User datagram protocol
A Brief overview:
Multimedia applications comprise of great importance in wireless medium because of their challenging and demanding nature. The wireless technologies like WiMAX, UMTS, etc are becoming popular worldwide resulting in demand of multimedia applications.
Transport Layer Protocols are responsible for end to end communication. Transport Layer Protocols considered in this thesis are UDP, SCTP and DCCP. These Protocols are described briefly.
The User Datagram Protocol (UDP) provides an unreliable service with no guaranteed delivery, no congestion control mechanism . So there is lack of QoS in UDP. But it is used in video streaming because of its less overhead.
Stream Control Transmission Protocol (SCTP) is a reliable and connection oriented transport layer protocol that provides ordered data delivery and also there is no error in that data. Another important feature supported by SCTP is Multi-homing, in this feature an end point can have support for multiple IP addresses or interfaces. SCTP also supports Multi-Streaming feature in which data to be sent can be portioned in to streams. Multi-homing and Multi-streaming can provide better bandwidth utilization .
Datagram Congestion Control Protocol (DCCP) is an un-reliable transport layer protocol that provides congestion control on datagrams in network . It has support for Explicit Congestion Notification (ECN). ECN supports for the notification of end-to-end network congestion .
Mobile WiMAX/IEEE 802.16e is a broadband wireless technology that provides support for both fixed and mobile broadband networks. Mobile WiMAX can support data rate theoretically up to 63 Mbps. A very important feature provided by Mobile WiMAX is QoS. It provides Service flows which enables end to end IP based QoS by using flow labels. In Mobile WiMAX scalability is provided in both network architecture and radio access technology so providing better flexibility in network deployment and services offered .
This thesis is based on the analysis of transport layer protocols using MPEG-4 traffic over Mobile WiMAX. To analyze the performance of transport layer protocols different performance measures like packet loss, throughput, delay and jitter will be used.
The output of this thesis will provide the best transport protocol for MPEG-4 traffic over Mobile WiMAX.
As multimedia applications are becoming popular and wireless broadband technologies are deployed, there is the need to assess the quality of experience experienced by users. In  author has presented an evaluation of VoIP sessions on a fixed WiMAX testbed, comparing the performance of UDP/RTP and DCCP.
In  author has explored the technical details and performance of WiMAX broadband access technology. The aim was to address whether WiMAX access technology for streaming video applications could provide comparable network performance to ADSL. The OPNET Modeler was used to design and characterize the performance of streaming MPEG-4 video to WiMAX and ADSL subscribers using packet loss, delay, jitter, and throughput.
In  author has used modulation schemes in Mobile WiMAX. Different modulation schemes like BPSK, QPSK, 16-QAM and 64-QAM are compared with TCP and different variants of TCP in terms of throughput and packet loss ratio.
In transportation of multimedia applications time is very important as compared to reliability. By using transport layer protocols like UDP, TCP and DCCP variants like CCID1, CCID2 and CCID3 the performance of MPEG-4 video is Analyzed . To analyze the performance of these transport layer protocols performance measures like throughput, packet loss, delay and jitter are used.
In  author has analyzed the performance of MPEG-4 video by using SCTP as transport layer protocol over 802.11 wireless access medium. SCTP retransmission overhead delay has is analyzed by using computer simulations. Among the SCTP streams differentiated transmission policies have been analyzed by using SCTP multi-streaming property.
Performance of WiBro a Korean version of Mobile WiMAX is analyzed by using traffic measurements . Transport layer protocols like UDP and TCP has been used to analyze the link capacity and good put performance. The performances measured with WiBro are then compared with those of HSDPA (High-speed Downlink Packet Access).
In  throughput performance of SCTP is evaluated over IEEE 802.11WLAN protocol. The performance is evaluated by using different number of hops between sender and receiver and the different SCTP window sizes at receiver side.
In  the performance of SCTP is analyzed by using streaming video over CDMA2000 wireless networks and cell phone. The performance is evaluated by analyzing quality of video received using a specific buffer size.
In  author has compared TCP with SCTP. Performance of MPEG-4 video is analyzed by transmitting it over SCTP.
The issues in video streaming using DCCP over wireless domain are focused in . In the Medium Access (MAC) layer the wireless packet loss information is available which is used by DCCP in order to separate the congestion losses from wireless losses.
TRANSPORT LAYER PROTOCOLS
This chapter is based on the description of transport layer protocols considered in this thesis. These protocols are discussed one by one as follows.
UDP is a connectionless transport layer protocol. A datagram can be sent at any time without any prior negotiation between the sender and receiver. Sender just send the datagram with the hope that receiver is ready to receive it .
Un-Ordered Data Delivery
In UDP there is no ordered data delivery and also duplicate packets can arrived at the receiver. So it means that a packet with Packet ID 2 can arrive before a packet with Packet ID 1. Also a packet with same ID can be received twice which is called packet duplication .
Flow control is the process of adjusting the data flow from sender to the receiver in order to ensure that the receiver side can handle or receive all the incoming data . As UDP is a connection less protocol, so flow control mechanism is not implemented in it.
Typically UDP is used in case of real-time video and audio streams as in these applications the recovery of lost packets is not needed. As UDP is an unreliable transport layer protocol so the receiver doesnot send any acknowledgement (ACK) signals to the sender. As no ACK mechanism is implemented in UDP, so the sender cannot determine the link capacity resulting in congestion in the network.
Selective Acknowledgement (SACK) in UDP
As the acknowledgement mechanism is not implemented in UDP, so selective acknowledgement sack (SACK) is also not available in UDP.
- The User Datagram Protocol (UDP), [online]. Avaialable: http://www.erg.abdn.ac.uk/users/gorry/eg3567/inet-pages/udp.html
- RFC 3286 - Introduction to Stream Control Transmission Protocol (SCTP), L. Ong, J.Yoakum, May 2002.
- RFC 4340 - Datagram Congestion Control Protocol (DCCP), E. Kohler, M. Handley, March 2006.
- RFC 3168 - The Addition of Explicit Congestion Notification (ECN) to IP, S. Floyd, D. Black, Sept. 2008.
- Mobile WiMAX Technical Overview by Intelibs, Inc [online]. Available: http://www.intelibs.com/upload/wimax_white_paperv1.pdf
- Bernardo, ”VoIP over WiMAX: Quality of experience evaluation”, IEEE Symposium on Computers and Communications, ISCC 2009, 2009, pp. 42- 47.
- W. Hrudey, "Streaming video content over IEEE 802.16/WiMAX broadband access," OPNETWORK 2008, Washington, DC, Aug. 2008.
- L.D. MALVIYA, “Simulation based comparison of different modulation schemes for mobile WiMAX using TCP and its variants”, 1st International Conference on Emerging Trends in Engineering and Technology (ICETET), 2008, pp. 168-171.
- Rashid Mehmood, “A comparative analysis of DCCP variants (CCID2, CCID3), TCP and UDP for MPEG-4 video applications”, 3rd international conference on information and communication technologies (ICICT), 2009, pp. 40-45.
- Li Wang, “MPEG-4 optimal transmission over SCTP multi-streaming in 802.11 wireless access media”, 7th Asia-Pacific Symposium on Information and Telecommunication Technologies, 2008, pp. 172-177.
- Hua Cai, “Performance measurement over mobile WiMAX/IEEE 802.16e network”, International Symposium on a World of Wireless, Mobile and Multimedia Networks, 2008, pp. 8.
- Guanhua Ye, “SCTP congestion control performance in wireless multi-hop networks”, Military Communications Conference (MILCOM 2002), 2002, vol. 2, pp. 934-939.
- C. L. Begg, “Suitability of SCTP for high quality video streaming over CDMA2000”, Australasian Telecommunication Networks and Applications Conference (ATNAC 2007), 2007, pp. 496-502.
- Zhao Lifen, “The performance of study of transmitting MPEG4 over SCTP”, Proceedings of 2003 International Conference on Neural Networks and Signal Processing, vol. 2, no. 2, 2003, pp. 4.
- B. Gorkemli, “Video streaming over wireless DCCP”, ICIP 2008 - 15th IEEE International Conference on Image Processing, 2008, pp. 4
- RFC 768 - User Datagram Protocol (UDP), J. Postel, August 1980. Available: http://www.ietf.org/rfc/rfc0768.txt
- Comparative analysis TCP-UDP [online]. Available: http://www.laynetworks.com/Comparative%20analysis_TCP%20Vs%20UDP.htm
- Flow Control [online]. Available: http://www.webopedia.com/TERM/F/flow_control.html