Cellular communications system with centralized base stations and distributed antenna units

• US 5,644,622 A
• Filed: 03/23/1995
• Issued: 07/01/1997
• Est. Priority Date: 09/17/1992
• Status: Expired due to Term

• Current Assignee: ADC Telecommunications Incorporated (TE Connectivity Limited)
• Original Assignee: ADC Telecommunications Incorporated (TE Connectivity Limited)
• Inventors: Russell, David S., Fischer, Larry G.
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): Oehling, G. J.
• Application Number:
  US08/409,738
• Time in Patent Office: 831 Days
• Field of Search: 379/58, 379/59, 379/60, 455/33.1, 455/33.2, 455/33.3, 455/33.4, 455/54.1, 455/56.1, 455/52.1, 455/53.1, 455/6.3, 359/152, 359/172, 359/173, 370/94.1, 370/95.1, 370/95.3
• US Class Current: 455/422.1
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 88/085 Access point devices with remote components

Abstract

A microcellular communications network has multiple base-station units all at a common location. Each unit has all-digital transmitters and receivers coupled by fiber optic cable to individual remote locations each having power amplifiers and diversity receivers which convert the RF signals directly between analog RF and digital signals in the RF band at the remote locations. The system includes filtering, framing, and multiplexing of multiple channels. The system also provides passive handoff and passive switching. The system may be deployed in two different stages.

Claims

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.

2. The system according to claim 1 wherein the modulator means and demodulator means in said head end unit and optical node unit are amplitude modulated (AM) so that the sub-band is carried over the one fiber path in analog format.

3. A microcellular communications system for providing mobile telephone service to a microcell area over a cable system and using digital modulation, 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 a subset of the transmitters, said subset comprising a sub-band;

analog-to-digital converter means for converting the cellular band content of the combined signal to a digitized stream of samples;

framer means for framing the digitized stream; and

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 further including;

demultiplexer means for receiving the framed stream and extracting the digitized RF signal corresponding to said subset of transmitters;

digital modulator means for receiving the digitized RF sub-band signal and applying a 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 digitized RF signal corresponding to said sub-band and producing a corresponding electrical signal for application to a digital demodulator, the digital demodulator producing a digital data stream corresponding to the sub-band;

framing means for framing the digitized stream; and

laser means for receiving the framed stream and applying a corresponding laser signal to the fiber path for transmission to the 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;

digital demodulator means for demodulating the modulated sub-band to produce a digital signal containing the digitized sub-band;

digital-to-analog converter means for converting the digital signal to a corresponding RF signal;

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;

analog-to-digital converter means for converting the analog RF signal to a corresponding digital signal;

digital modulator means for modulating the digital signal; and

optical transmitter means for applying a corresponding laser signal to the one fiber path.