Data dissemination has already been identified as one of the most important aspects for mobile environments and particularly so for large volumes of data such as video, with the additional constraints of speedy, accurate, and isochronous delivery to thousands of users. With the adoption of mobile broadcasting standards this factor has increased in importance. In this chapter, we present the respective issues involved, technical as well as financial and regulatory. The reader is provided with a brief, yet concise, picture of the most important traditional broadcasting techniques and video broadcasting standards for the mobile environment. We then conclude with a detailed comparative evaluation in order to better understand the merits of each approach.
As stated earlier, streaming popular videos has been a challenging problem, since a large client population demands the same item to be delivered and played out within a short period of time. This period should be smaller that the time tw a client is willing to wait after sending his request. Typically, there are on average a constant number of requests over a long time period for a popular video, which suggests that a single broadcast should suffice for each batch of requests. However, the capabilities of all entities involved (server, clients, and network) are finite and often of varying degree (e.g., effective available network and client bandwidth).
Key Terms in this Chapter
Streaming: The scheme under which clients start playing out the multimedia immediately or shortly after they have received the first portion without waiting for the transmission to be completed.
Digital Video Broadcasting Handheld (DVB-H): This is a standard published by ETSI (European Telecommunications Standards Institute) in order to implement mobile digital television networks.
Datacasting: The broadcasting of data over wireless networks, often used in conjunction with digital television for the provision of news, broadcasting program and other information.
IP Datacast (over: DVB-H) ( IPDC): This is an end-to-end broadcast system for delivery of any type of digital content and services using IP-based mechanisms optimized for devices with limitations on computational resources and battery.
Quality of Service (QoS): A notion stating that transmission quality and service availability can be measured, improved, and, to some extent, guaranteed in advance. QoS is of particular concern for the continuous transmission of multimedia information and declares the ability of a network to deliver traffic with minimum delay and maximum availability.
Terrestrial Digital: Multimedia Broadcasting (T-DMB): This is a digital radio transmission system for sending multimedia to mobile devices based on the Eureka 147 DAB (Digital Audio Broadcasting) standard.
Media Forward Link Only (MediaFLO): This is a proprietary standard developed by Qualcomm to broadcast video and data to mobile devices such as cell phones. The data transmission path is one-way, from the tower to the device.