Wi-Gig
Utilizing Unlicensed 60 GHz Spectrum
Usage Models
Wireless Display
• Desktop storage and display
• Projection to TV or projector in conference room or
• In-room gaming
• Streaming from camcorder to display
• Professional HDTV outside broadcast pickup
Distribution of HDTV
• Video streaming around the home
• Intra-large-vehicle applications (e.g. airplane, ferry)
• Wireless networking for office
• Remote medical assistance
Rapid upload/download • Rapid file transfer/sync
• Picture-by-picture viewing
• Airplane docking (manifests, fuel, catering, . .)
• Downloading movie content to mobile device
• Police surveillance data transfer
Replacement of Cable in the PAN
• 60 GHz millimeter wave transmission will scale the
speed of WLANs and WPANs to 6.75 Gbit/s over
distances less than 10 meters.
• This technology is the first of its kind and will eliminate
the need for cable around personal computers, docking
stations, and other consumer electronic devices. Highdefinition multimedia interface (HDMI), display port,
USB 3.0, and peripheral component interconnect
express (PCIE) 3.0 cables will all be eliminated.
• Fast downloads and uploads, wireless sync, and multigigabit-per-second WLANs will be possible over shorter
distances.
60 GHz Link Budget
• primary challenge with millimeter wave operation is the much
poorer path loss than in the microwave band. For example, the free
space path loss at 1 m for 60 GHz is 68 dB compared to 47 dB at 5
GHz. Even attenuation due to person obstructing the path ranges
between 10 – 15 dB We further compare a 60 GHz link budget to a
5 GHz 802.11n link budget, as follows. There is a 21 dB increase in
path loss from 5 GHz to 60 GHz.
• In addition current technology for low cost consumer devices in 60
GHz will reduce transmit power in 60 GHz by 6 dB as compared to 5
GHz. Based on the channel bandwidth increase of 50x, the increase
in noise bandwidth results in another 17 dB loss. And again current
60 GHz technology will initially result in 3 dB worse noise figure
than 5 GHz technology.
• However, the target applications and use
cases are shorter range for this technology
(leaning towards personal area networking),
so 10 dB can be added to the link budget
margin for 60 GHz compared to longer range 5
GHz system. In addition, typically 60 GHz
system design will be target a lower order
modulation than an 802.11n system due to
the large channel bandwidth, which could
result in a 5 dB gain. In summary there could
be a 32 dB loss (or larger) in link margin from
5 GHz to 60 GHz.
Physical layer
• 802.11ad defines four different PHY layers: Control PHY, SC PHY, OFDM
PHY and low-power SC PHY (LPSC PHY). Control PHY is MCS 0. SC starts at
MCS 1 and ends at MCS 12; OFDM PHY starts at MCS 13 and ends at MCS
24; and LPSC starts at MCS 25 and ends at MCS 31. MCS 0 to MCS 4 are
mandatory PHY MCSs. Here, we briefly describe the different PHYs and
their packet structures. The system clock rate is 2640 MHz, and this rate is
used for OFDM also. Control, SC and LPSC PHYs have a clock rate of 2/3 ×
2640 = 1760 MHz
• common with all 802.11 packet formats, the packet consists of a short
training sequence, a channel estimation sequence, the physical layer
convergence procedure (PLCP) header, MAC packet, and cyclic redundancy
check (CRC). Although there are different PHYs, they all have this unique
structure, which ensures implementers do not need to change packet
formats when using different PHYs. The only difference is that each PHY is
a different size and uses a different Golay code.
MAC Layer
• The primary challenge for the 60 GHz MAC is how to handle
directional transmissions used to mitigate the high
propagation loss of millimeter waves .
• Prior to 802.11ad, the 802.11 MAC relies on Omnidirectional transmissions for management and control
frames (e.g. beacons, RTS/CTS) to ensure they can be heard
by everyone in the BSS. With directionality, device
discovery becomes more complicated. Furthermore,
devices need to find the best direction for communication,
which necessitates support for a beam forming protocol.
Also the basic 802.11 concept of CSMA/CA has limitations
in the presence of directional transmissions.
• The 802.11ad super frame is called the beacon
interval and comprises a beacon transmission
interval (BTI), a data transfer interval (DTI),
and optional association beam forming
training (A-BFT) or announcement
transmission intervals (ATI)
• The DTI can include one or more service
periods (SPs) and contention-based access
periods (CBAPs).
Combating High Path Loss
Beam forming Protocol
• Because of the highly directional nature of 60 GHz communications, the transmitter and
receiver antennas need to be aligned in the right direction to obtain maximum gain. 802.11ad
supports up to four transmitter antennas, four receiver antennas, and 128 sectors.
Beam forming is mandatory in 802.11ad, and both transmitter-side and receiver-side beam
forming are supported.
Backward compatibility with existing
802.11 standards
• Fast session transfer (FST) protocol allows different streams or sessions to
transfer smoothly
• from one channel to another in the same band or different bands. This
protocol makes
• 802.11ad compatible with the forthcoming 802.11ac standard and other
existing standards,
• such as 802.11a/b/g/n. The protocol allows different radios in the same
device to operate
• simultaneously or not simultaneously. Devices with 802.11ac and
802.11ad can have same MAC
• address or different MAC addresses. If the same MAC address is used for
all the radios in
• different bands then FST is in transparent mode. If the MAC addresses
differ according to
• channel/band, then FST is not transparent.
Fast Session Transfer Protocol
• Fast session transfer (FST) protocol allows different streams
or sessions to transfer smoothly from one channel to
another in the same band or different bands.
• This protocol makes802.11ad compatible with the
forthcoming 802.11ac standard and other existing
standards, such as 802.11a/b/g/n. The protocol allows
different radios in the same device to operate
simultaneously or not simultaneously. Devices with
802.11ac and 802.11ad can have same MAC address or
different MAC addresses. If the same MAC address is used
for all the radios in different bands then FST is in
transparent mode. If the MAC addresses differ according to
channel/band, then FST is not transparent.
FST Process
Conclusion
• Wi-Fi products based on next generation gigabit per second
802.11 technology will be emerging on the market soon to
address use cases that demand
• higher throughput. 802.11ac will evolve in the 5 GHz bands
with wider channels and multi-user capability to address
broader coverage use cases typical of Wi-Fi devices, such as
higher resolution video coverage around the home.
802.11ad will address personal area networking use cases
new to 802.11 such as wireless docking with multi-gigabit
per second links based on large amount of available
spectrum in the 60 GHz band. 802.11ad will make use of
directional antennas and beamforming to enhance link
quality, and modifies channel access to address
directionality and spatial reuse.