WO2014062049A2

WO2014062049A2 - A method for wireless local area network (wlan) channel access prioritization

Info

Publication number: WO2014062049A2
Application number: PCT/MY2013/000178
Authority: WO
Inventors: Bin Abdullah MOHD ARIFF; Haseeb Shariq; Faheem Bin Mohd Ezani MUHAMMAD
Original assignee: Mimos Berhad
Priority date: 2012-10-19
Filing date: 2013-09-26
Publication date: 2014-04-24
Also published as: MY169614A; WO2014062049A3

Abstract

The present invention discloses a method for prioritizing channel access in a wireless communication network. The method comprising registering with an access point (102) by one or more station as priority stations (101) during a Contention Period established by the access point (102) operating in the Distributed Coordination Function. The registered priority stations (101) will trigger the access point (102) to switch from the Distributed Coordination Function to the Point Coordination Function and thereby establishing a Contention Free Period when there is urgency by these priority stations (101) to access a channel. During the Contention Free Period, the access point (102) will first poll the registered priority stations (101) with higher priority level and grant them the priority to access the channel than those priority stations (101) with lower priority level. The access point (102) will resume the Coordination Period when the maximum Contention-Free-Period duration is reached and/or all the registered priority stations (101) have transmitted.

Description

A METHOD FOR WIRELESS LOCAL AREA NETWORK (WLAN) CHANNEL

ACCESS PRIORITIZATION

FIELD OF INVENTION

The present invention relates to a wireless communications network. More particularly relates to a WLAN channel access prioritization method that favors a selected prioritized station for data transmission and reception over a channel. BACKGROUND

In current WLAN deployment, each associated station has equal access to a wireless medium via a Carrier Sense Multiple Accesses with Collision Avoidance (CSMA CA) protocol. Each station will have an equal chance for channel access even though one or more associated stations are sending urgent packets. As such, the delivery of the urgent packets by the associated stations would be greatly deferred.

In attempts to address the inefficiency of the wireless network at moving urgent packets, several station-assigned-priority mechanisms have thus been proposed. These proposed mechanisms primarily involve assigning different priorities to each station regardless whether of the stations are associated with urgent packets, and subsequently, based on the assigned priority levels, allocating capacity of the shared spectrum to each of the stations for data transmission. The higher priority stations, undoubtedly, have expedited the transport of their urgent packets. However, the inefficient use of the limited spectrum in the wireless network is still an issue. This is because the higher priority station will be always gaining the priority access to the wireless medium than those lower priority stations, despite the fact that the lower priority stations may have much higher urgency data to transmit than that of the higher priority station. As such, packets of those lower priority stations will always be queuing behind the packets of the higher priority stations.

In view of above, the present invention therefore proposes a WLAN channel access prioritization method by which stations will register themselves with an access device as priority stations during non-emergency situations. Verification of such registration will be performed against a centralized control list. Whenever there is an emergency, the access device will give priority to the registered stations. Otherwise, the registered stations will be treated equally with those unregistered stations instead of pre- ahocating each of them a capacity of wireless medium according to their priority levels.

SUMMARY

In one aspect of the present invention, disclosed a method for prioritizing channel access in a wireless communication network comprising an access point and a plurality of stations. The channel access prioritization method comprising mamtaining a list of registered priority stations in a centralized authentication database on the access point, registering with the access point by at least one station as a priority station during a Contention Period established by the access point operating in the Distributed Coordination Function; causing the access point to switch from the Distributed Coordination Function to the Point Coordination Function by a user when there is urgency by the at least one station to access a channel for data transmission, wherein the at least one station has been verified by the AP as one of its registered priority station; and granting a priority channel access to the verified priority station.

In accordance with an embodiment, the registered priority stations are pre- authorized to have priority access to a channel during a Contention-Free Period established by the AP operating under the Point Coordination Function.

In accordance with an embodiment, the step of registering with the access point by at least one station as a priority station during a Contention Period comprising: receiving by the access point a priority registration request transmitted by the at least one station; authenticating whether the at least one station is a registered priority station of the access point; verifying the registration attempt by the at least one station upon which has been deemed authentic by the access point; and registering die veiified station as a Priority Station by the access point. In accordance with a further embodiment, the authentication step comprising: retrieving identification information and the corresponding password associated with the identification information fr om the priority registration request; and matching the retrieve information against the information provided by the list of registered priority stations maintained by the access point hi the centralized authentication database.

In accordance with an embodiment, the step of granting a priority channel access to the verified priority station comprising: identifying and recording the verified registered priority stations in the network; arranging these verified priority stations in order of decreasing of their priority levels in a priority table; polling the verified priority stations according to the arrangement order of the verified priority station in the priority table; and repeating the polling process until all the verified priority stations has transmitted their data packets successfully or when the maximum Contention-Free Period duration is reached.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features, and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views: Figure 1 illustrates a data-link layer in accordance with one preferred embodiment of the present invention configured for managing operations of the Distributed Coordination Function (DCF) and the Point Coordination Function (PCF) defined by IEEE802.11 WLANs;

Figure 2 is a simplified block diagram illustrating operations during CP and CFP according to one embodiment of the present invention;

Figure 3 is a timing diagram illustrating data transmission by each station during the Contention Period of a wireless communications network in which a channel access prioritization protocol according to one embodiment of the present invention is employed and operates;

Figure 4 is a ti ming diagram illustrating data transmission by each station upon the trigger for the Contention-Free Period in accordance with one embodiment of the present invention;

Figure 5 is a flow chart depicting how the Contention Free Period is transitioned from the Contention Period and initiated by the AP when there is an urge for prioritized bandwidth allocation, according to one embodiment of the present invention; and Figure 6 is a flow chart depicting how the AP operates during the Contention-

Free Period to prioritize channel access by its registered Priority Station in accordance to one embodiment of the present invention. DETAILED DESCRIPTION

The present invention will now be described in detail with reference to the accompanying in drawings.

Figure I illustrates a data-link layer (10) in accordance with one embodiment of the present invention configured for managing operations of the Distributed Coordination

Function (DCF) (13) and the Point Coordination Function (PCF) (12) for prioritized bandwidth allocation. The data-link layer (10) of the illustrated embodiment in Figure 1 differs from a data-link layer under ΓΕΕΕ802.11 MAC schemes in that it further includes a coordination function scheme (11) that is implemented on top of the PCF (12) and the DCF (13). The coordination function scheme (12) includes a PCF triggering mechanism and a selective polling mechanism.

The PCF triggering mechanism is adapted to coordinate operational modes of Access Point (AP). Suitably, the PCF triggering mechanism triggers an Access Point to transition from its routine operational mode, DCF to the PCF when there is an urge for prioritizing bandwidth allocations. Upon initiation of PCF, this particular AP thereafter operates in Contention-Free Period (CFP) where each of its associated stations is no longer having an equal probability of gaining access to the channel for data transmission and/or reception. Nevertheless, the AP of the PCF will initiate the selective polling mechanism to perform polling on selected stations. The selected stations include those stations that have been previously registered with the AP and authenticated as a Priority Station. According to the selective polling process under the present invention, only Priority Stations are qualified to be polled for accessing a channel without contention. Non-Priority Stations, however, will be placed in a sleep mode and will never be polled when CFP operates.

Figure 2 is a simplified block diagram illustrating operations during CP and CFP according to one embodiment of the present invention. During operation in CP, each of the stations (100) in a WLAN communication network is given an equal fair chance for contenting a channel for data tiansmission and/or reception until the trigger for CFP by Priority Stations (101). The CP temporarily terminates and the CFP is initiated to operate when there is urgency by the Priority Stations (101) to achieve a rapid tiansmission of its data packets over a shared channel with limited capacity. Suitably, the Priority Stations (101) will send a CFP triggering request to the AP (102). The priority Stations (101), at the same time, will register with the AP (102) to participate in the polling process under the operation of CFP. Before fulfilling their request for initiation of the CFP and participation in the polling process, the AP (102) verifies if the Priority Stations (101) is authentic. This can be carried out by determining the consistency of the Priority Stations' (101) identification information and their corresponding passwords with information that have been previously registered by the Priority Stations (101) in a centralized authentication database. When the Priority Stations (101) are deemed authentic by the AP (102), the CFP is triggered, and the polling process is thus initiated to operate. It should be noted that only those verified Priority Stations (101) are qualified to be polled for the access to the channel. The Non-Priority Stations (103), suitably, which are not registered with the AP (102), will be prompted by the AP (102) during the CFP to adjust their network allocation vector (NAV) and their current transmission will be terminated. In other words, these Non-Priority Stations (103) will be placed in sleep mode until the channel becomes idle again and when the next CP is triggered. In accordance with the embodiment, a robin-round scheduler is used by the AP (102) to poll the verified Priority Stations (101) in a pre-configured sequence during the CFP. Through the use of the robin-round scheduler, the AP (102) maintains a list of the verified Priority Stations (101), in which the verified Priority Stations (101) are arranged in the order of their priority from high to low. The AP (102) will then poll the Verified Priority Station (101) according to the sequence provided in the list it maintains. For example, higher-placed verified Priority Stations (101) will be first polled and granted a channel access to transmit data before those lower-placed Priority Stations (101) in the list. As such, each of verified the Priority Stations (101) have data to transrnit have an equally chance of gaining an access to the channel.

Figure 3 is a timing diagram illustrating data transmission by each station (100) during the Contention Period of a wireless communications network in which a channel access prioritization protocol according to one embodiment of the present invention is employed and operates. As illustrated, when the Station 1 has reached a DIFS period, it starts sensing if there is any available channel to access. When there is an idle channel, the Station 1 will commence fransmitting its data packets over me channel to a respective receiving station within its DATA frame. The respective receiving station, upon successfully receiving the data packets, will transmit an Acknowledgement (ACK) fr ame to the Station 1 soon after the SIFS interval. Once the packets in the DATA fr ame have been transmitted, the duration field value of the fr ame will be used to inform the Station 2 and the Station 3 of the duration the Station 1 is required for transmission session over the channel. The Station 2 and the Station 3 will thereafter adjust their network allocation vector (NAV) with respect to the duration field value of the DATA fr ame they have heard fr om transmission by the Station 1 over the channel, and temporarily inactivate themselves fr om contenting with the Station 1 for the channel access until the transmission session of the Station 1 is completed.

The stations (100) will go into a back-off procedure when a channel has been sensed idle for a period of time that is greater than a DIFS. With the use of the back-off procedure, these particular stations (100) will defer their fransrnissions according to their random back-off time so as to prevent themselves from transmitting data over a common channel at the same time, especially when the preceding u-ansmission has just been completed. Still referring to Figure 3, the Station 2 and the Station 3 will go into a back- off state after having approached the BACKOFF frame. The Station 3 that has shorter back-off time than the Station 2 will begin transmission. The Station 1 and the Station 2 will subsequently update their NAV based on the duration field value of the DATA fr ame transmitted from the Station 3. The Station 1 and Station 2 will be placed into a sleep mode within their updated NAV and the Station 3 will access the channel without contention. As will be understood, the Station 1 and the Station 2 will only resume contending for the channel access immediately after the transmission session of the Station 3 has elapsed. Or else, either Station 1 or the Station 2 will have a priority access to a sensed idle channel when there is a DIFS interval. In the event when a user wishes a station to be given priority over other stations (100) in the network to access a channel for data transmission, especially when such a station (100) has some urgent data packets to transmit, the user will have to first register this particular station (100) with the AP (102) as a Priority Station (101). For further description, as shown in the illustrated embodiment in Figure 3, the Station 2, which wishes to gain a priority access to the channel for urgent data hansmission, will first transmit a DATA+REG frame to the AP (102). The DATA+REG includes the priority registration request, the identification information of the particular station, and also the corresponding password associated with the identification information of the particular station. The AP (102) will then authenticate the Station 2 when it is a Priority Station (101) and it has been previously registered with the AP (102), prior to granting the Station 2 a permission to trigger Contention-Free Period in which only registered Priority Stations (101) will be polled by the AP (102) in a pre-configured sequence for data transmission. The authentication is carried out by matching the data retrieved from the DATA+KEG against the respective information maintained a centralized authentication database regarding the acceptance of the Station 2 as a Priority Station (101). During the registration process, only the Station 2 is permitted to access a channel for communication with the AP (102). The Station 1 and the Station 3 will be placed in the sleep mode until the communication link established between the Station 2 and the AP (102) has terminated due to the time-out of the DATA+REG fr ame.

Figure 4 is a timing diagram illustrating data transmission by each station (100) upon the trigger for the Contention-Free Period in accordance with one embodiment of the present invention. As illustrated, when there is an urge for piioritized bandwidth by a station (100) and such a station (100) is verified as one of the Priority Stations (101) that has been previously registered with the AP (102), the AP (102) will transition its current operating DCF mode to the PCF mode. The PCF mode will establish a Contention-Free Period in which only Priority Stations (101) that have been previously registered with the AP (102) will be allowed for pooling for a channel access. The Non-Priority Stations (103), however, will be placed in the sleep mode, and will not be given a permission to content with the Priority Stations (101) to access a channel during the CFP. During the CFP, when there is an idle channel, and there are at least two Priority Stations (101) are identified in the Contention -Free Period, the AP (102) will employ a round-robin scheduler and thereby to arrange these Priority Stations (101) in such an order where Priority Stations (101) with higher prioiity data will be polled to transmit earlier than those with lower priority data. For example, the Priority Station 1, which has been placed at a higher position that that of the Priority Station 2, according to the Priority Table generated from the round-robin scheduler, will first receive the POLL frame from the AP (102). After receiving the POLL frame, the Priority Station 1 will wait for a SIFS interval and thereafter transmit its DATA frame. The transmitted packet will be piggybacked with an ACK frame, acknowledging the AP (102) that the transmission session of the Priority Station 1 has been completed.

Then, the AP (102) will issue the second POLL frame to the Priority Station 2, which is placed after the Priority Station 1. The polled Prioiity Station 2 will start transmitting soon after it senses a SIFS interval. An ACK fr ame will be sent fr om the receiving node of the Priority Station 2 and noted by the AP (102) to start polling its next Priority Station (101), when the data packets of the Priority Station 2 has been successfully transmitted. The AP (102) will teiminate the CFP, and the CF will resume, after all the Priority Stations (101) are polled or until the CFP maximum duration is reached.

Figure 5 is a flow chart depicting how the Contention-Free Period is transitioned from the Contention Period arid initiated by the AP (102) when there is an urge for prioritizing bandwidth allocation according to one embodiment of the present invention. As shown, during the Contention Period, the AP (102) detects if any Priority Station (101) is requesting to get priority access to a channel by receiving a Priority Registration request transmitted from the Priority Station (101), at step S200. Upon receipt of the Priority Registration request, the AP (102) will authenticate whether the station that has requested it to trigger the Contention-Free Period is a registered Priority Station (101), at step S201. The AP (102) will retrieve and match the identification information and the con-esponding password from Priority Registration request with information stored in a centralized authentication database. When the retrieved information is consistent with the information that has been previously registered by the particular with the AP (102) as a Priority Station (101), the station will therefore be verified as a registered Priority Station (101) at step S202. Consequently, the AP (102) will trigger the CFP at step S203. Now referring to Figure 6, once the CFP has initiated, the AP (102) will retrieve the list of its associated stations at step S204. Subsequently, at step S205, the AP (102) will differentiate those registered Priority Stations (101) that are deemed authentic duii ag the priority registration process fr om the hst of its associated stations. In addition to acquiring those pre-registered and verified Priority Stations (101) from the list of associated stations, the AP (102) will keep identifying whether there is an undetectable registered Priority Station (101) under the list of the associated stations, at step S206. After the AP (102) has assured that all the registered Priority Station is retrieved and recorded, the AP (102) will arrange these Priority Stations (101) in a Priority Table, at step S207. These Priority Stations (101) are arranged in an order of their data packet priority fr om high to low. The AP (102) will thereafter start polling each of its registered Priority Stations (101) by referring to the sequence of the stations in the Priority Table, at the step S208. Suitably, the AP (102) will poll the higher-placed Priority Stations (101) before the lower-placed Priority Stations (101). The polling process will be repeatedly carried out by the AP (102) unless all of the registered Priority Stations (101) have been successfully transmitted their data packets or the maximum CFP duration has expired, at step S209. The CP will resume, at step S210, and the CFP will be terminated at step S211 as the time-out of the maximum CFP duration.

As will be readily apparent to those skilled in the art, the present invention may easily be produced in other specific forms without departing from its essential characteristics. The present embodiments is, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within therefore intended to be embraced therein.

Claims

CLAIMS 1. A method for prioritizing channel access in a wireless cornmunication network comprising an access point (102) and a plurality of stations (100), the method comprising:

maintaining a list of registered priority stations (101) in a centralized authentication database on the access point (102), wherein the registered priority stations (101) are pre-authorized to have priority access to a channel during a Contention-Free Period established by the access point (102) operating under the Point Coordination

Function;

registering with the access point (102) by at least one station as a priority station (101) during a Contention Period established by the access point operating in the Distributed Coordination Function;

causing the access point (102) to switch from the Distributed Coordination

Function to the Point Coordination Function by a user when there is urgency by the at least one station (100) to access a channel for data transmission, wherein the at least one station has been verified by the access point (102) as one of its registered priority station (101); and

granting priority channel access to the verified priority station (101) during the Contention Free Period

2. A method as claimed in Claim 1, wherein the step of registering with the access point (102) by at least one station (100) as a priority station (101) during a Contention Period further comprising:

receiving by the access point (102) a priority registration request transmitted by the at least one station (100) ;

authenticating whether the at least one station (100) is a registered priority station (101) of the access point ( 102);

verifying the registration attempt by the at least one station (100) upon which has been deemed authentic by the access point (102); and

registering the verified station as a Priority Station (101) by the access point (102).

3. A method as claimed in Claim 2, wherein the authentication step further comprising: retrieving identification information and the corresponding password associated with the identifi cation information fr om the priority registration request; and

matching the retrieve iriforrnation against the information provided by the list of registered priority stations (101) maintained by the access point (102) in the centralized authentication database.

4. A method as claimed in Claim 1, wherein the step of granting a priority channel access to the verified priority station (101) further comprising:

identifying and recording the verified registered priority stations ( 101) in the network; arranging these verified priority stations (101) in order of decreasing of their priority levels in a priority table;

polling the verified priority stations (101) according to the arrangement order of the verified priority station (101) in the priority table; and

repeating the polling process unti l all the verified priority stations (101) has transmitted their data packets successfully or when the maximum Contention-Free Period duration is reached.