doc.: ieee 802.22-06/0206r1 submission november 2006 ivan reedeslide 1 ranging and location for...

November 2006

Ivan ReedeSlide 1

doc.: IEEE 802.22-06/0206r1

Submission

Ranging and Location for 802.22 WRANsIEEE P802.22 Wireless RANs Date: 2006-11-15

Name Company Address Phone email

Authors:

Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.22.

Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair Carl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at [email protected].>

Ivan Reede Montreal,CA 514-620-86522 [email protected]

November 2006

Ivan ReedeSlide 2

doc.: IEEE 802.22-06/0206r1

Submission

Abstract

A means to range802.22 links from base stations to customer premise equipment

inter customer premise equipments distances

inter base stations distances

Means to apply obtained results to establish the geographic location of these devices

November 2006

Ivan ReedeSlide 3

doc.: IEEE 802.22-06/0206r1

Submission

Location methods

• There are two basic data acquisition methods– Direction Finding– Ranging

• Both can be used together to determine a location from another location

• Both can be used without the other to determine a location from a group of other locations

November 2006

Ivan ReedeSlide 4

doc.: IEEE 802.22-06/0206r1

Submission

Direction Finding

• Conventionally performed by CW systems– CW time difference of arrival at the sensors– Results obtained from difference in time of arrival– Time difference (phase) between arials is converted to bearing– Requires known stable wave front

Source

Arial 1

Arial 2

November 2006

Ivan ReedeSlide 5

doc.: IEEE 802.22-06/0206r1

Submission

Ranging

• Difficult for some legacy PHY layers• Difficult for some legacy MAC layers• Well suited for higher bandwidth (fast) (PHY)

November 2006

Ivan ReedeSlide 6

doc.: IEEE 802.22-06/0206r1

Submission

Ranging over OFDM

• Well suited for PHY layer• May be supported by MAC layer• Requires a conceptually simple addition

November 2006

Ivan ReedeSlide 7

doc.: IEEE 802.22-06/0206r1

Submission

• OFDM receivers inherently effect range bearing information collection in normal operations

• Such information is required for their operation• Such information has not yet been recognized in any public

documentation as range bearing• In a 6 MHz BW channel, 1 meter ranging resolution may be

achieved

By the following means...

OFDM System ExampleAssertion Overview

November 2006

Ivan ReedeSlide 8

doc.: IEEE 802.22-06/0206r1

Submission

OFDM System ExampleFounding Premises

• OFDM systems transmit using a plurality of carriers• These carriers are at slightly different frequencies at RF, but

are harmonically related at baseband• They are related by the fact that they are all transmitted

simultaneously in a package called an OFDM symbol

November 2006

Ivan ReedeSlide 9

doc.: IEEE 802.22-06/0206r1

Submission

• The source of the OFDM symbol is usually an IFFT device• The symbol output is generally composed of a sum of sine

and cosine waves• All of these sine and cosine waves

– Start at the beginning of each symbol– End at the end of each symbol– Sine waves begin and end with zero values– Cosine waves begin and end with full amplitude values at symbol edges

OFDM System ExampleModel Overview

November 2006

Ivan ReedeSlide 10

doc.: IEEE 802.22-06/0206r1

Submission

• The receiver is generally composed of an FFT device• This device acts as a multi-carrier QPSK or n-QAM

demodulator• Each carrier can be demodulated as QPSK, 16-QAM,

64-QAM or other• As such, the OFDM receiver extracts amplitude and

phase information from each carrier


November 2006

Ivan ReedeSlide 11

doc.: IEEE 802.22-06/0206r1

Submission

• Current receiver designs use pilot carriers to align the constellation demodulation process

• Assume, by standardization– That a pilot carrier be emitted with a known phase

• The receiver, in aligning to this carrier, essentially effects a “phase lock” to this pilot

• It demodulates with a known phase resolution– ~±45° for QPSK, ~±7.5° for 64-QAM


November 2006

Ivan ReedeSlide 12

doc.: IEEE 802.22-06/0206r1

Submission

To demodulate QPSKphase lock must be

much better than ±45°

OFDM System ExampleQPSK Constellation

November 2006

Ivan ReedeSlide 13

doc.: IEEE 802.22-06/0206r1

Submission

To demodulate 16-QAMphase lock must be

much better than ±19°

OFDM System Example16-QAM Constellation

November 2006

Ivan ReedeSlide 14

doc.: IEEE 802.22-06/0206r1

Submission

To demodulate 64-QAMphase lock must be

much better than ±7.5°

OFDM System Example64-QAM Constellation

November 2006

Ivan ReedeSlide 15

doc.: IEEE 802.22-06/0206r1

Submission

• Transmitters internally use at least one clock• The symbols they transmit are related to this clock• By transmitting an OFDM symbol, they inherently

broadcast their space-time reference frame, relative to their geolocation and their clock

OFDM System ExampleTransmitter Space-Time Reference Frame

November 2006

Ivan ReedeSlide 16

doc.: IEEE 802.22-06/0206r1

Submission

Tx

Symbols emanatingfrom the transmitter

Transmitted wave conveys the Tx's Space-time frame

OFDM System ExampleTransmitter Space-Time Reference Frame

November 2006

Ivan ReedeSlide 17

doc.: IEEE 802.22-06/0206r1

Submission

• If the receiver knew exactly at what time the symbol was sent by the transmitter, the receiver could determine the distance from the flight time

• The receiver lacks this knowledge• The receiver, however, can lock an internal time

base (i.e. a counter) to the received wave• The receiver can therefore create a relative

space-time frame from a received OFDM symbol

OFDM System ExampleReceiver Premises

November 2006

Ivan ReedeSlide 18

doc.: IEEE 802.22-06/0206r1

Submission

• Assume a transmitter emits an OFDM symbol that contains a pilot carrier whose frequency is 3 KHz

• The wavelength associated with this frequency is ~100 km.

• A 64-QAM receiver, can lock its time base to this pilot within ±7.5°

• This creates a receiver relative space-time frame– in a 0-100 km radius to a 2.08 km resolution

OFDM System ExampleFundamental Operating Principles

November 2006

Ivan ReedeSlide 19

doc.: IEEE 802.22-06/0206r1

Submission

1

1

vp

10 p

sam ples

0 0 . 063 0 . 13 0 . 19 0 . 25 0 . 31 0 . 38 0 . 44 0 . 5 0 . 56 0 . 63 0 . 69 0 . 75 0 . 81 0 . 88 0 . 94 11

0

1B a s e b a n d t im e d o m a in s ig n a l

D A C ou tp u t sam p le #

OFDM System ExampleTransmitted 3 Khz Wave Symbol

November 2006

Ivan ReedeSlide 20

doc.: IEEE 802.22-06/0206r1

Submission

A ±7.5° quantizationamounts to ±2.08 km

space-time uncertainty

OFDM System ExampleReceiver Space-Time Reference Frame

November 2006

Ivan ReedeSlide 21

doc.: IEEE 802.22-06/0206r1

Submission

A ±7.5° quantizationamounts to a

100 km range ±2.08 kmspace-time frame

uncertainty

Rx

Tx

OFDM System ExampleReceiver 3 Khz wave Space-Time Reference Frame

November 2006

Ivan ReedeSlide 22

doc.: IEEE 802.22-06/0206r1

Submission

A ±7.5° quantizationamounts to a

100 km range ±2.08 kmspace-time frame

uncertainty

Rx

Tx

Receiver 3KHz wave Space-time frame

OFDM System ExampleReceiver 3 Khz wave Space-Time Reference Frame Snapshot

November 2006

Ivan ReedeSlide 23

doc.: IEEE 802.22-06/0206r1

Submission

• Assume the transmitter emits an OFDM symbol that contains a pilot carrier whose frequency is 6 KHz

• The wavelength associated with this frequency is ~50 km.• A 64-QAM receiver, can lock its time base to this pilot

within ±7.5°• This creates a wrapped relative space-time frame

– in a 0-50 km radius to a 1.04 km resolution– in a 50-100 km radius to a 1.04 km resolution

OFDM System Example(cont.)

November 2006

Ivan ReedeSlide 24

doc.: IEEE 802.22-06/0206r1

Submission

Transmitted 6 KHz wave symbol

1

1

vp

10 p

sam ples

0 0 . 063 0 . 13 0 . 19 0 . 25 0 . 31 0 . 38 0 . 44 0 . 5 0 . 56 0 . 63 0 . 69 0 . 75 0 . 81 0 . 88 0 . 94 11

0




November 2006

Ivan ReedeSlide 25

doc.: IEEE 802.22-06/0206r1

Submission

Rx

Tx

Receiver 3 and 6 Khz wave Space-time frame


November 2006

Ivan ReedeSlide 26

doc.: IEEE 802.22-06/0206r1

Submission

A ±7.5° quantizationover 360° amounts to ±1.04 km resolutionover a 50 km range space-time frame

uncertainty

Rx

Tx

Receiver 6 Khz wave Space-time frame

The space-time framewraps twice through 360°

in a 100 km range


November 2006

Ivan ReedeSlide 27

doc.: IEEE 802.22-06/0206r1

Submission

• Using both pilots, the OFDM 64-QAM receiver• May create a space-time frame

– With 1.04 km resolution– Within a 0-100 km radius


November 2006

Ivan ReedeSlide 28

doc.: IEEE 802.22-06/0206r1

Submission

Transmitted 3 and 6 KHz waves symbol

1 .755

1 .755

vp

10 p

sam ples

0 0 .063 0 .13 0 .19 0 .25 0 .31 0 .38 0 .44 0 .5 0 .56 0 .63 0 .69 0 .75 0 .81 0 .88 0 .94 12

0


D A C ou tpu t sam p le #

OFDM System ExampleTransmitted 3 and 6 Khz Wave Symbol

November 2006

Ivan ReedeSlide 29

doc.: IEEE 802.22-06/0206r1

Submission

Rx

Tx

Receiver 3 and 6 Khz wave Space-time frame

Using both wavesyields an unwrapped

2 km resolution100 km range

space-time frame


November 2006

Ivan ReedeSlide 30

doc.: IEEE 802.22-06/0206r1

Submission

• Assume the transmitter emits an OFDM symbol that contains a pilot carrier whose frequency is 12 KHz

• A 64-QAM receiver, can lock its time base to this pilot within ±7.5°

• Using these pilots, the OFDM 64-QAM receiver• May create a space-time frame

– With 0.52 km resolution– Within a 0-25 km radius– Within a 25-50 km radius– Within a 50-75 km radius– Within a 75-100 km radius


November 2006

Ivan ReedeSlide 31

doc.: IEEE 802.22-06/0206r1

Submission

Transmitted 12 KHz wave symbol

1

1

vp

10 p

sam ples

0 0 . 063 0 . 13 0 . 19 0 . 25 0 . 31 0 . 38 0 . 44 0 . 5 0 . 56 0 . 63 0 . 69 0 . 75 0 . 81 0 . 88 0 . 94 11

0




November 2006

Ivan ReedeSlide 32

doc.: IEEE 802.22-06/0206r1

Submission

Transmitted 3 and 6 and 12 KHz wave symbol

2 .227

2 .227

vp

10 p

sam ples

0 0 .063 0 .13 0 .19 0 .25 0 .31 0 .38 0 .44 0 .5 0 .56 0 .63 0 .69 0 .75 0 .81 0 .88 0 .94 14

2

0

2



OFDM System ExampleTransmitted 3 and 6 and 12 Khz Wave Symbol

November 2006

Ivan ReedeSlide 33

doc.: IEEE 802.22-06/0206r1

Submission

Rx

Tx

Receiver 3 and 6 and 12 Khz wave Space-time frame

Using all 3 wavesyields an unwrapped0.52 km resolution

100 km rangespace-time frame


November 2006

Ivan ReedeSlide 34

doc.: IEEE 802.22-06/0206r1

Submission

• With more pilot's, as follows

3000 100000 2083.33 5277.78 125006000 50000 1041.67 2638.89 6250

12000 25000 520.83 1319.44 312524000 12500 260.42 659.72 1562.548000 6250 130.21 329.86 781.2596000 3125 65.1 164.93 390.63192000 1562.5 32.55 82.47 195.31384000 781.25 16.28 41.23 97.66768000 390.63 8.14 20.62 48.83

1536000 195.31 4.07 10.31 24.413072000 97.66 2.03 5.15 12.215997000 50.03 1.04 2.64 6.25

Pilot Baseband Frequency (Hz)

Wavelength range (m)

'±7.5° rangeresolution (m)

'±19° rangeresolution (m)

'±45° rangeresolution (m)


November 2006

Ivan ReedeSlide 35

doc.: IEEE 802.22-06/0206r1

Submission

Transmitted 12 pilot wave symbol

6 .411

6 .411

vp

10 p

sam ples

0 0 .063 0 .13 0 .19 0 .25 0 .31 0 .38 0 .44 0 .5 0 .56 0 .63 0 .69 0 .75 0 .81 0 .88 0 .94 110

5

0

5



OFDM System ExampleTransmitted 12 Pilot Example Wave Symbol

November 2006

Ivan ReedeSlide 36

doc.: IEEE 802.22-06/0206r1

Submission

• Using multiple pilots, the OFDM 64-QAM receiver• May create a space-time frame

– With 1 m resolution– Within a 0-100 km radius

• It still does not know the transmitter to receiver distance

• It knows the space-time frame of the signal• It may lock its time base to that space-time frame


November 2006

Ivan ReedeSlide 37

doc.: IEEE 802.22-06/0206r1

Submission

• The receiving station can respond to queries, in a manner synchronous to the center of this space-time frame.

• The initial transmitter, when it receives a response from the station, can also establish a similar space time frame

• The discrepancy between the transmitter's initial space-time frame and the responses space-time frame reveals the total flight time

• Taking into account that the receiver is able to receive 12 dB SNR signals, the phase lock of real receiver must be much better and the total travel time can be estimated to within ~±0.5m resolution


November 2006

Ivan ReedeSlide 38

doc.: IEEE 802.22-06/0206r1

Submission

• Other stations, hearing query responses, may also perceive and measure space-time frame discrepancies.

• These discrepancies reveal flight times, within ~±0.5 m resolution

• A collectivity of stations can accumulate a wealth of space-time frame discrepancies

• Once collected and processed, this information reveals precise station location and channel characteristics


November 2006

Ivan ReedeSlide 39

doc.: IEEE 802.22-06/0206r1

Submission

Ranging Based Location Methods

• Time Sum Of Arrival (TSOA)• Time Difference Of Arrival (TDOA)• Absolute Range

For more details seeJuly 2006 presentation

November 2006

Ivan ReedeSlide 40

doc.: IEEE 802.22-06/0206r1

Submission

Ranging Based Location MethodsGeolocation Ranging Web Possibilities

BS

CPE4

CPE3

CPE2CPE1

CPE5

Range web valuesmay reveal elevationinfo / coax-lead-line

length

Z

November 2006

Ivan ReedeSlide 41

doc.: IEEE 802.22-06/0206r1

Submission

OFDM Ranging SummaryCosts

• Requires minimal if any ranging abilities in CPEs• Requires at least three located waypoints, at the BS or CPE or

some other known terrain characteristics• Economical

– it better exploits existing OFDM hardware– the pilot tones are already there for constellation sync– no special ranging symbols, symbols may be data bearing– practically no overhead– less overhead than any other location method– no external costs (such as GPS system costs + intsalltaion)

• Does not require many added abilities out of the CPE

November 2006

Ivan ReedeSlide 42

doc.: IEEE 802.22-06/0206r1

Submission

OFDM Ranging SummaryBenefits

• Simple, the pilot tones are already there for constellation sync• Fast and precise results, from a single query-response

– Provides the required resolution– Provides enough resolution for 3d location, including feed lines– Provides support for fixed devices– Provides support for mobility detection and tracking

• Is amenable to processing gain means on range and precision• Is self supportive, does not require external technology assists• Provides the ranging information needed to geolocate devices in

a simple, economical, elegant, inband and transparent fashion

November 2006

Ivan ReedeSlide 43

doc.: IEEE 802.22-06/0206r1

Submission

Alternatives?

• Is there another way to achieve the same goals?• Can we adapt this to allow OFDMA support?

November 2006

Ivan ReedeSlide 44

doc.: IEEE 802.22-06/0206r1

Submission

Alternatives?

• Is there another way to achieve the same goals?• Can we adapt this to allow OFDMA support?

The answer is YES ... to both questions

November 2006

Ivan ReedeSlide 45

doc.: IEEE 802.22-06/0206r1

Submission

Guard and Cyclic Prefix Needs

• In order to avoid filtering problems and multipath effects– A prefix is usually added to the transmitted signal– This provides time for filters to stabilize and stop “ringing”

• At the beginning of each symbol– Allows the receiving PHY to have some slack in its sync

• This slack has the apparent negative effect– Of negating the timing precision of the system

• This can be compensated after the FFT process

November 2006

Ivan ReedeSlide 46

doc.: IEEE 802.22-06/0206r1

Submission


v t( )

0

N 1

k

I k ei

2 k t

T

=

ii

0 t T

v t( )

0

N 1

k

I k ei

2 k t

T

=

ii

Tg

t T

November 2006

Ivan ReedeSlide 47

doc.: IEEE 802.22-06/0206r1

Submission


2

1 .125

vp

10 p

sam ples

0 0 .063 0 .13 0 .19 0 .25 0 .31 0 .38 0 .44 0 .5 0 .56 0 .63 0 .69 0 .75 0 .81 0 .88 0 .94 12

1

0

1



Starting discontinuity Tail end always aligns with the starting discontinuity

November 2006

Ivan ReedeSlide 48

doc.: IEEE 802.22-06/0206r1

Submission


2

1 .125

vp

10 p

sam ples

0 0 .063 0 .13 0 .19 0 .25 0 .31 0 .38 0 .44 0 .5 0 .56 0 .63 0 .69 0 .75 0 .81 0 .88 0 .94 12

1

0

1



Starting discontinuity has been masked by copyingtail end and inserting itas a cyclic prefix

November 2006

Ivan ReedeSlide 49

doc.: IEEE 802.22-06/0206r1

Submission


2

1 .125

vp

10 p

sam ples

0 0 .063 0 .13 0 .19 0 .25 0 .31 0 .38 0 .44 0 .5 0 .56 0 .63 0 .69 0 .75 0 .81 0 .88 0 .94 12

1

0

1



Initial filter ringing and inter-symbol interference has the time to decay before acquisition begins

November 2006

Ivan ReedeSlide 50

doc.: IEEE 802.22-06/0206r1

Submission


2

1 .125

vp

10 p

sam ples

0 0 .063 0 .13 0 .19 0 .25 0 .31 0 .38 0 .44 0 .5 0 .56 0 .63 0 .69 0 .75 0 .81 0 .88 0 .94 12

1

0

1


D A C ou tpu t sam p le #Signal acquisition interval does not have to be precisely aligned to get a valid orthogonal signal set

November 2006

Ivan ReedeSlide 51

doc.: IEEE 802.22-06/0206r1

Submission

Handling Guard and Cyclic Prefix

• Any time domain offset is mapped in the frequency domain• By a phase offset set in the recovered pilot carriers

– Phase offset values are proportional to pilot carrier frequency• The MAC may then compute the corresponding time offset

– Feed it back to the PHY for direct time stamp correction– Transmit correction data to the BS and other CPEs

• The BS receiving correction may compensate time offsets• Relaying CPEs have the option of

– Compensating– Relaying a compounded value back to the BS

November 2006

Ivan ReedeSlide 52

doc.: IEEE 802.22-06/0206r1

Submission


2

1 .125

vp

10 p

sam ples

0 0 .063 0 .13 0 .19 0 .25 0 .31 0 .38 0 .44 0 .5 0 .56 0 .63 0 .69 0 .75 0 .81 0 .88 0 .94 12

1

0

1



In the following examplewe will assume acquisitionstarted 12.5uSec before thereal symbol start

November 2006

Ivan ReedeSlide 53

doc.: IEEE 802.22-06/0206r1

Submission

Computing the PHY “slop”

• The PHY in its reception process– Acquires samples of the incoming signal– May establish a “sloppy” sync to symbol boundaries– Pass this “sloppy symbol” to the FFT– Which takes the acquires samples and decodes them– Into an array of vectors in an array of constellations

November 2006

Ivan ReedeSlide 54

doc.: IEEE 802.22-06/0206r1

Submission


Rotation is mappedto acquisition delay

3 KHz pilot tone

-15° ± 7.5°± 6.25 uSec± 2km

• The MAC can then acquire a first-order fix– By examination of the lowest frequency carrier– Normalize the array of vectors to this lowest frequency vector– This normalization yields a first order “slop” correction term

• The MAC can then predict the next tone angle

November 2006

Ivan ReedeSlide 55

doc.: IEEE 802.22-06/0206r1

Submission


Higher frequency pilot carrier is rotated more thanlower frequencypilot carrier

6 KHz pilot tone

• The MAC can then– Refine its error estimate by examining the next carrier– This normalization yields a higher order correction term

• Prediction in this example was 30° ± 15° (± 2 km)– This step reduces the ± 2 km down to ± 1 km

• The MAC can then predict the next tone angle

-30° ± 7.5°± 3.125uSec± 1 km

November 2006

Ivan ReedeSlide 56

doc.: IEEE 802.22-06/0206r1

Submission


12 KHz pilot tone

• Repeat the process with ever increasing frequency carriers– Until the desired range resolution is obtained

-60° ± 7.5°± 1.56 uSec± 500 m

November 2006

Ivan ReedeSlide 57

doc.: IEEE 802.22-06/0206r1

Submission


24 KHz pilot tone

• Repeat the process with ever increasing frequency carriers– Until the desired range resolution is obtained

-120° ± 7.5°± 0.78 uSec± 250 m

November 2006

Ivan ReedeSlide 58

doc.: IEEE 802.22-06/0206r1

Submission


192 KHz pilot tone

384 KHz pilot tone

-240° ± 7.5°± 0.39 uSec± 125 m

-480° ± 7.5°± 0.20 uSec± 62.5 m

November 2006

Ivan ReedeSlide 59

doc.: IEEE 802.22-06/0206r1

Submission


768 KHz pilot tone

1536 KHz pilot tone

-960° ± 7.5°± 0.10 uSec± 31.25 m

-1920° ± 7.5°± 0.05 uSec± 15.6 m

November 2006

Ivan ReedeSlide 60

doc.: IEEE 802.22-06/0206r1

Submission


768 KHz pilot tone

1536 KHz pilot tone

-3840° ± 7.5°± 0.025 uSec± 8 m

-7860° ± 7.5°± 0.0125 uSec± 4 m

November 2006

Ivan ReedeSlide 61

doc.: IEEE 802.22-06/0206r1

Submission


3072 KHz pilot tone

5997 KHz pilot tone

-15360° ± 7.5°± 0.0063 uSec± 2 m

-29985° ± 7.5°± 0.003 uSec± 1 m

November 2006

Ivan ReedeSlide 62

doc.: IEEE 802.22-06/0206r1

Submission

Compensating the PHY “slop”

• Once the desired resolution is reached• Store the normalization offset• Upon request from the BS, the CPE can transmit

– The normalization “space-time frame” time offset– The OFDMA “space-time” time offset to compensate flight time

November 2006

Ivan ReedeSlide 63

doc.: IEEE 802.22-06/0206r1

Submission


2

1 .125

vp

10 p

sam ples

0 0 .063 0 .13 0 .19 0 .25 0 .31 0 .38 0 .44 0 .5 0 .56 0 .63 0 .69 0 .75 0 .81 0 .88 0 .94 12

1

0

1



MAC knows that PHY acquisition frame is off set by 12.500 ±0.003 uSec

November 2006

Ivan ReedeSlide 64

doc.: IEEE 802.22-06/0206r1

Submission

Accommodating Guard

• This process allows for both– Real-life OFDM Receiver PHY sync limitations– OFDMA operation

• Where many CPEs – Share carrier resources in a given channel– Transmit in such a way to have all CPE space-time frames

• Arrive simultaneously at the BS• With space-time frame timing offset data

• This process allows the BS confirm its range estimates– By requesting a CPE additional pilots in OFDMA mode

November 2006

Ivan ReedeSlide 65

doc.: IEEE 802.22-06/0206r1

Submission

Pilot Tone Selection

• It is very important to understand– The the choice of a dozen pilots in these examples

• Is arbitrary, for example purposes only• Can dynamically be reduced or increased to

– Accommodate channel characteristics– Provide more statistical data– Allow for processing gain and artifact reduction

• In good 64-QAM, line of sight channels, 4 pilots are sufficient• In bad channels, many more pilots may be desired

– To compensate noise– To counteract and discard deviant pilot readings

November 2006

Ivan ReedeSlide 66

doc.: IEEE 802.22-06/0206r1

Submission

Resolution is NOT Precision

• It is very important to understand– That although this system has 2m/100km resolution capability– In practice, absolute precision is always lower than resolution

• Channel artifacts limit precision in radio-location systems– Mutipath (reflections, scatter, refraction-index variance)– Doppler, fading, weather-related media properties, etc...– They apply in various degrees to ALL radio-location systems– ALL radio-location systems are subject to similar limitations

• The goal is to meet 802.22 network geolocation precision needs– 100m for 67% of cases, 300m for 95% of cases; in a 100km range– 1km positional stability (CPE motion-cutoff threshold)

November 2006

Ivan ReedeSlide 67

doc.: IEEE 802.22-06/0206r1

Submission

Providing for OFDMA Flexibility

• It is proposed that a MAC to MAC primitive be created• To allow a CPE MAC to inform any receiving MACs• About the time offset value included in an emanated time frame

– At least 17 bits are needed for 1m resolution at 100km• To allow CPEs to transmit offset space-time frames to

• Allow transmission at an opportunistic time for OFDMA• Accommodate CPE Rx sync limitations• Future enhancements

• So the receiving MAC may – take into account said space-time frame “time” offset

November 2006

Ivan ReedeSlide 68

doc.: IEEE 802.22-06/0206r1

Submission

Providing OFDMA Hooks

• It is proposed that a MAC protocol primitive– Allows for inclusion or suppression from a CPE's spectrum

• Of the ranging pilots• To allow for OFDMA operation

– Without superposition of standard ranging pilots• From a universe of CPEs

• Optionally, if it is easy and simple– Allow the BS to specify alternate CPE to BS ranging carriers

• To allow coherent, simultaneous ranging of many CPEs• Validate and verify range estimates

November 2006

Ivan ReedeSlide 69

doc.: IEEE 802.22-06/0206r1

Submission

MAC Assisted Ranging SummaryBenefits

• Fast and precise results, from a single query-response– Provides the required resolution without high-speed clocks– Provides for OFDMA operation with real-life add-ons

• Is amenable to processing gain– Statistical processing can, over multiple samples

• Quantify, via standard deviation analysis– Noise and multi-path instability

• Reduce, by algorithms performing averaging processes– Noise (i.e. Effectively reducing BW)– Analyze unstable multi-path artifacts (wobble, Doppler...)

– Perform and correct for CPE clock drift and offset

November 2006

Ivan ReedeSlide 70

doc.: IEEE 802.22-06/0206r1

Submission


• Opens an opportunity to understand and and differentiate– Artifacts that are CPE specific– Artifacts that affect many CPEs in a region– Artifacts that affect all CPEs connected to a BS

• Analyze and understand how these artifacts affect the channel• Reduce, by futur algorithmic analysis

– Errors caused by these artifacts– Take corrective action

This may only be possible for in-band radio-location means

November 2006

Ivan ReedeSlide 71

doc.: IEEE 802.22-06/0206r1

Submission


• Simple, the pilot tones are already there for constellation sync– Pilot tone set may be flexible

• Accommodates fading• Avoids worst-case fading pilot carrier frequencies• Allows the BS to explore the channel characteristics

• Is self supportive, does not require external technology assists– Hardware time stamp is already needed for OFDMA– Extreme temporal precision is achieved by processing gain

• Provides the ranging information needed to geolocate devices in a simple, economical, elegant, inband and transparent fashion

November 2006

Ivan ReedeSlide 72

doc.: IEEE 802.22-06/0206r1

Submission

Topic for Jan 2007“Fractal Propagation” Location

BS

doc.: ieee 802.22-06/0206r1 submission november 2006 ivan reedeslide 1 ranging and location for...

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