CN101267410B - Method for realizing frequency domain balance of single-frequency network based on TD-SCDMA - Google Patents
Method for realizing frequency domain balance of single-frequency network based on TD-SCDMA Download PDFInfo
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Abstract
The invention discloses a TD-SCDMA-based SFN(single frequency network) frequency-domain equalizing method with two successive TS with the same guiding code, comprising the steps of: according to two adjacent guiding codes, obtaining channel impact response respectively by channel estimation algorithm; undergoing discrete Fourier Transform of 864 points to the channel impact response respectively to obtain frequency response of the corresponding channel; undergoing smoothing treatment for the frequency response to obtain smoothened frequency response h(k); undergoing frequency domain equalization for a received sequence to obtain a sequence y(k); undergoing discrete Fourier Transform for the sequence y(k) to obtain an equalized time sequence y(n) with length 864, dividing the sequence y(n) into two pieces according to constitution thereof, which belong to a right data block of TSi and a left data block of TSi+1. The invention effectively enhances data transmission efficiency without changing frame structure, which is not only appropriate for a frame structure of a low chip rate of 1.28M, but also frame structures of 3.84M and 7.68M.
Description
Technical field
The present invention relates to the digital mobile communication field, particularly relate to a kind of frequency-domain equilibrium method of realizing single frequency network based on TD-SCDMA (TD SDMA).
Background technology
At present, people no longer are satisfied with phone and messaging service to the demand of mobile communication, and a large amount of multimedia services emerge, and wherein television broadcasting even interactive television are one of interested application of people.
In the existing TD-SCDMA system, when needs sent downlink service data to user terminal, system distributed some physical channels to user terminal, then Data-carrying was sent to user terminal on these physical channels.When using existing TD-SCDMA system to send broadcasting service, system set up different physical channels need for different user terminals, sends respectively then, and when therefore existing TD-SCDMA system sent broadcasting service, its efficient was very low.Because the physical channel of system is limited, existing TD-SCDMA system synchronization can only be supported quite limited number of users.
In order to improve the efficient of TD-SCDMA system bearing broadcasting service, in the 3GPP agreement, propose to use single frequency network (SFN) to send broadcast data.So-called single frequency network is meant that a plurality of base station synchronization ground sends identical physical signalling, and the signal received of receiver is the stack of the signal of these base stations transmissions like this, and receiver itself is unaware of the existence of a plurality of base stations.In the TD-SCDMA system, can use one or more time slots of a frequency to constitute single frequency network, carry out downlink broadcast specially, also can use whole frequency to constitute single frequency network and carry out downlink broadcast.
The physical channel of TD-SCDMA standard adopts four-layer structure at present, and bottom two-layer is subframe and time slot.Each subframe lengths is 5ms, has comprised 7 conventional time slot and 3 special time slots that length is 675 μ s.These 3 special time slots are respectively DwPTS (descending pilot frequency time slot), GP (protection at interval) and UpPTS (uplink pilot time slot), and purposes is separately arranged.
In traditional TD-SCDMA system, it is different leading sign indicating number in the different base station transmission, and it also may be different leading sign indicating number in the different time-gap transmission of same base station.Yet in broadcast system based on single frequency network, different time-gap send in to lead sign indicating number be identical because each base station sends identical physical signalling, thus send between the different base station in to lead sign indicating number also be identical.
Traditional receiver detection method is handled in time domain, estimates the impulse response of channel, all must obtain its channel estimating to each spreading code.Then by setting up the joint-detection equation, the symbolic vector that large matrix is inverted and obtained launching.Even various shortcut calculations are arranged, the computation complexity that time domain is handled is still quite high.
If do not change existing standard, still using length is the GP of 16 chips, and the maximum multipath time delay that can tolerate of whole system was limited in the time of 16 chips so.In the broadcast system based on single frequency network, because the signal that terminal receives is the stack from a plurality of base station transmit signals, so the impulse response of channel also is the stack of each base station to the impulse response of terminal.Because each base station is different to the distance of terminal, the time delay expansion of the impulse response of channel is bigger, and multidiameter delay may surpass the protection range of GP.If the guard time of GP lengthening, will reduce the active data transmission time simply, increase extra expense.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of frequency-domain equilibrium method of realizing single frequency network based on TD-SCDMA, under the precondition that does not change frame structure, the computation complexity of receiver is reduced, can handle the technical barrier that single frequency network is brought, and can effectively improve data transmission efficiency.
For solving the problems of the technologies described above, the present invention is based on the frequency-domain equilibrium method that TD-SCDMA realizes single frequency network, two continuous TS adopt and lead sign indicating number in identical, and performing step is as follows:
(1) in adjacent two, lead sign indicating number, use channel estimation method, obtain respectively channel impulse response h1 (n) and h2 (n) (n=1,2 ..., L), wherein L is the maximum delay of channel impulse response;
(2) channel impulse response h1 (n) and h2 (n) are carried out 864 discrete Fourier transform (DFT) respectively, obtain the frequency response h1 (k) of respective channel and h2 (k) (k=1,2 ..., 864), wherein k is the sub-carrier indices number of frequency domain;
(3) h1 (k) and h2 (k) are carried out smoothing processing, obtain the frequency response h (k) after level and smooth;
(4) receiving sequence is carried out frequency domain equalization, obtain sequences y (k);
(5) sequences y (k) is carried out inverse discrete fourier transform, obtain length and be the time series y (n) after 864 the equilibrium, sequences y (n) is decomposed into two according to its formation, belong to the right data block of TSi and the left data block of TSi+1 respectively.
Do not use for two continuous TS and to lead sign indicating number in identical, method of the present invention is as follows:
The decline of step 1, current TS has a GP, and the decline of the TS in front also has a GP, satisfies the character of cyclic shift; The left data block of current TS, in lead sign indicating number, right data block and GP to form a length be 864 time series x (n), regard a symbol of zero padding-OFDM as;
Step 4, receiving sequence is adopted zero forcing algorithm, or adopt least-mean-square error algorithm, carry out frequency domain equalization, obtain sequences y (k);
Step 5, sequences y (k) are done inverse discrete fourier transform, obtain length and be 864 sequence x (n).Constitute left data block and the right data block of therefrom isolating this TS according to it.
Adopt frequency-domain equilibrium method of the present invention, lead the length of sign indicating number during the multidiameter delay of largest tolerable can reach, i.e. the time period of 144 chips.
Adopt frequency-domain equilibrium method of the present invention, can further improve transmission rate.The GP of each TS (time slot) does not need GP to isolate multidiameter delay without any value, can transmit data with it, and promptly the length of right data block is increased to 368 chips from 352 chips (chip).Thereby improve the spectrum efficiency of whole TD-SCDMA system.
FFT/IFFT (FFT/IFFT as well as) realizes with hardware usually, and it is very low to carry out balanced required calculation cost at frequency domain.Two continuous TS adopt and lead sign indicating number in identical, lead the length of sign indicating number during the multidiameter delay that system can tolerate can reach, and are extraordinary solutions for single frequency network.GP can be fully used, and with secured transmission of payload data, has avoided artificial waste.
Description of drawings
The present invention is further detailed explanation below in conjunction with accompanying drawing and embodiment:
Fig. 1 adopts the frequency-domain equilibrium method schematic diagram of leading sign indicating number in identical;
Fig. 2 adopts the frequency-domain equilibrium method schematic diagram of leading sign indicating number in the difference;
Fig. 3 is to the processing procedure schematic diagram of last TS in the embodiments of the present invention one;
Fig. 4 is to the processing procedure schematic diagram of first TS in the embodiments of the present invention two.
Embodiment
In the present invention, represent time slot, lead sign indicating number (midamble) in representing with M, represent that with GP protection at interval with TS (time slot).Each TS is made up of four parts, is respectively that length is the left data block of 352 chips, length be 144 chips in lead sign indicating number, length is the right data block of 352 chips, and length is the GP of 16 chips.
Realization precondition of the present invention is that continuous two TS adopt and lead sign indicating number in identical, and 7 TS that comprise a subframe adopt and lead sign indicating number in identical, and the whole subframes on certain frequency all adopt and lead sign indicating number in identical.If the parameter configuration of network side does not satisfy above-mentioned condition, still can use method of the present invention, just the multidiameter delay that can tolerate of system is limited in the guard time of GP.
For same broadcasting service, the data source that participates in each base station of broadcasting is fully synchronous, and the data source of indication refers to the information data symbol sebolic addressing that the base station sends synchronously and sends at one time here.There are a lot of methods can realize that base station synchronization sends data, such as, a kind of implementation method is to use GPS (global positioning system) system, increases timestamp simultaneously on packet, allows each base station according to the time of appointment on the timestamp packet be sent then.
After the base station sends data, be positioned at signal that the user terminal of radio network coverage receives and participate in the stack of signal of the base station of broadcasting for all.Among the present invention, use one or more time slot of existing TD-SCDMA system to send broadcasting service.
Referring to Fig. 1, wherein 100 is the multidiameter delay of channel impulse response, 101～109 plurality of continuous TS data that receive for terminal.Any one TS comprises three parts: left data block, in lead sign indicating number, right data block adds GP.In the monochromatic network broadcast system based on TD-SCDMA, it is identical to lead sign indicating number among adjacent two TS, leads sign indicating number 102 and 105 in promptly and adopts a same training sequence, leads sign indicating number 105 and 108 in perhaps to adopt a same training sequence.
TS data 103,104,105 altogether length be the time series of 864 chips be labeled as x (n) (n=1,2 ..., 864), it is regarded as an OFDM (OFDM) symbol.This sequence is carried out discrete Fourier transform (DFT), also can carry out 864 FFT, obtain length and be 864 sequence x (k) (k=1,2 ..., 864).Since in to lead sign indicating number 102 identical with 105, satisfy the character of cyclic shift, therefore can adopt the processing method of OFDM.
Frequency-domain equilibrium method of the present invention comprises following steps:
(1) according in lead the sign indicating number 102 and 105, use traditional channel estimation method, obtain respectively channel impulse response h1 (n) and h2 (n) (n=1,2 ..., L), wherein L is the maximum delay of channel impulse response.
(2) channel impulse response h1 (n) and h2 (n) are carried out 864 discrete Fourier transform (DFT) respectively, obtain the frequency response h1 (k) of respective channel and h2 (k) (k=1,2 ..., 864).
(3) h1 (k) and h2 (k) are carried out smoothing processing, obtain the frequency response h (k) after level and smooth.
(4) receiving sequence is carried out frequency domain equalization.Frequency domain equalization can adopt zero forcing algorithm, also can adopt least mean-square error (MMSE) algorithm.Such as for zero forcing algorithm, be specially, to each k (k=1,2 ..., 864), calculate y (k)=x (k)/h (k).
(5) sequences y (k) is carried out inverse discrete fourier transform, obtain length and be 864 sequences y (n), the time series after the equilibrium that Here it is.Sequences y (n) is decomposed into two according to its formation, belongs to the right data block of TSi and the left data block of TSi+1 respectively.
If the system configuration of network side does not satisfy continuous two TS and adopts and lead sign indicating number in identical, can avoid the high complexity of joint-detection at frequency domain equalization too.Its channel estimating is with aforementioned different, only utilize this time slot in lead the frequency domain channel that sign indicating number obtains and estimate a h (k).As shown in Figure 2, wherein 404 and 408 is respectively the GP of two TS, satisfies the character of cyclic shift.Can form a length to data 405,406,407,408 be 864 time series x (n), regards the symbol of ZP-OFDM (zero padding-OFDM) as, handles according to the method for ZP-OFDM.Time series x (n) is FFT changes, finish frequency domain equalization.And then carry out the IFFT conversion, obtain the time-domain signal of TSi+1.
Execution mode one
As shown in Figure 3, continuous two subframes also can adopt the method for frequency domain equalization of the present invention.Wherein, last time slot of last subframe is TS6, is the beginning time slot TS0 of back one subframe subsequently.According to method of the present invention, data 203,204,205 are used as an OFDM symbol.To this length is that 864 OFDM symbol x (n) makes 864 FFT, obtains frequency-region signal x (k).Frequency-region signal x (k) is done frequency domain equalization, obtain length and be 864 frequency-region signal y (k).At last y (k) is made 864 IFFT, obtaining length is the time-domain signal y (n) of 864chip.According to the formation of y (n), 203 is the right data block of TS6, and 204 is the left data block of TS0.
Execution mode two
TD-SCDMA has inserted transfer point between time slot TS0 and TS1, as shown in Figure 4, comprised 3 GP, a DwPTS and a UpPTS.Because the existence of this transfer point impacts frequency domain equalization, must carry out preliminary treatment.Data 302,303,304,305,306 are merged into a time series z (n).As follows to its processing method:
Step 4 is merged into a time series x (n) to data 301,307,308, and it is used as an OFDM symbol.
Carrying out frequency domain equalization according to execution mode one subsequently handles.
The invention describes the processing method of frame structure of the low spreading rate (low chip rate) of 1.28M, for the frame structure of 3.84M and 7.68M, thought of the present invention also is suitable for.
Claims (4)
1. realize based on TD-SCDMA that the frequency-domain equilibrium method of single frequency network, two continuous TS adopt and lead sign indicating number in identical for one kind, it is characterized in that comprising the steps:
Step 1, in adjacent two, lead sign indicating number, use channel estimation method, obtain channel impulse response h1 (n) and h2 (n) respectively, n=1,2 ..., L, wherein L is the maximum delay of channel impulse response;
Step 2, channel impulse response h1 (n) and h2 (n) are carried out 864 discrete Fourier transform (DFT) respectively, obtain the frequency response h1 (k) and the h2 (k) of respective channel, k=1,2 ..., 864;
Step 3, h1 (k) and h2 (k) are carried out smoothing processing, obtain the frequency response h (k) after level and smooth;
Step 4, receiving sequence is carried out frequency domain equalization, obtain sequences y (k);
Step 5, sequences y (k) is carried out inverse discrete fourier transform, obtain length and be the time series y (n) after 864 the equilibrium, sequences y (n) is decomposed into two according to its formation, belong to the right data block of TSi and the left data block of TSi+1 respectively.
2. the frequency-domain equilibrium method of realizing single frequency network based on TD-SCDMA as claimed in claim 1 is characterized in that: the described frequency domain equalization of step 4 adopts zero forcing algorithm, or adopts least-mean-square error algorithm.
3. the frequency-domain equilibrium method of realizing single frequency network based on TD-SCDMA as claimed in claim 1, it is characterized in that: owing between time slot TS0 and TS1, inserted transfer point, 3 GP that this transfer point is comprised, a DwPTS and a UpPTS merge into a time series z (n), carry out preliminary treatment more as follows: the convolution of calculating DwPTS and UpPTS and channel impulse response; From z (n), deduct convolution results, obtain sequence p (n); The left data block addition of sequence p (n) and TS1; Merge into a time series x (n) leading sign indicating number among the left data block of the right data block of TS0, TS1, the TS1, it is used as an OFDM symbol.
4. realize based on TD-SCDMA that the frequency-domain equilibrium method of single frequency network, two continuous TS do not use and lead sign indicating number in identical for one kind, it is characterized in that comprising the steps:
The decline of step 1, current TS has a GP, and the decline of the TS in front also has a GP, satisfies the character of cyclic shift; The left data block of current TS, in lead sign indicating number, right data block and GP to form a length be 864 time series x (n), regard a symbol of zero padding-OFDM as;
Step 2, according to the demodulation method of zero padding-OFDM, sequence x (n) is done preliminary treatment, make it satisfy the character of circular convolution;
Step 3, sequence x (n) is done discrete Fourier transform (DFT), obtain length and be 864 sequence x (k);
Step 4, receiving sequence is adopted zero forcing algorithm, or adopt least-mean-square error algorithm, carry out frequency domain equalization, obtain sequences y (k);
Step 5, sequences y (k) are done inverse discrete fourier transform, obtain length and be 864 sequence x (n), constitute left data block and the right data block of therefrom isolating this TS according to it.
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| US20020181615A1 (en) * | 2001-04-30 | 2002-12-05 | Alexandr Kuzminskiy | Frequency estimator for use in a receiver of packetised data, the receiver and a method of reception |
| CN1604662A (en) * | 2003-09-29 | 2005-04-06 | 凯明信息科技股份有限公司 | Method and equipment for detecting middle guiding code sequence in TD-SCDMA system |
| CN1688144A (en) * | 2005-06-06 | 2005-10-26 | 北京天碁科技有限公司 | Receiver and method for ID SCDMA system |
| EP1675337A1 (en) * | 2004-10-15 | 2006-06-28 | Mitsubishi Electric Information Technology Centre Europe B.V. | Frequency domain equaliser for single-carrier signals |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20020181615A1 (en) * | 2001-04-30 | 2002-12-05 | Alexandr Kuzminskiy | Frequency estimator for use in a receiver of packetised data, the receiver and a method of reception |
| CN1604662A (en) * | 2003-09-29 | 2005-04-06 | 凯明信息科技股份有限公司 | Method and equipment for detecting middle guiding code sequence in TD-SCDMA system |
| EP1675337A1 (en) * | 2004-10-15 | 2006-06-28 | Mitsubishi Electric Information Technology Centre Europe B.V. | Frequency domain equaliser for single-carrier signals |
| CN1688144A (en) * | 2005-06-06 | 2005-10-26 | 北京天碁科技有限公司 | Receiver and method for ID SCDMA system |
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Application publication date: 20080917 Assignee: SPREADTRUM COMMUNICATIONS (SHANGHAI) Co.,Ltd. Assignor: Xin Xin finance leasing (Beijing) Co.,Ltd. Contract record no.: X2021110000008 Denomination of invention: Frequency domain equalization method for SFN based on TD-SCDMA Granted publication date: 20100922 License type: Exclusive License Record date: 20210317 |
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