Application Note
AN042
Table of Contents
1 KEYWORDS ................................................................................................................... 1
2 INTRODUCTION............................................................................................................. 1
3 LOCATION ENGINE....................................................................................................... 3
3.1 NODE TYPES.............................................................................................................. 4
3.1.1 Reference node .................................................................................................................4
3.1.2 Blind Node........................................................................................................................4
3.2 THE LOCATION HARDWARE ......................................................................................... 4
3.2.1 Input..................................................................................................................................5
3.2.2 Output...............................................................................................................................5
4 RECEIVED SIGNAL STRENGTH INDICATOR (RSSI) ................................................. 6
4.1 OFFSET..................................................................................................................... 6
4.2 LINEARITY.................................................................................................................. 6
4.3 THEORETICAL SIGNAL PROPAGATION........................................................................... 7
4.4 RSSI – PRACTICAL CONSIDERATIONS ......................................................................... 7
4.4.1 Simple ways to filter the RSSI values................................................................................7
4.4.2 Calculated RSSI vs. measured RSSI.................................................................................8
5 DIFFERENT PARAMETERS – INFLUENCE................................................................. 9
5.1 A – RSSI VALUE MEASURED ONE METER FROM THE SENDER ...................................... 10
5.1.1 Measuring A ...................................................................................................................10
5.1.2 A versus calculated position...........................................................................................11
5.2 N – SIGNAL PROPAGATION COEFFICIENT ................................................................... 12
5.2.1 Measuring n....................................................................................................................13
5.3 NUMBER OF REFERENCE NODES ............................................................................... 14
6 SOFTWARE ALGORITHMS ........................................................................................ 15
6.1 SELECTION OF “BEST” REFERENCE NODES................................................................. 15
6.2 EXTENSION OF THE COVERED AREA........................................................................... 15
6.3 LEVEL/ FLOOR INDICATION ........................................................................................ 16
7 CONTROL SYSTEM/ CENTRAL ................................................................................. 18
8 GENERAL INFORMATION .......................................................................................... 19
8.1 DOCUMENT HISTORY................................................................................................ 19
9 IMPORTANT NOTICE .................................................................................................. 20
Application Note AN042 (Rev. 1.0)
SWRA095
Page 2 of 20
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