A kind of method of obtaining control word based on up closed loop Synchronization Control
Technical field
The present invention relates to TD SDMA (TD_SCDMA, Time Division-Synchronous Code Division Multiple Access) synchronous control technique, be particularly related to the method for obtaining control word (CW, Control Word) in a kind of TD_SCDMA system based on up closed loop Synchronization Control (Uplink Close LoopSynchronization Control).
Background technology
The TD_SCDMA system is that China proposes, the third generation (3G) synchronous CDMA system that has independent intellectual property right, in system, used the new technology of many moving communicating fields, as smart antenna, joint-detection, uplink synchronous, low spreading rate, multi-slot, variable spread spectrum system, adaptive power adjustment etc.Because the TD_SCDMA system is (in follow-up, abbreviate system as) communication characteristic, the interference of operational environment, multipath transmisstion and Doppler effect, thereby, system is to there being the requirement of comparison strictness synchronously, the TD_SCDMA system comprises down-going synchronous and uplink synchronous synchronously, subscriber equipment (UE, User Equipment) and base station (BS, Base Station) the main footpath of down link all is synchronous between, in the present invention, the uplink synchronous that is primarily aimed at system is described, promptly require to arrive BS synchronously from the main footpath of the upward signal of the different UEs of different distance in the sub-district, like this, can reduce the interference between each UE upward signal in the sub-district, increase the coverage of sub-district, simplify the base station receiver structure and improve power system capacity.
Below system being set up synchronous process is described.
When system during at idle pulley, set up down-going synchronous between UE and the BS, at this moment, do not set up uplink synchronous, UE can not obtain with BS apart from relevant information; In the starting stage that UE and BS set up formal link, UE is by random access procedure, estimates distance with BS according to the intensity of the pilot signal that receives, thereby calculates the emission lead that sends signal to BS, and it is synchronous to set up up open loop, and promptly uplink synchronous is caught; Because in communication process, UE constantly moves, thereby causes the change in location of UE, and the time that the signal that causes UE to send arrives BS also changes, be that the upward signal that each UE sends can not arrive BS synchronously, system synchronization is changed.Thereby, need BS to carry out up closed loop Synchronization Control, be also referred to as uplink synchronization tracking, be BS by the measuring synchronously of the training sequence that detects upward signal that UE sends and upward signal is comprised, estimate the lead of the transmitting time of UE, thereby produce the synch command word, be sent to UE, be used to control the Timing Advance that UE sends upward signal, arrive BS at synchronization, improve systematic function with the upward signal of controlling each UE transmission.
Fig. 1 is for having the method flow schematic diagram that obtains control word based on up closed loop Synchronization Control now, and referring to Fig. 1, this flow process comprises:
Step 101, BS carries out channel estimating according to the training sequence that comprises in the upward signal that receives;
In this step, BS preestablishes the critical threshold value of channel estimating, estimates threshold value according to the noise power and predefined signal to noise ratio (SNR, Signal Noise Ratio) the threshold value calculating channel of the training sequence that comprises in the upward signal.
Step 102 is obtained the channel impulse response position;
In this step, if the channel estimating threshold value is greater than the critical threshold value of channel estimating, then with the position of this UE channel estimating threshold value correspondence as the channel impulse response position, the channel impulse response position comprises channel impulse response initial value position, peak and end position.The position of promptly seeking initial value, maximum and end value in the position of channel estimating threshold value is respectively as initial value position, peak and the end position of this UE channel impulse response.
Step 103 is according to the channel impulse response position after present channel impulse response position and the certain delay of historical channel impulse response position prediction;
In this step, at present the channel impulse response position is designated as that h (n-1), historical channel impulse response position are designated as h (n-2), the channel impulse response position after certain delay is designated as h (n), and wherein, n is the subframe numbers in the actual treatment.According to the position h (n-1) of historical channel impulse response position h (n-2) and present impulse response, utilize the channel impulse response position h (n) after following prediction algorithm prediction necessarily postpones.Present channel impulse response position h (n-1) is carried out recursive average computation:
h(n-1)=(1-p)h(n-2)+ph(n-1) (1)
In the formula,
P is a forgetting factor, and h (n-1) is the present channel impulse response position of prediction.
Then, the present channel impulse response position of prediction is predicted according to historical synch command, the channel impulse response position h (n) after necessarily being postponed, predictor formula is as follows:
In the formula,
Wherein SS is simultaneous bias (Synchronization Shift) information that sends in the corresponding moment, and k is the step-length of simultaneous bias, and the step-length of simultaneous bias is disposed by high level, and D is the linear prediction time.
Calculate channel impulse response peak value position h after certain delay according to channel impulse response position h (n) after certain delay of obtaining
Peak
Step 104 is obtained the channel impulse response peak value position difference;
In this step, the channel impulse response peak value position difference DELTA equals the channel impulse response peak value position h after certain delay
PeakDestination channel impulse response peak h with the outer shroud synchronization settings
TargetDifference.That is:
Δ=h
peak-h
target (3)
Whether step 105 judges the channel impulse response peak value position difference greater than default channel impulse response peak value position difference threshold value,
If the channel impulse response peak value position difference is greater than default channel impulse response peak value position difference threshold value δ, i.e. Δ=h
Peak-h
Target>δ produces the CW that puies forward previous step-length;
If the channel impulse response peak value position difference is less than negative default channel impulse response peak value position difference threshold value δ, i.e. Δ=h
Peak-h
Target<δ produces the CW that delays a step-length;
If the channel impulse response peak value position difference greater than negative default channel impulse response peak value position difference threshold value less than channel impulse response peak value position difference threshold value, promptly-δ≤Δ=h
Peak-h
Target≤ δ produces a uncomfortable CW;
Step 106, BS sends to UE according to correspondence position in the synchronization shift information in the time slot format insertion subframe with the CW that produces in the available descending time slot of the next one;
Step 107, UE carries out up closed loop Synchronization Control according to the CW that receives.
In this step, UE carries out up closed loop Synchronization Control according to the information that the CW that receives comprises, and is correspondingly uncomfortable, in advance or delay a step-length and send upward signal.
By up closed loop synchronisation control means in the above-mentioned TD_SCDMA system as can be seen, by the training sequence in the upward signal is carried out channel estimating, with the maximum of the impulse response energy of channel estimating energy value as most powerful path, compare with the residing position of energy value peak value of most powerful path and the destination channel impulse response peak of outer shroud synchronization settings then, generate CW and carry out up closed loop Synchronization Control.And in the wireless environment of reality, because multipath situation complexity, if the impulse response peak most powerful path that BS only utilizes channel estimating to go out is judged whether the sync bit of UE changes and is generated CW, and carry out up closed loop Synchronization Control according to CW, cause erroneous judgement and misjudgement easily, for example, under the lower situation of the confidence level of channel estimating, this method compares and produces CW according to the channel impulse response peak value position difference with the channel impulse response peak value position difference threshold value of presetting and carries out up closed loop Synchronization Control, but in fact, because the confidence level of channel estimating is lower, the upward signal confidence level that shows the BS reception is lower, up link may be in disarmed state, do not need to generate CW and carry out up closed loop Synchronization Control by channel estimating, thereby cause erroneous judgement and misjudgement, influence the performance of TD_SCDMA system, reduced the reliability of up closed loop Synchronization Control in the TD_SCDMA system.
Summary of the invention
In view of this, a main purpose of the present invention is to provide a kind of method of obtaining control word based on up closed loop Synchronization Control, reduce BS and only utilize channel estimating generation CW to carry out erroneous judgement and the misjudgement that up closed loop Synchronization Control causes, improve the reliability of up closed loop Synchronization Control in the TD_SCDMA system.
For achieving the above object, the invention provides and a kind ofly obtain the method for control word based on up closed loop Synchronization Control, this method comprises:
Base station BS carries out joint-detection to the upward signal that receives, and obtains the transformat combination indication TFCI information that comprises in the upward signal, and TFCI is deciphered;
If the TFCI decode results not in the TFCI scope that sets in advance, produces unadjusted control words CW;
The channel impulse response peak value position after if the TFCI decode results in the TFCI scope that sets in advance, is carried out channel estimating and obtained certain delay according to the training sequence that comprises in the upward signal that receives; The difference of the channel impulse response peak value position after the certain delay of calculating and the destination channel impulse response peak of outer shroud synchronization settings, and according to difference and default channel impulse response peak value position difference threshold value, generation corresponding C W.
Channel impulse response peak value position after the training sequence that comprises in the described upward signal according to reception carries out channel estimating and obtains certain delay specifically comprises:
BS estimates threshold value according to the noise power and the predefined signal-noise ratio threshold value calculating channel of the training sequence that comprises in the upward signal;
If the channel estimating threshold value of obtaining is greater than the critical threshold value of channel estimating, then with the position of described channel estimating threshold value correspondence as the channel impulse response position;
According to the channel impulse response position after present channel impulse response position and the certain delay of historical channel impulse response position prediction;
Channel impulse response peak value position after necessarily being postponed according to the channel impulse response position calculation after certain delay of obtaining.
Channel impulse response position after the certain delay of described basis present channel impulse response position and historical channel impulse response position prediction specifically comprises:
The present channel impulse response position that recursive average computation is obtained prediction is carried out in present channel impulse response position;
According to historical synchronization shift information the channel impulse response position after necessarily being postponed is predicted in the present channel impulse response position of prediction.
The formula of described recursive average computation is:
h(n-1)=(1-p)h(n-2)+ph(n-1)
In the formula,
H (n-1) is the present channel impulse response position of prediction, and n is the subframe numbers in the actual treatment, and p is a forgetting factor, and h (n-2) is historical channel impulse response position, and h (n-1) is present channel impulse response position.
Described forgetting factor span is (0,1).
Described according to historical synchronization shift information to the prediction present channel impulse response position predict that the predictor formula of the channel impulse response position after necessarily being postponed is:
In the formula, h (n) is the channel impulse response position after certain delay, and h (n-1) is the present channel impulse response position of prediction, and SS is the synchronization shift information that sends in the corresponding moment, and k is the step-length of simultaneous bias, and D is the linear prediction time.
Described according to difference and default channel impulse response peak value position difference threshold value, produce corresponding C W and specifically comprise:
If difference greater than default channel impulse response peak value position difference threshold value, produces the CW that puies forward previous step-length;
If difference produces the CW that delays a step-length less than negative default channel impulse response peak value position difference threshold value;
If difference less than channel impulse response peak value position difference threshold value, produces a uncomfortable CW greater than negative default channel impulse response peak value position difference threshold value.
The span of described channel impulse response peak value position difference threshold value is (0,1).
This method further comprises:
BS inserts the CW that produces in the synchronization shift information of subframe correspondence position and is sent to user equipment (UE) according to time slot format in next descending time slot;
UE carries out corresponding up closed loop Synchronization Control according to the CW that receives.
As seen from the above technical solutions, provided by the inventionly a kind ofly obtain the method for control word based on up closed loop Synchronization Control, BS carries out joint-detection to upward signal, obtains TFCI information, and TFCI is deciphered; If the TFCI decode results produces uncomfortable CW not in the TFCI scope that sets in advance; Otherwise, the channel impulse response peak value position after carrying out channel estimating and obtain certain delay according to training sequence; The difference of the channel impulse response peak value position after the certain delay of calculating and the destination channel impulse response peak of outer shroud synchronization settings, and according to difference and default channel impulse response peak value position difference threshold value, generation corresponding C W.Use the present invention, having reduced BS only utilizes channel estimating generation CW to carry out erroneous judgement and the misjudgement that up closed loop Synchronization Control causes, avoid the up closed loop Synchronization Control of carrying out under the situation of channel estimating flase drop or false retrieval, improved the reliability and stability of up closed loop Synchronization Control in the TD_SCDMA system.
Description of drawings
Fig. 1 is up closed loop synchronisation control means schematic flow sheet in the existing TD_SCDMA system;
Fig. 2 is the positional structure schematic diagram of TFCI information in burst in the TD_SCDMA system;
Fig. 3 the present invention is based on the method flow schematic diagram that up closed loop Synchronization Control is obtained control word.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in further detail below in conjunction with the accompanying drawings and the specific embodiments.
The method of obtaining control word based on up closed loop Synchronization Control provided by the invention, by detection be included in the upward signal training sequence in transformat combination indication (TFCI in the same time slot, TransportFormat Combination Indicator), and it is deciphered, according to decode results the validity of up link is judged, if up link is effective, then carry out up closed loop Synchronization Control according to existing up closed loop synchronisation control means; If up link is invalid, then upward signal is not carried out up closed loop Synchronization Control.
Below TFCI information in the TD_SCDMA system that the present invention relates to is described, about the position of TFCI information in the uplink burst signal and the structure of uplink burst signal, specifically can be referring to 3rd Generation Partnership Project (3GPP, 3rd Generation Partnership Project) telecommunication standard (TS, Telecommunications Standards) 25.221 agreements.In below describing, abbreviate the uplink burst signal as upward signal.
Fig. 2 is the positional structure schematic diagram of TFCI information in burst in the TD_SCDMA system, referring to Fig. 2, in the TD_SCDMA system, a frame comprises two subframes, and each subframe comprises 7 conventional burst (Burst, also be time slot) and 3 special bursts, each conventional bursty data territory, TFCI territory, training sequence, SS territory and through-put power control (TPC, Transmission Power Control) territory, wherein, whether TFCI, SS and TPC exist by high level configuration decision
Training sequence is used to carry out channel estimating;
The SS territory is used for the Synchronization Control Timing Advance;
The TPC territory is used for power control;
The TFCI territory, be used to notify the current activation of recipient employed transformat combination, the recipient by TFCI can be correct data in the data field that receives are decoded, whether there is TFCI in the upward signal, determine by consultation when the call setup by the high level of communicating pair, and physical layer is configured by high level.
The chnnel coding of TFCI is independent of the data field part of subframe in the time slot, adopt single order or second order Reed-Muller sign indicating number to encode, for extremely short TFCI, for example, TFCI is 1 bit (bit) or 2bit, then repeats with simple, for example, the method of triplicate is encoded, and the TFCI behind the coding is assigned to that four TFCI territories, a corresponding TFCI territory to the send in two subframes, specifically:
If the data bit of the TFCI behind the coding is 4bit, because data field is unit with the symbol, at Quaternary Phase Shift Keying (QPSK, when Quaternary Phase Shift Keying) modulating, corresponding two bits of each symbol, thereby, the TFCI behind the coding is placed on the first, the 3rd TFCI territory of two subframes, the second, the 4th TFCI territory be a sky;
If the data bit of TFCI behind the coding is greater than 4bit, for example, 8bit, 16bit or 32bit, then the TFCI behind the coding will be distributed in four TFCI territories of two subframes equably.
The spread spectrum of TFCI behind the coding is identical with the data field of respective channel.
A frame transmission time that comprises burst is 10ms, if the coded combination transmission channel (Cctrch that constitutes by burst, Coded Composite Transport Channel) minimum transmission time of all transmission channels interval (TTI in, Transmission Timing Interval) is not less than 20ms, then the continuous TFCI territory of each frame is identical in the TTI, be that a TFCI territory in first subframe of a TFCI territory and next frame in the 1st subframe of present frame is identical, the 2nd TFCI territory in the 1st subframe is identical with the 2nd TFCI territory in first subframe of next frame, and by that analogy.
If send on a plurality of time slots of TFCI in a frame, then the TFCI territory of each time slot correspondence is identical.
Fig. 3 the present invention is based on the method flow schematic diagram that up closed loop Synchronization Control is obtained control word.Referring to Fig. 3, this flow process comprises:
Step 301, BS obtains the TFCI of up coding transmission channel by joint-detection, and TFCI is deciphered;
In this step, BS carries out joint-detection to UE by the upward signal that up coding transmission channel sends, and detect upward signal according to the time slot format of TD_SCDMA, obtain the TFCI information that is included in the upward signal, time slot format, joint detection results and the detected TFCI according to configuration carries out Reed-Muller decoding then.
It is similar that BS carries out in joint-detection and the existing TD_SCDMA system joint-detection to upward signal, do not repeat them here.And the time slot format of configuration, for example, for the time slot format of ARM12.2K, referring to 3GPP TS 34.108 agreements, the time slot format of configuration is 18.
Step 302 is carried out the validity of up link and is judged that if up link is effective, execution in step 303 if up link is invalid, produces a uncomfortable CW, execution in step 307 according to the TFCI decode results;
In this step, if the TFCI decode results is in the TFCI scope that sets in advance, think that then the TFCI decode results is correct, show that this up link is effective, promptly the data of this upward signal frame are with a high credibility, can utilize channel estimating to obtain up CW by up closed loop Synchronization Control algorithm computation, carry out up closed loop Synchronization Control, the TFCI scope that sets in advance is configured in high level.For instance, referring to 3GPP TS34.108 agreement, TFCI for ARM12.2K, the TFCI scope maximum of its high-rise configuration is 6, if decode results is 3, then in the TFCI scope of high level configuration, this up link is effective, and the up coded combination transmission channel that transmits upward signal is carried out up closed loop Synchronization Control.
In the practical application, if determine the TFCI decode results in the TFCI scope that sets in advance, the channel impulse response peak value position after the training sequence that comprises in the upward signal according to reception carries out channel estimating and obtains certain delay; The difference of the channel impulse response peak value position after the certain delay of calculating and the destination channel impulse response peak of outer shroud synchronization settings, and according to difference and default channel impulse response peak value position difference threshold value, produce corresponding C W, describe in detail again in follow-up.
If the TFCI decode results has exceeded the TFCI scope of high-rise configuration, think that then the TFCI decode results is wrong, show that this up link is invalid, promptly the data of this upward signal frame are with a low credibility, cannot utilize channel estimating to carry out up closed loop Synchronization Control, BS produces a uncomfortable CW, and up coded combination transmission channel is not carried out up closed loop Synchronization Control.
Step 303, BS carries out channel estimating according to the training sequence that comprises in the upward signal that receives;
In this step, BS estimates threshold value according to the noise power and predefined signal to noise ratio (SNR, Signal Noise Ratio) the threshold value calculating channel of the training sequence that comprises in the upward signal, and the SNR threshold value rule of thumb is provided with, preferably, can be set to 10.
Step 304 is obtained the channel impulse response position;
In this step, if the channel estimating threshold value is greater than the critical threshold value of channel estimating, then with the position of this UE channel estimating threshold value correspondence as the channel impulse response position, the channel impulse response position comprises channel impulse response initial value position, peak and end position.
Step 305 is according to the channel impulse response position after present channel impulse response position and the certain delay of historical channel impulse response position prediction;
In this step, at first, recursive average computation is carried out in present channel impulse response position:
h(n-1)=(1-p)h(n-2)+ph(n-1)
In the formula,
H (n-1) is the present channel impulse response position of prediction, and n is the subframe numbers in the actual treatment, and p is a forgetting factor, and span is (0,1), and h (n-2) is historical channel impulse response position, and h (n-1) is present channel impulse response position.
Then, according to historical synchronization shift information the channel impulse response position after necessarily being postponed is predicted in the present channel impulse response position of prediction:
In the formula, h (n) is the channel impulse response position after certain delay, SS is the synchronization shift information that sends in the corresponding moment, k is the step-length of simultaneous bias, and the step-length of simultaneous bias is disposed by high level, preferably, be set to 1/8th chips (1/8chip), D is the linear prediction time, and is relevant with the system time delay, is set to 4 subframes.
Calculate channel impulse response peak value position h after certain delay according to channel impulse response position h (n) after certain delay of obtaining
Peak
Step 306 is judged the channel impulse response peak value position h after necessarily postponing
PeakDestination channel impulse response peak h with the outer shroud synchronization settings
TargetDifference whether greater than default channel impulse response peak value position difference threshold value δ,
Preferably, the span of δ is (0,1).
If difference is greater than default channel impulse response peak value position difference threshold value δ, i.e. h
Peak-h
Target>δ produces the CW that puies forward previous step-length;
If difference is less than negative default channel impulse response peak value position difference threshold value δ, i.e. h
Peak-h
Target<δ produces the CW that delays a step-length;
If difference greater than negative default channel impulse response peak value position difference threshold value less than channel impulse response peak value position difference threshold value, promptly-δ≤h
Peak-h
Target≤ δ produces a uncomfortable CW;
So far, this flow process finishes.
BS after obtaining CW, can execution in step 307 to step 308.
Step 307, BS inserts the CW that produces in the subframe in the synchronization shift information correspondence position and is sent to UE according to time slot format in the available descending time slot of the next one;
Step 308, UE carries out up closed loop Synchronization Control according to the CW that receives.
In this step, UE carries out up closed loop Synchronization Control according to the information that the CW that receives comprises, and is correspondingly uncomfortable, in advance or delay a step-length and send upward signal.
As seen from the above-described embodiment, provided by the inventionly a kind ofly obtain the method for control word based on up closed loop Synchronization Control, BS obtains the TFCI of up coding transmission channel by joint-detection, and TFCI is deciphered; Carry out up link validity according to the TFCI decode results and judge,, generate CW the up coded combination transmission channel that transmits upward signal is carried out up closed loop Synchronization Control if determine that up link is effective; If determine that up link is invalid, generate uncomfortable CW up coded combination transmission channel is not carried out up closed loop Synchronization Control.By before up closed loop Synchronization Control, increasing according to the TFCI decode results being carried out the step that Radio Link validity is judged, make that the present invention is based on up closed loop Synchronization Control obtains CW and not only utilized channel estimation results, also utilized and passed through joint-detection, and the transmission channel format combination instruction after the Reed-Muller encoding and decoding, and this transmission channel format combination instruction reliability height, thereby reduced BS and only utilized channel estimating generation CW to carry out erroneous judgement and the misjudgement that up closed loop Synchronization Control causes, avoided the up closed loop Synchronization Control of carrying out under the situation of channel estimating flase drop or false retrieval, thereby strengthened the effect of up closed loop Synchronization Control, improve the reliability and stability of carrying out up closed loop Synchronization Control in the TD_SCDMA system by CW, improved the TD_SCDMA systematic function.
More than lift preferred embodiment; the purpose, technical solutions and advantages of the present invention are further described; institute is understood that; the above only is preferred embodiment of the present invention; not in order to restriction the present invention; within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.