PDF of this tutorialDelivery of IP–Based Streaming Services
Content providers, looking to distribute their targeted programming, typically deliver content from a central location to multiple remote locations simultaneously.
The IP multicast standard was developed to help minimize congestion when streaming bandwidth-intensive content over local-area networks (LANs) to the desktop. IP multicast allows multiple users to share one IP stream. Although IP multicast is important for local delivery of streaming content within a LAN, it does not overcome the limitations of terrestrial solutions for content delivery. Only satellites provide the option for ubiquitous (point-to-multipoint) delivery without incurring additional charges for delivery at each destination.
Satellites for Enterprises
Several well-known high-technology companies are already using satellites to deliver their IP streaming (e.g., corporate communications and training) content to the desktop at remote sites. These organizations recognized that satellites provide the critical advantage of bypassing the wide-area network (WAN) and dropping a video stream(s) directly from a rooftop antenna into a LAN.
For example, many companies have found that MPEG-1 video streams encoded at 1.5 Mbps produce acceptable video quality when viewed at the desktop. Most LANs have some ability to support 1.5 Mbps IP multicast services, yet total WAN bandwidth available to corporate offices is often limited to a single T1 circuit (1.536 Mbps). Smaller offices tend to have much less bandwidth. This bandwidth is needed to support e-mail, Internet access, and other business-critical applications. Such applications would be disrupted if organizations attempted to stream video content over a typical enterprise WAN. In addition, many enterprise WANs are not configured to support IP multicast transmissions, which makes it difficult to provide an effective solution.
Delivering the video stream by satellite enables enterprise networks to maximize the capabilities of an IP multicast stream by dropping the stream directly into the corporate office—eliminating the need to expand WAN capacity. This solution provides the best-case scenario for minimizing WAN bandwidth costs and traffic on each LAN.
As pictured, typical applications for business customers include the following:
- Transmission of multimedia (video and audio) content to the desktop
- Distribution of targeted subscription programming channels
Figure 1. Live and On-Demand Satellite Broadcasting
When evaluating the use of satellites for streaming content to enterprise networks, the satellite solution is economically feasible even with a few sites requiring access to the content. The solution becomes more cost-effective as the number of sites increases. The minimum number of sites varies by region because costs for alternative solutions vary regionally. Figure 2 provides a baseline for evaluation.
Figure 2. Minimum Number of Sites to Justify Satellite Distribution
Satellites for ISPs
To date, most streaming services on the Internet have been developed for low-bandwidth users with 28.8 kbps or 56 kbps modems. While existing infrastructure is adequate for these bandwidth requirements, it does not provide acceptable quality video to the desktop. As the need for bandwidth has increased, users have sought other means of enhancing their Internet access.
The emergence of digital subscriber line (DSL), cable modems, and other high-speed local access options has significantly increased the available bandwidth for residential and business users. Increasing connection speeds and the growing amount of content being streamed will dramatically increase the bandwidth requirements for ISPs. This growth in bandwidth is driving ISPs to seek cost-efficient bandwidth alternatives in order to meet customer expectations and control costs.
Content, technology, and service providers are taking advantage of satellites' ability to stream content over satellites for point-to-multipoint situations. Cable television has used this same model—broadcasting from one point to many points—for many years. Broadcasting content via satellite is economically viable for ISPs because they do not need to arrange for their own satellite link. The same amount of bandwidth can serve many ISPs at the same time.
Distribution of streaming content via satellite to ISPs is viable when the following things occur:
- Content being distributed is intended for Internet users
- Content is applicable to many people within a region or around the world
Satellite-Delivered Internet Services
While streaming content via satellite is becoming an increasingly important application, satellite transmission of Internet content has actually been viable for several years. Typical Internet use is an asymmetrical operation; users receive up to 10 times more data from the Internet than they transmit. The wide bandwidth of satellites can efficiently distribute information to ISPs (for relay to end users) while smaller pipes, either satellite or terrestrial, can be used to backhaul requests for information back to the Internet.
Internet Service Providers
The market for satellite delivery of Internet content is rapidly growing. Much of this growth is occurring outside the United States, where infrastructure is expensive or not available. Satellites provide several benefits that fuel the growth of Internet-provided services around the world:
- Satellites are wireless, so the only infrastructure required to activate the service at a remote site is the addition of a downlink system.
- In many areas of the world where telecommunications capabilities are underdeveloped or highly regulated, satellites provide the most cost-effective solution to ISPs looking to add Internet bandwidth.
The asymmetrical nature of Web interaction provides the opportunity to take advantage of DVB networks that maximize throughput on a transponder and minimize downlink antenna sizes. The typical configuration of a DVB–based network is shown in Figure 3. Since requests from a user to view a Web page require a small volume of data, they are supported using a low-speed backchannel. This backchannel could be a terrestrial or a satellite link as is appropriate for the site. Delivery of the Web-page information to the site requires a larger volume of data, so it is routed through the high-power DVB satellite link to an ISP and on to the end user.
Figure 3
DVB Internet access providers will soon offer services that will use satellites' capability to send point-to-multipoint information. Examples of these services include the following:
- Adding cache servers at ISP downlink sites to enable faster response times for end users. Cache servers have the ability to store popular Internet content locally at an ISP. Local storage of content enables end users to retrieve it faster. The information in these cache servers will be updated on a regional basis by satellite
- Bundling of streaming media services (as mentioned) with basic Internet access
Enterprise Networks
Many of the benefits of satellite-based Internet services for ISPs apply to the enterprise network. The applications apply to the delivery of Internet services, and even intranet services, for specific corporations.
The best opportunity for providing Internet or intranet services over satellite is to support multinational corporations with operations in many different countries, particularly developing nations. Many corporations are evaluating a hybrid terrestrial-satellite solution. In this solution, certain types of traffic, such as Internet services, are off-loaded to a satellite delivery service to ensure that Internet use by employees does not adversely impact mission-critical applications.
