Wireless IPTV issues
and solutions
Chen Zhifeng
Electrical and Computer Engineering
University of Florida
Outline
•
•
•
•
•
•
•
What is IPTV?
IPTV application and protocols
Wireless video technical considerations
Coding issues for wireless video and solutions
networking issues and solutions
802.11g Connectivity issues and solutions
System considerations
What is IPTV?
•
Traditional TV distribution technologies: terrestrial, satellite and cable.
--However, cable can be upgraded to two-way capability and can thus also
carry IPTV.
•
Two kinds of Internet Protocol Television:
a) IPTV
--supplied by a broadband operator using a closed network infrastructure
-- need a massive connectivity infrastructure upgrade
-- User experience is bound to their living rooms and set-top boxes.
b) Internet Television
--delivery of TV content over the public Internet
--anyone can create an endpoint and publish that on a global basis.
--the publisher has a direct communication channel to the consumer
IPTV application and protocols
•
live TV --real time
a)
multicasting
-- application layer : Client/Server mode
-- network layer: Internet Group Management Protocol (IGMP) version 2
--need support from multicast router
b)
P2P
--emulate an IP multicast tree at the application layer
--no need support from multicast router
•
Video on Demand --time shifted
--use Real Time Streaming Protocol (RTSP) as the application layer
--use Real-time Transport Protocol (RTP) and Real-time Transport
Control Protocol (RTCP) as the transport protocol
--Applications using RTP are less sensitive to packet loss, but typically
very sensitive to delays, so UDP is a better choice than TCP for such
applications.
Wireless video technical consideration
• Coding
– H.264
• Networking
– Application layer: RTSP
– Transportation layer : RTP/RTCP/UDP/NAT/STUN
– IP layer: Mobile IP
• Connectivity
– MAC layer: 802.11g/802.11e/802.11i/802.11n
– Physical layer
• System consideration
-- Platform and CPU capability
--Operation system and compiler environment
Coding issues for wireless video
• Why H.264?
Network Abstraction Layer --The network-friendly
design goal of H.264/AVC is addressed via the
Network Abstraction Layer that has been developed
to transport the coded video data over any existing
and future networks including wireless systems.
• Coding issues:
--compression efficiency
--Error-resilient mechanism
--Channel rate Fluctuate issue
--End-to-End Delay Control
--Complexity
H.264 coding for wireless channel
Compression efficiency
• Due to limited resources bandwidth and transmission
power, compression efficiency is the main target for
wireless video and multimedia applications.
• H.264 solutions
--Enhanced Motion compensation
--Intra Prediction
--Deblocking Filter
--Context-Adaptive Variable Length Coding (CAVLC) and
Context-Adaptive Binary Arithmetic Coding (CABAC)
Error-resilient mechanism
• Channel rate Fluctuate issue
H.264 solution:
--well-known temporal scalability
• End-to-End Delay Control
H.264 solution:
--slice-structured coding
--Flexible MB Ordering (FMO)
--Data partitioning
Complexity
• low complexity integer transform and quantization
• Still complexity issue: more complexity than H.263 and
MPEG-4
Solution: fast algorithms to reduce the complexity of
Motion Estimation
--hexagon-based search (HBS)
--Enhanced predictive zonal search (EPZS)
--hybrid unsymmetricalcross multihexagon-grid search
(UMHexagonS)
--variable blocksize best motion detection (VBBMD)
Networking issues
•
P2P issue:
--Network Address Translators (NAT) protocol block
the data transmitted directly between two clients
under different private networks in many P2P (Peer
to Peer) applications.
--RTP uses a dynamic port range makes it difficult for
it to traverse firewalls
•
Roaming Issue: roaming from one area to another
with different IP subnet
Transportation layer solutions
• Solution for Cone NAT
--STUN protocol
--used by google talk
• Solution for symmetric NAT
--Traversal Using Relay NAT (TURN)
--adopted in big enterprise network
*STUN: Simple Traversal of User Datagram Protocol
(UDP) Through Network Address Translators (NATs)
IP layer solution --Mobile IP
• Mobile IP
--A mobile node can have two addresses: a permanent home
address and a care-of address
--A home agent (HA) stores information about mobile nodes
whose permanent address is in the home agent's network.
--A foreign agent (FA) stores information about mobile nodes
visiting its network. Foreign agents also advertise care-of
addresses, which are used by Mobile IP.
• How to work:
--Receive: packets are intercepted by the home agent, which
then tunnels the packets to the mobile node's care-of address
with a new IP header. The packets are decapsulated at the end
of the tunnel to remove the added IP header and delivered to
the mobile node.
--Send: mobile node simply sends packets directly to the other
communicating node through the foreign agent.
Wireless vedio categories
• Video over WAN (wide area network)
– GSM network/3G network
• Video over MAN (Metropolitan Area Network )
– WiMAX network
• Video over LAN (local area network )
– WiFi network (course project focus on 802.11g)
• Video over PAN (Personal area network)
– Bluetooth/UWB network
IPTV over WLAN
802.11g Connectivity issues and solutions
•
Quality of Service (QoS) issue: Delay/delay jitter/Packet loss
--solution: prioritized access and scheduled access for WiFi
Multimedia (WMM), presented in 802.11e
•
Security issue:
--Solution: Wi-Fi Protected Access (WPA/WPA2) addressed by
802.11i
•
Bandwidth issue: although 802.11a/g achieve the maximum
datarate at 54Mbps, their throughput are around 22Mbps. What’s
more, the performance will drop-off while multi-users access at the
same time
--solution: Multiple In Multiple Out (MIMO) presented in 802.11n
•
Other issues should be considered:
--Interference from other radio: Microwave, cordless phone,
bluetooth, etc
--Roaming between two APs.
…
System considerations
• Platform and CPU capability
– Intel xscale platform: Xscale CPU, high
performance
– TI PMP platform: ARM9+DSP architecture
– Samsung platform: ARM9, relatively lower
performance
• Operation system and compiler environment
– Embedded Linux: open source but limited
resources for wireless multimedia
– WinCE: not open source but plentiful board
support package for wireless multimedia
application
REFERENCES
• [1] L. Yang, K. Yu, J. Li, and S. Li, “An Effective Variable
Block-Size Early Termination Algorithm for H.264 Video
Coding,” in IEEE RANSACTIONS ON CIRCUITS AND
SYSTEMS FOR VIDEO TECHNOLOGY, VOL. 15, NO.
6, JUNE 2005
• [2] T. STOCKHAMMER, and T. WIEGAND, “H.264/AVC
for Wireless Applications”
• [3]A. Leon-Garcia, and I. Widjaja, “Communication
Networks Fundamental Concepts and Key
Architectures,” 2nd edition
• [4] http://en.wikipedia.org/wiki/IPTV
• [5]http://www.masternewmedia.org/2005/06/04/iptv_vs_
internet_television_key.htm