High Sensitivity GPS Tracking Performance in Indoor Environment with Moderate Pedestrian Traffic Conditions Nadezda Sokolova B örje Forssell [email protected][email protected]. N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments. - PowerPoint PPT Presentation
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
High Sensitivity GPS Tracking Performance in Indoor Environment with Moderate Pedestrian
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
2
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
GPS Signal Challenges Indoors (1)
• Extremely weak LOS signal
• Shadowing and Fading effects
Heavy attenuation Multipath (short delay
multipath)
• Signal level differences Cross-correlation problems
• Interference from other RF systems
Cellular transmission Wireless internet
3
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
GPS Signal Challenges Indoors (2)
• Most of real life scenarios for users of handheld GPS devices include presence of other people around.
• A human body can produce up to 10 dB attenuation when blocking the signal path in close proximity to the receive antenna, while a person passing by the antenna at a distance of only a few meters affects signal reception a little less (<1 dB) [1].
• Effects of GPS signal obstruction by human body
should also be considered.
Wave scattering by a lossy dielectric cyllinder (approximation of an upright human body).
It is important to understand the indoor propagation environment for the development and design of future systems for positioning indoors.
4
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test Description (1)
-Same test equipment setup.
-Same satellite geometry (tests performed in 23 hours 56 minutes period).
-Same test path.-Warm start outside the
building.
Test A
Test B
Performed during a week day, people present in the building and along the test path.
Performed during a week end, no people present along the test path.
• Two tests were performed to investigate effects of human body interference effects on the tracking performance of a HSGPS receiver in the indoors environment.
5
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test Description (2)
Construction materials in the Electro- block.
Electro block views from the outside, passage inside the building, entrance.
6
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Description of the Test Equipment Setup
Parameter Value
Tracking L1, C/A code
Channels 16
Protocol UBX binary, NMEA
Tracking Sensitivity -158 dBm
Hot Start Sensitivity -148 dBm
Cold Start Sensitivity -142 dBm
Field test setup.
Main operating parameters of u-blox SuperSense HSGPS receiver.
Measurement path inside the Electro block, NTNU.
7
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test results (1)
• Signal strengths at the entrance varied from -136 dBm down to -144 dBm.
• C/No levels between 38
dBHz and 23 dBHz. • 6 satellites acquired and
tracked.
• Test A - two students passed by the receive antenna in about 1.5 meter distance. Result -loss of lock and necessity to reacquire the signals.
• Test initialisation outside
SVs C/No levels outside, at the entrance to the Electro block, test B, no people present.
SVs C/No levels outside, at the entrance to the Electro block, test A, people present.
8
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test results (2)
• C/No average levels measured for each particular satellite during both tests were almost the same, varying from 30.1 dBHz to 18.3 dBHz.
(giving signal levels of-156dBm to -144.2dBm).
• Signal losses due to change in type of material above the test path experienced in both tests.
• Test A- the receiver often loses lock on satellite signals.
• Test B- the receiver was able to continue tracking for longer periods.
• Inside the Electro block
C/No diagrams for each SV available under the tests inside the building.
9
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test results (3)
• Test A- navigation solutions put the receiver all the time at and around the entrance where the test was initialised.
• Test B- the receiver was able to produce navigation solutions which were spread along the test path.
SuperSense LEA-4H position solutions, test A (no people present).
SuperSense LEA-4H position solutions, test B (people present).
10
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Test results (4)
• As stated by the manufacturer, the HSGPS receiver used in the tests had tracking sensitivity like -158dBm and acquisition sensitivity (hot start) like -148dBm.
• GPS signal strength levels measured inside the Electro block were varying from -144,2dBm to -156dBm.
• With so extremely low signal strengths, signal attenuation caused by people in the building blocking the satellite signal paths or just passing by in close distance to the antenna can result in loss of signals even if the receiver has such a good tracking sensitivity as stated.
• More complex measurements and analyses should be performed to identify the exact degree of influence of this effect.
11
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
Conclusions
• A person blocking the satellite signal path or just passing by in close distance to the receive antenna can cause loss of signal and degraded accuracy in indoor and other degraded signal environments.
• Standing and moving people are additional and very unpredictable obstructions and sources of multipath that should be considered in combination with other effects degrading the GPS performance in pedestrian traffic environments.
• A user of a handheld GPS device should be aware of such limitations in order to use his device in the best way to get satisfactory results.
12
N. Sokolova, B.Forssell, HSGPS Tracking Performance in Indoor Environments
References
• [1] R.M.Allnutt, A.Dissanayake, K.T.Lin, C.Zaks, “Propagation considerations on L-band handheld communication service offerings via satellite”, IEEE Trans. on Antenna and Propagation, Vol.2, 1993, pp.800-803.
13
Integrated Low-Cost MEMS INS+HSGPS Performance for Pedestrian Navigation in a