WO2004006480A1 - Procede et appareil de reperage continu de codes d'etalement de spectre en mode cdma - Google Patents
Procede et appareil de reperage continu de codes d'etalement de spectre en mode cdma Download PDFInfo
- Publication number
- WO2004006480A1 WO2004006480A1 PCT/CN2002/000470 CN0200470W WO2004006480A1 WO 2004006480 A1 WO2004006480 A1 WO 2004006480A1 CN 0200470 W CN0200470 W CN 0200470W WO 2004006480 A1 WO2004006480 A1 WO 2004006480A1
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- WIPO (PCT)
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- code
- spreading code
- input
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7085—Synchronisation aspects using a code tracking loop, e.g. a delay-locked loop
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2201/00—Indexing scheme relating to details of transmission systems not covered by a single group of H04B3/00 - H04B13/00
- H04B2201/69—Orthogonal indexing scheme relating to spread spectrum techniques in general
- H04B2201/707—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation
- H04B2201/70701—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation featuring pilot assisted reception
Definitions
- the present invention belongs to the field of communication technology, and particularly relates to a synchronization tracking method for a spreading code in a receiving device of a CDMA communication system, and in particular, to a synchronization tracking method and device for a CDMA spreading code.
- the CDMA system has developed rapidly due to its unique advantages such as large capacity, soft capacity, soft handover, high voice shield volume and low transmit power, as well as anti-interference and confidentiality, and has become the first choice for third-generation cellular communication systems. technology.
- CDMA is a modulation and multiple access technology based on spread-spectrum communications.
- signals used by different users to transmit information are not distinguished by different frequencies or time slots, but by different coding sequences.
- both a base station transmitter and a mobile station transmitter use a spreading code to spread the digital information, and the receiving device uses a local spreading code to despread the spread spectrum signal to extract useful information. . Synchronization is to realize that the local spreading code and the received spreading code are completely consistent in structure, frequency and phase.
- the synchronization of the spreading code is divided into two steps: one is capturing, quickly determining the phase of the spreading code, so that the phase difference between the local spreading code and the receiving spreading code is less than one symbol width Tc; the second is tracking, finely adjusting the spreading code The phase of the local spreading code and the receiving spreading code are accurately synchronized, and this synchronization is maintained.
- the traditional CDMA system tracking method is a delay lock loop (DLL-Delay lock loop), which has been changed into a variety of tracking loops, such as a T-type dither loop (TDL-Tau- di ther loop), a dual-jitter loop (DDL- Double di ther loop) and so on.
- TDL-Tau- di ther loop T-type dither loop
- DDL- Double di ther loop DDL- Double di ther loop
- This type of loop is applied to the door technology sooner or later.
- Figure 1 shows a typical DLL structure.
- the specific working process is as follows:
- the received spread-spectrum signal r (t) enters the early-late correlator la, lb, and the punctual correlator lc, respectively, and performs correlation operations with three PN codes of different phases generated by the PN code generator 6.
- the despread signals obtained from the two branches a and b pass the adder 3 to obtain the error signal, and then the loop filter 4 is used to filter the loop noise to obtain the error.
- the signal is used to drive a voltage-controlled oscillator (VC0) to generate a control signal to control the clock phase of the PN code generator 6 to swing forward or backward, so as to closely follow the phase change of the received signal; the c branch in the figure is a demodulation branch.
- the received spread-spectrum signal is correlated with the local PN code adjusted by timing to obtain despread data for demodulation.
- Figure 2 shows the error function curve. It can be seen from the error curve that the sooner or later gate technique depends on the symmetry of the autocorrelation function of the spreading sequence, which makes this type of method have certain limitations. First, it is required that the two correlators leading and lagging must be accurately balanced, otherwise the output of the DLL will not be zero even when the tracking error is zero. Using TDL in the analog ring can solve this problem, but it will cause the degradation of tracking performance. For digital loops, this problem does not exist. Secondly, when multipath fading is considered, after multipath signals are superimposed, the correlation waveform becomes a series of superimposed autocorrelation peaks with different amplitudes and time intervals, and the synthesized waveform can no longer be symmetrical.
- the purpose of the present invention is to provide a method and device for synchronous tracking of spreading codes for CDMA.
- multipath transmission through an all-digital loop, an improved late-morning gate technique is used, and the deformation of the error function is not affected.
- Sensitive, combined with the idea of multi-path separation, combining the tracking of each path, is a multi-path tracking technology. And the method is simple, easy to implement, and has the purpose of high synchronization accuracy.
- a synchronization tracking method for a spread spectrum code for CDMA which is characterized in that:
- Originator Insert pilot symbols in the transmitted signal
- the receiving end extracting the pilot symbol from the received signal; and:
- Correlating the local spreading code used for tracking with the pilot symbols in the corresponding path to obtain three-way despread data refers to:
- the local spreading code used for tracking may include an early code of an early branch , The late code of the late branch, and the punctual code of the punctual branch; perform correlation calculation processing on the early branch, the late branch, and the punctual branch to obtain three-way despread data, and when multipath, each path is obtained by The three-way despread data described above.
- the separation of the despread data refers to: using known ideal correlation waveforms to separate the signals of each path (the obtained cases of despread data of each path have greatly reduced the overlap with each other).
- Discriminating the two difference signals after low-pass filtering to obtain a timing adjustment signal, and adjusting the chip clock refers to: When both input signals, that is, a set of differences, are less than zero, "-1" is output, and the received signal is delayed; when both input signals are greater than zero, “1” is output, and the received signal is advanced; When the two input signal signs are opposite, "0" is output, and the received signal is in the correct position;
- a control signal is generated to enter the PN code generator, and the phase of the local spreading code is adjusted to generate a spreading code for despreading.
- the distance between the paths is also calculated and used to calculate the multipath separation. deal with.
- the method for synchronously tracking a spreading code for CDMA includes the following steps:
- Correlation processing is performed between the local spreading code used for tracking and the pilot symbol in the corresponding path.
- the local spreading code used for tracking may include an early code of an early branch, a late code of a late branch, and punctuality
- the correlation operation processing may be performed on the early branch, the late branch, and the on-time branch to obtain three-way despread data, and when multipath is obtained, each path is obtained Three-way despread data;
- Performing the difference operation processing on the separated data, and the performing the difference operation processing is an addition operation processing, that is, using the early, late, and punctual three-way data to generate two-way difference signals;
- the two difference signals after low-pass filtering are discriminated, that is, when two input signals, that is, a group of difference values, are both less than zero, the output signal is delayed at this time; when both input signals are greater than zero, , "1" is output, and the received signal is advanced at this time; when the signs of the two input signals are opposite, "0" is output, and the received signal is at the correct position at this time;
- a control signal is generated to enter the PN code generator, and the phase of the local spreading code is adjusted to generate a spreading code for despreading.
- the distance between the paths is also calculated and used to calculate the multipath separation. deal with.
- the generating two-way difference signals by using three channels of early, late, and on-time data refers to: performing (on-time-early) and (late-on-time) operations to obtain two-way difference signals.
- the control signal is generated by the loop filtering to enter the PN code generator, and the phase of the local spreading code is adjusted to generate the spreading code, which is used for despreading.
- the adjustment step length is r. / N, generates a spreading code for despreading.
- a spreading code synchronization tracking device for CDMA includes a PN code generator, which is further characterized by: a warp separator, a correlator, an adder, a low-pass filter, a discriminator, and a loop filter; The output of the separator is the input of the multi-pass separator;
- the output of the multi-pass separator is the input of the adder
- the output of the adder is the input of a low-pass filter
- the output of the low-pass filter is the input of the discriminator
- the output of the discriminator is the input of the loop filter
- the output of the loop filter is the input of the PN code generator
- the inter-path distance data output by the PN code generator is another input of the multi-pass separator.
- the beneficial effect of the present invention is that, by providing a method and a device for synchronously tracking a spreading code for CDMA, in the case of multipath transmission, through an all-digital loop, an improved late-morning gate technique is used for the error function. Deformation is not sensitive, and combined with the idea of multi-path separation, combining the tracking of each path is a multi-path tracking technology.
- the method has the advantages of simple method, easy implementation, and high synchronization accuracy.
- Figure 1 is a schematic diagram of a DLL tracking loop.
- Figure 2 is the error function curve of the sooner or later gate technique.
- FIG. 3 shows a schematic diagram of a synchronous tracking loop designed according to the method of the present invention. detailed description
- the interval between leading and lagging is T c / N, and the adjustment step size is also T c / N.
- the first arriving path is the first path.
- the pilot symbol 10 is extracted from the received signal.
- 22a, 22b, 22c are local spreading codes used for the first path tracking, and are expressed as C (t- price + ⁇ ⁇ / ⁇ (early code), Cit-T.-TN) (late code), and C (t- ⁇ ) (just in time code), the price is the delay estimation of the first path.
- 23a, 23b, and 23c are local spreading codes for second-path tracking, and are expressed as C (t-f 2 + r.
- f 2 is the delay estimation of the second path.
- the local spreading code is obtained by continuously adjusting the delay of the PN code generator 21, and its initial value is given by synchronous acquisition.
- the pilot signal 10 is correlated with these two sets of spreading codes 22 and 23 (by two sets of correlators of 11, 12) to obtain corresponding despread data.
- the two sets of despread data enter the multipath separator 13.
- G IB G IB -R c (f ib -fj) G JC
- G G ic -i? C (f ,.- ;, c
- the two sets of despread data after multipath separation enter the adders 14a, 14b, 15a, and 15b, and The operations are as follows: (on time-early) and (late-on time). Get the two sets of differences. After that, these two sets of differences are filtered by low-pass filters (LPF) 16a, 16b, 17a, and 17b, respectively. After filtering, it enters the discriminators 18a and 18b.
- LPF low-pass filters
- the function of the discriminator is: when the two input signals (that is, a set of differences) are less than zero, the output indicates that the received signal is lagging; when both input signals are greater than zero, the output is " , Indicating that the received signal is ahead; when the signs of the two input signals are opposite, "0" is output, indicating that the received signal is in the correct position.
- the control signal is entered into the PN code generator 2 and adjusted locally.
- the phase of the spreading code is as follows: If the input control signal is greater than the threshold P., it means that the received signal is ahead, and the phase of the local spreading code should also be adjusted forward.
- the frequency code phase should also be adjusted backward; if the input control signal is between ⁇ P., it means that the synchronization is correct at this time, and the phase of the spreading code is not adjusted.
- the adjustment step is?; / N, which results in 22 and 23 sets of spreading.
- the frequency code is used for despreading.
- the distance f 2 -price 20 between the two paths at the current moment is also calculated and output to the multi-path separator 13 for the calculation of multi-path separation.
- the present invention counteracts the effects of multipath fading by multipath separation and three-way correlators participating in tracking together, making the algorithm insensitive to the symmetry of related waveforms, which can reduce tracking jitter and noise Effect, so that the overall performance of tracking is improved.
- the present invention has been described above with respect to the case of two-path tracking. For the case of more paths, the present invention is also applicable.
- the present invention is an improvement on the gate circuit sooner or later, without increasing the hardware complexity too much, and the output of the on-time branch can still be used for service demodulation.
- the present invention provides a method and device for synchronous tracking of spreading codes for CDMA.
- multipath transmission through an all-digital loop, an improved late-morning gate technique is used, which is not sensitive to the deformation of the error function, and Combined with the idea of multi-path separation, combining the tracking of each path is a multi-path tracking technology.
- the method is simple, easy to implement, and has a good effect of high synchronization accuracy.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
- Synchronisation In Digital Transmission Systems (AREA)
Description
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Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/CN2002/000470 WO2004006480A1 (fr) | 2002-07-03 | 2002-07-03 | Procede et appareil de reperage continu de codes d'etalement de spectre en mode cdma |
AU2002315741A AU2002315741A1 (en) | 2002-07-03 | 2002-07-03 | Method and apparatus for synchronous tracking of cdma spread spectrum code |
CN02819180.3A CN1561596A (zh) | 2002-07-03 | 2002-07-03 | 一种用于cdma的扩频码同步跟踪方法及装置 |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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PCT/CN2002/000470 WO2004006480A1 (fr) | 2002-07-03 | 2002-07-03 | Procede et appareil de reperage continu de codes d'etalement de spectre en mode cdma |
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Publication Number | Publication Date |
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WO2004006480A1 true WO2004006480A1 (fr) | 2004-01-15 |
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PCT/CN2002/000470 WO2004006480A1 (fr) | 2002-07-03 | 2002-07-03 | Procede et appareil de reperage continu de codes d'etalement de spectre en mode cdma |
Country Status (3)
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CN (1) | CN1561596A (zh) |
AU (1) | AU2002315741A1 (zh) |
WO (1) | WO2004006480A1 (zh) |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0718998A2 (en) * | 1994-12-22 | 1996-06-26 | Nec Corporation | De-spread code phase detection apparatus in spread spectrum type receiver |
JPH0918446A (ja) * | 1995-06-28 | 1997-01-17 | Oki Electric Ind Co Ltd | 同期追従回路 |
JPH09321663A (ja) * | 1996-05-28 | 1997-12-12 | Oki Electric Ind Co Ltd | 同期追従装置 |
JPH11234168A (ja) * | 1998-02-10 | 1999-08-27 | Sharp Corp | 拡散信号に対する相関処理の同期追従回路 |
CN1251479A (zh) * | 1998-10-19 | 2000-04-26 | 松下电器产业株式会社 | 扩频接收机 |
JP2001313590A (ja) * | 2000-04-27 | 2001-11-09 | Sharp Corp | 同期追従方式 |
-
2002
- 2002-07-03 CN CN02819180.3A patent/CN1561596A/zh active Pending
- 2002-07-03 AU AU2002315741A patent/AU2002315741A1/en not_active Abandoned
- 2002-07-03 WO PCT/CN2002/000470 patent/WO2004006480A1/zh not_active Application Discontinuation
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0718998A2 (en) * | 1994-12-22 | 1996-06-26 | Nec Corporation | De-spread code phase detection apparatus in spread spectrum type receiver |
JPH0918446A (ja) * | 1995-06-28 | 1997-01-17 | Oki Electric Ind Co Ltd | 同期追従回路 |
JPH09321663A (ja) * | 1996-05-28 | 1997-12-12 | Oki Electric Ind Co Ltd | 同期追従装置 |
JPH11234168A (ja) * | 1998-02-10 | 1999-08-27 | Sharp Corp | 拡散信号に対する相関処理の同期追従回路 |
CN1251479A (zh) * | 1998-10-19 | 2000-04-26 | 松下电器产业株式会社 | 扩频接收机 |
JP2001313590A (ja) * | 2000-04-27 | 2001-11-09 | Sharp Corp | 同期追従方式 |
Also Published As
Publication number | Publication date |
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AU2002315741A1 (en) | 2004-01-23 |
CN1561596A (zh) | 2005-01-05 |
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