doc.: ieee.802.11-03/562r0 submission july 2003 pope, texas instrumentsslide 1 ofdm modulation...
TRANSCRIPT
July 2003
Pope, Texas Instruments
Slide 1
doc.: IEEE.802.11-03/562r0
Submission
OFDM Modulation Methods for Higher Multipath
Tolerance in 10 MHz and 20 MHz Channels
Steve Pope
July 24, 2003
July 2003
Pope, Texas Instruments
Slide 2
doc.: IEEE.802.11-03/562r0
Submission
Scope of Presentation
The proposed methods address the requirement for higher multipath tolerance, and the requirement for 10 MHz channelization in addition to the standard 20 MHz channelization, in newly allocated spectrum including the 4.9 and 5.03 bands in Japan.
The newly proposed methods are not intended for use in the existing spectrum in which legacy 802.11b and 802.11a (U.S.) devices operate.
July 2003
Pope, Texas Instruments
Slide 3
doc.: IEEE.802.11-03/562r0
Submission
Outline of Proposed Methods
In the existing standard 802.11a and 802.11g OFDM modulation modes, the OFDM symbol length before cyclic extension is 3.2 usec, and the tone (subcarrier) spacing is 1 / 3.2 usec = 312.5 KHz.
These parameters are preserved unmodified in the proposed new methods.
The proposed methods involve two channelization options (10 MHz and 20 MHz), and three options for OFDM cyclic prefix length (0.8 usec, 1.6 usec, and 3.2 usec).
July 2003
Pope, Texas Instruments
Slide 4
doc.: IEEE.802.11-03/562r0
Submission
10 MHz Channelization 20 MHz Channelization
PrefixLength 0.8 1.6 3.2 0.8 1.6 3.2
# of data 24 24 24 48 48 48tones
# of pilot 2 2 2 4 4 4tones
tone number -13..13 -13..13 -13..13 -26..26 -26..26 -26..26range
length ofone OFDM 4.0 4.8 6.4 4.0 4.8 6.4symbol (usec)
line rate factor 0.5 0.4167 0.3125 1.0 0.8333 0.625
July 2003
Pope, Texas Instruments
Slide 5
doc.: IEEE.802.11-03/562r0
Submission
Beacons and Association
IBSS operation disallowed for these new methods
An AP is assigned a channel, a channelization width (10 MHz or 20 MHz) and a prefix length (0.8, 1.6, or 3.2 usec). All transmissions in the BSS will use this channelization/prefix combination.
A STA will passively scan a channel for (potentially) each of the 6 possible combinations of channelization and prefix length.
The beacon will also contain a newly-defined information element stating the channelization and prefix length
July 2003
Pope, Texas Instruments
Slide 6
doc.: IEEE.802.11-03/562r0
Submission
Illustration of Header Format (20 MHz)
SHORT SEQ. LONG SEQ. SIGNAL DATA ....
8 usec 8 usec 4 usec
20 MHz Channelization, 0.8 usec prefix
SHORT SEQ. LONG SEQ. SIGNAL DATA .....
8 usec 9.6 usec 4.8 usec
20 MHz Channelization, 1.6 usec prefix
SHORT SEQ. LONG SEQ. SIGNAL DATA
8 usec 12.8 usec 6.4 usec
20 MHz Channelization, 3.2 usec prefix
July 2003
Pope, Texas Instruments
Slide 7
doc.: IEEE.802.11-03/562r0
Submission
Illustration of Header Format (10 MHz)
SHORT SEQ. LONG SEQ. SIGNAL DATA ....
8 usec 8 usec 8 usec
10 MHz Channelization, 0.8 usec prefix
SHORT SEQ. LONG SEQ. SIGNAL DATA .....
8 usec 9.6 usec 9.6 usec
10 MHz Channelization, 1.6 usec prefix
SHORT SEQ. LONG SEQ. SIGNAL DATA
8 usec 12.8 usec 12.8 usec
10 MHz Channelization, 3.2 usec prefix
July 2003
Pope, Texas Instruments
Slide 8
doc.: IEEE.802.11-03/562r0
Submission
Other PHY characteristics
For the case of 20 MHz channelization and 0.8 usec prefix, PHY characteristics are as listed in 802.11a Section 17.5.2.
For the case of 10 MHz channelizaton and 0.8 usec prefix, the aSlotTime characteristic remains unchanged with a value of 9 usec.
For 1.6 usec and 3.2 usec prefix methods, longer slot times (values TBD) will be specified to support greater outdoor ranges.
July 2003
Pope, Texas Instruments
Slide 9
doc.: IEEE.802.11-03/562r0
Submission
Related Issues
The time required to receive beacons and associate is potentially lowered by draft 11k Site Report mechanisms
Draft 11e HCF mechanisms will help compensate for possible deficiencies in CSMA operation in large outdoor BSS’s