Intel® Wi-Fi Products
What Is a Preamble?

Note This article is intended for network security administrators who use advanced wireless security features.


It is the first part of the Physical Layer Convergence Protocol/Procedure (PLCP) Protocol Data Unit (PDU). A header is the remaining part of the data packets and has more information identifying the modulation scheme, transmission rate, and length of time to transmit the whole data frame.

Long preamble

  • PLCP with long preamble is transmitted at 1 Mbps regardless of transmit rate of data frames.
  • Total long preamble transfer time is a constant at 192 usec.
  • Compatible with legacy IEEE* 802.11 systems running at 1 and 2 Mbps

Short preamble

  • PLCP with short preamble: Preamble is transmitted at 1 Mbps and header at 2 Mbps.
  • Total short preamble transfer time is a constant at 96 usec.
  • Not compatible with legacy IEEE 802.11 systems operating at 1 and 2 Mbps

What does all this mean?

Most access points (AP) and broadband Wi-Fi routers are configured for a long preamble or have a setting that automatically detects the preamble and adjusts accordingly. A majority of client Wi-Fi adapters should also be pre-configured in the same manner as a precautionary measure for networks that may still employ legacy devices. Changing the default setting is not recommended. If you need to change the setting, see your equipment manufacturer before taking action.

This applies to:

Intel® Centrino® Advanced-N + WiMAX 6250
Intel® Centrino® Advanced-N 6200
Intel® Centrino® Advanced-N 6205
Intel® Centrino® Advanced-N 6205 For Desktop
Intel® Centrino® Advanced-N 6230
Intel® Centrino® Advanced-N 6235
Intel® Centrino® Ultimate-N 6300
Intel® Centrino® Wireless-N + WiMAX 6150
Intel® Centrino® Wireless-N 100
Intel® Centrino® Wireless-N 1000
Intel® Centrino® Wireless-N 1030
Intel® Centrino® Wireless-N 105
Intel® Centrino® Wireless-N 130
Intel® Centrino® Wireless-N 135
Intel® Centrino® Wireless-N 2200
Intel® Centrino® Wireless-N 2200 For Desktop
Intel® Centrino® Wireless-N 2230
Intel® Dual Band Wireless-AC 3160
Intel® Dual Band Wireless-AC 7260
Intel® Dual Band Wireless-AC 7260 for Desktop
Intel® Dual Band Wireless-N 7260
Intel® PRO/Wireless 2200BG Network Connection
Intel® PRO/Wireless 2915ABG Network Connection
Intel® PRO/Wireless 3945ABG Network Connection
Intel® WiFi Link 1000
Intel® WiFi Link 5300 and Intel® WiFi Link 5100 products
Intel® WiMAX/WiFi Link 5350 and Intel® WiMAX/WiFi Link 5150 products
Intel® Wireless WiFi Link 4965AGN
Intel® Wireless-N 7260

Solution ID: CS-025317
Last Modified: 01-Oct-2014
Date Created: 26-Dec-2006