1. Technology and Use Cases for TGac
Month Year
doc.: IEEE yy/xxxxr0
Technology and Use Cases for TGac
Date:
Authors:
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
Introduction
We look at various technologies for TGac, map the technologies to use cases and conclude that most of the gain is achieved with simple extensions to TGn
For use cases, we reference
WiFi Alliance (WFA) VHT Study Group Usage Models presented in 07/2988r4
John Doe, Some Company

3. Possible technologies
Wider channels
Higher order modulation and code rate
More spatial streams
Multi-user MIMO
OFDMA

4. Wider Channels Possible approaches Advantage Issues
Bond adjacent channels to form 80 MHz channel
Simultaneous transmission on non-adjacent channels
Advantage
Doubles the PHY data rate (sticker on the box still sells)
Negligible increase in cost over 11n
Issues
Bonding
Coexistence with 11n 20MHz & 40MHz
Non-adjacent channels
Significant receiver complexity to deal with OBSS
Frequency reuse
The number of available non-overlapping bonded channels will be lower
One 80MHz channel in GHz band
One 80MHz channel in GHz band
Can increase co-channel interference
Unknown whether a single channel can span multiple regulatory bands

5. Higher order modulation and code rate
256 QAM (was almost adopted in 11n)
1024 QAM
Higher code rate
7/8 (was almost adopted in 11n)
Advantage
Architecturally simple addition to the standard
Issues
Reduces robustness
Requires tighter Tx and Rx specs (e.g. phase noise)

6. More Spatial Streams Go beyond four steams in 11n, perhaps eight
Advantage
data rate increases as a function of number spatial streams
Issues
Size/power constrained devices may not be capable of supporting additional antennas
Antenna correlation/coupling if antennas need to be packed closer together
As we have seen in 11n, mobile/portable devices unlikely to support a large number of antennas

7. Multi-user MIMO 11n MIMO Multi-user MIMO
Spatial division multiplexing (SDM) – STA simultaneously transmits multiple streams to another STA
Multi-user MIMO
STA simultaneously transmits multiple streams to several other STAs
E.g. 4 antenna AP transmits two streams to STA1 and two streams to STA2
Advantage
Increases network capacity with client devices that only have few antennas
Issues
Multi-user MIMO on the downlink from AP to STA has higher complexity than 11n Tx Beamforming
Multi-user MIMO has very high complexity on uplink - would require precise transmit packet synchronization between STAs and transmit power control (similar to that required in CDMA cellular system)
Scheduling
As yet not well know how time variant is the channel

8. OFDMA Subdivide OFDM subcarriers to several STAs Advantage Issues
Used in cellular systems like Wimax
Advantage
More efficient method in usages with multiple lower rate clients, e.g. voice
Efficient uplink technique for ACK packets in response to downlink MU-MIMO packet
Issues
Has very high complexity on uplink - would require precise transmit packet synchronization between STAs and transmit power control
Scheduling
Does not increase maximum data rate or network capacity, only improves efficiency with multiple lower rate clients

9. WFA VHT Usage Models mapped to market volume and timing*
Relatively High 3a 1c 1b 2a 2b 1d 3b 1a 6a 2d 3d 4a 4b 3e 2c 1f 5b 1e 5a 2e 3c
Highlight these use cases on the next slide
Market Volume
Rela- tively Low
Later
Anticipated Market Timing For Mainstream Market
Sooner
* from 07/2988r4

10. WFA VHT Usage Models mapped to technologies
April 2007
doc.: IEEE /0570r0
WFA VHT Usage Models mapped to technologies
Category #
Usage model
MCS
Wider channel
MU-MIMO
OFDMA
More SS
1. Wireless Display 1a
Desktop Storage & Display X ? 1b
Projection to TV or projector in conf room (lightly compressed video) 1c
In room gaming (lightly compressed video) 1d
Streaming from camcorder to display (lightly compressed video) 1e
Broadcast TV field pick up 1f
Medical Imaging and Surgical Procedure Support
2. Distribution of HDTV 2a
Lightly compressed video streaming around the home 2b
Compressed video streaming around home 2c
Intra large vehicle (e.g. airplane) applications 2d
Wireless networking for office 2e
Remote medical assistance
3. Rapid upload/download 3a
Rapid sync-n-go file transfer 3b
Picture by picture viewing 3c
Airplane docking 3d
Movie content download to car 3e
Police / surveillance car upload
4. backhaul 4a
Multi-media mesh backhaul 4b
Point-to-point backhaul
5. Outdoor campus / auditorium 5a
Video demos / tele-presence in auditorium 5b
Public safety mesh
6. Manufacturing floor 6a
Manufacturing floor automation
Slide 10
Page 10
Eldad Perahia, Intel Corporation

11. Summary Wider channel benefits almost all applications
2x improvement
MCS enhancements benefit short range, direct link applications
Almost 2x improvement possible
Downlink MU-MIMO provides increased network efficiency for some applications
Only when long term, simultaneous traffic flows are present (e.g. video)
< 2x improvement; dependent on uplink/downlink traffic mix
Not clear that 2 hop MU-MIMO is better than direct link
More spatial streams may provide some benefit in certain environments
Cost and form factor prohibitive for most devices due to antenna requirements
Downlink OFDMA provides little benefit
Power saving and performance gain questionable
Uplink space/frequency multiplexing techniques
No compelling use case, especially considering complexity