1. Options for PBCC 22 Proposal
January 2001
doc.: IEEE /066
January 2001
Options for PBCC 22 Proposal
Anuj Batra Ph.D., Chris Heegard Ph.D., Eric J. Rossin Ph.D., Matthew B. Shoemake Ph.D., and Srikanth Gummadi
Texas Instruments
12500 TI Boulevard, MS 8653
Dallas, TX 75243
(214) ,
Anuj Batra et al., Texas Instruments
Anuj Batra et al., Texas Instruments

2. Increasing Throughput with a High Performance Preamble
January 2001
Increasing Throughput with a High Performance Preamble
Anuj Batra et al., Texas Instruments

3. Current Preamble and Header (P/H)
January 2001
doc.: IEEE /066
January 2001
Current Preamble and Header (P/H)
Long PLCP PPDU Format:
PLCP PREAMBLE
144 1Mbps
PLCP HEADER
48 1Mbps
PSDU
192 ms
Short PLCP PPDU Format:
SHORT PLCP PREAMBLE
72 1Mbps
SHORT PLCP HEADER
48 2Mbps
PSDU
96 ms
Preamble and header contains no information - overhead
Anuj Batra et al., Texas Instruments
Anuj Batra et al., Texas Instruments

4. Motivation for a Shorter P/H
January 2001
doc.: IEEE /066
January 2001
Motivation for a Shorter P/H
For short packets:
preamble and header spans a large portion of the packet
Large P/H wastes valuable resources and decreases the network throughput
Can reduce overhead by:
defining a new preamble, and
increasing the data rate for the header
Anuj Batra et al., Texas Instruments
Anuj Batra et al., Texas Instruments

5. New High Performance P/H
January 2001
doc.: IEEE /066
January 2001
New High Performance P/H
~38 ms
TIMING SYNC
88 11Msps
FRAME SYNC
72 11Msps
CHANNEL EST
168 11Msps
HEADER
48 5.5Mbps
PSDU
5.5 – 33 Mbps
PREAMBLE
Timing Synchronization Sequence: tones
complex tone at f0 = ±8.25 MHz
allows for easy detection of packet, carrier frequency offset, symbol timing
requires that the clocks to be locked
Frame Synchronization Sequence: PN sequences
can be used to determine the location within packet
can also be used for receiver diversity – select the antenna with best gain
Channel Estimation Sequence: deterministic sequence
first 160 symbols of a length 255 PN sequence
sequence is generated by using a minimal polynomial over GF(4)
Anuj Batra et al., Texas Instruments
Anuj Batra et al., Texas Instruments

6. Key Points of High Performance P/H
January 2001
doc.: IEEE /066
January 2001
Key Points of High Performance P/H
Increases throughput by reducing overhead
Designed to work at SNRs as low as 3–4 dB
Preamble can be used to estimate the channel
Supports most legacy rates: 5.5 and 11 Mbps
Also supports newer rates: 16.5, 22, 33 Mbps
High performance Preamble/Header can also be clocked at 16.5 MHz (more later)
Anuj Batra et al., Texas Instruments
Anuj Batra et al., Texas Instruments

7. Throughput with ACK January 2001 doc.: IEEE 802.11-01/066 January 2001
Anuj Batra et al., Texas Instruments
Anuj Batra et al., Texas Instruments

8. Throughput with NO ACK January 2001 doc.: IEEE 802.11-01/066
Anuj Batra et al., Texas Instruments
Anuj Batra et al., Texas Instruments

9. January 2001
doc.: IEEE /066
January 2001
Increasing the Data Rate to 33Mbps in Wireless Ethernet via Clock Switching
Anuj Batra et al., Texas Instruments
Anuj Batra et al., Texas Instruments

10. January 2001
Clock Switching
The existing IEEE b standard, and the TI proposed 22 Mbps extension to the standard, is based upon an 11 Msps symbol rate and a bandwidth occupancy of 20 MHz. In terms of modern digital communications techniques such as pulse shaping and adaptive equalization, a more aggressive symbol rate in the same bandwidth is practical. However, in order to deal with inter-operability with existing networks, the structure of the preamble, including the symbol rate of the preamble, must not change. A viable method to address these issues is to transmit an 11Msps preamble followed by a higher symbol rate encoded data rate. Means and issues involving the switch in the clock are addressed in this presentation. The suggested increase in rate by 50% to 16.5 Msps yields a data rate of 33 Mbps.
Reference: IEEE /386
Anuj Batra et al., Texas Instruments