Satellite radio full report

Seminar Report ’03 Satellite Radio

1. INTRODUCTION

We all have our favorite radio stations that we preset

into our car radios, flipping between them as we drive to

and from work, on errands and around town. But when

travel too far away from the source station, the signal

breaks up and fades into static. Most radio signals can only

travel about 30 or 40 miles from their source. On long trips

that find you passing through different cities, you might

have to change radio stations every hour or so as the

signals fade in and out.

Now, imagine a radio station that can broadcast its

signal from more than 22,000 miles (35,000 kill) away and

then come through on your car radio with complete clarity

without ever having to change the radio station.

Satellite Radio or Digital Audio Radio Service

(DARS) is a subscriber based radio service that is broadcast

directly from satellites. Subscribers will be able to receive

up to100 radio channels featuring Compact Disk digital

quality music, news, weather, sports. talk radio and other

entertainment channels.

Satellite radio is an idea nearly 10 years in the

making. In 1992, the U.S. Federal Communications

Commission (FCC) allocated a spectrum in the "S" band (2.3

GHz) for nationwide broadcasting of satellite-based Digital

Department Of AEI MES College Of Engineering 1


Audio Radio Service (DARS).. In 1997. the FCC awarded 8-

year radio broadcast licenses to two companies, Sirius

Satellite Radio former (CD Radio) and XM Satellite Radio

(former American Mobile Radio). Both companies have been

working aggressively to be prepared to offer their radio

services to the public by the end of 2000. It is expected that

automotive radios would be the largest application of

Satellite Radio.

The satellite era began in September 2001 when XM

launched in selected markets. followed by full nationwide

service in November. Sirius lagged slightly, with a gradual

rollout beginning _n February, including a quiet launch in

the Bay Area on June 15. The nationwide launch comes July

1.

To the average user, these systems will look very

similar to conventional AM/FM .radio systems, whether they

are used in the home, office, or on the road. However. the

real difference is in what the listener won't see. Rather than

receiving a signal from a tower antenna of a local radio

station, these new radios will receive signals from a set of

satellites in geosynchronous orbit. Programming will be up

linked from ground stations to the satellites and then

broadcast back to large geographic areas.

The programming will be up linked to the three

geostationary orbit satellites and then rebroadcast directly

to radios in the vehicles of CD Radio subscribers. Ground



based repeaters will be used in urban areas to provide a

clear and uninterrupted radio signal.

Fig. 1 The satellite station



2. BASIC COMPONENTS OF SATELLITE

RADIO

Each company has a different plan for its

broadcasting system, but the systems do share similarities.

Here are the key components of the three satellite radio

systems:

SATELLITES

GROUND REPEATERS

RADIO RECEIVERS

At this time, there are three space-based radio

broadcasters in various stages of development:

XM Satellite Radio launched commercial service in limited

areas of the United States on September 25, 2001. (They

were originally going to launch service September 12. but

postponed the event because of the terrorist attacks on the

United States.)

Sirius Satellite Radio is now operational in the United

States, with its official launch on July I, 2002.

WorldSpace is already broadcasting in Africa and Asia, and

will begin broadcasting in South America sometime soon.

XM Satellite radio and Sirius Satellite Radio have both



launched such a service. Satellite radio, also called digital

radio, offers' uninterrupted, near CD-quality music beamed

to the radio from space.

Taking a closer look, you will see slight variances in the

three satellite radio companies' systems. In the next three

sections, we will profile each of the companies offering

satellite radio services.

2.1 SATELLITES

2.1.1 XM SATELLITE RADIO

XM Radio uses two Boeing HS 702 satellites,

appropriately dubbed "Rock" and "Roll," placed in parallel

geostationary orbit, one at 85 degrees west longitude and

the other at 115 degrees west longitude. Geostationary

Earth orbit (GED) is about 22.223 miles (35,764 km) above

Earth, and is the type of orbit most commonly used for

communications satellites. The first XM satellite, "Rock,"

was launched on March 18.2001, with "Roll" following on

May 8. XM Radio has a third HS-702 satellite on the ground

ready to be launched in case one of the two orbiting

satellites fails.

XM Radio's ground station transmits a signal to its two

GED satellites. Which bounce the signals back down to radio

receiver son the ground. and the downlink will be in the



2.33-2.34 GHz frequency range. A spare satellite will be

kept on the ground for emergencies. The radio receivers are

programmed to receive and unscramble the digital data

signal, which contains up to 100 channels of digital audio. In

addition to the encoded sound, the signal contains

additional information about the broadcast. The song title,

artist and genre of music are all displayed on the radio. In

urban areas, where buildings can block out the satellite

signal, ground transmitters supplement XM's broadcasting

system.

2.1.2 SIRIUS SATELLITE RADIO

Unlike XM, Sirius does not use OED satellites. Instead,

its three SS/L-1300 satellites form an inclined elliptical

satellite constellation. Sirius says the elliptical path of its

satellite constellation ensures that each satellite spends

about 16 hours a day over the continental United States ,

with at least one satellite over the country at all times.

Sirius completed its three-satellite constellation on

November 30, 2000. A fourth satellite will remain on the

ground, ready to be launched if any of the three active

satellites encounter transmission problems.

The Sirius system is similar to that of XM. Programs

are beamed to one of the three Sirius satellites, which then

transmit the signal to the ground where the radio

receiver picks up one of the channels within the signal.

Signals are also be beamed to ground repeaters for listeners



in urban areas where the satellite signal-can be interrupted.

While XM offers both car and portable radios, Sirius is

concentrating on the car radio market. The Sirius receiver

includes two parts -- the antenna module and the receiver

module. The antenna module picks up signals from the

ground repeaters or the satellite. Amplifies the signal and

filters out any interference. The signal is then passed on to

the receiver module. Inside the receiver module is a chipset

consisting of eight chips. The chip set converts the signals

from 2.3 gigahertz (GHz) to a lower intermediate frequency.

Sirius also offers an adapter that allows conventional car

radios to receive satellite signals.

2.1.3 WORLDSPACE

So far, WorldSpace has been the leader in the satellite

radio industry. It put two or its three satellites, AfriStar and

AsiaStar, in geostationary orbit before either of the other

two companies launched one. AfriStar and AsiaStar were

launched in October 1998 and March 2000, respectively.

AmeriStar, which will offer service to South America and

parts of Mexico, is not yet scheduled for launch. Each

satellite transmits three signal beams carrying more than 40

channels of programming, to three overlapping coverage

areas or about 5.4 million square miles (14 million square

km) each. Each of WorldSpace satellites' three beams can

deliver over 50 channels of crystal clear audio and

multimedia programming via the 1,467- to 1,492-

megahertz (MHz) segment of the L-band spectrum. which



is allocated for digital audio broadcasting.

AfriStar is positioned in a 210 East geosynchronous

orbit and is controlled by the WorldSpace Operations Center

located in Washington, DC. The prime contractor for the

satellite is Alcatel Space Industries, and Matra Marconi

Space built the EuroStar 2000+ satellite bus. The uplink

frequencies are 7.025-7.075 GHz, and the downlink

frequencies are 1.452-1.492 GHz. Each AfriStar downlink

spot beam has capacity for ninety-six 16 kbit/s mono-AM-

quality signals that can be combined for fewer channels of

higher audio quality. The downlink signals in each spot

beam are combined into two Time Division Multiple Access

(TDMA) carriers. Uplink signals can be. accepted as TDMA

signals from control stations or, individually, as Frequency

Division Multiple Access (FDMA) signals from originating

program locations.

WorldSpace also launched AsiaStar in March 2000, a

DBS radio satellite that currently covers Asia(1050 East

orbit). In late 2000, WorldSpace plans to launch AmeriStar

(950 West orbit) to cover Latin America.

The United States is not currently part of

WorldSpace's coverage area The company has

invested in XM Radio and has an agreement with

XM to share any technological developments .

WorldSpace is going beyond one nation and eyeing

world domination of the radio market. That might be

overstating the company's intent a bit. But



WorldSpace does plan to reach the corners of our

world that most radio stations cannot . There are

millions of people living in WorldSpace's projected

listening area who cannot conventional radio station.

WorldSpace says it has a potential audience of about 4.6

billion listeners spanning five continents.

Fig 2 WoridSpace will be able to broadcast to the majority of

the

world's population when its AmeriStar satellite is launched.

WorIdSpace broadcasters uplink their signal to one of

the three satellites through a centralized hub site or an

individual feeder link station located within the global uplink

beam. The satellite then transmits the signal in one, two or

all three beams on each satellite. Receivers on the ground

then pick up the signal and provide CD-quality sound

through a detachable antenna.



Fig. 3 World space integrated solution

2.2 GROUND REPEATERS

Satellite radio reception, poses threats from weather,

tall building_ and mountains that can potentially interfere

with broadcasts.

To avoid the interference caused by tall structures,

both Sirius and XM Radio are supplementing their satellite

coverage with terrestrial transmitters, called ground

repeaters. If the satellite radio antenna is blocked by a

skyscraper, it should pick up signals from one of the ground

repeaters.

Getting signals from a satellite to receivers in cars or



in the home is a tall order. Although the microwaves the

satellites rely on are able to penetrate the atmosphere from

space, they need a "direct line of sight" and can only reach

their target if unimpeded by obstacles such as trees,

houses, or thunderstorms. Therefore, ground-based

repeaters are needed to prevent service interruption in

cities where tall buildings otherwise would block the line of

sight between radio receivers and the satellites. XM has

employed more than 1,000 of these terrestrial repeaters,

which have been strategically placed throughout the

continental United States to receive the XM signal directly

from the satellites, and then retransmit it to XM radios in

cars and homes. These repeaters have been installed in

densely populated cities, on the roofs of buildings, and in

mountainous areas where line of sight can be difficult to

maintain.

2.3 THE SATELLITE RADIO RECEIVER

Existing AM/FM car radio will not be able to receive

satellite radio broadcasts. Two options are available.

Replacement of the radio with a 3-band capable receiver

(AM, FM, Sirius or XM Satellite). Radios can be purchased as

a dealer option or can be directly purchased at consumer

retail stores, mail order and Internet stores. All major

manufactures are prepared to provide radios capable of

satellite radio reception.

A second option is the purchase an adaptor for existing

AM/FM radios. The adaptor will contain the satellite receiver,



along with display and control functions. Sirius and XM have

developed slightly different technologies which mean that

you can purchase a radio capable of receiving satellite

broadcasts from one company or the other. but not both..

You need a receiver, about the size of squashed shoe box,

which goes under a car in the trunk, along with a fist-sized

antenna that sits on the roof or trunk lid.

The receiving end is virtually the same for both

companies, but the satellite configurations are different: XM

Radio will use two satellites, and Sirius will use a

combination three. These receivers, somewhat akin to

AM/FM tuners, are made up of two parts: an "active"

antenna and a receiving module.

XM and Sirius Radio will work similarly. Each will

beam a combination of original and syndicated

programming to orbiting communications and terrestrial

satellites which will send out signals to the satellite radio

receivers. These receivers, somewhat akin to AM/FM tuners,

are made up of two parts: an "active" antenna and a

receiving module.

The antenna is active because it basically looks for

available signals to pick up from. Satellites it recognizes.

When it finds them, it amplifies them, filters out any

accompanying noise and interference, and then sends them

to the receiver, where most of the real work is done. En

route to the receiver, the signals are converted from analog



to digital. Once in the digital realm, they are analyzed for

quality, and then processed and combined to produce the

best digital "image" of the sound. The receiver also decrypts

the signals and finally converts them back to analog audio,

which can be sent to the radio' s speakers so one can hear

it.

The receiver connects to your existing car radio

through a device called an FM modulator that puts the

signal on an unused portion of the FM band. Or you can buy

a car radio -- called a "head unit" by industry insiders --

that's "satellite ready" to make a direct wired connection for

maximum audio quality.

On the open road, the receivers pick up a signal from

orbiting satellites. Sirius and XM have also built repeater

stations on the ground in major metropolitan areas to

maintain reception when the satellites are blocked by

buildings or other large structures.

One receiver utilizes a vehicles existing FM radio. A

small flat 2" disk antenna is attached to the outside of the

vehicle, a processing unit is placed in the trunk or

dashboard and a display and control screen mounted next

to the vehicle's FM radio. The display screen indicates the

selected channel number, channel name, song title and

artist.



Each receiver contains a proprietary chipset. XM

began delivering chipsets to its XM radio-manufacturing

partners in October 2000. The chipset consists of two

custom integrated circuits designed by ST Microelectronics.

XM has partnered with Pioneer. Alpine, Clarion, Delphi

Deleo, Sony and Motorola to manufacture XM car radios.

Each satellite radio receiver uses a small, car-phone-sized

antenna to receive the XM signal. General Motors has

invested about $100 million in XM, and Honda has also

signed an agreement to use XM radios in its cars. OM began

installing XM satellite radio receivers in selected models in

early 2001.

WorldSpace satellite receivers are capable of

receiving data at a rate of 128 kilobits per second (Kbps).

The receivers use the proprietary StarMan chip set,

manufactured by STMicroelectronics, to receive digital

signals from the satellites

3. TRANSMISSION AND RECEPTION

Digital radio works by combining two digital

technologies to produce an efficient and reliable radio

broadcast system.

Firstly, an audio compression system, called MPEG,

reduces the vast amount of digital information required to

be broadcast. It does this by discarding sounds that will not

be perceived by the listener - for example, very quiet



sounds that are masked by other louder sounds - and hence

not required to be broadcast, and efficiently packages

together the remaining information.

The second technology, COFDM (Coded Orthogonal

Frequency Division Multiplex) ensures that signals are

received reliably and robustly, even in environments

normally prone to interference. Using a precise

mathematical relationship, the digital data signal is split

across 1,536 different carrier frequencies, and also across

time. This process ensures that even if some of the carrier

frequencies are affected by interference. or the signal

disturbed for a short period of time, the receiver is still able

to recover the original sound.

The interference which disturbs FM reception, caused

by radio signals "bouncing" off buildings and hills

(multipath) is eliminated by COFDM technology. It also

means that the same frequency can be used across the

entire country, so no re-tuning of sets is necessary when

traveling, or taking a portable receiver to a different area.

Instead of having a different frequency for each radio

station, digital radio combines several services together in

what is called a multiplex.

The multiplex has a gross capacity of 2,300,000 bits.

which are used for carrying audio, data and an in-built

protection system against transmission errors. Of these



about half the bits are used for the audio and data services.

Throughout the day, the data capacity allocated to each

service can be varied by the broadcaster.

The UK Government has allocated seven multiplexes

on the radio spectrum 217.5 230.0 MHz, which will be used

for BBC and Commercial Radio for national. regional and

local services. Each multiplex can carry a mixture of stereo

and mono audio Services and data services too; the number

of each dependent on the quality required.

3.1 GENERATION OF THE DAB SIGNAL

How each service signal is coded individually at

source level, error protected and time interleaved in the

channel coder is shown in Figure 3.1. Then the services

are multiplexed in the Main Service Channel (MSC),

according to a pre-determined, but adjustable, multiplex

configuration. The multiplexer output is combined with

Multiplex Control and Service information, which travel in

the fast Information Channel (FIC), to form the transmission

frames in the Transmission Multiplexer. Fig 3.1 Finally,

Orthogonal Frequency Division Multiplexing (OFDM) is

applied to shape the DAB signal, which consists of a large

number of carriers. The signal is then transposed to the

appropriate radio frequency band, amplified and

transmitted.



Fig 4 Generation of DAB signal

3.2 RECEPTION OF A DAB SIGNAL

Figure 3.2 demonstrates a DAB receiver. The DAB

ensemble is selected in the analogue tuner, the digitized

output of which is fed to the OFDM demodulator and

channel decoder to eliminate transmission errors. The

information contained in the FIC is passed to the user

interface for service selection and is used to setup the

receiver appropriately. The MSC data is further processed in

an audio decoder to produce the left and right audio signals

or in a data decoder (packet Demux) as appropriate.



User InterfaceFig. 5 DAB receiver

3.3 FREQUENCY OF OPERATION

Digital radio is operated in a frequency range of

between 215 - 230 MHz (Mega Hertz). This part of the radio

spectrum is sometimes called Band III, or VHF, and was

previously used for some television transmissions and by

the military. The central frequency for the BBC National

Multiplex is 225.648MHz.

3.4 MULTI PATH INTERFERENCE

Multipath interference occurs when radio waves

bounce off buildings, hills, or other obstacles. This means

the waves reach the set at different times, causing

interference. This is a particular problem in the car. Digital

radio sets have processors which filter out interference and

correct errors, such as those caused by multipath, so no



interference. In fact, digital radio is designed to use

multipath to its advantage.

4. ADVANTAGES OVER ANALOG RADIO

Conventional analog radio cannot meet this standard,

simply because of the technology used and the transmission

environment in which it is broadcast.

As well - unlike AM and FM - digital radio reception

is virtually immune to interference, which means there are

no static growls or 'multi path' echoes (caused by signal

reflections off buildings or topographical features) to make

listening unpleasant. at home, or in the car, In short, digital

radio eliminates the noise that creeps into analog radio

transmission and reception

The reason digital radio is so reliable is because it

employs a 'smart' receiver. Inside each digital radio receiver

there is a tiny computer: a computer capable of sorting

through the myriad of reflected and atmospherically

distorted transmissions and reconstructing a solid, usable

signal for the set to process.

In contrast, an un-intelligent analog receiver cannot

differentiate the useful information from the useless noise.

It reproduces the entirety of whatever signal it is tuned to:

static, 'multipath' echoes, and all.



5. CONCLUSION

For the listener, digital radio will be more than just

'the best sound on the airwaves', it will be an intelligent

communications device that will offer more services and

conveniences than can be provided by conventional analog

technology.

For the broadcaster, digital radio is not just a way

to stay competitive with other forms of digital sound, but

one that offers numerous new business opportunities as

well.

It is a bright future for listeners and broadcasters alike:

a future that truly promises to provide 'the best sound on

the airwaves' for the world.



6. BIBLIOGRAPHY

1. D. Prabakaran, “WORLD SPACE- Satellite digital audio

broadcast service”. Electronics For You. Nov 2001,

Volume 33, No:11.

2. www.xmradio.com

3. www.siriusradio.com

4. www.worldspace.com

5. www.howstuffworks.com



ABSTRACT

Satellites are one of the greatest achievements of

mankind. They have been used for various applications like

communication, military application, weather forecasting

and so on. They play a big role in the case of television

channels and other entertainment networks. One of the

latest applications of satellites is the satellite radio.

Satellite radio is a subscriber based radio service that

broadcast directly from satellites. It is an advanced form of

mobile radio service where one can receive compact disc

quality music and other entertainment channels. Even if the

person is miles away from the radio station, the quality of

the program is not affected. The paper deals with the basic

structure of the satellite radio and its transmission and

reception procedures.

CONTENTS

1 INTRODUCTION 1

2 BASIC COMPONENTS OF SATELLITE RADIO 3



SATELLITES 4

2.11 XM Satellite radio 4

2.12 Sirius Satellite radio

5

2.13 World space Satellite radio

6

GROUND REPEATERS 8

RADIO RECEIVETRS 9

3 TRANSMISSION AND RECEPTION 12

3.1 Generation of DAB signal

13

3.2 Reception of DAB signal

14

3.3 Frequency of operation 15

3.4 Multipath interference 15

4 ADVANTAGES OVER ANALOG RADIO 16

5 CONCLUSION 17

CERTIFICATE



ACKNOWLEDGEMENT

I extend my sincere gratitude towards Prof.

P.Sukumaran Head of Department for giving us his

invaluable knowledge and wonderful technical guidance

I express my thanks to Mr. Muhammed Kutty our

group tutor and also to our staff advisor Ms. Biji Paul for

their kind co-operation and guidance for preparing and

presenting this seminar.

I also thank all the other faculty members of AEI

department and my friends for their help and support.


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Satellite radio full report