IEEE 802.11aa: Improvements on video transmission over Wireless LANs

IEEE 802.11aa: Improvements on video transmission over Wireless LANsSpeaker : Song-Ferng WangAdvisor : Dr. Ho-Ting WuDate : 2014/1/6IntroductionIEEE 802.11 multicast issues IEEE 802.11e EDCAIEEE 802.11aaConclusionsReferences

OutlineVideo applications are rapidly becoming the main source of traffic in the Internet. With the presence of IEEE 802.11 networks constantly expanding, and the growing use of mobile devices with high computational power and display capabilities.IntroductionThe first IEEE 802.11 wireless LAN standards were unable to handle efficient video transmission since the bandwidth was too small for the demands of video applications and they could only support a best-effortservice which is unacceptable for the QoS restraints of video transmission

IntroductionThe multicast mechanism provided by the legacy IEEE 802.11 is unreliable and cannot offer the necessary QoS for transmitting video streamsmulticast communication in IEEE 802.11 wireless LANs suffers from many problems.

Introductionthe MAC layer of IEEE 802.11 networks specifies that multicast frames can only be transmitted using the Basic Access scheme. Therefore, it cannot use the RTS/CTS mechanism to protect broadcasting of the frame. means that multicast transmission is unreliableissues about the scheduling and synchronization of receiving them

IEEE 802.11 multicast issues (1)IEEE 802.11 MAC specifies that multicast frames must be transmitted using one of the bit rates specified in the Basic Rate Set (BRS), which is a minimum set of bit rates that must be supported by all stations in a IEEE 802.11 wireless LAN to ensure that they can receive control frames.

IEEE 802.11 multicast issues (2)Compatibility with the relevant mechanisms defined by IEEE 802.1AVB (802.1Qat, 802.1Qav, 802.1AS) for multimedia stream transport.

To allow video streams to degrade in a graceful manner when the channel capacity is insufficient , by enabling packet discarding without any requirement for deep packet inspection. IEEE 802.11aaThe ability to prioritize between different video transport streams that belong in the same EDCA Access Category.Stream Classification Service (SCS)

A method for mitigating the effects of overlapping BSS environments to offer increased robustness , without the need for centralized management.IEEE 802.11aaImprovement for the multicast/broadcast mechanism of IEEE 802.11 in order to offer better link reliability and low jitter characteristics.802.11v Directed Multicast ServiceGroupcast with Retries (GCR) Unsolicited RetriesGroupcast with Retries (GCR) BlockAckIEEE 802.11aaconverts multicast traffic to unicast frames directed to each of the group recipients in a series. The transmission uses the normal acknowledgement policy and will be retransmitted until it is received correctly. 802.11v Directed Multicast ServiceThis mechanism allows the transmission of the multicast frames to be repeated a number of times.Groupcast with Retries (GCR) Unsolicited RetriesThis method extends the BlockAck mechanism specified in IEEE 802.11n for use in multicast transmissions to a group. The AP transmits a number of multicast frames and then requests from one or more of the recipients to acknowledge the receipt of the transmitted frames. Frames that have not been received correctly by one or more of the receivers can then be retransmitted. Groupcast with Retries (GCR) BlockAck

DCF (Distributed Coordination Function)(Station, STA)/(Carrier-Sense Multiple Access/Collision Avoidance, CSMA/CA)

IEEE 802.11 DCF

IEEE 802.11 DCFEDCA function in IEEE 802.11e to provide Quality of Service for video and voice streams specifies Access Categories (AC) with different priorities8 Traffic Category (TC)4 Access Category(AC)IEEE 802.11e EDCA

IEEE 802.11e EDCA

IEEE 802.11e EDCAThe IEEE 802.11aa amendment aims to increase the granularity of the EDCA access categories to allow for prioritization between different video streams.Stream Classification Service (SCS)

Stream Classification Service (SCS)The IEEE 802.11aa amendment provides a foundation for video stream transport over IEEE 802.11 wireless LANs. It provides a set of mechanisms such as the multiple multicast policies, the Stream Classification Service and the QLoad information element, but the use of them is open to the implementation. The choice of the appropriate mechanism, depending on the situation and the setting of its parameters, is an issue of great interest for future research.ConclusionsKostas Maraslis, Periklis Chatzimisios and Anthony Boucouvalas,IEEE 802.11aa: Improvements on video transmission over Wireless LANs, Communications (ICC), 2012 IEEE International Conference on Ad-hoc and Sensor Networking Symposium, pp. 115-119, June 2012IEEE 802.11eMay 2008

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