CN101079858A - A method for utilizing the synchronization header pre-distortion to eliminate frequency deviation in communication system - Google Patents
A method for utilizing the synchronization header pre-distortion to eliminate frequency deviation in communication system Download PDFInfo
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- CN101079858A CN101079858A CNA2006100782803A CN200610078280A CN101079858A CN 101079858 A CN101079858 A CN 101079858A CN A2006100782803 A CNA2006100782803 A CN A2006100782803A CN 200610078280 A CN200610078280 A CN 200610078280A CN 101079858 A CN101079858 A CN 101079858A
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Abstract
The invention relates to a method for removing the frequency deviation in the communication system with synchronous head predistortion, which comprises the following steps: (1) removing the frequency deviation of the synchronous head data signal according to the received synchronous head by the terminal; (2) determining the constellation chart rotating angle of the data signal after removing the frequency deviation by observing the constellation chart of the data signal acquired by the procedure (1) and the receiving signal-to-noise ratio of the data signal outputted after the calculation of the terminal; (3) regarding the constellation chart rotating angel of the data signal removed the frequency deviation as the synchronous head predistortion value and configuring the synchronous head predistortion value by the network controller; (4) proceeding with the predistortion process according to the synchronous head predistortion value configured by network controller by the base station; (5) removing the frequency deviation of the synchronous head data signal according to the predistortion synchronous head by the terminal. The method can remove the frequency deviation accurately and effectively in the communication system, which guarantees the normal operation of the system.
Description
Technical field
The present invention relates to a kind of method of cancellation in communication systems medium frequency skew, relate in particular to a kind of method of utilizing the skew of synchronous head predistortion cancellation in communication systems medium frequency.
Background technology
In the SCDMA system because base station transmitter and terminal receiver are used fully independently clock, therefore certainly exist a frequency departure between the two, simultaneously owing to have relative motion between base station and the terminal, Doppler effect also makes terminal and base station produce frequency departure, cause keeping in the baseband signal behind the terminal intermediate frequency demodulation residual carrier component, when residual carrier is accumulated to a certain degree, will produce erroneous judgement.Because the master clock at the collection of letters and the two ends of posting a letter is independent variation, so residual carrier also changes.Terminal need be carried out real-time frequency offset computations and elimination when restituted signal, wherein frequency offset computations mainly be exactly calculate indefinite carrier shift angle α between Chip just, cosine value sin (α), cos (α), so that remaining carrier component in the baseband signal after signal is separated timing removal intermediate frequency demodulation is finished the signal demodulation exactly; And the frequency shift (FS) elimination is meant that carrying out frequency shift (FS) when signal is modulated eliminates, so that guarantee that the portable terminal of base station reception transmits and the base station local oscillator does not have frequency departure, helps the base station to finish demodulation exactly.Existing frequency shift (FS) elimination algorithm is as follows:
1, can know that by the SCDMA system frame structure that demonstrates among Fig. 1 the data of the position emission of synchronous head SYNC are known and fixing;
2, terminal uses the synchronous head of base station to come the calculated rate skew, and its concrete step is as follows:
(1) calculates the average cos8 α and the sin8 α at the carrier shift angle of 78 chip adjacent one another are totally in 64 chip at 2 Symbol of synchronous head;
(2) calculate cos α and sin α with half-angle formulas;
(3) utilize the exemplary frequency deviation values that obtains, the data-signal after the synchronous head is carried out frequency shift (FS) eliminate.
There is following problem in existing frequency shift (FS) removing method in actual use: the work schedule of existing SCDMA system is the TDD sequential, requires the radio-frequency (RF) switch of base station must finish the transmitting-receiving conversion in 10ms.In the process of transmitting-receiving conversion, because radio-frequency devices needs a steady-state process, so unavoidably in intermediate frequency local oscillator, have the component of other high frequencies.Simultaneously because the influence of radio-frequency devices causes that local oscillation signal has certain shake in a period of time of data transmission, promptly the synchronous head data frequency received of terminal has certain deviation with data frequency thereafter.
Synchronous head is the purest part in the frame structure of SCDMA system, need to utilize synchronous head to do a large amount of calibrations and the work of signal extraction in the system, so the quality of synchronous head directly has influence on systematic function.Under the situation of frequency of occurrences deviation, if do not make pre-distortion, in the process of emission, because the variation of radio-frequency (RF) switch, frequency when issuing synchronous head is f1, frequency is f2 when issuing the data-signal after the synchronous head, and terminal is θ 1 at the difference on the frequency that synchronous head partly calculates so, and the difference on the frequency that the data-signal after synchronous head calculates is θ 2.There is frequency deviation θ=θ 1-θ 2 all the time in terminal, thereby causes mistake in judgment when utilizing synchronous head to go the calculated rate deviation.And do not eliminate because terminal realizes correct frequency shift (FS), correct demodulation also can't be finished in the base station.
For these reasons, be necessary to provide a kind of new type of frequency offset cancellation method to address the above problem in fact.
Summary of the invention
The object of the present invention is to provide a kind of method of utilizing the skew of synchronous head predistortion cancellation in communication systems medium frequency, make and adopted the communication system of this method can eliminate frequency departure more exactly, guarantee better communication quality.
To achieve these goals, the inventive method may further comprise the steps:
1. a method of utilizing the skew of synchronous head predistortion cancellation in communication systems medium frequency is characterized in that, said method comprising the steps of:
(1) terminal is eliminated the frequency shift (FS) of data-signal behind the synchronous head according to the synchronous head in the received downstream signal;
(2) observe the planisphere of the data-signal after the elimination frequency shift (FS) that obtains in the step (1) and the received signal to noise ratio that terminal is calculated this data-signal of back output, determine the planisphere anglec of rotation of the data-signal after the described elimination frequency shift (FS);
(3) with the planisphere anglec of rotation of the data-signal after the described elimination frequency shift (FS) as synchronous head predistortion value, and by the described synchronous head predistortion of network management configuration value;
(4) downstream signal after the base station is carried out pre-distortion and issued pre-distortion according to the synchronous head predistortion value of network management configuration;
(5) synchronous head in the downstream signal of terminal after according to described pre-distortion is eliminated the frequency shift (FS) of data-signal behind the synchronous head.
According to the present invention, described method can also may further comprise the steps:, cause when the base station Devices Characteristics changes that order execution in step (1)～(3) reconfigure described synchronous head predistortion value when the external environment factor changes.
Preferably, described step (4) and then may further comprise the steps, formula chip_sync (n)=chip_sync is adopted according to the described synchronous head predistortion value of network management configuration in the base station
0(n) * e
-in (θ+θ 1)Synchronous head in the downstream signal that issues is carried out pre-distortion, and wherein, chip_sync is the synchronous head after the pre-distortion, chip_sync
0Be original synchronous head, the difference on the frequency that θ 1 calculates at synchronous head for terminal in the step (1), θ is a synchronous head predistortion value, n=1,2...4 * 32.
According to the present invention, described communication system is eliminated the communication system of terminal frequency deviation for utilizing the base station down signal, SCDMA system for example, and described external environment factor is temperature and/or humidity.By method of the present invention, the frequency shift (FS) of downstream signal in the cancellation in communication systems effectively; Revise with the frequency jitter that the base station radio-frequency switch is brought; Can also dynamically adjust the degree of synchronous head being carried out predistortion by network management configuration.In addition, can directly realize method of the present invention by software upgrading, site operation is simple and convenient.
Description of drawings
Below, with reference to accompanying drawing method of the present invention is described in detail, wherein:
Fig. 1 is the schematic diagram of SCDMA system frame structure;
Fig. 2 is the flow chart that utilizes the method for synchronous head predistortion cancellation in communication systems medium frequency skew according to the present invention;
Fig. 3 is the signal constellation which of no frequency departure;
Fig. 4 is the signal constellation which of frequency of occurrences deviation;
The chart of Fig. 5 for concerning between expression synchronous head predistortion value and the terminal received signal to noise ratio.
Embodiment
Be example with the SCDMA system below, be described with reference to the accompanying drawings the concrete application mode of the inventive method, be to be understood that method of the present invention can use in any communication system of utilizing the base station down signal to eliminate the terminal frequency deviation.
As shown in Figure 2, when utilizing method of the present invention that the SCDMA system is carried out the frequency shift (FS) elimination, the existing frequency removing method that terminal at first adopts background technology partly to mention is according to the frequency shift (FS) of data-signal behind the elimination of the synchronous head in the received downstream signal synchronous head.
Can know by existing frequency shift (FS) elimination algorithm in the background technology, frequency data signal skew behind the frequency shift (FS) of synchronous head and the synchronous head signal is not necessarily identical, therefore in order more accurately frequency shift (FS) to be proofreaied and correct, the planisphere of the data-signal after the elimination frequency shift (FS) that observation post obtains and terminal are calculated the received signal to noise ratio of this data-signal of back output, determine the planisphere anglec of rotation of the data-signal after the described elimination frequency shift (FS).
Fig. 3 shows the not standard square planisphere of the data-signal of frequency of occurrences skew, and Fig. 4 shows the planisphere of the data-signal that has frequency shift (FS).If observed planisphere is the shown situation of Fig. 4, promptly planisphere is not a square, the frequency of synchronous head and synchronous head then are described after data frequency exist deviation need carry out the synchronous head pre-distortion.
With the anglec of rotation of the planisphere of viewed data-signal as synchronous head predistortion value, and by the described synchronous head predistortion of network management configuration value.Like this, the base station is before issuing synchronous head, according to described synchronous head predistortion value employing formula chip_sync (the n)=chip_sync of network management configuration
0(n) * e
-in (θ+θ 1)Synchronous head in the downstream signal that issues is carried out pre-distortion, and wherein chip_sync is the synchronous head after the pre-distortion, chip_sync
0Be original synchronous head, θ 1 difference on the frequency that existing frequency departure removing method calculates at synchronous head for terminal adopts, θ is a synchronous head predistortion value, because synchronous head has 4 Symbol, each Symbol has 32 chip, thus n=1,2...4 * 32.
Because radio-frequency (RF) switch is under tdd mode, the switching of periodically carrying out transmit-receive switch that need not stop, and certain stabilization time of stable needs of radio-frequency devices are so the data that issue behind synchronous head are chip (n)=chip
0(n) * e
-in (θ 2), chip wherein
0Be the data that the original needs in base station issue, chip is the data that have frequency departure behind the various devices such as initial data process radio frequency and switch, and θ 2 is that terminal adopts the existing frequency departure removing method difference on the frequency that data computation goes out behind synchronous head.
Terminal is behind the downstream signal after the process pre-distortion that receives the base station transmission, the frequency shift (FS) of data-signal behind the synchronous head elimination synchronous head after adopting existing frequency elimination algorithm according to pre-distortion equally, the difference on the frequency that partly calculates at synchronous head is θ 1+ θ like this, and utilizes the data-signal behind the synchronous head that this frequency departure calculates to be chip (n)=chip
0(n) * e
-in (θ 2-(θ+θ 1)Therefore when θ 2=θ 1+ θ, the downstream signal that terminal calculates is the original downstream signal of base station, can there be frequency departure, this just means, as long as the synchronous head predistortion value of webmaster setting satisfies θ=θ 1-θ 2, will can there be frequency departure in the data that terminal calculates, and observed data-signal planisphere will be square, and this moment data-signal signal to noise ratio the highest.
Fig. 5 shows the relation of synchronous head predistortion value and terminal received signal to noise ratio.When terminal does not have correctly to remove the carrier component of base station, when planisphere deflected, the received signal to noise ratio of terminal reduced; When terminal was correctly removed the carrier component of base station, planisphere was the square of standard, and the received signal to noise ratio of terminal is the highest.And along with the variation of synchronous head predistortion value, the received signal to noise ratio of terminal also can change.
Because after the device of certain base station was fixing, its switching characteristic was fixed.So the synchronous head predistortion value that obtains is fixed.Write down this synchronous head predistortion value, on webmaster, its basic parameter as this base station is configured, just can guarantee that the planisphere of data-signal is the square of standard, and signal to noise ratio is the highest.
It should be noted that external environment factors such as working as temperature, humidity changes, cause that synchronous head predistortion value also can change, and need reconfigure the predistortion value so that eliminate frequency shift (FS) effectively when the base station Devices Characteristics changed.
Different base stations, because the individual character of device, its predistortion value also can be different, also need to reconfigure the predistortion value.
By method of the present invention, the frequency shift (FS) of downstream signal in the cancellation in communication systems effectively; Can revise the frequency jitter that the base station radio-frequency switch brings; Can also dynamically adjust the degree of synchronous head being carried out predistortion by network management configuration.In addition, can directly realize method of the present invention by software upgrading, site operation is simple and convenient.
Claims (8)
1. a method of utilizing the skew of synchronous head predistortion cancellation in communication systems medium frequency is characterized in that, said method comprising the steps of:
(1) terminal is eliminated the frequency shift (FS) of data-signal behind the synchronous head according to the synchronous head in the received downstream signal;
(2) observe the planisphere of the data-signal after the elimination frequency shift (FS) that obtains in the step (1) and the received signal to noise ratio that terminal is calculated this data-signal of back output, determine the planisphere anglec of rotation of the data-signal after the described elimination frequency shift (FS);
(3) with the planisphere anglec of rotation of the data-signal after the described elimination frequency shift (FS) as synchronous head predistortion value, and by the described synchronous head predistortion of network management configuration value;
(4) downstream signal after the base station is carried out pre-distortion and issued pre-distortion according to the synchronous head predistortion value of network management configuration;
(5) synchronous head in the downstream signal of terminal after according to described pre-distortion is eliminated the frequency shift (FS) of data-signal behind the synchronous head.
2. the method for claim 1, it is characterized in that, described method and then may further comprise the steps:, cause when the base station Devices Characteristics changes that order execution in step (1)～(3) reconfigure described synchronous head predistortion value when the external environment factor changes.
3. the method for claim 1 is characterized in that, described step (4) and then may further comprise the steps, and formula chip_sync (n)=chip_sync is adopted according to the described synchronous head predistortion value of network management configuration in the base station
0(n) * e
-in (θ+θ 1)Synchronous head in the downstream signal that issues is carried out pre-distortion, and wherein, chip_sync is the synchronous head after the pre-distortion, chip_sync
0Be original synchronous head, the difference on the frequency that θ 1 calculates at synchronous head for terminal in the step (1), θ is a synchronous head predistortion value, n=1,2...4 * 32.
4. method as claimed in claim 2 is characterized in that, in the described step (4) and then may further comprise the steps, formula chip_sync (n)=chip_sync is adopted according to the described synchronous head predistortion value of network management configuration in the base station
0(n) * e
-in (θ+θ 1)Synchronous head in the downstream signal that issues is carried out pre-distortion, and wherein, chip_sync is the synchronous head after the pre-distortion, chip_sync
0Be original synchronous head, the difference on the frequency that θ 1 calculates at synchronous head for terminal in the step (1), θ is a synchronous head predistortion value, n=1,2...4 * 32.
5. the described method of one of claim as described above is characterized in that, described communication system is eliminated the communication system of terminal frequency deviation for utilizing the base station down signal.
6. method as claimed in claim 5 is characterized in that, described communication system is the SCDMA system.
7. as claim 1,2,3,4, one of 6 described methods, it is characterized in that described external environment factor is temperature and/or humidity.
8. method as claimed in claim 5 is characterized in that, described external environment factor is temperature and/or humidity.
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| CNB2006100782803A CN100566320C (en) | 2006-05-22 | 2006-05-22 | A kind of method of utilizing the skew of synchronous head predistortion cancellation in communication systems medium frequency |
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| CN100566320C CN100566320C (en) | 2009-12-02 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020042938A1 (en) * | 2018-08-31 | 2020-03-05 | 北京邮电大学 | Clustering-based frequency deviation determination and elimination method and device, and electronic apparatus |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020042938A1 (en) * | 2018-08-31 | 2020-03-05 | 北京邮电大学 | Clustering-based frequency deviation determination and elimination method and device, and electronic apparatus |
| US11218354B2 (en) | 2018-08-31 | 2022-01-04 | Beijing University Of Posts And Telecommunications | Clustering-based frequency deviation determination and elimination method and device, and electronic apparatus |
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