Radio communication system using frequency division multiplexing for transmission between a master station and a plurality of remote stations
First Claim
1. In a system for effecting two-way radio transmission between a master station and a plurality of remote stations, each remote station comprisingbaseband modulation means for modulating a signal channel to produce a baseband signal at a selected frequency;
- a transmitter including first means for modulating said baseband signal on a carrier fc whose frequency is uniquely assigned to the respective remote station and falls within a transmission band allocated to a first licensed frequency fr and second means for transmitting said modulated baseband signal to the master station as a channel signal;
a receiver including third means for receiving from said master station a multiplexed multi-channel signal modulated on a second licensed frequency ft and fourth means for downconverting said received signal to a nominal IF frequency;
demodulation means for demodulating said multi-channel IF frequency signal to a multi-channel baseband signal; and
demultiplexing means for locating a channel of information destined for the respective remote station in a specific section of the demodulated multi-channel baseband signal and for converting said channel located in the specific section of the baseband signal to a voice frequency channel;
said first means in said transmitter including a first local oscillator for effecting modulation of said baseband signal, and said fourth means in said receiver including a second local oscillator which is independent of said first local oscillator for downconverting said received signal.
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Accused Products
Abstract
A point-to-multipoint radio communication system includes a master station and a plurality of remote stations which communicate with the master station using frequency division multiplexing. Each remote station transmits on a separate frequency, but the respective frequencies of transmission by the remote stations are closely spaced so as to be contained within the band which is centered on a single licensed frequency. Thus, the system may operate with only a first licensed frequency for communication from the master station to the remote stations and a second licensed frequency for communications from the remote stations to the master station.
183 Citations
6 Claims
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1. In a system for effecting two-way radio transmission between a master station and a plurality of remote stations, each remote station comprising
baseband modulation means for modulating a signal channel to produce a baseband signal at a selected frequency; -
a transmitter including first means for modulating said baseband signal on a carrier fc whose frequency is uniquely assigned to the respective remote station and falls within a transmission band allocated to a first licensed frequency fr and second means for transmitting said modulated baseband signal to the master station as a channel signal; a receiver including third means for receiving from said master station a multiplexed multi-channel signal modulated on a second licensed frequency ft and fourth means for downconverting said received signal to a nominal IF frequency; demodulation means for demodulating said multi-channel IF frequency signal to a multi-channel baseband signal; and demultiplexing means for locating a channel of information destined for the respective remote station in a specific section of the demodulated multi-channel baseband signal and for converting said channel located in the specific section of the baseband signal to a voice frequency channel; said first means in said transmitter including a first local oscillator for effecting modulation of said baseband signal, and said fourth means in said receiver including a second local oscillator which is independent of said first local oscillator for downconverting said received signal. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification