Satellite radio

From Academic Kids

A satellite radio is a special digital radio that receives signals broadcast by communications satellite. This allows the listener to follow a single channel no matter where he or she is because the signal's reach is not limited by station power (as long as there are no major obstructions, such as buildings, in the line of sight between the antenna and the satellite).

Most services have news, weather, sports, and several music channels.

Contents

System design

Satellite radio uses the 2.3GHz S band in North America, and generally shares the 1.4GHz L band with local Digital Audio Broadcast (DAB) stations elsewhere. It is a type of direct broadcast satellite, and is strong enough that it requires no satellite dish to receive. Curvature of the Earth limits the reach of the signal, but due to the high orbit of the satellites, two or three are usually sufficient to provide coverage for an entire continent.

Local repeaters similar to broadcast translator boosters enable signals to be available even if the view of the satellite is blocked, for example, by skyscrapers in a large town. Major tunnels can also have repeaters. This method also allows local programming to be transmitted such as traffic and weather in major metropolitan areas, though this is not yet implemented.

Each receiver has an electronic serial number (ESN) to identify it. When a unit is activated with a subscription, an authorisation code is sent in the digital stream telling the receiver to allow access to the blocked channels. Most services have at least one "free to air" or "in the clear" (ITC) channel as a test, and some outside the U.S. have a few free programming channels, though this may end up being a bait and switch tactic to lure more listeners until satellite radio gains more widespread use.

Most (if not all) of the systems in use now are proprietary, using different codecs for audio data compression, different modulation techniques, and/or different methods for encryption and conditional access.

Like other radio services, satellite radio also transmits program-associated data (PAD or metadata), with the artist and title of each song or programme, and possibly the name of the channel.

United States

In the United States, two companies dominate satellite radio: XM Satellite Radio and Sirius Satellite Radio. A monthly fee is charged for both services (as of 2005 Sirius also offers a one time fee of nearly $500 valid for the lifetime of the equipment). Originally some XM music channels had commercials, while Sirius was commercial-free. As of March 2005 XM has 67 commercial-free music channels; 39 channels of news, sports, talk, and entertainment; 21 dedicated traffic and weather channels, 23 play-by-play sports channels, and a premium channel. Sirius has 65 music-only channels as well as traffic and weather reports for major cities. XM operates on two geostationary satellites while Sirius uses three geosynchronous satellites. Both services are available mainly via portable receivers in automobiles, but both have many accessories so one can listen at home through a home stereo, with a portable boombox, or online through a personal computer.

Some critics of the service have expressed concerns that satellite radio will lead to a decline in the number and variety of local radio stations and programming and greater concentration of mass media in the hands of fewer companies, and a loss of jobs in the radio industry. There are also concerns that the ability to transmit local channels on repeaters, which is currently prohibited by FCC regulation, is only a rulemaking proceeding away from being legalized and further threatening existing local broadcasters.

The footprint of both Sirius and XM is only the continental U.S.; it does not cover Hawaii, nor even Alaska as satellite TV does.

Success so far

As of April 1, 2005, XM claimed 3.7 million subscribers, and Sirius claimed 1.1 million.

One critical factor for the success of satellite radio is the deployment of in-car receivers. Both Sirius and XM have attempted to convince carmakers to equip vehicles with their receiver. As of 2005, the following manufacturers offer satellite radio as original equipment:

Canada

On November 1, 2004, the Canadian Radio-television and Telecommunications Commission (CRTC) began hearing applications for Canada's first satellite radio operations. Three applications have been filed: one by Standard Broadcasting and the CBC in partnership with Sirius, one by Canadian Satellite Radio in partnership with XM, and one at the last minute by CHUM Limited and Astral Media.

The first two would use the same systems already set up for the U.S., while CHUM's application is for a subscription radio service delivered through existing terrestrial DAB transmitters rather than directly by satellite (although satellites would be used to deliver programming to the transmitters). The CHUM service is all-Canadian; the other two applications propose to offer a mix of Canadian-produced channels and existing channels from their American partner services. All would comply with Canadian content rules.

A small "grey market" already exists for Sirius and XM receivers in Canada.

On June 16, 2005, the CRTC approved all three services. Official launch dates are not yet known.

United Kingdom

In the United Kingdom, satellite radio is delivered by Sky Television as part of their satellite television service. As of June 2004, there were around 90 radio stations on the Sky Digital service. Unlike in the U.S., where satellite radio is seen as a way of gaining additional choice, most major radio stations in the U.K. also simulcast on satellite radio. Reception is currently limited to stationary receivers, and is not available in automobiles.

See also: digital audio broadcasting

Asia, Africa and most of Europe

WorldSpace has its own satellites covering most of Europe, Asia and Africa. The signal can be received by specialised WorldSpace receivers. Many of the programs are available only to subscribers.

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