CN1744746A - Method for reducing search time of trapping TD-SCDMA carrier - Google Patents

Abstract

Dynamic channel allocation (DCA) is adopted in the indention. When new call arrives to system, as long as there is a one vacant channel, mobile control center allocates the channel to the call. After the call is ended, the channel is returned back to central storage area. The invention solves technique issue for quick accessing channel and raises quality of service of mobile communication. Features are: avoiding interference, minimized distance of reusing channel, using wireless resources in high efficiency and increasing system capacity.

Description

The TD-SCDMA carrier wave method of used search time is caught in a kind of minimizing

Technical field:

The present invention relates to mobile communcations system carrier signal search technique, the TD-SCDMA carrier wave method of used search time is caught in particularly a kind of minimizing.

Background technology:

The TD-SCDMA system has adopted four unique step search procedures: behind the mobile phone power-on, at first measure the carrier power in the TD-SCDMA band system band, and the power that records is sorted by power, and begin search from the strongest carrier wave.Initial cell is selected or search utilizes descending pilot frequency time slot (DwPTS) and broadcast channel (BCH) to carry out.In search of initial zone, user side (UE) searches a sub-district, and it is synchronous to set up DwPTS, obtains scrambler, and the control multi-frame is synchronous, reads BCH information then.UE reads searched (entirely) broadcast message to one or more BCH of sub-district, can determine to get back to above a few step or finish search of initial zone according to the UE as a result that reads.

Uplink synchronous is the important technology characteristics of TD-SCDMA system.The effect of synchro system will realize that exactly the local PN sign indicating number that produces is synchronous, promptly identical on the frequency with the PN sign indicating number in the signal that receives, and is consistent on the phase place.Synchronizing process comprises two stages in general:

(1) therefore receiver, needs an arrest process at the beginning and do not know whether the other side has sent signal, i.e. search and catch useful signal in certain frequency and time range.This stage is also referred to as initially just will be included signal and local signal that the other side sends in the hold-in range in the difference of phase place synchronously or synchronously thick, promptly when one of PN sign indicating number in the sheet.

(2), promptly continue to keep not losing synchronously synchronously because of ectocine in case after finishing this stage, then enter tracing process.That is to say that no matter because the frequency and the phase place at which kind of factor two ends are offset, synchro system can be adjusted, and makes receiving and transmitting signal still keep synchronous.

See also Fig. 1, the signal that receives carries out related operation with local PN sign indicating number in multiplier behind broadband filter.Track down and arrest device this moment, adjusts voltage-controlled Zhong Yuan, and the local nervuration of adjusting the generation of PN code generator is listed as pseudo-repetition rate and phase place, to track down and arrest useful signal.In case after capturing useful signal, then start the code tracking device, adjust voltage-controlled Zhong Yuan by it, local PN code generator and extraneous signal are kept synchronously.If owing to the seed collecting reason causes step-out, then restart new one and take turns and track down and arrest and tracing process.The effect of tracking down and arresting makes local PN coded signal synchronous with it in frequency and the useful PN coded signal of uncertain scope IT of time (phase place) exactly.Because despreading process was all carried out before carrier synchronization usually, carrier phase here is unknown.

Most of arrest methods are all utilized incoherent detection.The common feature of all arrest methods is with local signal and the signal multiplication of receiving (being related operation), obtains measuring of the two similitude, and compares with a threshold value, whether captures useful signal to judge it.Capture useful signal if confirm as, then begin tracing process, system is kept synchronously.Otherwise begin again to continue to track down and arrest.Usually adopt matched filter to track down and arrest method, this method has the function of identification code sequence, can utilize it to catch fast.

What adopt when switching in CDMA is traditional soft handover and direct-cut operation.From measuring process, the both carries out under the situation of not knowing the accurate position of UE, therefore need measure all adjacent sub-districts, carries out the selection of switch decision and Target cell according to given handoff algorithms and criterion then.Shortcoming is, the handover measurement time that UE needs is many, and the surveying work amount is also bigger, and handover delay is long.In addition, soft handover need have a plurality of base stations to provide service for a travelling carriage simultaneously, and the channel resource that takies is more, and the signaling complexity causes system loading to increase the weight of, and increases dl interference; Direct-cut operation is set up with target BS and is got in touch because be to disconnect earlier and being connected of former base station, and therefore can cause switching cutting off rate height, shortcoming that handover success rate is lower.So in TD-SCDMA, propose this notion of baton handover.

Air interface between portable terminal and the base station is a communication channel, and is subjected on a large scale and the influence of factor among a small circle.What is called effect on a large scale is owing to transmit by the caused decay of atmosphere.As:

1. path loss.

2. multipath loss.Reflected wave arrives reception antenna by different paths, thereby experiences different propagation delays and path loss.The multipath fading effect can make and be slackened when transmitting by channel.

In cdma system,, generally adopt to have the RAKE receiver of multipath diversity at receiving terminal in order to reduce the adverse effect of multipath fading.When multipath is delayed the duration that τ surpasses a chip, multipath signal is actually incoherent mutually and maybe can separates.RAKE receiver is made up of the tapped delay line model and the matched filter banks of frequency selective channel.Tapped delay line model with the independent tap weight value of statistics provides L duplicate of identical transmission signal in receiver, RAKE receiver utilizes a plurality of matched filter banks to detect L the strongest in the multipath signal branch path signal respectively, output weighting to each correlator merges then, so that the input that is better than the single channel correlator to be provided, carry out the demodulation judgement at last on this basis.The essence of tradition RAKE receiver is that rake receives its principle such as Fig. 2.

Have multiple mode that RAKE receiver is merged, the intersymbol interference after the merging can equivalence be an additive white Gaussian noise, and does not need equalizer after the RAKE reception.Wherein each dataway operation is the key that Data Detection is handled.It isolates one to strong multipath component, and bit synchronous is provided, and detects pilot data and indicates rotation, estimates the amplitude and the phase characteristic of wireless channel, and despreading.What wherein performance was best is that high specific merges.If adopt high specific to merge, at this moment the output signal-to-noise ratio maximum $\mathrm{SNR}=\frac{G}{\mathrm{\σ}^2}\underset{L=0}{\overset{L-1}{\mathrm{\Σ}}}\left|b\right|,$ G is a spreading gain, and σ ^2 is a noise power.Therefore, adopt high specific RAKE to merge the impulse response that to estimate multipath channel at receiving terminal, and improve the performance of RAKE receiver, just must collect the energy of multipath at receiving terminal as much as possible, do the complexity and the power consumption that can increase system hardware like this, for portable terminal is unpractical, and this is its major defect.

Reduce search time also with the quick selection of channel with have access to direct relation, general channel allocation generally comprises calls out access control, channel allocation, three steps of channel adjustment.In general, the performance evaluation index of channel allocation mainly contains following five kinds: the signaling traffic load in probability of call blocking, communication disruption probability (comprising quality of service descends and causes in the communication process communication termination probability and handover probability of failure), channel allocation time delay, channel utilization, the scheme implementation.When the selective channel allocative decision, overall goal is the search time that obtains higher channel utilization, lacks as far as possible.

Fixed channel assignment (FCA) extensively adopts in 1G and 2G communication system, but along with mobile communication system service is more and more diversified, different rates and service request business make that the change of system loading on time and space is very big, use FCA mode allocation of channel resources may not only can not improve channel efficiency, may also can cause the local failure of system.

Summary of the invention:

The purpose of this invention is to provide a kind of minimizing and catch the TD-SCDMA carrier wave method of used search time, mainly solve the technical problem that channel inserts problem fast, improve the mobile telecommunication service quality.

For solving the problems of the technologies described above, the present invention is achieved in that

The TD-SCDMA carrier wave method of used search time is caught in a kind of minimizing, and channel allocation is used dynamic channel allocation (DCA), when having new calling to arrive in the system, is idle as long as a channel is arranged, and movements control center just gives it with this channel allocation; Behind end of calling, this channel is got back to again in the central store district.

This channel adopts the logic ordering of according to priority dividing.

Should be finished by radio network controller based on the admittance control of priority, radio network controller (RNC) satisfies the newly-increased call list of admitting control to require based on signal interference ratio according to all that are provided by the base station, utilizes the priority parameters of its storage to adjudicate.

The complicated RAKE merging of portable terminal is put into base station (NodeB), carries out the RAKE multipath at transmitting terminal and merge.

Call out and adopt baton handover in the district more.

Smart antenna is used in this base station.

Compared with prior art, the present invention based on the DCA algorithm has following technique effect:

(1) can avoid interference preferably, make the channel reuse distance minimization, thereby utilize finite wireless resources expeditiously, improve power system capacity.

(2) can adapt to the asymmetric data service of uplink and downlink and the multimedia service of needs, especially its two-forty of 3G business.

(3) channel is not to give certain sub-district regularly, distributes but be concentrated in together, as long as enough link-qualities can be provided, idle channel can be distributed to the calling of demand in any sub-district.

Therefore DCA have the band efficiency height, can self-adapting network in load and interference variation, need not to carry out in advance advantage such as channel plan, insert and search time of system during handover thereby can shorten to a certain extent to call out.Adopt channel ordering according to priority in the selection of channel, more can improve channel utilization, shortcut calculation shortens the channel allocation time.

Baton handover combines the characteristics of the high channel utilance of the high success rate of soft handover and direct-cut operation, and this is the outstanding advantage of this technology just.Soft handover and direct-cut operation all are to carry out under the situation of not knowing the accurate position of UE, therefore need measure all adjacent sub-districts, carry out the selection of switch decision and Target cell according to given handoff algorithms and criterion then.And baton handover is because know the position that UE is definite, thus only need close UE one side a few sub-district consistent with the UE moving direction be measured, the required handover measurement time decreased of UE like this, the minimizing of surveying work amount, handover delay is also with regard to corresponding minimizing.In addition, owing to need the neighbor cell decreased number of monitoring, thereby the also corresponding signaling exchange that has reduced between UE, NodeB and the RNC, thereby shortened the UE Measuring Time.

Description of drawings:

Fig. 1 is that synchro system is tracked down and arrested and following principle figure in the prior art.

Fig. 2 is traditional RAKE receiver schematic diagram.

Fig. 3 is the flow chart of the inventive method.

Fig. 4 is a baton handover techniqueflow chart in the inventive method.

Fig. 5 is the schematic diagram of pre-RAKE technology in the inventive method.

Embodiment:

The inventive method is selected quick dynamic channel allocation schemes, makes no matter be that the acquisition pilot signal shortens search time as far as possible fast when mobile phone power-on or handover; By channel quality criteria and portfolio parameter channel resource is optimized configuration.

The core of DCA is channel search, distribution or heavily distributes fast.After new calling took place, system at first inserted and adjudicates whether ratifying this callings according to specific criterion, if this calling gets permission to insert, system will take situation according to existing channel resource and search for and distribute required channel for this Adds User.The method that sorts by priority is adopted in distribution to channel, can more effectively utilize channel, calls out access back system channel is adjusted.Processing is distinguished when calling out more, adopts baton handover, utilizes technology such as smart antenna and uplink synchronous, and when UE entered the switch area, RNC notified this base station to carry out switching and prepares, thereby reaches the purpose of quick, reliable and efficient switching.In the demodulation part, adopt pre-RAKE reception technique at last, on original RAKE receiver basis, improve, carry out the RAKE multipath at transmitting terminal and merge, receive with a simple adaptation, can reduce the complexity of portable terminal at receiving terminal.

The concrete enforcement of the inventive method is as follows:

1) channel is sorted by priority, fast DCA algorithm (seeing also Fig. 3):

In DCA, channel and sub-district do not have fixed relationship, and all channels all are placed in the central store district.When having new calling to arrive in the system, be idle as long as a channel is arranged, movements control center just gives it with this channel allocation.Behind end of calling, this channel is got back to again in the central store district, and channel is a dynamic assignment.As long as satisfy certain interference-limited condition, channel just can use in any one sub-district.The main thought of DCA is exactly to estimate the cost function of each alternative channel, and the channel allocation of the cost minimum of interference-limited condition is satisfied in selection then.

When selective channel, according to specific criterion, available channel is arranged, carry out the distribution of channel according to putting in order.Its ordering both can be the natural ordering according to the time slot among the TDMA, the ordering of the logic that also can according to priority divide.Here adopt method according to priority, first idle channel that promptly will search in channel search procedure is distributed to the user of proposition demand.Admittance control based on priority is finished by radio network controller (RNC), its objective is in order to improve resource utilization ratio as far as possible, reduces adjacent cells and disturbs, and shortens search time.RNC satisfies the newly-increased call list of admitting control to require based on signal interference ratio (SIR) according to all that are provided by base station (NodeB), utilizes the priority parameters of its storage to adjudicate.

When system adopted a plurality of carrier frequency, carrier frequency adopted fixed channel assignment, and the channel on each carrier frequency adopts dynamic channel allocation, and the different carrier frequency channels between different districts can be used mutually.DCA comprises channel allocation and two processes of channel adjustment fast, and the efficient of its algorithm and complexity depend primarily on multi-slot and many code channels control ability of portable terminal.

2) call out and adopt baton handover (seeing also Fig. 4) in the district more:

Because smart antenna is adopted in the base station of TD-SCDMA, can estimate user's data source checking (DOA) information, system is a uplink synchronous in addition, network can be determined the time migration of subscriber signal transmission, by the two-way time of signal, know the distance of UE, thereby obtain the accurate position of UE to NodeB.RNC according to a few neighbor cell of definite choice of location UE moving direction one side of UE as candidate cell, RNC notice UE detects and measures them, give RNC measurement report, whether made by RNC and to switch and with the judgement of which neighbor cell as Target cell, system sends instruction to UE and begins to switch then.Because the candidate cell decreased number, make the handover measurement time decreased that UE is required, handover delay also correspondingly reduces.In handoff procedure, disconnect former base station and set up communication link with target BS and almost carry out simultaneously, so the handover success rate height, cutting off rate is low.UE is with when current service cell keeps Traffic Channel to be connected, network is by the pertinent system information of the broadcast channel or the forward access channel notice UE Target cell of current service cell, scrambler, transmission time and vertical shift etc. as synchronous information, Target cell use, shortened the process of uplink synchronous, this means that also switching the needed time of implementation shortens.

3) pre-RAKE reception technique (seeing also Fig. 5):

In the TD-SCDMA system, the sign indicating number of expression sub-district is called descending synchronous code (SYNC-DL) sequence, launches at descending pilot frequency time slot (DwPTS).SYNC-DL is used for distinguishing neighbor cell, and associated process is determining of down-going synchronous, sign indicating number identification and Primary Common Control Physical Channel (PCCPCH).The base station will send DwPTS in the omnirange of sub-district or in the fixed beam direction, and it has played the effect of pilot tone and down-going synchronous simultaneously.DwPTS is that the SYNC-DL of 64chip and length are that the protection time slot (GP) of 32chip is formed by length.It is 64 basic SYNC-DL sign indicating number that whole system has 32 group length, a base station of the only sign of SYNC-DL and a code character, and each code character comprises 4 specific scramblers, the corresponding specific basic midamble code of each scrambler.

Using independently DwPTS in the TD-SCDMA system, is exactly in order to solve the Cell searching problem of TDD system under honeycomb and mobile environment.When adjacent cell uses identical carrier frequency, when the user under the mobile status started shooting at a sub-district intersectional region, because the particular design of DwPTS, it was present in the independent time slot that does not have other signals to disturb, the terminal that can guarantee the user is caught down-bound pilot frequency signal fast, finishes cell search process.

First task of digital demodulator is exactly pilot capture.Portable terminal must at first carry out the cell selecting process, enters the mobile communications network of appointment by this process, just can communicate then.The signal that this process analysis procedure analysis wireless receiver is received comprises the interference and the noise of the wide spectrum that is added in the some CDMA Channel on the selected frequency.

Digital demodulator comprises searcher, RAKE receiver and other Digital Signal Processing functional modules.Searcher is synchronized to the inner PN generator of mobile radio station on the pilot channel that receives, and this process is called pilot capture.RAKE receiver is carried out coherent detection with time phase place reference to receiving data then.

To improve the performance of RAKE receiver at present RAKE receiver, just must collect the energy of multipath at receiving terminal as much as possible, do the complexity and the power consumption that can increase system hardware like this, for portable terminal is this unpractical unfavorable factor, the present invention proposes an imagination, be exactly that the RAKE of complexity is merged, the complicated RAKE of portable terminal is merged be put into the base station.The RAKE multipath merges handles the reverse product of time domain of equal value in fact and received signal and multipath channel impulse response, and this product can be transferred to transmitting terminal is that the place, base station carries out, as long as know the multipath channel parameter of down link.

Because time division duplex (TDD) pattern has the up-downgoing channel reciprocity, thereby the up channel parameter that can utilize the base station to estimate is carried out the RAKE multipath merging of transmitting terminal.After transmitting terminal carries out the merging of RAKE multipath, can form at receiving terminal can the friendly signal that receives, receiving terminal can receive with a simple adaptation, and do not sacrifice receptivity, greatly reduce the complexity of portable terminal like this, it is that the place, base station has been beforehand with once " RAKE reception " that its result seems at transmitting terminal, is called " the pre-reception " visually.

In the system of tdd mode, after the base station receives an ascending time slot, utilize specific channel estimation technique to obtain the multipath channel impulse response h (t) of this ascending time slot, when the base station sends next descending time slot, will be through the transmission signal s (t) of spread spectrum with the emission again after the convolution in advance of the time domain complex conjugate of the multipath channel impulse response h (t) that estimates, promptly do emission again behind the pre-RAKE earlier.

For complete orthogonal intersection, the performance of RAKE and pre-RAKE can both improve, and, the performance of pre-RAKE will be got well the performance with RAKE, but this performance difference is not fairly obvious, therefore, can utilize pre-RAKE technology to reduce the complexity and the cost of travelling carriage.

When using non-complete orthogonal code, the performance of pre-RAKE will be better than the performance of RAKE widely, because the latter has also increased interference in received signal.This is because RAKE receiver is to be merged by high specific simultaneously to required user and other users' received signal, so, to compare with pre-RAKE, RAKE receiver has caused bigger multiple access to disturb.

Therefore, in the cdma system of tdd mode, adopt pre-RAKE technology not only not have the performance of sacrificial system, and travelling carriage only need receive and solve judgement with single footpath receiver that an adaptation constitutes, reduce the complexity and the cost of travelling carriage widely, had important use to be worth.

4) smart antenna

Smart antenna is for omnidirectional antenna, and coverage will increase under same transmitting power, can improve resource utilization ratio, shorten switching time, reduce cutting off rate, it is higher that physical layer design is got efficient, and the minimizing Cell searching reaches the interference when inserting at random etc.

Being preferred embodiment of the present invention only in sum, is not to be used for limiting practical range of the present invention.Be that all equivalences of doing according to the content of the present patent application claim change and modification, all should be technology category of the present invention.

Claims (6)

1, the TD-SCDMA carrier wave method of used search time is caught in a kind of minimizing, it is characterized in that: channel allocation is used dynamic channel allocation, when having new calling to arrive in the system, be idle as long as a channel is arranged, movements control center just gives it with this channel allocation; Behind end of calling, this channel is got back to again in the central store district.

2, the TD-SCDMA carrier wave method of used search time is caught in minimizing according to claim 1, it is characterized in that: this channel adopts the logic ordering of according to priority dividing.

3, the TD-SCDMA carrier wave method of used search time is caught in minimizing according to claim 2, it is characterized in that: should finish by radio network controller based on the admittance control of priority, radio network controller satisfies the newly-increased call list of admitting control to require based on signal interference ratio according to all that are provided by the base station, utilizes the priority parameters of its storage to adjudicate.

4, catch the TD-SCDMA carrier wave method of used search time according to claim 1 or 2 or 3 described minimizings, it is characterized in that: the complicated RAKE merging of portable terminal is put into the base station, carries out the RAKE multipath at transmitting terminal and merge.

5, catch the TD-SCDMA carrier wave method of used search time according to claim 1 or 2 or 3 described minimizings, it is characterized in that: call out and adopt baton handover in the district more.

6, catch the TD-SCDMA carrier wave method of used search time according to claim 1 or 2 or 3 described minimizings, it is characterized in that: smart antenna is used in this base station.

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