doc.: ieee 802.22-06/0130r2 submission september 2006 carlos cordeiro, philipsslide 1 a beacon-based...

September 2006

Carlos Cordeiro, Philips

Slide 1

doc.: IEEE 802.22-06/0130r2

Submission

A Beacon-based Proposal to IEEE 802.22.1

IEEE P802.22 Wireless RANs Date: 2006-09-13

Name Company Address Phone email Carlos Cordeiro Philips USA 914-945-6091 [email protected]

Monisha Ghosh Philips USA 914-945-6415 [email protected]

Vasanth Gaddam Philips USA 914-945-6424 [email protected]

Kiran Challapali Philips USA 914-945-6127 [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].>

September 2006


Slide 2

doc.: IEEE 802.22-06/0130r2

Submission

Outline

• Introduction

• The PHY Proposal

• The MAC Proposal

• Conclusions

September 2006


Slide 3

doc.: IEEE 802.22-06/0130r2

Submission

Introduction

• We propose a fully distributed beacon-based solution to be used for the protection of Part 74 (P74) devices

• In this proposal, the same channel is used for inter-beacon coordination and to notify the WRAN

• Some of the features of this proposal include:– Autonomous network formation amongst Part 74 beacon devices (DEV)– DEVs within radio range discover each other and conglomerate as to share the same

channel for beacon transmissions– Dynamic merging of multiple DEV networks can be done– Distribution of information on channels occupied by P74 devices

• Plus, feedback to Part 74 users on channel utilization as to promote better spectrum usage

– Sensing capability by DEVs– To allow for bi-directional communication, DEVs are also capable of receiving

beacons from the unlicensed secondary user (USU) – in this case, 802.22– A DEV can rebroadcast information received from neighboring DEVs

September 2006


Slide 4

doc.: IEEE 802.22-06/0130r2

Submission

The PHY

September 2006


Slide 5

doc.: IEEE 802.22-06/0130r2

Submission

PreamblePLCP header

Payload

Beacon Period and BP Length

mMaxBeaconLengthpSIFS+mGuardTime

mBeaconSlotLength

DE

V5

DE

V9

DE

V3

DE

V1

DE

V8 ...

DE

V8

Beacon Slots

Signaling slots

Highest-numbered unavailablebeacon slot seen by DEV 8

0 1 2 3 4 5

SSBP

mMaxBPLength

Largest NBP Lengthannounced

US

U1

US

U2

0 1 2 3

Largest FBPLength

announced

mMaxBPLength

Signaling slots

Superframe

September 2006


Slide 6

doc.: IEEE 802.22-06/0130r2

Submission

The PHY

• The range of beaconing device is same as the WRAN BS (upto 33 Km)

• Two PHY modes– Range, data-rate, receiver complexity trade-offs

• Single carrier modulation

• Receiver determines which mode is transmitted/received

• Energy sensing and preamble sensing

September 2006


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Submission

The PHY (Mode A)

September 2006


Slide 8

doc.: IEEE 802.22-06/0130r2

Submission

PHY-A Outline

• MAC payload is transmitted in one beacon slot

• BPSK, QPSK, 16-QAM modulation options

• Constraint length 5, Rate – ½ convolutional code– Rates 2/3 and ¾ with puncturing

• Used bandwidth: 200khz, with 15% roll-off.

• Symbol Rate: 5.75 sec

• Equalization provides performance improvement

September 2006


Slide 9

doc.: IEEE 802.22-06/0130r2

Submission

PPDU Frame Format

• PLCP preamble– Signal detection and synchronization

• PLCP HDR– PHY and MAC headers

• PSDU– Payload (MPDU), tail bits and pad bits

• Includes 2 byte frame check sequence (FCS)– The coding rate and modulation type is selected so that it fully utilizes the

beacon slot

PLCP Preamble PLCP HDR PSDU

150 symbols 112 symbols Fixed # of symbols

September 2006


Slide 10

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Submission

PLCP Preamble

• S1 to S7: each block consists of a 15-bit pseudo random sequence (TBD)

– S6: Inverted polarity compared with rest of the symbol blocks

• GI: Guard interval (CP or ZP)– Could be repetition of C1

• C1, C2: Repetition of a 15-bit sequence– Used for channel estimation

• BPSK modulation

S1 GIS7S6S5S4S3S2 C2C1

15 sym 150 symbols

September 2006


Slide 11

doc.: IEEE 802.22-06/0130r2

Submission

• PHY header – 2 bytes

• MAC header – 3 bytes

• HCS – 1 byte– Generated on PHY header and MAC header

– Generator polynomial: CCITT CRC-8:

• Tail bits are used to bring the coder to zero state

• BPSK modulation

PLCP Header

PHY HDRTail bits

MAC HDR + HCSTail bits

2 bytes 4 bits 4 bytes 4 bits

12378 xxxx

September 2006


Slide 12

doc.: IEEE 802.22-06/0130r2

Submission

PHY Header

• Rate – Coding rate and modulation type for PSDU – 3 bits

• Length – number of octets in the frame payload (before encoding)– 7 bits (0 – 127)

• 6 reserved (R) bits

0R

11MSB

1098765LSB

4MSB

32LSB

1R

15R

14R

13R

12R

Rate Length

Rate

(b4 b3 b2)

Modulation Type

Coding Rate

000 QPSK ½

001 QPSK 2/3

010 QPSK ¾

011 Reserved Reserved

100 16-QAM ½

101 16-QAM 2/3

110 16-QAM ¾

111 Reserved Reserved

September 2006


Slide 13

doc.: IEEE 802.22-06/0130r2

Submission

Encoding of PLCP HDR

• Rate – ½ convolutional coder

• BPSK modulation

• Transmitted in 112 symbols– Duration = 112 x TSYM

Rate - 1/2 Convolutional

codermapping Modulator

September 2006


Slide 14

doc.: IEEE 802.22-06/0130r2

Submission

PSDU

• Frame payload size before encoding: 0 – 127 bytes

• Frame check sequence: 2 bytes– CCITT CRC-16: generator polynomial

• Tail bits are not scrambled

• Pad bits are added in order to occupy the entire beacon slot

151216 xxx

FCSTail bits

Frame payload

0 – 127 bytes 2 bytes4

bits

Pad bits

Variable

September 2006


Slide 15

doc.: IEEE 802.22-06/0130r2

Submission

PSDU Encoding

• The PSDU data and FCS is first randomized

• 4 tail bits are appended to randomizer output

• The resulting vector is encoded using a rate – ½ convolutional coder and punctured according to the rate specified

• Optional interleaver

• BPSK, QPSK and 16-QAM mapping

PuncturerRate - 1/2

Convolutional coder

Interleaver(optional) mapping ModulatorRandomizer

September 2006


Slide 16

doc.: IEEE 802.22-06/0130r2

Submission

Rate – ½ Convolutional Code

• Constraint length = 5

• Generator poly – [23o 35o]

D DDDData in

Output A

+

Output B

+

September 2006


Slide 17

doc.: IEEE 802.22-06/0130r2

Submission

Puncturing and Bit-Insertion

• Defined for rate – 2/3 and rate – 3/4

Code rate ½ 2/3 ¾

Convolutional coder output A1B1 A1B1A2B2 A1B1A2B2A3B3

Puncturer output/bit-

inserter inputA1B1 A1B1A2 A1B1B2A3

Decoder input A1B1 A1B1A20 A1B10B2A30

September 2006


Slide 18

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Submission

Symbol Mapping (QPSK)

• The output of puncturer/interleaver is divided into groups of 2 bits and then converted into complex numbers using QPSK constellation mapping

• Normalization factor = 1/√2

Input bits

(b1b0)

I component Q component

00 -1 -1

01 -1 1

10 1 -1

11 1 1

September 2006


Slide 19

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Submission

Symbol Mapping (16-QAM)

• The output of puncturer/interleaver is divided into groups of 4 bits, Gray coded and then converted into complex numbers using 16-QAM constellation mapping

• Normalization factor = 1/√10

Input bits

(b1b0)

I component

00 -3

01 -1

10 3

11 1

Input bits

(b3b2)

Q component

00 -3

01 -1

10 3

11 1

September 2006


Slide 20

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Submission

Pulse Shaping

• The I and Q components of the signal are square root raised cosine (SQRC) filtered prior to modulation

• Roll-off factor is 0.15

September 2006


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Submission

The PHY (Mode B)

September 2006


Slide 22

doc.: IEEE 802.22-06/0130r2

Submission

PHY-B Outline

• MAC payload is transmitted in multiple superframes (in a fixed beacon slot)– Enables simple receiver architectures since less amount of data is

transmitted in each slot

• DSS using a 7-chip Barker spreading code

• BPSK/QPSK mapping

• Option to use short preamble

September 2006


Slide 23

doc.: IEEE 802.22-06/0130r2

Submission

PPDU Frame Format

• PLCP preamble– Signal detection and synchronization

• PHY HDR– PSDU Length

• PSDU– Payload (MPDU), tail bits and pad bits

• Includes 1 byte frame check sequence (FCS)

Long PLCP Preamble

PHY HDR PSDU

24 Bits 8 Bits Fixed # of Bits

Short PLCP Preamble

PHY HDR PSDU

12 Bits 8 Bits Fixed # of Bits

September 2006


Slide 24

doc.: IEEE 802.22-06/0130r2

Submission

PLCP Preamble

• Burst detection bits– Long preamble: 20 bits

– Short preamble: 8 bits

• Frame Detection: 4 bits

Burst DetectionFrame

Detection

20 Bits 4 Bits

Burst DetectionFrame

Detection

8 Bits 4 Bits

Long PLCP Preamble

Short PLCP Preamble

September 2006


Slide 25

doc.: IEEE 802.22-06/0130r2

Submission

• PHY header: 1 byte– Length: 5 bits (0-31)

• Indicates length of PSDU in octets

– Preamble type (PT): 1 bit

– Parity (P): 1 bit

– Reserved: 1 bit

PHY Header

3210

LSB7P

6PT

5R

4MSB

Length

September 2006


Slide 26

doc.: IEEE 802.22-06/0130r2

Submission

PSDU

• Frame payload size before encoding: 0 – 31 bytes

• Frame check sequence: 1 byte– CCITT CRC-8: generator polynomial

• Pad bits are added in order to occupy the entire beacon slot

FCSFrame payload

0 – 31 bytes 1 byte

Pad bits

Variable

12378 xxxx

September 2006


Slide 27

doc.: IEEE 802.22-06/0130r2

Submission

DSS Spreading

• All the bits are spread using a 7-chip code before transmission

• Preamble and header are transmitted using BPSK modulation

• PSDU is transmitted using either BPSK or QPSK

September 2006


Slide 28

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Submission

Preliminary Simulation Results for Mode A, Mode B and Spread DBPSK in AWGN

And Multipath

September 2006


Slide 29

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Submission

Mode A: Simulation Parameters

• Transmitter parameters– Packet size: 60 bytes– Rate-1/2 convolutional coding, QPSK

• Base data rate – 115.06 Kbps• Multipath channel – Complex exponential Rayleigh faded

– 200 KHz sampling rate and 1µs RMS delay spread: 3-path channel

• Matched filtering by using the ideal channel taps.• Equalization – Ideal MMSE Feed-forward filter taps (6 taps)• Position correction factor is determined by the position of the

peak in cross-correlator output.• Perfect timing is assumed.• Simulations for 10000 packets for each point

September 2006


Slide 30

doc.: IEEE 802.22-06/0130r2

Submission

Mode A – BER Vs. SNR in AWGN and multipath channel

• BER of 1e-5 @ about 5.75 dB SNR for AWGN

September 2006


Slide 31

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Submission

Mode A – PER Vs. SNR in AWGN and multipath channel

September 2006


Slide 32

doc.: IEEE 802.22-06/0130r2

Submission

Mode B: Simulation Parameters

• Transmitter parameters– Packet size: 8 bytes

– Spreading by length-7 Barker sequence, followed by BPSK modulation

• Base data rate: 17.746 Kbps

• Multipath channel – Real exponential Rayleigh faded– 200 KHz sampling rate and 1µs RMS delay spread: 3 path channel

• Matched filtering by using the ideal channel taps

• Position correction factor is determined by the position of the peak in cross-correlator output

• Perfect timing is assumed

• Simulations for 1000 packets for each point

September 2006


Slide 33

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Submission

Mode B – BER Vs. SNR in AWGN channel

September 2006


Slide 34

doc.: IEEE 802.22-06/0130r2

Submission

Mode B – BER Vs. SNR in multipath channel

September 2006


Slide 35

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Submission

Spread DBPSK: Simulation Parameters

• Multiple access based on spreading sequence– Spreading by a 16-bit PN sequence

• Interferers use a shifted version of this PN sequence

• Packet length: 45 bytes• Simulations for 10000 packets each• Multipath channel – Real exponential Rayleigh faded

– 200 KHz bandwidth and 1µs delay spread: 3-path channel

• Position correction factor is determined by the position of the peak in cross-correlator output

• Multiple beacon interference– Interference is present for the entire duration of the packet– Interferers are not synchronized in time

September 2006


Slide 36

doc.: IEEE 802.22-06/0130r2

Submission

Spread DBPSK – BER Vs. SNR in AWGN and multipath channel

September 2006


Slide 37

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Submission

Spread DBPSK – Performance with 2 interfering beacons

Multi-path channel,Matched-filter receiver

September 2006


Slide 38

doc.: IEEE 802.22-06/0130r2

Submission

Conclusions from preliminary simulations• Effect of multipath:

– Severe performance degradation in multi-path channels, for all modes.– Some form of channel estimation and correction is required to avoid this

performance degradation.– Mode A: Provides higher data rates, requires equalization.– Mode B: Lower data rates compared to mode A, requires matched filtering– Spread DBPSK: Lower data rates compared to modes A and B, requires

matched filtering.

• Effect of multiple beacons:– TDMA approach: Performance does not degrade with increasing number of

beacons, in fact can improve due to diversity reception of rebroadcast beacons.

– Spread DBPSK approach: Significant performance loss in beacon reception even in the presence of only 2 other beacons.

September 2006


Slide 39

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Submission

The MAC

September 2006


Slide 40

doc.: IEEE 802.22-06/0130r2

Submission

Disclaimer

• The following set of slides are restricted to present the updates and to summarize the MAC proposal described in documents 22-06-0130-01-0001 and 22-06-0129-00-0001 (presented in July/2006)

• The following updates together with document 22-06-0130-01-0000 represent the entire 802.22.1 MAC proposal

September 2006


Slide 41

doc.: IEEE 802.22-06/0130r2

Submission

Pedigree of 802.22.1 MAC Proposal

• The MAC proposal to 802.22.1 is based on an international standard for UWB– The WiMedia UWB MAC standardized by ECMA

• It also serves as the basis to the IEEE 802.15.5 draft mesh standard

• Therefore, it is a proven and future-proof technology– Silicon will soon start to become commercially available

September 2006


Slide 42

doc.: IEEE 802.22-06/0130r2

Submission

MAC Outline

• Beacon period

• Information elements (IE) related to:– Beacon

– Beacon period

– P74 devices

• Transmission and reception of beacons

• DEV discovery by WRAN

September 2006


Slide 43

doc.: IEEE 802.22-06/0130r2

Submission

Beacon Period Overview

• Within a superframe, there are two Beacon Periods (BPs)– Network BP (NBP): Used for communication and networking amongst

DEVs

– Foreign BP (FBP): Optional and used for receiving beacons from foreign networks (e.g., 802.22 – or simply, USU) that wish to communicate with the DEVs

• The BP provides a fully distributed and autonomous mechanism for coordination of DEVs, and better spectrum use by both P74 devices and 802.22

• The remaining of the superframe is termed as the Sense/Sleep/Beacon Period (SSBP)– Period used by DEVs for sensing channels, for out-of-band beaconing, etc

September 2006


Slide 44

doc.: IEEE 802.22-06/0130r2

Submission

NBP

Superframe (Tsf)

NetworkBeaconPeriod

ForeignBeaconPeriod

Superframe (32 MAS)

BPST BPST BPST

SSBP

Medium Access Slot(MAS)(TMAS)

FBP

SSBP

NBP FBP

The Network Beacon Period Overview

The Network Beacon contains Information regarding:

• Device Address (DevAddr)

• NBP and FBP Length

• Beacon Channel and Sub-Channel Number

• Beacon Slot Number

• List of Neighbors

• Sensing and Sleep Periods

• List of TV channels occupied by P74 devices, RSSI, start time and duration

• Location Information of DEV

• Authentication Key

• User specific information; Etc…

Every Part 74 beacon device (DEV) sends at least one beacon!

Slotted Network Beacon Period

DE

V 7

DE

V 2

DE

V 5

DE

V 1

DE

V 6

DE

V 3

DE

V 8

Network Beacon Period Length (DYNAMIC)

BeaconSlot

...

September 2006


Slide 45

doc.: IEEE 802.22-06/0130r2

Submission

NBP

Superframe (Tsf)

NetworkBeaconPeriod

ForeignBeaconPeriod

Superframe (32 MAS)

BPST BPST BPST

SSBP

Medium Access Slot(MAS)(TMAS)

FBP

SSBP

NBP FBP

The Foreign Beacon Period Overview

The USU Beacon contains information regarding:

• BS ID

• Info on DEV authentication

• Spectrum Occupancy (e.g., occupied, vacant, etc.)

• Prioritized channel list suggested for use by P74 devices

• USU quiet periods

• List of TV channels occupied by P74 devices, RSSI, start time and duration

• Location Information of USU

• Etc…

Allows for bi-directional communication!

Slotted Foreign Beacon Period

US

U 3

US

U 2

US

U 4

US

U 1

US

U 5

Foreign Beacon Period Length(DYNAMIC)

BeaconSlot

...

September 2006


Slide 46

doc.: IEEE 802.22-06/0130r2

Submission

PreamblePLCP header

Payload

Beacon Period and BP Length

mMaxBeaconLengthpSIFS+mGuardTime

mBeaconSlotLength

DE

V5

DE

V9

DE

V3

DE

V1

DE

V8 ...

DE

V8

Beacon Slots

Signaling slots

Highest-numbered unavailablebeacon slot seen by DEV 8

0 1 2 3 4 5

SSBP

mMaxBPLength

Largest NBP Lengthannounced

US

U1

US

U2

0 1 2 3

Largest FBPLength

announced

mMaxBPLength

Signaling slots

Superframe

September 2006


Slide 47

doc.: IEEE 802.22-06/0130r2

Submission

BP: Special Case

• The NBP could take over the entire superframe• This has the same behavior as the sending a beacon either

repeatedly or continuously, with the added benefit that the inter-beacon coordination channel is the same as the channel to notify the WRAN– Simplicity

NBP

Superframe

Network Beacon Period

Superframe

BPST BPST BPST

NBP

September 2006


Slide 48

doc.: IEEE 802.22-06/0130r2

Submission

Types of Information Elements

• A number of IEs are defined for both Network Beacons (NBP) and Foreign Beacons (FBP)

• Examples:

Network Beacon IEs

• BP Occupancy IE (BPOIE)

• Part 74 Occupancy IE (P74OIE)

• Hibernation Mode IE (for sleep periods)

• Channels to Sense IE

• Spectrum Occupancy IE

• Location Information IE

• Channel Change IE

• BP Switch IE

• Probe IE

• MAC Capabilities IE

• Operator/User/Application-specific IE; Etc…

Foreign Beacon IEs• Part 74 Occupancy IE (P74OIE)

• Spectrum Occupancy IE

• Prioritized Channel List IE (suggested for use by P74 incumbent devices)

• USU Quiet Period IE

• Location Information IE

• USU Descriptor IE

• DEV Authentication IE

• Etc…

September 2006


Slide 49

doc.: IEEE 802.22-06/0130r2

Submission

Types of Information Elements

• Two IEs of key importance are described here: Beacon Period Occupancy IE (BPOIE) and Part 74 Occupancy IE (P74OIE)

• BPOIE– Provides detailed information on the entire BP observed by the

DEV sending the IE

• P74OIE– Provides information on the channel usage by P74 incumbent

devices as known by the DEV sending the IE– Can be rebroadcast over multiple hops to increase protection to

P74 services and to offer better spatial reuse

September 2006


Slide 50

doc.: IEEE 802.22-06/0130r2

Submission

Beacon Period Occupancy IE (BPOIE)

• NBP Length and FBP Length• Mode Information

– Incremental or full dump• Beacon Slot Info Bitmap

– BP slot Status (details in the next slide)– Stateless bitmap (heard in previous BP)– 1-to-1 with the following DevAddr list

• List of corresponding DevAddr(s) from which a beacon was received in the previous superframe

– Included in ascending beacon slot order – If received with an invalid HCS, the DevAddr is set to BcstAddr.

octets: 1 1 1 1 1 K 2 … 2

Element ID Length (=2+K+2×N) NBP Length FBP LengthMode

Information

Beacon Slot Info Bitmap DevAddr 1 … DevAddr N

bits: 1 7

Mode Cycle Length

September 2006


Slide 51

doc.: IEEE 802.22-06/0130r2

Submission

Part 74 Occupancy IE (P74OIE)

• Mode Information– Incremental or full dump

• DevAddr– Address of DEV who made the report

• Channel No.– TV channel number of P74 device

• Sub-Channel No.– Sub-channel index within Channel No.,

if known• Start Time

– Start time of P74 service operation, if known

• Duration– Duration of P74 service operation,

if known• RSSI

– The received signal strength from the P74 device, if known

octets: 1 1 1 2 7 7

Element ID Length (=2+7×N)Mode

InformationDevAddr Part 74 Usage Info 1

…Part 74 Usage Info N

octets: 1 1 2 2 1

Channel No. Sub-Channel No.

Start Time Duration RSSI

bits: 1 7

Mode Cycle Length

September 2006


Slide 52

doc.: IEEE 802.22-06/0130r2

Submission

Beacon Transmission and Reception (I)

• At power-up, a DEV scans TV channels searching for DEV beacons first (at least 1 superframe per sub-channel)– If no beacon is received after the scan procedure

• If the DEV has a pre-programmed channel Ni (sub-channel i within TV channel N), or knows in which TV channel N the P74 device will operate

– sets its own BPST and sends the first beacon (in the first slot after the signaling slots) through channel Ni

• Else– As a result of sensing, selects a vacant channel N, sets its own BPST and sends the

first beacon (in the first slot after the signaling slots) through channel N i

– If another beacon is received• looks for an empty slot within mBPExtention(8) slots after highest-numbered

unavailable slot up to mMaxBPLength/2.

September 2006


Slide 53

doc.: IEEE 802.22-06/0130r2

Submission

Beacon Transmission and Reception (II)

• Within a TV channel, the sub-channel i where the beacon is transmitted can be:– Determined dynamically: long search procedure and higher delay– Pre-determined in the standard: fast discovery by both other DEVs

and USUs (i.e., 802.22)• Would this require regulatory approval?

• Once a slot is chosen by DEV, the beacon is always sent in the same slot unless – A collision is detected– Or contraction is required

September 2006


Slide 54

doc.: IEEE 802.22-06/0130r2

Submission

Beacon Transmission and Reception (III)

• Every DEV sends at least one beacon per BP• DEVs may transmit multiple beacons at multiple random times within a

BP, or transmit once over multiple slots. For example:– In case there are free slots– No or few number of neighboring DEVs

• This will facilitate detection by the WRAN and addresses the hidden node problem (see next slide)

Slotted Network Beacon Period

DE

V 7

DE

V 7

DE

V 7

DE

V 7

DE

V 3

Network Beacon Period Length (DYNAMIC)

BeaconSlot

...

September 2006


Slide 55

doc.: IEEE 802.22-06/0130r2

Submission

Beacon Transmission and Reception (IV): Addressing the Hidden Node Problem

• By transmitting multiple beacons at different random times, the hidden node is overcome

Picture courtesy of Shure Inc.

September 2006


Slide 56

doc.: IEEE 802.22-06/0130r2

Submission

Beacon Transmission and Reception (V)

• Upon receiving a beacon, a DEV processes it

• This includes determining the applicability of the information received and updating its own beacon, if needed. For example:– If the receiving DEV is “far enough away” (based on location

information) from the actual DEV reporting the P74 incumbent user, then there is no need to rebroadcast the P74OIE

– Information within the beacon shall not be rebroadcast for more than X number of hops

• A DEV rebroadcasts the relevant information obtained from its neighbors after processing all beacons received

September 2006


Slide 57

doc.: IEEE 802.22-06/0130r2

Submission

DEV Discovery by WRAN (I)

• Problem– How does the WRAN find out about DEVs?– What if the Beacon Channel Number is different from the

channel(s) the P74 device is operating?– A number of P74 devices may be operating in proximity (e.g., one

hop, two hops, …)

• A poor design choice would be to have each DEV to independently send a beacon through each channel occupied by a P74 device or WRAN– Interference to co-channel WRANs;– Collision of DEV beacons;– Power consumption of DEVs; etc.

September 2006


Slide 58

doc.: IEEE 802.22-06/0130r2

Submission

DEV Discovery by WRAN (II)

• Two options are possible:– Passive: The out-of-band measurement capability of the WRAN is used

to discover the BP of nearby DEVs• Scheme 1

– The WRAN knows a priori which sub-channel i the DEVs’ BP operate– A timely out-of-band measurement capability detects the DEVs’ BP within the

required Channel Detection Time• Scheme 2

– DEVs use pilot signals, with the WRAN employing a pilot detection scheme

– Proactive: DEVs switch to channels occupied by P74 services and transmit beacons through those channels

• This is also known as out-of-band beaconing• Through the BP, DEVs dynamically negotiate who will transmit beacons

through which P74 channels• Devices can take turn in beacon transmission and hence better mitigate fading

and shadowing• Both solutions are supported

September 2006


Slide 59

doc.: IEEE 802.22-06/0130r2

Submission

Conclusions

September 2006


Slide 60

doc.: IEEE 802.22-06/0130r2

Submission

Conclusions

• We have proposed a PHY and MAC layer that fully addresses the 802.22.1 requirements

• PHY– Two PHY modes– Single carrier modulation– Receiver determines which mode is transmitted/received– Energy sensing and preamble sensing

• MAC– Assured protection to Part 74 services– Fully distributed beaconing protocol– Unidirectional and bi-directional communication– Allows for better spectrum usage

doc.: ieee 802.22-06/0130r2 submission september 2006 carlos cordeiro, philipsslide 1 a beacon-based...

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