Diversity antenna selection

• US 6,002,672 A
• Filed: 12/20/1996
• Issued: 12/14/1999
• 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): Nguyen, Chau
• Assistant Examiner(s): WOLKOW, FREDERIC D
• Application Number:
  US08/777,674
• Time in Patent Office: 1,089 Days
• Field of Search: 455/277.1, 455/277.2, 455/133, 455/134, 455/135, 370/252, 370/328, 370/332, 370/334
• US Class Current: 370/252
• 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 for a wireless terminal having two antennas is disclosed which tests reception on both the main antenna and a diversity antenna during the period when the terminal is transmitting and tests reception of a different channel (for example, for mobile assisted hand-off) during an idle period when the terminal is neither receiving or transmitting data. The antenna with the greater signal strength is selected for the next frame. Thus, both diversity and mobile assisted hand-off measurements can be made with a single receiver.

Claims

1. A diversity antenna selection method for a terminal operating in a wireless communication system, said terminal including a single receiver, said method comprising the steps of:

a) receiving on a previously selected current antenna during a receive timeslot associated with a current channel by said receiver;

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

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

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

e) selecting the antenna with the best test results as the current antenna for a subsequent receive timeslot; and

wherein said step (c) comprises the step of testing for indications of signal and co-channel interference of the received signal and wherein step (e) further comprises the steps of;

A) determining whether the testing of the current antenna indicated the presence either of fading beyond a first threshold or co-channel interference beyond a second threshold, or both;

B) responsive to the presence of said indication of co-channel interference beyond said second threshold, selecting the other antenna for reception provided said other antenna satisfies a condition and establishing a hold condition preventing subsequent switching of the selected antenna for a specified number of frames;

C) responsive to the presence of said indication of fading beyond said first threshold, selecting the other antenna provided said other antenna has a greater signal strength and provided no hold condition is in place preventing said selection.

13. A wireless terminal comprising:

a receiver;

a first antenna;

at least one alternative antenna;

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

a controller adapted for controlling said switch according to the method as claimed in claim 1.

2. A diversity antenna selection method for a terminal operating in a wireless communication system, said terminal including a single receiver which includes a single synthesizer said method comprising the steps of:

a) receiving on a previously selected current antenna during a receive timeslot associated with a current channel by said receiver;

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

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

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

e) selecting the antenna with the best test results as the current antenna for a subsequent receive timeslot wherein step b) comprises the steps of;

tuning said synthesizer to a different channel;

testing reception on said different channel; and

then re-tuning said synthesizer to said current channel.

14. A wireless terminal comprising:

a receiver;

a first antenna;

at least one alternative antenna;

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

a controller adapted for controlling said switch according to the method as claimed in claim 2.

3. A diversity antenna selection method for a terminal operating in a wireless communication system, said terminal including a single receiver which includes a single synthesizer, said method comprising the steps of:

a) receiving on a previously selected current antenna during a receive timeslot associated with a current channel by said receiver;

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

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

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

e) selecting the antenna with the best test results as the current antenna for a subsequent receive timeslot wherein step b) comprises the steps of;

tuning said synthesizer to a different channel;

testing reception on said different channel when said terminal is neither transmitting nor receiving its receive timeslot; and

then re-tuning said synthesizer to said current channel.

15. A wireless terminal comprising:

a receiver;

a first antenna;

at least one alternative antenna;

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

a controller adapted for controlling said switch according to the method as claimed in claim 3.

4. A diversity antenna selection method for a terminal operating in a wireless communication system, said terminal including a single receiver which includes a single synthesizer, said method comprising the steps of:

a) receiving on a previously selected current antenna during a receive timeslot associated with a current channel by said receiver;

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

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

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

e) selecting the antenna with the best test results as the current antenna for a subsequent receive timeslot; and

wherein step b) comprises the steps of;

tuning said receiver to a different channel;

testing reception on said different channel when said terminal is neither transmitting nor receiving its receive timeslot; and

then re-tuning said receiver to said current channel; and

wherein both steps d) and e) occur either during a terminal idle period or during a terminal transmit timeslot.

5. The method as claimed in claim 4 wherein said steps (d) and (e) each comprise the step of measuring the received signal strength indication (RSSI) of the received signal and wherein said selecting the antenna step comprises the steps of:

determining whether the RSSI for either antenna is below a threshold;

responsive to said determining step determining one of said antenna'"'"'s RSSI is below said threshold, comparing the RSSI for each antenna to determine which had a stronger RSSI; and

selecting the antenna with the higher RSSI.

6. The method as claimed in claim 4 wherein said selecting step comprises continuing to receive on the current channel using the current antenna if step (d) satisfies a specified threshold and if not,

comparing the test reception results received by the alternative antenna with the test reception results received by the current antenna and selecting the antenna with the better results as the next current antenna.

16. A wireless terminal comprising:

a receiver;

a first antenna;

at least one alternative antenna;

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

a controller adapted for controlling said switch according to the method as claimed in claim 4.

7. A diversity antenna selection method for a terminal operating in a wireless communication system, said terminal including a single receiver which includes a single synthesizer, said method comprising the steps of:

a) receiving on a previously selected current antenna during a receive timeslot associated with a current channel by said receiver;

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

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

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

e) selecting the antenna with the best test results as the current antenna for a subsequent receive timeslot;

wherein step b) comprises the steps of;

tuning said receiver to a different channel;

testing reception on said different channel; and

then re-tuning said receiver to said current channel,

and wherein step (c) includes testing both the strength and quality of the received signal and said selection step comprises the steps of;

evaluating whether the quality of the signal received on the current antenna has been above a specified threshold over a specified number of timeslots of interest;

if not, evaluating whether the signal received on the other antenna satisfies a condition, and selecting the other antenna as the current antenna for the next timeslot of interest in the event said condition is satisfied, and, responsive to said other antenna satisfying said condition, evaluating whether the received signal strength of the signal received on the current antenna is sufficient, and indicating there has been a switch in the selection of the current antenna due to poor quality in the event said received signal strength is sufficient; and

if so, selecting the other antenna as the current antenna for a subsequent timeslot of interest in the event both the received signal strength of the other antenna is greater than the received signal strength of the current antenna and there has not been a previous switching of antennas due to poor quality within a predefined period.

17. A wireless terminal comprising:

a receiver;

a first antenna;

at least one alternative antenna;

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

a controller adapted for controlling said switch according to the method as claimed in claim 7.

8. A diversity antenna selection method for a terminal operating in a wireless communication system, said terminal including a single receiver which includes a single synthesizer, said method comprising the steps of:

a) receiving on a previously selected current antenna during a receive timeslot associated with a current channel by said receiver;

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

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

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

e) selecting the antenna with the best test results as the current antenna for a subsequent receive timeslot wherein step (e) comprises the steps of;

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

responsive to said quality satisfying said first condition, selecting the antenna with the greater Received Strength Signal Indication (RSSI) as the current antenna for a subsequent receive timeslot provided no previously set hold condition continues to exist;

responsive to said quality not satisfying said first condition;

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

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

A) selecting said other antenna as the current antenna for a subsequent receive timeslot; 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 timeslots of interest in the event said threshold was exceeded.

18. A wireless terminal comprising:

a receiver;

a first antenna;

at least one alternative antenna;

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

a controller adapted for controlling said switch according to the method as claimed in claim 8.

9. A diversity antenna selection method for a terminal operating in a wireless communication system, said terminal including a single receiver which includes a single synthesizer, said method comprising the steps of:

a) receiving on a previously selected current antenna during a receive timeslot associated with a current channel by said receiver;

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

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

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

e) selecting the antenna with the best test results as the current antenna for a subsequent receive timeslot wherein said testing reception steps each comprise the step of testing for indications of signal fading and co-channel interference of the received signal and wherein said selecting the antenna step comprises the steps of;

A) determining whether the testing of the current antenna indicated the presence either of fading beyond a first threshold or co-channel interference beyond a second threshold, or both;

B) responsive to the presence of said indication of co-channel inteference beyond said second threshold, selecting the other antenna for reception provided said other antenna satisfies a condition and establishing a hold condition preventing subsequent switching of the selected antenna for a specified number of frames;

C) responsive to the presence of said indication of fading beyond said first threshold, selecting the other antenna provided said other antenna has a greater signal strength and provided no hold condition is in place preventing said selection.

10. The method as claimed in claim 9 wherein the step of testing for indications of signal fading comprises evaluating the Received Signal Strength Indication (RSSI) against a specified threshold and wherein the step of testing for indications of co-channel interference comprise evaluating both the received signal strength and a parameter indicative of the quality of the received signal over a number of frames.

11. The method as claimed in claim 10 wherein said parameter comprises the bit error rate or the coded digital verification colour code.

19. A wireless terminal comprising:

a receiver;

a first antenna;

at least one alternative antenna;

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

a controller adapted for controlling said switch according to the method as claimed in claim 9.

12. A diversity antenna selection method for a terminal operating in a wireless communication system wherein there are multiple frequency channels and wherein for any given frequency channel the terminal receives information on a channel divided into first and second sets of timeslots, for which said first set of timeslots are of interest, and said second set of timeslots are not of interest such that there is a period of time between reception of a first set timeslot and the next first set timeslot, and wherein transmission and reception are on separate frequencies in which transmission is offset in time from reception such that transmission occurs during said period of time, and within said period of time there is also at least one idle period during which there is no information of interest to be received, and no data to be transmitted, said method comprising the steps of:

a) selecting a current antenna;

b) selecting a current channel;

c) receiving on said current channel using said current antenna during a first set timeslot;

d) tuning said receiver to another channel for mobile assisted hand off (MAHO) testing during the at least one idle period;

e) performing Diversity Measurement steps comprising;

i) re-tuning said receiver to said current channel after said MAHO testing is complete,

ii) testing reception on said current antenna, and

iii) testing reception on an alternative antenna;

f) selecting the antenna with the best test results as said current antenna; and

g) receiving on said current antenna during a subsequent first set timeslot;

wherein at least one of Diversity Measurement steps occur during the timeslot allocated to the terminal for transmission in such a manner that said transmission and said Diversity Measurement steps do not significantly interfere with each other.

20. A wireless terminal comprising:

a receiver;

a first antenna;

at least one alternative antenna;

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

a controller adapted for controlling said switch according to the method as claimed in claim 12.

21. A wireless terminal comprising:

a single receiver;

at least two antennas;

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

means for testing reception of a different channel received by said receiver;

means for testing reception of the current channel received by said receiver using said current antenna;

means for testing reception of the current channel received by said receiver using an alternative antenna; and

means for selecting antenna with the best test results as the current antenna for a subsequent receive timeslot wherein means for testing reception of the current channel received by said receiver using said current antenna includes means for testing both the strength and quality of the received signal and said means for selecting the antenna comprises;

means for evaluating whether the quality of the signal received on the current antenna has been above a specified threshold over a specified number of timeslots of interest;

responsive to a negative evaluation by said means for evaluating whether the quality of the signal received on the current antenna has been above a specified threshold over a specified number of timeslots of interest, means for evaluating whether the signal received on the other antenna satisfies a condition, and selecting the other antenna as the current antenna for the next timeslot of interest in the event said condition is satisfied, and, means, responsive to said other antenna satisfying said condition, for evaluating whether the received signal strength of the signal received on the current antenna is sufficient, and indicating there has been a switch in the selection of the current antenna due to poor quality in the event said received signal strength is sufficient; and

responsive to a positive evaluation by said means for evaluating whether the quality of the signal received on the current antenna has been above a specified threshold over a specified number of timeslots of interest, means for selecting the other antenna as the current antenna for a subsequent timeslot of interest in the event both the received signal strength of the other antenna is greater than the received signal strength of the current antenna and there has not been a previous switching of antennas due to poor quality within a predefined period.

22. A wireless terminal comprising:

a single receiver;

at least two antennas;

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

means for testing reception of a different channel received by said receiver;

means for testing reception of the current channel received by said receiver using said current antenna;

means for testing reception of the current channel received by said receiver using an alternative antenna; and

means for selecting the antenna with the best test results as the current antenna for a subsequent receive timeslot wherein said means for testing reception comprise means for testing for indications of signal fading and co-channel interference of the received signal and wherein said means for selecting the antenna comprises;

A) means for determining whether the testing of the current antenna indicated the presence either of fading beyond a first threshold or co-channel interference beyond a second threshold, or both;

B) responsive to the presence of said indication of co-channel inteference beyond said second threshold, means for selecting the other antenna for reception provided said other antenna satisfies a condition and establishing a hold condition preventing subsequent switching of the selected antenna for a specified number of frames; and

C) responsive to the presence of said indication of fading beyond said first threshold, means for selecting the other antenna provided said other antenna has a greater signal strength and provided no hold condition is in place preventing said selection.

23. A wireless terminal for operating in a wireless communication system wherein there are multiple frequency channels and wherein for any given frequency channel the terminal receives information on a channel divided into first and second sets of timeslots, for which said first set of timeslots are of interest, and said second set of timeslots arc not of interest such that there is a period of time between reception of a first set timeslot and the next first set timeslot, and wherein transmission and reception are on separate frequencies in which transmission is offset in time from reception such that transmission occurs during said period of time, and within said period of time there is also at least one idle period during which there is no information of interest to be received, and no data to be transmitted, said terminal comprising a receiver, at least two antennas and:

a) means for selecting a current antenna;

b) means for selecting a current channel;

c) means for receiving on said current channel using said current antenna during a first set timeslot;

d) means for tuning said receiver to another channel for mobile assisted hand off (MAHO) testing during the at least one idle period;

e) means for performing Diversity Measurement comprising;

i) re-tuning said receiver to said current channel after said MAHO testing is complete,

ii) testing reception on said current antenna, and

iii) testing reception on an alternative antenna;

f) means for selecting the antenna with the best test results as said current antenna; and

g) means for receiving on said current antenna during a subsequent first set timeslot;

wherein at least one of Diversity Measurement steps occur during the timeslot allocated to the terminal for transmission in such a manner that said transmission and said Diversity Measurement steps do not significantly interfere with each other.