User Manual

www.moxa.com [e-mail] 8
2009 Industrial Wireless Guidebook
Differentiating Between Wireless Technologies
1
IEEE 802.11n
In January 2004, IEEE made an announcement to form a new task force to develop new standards for the IEEE
802.11 standard. The goal of this task force was to allow wireless communication speed to reach a theoretic
number of 300 Mbps. Since the theoretic speed of this new standard, now called IEEE 802.11n, needs to reach
300 Mbps, the Physical Layer also needs to support a higher transmission speed that is at least 50 times faster
than IEEE 802.11b and 10 times faster than IEEE 802.11g. In addition to enhancing communication speed,
IEEE 802.11n also extends the communication distance to satisfy the growing needs of wireless applications.
To make this happen, IEEE 802.11n has added more specifications to the MIMO standard that allows IEEE
802.11n to be able to use multiple antennas to increase transmission speed. It also uses Alamouti coding
schemes to increase the transmission coverage.
There are two rival camps competing to dominate the IEEE 802.11n Physical Layer architecture: the World-
Wide Spectrum Efficiency, which is supported by Broadcom, and TGnSync, supported by Intel and Philips.
IEEE 802.11s
An 802.11s mesh network device is referred to as a mesh station (mesh STA). Mesh STAs form mesh links with
one another, over which mesh paths can be established using a routing protocol. 802.11s defines a default
mandatory routing protocol, or HWMP, yet allows vendors to operate using alternate protocols. HWMP is
inspired by a combination of AODV (RFC 3561[1]) and tree-based routing.
Mesh STAs are individual devices using mesh services to communicate with other devices in the network.
They can also collocate with 802.11 Access Points (APs) and provide access to the mesh network to 802.11
stations (STAs), which have broad market availability. Also, mesh STAs can collocate with an 802.11 portal that
implements the role of a gateway and provides access to one or more non-802.11 network. In both cases,
802.11s provides a proxy mechanism to provide addressing support for non-mesh 802 devices, allowing end-
points to be cognizant of external addresses.
802.11s also includes mechanisms to provide deterministic network access, congestion control, and power
saving.
Table: 802.11 Standards and Date Rate
Protocol
Release
Date
Spectrum Max. Speed
Typical Range
(indoor)
Typical Range
(outdoor)
802.11 1997 2.4–2.5 GHz 2 Mbps --- ---
802.11a 1999
5.15–5.35/5.47–5.725/
5.725–5.875 GHz
54 Mbps 30 m ---
802.11b 1999 2.4–2.5 GHz 11 Mbps 30 m 100 m
802.11g 2003 2.4–2.5 GHz 54 Mbps 30 m 100 m
802.11n 2008 2.4 GHz or 5 GHz bands 600 Mbps 50 m 125 m