1 / 9

OFDM Modulation Methods for Higher Multipath Tolerance in 10 MHz and 20 MHz Channels Steve Pope

This presentation discusses proposed methods for achieving higher multipath tolerance and channelization in newly allocated spectrum, while preserving existing OFDM modulation modes. The presentation includes details on channelization options and cyclic prefix lengths.

meriwether
Download Presentation

OFDM Modulation Methods for Higher Multipath Tolerance in 10 MHz and 20 MHz Channels Steve Pope

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. OFDM Modulation Methods for Higher Multipath Tolerance in 10 MHz and 20 MHz Channels Steve Pope spp@ti.com July 24, 2003 Pope, Texas Instruments

  2. 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. Pope, Texas Instruments

  3. 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). Pope, Texas Instruments

  4. 10 MHz Channelization 20 MHz Channelization Prefix Length 0.8 1.6 3.2 0.8 1.6 3.2 # of data 24 24 24 48 48 48 tones # of pilot 2 2 2 4 4 4 tones tone number -13..13 -13..13 -13..13 -26..26 -26..26 -26..26 range length of one OFDM 4.0 4.8 6.4 4.0 4.8 6.4 symbol (usec) line rate factor 0.5 0.4167 0.3125 1.0 0.8333 0.625 Pope, Texas Instruments

  5. 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 Pope, Texas Instruments

  6. 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 Pope, Texas Instruments

  7. 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 Pope, Texas Instruments

  8. 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. Pope, Texas Instruments

  9. 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 Pope, Texas Instruments

More Related