B&B Electronics ESR901WB - Manual - Manual (Page 15)

Introduction
Manual Documentation Number: ESR901WB-2907m pn6870-rev002
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104 – www.bb-elec.com
B&B Electronics Ltd – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445 – www.bb-europe.com
Chapter 1 5
Wireless Network Configurations
The 802.11 standard defines two modes of operation: infrastructure mode
and ad hoc mode. Infrastructure mode makes use of one or more access
points connected to a wired LAN. Wireless stations communicate with access
points to gain access to each other and/or the LAN. In the Basic Service Set
(BSS) several stations communicate with one access point, which is
connected to a wired LAN. In the Extended Service Set (ESS) two or more
access points connect to the LAN creating a subnetwork.
In ad hoc mode, also called Independent Basic Service Set (IBSS), access
points are not used. Wireless stations communicate directly with each other
in a peer-to-peer fashion. This mode allows individual computers to set up a
network where wireless infrastructure does not exist.
ESR901WB wireless serial servers can be configured to operate in
infrastructure or ad hoc mode. From the Web Configuration and
Management Interface you can set up the type of network, naming the
network (specifying the SSID, or service set identifier) and other parameters.
IEEE 802.11b
IEEE 802.11b standard specifies a WLAN that operates on the 2.4 GHz band
at data rates up to 11 Mbps. Equipment that conforms to the 802.11b
standard can interoperate with equipment conforming to faster (up to 54
Mbps) 802.11g equipment and they will interoperate. However, when
connected into the same network the 802.11g equipment will operate at the
11 Mbps limitation of the 802.11b equipment.
For media access, 802.11 wireless networks use CSMA/CA, a scheme in
which a station that intends to transmit ‘listens’ for traffic on the radio carrier
frequency and sends data packets if the frequency is clear. If the receiving
station receives the packet intact it sends an acknowledgement (ACK) to
confirm the packet has been received. If the transmitting station does not
receive an ACK it assumes a collision occurred and transmits again after a
random delay period.
Communication distances vary depending on the type and thickness of
material around a wireless node. The transmitter power output, the type of
antenna used and the amount of attenuation through materials also affects the