CN1241104A - Handing off wireless terminal in wireless telecommunications system - Google Patents
Handing off wireless terminal in wireless telecommunications system Download PDFInfo
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- CN1241104A CN1241104A CN99108337.7A CN99108337A CN1241104A CN 1241104 A CN1241104 A CN 1241104A CN 99108337 A CN99108337 A CN 99108337A CN 1241104 A CN1241104 A CN 1241104A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/02—Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
- H04W36/026—Multicasting of data during hand-off
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
Abstract
A wireless telecommunications system is disclosed that hands off a wireless terminal from one base station to another as the wireless terminal moves within a wireless telecommunications system. Each pair of communications channels (forward and reverse) that are used by the system for communication with a specific wireless terminal are not associated with a specific base station. Instead, the pair of communications channels are associated with the wireless terminal and are used by the wireless terminal both before and after a hand off. Before the hand off, the wireless terminal uses the pair of communications channels for communicating with a first base station. To accomplish the hand off to a second base station, the first base station stops using the communications channels at the same time that the second base station starts using them. Although the wireless terminal is handed off from the first base station to the second base station, re-tuning of the wireless terminal is not required.
Description
The present invention relates generally to communication, relate in particular to the technology from a base station handover wireless terminal to another base station in wireless telecommunication system because wireless terminal moves.
Fig. 1 has described a part of schematic diagram of a wireless telecommunication system in the prior art, and this system is that some wireless terminals (for example wireless terminal 101-1 is to 101-3) that are positioned at a geographic area provide wireless communication services.The heart of wireless telecommunication system is wireless switching center (" WSC "), and it also can be called mobile switching center or MTSO.Usually wireless switching center (for example WSC 120) is connected to by a plurality of base stations this system service, that be distributed to whole geographic area (for example base station 103-1 is to 103-5) and local and toll telephone and data network (for example local office 130, local office 138 and long-distance exchange 140).Wireless switching center also is responsible for setting up between first wireless terminal and second wireless terminal or between wireless terminal and Wireline terminal (for example the Wireline terminal 150) and keeping calling out, and this Wireline terminal is connected to this system through this locality and/or long-distance network.
Geographic area by the wireless telecommunication system service is divided into different zone, some spaces that are called " sub-district ".As shown in Figure 1, each sub-district is represented by a hexagonal pattern.Yet in fact each sub-district has an irregular shape, and it depends on the topography and geomorphology around the sub-district.General each sub-district comprises a base station, and this base station comprises that the base station is used for the radio station of the wireless terminal communication of this sub-district and antenna and comprises that also the base station is used for the transmission equipment with the wireless switching center communication.
For example, when the customer requirements of wireless terminal 101-1 transmitted information to the user of wireless terminal 101-2, data-message that has user profile of wireless terminal 101-1 emission was to base station 103-1.This data-message is forwarded to wireless switching center 120 by base station 103-1 through Wireline 102-1 subsequently.Because wireless terminal 101-2 is in the sub-district by base station 103-1 service, wireless switching center 120 return data message are to base station 103-1, and it is transmitted to wireless terminal 101-2 in this base station.
General wireless terminal with from its nearest base station communication.But because wireless terminal can move to another sub-district from a sub-district, the base station nearest from wireless terminal may change.Therefore, when wireless terminal when a sub-district moves to another sub-district, it usually with different base station communications.For example, if wireless terminal 101-1 withdraws from and move to the sub-district of base station 103-2 service from the sub-district of base station 103-1 service, then wireless terminal 101-1 finishes to begin with the communication of base station 103-1 the communication with base station 103-2.Wireless terminal finishes to begin to be defined as " handover " with the process of another base station communication with a base station communication in this specification.
Though there are some technology to be used to realize handover in the prior art, all these technology all attempt to do this process to such an extent that ingenious as much as possible making do not have any interruption that can feel in service similarly.
A kind ofly in the prior art be used to realize that the technology of handover is called " hard handoff switching ".Before hard handoff switched, wireless terminal used a pair of communication channel (is used for emission, and another is used for receiving) to be used for and first base station communication.When wireless terminal withdrawed from the sub-district of first base station services and enters the sub-district of second base station services, wireless terminal retuned to second pair of tuned channel with its radio station from first pair of communication channel and is used for and second base station communication.In addition, when wireless terminal retuned its radio station, wireless switching center was stopped using first base station and wireless terminal communication and is brought into use second base station.
For example, Fig. 2 has described the channel # 1 that is divided into four frequency bands frequency spectrum blocks to channel #4.If wireless switching center 120 allocated channel # 1 and #2 give base station 103-2 for base station 103-1 and channel # 3 and #4, then base station 103-1 can launch in channel # 1 and receive in channel # 2, and base station 103-2 can launch in #3 and receive in channel #4.Because base station 103-1 can not use identical channel to be used for communication with 103-2, between the base station without any co-channel interference.
Go on to say this example, suppose that wireless terminal 101-1 uses channel # 1 and #2 and base station 103-1 communication when the sub-district of wireless terminal 101-1 in base station 103-1 service.Later on withdraw from the sub-district of base station 103-1 service and when moving to the sub-district of base station 103-2 service as wireless terminal 101-1, wireless terminal 101-1 end in channel # 1 and #2 communication and begin in channel # 3 and #4 and base station 103-4 communication.In addition, when wireless terminal 101-1 when channel # 1 and #2 retune to channel # 3 and #4, wireless switching center 120 stop to send wireless terminal 101-1 subscribes to the signal of base station 103-1 and proceed-to-send signal to base station 103-2.In addition, when wireless terminal 101-1 retuned, wireless switching center 120 expections were received by base station 103-2 from the signal of wireless terminal 101-1, rather than are received by base station 103-1.
The advantage that hard handoff switches be it can with all multiplexing technique (frequency division multiplex (being called " FDM " later on) for example, time division multiplexing (being called " TDM " later on), code division multiplex (is called " CDM " later on, or the like) and all access technology (for example frequency division multiple access connections (being called " FDMA " later on), time division multiple access connects (being called " TDMA " later on), code division multiple access connects (being called " CDMA " later on), or the like) use together, another advantage that hard handoff switches is that its realization is a kind of quite simple process.
Yet the shortcoming that hard handoff switches is that it is a kind of process of destructible.If retuning of wireless terminal 101-1 is accurately not synchronous with the conversion from base station 103-1 to base station 103-2, then in service, may interrupt.A kind of like this mistake is not only inconvenient, and the sensation in poor service that is provided by wireless telecommunication system can be provided.This causes that then the user uses other competitive services and/or uses the less service that should obtain than them.Final result is owing to handover in the prior art is a kind of like this process of destructible, makes the owner of wireless telecommunication system lose annual income.
The second kind of technology that is used for the handover wireless terminal in the prior art is called " soft handover ".Before soft handover, wireless terminal uses a pair of communication channel (is used for emission, and another is used for receiving) to be used for and first base station communication.Withdraw from the sub-district of first base station services and before entering the sub-district of second base station services, wireless terminal begins and the communication on second pair of channel of second base station at wireless terminal.Later on wireless terminal finishes and the communication of first base station up to wireless terminal two base station communications on the channel with different.
Hard handoff switch and soft handover between main difference be to adopt soft handover not exist wireless terminal to stop using a base station and bring into use moment of second base station.Or rather, adopt soft handover one section significantly (for example more than several seconds or several seconds) at interval to be arranged during simultaneously with two base station communications at wireless terminal.On the contrary, adopt hard handoff to switch, do not exist wireless terminal simultaneously with time of two base station communications.
The advantage of soft handover is that it can use with all multiplexed and access technologies.Another advantage of soft handover is that it is firm.Produce redundant the intermittence of overlapping communication, and therefore less may have interruption in service.
Yet the shortcoming of soft handover has three aspects.The first, wireless terminal that can soft handover must comprise that two transceivers (each is used for and each base station communication) and needs coordinate the circuit of two transceivers.This has increased the cost of wireless terminal widely.
The second, wireless switching center that can soft handover must comprise through two independently channel and wireless terminal communication circuitry needed.This has increased the cost of wireless switching center.
The 3rd, soft handover requires wireless terminal to use two groups of communication channels every now and then, and this has hindered another wireless terminal and has used in them one, and this has reduced the traffic carrying capacity of communication system.
Therefore, need find a kind of technology to be used for from a base station handover wireless terminal to another base station, this technology is firm and than realizing soft handover more economically.
The present invention be a kind of can the handover wireless terminal wireless telecommunication system and do not have to be used in the prior art cost and the shortcoming of handoff techniques.Particularly the handover of the present invention's realization is firm as soft handover, and cost is in fact less.Particularly according to wireless terminal of the present invention transceiver of needs and only use one group of communication channel only.In addition, the present invention is applicable to all multiplexed and access technologies and all current wireless interface standards (for example IS-41, IS-54, GSM or the like).
By being switched to compare and contrast, hard handoff in key property of the present invention and the prior art can more easily understand the present invention.Switch according to hard handoff, in handover procedure, relate to wireless switching center, base station and wireless terminal.And realize handover of the present invention without wireless switching center and base station-wireless terminal can but needn't participate in and must not know that even handover takes place.
Switch according to hard handoff, wireless terminal will retune its transceiver.And the present invention allow wireless terminal before handover with use identical communication channel afterwards.
In other words, the different right communication channels with in each base station are relevant in hard handoff switches.Before handover, wireless terminal uses a pair of communication channel and first base station communication.In order to finish handover, wireless terminal retunes its transceiver to use the second pair of communication channel and second base station communication.The key property of prior art is that different right communication channels are used for being responsible for retuning to second pair from first pair with different base station communications and wireless terminal.
According to explanation embodiment of the present invention, communication channel and base station are irrelevant.But the every pair of communication channel is relevant with wireless terminal and wireless terminal before handover and use this afterwards to communication channel.Before handover, wireless terminal uses this that communication channel is used for and first base station communication.In order to be accomplished to the handover of second base station, this communication channel is stopped using in first base station when communication channel is brought into use in second base station.
Must be transformed into second base station from using first base station though the result is a wireless switching center, switch, need not retune the wireless terminal that it must be coordinated as hard handoff.This makes handover very firm.
Fig. 1 has described the schematic diagram of the wireless telecommunication system of prior art.
Fig. 2 describes the frequency spectrum blocks figure that is divided into a plurality of zero lap frequency bands.
Fig. 3 describes the schematic diagram that handover the present invention before illustrates the part of embodiment.
Fig. 4 has described the operational flowchart that the present invention illustrates embodiment.
Fig. 5 describes the flow chart according to the main aspect of the flow chart handover forward channel of Fig. 4.
Fig. 6 describes the flow chart according to the main aspect of the flow chart handover backward channel of Fig. 4.
Fig. 7 is described in the schematic diagram that handover the present invention afterwards illustrates the part of embodiment.
Fig. 8 describes two asynchronous timing signal figure of frequency.
Fig. 9 describes Frequency Synchronization but two asynchronous timing signal figure of phase place.
Figure 10 describes two synchronous timing signal figure.
Figure 11 describes the schematic diagram that the present invention illustrates the part of embodiment.
Figure 12 describes the block diagram according to the critical piece of the base station of explanation embodiment of the present invention.
Figure 13 describes the operational flowchart of explanation embodiment of the present invention.
Figure 14 is described in the present invention signal main among the embodiment and their correlation figure is described.
Fig. 3 describes a part of schematic diagram that the present invention illustrates embodiment, and they comprise: process Wireline 305-1 and 305-2 are connected to the base station 302-1 and the 302-2 of wireless switching center 301 respectively, and wireless terminal 303.When wireless terminal 303 withdraws from from the sub-district of base station 302-1 service and when moving to the sub-district of base station 302-2 service, wireless switching center 301 and base station 302-1 and 302-2 provide wireless communication services to wireless terminal 303.When wireless terminal 303 withdraws from from the sub-district of base station 302-1 service and when moving to the sub-district of base station 302-2 service, wireless terminal 303 is handed over to base station 302-2 from base station 302-1.
Illustrate that according to the present invention embodiment, Fig. 4 are described in the flow chart of steps that handover wireless terminal 303 comprises from base station 302-1 to base station 302-2.
In step 401, be one or more forward channels and one or more backward channel in known manner with available spectrum division.In addition, base station 302-1 and base station 302-2 can and receive on all backward channels in emission on all forward channels valuably.
In this specification, " forward channel " is defined as the communication channel that is sent to wireless terminal from the base station with calling out.Because illustrate embodiment can with an above wireless terminal communication, it must use a device to prevent that forward channel from disturbing each other.Be used for separately that the device of forward channel is called a kind of multiplexing technique and the present invention can use with any multiplexing technique.
When one embodiment of the present of invention are used frequency division multiplex, in a frequency band, only transmit a forward channel.Forward channel in the general frequency division multiplex frequency band is by discerning with the unique relevant frequency band of this forward channel.
When using time division multiplexing, single frequency band is used in a plurality of forward channel timesharing.Frequency band is temporarily assigned to time slot one by one, and the base station is transmitted in a plurality of wireless terminals in time slot.A forward channel in the general time division multiplexing frequency band is by discerning with the unique relevant time slot of this forward channel.
When using code division multiplex, a plurality of forward channels are shared and are used single frequency band.In addition, launch in each forward channel with identical frequency simultaneously.According to code division multiplex, a code will be multiply by for each calling of a wireless terminal in the base station, this code and the code quadrature that is used to multiply by other wireless terminals callings.Multiply by a code by the composite signal that will receive, this code is that the base station is used to multiply by calling, and each wireless terminal can go the multiplexed calling that is transmitted into it.General in the code division multiplex frequency band forward channel by with the unique relevant code identification of this forward channel.
In this specification, " backward channel " is defined as transmitting the communication channel of calling from the wireless terminal to the base station.Because the embodiment that illustrates can with more than one wireless terminal communication, it must use a kind of device to prevent that backward channel from disturbing each other.Be used for separately that the device of backward channel is called access technology, the present invention can use any access technology.
When the embodiment of the invention uses frequency division multiple access to connect, in a frequency band, only there is a backward channel to transmit.Backward channel in the general frequency division multiplex frequency band is by discerning with the unique relevant frequency band of this backward channel.
When using time division multiple access to connect, single frequency band is used in a plurality of backward channel timesharing.Frequency band is temporarily assigned to, and each is transmitted into these time slots in the slot cycle of a repetition and n the wireless terminal.A backward channel in the general time division multiplexing frequency band is by discerning with the unique relevant time slot of this backward channel.
When employing code division multiple access connected, a plurality of backward channels were shared and are used single frequency band.In addition, launch on each backward channel with identical frequency simultaneously from different wireless terminals.Connect according to code division multiple access, each wireless terminal will multiply by a code to the calling of base station for it, this code and the code quadrature that is used to multiply by from other wireless terminal callings.Multiply by a code by the composite signal that will receive, this code is the calling that wireless terminal is used to multiply by it, and multiplexed backward channel can be removed in the base station.General in the code division multiplex frequency band backward channel by with the unique relevant code identification of this backward channel.
It will be apparent to those skilled in the art that how can obtain frequency spectrum assigns to one or more forward channels and one or more backward channel.For example, if a channel requires the 30KHz spectral bandwidth, then the spectrum allocation may of 30MHz can be divided into 1000 channels.Be used to transmit signals to the base station because each wireless terminal requires a forward channel to be used for receiving from signal of base station and a backward channel, 500 in such 1000 channels can be assigned as forward channel, and other 500 as backward channel.
In step 402, the transmission of each base station and the transmission of each wireless terminal are synchronous, make every frame and each time slot begin simultaneously and finish.If the synchronous error amount is over half greater than a time slot duration, illustrate that then the advantage of embodiment will be cut down widely.The improvement that the present invention uses makes the synchronous error amount reduce to below half of one or one element duration.In this specification, one " position " is defined as a single binary signal and one " code element " is defined as an individual signals with two or more probable values.It will be apparent to those skilled in the art that the global position system that for example how to adopt in each base station (for example GPS receiver, or the like), the synchronous transmission that makes system is less than below half of duration of one or one code element.The another kind of technology that is used for synchronous transmission has been described in the appendix of this specification.
In step 403, wireless terminal 303 is set up a calling with base station 302-1, and this calling comprises forward channel 304 and backward channel 305 in known manner.It will be apparent to those skilled in the art that this calling can originate from wireless terminal 303 or another wireless terminal or a Wireline terminal that is connected to wireless switching center 301 through this locality and/or long-distance network.When wireless terminal 303 moves to beyond the cell boarder of base station 302-1 service, trigger handover and control immediately through step 404 and 405.
The handover of the wireless terminal 303 from base station 302-1 to base station 302-2 comprises two different steps: the handover of (1) forward channel 304, and the handover of (2) backward channel 305.Step 404 has been described the handover of forward channel 304 and step 305 has been described the handover of backward channel 305.Though step 404 and 405 is finished valuably simultaneously, two steps are independently, and one can be carried out before another.In addition, for only using a forward channel (for example paging system, or the like) or only using the wireless telecommunication system of a backward channel (for example follow the tracks of and supervisory control system, or the like), it will be apparent to those skilled in the art that and to omit step 404 or 405.
Because the process of handover forward channel 304 is different from the process of handover backward channel 305, so two kinds of processes separately are discussed.The main aspect of the handover forward channel 304 of Fig. 5 description at first is discussed.The main aspect of the handover backward channel 305 of Fig. 6 description is discussed later on.
When step 404 began, wireless terminal 303 was in the sub-district of base station 302-1 service and just be busy with a calling.This calling is included in the forward channel part that is transmitted into wireless terminal 303 in the forward channel from base station 302-1, and the backward channel part that is transmitted into base station 302-1 in backward channel from wireless terminal 303.
Be present in handover before with afterwards because call out, and comprise forward channel part and backward channel part because of calling out, the different aspect of calling is feasible can discuss them clearly so define.Therefore, in this specification:
● " the preceding forward channel part " of term call is defined as the calling part of launching in the forward channel before handover.
● " the back forward channel part " of term call is defined as the calling part of launching in the forward channel after handover.
● " the preceding backward channel part " of term call is defined as the calling part of launching in the backward channel before handover.
● " the back backward channel part " of term call is defined as the calling part of launching in the backward channel after handover.
In step 501, the preceding forward channel part that wireless switching center 301 emissions are called out is launched it to wireless terminal 303 to base station 302-1 and guiding base station 302-1 in forward channel 304.In addition, wireless switching center 301 also guides base station 302-2 not launch any signal (even not having unmodulated carrier) in forward channel 304, so that prevent the co-channel interference between base station 302-1 and 302-2.
In step 502, the preceding forward channel that base station 302-1 launches calling in known manner partly arrives wireless terminal 303, and in step 503, base station 302-2 does not launch any signal in forward channel 304.
In step 504, wireless terminal 303 is the preceding forward channel part of receipt of call in forward channel 304 in known manner.
In step 506, wireless terminal 303 withdraws from the sub-district of base station 302-1 service and moves to the sub-district that base station 302-2 serves.The transfer of any pattern (for example walking, driving, flight, by bike, or the like) can be used for moving from the wireless terminal 303 of base station 302-1 Serving cell and move to the sub-district of base station 302-2 service.
In addition, it will be apparent to those skilled in the art that wireless terminal 303 may be motionless when the border of the sub-district of base station 302-1 and 302-2 service moves through wireless terminal 303.To such an extent as to when existing too many wireless terminal to manage effectively for the base station, can realize moving of cell boarder, be sometimes referred to as " cell breathing " to alleviate the burden of base station by wireless switching center 301.According to cell breathing, make near the wireless terminal this cell boarder move forward into contiguous sub-district effectively by the cell boarder contraction of bearing heavy base station services.It should be appreciated by those skilled in the art that embodiments of the invention and the wireless system that uses cell breathing are compatible fully.
No matter wireless terminal 303 is to cross over cell boarder to move, and still because the cell breathing border moves through wireless terminal 303, when wireless terminal 303 withdraws from the sub-district of base station 302-1 service, is detected by wireless switching center 301 in step 507.It will be apparent to those skilled in the art that how wireless switching center 301 detects when wireless terminal 303 withdraws from the sub-district of base station 302-1 service.For example, when determining signal strength signal intensity from wireless terminal 303, base station 302-1 declines to a specific threshold value when following, this expression wireless terminal 303 will be handed over to another base station, and the message of these contents of an expression of base station 302-1 emission is to wireless switching center 301.
In step 508, the process of wireless switching center 301 beginning handover forward channels 304.From wireless switching center 301, the process of handover forward channel 304 comprises four parts:
(1) guiding base station 302-1 finishes the transmission of the preceding forward channel part of calling in the forward channel 304,
(2) after this guiding base station 302-1 does not launch any signal (even not having unmodulated carrier) in forward channel 304,
(3) the back forward channel of emission calling partly arrives base station 302-2, and
(4) guiding base station 302-2 begins the transmission of the back forward channel part of calling in forward channel 304 when base station 302-1 finishes transmission.
In step 509, base station 302-1 finishes the transmission in forward channel 304 and does not launch any signal (even not having unmodulated carrier) later on to forward channel 304, so that prevent the co-channel interference between base station 302-1 and 302-2.
In step 510, the back forward channel that base station 302-2 begins to launch calling when base station 302-1 finishes transmission partly arrives wireless terminal 303.
In step 511, the back forward channel part that wireless terminal 303 receives from the calling of base station 302-2 in forward channel 304 in known manner.It will be apparent to those skilled in the art that the embodiment according to explanation, the receiver that wireless terminal 303 does not need to retune it changes the handover of forward channel 304.In addition, when base station 302-2 began to launch the back forward channel part of calling when base station 302-1 finishes transmission, wireless terminal 303 was even with knowing its handover.Go through below after the step 405, discuss and control to step 406 from step 511.
Fig. 6 has described in detail aspect in step 405 handover backward channel 305 main.
Present performing step 601,602 and 603, these steps are illustrated in the state that embodiment takes place to illustrate before handover.In step 601, wireless terminal 303 is launched the preceding backward channel part of calling out in the sub-district of base station 302-1 service and at backward channel 305.The preceding backward channel that wireless terminal 303 is not launched this calling partly arrives any specific base stations, but omnidirectional radiation it make it be received by base station 302-1.Base station 302-2 also can receive the preceding backward channel part of handover this calling before, but this is optional.
In addition, wireless terminal 303 only is the device of emission on the backward channel 305 in the sub-district of the sub-district of base station 302-1 service or base station 302-2 service valuably, so that prevent the co-channel interference in backward channel 305.This is coordinated by wireless switching center 301, it know each wireless terminal where and this terminal using which channel, can prevent that therefore two devices of identical or neighbor cell from launching in same channel.
In step 602, base station 302-1 sends to wireless switching center 301 through the preceding backward channel part of backward channel 305 receipt of call and with it.
In step 603, wireless switching center 301 will partly receive as the preceding backward channel from the calling of wireless terminal 303 from the signal of base station 302-1.
In step 604, wireless terminal 303 withdraws from from the sub-district of base station 302-1 service and moves to the sub-district of base station 302-2 service.The step 604 of Fig. 6 is identical with step 506 among Fig. 5 discussed above.When wireless terminal 303 withdraws from from the sub-district of base station 302-1 service and when moving to the sub-district of base station 302-2 service, it is detected by wireless switching center 301 in step 605.
In step 605, the handover of mobile triggering backward channel 305 in step 606,607 and 608 of the wireless terminal 303 that detects by wireless switching center 301.
Present performing step 606,607 and 608, these steps are illustrated in the state that embodiment is described after handover takes place.
In step 606, wireless terminal 303 is launched the preceding backward channel part of calling out in the sub-district of base station 302-2 service and at backward channel 305.The preceding backward channel that wireless terminal 303 is not launched calling partly arrives any specific base stations, but omnidirectional radiation it make it be received by base station 302-2.Base station 302-1 can receive the preceding backward channel part of calling out before the handover, but this is optional.The key property that embodiment is described is that wireless terminal 303 does not need to know that it proceeds to 604 and 606 from step 601.Handover can be fully transparent, the signal that wireless terminal 303 does not need to retune its reflection machine or changes it by any way.As handover forward channel 304, the handover of backward channel 305 is finished by wireless switching center 301 and base station 302-1 and 302-2 fully.
In step 607, base station 302-2 passes through the back backward channel part of backward channel 305 receipt of call and sends it to wireless switching center 301.When wireless switching center 301 informing base station 302-2 began to launch the back forward channel part of calling, base station 302-2 began the back backward channel part of receipt of call valuably.
In step 608, wireless switching center 301 will be from the signal of base station 302-2 as the preceding backward channel part from the calling of wireless terminal 303, rather than the signal that arrives from base station 302-1, and the handover of backward channel 305 is finished.From step 608, control forwards the step 406 of Fig. 4 to.
In step 406, the handover of forward channel 304 and backward channel 305 is finished, and calls out and proceeds between wireless terminal 303 and base station 302-2.
Appendix
Fig. 7 is described in the handover of forward channel 304 and backward channel 305 and finishes explanation embodiment of the present invention afterwards, calls out and proceeds between wireless terminal 303 and base station 302-2.
This appendix is described in a kind of technology that is used for synchronous transmission in the wireless telecommunication system.
Each wireless terminal and each base station comprise a timing signal that is used for regularly it and other-end and base station communication.General timing signal does not provide precise time (for example the morning 3:18), but the waveform with constant frequency, and this frequency is set up one and is used for the cadence that follow wireless terminal and base station.
The timing signal of wireless terminal and the synchronous degree of timing signal of base station are depended in the communication easily of wireless terminal and base station.In other words, if the timing signal of the timing signal of wireless terminal and base station is asynchronous, the communication between wireless terminal and the base station may be difficulty or impossible.
The synchronization extent of two or more timing signals can not be by single parameter-definition.Synchronization extent is by two parameter-definitions: (1) frequency, and (2) phase place.For relation and the meaning that these two parameters are described, Fig. 8 has described a pair of figure of explanation timing signal to Figure 10.
Fig. 8 has described owing to have different frequencies and nonsynchronous two timing signal figure.And Fig. 9 has described two timing signal figure with same frequency, but they are still asynchronous, because they have different phase places.At last, Figure 10 has described owing to have identical frequency with identical phase place and two synchronous timing signal figure.Generally for wireless terminal and base station that can communication, the timing signal of wireless terminal must have identical frequency and phase place much at one with the timing signal of base station.
How the timing signal of synchronous radio terminal and the timing signal of base station are known.According to a kind of technology, its timing signal of base station is to wireless terminal.Wireless terminal uses from the timing signal of base station periodically or occasionally or continuously with its timing signal synchronously.Because the base station directs wireless terminal is its timing signal and the timing signal of base station synchronously, but base station its timing signal and the timing signal of wireless terminal synchronously, so the relation of base station and wireless terminal is asymmetric.Particularly the effect of base station resembles main website and the effect of wireless terminal resembles slave station.
Sometimes wireless terminal needs simultaneously or at short relatively time and two or more base station communication.In this case, the timing signal of wireless terminal is synchronous with the timing signal of all base stations of its communication valuably.This impliedly requires the timing signal in all base stations synchronous each other.In other words, when wireless terminal need be with two or more base station communication, the timing signal of wireless terminal need be synchronous with the timing signal of all base stations, and the timing signal of all base stations needs each other synchronously.In order to realize this point, the base station is synchronous each other with their timing signal, and wireless terminal is synchronous with its timing signal and one timing signal in the base station.
There are three kinds of technology to be used for the timing signal of synchronous a plurality of base stations.
According to first kind of technology, each base station comprises an independently but highly accurate timing source, is known and highly stable caesium clock as its vibration rate under various environmental conditions.The advantage of this technology is that it guarantees that effectively the timing signal of each base station is synchronous on frequency.And the shortcoming of this technology is because the independence of timing source, thus can not be on phase place synchronous timing signal.Therefore, as shown in Figure 9, this technology can only be created on the frequency rather than synchronous timing signal on phase place.
According to second kind of technology, all base stations obtain from the timing signal of the reference timing signal of single timing source emission.General timing source is positioned at wireless switching center, and reference timing signal is transmitted into each base station through the Wireline relevant with this base station.As first kind of technology, the advantage of second kind of technology is that it guarantees that effectively the timing signal of each base station is synchronous on frequency.Also as first kind of technology, the shortcoming of second kind of technology be can not be on phase place the synchronising base station timing signal.
Its reason is relevant with landform.Because not every base station and public main timing signal are equidistant, reference timing signal must pass through different distances from timing source to each base station.And because reference timing signal propagates into each base station with identical speed from timing source, reference timing signal arrives each base station with the slightly different time.The timing signal that arrives each base station with the slightly different time shows as inconsistent on the phase place in each timing signal of base station.
According to the third technology, each base station obtains the frequency of its timing signal from the one-period signal, and the phase place of its timing signal is from the second period signal.The timing signal that general base station obtains it is a basis: the frequency of (1) reference timing signal, and the phase place of (2) feedback signal.Particularly the base station is by finishing the phase alignment feedback signal of reference timing signal this point to produce the timing signal of base station.
Reference timing signal can be from the common timing source or from being designed to have the different timing source acquisition of same frequency.
Useful is that feedback signal is the point of two feedback control loops.According to first feedback control loop, feedback signal depends on the phase place of the timing signal of base station oneself.According to second feedback control loop, feedback signal depends on the phase place from the timing signal of one or more adjacent base stations.Feedback signal that useful is depend on the timing signal of the timing signal of base station oneself and adjacent base station boolean " with " or NAND function.
So it is advantageous using two feedback control loops, even because under the situation about changing in the timing signal of reference timing signal or one or more base stations, it also can make the base station obtain automatically and keep synchronously.Each base station is when following this mode in explanation embodiment, and the timing signal of each base station becomes synchronous with the timing signal of adjacent base station on frequency and phase place.
Figure 11 has described a part of schematic diagram of wireless telecommunication system, and it provides wireless communication services to the one or more wireless terminals in the geographic area.This wireless telecommunication system comprises: to 1102-4, their correlation as shown in the figure to 1103-4 and Wireline 1102-1 for wireless switching center 1101, base station 1103-1.Though wireless telecommunication system comprises four base stations, it will be apparent to those skilled in the art that how to constitute and use the wireless telecommunication system that comprises any amount base station.
According to wireless telecommunication system, reference timing signal is provided to base station 1102-1 each in the 1102-4.Useful is that reference timing signal is a periodic waveform (for example square wave or the like) that only has two values.
Reference timing signal can pass through (1) center timing source, or (2) local timing source is provided to each base station.For example, reference timing signal can be provided to one or more base stations from the center timing source, it can with a coexist place and be sent to the base station through Wireline of wireless switching center.On the other hand, reference timing signal can be provided to the base station from local timing source, it and the base station place that coexists.It will be apparent to those skilled in the art that some base stations can receive their reference timing signal from the center timing source, and other base stations receive their reference timing signal from local timing source.No matter each reference timing signal source, importantly each reference timing signal has that identical frequency-but they needn't be on phase place synchronously.
Each uses the reference timing signal of its reception to produce timing signal to base station 1102-1 in 1102-4.What timing signal was useful is a periodic waveform (for example square wave or the like) that only has two values.Below in conjunction with Figure 12 the details how timing signal produces is discussed.
The timing signal of each base station on frequency and phase place synchronously and have four kinds of purposes:
1) each base station uses its timing signal to be used for regularly the communication of the wireless terminal of its service;
2) its timing signal of each base station is used for these wireless terminals their timing signal synchronously to the wireless terminal of its service;
3) its timing signal of each base station is to one or more adjacent base stations; And
4) each base station uses timing signal from one or more adjacent base stations emissions to produce its timing signal.
In other words, in order to ensure the timing signal that produces by each base station in fact with the timing signal that produces by other base stations (on frequency and phase place) synchronously, each base station is valuably according to following 3 timing signals that produce it:
1) frequency of its reference timing signal,
2) phase place of its timing signal, and
3) phase place of the timing signal that receives from one or more adjacent base stations.
In conjunction with Figure 12 to 14, following description is discussed each base station and how to be produced its timing signal.
Figure 12 has described the block diagram of the major part of base station 1102-i (i from 1 to 4), it comprises valuably: phase-locked loop 1201, transmitting set 1202, coincidence gate (unanimity gate) 1203, wireless receiver 1204-1 are to 1204-n, transmitting antenna 1205 and reception antenna 1206, and their correlation as shown in the figure.At first describe these functions of components, their work and correlation is discussed in conjunction with Figure 13 and 14 then.
Phase-locked loop 1201 receives two inputs: (1) reference timing signal on lead 1103-i, and (2) are from the feedback signal of coincidence gate 1203.Phase-locked loop 1201 in known manner with the phase alignment feedback signal of reference timing signal to produce timing signal.From feed a input in transmitting set 1202 and the coincidence gate 1203 of the timing signal of phase-locked loop 1201.From a feed input of coincidence gate 1203 of the timing signal of phase-locked loop 1201, it produces an input of phase-locked loop 1201, and this is a feedback control loop that is used by wireless telecommunication system.
Transmitting set 1202 arrives the wireless terminal of base station 1103-i service and arrives one or more adjacent base stations through transmitting antenna 1205 emission timing signals in known manner.In a similar fashion, adjacent base station uses the timing signal of transmitting set 1202 emissions to produce their timing signal, and these signals receive by their emissions and by reception antenna 1206.
Feedback signal from coincidence gate 1203 is the Boolean function of its input.Particularly when and when having only when all its input to have identical value from the feedback signal of coincidence gate 1203 for true or for high.For example, coincidence gate 1203 can be boolean's AND gate or boolean's NOT-AND gate of known manner.Use is second feedback control loop that is used by this wireless telecommunication system according to the timing signal that the timing signal from other base stations of the timing signal for generating of this base station produces this base station.
Figure 13 has described the operational flowchart of wireless telecommunication system, the timing signal of its synchronous two base station: base station 1102-i and base station 1102-j.
In step 1310, base station 1103-i receives first reference timing signal as mentioned above in known manner.
In step 1311, first reference timing signal adopts the feedback signal of phase-locked loop 1201-i phase alignment from coincidence gate 1203-i as mentioned above.The output of phase-locked loop 1201-i is to be used for the timing signal of base station 1103-i and to be fed to coincidence gate 1203-i and transmitting set 1202-i.It will be apparent to those skilled in the art that how to constitute and use phase-locked loop 1201-i.
In step 1312, transmitting set 1202-i arrives one or more adjacent base stations (for example base station 1102-j) through transmitting antenna 1205-i emission timing signal in known manner.
In step 1313, base station 1103-i is in known manner through n the timing signal of n control channel reception that separates from n adjacent base station (for example base station 1102-j).For example, according to most of air interface standard (for example IS-41, IS-56, IS-95, GSM or the like), each base station is used for the wireless terminal of its service at a control channel emission timing signal.This timing signal is used for synchronously their clock and the clock of base station by wireless terminal as mentioned above.
Launch timing signal by the base station at control channel.Control channel is similar to Traffic Channel, except it is used for emission timing and other control informations rather than communication traffic amount.In addition, with identical, also can distinguish (for example control channel can pass through frequency, time or orthogonal code difference) each other from the control channel of different base station from the mutual diacritic mode of the Traffic Channel of different base station.
Because each base station 1103-i can receive n timing signal from n adjacent base station at n control channel, wireless receiver 1204-1 one in each reception and demodulation n the incoming timing signal and provide it to arrive coincidence gate 1203-i in the 1204-n is provided base station 1103-i.It will be apparent to those skilled in the art that how to constitute and use base station 1103-i to make its receive n timing signal from n other base stations.
In step 1314, be input to coincidence gate 1203-i with n timing signal from n other base stations from the timing signal of phase-locked loop 1201-i.Feedback signal from coincidence gate 1203-i is used in step 1311 as mentioned above.
In step 1320, base station 1103-j receives second reference timing signal as mentioned above in known manner.
In step 1321, second reference timing signal adopts the feedback signal of phase-locked loop 1201-j phase alignment from coincidence gate 1203-j as mentioned above.The output of phase-locked loop 1201-j is to be used for the timing signal of base station 1103-j and to be fed to coincidence gate 1203-j and transmitting set 1202-j.It will be apparent to those skilled in the art that how to constitute and use phase-locked loop 1201-j.
In step 1322, transmitting set 1202-j arrives one or more adjacent base stations (for example base station 1102-i) through transmitting antenna 1205-j emission timing signal in known manner.
In step 1323, base station 1103-j is in known manner through n the timing signal of n control channel reception that separates from n adjacent base station (for example base station 1102-i).For example, according to most of air interface standard (for example IS-41, IS-56, IS-95, GSM or the like), each base station is used for the wireless terminal of its service at a control channel emission timing signal.Timing signal is used for synchronously their clock and the clock of base station by wireless terminal as mentioned above.
Launch timing signal by the base station at control channel.Control channel is similar to Traffic Channel, except it is used for emission timing and other control informations rather than communication traffic amount.In addition, with identical, also can distinguish (for example control channel can pass through frequency, time or orthogonal code difference) each other from the control channel of different base station from the mutual diacritic mode of the Traffic Channel of different base station.
Because each base station 1103-j can receive n timing signal from n adjacent base station at n control channel, wireless receiver 1204-1 one in each reception and demodulation n the incoming timing signal and provide it to arrive coincidence gate 1203-j in the 1204-n is provided base station 1103-j.It will be apparent to those skilled in the art that how to constitute and use base station 1103-j to make its receive n timing signal from n other base stations.
In step 1324, be input to coincidence gate 1203-j with n timing signal from n other base stations from the timing signal of phase-locked loop 1201-j.Feedback signal from coincidence gate 1203-j is used in step 1321 as mentioned above.
When the step of Figure 13 was finished in all base stations of whole wireless telecommunication system, the timing signal of each base station became synchronously, and will keep synchronously for the timing signal of each other base station.
Figure 14 has described and the timing signal series that the base station is relevant, and it helps to understand the wireless telecommunication system of Figure 11.Signal 1401 explanations are as the reference timing signal of phase-locked loop 1201-i input.The timing signal that signal 1402 explanations are exported from phase-locked loop 1201-i, the forward position of its phase alignment signal 1405, it is the feedback signal from coincidence gate 1203-i.The timing signal that signal 1403 and 1404 expressions receive from other base stations and signal 1405 are boolean's AND-functions of the output of phase-locked loop 1201-i and the timing signal that receives from other base stations.
Should be appreciated that the foregoing description is explanation of the present invention, those skilled in the art can make many modifications and not deviate from scope of the present invention.Therefore these changes are included in the scope of following claims and their equivalents.
Claims (32)
1. method comprises:
The preceding forward channel part of launching calling from first base station a forward channel is to wireless terminal; And
The back forward channel part of launching described calling from second base station described forward channel is to described wireless terminal;
Before wherein said calling described the end of transmission of forward channel part the time transmission of the described back forward channel part of described calling begin.
2. the method for claim 1, wherein said first base station services first sub-district, described second base station services second sub-district, the end of transmission of forward channel part before described calling described when described wireless terminal leaves described first sub-district.
3. the method for claim 1, wherein said forward channel are that forward channel part and described back forward channel partly take identical time slot before a time division multiplex channel and described calling described in described time division multiplex channel.
4. the method for claim 1, wherein said forward channel are forward channel part and described back forward channel part identical codes of use in described code division multiplex channel before code division multiplex channel and described calling described.
5. the method for claim 1 also comprises step:
Described first base station of process receives the preceding backward channel part from the described calling of described wireless terminal in a backward channel; And
Described second base station of process receives the back backward channel part from the described calling of described wireless terminal in described backward channel;
The reception of the described back backward channel of described calling began when wherein the reception of backward channel part finished before described calling described.
6. method as claimed in claim 5, wherein when described wireless terminal leaves described first sub-district before described calling described the reception of backward channel part finish.
7. method as claimed in claim 5, wherein said backward channel are that the described preceding forward channel part of time division multiple access connection channel and described calling takies identical time slot with described back forward channel part in described time division multiple access connection channel.
8. method as claimed in claim 5, wherein said backward channel are the described preceding forward channel parts and described back forward channel part identical code of use in described code division multiple access connection channel of a code division multiple access connection channel and described calling.
9. wireless telecommunication system comprises:
First base station, the preceding forward channel part that is used for calling out a forward channel emission from one first base station is to wireless terminal; And
Second base station is used for launching the back forward channel part of described calling to described wireless terminal from one second base station in described forward channel;
Wherein before described calling described in the end of transmission of forward channel part the transmission of the described back forward channel part of described calling begin.
10. wireless telecommunication system as claimed in claim 9, wherein said first base station services first sub-district, described second base station services second sub-district, the end of transmission of forward channel part before described calling described when described wireless terminal leaves described first sub-district.
11. being the described preceding forward channel parts of a time division multiplex channel and described calling, wireless telecommunication system as claimed in claim 9, wherein said forward channel in described time division multiplex channel, take identical time slot with described back forward channel part.
12. being the described preceding forward channel part and the described back forward channel parts of a code division multiplex channel and described calling, wireless telecommunication system as claimed in claim 9, wherein said forward channel in described code division multiplex channel, use identical code.
13. wireless telecommunication system as claimed in claim 9 also comprises:
A wireless switching center is used for through described first base station in the preceding backward channel part of a backward channel reception from the described calling of described wireless terminal; And described second base station of process receives the back backward channel part from the described calling of described wireless terminal in described backward channel;
The reception of the described back backward channel part of described calling when wherein backward channel partly receives end before described calling described begins.
14. wireless telecommunication system as claimed in claim 13, wherein when described wireless terminal leaves described first sub-district before described calling described the reception of backward channel part finish.
15. being the described preceding forward channel parts of a time division multiple access connection channel and described calling, wireless telecommunication system as claimed in claim 13, wherein said backward channel in described time division multiple access connection channel, take identical time slot with described back forward channel part.
16. wireless telecommunication system as claimed in claim 13, wherein said backward channel are the described preceding forward channel part and described back forward channel part identical code of use in described code division multiple access connection channel of a code division multiple access connection channel and described calling.
17. a method comprises:
In a backward channel, receive preceding backward channel part through first base station from the calling of wireless terminal; And
In described backward channel, receive back backward channel part through second base station from the described calling of described wireless terminal;
The reception of the described back backward channel part of described calling when wherein the reception of backward channel part finishes before described calling described begins.
18. method as claimed in claim 17, wherein said first base station services first sub-district, described second base station services second sub-district, the reception of backward channel part finishes before described calling described when described wireless terminal leaves described first sub-district.
19. being the described preceding forward channel parts of a time division multiple access connection channel and described calling, method as claimed in claim 17, wherein said backward channel in described time division multiple access connection channel, take identical time slot with described back forward channel part.
20. method as claimed in claim 17, wherein said backward channel are the described preceding forward channel part and described back forward channel part identical code of use in described code division multiple access connection channel of a code division multiple access connection channel and described calling.
21. method as claimed in claim 17 also comprises step:
The preceding forward channel part of launching described calling from described first base station a forward channel is to described wireless terminal; And
The back forward channel part of launching described calling from described second base station described forward channel is to described wireless terminal;
Wherein before described calling described in the end of transmission of forward channel part the transmission of the described back forward channel of described calling begin.
22. method as claimed in claim 21, the wherein end of transmission of forward channel part before described calling described when described wireless terminal leaves described first sub-district.
23. being the described preceding forward channel parts of a time division multiplex channel and described calling, method as claimed in claim 21, wherein said forward channel in described time division multiplex channel, take identical time slot with described back forward channel part.
24. being the described preceding forward channel part and the described back forward channel parts of a code division multiplex channel and described calling, method as claimed in claim 21, wherein said forward channel in described code division multiplex channel, use identical code.
25. a wireless telecommunication system comprises:
A wireless switching center is used for through first base station in the preceding backward channel part of a backward channel reception from the calling of wireless terminal; And in described backward channel, receive back backward channel part from the described calling of described wireless terminal through second base station;
The reception of the described back backward channel of described calling when wherein backward channel partly receives end before described calling described begins.
26. wireless telecommunication system as claimed in claim 25, wherein said first base station services first sub-district, described second base station services second sub-district, the reception of backward channel part finishes before described calling described when described wireless terminal leaves described first sub-district.
27. being the described preceding forward channel parts of a time division multiple access connection channel and described calling, wireless telecommunication system as claimed in claim 25, wherein said backward channel in described time division multiple access connection channel, take identical time slot with described back forward channel part.
28. wireless telecommunication system as claimed in claim 25, wherein said backward channel are the described preceding forward channel part and described back forward channel part identical code of use in described code division multiple access connection channel of a code division multiple access connection channel and described calling.
29. wireless telecommunication system as claimed in claim 25, wherein:
The preceding forward channel part of described calling is launched to described wireless terminal in described first base station a forward channel from one first base station; And
The back forward channel part of described calling is launched to described wireless terminal in described second base station described forward channel from one second base station;
Wherein before described calling described in the end of transmission of forward channel part the transmission of the described back forward channel part of described calling begin.
30. wireless switching center as claimed in claim 29, the wherein end of transmission of forward channel part before described calling described when described wireless terminal leaves described first sub-district.
31. being the described preceding forward channel parts of a time division multiplex channel and described calling, wireless switching center as claimed in claim 29, wherein said forward channel in described time division multiplex channel, take identical time slot with described back forward channel part.
32. being the described preceding forward channel part and the described back forward channel parts of a code division multiplex channel and described calling, wireless switching center as claimed in claim 29, wherein said forward channel in described code division multiplex channel, use identical code.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN99108337.7A CN1241104A (en) | 1998-06-10 | 1999-06-09 | Handing off wireless terminal in wireless telecommunications system |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US095235 | 1987-09-11 | ||
| CN99108337.7A CN1241104A (en) | 1998-06-10 | 1999-06-09 | Handing off wireless terminal in wireless telecommunications system |
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| CN1241104A true CN1241104A (en) | 2000-01-12 |
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| CN99108337.7A Pending CN1241104A (en) | 1998-06-10 | 1999-06-09 | Handing off wireless terminal in wireless telecommunications system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110140226A (en) * | 2016-11-23 | 2019-08-16 | Tdk电子股份有限公司 | The device of touch feedback and the device with the device are provided |
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1999
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110140226A (en) * | 2016-11-23 | 2019-08-16 | Tdk电子股份有限公司 | The device of touch feedback and the device with the device are provided |
| CN110140226B (en) * | 2016-11-23 | 2023-05-16 | Tdk电子股份有限公司 | Device for providing haptic feedback and apparatus having the same |
| US11653569B2 (en) | 2016-11-23 | 2023-05-16 | Tdk Electronics Ag | Device providing haptic feedback, and component comprising said device |
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