ch 10. multimedia communications over wmns
DESCRIPTION
Ch 10. Multimedia Communications over WMNs. Myungchul Kim [email protected]. WMN high number of traversed hops Wireless channels Dynamic behavior of network nodes. Introduction. Communication requirements Dealy and bandwidth Multimedia applications: interactive and streaming - PowerPoint PPT PresentationTRANSCRIPT
![Page 2: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/2.jpg)
– WMN
• high number of traversed hops
• Wireless channels
• Dynamic behavior of network nodes
Introduction
![Page 3: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/3.jpg)
• Communication requirements– Dealy and bandwidth
– Multimedia applications: interactive and streaming
– Voice: max dealy constraint ~150ms : forward error correction
– Streaming: a few seconds: automatic repeat request
Multimedia characteristics and QoS requirements
![Page 4: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/4.jpg)
• Robustness issues– MPEG
Multimedia characteristics and QoS requirements
![Page 5: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/5.jpg)
• Perceived quality evaluation– Throughput and packet loss rate?
– Subjective experiments
• Mean opinion score (MOS)
– Objective quality measures
• Perceptual evaluation of speech quality (PESQ)
• Perceptual evaluation of audio quality (PEAQ)
• The mean squared error (MSE)
• Peak signal-to-noise ratio (PSNR)
Multimedia characteristics and QoS requirements
![Page 6: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/6.jpg)
• Perceived quality evaluation• Peak signal-to-noise ratio (PSNR)
Multimedia characteristics and QoS requirements
![Page 7: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/7.jpg)
– Multimedia: bandwidth degradation, network latency, and radio interference
– 802.11: speeds up to 100Mb/s, QoS support, fast handoff, and mesh functionalities,…
• Network capacity– 802.11n: MIMO
– Multiple nodes
Protocols and open issues
![Page 8: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/8.jpg)
• Network latency– Single-radio: half-duplex
– Multiradio mesh networks
– UCSB MeshNet result
Protocols and open issues
![Page 9: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/9.jpg)
• Handoff– Max allowed delay during handoff cannot exceed 50ms
– 802.11r: IP-based telephony over 802.11-enabled phones by speeding up handoffs between APs
– Layer 2 roaming delay: scanning, reassociation, and re-authentication
– Passive scanning: 100ms
– Active scanning: 20 – 300 ms
– Peremptive scanning
– A mobile device cannot know if necessary QoS resources are available at a new AP until after the handoff
– 802.11e: admission control
Protocols and open issues
![Page 10: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/10.jpg)
• Network routing– Proactive routing
– Reactive routing
– Routing metrics
– As the sender and receiver move, link quality metrics cannot quickly track the change in the link quality.
– No perfect protocol for QoS
– Adv of Multipath multimedia streaming
• High aggregate bandwidth to realtime multimedia applications
• Data partitioning
• Reduce the chance of interrupting the service due to node mobility.
Protocols and open issues
![Page 11: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/11.jpg)
– Satisfactory QoS level in WMNs?
– Multiple paths
• Streaming services– Routing?
– Multiple transmission paths
– Multiple Description Coding (MDC)
Innovative multimedia applications
![Page 12: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/12.jpg)
• Streaming services– Layered coding
– How to optimally subdivide multimedia traffic over different paths
• Interactive voice services– Issues related with network congestion, delay and link quality
– The capacity is related to the channel bandwidth, voice codec, packetization interval and data traffic in the system
– VoIP over 802.11b using G.711 codec -> 800kb/s and 6 calls
– Node congestion depends more on the number of packets that need to be processed than on the actual bandwith
– Put more than one voice frame into the same packet -> delay increases -> end-to-end dealy increase
– Number of hops: from ten (with a single hop) to one when four hops
Innovative multimedia applications
![Page 13: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/13.jpg)
• Interactive voice services– Traffic delay variations
– QoS mechanism
• Prioritization of voice
• Changes to the 802.11 to reduce the jitter and delay by changing the transmission scheme
– Multiple description speech coding
– Roaming
– Dejitter buffers
– Adaptively adjust the dejitter buffer size to the network conditions so that the end-to-end delay is always kept as small as possible.
– Handoff-prediction with audio time-scaling
Innovative multimedia applications
![Page 14: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/14.jpg)
• Intervehicle communications– 802.11p
– Applications: road information, obstacle avoidance and automatic driving, virutal meeting,
– Different from generic MANET
• Driver behavior
• Mobility constraints
• High speeds
Innovative multimedia applications
![Page 15: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/15.jpg)
• Intervehicle communications– Routing layer
• Rapid changes in intervehicle networks
• Network fragmentation
• Effective network diameter is small
• The presence of redundant paths is often limited
• The number of nodes within the communications range grows linearly with the increase in the radio range.
• Roadside APs: the time interval in which the link is available is limited to a few seconds -> fast handoffs
Innovative multimedia applications
![Page 16: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/16.jpg)
• Intervehicle communications– Cross-layer design
– 97% communication for the urban and less than 50% for the rural
– High-speed mobility of network nodes and multihop communications.
Innovative multimedia applications
![Page 17: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/17.jpg)
• Real-time multiplayer games– Movement of the game characters
– The highest demand on QoS requirements and round-trip delays up to 150 ms with minimum jitter and low packet loss rate
– Bandwidth is not so important
– Players’ perception of jitter
– Routing protocols and QoS techniques
• End-to-end communications delay and jitter
– Cross-layer design• AODV: desabling its local repair property and implementing
a backup route mechanism
– Traffic menagment level• Priority queueing, timeouts, and real-time neighbor-aware
rate control
Innovative multimedia applications
![Page 18: Ch 10. Multimedia Communications over WMNs](https://reader035.vdocuments.site/reader035/viewer/2022070410/568146b9550346895db3e495/html5/thumbnails/18.jpg)
• Real-time multiplayer games– Movement of the game characters
– The highest demand on QoS requirements and round-trip delays up to 150 ms with minimum jitter and low packet loss rate
– Bandwidth is not so important
– Players’ perception of jitter
– Routing protocols and QoS techniques
• End-to-end communications delay and jitter
– Cross-layer design• AODV: desabling its local repair property and implementing
a backup route mechanism
– Traffic menagment level• Priority queueing, timeouts, and real-time neighbor-aware
rate control
Innovative multimedia applications