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Reasons for Network-based Positioning (2/2)
For scenarios wherein there are many AMSs requesting LBSin a short time or with high accuracy, handset-based
positioning is a better choice
However, for other scenarios, network-based positioning ismore efficient and introduces less complexity to the system
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Problems in D4
In D4, only the following text about network-basedpositioning is mentioned and the description is not clear
AMS and ABS capability to enable measurement of RTD based on
ranging channel transmission (U-TDOA and TOA) (see Subclause
6.3.25)
There are currently two types of ranging channel and the above textdoes not specify which type
According to D4, both types of ranging channel allocation are
contention-based so its unlikely for AMS to meet E911requirement due to intra-cell interference
Only the allocation for initial ranging, handover ranging, periodic
ranging is mentioned in D4 and all are contention-based
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Definition of Terminology
TOA measurement algorithm
The algorithm used to measure the TOA of the positioning reference signal sent
by the target AMS to the serving/neighbor ABSs. The TOA measurements can
be transformed to the distances between the target AMS and the
serving/neighbor ABSs.
Positioning algorithm
The algorithm which computes theposition of the target AMS using TOAmeasurements.
If TOA measurements are used for the computation of position, it is called U-
TOA positioning algorithm.
If relative differences of TOA measurements are used for the computation of
position, it is called U-TDOA positioning algorithm.
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Proposed U-TDOA/TOA Positioning Mechanism (1/4)
Scenario #1:
Serving cell interference: noneCooperative neighboring cell interference: none
One reference signal transmission for one TOA measurement Physical ranging channel for non-synchronized AMSs is utilized as reference signal for
uplink TOA measurement
Dedicated radio resource for one AMS so as to suppress intra-cell interference An assignment A-MAP is used to allocate the radio resource to a specific AMS for LBS
ranging
Dedicated radio resource among cooperative cells so as to suppress inter-cellinterference Inter-BS coordination is used to silence the radio resource for LBS ranging in
cooperative cells
More than one TOA measurements can be conducted over a period of time toimprove positioning result The number of TOA measurements can be adjusted by serving BS and broadcasted to
MSs e,g,: the adjustment is based on current traffic load
The number of TOA measurements can be fixed and predefined in the system
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Proposed U-TDOA/TOA Positioning Mechanism (4/4)
Network or Serving ABS Initiation
MS Serving BS Cooperative BSs
Select cooperative BSs
Necessary Information for Positioning
Radio Resource Allocation for Positioning
Positioning Reference SignalSame Time
Instant Reference Signal
Detection & TOA
Measurement
Reference Signal
Detection & TOA
Measurement
TOA Measurement Results
Positioning
Positioning Results
1
2
3
4 55
Repeat Step
3~6 Several
Times
Repeat Step
3~6 Several
Times
Repeat Step
3~6 Several
Times
6
7
8
9
Network-based Positioning
is initiated by the Network
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Text Proposal
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Serving ABS and two neighbor ABSs cooperate to perform positioning
Format 0 non-synchronized ranging signal is transmitted by the AMS to be
positioned
Code index of Zadoff-Chu sequence adopted by the AMS is known to the serving
and neighbor ABSs
Serving and neighbor ABSs execute TOA measurements for the ranging signal
transmitted by the AMS U-TDOA/TOA positioning is computed using algorithm [4] based on TOA
measurements of serving and neighbor ABSs
Block diagram of TOA measurement algorithm is shown in the figure below
TOA Measurement Algorithm
RangingSignal
Timing
LPF RCPRemoval
FFT Extraction ofRanging Code
ZeroPadding
IFFT PeakTest
ObtainTiming
Ranging CodeRCP: Ranging Cyclic Prefix
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References
[1] IEEE C80216m-09/2086, Evaluation of D-TDOA Positioning
[2] IEEE P802.16m/D4. DRAFT Amendment to IEEE Standard for Local and
metropolitan area networksPart 16: Air Interface for Broadband Wireless Access
SystemsAdvanced Air Interface / January 2010
[3] IEEE 802.16m-07/002r9, IEEE 802.16m System Requirement Document (SRD)/2009-09-24
[4] Fletcher, R., (1971): A Modified Marquardt Subroutine for Nonlinear Least Squares.
Rpt. AERE-R 6799, Harwell