CN104159286A - Uplink time synchronization method of LTE system of GEO satellite - Google Patents
Uplink time synchronization method of LTE system of GEO satellite Download PDFInfo
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- CN104159286A CN104159286A CN201410321599.9A CN201410321599A CN104159286A CN 104159286 A CN104159286 A CN 104159286A CN 201410321599 A CN201410321599 A CN 201410321599A CN 104159286 A CN104159286 A CN 104159286A
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- synchronous error
- uplink
- geo satellite
- time
- uplink frame
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Abstract
The invention relates to the time synchronization technology of wireless communication systems, in particular to an uplink time synchronization method of an LTE system of a GEO satellite. According to the method, on the premise of being compatible with the conventional LTE air interface standard, a standard frame structure which is 10 ms in length can be used; by performing estimation compensation on synchronization errors, a transmission time on the side of user equipment and a start time of a base receiving window are corrected to realize the protection of the subcarrier orthogonality in the OFDM technology by the uplink synchronization of the GEO satellite; a transformational LMS algorithm is designed according to the characteristics of the system to realize quick estimation of the synchronization errors; user equipment platforms with different moving speeds can be adapted by setting update velocity; the method is high in structural universality, lower in complexity and easy to realize, and can meet a requirement of time synchronization on the LTE system of the GEO satellite, as well as a requirement of standard compatibility on a conventional LTE air interface.
Description
Technical field
The present invention relates to the Time synchronization technique of wireless communication system, particularly a kind of method of GEO satellite LTE system uplink time synchronized.
Background technology
For land mobile communication system, satellite mobile communication system has the advantages such as broad covered area, outdoor channel quality is high, survivability is strong, is widely used in the fields such as the communication network development from far-off regions, rescue and relief work emergency communication, military communication.Be accompanied by the further popularization of China LTE commercialization, land mobile communication network just progressively completes the evolution to the 4G epoch by 3G, also becomes the important development direction of current satellite mobile communication system taking LTE technical system as basic satellite mobile communication system evolution of new generation.
Land mobile communication systems air interface is applied in and in satellite mobile communication system, is faced with that propagation delay time is large, frequency resource is in short supply, beam coverage area is excessive, time synchronized is difficult and the problems such as signal interference free performance is poor.With regard to time synchronization problem, on the one hand due to different user terminals present position scattered band in satellite mobile communication overlay area wide (simple beam covering radius 200～350km) and mobility different, for example: aircraft (the about 900km of speed h, highly about 10km), boats and ships (the about 40km of speed h), vehicle (the about 80km of speed h) and pedestrian (the about 7km of speed h); Fixed statellite on geo-stationary orbit can be affected and the variation of occurrence positions by the factor such as the irregularly shaped of the earth and ground month gravitation on the other hand.Therefore, the distance that user terminal in different platform arrives satellite, changing at any time, has caused subscriber equipment also changing at any time to the propagation delay time of satellite, thereby has caused time synchronization error.Maximum at the highest Layer in Mohe Region subscriber equipment of CHINESE REGION latitude spreads out of the time difference | Δ t
max|=1.2407ms, maximum transmission distance is poor is about 372.2 kilometers, and the maximum synchronous error of system can not be greater than this value.Meanwhile, the long time delay feature (the about 270ms of single-hop transmission time delay) of satellite system link transmission, make that base station cannot be real-time by each terminal uplink synchronous Error Feedback to user terminal.User terminal is not in the situation that obtaining Real-Time Scheduling; can there is the constantly cumulative of uplink synchronous error; exceed Cyclic Prefix and protection gap length during when adding up; this time slot upward signal can produce and crosstalk the signal of next time slot user; cause upward signal interference problem, have a strong impact on systematic function.
At present; adopt the method that adds long loop prefix and protection interval for the LTE standard of TDD full-duplex mode; the protection interval of user under GEO satellite simple beam is extended to 2.16ms by the method; and by primary standard, a whole frame extended length is to 16ms, the method for this simple growth data frame length can cause approximately 60% system capacity loss.Therefore, although this method can avoid most upward signal to disturb, brought again power system capacity significantly to reduce simultaneously and with the new problem of ground system poor compatibility.
Summary of the invention
For deficiency of the prior art, the invention provides a kind of method of GEO satellite LTE system uplink time synchronized, carry out the synchronous error in predictive user a period of time by the synchronous error of observation unit sub-signal, error is judged in advance and compensated, make GEO satellite LTE system to realize uplink synchronous at the existing LTE air-interface standard of application, be suitable for equally the GEO satellite mobile communication system that uses LTE air-interface standard under TDD full-duplex mode.
According to design provided by the present invention, a kind of method of GEO satellite LTE system uplink time synchronized, comprises following steps:
Step 1, cycle rate counter initialization;
Step 2, the ZC serial correlation of the n a having arrived signal is calculated to the uplink synchronous error sequence of observations { X
1, X
2..., X
n;
Step 3, according to the contiguous sorting criterion of stationary time series, weighting a is set
minitial value;
Step 4, by observation n uplink frame synchronous error value { X
1, X
2..., X
n, the synchronous error offset Y of m uplink frame of prediction
m, wherein, m=n+1;
Step 5, judge predictive compensation value Y
mwhether conform to a predetermined condition, if meet, return to step 4, wherein, n=n+1, predicts the synchronous error offset of next uplink frame, otherwise, proceed to step 6;
Step 6, correction UE equipment transmitting time, by the offset sequence { Y having predicted
1, Y
2..., Y
nexpectation E[Y] revise NTA value, X
t=X-E[Y], return to step 1, the synchronous error after observation adjustment again, wherein, X is the synchronous error of a current n uplink frame, X
tfor the revised synchronous error of a current n uplink frame.
In described step 4, pass through to use the synchronous error value { X of LMS adaptive filter algorithm to the n of a current observation uplink frame
1, X
2..., X
n, the synchronous error offset Y of m uplink frame of prediction
m, that is:
m=n+1, m is weighted value renewal rate, and e (n) is evaluated error, and e* (n) asks conjugation, d for evaluated error
nfor upper cycle time offset expectation, R is synchronous error { X
1, X
2... X
nautocorrelation matrix.
In described step 5, predetermined condition is-T
cP<Y
i<T
gT, wherein T
cPfor circulating prefix-length, T
gTfor protection gap length.
The beneficial effect of the method for GEO satellite LTE system uplink time synchronized of the present invention:
1. the present invention is under the prerequisite of the existing LTE air-interface standard of compatibility; use the standard frame of 10ms length; by synchronous error is carried out to estimation compensation; revise the transmitting time of subscriber equipment transmitter side and the time started of base station receive window, realized the synchronously protection to OFDM technology sub-carriers orthogonality of GEO satellite uplink.
2. the present invention realizes the quick estimation of synchronous error with the LMS algorithm of system feature design transformation, can be by the setting of renewal rate being adapted to the user equipment platforms of different translational speeds, implementation structure highly versatile, and complexity is lower, be easy to realize, can meet that GEO satellite LTE communication system requires the time synchronized of carrier wave orthogonality and the compatible requirement of existing LTE air-interface standard.
Brief description of the drawings:
Fig. 1 is schematic diagram of the present invention;
Fig. 2 is schematic flow sheet of the present invention.
Embodiment:
Below in conjunction with accompanying drawing and technical scheme, the present invention is further detailed explanation, and describe embodiments of the present invention in detail by preferred embodiment, but embodiments of the present invention are not limited to this.
Suppose that single GEO satellite system access user uplink frame quantity is N, unidirectional transmission time delay is
and suppose each user uplink synchronous error X
ifor obeying the random process of certain distribution, upward signal reaches base station, and the observation window time started is:
Therefore do not changing as far as possible under the prerequisite of frame structure, for eliminating X
ion the impact of the time of advent, the present invention passes through synchronous error X
ithe performance that periodically predictive compensation is adjusted to improve up time synchronized.Suppose and introduce offset Y
ithe observation window time started be:
Referring to Fig. 1～2, a kind of method of GEO satellite LTE system uplink time synchronized, comprises following steps: step 1, cycle rate counter initialization;
Step 2, the ZC serial correlation of the n a having arrived signal is calculated to the uplink synchronous error sequence of observations { X
1, X
2..., X
n;
Step 3, according to the contiguous sorting criterion of stationary time series, weighting a is set
minitial value;
Step 4, by observation n uplink frame synchronous error value { X
1, X
2..., X
n, the synchronous error offset Y of m uplink frame of prediction
m, wherein, m=n+1;
Step 5, judge predictive compensation value Y
mwhether conform to a predetermined condition, if meet, return to step 4, wherein, n=n+1, predicts the synchronous error offset of next uplink frame, otherwise, proceed to step 6;
Step 6, correction UE equipment transmitting time, by the offset sequence { Y having predicted
1, Y
2..., Y
nexpectation E[Y] revise NTA value, X
t=X-E[Y], return to step 1, the synchronous error after observation adjustment again, wherein, X is the synchronous error of a current n uplink frame, X
tfor the revised synchronous error of a current n uplink frame.
In described step 4, pass through to use the synchronous error value { X of LMS adaptive filter algorithm to the n of a current observation uplink frame
1, X
2..., X
n, the synchronous error offset Y of m uplink frame of prediction
m, that is:
m=n+1, m is weighted value renewal rate, and e (n) is evaluated error, and e* (n) asks conjugation, d for evaluated error
nfor upper cycle time offset expectation, R is synchronous error { X
1, X
2... X
nautocorrelation matrix.
In described step 5, predetermined condition is-T
cP<Y
i<T
gT, wherein T
cPfor circulating prefix-length, T
gTfor protection gap length.
The step of the method for the above-described GEO satellite LTE system uplink time synchronized of foundation, establish i OFDM time domain transmission symbol table of UE equipment and be shown:
By the compensation to synchronous error, go the signal receiving behind interval to be:
r
i[t-E(Z)]＝[s
i[t-E(Y)]*h[t-E(Y)]+n(t)]*g[t-iT
i-T
g-E(Y)]。
Wherein, the significant character length that OFDM time domain sends is T
u, protection gap length is T
g, total symbol lengths is T
i=T
u+ T
g, N is the sub-way of OFDM time domain, S
k ifor signal number certificate, g (t-iT
i) be impulse waveform, h[t] be the multipath channel of signal process, * is convolution algorithm.
The present invention is based on the method for GEO satellite LTE system uplink time synchronized, through estimation error, judgement and compensation adjustment process, finally realize the up time synchronized of GEO satellite LTE communication system under tdd mode, its implementation structure is general, and complexity is lower, be easy to realize, can meet that GEO satellite LTE communication system requires the time synchronized of carrier wave orthogonality and the compatible requirement of existing LTE air-interface standard.
Claims (3)
1. a method for GEO satellite LTE system uplink time synchronized, is characterized in that: comprise following steps:
Step 1, cycle rate counter initialization;
Step 2, the ZC serial correlation of the n a having arrived signal is calculated to the uplink synchronous error sequence of observations { X
1, X
2..., X
n;
Step 3, according to the contiguous sorting criterion of stationary time series, weighting a is set
minitial value;
Step 4, by observation n uplink frame synchronous error value { X
1, X
2..., X
n, the synchronous error offset Y of m uplink frame of prediction
m, wherein, m=n+1;
Step 5, judge predictive compensation value Y
mwhether conform to a predetermined condition, if meet, return to step 4, wherein, n=n+1, predicts the synchronous error offset of next uplink frame, otherwise, proceed to step 6;
Step 6, correction UE equipment transmitting time, by the offset sequence { Y having predicted
1, Y
2..., Y
nexpectation E[Y] revise NTA value, X
t=X-E[Y], return to step 1, the synchronous error after observation adjustment again, wherein, X is the synchronous error of a current n uplink frame, X
tfor the revised synchronous error of a current n uplink frame.
2. the method for GEO satellite LTE system uplink time synchronized according to claim 1, is characterized in that: in described step 4, pass through to use the synchronous error value { X of LMS adaptive filter algorithm to the n of a current observation uplink frame
1, X
2..., X
n, the synchronous error offset Y of m uplink frame of prediction
m,
Wherein, m=n+1, m is weighted value renewal rate, and e (n) is evaluated error, and e* (n) asks conjugation, d for evaluated error
nfor upper cycle time offset expectation, R is synchronous error { X
1, X
2... X
nautocorrelation matrix.
3. the method for GEO satellite LTE system uplink time synchronized according to claim 1, is characterized in that: in described step 5, predetermined condition is-T
cP<Y
i<T
gT, wherein T
cPfor circulating prefix-length, T
gTfor protection gap length.
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| CN105915315A (en) * | 2016-04-15 | 2016-08-31 | 哈尔滨工业大学 | LTE frame structure improving method facing random access in air-ground integrated system and obtained LTE frame structure |
| CN107197517A (en) * | 2017-08-02 | 2017-09-22 | 电子科技大学 | The LTE satellite uplink synchronous method being grouped based on TA |
| CN107748682A (en) * | 2017-10-31 | 2018-03-02 | 广东欧珀移动通信有限公司 | Background application management-control method, device, storage medium and electronic equipment |
| CN108809438A (en) * | 2017-04-27 | 2018-11-13 | 深圳市中兴微电子技术有限公司 | A kind of time difference compensation method and apparatus |
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| CN101082812A (en) * | 2006-06-01 | 2007-12-05 | 模拟装置公司 | Self-compensation closed-loop adaptive control system |
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| CN105915315A (en) * | 2016-04-15 | 2016-08-31 | 哈尔滨工业大学 | LTE frame structure improving method facing random access in air-ground integrated system and obtained LTE frame structure |
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| CN108809438A (en) * | 2017-04-27 | 2018-11-13 | 深圳市中兴微电子技术有限公司 | A kind of time difference compensation method and apparatus |
| CN108809438B (en) * | 2017-04-27 | 2020-03-06 | 深圳市中兴微电子技术有限公司 | Time difference compensation method and device |
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| CN107748682A (en) * | 2017-10-31 | 2018-03-02 | 广东欧珀移动通信有限公司 | Background application management-control method, device, storage medium and electronic equipment |
| CN107748682B (en) * | 2017-10-31 | 2020-11-13 | Oppo广东移动通信有限公司 | Background application control method and device, storage medium and electronic equipment |
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Application publication date: 20141119 |