a set of Doppler spread fitting data to be used for the Doppler spread compensation on the basis of chip(s).
- the method and apparatus provided by the present invention for estimating the Doppler spread in a mobile communication receiver a set of Doppler spread fitting data, which can be used for compensating the Doppler spread on the basis of chip(s) or symbol(s), are acquired through fitting the plurality of estimated value of the Doppler spread acquired by segment processing the training sequence extracted from the received signal.
- the method proposed by the present invention meets the channel related performance requirements while a receiver is in a high-speed moving, and improves the accuracy of the Doppler spread estimation, and thus efficiently improve the overall performance of the receiver in a mobile communication system.
- FIG. 1 is a schematic diagram of the structure of a communication burst in a TD-
- Fig. 2 is a schematic flow chart of a method for estimating the Doppler spread according to an embodiment of the present invention.
- Fig. 3 is a block diagram of a means for estimating the Doppler spread according to an embodiment of the present invention.
- Fig. 4 is a block diagram of a processing means in an apparatus for estimating the Doppler spread according to an embodiment of the present invention.
- similar symbols indicate similar or corresponding features or functions.
- the method and apparatus provided by the present invention for estimating the Doppler spread in a mobile communication receiver are primarily characterized in that conventional signal value estimation of the Doppler spread on the basis of burst is improved to multiple value estimation of the Doppler spread in a same burst, and thus a possibility is given to perform the Doppler spread compensation on the basis of chip(s) or symbol(s).
- a training sequence comprising the characteristics of a channel is extracted from a received signal; secondly the extracted training sequence is segmented to obtain a plurality of initial training sequence segments; and subsequently the plurality of initial segments of a training sequence obtained by segmenting is processed to acquire a plurality of corresponding estimated values of the Doppler spread; finally, the plurality of acquired estimated values of the Doppler spread is fitted to acquire a set of Doppler spread fitting data, which can be used for compensating for the Doppler spread on the basis of chip(s) or symbol(s).
- FIG. 2 A flow chart describing a method for estimating the Doppler spread according to an embodiment of the present invention is illustrated in Fig. 2. The method provided by the invention for estimating the Doppler spread will be described in detail with reference to
- Step SlO a training sequence comprising the characteristics of a channel is extracted from a received signal.
- the coherent demodulation is usually achieved by inserting a known training sequence into the transmitted signal and estimating the time varying channel with the changes of the known training sequence at the receiving end.
- the distorted training sequence extracted at the receiving end after transmission over the channel is [m ⁇ ,m 2 ,---,m ⁇ ] , wherein the symbol '-' indicates the distortion of signal generated by transmitting through the transmission channel.
- Step S20 extracted training sequence is segmented to obtain a plurality of initial training sequence segments. Extracted training sequence is segmented to obtain a plurality of initial training sequence segments, M l ,M 2 ,---M L , wherein L is the number of initial training sequence segments obtained by segmenting.
- Step S30 the plurality of initial training sequences obtained by segmenting is processed to acquire a plurality of corresponding estimated values of the Doppler spread.
- a training sequence completely identical to the one sent at the transmitting end is generated to obtain [m ⁇ ,m 2 ,---,m ⁇ ].
- the generated training sequence is segmented according to the procedure described in the step S20 in order that the acquired plurality of training sequence segments correspond to the plurality of initial training sequence segments one by one, i.e. the numbers of the segments are the same and the segments with the same sequential number have the same length, it can be acquired as the following expression:
- M 1 , M 2 , M 3 , M 4 correspond to M 1 , M 2 , M 3 , M 4 respectively one by one.
- the correlation results are acquired by performing the correlation calculation on the above multiple training sequence segments having one to one correspondence with the multiple initial training sequence segments based on the following expression:
- / ⁇ 1,2,3,4 ⁇ is the sequential number of the training sequence segments
- symbol H indicates a conjugate transposition calculation
- the resulting correlation results are associated with the Doppler spread suffered by the midpoint (/ - l/2)k of each training sequence segment respectively.
- the items directly associated with the Doppler spread in the four correlation results are expressed as follows:
- f dJ is the actual Doppler spread suffered by the midpoints of the plurality of initial training sequence segments.
- the resulting plurality of initial estimated values are grouped in such a way that each group containing two consecutive values, resulting in L - 1 groups:
- Variables based on the Doppler spread are acquired by multiplying the conjugate of a correlation result in each group with another correlation result in the same group:
- Step S40 the acquired plurality of estimated values of the Doppler spread are fitted to acquire a set of Doppler spread fitting data, which can be used for compensating for the Doppler spread on the basis of chip(s) or symbol(s).
- Various methods for fitting the data based on known sample points i.e. acquired plurality of estimated values of the Doppler spread
- such as the minimum square error fitting, the spline fitting, etc are described in detail in the numerical estimation theory and will not be explained again here.
- the effective range of the above fitting data acquired by fitting the plurality of estimated values of the Doppler spread can be extended to the whole burst corresponding to the training sequence according to the coherent feature of a channel, and therefore the
- Doppler spread fitting data corresponding to the fitting curve can be used for compensating for the Doppler spread on the basis of chip(s) or symbol(s).
- the method described above in connection with Fig. 2 for estimating the Doppler spread in a receiver of a mobile communication system can be implemented in the form of software or hardware, as well as in the form of a combination of software and hardware.
- FIG. 3 A block diagram according to a Doppler spread estimate apparatus according to an embodiment of the present invention is showed in Fig. 3.
- the apparatus for Doppler spread estimation of the invention will be described in detail in conjunction with Fig. 3 and Fig. 4 hereinafter.
- an apparatus for estimating the Doppler spread in a mobile communication system comprises an extracting means 10, a first segmenting means 20, a processing means 30 and a fitting means 40.
- a training sequence comprising the characteristic of the channel is extracted by the extracting means 10 from the received signal, wherein the training sequence is an anticipated training sequence having suffered from the wireless channel fading, and the anticipated training sequence is known.
- the extracted training sequence is segmented by the first segmenting means 20 to obtain a plurality of initial training sequence segments, and the number of the plurality of initial training sequence segments is larger than 2.
- the processing means 30 comprises a sequence generating means 31, a second segmenting means 32, a correlation processing means 34, a grouping means 36, and an operating means 38.
- the sequence generating means 31 generates known anticipated training sequences; the second segmenting means 32 segments the known anticipated signal sequences as described in equation (2), resulting in that the number of the plurality of known training sequence segments obtained by segmenting equal the number of the plurality of initial training sequence segments obtained by the first segmenting means, and the segments with the same sequential number in these two group of segments have the same length; the correlation processing means 34 performs the correlation processing as described in equation (3) for each corresponding segment in the plurality of known training sequence segments and the plurality of initial training sequence segments, to acquire multiple correlation results; the grouping means 36 performs the grouping as described in equation (5) for the resulting plurality of correlation results to acquire a plurality of groups with each comprising two consecutive correlation results, respectively; the operation means 38 performs the processing as described in the equations (6)-(8) for the correlation results in the plurality of groups to acquire a plurality of estimated values of the Doppler spread.
- the fitting means 40 fits the resulting plurality of estimated values of the Doppler spread to acquire a set of Doppler spread fitting data, which can be used for compensating for the Doppler spread on the basis of chip(s) or symbol(s).
- the method and apparatus provided by the present invention for estimating the Doppler spread in a mobile communication receiver can be applied to both a cellular communication system and a wireless LAN communication system as well as to various communication systems in which there is a relative motion between a receiver and a transmitter.
Abstract
A method and apparatus for estimating the Doppler spread in a mobile communication receiver are invented. The method and apparatus acquire a set of Doppler spread fitting data for compensating the Doppler spread on the basis of chip, by fitting a plurality of estimated value of the Doppler spread acquired by segment processing a training sequence extracted from a received signal, and thus overcome the defect of poor dynamic performance of Doppler spread estimation in conventional methods, in which single value estimation of Doppler spread and compensation for Doppler spread on the basis of burst are used.
Description
A METHOD AND APPARATUS FOR ESTIMATING DOPPLER SPREAD
FIELD OF THE INVENTION The present invention relates to a mobile communication system, in particular to a method and apparatus for estimating the Doppler spread used in receivers of mobile communication systems.
BACKGROUND OF THE INVENTION The radio signal may be blocked by barriers on its propagation path, resulting in reflection, diffusion, and attenuation, etc, and thereby resulting in multipath effect, which makes the signal received by the antenna side of a receiver actually is the linear superposition of multipath signals from various paths. Furthermore, multipath signals from different paths have different time delays, amplitudes, phases and frequencies. On the other hand, there may be Doppler effect for radio signal on its propagation when the radio signal receiver is in a motion state, i.e. the signal frequency varies when a mobile receiver is moving relative to the transmitter, and the phase relationship among the signals with various incidence paths may vary with time, resulting in that the frequency spectrum of received signal is spread, i.e. resulting in Doppler spread. The Doppler spread essentially describes the changing speed of time- varying channels in a mobile communication system, in general, rayleigh fading or rapid fading can be used to indicate the statistical characteristics of signal fading of the radio signal suffered in a motion state and transmitted in a multipath environment.
With the development of mobile communication technology, increasing higher requirements are required on the supported- speed and the quality of received signals in mobile communication systems. For example, the system design and device specification of 3rd generation terrestrial cellular mobile communication system are required to support data transmission for mobile terminals with speed of up to 120~150km/hour. The Doppler spread caused by high-speed motion of a signal receiver relative to a transmitter makes signal change and signal distortion inevitable, thus affects the reception performance of the system and even the correct reception of data. Therefore, in a mobile communication system, especially when a mobile terminal is in a high-speed motion state, in order to track
the dynamic changes of channels effectively, it is necessary to estimate the Doppler spread in a mobile communication system.
Many advantages are brought to the communication system by accurately estimating the Doppler spread. Firstly, the estimated information of the Doppler spread can be used to improve the performance of the decoder of a receiver and decrease the bit error rate; secondly, the estimated information of the Doppler spread can be used to improve the efficiency of radio resources management, e.g. in layered cells, such information can be used by the network to conjecture the moving speed of a mobile terminal, thus to adjust the policies of channel allocation and cell handover, decrease the signaling overhead of dynamic resources, and improve the operating efficiency of the system. Furthermore, the estimated information of the Doppler spread can also be used to optimize parameters of a communication system, e.g. optimizing the data interleaving interval to decrease the reception delay, etc.
In general, methods of estimating pilot signals to determine an estimated value of the Doppler spread are used to estimate the Doppler spread. For example, the Doppler offset is estimated by inserting known training sequences in the data at the sending end, retrieving and processing anticipated training sequences at the receiving end, thus to acquire the estimated value of the Doppler spread corresponding to the data of current burst. The structure of a burst in the TD-SCDMA system is illustrated in Fig. 1, including a communication data segment 1, a communication data segment 2, and a training sequence
3, in which the communication data segments 1 and 2 carry user data, the training sequence 3 is a known pseudo random code sequence, which mainly used for estimating the channel parameters including the Doppler spread. For simplicity, control segments and guard spaces, which possibly inserted at side of a burst and other locations, are omitted in the figure. In general, a method of compensating the Doppler spread in the above- mentioned burst structure is to firstly process received training sequences to acquire an estimated value of the Doppler spread, and then use the acquired estimated value of the Doppler spread to compensate the whole burst for the suffered Doppler spread, so as to recover the communication data segments included in the burst. The above-mentioned method of estimating the Doppler spread with a burst as a unit can accurately reflect the fading characters of a channel while a mobile terminal moving slowly. When the motion state of the mobile terminal changes, especially when the mobile terminal is in a high-speed move, the channel fading and the relevant channel
performance change significantly, and the method of using one estimated value of the Doppler frequency shift or an average value of multiple estimated values of the Doppler frequency shift as the parameters for estimating the Doppler spread to recover all the data in the current burst can not correctly reflect the actual channel fading character, thus the accuracy for recovering the data is affected inevitably, and thereby the whole performance of the receiver is affected.
To solve the above problems, a more efficient method for estimating the Doppler spread is required to overcome the defect of poor dynamic performance in conventional Doppler spread estimation methods, in which compensation is performed with a burst as an unit.
OBJECT AND SUMMARY OF THE INVENTION
One purpose of the present invention is to provide a method and apparatus for estimating the Doppler spread used in a mobile communication receiver. The method and apparatus acquire a plurality of estimated values of the Doppler spread by processing the training sequences extracted from a received signal and use them for the Doppler spread compensation on the basis of chip(s) or symbol(s), and thus to overcome the defects of poor dynamic performance in conventional Doppler spread estimation methods, in which single value estimation of Doppler spread and compensation for Doppler spread on the basis of burst are used.
To realize the objects of the present invention, a method for estimating the Doppler spread in a receiver of a mobile communication system is provided, comprising the steps of: extracting a training sequence comprising the characteristics of a channel from a received signal; segmenting the extracted training sequence to obtain a plurality of initial training sequence segments; processing the plurality of initial training sequence segments obtained by segmenting to acquire a plurality of corresponding estimated values of the Doppler spread; and fitting the plurality of acquired estimated values of the Doppler spread to acquire a set of Doppler spread fitting data to be used for the Doppler spread compensation on the basis of chip(s).
To realize the objects of the present invention, an apparatus for estimating the Doppler spread in a receiver of a mobile communication system is provided, comprising: an extracting means, for extracting a training sequence comprising the characteristics of a channel from a received signal; a first segmenting means, for segmenting the extracted training sequence to obtain a plurality of initial training sequence segments; a processing means, for processing the plurality of initial training sequence segments obtained by segmenting to acquire a plurality of corresponding estimated values of the Doppler spread; and a fitting means, for fitting the plurality of acquired estimated values of the Doppler spread to acquire a set of Doppler spread fitting data to be used for the Doppler spread compensation on the basis of chip(s).
In summary, the method and apparatus provided by the present invention for estimating the Doppler spread in a mobile communication receiver, a set of Doppler spread fitting data, which can be used for compensating the Doppler spread on the basis of chip(s) or symbol(s), are acquired through fitting the plurality of estimated value of the Doppler spread acquired by segment processing the training sequence extracted from the received signal. Compared to conventional methods using single value estimation of the Doppler spread and performing estimation and compensation on the basis of burst, the method proposed by the present invention meets the channel related performance requirements while a receiver is in a high-speed moving, and improves the accuracy of the Doppler spread estimation, and thus efficiently improve the overall performance of the receiver in a mobile communication system.
Other objects and effects of the present invention will become much clearer and easier to understand through the following description in conjunction with accompanying drawings and the contents of appended claims, and with more thorough understanding of the present invention.
BRIEF DECRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of the structure of a communication burst in a TD-
SCDMA mobile communication system.
Fig. 2 is a schematic flow chart of a method for estimating the Doppler spread according to an embodiment of the present invention.
Fig. 3 is a block diagram of a means for estimating the Doppler spread according to an embodiment of the present invention.
Fig. 4 is a block diagram of a processing means in an apparatus for estimating the Doppler spread according to an embodiment of the present invention. In all the drawings, similar symbols indicate similar or corresponding features or functions.
DETAILED DESCRIPTION OF THE INVENTION
The method and apparatus provided by the present invention for estimating the Doppler spread in a mobile communication receiver are primarily characterized in that conventional signal value estimation of the Doppler spread on the basis of burst is improved to multiple value estimation of the Doppler spread in a same burst, and thus a possibility is given to perform the Doppler spread compensation on the basis of chip(s) or symbol(s). According to the present invention, firstly, a training sequence comprising the characteristics of a channel is extracted from a received signal; secondly the extracted training sequence is segmented to obtain a plurality of initial training sequence segments; and subsequently the plurality of initial segments of a training sequence obtained by segmenting is processed to acquire a plurality of corresponding estimated values of the Doppler spread; finally, the plurality of acquired estimated values of the Doppler spread is fitted to acquire a set of Doppler spread fitting data, which can be used for compensating for the Doppler spread on the basis of chip(s) or symbol(s).
A flow chart describing a method for estimating the Doppler spread according to an embodiment of the present invention is illustrated in Fig. 2. The method provided by the invention for estimating the Doppler spread will be described in detail with reference to
Fig. 2 below.
Step SlO: a training sequence comprising the characteristics of a channel is extracted from a received signal.
In a mobile communication system, the coherent demodulation is usually achieved by inserting a known training sequence into the transmitted signal and estimating the time varying channel with the changes of the known training sequence at the receiving end.
It is assumed that the known training sequence transmitted at the transmitting end is
[mι,m2,---,mκ ] , the distorted training sequence extracted at the receiving end after
transmission over the channel is [mι,m2,---,mκ ] , wherein the symbol '-' indicates the distortion of signal generated by transmitting through the transmission channel.
Step S20: extracted training sequence is segmented to obtain a plurality of initial training sequence segments. Extracted training sequence is segmented to obtain a plurality of initial training sequence segments, Ml,M2 ,---M L , wherein L is the number of initial training sequence segments obtained by segmenting.
It is assumed that the length of the known training sequence is K = 4k, the extracted training sequence is divided equally into 4 parts, and the resulting plurality of initial training sequence segments can be expressed as:
The method is described in this embodiment in a way that a training sequence is divided equally into 4 parts in length, i.e. L = 4. It should be explained that it is not necessary for the length of the above training sequences obtained by segmenting to be equal to each other, furthermore, it is not necessary for the length of the known training sequence to be integral multiple of 4. In practice, a sequence can be segmented as demand. The number of initial training sequences obtained by segmenting should be larger than 2, and the design of the specific value can be determined by taking into account various factors, such as the statistical characters of the channel caused by current motion state of the receiver, the complexity of estimating the Doppler spread and fitting, as well as the required estimation precision, etc.
Step S30: the plurality of initial training sequences obtained by segmenting is processed to acquire a plurality of corresponding estimated values of the Doppler spread.
Firstly, a training sequence completely identical to the one sent at the transmitting end is generated to obtain [mι,m2,---,mκ]. The generated training sequence is segmented according to the procedure described in the step S20 in order that the acquired plurality of training sequence segments correspond to the plurality of initial training sequence segments one by one, i.e. the numbers of the segments are the same and the segments with
the same sequential number have the same length, it can be acquired as the following expression:
R1 = M1 - M? (3)
Wherein, / = {1,2,3,4} is the sequential number of the training sequence segments, the symbol H indicates a conjugate transposition calculation, and the resulting correlation results are associated with the Doppler spread suffered by the midpoint (/ - l/2)k of each training sequence segment respectively. The items directly associated with the Doppler spread in the four correlation results are expressed as follows:
Wherein, fdJ is the actual Doppler spread suffered by the midpoints of the plurality of initial training sequence segments.
The resulting plurality of initial estimated values are grouped in such a way that each group containing two consecutive values, resulting in L - 1 groups:
(R15R2 ), (R25R3 ) and (R3, R4 ) (5) Variables based on the Doppler spread are acquired by multiplying the conjugate of a correlation result in each group with another correlation result in the same group:
F; = R; χ R;+1 (6) wherein [J indicates the conjugate calculation. The following can be acquired by simplifying the above expression: F1 = e j2πk fd l (7)
(L -I ) estimated values of the Doppler spread having one to one correspondence with each group described in equation (5) can be acquired by processing the acquired result to extract corresponding phase information:
W
wherein, / = 1,2,3 , #>(•) is the functional operation for extracting the phase information.
Step S40: the acquired plurality of estimated values of the Doppler spread are fitted to acquire a set of Doppler spread fitting data, which can be used for compensating for the Doppler spread on the basis of chip(s) or symbol(s). A set of Doppler spread fitting data, which corresponds to a Doppler spread fitting curve, can be acquired by fitting the plurality of estimated values of the Doppler spread [fd l I / = 1,2,3} obtained in step S30. Various methods for fitting the data based on known sample points (i.e. acquired plurality of estimated values of the Doppler spread), such as the minimum square error fitting, the spline fitting, etc, are described in detail in the numerical estimation theory and will not be explained again here.
The effective range of the above fitting data acquired by fitting the plurality of estimated values of the Doppler spread can be extended to the whole burst corresponding to the training sequence according to the coherent feature of a channel, and therefore the
Doppler spread fitting data corresponding to the fitting curve can be used for compensating for the Doppler spread on the basis of chip(s) or symbol(s).
The method described above in connection with Fig. 2 for estimating the Doppler spread in a receiver of a mobile communication system can be implemented in the form of software or hardware, as well as in the form of a combination of software and hardware.
A block diagram according to a Doppler spread estimate apparatus according to an embodiment of the present invention is showed in Fig. 3. The apparatus for Doppler spread estimation of the invention will be described in detail in conjunction with Fig. 3 and Fig. 4 hereinafter.
As illustrated in Fig. 3, an apparatus for estimating the Doppler spread in a mobile communication system according to an embodiment of the invention comprises an extracting means 10, a first segmenting means 20, a processing means 30 and a fitting means 40.
Firstly, a training sequence comprising the characteristic of the channel is extracted by the extracting means 10 from the received signal, wherein the training sequence is an anticipated training sequence having suffered from the wireless channel fading, and the anticipated training sequence is known. Secondly, the extracted training sequence is segmented by the first segmenting means 20 to obtain a plurality of initial training sequence segments, and the number of the plurality of initial training sequence segments is larger than 2.
Subsequently, the pluralities of initial training sequence segments obtained by segmenting are processed by the processing means 30 to acquire a plurality of estimated values of the Doppler spread. The processing means 30 comprises a sequence generating means 31, a second segmenting means 32, a correlation processing means 34, a grouping means 36, and an operating means 38. The sequence generating means 31 generates known anticipated training sequences; the second segmenting means 32 segments the known anticipated signal sequences as described in equation (2), resulting in that the number of the plurality of known training sequence segments obtained by segmenting equal the number of the plurality of initial training sequence segments obtained by the first segmenting means, and the segments with the same sequential number in these two group of segments have the same length; the correlation processing means 34 performs the correlation processing as described in equation (3) for each corresponding segment in the plurality of known training sequence segments and the plurality of initial training sequence segments, to acquire multiple correlation results; the grouping means 36 performs the grouping as described in equation (5) for the resulting plurality of correlation results to acquire a plurality of groups with each comprising two consecutive correlation results, respectively; the operation means 38 performs the processing as described in the equations (6)-(8) for the correlation results in the plurality of groups to acquire a plurality of estimated values of the Doppler spread.
At last, the fitting means 40 fits the resulting plurality of estimated values of the Doppler spread to acquire a set of Doppler spread fitting data, which can be used for compensating for the Doppler spread on the basis of chip(s) or symbol(s). It should be understood by those skilled in the art that the method and apparatus provided by the present invention for estimating the Doppler spread in a mobile communication receiver can be applied to both a cellular communication system and a
wireless LAN communication system as well as to various communication systems in which there is a relative motion between a receiver and a transmitter.
Also, it should be understood by those skilled in the art that there can be various improvements for the method and apparatus disclosed by the present invention for estimating the Doppler spread in a mobile communication receiver without departing from the contents of the present invention. Therefore, the protection scope of the present invention should be defined by the contents of appended claims.
Claims
1. A method for estimating a Doppler spread in a receiver of a mobile communication system, comprising the steps of: (a) extracting a training sequence comprising the characteristics of a channel from a received signal;
(b) segmenting the extracted training sequence to obtain a plurality of initial training sequence segments;
(c) processing the plurality of initial training sequence segments obtained by segmenting to acquire a plurality of corresponding estimated values of the Doppler spread; and
(d) fitting the acquired plurality of estimated values of the Doppler spread to acquire a set of Doppler spread fitting data, further used for the Doppler spread compensation on the basis of chip(s) and symbol(s).
2. The method as claimed in claim 1, wherein the training sequence extracted in step (a) is an anticipated training sequence, which has suffered from the fading of the wireless channel, and the anticipated training sequence is known.
3. The method as claimed in claim 1, wherein the number of the plurality of initial training sequence segments obtained by segmenting in step (b) is larger than 2.
4. The method as claimed in claim 1, wherein step (c) comprises the steps of:
(i) segmenting the known anticipated training sequence to make the plurality of known training sequence segments obtained by segmenting corresponding to the plurality of initial training sequence segments, respectively;
(ii) performing correlation processing for each of the plurality of known training sequence segments and the corresponding one of the plurality of initial training sequence segments to acquire a plurality correlation results; (iii) grouping the plurality of correlation results to acquire a plurality of groups with each comprising two consecutive correlation results;
(iv) processing the correlation results of the plurality of groups to acquire a plurality of estimated values of the Doppler spread.
5. The method as claimed in claim 4, wherein the number of the plurality of initial training sequence segments obtained by segmenting in step (b) equal the number of the plurality of known training sequence segments obtained by segmenting in step (i), and the segments with the same sequential number have the same length.
6. The method as claimed in claim 4, wherein step (iv) comprises: performing a conjugate multiplication operation for two correlation results in each group to acquire a plurality of conjugate multiplication results; extracting corresponding phase information from the acquired plurality of conjugate multiplication results; and computing a plurality of estimated values of the Doppler spread based on the extracted phase information.
7. An apparatus for estimating the Doppler spread in a receiver of a mobile communication system, comprising: an extracting means, for extracting a training sequence comprising the characteristics of a channel from a received signal; a first segmenting means, for segmenting the extracted training sequence to obtain a plurality of initial training sequence segments; a processing means, for processing the plurality of initial training sequence segments obtained by segmenting to acquire a plurality of corresponding estimated values of the Doppler spread; and a fitting means, for fitting the acquired plurality of estimated values of the Doppler spread to acquire a set of Doppler spread fitting data to be used for the Doppler spread compensation on the basis of chip(s) and symbol(s).
8. The apparatus as claimed in claim 7, wherein the training sequence extracted by the extracting means is an anticipated training sequence, which has suffered from the fading of the wireless channel, and the anticipated training sequence is known.
9. The apparatus as claimed in claim 7, wherein the number of the plurality of initial training sequence segments segmented by the first segmenting means is larger than 2.
10. The apparatus as claimed in claim 7, wherein the processing means comprises: a sequence generating means, for generating known anticipated training sequence; a second segmenting means, for segmenting the known anticipated training sequence in order that the plurality of known training sequence segments segmented by the second segmenting means correspond to the plurality of initial training sequence segments respectively; a correlation processing means, for performing correlation processing for each of the plurality of known training sequence segments and the corresponding one of the plurality of initial training sequence segments to acquire a plurality of correlation results; a grouping means, for grouping the plurality of correlation results to acquire a plurality of groups with each comprising two consecutive correlation results; an operation means, for processing the correlation results of the plurality of groups to acquire a plurality of estimated values of the Doppler spread.
11. The apparatus as claimed in claim 10, wherein the number of the plurality of initial training sequence segments segmented by the first segmenting means equal the number of the plurality of known training sequence segments segmented by the second the segmenting means, and the segments with the same sequential number have the same length.
12. The apparatus as claimed in claim 10, wherein the operation means comprises: a conjugate multiplication means, for performing a conjugate multiplication operation on two correlation results in each group to acquire a plurality of conjugate multiplication results; a phase extracting means, for extracting the corresponding phase information from the acquired plurality of conjugate multiplication results; and a division means, for computing a plurality of estimated values of the Doppler spread based on the extracted phase information.
13. A mobile terminal, comprising: a signal receiving means, for receiving the signal suffered from fading of a wireless channel; a Doppler spread estimating apparatus, for acquiring a plurality of estimated values of the Doppler spread, which are used for compensating for the Doppler spread on the basis of chip(s) and symbol(s); and a signal processing means, for performing subsequent processing based on the acquired estimated values of the Doppler spread.
14. The mobile terminal as claimed in claim 13, wherein the Doppler spread estimating apparatus comprises: an extracting means, for extracting a training sequence comprising the characteristics of a channel from a received signal; a first segmenting means, for segmenting the extracted training sequence to obtain a plurality of initial training sequence segments; a processing means, for processing the plurality of initial training sequence segments obtained by segmenting to acquire a plurality of corresponding estimated values of the Doppler spread; and a fitting means, for fitting the acquired plurality of estimated values of the Doppler spread to acquire a set of Doppler spread fitting data, the fitting data can be used for the Doppler spread compensation on the basis of chip(s) and symbol(s).
15. The mobile terminal as claimed in claim 14, wherein the training sequence extracted by the extracting means is an anticipated training sequence, which suffered from the fading of the wireless channel, and the anticipant training sequence is known.
16. The mobile terminals as claimed in claim 14, wherein the number of the plurality of initial training sequence segments segmented by the first segmenting means is larger than 2.
17. The mobile terminal as claimed in claim 15, wherein the processing means comprises: a sequence generating means, for generating known anticipated training sequence; a second segmenting means, for segmenting the known anticipated training sequence in order that the plurality of known training sequence segments segmented by the second segmenting means correspond to the plurality of initial training sequence segments respectively; a correlation processing means, for performing correlation processing on each of the plurality of known training sequence segments and the corresponding one of the plurality of initial training sequence segments to acquire a plurality of correlation results; a grouping means, for grouping the plurality of correlation results to acquire a plurality of groups with each comprising two consecutive correlation results; and an operation means, for processing the correlation results of the plurality of groups to acquire a plurality of estimated values of the Doppler spread.
18. The mobile terminal as claimed in claim 17, wherein the number of the plurality of initial known training sequence segments segmented by the first segmenting means equal the number of the plurality of initial training sequence segments segmented by the second the segmenting means, and the segments with the same sequential number have the same length.
19. The mobile terminal as claimed in claim 18, wherein the operation means comprises: a conjugate multiplication means, for performing a conjugate multiplication operation on two correlation results in each group to acquire a plurality of conjugate multiplication results; a phase extracting means, for extracting the corresponding phase information from the acquired plurality of conjugate multiplication results; and a division means, for computing a plurality of estimated values of the Doppler spread based on the extracted phase information;
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN200510004078.1 | 2005-01-06 | ||
| CN200510004078 | 2005-01-06 |
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| Publication Number | Publication Date |
|---|---|
| WO2006072864A1 true WO2006072864A1 (en) | 2006-07-13 |
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| Application Number | Title | Priority Date | Filing Date |
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| PCT/IB2005/054401 WO2006072864A1 (en) | 2005-01-06 | 2005-12-27 | A method and apparatus for estimating doppler spread |
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| WO (1) | WO2006072864A1 (en) |
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| CN109302365A (en) * | 2017-12-21 | 2019-02-01 | 上海创远仪器技术股份有限公司 | A kind of TD-SCDMA analyzer frequency deviation estimating method based on multistage calculus of finite differences |
| CN111294301A (en) * | 2019-04-25 | 2020-06-16 | 展讯通信（上海）有限公司 | Doppler estimation method and device, storage medium and terminal |
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