Design of a QoS enabled WLAN

1. Design of a QoS enabled WLAN Samuel Senkindu Supervisor: Prof H. Anthony Chan Department of Electrical Engineering University of Cape Town

2. Presentation Outline • Introduction • Problem Definition • QoS in WLAN • QoS Policy Management • Conclusion

3. INTRODUCTION • NGN (ITU-T)provide user with a rich set of multimedia services. • End to End QoS is critical in the delivery of the services. • NGN envisages the use of policy based QoS control

4. INTRODUCTION NETWORK TRANSPORT LAYER CONTROL LAYER ACCESS NETWORK APPLICATION SERVICES LAYER ISDN MEDIA GATEWAY FOR LEGACY NEWTORKS ADSL UMTS SOFTSWITCH WLAN

5. Problem Definition • WLAN is critical NGN access network, but has least developed QoS mechanisms, due to its contention based medium access mechanism. • Another shortcoming is that existing WLAN QoS schemes implement QoS on individual networks independently.

6. Challenge • To become a telecom grade access network WLAN must address: • service differentiation, on wireless medium through QoS. • WLAN QoS management by a network policy based QoS control mechanism.

7. QoS in the WLAN • The first step in our 2 step approach, is to address QoS on the wireless medium. • Legacy WLAN 802.11 medium access is contention based, with no QoS. • IEEE 802.11e introduced QoS on wireless medium by enhancing MAC layer. • Uses enhanced distributed channel access (EDCA), and hybrid coordination function controlled channel access (HCCA) mechanisms. • We consider HCCA in our scheme.

8. IEEE 802.11e - HCCA • Access to the medium is controlled by an HCCA coordinator (HC). • HC resides in the QoS enabled AP (QAP). • QoS enabled non-AP station (QSTA) that requires access to the medium sends a request frame to HC/AP containing: • the required mean data rate, • frame sending size, • maximum service interval (MSI) • If request is accepted (based on an admission control policy), HC/AP uses parameters in request frame to generate a channel access schedule for all the QSTAs in the network. • The HC/AP grants QSTAs appropriate transmission opportunities through polling.

9. Our Enhancement of HCCA • IEEE 802.11e proposes a simple scheduler as a reference. • Disadvantage of simple scheduler is that admission control is on first-come first-serve basis. • Low priority traffic can experience bandwidth starvation. • We propose to use a class based queuing (CBQ) admission control mechanism to provides a fairer allocation of bandwidth.

10. Class Based Queuing (CBQ) LINK VOICE WEB TRAFFIC VIDEO • In cases where video uses less than 50% of the bandwidth, the balance can be borrowed by video or web traffic. • CBQ will enable scheduler to provide minimal bandwidth guarantee to low priority traffic. 50% 30% 20%

11. WLAN in IMS • In policy based network, QoS on the WLAN should be centrally controlled by the AP or wireless router. • However the AP does not know anything about network QoS policy. • This situation can be addressed by integrating WLAN in IMS. This is second step in solution. • IMS would provide centralized network management of QoS on the WLAN.

12. QoS Policy Management • Uses a client-server relationship (RFC 2748). Common Open Policy Service (COPS) protocol Client Policy Enforcement Point (PEP) at AP: enforces QoS policy decisions Server Policy Decision Point (PDP): QoS policy decision

13. Scope of Work Scope of this work COPS Policy Enforcement Point (PEP) at AP: enforces QoS policy decisions Policy Decision Point (PDP): QoS policy decision • The end result of this work, is to come up with an intelligent manageable QAP, that can be plugged into a policy based network, such as an IMS network.

14. Proposed Scheme QoS enabled phone (QSTA) Policy based QAP acting as HC, using class based queuing (CBQ). Wireless link layer flows mapped to diffserv on wired interface IEEE 802.11e HCCA for QoS Multimedia Server Farm QoS enabled stations (QSTA) 802.11e PC

15. How Our Scheme Fits In Key: HSS: Home Subscriber Service P-CSCF: Proxy Call Session Control Function (CSCF) I/S-CSCF: Interrogating/ Serving CSCF PCRF: Policy and Charging Rule Function in IMS release 7 SPR: Service Policy Repository in IMS release 7 IMS CORE Signaling path SPR (IMS release 7) PDP (PCRF) HSS Data path Sp QoS policy rules downloaded from HSS (IMS release 6) COPS DIAMETER WLAN ACCESS NETWORK SIP SIP P-CSCF AP acting as PEP enforces QoS according to policy rules I/S-CSCF Bearer plane User accesses service, with QoS

16. Conclusion • Proposed scheme to realize AP as PEP in a policy based network such as IMS. • Able to utilize IMS capabilities. • Help in effort to establish WLAN as telecom access network. • Use of low cost WLANs will help in opening up new areas for service coverage such as: • rural areas • areas deemed commercially unviable to serve with existing technologies: such as low density population areas, temporary/transit settlements, or game parks • Simulations ongoing to validate scheme.

17. Relevant Standards • IT-T NGN Focus Group recommendations • 3GPP/ TISPAN Release 6/7 IMS Technical Specifications • IEEE 802.11e MAC QoS Enhancements • RFC 3084 - COPS Usage for Policy Provisioning (COPS-PR) • RFC 2748 - The COPS (Common Open Policy Service) Protocol. • RFC 2475 - An Architecture for Differentiated Services. • RFC 3260 - New Terminology and Clarifications for Diffserv

18. Design of a QoS enabled WLAN THANK YOU. Questions?