1. IEEE 802.11ad Overview for CWPAN
April 2007
doc.: IEEE /0570r0
March 2011
IEEE ad Overview for CWPAN
Date:
Authors:
Eldad Perahia, Intel Corporation
Eldad Perahia, Intel Corporation

2. March 2011
Motivation for 60 GHz
Eldad Perahia, Intel Corporation

3. Outline 802.11ad task group background
March 2011
Outline
802.11ad task group background
Summary of ad Enhancements
PHY
MAC
Beamforming
Coexistence with other 60 GHz systems
Eldad Perahia, Intel Corporation

4. History Very High Throughput Study Group 802.11ad
March 2011
Very High Throughput Study Group
802.11ad
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
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
Eldad Perahia, Intel Corporation

5. Project Authorization Request (PAR)
March 2011
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 c
Enable fast session transfer between PHYs
Maintain the user experience
Fast session transfer provides seamless rate fall back between VHT and n for multi-band devices
Provides expected WLAN coverage from combo /5 GHz devices
Does not mandate multi-band devices
As an amendment to , VHT maintains the user experience
maintaining the network architecture of the system
E.g. infrastructure basic service set, extended service set, access point, station
Reuse and maintain backward compatibility to management plane
E.g. association, authentication, security, measurement, capability exchange, MIB
Coexistence
Coexistence with c 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
Eldad Perahia, Intel Corporation

6. 802.11ad Official Timeline PAR approved: Dec 09, 2009
March 2011
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
Eldad Perahia, Intel Corporation

7. Summary of 802.11ad Enhancements
March 2011
Summary of ad Enhancements
Item
Feature
Technical details
Network architecture
Infra-BSS, IBSS, PBSS
Backward compatibility to 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
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
Eldad Perahia, Intel Corporation

8. March 2011
PHY
Eldad Perahia, Intel Corporation

9. OFDM Sampling Rate (MHz)
March 2011
Channelization
Channel ID
Center Freq.
(GHz)
Channel width
OFDM Sampling Rate (MHz)
SC Chip Rate (MHz) 1
58.32
2.16
2640
1760 2
60.48 3
62.64 4
64.80
Same channelization as c, compatible mask requirement for coexistence
Eldad Perahia, Intel Corporation

10. PHY Overview (1/2) Different PHY types for different usages:
March 2011
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
Eldad Perahia, Intel Corporation

11. PHY Overview (2/2) Interoperable devices
March 2011
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
Eldad Perahia, Intel Corporation

12. Short Training Field (STF)
March 2011
Short Training Field (STF)
Control
PHY:
Gb128
STF=38xGb128, -Gb, -Ga (2.91 us)
CEF …
-Gb128
SC/OFDM:
Ga128
STF=16xGa128,-Ga (1.09 us)
-Gb128
-Ga128 …
-Ga128 …
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
Eldad Perahia, Intel Corporation

13. Channel Estimation Field (CEF)
March 2011
Channel Estimation Field (CEF)
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 …
Gb128
-Gb128
v128
OFDM:
STF
CEF (655 ns)
v512
u512 …
-Gb128
v128
-Ga128
Ga128
Gb128
Eldad Perahia, Intel Corporation

14. Header and Data Field Transmission
March 2011
Header and Data Field Transmission
Scrambler
Encoder
Modulator
Spreading
Symbol Blocking
GI Insertion
Control:
Symbol Blocking
GI Insertion
SC:
Pilot Insertion
IDFT
GI Insertion
OFDM:
Eldad Perahia, Intel Corporation

15. March 2011
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
Eldad Perahia, Intel Corporation

16. Single Carrier PHY Block size – 512 symbols 448 data symbols
March 2011
Single Carrier PHY
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
MCS Index
Modulation
NCBPS
Repetition
Code Rate
Data Rate (Mbps) 1
π/2-BPSK 2
1/2
385
770 3
5/8
962.5 4
3/4
1155 5
13/16 6
π/2-QPSK
1540 7
1925 8
2310 9
2502.5 10
π/2-16QAM
3080 11
3850 12
4620
Mandatory
Eldad Perahia, Intel Corporation

17. Low Power Single Carrier PHY
March 2011
Low Power Single Carrier PHY
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)
Eldad Perahia, Intel Corporation

18. OFDM PHY Sampling Rate = 2640 MHz Exactly 1.5x the SC symbol rate
March 2011
OFDM PHY
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)
MCS index
Modulation
Code Rate
NBPSC
NCBPS
NDBPS
Data Rate 13
SQPSK
1/2 1
336
168
693.00 14
5/8
210
866.25 15
QPSK 2
672 16
420 17
3/4
504 18
16-QAM 4
1344 19
840 20
1008 21
13/16
1092 22
64-QAM 6
2016
1260 23
1512 24
1638
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
Eldad Perahia, Intel Corporation

19. March 2011
MAC
Eldad Perahia, Intel Corporation

20. March 2011
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
CSMA/CA has limitations in the presence of directionality
How to exploit spatial frequency reuse in face of directional communication
Eldad Perahia, Intel Corporation

21. March 2011
New MAC features
A new network architecture named Personal Basic Service Set (PBSS), while retaining the existent 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)
Eldad Perahia, Intel Corporation

22. March 2011
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
Eldad Perahia, Intel Corporation

23. Beacon Interval (BI) structure
March 2011
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 EDCA
Eldad Perahia, Intel Corporation

24. March 2011
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 directional access
Access during SPs is reserved to specific STAs as announced in the schedule or granted by the PCP/AP
MAC efficiency is above (or very close to) 90% of the PHY rate for payload sizes larger than 8Kbytes
Eldad Perahia, Intel Corporation

25. Fast session transfer (FST) for multi-band operation
March 2011
Fast session transfer (FST) for multi-band operation
Enables seamless integration of 60GHz with a/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
60 GHz
(ant, FEM, RFIC)
BB & Lower
MAC for 60G
(802.11ad)
5 GHz
2.4 GHz
BB & Lower MAC
(802.11b/a/g/n/ac)
Common Upper MAC (management)
Fast Session Transfer (802.11ad)
Eldad Perahia, Intel Corporation

26. March 2011
Beamforming
Eldad Perahia, Intel Corporation

27. March 2011
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
Eldad Perahia, Intel Corporation

28. Beamforming Protocol Overview
March 2011
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
Eldad Perahia, Intel Corporation

29. Overview of TX Sector Level Sweeps
March 2011
Overview of TX Sector Level Sweeps
STA 2 1 3 4
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)
Eldad Perahia, Intel Corporation

30. Overview of RX Sector Level Sweeps
March 2011
Overview of RX Sector Level Sweeps
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 1 2
RX Sector Sweep is
used to initiate beamforming
on this link 4 3
Simple Antenna
Device
Eldad Perahia, Intel Corporation

31. Sector Level Sweep Packet Sequence
March 2011
Sector Level Sweep Packet Sequence
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
Eldad Perahia, Intel Corporation

32. March 2011
Coexistence
Eldad Perahia, Intel Corporation

33. Coexistence with other 60 GHz systems
March 2011
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 c CMS is adopted
AP should not start a BSS where the signal level is above a threshold or upon detecting a c CMS preamble at >= -60 dBm
In a/n, MCS 0 (BPSK, R=1/2) receive sensitivity is -82 dBm and non detection level is -62 dBm → 20 dB difference
In ad, SC MCS 1 receive sensitivity is -68 dBm → 8 dB difference with respect to required c CMS preamble detection threshold
Requirement of detection of c CMS preamble is 12dB more stringent than a/n and non 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
Eldad Perahia, Intel Corporation

34. Acronyms (1/3) March 2011 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
Eldad Perahia, Intel Corporation

35. Acronyms (2/3) March 2011 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
Eldad Perahia, Intel Corporation

36. Acronyms (3/3) March 2011 VHT – very high throughput
WG – working group
WPAN – wireless personal area networking
Eldad Perahia, Intel Corporation

37. March 2011
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
Eldad Perahia, Intel Corporation