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LongRanger 2020 Family Description
[ Specifications
| Antennas
]
The LongRanger 2020 line of spread spectrum radios provides an
off-the-shelf, ready-to-install solution to a number of long-range Closed
Loop communication applications. The product was designed from the ground up
with emphasis on performance, reliability, and flexibility and has been
qualified under the most stringent temperature, shock, and vibration
conditions. The LongRanger 2020 is currently in use as the
communication medium in many KMT1700 & KMT1800 Closed Loop Traffic
Control Systems. It is one of the only spread spectrum transceivers that
allow for full control of RTS & CTS for serial communications.
Spread Spectrum Technology
The LongRanger 2020 uses direct sequence spread spectrum
technology implemented with the Stanford Telecom STEL-2000A. This
integrated circuit was developed with the participation of UC Wireless
specifically for the LongRanger 2020 product line. The STEL-2000A
matched-filter despreading technique provides unsurpassed synchronization
speed, required for burst communications. Pseudonoise (P/N) spreading
codes up to 64 chips ensure high processing gain to maintain
communications in the most adverse environments.
Automatic RF Channel Selection
The high processing gain of the LongRanger 2020 offers
substantial immunity to interference. However, the spread spectrum bands
are unlicensed, and therefore interference from other radios can still
occur. The LongRanger 2020 offers an automatic RF channel selection
option which finds a clear channel within 300 ms after interference has
interrupted communications. In contrast, with fixed-frequency radios,
communications may stop until the equipment is manually reset to a clear
channel.
Time Division Multiple Access (TDMA)
The LongRanger 2020 can be configured for TDMA operation,
allowing multiple radios to share one channel without mutual interference.
This is accomplished by coordinated allocation of transmit/receive time
slots to each radio in the channel.
TDMA is essential when the number of communication links required in a
limited geographical area exceeds the number of available channels. For
example, if 12 channels are available, 48 links can operate at one quarter
of the data rate, with four links sharing each channel.
High-Performance 2.4 GHz OPERATION
For long-range communications, a high antenna tower may be required,
necessitating long cable runs between the antenna and the radio. There is
some signal loss in all cables, increasing with cable length and signal
frequency. In the 900-MHz band, performance can be maintained with
reasonably priced cables. However, minimizing signal loss at 2.4 GHz
requires the use of very expensive large-diameter cables.
To address this problem, UC Wireless has separated the 2.4-GHz radio
into two sections: an indoor unit, operating at a lower intermediate
frequency, and an outdoor up/down converter located at the antenna. The
up/down converter includes the systemâs low-noise 2.4 GHz receiver and the
transmitter power amplifier, so the received and transmitted signals are
not degraded by cable losses. Between the up/down converter and the indoor
unit, signals are at a lower frequency, so losses are substantially
reduced. This allows the use of less expensive cable with no loss of
transmitter output power and receive sensitivity.
Closed Loop System Configurations
The LongRanger 2020 can be set up for a wide variety of Closed
Loop System
configurations. These configurations include point-to-point (Central
Computer to Master),
multiple-point-to-point (Master to Locals), and point-to-multipoint links.
The LongRanger 2020 can also be set up as a repeater when a
line-of-sight obstruction must be bypassed or ranges greater than 50 km
are required.
Flexible User Interface
The LongRanger 2020 is shipped ready to operate with default
parameters that are suitable for most applications. However, a large
number of parameters are configurable, allowing the user to customize the
radio for many non-standard applications. Some of the programmable
parameters include:
- Separate transmit and receive channels in 128 KHz steps.
- Spreading Codes and code length (15/31/63).
- BPSK or QPSK modulation
- Number of TDMA slots and slot time
- Synch/asynch modes, data rates, and clock sources
- RS-232, EIA530 (RS-422), or V.35 electrical interfaces
- RTS/CTS flow control options
These and other parameters are easily configurable using either a menu
driven command interface, or a Hayes compatible command set sent by a
terminal connected to the radio's rear panel connector. Configuration
changes can be stored in the radio's non-volatile memory and automatically
recalled on power up.
In-Field Software Updates
UC Wireless offers the features required for a vast range of
configuration and performance options. However, features as yet unforeseen
will inevitably become desirable or even essential in the future. The
LongRanger 2020 will not be made obsolete by such technological
changes, since its operation is controlled by software contained in Flash
EPROM. When new features become available, the radio can be upgraded in
less than one minute by software available from UC in their Software Downloads
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