Cellular communications system having passive handoff

• US 5,621,786 A
• Filed: 08/23/1994
• Issued: 04/15/1997
• 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: Wala, Philip M., Brennan, Jeffrey, Fischer, Larry G.
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): OEHLING, GEORGE J
• Application Number:
  US08/294,742
• Time in Patent Office: 966 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, 370/94.1, 370/95.1, 370/95.3, 359/152, 359/172, 359/173, 375/260
• US Class Current: 455/436
• 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 passive handoff cellular communication system includes a cell divided into a plurality of zones. A base station is connected by transmission apparatus to a plurality of antenna units. The base station includes analog RF signal generation circuitry for generating a plurality of RF signals on different channels and a first switch responsive to a first control signal for switching and combining the RF signals to form a composite RF signal for each zone. Analog-to-digital conversion circuitry converts the composite signal for each zone to a digitized stream of samples and applies the samples to the transmission apparatus for transmission to each corresponding antenna unit. Each antenna unit includes digital-to-analog conversion circuitry for receiving the digitized stream of samples from the base station, reconstructing a corresponding composite analog RF signal, and applying an amplified signal to the antenna The base stations further include a second switch and combining means responsive to a second control signal for selectively combining the RF signals from the antenna units to form a plurality of composite signals for application to the receivers of the base station. A controller monitors the digitized streams of samples from all of the antenna units, digitally analyzes the energy level of each channel in each zone, and generates the first and second control signals to selectively control the zones in which each channel is broadcast and the zone from which each channel is received.

Claims

1. A cellular communications system including a cell divided into a plurality of zones, wherein a plurality of telephone signals are transmitted to and received from a plurality of mobile units in the zones using RF transmission, comprising:

a cell base station unit connected by transmission means to a plurality of antenna units, at least one antenna unit located in each zone, each antenna unit having an antenna located for broadcast and reception of signals in the associated zone, the base station unit including;

analog RF signal generation means for generating a plurality of separate RF signals on different channels for carrying telephone signals to mobile units in the cell;

first switch means responsive to a first control signal for switching and combining the RF signals to form a composite RF signal for each zone, the composite analog signal for each zone containing multiple selected channels;

analog-to-digital conversion means for convening the composite analog signal for each zone directly to a corresponding digitized stream of samples; and

means for applying the digitized stream of samples to the transmission means for transmission to each corresponding antenna unit;

wherein each antenna unit further includes;

digital-to-analog means for receiving the digitized stream of samples from the base station unit, reconstructing a corresponding composite analog RF signal representing all the multiple selected channels;

means for amplifying the composite analog RF signal; and

means for applying the amplified signal to the antenna so that it is broadcast into the zone associated with the antenna unit;

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

means for applying the digitized stream of samples to the transmission means for transmission to the base station unit;

wherein each base station unit further includes;

digital-to-analog converter means for receiving the digitized stream of samples from each antenna unit, and reconstructing a single analog RF signal representing multiple channels received at each antenna unit;

second switch means responsive to a second control signal for selectively combining the analog RF signals from the antenna units to form a plurality of composite analog signals for application to receivers of the base station, each of the composite signals comprising one or more of the RF signals from the antenna units; and

control means for monitoring the digitized streams of samples from all of the antenna units and digitally analyzing the energy level of each channel in each zone, and in response thereto generating the first and second control signals to selectively control the zones in which each channel is broadcast and the zone from which each channel is received.

2. A system according to claim 1 further wherein said control means includes fade control means for monitoring the fading of an RF signal received in a zone and for generating the second control signal to switch the zone from which the RF signal is obtained, whereby a diversity function is obtained.

3. A system according to claim 2 further wherein said fade control means can achieve said monitoring and switching within 1 second.

4. A cellular communications system including a cell divided into a plurality of zones, wherein a plurality of telephone signals are transmitted to and received from a plurality of mobile units in the zones using RF transmission, comprising:

a cell base station unit connected by transmission means to a plurality of antenna units, at least one antenna unit located in each zone, each antenna unit having an antenna located for broadcast and reception of signals in the associated zone, the base station unit including;

analog RF signal generation means for generating a plurality of RF signals on different channels for carrying telephone signals to mobile units in the cell;

first switch means responsive to a first control signal for switching and combining the RF signals to form a composite RF signal for each zone, the composite signal for each zone containing selected channels;

analog-to-digital conversion means for converting the composite signal for each zone to a corresponding digitized stream of samples;

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

wherein each antenna unit further includes;

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

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 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 data streams to the transmission means for transmission to the base station unit;

wherein each base station unit further includes;

digital-to-analog converter means for receiving the digitized streams of samples from each antenna unit, and reconstructing an analog RF signal for each antenna unit;

second switch means responsive to a second control signal for selectively combining the RF signals from the antenna units to form a plurality of composite signals for application to receivers or the base station unit, each of the composite signals comprising one or more of the RF signals from the antenna units; and

control means for monitoring the digitized streams of samples from all of the antenna units and digitally analyzing the energy level of each channel in each zone, and in response thereto generating the first and second control signals to selectively control the zones in which each channel is broadcast and the zone from which each channel is received.

5. A system according to claim 4 further wherein said control means includes fade control means for monitoring the fading of an RF signal received in a zone and for generating the second control signal to switch the zone from which the RF signal is obtained, whereby a diversity function is obtained.

6. A system according to claim 5 further wherein said fade control means can achieve said monitoring and switching within 1 second.