Impairment determination for a diversity antenna selection process

• US 6,118,773 A
• Filed: 12/20/1996
• Issued: 09/12/2000
• Est. Priority Date: 10/25/1996
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Nortel Networks Corporation
• Inventors: Todd, Stephen Ross
• Primary Examiner(s): Martin-Wallace, Valencia
• Assistant Examiner(s): Nguyen, Kim T.
• Application Number:
  US08/772,669
• Time in Patent Office: 1,362 Days
• Field of Search: 455/552, 455/462, 455/126, 455/63, 455/513, 455/436, 455/62, 455/222, 455/433, 455/67.1, 455/562, 455/277.1, 455/33.3, 455/277.2, 455/555, 375/267, 375/200, 375/347, 370/338, 370/331, 370/310, 370/346, 370/335, 370/320, 370/334
• US Class Current: 370/334
• CPC Class Codes: H04B 7/0808 comparing all antennas before reception
• CPC Class Codes: H04B 7/0811 during preamble or gap period
• CPC Class Codes: H04B 7/0825 with main and with auxiliary or diversity antennas
• CPC Class Codes: H04L 1/06 using space diversity

Abstract

A diversity selection process which tests to determine whether poor reception is caused by co-channel interference or multipath fading is disclosed. The impairment is determined by first testing the quality over several frames. Unless the quality is poor over these several frames, the system tests for multipath fading by selecting the antenna with the greater signal strength, provided no hold condition exists. However, if poor quality has been present over the several frame period, the system selects the other antenna if its RSSI is greater. However, the system also tests the RSSI received on the current antenna and determines the impairment was co-channel interference if the signal of quality was sufficiently high. In which case a hold condition is set for a number of frames to prevent excessive switching.

Claims

1. A diversity selection process for a transceiver with at least two antennas, wherein said transceiver communicates using transmissions which comprise frames, the process comprising, for a given frame:

a) selecting one of said at least two antennas as a current antenna based on a best antenna determination made prior to the given frame;

b) evaluating whether a quality indication of a signal received on the current antenna satisfies a first condition;

c) responsive to said quality indication satisfying said first condition, determining which of the at least two antennas has the greater Received Signal Strength lndication (RSSI), and selecting this antenna as the best antenna for a subsequent frame provided a hold condition does not exist;

d) responsive to said quality indication not satisfying said first condition;

i) evaluating whether the signal received on an other antenna satisfies a second condition;

ii) responsive to said other antenna signal satisfying said second condition;

A) selecting said other antenna as the best antenna for a subsequent frame; and

B) evaluating whether the received signal strength of the signal received on the current antenna exceeds a threshold, and setting a hold condition for a specified number of frames in the event said threshold was exceeded.

2. The method as claimed in claim 1 wherein said first condition is satisfied if said quality indication of the received signal satisfies a minimum threshold for a specified number of frames.

3. The method as claimed in claim 2 wherein said quality indication comprises a determination of one or both of the bit error rate or the coded digital verification colour code of the received signal.

4. The method as claimed in claim 3 wherein step (c) comprises the steps of, responsive to said quality satisfying said first condition:

i) evaluating whether a hold condition on the current antenna exists, and if so, decreasing a hold counter associated with said hold condition; and

ii) responsive to no hold condition existing, selecting the antenna with the greater RSSI as the best antenna for a subsequent frame.

5. The method as claimed in claim 3 further comprising the step of, prior to step (b), evaluating whether a hold condition on the current antenna exists, and if so, decreasing a hold counter associated with said hold condition and proceeding without changing the selection of the best antenna.

6. The method as claimed in claim 4 wherein step (d)(i) comprises comparing the RSSI of the signal received by said other antenna against a threshold.

7. The method as claimed in claim 4 wherein step (d)(i) comprises comparing an indication of the quality of the signal received by said other antenna against a threshold.

8. The method as claimed in claim 1 wherein step (b) comprises the steps of:

i) evaluating whether the bit error rate of the received signal exceeds a threshold;

ii) responsive to said threshold being exceeded, incrementing a counter, otherwise resetting said counter in the event said threshold was not exceeded; and

iii) comparing said counter to a predetermined value and determining said quality indication of the signal received on the current antenna satisfies a first condition if said counter exceeds said predetermined value.

9. A diversity antenna selection method for a terminal having at least two antennas operating in a wireless communication system comprising, for a given frame:

a) selecting one of said at least two antennas as a current antenna based on a best antenna determination made prior to the given frame and receiving a signal on said current antenna during a receive timeslot associated with a current channel;

b) testing reception of a different channel received by said terminal;

c) testing reception of the current channel received by said current antenna;

d) testing reception of the current channel received by an alternative antenna; and

e) selecting a best antenna for a subsequent frame as the antenna with the best test results, wherein step (e) comprises;

1) evaluating whether a quality indication of a signal received on the current antenna satisfies a first condition;

2) responsive to said quality indication satisfying said first condition, determining which of the at least two antennas has the greater Received Signal Strength Indication (RSSI), and selecting this antenna as the best antenna for a subsequent frame provided a hold condition does not exist;

3) responsive to said quality indication not satisfying said first condition;

i) evaluating whether the signal received on an other antenna satisfies a second condition;

ii) responsive to said other antenna signal satisfying said second condition;

A) selecting said other antenna as the best antenna for a subsequent frame; and

B) evaluating whether the received signal strength of the signal received on the current antenna exceeds a threshold, and setting a hold condition for a specified number of frames in the event said threshold was exceeded.

10. A diversity selection process for a transceiver with at least two antennas, wherein said transceiver communicates using transmissions which comprise frames, the process comprising the steps of:

i) determining a received signal strength indication (RSSI) received by each antenna;

ii) determining an indication as to the quality of the signal on a current antenna wherein said current antenna is selected from said at least two antennas;

iii) evaluating whether the quality of the signal received on the current antenna has been sufficient for a specified period;

iv) responsive to said evaluating step determining the quality has not been sufficient over said period, evaluating whether the signal received by another antenna satisfies a condition;

v) responsive to the signal received by said other antenna satisfying said condition;

a) selecting the other antenna as the current antenna during a subsequent frame; and

b) responsive to the received signal strength of the signal received by the current antenna having exceeded a specified threshold, establishing a hold on subsequent switching for a specified number of frames.

11. The method as claimed in claim 10 further comprising the step of:

vi) responsive to said evaluating step determining the quality has been sufficient for the specified period, selecting the antenna with the greater RSSI as the current antenna for a subsequent frame provided no hold has been set.

12. The method as claimed in claim 11 wherein the step of determining the received signal strength indication (RSSI) received by each antenna comprises measuring the RSSI of a current channel received on one antenna, then measuring the RSSI of the current channel received on the other antenna, wherein both of said measuring steps occur when said transceiver is either idle or transmitting and wherein said method further comprises the step of tuning the transceiver to another channel and testing the reception on said other channel when said transceiver is not transmitting.

13. A wireless terminal comprising:

a receiver for receiving transmissions which compose frames;

a first antenna;

at least one alternative antenna;

a switch for selecting which antenna provides input signal to said receiver; and

a controller for controlling said switch according to instructions stored in memory, said instructions when executed, causing said terminal to carryout a process comprising, for a given frame;

a) selecting one of said at least two antennas as a current antenna based on a best antenna determination made prior to the given frame;

b) evaluating whether a quality indication of a signal received on the current antenna satisfies a first condition;

c) responsive to said quality indication satisfying said first condition, determining which of the at least two antennas has the greater Received Signal Strength Indication (RSSI), and selecting this antenna as the best antenna for a subsequent frame provided a hold condition does not exit;

d) responsive to said quality indication not satisfying said first condition;

i) evaluating whether the signal received on an other antenna satisfies a second condition;

ii) responsive to said other antenna signal satisfying said second condition;

A) selecting said other antenna as the best antenna for a subsequent frame; and

B) evaluating whether the received signal strength of the signal received on the current antenna exceeds a threshold, and setting a hold condition for a specified number of frames in the event said threshold was exceeded.

22. The terminal as claimed in claim 13 further comprising instructions stored in said memory such that said first condition is satisfied if said quality indication of the received signal satisfies a minimum threshold for a specified number of frames.

23. The terminal as claimed in claim 22 further comprising instructions stored in said memory such that quality indication comprises a determination of one or both of the bit error rate or the coded digital verification colour code of the received signal.

24. The terminal as claimed in claim 23 wherein said instructions for step (c) comprises instructions for, responsive to said quality satisfying said first condition:

i) evaluating whether a hold condition on the current antenna exists, and if so, decreasing a hold counter associated with said hold condition; and

ii) responsive to no hold condition existing, selecting the antenna with the greater RSSI as the best antenna for a subsequent frame.

25. The terminal as claimed in claim 24 wherein said instructions for step (d)(i) comprises instructions for comparing the RSSI of the signal received by said other antenna against a threshold.

26. The terminal as claimed in claim 24 wherein said instructions for step (d)(i) comprises instructions for comparing an indication of the quality of the signal received by said other antenna against a threshold.

27. The terminal as claimed in claim 13 wherein said instructions for step (b) comprises instructions for:

i) evaluating whether the bit error rate of the received signal exceeds a threshold;

ii) responsive to said threshold being exceeded, incrementing a counter, otherwise resetting said counter in the event said threshold was not exceeded; and

iii) comparing said counter to a predetermined value and determining said quality indication of the signal received on the current antenna satisfies a first condition if said counter exceeds said predetermined value.

14. A wireless terminal comprising:

a receiver for receiving transmissions which comprise frames;

a first antenna;

at least one alternative antenna;

a switch for selecting which antenna provides input signal to said receiver; and

a controller for controlling said switch according to instructions stored in memory, said instructions, when executed, causing said terminal to carryout a process comprising, for a given frame;

a) selecting one of said at least two antennas as a current antenna based on a best antenna determination made prior to the given frame and receiving a signal on said current antenna during a receive timeslot associated with a current channel;

b) testing reception of a different channel received by said terminal;

c) testing reception of the current channel received by said current antenna;

d) testing reception of the current channel received by an alternative antenna; and

e) selecting a best antenna for a subsequent frame as the antenna with the best test results, wherein step (e comprises;

1) evaluating whether a quality indication of a signal received on the current antenna satisfies a first condition;

2) responsive to said quality indication satisfying said first condition, determining which of the at least two antennas has the greater Received Signal Strength Indication (RSSI), and selecting this antenna as the best antenna for a subsequent frame Provided a hold condition does not exist;

3) responsive to said quality indication not satisfying said first condition;

i) evaluating whether the signal received on an other antenna satisfies a second condition;

ii) responsive to said other antenna signal satisfying said second condition;

A) selecting said other antenna as the best antenna for a subsequent frame; and

B) evaluating whether the received signal strength of the signal received on the current antenna exceeds a threshold, and setting a hold condition for a specified number of frames in the event said threshold was exceeded.

15. A wireless terminal comprising:

a transceiver for receiving transmissions which comprise frames;

a first antenna;

at least one alternative antenna;

a switch for selecting which antenna provides input signal to said receiver; and

a controller for controlling said switch according to instructions stored in memory said instructions, when executed, causing said terminal to carryout a process comprising, for a given frame;

i) determining the received signal strength indication (RSSI) received by each antenna;

ii) determining an indication as to the quality of the signal on the current antenna;

iii) evaluating whether the quality of the signal received on the current antenna has been sufficient for a specified period;

iv) responsive to said evaluating step determining the quality has not been sufficient over said period, evaluating whether the signal received by said other antenna satisfies a condition;

v) responsive to the signal received by said other antenna satisfying said condition;

a) selecting the other antenna as the current antenna for reception during a subsequent frame; and

b) responsive to the received-signal strength of the signal received by the current antenna having exceeded a specified threshold, establishing a hold on subsequent switching for a specified number of frames; and

vi) responsive to said evaluating step determining the quality has been sufficient for the specified period, selecting the antenna with the Greater RSSI as the current antenna for a subsequent frame provided no hold has been set;

wherein the step of determining the received signal strength indication (RSSI) received by each antenna comprises measuring the RSSI of the current channel received on one antenna, then measuring the RSSI of the current channel received on the other antenna, wherein both of said measuring steps occur when said transceiver is either idle or transmitting and wherein said method further comprises the step of tuning the transceiver to another channel and testing the reception on said other channel when said transceiver is not transmitting.

16. A wireless terminal which communicates using transmissions which comprise frames, said terminal comprising:

a receiver;

a first antenna;

at least one alternative antenna;

a switch for selecting which antenna provides an input signal to said receiver;

means for selecting a previously determined best antenna as a current antenna selected by said switch;

means for evaluating whether a quality indication of the signal received on the current antenna satisfies a first condition;

first means, responsive to said quality satisfying said first condition, for determining the antenna with the greater Received Strength Signal Indication (RSSI) and selecting this antenna as the best antenna for the next frame provided no previously set hold condition continues to exist; and

second means, responsive to said quality not satisfying said first condition, for;

i) evaluating whether the signal received on an other antenna satisfies a second condition;

ii) responsive to said other antenna signal satisfying said second condition;

A) selecting said other antenna as the best antenna for a subsequent timeslot of interest; and

B) evaluating whether the received signal strength of the signal received on the current antenna exceeds a threshold, and setting a hold condition for a specified number of frames in the event said threshold was exceeded.

17. The terminal as claimed in claim 16 wherein said first means, responsive to said quality satisfying said first condition, comprises:

means for evaluating whether a hold condition on the current antenna exists, and if so, decreasing a hold counter associated with said hold condition; and

means, responsive to no hold condition existing, for selecting the antenna with the greater RSSI as the best antenna for a subsequent timeslot of interest.

18. The terminal as claimed in claim 17 further comprising means for evaluating whether a hold condition on the current antenna exists, and if so, decreasing a hold counter associated with said hold condition and proceeding without changing the selection of the best antenna.

19. A Terminal as claimed in claim 16 further comprising;

a) means for receiving on a previously selected current antenna during a receive timeslot associated with a current channel;

b) means for testing reception of a different channel;

c) means for testing reception of the current channel by said current antenna;

d) means for testing reception of the current channel by an alternative antenna; and

e) means for selecting the antenna with the best test.

20. A wireless terminal comprising.

a transceiver system;

at least two antennas;

i) means for determining the received signal strength indication (RSSI) received by each antenna;

ii) means for determining an indication as to the quality of the signal on a current antenna;

iii) means for evaluating whether the quality of the signal received on the current antenna has been sufficient for a specified period;

iv) means, responsive to said means for evaluating determining the quality has not been sufficient over said period, for evaluating whether the signal received by an other antenna satisfies a condition;

v) means, responsive to the signal received by said other antenna satisfying said condition, for;

a) selecting the other antenna as the current antenna for reception during a subsequent frame; and

b) responsive to the received signal strength of the signal received by the current antenna having exceeded a specified threshold, establishing a hold on subsequent switching for a specified number of frames.

21. The terminal as claimed in claim 20 wherein the means for determining the received signal strength indication (RSSI) received by each antenna comprises means for measuring the RSSI of a current channel received on one antenna, then measuring the RSSI of the current channel received on the other antenna, wherein both of said measuring steps occur when said transceiver is either idle or transmitting and wherein said terminal further comprises means for tuning the transceiver to another channel and testing the reception on said other channel when said transceiver is not transmitting.