Cellular communications system with centralized base stations and distributed antenna units

• US 5,627,879 A
• Filed: 03/02/1994
• Issued: 05/06/1997
• 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: Ratliff, Charles R., Wala, Philip M., Brennan, Jeffrey, Fischer, Larry G., Russell, David S.
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): OEHLING, GEORGE J
• Application Number:
  US08/204,660
• Time in Patent Office: 1,161 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, 359/152, 359/172, 359/173, 370/94.1, 370/95.1, 370/95.3, 375/260
• US Class Current: 370/328
• 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 includes a plurality of base station units and corresponding antenna units. The base station units are housed in a common location. Each includes either conventional transmitters and receivers or all digital transmitter and receiver equipment, and interface circuitry to a mobile telecommunications switching office. The microcell traffic output is applied to a frame generator/multiplexer. The output of the frame generator/multiplexer is applied to a digitally modulated laser. The laser output is conveyed by fiber to a remote antenna unit, which demultiplexes the microcell traffic signal and applies it to a digital-to-analog converter. The output of the digital-to-analog converter is applied to a power amplifier, which in turn is connected to a main antenna. RF signals from the mobile units are received at both a main and a diversity antenna. The received signals are filtered, digitized, multiplexed together and transmitted over the optical fiber back to the base station. The strongest signal is selected for use.

Claims

1. A microcellular communications system, comprising:

a plurality of commonly located microcell base station units each connected by a fiber path to a plurality of corresponding antenna units for transmission of microcell traffic, each base station unit including;

RF transmitters and receivers, one for each channel assigned to the microcell;

combiner means for combining an analog RF signal output from the transmitters;

analog-to-digital means for converting the single combined analog signal to a digitized stream of samples;

framing means for framing the digitized stream;

means for receiving the framed stream and for digitally modulating a laser signal with the framed stream for application to the fiber path for transmission to the corresponding antenna unit; and

optical receiver means for detecting the framed stream modulated on the fiber path,

wherein each antenna unit further includes;

demultiplexer means for receiving the framed stream and extracting the digitized stream;

digital-to-analog means for receiving the digitized stream and reconstructing the analog RF signal output;

amplifier means for amplifying the reconstructed analog signal;

antenna means for receiving the amplified signal and broadcasting it into a microcell area;

means for receiving an RF microcell traffic signal received at the antenna unit;

analog-to-digital converter means for converting the received RF microcell traffic signal to a digitized RF signal data stream;

framer means for framing the digitized RF signal data stream; and

laser means for receiving the framed RF signal data stream and for digitally modulating a laser signal with the framed RF signal data stream for application 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 RF signal data stream from the antenna unit and extracting the digitized RF signal data stream; and

digital-to-analog converter means for receiving the digitized RF signal data stream and reconstructing the analog RF microcell traffic signal representing all channels assigned to the microcell, the RF microcell traffic signal being applied to the receivers.

2. The system according to claim 1 further including means for multiplexing at least one additional channel with the microcell traffic carried on the fiber path.

3. The system according to claim 2 wherein the at least one additional channel includes a plurality of additional channels, some of the additional channels are for the provision of alternate services.

4. The system according to claim 3 wherein at least one of the additional channels is a personal communications network (PCN) channel.

5. The system according to claim 3 wherein at least one of the additional channels is a paging service channel.

6. The system according to claim 2 wherein at least one of the additional channels is an alarm channel.

7. The system according to claim 2 wherein at least one of the additional channels is a voice channel to carry two-way point-to-point voice grade communication between the base station unit and one of the antenna units.

8. A microcellular communications system utilizing a switched telephone network for transmission of RF signals, comprising:

a plurality of commonly located microcell base station units and a plurality of associated antenna units, each base station unit including;

RF transmitters and receivers, one for each channel serviced by the base station unit;

combiner means for combining an analog RF signal output from a subset of the transmitters;

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

framer means for framing the digitized stream to a signal format compatible with the switched telephone network; and

first interface means for interfacing the framed signal with the switched telephone network and addressing it to a corresponding antenna unit of the plurality of associated antenna units;

wherein each antenna unit includes;

second interface means for interfacing to the switched telephone network to receive the framed signal;

demultiplexer means for receiving the framed signal and extracting the digitized stream;

digital-to-analog converter means for receiving the digitized stream and reconstructing the combined analog RF signal output;

power amplifier means for amplifying the reconstructed signal;

antenna means for receiving the amplified signal and broadcasting it into a microcell area;

receiver means for receiving an RF microcell traffic signal received at the antenna unit;

analog-to-digital converter means for converting the received RF microcell traffic signal to a digitized RF signal data stream; and

framer means for framing the digitized RF signal data stream to a signal format compatible with the switched telephone network;

the second interface means further receiving the RF signal data stream and transmitting it over the switched telephone network to the corresponding base station unit;

wherein the first interface means further interfaces to the switched telephone network to receive the framed RF signal data stream, and each base station unit further includes;

demultiplexer means for receiving the framed RF signal data stream from the antenna unit and extracting the digitized RF signal data stream; and

digital-to-analog converter means for receiving the digitized RF signal data stream and reconstructing the analog RF signal representing at least the entire subset of channels, the RF microcell traffic signal being applied to the receivers.

9. A microcellular communications system, comprising:

a plurality of commonly located microcell base station units each connected by a fiber path to a corresponding antenna unit of a plurality of antenna units, each base station unit including;

RF transmitters and receivers for each channel serviced by the base station unit;

combiner means for combining an analog RF signal output from the transmitters to form an analog combined signal;

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

framer 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 antenna unit;

each antenna unit including;

demultiplexer means for receiving the framed stream and extracting the digitized stream;

digital-to-analog converter means for receiving the digitized stream and reconstructing the analog combined RF signal output;

power amplifier means for amplifying the reconstructed signal;

primary antenna means for receiving the amplified signal and broadcasting it into a microcell area;

receiver means for receiving a primary RF microcell traffic signal received at the primary antenna means;

first analog-to-digital converter means for converting the received primary RF microcell traffic signal to a primary digitized data stream;

diversity antenna means for receiving a diversity RF traffic signal;

second analog-to-digital converter means for converting the received diversity RF traffic signal to a diversity digitized data stream;

framer means for framing the primary and diversity digitized data streams; and

digitally modulated laser means for receiving the framed primary and diversity traffic 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 primary and diversity traffic stream from the antenna unit and extracting the primary and diversity digitized data streams;

third digital-to-analog converter means for receiving the primary digitized data stream and reconstructing the analog primary RF microcell traffic signal; and

fourth digital-to-analog converter means for receiving the diversity digitized data stream and reconstructing the analog diversity RF microcell traffic signal, the strongest of the primary or diversity RF microcell traffic signal being selected.

10. A cellular communications system having a cell with a plurality of assigned channels, comprising:

a cell base station unit connected by transmission means to a corresponding antenna unit having an antenna located for broadcast and reception of signals in an area associated with the cell, the base station unit including;

a plurality of RF separate analog transmitters and separate analog receivers for each channel assigned to the cell;

combiner means for combining the RF analog signals output from the transmitters;

analog-to-digital conversion means for converting the combined analog signal to a digitized stream of samples representing all the channels together;

framing means for framing the digitized stream;

means for modulating the digitized samples onto the transmission means for transmission to the corresponding antenna unit; and

receiver means for receiving a digital bit stream from the transmission means from the corresponding antenna unit;

wherein the antenna unit further includes;

demultiplexer means for receiving the framed stream and extracting the digitized stream;

digital-to-analog means for receiving the digitized stream and reconstructing the single RF signal output representing all the channels together;

amplifier means for amplifying the reconstructed signal;

means for applying the amplified signal to the antenna so that it is broadcast into an area associated with the cell;

means for receiving an RF signal received at the antenna;

analog-to-digital converter for converting the received RF signal representing all the channels assigned to the cell together to a digitized data stream;

framer means for framing the digitized data stream; and

means for receiving the framed stream and applying it to the transmission means for transmission to the base station unit;

wherein the base station unit further includes;

demultiplexer means for receiving the framed signal from the antenna unit and extracting the digitized data stream;

digital-to-analog converter for receiving the digitized data stream and reconstructing the RF analog signal representing all the channels together; and

means for applying the RF reconstructed analog signal to the receivers.

11. A cellular communications system including a cell, comprising:

a cell base station unit connected by transmission means to a corresponding antenna unit having an antenna located for broadcast and reception of signals in an area associated with the cell, the base station unit including;

a plurality of separate analog RF signal generation means for generating a corresponding plurality of RF separate analog signals on different channels carrying telephone signals to mobile units in the cell area, and for combining the RF separate analog signals to form a single composite analog RF signal representing all the channels together;

analog-to-digital conversion means for converting the single composite analog signal to a digitized stream of samples representing all the channels together and applying the digitized stream of samples to the transmission means for transmission to the corresponding antenna unit;

wherein the antenna unit further includes;

digital-to-analog means for receiving the digitized stream of samples from the base station unit, reconstructing the corresponding single composite analog RF signal representing all the channels together, amplifying the composite analog RF signal, and applying the amplified signal to the antenna so that it is broadcast into the area associated with the cell;

analog-to-digital means for receiving an analog RF signal received at the antenna and representing all the channels assigned to the cell together, converting the received RF signal directly to a digitized stream of samples and applying the digitized stream of samples to the transmission means for transmission to the base station unit; and

wherein the base station unit further includes;

digital-to-analog converter means for receiving the digitized stream of samples from the antenna unit, and reconstructing the single analog RF signal representing all the channels together.

12. A cellular communications system including a cell, comprising:

a cell base station unit connected by transmission means to a corresponding antenna unit having an antenna located for broadcast and reception of signals in an area associated with the cell, the base station unit including;

analog RF signal generation means for generating a plurality of RF signals on different channels carrying telephone signals to mobile units in the cell area, and for combining the RF signals to form a composite analog signal;

analog-to-digital conversion means for converting the composite analog signal to a digitized stream of samples directly representing the composite analog signal;

digital filter means for filtering the digitized stream of samples and generating a plurality of individual digitized streams each corresponding to at least one of the channels, and for applying the individual digitized streams of samples to the transmission means for transmission to the corresponding antenna unit;

wherein the antenna unit further includes;

digital-to-analog means for receiving the individual digitized streams of samples from the base station unit, reconstructing a corresponding composite analog RF signal, amplifying the composite analog RF signal, and applying the amplified signal to the antenna so that it is broadcast into the area associated with the cell;

analog-to-digital means for receiving an RF signal received at the antenna and converting the received RF signal to a digitized stream of samples;

digital filter means for filtering the digitized stream of samples derived from the received RF signal and generating a plurality of individual digitized streams of samples each corresponding to at least one of the channels, and for applying the individual digitized streams to the transmission means for transmission to the base station unit; and

wherein the base station unit further includes;

digital-to-analog converter means for receiving the individual digitized streams of samples from the antenna unit, reconstructing the analog RF signals corresponding to each individual stream, and applying the analog RF signals to receivers of the base station unit.

13. A system according to claim 12 further wherein the transmission means comprises a switched telephone network.