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USO0RE43705E

(19) United States (12) Reissued Patent

(10) Patent Number:

Sherman (54)

(75)

US RE43,705 E

(45) Date of Reissued Patent:

Oct. 2, 2012

METHOD AND SYSTEM FOR OPTIMALLY

7,068,633 B1*

SERVING STATIONS ON WIRELESS LANS USING A CONTROLLED CONTENTION/RESOURCE RESERVATION PROTOCOL OF THE IEEE 802.11E STANDARD

2005/0041670 A1*

2/2005

2008/0049761 A1*

2/2008 Lin et a1.

Inventor:

2010/0080188

A1*

6/2006 H0 .............................. .. 370/338

4/2010

Lin et a1. . Ho et a1.

2010/0080196 A1*

4/2010 Ho et a1.

2010/0085933 A1*

4/2010

.. 370/395.21

.. 370/395.21 .....

. . . . . ..

370/329

370/336

Ho et a1. ..................... .. 370/329

OTHER PUBLICATIONS

Matthew J. Sherman, Succasunna, NJ

J. Grier, Wireless LANsilmplementing InterOperab/e Networks,

(Us)

Macmillan Technical Publishing, (International Standard Book No.

(73) Assignee: AT&T Intellectual Property II, LP., Reno, NV (U S)

(21) Appl.No.: 12/587,884

1-57870-081-7), Chapter 3, pp. 89-125 (1999). R. O’Hara and A. Petrick, The IEEE 802.11 HandbookiA Design

er’s Companion, IEEE, New York, NY (ISBN 07381-1855-9) pp. 7-19 (1999).

(Continued) (22) Filed:

Oct. 15, 2009 Primary Examiner * Robert Scheibel Assistant Examiner * Duc Duong

Related U.S. Patent Documents

Reissue of:

(64) Patent No.:

7,289,529

Issued:

Appl. No.: Filed: US. Applications: (60)

(51) (52) (58)

(57)

Oct. 30, 2007

10/230,116 Aug. 29, 2002

Provisional application No. 60/335,504, ?led on Oct. 31, 2001.

U.S. Cl. ...................................... .. 370/461; 370/462

See application ?le for complete search history. References Cited

(BSS). A Hybrid Coordinator (HC) is co-located with the

8/2001 Evans et a1. 9/2001 Chuah 5/2003 Chuah 10/2004

Lin et a1. ..................... .. 370/338

6,850,981 B1*

2/2005 H0 et a1. ..

7,031,287 B1*

4/2006

Contention/Resource

Reservation protocol

de?ned in the IEEE Standard 802.11(e). The HC transmits Contention Control (CC) frames and initiates Controlled Contention Intervals (CCI) having a selected number of slot ted intervals. HC receives Resource Reservations (RR) detail ing bandwidth needs from STA contenders during a speci?ed time interval called the Controlled Contention Interval (CCI.). Several parameters are installed in each CC for con tention control purpose. The several parameters are con

U.S. PATENT DOCUMENTS

6,804,222 B1*

tionary, airlinked to an access point as a Basic Service Set

Controlled

(2006.01)

Field of Classi?cation Search ...................... .. None

6,282,187 Bl 6,285,665 Bl 6,567,416 B1

A method for optimally serving Stations (STA) on Wireless Local Area Network (LAN) using a Controlled Contention/ Resource Reservation protocol of the IEEE 802.1 1e standard. The Wireless LAN includes multiple STAs, mobile or Sta access point for allocating the bandwidth for the BSS using a

Int. Cl. H04L 12/417

(56)

ABSTRACT

trolled to optimize ef?cient use of the wireless medium and reduce access delays for RR frames contending for the wire less medium.

10 Claims, 13 Drawing Sheets

H0 et a1. ..................... .. 370/338

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US RE43,705 E Page 2 OTHER PUBLICATIONS

Takahiro Suzuki, Shuji Tasaka, “Performance Evaluation of Multi media Transmission With the PCP of the IEEE 802.11 Standard MAC

Takahiro Suzuki et a1, “Performance Evaluation of Priority-based Multimedia Transmission With the PCP in an IEEE 802.11 Standard

Wireless LAN,” Proceedings ofthe IEEE 12th International Sympo sium on Personal, Indoor and Mobile Radio Communications, Sep. 30 through Oct. 3, 2001.

Protocol”, Technical Study Report of The Institute of Electronic, Information and Communication Engineers (IEICE) IN2000-144, vol. 100, No. 456, pp. 67-72, The Institute of Electronic, Information and Communication Engineers, Nov. 15, 2000.

* cited by examiner

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3208%.5:620.3 80P8.3? $8N3.0 $N2mE85N.d0 53$5q32.60 E63m8608 52R@3°68 ~EN832E [email protected]; [email protected] 6838.20.

US RE43,705 E 1

2

METHOD AND SYSTEM FOR OPTIMALLY SERVING STATIONS ON WIRELESS LANS USING A CONTROLLED CONTENTION/RESOURCE RESERVATION PROTOCOL OF THE IEEE 802.11E STANDARD

wishes to send a RR for an appropriate TC, it will chose a random number between 0 and 1 . If the random number is less

than or equal to the PP value, the STAs is permitted to transmit the RR. It then randomly selects a CC_OP in which to trans mit (Note: the current draft of 802.11.e has eliminated the PP value, so STAs transmit a RR during a CCI whenever a

permitted TC has one to transmit). Since other STAs may be

transmitting RR frames, there is a possibility that multiple Matter enclosed in heavy brackets [ ] appears in the original patent but forms no part of this reissue speci?ca

RRs will be transmitted in a CC_Op, and none will be

received correctly (though it is possible due to RF capture effects one will be correctly received despite the contention).

tion; matter printed in italics indicates the additions made by reissue.

Such a CC_OP would be considered collided or “busy”. If

only one R is transmitted in the CC_Op, it most likely will be received correctly (although, due to interference or noise on the wireless medium or propagation issues it is possible, it will be lost anyway). And ?nally, some CC_OPs will not contain any RR, and in some sense those “empty” CC_OPs

This application claims the bene?t of the ?ling date of Provisional Application Serial No. 60/335,504, ?led Oct. 31, 2001, entitled “Methods For Allocating Controlled Opportu nities In A Mediaplex Controlled Interval”, assigned to the

waste bandwidth on the medium.

same assignee as that of the present invention and fully incor

porated herein by reference.

20

eters are used by the STA, there is no detail on how the key parameters are determined and set by the HC. What is needed in the art are methods which advantageously set the param eters for the CC/RR protocol so as to optimize performance

BACKGROUND OF THE INVENTION

1. Field of the Invention This invention relates to wireless communication methods and system. More particularly, the invention relates to a

While [00/331 and 802.11e detail the overall protocol, required frame formats, and how the transmitted CC param

25

method and system for optimally serving stations on Wireless

for e?icient use of the medium.

SUMMARY OF THE INVENTION

LANs using a Controlled Contention/Resource Reservation

protocol of the IEEE 802.11e standard. 2. Description of the Prior Art IEEE 802.11 is a standards body developing Wireless

Wireless LANs operating under the IEEE 802.11(e) pro 30

STAs (MS). The protocols provide centralized control of the wireless media during speci?ed periods of time called Con

Local Area Network (WLAN) Standards [802.11, 802.11a, 802.11b]. Recently, that body has started development of a supplement that would specify the support of Quality of Ser vice (QoS) within 802.1 1 WLANs. This work is being carried out by the 802.1 1e Task Group, and the most current draft of

tocol include an Access Point serving a plurality of Mobile

tention Free Periods (CFPs) and Contention Free Bursts

(CFBs). A Hybrid Coordinator (HC), typically co-located 35

the QoS extensions being developed (as of the writing of this

with the Access Point, allocates bandwidth among the MS contenders. The HC regularly transmits Contention Control

(CC) frames, which initiate Controlled Contention Intervals

application) can be found in [802.1 1e]. A set of protocols has

(CCI) having a selected number of slotted intervals. The HC

been proposed for use in 802.1 1(e) based on centralized con

receives Resource Reservations (RR) detailing bandwidth

trol of the wireless media. In this protocol set, during speci ?ed periods of time called Contention Free Periods (CFPs) and Contention Free Bursts (CFBs), STATIONs (STA) may only use the wireless medium when granted permission from the Hybrid Coordinator (HC). The HC is responsible for allocating bandwidth on the wireless medium and ensuring that QoS needs are met. The HC generally grants the use of the medium to a STA by polling it. This transfers control of the medium to that STA for a limited period of time. Control of the medium must then revert to the HC. A problem which is addressed within the 802.11e draft is how to make the HC aware of changing bandwidth needs for the STA it serves. A protocol included in 802.11e for doing this was ?rst proposed in [00/33] to the 802.11 community. The protocol is termed the Contention Control/ Resource Res

ervation (CC/RR) protocol. In this protocol, the HC grants the medium for use by Resource Reservation (RR) frames by transmitting a Contention Control (CC) frame. Only RR

40

needs from the MS contenders during a speci?ed time interval of the CC called the Controlled Contention Interval (CCI). Each CCI has several parameters including a number of slots or Controlled Contention Opportunities (CC_OP), an optional Permission Probability (PP) and a set of ?ags indi

45

cating which Tra?ic Categories (TC) may compete for the CC_OPs. When an MS contender receives a CC, an RR is

50

which wastes bandwidth, or some CC_OP or slots may not

55

frames may be transmitted during the time period speci?ed by the CC frame. This time period is called the Controlled Con tention Interval (CCI). The RR frames detail the bandwidth needs of the STA transmitting them. Several parameters for the CCI are speci?ed by the CC frame. These include a

Permission Probability (PP), the number of Controlled Con tention Opportunities (CC_OPs), and a set of ?ags indicating which Tra?ic Categories (TC or Priorities) may compete for

transmitted which speci?es the bandwidth needs of the MS contender and is assigned a CC_OP slot if it succeeds in drawing a random number less than the PP. Since other MS contenders may be transmitting RR frames, there is the pos sibility of collision and none will be received in the CCI, contain a RR, which also wastes bandwidth. An algorithm sets the CCI parameters to optimize e?icient use of the medium and reduce access delays for RR frames contending for the wireless medium. Ef?cient use is de?ned in terms of network service time or bandwidth utilization. The algorithm assumes: First, each CCI contains at least one slot or CC_OP; second, there is no limit or at least a large limit on the number

60

of CC_OPs in a CCI; third, perfect knowledge or an estimate of the number of contenders is available. The algorithm stores the value (a) Max_Empty_CCI de?ned as a selected number

of Empty_CCIs to end the cycle for serving contenders and

the medium with RR frames during an upcoming CCI. The

(b) Max_Contendr de?ned as the maximum number of con tenders the HC desires to serve in a single CCI. In step 1, a counter Empty_CC is set to 0. Step 2 estimates the number of

protocol states that when a STA receives a CC message and

contender based on prior CCI results and tra?ic models. Step

65

US RE43,705 E 3

4

3 conducts a test to determine if the number of contenders is less than 1 . A “no” condition resets the Empty_CCI counter to

FIG. 11 is a How diagram for optimally serving contenders in the Wireless LAN of FIG. 1 using the CC/RR protocol of IEEE 802.11 (e).

0. A “yes” increments the Empty_CCI counter. Step 3 trans fers to Step 4 Which starts a test: Cntndrs>than the stored

DESCRIPTION OE PREFERRED EMBODIMENT

Max_Cntndrs. A “yes” calculates a Permission Probability Max_Cntndrs/Contender in step 5 and sets

Before describing the present invention, a brief revieW of

Cntndrs:Max_Cntndrs. A “no” condition indicates a Permis

sion Probability of 1. Both Steps 4 and 5 transfer to Step 6

the IEEE 802.11 Wireless LAN Standard is believed appro

Which Determines Optimum CC_OPs and approximates the

priate for a better understanding of the invention. The IEEE 802.11 standard de?nes over-the-air protocols

overhead as 1 or 2 slots. Step 6 transfers to Step 7 Which performs a test” CC_OPs