WRAN 802-22

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*	CADENCE DESIGN SYSTEMS, INC.	
The Evolution of Spectrum Sharing in the IEEE 802.22 WRAN Standards Process
John Notor
February 21, 2006
Rev 2
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Background
The IEEE 802.22 Wireless Regional Area Network (WRAN) Working Group is developing a point to multipoint fixed wireless access network standard intended to operate world wide in the unused segments of the terrestrial TV broadcast bands.
To date, only the US Federal Communications Commission (FCC) has created an initiative to allow this to take place – the so-called TV Band NPRM 1.
Other regulatory agencies world wide have expressed interest in similar initiatives.
This presentation is a snapshot of the present activity based mostly on publicly available material (see Bibliography).
1. Notice of Proposed Rulemaking (NPRM).
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802.22 Network Overview [ref 1]
 DSL rates to the edge of coverage.
 Lightly licensed base station (BS).
 Unlicensed CPE’s
 Base station power: > +36 dBm
 CPE Tx Power: +36 dBm EIRP
2. Customer Premise Equipment (CPE) 
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802.22 Network Overview [ref 8]
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Spectrum Sensing to Protect Incumbents
Licensed Incumbents:
TV Broadcasters:
NTSC (US/Canada/Japan analog TV), ATSC (US, Canada DTV), PAL (Europe analog TV), SECAM (France analog TV), DVB-T (Europe/worldwide DTV).
Land Mobile Radio Networks:
Public Safety (police, fire, etc.), Commercial (cabs, towing services, etc.)
Wireless Microphones and other TV broadcast related devices (in the US, FCC rules, Part 74 Low Power Auxiliary Station devices).
802.22 Approach:
Avoid operating on Land Mobile Radio channels.
Use planning, GPS, databases for Base Station planning, licensing.
Use Base Station authorization/control and distributed sensing, in BS and CPE’s, to avoid unintentional operation on TV channels.
Use sensing to mitigate interference to Part 74 devices.
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TV Broadcast - Analog TV
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TV Broadcast – US DTV
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TV Broadcast – Europe, worldwide DTV
Digital TV (DVB-T) Spectrum [ref 13]
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Part 74 Devices, Including Wireless Microphones [ref 7]
Wireless microphones are devices covered under Part 74 of the FCC rules:
They are classified by the FCC as “Low Power Auxiliary Stations”.
May be operated in the TV band by TV broadcast license holders under the aegis of their broadcast license. 
Wireless microphones are licensed secondary users of the TV spectrum.
Most wireless microphones use analog FM transmission, although there are some digital units.
Occupied bandwidth is limited to 200 kHz by FCC rules.
Power output is limited to < 50 mW in VHF, < 250 mW in UHF, 85% of units operate at < 50 mW.
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Typical Wireless Mic Link Performance [ref 7]
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Typical Wireless Microphone Spectra
The following show some typical spectra for wireless microphones:
Low frequency voice content spectrum.
High frequency voice content spectrum.
An unmodulated spectrum.
Most of the signal energy is contain in about a 40 kHz bandwidth.
The no modulation case is the worst case in terms of spectrum width because of short term carrier drift.
The character of the spectral shape is somewhat amorphous, so a relatively high CNR is required to assure good probability of detection.
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Low Voice Spectrum: Resolution BW = 10 kHz
 Courtesy of Ahren Hartman, Shure, Inc.
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High Voice Spectrum: Resolution BW = 10 kHz 
 Courtesy of Ahren Hartman, Shure, Inc.
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Unmodulated Spectrum: Resolution BW = 10 kHz
 Courtesy of Ahren Hartman, Shure, Inc. 
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Sensing Parameters: Estimates and Analysis
 courtesy of Gerald Chouinard, CRC, Canada [ref 12]
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Sensing Parameters: Estimates and Analysis 
 courtesy of Gerald Chouinard, CRC, Canada [ref 12]
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Sensing Parameters: Estimates and Analysis 
 courtesy of Gerald Chouinard, CRC, Canada [ref 12]
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Sensing Parameters: Estimates and Analysis 
 courtesy of Gerald Chouinard, CRC, Canada [ref 12]
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Notor’s Calculation of Wireless Mic DFS Threshold
Assume the following:
Use an energy detection approach, 40 kHz bandwidth. 
Required CNR in a 40 kHz bandwidth for high probability of detection: ~16 dB.
High CNR requirement needed to overcome the noise like properties of voice/music modulation.
Assume a 5 dB receiver noise figure.
Calculation
kTB: -174 dBm/Hz
Noise gain, 40 kHz BW: + 46 dB
Receiver noise figure: + 5 dB
Required CNR: + 16 dB
DFS Threshold: -107 dBm
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DTV Co-Channel Sensing
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Beacon vs Wireless Mic Sensing [ref 7]
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802.22 Key Proposals in Play for March
ETRI-FT-Philips-Samsung Proposal: PHY [ref 3,4,5,8]
OFDMA both in uplink and downlink
QPSK, 16-QAM, and 64-QAM, spreaded-QPSK 
OQAM is also being considered, but it has been submitted as a separate contribution
More than 30 sub channels per TV channel
Contiguous channel bonding up to 3 TV channels (and beyond in a stack manner)
Data rate range from 5Mbps to 70Mbps
TDD, FDD
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802.22 Key Proposals in Play for March
ETRI-FT-Philips-Samsung Proposal: Sensing [ref 3,4,5,8]
Dual Sensing Strategy: Energy detection and Fine/Feature detection
Energy Detection: To meet the speed and power requirement
Power spectrum distribution in the entire band is obtained
On request basis, detect the power level of selected channel in very short time
Examples are MRSS, RSSI
Fine/Feature Detection: To meet the minimum sensitivity requirement
Fine sensing is applied for the selected channel 
Feature Detection: detecting digital modulated signals
Examples include CSFD, field-sync detection
FFT based spectral analysis: detecting narrowband analog modulated signals, most of part 74 devices
Distributed Sensing Strategy : Frequency usage information is collected and managed at Base-station
Either the BS makes the detection decision based on the collective measurement results or CPE’s can make the decision 
Can be implemented as a stand alone sensing block with an omni-directional antenna
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802.22 Key Proposals in Play for March
ST-Runcom Proposal: PHY [ref 9]
Duplexing Technique: TDD
Multiple Access Method: TDMA/OFDMA
OFDM Symbols allocated by TDMA
Sub-Carriers within an OFDM Symbol allocated by OFDMA
Diversity: Frequency, Time, Code, Space
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802.22 Key Proposals in Play for March
ST-Runcom Proposal: Sensing [ref 9]
RF Sensing simultaneously with transmission using Dynamic Frequency Hopping (DFH).
During a DFH operation cycle
BS schedules the system to switch (hop) to channel (set) A
BS and CPEs perform data transmissions on channel (set) A
BS performs, and schedules CPEs to perform spectrum sensing on channel [0, A-n] and [A+n, N]
CPEs report sensing measurement results
BS performs report processing
BS performs channel selection and acquisition
BS announces DFS decision for the next operation cycle
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802.22 Key Proposals in Play for March
ST-Runcom Proposal: Sensing [ref 9]
Validation time – The latest time a channel is validated to be vacant
Grace period – The maximum period of time a incumbent can tolerate interference for 
 LE operations, from the beginning of the incumbent’s operations
��
Initial Sensing�
Validation time of CH A�
�
Transmitting on CH A�
Sensing on CH ([0, A-n], [A+n, N])�
 Less than Grace Period �
Validation time of CH B�
Time�
 Less than Grace Period �
Transmitting on CH B�
Sensing on CH ([0, B-n], [B+n, N])�
�
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802.22 Spectrum Sensing Tiger Team
Meets via telecon and email (802.22 reflector).
Purpose: to pursue closure on the Spectrum Sensing Simulation Model [ref 10].
Process (Notor’s view):
Propose and evaluate proposals for determining sensing efficacy.
Develop agreed-upon sensing scenarios.
This is a stepping stone on the way to “defining what done looks like”.
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Sensing Tiger Team: Working Toward Clarity [ref 13]
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Final Thoughts
Within the IEEE 802.22 Working Group process, sensing
technology at the conceptual, strategic and practical level are still in the early stages of definition/implementation.
In addition to the issues pointed to in this presentation, there is a need to extend sensing beyond just co-channel sensing, to account for the TV receiver’s limitations and the proposed change of regulatory paradigm:
Imperfect reception of a weak signal in the presence of one or more strong signals in the band.
The lack of taboo channel planning in a geographic region, which, in the past, avoided assigning TV channels to certain frequencies to minimize the negative impact on reception of other channels due to poor receiver characteristics.
The need to set transmit power levels in a friendly way given near far issues, and planning issues.
Finally, there continues to be a lack of coherent and common understanding about the strengths and weaknesses of a sensing approach to co-existence in the radio, regulatory, and broadcast communities.
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Bibliography
The following documents are referenced in this presentation, and are available on the IEEE 802.22 web site: http://www.ieee802.org/22/.
September 2005:
1. 22-05-0007-46-0000_RAN_Requirements.doc
November 2005:
22-05-0096-00-0000_Thomson_Proposal_Presentation.ppt.
22-05-0100-01-0000_Samsung_Proposal_Presentation.ppt.
22-05-0105-01-0000_Philips-FT_PHY-MAC_Proposal_Presentation.ppt.
22-05-0109-01-0000_ETRI-SEM-GATech_Proposal_Presentation.ppt
January 2006:
22-06-0006-00-0000_UHF_TV_ Band_White_Spaces.ppt
22-06-0007-01-0000_Primary-User-Protection-in-802.22-Proposals.ppt
22-06-0005-01-0000_ETRI-FT-Philips-Samsung_Proposal.ppt
22-05-0097-02-0000_STM-Runcom_PHY-MAC_Proposal_Presentation.ppt
22-06-0028-01-0000-Spectrum-Sensing-Simulation-Model-GC.doc
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Bibliography
The following documents are not available publicly:
Shure_IEEE_BTS_Presentation_101105.ppt.
Sensing Thresholds-r4.xls, Gerald Chouinard, Communications Research Center, Canada, gerald.chouinard@crc.ca 
Geometry for Scenario 2.ppt, Soo-Young Chang, Huawei Technologies 
The following are available on the web:
DVB-T Transmission Systems, Glenn Doel http://www.itu.int/ITU-R/conferences/rrc/rrc-04/intersession/workshops/damaskus/docs/Presentations/ntl_1_DVB-T_systems.pdf
18-04-0030-04-0000-proposal-part-15-244-cognitive-radio-operation-in-tv-band.ppt, John Notor http://grouper.ieee.org/groups/802/18/Meeting_documents/2004_July/18-04-0030-01-0000-proposal-part-15-244-cognitive-radio-operation-in-tv-band.ppt
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Sensing Thresholds-r4.xls
Sensing Thresholds-r4.xls