CN1599304A - Hard switchover method based on link quality - Google Patents

Abstract

The invention relates to a hard switchover method based on the quality of the chain circuit. Its features lie in the following steps: a. gets the current FER; b. judge the current area whether is the boundary area and if it is the boundary area, enter the step c and if not, go back to a; c. calculate the average FER; d. judge whether the average FER is bigger than the permitted maximum FER by the chain circuit. If it is, enter the step e and if not, go back to the step a; e. touch off the hard cut. The advantages are easily and flexibly operation and can guarantee the quality of the chain circuit better.

Description

A kind of method for hard switching based on link-quality

Technical field

The present invention relates to the communications field, relate in particular to a kind of method for hard switching based on link-quality.

Technical background

CDMA is the system of a self-interference, and two big characteristics power control and switchings of its technology have directly determined the quality of system.In radio CDMA network system, for the continuity that guarantees that the mobile subscriber converses, switching is absolutely necessary.Handover success rate will directly have influence on the performance of system, and a good changing method can improve the preceding reverse capacity of system, reduce the cutting off rate of system.

Switching is meant the edge that arrives original Serving cell when travelling carriage, in the time of will entering another Serving cell, and the process that the link between former base station and the travelling carriage is replaced by the link between new base station and the travelling carriage gradually.

Direct-cut operation is meant that travelling carriage disconnects earlier and the linking of current service cell, then the process that links of foundation and another Serving cell.The switching of different frequent points under the same BSC, the switching of no A3/A7 link path between different B SC, and hard-switching technology is often all adopted in the switching of striding between the network of manufacturer.Direct-cut operation has several different methods, different occasions may adopt different method for hard switching, and in the network there be the main method for hard switching that uses at present: Pilot Beacon Hard Handoff (pilot beacon direct-cut operation), RTD Hard Handoff (loop time delay direct-cut operation), Mobile Assisted Hard Handoff (mobile phone assisted hard hand) etc.

The technical scheme of prior art one:

The pilot beacon direct-cut operation: there are four frequencies (F0 is to F3) hypothetical boundary sub-district 1, its neighbor cell 2 has three frequencies (F0 is to F2), if adopt the method for pilot beacon direct-cut operation, need be in neighbor cell 2, add the pilot beacon that frequency is F3, when mobile phone in the process that sub-district 1 frequency F3 converses, can detect the dummy pilot signal of sub-district 2, BSC can trigger direct-cut operation according to the power of this signal, make mobile phone switch to and proceed conversation on certain true pilot tone (F0, F1, F2) of sub-district 2, as shown in Figure 1.

Can't call out on the pilot beacon, the pilot beacon that increases in system only is to be used for assisting carrying out direct-cut operation, can increase network construction cost like this.

For example: the footprint shapes of expressway is that an arrowband is capable usually, as shown in Figure 2.At border cell,,, will cause the power system capacity utilance to reduce like this in order to guarantee that the user move not call drop to all directions, need allow mobile phone switch in advance by the parameter setting if use the RTD direct-cut operation.If use the pilot beacon direct-cut operation, need increase a pilot beacon in each outlet of expressway, cost is too high.If use the link-quality direct-cut operation, these problems just have been readily solved.

The technical scheme of prior art two:

The RTD direct-cut operation: the distance of mobile phone apart from the base station can be known by RTD in the base station, utilizes the distance of this estimation, defines a suitable thresholding then and removes to trigger direct-cut operation.(do not have PilotBeacon) equally as shown in Figure 1, mobile phone is 1 frequency F3 in the sub-district, then away from sub-district 1, after the distance from sub-district 1 reaches certain thresholding, triggers direct-cut operation, and mobile phone is switched on the sub-district 2.

This mode need not be added new hardware device, can not increase network construction cost.

Because multipath effect, the distance of utilizing RTD to estimate may be inaccurate; If a plurality of neighbor cells are arranged, and the direction that moves of user is difficult to determine suitable Target cell when uncertain.Cover leak or sub-district covering out-of-shape if system exists, the RTD direct-cut operation will cause the capacity of border cell to reduce.

For example: suppose that there are two frequencies (F1, F2) base station, F2 has one to cover leak (as shown in Figure 3).Mobile phone will switch to F1 from F2, use the RTD direct-cut operation, if before the RTD thresholding is set in leak, this will reduce the capacity of F2; If RTD is set in the covering edge of F2,, mobile phone will cause call drop when entering the covering leak.Use the link-quality direct-cut operation to settle the matter once and for all.

Summary of the invention

The objective of the invention is to propose a kind of method for hard switching,, improve the direct-cut operation success rate to reduce cutting off rate based on link-quality, the service quality that assurance meets the demands, and reduce system interference, reverse capacity before the increase network.

For this reason, the present invention adopts following scheme:

A kind of method for hard switching based on link-quality, it may further comprise the steps:

A, obtain current FER;

B, judge whether current area is border cell, if enter step c; Otherwise return step a;

C, calculating mean F ER;

Do you d, judge that mean F ER is greater than the maximum FER of permission of link? if enter step e; If not, then return step a;

E, triggering direct-cut operation.

Among the described step c, this FER is forward direction FER.

Described method, the maximum FER of permission of link adopts following formula to calculate:

$\mathrm{Average}\_\mathrm{FER}\left(t\right)=\left(\frac{F-1}{F}\right)*(P\_\mathrm{FER}(t-1))+\left(\frac{1}{F}\right)*(C\_\mathrm{FER}\left(t\right))$

Wherein:

T is the time;

C_FER (t) is the value of current forward direction FER;

P_EER (t-1) is the value of last forward direction FER;

The F:FER weight factor.

Also comprise the step of calculating the forward traffic channel gain among the described step c; In the described steps d, also comprise and judge the step of forward traffic channel gain greater than the Traffic Channel gain threshold? if then enter step e; If not, then return step a.

Described Traffic Channel gain threshold computing formula is:

TriggeredTCG＝MinChnGain+MaxTCG*(MaxChnGain-MinChnGain)--(2)

Wherein:

TriggeredTCG is for triggering direct-cut operation forward traffic channel gain threshold;

MinChnGain is the forward traffic channel least gain;

MaxChnGain is the forward traffic channel maximum gain.

Among the described step c, this FER is inverted-F ER.

Described method, the maximum FER of permission of link adopts following formula to calculate:

$\mathrm{Average}\_\mathrm{FER}\left(t\right)=\left(\frac{F-1}{F}\right)*(P\_\mathrm{FER}(t-1))+\left(\frac{1}{F}\right)*(C\_\mathrm{FER}\left(t\right))$

Wherein:

T is the time;

C_FER (t) is the value of current inverted-F ER;

P_FER (t-1) is the value of last inverted-F ER;

The F:FER weight factor.

Described step c also comprises the step of calculating reverse Eb/Nt; Does described steps d also comprises judge that reverse Eb/Nt is greater than reverse Eb/Nt thresholding? if enter step e; If not, then return step a.

The computing formula of described reverse Eb/Nt thresholding is:

TriggeredMaxEbNt＝PwrMinEbNt+MaxEbNt*(PwrMaxEbNt-PwrMinEbNt)

Wherein,

TriggeredMaxEbNt is the triggering thresholding of this hard handover approach;

PwrMinEbNt is the minimum Eb/Nt of power control Traffic Channel;

PwrMaxEbNt is the maximum Eb/Nt of power control Traffic Channel.

Described FER can obtain by PMRM (the power measurement report message) message that mobile phone reports, and also can go out (Erase Indicator Bit) by E and wipe indicating bit and obtain.

The beneficial effect that technical solution of the present invention is brought:

1, provides a kind of new hard handoff decision method, solved power system capacity decline when multifrequency covers, the problem that cutting off rate and direct-cut operation mortality increase.Can better embody the benefit that the multifrequency environment brings to network system.

2, the triggering of link-quality direct-cut operation is based on preceding, inverted-F ER, and forward traffic channel gains, oppositely the Eb/Nt set point.Can only consider also to take all factors into consideration wherein a kind of, have bigger adaptability and flexibility various conditions.Adopt this method for hard switching in the multifrequency covering system, only the communication quality of mobile phone can not be guaranteed, and has also improved the capacity of system to greatest extent, makes forward direction and reverse link-quality reach optimum.

What 3, the link-quality direct-cut operation adopted is sector (Sector) level data configuration mode, when carrying out the network optimization and parameter testing, can be as accurate as the sector, has strengthened adaptability and flexibility that grid optimization and parameter are provided with.

Cover leak if 4 multi frequency systems exist, the link-quality direct-cut operation can improve the capacity utilance of system to greatest extent, avoids unnecessary capacitance loss.

5, in places such as large-scale market place builet below the ground or subways, the place of each inlet all is a border cell, uses the link-quality method for hard switching very suitable.

6, use the direct-cut operation and other the method for hard switching (RTD, Pilot Beacon etc.) of link-quality simultaneously, can better guarantee the quality of border cell communication link.

7, at some special occasions, RTD and Pilot Beacon are also inapplicable, and can adopt the link-quality method for hard switching this moment, and the scope of application of this method is very wide, are not subjected to the restriction of conditions such as ground l network.

Description of drawings

Fig. 1 is a pilot beacon direct-cut operation schematic diagram in the prior art;

Fig. 2 be in the prior art link-quality direct-cut operation in the application of expressway;

Fig. 3 is the application of link-quality direct-cut operation in covering the leak system in the prior art;

Fig. 4 is a link-quality direct-cut operation schematic diagram of the present invention;

Fig. 5 is the direct-cut operation schematic flow sheet that the present invention is based on forward direction FER:

Fig. 6 is the direct-cut operation schematic flow sheet that the present invention is based on forward direction FER and forward traffic channel gain;

Fig. 7 is the direct-cut operation schematic flow sheet that the present invention is based on inverted-F ER;

Fig. 8 is the direct-cut operation schematic flow sheet that the present invention is based on inverted-F ER and reverse Eb/Nt;

Fig. 9 is the direct-cut operation schematic flow sheet that the present invention is based on forward direction FER.

Embodiment

Below in conjunction with Figure of description the specific embodiment of the present invention is described.

The brief introduction of link-quality direct-cut operation:

As shown in Figure 4, mobile phone is in the enterprising words that work of frequency F2 (white portion), and beginning is away from the sub-district, and the link-quality of this moment can be worse and worse, preceding inverted-F ER, and forward emitting power, oppositely Eb/Nt can raise.We can take all factors into consideration these values, when reaching some thresholdings, with regard to the direct-cut operation of trigger link quality.After direct-cut operation triggered, mobile phone can be proceeded conversation on frequency F1 (gray area).

It is an important parameters that the link-quality direct-cut operation triggers thresholding, and the value of this parameter depends on the poorest quality that audio call can be tolerated.

The factor relevant with link-quality has 4, is respectively forward direction FER, inverted-F ER, forward traffic channel gain, reverse Eb/Nt.Above-mentioned each factor can be used separately, also can be used in combination mutually, and concrete use can be adopted flexibly according to network condition.

Based on this thought, link-quality direct-cut operation of the present invention can use single-factor (only considering preceding, inverted-F ER) and double factor (forward direction is taken all factors into consideration the Traffic Channel gain of FER, oppositely takes all factors into consideration FER and Eb/Nt set point) dual mode.

This shows that link-quality direct-cut operation of the present invention can derive four kinds of triggering modes:

1, based on the triggering mode of forward direction FER.

2, based on forward direction FER and forward traffic channel gain triggering mode.

3, based on the triggering mode of inverted-F ER.

4, based on inverted-F ER and the reverse triggering mode of Eb/Nt.

We are defined as follows the parameter meaning:

1.MaxFwdFer: the maximum FER that allows of link-quality direct-cut operation forward link, percentage is represented.

2.MaxRevFer: the maximum FER that allows of link-quality direct-cut operation reverse link, percentage is represented.

3.MaxTCG: link-quality direct-cut operation forward traffic channel maximum gain, percentage is represented.

4.MaxEbNt: the link-quality direct-cut operation oppositely allows maximum Eb/Nt to set, and percentage is represented.

5.Factor:FER weight factor, 1 to 255.More for a short time being illustrated among the mean F ER that this value is provided with, recent FER weight is big more.It is big more that this value is set, and among the expression mean F ER, the FER weight of preceding one-shot measurement is big more.

6.CellType: cell type, whether expression is border cell.

Measure entry condition:

The link-quality direct-cut operation need be measured link-quality, as the foundation of hard handoff decision before triggering.There are two kinds of different modes to start link quality measurements.

1, is the border cell pilot tone that to carry out the link-quality direct-cut operation when BSC finds reference pilot, then starts link quality measurements.

2, be the border cell pilot tone that to carry out the link-quality direct-cut operation when BSC finds reference pilot, and when all pilot frequency intensities are all less than T_ADDG (thresholding that strength ratio T_ADD is slightly good) in the phone activated set, then start link quality measurements.

Introduce the execution mode under the various situations of the present invention below in detail:

One, based on the direct-cut operation of forward direction FER

As shown in Figure 5, be the direct-cut operation flow process that the present invention is based on forward direction FER:

The FER of forward link can obtain by PMRM (the power measurement reportmessage) message that mobile phone reports, and also can wipe indicating bit by EIB (Erase Indicator Bit) and obtain.If adopt RC1, we are by the FER of PMRM message acquisition forward direction, if adopt RC2, we also can add up the FER of forward direction by EIB (Erase Indicator Bit).

Computing formula:

$\mathrm{Average}\_\mathrm{FER}\left(t\right)=\left(\frac{F-1}{F}\right)*(P\_\mathrm{FER}(t-1))+\left(\frac{1}{F}\right)*(C\_\mathrm{FER}\left(t\right))----\left(1\right)$

In the formula, the t express time.

C_FER (t): the value of current forward direction FER, can try to achieve by PMRM, also can try to achieve by EIB.

P_FER (t-1): the value of last forward direction FER.

F:FER weight factor, scope are 1 to 255.

Use as above formula calculating mean F ER, as the condition of judgement.We need consider the unexpected fluctuation of FER, and we should not trigger switching this situation, adopt a weight factor (Factor) to make current and last FER all will consider, can avoid this situation.Specifically value of setting of this weight factor, need in actual environment, test or emulation after determine.

According to formula, weight factor can be selected by two kinds of different situations:

If 1 network place landform is more smooth, there is not too high building, generally there is not the unexpected fluctuation of FER, this weight factor should be selected less value.

If the many mountains of landform, 2 network place, many high constructures are easy to generate rapid fading like this, and this weight factor will be selected bigger value.

Usually, the computing formula of FER is as follows:

$\mathrm{FER}(\%)=\frac{\mathrm{number}\_\mathrm{bad}\_\mathrm{frames}}{\mathrm{number}\_\mathrm{tatal}\_\mathrm{frames}}*100\%$

Wherein:

Number_bad_frames: the mistake number of frames of receiving.

Number_tatal_frames: the totalframes amount of receiving.

Trigger condition:

A) reference pilot is a border cell

B) mean F ER is greater than MaxFwdFer.

Two, based on the direct-cut operation of forward direction FER and forward traffic channel gain

As shown in Figure 6, be to the present invention is based on forward direction FER and forward traffic channel gain direct-cut operation schematic flow sheet.

The computing formula of forward direction mean F ER is with formula 1.

The forward traffic channel gain is another forward link quality index.Forward traffic channel gain threshold computing formula:

TriggeredTCG＝MinChnGain+MaxTCG*(MaxChnGain-MinChnGain)--(2)

In the formula:

TriggeredTCG: expression triggers direct-cut operation forward traffic channel transmitting power thresholding.

MinChnGain: expression forward direction minimum emissive power.

MaxChnGain: expression forward direction maximum transmission power.

If MaxTCG equals 0%, expression triggers thresholding and equals the forward direction minimum emissive power; If MaxTCG equals 100%, expression triggers thresholding and equals the forward direction maximum transmission power.

Trigger condition:

1, reference pilot is a border cell;

2, the forward traffic channel gain is greater than TriggeredTCG;

3, mean F ER is greater than MaxFwdFer.

Three, based on the direct-cut operation of inverted-F ER:

As shown in Figure 7, be the direct-cut operation flow process that the present invention is based on inverted-F ER:

All the computing formula of inverted-F ER is with formula 1; But wherein use the value of current inverted-F ER and the value of last inverted-F ER.

BSC can be by the quality of reverse frames, and the direct quality of judgment frame is carried out the statistics of frame error rate.The computing formula of this method for hard switching and trigger condition are with " based on the direct-cut operation of forward direction FER " method.

Four, based on inverted-F ER and the reverse direct-cut operation of Eb/Nt

As shown in Figure 8, be the direct-cut operation schematic flow sheet that the present invention is based on inverted-F ER and reverse Eb/Nt, as can be seen from the figure, this method has increased the judgement to reverse Eb/Nt on the basis of " based on the direct-cut operation of inverted-F ER ".

The computing formula of average inverted-F ER is with formula 1; But wherein use the value of current inverted-F ER and the value of last inverted-F ER.

The computing formula of reverse Eb/Nt thresholding:

TriggeredMaxEbNt＝PwrMinEbNt+MaxEbNt*(PwrMaxEbNt-PwrMinEbNt)--(3)

In the formula,

TriggeredMaxEbNt: the triggering thresholding of this hard handover approach, unit is dB.

PwrMinEbNt: the minimum Eb/Nt of expression power control Traffic Channel, unit is dB.

PwrMaxEbNt: the maximum Eb/Nt of expression power control Traffic Channel, unit is dB.

If MaxEbNt equals 0%, expression triggers the minimum Eb/Nt that thresholding equals power control; If MaxEbNt equals 100%, expression triggers the maximum Eb/Nt that thresholding equals power control.

Trigger condition:

1, reference pilot is a border cell;

2, current Eb/Nt set point is greater than TriggeredMaxEbNt;

3, mean F ER is greater than MaxRevFer.

Whole process triggers example:

As shown in Figure 8, suppose that BSS adopts the link-quality method for hard switching based on forward direction FER, after receiving the pilot strength measurement report message (PSMM) of MS, measure to start and adjudicate.Measure entry condition if satisfy, then transmission power control parameter message (PCNPM) is given MS, allows MS report forward direction mistake frame condition.BSS misses the calculating of frame and the judgement of direct-cut operation after receiving the Power Measurement Report Message that MS reports (PMRM), in case satisfy the condition of direct-cut operation, just send switch indicating information (HDM) to MS.MS is after receiving this message, and direct-cut operation continues conversation to corresponding target carrier frequency.

As shown in Figure 9, be the direct-cut operation schematic flow sheet that the present invention is based on forward direction FER, the relation between four kinds of hard handoff decisions.These four kinds of methods are to measure and trigger direct-cut operation from different angles, and certain contact and difference are also arranged between them.

1, forward direction and oppositely between relation: general, in cdma system, forward direction and oppositely be symmetrical with relevant.The forward direction variation often means oppositely also variation, so reverse situation was similar before we can think when adjudicating, thereby only uses the data of a direction to adjudicate, such simplicity of design and effectively.In the BSS side, can obtain the oppositely quality of each frame easily, measurement inverted-F ER is more timely and accurate than measuring forward direction FER, and folk prescription is reversed judgement to our general the use.Certainly consider simultaneously that oppositely such judgement is more accurate before preferably.

2, the relation of single-factor and double factor: single-factor is exactly only to consider that FER, double factor are that forward direction also will be considered the gain of Traffic Channel, oppositely also will consider the EbNt set point except considering FER.The single-factor flow process is simple, and overhead is little; The double factor input information is abundant, can make judgement more accurately.

3, four kinds of decision methods are relatively independent, can use separately also and can use simultaneously in conjunction with several method.Because the flexibility of method itself, to the use of the whole bag of tricks without limits, can select arbitrarily and make up this four kinds of methods according to actual conditions, with the different network system of better adaptation.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claims.

Claims (10)

1, a kind of method for hard switching based on link-quality is characterized in that may further comprise the steps:

A, obtain current FER;

B, judge whether current area is border cell, if enter step c; Otherwise return step a;

C, calculating mean F ER;

Do you d, judge that mean F ER is greater than the maximum FER of permission of link? if enter step e; If not, then return step a;

E, triggering direct-cut operation.

2, the method for claim 1 is characterized in that among the described step c that this FER is forward direction FER.

3,, it is characterized in that the maximum FER of permission of link adopts following formula to calculate as method as described in the claim 2:

$\mathrm{Average}\_\mathrm{FER}\left(t\right)=\left(\frac{F-1}{F}\right)*(P\_\mathrm{FER}(t-1))+\left(\frac{1}{F}\right)*(C\_\mathrm{FER}\left(t\right))$

Wherein:

T is the time;

C_FER (t) is the value of current forward direction FER;

P_FER (t-1) is the value of last forward direction FER;

The F:FER weight factor.

4,, it is characterized in that also comprising among the described step c step of calculating the forward traffic channel gain as method as described in the claim 2; In the described steps d, also comprise and judge the step of forward traffic channel gain greater than the Traffic Channel gain threshold? if then enter step e; If not, then return step a.

5, method as claimed in claim 4 is characterized in that described Traffic Channel gain threshold computing formula is:

TriggeredTCG＝MinChnGain+MaxTCG*(MaxChnGain-MinChnGain)--(2)

Wherein:

TriggeredTCG is for triggering direct-cut operation forward traffic channel gain threshold;

MinChnGain is the forward traffic channel least gain;

MaxChnGain is the forward traffic channel maximum gain.

6, the method for claim 1 is characterized in that among the described step c that this FER is inverted-F ER.

7, method as claimed in claim 6 is characterized in that the maximum FER of permission of link adopts following formula to calculate:

$\mathrm{Average}\_\mathrm{FER}\left(t\right)=\left(\frac{F-1}{F}\right)*(P\_\mathrm{FER}(t-1))+\left(\frac{1}{F}\right)*(C\_\mathrm{FER}\left(t\right))$

Wherein:

T is the time;

C_FER (t) is the value of current inverted-F ER;

P_FER (t-1) is the value of last inverted-F ER;

The F:FER weight factor.

8, method as claimed in claim 7 is characterized in that described step c also comprises the step of calculating reverse Eb/Nt; Does described steps d also comprises judge that reverse Eb/Nt is greater than reverse Eb/Nt thresholding? if enter step e; If not, then return step a.

9, method as claimed in claim 8 is characterized in that the computing formula of described reverse Eb/Nt thresholding is:

TriggeredMaxEbNt＝PwrMinEbNt+MaxEbNt*(PwrMaxEbNt-PwrMinEbNt)

Wherein,

TriggeredMaxEbNt is the triggering thresholding of this hard handover approach;

PwrMinEbNt is the minimum Eb/Nt of power control Traffic Channel;

PwrMaxEbNt is the maximum Eb/Nt of power control Traffic Channel.

10, the method for claim 1, it is characterized in that described FER can obtain by PMRM (the power measurement report message) message that mobile phone reports, and also can wipe indicating bit by EIB (EraseIndicator Bit) and obtain.

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