1. July 2004
40 / 20 / 10 MHz Channelization for Robust, High-Performance, Cost-Effective n Operation
Jan Boer, Agere Systems, Inc.
Jeff Gilbert, Atheros Communications, Inc.
Eldad Perahia, Cisco Systems, Inc.
John Sadowsky, Intel Corporation
Nico van Waes, Nokia Corporation
Wim van Houtum, Royal Philips Electronics
Takushi Kunihiro, Sony Corporation
Masuhiro Takagi, Toshiba Corporation
July 2004
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

2. The Trend of Increasing Bandwidth
July 2004
The Trend of Increasing Bandwidth
The Cellular History
Continuous increase in channel bandwidth
AMPS/TDMA – kHz
GSM – kHz
IS-95 cdma – MHz
WCDMA – MHz
Different technologies
but we will show that the same principles apply to WLAN
Currently there is over 600 MHz of unlicensed spectrum available to WLAN in many regions. This number is continually growing
Increasing Bandwidth
and
Increasing Capacity
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

3. 40 / 20 / 10 MHz Operation Our core position on 40 MHz operation:
July 2004
40 / 20 / 10 MHz Operation
Our core position on 40 MHz operation:
It is mandatory for a .11n device to support 20MHz legacy channelization
It is mandatory for an .11n device to support 20MHz and 40MHz n channelization if obtained a type-approval for a region that allows 40MHz channelization.
A 20/40 MHz .11n device shall be able to interoperate with a 20 MHz only n device while supporting 40MHz operation with 20/40 MHz .11n devices.
Operation in 10MHz and 20MHz modes can be used if required by spectral availability or regulations
Performance will be inherently lower than 40MHz modes
However, performance will be maximized in these lower bandwidth modes when they are only the option
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

4. Channel Bandwidth Position
July 2004
Channel Bandwidth Position
Support 10, 20 and 40 MHz channels as available in each region to provide optimal global flexibility for 11n applications.
MHz total
825 MHz total
575 MHz total
MPHPT
FCC
20 MHz Mandatory
10 MHz Optional
20 MHz Mandatory
10 MHz Mandatory
MPHPT (-5.725)
FCC
ETSI
20 MHz Mandatory
20 MHz Mandatory
40 MHz Mandatory
20 MHz Mandatory
40 MHz Mandatory
FCC
10 MHz Mandatory
20 MHz Optional
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

5. 20 MHz vs. 40 MHz Cost and Performance
July 2004
20 MHz vs. 40 MHz Cost and Performance
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

6. Shannon Capacity: 2B or not 2B
July 2004
Shannon Capacity: 2B or not 2B
40 MHz wins the Shannon argument!
350
300
250
200
Capacity (Mbps)
40 MHz
150
100
20 MHz 50 5 10 15 20 25 30
SNR (dB)
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

7. Over-The-Air Effective Data Rate - Model D
July 2004
Over-The-Air Effective Data Rate - Model D
Effective Data Rate (Mbps)
Even using twice as many radio chains cannot compensate for the use of only 20MHz
Post Detection SNR (dB)
Post Detection SNR includes simulated channel estimation error but no other impairments
OTA = “over the air” effective data rate – includes PER effects but not preamble & MAC overheads
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

8. Comparison of 20 & 40 MHz with Comparable Throughput Systems
July 2004
Comparison of 20 & 40 MHz with Comparable Throughput Systems
4x4 20 MHz
2x2 40 MHz
Comparable Peak Rate
216 Mbps
243 Mbps
Required SNR for MAC
> dB (extrapolated) need low phase noise, quant. noise, PA non-lin.
~26 dB relaxed impairment requirements
RF Costs
Higher - 4 RF chains
Lower - 2 RF chains
Analog Costs
Same A/D, more filters
Same A/D, fewer filters
Digital Costs
Higher 4 x digital filters 4 x 64 pt FFT 4x4 matrix inv (v difficult)
Lower 2 x digital filters 2 x 128 pt FFT 2x2 matrix inverse
Future: x4 peak rate
Near 500Mbps!!!
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

9. Resource Sharing Implications of Wider Bandwidth Systems
July 2004
Resource Sharing Implications of Wider Bandwidth Systems
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

10. WLAN Resource Sharing Co-channel BSSs share channel resource
July 2004
WLAN Resource Sharing
Co-channel BSSs share channel resource
All STAs respect all decoded duration fields
All STAs respect all decode NAVs
Our 40 MHz solution
Robust legacy (20 MHz) compatible preamble
Defines a broad contention footprint relative to the HT footprint
Actually wider contention footprint than 20 MHz BSS (due to frequency diversity of duplicate format preamble)
This enhances adjacent co-channel BSS channel sharing
HT Footprint
Area where BSS delivers usable HT data
Size of BSS depends on minimal rate
Contention Footprint
Area where preamble can be detected and decoded.
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

11. WLAN Resource Sharing Compare A and B have disjoint 20 MHz channels
July 2004
WLAN Resource Sharing A B
Adjacent co-channel BSSs will effectively divide channel resource because they act as a common contention pool.
Broad contention footprints
Due to duplicate format preamble
Contention footprints overlap and largely cover combined HT footprints
Minimize hidden nodes
Compare
A and B have disjoint 20 MHz channels
vs.
A and B share a common 40 MHz channel
Common 40 MHz channel is superior! Next slide please.
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

12. WLAN Resource Sharing Denied traffic!
July 2004
WLAN Resource Sharing
Compare
A and B have disjoint 20 MHz channels
vs.
A and B share a common 40 MHz channel
Denied traffic!
Erlang outage capacity of common resource pool
= 1.4 x combined Erlang outage capacity of disjoint pools
Note Pessimistic Assumption: 40 MHz capacity = 2 x 20 MHz capacity
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

13. Cellular Re-use – Simulation
July 2004
Cellular Re-use – Simulation
28 vs. 14 Channels in 5GHz (ref TGn CC earlier draft)
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

14. Cellular Re-use – Simulation Conditions
July 2004
Cellular Re-use – Simulation Conditions
4 STA, 1 AP per BSS, 20m ring round AP
TGn CC conditions
2x2 ZF Receiver
MAC simulation with realistic simulation of interference (multiple interference regions per packet, multiple interferers …)
MAC-level Aggregation. TGe TXOP.
Link Adaptation
Receiver threshold adapted to consider nearest neighbour BSS as interference
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

15. Cellular Re-use - Results
July 2004
Cellular Re-use - Results
Metric
Units
20 MHz
40 MHz
Throughput for central BSS
Mbps 36 44
Width of channel
MHz 20 40
Area of BSS m2
2512
Number of BSS in tile 28 14
Area of cellular tile
70336
35168
Throughput/MHz/Area
Mbps/ MHz/m2
2.56e-05
3.1e-05
Relative to 20MHz 1
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

16. July 2004
Conclusions
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi

17. Why 40/20/10 MHz for 11n? Cost and Efficiency
July 2004
Why 40/20/10 MHz for 11n?
Cost and Efficiency
Provides a robust high throughput solution
Provides a low cost high throughput solution
Provides a low power high throughput solution
All relative to the 20 MHz alternative
Proposals should still maximize performance in 20 / 10 MHz when that is the only option due to spectrum availability
Full interoperability with 20 MHz STAs
See IEEE presentation /0772 for details
J. Boer, J. Gilbert, E. Perahia, J. Sadowsky, N. Waes, W. Houtum, T. Kunihiro, M. Takagi