The present invention is generally related to wireless communication systems. More particularly, the present invention is related to path-based traffic stream (TS) admission control mechanisms in mesh-type wireless communication networks having centralized or distributed admission control architecture.
A wireless local area network (WLAN) mesh network is an IEEE 802.11-based wireless distribution system (WDS) including two or more mesh points (MPs) interconnected via IEEE 802.11 links and communicating via WLAN mesh services.
Referring still to
Therefore, a method and apparatus for performing path-based TS admission control in wireless mesh networks is desired.
The present invention is related to a method and apparatus for implementing path-based TS admission control in a wireless mesh network having a distributed and/or centralized admission control architecture. When the wireless mesh network utilizes distributed admission control architecture, a source MP (S.MP) transmits a request for TS admission requiring certain resources/QoS. The request propagates through the wireless mesh network until a destination MP (D.MP) is reached and an admitted path is determined. If an intermediate MP is unable to meet the requested resources/QoS for the TS, the S.MP is notified. When the wireless mesh network utilizes centralized admission control architecture, an S.MP requests a route to the D.MP from a central controller. The central controller maintains a status of MPs in the wireless mesh network, and selects a best route to handle the TS to satisfy the requested resources/QoS.
A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example and to be understood in conjunction with the accompanying drawing wherein:
Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone (without the other features and elements of the preferred embodiments) or in various combinations with or without other features and elements of the present invention.
When referred to hereafter, the terminology “MP” includes but is not limited to a WTRU, a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a user station (STA) or any other type of device capable of operating in a wireless environment. When referred to hereafter, the terminology “AP” includes but is not limited to a Node-B, a base station, a site controller or any other type of interfacing device in a wireless environment.
The present invention is a method and apparatus for path-based TS admission control. In a preferred embodiment of the present invention, a WLAN mesh network has distributed admission control architecture. Accordingly, each MP of the WLAN mesh network shares the responsibility for controlling TS admission, as opposed to this function of the WLAN mesh network being performed at a central location, such as a gateway or an AP.
An MP may use the following admission criteria parameters to determine whether requested resources/QoS can be satisfied. It should be understood that the following list of parameters is not exhaustive, it is merely exemplary, and multiple parameters may be used in any combination as desired.
1) Channel occupancy: Individual MPs measure their channel utilization, defined as the percentage of time the physical layer senses that the medium busy, as indicated by either the physical or virtual carrier sense mechanism.
2) Buffer occupancy: An MP measures the buffer occupancy of its queue of the required access class.
3) Link conditions: An MP measures the number of frame retransmissions, missing acknowledgement (ACK), or the like.
In a preferred embodiment, the present invention utilizes channel occupancy (CO) for determining whether a given MP is capable of satisfying a requested resources/QoS. Each MP measures CO constantly, or at dynamic or predetermined intervals. A TS will be admitted by a given MP if the MP CO, after admitting the TS, remains below a threshold CO, COthreshold. This can be shown as follows:
COCurrent+ΔCO<COthreshold Equation (1)
where COcurrent is the CO before admission of the TS, ΔCO is the change in CO due to the admitted TS, and COthreshold is a predetermined or dynamic threshold which the given MP cannot exceed and still guarantee the requested resources/QoS.
Alternatively, a CO admission parameter may be applied per TS at a given MP. In this manner, an MP may select a more stringent COthreshold for a given TS carrying real time services, such as voice over internet protocol (VoIP). For deterministic admission control this may require a quota for each TS as follows:
COcurrentTS1+ΔCOTS1<COthresholdTS1. Equation (2)
In both Equations 1 and 2, the calculation of ΔCO must consider both the incoming and outgoing effects of admission of a TS. For an intermediate MP, the admission control considers both the capacity of the MP to process the incoming TS, (i.e., incoming admission control), as well as the capacity of the MP to transmit the outgoing TS, (i.e., outgoing admission control). For an S.MP, only the outgoing admission control need be considered. For the D.MP, only the incoming admission control need be considered.
Referring still to
If the receiving MP admits the TS at step 220, but does not admit the TS with the requested resources/QoS requirements at step 230, the receiving MP transmits an ADDTS Resp message to the S. MP indicating a modified resources/QoS offer (step 250), before returning back to step 210 for further action by the S.MP. If the requested resources/QoS is met by the receiving MP in step 230, it must then be determined whether the current MP is in fact the D.MP (step 260). If not, the receiving MP transmits an ADDTS Req message to the next MP in the admitted path (step 270), and the process 200 returns to step 220 for the determination of TS admission by the next MP. Optionally, the current MP sends an ADDTS Resp message to the S.MP indicating success (step 265).
If the receiving MP is in fact the D.MP, then the D.MP sends a path admission (PA) response (PA Resp) message to the S.MP via any route (step 280). The S.MP is now ready to begin a session with the -D.MP using the admitted path (step 290).
A PA Resp timeout mechanism is preferably employed at the S.MP, although it is not required. When a timeout mechanism is employed, a timer is initialized and is started when the S.MP transmits the ADDTS Req message. If the PA Resp is not received before a predetermined timeout threshold, the S.MP may abandon the ADDTS Req and optionally transmit another ADDTS Req message along the same or another admitted path. Alternatively, the delay can be measured via time stamping the PA Resp and the TS can be terminated if the delay requirement is not satisfied when the PA Resp is received at the S.MP.
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In an alternative embodiment of the invention, centralized TS admission control architecture is implemented in a WLAN mesh network. In this type of WLAN mesh network, a central controller performs the TS admission control functions for the entire WLAN mesh network.
If it is determined in step 530 that the selected route does meet the S.MP's resources/QoS requirements, the central controller transmits an add TS commit (ADDTS commit) message to the S.MP and all intermediate MPs comprising the selected path (step 550). Each MP receiving the ADDTS Commit message determines whether it can satisfy the requested resources/QoS (step 560). If any of the intermediate MPs are unable to support the requested resources/QoS, the MPs unable to satisfy the requested resources/QoS transmit an add TS Reject (ADDTS Rej) message, to the central controller, indicating the MP's inability to meet the requested resources/QoS (step 570). The process 500 central controller then proceeds with steps 540 and 545 as described above. If all intermediate nodes determine they can satisfy the requested resources/QoS in step 560, a session may now begin for a TS from the S.MP to the D.MP along the selected path (step 580).
However, if one or both of the MP 604 and the D.MP 606 is unable to satisfy the requested resources/QoS of the ADDTS Commit messages, the MP 604 and the D.MP 606 transmit ADDTS Rej messages to the centralized controller 608 (step 635, 640). The MP 604 transmits an ADDTS Rej message to the centralized controller 608 containing resources/QoS that the MP 604 can currently satisfy (step 635). Similarly, the D.MP 606 transmits an ADDTS Rej message to the centralized controller 608 containing resources/QoS that the D.MP 606 can currently satisfy (step 640). The centralized controller 608 updates its resource database, and transmits an ADDTS Mod message to the S.MP 602 containing the best available resources/QoS for a TS to the D.MP 606 (step 645). The S.MP 602 may then transmit an ADDTS Req message containing new resources/QoS requirements (step 650). The process then repeats itself, until resources/QoS that can be satisfied is achieved and a session begins.
Optionally, in order to release resources back to the mesh network 600, when a session is terminated (step 660), the S.MP 602 transmits a delete TS request (DELTS Req) message to the centralized controller 608 (step 665). The centralized controller 608 updates its resource database accordingly, and transmits a DELTS Req message to the MP 604 instructing the MP 604 to terminate the TS (step 670). Similarly, the centralized controller 608 transmits a DELTS Req message to the D.MP 606 instructing the D.MP 606 to terminate the session (step 675). Alternatively, a TS time-out mechanism may be employed for releasing resources back to the mesh network 600. For example, when an in-session TS is idle for longer than a predetermined period of time, the session is terminated and the resources are released to the mesh network 600.
In a distributed admission control wireless mesh network, the message processor 740 generates ADDTS Req messages when the MP 700 is an S.MP or an intermediate MP. The message processor 740 generates optional ADDTS Resp messages when the MP 700 is acting as an intermediate MP. When a rejection or modified resources/QoS is offered, the message processor 740 informs the resource (QoS) manager 750 of the offered resources/QoS.
In a wireless mesh network utilizing a centralized admission controller, the message processor 740 generates ADDTS Req messages and ADDTS Rej messages for transmission to the centralized controller. The message processor 740 further processes received ADDTS Commit and ADDTS Modify messages from the centralized controller, and informs the resource (QoS) manger 750 of the required or offered resources.
The resource (QoS) manager 750 determines available resources of the MP 700, such as CO, buffer occupancy, or the like. The resource (QoS) manager 750 determines whether resources/QoS requirements of an ADDTS Req message is capable of being satisfied by the MP 700. When TS specific CO is used to determine whether to admit a TS, the resource (QoS) manger 750 determines CO for each TS, as described above. The resource (QoS) manager 750 further determines the requested resources/QoS for ADDTS Req messages when the MP 700 is the S.MP of a TS. Information provided from the message processor 740 is used to manage resources of the MP 700 and make appropriate resource requests to other MPs in the wireless mesh network.
In a wireless mesh network utilizing a centralized admission controller, a PA message processor 760 generates DELTS Req messages for transmission to the centralized controller when the MP 700 is the S.MP of a TS to be terminated. The PA message processor 760 processes received DELTS Req messages from the centralized controller when the MP 700 is an intermediate MP. The PA message processor 760 informs the resource (QoS) manager 750 of released resources.
In a wireless mesh network utilizing distributed admission control architecture, the PA message processor 760 generates PA Resp messages when the MP 700 is the D.MP. The PA message processor 760 also implements any timeout mechanism for receiving a PA Resp message containing the admitted path, such as the one described above, when the MP 700 is the S.MP. When the MP 700 is the S.MP, upon receiving the PA Resp message, the PA message processor 760 informs the resource (QoS) manager 750 of the allocated resources in the admitted path for commencement of the session.
The resource database 840 stores resource information of all of the MPs in the mesh network and maintains current resources/QoS capabilities of all of the MPs. The resource database 840 may acquire resource information from, for example, queries, synchronization signaling, response to beacons, and by received ADDTS Req messages, ADDTS Commit messages, and ADDTS Rej messages processed by the ADDTS message processor 860.
The best route selector 850 calculates traffic loads on the various routes between the S.MP and the D.MP. Based on calculated traffic loads, system operator preferences, and resources/QoS requirements of the TS, the best route selector 850 selects the best route and informs the resource database 840 accordingly.
The message processor 860 generates ADDTS Commit messages and ADDTS Modify messages in response to ADDTS Req messages and ADDTS Rej messages, respectively. The message processor 860 informs and updates the resource database 840 as available resources are reported in the mesh network. The message processor 860 also generates DELTS Req messages for transmission to intermediate MPs in response to DELTS Req messages received from the S.MP. The message processor 860 informs the resource database 840 of released resources.
The functionality of the admission control units 730 and 830 described above may be incorporated into an integrated circuit (IC) or be configured in a circuit comprising a multitude of interconnecting components.
In another embodiment of the present invention, an admission control mandatory (ACM) field per access category (AC) is included in an ADDTS Req message transmitted by a S.MP. The ACM field indicates to intermediate MPs whether admission control is required for the AC of the TS. If admission control is not required, the TS can be sent directly with no need for resources/QoS guarantees or negotiations. This is particularly useful for low priority data that does not require minimal latency in transmission such as, for example, large file transfers.
Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. Other variations which are within the scope of the invention as outlined in the claims below will be apparent to those skilled in the art.
This application claims the benefit of U.S. Provisional Application No. 60/660,599, filed on Mar. 11, 2005, which is incorporated herein by reference as if fully set forth.
| Number | Date | Country | |
|---|---|---|---|
| 60660599 | Mar 2005 | US |