1. Wireless Networking Business Unit
March 2002
Suggested Criteria for High Throughput Extensions to IEEE Systems
Sean Coffey
Wireless Networking Business Unit
Texas Instruments
141 Stony Circle, Suite 210
Santa Rosa, CA 95401
Sean Coffey, Texas Instruments

2. March 2002
Overview
Recap of current context in high data rate extensions in IEEE
Throughput, Rate, Range: suggested criteria
Backwards compatibility and upgrade path issues
PHY, MAC, and beyond: suggested scope
Sean Coffey, Texas Instruments

3. Recap of higher rates & 802.11 11b and 11a completed in September 1999
March 2002
Recap of higher rates &
11b and 11a completed in September 1999
March 2000 – present: Task Group G, charged with developing a PHY with rate > 20 Mbps in the 2.4 GHz band (ongoing)
Ordinarily, next logical step would be analogous effort in the 5 GHz band, but …
… tentative 11g solution complicates the situation
Sean Coffey, Texas Instruments

4. March 2002
“g = b + a”
Current draft combines aspects of 11b and 11a in the 2.4 GHz band
11a PHY taken as is, and placed in 2.4 GHz band
Draft also allows for PBCC-22 & -33 (b extension) and CCK-OFDM (b-to-a-in-packet format)
Compatibility possible due to functionality of the common MAC
Provides a path to dual-band devices
Sean Coffey, Texas Instruments

5. Possible directions for extensions
March 2002
Possible directions for extensions
Extend rates simultaneously in both bands
Preserves dual-band convergence from g
Places extra requirements on performance OR
Extend rates only at 5 GHz
No 2.4 GHz issues to be considered
Similar barrier to adoption as existing 11a-only
Sean Coffey, Texas Instruments

6. March 2002
Suggested direction
Set criteria in terms of “extensions to wireless LANs”
Keep our options open!
Sean Coffey, Texas Instruments

7. Spectral efficiency vs. “Rate”
March 2002
Spectral efficiency vs. “Rate”
Can immediately get higher numbers by “channel bonding”
This is a poor idea
Always an option with any system
Criteria should be set up in terms of rates per channel
I.e., spectral efficiency
Sean Coffey, Texas Instruments

8. Rates, throughput and range
March 2002
Rates, throughput and range
Current 11a, 1000 byte packets:
Sean Coffey, Texas Instruments

9. Rates, throughput and range
March 2002
Rates, throughput and range
One possible future: X
Sean Coffey, Texas Instruments

10. Rates, throughput and range
March 2002
Rates, throughput and range
A more interesting goal: . . .
Sean Coffey, Texas Instruments

11. Net throughput must account for various types of overhead
March 2002
Throughput vs. Rate
Net throughput must account for various types of overhead
Header (20 us)
SIFS time (16 us)
Acknowledgement (incl. header) (24 us)
DIFS time (34 us)
Backoff, etc.
Note that top “rate” does not even appear on previous graphs
Sean Coffey, Texas Instruments

12. Overhead reduction: Initial examples
March 2002
Overhead reduction: Initial examples
Packet aggregation: ensure maximum data payloads
1500 “54” Mbps -> 37 Mbps
420 “54” Mbps -> 21 Mbps
420 “100” Mbps -> 26 Mbps
Was in 11e, but has been removed
Burst acks: reduce acknowledgement traffic
11e currently provides for this
Sean Coffey, Texas Instruments

13. March 2002
Range extension
Target should be higher effective throughputs at ranges that at least match current top rates
Sean Coffey, Texas Instruments

14. Overhead constraints Constellation affects required preamble length
March 2002
Overhead constraints
Constellation affects required preamble length
Code changes affect required SIFS time
Bit loading requires more channel measurement information
Challenge is to introduce changes that do not require increase in overhead elsewhere
Sean Coffey, Texas Instruments

15. March 2002
Suggested criterion
Criterion can be set up in terms of higher throughput
E.g., “must have 2x throughput advantage over existing systems”
This implies increased spectral efficiency
Allows invention in terms of how overall system is used
Sean Coffey, Texas Instruments

16. Backwards compatibility
March 2002
Backwards compatibility
Backwards compatibility comes with many constraints …
… however, it is vital for the success of any communications protocol
A possible approach: require backwards compatibility, but in the “wide sense”
Proposals would have wide latitude in how they achieve the required backwards compatibility
Sean Coffey, Texas Instruments

17. PHY, MAC, and beyond: suggested scope
March 2002
PHY, MAC, and beyond: suggested scope
In the past, study groups have been classified informally at the outset: e.g., PHY or MAC
This is unnecessary and has the potential for problems
Study group should be empowered to recommend all appropriate changes at every layer
This is not the same as saying that proposals can ignore the OSI model
Sean Coffey, Texas Instruments

18. March 2002
Summary
Study group should emphasize high performance (throughput/rate) WLANs in general
SG should emphasize overall performance
Backwards compatibility is vital
SG should have broad scope and the authorization to recommend all necessary changes
Sean Coffey, Texas Instruments