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Mobile satellite communication & vsat Supervised by: Dr. Hasan Abbas Presented by: E. Nagham Abbas WHY SATELLITE?

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slide2
Supervised by:

Dr. Hasan Abbas

Presented by:

E. Nagham Abbas

slide3

WHY SATELLITE?

As internet traffic continues to grow at exponential rates world wide, internet services providers (ISP’S) everywhere are faced with the challenge of keeping up with demand for network bandwidth . Satellite-based internet connections are one of those solutions . Vsat has offered ISP’S and telecommunications service providers easily scalable.

key benefits
1- faster installation:

Satellite services are usually activated much more quickly

than terrestrial fiber. An antenna , modem and satellite

circuit can be provisioned in a few weeks.

As a network grows, additional capacity can be obtained

in just as short a time.

KEY BENEFITS:
2 better network performance
2-better network performance

Satellite connections enhance network performance by linking directly

to an internet backbone, bypassing congested Terrestrial lines and

numerous router hops. In addition, dedicated Space segment, local

loop circuits and ports into a major Internet backbone mean ISP’s

do not share infrastructure, Another reason for slow or degraded

connections over the traditional fiber line.

3 lower network costs
3-lower network costs:

The broadcast nature of satellites allows for the simultaneous

delivery of information to wide geographic areas without regard

to terrestrial infrastructure or geographic barriers.

This translates into a pricing structure that is distance insensitive,

keeping costs down for international ISP’s, in addition, satellite

capacity is easily matched to actual traffic patterns, meaning ISP’s

pay only for what they need.

network architecture
Network architecture

the network architecture consists of the three entities:

  • user segment
  • ground segment
  • space segment.
network architecture cont
Network Architecture (cont)
  • The User Segment: The user segment comprises of user terminal units:

Terminals can be categorised into two main classes:

  • Mobile terminals :Mobile terminals can be divided into two categories: mobile personal terminals and mobile group terminals.

Mobile personal terminals :often refer to hand-held and palm-top devices, on board a mobile platform, such as a car.

the user segment cont
The User Segment (cont)

Mobile group terminals:

are designed for group usage and for installation on board a

collective transport system such as a ship, cruise liner, train, bus

or aircraft.

  • Portable terminals: lap-top computer.
slide11
The Ground Segment:

The ground segment consists of three main network elements:

  • gateways, sometimes called fixed Earth stations (FES)
  • the network control centre (NCC)
  • the satellite control centre (SCC).
slide12
the ground segment
  • Gateways provide fixed entry points to the satellite access network by public switched telephone network (PSTN) and public land mobile network (PLMN) .

Figure 2.2 shows a gateway’s internal structure:

slide13
the ground segment

the traffic channel equipment (TCE) and RF/ IF components

together form the gateway transceiver subsystem (GTS).

The gateway subsystem (GWS) consists of both the GTS and the

gateway station control (GSC).

  • The NCC, also known as the network management station

(NMS) is connected to theCustomer information Management

System (CIMS) to co-ordinate access to the satellite resource and

performs the logical functions associated with network

management and control.

the ground segment
the ground segment

these two logical functions can be summarized as

follows:

  • Network management functions: The network management functions include:
  • Development of call traffic profiles
  • System resource management and network synchronisation
  • Operation and maintenance (OAM) functions
  • Congestion control
  • Provision of support in user terminal commissioning
  • Call control functions include:
  • Common channel signalling functions
  • Definition of gateway configurations
slide15
the ground segment
  • The SCC monitors the performance of the satellite constellation and controls a satellite’s position in the sky.
  • The CIMS is responsible for maintaining gateway configuration data;and processing call detail records.
  • The Space Segment:

The space segment provides the connection between the users of

the network and gateways.

The space segment consists of one or more constellations of

satellites each with an associated set of orbital and individual

satellite parameters.

satellite constellations
Satellite Constellations

Satellites can be positioned in orbits with different heights and shapes

(circular or elliptical). Based on the orbital radius, all satellites fall into

one of the following three categories;

1. LEO: Low Earth Orbit.

2. MEO: Medium Earth Orbit.

3. GEO: Geostationary Earth Orbit.

The orbital radius of the satellite greatly effects its capabilities and

design.

Satellites are also classified in terms of their payload. Satellites that

weigh in the range of 800-1000 kg fall in the "Small" class, whereas

the heavier class is named as "Big" satellites. GEO satellites are

typically "Big" satellites, whereas LEO satellites can fall in either class

satellite constellations18
Satellite Constellations
  • Table 2 summarizes the design issues related to different type of satellite constellations.
slide19
Operational Frequency:

Mobile-satellite systems now operate in a variety of frequency bands,

depending on the type of services offered.

Communications between gateways and satellites, known as feeder

links, are usually in the C-band or Ku-band, although recently the

broader bandwidth offered by the Ka-band has been put into operation

by satellite-personal communication Network (S-PCN) operators.

logical channels
Logical Channels:
  • Traffic Channels:

Mobile-satellite networks adopt a similar channel

structure to that of their terrestrial counterparts.

They are divided into traffic channels and control

channels.

Satellite-traffic channels (S-TCH) are used to carry

either encoded speech or user data.

slide22
traffic channel (Cont )

Four forms of traffic channels :

  • Satellite full-rate traffic channel (S-TCH/F): Gross data rate of 24 kbps
  • Satellite half-rate traffic channel (S-TCH/H): Gross data rate of 12 kbps
  • Satellite quarter-rate traffic channel (S-TCH/Q): Gross data rate of 6 kbps
  • Satellite eighth-rate traffic channel (S-TCH/E): Gross data rate of 3 kbps
slide23
traffic channel (Cont)

These traffic channels are further categorised into speech traffic channels and data traffic channels.

Table 2.2 summarises each category.

control channels
Control Channels:

Control channels are used for carrying signalling and

synchronisation data.

[Table 2.3 summarises the different categories]

slide28

Logical Channels (cont):

  • Additional logical channels in the physical layer
land mobile channel characteristics

Land Mobile Channel Characteristics:

Introduction

there are two types of channel to be considered: the mobile channel, between the mobile terminal and the satellite.

the fixed channel, between the fixed Earth station or gateway and the satellite.The basic transmission chain is shown in Figure 4.1.

In a mobile’s case, the local operational environment has a significant impact on the achievable quality of service (QoS).

In the mobile-link, a service availability of 80–99% is usually targeted, whereas for the fixed-link, availabilities of 99.9–99.99% for the worst-month case can be specified.

local environment
Local Environment
  • The received land mobile-satellite signal consists of the combination of three components:
  • the direct line-of-sight (LOS) wave.
  • the diffuse wave.
  • the specular ground reflection.

The direct LOS wave arrives at the receiver without reflection from

the surrounding environment. The only L-/S-band propagation

impairments that significantly affect the direct component are free

space loss (FSL) and shadowing. FSL is related to operating

frequency and transmission distance. Systems operating at above

10 GHz need to take into account tropospheric impairments

Shadowing occurs when an obstacle, such as a tree or a building,

impedes visibility to the satellite.

local environment31
Local Environment

The diffuse component comprises multipath reflected signals

from the surrounding environment, such as buildings, trees and

telegraph poles.

The specular ground component is a result of the reception of the

reflected signal from the ground near to the mobile.

three broad categories:

† Urban areas, characterised by almost complete obstruction of the direct wave.

† Open and rural areas, with no obstruction of the direct wave.

† Suburban and tree shadowed environments, where intermittent

partial obstruction of the direct wave occurs.

channel characteristics
Channel Characteristics

if the signal power can be reduced while maintaining the same

grade of service (BER).

This can be achieved by adding extra or redundant bits to the

information content, using a channel coder.

The two main classes of channel coderare: block encoders and

convolutional encoders.At the receiver, the additional bits are

used to detect any errors introduced by the channel.

There are two techniques employed in satellite communications

to achieve this:

† Forward error correction (FEC), where errors are detected and

corrected for at the receiver;

† Automatic repeat request (ARQ), where a high degree of

integrity of the data is required, and latency is not a significant

factor.

location management
Location Management:
  • Operations:

Location management is concerned with network functions that allow

mobile stations to roam freely within the network coverage area. It is

a two-stage process that allows the network to locate the current

point of attachment The first stage is location registration or location

update, while the second stage is the call delivery as shown in Figure

(6.3) .

  • In the location registration stage, the mobile station periodically

notifies the network of its new point of attachment, allowing the

network to authenticate and to update the user’s location profile.

  • In the call delivery stage, the network queries the user’s location

profile and locates the current position of the mobile terminal by

sending polling signals to all candidate access ports through which

an MS can be reached.

handover management
Handover Management:
  • Phases of Handover: Handover management ensures that an active call connection is maintained when the mobile terminal moves and changes its point of attachment to the network. Three main phases are involved in handover:
  • handover initiation.
  • handover decision .
  • handover execution.

The main task involved in the handover initiation phase is

gathering of information such as the radio link measurements.

slide37
phases of handover (Cont)

If the radio link quality falls below a predefined threshold, a

handover will be initiated.

Based on measurements, the handover decision phase will select

the target resources.

In handover execution, new connections are established and old

connections are released by performing signalling exchanges

between the mobile terminal and the network .

A handover can be initiated due to poor radio link performance

or other QoS degradation.

handover types
Handover types:

Stand-alone Satellite Network: handover occurs due mainly to

the motion of the satellite.

there are two main handover categories:

1-Intra-FES Handover: This type of handover occurs due to

the change of spot-beams caused by the motion of the satellite.

The satellite motion sults in a change or degradation in the radio

link quality, rewhich is then used to determine whether a handover

should be initiated.

This type of handover is further divided into:

  • inter-beam handover.
  • inter-satellite handover.
slide40
intra FES handover
  • Inter-beam handover refers to the transfer of a call from one

spot-beam to another of the same satellite.

Such handover is due mainly to the satellite motion.

  • Inter-satellite handover refers to the transfer of a call from

one satellite to another, This type of handover is due to the

low elevation angle as a result of the satellite motion.

As the elevation angle becomes lower, the propagation path

loss and the depth of shadowing increase, resulting in a

decrease in the received power.

inter fes handover
Inter-FES Handover:

Inter-FES handover refers to the change from one FES to another

during a call. in order to avoid frequent changes in the signalling

and traffic link, it is usual that the call would still carry on with

the original FES. This FES is called the anchor FES during the

handover process.

slide45
inter FES Handover (Cont )

inter-FES handover is rare – only mobile terminals associated

with a high degree of mobility, such as in high speed trains or

aero planes, may experience this type of handover.

Unlike intra-FES handover, which affects mainly on-going calls,

inter-FES has a great impact on the network as it implies a transfer

of routing control from one FES to another.

s pcn interfaces and signalling protocol architecture
S-PCN Interfaces and Signalling Protocol Architecture

use the GSM protocols as the baseline protocols for carrying out the satellite network control functions.

Figure 6.2 shows the network interfaces. A brief description on the

interfaces follows:

  • S-Um-interface: used for signalling between a Gateway Transceiver System (GTS) and an MS.
  • A-interface: between(GWS) ,(GMSC) This interface is used to carry information on GWS management, call handling and mobility management .
  • Abis-interface: this is an internal GWS interface linking the GTS part to the GSC part.

used to support the services offered to the users.

  • B-interface: uses the MAP/B protocol allowing the GMSC toretrieve or update local data stored in the VLR.
s pcn interfaces and signalling protocol architecture cont
S-PCN Interfaces and Signalling Protocol Architecture (cont)
  • C-interface: uses the MAP/C protocol allowing the GMSC to interrogate the appropriate HLR in order to obtain MS location information.
  • D-interface uses the MAP/D protocol to support the exchange of data between an HLR and VLR of the same GMSC.
  • E-interface: uses the MAP/E protocol to support the exchange of messages between the relay GMSC and the anchor GMSC during an inter-GMSC handover.
  • F-interface: between the GMSC and the AuC/EIR. It uses the MAP/F protocol for user authentication.
  • G-interface: uses the MAP/G protocol between VLRs of different GMSCs in order to transfer subscriber data.
s pcn interfaces and signalling protocol architecture cont49
S-PCN Interfaces and Signalling Protocol Architecture (cont)

H-interface: between the HLR and the AuC .

When an HLR receives a request for authentication and

ciphering data for a mobile subscriber and if the data

requested is not held at the HLR, it will send a request

to the AuC to obtain the data.

Figure 6.2 Functional interfaces of a system

vsat networks
VSAT Networks

due to high performance requirements, design of earth station is

quite complicated. This increases the costs and the need for

maintainence. Very Small Aperture Terminals (VSAT) provides a

solution to this problem.

The key point in VSAT networks is that either the transmitter or

the receiver antenna on a satellite link must be larger.

In order to simplify VSAT design, a lower performance microwave

transceiver and lower gain dish antenna (smaller size) is used.

They act as bidirectional earths stations that are small, simple and

cheap enough to be installed in the end user's premise.

what is vsat
What is vsat?
  • It is an earthbound station used for satellite communications of data, voice and video signals.
  • A vsat consists of two parts:
  • A transceiver that is placed outdoors
  • Device that is placed indoors to interface the transceiver with the end user’s communications device.
  • Vsat can handle up to 1 MBPS (1 million bits per second).
  • Vsat systems can be relatively small (1-2 meter antenna ) and easily installed.
what is vsat52
What is vsat?

The transceiver receives or sends a signal to a satellite

transponder in the sky. The satellite sends and receives signals

from a ground station computer that acts as a hub for the system.

Each end user is interconnected with the hub station via the

satellite, forming a star topology. The hub controls the entire

operation of the network. For one end user to communicate with

another, each transmission has to first go to the hub station that

then retransmits it via the satellite to the other end user's VSAT.

how does it work
How does it work?

For best results, the network should be designed to exploit the

Unique virtue of satellite in geostationary orbit namely that

it can be a shared resource available, as needed, to many users

spread Over a very large proportion of the earth’s surface.

This is the concept of bandwidth-on demand.

Satellite internet :

  • The data travels from the satellite equipment at the customers location to the satellite, and then to the teleport for routing to the internet.
turbo internet
Turbo Internet:
  • With the increasing popularity of the World Wide Web, the

demand for speedy downloads is increasing. The main

bottleneck is the analog telephone line, which is incapable of

supporting higher data rates.

An end user overcomes the telephone line barrier and is capable

of receiving data at 400 kbps. This is much faster than typical

analog modems (28.8 kbps), A connection is setup with the local ISP using the analog telephone line modem.

Instead of directing the data to the requesting node, data is

directed to the Network Operations Centre (NOC).

operation of vsat networks
Operation of VSAT Networks

VSAT networks are typically arranged in a star based topology,

where each remote user is supported by a VSAT.

The Earth hub station acts as the central node and employs a

large size dish antenna with a high quality transceiver.

The satellite provides a broadcast medium acting as a common

connection point for all the remote VSAT earth stations.

Typical examples are central office, Banking institutions with

branches all over the country, backbone links for an ISP and

Airline ticketing system.

since all connections must pass through the hub ES node. The

data link supported from the hub to the VSAT is typically slower

(19.2 kbps) than that in the reverse direction (512kbps).

benefits of vsat
Benefits of vsat

Our vsat technology offers many advantages

  • Ease of implementation

After the order is placed, putting up a vsat network can be done

in a matter of days.

the antenna dish can be installed virtually anywhere, the size of

the antenna dish ranges from 1.8m to 2.4m in diameter depending

on the type of the applications .

Likewise, moving the vsat unit to a new location can be done very

quickly.

availability 2
availability2-

The wireless nature of vsat system allows its installation at

virtually any location within the footprint of the Satellite .

With this advantages, customers may setup offices in a promising

location without being constrained by the availability of terrestrial

lines. At the same time, customers may relocate offices to a lower

cost area and still maintain the communication link with the use of

our Vsat links.

3 reliability
3-Reliability

Satellite communication is extremely reliable. our vsat system has

a Bit Error Rate (BER) of approaching 1x10^-9.

our vsat master Earth station has built-in redundancy that ensures

continuous operations in case of failure.

regardless of where the sites are located, each vsat remote unit

receives the same level of performance and signal quality.

4-lower cost

As customers add more services, they will find that the

incremental cost is very low compared to terrestrial networks.

the monthly service fees are fixed and priced according to the

network capacity, not the distance between the head-office

and branch locations.

As a result, customers pay only for the amount of data throughput

used.

slide62
5-security

Satellite networks offer excellent security against on authorized access.

Gaining access to a vsat system is virtually impossible Without authorization.

typical vsat applications
Typical vsat applications

corporate communications can be divided into the following categories :

1-interactive applications

The interactive applications can be based on centralized

or distributed concept. In a centralized system, all terminals in the

offices operate “on-line” and communicate intermittently with the

host of servers at the data center.

In a distributed system, each remote office has terminals linked to

its local host or servers.

slide64
interactive application( Cont )

the servers then communicate with each other in a (WAN).

Besides real-time data applications, our Vsat network supports two-

way voice capability for telephone or facsimile, remote offices can

make phone calls to each other or to central headquarters by passing

the local public phone network.

2-File transfer:

These applications send a large amount of data in one transaction.

These include the use of the TCP/IP file transfer protocol (FIP) to

transfer files and the printing of a large reports.

slide65
3- file broadcast:

a recent file transfer application requires support offile broadcast

or IP multicast these applications send the data to multiple sites

in one transaction.

Using a vsat network, a large file can be distributed to hundreds

of sites simultaneously, our vsat network Supports IP multicast,

which improves broadcast performance even more.

similarities and differences between a mobile satellite network and a gsm network
Similarities and differences between a mobile-satellite network and a GSM network:
  • Similarities:The frequency re-use concept adopted in the GSM

network can be applied to the S-PCN.

A satellite spot-beam coverage is equivalent to a GSM cell coverage.

Higher layer protocols of the GSM network may be adopted in the

S-PCN with possible modifications.

  • Differences:Longer propagation delays in the S-PCN due to the

long satellite-to-earth path and to the longer distance between the

FES and the user terminal.

  • Higher attenuation in the radio signal .
  • Larger variations in conversational dynamics in voice communications.
  • Increased echoes .
similarities and differences between a mobile satellite network and a gsm network cont
Similarities and differences between a mobile-satellite network and a GSM network (cont):
  • Delay in double-hop connection for mobile-to-mobile call may become

Unacceptable.

  • Higher attenuation in the radio signal in the satellite network due

to the longer propagation delay.

  • A spot-beam coverage is much larger than a terrestrial cellular

Coverage resulting in lower inter-spot-beam handover probability.

  • A power control mechanism is required in a satellite network as

the satellite power is shared by all the spot-beams over the entire

coverage area .

  • Line-of-sight operation is required in a satellite network in order to

compensate for the high attenuation in the radio signal in

contrast to the use of multipath signals in terrestrial cellular

mobile networks.

similarities and differences between a mobile satellite network and a gsm network cont68
Similarities and differences between a mobile-satellite network and a GSM network (cont):
  • Adjacent cell interference in a terrestrial cellular network is a function

of power and cellular radius; whereas adjacent spot- beam

interference is a function of power and sidelobe characteristics

of the satellite antenna Array.

  • User terminals can access by any one of the gateways in satellite

networks in contrast to terrestrial network access in which the user

terminal in any given cell can only access an MSC associated with that

cell.

  • Optimum call routing is possible in satellite networks by routing

the call to the nearest gateway to the called party. This is impossible

in existing GSM networks.

  • Do¨ppler shift can be considerable in a satellite network especially

during the initial period of operation.

references
References:
  • mobile satellite communication networks
  • http://www.wiley.co.uk or http://www.wiley.com
  • mobile satellite
  • http://www.cs.berkeley.edu/randy/courses/cs294.596/cs294-7.s96.html
  • mobile communication:satellite system-jochen schillerr
  • http://www.jochenschiller.de