Cellular communications system with centralized base stations and distributed antenna units

Claim 1

A microcellular communications system for providing mobile telephone service to a microcell area over a cable system, comprising: a microcell base station unit connected by a fiber path to a head end unit located in a head end station of a cable television distribution system having a plurality of optical nodes connected to the head end unit over respective fiber paths, the base station unit including: a plurality of RF transmitters and receivers, one for each channel assigned to the microcell, the plurality of channels making up a cellular band; combiner means for combining the RF signal output from the transmitters; analog-to-digital converter means for converting the cellular band content of the combined signal to a digitized stream of samples; first framing means for framing the digitized stream; and digitally modulated laser means for receiving the framed stream and applying a corresponding laser signal to the fiber path for transmission to the head end unit; the head end unit including: demultiplexer means for receiving the framed stream and extracting the digitized RF signal; digital-to-analog converter means for receiving the digitized RF signal and reconstructing an analog RF signal containing the cellular band; one or more filter means for separating the cellular band into a plurality of sub-bands, each sub-band containing a sub-set of said plurality of channels; modulator means for modulating one of said sub-bands and applying the modulated output to an optical transmitter producing a corresponding optical signal for application to one of said fiber paths connected to a optical node; optical receiver means for receiving a modulated optical signal carrying a sub-band and producing a corresponding electrical signal for application to a demodulator for demodulating the sub-band to produce a corresponding analog RF signal including the sub-band; analog-to-digital converter means for receiving the RF signal from the demodulator and converting the RF signal to a digitized data stream; second framing means for framing the digitized stream; and digitally modulated laser means for receiving the framed stream and applying a corresponding laser signal to the fiber path for transmission to the corresponding base station unit; wherein each base station unit further includes: demultiplexer means for receiving the framed microcell traffic stream from the antenna unit and extracting the digitized RF signal; digital-to-analog converter means for receiving the digitized RF signal and reconstructing the analog RF signal, the RF signal being applied to the receivers; and an optical node unit located at the optical node of the cable television system, the optical node unit including: optical receiver means for receiving the modulated sub-band on said one fiber path; demodulator means for demodulating the modulated sub-band to produce an RF signal containing the sub-band; amplifier means for amplifying the RF signal for transmission from a main antenna; filter means for filtering out the sub-band from the RF signal received at the main antenna; modulating means for modulating the received sub-band; and optical transmitter means for applying a corresponding optical signal to the one fiber path.