User's Manual

Table Of Contents
Ad-Hoc Networks
AT+i Programmer‘s Manual Version 8.32 20-1
20 Ad-Hoc Networks
An Ad-Hoc network is a Wireless Local Area Network (WLAN) in which some of the
stations are part of the network only for the duration of a communications session or, in
the case of mobile or portable devices, while in some close proximity to the rest of the
network.
Ad-hoc networks do not require an Access Point (AP) to enable communication among
stations. Each station can create a new Ad-Hoc network or join an existing one. Networks
can freely merge into a single network or split into smaller ones, thus adapting to
changing conditions such as topology, signal strength, and proximity to nearby Ad-Hoc
networks. Combined with an iChip configured as an iRouter, an Ad-Hoc network can
connect to the Internet through a dial-up or GPRS modem.
20.1 Configuration
Configuring the iChip to operate as a station in an Ad-Hoc network requires setting the
following parameters:
WLSI must be set to either ‗!‘ or ‗!<SSID>‘. When it is set to ‗!‘, iChip continuously
searches for existing Ad-Hoc networks in its vicinity and joins the one having the
strongest signal. When it is set to ‗!<SSID>‘, iChip searches for an Ad-Hoc network
having the specified Service Set IDentifier (SSID). If it finds one it joins it, otherwise
it creates a new network with this SSID.
WLCH must be set to a default value. This value indicates the communication
channel (1-13) to be used for beacon transmission in the Ad-Hoc network. When
iChip joins an already existing network, it adopts the channel used by that network. If
WLSI=!<SSID> and WLCH=0, iChip will only join an already existing network.
20.2 iChip Behavior in Ad-Hoc Mode
20.2.1 Automatic Scanning for Existing Ad-Hoc Networks
After power-up, iChip automatically attempts to locate and connect to an Ad-Hoc
network, unless the WLSI parameter (SSID) is set to (*).
If the WLSI parameter contains an SSID string preceded by (!) or set to (!), iChip scans
for Ad-Hoc networks only.
20.2.2 Creating a New Ad-Hoc Network
If iChip does not detect any Ad-Hoc networks in its vicinity, and the WLSI parameter
contains an SSID, iChip creates a new Ad-Hoc network with its own BSSID.
20.2.3 Joining an Existing Ad-Hoc Network
If iChip detects Ad-Hoc networks in its vicinity and the WLSI parameter is set to (!),
iChip joins the network having the strongest signal. Otherwise, iChip joins the network
whose SSID is set by the WLSI parameter.