Wireless Location in CDMA Cellular Radio Systems
With the increasing market penetration of cellular telephones, the number of E-911 calls placed by cellular telephones has grown cons- erably. This growth in E-911 calls led to a 1996 FCC ruling requiring that all cellular, PCS, and SMR licensees provide location information for the support of E-911 safety services. The provision of such location information is to be implemented in two phases. Phase I, whose deadline has already been passed, requires that wireless carriers relay the caller’s telephone number along with location of the cell site and/or sector se- ing the call, to a designated Public Safety Answering Point (PSAP). This information allows the PSAP to return the call if disconnected. Phase II, to be completed by October 1, 2001, is much more stringent and requires that the location of an E-911 caller be determined and reported with an rms location accuracy of 125 m in 67% of the cases. The applications of wireless location technology extend well beyond E-911 services. Location information can be used by cellular telephone operators themselves for more effective management of their radio - sources, so as to achieve greater spectral efficiencies. Resource m- agement algorithms such as hand-offs between cell sites, channel assi- ments, and others can all benefit from subscriber location information. Location information obtained from vehicular based cellular telephones can be used as an input to Intelligent Transportation Systems (ITS), and in particular traffic management and traveler information systems.
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LOCATION METHODS AND IMPAIRMENTS
PERFORMANCE OF LOCATION IN CDMA SYSTEMS
TOA ESTIMATION IN MULTIPLEACCESS INTERFERENCE
ANALYSIS AND MITIGATION OF NLOS EFFECTS
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accurate location algorithm amplitudes and delays analysis antenna approach assumed autocorrelation function CDMA CDMA systems cellular systems Chapter code acquisition code phase code tracking computing covariance Cramér-Rao bound CRLB cross-correlation defined delay estimation derived developed effect equation estimate bias Gaussian approximation Gold codes handoff IEEE IEEE Trans Kalman filtering linear lines of position location algorithms location error location estimate location in CDMA location methods location system loop matrix microcells mitigate multipath fading multipath propagation multiple-access interference NC-DLL near-far ratio NLoS bias NLoS BSs NLoS error NLoS propagation nonlinear number of BSs parameter estimators path loss performance PN sequences radiolocation random variables range estimates scattering shown in Fig simulations spread spectrum spreading codes standard deviation Taylor series TDoA estimates TDoA location techniques time-based ToA and TDoA ToA measurements ToA method ToA or TDoA users Vehicular Technology wireless location