Radio telephone system

• US 3,906,166 A
• Filed: 10/17/1973
• Issued: 09/16/1975
• Est. Priority Date: 10/17/1973
• Status: Expired due to Term

• Current Assignee: Albert J. Mikulski, Charles N. Lynk Jr, James J. Mikulski, John F. Mitchell, John H. Sangster, Martin Cooper, Richard W. Dronsuth, Roy A. Richardson
• Original Assignee: Albert J. Mikulski, Charles N. Lynk Jr, James J. Mikulski, John F. Mitchell, John H. Sangster, Martin Cooper, Richard W. Dronsuth, Roy A. Richardson
• Inventors: Cooper, Martin, Dronsuth, Richard W., Mikulski, Albert J., Lynk, Charles N. Jr., Mikulski, James J., Mitchell, John F., Richardson, Roy A., Sangster, John H.
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Brigance, Gerald L.
• Application Number:
  US05/403,725
• Time in Patent Office: 699 Days
• Field of Search: 179/41A 325/16,55,64
• US Class Current: 455/437
• CPC Class Codes: H04B 1/50 using different frequencies for the two directions of communication
• CPC Class Codes: H04W 84/042 Public Land Mobile systems, e.g. cellular systems
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A portable duplex radio telephone system includes at least one base station transmitter having a predetermined base transmission range, and a plurality of portable or mobile units each having a predetermined portable maximum transmission range predeterminately shorter than the base transmission range. Satellite receivers are deployed about the base station within the base station transmission range for receiving transmissions from the portable units. The base station transmitter transmits signals on a signalling channel and on at least one communications channel. Each transmitter signalling and communications channel has a frequency that is paired or associated with a receiving frequency of the satellite receivers. In a multiple base station system, the portable receiver has means for scanning the base station transmitter signalling frequencies and for tuning the portable transmitter to the signalling frequency associated with the frequency of the strongest signalling signal received from the base transmitter. When communication is initiated, the portable transmitter and receiver are automatically retuned to one of the communications channels as determined by the strongest signalling frequency received by the portable receiver and by channel availability. Means are also provided in the system to continuously locate a portable unit and switch the operating frequency thereof as the portable unit moves between base station transmitter coverage areas. Further means are provided to automatically reduce the output power of each portable transmitter to the minimum level required for satisfactory communications in order to reduce battery drain and the interference caused by the portable transmitters.

Claims

1. A portable radio telephone system comprising:

a first base station transmitter site having a first predetermined coverage area and means for simultaneously transmitting signals on a first outgoing signalling channel and a plurality of first outgoing communications channels;

a plurality of first receiver sites associated with said first base station transmitter site, each first receiver site having a first predetermined reception area smaller than said first predetermined coverage area, each of said first receiver sites being located for causing at least a portion of each of said first reception areas to overlap a portion of said first coverage area, each first receiver site having means for simultaneously receiving signals on a first incoming signalling channel paired with said first outgoing signalling channel and a plurality of first incoming communications channels, each of said first incoming communications channels being paired with one of said first outgoing communications channels;

means connecting said first base station transmitter site and said first receiver sites, said connecting means including means for comparing the strength of the signals received by said first receiver sites and for placing the first receiver site receiving the strongest signal on the first incoming signalling channel in electrical communication with said first base station transmitter site;

a second base station transmitter site having a second predetermined coverage area and means for simultaneously transmitting signals on a second outgoing signalling channel and a plurality of second outgoing communications channels;

a plurality of second receiver sites associated with said second base station transmitter site, each second receiver site having a second predetermined reception area smaller than said second predetermined coverage area, each of said second receiver sites being located for causing at least a portion of each of said second reception areas to overlap a portion of said second coverage area, one of said second receiver sites being located for causing at least a portion of the second reception area thereof to overlap a portion of said first coverage area, each second receiver site having means for simultaneously receiving signals on a second incoming signalling channel paired with said second outgoing signalling channel and a plurality of second incoming communications cHannels, each of said second incoming communications channels being paired with one of said second outgoing communications channels; and

means connecting said second base station transmitter site and said second receiver sites, said last mentioned connecting means including means for comparing the strength of the signals received by said second receiver sites and for placing the second receiver sites receiving the strongest signal on the second incoming signalling channel in electrical communication with said second base station transmitter.

2. A system as recited in claim 1 further including at least one portable unit comprising a portable transmitter having a predetermined range less than the range of said first and second base station transmitters site, said portable transmitter having an adjustable operating frequency for transmitting a signal on one of said incoming signalling and communications channels, a portable receiver having an adjustable operating frequency for receiving a signal on one of said outgoing signalling and communications channels, scanning means connected to said portable receiver for rendering said portable receiver operative to sequentially receive signals on each of said outgoing signalling channels, a signal strength detector responsive to the strength of the signals received by said portable receiver connected thereto, and logic means connected to said portable transmitter and to said signal strength detector, said logic means being responsive to said signal strength detector for adjusting the operating frequency of said portable transmitter to the frequency of the incoming signalling channel associated with the strongest received outgoing signalling channel.

3. A system as recited in claim 2 wherein said connecting means further includes means for causing the base station transmitter site communicating with the receiver site receiving the strongest signal on the incoming signalling frequency from said portable unit to transmit a signal on the associated outgoing signalling frequency to said portable unit to assign one of the incoming and outgoing communications channels assigned to the receiver site receiving the strongest signal to said portable unit.

4. A system as recited in claim 3 wherein said portable unit includes means responsive to signals from one of said base station transmitter sites for changing the operating frequency of the portable transmitter and receiver in response thereto.

5. A system as recited in claim 4 wherein each of said base station transmitter sites includes receiving means for monitoring the strength of communications channel transmissions from said portable unit.

6. A system as recited in claim 5 further including means for comparing the strength of the communications channel transmissions received at said base station transmitter sites for determining the geographic location of said portable unit, and for assigning an incoming and an outgoing communications channel thereto for communicating with the receiver site located nearest said portable unit in accordance with said comparison.

7. A system as recited in claim 6 further including means for comparing the magnitude of the signals received by receiving means in any of said receiver sites with a predetermined level, and for causing the transmitter site communicating with a receiver site receiving a signal having an amplitude greater than said predetermined level to transmit a power reduction signal to said portable unit to reduce the power output thereof.

8. A system as recited in claim 7 wherein said portable unit includes power control means connected to said portable receiver and said portable transmitter, said power control means being responsive to a power reduction signal received by said portable receiver for reducing the power output of said portable transmitter in accordance therewith.

9. A system as recited in claim 8 wherein said base station transmitter sites and receiver sites are coupled to a wire line telephone network, And wherein said portable unit includes tone generating means for generating dialing tones for addressing said network.

10. A communications system comprising:

a first base station site located in a first predetermined geographic area and including means for receiving and transmitting signals on a plurality of first radio channels, each of said first radio channels having a predetermined carrier frequency, the carrier frequencies of individual ones of said first radio channels being separated by at least a first predetermined frequency separation;

a second base station site located in a second predetermined geographic area adjacent said first predetermined geographic area, said second base station site including means for receiving and transmitting signals on a plurality of second radio channels, each second radio channel having a predetermined carrier frequency different from the carrier frequencies of said first radio channels, the carrier frequencies of the individual ones of said second channels being separated by at least said first predetermined frequency separation, the carrier frequencies of each of said second channels being further separated from the carrier frequencies of each of said first channels by at least said first frequency separation;

a third base station site located in a third predetermined geographic area non-adjacent to said first geographic area, said third base station site including means for receiving and transmitting signals on a plurality of third radio channels, each of said third radio channels having a predetermined carrier frequency different from the carrier frequencies of said first and second radio channels, the carrier frequencies of individual ones of said third channels being separated by at least said first predetermined frequency separation, the carrier frequencies of each one of said third channels being separated from the carrier frequency of one of said first channels by a second predetermined frequency separation, said second predetermined frequency separation being less than said first predetermined frequency separation;

means connected to said first, second and third base station sites for transferring signals between said base station sites;

a plurality of first receiver sites each including means for receiving signals on said plurality of first radio channels, each of said first receiver sites being located in a predetermined geographic area smaller than said first predetermined geographic area wherein the geographic area of each of said first receiver sites overlaps said first geographic area;

a plurality of second receiver sites each including means for receiving signals on said plurality of second radio channels, each of said second receiver sites being located in a predetermined geographic area smaller than said second geographic area wherein the geographic area of each of said second receiver sites overlaps said second geographic area, one of said second receiver sites including means for receiving signals on said plurality of first radio channels, the geographic area of said one of said second receiver sites overlapping both said first and second predetermined geographic areas;

a plurality of third receiver sites each including means for receiving signals on said plurality of third radio channels, each of said third receiver sites being located in a predetermined geographic area smaller than said third predetermined geographic area wherein the geographic area of each of said third receiver sites overlaps said third geographic area; and

means for connecting each of said first, second and third receiver sites to said first, second and third base station sites, respectively.

11. A communications system as recited in claim 10 further including;

a fourth base station site located in a fourth predetermined geographic area non-adjacent to said first predetermined geographic area, said fourth predetermined geographic area being separated from said first predetermined geographIc area by a predetermined geographic separation greater than the separation between said first and third predetermined geographic areas, said fourth base station site including means for receiving and transmitting signals on at least one of said first radio channels.

12. A portable radio telephone system as claimed in claim 1, further including a portable unit comprising:

means for receiving messages on one of a plurality of outgoing signalling channels and outgoing communications channels, each outgoing communications channel being associated with one of said outgoing signalling channels, each of said outgoing communications channels and outgoing signalling channels having a different predetermined carrier frequency;

means for transmitting messages on one of a plurality of incoming signalling channels and incoming communications channels, each of said incoming signalling channels being associated with only one of said outgoing signalling channels and having a carrier frequency having a predetermined frequency relationship to the carrier frequency of the outgoing signalling channel associated therewith, each of said incoming communications channels being associated with one of said incoming signalling channels and having a carrier frequency different from the carrier frequency thereof;

scanning means connected to said receiving means for sequentially rendering said receiving means operative to receive messages on each of said outgoing signalling channels;

sample and storage means connected to said receiving means for determining the strongest one of the outgoing signalling channels received by said receiving means and storing an indication thereof;

transmitter control means connected to said transmitting means, said transmitter control means including means for rendering said transmitting means operative, said transmitter control means being further connected to said sample and storage means and responsive thereto for adjusting the carrier frequency of said transmitting means to the carrier frequency of the incoming signalling channel associated with the strongest outgoing signalling channel; and

logic means connected to said receiving means and to said transmitter control means, said logic means being responsive to predetrmined messages received by said receiving means on the strongest of said outgoing signalling channels for rendering said receiving means operative on one of the outgoing communications channels associated with said strongest outgoing signalling channel, and for adjusting the carrier frequency of said transmitting means to the carrier frequency of one of said incoming communications channels associated with the incoming signalling channel associated with said strongest outgoing signaling channel.

13. A portable unit as recited in claim 12 further including power control means connected to said transmitting and receiving means, said power control means being responsive to a power control signal received by said receiving means for reducing the power output of said transmitting means.

14. A portable unit as recited in claim 13 further including microphone means, said transmitter control means including voice operated control means connected to said microphone means and said transmitting means, said voice operated control means being responsive to signals from said microphone means for rendering and transmitting means operative.

15. A portable unit as recited in claim 13 wherein said scanning means includes a frequency synthesizer.

16. A portable unit as recited in claim 15 further including means for generating signalling tones that are compatible with wire line telephone dialing tones.

17. A radio telephone system for operation in conjunction with a wire line telephone system, including in combination:

a plurality of base station transmitter means, each including means for simultaneously transmitting signals on a plurality of different base transmission frequencies, said transmitting means each havIng a predetermined geographic location, transmission range and coverage area;

a plurality of portable units each having a portable receiver for receiving transmissions from said base station transmitter means on each of said base transmission frequencies, and a portable transmitter having a shorter range and smaller coverage area than said base station transmitter means, said portable transmitter having means for transmitting on one of a plurality of portable transmission frequencies different from said base transmission frequencies, each portable transmission frequency being associated with one of said base transmission frequencies, said portable receiver including means for sampling the base transmission frequencies and determining the strongest one thereof, and means responsive to said sampling means connected to said portable transmitter for adjusting the frequency thereof to the portable transmission frequency associated with the strongest received base transmission frequency; and

a plurality of base station receiver means for receiving transmissions from said portable transmitter on said portable transmission frequencies, the number of base station receiver means being greater than the number of base station transmitter means, each of said base station transmitter means having one of said base station receiver means geographically co-located therewith, the other receiver means being deployed about said base station transmitter means and separated therefrom by approximately twice the transmission range of said portable transmitter, each of said base station receiver means having a reception area thereabout substantially equal to the coverage area of said portable transmitter, at least a portion of the reception area of each of said receiver means overlapping a portion of the coverage area of one of said base station transmitter means.

18. A radio telephone system as recited in claim 17 wherein each of said base station transmitter means and each of said base station receivers is electrically coupled to said wire line telephone network for providing communications therewith.

19. A radio telephone system as recited in claim 18 wherein each of said portable units has a unique address, and means for transmitting signalling tones representative of a particular address for establishing communications with the unit having said particular address, and computer means coupled to said base station transmitter means for receiving and storing a representation of each of said addresses.

20. A radio telephone system as recited in claim 19 further including means for transmitting a particular address in response to dial signals received from said wire line telephone network for establishing communications between said wire line network and the unit having said particular address.

21. A radio telephone system for operation in conjunction with a wire line telephone network including in combination:

a first base station transmitter having a first predetermined geographic coverage area for simultaneously transmitting signals on a plurality of first outgoing channels having at least a first predetermined frequency separation between adjacent channels;

a plurality of first receiver sites coupled to said first base station transmitter and located within said predetermined geographic coverage area, each of said receiver sites having a first predetermined reception area smaller than said first geographic coverage area, each first receiver site being adapted to simultaneously receive signals on a plurality of first incoming channels having frequencies different than said first outgoing channels, each of said first incoming channels being associated with one of said first outgoing channels, the frequency separation between adjacent ones of said first incoming channels being substantially equal to frequency separation between adjacent ones of said first outgoing channels;

a second base station transmitter located outside said first predetermined geographic covErage area having a second predetermined geographic coverage area for simultaneously transmitting signals on a plurality of second outgoing channels each channel having a frequency different than any of the frequencies of said first outgoing channels, the frequency separation between adjacent ones of said second outgoing channels being equal to at least said first predetermined frequency separation, each of said second outgoing channels being separated in frequency from one of said first outgoing channels by less than said first predetermined frequency separation; and

a plurality of second receiver sites coupled to said second base station transmitter and located within said second predetermined coverage area, each of said second receiver sites having a second predetermined reception area smaller than said second geographic coverage area, each receiver site being adapted to receive signals on a plurality of second incoming channels having frequencies different than the frequencies of said first and second outgoing channels and said first incoming channels, each of said second incoming frequencies being associated with one of said second outgoing channels, the frequency separation between adjacent ones of said second incoming channels being substantially equal to the frequency separation between adjacent ones of said second outgoing channels, each of said second incoming channels being separated in frequency from one of said first incoming channels by less than said first predetermined frequency separation.

22. A radio telephone system as recited in claim 21 wherein each of said first outgoing channels is paired with a particular single one of said first incoming channels, and each of said second outgoing channels is paired with a particular single one of said second incoming channels, each channel pair forming a duplex channel.

23. A radio telephone system as recited in claim 22 wherein a particular one of each of said first and second outgoing channels is designated a signalling channel and each of said first and second base station transmitters includes means for transmitting digital signals on the predetermined one of each of said first and second outgoing channels designated as a signalling channel, respectively, each of the receiver sites located within said first predetermined geographic area including means for receiving digital signals on the incoming channel paired with said first outgoing signalling channel, and each of the receiver sites located within said second predetermined geographic area including means for receiving digital signals on the incoming channel paired with said second outgoing channel.

24. A radio telephone system as recited in claim 23 wherein the other ones of said incoming and outgoing channels are designated as voice channels and each of said first and second base station transmitters includes means for simultaneously transmitting voice signals on the ones of said first and second outgoing channels denoted as voice channels, respectively, and each of said first and second receiver sites includes means for receiving voice messages on the incoming channels paired with said first and second outgoing voice channels, respectively.

25. A radio telephone system as recited in claim 24 wherein each of said receiver sites includes means for sensing the strength of the incoming voice and digital signals received thereby.

26. A radio telephone system as recited in claim 25 further including means connected to said receiver sites and said wire line telephone network for comparing the strengths of the incoming digital signals received by said first and second receiver sites and for electrically coupling the one of said first receiver sites receiving the strongest digital signal and the one of said second receiver sites receiving the strongest digital signal to said wire line telephone network.

27. A radio telephone system as recited in claim 26 further including a plurality of portable units operable in said first and second predeterMined geographic areas, each portable unit having a portable transmitter having a portable geographic coverage area substantially similar to one of said first and second reception areas and a portable receiver having a portable reception area substantially similar to one of said first and second geographic coverage areas, said portable transmitter being automatically tunable to one of said first and second incoming channels and said portable receiver being automatically tunable to one of said first and second outgoing channels in response to control signals from one of said base station transmitters.

28. A radio telephone system as recited in claim 27 further including means connected to said first and second base station transmitters and responsive to the strength of the signals received by said receiver sites on one of said incoming signalling channels for causing one of said base station transmitters to transmit a signal on the outgoing signalling channel paired with said one of said incoming signalling channels for causing said portable transmitter to automatically tune to the incoming voice channel of the receiver site receiving the strongest signal on the incoming signalling channel thereof and to automatically cause said portable receiver to tune to the outgoing voice channel paired therewith.

29. A radio telephone system as recited in claim 28 further including a plurality of location receivers, one of said location receivers being located in each of said first and second predetermined geographic areas for receiving signals on each of said voice channels, said location receivers including means for determining the strength of the voice channel signals received thereby for determining the geographic location of said portable units, said location receivers including means connected to said base station transmitters for causing one of said base station transmitters to transmit a signal for tuning the portable transmitters and receivers of said portable units in accordance with the geographic location thereof.

30. A radio telephone system as recited in claim 21 wherein said first predetermined frequency separation is 25 KHz, each of said first outgoing channels is separated from one of said second outgoing channels by 8.33 KHz, and each of said first incoming channels is separated from one of said second incoming channels by 8.33 KHz.

31. A radio telephone system as recited in claim 21 including a predetermined number of base station transmitters, each having a predetermined geographic coverage area, each having means for simultaneously transmitting signals on a plurality of outgoing channels, each outgoing channel having a different frequency, the outgoing channels of each individual base station transmitter being separated by at least said first predetermined frequency separation, the frequency separation between outgoing channels of different transmitters being equal to said first predetermined frequency separation divided by the number of base station transmitters comprising said plurality of base station transmitters.