CN100405868C - Wireless communication system and wireless tunnel controlling method - Google Patents
Wireless communication system and wireless tunnel controlling method Download PDFInfo
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Abstract
To control switching of channels, in response to a condition of electric wave propagation which changes abruptly in a short time.A control device 260 obtains a receive level and a frame error rate (FER) for each prescribed time or each prescribed number of frames, on the basis of a receive level measuring unit 241 and a frame error monitoring unit 242. In the control unit 240, a first rate threshold and a second rate threshold sought for compensating communication quality are compared with FER respectively, and also the receive level and a level threshold sought for compensating communication quality are compensated. The control unit 240 adds prescribed counter values according to the compared result. The control unit 240 compares each counter value respectively with first to fourth consecutive number-of-times thresholds, sought for preventing channel switch under abruptly short-time changing conditions. When one of counter values exceeds the corresponding consecutive number-of-times threshold, the control unit 240 performs channel switching and the like.
Description
Technical field
The present invention relates to wireless communication system and wireless channel control method, particularly relate to the wireless channel control method of structure He this system of the wireless communication system that utilizes time-division multiple access (TDMA).
Background technology
Introduced the wireless communication system of various structures at wireless communication field.Wherein, be called as personal handyphone system (Personal Handyphone System :) hereinafter referred to as PHS, the time division multiplexing that utilizes time-division multiple access (TDMA) (Time Division Multiple Access: hereinafter referred to as TDMA) technology that the frame of regulation is carried out a plurality of channels carries out the wireless communication system of information transmit-receive and has stipulated detailed structure and action by wireless tender ACSA of civic organization (Association of Radio Industries andBusinesses: hereinafter referred to as ARIB) in " RCR STD-28 " standard, is a kind of wireless communication system that is widely used and uses.
Wireless communication system is the vicissitudinous system of state that uses wave path between terminal and terminal-base station in moving, therefore, when communication quality changes in the communication, channel during employing will be used switches to other vacant channels from the channel that is using and continues information communication, the technology that is called as " channel switch (being also referred to as handover) ", for PHS also in above-mentioned standard specified in more detail the program switched of channel.The changeover program of record in the 4.4.3.8.5 chapter of above-mentioned standard (with reference to the 440-447 page or leaf) for example.In addition, above-mentioned standard code be in order to carry out smoothly that channel switches and regulated procedure, under which type of communications status, carry out the judgement that channel switches (handover), by the specification of each carrier wave and the functions of the equipments decision of device provisioning manufacturer, for example special technical scheme of opening the various channel switching methods of putting down in writing in the 2001-169323 communique.
PHS was with in existing electric wave coverage area (hereinafter referred to as the zone) narrow like this about the radius 200m of a plurality of each base station originally, terminal moves the system that makes up into prerequisite with walking speed more leisurely, with moving with terminal high-speed is that other wireless communication system of prerequisite is compared, and it is the low system of frequency that channel switches.
In city development in recent years, increased the building of easy formation radio wave attenuation, the electric wave that base station-terminal room occurred arrives the path and has a plurality of multipaths, and is easy to generate the situation of the moving body high-speed mobile of reflection waves such as in this zone (different with terminal self) vehicle.Therefore, base station in the short time-terminal room electric wave arrives the high frequency of the situation ground generation that the path changes or is blocked.After such situation takes place, though short time just, in the base station-the radio wave propagation state of the channel of terminal room communication can show rapid variation, when each state variation, all carry out in the system that channel switches, channel switches frequent the generation, has increased burden for the disposal ability of base station.And, when channel switched, the instantaneous interruption of communication can take place on the principle, therefore conversation sound sounds that desultory number of times increases in the communication, also is not wish the thing that takes place for the terminal use.
Under said circumstances, the rapid variation of spread state short time also can cause the moment of data error etc. to be taken place, but the radio wave propagation state returns to original state after this phenomenon.Promptly, recognize: since phenomenon take place the back original in the base station-quality of the communication channel that terminal room uses do not descend, thereby not as not carrying out the channel switching, the increase of the increase of base station load and the conversation interruption number of times that the user feels be can control like this, the running of entire system and the convenience that the user uses improved.Be necessary to provide a kind of, switch, realize the wireless communication system that can provide stabilized communication carrier wave that wireless communication system is provided and terminal use by on the basis of considering the propagation state that actual capabilities produce, carrying out channel.
On the other hand, according to radio wave propagation state difference, also exist the remarkable deterioration of communication quality, must carry out the situation that channel switches, only, might can't provide suitable service being used for the benchmark raising that channel switches.
The objective of the invention is,, provide a kind of and can implement wireless communication system and the wireless channel control method that channel switches according to short time radio wave propagation State Control jumpy at above-mentioned existing problems.In addition, the purpose of this invention is to provide a kind of channel switch frequently take place, communication quality is good, and suppress the increase of the increase of base station load and the conversation interruption number of times that the user feels, improve the utilization degree of entire system and the wireless communication system and the wireless channel control method of user's ease of use.
The objective of the invention is provides a kind of wireless communication system and wireless channel control method with simpler structure and program.
Summary of the invention
For achieving the above object, wireless communication system of the present invention and wireless channel control method comprise following structure and step.
A kind of wireless channel control method is used for controlling the handover that channel that the channel that the radio communication between wireless terminal and the base station is used switches to other channel of same base station switches and switch to the channel of other base station, may further comprise the steps:
The control device of base station every stipulated time or regulation frame number obtain the incoming level of the wireless signal that receives from wireless terminal and based on frame the step of frame error rate of the error that occurs;
Frame error rate that control device is relatively obtained respectively and predefined the 1st error-rate threshold and the frame error rate of obtaining and the 2nd big error-rate threshold of predefined ratio the 1st error-rate threshold, the judgment frame error rate be less than the 1st error-rate threshold, or more than or equal to the 1st error-rate threshold less than the 2nd error-rate threshold, or be step more than or equal to the 2nd error-rate threshold;
Incoming level that control device is relatively obtained and predefined level threshold judge that incoming level is less than described level threshold or more than or equal to the step of level threshold;
Control device frame error rate more than or equal to the 1st error-rate threshold less than the 2nd error-rate threshold and respectively corresponding incoming level less than level threshold and more than or equal to the 1st and the 2nd counter of level threshold and frame error rate more than or equal to the 2nd error-rate threshold and respectively corresponding incoming level less than level threshold and the 3rd and the 4th counter more than or equal to level threshold in, the step that makes the counter of regulation add counting or subtract counting or make zero according to judged result;
The step of the value of each counter of control device comparison and the 1st to the 4th corresponding with it respectively read-around ratio threshold value; And
Control device carries out in any one value in the middle of the 1st to the 4th counter that channel switches or the step of handover during more than or equal to the 1st to the 4th read-around ratio threshold value of correspondence;
Wherein, even described the 3rd read-around ratio threshold setting is also to carry out channel the relatively shorter time to switch, guarantee communication quality;
The described the 1st with the 4th read-around ratio threshold setting for switching, guarantee communication quality at the relative channel that carries out when longer of described the 3rd read-around ratio threshold value time corresponding of the time ratio of these state continuances;
Described the 2nd read-around ratio threshold setting carries out the channel switching when all grow than in the middle of described the 1st, the 3rd and the 4th read-around ratio threshold value time corresponding any one in the duration.
A kind of wireless communication system comprises:
Be used for the antenna of receiving and sending messages by radio and wireless terminal;
Measure by the incoming level measurement section of described antenna from the incoming level of the wireless signal of wireless terminal reception;
Be used for monitoring the error that frame produces, the frame error monitoring unit of obtaining frame error rate; And
Have in advance memory have defined threshold memory, control will and wireless terminal between radio communication in the channel that the uses channel that switches to other channel of same base station switch and switch to the control device of handover of the channel of other base station,
Described control device comprises:
Draw the unit of incoming level and frame error rate according to the output of described incoming level measurement section and described frame error monitoring unit every stipulated time or regulation frame number;
Frame error rate of relatively obtaining respectively and predefined the 1st error-rate threshold and the frame error rate of obtaining and the 2nd big error-rate threshold of predefined ratio the 1st error-rate threshold, the judgment frame error rate be less than the 1st error-rate threshold, more than or equal to the 1st error-rate threshold less than the 2nd error-rate threshold, still more than or equal to the unit of the 2nd error-rate threshold;
Incoming level of relatively obtaining and predefined level threshold judge that incoming level is less than described level threshold or more than or equal to the unit of level threshold;
Frame error rate more than or equal to the 1st error-rate threshold less than the 2nd error-rate threshold and respectively corresponding incoming level less than level threshold and more than or equal to the 1st and the 2nd counter of level threshold and frame error rate more than or equal to the 2nd error-rate threshold and respectively corresponding incoming level less than level threshold and the 3rd and the 4th counter more than or equal to level threshold in, the unit that makes the counter of regulation add counting or subtract counting or make zero according to judged result;
The unit of the value of each counter of comparison and the 1st to the 4th corresponding with it respectively read-around ratio threshold value; And
Carry out when any one value is more than or equal to the 1st to the 4th read-around ratio threshold value of correspondence in the middle of the 1st to the 4th counter and switch or the unit of handover;
Wherein, even described the 3rd read-around ratio threshold setting is also to carry out channel the relatively shorter time to switch, guarantee communication quality;
The described the 1st with the 4th read-around ratio threshold setting for switching, guarantee communication quality at the relative channel that carries out when longer of described the 3rd read-around ratio threshold value time corresponding of the time ratio of these state continuances;
Described the 2nd read-around ratio threshold setting carries out the channel switching when all grow than in the middle of described the 1st, the 3rd and the 4th read-around ratio threshold value time corresponding any one in the duration.
According to the present invention, even when the radio wave propagation state takes place sharply to change at short notice, also the execution that can switch according to radio wave propagation state restricting channel is carried out channel and is switched when the deterioration of communication quality continues.And, the present invention can provide a kind of channel to switch frequently generation, communication quality is good, and suppresses the wireless communication system of increase, the utilization that improves entire system and user's ease of use of the increase of base station load or the dropped calls number of times that the user feels.According to the present invention, can be so that more simple structure and program provide a kind of wireless communication system and wireless channel control method.
Description of drawings
Fig. 1 is the network structure of expression wireless communication system architecture.
Fig. 2 is the block diagram of the architecture of base station of expression wireless communication system.
Fig. 3 is the variation of radio wave propagation state in the explanation wireless communication system and the key diagram (1) that phenomenon takes place.
Fig. 4 is a radio wave propagation state variation and the key diagram (2) that phenomenon takes place in the explanation wireless communication system
Fig. 5 is the key diagram of an example of the concrete radio propagation path state variation that takes place of expression.
Fig. 6 is the action flow chart (its 1) of expression channel switching control program action.
Fig. 7 is the action flow chart (its 2) of expression channel switching control program action.
Fig. 8 is the action flow chart (its 3) of expression channel switching control program action.
Fig. 9 is the key diagram of explanation radio propagation path state measurement principle.
Figure 10 is the key diagram of expression channel switch control logic example.
Figure 11 is the action sequence figure of the action example of expression wireless communication system.
Figure 12 is the action sequence figure of other action example of expression wireless communication system.
Figure 13 is the key diagram of the example of expression incoming level, FER and the switching of generation channel.
Figure 14 represents the relation of read-around ratio threshold value and switching times.
Embodiment
As the radio wave propagation state, channel switched the enforcement of (in the following description and accompanying drawing also be recited as Tch switch) or handover (in the following description and accompanying drawing also be recited as H.0)/do not implement carry out careful control according to the value of level and FER and duration thereof at the error rate (Frame Error Rate :) of the level of base station measurement electric wave and the frame propagated hereinafter referred to as FER.Below utilize accompanying drawing to describe the embodiment of wireless communication system of the present invention and wireless channel control method in detail.
Fig. 1 is the network structure of expression wireless communication system architecture.
On same figure, demonstrate time slot 1 in a plurality of time-division multiplex channels that terminal 1 (PS1) 140-1 utilizes frame 160 carries out information transmit-receive via radio propagation path 150-1 and base station (CS1) situation.In addition, in the figure, during " O " expression that shows in each time slot is used (in the communication), " i " is expressed as sky.The frequency of the radio propagation path 150-1 of this frame is propagated in " f1 " expression of frame 160 left sides record.When terminal 140 communicates with other terminal that belongs to wireless communication system communication network in addition, go up unshowned other terminal by other communication network (for example public network) 100 with figure by base station control station (CSC) 110 and carry out information transmit-receive.
In the wireless communication system 10, when the rapid variation of short time takes place the state of radio propagation path 1 50, be controlled to be Tch switching or H.O and frequently do not take place.The Tch here switches and is meant that the communication that the time slot 1 by frame 160 among this figure is carried out switches to that any one good time slot of electric wave state continues to communicate by letter in the empty slot of different other frame (not shown on the figure) of the frequency of the empty slot (time slot 2～4) of the same frame of the same area or the same area.And H.O is meant that the communication that the time slot 1 by frame 160 among this figure is carried out switches to that any one good time slot of electric wave state continues communication in the frame (not shown on the figure) of other zone (for example 120-2).In addition, in the following explanation of present embodiment, above-mentioned time slot is also referred to as channel.
Fig. 2 is the block diagram of the architecture of base station of expression wireless communication system.
Base station 130 comprises the antenna 200 that carries out information transmit-receive by radio and terminal 140, the coupler 210 that information to reception/transmission is coupled/separates, carry out wireless signal is converted to the transmission wireless device 220 of the Signal Processing of transmitting-receiving between the signal of telecommunication etc. and the terminal 140 and receives wireless device 230, the signal of transmitting-receiving between base station control station 110 and the terminal 140 is handled the signal control device 240 of (for example modulation and demodulation), to and base station control station 110 between the wire circuit control device 250 handled of signal of transmitting-receiving, and the control device 260 that base station 130 integral body are controlled.Said apparatus connects by control line 270 respectively.
Control device 260 comprises operation program and the memory of data 262 of control with microcomputer (processor) 261 and memory base station 130, and operation is used to carry out the program Tch/CNT263 of wireless channels such as channel switching control of the present embodiment of following detailed description.This program 263 is incoming level (following level that also simply are called of the frame that receives from terminal measured according to incoming level measurement section 241, also be recited as LEVEL or L in the accompanying drawings), the value of the frame error rate FER that measures of frame error monitoring unit 242 and the duration of level or FER, judgement could be carried out the program that channel switches, according to state/behaviour in service control channel switching of radio propagation path 150.Specifically following control: when returning original state after the rapid variation of radio wave propagation state generation short time, not carrying out channel switches, during big the and longer duration of radio wave propagation state variation, carry out the channel that switches to the better channel of state and switch (perhaps handover).
Before the detailed content of explanation wireless communication system of the present invention and wireless channel control method, the state variation of the radio wave propagation that takes place in the wireless communication system 10 and the phenomenon of generation are described at first.Fig. 3 is the variation of radio wave propagation state in the explanation wireless communication system and the key diagram (1) that phenomenon takes place.
As the record of Fig. 3 (a), terminal 140 is utilized the time slot (channel) of base station 130 and frame 160 while 1 communicating by letter when mobile the following variation of radio wave propagation state on the road R between building B 1 and the B2:
(1) at moment T1, terminal 140 is positioned at the position of 140-a, via radio propagation path 150-a receiving frame 160-a (shown in Fig. 3 (b)).
(2) at moment T2, after terminal 140 moves to the position of 140-b, to be blocked by building B 2 from the electric wave of radio propagation path 150-a, the transmitting-receiving of frame 160-b is carried out via the radio propagation path 150-b by building B 1 reflection.
(3) then, at moment T3, after terminal 140 moves to the position of 140-c,, thereby carry out the transmitting-receiving of frame 160-c via radio propagation path 150-c because can see base station 130 from terminal 140.
That is, near moment T2, owing to carry out the transmitting-receiving of frame, thereby as Fig. 3 (b) shown in, only at frame 150 reception timing respective offsets 160-t this period via the long radio propagation path 150-b of the propagation path that reflected by building B 1.
Fig. 4 is a radio wave propagation state variation and the key diagram (2) that phenomenon takes place in the explanation wireless communication system.Because a plurality of paths appear in the variation of terminal location, thereby produce disturbing wave, incoming level changes etc.Because this timing slip, the influence of disturbing wave or the variation of incoming level, the information 1600 of time slot 1 can't correctly be received, and mistake occurs among synchronization character UW1640 in the information 1600 and the self-correcting code CRC1680, so just detects frame error.But after terminal 140 moved to the position of 140-c at moment T3 in Fig. 3 (a), such phenomenon just returned to the original state that does not have error at short notice.Also have, the numeral in the information 1600 shown in Figure 4 is a bit number, and what each information was represented respectively is: R, transient response oblique wave time; SS starts symbol PR, preamble; UW, synchronization character CI, channel type SA, SACCH (subsidiary control channel); G, guiding position CRC, cyclic redundancy check (CRC) position.
Under above-mentioned condition, because the quality of the communication channel that original base station one terminal room uses is being kept, do not switch not as not carrying out channel, so just suppress the increase of base station 130 loads and the conversation of user's sensation and be interrupted the increase of number of times, and improved the utilization degree of entire system and the convenience that the user uses.Therefore, the wireless communication system of present embodiment has the function of considering to come after the actual propagation state that takes place in the base station 130 the control channel switching.
Fig. 5 is the key diagram of an example of the concrete radio propagation path state variation that takes place of expression.Return the phenomenon of original state after the rapid variation (the short time deterioration takes place FER) of the above-mentioned radio wave propagation state generation short time of (a) expression of this figure.And the state variation of this figure (b) expression radio wave propagation is big and the phenomenon of longer duration (level reduces and the FER deterioration continues), particularly represents the example when the read-around ratio of threshold value that level reduces, surpasses FER is above stipulated number.The wireless communication system of present embodiment does not carry out channel and switches under situation shown in this figure (a), carrying out the channel that switches to the good channel of state under situation shown in this figure (b) switches, and following meeting illustrate by other accompanying drawing (Figure 10), controls in detail whether carrying out the channel switching according to the content (degree of variation and duration) of phenomenon.
Fig. 6, Fig. 7 and Fig. 8 are respectively action flow chart (1)～(3) of the action of the program Tch/CNT263 in the expression base station 130.Fig. 9 is the key diagram of the radio propagation path state measurement principle carried out in the action of read-me 263.Figure 10 is the key diagram of the channel switch logic example of representation program 263 execution.Below describe the wireless channel controlled function in detail by these accompanying drawings.What in addition, each symbol in the middle of accompanying drawing and the following explanation was represented respectively is F1: 1FER threshold value (%); F2: 2FER threshold value (%), and F1＜F2; A, b, c, d: the 1st～the 4th read-around ratio counter (inferior); A0, b0, c0, d0: the 1st～the 4th read-around ratio threshold value (inferior), and a0＜b0, c0＜d0; L0: level threshold (dB μ V).
(1) begins communication (information transmit-receive) between terminal 140 and the base station 130 according to RCR STD-28 regulated procedure after, the control microcomputer 261 of control device 260 (following simple table is shown control device) begins to carry out control and treatment (Fig. 6: S1000), and initialization counter (being the 1st～the 4th these 4 counters of representing with a, b, c, d in the present embodiment) (Fig. 6: S1010) that the state generation read-around ratio of electric wave state is counted.These counters suitably are arranged in the memory 262, perhaps also specialized hardware can be set.
(2) control device 260 by incoming level measurement section 241 and frame error monitoring unit 242, is measured level and FER (Fig. 6: S1020～1040) every for example 100mS (20 frame) according to the operating principle of Fig. 9.Specifically, as shown in Figure 9, with 20 frames is that level and FER (Fig. 6: S1020) measure in a measurement unit 3000, gathering 240 frames (12 measurement units, the moment (Fig. 6: S1030) of measurement result 300 1200mS), level is obtained the mean value L of 240 frames, and the FER that FER is then obtained 240 frames amounts to F (Fig. 6: S1040).FER amounts to F and can utilize the FER total of per 20 frames or the margin of error of mean value or 240 frames etc. to draw, and the 1st and the 2nd FER threshold value F1 and F2 can come correspondingly suitably to set according to ask method and the unit that FER amounts to F.Control device 260 is taken into the measurement result of 20 frames of newly obtaining, and removes the measurement result of 20 frames the earliest after the processing of relevant initial 240 frame 300-1 finishes, equally to (300-2～N) obtains L and F with immediate 240 frames now.When the number of times that control device 260 surpasses threshold value at the L of above-mentioned 240 frames and F is a N continuous time, implement Tch switching/H.O.In addition, according to the degree of incoming level and FER, N uses these 4 types of a0, b0, c0, d0 respectively.
As shown in figure 10, the wireless channel switching controls is to judge that could carry out the state that channel switches be divided into a plurality of controls of carrying out according to the value of L and F and their lasting number of times, is in the present embodiment to come control channel to switch according to 6 states (4000-4050) that 2 threshold values (F1, F2) with the threshold value L0 of L and F are divided into.In addition, in the present embodiment, the F situation littler than 1FER threshold value F1 (Figure 10 4000,4010) illustrated as actions such as not carrying out the channel switching down, but can be made as equally in this state, the 5th counter and the 5th read-around ratio threshold value e0 are set and carry out action such as channel switching.
(3) F of 260 pairs of present embodiments of control device and 1FER threshold value F1 (for example being 30% in the present embodiment) compare (Fig. 6: S1050), if F is littler than F1, the running of then judging wireless communication system is no problem, returns step S1020 then and continues the measurement of above-mentioned (2).On the other hand, if F is more than or equal to F1 (Fig. 6: S1050), then again F and 2FER threshold value F2 (for example being 50% in the present embodiment) are compared (Fig. 7: S1060), and with F little (situation of F1≤F＜F2=and F are more than or equal to the situation of the F2 (separate processes of F2≤F) than F2.In addition, F equates that with each threshold value F1, F2 the processing under the situation can suitably determine.And, level L, each counter and separately threshold value equate under the situation processing too.
When (4) F is more than or equal to F1 and less than F2, control device 260 implement to make the 2nd counter b add 1 and make the 3rd counter c and the 4th counter d make zero (Fig. 7: S1070), relatively L and threshold value L0 (for example being 25dB μ V in the present embodiment) (Fig. 7: S1080).
When (5) L is less than L0, control device 260 make the 1st counter a add 1 (Fig. 7: S1100), L then makes the 1st counter (Fig. 7: S1110) that makes zero during more than or equal to L0.Then, control device 260 compares the value of the 1st counter a and threshold value (the 1st continuous threshold value) a0 of this counter (for example is 19 in the present embodiment, the state 4020 (state that FER is little, level is low) of expression Figure 10 continues 19 times (about 3 seconds) in succession), and threshold value (the 2nd continuous threshold value) b0 of the value of comparison the 2nd counter b and this counter (for example be 39 in the present embodiment, the state 4030 (state that FER is little, level is high) of expression Figure 10 continues 39 times (about 5 seconds) in succession) (Fig. 7: S1120).
(6) if any one in the middle of the 1st counter a or the 2nd counter b more than or equal to separately threshold value a0b0 (S1120), then transfer to step S1180, control device 260 is implemented channel and is switched (or transfer) (Fig. 8: S1180) back end process (Fig. 8: S1190).On the other hand, control device 260 does not carry out channel and switches, but return step S1020 under the above-mentioned situation in addition of step S1120, repeats above-mentioned (2)～(6), continues to handle.In addition, under the situation of carrying out the channel switching, begin the channel after the new switching is handled (Fig. 6: S1000).
When (7) F was more than or equal to F2 among the step S1060, control device 260 made the 2nd counter b and the 4th counter d add 1 (Fig. 8: S1130), compare L and threshold value L0 (Fig. 8: S1140).
When (8) L is less than L0, control device 260 make the 1st counter a and the 3rd counter c add 1 (Fig. 8: S1150), and L is during more than or equal to L0, makes the 1st counter a and the 3rd counter c (Fig. 8: S1160) that makes zero.Then, control device 260 compares the value of the 3rd counter c and threshold value (the 3rd continuous threshold value) c0 of this counter (for example is 4 in the present embodiment, the state 4040 of expression Figure 10 (FER is big and level is low, be necessary to carry out the state that channel switches most) continues 4 times (about 1.5 seconds) in succession), and threshold value (the 4th continuous threshold value) d0 of the value of comparison the 4th counter d and this counter (for example be 19 in the present embodiment, the state 4050 (FER height, the state that level is high) of expression Figure 10 continues 19 times (about 3 seconds) in succession) (Fig. 8: S1170).
(9) if any one in the middle of the 3rd counter c or the 4th counter d more than or equal to separately threshold value c0/d0, then control device 260 is implemented channels and is switched (or transfer) (Fig. 8: S1180) back end process (Fig. 8: S1190).On the other hand, control device 260 does not carry out channel and switches under the above-mentioned situation in addition of step S1170, but returns step S1020, repeats above-mentioned (2)～(9), continues to handle.Under the situation of carrying out the channel switching, begin the channel after the new switching is handled (Fig. 6: S1000).In addition, control device 260 also can be in step S1170 compare (S1170) with the value of the 1st counter a or the 2nd counter b with separately threshold value a0b0, if any one is more than or equal to threshold value then implement channel and switch (S1180).
As mentioned above, consider the propagation state that may occur in the middle of the reality, be controlled to be: (i) under and the situation that level is also low many in error, because communication quality significantly worsens, even thereby the short time also to carry out channel and switch to guarantee communication quality, though (ii) error is many but under the situation that level is high, perhaps under the situation that more or less error and level are low, according to definite how processing of the duration of above-mentioned phenomenon, if this phenomenon continues for a long time, then carrying out channel switches and guarantees communication quality, (iii) under the situation that more or less error and level are high, be considered as communication quality and worsen not quite, only under this phenomenon situation also longer, carry out channel and switch than the above-mentioned phenomenon duration.
Fig. 5 describes as reference, then is somebody's turn to do figure (b) expression said circumstances (i), owing to the situation that L is low, FER is big continues for 4 times in succession, thereby carries out the channel switching.This figure (a) represents (ii) above-mentioned and situation (iii), though the big state continuance of FER 4 times, L is also big, and FER recovered original state, thereby does not carry out channel to switch and continue utilization.Like this, the mode of not carrying out the channel switching under the situation that can keep by quality in the communication channel of using between base station 130 and the terminal 140 with intentionallying, thereby the conversation that load increases and the user feels that can suppress base station 130 is interrupted the increase of number of times, has improved the operation of entire system and the convenience that the user uses.
As other explanation, the foregoing description explanation be to be 1.89～1.92GHz with RCR STD-28 predetermined band, to be that the PHS that the frame of 5mSec. repeats to receive and dispatch is in the wireless communication system of prerequisite to the multiplexed length of 4 channels (time slot), have 6 appropriate state (Figure 10: 4000～4050) and each threshold value carry out the example of channel switching controls.Can in PHS, carry out constantly more preferably than finer control of the control shown in the foregoing description or more rough on the contrary control, perhaps in other wireless communication system, as long as the requirement that environment, behaviour in service or user are set according to this system, change number and the number of numerical value and counter and the read-around ratio threshold value of each counter of the level threshold of FER and L, can be suitable for the channel switching controls of present embodiment.
Figure 11 is the action sequence figure of the action of expression wireless communication system, expression Tch change action.Followingly this action is described with reference to Fig. 1 and Figure 11.
Terminal (PS1) 140-1 and base station (CS1) 130-1 are before communicating by letter, after establishing communication (S2000) according to transmission/reception program of the 4.4.3.8 of RCR STD-28 regulation, enter and to carry out the communication central (S2100) of information transmit-receive by distributed time slot (for example being that frequency is the time slot 1 of the frame of f1 in the present embodiment).
After the communication beginning, with the variation of the moving state of terminal (PS1) 140-1 and surrounding enviroment the deterioration (S2200) of level and FER takes place accordingly, base station (CS1) 130-1 carries out the channel switching controls by Fig. 6～Figure 10 explanation.For example, if the timing slip 160-t of Fig. 3 is little and restore to the original state at short notice, then do not carry out channel and switch and continue communication, if but terminal 140-1 move near adjacent areas 120-2, the big state continuance of state that level is low or FER was then implemented Tch and is switched after the stipulated time.
Specifically, the Tch changeover program of stipulating among the 4.4.3.8.5.1 according to RCR STD-28 selects other empty slot (for example being that frequency is the time slot 4 of the frame of f2 in the present embodiment) in the same area 120-1 to carry out channel switching (S2300), then, terminal (PS1) 140-1 and base station (CS1) 130-1 utilize frequency to be the time slot 4 of the frame of f2 continue to receive and send messages (S2400).
Figure 12 is the action sequence figure of the action of expression wireless communication system, the action of expression H.O.Followingly this action is described with reference to Fig. 1 and Figure 12.
Terminal (PS1) 140-1 and base station (CS1) 130-1 are before communicating by letter, after establishing communication (S2000) according to transmission/reception program of the 4.4.3.8 of RCR STD-28 regulation, enter and to carry out the communication central (S2100) of information transmit-receive by distributed time slot (for example being that frequency is the time slot 1 of the frame of f1 in the present embodiment).
After the communication beginning, with the variation of the moving state of terminal (PS1) 140-1 and surrounding enviroment the deterioration (S2200) of level and FER takes place accordingly, base station CS1 carries out the channel switching controls by Fig. 6～Figure 10 explanation.For example, if the timing slip 160-t of Fig. 3 is little and reinstatement at short notice, then do not carry out channel and switch continuation communication, if but terminal 140-1 moves near the adjacent area 120-2, the big state continuance of state that level is low and FER is after the stipulated time, then base station control station (CSC) 110 and base station (CS2) 130-2 Joint Implementation H.O.
Specifically, other empty slot in other regional 120-2 of the H.O procedure Selection of stipulating among the 4.4.3.8.5.4 according to RCR STD-28 (for example being that frequency is the time slot 4 of the frame of f2 in the present embodiment) carries out channel and switches (S2350), then, terminal (PS1) 140-1 and base station (CS2) 130-2 utilize frequency to be the time slot 4 of the frame of f2 continue to receive and send messages (S2450).
(the 1st of each threshold value is determined method)
Below explanation threshold value F1, F2, L0, a0, b0, c0, each data of d0 determines.
Figure 13 is the key diagram of the example of expression incoming level, FER and the switching of generation channel.Example shown in Figure 13 is in the wireless communication system that is in operation, and is object actual measurement incoming level and FER with a plurality of base stations that are in the middle of the various environment, and the pass of level and FER tied up on the chart shows.
At first obtain the situation occurred of each FER of incoming level place.For example, obtain about 13,000 points at place, 1 base station.In addition, incoming level is for example represented with integer value as shown in figure 13.Because if the quality between radio zone judges with mean value, when taking place, sudden FER deterioration is easy to generate error, therefore preferably judge according to central value (representing with circle among Figure 13).Consider in communication when FER takes place the influence to quality, whether present embodiment according to the central value place FER takes place is set threshold value L0 as the incoming level of the processing startup judgment standard of Tch switchings/H.O.That is, the threshold value L0 of incoming level is after each incoming level is obtained the central value of the FER that is obtained, and these central values are 0 the minimum value (being 25dB μ V among Figure 13) of the central incoming level of incoming level.Central value is beyond 0 the incoming level, also can be for example to satisfy number % with the minimum value of incoming level in the middle of the incoming level of inferior suitable benchmark.
In addition, for the threshold value (F1, F2) of FER, be that benchmark is considered with the FER that takes place abruptly.Because the FER that takes place abruptly probably returns original state at short notice, thereby can switch to principle with restricting channel under this state and determine threshold value F1, F2.For example, the maximum (representing with triangle among Figure 13) of the FER that takes place according to each incoming level place makes approximation curve (approximate expression), obtains value at the FER of determined incoming level L0 with reference to FER approximation curve (approximate expression).In addition, except the maximum of utilizing FER makes the approximation curve, mean value that also can suitably utilize the data of for example getting right quantity from the big value of FER etc. can be considered to the data of sudden generation.The threshold value F1 of FER, F2 can be set in 5～10% scopes up and down of the value of obtaining.In addition, F1 also can utilize preset threshold in for example existing base station.
For example, in Figure 13, be 25dB μ V at level threshold L0, with reference to the peaked approximation curve of FER that is represented by dotted lines, obtain 50% weak value as FER.Therefore can establish the 2nd error-rate threshold F2 is 50[%].In addition, also can establish the 1st error-rate threshold F1 is 40[%] etc., but use the 30[% that sets in the existing base station in the present embodiment].
Then, the setting of just continuous frequency threshold value a0～d0 describes.Because F1 and the F2 that determines as mentioned above arranged and for example had c0, the d0 that sets in the base station now, be starting point therefore with these values, determine read-around ratio threshold value a0, the b0 of FER under the state of F1～F2 according to the condition of a0＞c0, b0＞d0, a0＜b0.For example, c0=1.5s (read-around ratio is 4 times), during d0=3s (read-around ratio is 19 times), a0 be 2s, 2.5s, 3s...b0 be 3.5s, 4s, 4.5s, 5s... etc. bit by bit (for example every 0.5s) do and add computing, under various combinations, confirm the effect state of calling quality state and communication data integral body.Also have, the interval amplitude of variation can be other appropriate time except above-mentioned 0.5s interval.In the test of implementing these combinations, softening terms up to mean value that H.0 adds the Tch switching times and the pass of air time as the regulation place of observation station (for example receive the place of constant time lag or be easy to generate the place of disturbing wave) successively is 10 minutes 1 time.Also have, 10 minutes 1 time benchmark can be according to the suitably changes such as disposal ability of base station.Can also measure the switching times when a0, b0 are changed in addition, set a0, b0 then and make it to be minimum switching value.
Figure 14 is the figure of the relation of expression read-around ratio threshold value and switching times.Tch switches the situation (among the figure 510) of the situation comprise base station initiated switching (among the figure 500) and starting terminal.Therefore, only increase the read-around ratio threshold value, the total number of times that Tch switches (among the figure 520) may not reduce.Therefore change a0, b0 as mentioned above and measure the Tch switching times of locating as the regulation place of observation station, thereby setting a0, b0 switch starting terminal and the total number of times of base station initiated switching becomes minimum (or minimum).The result obtains for example a0=3s (read-around ratio is 19 times), the such value of b0=5s (read-around ratio is 39 times).
(the 2nd of each threshold value is determined method)
At first, obtain the situation occurred of each FER of incoming level place equally in the base station with above-mentioned, and obtain F1, F2, L0.At this, the value of L0 is guaranteeing that quality is the incoming level of purpose, but when not thinking that the people of actual use is imperceptible slightly when quality deterioration is problem, can set lower value.In fact at the scene find in the test, below the value of determining according to data, also can converse usually no problemly, find that also mistake on duty is hanged down the back, the speech quality variation is not carried out H.O/Tch change action (H.O expends time in) at once yet.In addition, with regard to F1, F2, can be described as maximum because the value of obtaining according to the data of being obtained is seen from the viewpoint that keeps quality, therefore actual determined value can be below it.Therefore, except a0, b0, F1, the F2 that obtains, the value of L0 are changed, determine threshold value separately.And also can make its variation equally to c0, d0.
The variation of a0, b0 is same as described above, being starting point at c0, the d0 of existing base station sets for example, makes its variation according to the condition of a0＞c0, b0＞d0, a0＜b0.For example, c0 is that 1.5s, d0 are when being 3s, a0 be 2s, 2.5s, 3s...b0 be 3.5s, 4s, 4.5s, 5s... so bit by bit (for example every 0.5s) do and add computing, under various combinations, confirm the effect state of calling quality state and communication data integral body.
On the other hand, L0 will be assumed to the maximum that can set according to the level threshold that the data of being obtained are determined with above-mentioned different, separate level threshold downwards from this value, make it to change successively.For example, can be starting point with the 25dB that determines according to the data of being obtained as mentioned above, be reduced to 20dB, 15dB, and a0, b0 changed at each level threshold.Also have, the separation amplitude can be suitable amplitude.In addition, the 25dB that determines according to the data of being obtained also can not test, and begins test from 20dB.
When L0 is changed, if, speech quality variation low owing to being worth do not carried out H.O/Tch change action (H.O expends time in) yet at once, thereby can measure the point that should carry out H.O and (for example 30～35dB) of the PS level go up the H.O/Tch switching times according to original level, whether judgement becomes until the H.O startup is expended time in, and at first selects for example 20dB then.
In addition, about F1, F2, with the F1, the F2 that determine according to the data of being obtained is the upper limit, for example be spaced apart 10%, satisfying in the test of combination of condition of F1＜F2, softening terms successively up to concerning average out to 10 minutes 1 time as the H.0+Tch switching times of the regulation place of observation station (for example receive the place of constant time lag as mentioned above or be easy to generate the place of disturbing wave) and air time.The order that condition is relaxed (change value) can be the order of F2, a0, b0, F1.This is the order little to the influence of tonequality.Speech quality is along with the variation of relaxing of condition, but preferential to reduce the observation station H.O/Tch of place switching times, the result obtains a0=3s, b0=5s, F1=30%, F2=50%.
In addition, also can measure the Tch switching times when making each changes of threshold, set each threshold value then and make it to become minimum switching value.The longitudinal axis is made as the switching times of measurement, transverse axis is made as a0, b0, c0, d0, be illustrated in and just obtain the chart identical on the chart with Figure 14.In addition, represent that with transverse axis F2, a0, b0, F1 also obtain the result that total switching times shown in Figure 14 has minimum value.
Like this, can soften terms successively from the threshold value of determining according to existing value of setting and the data of obtaining, the communications status when confirming this determines whether to satisfy the observation station place and reduces the requirement that H.O/Tch switches frequency.
According to the present invention, even when the radio wave propagation state takes place sharply to change at short notice, also the execution that can switch according to radio wave propagation state restricting channel is carried out channel and is switched when the deterioration of communication quality continues.And the present invention can provide a kind of channel to switch frequently to take place, communication quality is good, suppress the wireless communication system of increase, the utilization that improves entire system and user's ease of use of the increase of base station load or the dropped calls number of times that the user feels.According to the present invention, can be so that more simple structure and program provide a kind of wireless communication system and wireless channel control method.
Claims (11)
1. wireless channel control method, be used for controlling the handover that channel that the channel that the radio communication between wireless terminal and the base station is used switches to other channel of same base station switches and switches to the channel of other base station, it is characterized in that, may further comprise the steps:
Every stipulated time or regulation frame number obtain the incoming level of the wireless signal that receives from wireless terminal and based on frame the step of frame error rate of the error that occurs;
Frame error rate of relatively obtaining respectively and predefined the 1st error-rate threshold and the frame error rate of obtaining and the 2nd big error-rate threshold of predefined ratio the 1st error-rate threshold, the judgment frame error rate be less than the 1st error-rate threshold, or more than or equal to the 1st error-rate threshold less than the 2nd error-rate threshold, or more than or equal to the step of the 2nd error-rate threshold;
Incoming level of relatively obtaining and predefined level threshold judge that incoming level is less than described level threshold or more than or equal to the step of level threshold;
Frame error rate more than or equal to the 1st error-rate threshold less than the 2nd error-rate threshold and respectively corresponding incoming level less than level threshold and more than or equal to the 1st and the 2nd counter of level threshold and frame error rate more than or equal to the 2nd error-rate threshold and respectively corresponding incoming level less than level threshold and the 3rd and the 4th counter more than or equal to level threshold in, the step that makes the counter of regulation add counting or subtract counting or make zero according to judged result;
The step that the value of each counter and the 1st to the 4th corresponding with it respectively read-around ratio threshold value are compared; And
When any one value in the middle of the 1st to the 4th counter during, carry out and switch or the step of handover more than or equal to the 1st to the 4th read-around ratio threshold value of correspondence;
Wherein, described the 3rd read-around ratio threshold setting is for making that carrying out channel in the given time switches to guarantee communication quality;
The described the 1st carries out channel for described the 3rd read-around ratio threshold value time corresponding of time ratio of this state continuance is relative when longer with the 4th read-around ratio threshold setting switches to guarantee communication quality;
Described the 2nd read-around ratio threshold setting switches for carrying out channel in the duration when all longer than in the middle of described the 1st, the 3rd and the 4th read-around ratio threshold value time corresponding any one.
2. wireless channel control method as claimed in claim 1, it is characterized in that, for described level threshold, with reference to the central value of obtaining the frame error rate corresponding in the incoming level and the relation between the frame error rate of regulation base station measurement, be that minimum incoming level is set at described level threshold in the middle of 0 the incoming level with this central value with each incoming level.
3. wireless channel control method as claimed in claim 2, it is characterized in that, for the described the 1st and described the 2nd error-rate threshold, reference is in the incoming level of regulation base station measurement and the relation between the frame error rate, maximum according to the frame error rate corresponding with each incoming level makes curve of approximation or approximate expression, obtain the frame error rate corresponding based on curve of approximation that makes or approximate expression with predefined level threshold, with the value of this frame error rate or before and after it value in prescribed limit be set at the described the 1st and/or described the 2nd error-rate threshold.
4. wireless channel control method as claimed in claim 1, it is characterized in that, for the described the 1st and described the 2nd read-around ratio threshold value, big according to the 1st read-around ratio threshold ratio the 3rd read-around ratio threshold value, the 2nd read-around ratio threshold ratio the 4th read-around ratio threshold value is big, and the little condition of the 1st read-around ratio threshold ratio the 2nd read-around ratio threshold value, interval amplitude with regulation changes it successively, the number of times of channel switching of place, measurement regulation base station and handover becomes minimum with the switching times total or the value in expected range is set at the described the 1st and the 2nd read-around ratio threshold value respectively.
5. wireless channel control method as claimed in claim 4, it is characterized in that, to with the described the 3rd and described the 4th read-around ratio threshold value, according to the little condition of the 3rd read-around ratio threshold ratio the 4th read-around ratio threshold value, interval amplitude with regulation changes it successively respectively, regulation base station place channel is switched and the number of times total of handover becomes minimum or the value in expected range is set at the described the 3rd and the 4th read-around ratio threshold value respectively.
6. wireless channel control method as claimed in claim 1, it is characterized in that, for described level threshold, reference is in the incoming level of regulation base station measurement and the relation between the frame error rate, obtain the central value of a plurality of frame error rate corresponding with each incoming level, be that minimum incoming level threshold value is the upper limit in the middle of 0 the incoming level with this central value, described level threshold reduced successively with the interval amplitude of regulation
For the described the 1st and the 2nd frame error rate threshold value; Reference is in the incoming level of regulation base station measurement and the relation between the frame error rate; Maximum according to the frame error rate corresponding with each incoming level makes curve of approximation or approximate expression; Obtain the frame error rate corresponding with level threshold based on the curve of approximation that makes or approximate expression; And take the value of this frame error rate or its up and down the value in the prescribed limit as the upper limit; Interval amplitude with regulation changes the described the 1st and the 2nd error-rate threshold successively
For the described the 1st and the 2nd read-around ratio threshold value, big according to the 1st read-around ratio threshold ratio the 3rd read-around ratio threshold value, the 2nd read-around ratio threshold ratio the 4th read-around ratio threshold value big and the little condition of the 1st read-around ratio threshold ratio the 2nd read-around ratio threshold value, with the regulation the interval amplitude make the described the 1st and described the 2nd read-around ratio threshold value change successively
Various threshold values combination measuring gages decide place, base station channel switches and the number of times of handover, the switching times total are become minimum or the value in expected range is set at each threshold value respectively.
7. wireless channel control method as claimed in claim 1, it is characterized in that, described level threshold is the degree of 25dB μ V, and, the the described the 1st and the 2nd error-rate threshold is respectively 30% and 50% degree, and described the 1st, the 2nd, the 3rd and the 4th read-around ratio threshold value is respectively the degree of 19 times, 39 times, 4 times and 19 times, perhaps is respectively and 3 seconds, 5 seconds, 1.5 seconds and 3 seconds corresponding number of times.
8. wireless channel control method as claimed in claim 1 is characterized in that, described add the counting or subtract the counting or the step that makes zero further comprising the steps of:
Frame error rate makes the 2nd counter add 1 more than or equal to the 1st error-rate threshold during less than the 2nd error-rate threshold, when further incoming level is less than level threshold, makes the 1st counter add 1 step; And
Frame error rate makes the 4th counter and/or the 2nd counter add 1 during more than or equal to the 2nd error-rate threshold, when further incoming level is less than level threshold, makes the 3rd counter and/or the 1st counter add 1 step.
9. wireless channel control method as claimed in claim 1 is characterized in that, described add the counting or subtract the counting or the step that makes zero further comprising the steps of:
Frame error rate during less than the 2nd error-rate threshold, makes zero the 3rd and the 4th counter more than or equal to the 1st error-rate threshold, when further incoming level is not less than level threshold, and the step that the 1st counter is made zero; And
The step that frame error rate makes zero the 1st counter and/or the 3rd counter when being not less than level threshold more than or equal to the 2nd error-rate threshold and incoming level.
10. wireless channel control method as claimed in claim 1 is characterized in that, described radio communication is the radio communication in the personal handyphone system.
11. a wireless communication system comprises:
Be used for the antenna of receiving and sending messages by radio and wireless terminal;
The incoming level measurement section is measured via the incoming level of described antenna from the wireless signal of wireless terminal reception;
The frame error monitoring unit is used for monitoring the error that frame produces and obtains frame error rate; And
Control device, have the memory that stores defined threshold in advance, control and wireless terminal between radio communication in the channel that the uses channel that switches to other channel of same base station switch and switch to the handover of the channel of other base station, this control device comprises:
Every stipulated time or regulation frame number,, obtain the unit of incoming level and frame error rate according to the output of described incoming level measurement section and described frame error monitoring unit;
Frame error rate of relatively obtaining respectively and predefined the 1st error-rate threshold and the frame error rate of obtaining and the 2nd big error-rate threshold of predefined ratio the 1st error-rate threshold, the judgment frame error rate be less than the 1st error-rate threshold, or more than or equal to the 1st error-rate threshold less than the 2nd error-rate threshold, or more than or equal to the unit of the 2nd error-rate threshold;
Incoming level of relatively obtaining and predefined level threshold judge that incoming level is less than described level threshold or more than or equal to the unit of level threshold;
Frame error rate more than or equal to the 1st error-rate threshold less than the 2nd error-rate threshold and respectively corresponding incoming level less than level threshold and more than or equal to the 1st and the 2nd counter of level threshold and frame error rate more than or equal to the 2nd error-rate threshold and respectively corresponding incoming level less than level threshold and the 3rd and the 4th counter more than or equal to level threshold in, the unit that makes the counter of regulation add counting or subtract counting or make zero according to judged result;
The unit of the value of each counter of comparison and the 1st to the 4th corresponding with it respectively read-around ratio threshold value; And
Carry out when any one value is more than or equal to the 1st to the 4th read-around ratio threshold value of correspondence in the middle of the 1st to the 4th counter that channel switches or the unit of handover;
Wherein, described the 3rd read-around ratio threshold setting switches to guarantee communication quality for carrying out channel in the given time;
The described the 1st with the 4th read-around ratio threshold setting for switching, guarantee communication quality at the relative channel that carries out when longer of described the 3rd read-around ratio threshold value time corresponding of the time ratio of these state continuances;
Described the 2nd read-around ratio threshold setting carries out the channel switching when all grow than in the middle of described the 1st, the 3rd and the 4th read-around ratio threshold value time corresponding any one in the duration.
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| JP2003388771A JP4283644B2 (en) | 2003-11-19 | 2003-11-19 | Wireless communication system and wireless channel control method |
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| US8780944B2 (en) * | 2005-08-26 | 2014-07-15 | Qualcomm Incorporated | Method and apparatus for reliable signaling in wireless communication |
| KR100748086B1 (en) * | 2005-11-10 | 2007-08-09 | 한국전자통신연구원 | Method for balancing quality of wireless communication channel and wireless communication apparatus using the same |
| JP4992593B2 (en) * | 2007-07-26 | 2012-08-08 | 富士通モバイルコミュニケーションズ株式会社 | Mobile radio terminal device |
| US8265041B2 (en) | 2008-04-18 | 2012-09-11 | Smsc Holdings S.A.R.L. | Wireless communications systems and channel-switching method |
| JP6763404B2 (en) | 2016-01-08 | 2020-09-30 | 富士通株式会社 | Wireless communication devices, wireless communication systems and processing methods |
| JP6627889B2 (en) | 2016-01-08 | 2020-01-08 | 富士通株式会社 | Wireless communication device, wireless communication system and processing method |
| CN111556410A (en) * | 2020-05-20 | 2020-08-18 | 南京中芯声学技术研究院 | Indoor sound amplification system working mode switching method based on multi-working mode microphone |
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| WO1995035006A1 (en) * | 1994-06-14 | 1995-12-21 | Nokia Telecommunications Oy | Handover in a mobile communication system |
| CN1255815A (en) * | 1999-05-21 | 2000-06-07 | 深圳市中兴通讯股份有限公司 | Switching control method based on dynamic priority in small region |
| WO2001052576A1 (en) * | 2000-01-12 | 2001-07-19 | Mitsubishi Denki Kabushiki Kaisha | Mobile communication terminal |
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| JP2912329B1 (en) * | 1998-01-27 | 1999-06-28 | 静岡日本電気株式会社 | Channel switching judgment method |
| JP2933615B1 (en) * | 1998-07-15 | 1999-08-16 | 静岡日本電気株式会社 | Channel switching decision device in digital cordless |
| JP4297568B2 (en) * | 1999-09-02 | 2009-07-15 | 富士通株式会社 | Radio communication control apparatus and mobile radio communication system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1995035006A1 (en) * | 1994-06-14 | 1995-12-21 | Nokia Telecommunications Oy | Handover in a mobile communication system |
| CN1255815A (en) * | 1999-05-21 | 2000-06-07 | 深圳市中兴通讯股份有限公司 | Switching control method based on dynamic priority in small region |
| WO2001052576A1 (en) * | 2000-01-12 | 2001-07-19 | Mitsubishi Denki Kabushiki Kaisha | Mobile communication terminal |
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