1. MSIT 413 Wireless Technology Project
Team members: Jiaxi Wang,Pranith, Xin Zhou, Simeng Liu
Topic: Navigation system (GPS)

2. Part 1: Mainstream satellite navigation systems
Global Navigation Satellite System (GNSS)
Global Positioning System (GPS)
Global Satellite Navigation System (GLONASS)
Galileo (In development)
Compass (In development)
Regional Satellite Navigation Systems
BeiDou Navigation Satellite System (BDS)
Quasi-Zenith Satellite System (QZSS)
Indian Regional Navigational Satellite System (IRNSS)

3. Global Positioning System (GPS)
Country of origin: United Stated
Coverage: Global
Total satellites: 32
Precision: 5 meters
Created by the U.S. Department of Defense

4. Global Satellite Navigation System (GLONASS)
Country of origin: Russia
Coverage: Global
Total satellites: 24
Precision: meters
More efficiently at northern latitudes
Operated by the Russian Aerospace Defense Forces

5. The image shows the orbit and constellation of GLONASS (left) and GPS (right).

6. Galileo (In development)
Country of origin: European Union
Coverage: Global
Being operated entirely by civilians
Number of satellites: 30
Expected to be completed in 2019

7. Different categories of service
Low accuracy services: to general public, free of charge
High accuracy services: provided with a certain amount of fee to individuals and companies with the need.
High accuracy services are able to provide location services to its subscribers with accuracy of with only a couple centimeters deviations from the actual location.

8. Compass (In development)
Country of origin: China
Also known as Beidou 2
Coverage: Global
Number of satellites: 35
Expected to be completed in 2020

9. Used on different fields including:
Telecom services
Water resources
Public transportation
Forest fire prevention and public safety.

10. Indian Regional Navigational Satellite System(IRNSS)
Country of origin: India
Coverage: regional
Type: Millitary, Commercial
Total Satellites: 7
3 located in geostationary orbit
4 are inclined geosynchronous orbit
Status: Operational

11. The Quasi-Zenith Satellite System (QZSS)
Country of origin: Japan
Three satellites, each 120° apart, in highly incllined.
Coverage: regional
Total satellites: 4
Expected to be completed in 2018

12. Global Positioning System
System is made up of at least 24 satellites orbiting the Earth.there are 31 operational satellites in the GPS constellation.
The GPS satellite constellation transmits a signal for its own use and a separate signal that anyone with the technological wherewithal is free to access

13. The Satellite Blocks and Network
There are four types of functioning satellites in the GPS constellation, known as Blocks, with a fifth on the way.
Block IIA: in service for over 20 years.
Block IIR: in service 1997 with the last launched in The 12 orbiting IIRs are the core of today's Global Positioning System.
Block IIR(M):satellites began launching in 2005
- new jam-resistance for military signal
-the first to broadcast on L2C, a second civilian signal
-L2C is designated for use in commercial applications, improving on accuracy for dual- frequency receivers, higher power and better signal penetration in area with heavy vegetation.

14. The Satellite Blocks and Network
Block IIF: Began service in 2010 and the second was launched in 2011.Capable of broadcasting on the L5 frequency, the third frequency intended for civilian use
Under development is GPS Block III. The goal of GPS III is to add a fourth civilian GPS signal, L1C, which will allow the GPS network to interact with satellite navigation systems maintained by other governments such as Russia, Europe and possibly China.
The Navstar GPS Constellation

15. The GPS signal Transmits two radio signals : L1 and L2
Civilian GPS uses the L1 signal frequency ( MHz) in the UHF band
The GPS signal contains three different bits of information :
Pseudo random code: I. D. code that identifies which satellite is transmitting information.
Almanac data:data that describes the orbital courses of the satellites. Every satellite will broadcast almanac data for EVERY satellite.
Ephemeris data: data that tells the GPS receiver where each GPS satellite should be at any time throughout the day. Each satellite will broadcast its OWN ephemeris data showing the orbital information for that satellite only.

16. GPS receiver
A GPS receiver's job is to locate four or more of these satellites, figure out the distanc­e to each, and use this information to deduce its own location. This operation is based on a simple mathematical principle called trilateration.
2-D and 3-D Trilateration: 3-dimensional trilateration isn't much different from 2-dimensional trilateration, but it's a little trickier to visualize.So instead of a series of circles,you get a series of spheres.

17. GPS Calculation
The satellite begins transmitting the pseudo-random code. The receiver begins running the same digital pattern also exactly at that time. When the satellite's signal reaches the receiver, its transmission of the pattern will lag a bit behind the receiver's playing of the pattern.
The length of the delay is equal to the signal's travel time. The receiver multiplies this time by the speed of light to determine how far the signal traveled. Assuming the signal traveled in a straight line, this is the distance from receiver to satellite.
Every satellite contains an expensive atomic clock, but the receiver itself uses an ordinary quartz clock, which it constantly resets. In a nutshell, the receiver looks at incoming signals from four or more satellites and gauges its own inaccuracy.

18. Route Selection Algorithms
From the departure point, there are so many routes to the destination.
How can computer always determine the routes we would like to go precisely?

19. Dijkstra's algorithm
Dijkstra designed this algorithm at the Mathematical Center in Amsterdam in 1956 to demonstrate capabilities of a new computer.
Purpose: to get the shortest path
Node - Intersection
Edge - Distance
Visit all nodes and calculate all paths.
Core of modern route selection algorithms.

20. Greedy Best-First-Search Algorithm
Greedy BFS: nodes with shortest estimated(heuristic) distance to destination
Dijkstra's: nodes with shortest distance to the source
Greedy Best-First-Search (quicker) Dijkstra's algorithm

21. Greedy Best-First-Search Algorithm
Greedy BFS: does not always give us a shortest path if there are obstacles.
Dijkstra: always gives us a shortest path, altough it takes much efforts.
Greedy BFS Dijkstra

22. A* algorithm
Combine Dijkstra's algorithm and Greedy Best-First-Search.
f(n) = g(n) + h(n)
g(n): distance from source to the node
h(n): distance from the node to the destination

23. Assisted GPS
Often abbreviated as A-GPS - In fact, it is a 3GPP standard
Uses mobile network to enhance positioning performanace
Two modes: - Mobile Station Based (MSB) - Mobile Station Assisted (MSA)

24. A-GPS
Time-to-first-fix (TTFF) - Time duration that a device fixes its location after a cold boot
The faster the device moves, the longer the TTFF - Many users choose to stop moving in order to shorten TTFF
Solution: MSB

25. A-GPS
MSB mode - Device acquires almanac and precise time from A-GPS servers - Calculate locally and perform first fix
Field test (MSB) - HTC Artemis (Windows Mobile 5.0) - TTFF without A-GPS: 3 minutes, with A-GPS: < 1 minute - Very economical: EDGE data connection, KB level of data usage

26. A-GPS
MSA mode - Minimal device operation: only needs minimal signals from satellite - A-GPS server provides rest of data and offload calculations - Positioning data are sent back to device
Drawback of MSA mode - Service is not free

27. Cell tower triangulation
Lightweight solution comparing with GPS D positioning - No TTFF
Every cell tower is unique - Mobile country code (MCC), Mobile network code (MNC), Location area code (LAC), Cell ID (CID), Absolute radio frequency channel number (ARFCN), Base station identity code (BSIC), etc Public database with cell towers’ geolocation

28. Cell tower triangulation
Signal strength -> Distance
Unique cell towers -> Geolocation
Minimum 3 cell towers required - FCC claims that 3 cell towers can locate a device within an area of about 0.75 sq mi

29. Wi-Fi indoor positioning
No satellite signals available indoor
Public buildings have demand for indoor positioning - High Wi-Fi coverage rate - Only needs 2D positioning - No interference from different floors

30. Wi-Fi indoor positioning
Wi-Fi access point fingerprinting - MAC address is globally unique - AP won’t be moving often
Similar to cell tower triangulation

31. Wi-Fi indoor positioning
Angle of Arrival (AoA) - Multipath signals -> multiple antennas - AoA -> distance between AP and client -> triangulation positioning - Complicated algorithms required

32. PowerSpy
PowerSpy: Location Tracking using Mobile Device Power Analysis - Power consumption -> location
Known facts - Power consumption depends on cellular signal strength - Device moving at driving speed -> minor random interference dropped

33. PowerSpy
Basic assumption - Cell towers will not move frequently Signal strength distribution is stable

34. PowerSpy
Smartphone moving along same route -> similar power consumption pattern - Prerecord power consumption profile Experiments show that even different phones have similar power profile

35. PowerSpy
Pattern match with machine learning - Time variation - Partial match
Estimate user’s actual route by putting pieces together

36. Q&A