An extension of IEEE 802.11e QoS for MESH Networks Daniela Maniezzo, UCLA

WLAN Mesh: how to guarantee the QoS?? In a ESS WLAN Mesh Net a Mesh Portal is a gateway with another networks IEEE 802.11e gives a strategy to assure differentiation among up to four access categories, on the basis of ad hoc AIFS (Arbitration Inter Frame Space) and backoff parameters, but it was projected for single-hop networks, i.e. for an infrastructured BSS built around the Access Point IEEE 802.11e, nevertheless, provides an efficient, easy and fully distributed way to introduce the concept of “service priority” in the IEEE 802.11 ’99 standard, so it’s natural to investigate the possibility of its extension to multihop ad hoc networks as the future IEEE 802.11s

RELAY and OUT_BSS flows MeshP1 MeshP3 MeshP2 STA6 STA3 STA2 STA1 STA5 STA4 A Mesh Point has to deal with both traffic originated by other Points (for which it is a relay) and its own traffic directed to out-of-its-BSS nodes

Related Work Jangeun Jun and Mihail L. Sichitiu, "Fairness and QoS in Multihop Wireless Networks", in Proc. of the IEEE Vehicular Technology Conference (VTC 2003), Orlando, FL, Oct. 6-9, 2003. G G Node2 Node1 2G D S1 S2 Fairness study of a two-node network forwarding packets to a destination D of the offered load G [...] “without a modified MAC or network layer, as the offered load increases, the node closest to the destination (node 1) will gradually but completely starve the node further away from the destination.”

RELAY and OUT_BSS flows (cont'd) Notice that granting the co-existance of these two different kinds of flows means that each Mesh Point must be able to assure a fair amount of bandwidth to both its outgoing data and the packets sent by its peers: STA Who shall I serve? MeshPi MeshPj MeshPk We need to distinguish between Relay and Out_BSS flows and to deal with them differently according to a proper service policy (QoS parameters)

Proposed Idea (1): Multiple Tx queues at the MeshP (1/3) Mesh Pi Mesh Pk Mesh Pj STA Relay Out_BSS ??? The amount of service given to each kind of queue depends on the status of the queues themselves and must be set adaptively!!

Multiple Tx queues at the Mesh Points (2/3) …how to be fair??? Relay Out_BSS In the following we will suppose to have a mechanism of distributed admission control that checks which resources are currently available in the network along the path between the source/destination pair and rejects the new Out_BSS flow or finds a different route in case of congestion. This mechanism may also indicate which is the maximum bandwidth share permitted to the new flow.

Multiple Tx queues at the Mesh Points (3/3) Relay and Out_BSS flows contain frames belonging to different access category (AC). Relay Out_BSS ??? AC0 AC1 AC2 AC3 In 802.11e the amount of service given to each AC is fixed statistically by != AIFSs and backoff window sizes. In the same way we propose to use up to 8 AIFSs and backoffs, set by the MeshAP in a fully distributed way

Mesh: multiple queues and QoS Relay Out_BSS ??? AC0 AC1 AC2 AC3 Our purpose: the scheduler sets the proper channel access parameters, mainly the AIFSs different amount of service between Relay and Out_BSS require != AIFSs the first AC who wins a TXOP is served by the Mesh Point BUT: how to grant the “quality of service”????

Mesh: multiple queues and QoS Relay Out_BSS AC0 AC1 AC2 AC3 AIFS0, AIFS1, AIFS2, AIFS3 BW0, BW1, BW2, BW3 BW = backoff window Find out metrics that can be used by the Mesh Point to set the AIFSs/BWs In each queue, order the packets on the basis of the number of hops traversed When an AC wins TXOP, it picks the Head Of Line

Proposed Ides (2):Traffic Destinations Most of traffic of a WLAN Mesh Network goes through the Mesh Portals that connect the ESS with other networks and Internet (office networks - Campus/Community/Public Access Net scenarios) During the Routing Procedure: Distinction between Mesh Points and Mesh Portals

Proposed Idea (2) Priority DIFS function of the distance from the Mesh Portal Portal Priority Portal

Any idea or other suggestions?