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?????????

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... / TOA/TDOA/RTOF ... Factors that affect GPS accuracy Imperfect satellites ... Ranging / Global Positioning System ... – PowerPoint PPT presentation

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Title: ?????????


1
?4? ????
2
?????????????????????????? ????????????????
????
3
????
  • ?3?????????
  • ????????(???????,???,???????,???)
  • ?????????
  • ???????????,???????????(????,??????,????????,?????
    ?)????????????

4
????
4.1 ???? 4.2 ???? 4.3 ???? 4.4 ???????????? ?????
????????
5
????????
  • ???????
  • ????
  • ????????
  • ?????????
  • ??????????????
  • ???????????
  • ????(????)
  • ????????(????)
  • ????????(????)

6
????
4.1 ???? 4.2 ???? 4.3 ???? 4.4 ???????????? ?????
??????????????
7
????????
  • ????GPS,??
  • ??????
  • ????????
  • ??????A-GPS

8
????
?????????????????????????????,?????????????
??????,???????????????????,???????????????????????
???????????????,?????????????,????????
  • ?????????
  • ??GPS
  • ???GLONASS
  • ?????
  • ????
  • GPS?????????????????

???? ?????? ???????? ??????
9
GPS????
GPS???Navigation Satellite Timing and Ranging /
Global Positioning System???,???????????????,?????
??????????????????????????????????????????????????
? ?1973????????????????GPS??????1993?????,?????20
?,??300???,???????????????????????????????????????
?????????????,???????????????????
10
GPS System
11
GPS Satellite
12
Key Features of GPS Satellites
Each GPS satellite has a VERY accurate (atomic)
clock
All GPS satellites are exactly synchronized to a
master ground clock
Each satellite transmits a unique Pseudo-Random
Noise (PRN) Code
The position and clock of each satellite is
precisely known and constantly monitored on ground
13
GPS Signal
  • 50 bps data signal, modulated by a Pseudo-Random
    Noise (PRN) code, which repeats every 1 ms
    transmitted at 1,575.42 MHz (L1).
  • Nominal received power on ground is -163 dBW
    (5x10-17 W)thats VERY low!!!
  • Compare it to typical received power in a mobile
    communications system (GSM) of a few mWGPS
    received power is 100 trillion times lower!

14
GPS????
  • 1973?,???????GPS??
  • 1983?,?????????????
  • 1989?,??????GPS????
  • 1994?,????????,????
  • 2000?,?????????/???????????

???? ?????? ???????? ??????
15
GPS????
  • ??????
  • 24????? ???6????55????????????????????28??
  • ??????(???????)
  • 1?????(??1???)
  • 4???????
  • 6??????
  • ??????
  • GPS???

???? ?????? ???????? ??????
16
GPS????
  • ??A?B?C???????,???????D???,????D???

17
GPS Receiver Position Calculation
How does 3-dimensional (3D) positioning work?
If you know the distance to 4 KNOWN locations
The fourth sphere (not shown) will intersect only
one of these two locations.
The third sphere will intersect the circle formed
by the other two spheres. This will now create
only two possible locations.
The two spheres will intersect forming a circle.
The location will be somewhere on the
circumference of this circle.
The location will be somewhere on the surface of
the sphere
3 Dimensional Fix!
18
??????
GPS???????????????????????????????,???????????????
?????????
??????????????????????????????????????????????????
???????,?????????????????????,???????????????????,
????(PR)?
D c?t ?t t2 - t1
19
(No Transcript)
20
GPS????
  • ?GPS???????,?????1?0????????????(????)???????
  • GPS????????????,??????C/A?????P(Y)?
  • C/A???1.023MHz,???1??,???300m
  • P???10.23MHz,???0.1??,???30m?
  • Y???P????????,???????
  • ??????????????????????????????????????????????????
    ,???????????????????????????????,?????????????????
    ????????????,???WGS-84????????????????????

21
????
????????GPS???????,??????????????A????????,??A??
???????????????????????????,??????A????????,?A????
?????????????????????????????,?????A??????????????
???????????,??????????????????
22
(No Transcript)
23
GPS????
  • GPS?????????????????,????????????????????,???????
    ?????GPS????????,??????????,????????GPS???????,???
    ????????????,?????????,????????GPS???????

??????????????????????????????????????,???????????
??????,????????????????????????????(Hydrogen)??(Ce
sium)??(Russium)?????????????100?????1????????????
????????????
24
??GPS????
  • ?GPS?????,????????
  • ?????????????????,?????????????????????????
  • ????????????????????????????
  • ?????????????????,??????????????????
  • ?????????????????,?????????????????????????,?
    ????GPS???????????

25
(No Transcript)
26
WGS-84 ???
WGS-84???(World Geodetic System?1984 Coordinate
System) ???????????????????????,???????????Z???BIH
(????)1984.0????????(CTP)??,X???BIH
1984.0??????CTP?????,Y??Z??X??????????,??1984?????
?????
27
????
  • ?????????????????????,????????????????????????????
    ??????????????????
  • ?????????????????????,????????????????????????????
    ??????

28
(No Transcript)
29
(No Transcript)
30
???GPS?
31
???GPS???
32
GPS?????
  • ??
  • ???
  • ????,???????
  • ??
  • ?????
  • ?????
  • ??GPS???

???? ?????? ???????? ??????
33
GPS????????
  • ?????????????
  • ???????????????????????
  • ?????,????????????????,????,??????

???? ?????? ???????? ??????
34
GPS????????
  • ?????,?????
  • ??????,????,????,??????,???????????????????
  • ????????????

???? ?????? ???????? ??????
35
??????
  • GSM????
  • ????????????
  • ????????????
  • ????????????????
  • ???????????,??????????

???? ?????? ???????? ??????
36
??????
  • COO??(Cell of Origin)
  • ?????????????????????
  • ??????????????
  • ????????,???????????????,????
  • ???????,??????

???? ?????? ???????? ??????
37
?????????
  • ????Trilateration
  • ????????????????
  • ?????????,??????

38
?????????
  • ??????/???(TOA/TDOA/RTOF)

TOA
TDOA
RTOF
39
??TOA????
  • ????
  • ?????????,??????????????????,?????????????????????
    ??
  • ??
  • ???
  • ????????????
  • ?????????????????

40
??TDOA???
  • ??
  • ?????????????????????,????????????????????????????
    ??,???????????,????????????????????

41
??????
  • ToA/TDoA???
  • ??????????
  • ?????????????????,???
  • AoA???

???? ?????? ???????? ??????
42
???????????
  • ??
  • ???GPS???,???????
  • ?????
  • ???????,???????
  • ??
  • ????????
  • ?????????,????

???? ?????? ???????? ??????
43
??????????
  • ??E-911??
  • ???????,???????????,????????
  • ?????????,??ToA,TDoA,AoA,RSS,A-GPS
  • ???????????,????

???? ?????? ???????? ??????
44
????????
  • ????????
  • ????
  • ??????????,?????????????
  • ???????,??????
  • ?????????
  • ????(GPS)?????,?????
  • ??????????????

???? ?????? ???????? ??????
45
????????
  • ???????????????ToA,TDoA,AoA??????????
  • RSS????
  • ??????????
  • ?????????(???Wi-Fi?ZigBee)
  • ???????????RFID????

???? ?????? ???????? ??????
46
RFID??????
  • ????
  • ??????RFID??
  • ???????RFID?????????,?????????
  • ??????,??????????
  • ????
  • ????
  • ????

???? ?????? ???????? ??????
47
??????
  • A-GPS
  • GPS?????????????
  • ????????????
  • ??????????????
  • ???????????

???? ?????? ???????? ??????
48
Factors that affect GPS accuracy
  • Imperfect satellites
  • Atmospheric effects
  • Multipath
  • Interferences
  • Signal strength
  • Geometry of the satellites used (DOP)
  • Receiver components

49
Atmosphere
Theoretical path
Actual path, delayed, phase shifted, attenuated
50150km
Ionosphere
Stratosphere
Troposphere
10km
50
Multipath
Direct Signal
Ground reflections
51
Multipath (2)
52
Signal Strength
53
Interference
54
Pros and Cons of GPS
  • PROS
  • It is a global system
  • In nominal conditions it is accurate (5-10m)
  • It is free for users!
  • CONS
  • It does not work indoors and presents degraded
    performance in high-density urban environments
  • In cold start without any previous information
    about the satellites it may take several minutes!

55
Solutions to Cons
  • It does not work indoors and presents degraded
    performance in high-density urban environments
  • In cold start without any previous information
    about the satellites it may take several minutes!
  • INCREASE RECEIVER SENSITIVITY!
  • AVOID HAVING TO WAIT TO DECODE NAVIGATION MESSAGE!

A-GPS
56
What is Assisted-GPS?
57
The concept of A-GPS
  • We have a rough estimate of the user position,
    then we can provide information about what
    satellites are in view
  • It can be as rough as 100s of kms
  • We can also give synchronisation information to
    aid the GPS receiver to acquire the satellites
    signals doppler shift and code phase delay.
  • We allow the receiver to (coherently) accumulate
    more signal -gt higher SNR! better
    sensitivity
  • The receiver starts looking for the satellites
    right where they are timing information it
    is immediately extracted
  • We can then provide the navigation data to the
    GPS receiver, and then we do not need to wait to
    decode the data from the satellite
  • This is achieved by having a reference GPS
    receiver station which is constantly receiving
    and decoding the GPS signals in view and
    extracting signal parameters (navigation data,
    signal doppler and signal delay)

58
The concept of A-GPS
  • A GPS monitoring station constantly receives
    signals from all visible satellites
  • It stores the navigation data, together with SV
    acquisition data
  • The A-GPS receiver is relatively close to the
    monitoring station so that it sees the same SVs.
  • The GPS receiver can request assisting data and
    then use it for a fast TTFF
  • The reference receiver sends signal measurements.

Dti Dfi
SV1 Code phase chips Doppler
Hz Navigation data SV2 Code
phase chips Doppler Hz
Navigation data SV3 Code phase
chips Doppler Hz Navigation
data
Lat 436415.360 Lon -1234749.083
59
Assisted-GPS (A-GPS)
  • In essence A-GPS is very similar to GPS except
    that a wireless network stores the GPS
    information
  • Time, position of the UE, GPS data
  • This information is referred to as Assistance
    Data
  • Assistance data is provided to the UE through the
    wireless network during positioning sessions
  • Allows UE to quickly acquire and measure GPS
    satellite signals

60
??????(?)
??AP?? ????Wi-Fi??????,?????,??AP???,???????
???? ?????? ???????? ??????
61
??????(?)
  • ????
  • ?????????????
  • ??????????,???????????

???? ?????? ???????? ??????
62
????
63
????
4.1 ???? 4.2 ???? 4.3 ???? 4.4 ???????????? ????,
???????????????
64
4.3 ????
  • ???????
  • ??????????????
  • ?????????????????
  • ??????????????????????????
  • ??????
  • ???????(ToA)
  • ????????(TDoA)
  • ?????????(RSS)

65
?????????
???? ????? ??????
  • ToA?TDoA??????????
  • ????????????????????????,???????
  • ?????????????
  • ????????????

66
?????????
???? ????? ??????
  • ????
  • ?????????
  • ????N?????
  • ??N??????????,????N???
  • ????????????????
  • ??????????????????,????
  • ??????????

67
?????????
???? ????? ??????
  • LANDMARC?????????????
  • ???????,??????RFID????????
  • ????????????????????????????,????,???1m????

68
(No Transcript)
69
??????????????????????????
70
???????
71
???????
72
???????,???????????????????????,???1???3???????,??
2???4?????,???????????????????????????,???????????
????1,????3?????????????????????????????,?????????
?????,????????????RFID?????????????
73
??????
  • ??????????????????????????????????(LBS)
  • ???????(Location Based Service,LBS)??????GIS
    ??????????????????????

??????? ??????
??????????????
???????????(????????) ???????????(???????????)
?????????(?????????10 m ???????????)
74
???????,???????????,??????????????????????????????
????,????????????????????
75
??????
  • ????,??????????????,???????????????????????????
    ??,????????????
  • ?????????????????????????????????????????????????
    ?,?????????????????????????????????????????

76
Examples
Chinese Food Fan Consumer habits protection
Psychiatric patient Location Privacy
77
Location-Based Services
query, user, location, time
local info, POIs,
LBS Provider
Alice
  • Problems of revealing location to LBS provider
  • Sensitive information can be inferred from
    location
  • Example being at the hospital, lawyer, church
  • Profiling daily routines, deviation from them,
    etc.
  • Please rob me

78
????????
??????
??
??????
79
??????
  • 1.??????
  • ??????????????,????????????,??????????????????
    ????
  • ??????????????????

80
??????
  • 2.????
  • ??????????????????(???????????)?

81
??????
  • 3.????
  • ????????????????????????????,???????????????,???
    ????,???????

82
??????
????????????????k- 1 ?????????????????????????????
??,???????????,??????????????????
  • 4. K-????
  • 1998?P.Samarati?L.Seweney?PODS???????,??????????
  • ?????????????????????K?1??????,???????K????,?
    ?????????????????K??????,???????????????
  • ?????????,???????????????????,????????

83
Example
Release Table
External Data Source
Name Birth Gender ZIP Race
Andre 1964 m 02135 White
Beth 1964 f 55410 Black
Carol 1964 f 90210 White
Dan 1967 m 02174 White
Ellen 1968 f 02237 White
84
K-????
85
K-????
k ???????,??????????????? ?????,k
???,??????,?????????????????????????????????????k
100 ????,??????????????,????????????????,?????????
??,? ?????????????
86
????
4.1 ???? 4.2 ???? 4.3 ???? 4.4 ???????????? ?????
?????????????
87
4.4 ????????????
  • ????
  • ????????????
  • ???????????
  • ????????????????????
  • ????
  • ?? vs. ??
  • ???? vs. ?????
  • ???? vs. ????

88
4.4 ????????????
  • ?????????
  • ???????????????
  • ??????????????
  • ??????????,???????
  • ?????
  • ?????,??????????500??
  • ????????????
  • ?????????????(?RFID??)??

89
Thank you!
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