Reference Manual

May 25, 2005: PCTEL has discontinued the marketing of the SoftAP Driver.
July 23, 2005: Click here for an alternative solution.

Overview

The PCTEL SoftAP package allows your Windows WLAN-equipped computer to behave like a regular Wireless LAN Access Point so that other WLAN-equipped computers within radio range can communicate with each other. This document describes how to use NAT32 together with the PCTEL driver to give those computers Internet access.

Setup and Configuration

The PCTEL SoftAP software supports a wide range of 802.11a/b/g adapters. Even if your adapter brand is not listed, it is worthwhile running this small utility program NicReader.exe to check if your adapter uses a compatible WLAN Chipset.

The PCTEL Setup program replaces your existing WLAN device driver with a special PCTEL driver, and that driver can subsequently be switched between station mode and host access point mode by running a small control application.

In station mode, the computer behaves like a normal WLAN client and uses the Windows TCP/IP settings configured in Control Panel, Network and Dial-Up Connections. Most users will have configured the adapter to Obtain an IP address automatically, in which case Windows uses the DHCP protocol to fetch settings from a DHCP Server on the network to which the adapter connects.

In host access point mode, the adapter can no longer reach a DHCP server, and so the DHCP configuration attempt fails. In this case, Windows assigns a temporary 169.254.x.y IP address to the adapter and then periodically checks to see if a DHCP server can be reached. On Windows XP platforms, there exists an Alternate Configuration TCP/IP configuration option which lets you specify a set of values to be used in case DHCP configuration fails. In this test, the following Alternate Configuration was used:

        IP Address:  192.168.1.1
        Mask:        255.255.255.0
        Gateway:     none
        DNS Address: none

To use NAT32 with the PCTEL driver, you can either specify an Alternate Configuration under Windows XP, or just continue using the 169.254.x.y address on the adapter. Configure NAT32 to use the WLAN adapter as its Private Interface, and your Internet-connected adapter (which can be a Dial-Up Networking connection) as the Internet Interface. Note that even though NAT32 displays a warning if the private LAN adapter has a failed DHCP configuration, you can still select the adapter and use it in the normal way.

When an external computer then connects to your Access Point, it too will request TCP/IP configuration via DHCP, and the NAT32 DHCP Server will then assign an IP address on the configured network, as well as a Gateway and DNS Server address pointing to NAT32's private IP address. The external computer will then have access to all computers on the private network and to the Internet (via NAT32). If you don't want to allow the external computers to access the Internet, simply turn off IP mapping within NAT32 with the command: ipmap p off.

The PCTEL driver continues using the Encryption settings of the original driver, and it also supports Access Control via a MAC-address list.

Performance

Initial tests with just one external computer connected showed that networking performance was good. Switching between modes did take several seconds, but because this is done infrequently, it is not likely to be a problem.

Summary

The PCTEL SoftAP software is a very useful package and can be purchased on-line for USD $19.95. Because it allows the WLAN adapter mode to be switched, it can easily be used on a laptop computer to give other computers temporary WLAN or Internet access. But it can also be used on a desktop machine as a low-cost alternative to a hardware Access Point.

Several WLAN vendors have announced plans to ship the PCTEL driver with their hardware starting in Q1/2005.

SEE ALSO

ipmap