How to Improve Forward Link Positioning for Cellular Networks? III. Hearability and Accuracy

How to Improve Forward Link Positioning ... ? I. Introduction
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

Hearability Issue

Hearability of a forward-link positioning system usually is quantified by how many reference signals a terminal may utilize to make a positioning fix in a pre-defined positioning duration.  In theory, a terminal need measure parameters of only 4 different reference signals for a precise three-dimension fix.  However, more reference signals a terminal can use, more diversity benefits a terminal may use for a more accurate positioning fix.

A hearability issue of a cellular positioning network generally is a dimension limitation issue.  It mostly is due to limitations of network geometry and network deployment.  In other words, it is a network issue.  For example, for a given cellular network, say a CDMA2000 1x RTT network or a WCDMA network, its hearability mainly depends on a network topology of the cellular network and a frequency reuse factor of the cellular network.  The network topology including network sectorization may affect achievable DoP values for positioning.  The frequency reuse factor may have a significant impact on co-channel interference to a terminal, which in turn relates to the positioning accuracy achievable by the terminal.  Hearability of an exemplary CDMA2000 1x RTT network is shown in Figure 1.

Figure 1. The hearability of CDMA2000 1x Pilots for AFLT, IEEE ICC 2008 "cdma2000 Highly Detectable Pilot" 
On the other hand, since major considerations for an actual deployment of cellular network base stations are voice and data service capacity, environmental impact and financial limitations, etc.,  a mobile phone network usually is not optimized for mobile positioning in nature.

Accuracy Issue

Positioning accuracy of cellular network forward link positioning is a dimension limitation issue.  Mainly the accuracy is limited by a frequency reuse factor and available bandwidth.  In general, given a certain positioning duration, wider bandwidth received reference signals have, more uncorrelated signal samples a terminal can obtain.  On the other hand, it is known that an achievable SNR highly depends on the frequency reuse factor of a cellular network.  More particularly, a CRLB of the achievable positioning accuracy is asymptotically linear to the number of uncorrelated signal samples and SNR value in dB.

In addition, from a signal processing or a receiver design perspective, a correlation between received signal samples largely depends on a sampling frequency on the received signals and achievable multipath resolution.  Multipath resolution is a function of both a channel delay profile and a bandwidth of received signals.  For example, a statistic delay profile of an exemplary cellular network is shown in Figure 2.  Additional discussions on the statistic delay profile can be found in another blog, "How Wider A Wideband Channel Should be?".   In general, wider the bandwidth of a transmit signal is and  higher the multipath resolution of a channel is achievable.

Figure 2. A statistic model of delay spread. 

Additional Reference

[1] E. Sousa, V. Jovanovic, C. Daigneault, “Delay spread measurements for the digital cellular channel in Toronto”, IEEE Trans. on Vehicular Technology, Nov 1994
[2] J. Ling, D. Chizhik, D. Samardzija, R. Valenzuela, “Wideband and MIMO measurements in wooded and open areas”, Lucent Bell Laboratories,
[3] K. Baum, “Frequency-Domain-Oriented Approaches for MBWA: Overview and Field Experiments”, Motorola Labs, IEEE C802.20-03/19, March 2003
[4] L. Greenstein, V. Erceg, Y. S. Yeh, M. V. Clark, “A New Path-Gain/Delay-Spread Propagation Model for Digital Cellular Channels,” IEEE Transactions on Vehicular Technology, VOL. 46, NO.2, May 1997, pp.477-485.
[5] A. Algans, K. I. Pedersen, P. Mogensen, “Experimental Analysis of the Joint Statistical Properties of Azimuth Spread, Delay Spread, and Shadow Fading,” IEEE Journal on Selected Areas in Communications, Vol. 20, No. 3, April 2002, pp. 523-531.
[6] Spatial Channel Model AHG (Combined ad-hoc from 3GPP & 3GPP2), “Spatial Channel Model Text Description ”, 3GPP, 2003

Comments

Post a Comment

Popular posts from this blog

Hack Apple TV for Watching Chinese TVs and Videos

Image
[ Hack Patriot Box Office for Watching Chinese Videos and TVs ] Figure 1.   Apple TV Apple TV (ATV) is a  multi-function set-top box  designed by Apple Inc. originally as a  networked media player  for streaming multimedia contents to a television or an external monitor.  Now, it seemingly evolves into a iPod Touch without a touch screen but with a relatively inexpensive MSRP price tag of $99.  (Indeed, if you have an old generation iPod Touch, you may think about mirroring or airplay it onto a television instead.)  On March 7, 2012, Apple Inc. released a  3rd generation ATV (ATV3)   that includes a 32 nm ARM Cortex-A9 Apple A5 SoC (the same process as used in a 5th generation iPod Touch, a new iPad 2 and an iPad Mini) and 512MB mobile DDR2 memory (the same amount of memory as used in an iPhone 4).  An ATV3 has a buit-in 6 W power supply with no cooling fan necessary.  Unfortunately, until now, there is no publ...
Read more

Hack Patriot Box Office for Watching Chinese Videos and TVs

As requested by friends, this blog is dedicated to explain a simple way for watching Chinese TV programs and movies on a television or monitor for free using a special media player instead of a computer.  Compared with many well-known approaches watching Chinese TVs on a computer, this one seems much more operation-friendly as well as eco-friendly.  It is attractive for many Chinese families who may not always be technical savvy.  In addition, as I know, the operation cost or power consumption of this kind of MIPS-based media players is relatively low.  Its total power consumption usually is no more than 15 watts.  Meanwhile, a typical power consumption of a PC CPU, even some mobile or laptop CPUs,  itself is known to be between 50 watts and 100 watts.  Even a power efficient Intel Atom CPU usually is inside a range between 5 and 20 watts, as I remember.  Nowadays a typical home desktop demands a power supply of no less than 250 watts, not to men...
Read more

How to Broadcast Multimedia Contents? II Lessons from The Channel

Image
What Is The Next for Mobile System Design? I A Single-Cell Model Perspective on Downlinks [How to Broadcast Multimedia Contents? I Introduction] [How to Broadcast Multimedia Contents? IV Hierarchical Modulation] [How to Broadcast Multimedia Contents? V Overloaded Transmission and IC] [How to Broadcast Multimedia Contents? VI Open-Loop MIMO for BCMCS] [How to Broadcast Multimedia Contents? VII Network Layer or Stream Layer Design] COST 231 model, which was developed by European COST Action 231, and its variations are the most popular radio propagation model adopted in various standardization bodies, such as 3GPP, 3GPP2 and IEEE. Its modifications include COST 231-Hata Model and COST 231-Walfisch-Ikegami Model . The mathematical formulation of the COST 231-Hata model path loss in dB is PL = 46.3 + 33.9 logf - 13.82log h BS - a( h MS ) + [ 44.9-6.55logh BS ] log d + C which features a carrier frequency f between 800MHz and 2GHz, an above-neighborhood base station antenna w...
Read more