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doc.: IEEE 802.11-11/0459r1
Submission
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 1
IEEE 802.11ad Overview for CWPANDate: 2011-03-19
Name Company Address Phone email Eldad Perahia Intel
Corporation
2111 NE 25th Ave Hillsboro, OR 97124
503-712-8081 [email protected]
Carlos Cordeiro Intel Corporation
2111 NE 25th Ave Hillsboro, OR 97124
Authors:
doc.: IEEE 802.11-11/0459r1
Submission
Motivation for 60 GHz
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 2
Australia
China
Korea
Japan
EU
Canada
USA
57 58 59 60 61 62 63 64 65 66 67
Spectrum Allocation (GHz)
doc.: IEEE 802.11-11/0459r1
Submission
Outline
• 802.11ad task group background• Summary of 802.11ad Enhancements• PHY• MAC• Beamforming• Coexistence with other 60 GHz systems
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 3
doc.: IEEE 802.11-11/0459r1
Submission
History
Very High Throughput Study Group• Started in May 2007 initially to
address Very High Throughput for < 6GHz IMT-Advanced operation
• Initial discussions on 60 GHz started in Nov 2007
• 60 GHz PAR approved Dec 2008
802.11ad• Task group started Jan 2009• Task group documents
– Functional Requirements– Evaluation Methodology– Channel Models– Usage Models
• Complete proposal approved May 2010 to create draft 0.1
• D1.0 approved by WG in Sept 2010
• D2.0 completed by TG in March 2011
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 4
doc.: IEEE 802.11-11/0459r1
Submission
Project Authorization Request (PAR)
• The 60 GHz ISM band provides the opportunity for much wider band channels than in <6 GHz enabling single link throughputs greater than 1 Gbps
• Two aspects of the PAR ensure distinct identity from 802.15.3c– Enable fast session transfer between PHYs – Maintain the 802.11 user experience
• Fast session transfer provides seamless rate fall back between VHT and 802.11n for multi-band devices– Provides expected WLAN coverage from combo 60 + 2.4/5 GHz devices– Does not mandate multi-band devices
• As an amendment to 802.11, VHT maintains the 802.11 user experience– maintaining the network architecture of the 802.11 system
• E.g. infrastructure basic service set, extended service set, access point, station– Reuse and maintain backward compatibility to 802.11 management plane
• E.g. association, authentication, security, measurement, capability exchange, MIB• Coexistence
– Coexistence with 802.15.3c in the 60 GHz band is an important issue to VHT demonstrated by being explicitly called out in the PAR scope
– Furthermore, the task group will produce a coexistence assurance document
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 5
doc.: IEEE 802.11-11/0459r1
Submission
802.11ad Official Timeline
• PAR approved: Dec 09, 2009• Initial Working Group Letter Ballot: September 2010• Recirculation Working Group Letter Ballot: March
2011• Initial Sponsor Ballot: planned for December 2011• Recirculation Sponsor Ballot: planned for March 2012• Final Working Group Approval: planned for July 2012• RevCom & Standards Board Final Approval: planned
for December 2012
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 6
doc.: IEEE 802.11-11/0459r1
Submission
Summary of 802.11ad Enhancements
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 7
Item Feature Technical details
Network architecture
Infra-BSS, IBSS, PBSS Backward compatibility to 802.11 + native WPAN support
Medium access Scheduled access and contention access
Enables both the low power and the high performance devices
Power saving Advanced power saving techniques
Can be more power efficient than today’s 802.11
Security mechanism
GCMP Secure communication at Gbps rates
PHY SC and OFDM, with common preamble and coding
• Up to 7Gbps with OFDM
• Up to 4.6Gbps with SC
Beamforming Unified and flexible beamforming scheme
Enables robust communication at ranges beyond 10m
Fast session transfer
Multi-band operation across 2.4/5/60 GHz
Built-in efficient and seamless support for multi-band radios
doc.: IEEE 802.11-11/0459r1
Submission
PHY
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 8
doc.: IEEE 802.11-11/0459r1
Submission
Channelization
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 9
Channel ID
Center Freq.(GHz)
Channel width(GHz)
OFDM Sampling Rate (MHz)
SC Chip Rate (MHz)
1 58.32 2.16 2640 1760
2 60.48 2.16 2640 1760
3 62.64 2.16 2640 1760
4 64.80 2.16 2640 1760
Same channelization as 802.15.3c, compatible mask requirement for coexistence
doc.: IEEE 802.11-11/0459r1
Submission
PHY Overview (1/2)
• Different PHY types for different usages:– Control PHY
• Designed for low SNR operation prior to beamforming– Single Carrier PHY
• SC enables low power/low complexity transceivers• Low Power SC
– Additional support for further reduction in implementation processing power with simpler coding and shorter symbol structure
– OFDM PHY• High performance in frequency selective channels• Maximum data rates using up to 64 QAM
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 10
doc.: IEEE 802.11-11/0459r1
Submission
PHY Overview (2/2)
• Interoperable devices– Control PHY and SC PHY mandatory for all devices
• PHY design simplified with common properties between Control, SC and OFDM PHYs– Common packet structure
– Same Golay sequences used for preamble training fields– Common LDPC structure for coding
• Embedded support for BF
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 11
doc.: IEEE 802.11-11/0459r1
Submission
Short Training Field (STF)
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 12
• STF used for packet detection, AGC, frequency offset estimation, synchronization
• Ga, Gb composed of 128 sample Golay sequence, transmitted using π/2-BPSK at SC symbol rate
• Complementary sequences are used to differentiate control MCS and high rate MCSs
Slide 12
ControlPHY:
Gb128 Gb128
STF=38xGb128, -Gb, -Ga (2.91 us) CEF
… -Gb128
SC/OFDM:
Ga128 Ga128
STF=16xGa128,-Ga (1.09 us) CEF
… -Gb128
-Gb128 -Ga128
-Ga128
…
…
doc.: IEEE 802.11-11/0459r1
Submission
Channel Estimation Field (CEF)March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 13
• CEF is used for channel estimation and an indication of modulation type
• Ga, Gb composed of 128 sample Golay sequence, transmitted using π/2-BPSK at SC symbol rate
SC/Control:
Ga128 -Ga128
STF CEF (655 ns)
u512 v512
… -Ga128 Gb128 -Ga128-Gb128 Ga128 -Gb128 -Gb128-Ga128-Gb128
v128
OFDM: STF CEF (655 ns)
v512 u512
… -Gb128
v128
-Ga128Ga128 Ga128 -Gb128 -Ga128-Gb128 -Ga128 Gb128 -Ga128-Gb128
doc.: IEEE 802.11-11/0459r1
Submission
Header and Data Field Transmission
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 14
Scrambler Encoder Modulator
SC:Symbol
Blocking
OFDM: IDFTGI
Insertion
GI Insertion
Control:Symbol
BlockingGI
InsertionSpreading
Pilot Insertion
doc.: IEEE 802.11-11/0459r1
Submission
Control PHY• Designed for very low SNR operation to close link prior to
beamforming– Mandatory single carrier mode with data rate ~27.5 Mbps (MCS 0)– 32 sample Golay spreading sequence, also mitigates against longer delay
spread channels– π/2 - Differential BPSK modulation: more robust in the presence of phase
noise allowing for shorter training fields• Rate ½ coding used, shortened from the common 3/4 LDPC code
– Effective shorter block size: 336 bits– Short LDPC code is more efficient for short packets– Bits are evenly divided between codewords to allow equal protection
• Packet length limitations– A-MPDU aggregation is not allowed using Control MCS– Maximum length is limited to 1024 bytes
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 15
doc.: IEEE 802.11-11/0459r1
Submission
Single Carrier PHY
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 16
MCS Index Modulation NCBPS Repetition Code RateData Rate
(Mbps)
1 π/2-BPSK 1 2 1/2 3852 π/2-BPSK 1 1 1/2 7703 π/2-BPSK 1 1 5/8 962.54 π/2-BPSK 1 1 3/4 11555 π/2-BPSK 1 1 13/16 1251.256 π/2-QPSK 2 1 1/2 15407 π/2-QPSK 2 1 5/8 19258 π/2-QPSK 2 1 3/4 23109 π/2-QPSK 2 1 13/16 2502.5
10 π/2-16QAM 4 1 1/2 308011 π/2-16QAM 4 1 5/8 385012 π/2-16QAM 4 1 3/4 4620
Man
dat
ory
• Block size – 512 symbols• 448 data symbols• 64 GI symbols; fixed
sequence (Ga64)• Tracking purposes• Can be used for
equalization• Symbol Rate = 1760 MHz• π/2 rotation applied to all
modulations
• To reduce PAPR for BPSK• To enable GMSK
equivalent modulation
doc.: IEEE 802.11-11/0459r1
Submission
Low Power Single Carrier PHY
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 17
• The FEC is one of the major contributor to the relatively high power consumption of the SC mode
• Simple FEC: – Reed Solomon (224, 208) for high data rate– Outer Reed Solomon (224, 208) + Inner block code (N,8)
doc.: IEEE 802.11-11/0459r1
Submission
OFDM PHY
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 18
• Spread QPSK (SQPSK) used for two lowest rates
• Symbol interleaver for 16 QAM and 64 QAM embedded in modulator• 16 QAM – 2 code words per symbol• 64 QAM – 3 code words per symbol
MCS index Modulation Code Rate NBPSC NCBPS NDBPS Data Rate
13 SQPSK 1/2 1 336 168 693.00
14 SQPSK 5/8 1 336 210 866.25
15 QPSK 1/2 2 672 336 1386.00
16 QPSK 5/8 2 672 420 1732.50
17 QPSK 3/4 2 672 504 2079.00
18 16-QAM 1/2 4 1344 672 2772.00
19 16-QAM 5/8 4 1344 840 3465.00
20 16-QAM 3/4 4 1344 1008 4158.00
21 16-QAM 13/16 4 1344 1092 4504.50
22 64-QAM 5/8 6 2016 1260 5197.50
23 64-QAM 3/4 6 2016 1512 6237.00
24 64-QAM 13/16 6 2016 1638 6756.75
• Sampling Rate = 2640 MHz• Exactly 1.5x the SC
symbol rate• 512 point FFT (193.9 ns)
• 336 data subcarriers• 16 pilot subcarriers• 3 null subcarriers at DC
• GI length of 128 samples (48.5 ns)
doc.: IEEE 802.11-11/0459r1
Submission
MAC
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 19
doc.: IEEE 802.11-11/0459r1
Submission
MAC Challenges
• The primary challenge for the MAC is how to deal with directional communication, which is used to combat the high propagation loss in 60 GHz– Device discovery becomes a non-trivial problem– Devices need to find the direction for communication, which
necessitates the support for beamforming– 802.11 CSMA/CA has limitations in the presence of directionality– How to exploit spatial frequency reuse in face of directional
communication
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 20
doc.: IEEE 802.11-11/0459r1
Submission
New MAC features
• A new network architecture named Personal Basic Service Set (PBSS), while retaining the existent 802.11 network architectures
• Channel access that support directionality and spatial frequency reuse, including both random access and scheduled access
• A unified and flexible beamforming scheme that can be tuned to simple, low power devices as well as complex devices
• Enhanced security (GCMP), link adaptation and power saving• Multi-band support (fast session transfer)
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 21
doc.: IEEE 802.11-11/0459r1
Submission
Personal BSS (PBSS)
• New network architecture in addition to infrastructure BSS and IBSS, which are also supported
• PBSS is defined to address some unique usages and challenges of 60GHz communication– Usages: Rapid sync-n-go file transfer, projection to TV/projector,
etc.– Challenges: directional channel access, power saving, etc.– Ad hoc network similar to
the IBSS, but:• A STA assumes the role of the
PBSS Central Point (PCP)• Only the PCP transmits
beacon frames
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 22
802.11 MAC/PHY
802.11 Personal BSS
STA 1/PCP STA 2
doc.: IEEE 802.11-11/0459r1
Submission
Beacon Interval (BI) structure
• Beacon transmission interval (BTI): AP/PCP performs one or more beacon transmissions potentially in different directions
• Association beamforming training (A-BFT): BF for BSS joining, BF link re-establishment, etc. Efficient by using beacon to bootstrap BF
• Announcement time (AT): used to convey control/management between AP/PCP and STA
• Data transfer time (DTT): prescribed STAs access the channel during SP, negotiated between AP/PCP and STA or dynamically allocated. Any STA can access the channel during CBAP; access is based on 802.11 EDCA
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 23
3) Announcement Time:Association, schedule, etc.
1)BTI
2)A-BFT
3)AT
4)DTT
Beacon Interval
time
Omni
1) Beacon Transmission Interval: discover new STAs
2) Association BeamForming Training:BF between AP/PCP and STAs
4) Data Transfer Time:Service Period (SP) and
Contention-based Access Period (CBAP)
CBAP SP
SP
SP
doc.: IEEE 802.11-11/0459r1
Submission
Channel Access
• Channel access is coordinated using a schedule, which is delivered by the PCP/AP to non-PCP/non-AP STAs
• STAs are permitted to transmit data frames during contention-based periods (CBPs) and service periods (SPs)– Access during CBPs is based on
EDCA fine-tuned for directionalaccess
– Access during SPs is reserved to specific STAs as announced in the schedule or granted by the PCP/AP
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 24
MAC efficiency is above (or very close to) 90% of the PHY rate for payload sizes larger than 8Kbytes
0
500
1000
1500
2000
2500
3000
3500
4000
0.5 1 2 4 8 16 32 64T
hro
ug
hp
ut
(Mb
ps
)Payload size (Kbytes)
0.952Gbps 1.9Gbps 3.8Gbps
doc.: IEEE 802.11-11/0459r1
Submission
Fast session transfer (FST) for multi-band operation
• Enables seamless integration of 60GHz with 802.11a/b/g/n/ac
• Allows transition of communication from any band/channel to any other band/channel
• Supports both simultaneous and non-simultaneous operation
• Supports both transparent and non-transparent FST– Transparent: the MAC address is
the same in both bands/channels– Non-transparent: the MAC
addresses are different
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 25
60 GHz(ant, FEM, RFIC)
BB & Lower MAC for 60G
(802.11ad)
5 GHz(ant, FEM, RFIC)
2.4 GHz(ant, FEM, RFIC)
BB & Lower MAC(802.11b/a/g/n/ac)
Common Upper MAC (management)
Fast Session Transfer (802.11ad)
doc.: IEEE 802.11-11/0459r1
Submission
BEAMFORMING
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 26
doc.: IEEE 802.11-11/0459r1
Submission
Beamforming
• High antenna gains require mechanisms to point the antennas, since beamwidths will be narrow (e.g. ~13 dB gain corresponds to ~45 degree beamwidth)
• Pointing must automatically find the best path to potentially avoid obstructions
• Beamforming encompasses different techniques – switched beams, phased/weighted arrays, multiple arrays
• Beamforming protocol must support interoperable devices with different technologies
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 27
doc.: IEEE 802.11-11/0459r1
Submission
Beamforming Protocol Overview
• Specification employs:– Directional TX / low gain (quasi-omni) RX for acquisition in
sector level sweep (SLS) phase – Beam refinement phase (BRP) adds RX gain and final adjustment
for combined TX and RX– Tracking during data transmission to adjust for channel changes
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 28
doc.: IEEE 802.11-11/0459r1
Submission
Overview of TX Sector Level Sweeps
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 29
• For the initial connection between two devices (STA and AP/PCP), one will receive with a quasi-omni-directional antenna while the other sends a sequence of frames covering different TX sectors
• For direct connections between two STAs in a PBSS
PCP(PBSS Control Point)
STA
doc.: IEEE 802.11-11/0459r1
Submission
Overview of RX Sector Level Sweeps
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 30
• A device with a simple antenna may not have enough TX gain to reach a distant receiver that is using an omni-directional receiving antenna
• RX Sector Sweep may be employed by the device with the higher performance antenna system
• Allows a simple antenna device, like a handset, to connect at greater range
Simple Antenna Device
RX Sector Sweep isused to initiate beamformingon this link
doc.: IEEE 802.11-11/0459r1
Submission
Sector Level Sweep Packet Sequence
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 31
CDOWN=31Sector Id=14
CDOWN=30Sector Id=10
CDOWN=29Sector Id=25
CDOWN=0Sector Id=3
CDOWN=31Sector Id=1
Best Sector=25
Transmit Sector Sweep
Receive Sector Sweep
Sector Sweep Feedback
Forward Sector Sweep
Initiator
Responder
Sector Sweep
ACK
Reverse Sector Sweep
CDOWN=30Sector Id=1
Best Sector=25
CDOWN=29Sector Id=1
Best Sector=25
CDOWN=0Sector Id=1
Best Sector=25
• Each packet in the transmit sector sweep includes countdown indication (CDOWN), a Sector ID, and an Antenna ID
• The best Sector ID and Antenna ID information are fed back with the Sector Sweep Feedback and Sector Sweep ACK packets
doc.: IEEE 802.11-11/0459r1
Submission
COEXISTENCE
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 32
doc.: IEEE 802.11-11/0459r1
Submission
Coexistence with other 60 GHz systems• The same channelization as other 60 GHz systems is used, and the same
SC chip rate as that of 802.15.3c CMS is adopted• AP should not start a BSS where the signal level is above a threshold or
upon detecting a 802.15.3c CMS preamble at >= -60 dBm– In 802.11a/n, MCS 0 (BPSK, R=1/2) receive sensitivity is -82 dBm and non-802.11
detection level is -62 dBm → 20 dB difference– In 802.11ad, SC MCS 1 receive sensitivity is -68 dBm → 8 dB difference with
respect to required 802.15.3c CMS preamble detection threshold– Requirement of detection of 802.15.3c CMS preamble is 12dB more stringent than
802.11a/n and non-802.11 detection!• STAs can perform channel measurements and report results to AP/PCP• Several mechanisms can be used to mitigate interference with other 60
GHz systems, including:– Change operating channel, beamforming, reduce transmit power, move the BTI
(and thus the BI) in case of an AP or PCP, change or request the change of scheduled SPs and CBPs in the BI, defer transmission for a later time
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 33
doc.: IEEE 802.11-11/0459r1
Submission
Acronyms (1/3)
• A-BFT - Association beamforming training
• ACK - acknowledgment• AP – access point• AT - Announcement time• BB - baseband• BF - beamforming• BPSK - binary phase shift keying• BRP - beam refinement protocol • BTI - beacon transmission interval• CBAP – contention-based access period • CE, CEF – channel estimation field• CMS – common mode signaling
• CSMA/CA - carrier sense multiple access with collision avoidance
• DTT - Data transfer time• FFT - Fast Fourier Transform• FEM – front-end module• FST – fast session transfer• GCMP - Galois/Counter mode protocol• GMSK - Gaussian minimum shift
keying• GI – guard interval• IBSS – independent basic service set• ID - identification• Infra-BSS – infrastructure basic service
set
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 34
doc.: IEEE 802.11-11/0459r1
Submission
Acronyms (2/3)
• ISM - industrial, scientific, and medical• LDPC - low-density parity check• MCS – modulation, coding scheme• MAC - medium access control• MIB - management information base• OFDM - orthogonal frequency division
multiplexing• PAR - Project Authorization Request• PAPR - Peak-to-Average Power Ratio• PBSS - personal basic service set • PCP - PBSS control point • PHY - physical layer• QAM - quadrature amplitude
modulation
• QPSK - quadrature phase shift keying• RFIC – radio frequency integrated
circuit• RX – receive or receiver• SC – single carrier• SLS - sector level sweep • SNR – signal to noise ratio• SP – service period• SQPSK – spread QPSK• STA – station• STF – short training field• TG – task group• TX – transmit or transmitter
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 35
doc.: IEEE 802.11-11/0459r1
Submission
Acronyms (3/3)
• VHT – very high throughput• WG – working group• WPAN – wireless personal area
networking
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 36
doc.: IEEE 802.11-11/0459r1
Submission
References
• P802.11ad Draft 1.2• Cordeiro, Carlos, “PHY/MAC Complete Proposal to
TGad”, May 16, 2010, 11-10/0432r2• Hansen, Christopher, “Beamforming Introduction”,
May 16, 2010, 11-10/0430r1• Cordeiro, Carlos and Shankar, Sai, “Next Generation
Multi-Gbps Wireless LANs and PANs”, IEEE Globecom 2010, Dec 2010
March 2011
Eldad Perahia
, Intel Corpor
ation
Slide 37
