Monday, April 2, 2012

How to Improve Forward Link Positioning for Cellular Networks? I. Introduction

How to Improve Forward Link Positioning ... ? III. Hearability and Accuracy
1x HDP Enhancements
Enhanced Location Based Services Support in cdma2000
Enhance Downlink Positioning in WiMAX/16m
How Wide A Widband Channel Should Be?
IEEE ICC 2008 Tutorial, Location Based Services for Mobiles
Location Based Services for Mobiles: I. Introduction

There are many ways locating a mobile in a cellular network. The basic methods include dead reckon, proximity sensing, signal signature tracking, trilateration, multilateration, triangulation, etc. Some major approaches for cellular networks can be illustrated in Figure 1.

Figure 1. Mobile Positioning Techniques, IEEE ICC 2008 "Location Based Services for Mobiles"

Positioning performance is understood through quantifying the two parameters, hearability and accuracy. Hearability indicates how many hearable good references a terminal can track in a single snapshot. A typical number should be not less than 4. Accuracy is a well-known parameter for understanding the stability of each fix.  Usually it is quantified through the 2nd order statistics of fixes. A comparison of several mobile positioning schemes is shown in Figure 2.

Figure 2. A comparison of mobile positioning schemes
For cellular network forward link positioning, its performance is determined by 1) reference signal bandwidth, 2) channel delay spread profile, 3) co-channel interference  and 4) dilution of precision ( DoP ) or network topology.

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