2000, 2001 Cirronet
Incorporated
1
M-2410-0007 Rev -
Introduction
The SEM2410 family of products from Cirronet
Incorporated provides wireless
Ethernet connectivity between networks located more than 5 miles apart. Built around the
WIT2410 frequency hopping spread spectrum data modem, SEM products provide a
10BaseT connection to Ethernet networks. SEM products operate in a point-to-point
mode or a point-to-multipoint mode using a star configuration. The center of the “star” is
the Master device and the remote SEMs are Slave devices. Peer-to-peer communication
is accomplished by using the master SEM device to relay datagrams from one slave SEM
device to another slave SEM device.
Contained in ruggedized enclosures, SEM products are designed for factory and
industrial applications. The communication between SEM products is performed using
the WIT2410 over-the-air protocol. Thus the SEM products are 802.3 compatible but not
802.11 compatible and provide 460Kbps data throughput. Certified by the FCC and
ETSI, and CE marked, SEM products can be deployed license-free around the world.
The SEMs enjoy the same benefits of frequency-hopping spread spectrum technology
that the WIT2410s do. Namely, the immunity to multipath fading and resistance to
jamming that is provided by changing frequency every few milliseconds. Operating in the
2.4GHz ISM band, SEMs can be used license-free worldwide and are not subject to the
congestion in the 900MHz band caused by cordless telephones.
The radios in SEM products include a robust over-the-air protocol. This protocol insures
error-free data through the use of a 24-bit CRC and ARQ to detect errors and to
automatically request a retransmission. All of this is transparent to the network which just
sees complete error-free data.
