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Method and apparatus for collecting subframes of satellite navigation data

a satellite navigation and data collection technology, applied in the field of satellite navigation data collection subframes, can solve the problems of affecting the ttff performance of the receiver, the need for the receiver to wait for another 30 seconds, and the considerable time consumption of the receiver, so as to facilitate the receiver, reduce the time to collect required data such as ephemeris, and improve the ttff performan

Inactive Publication Date: 2010-02-25
MEDIATEK INC
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Benefits of technology

[0007]An objective of the present invention is to provide a subframe collecting method. By using the subframe collecting method, the time to collect required data such as ephemeris can be significantly reduced, and thereby TTFF performance can be improved. For example, the present invention is of advantageous for twinkle receiving. When a vehicle carrying a receiver passes by a tree or tall building, signal fading may occur temporarily. The subframe collection method can facilitate the receiver to rapidly collect required data in a shorter period of time.
[0008]Another objective of the present invention is to provide a subframe collecting apparatus. The subframe collecting apparatus implements the subframe collecting method to collect ephemeris in a shorter period of time.

Problems solved by technology

If, unfortunately, the subframe of the next page also has an error, the receiver again needs to wait for another 30 seconds.
This results in considerably long time consumption, and thereby seriously influencing TTFF performance of the receiver.

Method used

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  • Method and apparatus for collecting subframes of satellite navigation data
  • Method and apparatus for collecting subframes of satellite navigation data
  • Method and apparatus for collecting subframes of satellite navigation data

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Embodiment Construction

[0022]The present invention will be described in detail as follows.

[0023]Collection of ephemeris is done by collecting correct Subframes 1 to 3 of navigation data. As mentioned, a subframe consists of 10 words. Word error rate (WER) is directly related to signal intensity. FIG. 4 is a diagram shows relationship between WER and signal CNR (carrier to noise ratio). As shown, the lower CNR is, the worse WER is. When CNR drops below 30 dB-Hz, WER will considerably raise. Assume that single word error rate (WER) is r, 10 words error rate will be 1−(1−r)10. For example, when CNR is 30 dB-Hz, single word error rate is about 0.04, then 10 words error rate will be 1−(1−0.04)10=0.3352. It is clear that the error rate is significantly greater when 10 words are considered as a sub-unit. Accordingly, we can divide a subframe into smaller sub-units. Each sub-unit can have 1 word, 2 words or 5 words. As the example described above, if the single word error rate r is 0.04, then

[0024]10 words error ...

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Abstract

A method and apparatus for collecting subframes of navigation data of satellites are disclosed. In the method of the present invention, the subframe is divided into several sub-units, each sub-units includes one or more words. When a receiver receives a subframe with a subframe ID, the respective required sub-units of the subframe are checked. A dummy sub-unit is not necessary to be considered. Valid ones of the required sub-units are collected. If not all the required sub-units of the subframe have been collected, the absent sub-units are to be collected when the next subframe with the same subframe ID is received. Some protection schemes can be applied to raise the reliability of such sub-unit collection. Especially when the signal is weak or unstable, the present invention may significantly improve the TTFF (Time To First Fix) performance of the receiver.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]The present application is a continuation application of U.S. patent application Ser. No. 11 / 620,303, filed on Jan. 5, 2007, which is incorporated herein by reference.TECHNICAL FIELD OF THE INVENTION[0002]The present application relates to time-to-first-fix (TTFF) reduction in satellite communication, more particularly, to a novel method for collecting subframes of satellite navigation data. By using this method, TTFF performance can be improved. The present invention also relates to a Global Navigation Satellite System (GNSS) receiver implementing the subframe collection method.BACKGROUND OF THE INVENTION[0003]Satellite positioning has been widely used in various applications. In satellite positioning systems such as Global Navigation Satellite System (GNSS), a cold start state means that no information such as receiver position, observation time, satellite navigation information (e.g. almanac or ephemeris) are available.[0004]For a GNSS ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G01S19/27G01S19/25G01S19/24
CPCH04L1/08G01S19/24
Inventor LI, KUAN-IHUANG, KUNG-SHUANCHEN, KUN-TSO
Owner MEDIATEK INC
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