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How Wireless Broadband Works
The
type of wireless broadband most often used by businesses to link facilities
at different addresses is a local multipoint distribution system (LMDS).
It has a total bandwidth of 1.3GHz, which is achieved by sending data
short distances in the microwave frequencies of the 27.5GHz-to-31.3GHz
radio spectrum.
Network:
The LAN sends data to a point-to-multipoint router located with an
antenna on the roof. Antenna signals are picked up by one of several
other antennas about three miles apart that receive and broadcast
signals to other antennas.
Cell
Links: The cells are linked by point-to-point antennas, which broadcast
a highly targeted signal between two antennas that are aimed at each
other.
Identification:
Although all LANs in the LMDS network receive the same radio transmissions,
each pays attention only to the signals that bear its address.
Internet:
A request made for an Internet page is passed from one cell to another
until it reaches a cell that functions as a distribution node. That
cell passes the request to a land-wired Internet connection.
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Fixed Wireless Network Architecture
To
offer high-speed Internet services, a fixed wireless carrier creates
a data network that operates over MDS, MMDS, or ITFS frequencies.
The following diagram provides a high-level look at a typical broadband
fixed wireless network, including a fixed wireless headend that connects
to a central antenna that broadcasts data directly to home and business
locations, or to smaller cell sites, which in turn reach remote pockets
of businesses or residences. Data is either sent back upstream from
customers over wireless frequencies or through traditional dial-up
telephone modem connections.
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Fixed Wireless Headend
The
fixed wireless headend is the control point for the broadband access
network. A carrier-class IP switch or router interfaces with the backbone
data network offering connectivity to remote content servers, as well
as the global Internet. This switch/router also connects to a wireless
cable modem termination system (CMTS) that coverts data from a wide
area network (WAN) protocol, such as packet over SONET, into digital
signals that are modulated for transmission over the wireless network.
These signals are then converted into wireless microwave frequencies
through a transceiver and broadcast through an antenna to customer
home or business locations. Like their counterparts that operate over
cable TV systems, a wireless CMTS unit typically provides a dedicated
27 Mbps per downstream 6 MHz data channel that is shared by active
users. Upstream speeds are typically below 1 Mbps. Content and application
servers are typically located at the fixed wireless headend, as are
network management and operations support systems. If the carrier
were offering IP telephony, voice calls would be directed by the headend
router to a IP telephony gateway, and then onto the public switched
telephone network (PSTN).
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Business Environment
In
a business environment, an antenna and transceiver receive the incoming
data signal and transmit it over coaxial cable lines to the broadband
modem, which interfaces with a local area network (LAN) through an
Ethernet hub, switch or router, providing access to multiple users.
See other: wireless
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Home Environment
An
antenna and transceiver at the home receive the incoming data signal
and transmit it over in-home coaxial cable lines to a broadband modem.
The modem connects to an Ethernet card in the PC with Category 5 cabling
and RJ-45 connectors or a Universal Serial Bus (USB) interface.
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