Assignment for Mobile Satellite

8/6/2019 Assignment for Mobile Satellite

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1.

Radio Communication

Service

Frequency Band (uplink /

downlink) GHz

Terminology

Fixed Satellite Service

(FSS)

6 / 4 C band

8 / 7 X band14 / 11 – 12 Ku band

30 / 20 Ka band

50 / 40 V band

Mobile Satellite Service

(MSS)

1.6 / 1.5 L band

30 / 20 Ka band

Broadcasting Satellite

Service (BSS)

2 / 2.2 S band

12 Ku band

2.6 / 2.5 S band

FSS

Above 30 GHz is for technology development

20 – 30 GHz has little interference, large bandwidth

12 – 14 GHz for Satellite broadcasting for MEASAT 3a

7 – 8 GHz reserved by agreement between administrators or governmental use

4 – 6 GHz TV broadcasting service such as ASTRO

The services implement Point to Point communication and network via

satellite between fixed Stations and utilize C-Band and lower power portion of Ku-

Band spectrum. Very Small Aperture Terminal (VSAT) is an application for fixed

Satellite Services. VSAT services provide wide area coverage, offers borderless

communication within the satellite coverage area and reachable to remote areas with

digital transmission such as oil rig far out at sea and a station in a dense tropical

jungle. VSATs are most commonly used to transmit narrowband data (point of sale

transactions such as credit card), or broadband data (for the provision of Satellite

Internet access to remote locations, VoIP or video).



MSS

The Services implement Point to Point communication and network via

satellite between mobile stations. Services are available to the maritime users and

land users in any locations that require long distance portable telephony, fast and

instantaneous communications setup. Satellite phone is a type of mobile phone that

connects to orbiting satellites instead of terrestrial cell sites. Depending on the

architecture of a particular system, coverage may include the entire Earth, or only

specific regions.

The mobile satellite service makes use of the following bands:

a. VHF (very high frequency, 137 – 138MHz downlink and 148 – 150MHz uplink)

and UHF (ultra high frequency, 400 – 401MHz downlink and 454 – 460MHz

uplink). These bands are for non-geostationary systems only.

b. About 1.6GHz for uplinks and 1.5GHz for downlinks, mostly used by

geostationary systems such as INMARSAT; and 1610 – 1626.5MHz for the

uplink of non-geostationary systems such as GLOBALSTAR.

c. About 2.2GHz for downlinks and 2GHz for uplinks for the satellite component

of IMT2000 (International Mobile Telecommunications).d. About 2.6GHz for uplinks and 2.5GHz for downlinks.

e. Frequency bands have also been allocated at higher frequencies such as Ka

band.

BSS

Broadcasting Satellite system is the services for distribution of video and

audio streams through satellite. Usually utilize Ku-Band and propagate circular

polarization wave pattern; however there is a trend for Ka-Band for broadband

application. Astro is a subscription-based direct broadcast satellite (DBS) or direct-to-

home satellite television and radio service initially in Malaysia and is broadcast high-

power Ku-band transmissions utilizing the transponders of the MEASAT satellite

system.

The broadcasting satellite service makes use of downlinks at about 12 GHz.The uplink is operated in the FSS bands and is called a feeder link.



Typically, there are four types of base station as follows.

i. Macrocell

- Macrocell provides radio coverage served by a power cellular base

station. It is suitable to be deployed in location where no existing

coverage. The coverage is approximately 6km while the area is 80km2.

- The antennas for macrocells are mounted on ground-based masts,

rooftops and other existing structures, at a height that provides a clear

view over the surrounding buildings and terrain. Macrocell base

stations have power outputs of typically 10 watts.

ii. Microcell

- To improve signal strength or increase capacity in a smaller area then a

microcell may be used. This has a range of approximately 300 meters

in the best conditions.

- Several microcell base stations can also be used as an alternative to a

single macrocell. Microcells can also be used temporarily at big public

events where the existing local system is insufficient.

iii. Picocell

-

Picocells are used in places like airports, offices or shopping centreswhere call numbers can be very high. They have a range of somewhere

between 50 and 100 meters.

iv. Femtocell

- Femtocell has the least area of coverage which is normally

implemented for home or small office. The range of coverage is 10

meters.



2. i.

Geosynchronous Orbit

A geosynchronous orbit is also known as geostationary orbits, because

satellites in these orbits circle the Earth at the same rate as the Earth spins. The

satellite takes 23 hours, 56 minutes, and 4.09 seconds to make one full revolution at

approximately 35,790 km above the Earth. The satellites are located near the equator

since at this latitude, there is a constant force of gravity from all directions.

Geosynchronous orbits allow the satellite to observe almost a full hemisphere

of the Earth. These satellites are used to study large scale phenomenon such as

hurricanes, or cyclones. Since these satellites are very far away, they have poor

resolution. The disadvantage is that these satellites have trouble monitoring activities

near the poles.

LEO and MEO Orbit

As technology has progressed, low-altitude earth orbits (LEOs; less than 600

mi or 1000 km) and medium-altitude earth orbits (MEOs; less than 8000 mi or 14,400

km) have acquired some distinct advantages for mobile services. The lower-altitude

satellites have much shorter paths from base stations and mobile earth terminals as

compared with satellites in geostationary orbit. Thus RF power requirements and path

delay are much smaller. The consequence is that the mobile earth terminals can use

low-gain antennas that need little or no tracking while still using low-power

transmitters and the system does not degrade from delay with multiple hops.

Molniya Orbits

Another orbit use in communication satellite is Molniya orbit which is highly

inclined to guarantee good elevation over selected positions during the northern

portion of the orbit. A satellite at the horizon has zero elevation and a satellite directly

overhead has elevation of 90 degrees. Furthermore, the Molniya orbit is designed so

that the satellite spends the great majority of its time over the far northern latitudes,

during which its ground footprint moves only slightly. Its period is half day, so that

the satellite is available for operation over the targeted region for nine hours every

revolution. Therefore, three Molniya satellites can provide uninterrupted coverage.



ii.

F = Gravitational Force

√

But,

√

√

Where

r is the radius from center of earth,

m is the mass of earth, 5.97 x 1024

G is gravitational constant, 6.67 x 10-11



iii.

using the equation derived in ii,

√

√

r = 42,227 km

h = r – radius of earth

h = r – 6378

h = 35,849 km

iv.

Apply the formula derived in ii,

Given h = 500 km

r = h + radius of earth

r = 500 km + 6378 km

= 6878 km

√

√



Antenna Gain

To calculate Gtransmitter,

Gtransmitter = η (πD/λ 2)

For efficienct of 55%,

Gtransmitter (dBi) = 20 log (D/λ) + 7.3

Transmit Power

To calculate Ptransmit,

SNR = Preceiver – Pnoise

but,

Preceiver = Ptransmit + Gtransmitter + Greceiver – Losses

Therefore,

SNR = Preceiver – Pnoise

Ptransmit = SNR – Gtransmitter – Greceiver + Losses + Pnoise

but

Pnoise = 10 log (K Tsystem B) where Tsystem = Treceiver + Tantenna

Therefore,

Ptransmit = SNR – Gtransmitter – Greceiver + Losses + 10 log (K Tsystem B)

Free Space Loss

LFS = 20 log [4πR/λ]



3. Given that, SNR = 10 dB, E= 15°, f=10GHz, Gr=30dBi

λ = c/f, = 3mm

Assumption:

a. Diammeter of antenna is 2m

b. Efficiency of antenna is 55%


= 20 log (2/3mm) + 7.3

= 43.78 dBi

Referring to table 30, at 10GHz,

Tantenna = 85K, Treceiver = 75K

Tsystem = Tantenna + Treceiver

Tsystem = 160K

Pnoise = 10 log (K Tsystem B)

Pnoise = – 106.56 dBW


Since the height of the satellite from the earth surface is 35849 km,

LFS = 20 log [4π(35849km)/3mm]

= 223.53 dB

Accoding to Figure 5.30,

The Elevation of 15° produces atmospheric loss of 0.2 dB


= 10 – 43.78 – 30 + 223.53 + 0.2 – 106.56

= 53.39 dBW



4. R=500km, f=1.5GHz, E=60°, G=3dBi

λ = c/f, = 200mm

Assumption:

a. Diammeter of antenna is 2m

b. Efficiency of antenna is 55%


= 20 log (2/200mm) + 7.3

= 27.30 dBi

Referring to table 30, at 1.5 GHz,

Tantenna = 35K, Treceiver = 35K

Tsystem = Tantenna + Treceiver

Tsystem = 70K

Pnoise = 10 log (K Tsystem B)

Pnoise = 10 log [K (70) (1.5GHz)]

Pnoise = – 118.39 dBW


Since the height of the satellite from the earth surface is 500 km,

LFS = 20 log [4π(500km)/200mm]

= 149.94 dB

Since the frequency is less than 10 GHz, the atmospheric attenuation is negligible.


= 10 – 27.30 – 3 + 149.94 – 118.39

= 11.25 dBW



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Assignment for Mobile Satellite

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