CN100459793C - Method and apparatus for whole channel primary searching - Google Patents

Abstract

A method for searching all frequency band cell includes measuring RSSI value of frequency point in all frequency band by applying fixed AGC gain value and calculating out AGC regulation increment required by next time of all frequency band RSSI measurement as per obtained RSSI value, repeating above said step till AGC regulation increment is less than a certain threshold, sequencing power of all frequency band frequency point RSSI according to RSSI result of the last all frequency measurement. The device for realizing said method is also disclosed.

Description

A method and device for full-frequency cell search

technical field

The present invention relates to a full frequency band cell search technology for code division multiple access (CDMA) system terminals, in particular to an automatic gain control (AGC) adjustment method for full frequency band cell search and a device based on the method.

Background technique

With the development of wireless communication technology, more and more users use mobile terminals for wireless communication. At the same time, users who own mobile terminals have higher requirements for wireless communication technology and mobile terminals. For example, for users who often go on business trips or travel, the communication capability of the mobile station in the roaming state is very important. In a CDMA system, when a mobile station roams from one country or region to another and there are differences in spectrum planning between the two countries or regions, or when the mobile station is out of the service area for a long time, in order to be able to timely When a new network is found, the mobile station must search for cells in the entire frequency band to confirm whether there are available network resources in the entire frequency band.

For the case where the mobile station roams to other countries or regions, the mobile station needs to complete at least one full frequency band search to find an available network; for the case where the mobile station is not in the service area for a long time, the mobile station must continuously repeat the full frequency band search process. until returning to the network coverage area. Generally, the process of searching for the whole frequency band takes a long time, which will lead to a decrease in the working efficiency of the mobile station. In addition, no matter which of the above situations, the mobile station is always in the working state when performing full frequency band search, which will lead to excessive consumption of the battery of the mobile station, thereby greatly reducing the standby time of the mobile station and the service life of the battery. Therefore, improving the speed of full frequency band search is a key issue to improve the working efficiency and usage efficiency of the mobile station.

At present, there are many ways to improve the speed of full-band search, one of which is to use the received signal strength indicator (RSSI), the principle is: generally speaking, the RSSI power near the working frequency point is higher than that near other idle frequency points. The RSSI power is usually higher. Therefore, before searching for available cells, sort the RSSI power values (hereinafter referred to as RSSI values) of the frequency points of the entire frequency band, that is, first measure the RSSI values of all frequency points in the entire frequency band. According to the measurement results, sort all the frequency points according to the size of the RSSI value, and then set the priority of cell search for all frequency points according to the sorting results, and perform cell search according to the priority order of the frequency points, that is, after the search When the cell is available, the frequency point with strong RSSI power is preferred to the frequency point with low power.

However, the RSSI value of the working frequency point varies widely. Taking TD-SCDMA terminal as an example, the maximum RSSI value of the received signal is -25 decibel milliwatts (dBm), the minimum value is -108dBm, and the variation range reaches 83 decibels (dB), in addition, the RSSI value between different frequency points of the frequency band also has a large range of variation, but at present, the sampling and quantization bits of the analog-to-digital converter (ADC) are generally 4 to 12 bits, and the variation of the RSSI value is It may exceed the representation range of the ADC. Therefore, it is usually necessary to adjust the automatic gain control (AGC) gain value to adjust the RSSI value so that the adjusted RSSI value is within the quantization range of the ADC.

The adjustment of the RSSI value is to add the AGC adjustment increment to the value measured by the RSSI. When the RSSI value range is too large, after the AGC adjustment, the value range will be narrowed, which is convenient for quantization and analog-to-digital conversion of the RSSI value. Conversely, if the range of RSSI values is too small, adjusting the AGC can expand the range of values to facilitate quantization and analog-to-digital conversion of the values.

Currently in the full-band cell search, most AGC adjustment methods use a fixed AGC gain value, that is, the AGC gain value remains unchanged for the RSSI values of all frequency points during the entire frequency point sorting process.

This method of using a single AGC gain value has obvious disadvantages. Before performing full-band frequency point measurement, the mobile terminal cannot determine the RSSI power of the actual operating frequency point. Therefore, when the signal power of the actual operating frequency point is relatively large, If the AGC gain value is set too large, the RSSI value of the actual operating frequency point will be saturated; conversely, when the signal power of the operating frequency point is relatively small, if the AGC gain value is set too small, the effective digits of the RSSI value of the operating frequency point will will be too little. In the above two cases, the frequency point measurement cannot achieve a certain measurement accuracy, and the real working frequency point may not be ranked before the interference frequency point, so that the results sorted according to the frequency point RSSI value have large errors and even lose meaning. The final result is that the full-frequency cell search process has to spend more time eliminating interference frequency points, which greatly increases the successful access time of the entire cell search and becomes the bottleneck of cell search performance.

Another AGC adjustment method is to measure the RSSI value of each frequency point multiple times, and adjust the AGC gain value of this frequency point according to the last RSSI measurement result of a certain frequency point until the AGC gain value stabilizes in a reasonable range. Inside.

The advantage of this method is that it can provide more accurate measurement values than the first method, but it also has obvious defects: First, performing multiple measurements on each frequency point will lead to a long cycle of frequency point measurement in the entire frequency band and poor timeliness ; Secondly, the AGC gain values between the frequency points are different, which is easy to introduce measurement errors; thirdly, this method does not take into account the correlation between the frequency points and make reasonable use of it; finally, this method is easy affected by noise and fading.

Contents of the invention

The main purpose of the present invention is to provide a method for cell search in a full frequency band, which adjusts the AGC gain value in a flexible and fast manner, and improves the speed and accuracy of cell search in a full frequency band.

Another object of the present invention is to provide a cell search device for all frequency bands, which realizes flexible and fast adjustment of the AGC gain value.

The purpose of the present invention is achieved through the following technical solutions:

A method for searching for a full frequency band cell, comprising the steps of:

A. Set the automatic gain adjustment AGC initial gain value to the current AGC gain value;

B. Measure the received signal strength indication RSSI value of the frequency points in the whole frequency band, adjust all detected RSSI values by using the current AGC gain value, and calculate the AGC adjustment increment according to all RSSI values after gain adjustment;

C, judge whether the absolute value of the AGC adjustment increment is less than the AGC gain adjustment threshold set, if yes, then perform step D, otherwise, use the sum of the current AGC gain value and the calculated AGC adjustment increment as the new AGC gain value, Judging whether the new AGC gain value exceeds the maximum range of the AGC, if yes, execute step D, otherwise, use the new AGC gain value as the current AGC gain value, and then return to step B.

D. Sort all the RSSI values obtained from the last measurement, set the priority of each frequency point according to the sorting result, and then perform cell search according to the priority order.

Wherein, the method further includes: setting the RSSI target value,

The calculation of the AGC adjustment increment in step B is the difference between the maximum RSSI value in the current measurement frequency point and the RSSI target value.

Wherein, the target RSSI value can be set as any value that makes the RSSI value not saturated and makes the RSSI value have a preset effective number of digits.

Preferably, the target RSSI value is 0dB.

Wherein, the AGC initial gain value may be set to any value that does not saturate the maximum RSSI value.

Preferably, the AGC initial gain value is 40dB.

Wherein, the method further includes: setting the AGC gain adjustment threshold,

Wherein, in step B, measuring the RSSI values of frequency points in the whole frequency band is: measuring the RSSI values of all frequency points in the whole frequency band, or measuring the RSSI values of equally spaced frequency points in the whole frequency band.

A device 20 for full-frequency cell search includes a radio frequency module 21, a measurement sequencing module 22, a control module 23, and a cell search module 24, wherein,

The radio frequency module 21 receives the wireless radio frequency signal through the antenna of the mobile terminal, and outputs the radio frequency signal to the measurement ordering module 22;

The measurement sorting module 22 receives the radio frequency signal transmitted by the radio frequency module 21, measures the RSSI value of the frequency points in the whole frequency band, uses the current AGC gain value to adjust all detected RSSI values, and calculates according to all RSSI values after gain adjustment AGC value adjustment increment, sorting the RSSI values of frequency points in the whole frequency band, setting the priority of each frequency point according to the sorting result, and outputting the priority and sorting result to the cell search module 24;

The cell search module 24 performs cell search according to the sorting and priority results output by the measurement sorting module 22;

The control module 23 sets the radio frequency carrier frequency and the AGC initial gain value of the radio frequency module 21 and the measurement ordering module 22,

When the absolute value of the AGC value adjustment increment calculated by the measurement sorting module 22 is less than the AGC gain adjustment threshold set, a sorting indication signal is sent to the measurement sorting module 22;

When the absolute value of the AGC adjustment increment is not less than the set AGC gain adjustment threshold, the sum of the current AGC gain value and the calculated AGC adjustment increment is used as the new AGC gain value, if the new AGC gain value exceeds the maximum range of AGC , then send a sorting indication signal to the measurement sorting module (22), otherwise, use the new AGC gain value as the current AGC gain value, and send a measurement indication signal to the measurement sorting module (22).

Wherein, the measurement ordering module 22 includes an RSSI measurement unit 221, an AGC increment calculation unit 222 and an RSSI ordering unit 223,

The RSSI measurement unit 221 receives the measurement indication signal of the control unit 23, measures the RSSI value of the frequency points in the whole frequency band, and transmits the result to the AGC increment calculation unit 222;

The AGC increment calculation unit 222 calculates the AGC value adjustment increment according to the measurement result sent by the RSSI measurement unit 221, and outputs the calculated AGC value adjustment increment to the control device 23;

The RSSI sorting unit 223 receives the sorting indication signal of the control module 23, sorts the RSSI values of the frequency points in the whole frequency band sent by the RSSI measurement unit 221, sets the priority of each frequency point according to the sorting result, and then compares the priority and the sorting result Output to cell search module 24.

The method for searching a full-band cell of the present invention sets the initial value of the AGC gain, and fixes the AGC gain value to measure the RSSI value of the frequency point in the full-band, and calculates the next possible full-band measurement process according to the measurement result of the RSSI value The adjustment increment of the AGC in the middle, so as to obtain the new AGC gain value, repeat the above steps until the AGC adjustment increment meets the end condition, at this time, the AGC adjustment process is terminated and the sorting of the frequency point power of the whole frequency band is performed according to the last measured RSSI value process, and then perform a cell search based on the sorted results. By adopting the method of the invention, not only can the working frequency point be highlighted, so that the accuracy of cell search can be increased, but also the speed of cell search can be improved. The device of the present invention is based on the method of the present invention, so the device of the present invention has the advantages of accurate and fast measurement, thereby improving the satisfaction of mobile terminal users.

Description of drawings

Fig. 1 is the method flow chart of the whole frequency band cell search of a preferred embodiment of the present invention;

Fig. 2 is a structural diagram of a device for cell search in all frequency bands according to the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The method of the present invention is to use a fixed AGC gain value to measure the RSSI value of the frequency points in the full frequency band, and calculate the AGC adjustment increment according to the measured RSSI value to obtain a new AGC gain value, and repeat the above steps until the AGC adjustment increment If the end condition is satisfied, the AGC adjustment process is terminated at this time, and the sorting process of the frequency point power of the whole frequency band is performed according to the RSSI value obtained from the last measurement, and then the cell search is performed according to the sorting result.

Fig. 1 is the method flowchart according to the whole frequency band cell search of the present invention, as can be seen from Fig. 1, the present invention comprises the following steps:

Step 101: Set the initial AGC gain value of the mobile terminal, which is used for the initial measurement of the frequency points of the whole frequency band, and set the initial AGC gain value as the current AGC gain value.

The AGC initial gain value can be set to any value that does not saturate the maximum RSSI value. In this embodiment, the AGC initial gain value is set to 40dB, which is a preferred value because the initial value is usually not so large that the maximum RSSI value saturation.

Step 102: Continuously detect RSSI values for all frequency points in the whole frequency band and perform gain adjustment on all detected RSSI values by using the current AGC gain value.

The formula for calculating the RSSI value of frequency point i is: ${\mathrm{RSSI}}_i=\underset{k=0}{\overset{N}{\mathrm{\Σ}}}{\left|\right|r_i\left(k\right)\left|\right|}^2$

Among them, ‖‖ ² represents the complex number modulus; k is the sequence number of the chip, and its value range is from 0 to N; N is the average length of the chip; for the frequency division duplex (UTRA FDD) mode of Universal Terrestrial Radio Access, r _i (k) is any baseband complex signal received by the mobile terminal at frequency point i. For the time division duplex (UTRA TDD) mode of Universal Terrestrial Radio Access, r _i (k) is the RSSI _i is a received signal strength indicator of frequency point i.

The value of RSSI _i ' after gain adjustment is performed on RSSI _i by using the current AGC gain value.

Step 103: Calculate the adjustment increment of the AGC.

In this embodiment, all RSSI values obtained by this measurement are used to calculate the adjustment increment of AGC, and the calculation formula of AGC adjustment increment is: ΔAGC _next =RSSI _target '-RSSI _max '(dB)

Wherein, RSSI _target 'is the maximum RSSI value of the expected frequency point set in advance, that is, the target RSSI value. The target RSSI value can be set as any value that makes the RSSI value not saturated and makes the RSSI value have enough effective digits. In this implementation In the example, it is set to 0dB, and RSSI _max ′ is the maximum value of RSSI values of frequency points in the whole frequency range measured in step 102 .

Step 104: Judging whether the absolute value of the AGC adjustment increment is smaller than the preset AGC gain adjustment threshold, if yes, execute step 107; otherwise, execute step 105.

The AGC gain adjustment threshold is the tolerance of the AGC gain value set in consideration of the influence of measurement error and noise and fading. In this embodiment, the AGC gain adjustment threshold is set to 15dB, that is, if RSSI _max 'satisfies- 15dBm≤RSSI _max ′≤15dBm, it is considered that the current AGC gain value meets the measurement requirements.

Step 105: Calculate a new AGC gain value according to the current AGC gain value and the calculated AGC adjustment increment, and set the new AGC gain value as the current AGC gain value.

The formula for calculating the new AGC gain value is: AGC _next = AGC _last + ΔAGC _next

Among them, AGC _last is the AGC gain value set during the last full-band RSSI measurement, ΔAGC _next is the AGC adjustment increment calculated in step 103, and AGC _next is the value set for the next full-band internal frequency point RSSI value measurement New AGC gain value.

Step 106: Judging whether the current AGC gain value exceeds the maximum range of the AGC, if yes, execute step 107; otherwise, return to step 102, and use the new current AGC gain value for the next measurement.

Usually, the maximum range of AGC is determined by hardware conditions.

Step 107: sort the frequency points of the whole frequency band, and set the priority of each frequency point according to the sorting result, and then perform step 108.

Any known sorting method can be used to sort the frequency points of the whole frequency band, such as the bubble method or the dichotomy method. After the sorting, the priority of the frequency points is set according to the sorting result, that is to say, the priority of the frequency points at the top of the sorting position is high, and the priority of the frequency points at the bottom of the sorting position is low.

Step 108: Perform cell search according to the priority order of frequency points in the whole frequency band.

In this embodiment, the basic steps of the cell search are: according to the sorting results, the cell search process is performed frequency by frequency in sequence until the first frequency point that can be camped on is successfully searched. The specific search technology is the same as the prior art, and will not be repeated here.

In step 102 of the above-mentioned embodiment, the RSSI value of the frequency points of the whole frequency band is measured one by one, that is, the RSSI value of each frequency point is measured. In other embodiments of the present invention, the RSSI value of the frequency points of the whole frequency band can also be measured Perform interval measurement, that is, instead of measuring the RSSI values of all frequency points, measure the RSSI values of some equally spaced frequency points. Preferably, the measurement interval usually depends on the bandwidth of the system. For a system with a chip rate of 3.84M chips/second, its system bandwidth is about 5MHz, and a measurement interval of 200KHz, 400KHz, 800KHz or 1600KHz can usually be used; and For a system with a chip rate of 1.28M chips/second, its system bandwidth is about 1.6MHz, and a measurement interval of 200KHz or 400KHz can usually be used.

The advantage of measuring frequency points at equal intervals in the whole frequency band is that the cell search time can be shortened to some extent.

In the above embodiments, the AGC adjustment increment is the difference between the target RSSI value and the maximum RSSI value measured this time. In other embodiments of the present invention, a similar method is used to calculate the AGC adjustment increment. For example, in another embodiment, an AGC adjustment step value, such as 20dB, is preset, and after the measurement of the RSSI value of frequency points in the entire frequency band is completed, the AGC adjustment is calculated using the same method as the above-mentioned embodiment increment. If the absolute value of the AGC adjustment increment is greater than the adjustment step size, the AGC gain value is readjusted according to the size of the adjustment step size, that is, the AGC gain value is added or subtracted from the step size value to obtain a new AGC gain value, and then Repeat the above steps until the absolute value of the adjustment increment is smaller than the adjustment step, sort the measurement results of the latest RSSI value, and then perform cell search according to the sorting results.

Based on the above method, the present invention also provides a cell search device for all frequency bands. FIG. 2 is a structural diagram of the device. As shown in the figure, the cell search device 20 includes a radio frequency module 21 , a measurement sequencing module 22 , a control module 23 and a cell search module 24 .

Wherein, the radio frequency module 21 receives the wireless radio frequency signal through the antenna of the mobile terminal, and outputs the radio frequency signal to the measurement sorting module 22; the measurement sorting module 22 receives the wireless radio frequency signal output by the radio frequency module 21, and measures the RSSI value of the frequency points in the whole frequency band, Calculate the AGC adjustment increment and sort the frequency points in the whole frequency band according to the RSSI value, and output the sorting result to the cell search module 24 of the mobile terminal; the control module 23 controls the work of the radio frequency module 21 and the measurement sorting module 22, and sets The operating parameters of the radio frequency module 21 and the measurement ordering module 22, such as the radio frequency carrier frequency and the AGC initial gain value, the control module 23 receives the AGC adjustment increment output by the measurement ordering module 22 to determine whether to perform ordering, and if so, to the measurement ordering module 22 Send a sorting indication signal; otherwise, measure the indication signal to the measurement sorting module 22, and continue to measure the RSSI values of the frequency points in the whole frequency band.

In the measurement sorting module 22 , there are an RSSI measuring unit 221 , an AGC increment calculating unit 222 and an RSSI sorting unit 223 . The RSSI measurement unit 221 performs the measurement of the RSSI value of the full-band frequency point according to the radio frequency signal transmitted by the radio frequency module 21, and then outputs the measured RSSI value to the AGC increment calculation unit 222 and the RSSI sorting unit 223; the AGC increment calculation unit 222 Calculate the AGC adjustment increment of the next full-band frequency point measurement according to the RSSI value, then the AGC adjustment increment value is output to the control module 23, and whether the AGC adjustment increment satisfies the end condition is judged by the control module 23, if yes, then to the control module 23 The RSSI sorting unit 223 outputs a sorting indication signal, activates the RSSI sorting unit 223 to perform full sorting on the output values of the RSSI measuring unit 221, and sets priority for each frequency point according to the sorting result, and then outputs the sorting and priority results to The cell search module 24; otherwise, output a measurement instruction signal to the RSSI measurement unit 221, instructing the RSSI measurement unit 221 to use the new AGC gain value to measure the RSSI value of all frequency points in the frequency band.

Appropriate improvements can be made to the method and device according to the present invention in the specific implementation process to meet the specific needs of specific situations. Therefore, it can be understood that the specific implementation manners according to the present invention are only exemplary, and are not intended to limit the protection scope of the present invention.

Claims (9)

1. A method for full frequency band cell search, characterized in that the method comprises the steps: A. Set the automatic gain adjustment AGC initial gain value to the current AGC gain value; B. Measure the received signal strength indication RSSI value of the frequency points in the whole frequency band, adjust all detected RSSI values by using the current AGC gain value, and calculate the AGC adjustment increment according to all RSSI values after gain adjustment; C, judge whether the absolute value of the AGC adjustment increment is less than the AGC gain adjustment threshold set, if yes, then perform step D, otherwise, use the sum of the current AGC gain value and the calculated AGC adjustment increment as the new AGC gain value, Determine whether the new AGC gain value exceeds the maximum range of the AGC, if yes, then perform step D, otherwise, use the new AGC gain value as the current AGC gain value, and then return to step B; D. Sort all the RSSI values obtained from the last measurement, set the priority of each frequency point according to the sorting result, and then perform cell search according to the priority order. 2. The method according to claim 1, further comprising: setting the RSSI target value, The calculation of the AGC adjustment increment in step B is the difference between the maximum RSSI value in the current measurement frequency point and the RSSI target value. 3. The method according to claim 2, characterized in that the RSSI target value can be set as any value that makes the RSSI value unsaturated and makes the RSSI value have a preset effective number of digits. 4. The method according to claim 3, wherein the RSSI target value is 0dB. 5. The method according to claim 1, wherein the AGC initial gain value can be set to any value that does not saturate the maximum RSSI value. 6. The method according to claim 5, wherein the AGC initial gain value is 40dB. 7. The method according to claim 1, characterized in that, in step B, measuring the RSSI values of frequency points in the whole frequency band is: measuring the RSSI values of all frequency points in the whole frequency band, or measuring the frequency points at equal intervals in the whole frequency band The RSSI value of the point. 8. A device for full-frequency cell search, located in a mobile terminal, characterized in that the device (20) includes a radio frequency module (21), a measurement ordering module (22), a control module (23) and a cell search module (24 ),in, The radio frequency module (21) receives the wireless radio frequency signal through the antenna of the mobile terminal, and outputs the radio frequency signal to the measurement ordering module (22); The measurement sorting module (22) receives the radio frequency signal transmitted by the radio frequency module (21), measures the RSSI value of the frequency points in the whole frequency band, adopts the current AGC gain value to adjust all detected RSSI values, and adjusts the value according to the gain adjusted All RSSI values calculate the AGC value adjustment increment, sort the RSSI values of the frequency points in the whole frequency band, set the priority of each frequency point according to the sorting results, and output the sorting and priority results to the cell search module (24); The cell search module (24) performs cell search according to the sorting and priority results output by the measurement sorting module (22); Control module (23) is provided with the radio frequency carrier frequency of radio frequency module (21) and the AGC initial gain value of measurement sorting module (22); When the absolute value of the AGC value adjustment increment calculated by the measurement sorting module (22) is less than the AGC gain adjustment threshold set, a sorting indication signal is sent to the measurement sorting module (22); When the absolute value of the AGC adjustment increment is not less than the set AGC gain adjustment threshold, the sum of the current AGC gain value and the calculated AGC adjustment increment is used as the new AGC gain value, if the new AGC gain value exceeds the maximum range of AGC , then send a sorting indication signal to the measurement sorting module (22), otherwise, use the new AGC gain value as the current AGC gain value, and send a measurement indication signal to the measurement sorting module (22). 9. The device according to claim 8, characterized in that the measurement ordering module (22) comprises an RSSI measurement unit (221), an AGC increment calculation unit (222) and an RSSI ordering unit (223), The RSSI measurement unit (221) receives the measurement instruction signal of the control unit (23), measures the RSSI value of the frequency points in the whole frequency band, and transmits the result to the AGC increment calculation unit (222); The AGC increment calculation unit (222) calculates the AGC value adjustment increment according to the measurement result sent by the RSSI measurement unit (221), and outputs the calculated AGC value adjustment increment to the control device (23); The RSSI sorting unit (223) receives the sorting indication signal of the control module (23), sorts the RSSI values of the frequency points in the whole frequency band sent by the RSSI measuring unit (221), and sets the priority of each frequency point according to the sorting result, and then The ranking and prioritization results are output to a cell search module (24).

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