Communications network utilizing transmitter and channel diversity to mitigate path impairments

• US 6,847,997 B1
• Filed: 04/19/2000
• Issued: 01/25/2005
• Est. Priority Date: 04/19/2000
• Status: Expired due to Fees

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Kleiner, Norbert
• Primary Examiner(s): Jean, Frantz B.
• Assistant Examiner(s): BARQADLE, YASIN M
• Application Number:
  US09/553,232
• Time in Patent Office: 1,742 Days
• Field of Search: 709/200, 709/201, 709/203, 709/217, 709/218, 709/219, 709/220, 709/223, 709/224, 455/452.16, 455/452.2, 455/453, 455/450
• US Class Current: 709/224
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: H04W 76/10 Connection setup

Abstract

Communications path impairments are mitigated within a wireless communications system (10) comprising fixed, mobile, and portable subscriber units (SUs 1-N), server nodes (S1-SN), and a network operations center (NOC 2). Each SU can be served by at least two different server nodes, each communicating over a different channel. The SUs and/or the server nodes periodically evaluate the quality of the SU communications links and determine the link having optimum quality. The SU or the server node informs the NOC of the determination. Subsequent communications with the SU during the period are conducted using the optimum communications link. In the event of a temporary path impairment, an alternate communications link is promptly established to maintain uninterrupted communications with the SU. In another embodiment, the NOC performs the quality evaluation and/or determines the optimum communications link to the SU. The NOC communicates with the server nodes over separate communications links.

Claims

1. A method of mitigating path impairments in a wireless communications system comprising at least one subscriber unit and a plurality of server nodes interconnected by a plurality of wireless communication links, the method comprising:

establishing one of the plurality of wireless communications links as an active link between the at least one subscriber unit and one of the plurality of server nodes;

measuring periodically the quality of the active link;

determining whether the active link provides superior quality of communications compared with the other links of the plurality of wireless communications links;

evaluating the results of the determining step according to criteria to determine if an override is necessary to prevent overloading one of the server nodes;

ordering subsequent communications with the subscriber unit to be over the active link having the optimum quality if an override is not necessary, and otherwise selecting another of the plurality of wireless communications links; and

continuously performing the measuring, deter and evaluating steps to thereby assign a new one of the plurality of wireless communications links when the active link is yielded in response to the evaluating step.

2. The method recited in claim 1 wherein each communications link utilizes a different communications channel.

3. The method recited in claim 1 wherein each communications link is a wireless link, and wherein the subscriber units are from the group consisting of fixed subscriber units, mobile subscriber units, and portable subscriber units.

4. The method recited in claim 1 wherein determining is performed by the at least one subscriber unit.

5. The method recited in claim 4 wherein the communications system further comprises a network operations center coupled to the plurality of server nodes, the method further comprising:

the at least one subscriber unit communicating to the network operations center a determination of a communications link having optimum quality.

6. The method recited in claim 5, wherein;

the network operations center performs the evaluating step.

7. Method recited in claim 1 wherein determining is performed by one of the plurality of server nodes.

8. The method recited in claim 7 wherein the communications system further comprises a network operations center coupled to the plurality of server nodes, the method further comprising:

the one of the plurality of server nodes communicating to the network operations center a determination of a communications link having optimum quality.

9. The method recited in claim 8 wherein the communications system further comprises an additional communications link between the network operations center and the plurality of server nodes, and wherein the one of the plurality of server nodes uses the additional communications link to communicate the determination to the network operations center.

10. The method recited in claim 8, the method further comprising:

the network operations center overriding the determination; and

the network operations center ordering the at least one subscriber unit to use a communications link that does not have optimum quality instead of using the communications link having the optimum quality.

11. The method recited in claim 1 wherein the communications system further comprises a network operations center coupled to the plurality of server nodes, the method further comprising:

the network operations center performing the determining.

12. The method recited in claim 11, the method further comprising:

the network operations center communicating to one of the plurality of server nodes a determination of a communications link having optimum quality.

13. The method recited in claim 1 wherein quality involves at least one of the group including signal strength, bit error rate, and block error rate.

20. The method recited in claim 1 wherein the criteria comprises one of the group consisting of seniority, priority, prediction and capacity.

14. A network control node for use in a wireless communications system having a subscriber unit communicating with a plurality of server nodes on first and second wireless communications links, the server nodes periodically transmitting indications of quality of communications with each of the subscriber units over their respective communications links, the network control node comprising:

a receiver configured to receive each of the periodically transmitted indications of quality of communications from the server nodes over a third wireless communications link; and

a module to store the indications, the module including a data processing system that includes a processing element and a memory, the data processing system operable to execute at least one computer program stored in the memory to control communications between the subscriber unit and the server nodes, the at least one computer program when executed comprising the operations of;

establishing one of the first and second wireless communications links as an active link between the at least one subscriber unit and one of the plurality of server nodes;

periodically determining whether the active link provides superior quality of communications compared with the other of the first and second wireless communications links;

evaluating the results of the determining operation according to criteria to determine if an override is necessary to prevent overloading one of the server nodes;

ordering subsequent communications with the subscriber unit to be over the active link having the optimum quality if an override is not necessary, and otherwise selecting the other of the first and second wireless communications links; and

continuously performing the measuring, determining and evaluating operations to thereby assign the other of the first and second wireless communication links when the active communications link is yielded in response to the evaluating operation.

15. The network control node recited in claim 14, and further comprising a transmitter, and wherein the at least one computer program when executed comprises an additional operation of:

transmitting over the third communications link an order to one of the server nodes to perform the ordering.

16. The network control node recited in claim 14, wherein the at least one computer program when executed comprises an additional operation of:

controlling the subscriber unit to perform the ordering.

17. A server node for use in a wireless communications system having a plurality of subscriber units and a network control node, the server node comprising:

at les one transceiver to periodically establish a wireless communication with one of the plurality of subscriber units over a plurality of first wireless communications links;

an element to periodically provide an indication of quality of communications between the server node and the one of the plurality of subscriber units on each of the first communications links;

the at least one transceiver communicating the periodically provided indication of quality to the network control node over a second wireless communications link; and

a data processing system that includes a processing element and a memos the data processing system operable to execute at least one computer program stored in the memory to measure the indication of quality on each of the first wireless communications links, the at least one computer program when executed comprising the operations of;

establishing one of the first less communications links as an active link between the server node and the one of the plurality of subscriber units;

determining whether the active link provides superior quality of communications compared with others of the plurality of first wireless communications links;

evaluating the results of the determining operation according to criteria to identify an optimal link of the plurality of first wireless communications links and to determine if an override is necessary to prevent overloading the server node;

ordering subsequent communications with the one of the plurality of subscriber units to be over the optimal link if an override is not necessary, and otherwise selecting another of the plurality of first wireless communications links as the active link; and

continuously performing the measuring, determining and evaluating operations to thereby assign a new one of the first wireless communications links when the active link is yielded in response to the evaluating operation.

18. The server node recited in claim 17 wherein the at least one computer program when executed further comprises the operations of:

measuring quality of communications on each of the first communications links using one technique from the group including signal strength, bit error rate, and block error rate; and

determining which technique provides optimum quality.

19. The server node recited in claim 18 wherein the at least one computer program when executed comprises the additional operations of:

determining whether each of the first communications links is currently active;

if so, performing the measuring; and

if not, initiating a communications exchange with one of the subscriber units over the non-active first communications link, and subsequently performing the measuring.