General Information
GINA User’s Manual
1-4
© 2001 GRE America, Inc. All rights reserved. This material is the property of GRE America, Inc. Copying or reproducing this material
is strictly prohibited. All violators shall be prosecuted to the fullest extent of the law.
3/01 (rev. 3)
narrow-band signal and spreads it over a broader portion of the radio
frequency band.
KEY-UP TIME
— The time that a radio requires when switching from
transmit to receive and vice-versa. There is no key-up time required due
to an internal buffer. Except for Models 5000N38 and 7000N38, data can
be received and transmitted through the RS-232 port simultaneously in a
full duplex mode using TDD (time division duplex).
NOTE:
Key-up time and spreading code length are interrelated. In a
direct sequenced technique, the spread sequence system must (in real
time) attempt to match its despreading code with the incoming radio
signal in order to determine the validity of the data. The longer the
spreading code, the longer the receiver must search before it can deter-
mine that a valid data signal is being transmitted.
SYNCHRONIZATION
— Applied each time that the radio switches
between transmit and receive, synchronization produces direct overhead
on each transmitted message, thereby reducing radio efficiency. In appli-
cations involving very long, constant messages (such as a large file trans-
fer), synchronization time becomes less of a deciding factor.
MULTIPATH
— Radio signals may take several paths to reach the
intended receiver. The receiver must sort out the main path from all the
‘ghost’ images. The longer the spreading factor and/or the faster the raw
data rate, the more difficult (and eventually impossible) it is to sort out the
signals, resulting in a loss of robust communication.
NUMBER OF CHANNELS
— The number of channels varies per
GINA model. Models 6000N5, and 6000NV-5 have 21 channels provided
in the 902 - 928 MHz frequency range. Models 8000N-5 and 8000NV-5
have 37 channels provided in the 2.404 - 2.478 GHz frequency range.
Note that the channels are overlapping and, depending on the unit separa-
tion, only one channel may be used.
PROCESSING GAIN MEASUREMENTS
— Since processing gain is
a function of the RF bandwidth of the transmitted signal compared to the
bit rate of the data, the theoretical calculation is:
10Log(Spreading Code Rate) x (Main Lobe Factor)
RF Data Rate
NOTE:
Assuming that the RF main lobe of [sin x/]2 for direct sequence is
0.88 (main lobe factor) times the bandwidth spreading code clock rate.
RANGE
— The communication distance between GINA’s may vary
according to environment and application. (Robustness and range are
almost interchangeable terms; robustness and range vary according to the
antenna system used.)