CN1355621A - Switching method based on dual-window measurement of mobile station - Google Patents

Abstract

The present invention relates to a switching method based on movable desk twin window measuring in CDMA system. The method applies the measurement to the signal, accoridng to the requirement of switching target to select the big or small of measuring average window and to report the measured result upwards, the decide whether it is switched or not according to the switching cirterion. The present invention features considering the switching requirement at the time of selecting the measuring average window to confirm at least one selecting scheme for dynamically selecting the average window, and thus it is ensured the requirement of quick switching as well as the number of times and time relay of switching to be carried out under the satisfied conditions.

Description

A kind of changing method based on dual-window measurement of mobile station

The present invention relates to cdma system, relate to a kind of changing method in the cdma system specifically based on dual-window measurement of mobile station.

In cell mobile communication systems in the future, in order to increase power system capacity, it is littler that the coverage of sub-district will become, and becomes Microcell even picocell, and at this moment, frequent switching makes handover management seem even more important.In the second generation and 3-G (Generation Three mobile communication system), extensively having adopted the auxiliary handoff algorithms of travelling carriage is travelling carriage HO algorithm.By the pilot signal strength of each sub-district of moving table measuring, when the signal energy of adjacent cell reached a certain the requirement, then travelling carriage switched to the base station in service sector application by up link.Because the influence of mobile channel, travelling carriage must could obtain reliable measurement result through an averaging process to each base station signal, the speed that the size of average window influence is meanwhile switched and the number of times of switching.Common average window has two kinds of rectangular window and window indexs, because window index is comparatively complicated, so generally in the practical application adopt simple rectangular window average.In the cdma cellular mobile communication system in the distinctive soft switching process, travelling carriage need be measured pilot signal (CPICH) intensity of each base station in active set (Active set), candidate collection (candidate set), the adjacent collection (neighbor set), consider the complexity of travelling carriage structure, these measurements are that a time sharing shared receiver is finished, if the Measuring Time to each base station pilot signals is long, can cause the increase of handover delay.In hand-off execution process,, can have a strong impact on the quality of switching the back link if the carrier/interface ratio of Target cell is lower.So it is very crucial that average window is measured in suitable selection.Do not retrieve at present the relevant domestic and foreign literature that addresses the above problem as yet.

The objective of the invention is to propose a kind of employing to signal measurement, Dynamic Selection is measured the average window size and measurement result is reported, and the method for switching according to this result.

A kind of changing method based on dual-window measurement of mobile station provided by the invention comprises the steps:

(1) under known travelling carriage translational speed condition,, select the switch decision window to measure according to the result of tachometric survey;

(2) according to the result of window tachometric survey, carry out switch decision;

(3), carry out and switch according to the result of judgement;

Select the size of average window to comprise according to translational speed in the described step (1): if mobile station speed too fast (greater than 100 li/hour) then measure with short window;

If mobile station speed too slow (less than 3 kilometers/hour) then with long window measurement;

If mobile station speed is a middling speed, then measure with short window earlier, measure with long window again according to court verdict;

According to the result of window tachometric survey, carry out switch decision and comprise in the described step (2): if mobile station speed greater than 100 li/hour, then directly carries out switch decision according to short window measurement result;

If mobile station speed less than 3 kilometers/hour, then directly carries out switch decision according to long window measurement result;

If in the mobile station speed 3-100/hour between, then,, adjudicate according to long window measurement result again if judgement can be switched earlier according to short window measurement result judgement;

Travelling carriage to middling speed in the described step (2) adopts the switch decision algorithm of double window mouth as follows: the middling speed travelling carriage uses narrow window, and (length is d _Avs) average signal level (or other physical quantitys) of searching near district, if adjacent cell B does not satisfy switching condition with the average signal level of present sub-district A, then travelling carriage is searched for another adjacent cell C, if but satisfy switching condition, then further to widen average window be d to travelling carriage _Avw(d _Avw＞d _Avs), still satisfy switching condition if at this moment record the average signal level of two base stations, then switch, otherwise return next adjacent cell C of search;

Using the switch decision algorithm to carry out switch decision in the described step (2) further comprises: soft handover and direct-cut operation;

If what measure is common-frequency cell signal, then adopt the soft handover judgement; Described soft handover judgement is meant what the utilization following formula was realized:

The size of setting active set is Active_size=N, $M_{\mathrm{new}}\≥S\·\left(\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{M}_i\right)+(1-S)\·M_{\mathrm{Best}}-h_{\mathrm{add}}----\left(1\right)$

M _NewBe monitored base stations signal measurement mean value, M _BestBe effective centralized base-station Optimal Signals measured value, M _iBe base station signal measured value in the active set, S is a filterable agent, h _AddBe that active set adds sluggish parameter;

When the base station signal quality that monitors when travelling carriage satisfies (1), monitor cell is added active set, make travelling carriage and a plurality of cell communication;

Otherwise, when the cell signal in active set that receives when travelling carriage satisfies (2), active set is deleted out in the sub-district of link quantities difference in the active set.Then, $M_j\≤S\·\left(\underset{i=1,i\≠j}{\overset{N}{\mathrm{\Σ}}}{M}_i\right)+(1-S)\·M_{\mathrm{worst}}+h_{\mathrm{drop}}----\left(2\right)$ M _jBe that the base station signal that may delete in the active set is measured average, M _WorstBe that base station signal the poorest in the active set is measured average, h _DropIt is the sluggish parameter of deletion;

If what measure is the signal of different frequency, then adopt hard handoff decision: described direct-cut operation is that the following formula of utilization is realized: M _New〉=M _Now+ h (3);

M _NowBe the signal measurements of current area, M _NEWIt is the signal of the adjacent sub-district that measures;

In the described step (3), result according to judgement, the execution switching is meant the SIR (being used to characterize carrier/interface ratio) with the CPICH of the Radio Link of cycle monitoring switching mobile station to target sub-district, if SIR reaches a threshold value (predetermined level), then continues to carry out to switch;

Otherwise the ongoing switching of forced termination keeps original link, and informing base station controller handoff failure.

The present invention is described in further detail below in conjunction with accompanying drawing.

Fig. 1 is the handover schematic diagram of cdma system; Fig. 2 is the inventive method flow chart; Fig. 3 is the signaling process figure of changing method of the present invention; Fig. 4 is the graph of a relation of sluggish parameter and switching times in the simulation result of handoff algorithms; Fig. 5 is the graph of a relation in sluggish parameter and crosspoint.

Fig. 1 is the handover schematic diagram of cdma system.In mobile cellular system, wireless coverage area has overlapping sub-district to constitute by many, and travelling carriage 1 moves the signal quality of the measurement base station 1,2 that travelling carriage can not stop to sub-district 2 from the sub-district.When the signal quality of the base station 2 that measures satisfies Radio Link switch decision condition, base station 2 can be added active set; When the poor signal quality of base station 1 arrives certain switching condition, with the link circuit deleting between base station 1 and the travelling carriage.Usually, make switching according to the quality situation of Radio Link, also may be according to other reason, for example: load balance, switching be made in transmitting power adjustment etc.

Fig. 2 is a method flow diagram of the present invention.

At first, under known travelling carriage translational speed condition,, select the switch decision window to measure 210 according to the result of tachometric survey.Method of the present invention is to select the size of average window according to the speed of travelling carriage.For at a high speed as greater than 100 kilometers/hour travelling carriage, because of it needs to switch faster, adopt narrow window average, reduce time delay; For the travelling carriage of low speed (less than 3 kilometers/hour), slower because of its signal variation, adopt wide window average, reduce and measure number of times; Travelling carriage for middling speed, then it is carried out dual-window measurement, concrete grammar is as follows: it is average that first signal to measurement carries out narrow window, then average result is carried out switch decision, if satisfy the condition that to switch, it is average again the signal of measuring to be carried out wide window, and then the average result of wide window is carried out switch decision, just switches otherwise does not switch if satisfy switching condition.

In the handoff algorithms of the prior art, measure the general single average window that adopts, perhaps adopt double window average simultaneously.For the former, single average window is if wide window is relatively large to travelling carriage handover delay at a high speed; If adopt narrow window, for the travelling carriage of low speed, switch decision is made mistakes easily.For a kind of method in back, to measure and all adopt double window on average to increase the measurement time delay, time delay for switching strengthens.And employing this method has then reduced the influence of above-mentioned situation.

Simultaneously, for the selection of average window a plurality of criterions can be arranged, the present invention provides, and to select the criterion of window size according to mobile station speed be wherein easily realize a kind of, and the criterion that adopts other also is feasible.

For the physical quantity of switch decision, what the present invention adopted is the level value of signal, adopts the physical quantity (as the SIR of CPICH, RSCP etc.) of other measurement, and the method is suitable equally, just the threshold value difference of switch decision.

Secondly, according to the result of window tachometric survey, carry out switch decision 220.The judgement of switching acts according to being different in soft handover and direct-cut operation situation, and the present invention has proposed the decision method of a kind of direct-cut operation and a kind of soft handover respectively, can be referring to Chinese patent 98126057.8 for the judgement of switching type.

For direct-cut operation, set the base station A that travelling carriage receives, the signal level of B is respectively a (d) and b (d), and the level after average is respectively a (d) and b (d), and x (d) represents the poor of two base station average signal levels receiving:

X (d)=a (d)-b (d), (x _s(d), x _w(d) be respectively narrow window of employing and the average difference of wide window)

If x (d)＜-h (1) then decision switch, otherwise continue other cell signal of monitoring.If the employing dual-window measurement is judged x earlier _s(d) and x _w(d) (1) formula whether, corresponding different respectively sluggish parameter h _sAnd h _wThat is: travelling carriage earlier uses narrow window (length is d _Avs) average signal level of searching near district, if adjacent cell B and the average signal level (x of sub-district A at present _s(d) 〉=-h _s), h _sLag parameter when adopting narrow window, then travelling carriage is searched for another adjacent cell C, if but { x _s(d)＜-h _s, then further to widen average window be d to travelling carriage _Avw(d _Avw＞d _Avs), if at this moment record the average signal level x of two base stations _w(d) 〉=-h _w{ x _w(d)≤-h _w, h _wLag parameter when adopting wide window then switches, otherwise returns next adjacent cell C of search.

For soft handover, the size of setting active set is Active_size=N, $M_{\mathrm{new}}\≤S\·\left(\underset{i=1,}{\overset{N}{\mathrm{\Σ}}}{M}_i\right)+(1-S)\·M_{\mathrm{Best}}-h_{\mathrm{add}}----\left(2\right)$

M _NewBe monitored base stations signal measurement mean value, M _BestBe effective centralized base-station Optimal Signals measured value, M _iBe base station signal measured value in the active set, S is a filterable agent, h _AddBe that active set adds sluggish parameter.

Otherwise, $M_j\≤S\·\left(\underset{i=1,i\≠j}{\overset{N}{\mathrm{\Σ}}}{M}_i\right)+(1-S)\·M_{\mathrm{Best}}-h_{\mathrm{drop}}----\left(2\right)$

M _jBe that the base station signal that may delete in the active set is measured average, h _DropIt is the sluggish parameter of deletion.

No matter be direct-cut operation or soft handover, after satisfying transfer criterion, base station controller can send switching command to travelling carriage, starts timer (as TIMER1) simultaneously, do not finish information if in the set time, receive the switching of travelling carriage, just think handoff failure.

At last, after travelling carriage receives switching command, carry out and switch, carry out the configuration 230 of Radio Link.In the process of implementation, with the SIR (be used to characterize carrier/interface ratio) of cycle monitoring travelling carriage,, then continue to carry out to switch if SIR reaches a threshold value (predetermined level) with the CPICH of the Radio Link of the Target cell that switches to; Otherwise the ongoing switching of forced termination keeps original link, and informing base station controller handoff failure.

General switching controls realizes by timer (TIMER1) that just this method both by timer, is controlled switching by measured SIR (being used to characterize carrier/interface ratio) value again in the process of implementation, can accelerate the termination to the failure switching, improves systematic function.

Fig. 3 is the signaling process figure of this changing method, has described the signaling procedure that switches.

At first be that travelling carriage is measured according to the requirement of measuring control messages, and send measurement report.

Base station controller is made switch decision according to measurement report, through base station controller upper strata algorithm, and the decision Target cell.

Base station controller sends the order of switching then.Carry out in the process of switching at travelling carriage, travelling carriage can be monitored the link-quality of its Target cell, can not meet the demands (SIR that uses CPICH here is as the judgement foundation) in case be found to the quality of new sub-district, will stop switching, keep original link to Target cell.

Fig. 4 is the graph of a relation of sluggish parameter and switching times in the simulation result of handoff algorithms; This figure is based on the simulation result of the inventive method.Horizontal work mark is the excursion of sluggish parameter, and ordinate is the average time that switches.From simulation result as can be seen based on the switching times of the handoff algorithms of dual-window measurement between wide window and narrow window.

Mathematical Modeling is set up as follows:

Suppose that travelling carriage switches two minizones, two base station A (NodeB1) and B (NodeB2) are at a distance of D rice, as shown in the figure.Moving table measuring signal of base station, measured value are respectively a (d) and b (d), are a (d) and b (d) through the average back of rectangular window, and unit is a decibel.The transmitting power of supposing the base station is identical, moving table measuring to base station signal strength passed through path loss, shadow fading and Rayleigh fading. wherein, the influence of Rayleigh fading can be passed through the average cancellation of window.D represents the air line distance between travelling carriage and base station A.

a(d)＝K ₁-K ₂log(d)+u(d)

b(d)＝K ₁-K ₂log(D-d)+υ(d) d∈(0，D)

K wherein ₁And K ₂Be the parameter of path loss, in the city, K ₂Representative value be 30.{u (d) and { υ (d) } expression shadow fading, they be independent, with the zero-mean stable state Gaussian random process that distributes.After the process rectangular window was average, the average signal level from base station A and base station B that travelling carriage receives was respectively: $\stackrel{\‾}{a}\left(c\right)=\frac{1}{d_{\mathrm{av}}}{\∫}_0^{d_{\mathrm{av}}}a(d-x)\mathrm{dx}$ $\stackrel{\‾}{b}\left(d\right)=\frac{1}{d_{\mathrm{av}}}{\∫}_0^{d_{\mathrm{av}}}b(d-x)\mathrm{dx}$

x(d)＝ a(d)- b(d)

Switch determining method is as follows: generally speaking, travelling carriage uses narrow window, and (length is d _Avs) average signal level of searching near district, if adjacent cell B satisfies (x with the average signal level of sub-district A at present _s(d) 〉=-h _s), h _sLag parameter when adopting narrow window, then travelling carriage is searched for another adjacent cell C, if but { x _s(d)＜-h _s, then further to widen average window be d to travelling carriage _Avw(d _Avw＞d _Avs), if at this moment record the average signal level x of two base stations _w(d) 〉=-h _w{ x _w(d)≤-h _w, h _wLag parameter when adopting wide window then switches, otherwise returns next adjacent cell C of search.

Two average length of window are elected d as _Avs=15m and d _Avw=30m, K ₁=0dB, K ₂=30dB, according to switching times, handover delay and d _AvBetween relation, adopt the handoff algorithms analytical model in the list of references [1], obtain anti-true result of the present invention.

Fig. 5 is the graph of a relation in sluggish parameter and crosspoint.Abscissa is sluggish parameter, and ordinate is the position in crosspoint.In order to set the standard of a handover delay, we have adopted the definition in the crosspoint (crossoverpoint) of using in [1], [2]: on the crosspoint, the probability that travelling carriage is communicated by letter with sub-district A maintenance is set up the probability of communicating by letter with sub-district B simultaneously and is just reached 0.5 less than 0.5.Therefrom as can be seen, adopt identical sluggish parameter to judge and switch, the handover delay that adopts this algorithm is between wide window and narrow window.

Complex chart 4 and Fig. 5 adopt the measurement of double window mouth to adjudicate switching as can be known, can obtain a good balance between handover delay and switching times.

Complex chart 4 and Fig. 5 be as can be known:

1. the handover delay of employing double window mouth between the handover delay of two single windows, is worked as h equally _w＞h _sThe time, handover delay is tending towards the handover delay of wide window, works as h _w＜h _sThe time, handover delay is tending towards the handover delay of narrow window.

2. by selecting suitable parameters: d _Avs, d _Avw, h _sAnd h _w, this obtains more efficiently balance between to contradiction can and to switch average time at handover delay.

The invention discloses in a kind of cdma system switching changing method based on dual-window measurement of mobile station.This method is applicable to by various measure physical quantities makes switch decision, and is applicable to various cdma communication systems.Described method adopts to be measured the monitor signal to the Target cell carrier/interface ratio, according to the target call that switches, Dynamic Selection is measured the average window size and measurement result is reported, whether decision switches according to transfer criterion, both guarantee the requirement of switching fast, guaranteed number of times and the handoff failure probability reliability that low speed switches under satisfied condition switched again.Another advantage of the present invention is number of times and the handover delay that control is switched, and already present relatively method has more excellent characteristic.The present invention has provided the basic skills of switch decision, is applicable to various cdma systems.

Claims (6)

1, a kind of in the WCDMA system based on the changing method of dual-window measurement of mobile station, it is characterized in that may further comprise the steps:

Step 1: under known travelling carriage translational speed condition,, select the switch decision window and window speed is measured (210) according to velocity measurement;

Step 2:, carry out switch decision (220) according to the result of window tachometric survey;

Step 3:, carry out and switch (230) according to the result of judgement.

2, in the WCDMA according to claim 1 system based on the method for the switching of dual-window measurement of mobile station, it is characterized in that: described step 1 selects decision window to comprise according to mobile station speed in (210): if mobile station speed too fast (greater than 100 li/hour) then measure with short window;

If mobile station speed too slow (less than 3 kilometers/hour) then with long window measurement;

If mobile station speed is a middling speed, then measure with short window earlier, measure with long window again according to court verdict.

3, in the WCDMA according to claim 1 system based on the method for the switching of dual-window measurement of mobile station, it is characterized in that: according to the result of window tachometric survey, carry out switch decision and comprise in the described step 2 (220):

If mobile station speed greater than 100 li/hour, then directly carries out switch decision according to short window measurement result;

If mobile station speed less than 3 kilometers/hour, then directly carries out switch decision according to long window measurement result;

If in the mobile station speed 3-100/hour between, then,, adjudicate according to long window measurement result again if judgement can be switched earlier according to short window measurement result judgement.

4, in the WCDMA according to claim 1 system based on the method for the switching of dual-window measurement of mobile station, it is characterized in that: the travelling carriage to middling speed in the described step 2 (220) adopts the switch decision algorithm of double window mouth as follows: the middling speed travelling carriage uses narrow window, and (length is d _Avs) average signal level (or other physical quantitys) of searching near district, if adjacent cell B does not satisfy switching condition with the average signal level of sub-district A at present, then travelling carriage is searched for another adjacent cell C;

If satisfy switching condition, then further to widen average window be d to travelling carriage _Avw(d _Avw＞d _Avs);

Still satisfy switching condition if at this moment record the average signal level of two base stations, then switch, otherwise return next adjacent cell C of search.

5, in the WCDMA according to claim 4 system based on the method for the switching of dual-window measurement of mobile station, it is characterized in that: utilization switch decision algorithm further comprises in the switch decision: soft handover and direct-cut operation; If that measures is common-frequency cell signal then adopts the soft handover judgement that described soft handover judgement is that the following formula of utilization is realized:

As signal reinforcement this moment, the size of setting active set is Active_size=N, $M_{\mathrm{new}}\≥S\·\left(\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{M}_i\right)+(1-S)\·M_{\mathrm{Best}}-h_{\mathrm{add}}----\left(1\right)$

M _NewBe monitored base stations signal measurement mean value, M _BestBe effective centralized base-station Optimal Signals measured value, M _iBe base station signal measured value in the active set, S is a filterable agent, h _AddBe that active set adds sluggish parameter; When the base station signal quality that monitors when travelling carriage satisfies (1), monitor cell is added active set, make travelling carriage and a plurality of cell communication;

Otherwise, when the cell signal in active set that receives when travelling carriage satisfies (2), active set is deleted out in the sub-district of link quantities difference in the active set; Then, $M_j\≤S\·\left(\underset{i=1,i\≠j}{\overset{N}{\mathrm{\Σ}}}{M}_i\right)+(1-S)\·M_{\mathrm{worst}}+h_{\mathrm{drop}}----\left(2\right)$ M _jBe that the base station signal that may delete in the active set is measured average, M _WorstBe that base station signal the poorest in the active set is measured average, h _DropIt is the sluggish parameter of deletion;

If what measure is the signal of different frequency, then adopt hard handoff decision: described direct-cut operation is that the following formula of utilization is realized:

M _new≥M _now+h (3)；

M _NowBe the signal measurements of current area, M _NEWIt is the signal of the adjacent sub-district that measures.

6, in the WCDMA according to claim 1 system based on the method for the switching of dual-window measurement of mobile station, it is characterized in that: in the described step 3 (230) according to the judgement the result, the execution switching is the SIR (being used to characterize carrier/interface ratio) with the CPICH of the Radio Link of cycle monitoring switching mobile station to target sub-district, if SIR reaches a threshold value (predetermined level), then continue to carry out to switch; Otherwise the ongoing switching of forced termination keeps original link, and notice RNC handoff failure.

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