CN1128560C - Cross-region switching method for mobile terminals - Google Patents

Abstract

A method for handover of a mobile terminal. When a mobile station is handed over from a macro cell or a micro cell to a micro cell, it determines the movement trend of the mobile station relative to the target cell by analyzing the historical data of the target cell measured by the mobile station. Under the premise of considering the dynamic priority of the target cell, power budget and other factors, the preferred target cell is determined by approximating the slope of the direction line corresponding to each target cell, so that the mobile station is preferentially handed over to the target cell that is gradually approaching the mobile station .

Description

The take advantage of a situation method of handover of portable terminal

The present invention relates to a kind of method of handover in the mobile communcations system, specifically, is a kind of method that portable terminal (travelling carriage) is switched to microcellulor from macrocellular or microcellulor.

The switching of portable terminal between sub-district (honeycomb) is directly connected to the quality of communications of Mobile Terminals quality.In the prior art, existing multiple different handover scheme.Wherein, some is at the fast moving terminal.In the mobile communcations system of double frequency multilayer, for fear of the frequent switching between microcellulor of the travelling carriage of fast moving, general using directly or the translational speed of round-about way estimation travelling carriage, then the travelling carriage of fast moving is switched in the macrocellular, travelling carriage at a slow speed switches in the microcellulor.As in patent WO 97/00587, proposing a kind of method of direct measurement mobile station speed.Travelling carriage has exceeded the threshold value that sets in advance if the base station measures the variation that the frequency of travelling carriage takes place when fast moving, then judge it is travelling carriage fast.Do not further consider the influence of moving direction to switching of travelling carriage in this scheme, and in fact the factor of moving direction is also very important.In patent WO 95/28813, considered the moving direction of travelling carriage in the disclosed scheme.In this scheme, measure travelling carriage at Microcell time registered and the moving direction that defines this travelling carriage.If the time that records in certain sub-district is less than the Preset Time of this Microcell, and the approach axis of this travelling carriage in each sub-district be different from the direction of leaving away, and then indicating this travelling carriage is the fast moving platform.Here, the moving direction of travelling carriage is as just the supplementary means of judging mobile station speed, rather than directly reference factor is switched in conduct.If it is a fast moving platform that a travelling carriage is judged, this travelling carriage can be switched to macrocellular undoubtedly so, and still, this scheme does not have to solve the problem switch to the close honeycomb of travelling carriage.When switching, if travelling carriage is in fact leaving Target cell gradually, along with distance widens, the quality of communication descends rapidly, and can switch once more soon so.

The objective of the invention is to, propose a kind of method of new selection switching target small area, the method can switch to travelling carriage the close sub-district of travelling carriage, avoids not frequent switching, improves the reliability of switching, and improves communication quality.

For achieving the above object, the present invention includes following steps: the record measurement data; Calculate the mean value of measurement data; When needs switch, select Target cell; To qualified Target cell list ordering; Switch; It is characterized in that:

During to qualified Target cell list ordering, take all factors into consideration the slope of the direction straight line of the power budget of dynamic priority, sub-district of each sub-district and match; Under the identical situation of the Several Factors such as power budget of the dynamic priority of sub-district, sub-district, if the slope symbol difference of the direction straight line of each match, slope is that positive straight line corresponding district is preferential; If the symbol of the slope of each fitting a straight line is identical, the straight line corresponding district that slope absolute value is big is preferential.

The direction straight line of described match is meant the straight line that obtains by the following method:

Base station controller is preserved N (N gets 16～32) level mean value of adjacent cell:

Level(Xi)(Xi＝1～N)；

If the orthogonal polynomial of match direction straight line is

Wherein $\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="C0011638700112.png"\; state="\{\{state\}\}">b</figure-callout>}1=\frac{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{X}_i{p_0}^2\left(X_i\right)}{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{p_0}^2\left(X_i\right)}=\frac{N+1}{2}$

Equation S (the X of match _i)=a1*p ₀(X _i)+a2*p ₁(X _i)

Obtain the linear equation of match

S(X _i)＝a2*X _i+a1-a2*b1

Its slope a2 ^*Can calculate with least square method.

Describe the present invention below in conjunction with drawings and Examples.

Fig. 1 is a flow chart of the present invention;

Fig. 2 is the schematic diagram of the level intensity of the Target cell that arrives of moving table measuring with the rule of variable in distance;

Fig. 3 is that the position between sub-district, travelling carriage place and the adjacent cell concerns schematic diagram in the embodiments of the invention;

Fig. 4 is the fitting a straight line figure of contiguous two sub-districts of travelling carriage in the embodiments of the invention.

As can be seen from Figure 1, realization of the present invention has following step: the record measurement data, calculating mean value judges whether and should switch according to result of calculation, when should switching, selects Target cell and switches.These are basic to be consistent basically with prior art.Contribution of the present invention is: when Target cell more than one, and under the essentially identical situation of other factors, the slope by match direction straight line decides and switches to which sub-district.Below respectively each step is described, to will only simply describing with the essentially identical content of prior art.

1. record measurement data

Travelling carriage approximately reported the one-shot measurement report every 0.5 second, wherein comprise the measurement level of maximum 6 adjacent cells.Because the adjacent cell that reports for twice is not necessarily identical, after a time, can keep the data that exceed 6 adjacent cells at buffer area.In measurement report, also comprise simultaneously the up-downgoing level and the error rate, Timing Advance or the like.

2. calculate the mean value of the measured value of each sub-district

The window value of supposing calculating mean value is W, after receiving W measurement report, just can access first mean value so.After this, after receiving a new measurement report, be eliminated in order to the oldest measurement report in averaging last time, is changed by up-to-date measurement report numerical value.This seems a sliding window, so be called as window value in order to the number W of the measurement report of averaging.Like this, whenever receive a measurement report, obtain a up-to-date mean value according to a up-to-date W measurement report.The buffering area of base station controller can be preserved N mean value.Mean value can more correctly reflect the rule that actual level changes.The mean value that calculates comprises the power on mean value of the gentle error rate of this sub-district up-downlink direction, the mean value of distance, mean value of adjacent cell level or the like.

3. switch decision if switch, is selected Target cell

This process mainly is that the relevant parameters that is provided with in mean value and the database of this sub-district that calculates and adjacent cell is compared.If exist the level of up-downgoing too low, perhaps the error rate is too high, and perhaps travelling carriage will determine to switch apart from base station reason too far away or the like.If what trigger is switching between the sub-district, must from measurement report, select suitable Target cell so.

4. Target cell list ordering

The Target cell that satisfies switching condition may more than one.Need sort to these Target cells.Begin to attempt from first Target cell because always switch,, promptly generally can switch to and come first Target cell so come the Target cell success rate for switching height of front.Ordering needs to consider following factor: the dynamic priority of sub-district, the power budget of sub-district and travelling carriage be the mobile trend of each Target cell relatively.Under the essentially identical situation of Several Factors, what play a decisive role is exactly the travelling carriage mobile trend of each Target cell relatively in front.The travelling carriage mobile trend of each Target cell is relatively represented with the slope of following match direction straight line.

5. match direction straight line

The present invention utilizes the variation of level mean value of the bcch carrier of certain Target cell that moving table measuring arrives, and estimates the mobile trend between travelling carriage and this sub-district.

According to the principle of radio wave propagation, when electric wave is propagated at free space, square being inversely proportional to of the intensity of signal and distance.Rayleigh fading or the like effect also can take place such as multipath fading except that with the variable in distance in the environment more complicated of practical application, electric wave signal in communication process.So in fact electric wave is along with the increase of distance, the strength retrogression of electric wave gets faster.

Moving table measuring to the level intensity of certain Target cell be that bcch carrier obtains after the various decay of experience in this sub-district.Fig. 2 has shown the Changing Pattern of the level that moving table measuring arrives.Can find out clearly that from Fig. 2 measuring has following rule between level and the distance:

Distance is near more, and level is high more;

Distance is near more, and level is along with variable in distance is big more;

Between short distance, the relation between level and the distance can be similar to straight line

Express.

Because measuring level value is some statistical values, can not drop on fully on certain bar straight line.A kind of methods of numerical is to utilize least square method, moving table measuring to N level value of Target cell bcch carrier be fitted on the straight line.The slope of this straight line can illustrate the relation between level variation and the mobile trend comparison image:

Positive slope shows that travelling carriage and sub-district are close

Negative slope show travelling carriage and sub-district away from

Under the identical situation of slope symbol, the slope that absolute value is big shows travelling carriage and sub-district

Between the distance more approaching; On the contrary, distant.

According to above-mentioned principle, match is corresponding to the traverse line of each Target cell by the following method:

1) base station controller is preserved N level mean value of adjacent cell:

(N herein of Xi=1～N) can get 16～32 to Level (Xi);

2) orthogonal polynomial of establishing match direction straight line is

Wherein $b1=\frac{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{X}_i{*p_0}^2\left(X_i\right)}{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{p_0}^2\left(X_i\right)}=\frac{N+1}{2}----\left(2\right)$ In the formula, Xi is the node of orthogonal polynomial, just is meant the sequence number of adjacent cell level mean value here, so Xi=1～N

3) establish the equation of match

S(X _i)＝a1*p ₀(X _i)+a2*p ₁(X _i) (3)

According to formula (1), the direction linear equation that (2) and (3) obtain match is

S (X _i)=a2*X _i+ a1-a2*b1 (4) coefficient a2 as can be seen from formula (4) ^*It is exactly the slope of this fitting a straight line.

According to principle of least square method, the quadratic sum multinomial $I(a,b)=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{(\mathrm{Level}\left(X_i\right)-S\left(X_i\right))}^2----\left(5\right)$ Solution space minimal point (a1 ^*, a2 ^*) have:

Calculate coefficient a2 ^*For: ${a2}^{*}\frac{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\mathrm{Level}\left(X_i\right)*p_1\left(X_i\right)}{\underset{i=1}{\overset{\mathrm{<figure-callout\; id="1"\; label="N\; p"\; filenames="C0011638700112.png"\; state="\{\{state\}\}">N</figure-callout>}}{\mathrm{\&Sigma;}}}{p_{}}^{}{{}_1}^2\left(X_i\right)}=\frac{6*\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\mathrm{Level}\left(X_i\right)*({2X}_i-(N+1))}{N*(N-1)*(N+1)}----\left(7\right)$

6. slope ratio is determined final switching target small area

Under the approaching substantially situation of other factors of selected a plurality of Target cells,, determine different degree of priority by the slope of relatively more corresponding fitting a straight line with them:

If the symbol difference of slope, positive slope is preferential;

If the symbol of slope is identical, the slope that absolute value is big is preferential.

Decide switching target to be specifically described below by an embodiment to slope with the fitting a straight line among the present invention.

Fig. 3 represents the situation that travelling carriage moves in microcellulor (sub-district) 2,1 among the figure and 3 is two contiguous honeycombs (sub-district), the 4th, and contiguous macrocellular (sub-district).

Suppose to move to microcellulor 3 in the travelling carriage microcellulor 2.Microcellulor 1 and microcellulor 3 all are the adjacent cells of microcellulor 2.When switching in honeycomb 2, microcellulor 1 and 3 is all chosen as Target cell.Because travelling carriage moves towards microcellulor 3, moving table measuring is to the variation such as the following table (selecting N=20 herein) of the level mean value of microcellulor 1:

Xi(N)	Level(Xi)	Xi	Level(Xi)
				1	24	11	17
2	23	12	16
				3	22	13	16
4	23	14	14
				5	21	15	15
6	21	16	15.5
				7	21	17	16
8	20	18	14

9	19	19	12
				10	19	20	13

Calculating the straight slope corresponding with honeycomb 1 is: A2 ^*=-0.603

Moving table measuring is to the variation such as the following table (selecting N=20 herein) of the level mean value of microcellulor 3:

Xi(N)	Level(Xi)	Xi(N)	Level(Xi)
				1	14	11	18
2	15	12	18
				3	16	13	19
4	16	14	20
				5	16	15	17
6	17	16	18
				7	16	17	20
8	18	18	21
				9	19	19	23
10	18	20	22

The slope that calculates the straight line corresponding with honeycomb 3 is: A2 ^*=0.291

Relatively result of calculation shows microcellulor 3 preferential and microcellulors 1.

Also can visually see from Fig. 4, although the level of the Target cell that moving table measuring obtains has fluctuating, total trend still is certain.The level of honeycomb 3 is progressively rising among Fig. 4, and the level of honeycomb 1 is descending gradually.From switching the angle of reliability, obviously should switch in the microcellulor 3 so.

Adopt the changing method among the present invention, when the decision portable terminal switches, not only take all factors into consideration the dynamic priority of each sub-district, the factors such as power budget of sub-district, and considered the mobile trend of portable terminal, travelling carriage can be switched to the close sub-district of travelling carriage, thereby improve the reliability of switching, improve the communication quality of travelling carriage.

Claims (2)

1, a kind of portable terminal method of handover of taking advantage of a situation may further comprise the steps: the record measurement data; Calculate the mean value of measurement data; When needs switch, select Target cell; To qualified Target cell list ordering; Switch; It is characterized in that:

During to qualified Target cell list ordering, take all factors into consideration the slope of the direction straight line of the power budget of dynamic priority, sub-district of each sub-district and match;

Under the identical situation of the Several Factors such as power budget of the dynamic priority of sub-district, sub-district, if the slope symbol difference of the direction straight line of each match, slope is that positive straight line corresponding district is preferential; If the symbol of the slope of each fitting a straight line is identical, the straight line corresponding district that slope absolute value is big is preferential;

The direction straight line of a certain sub-district of described match is meant the straight line that obtains by the following method:

Base station controller is preserved N level mean value of adjacent cell:

Level(Xi)(Xi＝1～N)；

If the orthogonal polynomial of match direction straight line is

Wherein $b1=\frac{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{X}_i*{p_0}^2\left(X_i\right)}{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{p_0}^2\left(X_i\right)}=\frac{N+1}{2}$

Equation S (the X of match _i)=a1*p ₀(X _i)+a2*p ₁(X _i)

Obtain the linear equation of match

S(X _i)＝a2*X _i+a1-a2*b1

Its slope a2 ^*Can calculate with least square method.

2, according to the take advantage of a situation method of handover of the described portable terminal of claim 1, it is characterized in that: the span of described N is 16～32.

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