System and method for monitoring performance of wireless LAN and dynamically adjusting its operating parameters

• US 5,889,772 A
• Filed: 04/17/1997
• Issued: 03/30/1999
• Est. Priority Date: 04/17/1997
• Status: Expired due to Term

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Fischer, Matthew J., Kern, William F.
• Primary Examiner(s): Patel, Ajit
• Assistant Examiner(s): LEE, CHI HO A
• Application Number:
  US08/839,836
• Time in Patent Office: 712 Days
• Field of Search: 370/315, 370/322, 370/328, 370/332, 370/348, 370/346, 370/349, 370/373, 370/414, 370/416, 370/910, 370/431, 370/437, 370/443, 455/54, 455/58, 455/69
• US Class Current: 370/346
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds

Abstract

A station in the WLAN monitors each transmitted frame to determine whether the frame transmission was protected by an existing outstanding airtime reservation. If a frame is transmitted without an airtime reservation and no response frame is received, the station assumes that the transmission failed due to contention, and monitors the number of contention attempts made to transmit each frame, and the number of failures to receive an acknowledgement. Based on this information, the station dynamically adjusts an RTS/CTS threshold used to determine whether or not an RTS/CTS exchange mechanism should be enabled. If a frame is transmitted during a time interval protected by an outstanding airtime reservation and no response frame is received, the station assumes that the transmission failed due to a bit error, and monitors the number of bit error rate (BER) attempts made to transmit each frame, and the number of BER failures to receive an acknowledgement. Based on this information, the station dynamically adjusts a fragmentation threshold used to determine whether or not a data frame fragmentation mechanism should be enabled.

Claims

1. A controller for a wireless local area network (WLAN), comprising:

a data processing unit arranged at a transmitting station for supplying frames to be transmitted to a destination station and receiving acknowledgements that the frames are received by the destination station, and

a control unit responsive to said data processing unit for monitoring the number of attempts made to transmit each frame and the number of failures to receive an acknowledgement in response to transmission of the frame, to dynamically control transmission of airtime reservation requests sent to the destination station,

wherein said control unit is adapted for determining the average number of attempts made to transmit the frames to destination stations and the average number of failures to receive an acknowledgement for the WLAN, to determine deviation of operating conditions for each of the destination stations from average operating conditions for the WLAN.

2. The controller of claim 1, wherein said control unit is responsive to said data processing unit for dynamically controlling fragmentation of data frames sent to the destination station.

3. The controller of claim 2, wherein said control unit is responsive to said data processing unit for determining whether an airtime reservation is provided for transmission of each of the frames.

4. The controller of claim 3, wherein said control unit is adapted for dynamically adjusting a threshold level for transmission of the airtime reservation requests to the destination station based on the number of attempts made to transmit a frame to the destination station and the number of failures to receive an acknowledgement, when the airtime reservation is not provided for transmission of the frame.

5. The controller of claim 3, wherein said control unit is adapted for dynamically adjusting a threshold level for fragmentation of the data frames transmitted to the destination station based on the number of attempts made to transmit a frame to the destination station and the number of failures to receive an acknowledgement, when the airtime reservation is provided for transmission of the frame.

6. The controller of claim 1, further comprising a queuing unit responsive to said control unit for controlling priorities of the frames sent to the destination station in accordance with the deviation of the operating conditions for the destination station from the average operating conditions for the WLAN.

7. A method of dynamically adjusting operating parameters of a WLAN, comprising the steps of:

monitoring transmission of each frame to destination stations in the WLAN,

checking whether or not an airtime reservation is obtained for protecting transmission of each frame,

monitoring whether an acknowledgement is received in response to each transmitted frame,

for each destination address of the WLAN, maintaining a count of contention attempts indicative of the number of attempts to transmit the frame to each destination station when no airtime reservation is available,

for each destination address of the WLAN, maintaining a count of contention failures indicative of the number of failures to receive the acknowledgement when no airtime reservation is available,

for each destination address of the WLAN, producing an airtime reservation threshold level for transmitting an airtime reservation request before a data frame if a parameter of the data frame exceeds the airtime reservation threshold level,

incrementing the count of contention attempts for a first destination address each time when a frame unprotected by the airtime reservation is transmitted to a first destination station corresponding to the first destination address,

incrementing the count of contention failures for the first destination address each time when no acknowledgement is received in response to the unprotected frame, and

for the first destination address, adjusting the airtime reservation threshold level in accordance with the ratio of the incremented count of contention failures to the incremented count of contention attempts.

8. The method of claim 7, further comprising the steps of:

for each destination address of the WLAN, maintaining a count of protected attempts indicative of the number of attempts to transmit the frame to each destination station when the airtime reservation is available,

for each destination address of the WLAN, maintaining a count of protected failures indicative of the number of failures to receive the acknowledgement when the airtime reservation is available,

for each destination address of the WLAN, producing a fragmentation threshold level for fragmenting a data frame if a parameter of the data frame exceeds the fragmentation threshold level,

incrementing the count of protected attempts for the first destination address each time when a frame protected by the airtime reservation is transmitted to the first destination station corresponding to the first destination address,

incrementing the count of protected failures for the first destination address each time when no acknowledgement is received in response to the protected frame, and

adjusting the fragmentation threshold level for providing fragmentation of data frames to be transmitted to the first destination station in accordance with the ratio of the incremented count of protected failures to the incremented count of protected attempts.

9. The method of claim 7, further comprising the steps of:

determining an average count of contention attempts and an average count of contention failures for the WLAN,

modifying the average counts of contention attempts and contention failures based on the incremented counts of contention attempts and contention failures, and

adjusting an average airtime reservation threshold level for the WLAN in accordance with the ratio of the modified average count of contention failures to the modified average count of contention attempts.

10. The method of claim 9, further comprising the step of comparing the adjusted airtime reservation threshold level for the first destination address with the adjusted average airtime reservation threshold level to control priority of a frame to be sent to the first destination station.

11. The method of claim 10, further comprising the steps of:

determining an average count of protected attempts and an average count of protected failures for the WLAN,

modifying the average counts of protected attempts and protected failures based on the incremented counts of protected attempts and protected failures, and

adjusting an average fragmentation threshold level for the WLAN in accordance with the ratio of the modified average count of protected failures to the modified average count of protected attempts.

12. The method of claim 11, further comprising the step of comparing the adjusted fragmentation threshold level for the first destination address with the adjusted average fragmentation threshold level to control priority of a frame to be sent to the first destination station.

13. A controller for a wireless communication station, comprising:

first means for monitoring transmission of frames to destination stations,

second means for determining whether or not an airtime reservation is obtained for protecting transmission of the frames,

third means for determining whether acknowledgements are received in response to the transmitted frames,

fourth means responsive to said first, second and third means for maintaining a count of protected attempts indicative of the number of attempts to transmit the frames to the destination station when the airtime reservation is available,

fifth means responsive to said first, second and third means for maintaining a count of protected failures indicative of the number of failures to receive the acknowledgements when the airtime reservation is available, and

first control means responsive to said fourth and fifth means for controlling fragmentation of data to be transmitted to the destination stations.

14. The controller of claim 13, further comprising:

sixth means responsive to said first, second and third means for maintaining a count of unprotected attempts indicative of the number of attempts to transmit the frames to the destination station when no airtime reservation is available,

seventh means responsive to said first, second and third means for maintaining a count of unprotected failures indicative of the number of failures to receive the acknowledgements when no airtime reservation is available, and

second control means responsive to said sixth and seventh means for enabling airtime reservation requests before transmitting the data to the destination stations.