System and method for using an adaptive hybrid coordination function (HCF) in an 802.11E wireless LAN

• US 7,664,089 B2
• Filed: 01/12/2007
• Issued: 02/16/2010
• Est. Priority Date: 01/12/2007
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Zhao, Yun
• Primary Examiner(s): Moe; Aung S
• Assistant Examiner(s): Pasia; Redentor M
• Application Number:
  US11/653,159
• Publication Number:
  US 20080171550A1
• Time in Patent Office: 1,131 Days
• Field of Search: 370230-2351, 370/252, 370/253, 370328-329, 370/338, 370/420, 370443-448, 370461-462, 709220-221, 709223-225, 709231-233, 710/29, 710/36, 710/58
• US Class Current: 370/338
• CPC Class Codes: H04W 74/002 Transmission of channel access control information
• CPC Class Codes: H04W 74/02 Hybrid access
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A system comprises a network congestion monitoring module for monitoring a congestion-related metric of a wireless medium, the congestion-related metric being based on traffic class, e.g., average contention window; a contention-period/contention-free-period (CP/CFP) adaptation module coupled to the network congestion monitoring module for generating CP/CFP information, e.g., CP/CFP duration information and/or traffic class shifting information, in response to the at least one congestion-related metric; a point coordinator module coupled to the CP/CFP adaptation module for coordinating access to the wireless medium using a point coordination function, e.g., HCCA, based on the CP/CFP information; and a distributed coordinator module coupled to the CP/CFP adaptation module for coordinating access to the wireless medium using a distributed coordination function, e.g., EDCA, based on the CP/CFP information.

Claims

1. A system comprising:

a network congestion monitoring module for monitoring a congestion-related metric of a wireless medium, the congestion-related metric being based on traffic class;

a contention-period/contention-free-period (CP/CFP) adaptation module coupled to the network congestion monitoring module for generating CP/CFP information in response to the at least one congestion-related metric;

a point coordinator module coupled to the CP/CFP adaptation module for coordinating access to the wireless medium using a point coordination function based on the CP/CFP information; and

a distributed coordinator module coupled to the CP/CFP adaptation module for coordinating access to the wireless medium using a distributed coordination function based on the CP/CFP information;

wherein the CP/CFP adaptation module computes a normalized contention-window metric based on the function

$\mathrm{CW}<br><br>\_<br><br>\mathrm{avg}=\frac{\left[a_1·<br><br>{\mathrm{CW}}_{\mathrm{—<br><br>}}<br><br>\mathrm{VO}+a_2·<br><br>{\mathrm{CW}}_{\mathrm{—<br><br>}}<br><br>\mathrm{VI}\right]}{\left[a_3·<br><br>{\mathrm{CW}}_{\mathrm{—<br><br>}}<br><br>\mathrm{BE}+a_4·<br><br>{\mathrm{CW}}_{\mathrm{—<br><br>}}<br><br>\mathrm{BK}\right]},$

where CW_VO is an average contention window for voice traffic of substantially all wireless stations in a service set, CW_VI is an average contention window for video traffic of substantially all wireless stations in the service set, CW_BE is an average contention window for best effort traffic of substantially all wireless stations in the service set, CW_BK is an average contention window for background traffic of substantially all wireless stations in the service set, and a1, ct2, a3 and a4 are weight values based on traffic class.

2. The system of claim 1, wherein the system includes a video distribution system.

3. The system of claim 1, wherein the CP/CFP adaptation module controls CP/CFP duration, and the CP/CFP information specifies the CP/CFP duration.

4. The system of claim 1, wherein the CP/CFP adaptation module controls traffic class shifting, and the CP/CFP information specifies at least a portion of at least one traffic class to operate during the CFP.

5. The system of claim 4, wherein the CP/CFP adaptation module generates CP/CFP information that specifies shifting voice and video traffic classes to the CFP in response to a predetermined result of a comparison of information based on the congestion-related metric against a predetermined threshold.

6. The system of claim 4, wherein the CP/CFP adaptation module generates CP/CFP information that specifies shifting voice and video traffic classes to the CP in response to a predetermined result of a comparison of information corresponding to the congestion-related metric against a predetermined threshold.

7. The system of claim 1, wherein the congestion-related metric includes average contention window size per traffic class.

8. The system of claim 1, wherein the network congestion monitoring module monitors a plurality of congestion-related metrics including contention window size and retry count, and wherein the CP/CFP adaptation module generates a normalized network congestion index from the plurality of congestion-related metrics.

9. The system of claim 8, wherein the normalized network congestion index (network_congestion_index) is based on the function

$\mathrm{network\_congestion}\; <li></li>\mathrm{\_index}=c_1·<br><br>\mathrm{CW\_avg}+c_2·<br><br>\frac{\mathrm{packet\_error}}{\mathrm{MAX\_ERROR}}+c_3·<br><br>\frac{\mathrm{retry\_number}}{\mathrm{MAX\_RETRY}<br><br>\mathrm{\_NUMBER}},$

where

$\underset{i}{\sum <br><br>}<br><br><br><br>c_i=1,$

c_i is a weight value based on congestion-metric type, packet_error is an averaged number of packet errors from substantially all wireless stations in a service set, retry_number is an averaged retry count from substantially all wireless stations in the service set;

MAX_ERROR is a predefined maximum number of packet errors, and MAX_RETRY_NUMBER is a predefined maximum number of retry count.

10. The system of claim 1, further comprising one or more wireless stations coupled to the wireless medium, each station including a network congestion monitoring agent for monitoring a congestion-related metric of the wireless medium and for transmitting information corresponding to the congestion-related metric to the network congestion monitoring module.

11. A method comprising:

monitoring a congestion-related metric of a wireless medium, the congestion-related metric being based on traffic class;

generating contention-period/contention-free-period (CP/CFP) information in response to the at least one congestion-related metric;

controlling access to the wireless medium using a hybrid coordination function based on the CP/CFP information, the controlling including

coordinating access to the wireless medium using a point coordination function based on the CP/CFP information; and

coordinating access to the wireless medium using a distributed coordination function based on the CP/CFP information;

wherein the monitoring includes monitoring a plurality of congestion-related metrics including contention window size and retry count; and

the generating includes generating a normalized network congestion index from the plurality of congestion-related metrics based on the function

${\mathrm{network}}_{\mathrm{—<br><br>}}<br><br>{\mathrm{congwestion}}_{\mathrm{—<br><br>}}<br><br>\mathrm{index}=a_3·<br><br>{\mathrm{CW}}_{\mathrm{—<br><br>}}<br><br>\mathrm{avg}+a_2·<br><br>\frac{{\mathrm{packed}}_{\mathrm{—<br><br>}}<br><br>\mathrm{error}}{{\mathrm{MAX}}_{\mathrm{—<br><br>}}<br><br>\mathrm{ERROR}}+a_3·<br><br>\frac{{\mathrm{retry}}_{\mathrm{—<br><br>}}<br><br>\mathrm{number}}{{\mathrm{MAX}}_{\mathrm{—<br><br>}}<br><br>{\mathrm{RETRY}}_{\mathrm{—<br><br>}}<br><br>\mathrm{NUMBER}},$

$\mathrm{where}<br><br>\underset{i}{\sum <br><br>}<br><br><br><br>c_i=1,$

C_i is a weight value based on congestion-metric type, packet_error is an averaged number of packet errors from substantially all wireless stations in a service set, retry_number is an averaged retry count from substantially all wireless stations in the service set;

MAX_ERROR is a predefined maximum number of packet errors, and MAX_RETRY_NUMBER is a predefined maximum number of retry count.

12. The method of claim 11, wherein the controlling includes controlling CP/CFP duration, and the CP/CFP information specifies the CP/CFP duration.

13. The method of claim 11, wherein the controlling including controlling traffic class shifting, and the CP/CFP information specifies at least a portion of at least one traffic class to operate during the CFP.

14. The method of claim 13, further comprising comparing information based on the congestion-related metric against a predetermined threshold, and wherein the generating includes generating CP/CFP information that specifies shifting voice and video traffic classes to the CFP in response to the comparison.

15. The method of claim 13, further comprising comparing information based on the congestion-related metric against a predetermined threshold, and wherein the generating includes generating CP/CFP information that specifies shifting voice and video traffic classes to the CP in response to the comparison.

16. The method of claim 11, wherein the congestion-related metric includes average contention window size per traffic class.

17. The method of claim 16, wherein the generating includes computing a normalized contention-window metric based on the function

$\mathrm{CW\_avg}=\frac{\left[{\mathrm{\alpha \; <li></li>}}_1·<br><br>\mathrm{CW\_VO}+{\mathrm{\alpha <br><br>}}_2·<br><br>\mathrm{CW\_VI}\right]}{\left[{\mathrm{\alpha <br><br>}}_3·<br><br>\mathrm{CW\_BE}+{\mathrm{\alpha <br><br>}}_4·<br><br>\mathrm{CW\_BK}\right]},$

where CW_VO is the average contention window for voice traffic of substantially all wireless stations in a service set, CW_VI is the average contention window for video traffic of substantially all wireless stations in the service set, CW_BE is the average contention window for best effort traffic of substantially all wireless stations in the service set, CW_BK is the average contention window for background traffic of substantially all wireless stations in the service set, and α

₁, α

₂, α

₃ and α

₄ are weight values based on traffic class.

18. The method of claim 11, further comprising

monitoring by a wireless station a congestion-related metric of the wireless medium;

and

transmitting by the wireless station information corresponding to the congestion-related metric to an access point.

19. A system, comprising:

a network congestion monitoring agent for monitoring a congestion-related metric of a wireless medium, the congestion-related metric being based on traffic class, and for transmitting information based on the congestion-related metric to an access point;

a contention-period/contention-free-period (CP/CFP) adaptation agent for receiving CP/CFP information from the access point;

a point coordinator agent coupled to the CP/CFP adaptation agent for coordinating access to the wireless medium using a point coordination function based on the CP/CFP information; and

a distributed coordinator module coupled to the CP/CFP adaptation agent for coordinating access to the wireless medium using a distributed coordination function based on the CP/CFP information;

wherein the CP/CFP adaptation agent computes a normalized contention-window metric based on the function

$\mathrm{CW}<br><br>\_<br><br>\mathrm{avg}=\frac{\left[a_1·<br><br>{\mathrm{CW}}_{\mathrm{—<br><br>}}<br><br>\mathrm{VO}+a_2·<br><br>{\mathrm{CW}}_{\mathrm{—<br><br>}}<br><br>\mathrm{VI}\right]}{\left[a_3·<br><br>{\mathrm{CW}}_{\mathrm{—<br><br>}}<br><br>\mathrm{BE}+a_4·<br><br>{\mathrm{CW}}_{\mathrm{—<br><br>}}<br><br>\mathrm{BK}\right]}$

where CW_VO is an average contention window for voice traffic of substantially all wireless stations in a service set, CW_VI is an average contention window for video traffic of substantially all wireless stations in the service set, CW_BE is an average convention window for best effort traffic of substantially all wireless stations in the service set, CW_BK is an average contention window for background traffic of substantially all wireless stations in the service set, and a1, ct2, a3 and a4 are weight values based on traffic class.