doc.: ieee 802.22-06/0130r2 submission september 2006 carlos cordeiro, philipsslide 1 a beacon-based...
TRANSCRIPT
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
Carlos Cordeiro, Philips
Slide 2
doc.: IEEE 802.22-06/0130r2
Submission
Outline
• Introduction
• The PHY Proposal
• The MAC Proposal
• Conclusions
September 2006
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 4
doc.: IEEE 802.22-06/0130r2
Submission
The PHY
September 2006
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 7
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Submission
The PHY (Mode A)
September 2006
Carlos Cordeiro, Philips
Slide 8
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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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 10
doc.: IEEE 802.22-06/0130r2
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
Carlos Cordeiro, Philips
Slide 11
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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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 14
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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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 18
doc.: IEEE 802.22-06/0130r2
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
Carlos Cordeiro, Philips
Slide 19
doc.: IEEE 802.22-06/0130r2
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
Carlos Cordeiro, Philips
Slide 20
doc.: IEEE 802.22-06/0130r2
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
Carlos Cordeiro, Philips
Slide 21
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Submission
The PHY (Mode B)
September 2006
Carlos Cordeiro, Philips
Slide 22
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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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 25
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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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 28
doc.: IEEE 802.22-06/0130r2
Submission
Preliminary Simulation Results for Mode A, Mode B and Spread DBPSK in AWGN
And Multipath
September 2006
Carlos Cordeiro, Philips
Slide 29
doc.: IEEE 802.22-06/0130r2
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 31
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Submission
Mode A – PER Vs. SNR in AWGN and multipath channel
September 2006
Carlos Cordeiro, Philips
Slide 32
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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
Carlos Cordeiro, Philips
Slide 33
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Submission
Mode B – BER Vs. SNR in AWGN channel
September 2006
Carlos Cordeiro, Philips
Slide 34
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Submission
Mode B – BER Vs. SNR in multipath channel
September 2006
Carlos Cordeiro, Philips
Slide 35
doc.: IEEE 802.22-06/0130r2
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
Carlos Cordeiro, Philips
Slide 36
doc.: IEEE 802.22-06/0130r2
Submission
Spread DBPSK – BER Vs. SNR in AWGN and multipath channel
September 2006
Carlos Cordeiro, Philips
Slide 37
doc.: IEEE 802.22-06/0130r2
Submission
Spread DBPSK – Performance with 2 interfering beacons
Multi-path channel,Matched-filter receiver
September 2006
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 39
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Submission
The MAC
September 2006
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
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
Carlos Cordeiro, Philips
Slide 59
doc.: IEEE 802.22-06/0130r2
Submission
Conclusions
September 2006
Carlos Cordeiro, Philips
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