CN100456872C - Method and apparatus for performing handoff in a CDMA system through use of repeaters - Google Patents
Method and apparatus for performing handoff in a CDMA system through use of repeaters Download PDFInfo
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- CN100456872C CN100456872C CNB988115603A CN98811560A CN100456872C CN 100456872 C CN100456872 C CN 100456872C CN B988115603 A CNB988115603 A CN B988115603A CN 98811560 A CN98811560 A CN 98811560A CN 100456872 C CN100456872 C CN 100456872C
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
- H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
- H04B7/2603—Arrangements for wireless physical layer control
- H04B7/2606—Arrangements for base station coverage control, e.g. by using relays in tunnels
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/0005—Control or signalling for completing the hand-off
- H04W36/0055—Transmission or use of information for re-establishing the radio link
- H04W36/0079—Transmission or use of information for re-establishing the radio link in case of hand-off failure or rejection
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/08—Reselecting an access point
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/24—Reselection being triggered by specific parameters
- H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
- H04W36/302—Reselection being triggered by specific parameters by measured or perceived connection quality data due to low signal strength
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- H—ELECTRICITY
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- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
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Abstract
A method and apparatus for providing handoff between two communication systems. The systems can be CDMA systems operating at different frequencies or systems employing different technologies. In the first system, a base station (4) is configured to provide communications to two or more sectors, with at least one sector assigned to a corresponding repeater (8) which provides coverage overlapping that of both systems. As the remote station (6) moves into the coverage area of the repeater (8), the pilot signal of the repeater (8) is identified, measured and sent to the first system. If the measured pilot signal is above a predetermined add threshold, the repeater (8) is added to the active set of the remote station. The first system can handoff the remote station (6) to the second system: (1) upon initiation of a soft handoff by the base station of the first system; (2) if the pilot signal strength of the repeater (8), as measured by the remote station (6), exceeds a predetermined handoff threshold; (3) if the base station (4) of the first system is dropped from the active set of the remote station (6); (4) if the repeater of the first system is dropped from the active set of the remote station (6); or (5) if the base station (4) and repeater (8) of the first system are dropped from the active set of the remote station (6).
Description
Technical field
The present invention relates to communication, more particularly, the present invention relates to by adopting transponder in cdma system, to carry out the method and apparatus of handover.
Background technology
The employing of code division multiple access (CDMA) modulation technique is to have one of several technology that the system of a large number of users is convenient to communicate.Although such as other technology of time division multiple access (TDMA), frequency division multiple access (FDMA) with such as the AM modulation scheme of amplitude companded single sideband (ACSSB) is known, CDMA has remarkable advantages than these other technology.The United States Patent (USP) 4,901,307 that is entitled as " spread spectrum multiple access communication that utilizes satellite or land transponder " has disclosed the application of CDMA technology in multi-address communication system, and this patent has transferred assignee of the present invention, is hereby incorporated by reference.The United States Patent (USP) 5,103,459 that is entitled as " system and method that produces signal waveform in the cdma cellular telephone system " has disclosed the application of CDMA technology in multi-address communication system, and this patent has transferred assignee of the present invention, is hereby incorporated by reference.Cdma system can be designed to meet " the TIA/EIA/IS-95 travelling carriage-base station compatible standard of dual mode wideband spread spectrum cellular ", hereinafter referred to as the IS-95 standard.
At above-mentioned United States Patent (USP) 4,901,307 and 5, in 103,459, disclosed a kind of multiple access technology, wherein, a large amount of mobile telephone system users, (each user has a transceiver, is also referred to as remote station) utilized the cdma spread spectrum communication signal transponder or land base station (being also referred to as base station or cell site) communicated via satellite.In utilizing cdma communication, in adjacent cell site, can reuse frequency spectrum.Therefore the higher spectrum efficiency that the use of CDMA technology causes Billy can realize with other multiple access technology allows to increase system user capacity.
As described herein-in, the base station is meant the physical hardware that communicates by it.The sub-district is meant therein the geographical that can communicate with the base station.Microzonation can be divided into a plurality of sectors, the sector can be overlapping or non-overlapped.In the cdma communication system of example, the communication by a plurality of sectors can be supported in each base station.In this manual, sector and sub-district also can refer to the physical hardware that communicates by it, and this is relevant with the term content that is adopted.System is meant one group of base station by a public system controller control.
The traditional F M cell phone system that the U.S. adopted is commonly referred to advanced mobile phone service (AMPS), describes in detail and sees at the standard EIA/TIA-553 of Electronic Industries Association " travelling carriage-land compatible technique standard ".In this traditional F M cell phone system, operational frequency band division is become channel, bandwidth is 30KHz usually.From geography the system business zoning is divided into base station overlay area, its size can change.Operational frequency channels is divided in groups.With the frequency component dispensing area of coverage, it is minimum that the possibility that makes same channel disturb reduces to by this way.For example, consider a kind of system, 7 group of frequencies are wherein arranged, the area of coverage is equal-sized hexagon.Employed frequency is not used in 6 adjacent areas of coverage in an area of coverage.
In traditional cellular system, when remote station strides across border between the area of coverage of two different base stations, adopt handover to allow to communicate connection.In the AMPS system, existing when determining that with the base station received signal intensity of remote station has dropped under the predetermined threshold when what handle to call out, begin handover from a base station to another base station.Low signal strength signal intensity indication means the coverage area boundary of remote station near the base station.When signal level is lower than predetermined threshold, now use the base station queries system controller, to determine that whether adjacent base station is to receive the remote station signal than the better signal strength signal intensity of current base station.
System controller responds to the inquiry with the base station now, and the message of hand-off request is sent to adjacent base station.With the adjacent dedicated scan receiver of each base station employing in base station, its seeks the signal that the remote station on the channel of working is sent just thereon with now.If an adjacent base station so, attempts to be handed over to this adjacent base station to appropriate signal level of system controller report, be called target BS now.Then, by selecting an idle channel to begin handover in the channel group that from target BS, is adopted.Send control messages to remote station, order it to switch to the new channel of supporting by target BS from current channel.Meanwhile, system controller will be called out to connect from existing and switch to target BS with the base station.This process is called hard handoff and switches.Term " firmly " is used for expression " ' cutting off before making action ' feature of handover ".
In traditional system,, call out connection and be interrupted (disconnection) if unsuccessful to the handover of target BS.The reason that can occur the hard handoff handoff failure why has a plurality of.At first, if there is not operational idle channel in target BS, handover can be failed.Secondly, if the signal from remote station is received in adjacent base station report, in fact, in fact this base station receives the signal from different remote station, and described different remote station utilize same channel and a remote base station to communicate, and handover also can be failed.This report mistake is led this and is caused the base station that a mistake is transferred in the calling connection, normally is not enough to keep a platform of communication from the signal strength signal intensity of actual remote station.The 3rd, if remote station fails to receive the order of switching channels, the handover failure.The practical operation experience shows that the handover failure often occurs, and this has greatly reduced the reliability of system.
Another FAQs in traditional AMPS telephone system appears at the boundary vicinity of remote station between two areas of coverage when keeping one period cycle duration.In this case, when remote station changed the position, when other reflection in the area of coverage or the displacement of assimilate structural reform were put, perhaps owing to measuring uncertainty, signal level can rise and fall with respect to each base station.The signal level fluctuating can cause " table tennis " situation,, makes repetitive requests here, switch call back and forth between two base stations.This additional inessential handover has increased to be called out by the probability of unfavorable disconnection.In addition, repeated handoffs is even success also can have a negative impact to signal quality.
At the United States Patent (USP) 5 that is entitled as " method and apparatus that soft handover is provided in the cdma cellular telephone system ", 101, in 501, this patent was authorized on March 31st, 1992, transferred assignee of the present invention, be hereby incorporated by reference, disclosed a kind of method and system, during the handover that CDMA calls out, provide and the communicating by letter of remote station by an above base station.Utilize such handover, do not interrupted with the handover of base station to target BS from existing with communicating by letter of cellular system.Can regard such handover as " soft " handover, wherein, stop with before first now uses the communicating by letter of base station, foundation with will become second and communicate by letter now with the target BS of base station the time.
Disclosed another kind of soft handover in the United States Patent (USP) 5,267,261 that is entitled as " the auxiliary soft handover of travelling carriage in the cdma cellular communication system ", this patent was authorized November 30 in 1993, had transferred assignee of the present invention, was hereby incorporated by reference.5,267, in the system of No. 261 United States Patent (USP)s, soft handover procedure is based on to measure on the remote station and is controlled by the intensity of each base station institute pilot transmitted signal in the system.These pilot frequency intensity measurings result helps soft handover procedure by being convenient to discern feasible base station hand-off canaidates.
Especially, the 5th, 267, in the system of No. 261 United States Patent (USP)s, the signal strength signal intensity of the pilot signal of remote station monitoring adjacent base station.In fact the area of coverage of adjacent base station does not need and the area of coverage adjacency of setting up the base station of efficient communication.When the measure signal intensity from the pilot signal of an adjacent base station surpasses predeterminedly when increasing threshold value, remote station sends to system controller with the base station with signal strength signal intensity message through existing.System controller commander target BS is set up and the communicating by letter and command remote station through now communicating by letter by target BS the time with base station foundation of remote station, keeps simultaneously and now uses communicating by letter of base station.For other base station, this process can continue.
Be reduced to predetermined falling-threshold value when following when remote station detects corresponding to remote station the signal strength signal intensity of the pilot tone by its base station that communicates, remote station is through now with the measure signal intensity of base station to system controller report corresponding base station.System controller sends command messages to and is identified base station and remote station, stops and is identified communicating by letter of base station, keeps simultaneously with other and now uses communicating by letter of base station.
Although above-mentioned technology is very suitable for by the calling transfer between the base station in the same cellular system of identical systems controller control, but, remote station moves in the area of coverage of the base station of the base station of just working under different frequency or another cellular system serving, and more situation of difficult occurred.Between frequency and/or in the inter-system handoff, a complicated factor is because emission and the received signal under two frequencies simultaneously that the hardware limitation causes.In inter-system handoff, another complicated factor is, each system is by a different system controller control, do not have direct link usually between the system controller of the base station of first system and second system, and vice versa.Two systems repel during handover procedure, provide with remote station in communicate by letter.Even can provide link between the system that exists between two systems so that between system during soft handover, the dissimilar feature of two systems makes soft handover procedure further complicated usually.
When resource can not provide carry out between frequency and/system between during soft handover, if keep uninterrupted service, from a frequency to another frequency and/or the execution of the calling from a system to another system ' the hard handoff switching ' that connect become very crucial.Between frequency and/or inter-system handoff should carry out causing probably between the system calling out on time that successful connection shifts and the position.Have only when following situation for example and should make handover:
(1) can provide idle channel in the target BS;
(2) remote station is at target BS with now use within the scope of base station; And
(3) remote station is positioned on the position of the order that guarantees the reception switching channels.Ideally, hard handoff switches and should carry out by this way between each this frequency and/or between system, and what promptly make ' table tennis ' hand-off request between the base station of different system may reduce to minimum.
Weaken the quality of cellular communication between existing frequency with these and other shortcoming of inter-system handoff technology.When the cellular system of competition continues to increase, can the further deterioration of predicted performance.So, need between a kind of frequency that can carry out calling out between the base station handover reliably and the inter-system handoff technology.
Summary of the invention
The invention provides the method in a kind of communication system, may further comprise the steps: in the signal strength signal intensity of remote station measurement from the signal of transponder; The signal strength measurement of transponder is compared with the increase threshold value of being scheduled to; Begin the handover of remote station from first base station to second base station in response to the result of comparison step; Wherein the signal from transponder is a pilot signal; Wherein discerned by the skew of short PN sequence spreading from the pilot signal of transponder, from the skew of the short PN sequence spreading of first base station of at least one pilot signal of being used as first base station, the skew of this weak point PN sequence spreading is unique; Wherein from transponder emission pilot signal, so that the area of coverage of the equitant transponder of the area of coverage that is provided with first base station to be provided at least, and the area of coverage that the equitant transponder of the area of coverage that is provided with second base station is provided at least.
The present invention also provides a kind of system that carries out the handover of remote station from first base station to second base station, comprising: what be connected with first base station provides the transponder of signal to remote station; First system controller that is connected with first base station; Second system controller that is connected with first system controller with second base station; Wherein begin handover based on measurement result by first system controller from the signal of transponder in remote station; Wherein the signal from transponder is a pilot signal; Wherein discerned by the skew of short PN sequence spreading from the pilot signal of transponder, from the skew of the short PN sequence spreading of first base station of at least one pilot signal of being used as first base station, this weak point PN sequence spreading is unique; Wherein from transponder emission pilot signal, so that the area of coverage of the equitant transponder of the area of coverage that provided with first base station to be provided at least, and the area of coverage that the equitant transponder of the area of coverage that is provided with second base station is provided at least.
The present invention is for carrying out the method and apparatus of handover between two communication systems by the employing transponder.System can be cdma system of working on different frequency or the system that adopts different technologies, as CDMA and AMPS.In the embodiment of example, in first system, base station configuration is become the covering provide two or more sectors.One or more sectors are relevant with the area of coverage (this is also referred to as the sub-district) around the base station.Each is relevant with each transponder that is positioned at cell boarder in remaining one or more sector.Each transponder provides communication for the area of coverage around each transponder.
In the embodiment of example, the little area overlapping of the area of coverage of transponder and first system is so that can carry out handover between base station and transponder.In the embodiment of example, the area of coverage of transponder also with a little area overlapping of second system so that between the base station (or transponder) of the base station of first system or the transponder and second system, can carry out handover.
In the embodiment of example, the transponder of the pilot signal of base station and first system is distinguished by the skew of different public short PN extended codes, and short PN extended code is used for data are expanded.On the other hand, pilot signal can be distinguished by different Walsh covering or other recognition feature.Be positioned at first system the sub-district remote station with now use base station communication accordingly.When remote station entered in the area of coverage of transponder, the pilot signal of transponder was discerned and is measured by remote station and it is sent to and now uses the base station.If the pilot signal of measuring is higher than predetermined increase threshold value, so, transponder can be increased to the existing of remote station with group, can be simultaneously with now communicate with base station and transponder.One among at least four embodiment of first system utilization can be the base station of communication diversion to second system.
In first embodiment, first system beginning during by the existing soft handover with base station and the transponder area of coverage of first system the base station of communication diversion to second system.When the area of coverage of transponder was total to the position in (subclass) of the sub-district of second system, this embodiment work was fine.Therefore, first system is guaranteed fully, can set up reliably and the communicating by letter of the base station of second system.
In a second embodiment, if the pilot signal strength of transponder (being measured by remote station) surpasses predetermined handoff threshold, so, first system gives the base station of second system communication diversion.Predetermined handoff threshold can be set at and be higher than predetermined increase threshold value, and the latter is used for transponder is increased to the existing with group of remote station.Even when the area of coverage of transponder was not total to the position in the neighbor cell of second system, this embodiment also worked fine.
In the 3rd embodiment, if throw off with group from the existing of remote station the base station of first system, so, first system gives the base station of second system communication diversion.In the embodiment of example, remote station is periodically measured the pilot signal of existing usefulness base station and transponder and is given first system with measurement report.If the existing pilot signal strength with the base station of first system (being measured by remote station) is lower than the predetermined down threshold value, so, the base station is existing with removing the group from remote station.When this thing happens, first system can suppose that remote station has fully been come into the area of coverage of second system, can begin the handover of remote station to the second system.
In the 4th embodiment, if the transponder of first system is thrown off with group from the existing of remote station, first system gives the base station of second system communication diversion.This embodiment especially can be applicable in the system design, and wherein the area of coverage of transponder is included in the area of coverage of second system (for example AMPS system), need be to the handover of this second system.
In the 5th embodiment, if the two is thrown off with group from the existing of remote station with base station and transponder for first system existing, so, first system gives the base station of second system communication diversion.When the existing of first system is reduced to the predetermined down threshold value when following with the two pilot signal strength of base station and transponder, first system can suppose that remote station has been gone to beyond the coverage of first system.Therefore, attempt to do the handover of remote station to the second system.
The accompanying drawing summary
From the detailed description of doing below in conjunction with accompanying drawing, features, objects and advantages of the invention will be clearer, and wherein, similar reference symbol is done corresponding expression in whole accompanying drawing.
Fig. 1 is the schematic diagram of the communication system of example, comprises a plurality of base stations and a transponder of communicating by letter with remote station.
Fig. 2 is that the forward of example connects the block diagram that transmits and receives subsystem.
Fig. 3 is the block diagram of the example channels element in the base station.
Fig. 4 is the block diagram of the example demodulator in the remote station.
Fig. 5 A-5B is the block diagram of the example transponder that communicates by airlink and transmission line link respectively.
Fig. 6 A-6C is three exemplary plot of the area of coverage that provided by the base station of two communication systems and transponder.
Embodiment
With reference to the accompanying drawings, Fig. 1 represents an example communication system of the present invention, and it comprises a plurality of base stations 4 of communicating by letter with a plurality of remote station 6 (remote station only is shown among the figure for the sake of simplicity).The system controller of all base stations 4, public switch telephone network (PSTN) and other communication system in system controller 2 and the communication system is connected.Communicating by letter between the user on the user that system controller 2 coordinates to be connected in PSTN and other system and the remote station 6.Each base station 4 can provide communication by zero extremely a plurality of transponders 8, and transponder is used for forward link signals being retransmitted or being replayed to remote station 6 and from remote station 6 reception reverse link signal.Transponder 8 can pass through terrestrial radio current source road or other transmission link, is connected to base station 4 as optical fiber link or transmission line.4 take place at forward link by signal path 10 to the communication of remote station 6 from the base station, and 4 communication takes place at reverse link by signal path 12 to the base station from remote station 6.
The forward link that Fig. 2 illustrates example transmits and receives the block diagram of hardware.In base station 4, data source 110 comprises the data that will be transmitted to remote station 6.In the embodiment of example, data offer element in channel 112, and it is divided, data are carried out the CRC coding and inserted code tail bits according to system's needs data.In the embodiment of example, 112 pairs of data of element in channel, CRC parity bit and code tail bits are carried out convolutional encoding, and coded data is interweaved, and with the head of a household PN sequence interleaving data being carried out scramble, and with walsh sequence scramble data are covered.To offer modulator and transmitter (MOD and TMTR) 114 (only illustrating among Fig. 2 for simplicity) corresponding to the traffic channel and the merging of pilot signal data of each sector.The short PN sequence of each modulator and transmitter 114 usefulness is carried out spread spectrum to cover data.In the embodiment of example, concerning the skew of these adjacent modulators and transmitter, it is unique being chosen as with the skew of the short PN sequence of each modulator and transmitter 114.With homophase or quadrature are sinusoidal wave mutually growth data is modulated then, modulating data is carried out filtering, up-conversion and amplification.On forward link 10, launch forward link signals by antenna 116.
In remote station 6, forward link signals is received by antenna 132 and is provided for receiver (RCVR) 134.Receiver 134 pairs of signal filterings, amplification, down-conversion, quadrature demodulation and quantifications.Digitalized data is offered demodulator (DEMOD) 136, and the latter goes expansion with short PN sequence to data, goes to cover to removing growth data with walsh sequence, and goes rotation with the pilot signal of recovering to going cover data.Will from different correlators in the demodulator 136 go spin data to merge and with separating scramble with head of a household PN sequence.Descrambling (or demodulation) data are offered decoder 138, and the latter carries out the inverse operation of the coding that carries out in element in channel 112.Decoded data is offered data sink 140.
At above-mentioned United States Patent (USP) 4,901,307 and 5,103, above-described forward link signals has been described in further detail in 459 has handled.These patents have also been described the reverse link signal processing, and are not shown among Fig. 2 for the sake of simplicity.The present invention can also be applied to other communication system, as the system described in the PA496 U.S. Patent application of submitting on November 3rd, 1997 that is entitled as " High Rate Packet Data method for transmitting and device ", this patent transfers assignee of the present invention, and is at this that it is incorporated by reference.
Fig. 3 illustrates the block diagram of the element in channel 112 of example.In the embodiment of example, element in channel 112 comprises at least one traffic channel 212 and at least one pilot channel 232.In each traffic channel 212, CRC encoder 214 receives traffic data, carries out the CRC coding and can insert a group coding tail position (for example according to the IS-95 standard).The CRC coded data is offered convolution coder 216, and it is encoded with the convolutional code certificate.In the embodiment of example, convolution code is by the IS-95 standard code.Coded data is offered interleaver 218, and it is resequenced to the code sign in the coded data.In the embodiment of example, interleaver 218 is block interleavers that the code sign in 20 milliseconds the coded data block is resequenced.Intercrossed data is offered multiplier 220, and it is with the head of a household PN sequence data being carried out scrambler.Long PN sequence is same as distributes to the sequence of specifying the remote station that communicates.The scrambler data offer multiplier 222, and it covers data with the walsh sequence of distributing to this traffic channel 212.Cover data offers booster element 224, and it carries out bi-directional scaling to data, makes can keep required every potential energy-noise ratio E in remote station 6
b/ I
0, make transmitting power reduce to minimum simultaneously.Scaled data is offered switch 230, and it will be sent to suitable adder 240 from the data of traffic channel 212.Each adder 240 do for oneself in the future specified all traffic channels 212 of particular sector and the signal plus of pilot channel 232.Consequential signal from each adder 240 offers modulator and transmitter 114, and they carry out function in above-mentioned mode.
Element in channel 112 comprises at least one pilot channel 232.The number of required pilot channel 232 depends on system requirements.In the embodiment of example, each sector is relevant with the pilot signal with identical walsh covering (for example walsh code 0) and short PN skew, and from the PN skew of these adjacent sectors, this weak point PN skew is unique.In another embodiment, each sector can be relevant with the pilot signal with identical short PN skew and Walsh covering, and from the Walsh covering of these adjacent sectors, it is unique that this Walsh covers.Can adopt other unique recognition feature to distinguish the signal of different sectors, this within the scope of the invention.
For each pilot channel 232, pilot data is offered multiplier 234, it uses pilot tone walsh sequence cover data.In the embodiment of example, the pilot data of all pilot channels 232 is identical, comprises complete 1 sequence.The pilot data that covers is offered booster element 236, and it carries out bi-directional scaling with scale factor to pilot data, to keep required pilot signal level.The proportional zoom pilot data is offered switch 230, and it is sent to suitable adder 240 to the data from pilot channel 232.In the embodiment of example, in modulator and transmitter 114, expand with corresponding short PN sequence.
Aforesaid hardware is to be used to provide one of many embodiment that a plurality of sectors are covered by single base station.June 27 nineteen ninety-five submit to be entitled as " dynamic sectionization in the spread spectrum communication system " 08/495, disclosed the another kind of method and apparatus of adaptive sectorization emission in 382 U.S. Patent applications, this patent has transferred assignee of the present invention, and is at this that it is incorporated by reference.In above-mentioned PA446 U.S. Patent application, another has been described to specific region method for transmitting and device.Other hardware architecture also can be designed to carry out function described here.These different architectures within the scope of the present invention.
Fig. 4 illustrates the block diagram of the demodulator of example in the remote station 6.Forward link signals is received and offers receiver 134 by antenna 132, and it is handled signal in the above described manner.Digitlization I and Q data are offered demodulator 136.In demodulator 136, data offer at least one correlator 310.Each correlator 310 different multi-path components are to received signal handled.In correlator 310, data offer short PN despreader 320, and it goes expansion with short PN sequence to I and Q data, go I and the Q data expanded with acquisition.It is by the inverse process of lacking the expansion that the PN expander carries out modulator and transmitter 114 in that short PN goes to expand.
Go to expand the I data and offer multiplier 322a and pilot correlator 326a, offer multiplier 322b and pilot correlator 326b and go to expand the Q data.Multiplier 322a and 322b multiply each other I and Q data respectively with the walsh sequence of distributing to correlator 310 (Wx).I and Q data from multiplier 322a and 322b offer accumulator (ACC) 324a and 324b respectively.In the embodiment of example, the data accumulation on 324 pairs 64 chip-spaced of accumulator (length of walsh sequence).From accumulator 324 go cover I and the Q data offer carrier dot product circuit 328.Pilot correlator 326a and 326b go to cover and carry out filtering to going to cover signal to I and Q data with the pilot tone walsh sequence (PWy) of distributing to correlator 310.Filtered pilot tone is offered carrier dot product circuit 328, and it calculates the dot product of two vectors (pilot tone and data) in mode known in the art.Described an exemplary embodiment of carrier dot product circuit 328 in being entitled as No. 5506865 United States Patent (USP) of " pilot frequency carrier wave carrier dot product circuit " in detail, this patent transfers assignee of the present invention, is hereby incorporated by reference.Carrier dot product circuit 328 will be mapped on the vector corresponding to the filtering pilot tone corresponding to the vector that goes cover data, and the amplitude of two vectors is multiplied each other, and the scalar output of signed is offered combiner 330.Data after combiner 330 will merge and will merge from the output that is assigned with the correlator 310 that carries out demodulation to received signal send long PN despreader 332 to.The long PN sequence of long PN despreader 332 usefulness is gone expansion and demodulating data is offered decoder 138 data.
Can calculate the pilot signal strength of certain relevant device 310 according to the filtering pilot tone of pilot correlator 326a and 326b.In addition, can carry out filtering, so that more reliable measurement result to be provided to pilot signal strength measurements.The U.S. Patent application of submitting on September 27th, 1,996 08/722 that is entitled as " measure link method for quality and device in the spread spectrum communication system ", the method and apparatus that carries out pilot signal measurement has been described in 763, this patent transfers assignee of the present invention, is hereby incorporated by reference.
In many communication systems, adopt transponder to improve the area of coverage and increase capacity.The signal of transponder reception sources device amplifies signal, with signal forwarding or relay to the destination device.Usually, transponder provides the two-way forwarding or the relay of forward and reverse link signal between the communicator.Typically, transponder provides Signal Regulation (for example, amplification, filtering and may also have frequency inverted), but signal processing or control are not provided.
Fig. 5 A and 5B illustrate the block diagram of the transponder of example.In Fig. 5 A, transponder 8a communicates with the base station by land or satellite link 410.Link 410 can be the land or microwave link from source base station, perhaps from the satellite link of communication satellite (for example GLOBALSTAR communication satellite).Forward link signals from the base station is received and offers duplexer 414 by donor antenna 412.Duplexer 414 sends forward link signals to amplifier (AMP) 416, and the latter amplifies signal.Although not shown in Fig. 5 A for the sake of simplicity, also can provide filtering and/or frequency inverted.Signal after the amplification sends to by duplexer 418 and is transmitted to remote station by server antenna 420.Service antenna 420 also receives the reverse link signal from remote station.Reverse link signal transmits by duplexer 420 and offers amplifier (AMP) 422, and the latter amplifies signal.Have again,, also can provide filtering and/or frequency inverted although not shown in Fig. 5 A for the sake of simplicity.Signal after the amplification transmits by duplexer 414 and is transmitted to the base station from antenna 412.
Transponder 8b shown in Fig. 5 B works in the mode that is similar to the transponder 8a shown in Fig. 5 A.Yet transponder 8b is by transmission line link 424 and base-station interface, and the transmission line interface can comprise optical fiber link, coaxial cable link or other link.
Microzonation is divided into a plurality of sectors many benefits are provided in cdma communication system.At first, the traffic channel (for example walsh code) owing to reusing between each sector can increase capacity.Secondly, can also improve reliability by the soft handover that uses two or more sectors.
In the cdma communication system of the example that above-mentioned U.S. Patent application 08/495,382 is disclosed, base station configuration can be become provide communication by single sector or a plurality of sector.The area of coverage of base station (or sub-district) can be divided into a plurality of sectors.Communicating by letter between remote station and the base station can take place by one or more sectors.Coordinated this point by a public base station except the communication of each sector by the sub-district, each sector has the attribute (for example, each sector has its own traffic channel group and the pilot signal of oneself) of sub-district.For the IS-95 system, each sector is relevant with the different skews of short PN extended code.Therefore, by measuring short PN skew, can determine the identity of this sector by particular sector pilot transmitted signal.
In the embodiment of example, base station configuration becomes to two or more sectors provides covering.One or more sectors can be relevant with the area of coverage around the base station.Remaining sector can be relevant with the transponder on placing cell boarder.For example, microzonation can be divided into two sectors.Can make base station work then, give to be positioned at three, two relevant sectors of wherein sub-district with the base station and a sector of being correlated with transponder provides covering.
First exemplary plot of the covering that is provided by the base station of two communication systems and transponder is provided Fig. 6 A.In Fig. 6 A, make base station 4 work, the covering to two sectors is provided.A sector is relevant with sub-district 22.Second sector is relevant with the transponder that the area of coverage 26 is provided.In the embodiment of example, the two all works sub-district 22 and the area of coverage 26 under same frequency and overlapping, so that the remote station that moves along road 30 can soft handover when being positioned at shadow region 39.Base station 4 and transponder 8 are parts of first communication system.
In the exemplary plot shown in Fig. 6 A, provide by the second communication system with communicating by letter in 22 adjacent areas of sub-district.This second communication system can be another cdma system of working on different frequency, or the system of the another kind of communication technology, as AMPS.The base station 14 of second system provides the covering to sub-district 24.With first system similarity, base station 14 also can be with many sectors pattern work, provides covering to the adjacency area of coverage 28 by transponder 18.Notice that in this example, the area of coverage 26 is in sub-district 24.
Second exemplary plot of the area of coverage that is provided by base station and transponder is provided Fig. 6 B.In Fig. 6 B, the area of coverage 26 is overlapping with sub-district 24, but not exclusively is included in the sub-district 24 (similar to the situation of Fig. 6 A).The area of coverage 26 can be used to connect the area of coverage between first and second system.Not shown transponder 18 among Fig. 6 B for the sake of simplicity.
The 3rd exemplary plot of the covering that is provided by base station and transponder is provided Fig. 6 C.In Fig. 6 C, the area of coverage 26 is overlapping with sub-district 24, but coordination in sub-district 24 not.In addition, sub-district 22 and 24 is adjacency not, so to the middle handover of transponder 8, the handover of base station 4 to base station 14 is not impossible.Also have, for the sake of simplicity not shown transponder 18 among Fig. 6 C.
In the embodiment of example, first system grasps the area of coverage 26 and sub-district 22 and 24 overlapping knowledge in advance.First system also grasps the knowledge of base station 14 by the control of second system in advance.In the embodiment of example, first system is connected to second system, can begin from the handover of the remote station of first system of system to the second.
In the present invention, when remote station moves to second system from first system, vice versa, can adopt transponder to begin the handover of two remote station between the system.With reference to figure 6A, suppose remote station along road 30 from moving left to the right side.Beginning, remote station is positioned at sub-district 22, communicates with base station 4.When remote station was come in the shadow region 30, remote station also received the pilot signal from transponder 8.Remote station is carried out demodulation to the pilot signal from transponder 8, determines the identity of new pilot tone, and to base station 4 these pilot signal strengths of report and identity (for example, the PN of pilot signal skew or walsh code.Base station 4 compares the pilot signal strength of report with the increase threshold value of being scheduled to, if pilot signal strength surpasses the predetermined threshold value that increases, can be increased to the existing with in organizing of remote station to transponder 8.Now comprise the tabulation of base station (and/or transponder), set up existing communication by it with group.Then, base station 4 can be according to above-mentioned United States Patent (USP) 5,101,501 and 5,267, and the method described in 261 is carried out the soft handover of remote station.In the present invention, the handover of communicating by letter between long-range and base station 4 to the base station 14 can be implemented by one of at least four embodiment.
In first embodiment, first system just begins the handover of communicating by letter between remote station and base station 4 to the base station 14 behind beginning and the soft handover of transponder 8.With reference to figure 6A, the area of coverage 26 is common position in sub-district 24.In the systems organization stage or by suitably locating base station and transponder can guarantee this.In this case, first system is supposed reasonably that the remote station that is in usefulness transponder 8 soft handovers is also in the area of coverage of base station 14.This information can be used for beginning to the base station 14 handover when remote station is in the area of coverage of transponder 8.
In a second embodiment, in case after measuring enough pilot signal strengths of transponder 8, first system just begins the handover of communicating by letter between remote station and base station 4 to the base station 14.In this embodiment, when the report pilot signal strength of transponder 8 (measuring) when being higher than predetermined increase threshold value by remote station, as mentioned above, the handover of base station 4 beginnings and transponder 8.Yet, because the area of coverage 26 can not be total to the position in sub-district 22, shown in Fig. 6 B-6C, when the handover of beginning and transponder 8, first system is not the handover that begins from the base station 4 14 the communications to the base station immediately, can cause the disconnection of communicating by letter because so do.But remote station continues to measure the pilot signal strength of transponder 8, and gives base station 4 with measurement report.Base station 4 can compare the pilot measurement result with predetermined handoff threshold, and the latter is set at and is higher than predetermined increase threshold value.When the report pilot signal strength of transponder 8 was higher than predetermined handoff threshold, first system began the handover of communicating by letter between remote station and base station 4 to the base station 14.For the area of coverage shown in Fig. 6 A-6B, the second embodiment work is fine.
Predetermined handoff threshold can according to the measurement result of pilot signal strength on the whole area of coverage 26 pilot signal strength measurements of road 30 (for example along) set or according to expectation the result of calculation of pilot signal strength (for example, utilize Effective Radiated Power (ERP) and r
4Propagate law, r is the distance from transponder 8 here).As an example, predetermined handoff threshold can be set at than the predetermined high 5dB of threshold value that increases, can adopt other value certainly based on system design, this is within the scope of the present invention
In the 3rd embodiment, when base station 4 when remote station existing throws off with group, first system begins the handover of communicating by letter between remote station and base station 4 to base station 14.In the embodiment of example, remote station is periodically measured its existing giving with the pilot signal of base station in the group and transponder and with these measurement report and is now used the base station.Now pilot measurement result and predetermined down threshold value are compared with the base station.If the pilot measurement result is lower than the predetermined down threshold value, so, corresponding to existing with removing the group from remote station of the base station of this pilot signal, as described in above-mentioned United States Patent (USP) 5101510 and 5267261.In this embodiment, if be lower than the predetermined down threshold value from the pilot signal of base station 4, so, first system can suppose that remote station has been come in the sub-district 24.Therefore, when base station 4 when remote station existing throws off with group, first system begins the handover of communicating by letter of remote station and base station 4 to base station 14.For by the area of coverage shown in Fig. 6 A-6B, the 3rd embodiment also works fine.
In the 4th embodiment, when transponder 8 when remote station existing throws off with group, first system begins the handover of communicating by letter between remote station and base station 4 to base station 14.In this embodiment, communicating by letter between remote station and the transponder 8 kept the long as far as possible time.Yet, if when the pilot signal strength of transponder 8 is lower than the predetermined down threshold value, first system postulation, remote station is in the area of coverage of second system.Therefore, when transponder 8 when remote station existing throws off with group, the handover that first system communicates by letter between beginning remote station and base station 4 to base station 14.For by the area of coverage shown in Fig. 6 A, the 4th embodiment also works fine.
In the 5th embodiment, when base station 4 and transponder 8 when remote station existing throws off with group, first system begins the handover of communicating by letter between remote station and base station 4 to base station 14.In this embodiment, communicating by letter between remote station and base station 4 and/or the transponder 8 kept the long as far as possible time.Yet when if the pilot signal strength of base station 4 and transponder 8 is lower than the predetermined down threshold value, first system postulation, remote station have been gone to outside the area of coverage of first system.Therefore, when base station 4 and transponder 8 when remote station existing throws off with group, first system begins the handover of communicating by letter between remote station and base station 4 to base station 14.For by the area of coverage shown in Fig. 6 A-6C, the 5th embodiment also works fine.
Aforesaid second, third and the 5th embodiment provide and make ' table tennis ' of handover between two systems reduce to minimum hypothesis.In a second embodiment, this hypothesis is provided by the predetermined difference that increases between threshold value and the predetermined handoff threshold.In the 3rd and the 5th embodiment, this hypothesis is provided by the predetermined increase threshold value of base station and transponder and the difference between the predetermined falling-threshold value.
Although being the existing communication period between remote station and base station, above-mentioned handover takes place,, this handover of second system also can take place when remote station is idle.When remote station during, can measure the pilot signal of transponder 8 along road 30 walking.In first embodiment of idle pulley handover, remote station reports to first system with the pilot measurement result.First system can utilize the handover of above-mentioned arbitrary embodiment execution to second system.Handover can be realized by the interface message of launching between base station and the remote station.In second embodiment of idle pulley handover, the remote station monitoring Global is sent message elsewhere, and the latter plays on the area of coverage of transponder.Message is sent in the whole world elsewhere can command the new frequency of remote station to one or another system (for example AMP system).In the 3rd embodiment of idle pulley handover, remote station monitoring expansion neighborhood list message, the latter plays on the area of coverage of transponder.Expansion neighborhood list message can represent to have only the neighborhood of this remote station to be in another frequency and another system.Expansion neighborhood list message is described in the CDMA standard that is entitled as " personal station of ANSIJ-STD-008:1.8 to 2.0GHz code division multiple access (CDMA) PCS Personal Communications System-base station compatible requires ".It is contemplated that other embodiment that carries out handover with idle pulley, this within the scope of the present invention.
Although a transponder only is shown for the first system diagram 6A-6C,, can adopt a plurality of transponders.Can adopt transponder to expand the area of coverage that can carry out handover.In addition, can adopt transponder to link the non-adjacent area of coverage (for example transponder that connects with series system) of two systems.The knowledge of the particular transponder that grasp in advance of the system of beginning handover and adjacent system are overlapping.System adopts the identity report and/or the pilot signal strength of this information and this transponder to begin handover.
The present invention can also utilize pilot beacon to implement, and the latter only launches pilot signal (not having traffic channel).Can adopt pilot beacon to combine with above-mentioned first three embodiment.Pilot beacon provides necessary pilot tone identification and signal strength measurement simultaneously to the least interference of area of coverage generation on every side.Usually, can adopt from any signal of transponder or pilot beacon emission and help handover procedure.
Provide above description to make any professional and technical personnel of this area can make or use the present invention to preferred embodiment.For one of skill in the art, be obvious to the various improvement of these embodiment, defined General Principle here can be applied to other embodiment, and need not to utilize invention ability.Therefore, the embodiment shown in the present invention does not wish to be limited to here, but meet and the corresponding to wide region of the principle that disclosed here and novel feature.
Claims (22)
1. a kind of method in the communication system is characterized in that said method comprising the steps of:
In the signal strength signal intensity of remote station measurement from the signal of transponder;
The signal strength measurement of transponder is compared with the increase threshold value of being scheduled to;
Begin the handover of remote station from first base station to second base station in response to the result of comparison step;
Wherein the signal from transponder is a pilot signal;
Wherein discerned by the skew of short PN sequence spreading from the pilot signal of transponder, from the skew of the short PN sequence spreading of first base station of at least one pilot signal of being used as first base station, the skew of this weak point PN sequence spreading is unique;
Wherein from transponder emission pilot signal, so that the area of coverage of the equitant transponder of the area of coverage that is provided with first base station to be provided at least, and the area of coverage that the equitant transponder of the area of coverage that is provided with second base station is provided at least.
2. the method for claim 1 is characterized in that: from the pilot signal of transponder by Walsh cover discern, in the Walsh of the pilot signal of first base station covered, it was unique that this Walsh covers.
3. the method for claim 1, it is characterized in that: the two works first base station and transponder on a shared frequency.
4. the method for claim 1 is characterized in that: work being different from the frequency of transponder frequency in second base station.
5. the method for claim 1, it is characterized in that: transponder is by the terrestrial link and first base station communication.
6. the method for claim 1 is characterized in that: transponder is by the transmission line link and first base station communication.
7. the method for claim 1 is characterized in that: make the work of first base station so that the covering to a plurality of sectors to be provided, a sector is associated with transponder.
8. the method for claim 1 is characterized in that: if the signal strength measurement of transponder surpasses predetermined increase threshold value, begin to carry out the handover step.
9. the method for claim 1 is characterized in that further comprising step:
The signal strength measurement of transponder is compared with the handoff threshold of being scheduled to; And
If the signal strength measurement of transponder surpasses predetermined handoff threshold, begin to carry out the handover step.
10. method as claimed in claim 9 is characterized in that: predetermined handoff threshold is set at and is higher than predetermined increase threshold value.
11. method as claimed in claim 9 is characterized in that: predetermined handoff threshold is to set according to the signal strength measurement on the whole area of coverage of transponder.
12. method as claimed in claim 9 is characterized in that: predetermined handoff threshold is to set according to the signal strength signal intensity of calculating on the whole area of coverage of transponder.
13. the method for claim 1 is characterized in that further comprising step:
In the signal strength signal intensity of remote station measurement from first signal of base station;
The first signal of base station intensity measurements and predetermined down threshold value are compared; And
If the first signal of base station intensity measurements is lower than the predetermined down threshold value, begin to carry out the handover step.
14. method as claimed in claim 13 is characterized in that:, begin to carry out the handover step if the signal strength measurement of transponder and the first signal of base station intensity measurements are lower than the predetermined down threshold value.
15. a system that carries out the handover of remote station from first base station to second base station is characterized in that described system comprises:
What be connected with first base station provides the transponder of signal to remote station;
First system controller that is connected with first base station;
Second system controller that is connected with first system controller with second base station;
Wherein begin handover based on measurement result by first system controller from the signal of transponder in remote station;
Wherein the signal from transponder is a pilot signal;
Wherein discerned by the skew of short PN sequence spreading from the pilot signal of transponder, from the skew of the short PN sequence spreading of first base station of at least one pilot signal of being used as first base station, this weak point PN sequence spreading is unique;
Wherein from transponder emission pilot signal, so that the area of coverage of the equitant transponder of the area of coverage that provided with first base station to be provided at least, and the area of coverage that the equitant transponder of the area of coverage that is provided with second base station is provided at least.
16. system as claimed in claim 15 is characterized in that: the two works first base station and transponder on a shared frequency.
17. system as claimed in claim 15 is characterized in that: work being different from the frequency of transponder frequency in second base station.
18. system as claimed in claim 15 is characterized in that: transponder is connected to first base station by terrestrial link.
19. system as claimed in claim 15 is characterized in that: transponder is connected to first base station by the transmission line link.
20. system as claimed in claim 15 is characterized in that: if the signal strength measurement of transponder surpasses predetermined increase threshold value, the beginning handover.
21. system as claimed in claim 15 is characterized in that: if the first signal of base station intensity measurements is lower than the predetermined down threshold value, the beginning handover.
22. system as claimed in claim 15 is characterized in that: if the signal strength measurement of the first signal of base station intensity measurements and transponder is lower than the predetermined down threshold value, the beginning handover.
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| US5218715A (en) * | 1991-01-15 | 1993-06-08 | Orion Industries, Inc. | Multi-donor booster operation and system |
| US5697055A (en) * | 1994-10-16 | 1997-12-09 | Qualcomm Incorporated | Method and apparatus for handoff between different cellular communications systems |
| US6108364A (en) * | 1995-08-31 | 2000-08-22 | Qualcomm Incorporated | Time division duplex repeater for use in a CDMA system |
-
1998
- 1998-11-25 CN CNB988115603A patent/CN100456872C/en not_active Expired - Fee Related
- 1998-11-25 EP EP98960489A patent/EP1034683A1/en not_active Withdrawn
- 1998-11-25 AU AU16073/99A patent/AU759370B2/en not_active Ceased
- 1998-11-25 KR KR1020007005681A patent/KR20010032440A/en not_active Application Discontinuation
- 1998-11-25 JP JP2000522757A patent/JP2001524793A/en active Pending
- 1998-11-25 WO PCT/US1998/025219 patent/WO1999027747A1/en not_active Application Discontinuation
- 1998-11-25 IL IL13627398A patent/IL136273A0/en unknown
- 1998-11-25 CA CA002311623A patent/CA2311623A1/en not_active Abandoned
- 1998-11-25 BR BR9815435-4A patent/BR9815435A/en not_active Application Discontinuation
- 1998-11-25 RU RU2000116264/09A patent/RU2000116264A/en not_active Application Discontinuation
- 1998-11-25 ID IDW20001012A patent/ID27894A/en unknown
-
2000
- 2000-05-19 FI FI20001211A patent/FI20001211A/en not_active Application Discontinuation
- 2000-05-25 NO NO20002671A patent/NO327951B1/en not_active IP Right Cessation
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996031078A1 (en) * | 1995-03-30 | 1996-10-03 | Qualcomm Incorporated | Method and apparatus for mobile unit assisted cdma to alternative system hard handoff |
| WO1997031487A2 (en) * | 1996-02-23 | 1997-08-28 | Nokia Telecommunications Oy | Handover in a mobile communication system |
Also Published As
| Publication number | Publication date |
|---|---|
| KR20010032440A (en) | 2001-04-25 |
| EP1034683A1 (en) | 2000-09-13 |
| ID27894A (en) | 2001-05-03 |
| WO1999027747A1 (en) | 1999-06-03 |
| CN1302518A (en) | 2001-07-04 |
| NO20002671D0 (en) | 2000-05-25 |
| BR9815435A (en) | 2001-09-11 |
| NO20002671L (en) | 2000-07-18 |
| RU2000116264A (en) | 2002-05-27 |
| IL136273A0 (en) | 2001-05-20 |
| CA2311623A1 (en) | 1999-06-03 |
| NO327951B1 (en) | 2009-10-26 |
| AU1607399A (en) | 1999-06-15 |
| AU759370B2 (en) | 2003-04-10 |
| JP2001524793A (en) | 2001-12-04 |
| FI20001211A (en) | 2000-07-18 |
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