Data communications system transmitter selection method and apparatus

• US 4,670,906 A
• Filed: 08/06/1986
• Issued: 06/02/1987
• Est. Priority Date: 04/02/1986
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Thro, Stuart W.
• Primary Examiner(s): Ng, Jin F.
• Application Number:
  US06/894,084
• Time in Patent Office: 300 Days
• Field of Search: 455/33, 455/52-54, 455/56, 455/62, 179/2 EB
• US Class Current: 455/525
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/302 due to low signal strength
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 distributing total power among users or channels

Abstract

A data communications system is described which comprises a general communications controller (GCC), a plurality of channel communications modules (CCM) and associated co-located transmitters and receivers, and a plurality of portable radios. Message signals carrying alphanumeric information are communicated between the GCC and the portable radios by way of a radio channel. Each CCM receiver takes a signal strength measurement every time it receives a message signal from a portable radio. The GCC gathers the signal strength measurements from the GCC receivers receiving the same message signal and computes the radio channel path loss between the portable radio and each base/transmitter-receiver site which received that portable radio'"'"'s message. The GCC next determines how much transmitter power each base transmitter site can deliver to the portable radio'"'"'s receiver. The GCC can then determined (a) which sites are capable of delivering a message to the portable radio, and (b) which sites can be simultaneously used for other traffic without producing harmful interference to the first transmission. Since the GCC can manage the levels of co-channel interference, multiple messages may be simultaneously sent from several base transmitters to several portable radios. This mode of system operation provides for greatly enhanced information throughput.

Claims

1. A method for use in a primary station of a communications system communicating message signals via a communications medium between the primary station and a plurality of remote stations located anywhere in a geographical area, said primary station including control means and a plurality of base stations, each base station including transmitting means for transmitting message signals modulated on a first carrier signal and receiving means colocated with the transmitting means for re-eiving message signals modulated on a second carrier signal, and said remote stations including transmitting means for transmitting message signals modulated on the second carrier signal and receiving means for receiving message signals modulated on the first carrier signal;

said method for selecting at least one of the base station transmitting means for transmitting message signals to a targe remote station, said method comprising the steps of;

(a) measuring the signal strength of the carrier signal that is received by any of the base station receiving means from said target remote station during each transmission therefrom;

(b) computing an estimate of the communications medium path loss between each base station receiving means and said target remote station using the measured signal strength for that base station receiving means;

(c) computing an estimate of the signal strength receivable at said target remote station from each base station transmitting means using the computed path loss estimate for the base station receiving means colocated with that base station transmitting means; and

(d) selecting at least one of the base station transmitting means having a computed receivable signal strength estimate that has a magnitude greater than a predetermined receive sensitivity threshold of said target remote station'"'"'s receiving means.

2. The method according to claim 1, wherein said step c) further includes the step of weighting the computer receivable signal strength estimate of each base station transmitting means by a prioritization factor pre-selected for that base station transmitting means.

3. The method according to claim 1, further including the step of (e) modulating a message signal on the first carrier signal of the base station transmitting means selected in step (d).

4. The method according to claim 1, further including the step of (e) disabling those of the other base station transmitting means whose modulated first carrier signal would produce interference with the reception of a message signal by the target remote station.

5. The method according to claim 1, further including the steps of:

(e) repeating steps (a), (b) and (c) for a second target remote station; and

(f) selecting at least one of the other base station transmitting means that does not interfere with communications with the first target remote station and which has a computed receivable signal strength estimate that has a magnitude greater than the predetermined receive sensitivity threshold of the second target remote station receiving means.

6. The method according to claim 1, further including the steps of;

(e) adjusting the computed receivable signal strength estimate of the selected base station transmitting means for the computed receivable signal strength estimate of all other active base station transmitting means allowed to simultaneously transmit meassage signals to other remote stations; and

(f) after a predetermined time interval, modulating a message signal on the first carrier signal of the selected base station transmitting means if its adjusted receivable signal strength estimate does not have a magnitude greater than the predetermined receive sensitivity threshold of said target remote station'"'"'s receiving means.

7. The method according to claim 1, further including the steps of:

(e) adjusting the computed receivable signal strength estimate of the selected base station transmitting means for the computed receivable signal strength estimate of all other active base station transmitting means allowed to simultaneously transmit message signals to other remote stations; and

(f) modulating a message signal on the first carrier signal of the selected base station transmitting means if the magnitude of its adjusted receivable signal strength estimates is greater than the predetermined receive sensitivity threshold of said target remote station'"'"'s receiving means.

8. The method according to claim 1, wherein said step (d) further includes the step of selecting a second base station transmitting means having a computed receivable signal strength estimate that has a magnitude greater than the predetermined receive sensitivity threshold of the target remote station'"'"'s receiving means;

and said method further including the step of (e) modulating a message signal on the first carrier signal of the first selected base station transmitting means and thereafter on the first carrier signal of the second selected base station transmitting means.

9. The method according to claim 1, wherein said step (d) further includes the step of selecting a second base station transmitting means having a computed receivable signal strength estimate that has a magnitude greater than the predetermined receive sensitivity threshold of the target remote station'"'"'s receiving means;

and said method further including the step of (e) modulating a message signal on the first carrier signal of both the first selected base station transmitting means and the second selected base station transmitting means.

10. A method for use in a primary station of a communications system communicating message signals via a communications medium between the primary station and a plurality of remote stations located anywhere in a geographical area, said primary station including control means and a plurality of base stations, each base station including transmitting means for transmitting message signals modulated on a first carrier signal and receiving means colocated with the transmitting means for receiving message signals modulated on a second carrier signal, and said remote stations including transmitting means for transmitting message signals modulated on the second carrier signal and receiving means for receiving message signals modulated on the first carrier signal;

said method for selecting at least one of the base station transmitting means for transmitting message signals to a target remote station, said method comprising the steps of;

(a) measuring the signal strength of the carrier signal that is received by any of the base station receiving means from said target remote station during each transmission therefrom;

(b) computing an estimate of the communications medium path loss between each base station receiving means and said target remote station using the measured signal strength for that base station receiving means;

(c) computing an estimate of the signal strength receivable at the target remote station from each base station transmitting means using the computed path loss estimate for the base station receiving means colocated with that base station transmitting means;

(d) for each base station transmitting means, adjusting its computed receivable signal strength estimate for the computed receivable signal strength estimate of all other base station transmitting means allowed to simultaneously transmit message signals to other remote stations; and

(e) selecting at least one of the base station transmitting means having an adjusted receivable signal strength estimate that has a magnitude greater than a predetermined capture threshold of the target remote station'"'"'s receiving means.

11. The method according to claim 10, wherein said step (d) further includes the step of weighting the adjusted receivable signal strength estimate of each base station transmitting means by a prioritization factor pre-selected for that base station transmitting means.

12. The method according to claim 11, wherein said weighting step includes the step of weighting the adjusted receivable signal strength estimate of each base station transmitting means by a second prioritization factor preselected for that base station transmitting means to produce a second adjusted receivable signal strength estimate , the first and second adjusted receivable signal strength estimate for each base station transmitting means corresponding to first and second communications medium reuse states for that base station transmitting means.

13. The method according to claim 10, further including the step of (f) modulating a message signal on the first carrier signal of the base station transmitting means selected in step (e).

14. The method according to claim 10, further including the step of (f) disabling those of the other base station transmitting means whose modulated first carrier signal would produce interference with the reception of a message signal by the target remote station.

15. The method according to claim 10, further including the steps of:

(f) repeating steps (a), (b), (c) and (d) for a second target remote station; and

(g) selecting at least one of the other base station transmitting means that does not interfere with communications with the first target remote station and which has a computed receivable signal strength estimate that has a magnitude greater than the predetermined capture threshold of the second target remote station receiving means.

16. The method according to claim 10, wherein said step (e) further includes the step of selecting a second base station transmitting means having a computed receivable signal strength estimate that has a magnitude greater than the predetermined capture threshold of the target remote station'"'"'s receiving means;

and said method further including the step of (f) modulating a message signal on the first carrier signal of the first selected base station transmitting means and thereafter on the first carrier signal of the second selected base station transmitting means.

17. The method according to claim 10, wherein said step d) further includes the step of selecting a second base station transmitting means having a computed receivable signal strength estimate that has a magnitude greater than the receive sensitivity threshold of the target remote station'"'"'s receiving means;

and said method further including the step of (e) modulating a message signal on the first carrier signal of both the first selected base station transmitting means and the second selected base station transmitting means.

18. A method of maximizing reuse of base stations for substantial simultaneous communications via a communications medium between two or more base stations and different remote stations associated therewith, each base station including transmitting means for transmitting message signals modulated on a first carrier signal and receiving means colocated with the transmitting means for receiving message signals modulated on a second carrier signal, and said remote stations including transmitting means for transmitting message signals modulated on the second carrier signal and receiving means for receiving message signals modulated on the first carrier signal;

for each transmission from a remote station, said method comprising the steps of;

(a) measuring the signal strength of the carrier signal that is received by any of the base station receiving means from said remote station during each transmission therefrom;

(b) computing an estimate of the communications medium path loss between each base station receiving means and said remote station using the measured signal strength for that base station receiving means;

(c) computing an estimate of the signal strength receivable at said remote station from each base station transmitting means using the computed path loss estimate for the base station receiving means colocated with that base station transmitting means; and

(d) allowing an inactive base station transmitting means to transmit a message signal to said remote station if its computed receivable signal strength estimate adjusted for the computed receivable signal strength estimate of all active base station transmitting means is greater than a predetermined capture threshold of said remote station'"'"'s receiving means.

19. Control means for a primary station of a communications system communicating message signals via a communications medium between the primary station and a plurality of remote stations located anywhere in a geographical area, said primary station further including a plurality of base stations, each base station including transmitting means for transmitting message signals modulated on a first carrier signal and receiving means colocated with the transmitting means for receiving message signals modulated on a second carrier signal, and said remote stations including transmitting means for transmitting message signals modulated on the second carrier signal and receiving means for receiving message signals modulated on the first carrier signal;

said control means comprising;

means for measuring the signal strength of the carrier signal that is received by any of the base station receiving means from a remote station during each transmission therefrom;

means for computing an estimate of the communications medium path loss between each base station receiving means and said remote station using the measured signal strength for that base station receiving means;

means for computing an estimate of the signal strength receivable at said remote station from each base station transmitting means using the computed path loss estimate for the base station receiving means colocated with that base station transmitting means; and

means for selecting at least one of the base station transmitting means having a computed receivable signal strength estimate that has a magnitude greater than a predetermined receive sensitivity threshold of said remote station'"'"'s receiving means.

20. The control means according to claim 19, wherein said signal strength computing means further includes means for weighting the computed receivable signal strength estimate of each base station transmitting means by a prioritization factor pre-selected for that base station transmitting means.

21. The control means according to claim 19, further including means for disabling those of the other base station transmitting means whose modulated first carrier signal would produce interference with the recognition of the message signal by the selected remote station.

22. The control means according to claim 19, further including means for modulating a message signal on the first carrier signal of the selected base station transmitting means.

23. Control means for a primary station of a communications system communicating message signals via a communications medium between the primary station and a plurality of remote stations located anywhere in a geographical area, said primary station including control means and a plurality of base stations, each base station including transmitting means for transmitting message signals modulated on a first carrier signal and receiving means colocated with the transmitting means for receiving message signals modulated on a second carrier signal, and said remote stations including transmitting means for transmitting message signals modulated on the second carrier signal and receiving means for receiving message signals modulated on the first carrier signal;

said control means comprising;

means for measuring the signal strength of the carrier signal that is received by any of the base station receiving means from a remote station during each transmission therefrom;

means for computing an estimate of the communications medium nath loss between each base station receiving means and said remote station using the measured signal strength for that base station receiving means;

means for computing an estimate of the signal strength receivable at said remote station from each base station transmitting means using the computed path loss estimate for the base station receiving means colocated with that base station transmitting means;

means for adjusting the computed receivable signal strength estimate of each base station transmitting means for the computed receivable signal strength estimate of all other base station transmitting means allowed to simultaneously transmit message signals to other remote stations; and

means for selecting at least one of the base station transmitting means having an adjusted receivable signal strength estimate that has a magnitude greater than a predetermined capture threshold of said remote station'"'"'s receiving means.

24. The control means according to claim 23, wherein said signal strength computing means further includes means for weighting the adjusted receivable signal strength estimate of each base station transmitting means by a prioritization factor pre-selected for that base station transmitting means.

25. The control means according to claim 23, further including means for disabling those of the other base station transmitting means whose modulated first carrier signal would produce interference with the recognition of the message signal by the selected remote station.

26. The control means according to claim 23, further including means for modulating a message signal on the first carrier signal of the selected base station transmitting means.

27. Control means for maximizing reuse of base stations for substantially simultaneous comunications via a communications medium between two or more base stations and different remote stations associated therewith, each base station including transmitting means for transmitting message signals modlated on a first carrier signal and receiving means colocated with the transmitting means for receiving message signals modulated on a second carrier signal, and said remote stations including transmitting means for transmitting message signals modulated on the second carrier signal and receiving means for receiving message signals modulated on the first carrier signal;

and control means comprising;

means for measuring the signal strength of the carrier signal that is received by any of the base station receiving means from a remote station during each transmission therefrom;

means for computing an estimate of the communications medium path loss between each base station receiving means and said remote station using the measured signal strength for that base station receiving means;

means for computing an estimate of the signal strength receivable at said remote station from each base station transmitting means using the computed path loss estimate for the base station receiving means colocated with that base station transmitting means; and

means for allowing an inactive base station transmitting means to transmit a message signal to said remote station if its computed receivable signal strength estimate adjusted for the computed receivable signal strength estimate of all active base station transmitting means is greater than a predetermined capture threhold of said remote station'"'"'s receiving means.