Milestone Technologies Inc. PO Box 37145 Raleigh, NC 27627 phone: (919) 856-0700 fax: (919) 856-8600 www.milestonetechnologies.com info@milestonetechnologies.com Setting Up A Data Broadcasting Network This article explains what data broadcasting is at a fundamental level. Subsequent sections provide information needed to help understand what is involved in setting up a data broadcasting network. 1.0 What is Data Broadcasting? In the simplest of terms, data broadcasting, sometimes called datacasting, is the distribution of data from a single location to multiple locations at the same time. Most data is distributed today using point to point communications methods. In point to point communications, if you want to send a one megabyte file to 500 locations, you must send it 500 times, once to each destination. The typical modem connection from one PC to another is a common example of point to point communications. An analogy to help explain data broadcasting would be to think of how people communicate at a party or a large gathering. If you have several friends with whom you would like to speak, you might have a conversation with each of them, one at a time, before the party is over. You would each have something to say and thus have a two-way conversation. This is an example of point to point communications. If you are the host of the event and you have something to say to a large number of guests, they would listen as you broadcast your message to everyone at the same time. This analogy illustrates certain principles about data broadcasting. As a recipient (the receiver) of a broadcast message, you can only listen to what the person talking (the transmitter) has to say. You do not have the opportunity to say something back during the middle of the broadcast if you missed a word or did not hear a part of the message. Data broadcasting is much the same way. The receiving computers can only listen to the incoming broadcast message. They are not able to respond to the sender while the broadcast message is being sent. In a pure broadcast only system, the receivers have no way to communicate with the host. It is often desirable for the host to be able to confirm that the remote sites actually received the data that was sent. These are communications methods employed in addition to the broadcast system, and are not typically considered to be part of it. Options for implementing return paths will be discussed later. You are already familiar with the concepts of broadcasting. Each time you listen to your radio or watch TV, you are experiencing the results of a broadcast. The radio or TV are simply receivers which can listen to the incoming messages. They do not have a way to communicate with the station that sent the message. The station that broadcasts the programs does not have a way to determine if these programs are being received, or if the TV or radio receiver is even turned on. In data broadcasting, instead of just sending sound and images, any type of information can be broadcast. This includes data files, software programs, digital video or digital audio. 2.0 Why Use Data Broadcasting? Data broadcasting has several advantages. The most obvious is that it permits data to be sent to a virtually unlimited number of locations in about the same amount of time as it takes to send it to one or two locations. If you only have three of four locations which require the same data, this might not sound like a big deal. If you are the owner of a chain of stores with 10,000 locations spread across the United States, and you need to get the same data to them every day, then data broadcasting is the obvious choice. The same logic would apply if you operate an information distribution business with thousands of subscribers. Data broadcasting is typically used when one or more of the conditions below is met. Data broadcasting is ideal if you have- 1) a large number of locations which need the same data 2) a significant amount of data to send on a regular basis 3) a need for the data to be delivered in a timely manner 4) reliability and security issues to consider 5) a need to keep communications costs low even when the number of sites increases 3.0 Why Not Just Use The Internet? The Internet is growing rapidly as a means of delivering data to a large number of locations. No doubt to some extent it has been able to serve as a replacement for some low speed data broadcasting networks. The Internet still has limitations that prevent it from serving as a replacement for many data broadcast needs. Problems with speed and reliability continue to limit the usefulness of the Internet for delivering mission critical data to a large number of locations in a timely manner. This is especially true if data must be delivered during the business day when peak usage can clog the Internet's resources, reducing effective data rates for communications. Concerns relating to security when sending sensitive data over the Internet are still sufficient to motivate many companies to maintain their own private networks. In the long run, the Internet may grow sufficiently in infrastructure and bandwidth to allow a greater number of data distribution needs to be met than what is currently handled today. Increased usage of IP multicasting technologies will help to more efficiently utilize available net resources. Work is underway to increase the available data capacity of the Internet. Growth in the demand for bandwidth at the present time seems to be increasing more rapidly than the capacity can be increased. In the short term, it seems likely that the increased usage of the net will cause a strain on its resources that further limit its usefulness as a reliable point to multi-point distribution medium. This increases the desirability and advantages of utilizing a dedicated data broadcasting system not dependant on the Internet. 4.0 What Is Involved In Assembling A Data Broadcasting Network? A data broadcasting network consists of three basic elements as follows: 1) a distribution means, such as Direct Broadcast Satellites (DBS) 2) the hardware for each receive site, such as a satellite dish and data receiver 3) the software to transport and manage your data We will look at each of these elements very briefly. 4.1 The Distribution Means When considering a distribution means, you must take into account a number of factors. These factors to be generally considered are: a) the geographic area over which your sites are located b) the type of sites (business or consumer) to be reached c) the type of data to be distributed (files, real time audio or video, etc.) d) how much data you need to send e) the time sensitivity of the data (how quickly does it need to get there?) f) your budget for hardware and software for each site g) your budget for communications time h) requirements for feedback from each site to the host All of these factors considered together will help you to narrow down your choices to the methods that best suit your needs. The options most commonly used for data broadcasting are listed below. a) Direct Broadcast Satellites (DBS) b) Two-way Very Small Aperture Terminals (VSAT) satellite services c) FM subcarriers d) Vertical Blanking Interval (VBI) of analog TV signals (In the future, DTV (Digital Television) or HDTV (High Definition Television) will likely play a major role in data broadcasting.) There are advantages and disadvantages to each of these methods, but for most corporate applications where data broadcasting is the primary means of distributing data to remote locations, DBS systems offer some of the best capabilities for the money invested. They typically offer low cost flexible hardware, high speed data channels, fixed communication costs, and wide area coverage. The reliability of today's systems is excellent. 4.2 Hardware Required At Each Receiving Location The hardware required at each receive site depends on the medium chosen for distributing data. Typically you will need some type of receiving antenna, a data receiver, and usually a connection to a PC or a terminal to process and utilize the incoming data. For a DBS system, small dishes of one meter in diameter or less are often utilized in connection with a digital high speed data receiver. The data receiver may be connected to a PC using either LAN or serial ports. Many models available today can handle a variety of data rates from 1200 bits/sec up to several megabits/sec. For multimedia applications, different hardware may be required depending upon the type of data to be distributed. For example, if you intend to transmit digital video and/or audio to be received and viewed real time, you will need hardware and displays to accommodate that. If however, you only intend to transmit the digital multimedia files containing the data for later playback, then your equipment and bandwidth requirements will be different than those of a real time system. The latter approach to transmitting digital video and audio, is sometimes referred to as a store and forward system. It is usually less costly to implement a store and forward system than it is to implement a real time digital video network because bandwidth (data rate) requirements are usually lower. 4.3 Data Broadcasting Software Data broadcasting software may be needed to perform a variety of functions depending on the type of data to be distributed, the hardware utilized, and the intended usage of the network. For example, data broadcasting software may be needed to a) transmit files reliably b) configure and manage the network hardware (perform addressing, port configurations, etc.) c) schedule and manage data broadcast sessions (what data goes to which sites, when, etc.) d) handle the transmission and playing of real time digital video or audio e) other special functions as the application may dictate MTI's SATX software is primarily designed as a file transfer tool. New products under development will help to serve other functions relating to data broadcast scheduling, management and addressing. Your hardware vendor may provide software to help configure and control various functions associated with the data receivers. Care must be taken to integrate the data broadcast software with the application software so that the two can work together seamlessly. Basically, the application software needs to know when a file has been received, and what to do with that file once the data broadcast software has indicated that the download is complete and error free. 5.0 Deciding on a Network Architecture If you are creating a data broadcast network, you have one of three basic options to choose from. These options are: a) One-way (1-way) or pure broadcast network- no feedback from remote sites to host b) One and a half way (1 1/2) network- limited feedback is provided to the host from receive sites c) Two-way (2-way) network- remote sites can send and receive data The option you choose depends on the amount of data which needs to be sent from the receive sites back to the host. If you have a reliable data broadcasting network and do not have a requirement to receive confirmations of file deliveries or feedback from the remote sites, then a one way system may work fine for you. This is known as a pure broadcast system, where truly all of the information is one- way, and no feedback is sent from the receive sites back to the host. Many DBS systems are pure broadcast networks. Milestone Technologies' SATX software works well in pure broadcast systems. In many situations, even though the majority of the information is outbound from the host to the remote sites, the need still exists to send data from the receiving sites back to the host. Some type of return path must be established. This return path can be used to confirm the delivery of data files or it can be used to send back diagnostic monitoring logs. It could even be used to replace a lost segment of a large file that was not received during the broadcast. In systems where most of the information is sent to the remote sites and only a relatively small percentage is sent from the remote sites back to the host, a one and a half way system works well. The return data path in a one and a half way system may be a simple dial up line but other physical methods are possible. The Internet, for example, is often acceptable as a return path. The key here is that the benefits of a data broadcast network are still realized, but a return path can greatly enhance the value, confidence, and in some cases, the reliability of the broadcast system. Some applications require a two way link to be established to each site. The amount of data sent from a remote site back to the host may be almost as great in volume as the amount of data it receives. In these situations, a two-way network is the only practical solution. A two way VSAT (Very Small Aperture Satellite) network is often implemented to serve these needs. Since the system is a satellite network, it is important to realize that a natural data broadcast capability is by default a part of the system. This is because most satellite hardware can be placed in a "broadcast mode" so that all sites, or a specific group of sites, can receive incoming data that is broadcast simultaneously. Therefore, even in two-way satellite systems, data broadcasting can still be used to maximize bandwidth and efficiently deliver large amounts of information to multiple sites, or even the entire network simultaneously. 6.0 Learning More This introductory overview has only scratched the surface regarding what is needed to create a data broadcasting network. If you would like to learn more, additional information is available on this site. Choose the "Learn More" menu section for additional articles to download. The best way to learn about how to set up your own data broadcast system is to contact Milestone Technologies Inc. and let us help you with your projects. (C) Copyright 1999, Milestone Technologies Inc. All Rights Reserved SATX(TM) is a trademark of Milestone Technologies Inc.