1. MULTIMEDIA ENTERTAINMENT Abhilash

2. Contents Introduction Music delivery over cellular networks Issues and Solutions Conclusion References

3. Introduction Multimedia is the use of several different media (e.g. text, audio, graphics, animation, video, and interactivity) to convey information. Multimedia also refers to the use of computer technology to create, store, and experience multimedia content. As the information is presented in various formats, multimedia enhances user experience and makes it easier and faster to grasp information. Require high bandwidth, low end-to-end delay, and synchronization.

4. Background The evolution of multimedia can be traced through three major stages  Stand alone applications and CD-ROM based applications.  Creation of large scale video servers.  Creation of content that can be delivered by means of low cost and bandwidth

5. Music delivery over cellular networks With multimedia entertainment music can be delivered over cellular networks. The users are given an option of downloading music on the move. Mobile phones equipped with wireless technology can provide a platform for downloading music.

6. Contd.. Downloadable music is one of the more important features of multimedia. The consumer will need seamless distribution of music that supports mobile and nomadic services. The system is designed as an ABS (always best served) model.

7. What is an ABS? ABS is an emerging model supporting mobile and ubiquitous computing, and its key service is to allow nomadic users to switch terminal and network technology so as to obtain the best connection available.

8. System Architecture

9. Contd.. The architecture is comprised of three components Mobile clients Intermediate system Set of web server replicas

10. Mobile clients – music handheld devices connected through wireless network access points Intermediate system – manages all the communications between the handheld device and the wired internet infrastructure. It has three subsystems Application gateway – guarantees reliable communication between the IS and the mobile client Discovery – discovers the music resources on the web Download Manager – downloads the songs that have been identified by the Discovery system Web server replicas – distributed over the internet which function as replicated music repositories

11. A number of problems arise while using the IP stack in a wireless context. The IP stack is not designed to handle mobility and effectively manage the wireless connections. The service replication built into IP leads to unwanted feature interactions with similar services provided by wireless networks.

12. Issues with music distribution Connection continuity Packet loss Resource management

13. Issue 1 – Connection Continuity If the wireless link is interrupted for a prolonged time, the download may just be aborted. The application should have the following requirements Automatically switch connection in case of network failure or handoffs Automatically freeze a download in case of absence of networks Automatically resume a download frozen by absence of networks Freeze a download if required by the user Resume a download interrupted by the user Transfer the download to a different terminal if required by the user

14. Solution The ABS system needs to modify at least a layer of the IP stack. A promising solution is to build an application in the session layer.  This layer is called the Session Management Layer (SML). Such a layer could effectively support all the issues by using an ID based mechanism to provide services for the nomadic applications. Also the session layer is responsible for initiating and terminating user sessions.

15. Protocol stack

16. Contd.. SML supports  End-to-end IP continuity of a download activity in the face of failures, link outages or handovers.  A price/performance sensitive vertical roaming scheme for switching across alternative wireless technologies (eg., WiFi, cellular).

17. Contd.. The goal is achieved by freezing the download state activity at the session layer when handoffs are detected, thus permitting resumption of the music data stream as soon as the problems have cleared.

18. Experimental Assessments Performance of the system when the user is moving along a path covered by different radio technologies Performance of the system when the user nomadically changes his download device

19. Network coverage and download processes

20. Download time comparison

21. Result The ABS system provides the best download performance across different network technologies. The ABS system completes downloads whenever and wherever possible, regardless of noncontinuous network coverage.

22. Issue 2 – Packet loss A fundamental issue in transport of fragmented audio data is the priority distinction. It is essential to have the critical data to decode any of the remaining data. This is why appropriate techniques have to be utilized to transport the critical data more reliably than the lower priority data.

23. Solution There are two solutions to increase the reliability of data transport.  Retransmission based transport – the data packets are replicated only if the original packet is lost.  Redundancy based transport – the sender replicates the data elements. Probability of data loss is decreased but bandwidth usage increases

24. Contd.. Data are arranged in different packets, depending on priority. Higher priority packets are transmitted before lower priority packets. This allocates more time to retransmission attempts for the critical packets. However, in streaming applications there is a definite deadline for data delivery, which limits the number of retransmission attempts.

25. Retransmission

26. Reserve fixed size slots for each frame and a reservoir area for codewords that do not fit in the base slot.

28. Packetization scheme for retransmission

29. The loss rate for the critical packets is assumed to be low due to retransmissions. If one of the critical packets is lost, error propagation to the other frames is restricted to the reservoir section only. Critical data sections are interleaved among the critical packets to avoid loss of adjacent packets. This allows us to employ traditional frame-based error concealment techniques to recover the missing frames.

30. Redundancy based transmission Transport and packetization techniques based on added redundancy can be relatively cost efficient, especially if the proportional amount of critical data is low. This is because only the critical portion of the data has to be replicated.

31. Redundancy

32. If multiple packets are lost, the number of lost critical sections can be limited by designing rules for shuffling and adding redundancy carefully. Most importantly, no critical sections of two different frames should be written in the same set of redundant packets. It is also beneficial to use pseudorandom shuffling sequences instead of direct interleaving for the non- critical data elements.

33. Issue 3 – Resource management Multimedia traffic puts heavy bandwidth demand on the cellular network. Bandwidth is the most critical resource in cellular networks and thus requires mechanisms to efficiently use the available bandwidth. In cellular networks carrying multimedia traffic, resource allocation and management is an important issue.

34. Resource management performed in the mobile networks is commonly referred to as Channel Allocation. A number of channel allocation algorithms have been developed to efficiently utilize the available spectrum. Fixed Channel Allocation (FCA) Dynamic Channel Allocation (DCA) Hybrid Channel Allocation (HCA)

35. Resource Allocation The support for multimedia services in mobile cellular networks increases network congestion and requires the use of microcellular architecture. This architecture introduces the problem of frequent handoffs and makes resource allocation difficult. In these networks, the resource allocation schemes have to be designed such that a call can be assured a certain QoS once it is accepted into the network.

36. Resource Allocation Schemes Admission Threshold (AT) based scheme – resource management is done by periodically calculating the admission threshold and by blocking all new call connection requests once the threshold is reached. If a call connection request arrives at time t 0, then the following conditions must be satisfied At time t 0 + T, the handoff probability in the current cell as well as the adjacent cells must not exceed P HD. At time t 0 + T, the overload probability must not exceed P OL. At time t 0 + T, the overload probability in the adjacent cells due to traffic handoffs must be smaller than P OL.

37. Contd.. Resource Sharing (RS) based scheme – This scheme employs a resource sharing mechanism that reacts to rapidly changing traffic conditions in a cell. It differentiates the new call on basis of its traffic class and a particular decision is taken. For real time call connections, a new call is blocked if no bandwidth is available to service the request. Some of the resource sharing schemes are Complete Partition (CP) Complete Access (CA) Restricted Access (RA)

38. Contd.. Resource Reservation (RR) based scheme – In this scheme, the decision to accept a call depends on the bandwidth available in the cell in which the call arrives and in the adjacent cells. For real time call connections, bandwidth reservation is performed in all cells adjacent to the cell in which the call arrives. A connection is refused if either the bandwidth is not available in the cell or sufficient bandwidth cannot be reserved in the adjacent cells.

39. Issues in Resource Reservation The resource reservation scheme can provide the best service but there is a tradeoff between service quality and processing overhead. One issue is to determine in which cells the reservation needs to be performed. The next issue is to determine how much bandwidth needs to be reserved in surrounding cells. Another issue is to determine when to release and reserve bandwidth in the surrounding cells.

40. Resource Reservation with Renegotiation RRN uses resource reservation in surrounding cells for real time traffic and bandwidth readjustment for non real time calls. Resource Reservation – Bandwidth is reserved in all cells adjacent to the cell in which the call arrives. When a call hands off to another cell,if enough bandwidth is not available, it uses the bandwidth reserved in the target cell. When a call is successfully handed off to another cell, we release the bandwidth reserved for the call earlier and reserve bandwidth in the cell cluster of the new cell.

41. Bandwidth Reservation

42. New call setup When a call connection is requested, the base station determines the bandwidth B available to service the calls. If B is more than the requested bandwidth B r, the base station then calculates the bandwidth B res it needs to reserve in the adjacent cells. The information from other cells in the cell cluster is gathered and if B res can be reserved, the call is accepted. If B res is not available in all cells of the cell cluster, the call is blocked.

43. New call setup

44. Conclusion

45. References