doc.: ieee 802.22-06/0007r1 submission january 2006 steve shellhammer, qualcommslide 1 primary user...

January 2006

Steve Shellhammer, Qualcomm

Slide 1

doc.: IEEE 802.22-06/0007r1

Submission

Primary User Protection in 802.22 ProposalsIEEE P802.22 Wireless RANs Date: 2006-01-16

Name Company Address Phone email Steve Shellhammer Qualcomm 5775 Morehouse Dr

San Diego, CA 92121 (858) 658-1874 [email protected]

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].>

January 2006


Slide 2

doc.: IEEE 802.22-06/0007r1

Submission

Purpose of the Presentation• In November 2005 ten proposals were submitted to IEEE

802.22• Many of these proposals include techniques for protecting

primary users– Primary users in this band refers to DTV and Part 74 devices– This is often referred to as “vertical sharing”– Similarly, “horizontal sharing” is sharing between systems with equal

access rights

• This presentation summarizes these protection techniques• This presentation does not attempt to evaluate the

proposals, just to summarize• This presentation does not address other aspects of the

proposals

January 2006


Slide 3

doc.: IEEE 802.22-06/0007r1

Submission

Proposal DocumentsCompany Documents

Communication Research Center (CRC), Canada 22-05-0057r0, 22-05-0063r0

ETRI, Samsung Electro-magnetics, and Georgia Tech 22-05-0108r0, 22-05-0109r0

Huawei Technologies 22-05-0106r0, 22-05-0107r1

Institute for Infocomm Research 22-05-0093r0, 22-05-0094r0

Nextwave 22-05-0091r0, 22-05-0092r0

Nanotron 22-05-0101r0, 22-05-0102r0

Phillips and France Telecom 22-05-0103r0, 22-05-0104r0, 22-05-0105r1

Samsung 22-05-0099r0, 22-05-0100r1

ST Microelectronics and Runcom 22-05-0097r0, 22-05-0098r0

Thomson 22-05-0095r0, 22-05-0096r0

January 2006


Slide 4

doc.: IEEE 802.22-06/0007r1

Submission

CRC Canada

• The protection mechanism in this proposal is the broadcasting of which TV channels are occupied over the ATSC-DTV forward link– This mechanism is assumed to based on knowledge of the

geographic location and access to a database of TV channel utilization

January 2006


Slide 5

doc.: IEEE 802.22-06/0007r1

Submission

ETRI/Samsung/Georgia Tech

• Two methods of processing the received signal are suggested for generating parameter that can be used to decide which TV channels are occupied– Coarse – Multi-resolution Spectrum Sensing

– Fine – Analog Autocorrelation

• It is suggested that all the processing be done in the analog domain.

• This is an implementation choice and could equally be done in the digital domain

January 2006


Slide 6

doc.: IEEE 802.22-06/0007r1

Submission


Cognitive WRAN Architecture

Transmitter(RF/IF)

Receiver(RF/IF)

Coarse“MRSS”

Fine“AAC”

Low SpeedADC

PHY(Baseband)

MAC

SW orDuplexer

Sensing Receiver

Directive Antenna

Omni Antenna

January 2006


Slide 7

doc.: IEEE 802.22-06/0007r1

Submission

Multi-resolution Spectrum Sensing

• It is suggested that the coefficients of the Wavelet Transform are generated by correlating the received signal with the a given wavelet basis function in the analog domain

• The coefficient is converted to digital format using a low-speed ADC

• The wavelet basis function is changed to calculate another wavelet transform coefficient

• These wavelet transform coefficients are then used to decide if a channel is occupied

January 2006


Slide 8

doc.: IEEE 802.22-06/0007r1

Submission

Multi-resolution Spectrum Sensing

Block Diagram of Multi-resolution Spectrum Sensing

X ADC

v(t)*fLO(t)

Driver Amp CLK#2

MACTiming Clock

Wavelet Generator

CLK#1

x(t)

w(t)

z(t) y(t)

January 2006


Slide 9

doc.: IEEE 802.22-06/0007r1

Submission

Multi-resolution Spectrum Sensing• Example of spectrum analysis using MRSS

The spectrum of the wireless microphone signal

The corresponding signal spectrum detected with the MRSS technique

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 106

-100

-80

-60

-40

-20

0

20

40

Frequency

Pow

er S

pect

rum

Mag

nitu

de (

dB)

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 106

-120

-110

-100

-90

-80

-70

-60

-50

Frequency (Hz)

PS

D (

dB)

January 2006


Slide 10

doc.: IEEE 802.22-06/0007r1

Submission

Analog Autocorrelation• The autocorrelation of a random process is the expected

value of the product of the signal and a delayed version of the signal

• The proposal suggests calculating the autocorrelation function in the analog domain.

• The delay value is varied and the process is repeated• The low-speed ADC converts the autocorrelation value to

digital format• The proposal claims that this technique can be used for

blind detection• The proposal states that this can also be used for signal

classification

January 2006


Slide 11

doc.: IEEE 802.22-06/0007r1

Submission

Analog Autocorrelation

Block Diagram of Analog Autocorrelation

Multiplication Integrate

x(t)

Delay Td

Low SpeedADC

x(t-Td))

Decision Making

FIR

Sensing Antenna

January 2006


Slide 12

doc.: IEEE 802.22-06/0007r1

Submission


• The MAC maintains several lists– Set of TV channels used by CPE

– Set of TV channels used by base station

– Set of five candidate TV channels

– Set of occupied TV channels

– Set of disallowed TV channels

• The MAC provides a quiet period for sensing the spectrum– The lists are update after the sensing period

January 2006


Slide 13

doc.: IEEE 802.22-06/0007r1

Submission


• The downlink channel descriptor is modified to include these lists

• The MAC includes a procedure for switching channels– There seems to be an option for only a subset of the CPEs to

change channels

• The CPEs report their sensing results to the BS in response to a request

January 2006


Slide 14

doc.: IEEE 802.22-06/0007r1

Submission

Question for ETRI/Samsung/Georgia Tech• Are MRSS and AAC intended to operate in parallel or in

series?• How long does it take to calculate the wavelet transform

coefficients using this analog technique?• How are the wavelet transform coefficients from MRSS

used to decide if a channel is occupied or not?• Do you have any simulation results showing probability of

detection and false alarm rate using MRSS?• How is the autocorrelation function used to decide whether

the channel is occupied?• How is AAC used for blind detection? Don’t you need

some knowledge of the signal to fix your decision rule?• Do you have any simulation results showing probability of

detection and false alarm rate using AAC?

January 2006


Slide 15

doc.: IEEE 802.22-06/0007r1

Submission

Huawei Technologies

• The proposal suggest dividing each TV channel into sub-channels

• It would be possible to populate a subset of sub-channels

• This is intended to reduce interference caused to wireless microphones

January 2006


Slide 16

doc.: IEEE 802.22-06/0007r1

Submission

Institute for Infocomm Research

• Time is allocated after the downlink sub-frame and before the uplink sub-frame for spectrum sensing

• The channel is divided into sub-channels which consist of 48 data sub-carriers

• To avoid interference to wireless microphones some of these sub-channels may be nulled out– Since the sub-channels may consist of non-adjacent sub-carriers

several methods are proposed for nulling out a contiguous set of sub-carriers

January 2006


Slide 17

doc.: IEEE 802.22-06/0007r1

Submission

Institute for Infocomm Research

• The proposal also includes an option to null out some sub-carriers for sensing while transmitting on the other sub-carriers

`

Pilot subcarrier

Control subcarrier

Null subcarrier (Sensing)

Configuration II

Configuration I

January 2006


Slide 18

doc.: IEEE 802.22-06/0007r1

Submission

Questions for Infocomm

• Have you performed any tests to see if nulling out a portion of the TV channel will effectively prevent interference with wireless microphones operating in that part of the TV channel?

• Have you performed any simulations to demonstrate that you can effectively listen on a nulled sub-carrier while adjacent sub-carriers are populated?

• What type of signals (e.g. DTV or wireless microphones) can be detected using this approach?

January 2006


Slide 19

doc.: IEEE 802.22-06/0007r1

Submission

Nextwave• The proposal states that the MAC includes a number of

procedures for managing sharing of the spectrum. The listed procedures are,– Testing channels for other users including specific spectrum users

– Discontinuing operations after detecting other users including specific spectrum users

– Detecting other users including specific spectrum users

– Scheduling for channel testing

– Requesting and reporting of measurements

– Selecting and advertising a new channel

• The proposal does not seem to include the details of these procedures

January 2006


Slide 20

doc.: IEEE 802.22-06/0007r1

Submission

Questions for Nextwave

• When can you supply the details of the MAC procedures listed in your proposal?

January 2006


Slide 21

doc.: IEEE 802.22-06/0007r1

Submission

Nanotron

• This proposal does not include any material on protection of primary users

January 2006


Slide 22

doc.: IEEE 802.22-06/0007r1

Submission

Philips and France Telecom

• PHY Summary– Energy Detector

– Smoothed PSD estimator

– ATSC detector based on correlation with PN511 signal

• MAC Summary– New Spectrum Management (SM) Layer

– Support for quiet period

– Reports on spectrum measurements

January 2006


Slide 23

doc.: IEEE 802.22-06/0007r1

Submission


• Energy Detector– Estimate received signal strength indicator (RSSI)

– Estimate noise power

– Detector compares RSSI and scaled version of the noise power estimate

January 2006


Slide 24

doc.: IEEE 802.22-06/0007r1

Submission


• Part 74 Feature Detector– Using the FFT from the OFDMA PHY calculate the

periodogram as an estimate of the power spectral density

– Then calculate the mean and variance of the PSD

– The detector then compares the PSD with a linear function of the mean and variance

– This allows detecting non-uniformity of the PSD

January 2006


Slide 25

doc.: IEEE 802.22-06/0007r1

Submission


• ATSC DTV Feature Detector– The received signal is correlated with the know PN511

signal

– The running mean and variance of the correlator output are calculated

– The detector compares the variance with a scaled version of the mean

January 2006


Slide 26

doc.: IEEE 802.22-06/0007r1

Submission


• Cognitive MAC (CMAC)– Scheduled quiet periods for spectrum sensing

– A CPE can perform in-band sensing during a quiet period

– A CPE can perform out-of-band sensing either during a quiet period or outside of a quiet period

– There is a mechanism for base stations to attempt to synchronize their quiet periods with overlapping WRAN cells, to improve spectrum sensing

January 2006


Slide 27

doc.: IEEE 802.22-06/0007r1

Submission


• Cognitive MAC Frames– MAC Frames sent by the base station to request the

CPE performs spectrum sensing and reports results

– Two types of measurement reports: regular and urgent

– Regular reports send measurement results to base station on a regular interval

– An urgent report is sent to indicate that a primary user has been detected by the CPE in the occupied TV band

January 2006


Slide 28

doc.: IEEE 802.22-06/0007r1

Submission


• Cognitive MAC Frames– If the CPE has allocated TX time then after a quiet

period the CPE reports an abbreviated report in a measurement frame specifying which TV channels are occupied

– Subsequently the BS can then request more detailed measurement reports

– If the CPE does not have allocated TX time then there is a Urgent Coexistence Situation (UCS) time slot that can be used to transmit the urgent abbreviated report

January 2006


Slide 29

doc.: IEEE 802.22-06/0007r1

Submission


• Cognitive MAC Frames– The UCS notification slot can be accessed either using

a contention-based protocol, like CSMA/CA or it can use a contention-based CDMA mechanism using a randomly selected code

– If the BS does not receive a report from the CPE it may be due to interference from an in-band primary user

– Under this condition the BS shall infer that the channel is occupied by a primary user and change to another channel

January 2006


Slide 30

doc.: IEEE 802.22-06/0007r1

Submission


• Cognitive MAC Frames– There are multiple messages for reporting spectrum

sensing results• MAC Frames for reporting measurement statistics

• MAC Frame for reporting only the results of the detection algorithm specifying which channels are occupied and which are not

• Subfields in the MAC header to indicate a UCS and which channel in which it was detected

– By maintaining a list of backup channels, at BS and CPEs, the proposal supports recovery from the detection of an in-band primary user

January 2006


Slide 31

doc.: IEEE 802.22-06/0007r1

Submission

Questions for Philips and France Telecom

• Do you have any simulation results for the three detectors suggested in this proposal?

January 2006


Slide 32

doc.: IEEE 802.22-06/0007r1

Submission

Samsung

• The proposal emphasizes the need for distributed sensing

• The proposal correctly identifies that the distributed sensing information must be fused together at the base station– Data Fusion: Combining processed information to make centralized

decision

– Decision Fusion: Combine localized decisions into a centralized decision

• The authors state that the data fusion and decision fusion architectures are fairly independent of the individual decision algorithms employed at the CPEs

January 2006


Slide 33

doc.: IEEE 802.22-06/0007r1

Submission

Samsung

• The authors identify that the WRAN is solving a distributed Hypothesis Testing problem.

• The proposal suggest two types of detectors– Energy Detector

– Cyclostationary Detector

• The proposal assumes that the samples of the received signal are independent

January 2006


Slide 34

doc.: IEEE 802.22-06/0007r1

Submission

Samsung

• The authors point out that energy detection is a good approach when you do not have any a priori information about the signal

• The authors point out that energy detection is optimum for detecting Gaussian signal in additive white Gaussian noise

• For data fusion in the energy detector the proposal suggests summing the individual sensed energy values and using that sum as the decision statistic

January 2006


Slide 35

doc.: IEEE 802.22-06/0007r1

Submission

Samsung

• For decision fusion based the authors suggest summing the individual decisions from each of the CPEs an comparing that sum-of-decisions to a threshold to calculate the centralized decision

January 2006


Slide 36

doc.: IEEE 802.22-06/0007r1

Submission

Samsung

• The proposal gives some background on cyclostationary processes

• The authors state that the cyclostationary detector does not have the problem with noise that the energy detector has, since detection can theoretically be done irrespective of the noise power level

• Energy detection is a special case of cyclostationary detector, since the power spectral density is a subset of the spectral correlation density function

January 2006


Slide 37

doc.: IEEE 802.22-06/0007r1

Submission

Samsung

• One of the advantages of using the cyclostationary detector is the fact that it can be used for both detection and classification

• Another advantage of the cyclostationary detector is that it is extensible to be able to handle new signals that may be introduced in the band in the future

January 2006


Slide 38

doc.: IEEE 802.22-06/0007r1

Submission

Questions for Samsung

• Why do you believe that the data fusion and decision fusion architectures are fairly independent of the individual decision algorithms employed at the CPEs?

• How can you assume that the samples of the received signal are independent?

• What practical issues arise due to detection of a signal corrupted by noise using a cyclostationary detector?

January 2006


Slide 39

doc.: IEEE 802.22-06/0007r1

Submission

ST Micro and Runcom

• This proposal describes the trade-offs in allocating time for quiet periods for spectrum sensing– Spectrum sensing can be performed reliably without

interference caused by WRAN transmissions

– The sensing period will increase latency over the WRAN network

– The sensing period will decrease WRAN network throughput

January 2006


Slide 40

doc.: IEEE 802.22-06/0007r1

Submission

ST Micro and Runcom

• The proposal suggests three methods of scheduling spectrum sensing– Non-overlapping with data transmissions

• Sensing is only performed during quiet periods

– Full-overlap with data transmissions• Sensing can be performed during data transmissions

– Selective-overlap with data transmission• Sensing can be performed on selective channels during data

transmission

January 2006


Slide 41

doc.: IEEE 802.22-06/0007r1

Submission

ST Micro and Runcom

• Selective-overlap sensing– If a channel has enough frequency separation from the

utilized channel it is possible to perform reliable sensing on that channel during data transmission

Spectrum in useSpectrum gap Spectrum being sensedSpectrum being sensed Spectrum gap

Frequency

January 2006


Slide 42

doc.: IEEE 802.22-06/0007r1

Submission

ST Micro and Runcom

• The proposal suggests that the WRAN use dynamic frequency hopping (DFH)

• After the sensing period the BS selects one of the available TV channels and network hops to that channel for a specified time.

• How long the network dwells on each TV channel can be changed dynamically

• By changing operating frequency the set of TV channels that cannot be sensed during data transmission changes, which improves spectrum sensing

January 2006


Slide 43

doc.: IEEE 802.22-06/0007r1

Submission

ST Micro and Runcom

• Since two neighboring WRAN cells could potentially select the same channel the proposal introduces a method of avoiding this event– One cell waits until the adjacent cell selects it new operating

frequency

– It decodes the message from the adjacent BS

– Then it selects a different operating frequency

• This method required adjacent BS to be able to decode messages from each other

January 2006


Slide 44

doc.: IEEE 802.22-06/0007r1

Submission

ST Micro and Runcom

Validation time of CH A

Operating on CH ASensing on CH ([0, A-n],

[A+n, N])

Validation time of CH C

Operating on CH BSensing on CH ([0, B-n],

[B+n, N])

Time

System A

Validation time of CH B

Validation time of CH D

Operating on CH DSensing on CH ([0, D-n],

[D+n, N])

Operating on CH CSensing on CH ([0, C-n],

[C+n, N])

Time

System B

Validation time of CH CAnnounce to use CH C

Collision free

January 2006


Slide 45

doc.: IEEE 802.22-06/0007r1

Submission

ST Micro and Runcom

• Sensing reports can be in one of two forms– Bit vector reports specifying one of four states of the channel:

• Occupied by a licensed system• Occupied by another 802.22 system• Noisy• Vacant

– Raw data reports transmit the raw data

• The proposal describes several methods for scheduling the reporting– Polling– Poll-me– Contention

January 2006


Slide 46

doc.: IEEE 802.22-06/0007r1

Submission

Questions for ST Micro and Runcom

• How many TV channels need to be available for use so that dynamic frequency hopping can be used effectively?

• What does the WRAN network do if there is insufficient available TV channels?

January 2006


Slide 47

doc.: IEEE 802.22-06/0007r1

Submission

Thomson

• The proposal describes dynamic frequency selection (DFS) as required in 802.22

• The proposal recommends utilizing quiet periods for sensing

• The proposal recommends techniques for detecting ATSC DTV signals– Sensing Method 1

– Sensing Method 2

January 2006


Slide 48

doc.: IEEE 802.22-06/0007r1

Submission

Thomson

• Sensing Method 1– First step is to detect the pilot using filtering and PLL

– Using pilot down convert to baseband

– Use a matched filter on the PN511 sequence

– As an alternative use a matched filter on the PN63 sequence

– The proposal also lists several other signal features that can be used to detect the ATSC DTV signal

January 2006


Slide 49

doc.: IEEE 802.22-06/0007r1

Submission

Thomson

• Sensing Method 2– This method does not require extracting the pilot

– A complex autocorrelation is performed

– The detector identifies peaks in the autocorrelation signal

– The autocorrelation signal may be smoothed using an IIR digital filter

January 2006


Slide 50

doc.: IEEE 802.22-06/0007r1

Submission

Thomson

• The proposal introduces a novel method for improving the estimate of timing an frequency by utilizing the received signal from a stronger DTV station

• This method relies on the tight frequency tolerances in DTV– 1 KHz

January 2006


Slide 51

doc.: IEEE 802.22-06/0007r1

Submission

Thomson

• The proposal includes recommendations on the design of the omnidirectional sensing antenna– Concern is raised about the difficulty in designing an omni antenna that

operates over the entire UHF band without spatial nulls

– The proposal suggests using two antennas and alternating sensing. This eliminates the nulls at the cost of twice the time required for sensing

• The proposal also includes a recommendation on the design of a device that can be used to detect if the antenna is not properly aligned

January 2006


Slide 52

doc.: IEEE 802.22-06/0007r1

Submission

Questions for Thomson

• Do you have any simulation results for the two sensing methods you proposed?

January 2006


Slide 53

doc.: IEEE 802.22-06/0007r1

Submission

Summary

• This proposal attempts to summarized the portion of each proposal that addresses protection of primary users

• There is a follow-up presentation on Cognitive Radio Framework for Protection of Primary Users