SDR

2.3 Advantages of SDR

For Radio Equipment Manufacturers and System Integrators, SDR

Enables:

• A family of radio “products” to be implemented using a common

platform architecture, allowing new products to be more quickly

introduced into the market.

• Software to be reused across radio "products", reducing

development costs dramatically.

• Over-the-air or other remote reprogramming, allowing "bug fixes"

to occur while a radio is in service, thus reducing the time and costs

associated with operation and maintenance.

For Radio Service Providers, SDR Enables:

• New features and capabilities to be added to existing infrastructure

without requiring major new capital expenditures, allowing service

providers to quasi-future proof their networks.

• The use of a common radio platform for multiple markets,

significantly reducing logistical support and operating expenditures.

• Remote software downloads, through which capacity can be

increased, capability upgrades can be activated and new revenue

generating features can be inserted.

For End Users - from business travelers to soldiers on the battlefield,

SDR technology aims to:

• Reduce costs in providing end-users with access to ubiquitous

wireless communications – enabling them to communicate with

whomever they need, whenever they need to and in whatever

manner is appropriate.

2.4 Current Satellite communication System in Indian Railways

Very Small Aperture Terminal (VSAT) Network provides Point

to Point or Point to Multi Point data connectivity using Geostationary

Satellite as repeater location. As satellite is being used as repeating

stations, the data originating and terminating point can be anywhere

on the earth. VSAT networks are typically used for Video

Surveillance, Video Conferencing, Consumer Internet, Point of Sale,

Distance Education, Industrial ERP, Internet Kiosk etc. Railway is

using them to provide data connectivity between various goods

terminals and CRIS as well as for video conferencing applications. It

shall also be used for Accident Site Communication for voice, data

and video transmission.

VSAT Network Components

a) The network works in Star as well as Mesh architecture and

consists of

i) Hub Earth Station

ii) Remote Earth Station

iii) Satellite Transponder & Space Link

iv) Network Control Centre

v) Interface Equipment

Each of above equipments has been described in detail

below.

b) At Data level, the Network uses TCP/IP for Data

transmission. The Architecture of VSAT Network under development

for Railways is shown later. As can be seen all external Data Devices

interact with interface units only both at Remote as well as Hub End

thus making the VSAT Network system transparent to external

systems. i.e. PC, Telephone through IP interface interacts with the

interface unit i.e. DW 7700 at remote end. Similarly on Hub end, all

external data devices interacts with Enterprise LAN level only thus

making the VSAT Network transparent to external systems.

c) At RF level, the Networks operate in 3 bands i.e. C Band, XC

Band and Ku Band. Railway is using Ku band System. Ku Band system

operates on up link frequency of 14.25 to 14.5 GHz and Down Link

Frequency of 11.45 to 12.75 GHz. Up link frequencies is the carrier

frequency on which Hub or remote earth station transmits the Signal

to Satellite. Down Link Frequency is the Carrier frequency on which

Satellite transmits the Signal to Hub or remote earth station.

2.4.1 Hub Earth Station

This station is Heart of the entire Network. The communication

between remotes or remote to external networks is established

through Hub Earth Station only. It is responsible for collecting the

data from enterprise LAN’s, Address Translation, converting data

into IF and RF Signals and transmitting them to Satellite and further

to remote earth stations, maintaining the integrity checks for all

remote earth stations, time synchronization for all remote earth

stations, tracking of Satellite, converting the RF received from

Remote to Data Signals in appropriate format to be delivered at

Enterprise level etc.

The Hub Earth Station consists of following

Antenna Sub Systems: It consists of 9 meter (or above) Cassegrain

feed, parabolic reflector, Sub Reflector, Low Noise Amplifiers and its

integration modules like Cables, Wave Guides, Connectors,

Dehydrators, Tracking Mechanisms etc. This system should have

clear line of sight availability towards the satellite. The Antenna

Control system can position the Antenna anywhere in vertical and

horizontal plane thus taking care of Satellite drifts as well as change

of Satellite.

RF Sub System: It converts the IF Signals of 70 MHz typically to RF

frequency signals suitable for Satellite transmission. It also amplifies

the Signal for transmission to Satellite.

IF Sub System: The Modulated base band signals are first converted

to IF Signals and also amplified here before they are fed to RF Sub

Systems.

Base band Equipment: This sub system consists of elements for

interacting with interface devices, time synchronization, modulating

the data signals for transmission, demodulating the signals received,

address translation, interacting with Network Monitoring Systems.

All sub systems here work on proprietary software. Few Sub systems

work on proprietary hardware also. Therefore, these equipments are

highly Vendor specific.

Network Monitoring Systems: It is a high end Server. This

equipment also works on proprietary software. The network is

managed as well as configured using this system only. All history and

configuration data is kept in Open End RDBMS. In Railway Network,

they are kept in Oracle Enterprise. The system also provides SNMP

(Simple Network Management Protocols) traps for all the devices

working on IP. These traps can be used by Open End Software like

HPOV etc which can generate many configurable reports for

management purposes.

A typical Network Component for the Railway Hub under

Construction is given below.

HUB LAN would consists of Following

1. DNCC: BA Allocation

2. IPGW: Packet Switching

3. Packet shaper: Monitor and Control

4. Gatekeeper: Call Setup

5. Audio Codec With phone: Test Call

6. Cisco L3: Route Traffic towards Central Site

Space Link i.e. Satellite

The VSAT communication depends entirely on Satellite. A

satellite is a nothing but a microwave repeater in Geo synchronous

orbit above the earth. All Hub and Remote Earth Equipment

communicates via Satellite.

A typical Block Diagram of Satellite is shown below.

Satellites are of different types namely

i) Communications Satellites (Used for VSAT Network)

ii) Weather Satellites

iii) Remote Sensing Satellites

iv) Science Research Satellites

v) GPS Satellites

Two elements which are common to all the four types of satellites are

PAYLOAD - Equipment a satellite needs to do its job. Include

antennas, cameras, radar and electronics. Payload is different for

every satellite. For Example, payload for a weather satellite includes

cameras, while payload for a communication satellite includes

antennas.

BUS - Part of the satellite that carries the payload and its equipment

into space. It holds all the satellite parts together and provides

electrical power, computers, and propulsion to the spacecraft. It also

contains equipment that allows the satellite to communicate with

earth.

Satellites rotate around earth in orbits. The different types of

orbits are Equatorial Orbit, Polar Orbit, Inclined Orbit and Elliptical

Orbit. The time of travel around earth is dependent on the distance of

Satellite from earth. At altitude of 22300 miles, the Satellite takes

exactly 24 hours to circle around earth. All orbits at this altitude are

called Geosynchronous Orbits. If the Satellite is in Equatorial Orbit at

the altitude of 22300 miles and is rotating in the same direction as of

earth, it will be stationary with respect to earth. All communication

Satellite use geosynchronous orbits only to avoid the need for

realigning the Antenna.

Three geo synchronous satellites can be used for full earth

coverage. The transmission of a signal up to the satellite and back

down is called a hop. Transmission delay for one hop is between

240msec. and 270msec.

One geo synchronous satellite can transmit to approximately

42% of the earth’s surface. North and South poles cannot receive

signals from a geo synchronous satellite. The area covered by a single

satellite antenna is called a “footprint”. Figure below gives you the

footprint of one of the Satellites.

Satellite Footprint

The Satellite position changes due to solar and lunar

gravitational pull. The Satellite owner needs to monitor the position

of satellite at all times and correct for satellite drift. The tracking

mechanisms are therefore provided in the Hub equipment Antenna

Sub Systems to take care of this drift.

The Satellite uses different types of beams for communicating

with Earth Stations. The beams used are - GLOBAL BEAM: covering

42% of earth surface. Beam width 18degree, DUAL SPOT BEAMS,-

MULTIPLE SPOT BEAMS,- DUAL POLARIZED SPOT BEAMS

Polarization of Electro Magnetic waves is used by Satellites to

increase the channel capacity as multiple signals can be transmitted

at same frequency. The Polarization used by Satellites is linear or

Circular. Every Earth Station has to be configured to work on the

Polarization being used by Satellites.

The Uplink and Dnlink Frequencies which are in use in

different bands are as under

Railways is using Ku Band for their VSAT Network which will

work on INSAT 4C-R

The transponders provide the frequency space on Satellite.

Each transponder is of 36 MHz Different Satellites carry different

number of transponders. A fraction of transponder can be used.

Railway is hiring 9 MHz frequency space on INSAT 4C-R for their

VSAT Network.

VSAT Network operator has to divide the hired transponder

space into Transmit and Receive Segment. As the transmission power

of remote earth station is limited, their requirement of frequency

spectrum is limited but higher number of smaller bands are required

to cater for large number of remote stations. While one bigger band is

required at transponder for signal transmitted from Hub as it is high

power signal and contains data for all remotes.

To adjudge the availability of Satellite communication, a link

budget calculation is done taking the least available Satellite Power,

Antenna Size, transponder sizing for receive and transmit segments

etc.

All transponder space is allocated by Department of Space.

Remote Earth Station

Remote Earth Station consists of

i) A Parabolic Antenna 1.2 or 1.8 Meters of Size for Ku band system

and 3.2 to 3.8 meter size for C and XC band system with Feed for

transmit Signals.

ii) An outdoor unit called ODU and Low Noise Amplifier for received

signal.

iii) Indoor Unit

iv) Power Supply Arrangements

v) Protection and Earthing Arrangements

Indoor Unit interact with the Antenna System as well as

external data devices through Ethernet LAN ports. A typical remote

earth installation over Railway has been shown below.

All remote installations require feeding of latitude and

longitude information which determines its location with respect to

Satellite as well as Hub Earth Station.

The supported rates for data transmission in up-to 1 MBPS as

per the guidelines of DOT.

The protocol and encryption used for transmission of Data

between Hub and Remote station is usually proprietary items and

therefore, the Hub and Remote devices have to be of same Vendor. As

these are proprietary devices, the features supported by them differ

from make to make. The features supported by the remote installed

on Railway System are given below.

o Inbound HIS 512Kbps /1Mbps

o MPLS QoS

o DHCP server and relay support

o IGMPv2 for multicast to LAN

o VLAN Tagging

o ICMP support (pings, etc.)

o Embedded web server for remote status query and

configuration

o NAT/PAT

o RIP V2

o DNS caching and preload

o Inroute IP header compression

o RTP header compression

o PEP and inroute prioritization

o PEP and TCP payload compression

o Secondary satellite frequency support

o CBR support for real-time applications

o VADB

As these devices use proprietary protocol as well as encryption, the

communication is highly secure.

Interface Equipment

The VSAT Network is interfaced with the external data devices

by using Router or Router Switch combinations at Hub Earth

Stations. At Remote Station, Ethernet LAN output is provided as

standard interface. This can directly be connected to any device

having Ethernet interface.

The applications Servers like FOIS Server of Railway, IP Exchange for

Voice Networks and MPEG Server for Video Streaming applications

and Web Servers for providing Internet application have to be

interfaced with VSAT network through a router switch combination

only.

Network Control Center

Network Control Center is responsible for administering and

managing the whole of the VSAT Network as well as each of the

application working on the Network. This is carried out through

Network Management System specific to Network as well as using

other tools mostly SNMP based.

This Center also generates various analysis reports not only for

Network part but for day to day operation of each of application

running on the Network.

One of the most important parameters is analyzing the traffic

flow and taking corrective actions for optimum working of all

applications. This has been described in detail in Bandwidth

Management para.

This Center also tracks the performance of all the remote sites

connected and get them attended in case of any fault.

Bandwidth Management

Management of Bandwidth is a very important parameter on

VSAT networks as the cost of Bandwidth on Satellite is very high.

C and XC Band VSAT Networks worked on principles of

dedicated bandwidth allotment for each application. The utilization

of bandwidth in such systems was poor as most of the data devices

remain dormant for considerable period.

Ku Band VSAT Networks work on Shared bandwidth principles.

Here only priorities and grouping of traffic can be defined. Priorities

can be defined for a group consisting of Data Transmitting device,

Data Receiving Device etc. Within the group each member will have

an equal right for the bandwidth. Therefore as more and more

member of the group become active, each one will get lesser

bandwidth. As more and more member become dormant, the

available bandwidth for the remaining members will be higher.

Priorities can be set for different groups based on sensitivity of

applications. Therefore a high priority group will get precedence for

bandwidth allocation than a lower priority group. This results in a

very effective utilization of Bandwidth.

Packet Shaper Software is used for management of bandwidth

in transmit path. While it can be managed using Network

Management System tool in receive path.

Miscellaneous

The performance of VSAT equipment both at Hub Earth Station

and Remote Earth Station is affected by ambient conditions.

Hub Equipment generates a very high amount of heat.

Continuous heat dissipation and marinating Normal temperature is

an extremely important consideration for proper functioning of VSAT

Hub Equipment.

Some of the important items which are considered necessary

for proper functioning of Remote Earth Station are as given below

i) Maintain the Room Temperature.

ii) Use On line UPS.

iii) Good Quality Earthing to be maintained.

iv) Dust free environment to be maintained

v) Sufficient air circulation & access to Indoor Unit be there

vi) Switch on the VSAT first and then switch on other

accessories

vii) Follow the Switch on Sequence strictly

viii) Report any Problem related to any equipments to Hub

ix) While doing so report full Problems and complete

observations to Hub

x) Use the Computer only for Intended applications

xi) Make sure your Computers are Virus FREE

xii) Log all activities related to equipment failures & Engineer

visits in a Log Book

xiii) Allow authorized and Trained People only to operate the

system.

xiv) Do not switch on the VSAT immediately after switch off.

xv) Do not Move the Indoor Unit after installation.

xvi) Do not keep any article on Indoor Unit.

xvii) Do not obstruct the air vents in front of the Indoor Unit.

xviii) Do not Use air cooler (water) for cooling.

xix) Do not Bend IFL cable

xx) Do not use the PC for any other application

xxi) Do not do any local servicing of the equipments

xxii) Do not shift the equipments from one place to another in

absence of trained persons

xxiii) Do not load any software programs on the PC except the

application

Chapter-3

Disadvantages with the current system

Non versatile system, whenever there is a requirement for

enhancement in the modulation techniques or security features of

the system it is not a simple task to do. Total hardware must be

changed, due to usage of outdated techniques in system design.

Huge initial cost

A huge maintenance cost, if at all changes has to be done.

Latency, The speed of light being what it is, and the fact that the

satellites are 23,000 miles above the equator; it takes the signal

approximately 0.26 seconds to get to the satellite and back. This bit of

delay can play havoc with certain types of applications. Some

interactive applications (such as dumb terminal with remote echo)

can be nearly unusable unless appropriate measures are taken. There

are also non WAN-friendly applications out there (including ones

that purport to be WAN-friendly) that require an inordinate number

of data exchanges for even the most trivial of functions: It should be

pointed out that these applications are typically poor candidates for

any WAN application - be they terrestrial or otherwise.

Occasional outages due to the sun, lasting a few minutes occurring

once or twice a year where the Sun moves directly in line with the

satellite. The Sun, being a very powerful source of radio signals,

temporarily jams the satellite signal. These outages can be predicted

very precisely and last only a short time. (Most users can tolerate

"scheduled" outages - it is those "unscheduled" ones that cause the

most problem...)

Occasional outages due to weather. Occasionally, very heavy

precipitation will block the signal for short periods. These outages

are fairly rare and don't normally last for more than a few minutes.

Another possibility is that of snow building up in a dish, but proper

system design (e.g. installation of covers, heaters, and occasional

vigilance and, in a worst-case scenario, the use of a broom) can

prevent such outages from ever happening in the first place.

Failure of the Satellite itself. Fortunately, this is extremely rare.

Satellites are some of the most reliable pieces of equipment made -

and they are loaded with redundant systems. Even in the event of a

failure, it is practical to restore service simply by pointing the

antenna at a different satellite.

Chapter - 4

Proposed System Block Diagram

(Fig-1)Block Diagram of the entire system

(Fig-2) VSAT Hub Station Block DiagramAntenna

SDR Using MATLAB ()

ADC

DAC

Antenna

SDR Using MATLAB (TRX)

DAC

ADC

(Fig-3) Functional Blocks in the ground station

Chapter-5

Modules in the Block diagram

(Fig-1) shows the block diagram of entire satellite communication

system in Indian Railways.

1. Geosynchronous Satellite

2. Teleport

3. NOC

4. Satellite hub

5. Costumer location

6. Satellite modem & Router

7. Networked workstations

(Fig-2) shows the block diagram of VSAT hub station.

8. SDR using matlab

9. ADC

10. DAC

11. Satellite Dish Antenna

(Fig-3) shows the block diagram of ground station

12. SDR using matlab

13. ADC

14. DAC

15. Satellite Dish Antenna

Chapter – 6

Description of Block diagram

6.1 Geosynchronous Satellite

A satellite’s orbit around the earth repeats time to time over points on the

earth, lies over the equator, circular, and direction of the satellite is same as

the earth then such a satellite is called as ‘Geosynchronous satellite’. And

the orbit of such a satellite is called as Geosynchronous

orbit/Geostationary Orbit.

Geosynchronous satellites are majorly used for communication. Like video

conferencing, distance calling, direct to home televisions etc. today

communication between corners of the earth has become possible due to

this Geosynchronous satellite network. This had made international calls

also cheaper. There are approximately 300 operational geosynchronous

satellites dedicated for communication.

Geostationary satellites appear to be fixed over one spot above the equator.

Receiving and transmitting antennas on the earth do not need to track such

a satellite. These antennas can be fixed in place and are much less

expensive than tracking antennas. These satellites have revolutionized

global communications, television broadcasting and weather forecasting,

and have a number of important defense and intelligence applications.

One disadvantage of geostationary satellites is a result of their high

altitude: radio signals take approximately 0.25 of a second to reach and

return from the satellite, resulting in a small but significant signal delay.

This delay increases the difficulty of telephone conversation and reduces

the performance of common network protocols such as TCP/IP, but does

not present a problem with non-interactive systems such as television

broadcasts.

6.2 Teleport

Teleport is the one which transfers data very fast from one place to

another.

Unlike VSAT’s these are big in size. It’s a terminal used for data transfer

between geosynchronous satellite and Hub station.

6.3 NOC

A Network Operations Center (NOC) and its uses vary from provider to

provider, but most provide a number of services to both customers and

non-customers alike.

Most NOCs are the front line for customer support, for a wide range of

issues, including emergency support for folks encountering Denial of

Service attacks, loss of connectivity, and security issues.

Some companies have Customer Service centers that escalate internally to

their NOC for outages that affect more than one customer. An example may

be if your T1 is down and it is delivered to your provider via a CT3 and the

entire CT3 is down the NOC would work on the single DS3/CT3 outage

instead of the 28 individual customer outages.

Some companies reserve their NOC for inter-company and intra-company

communications and do not speak directly to customers except in the rare

case that they require additional information and their Customer Service

Center fails to collect the information or lacks the technical skills to

properly collect the information.

When contacting another NOC, Identify yourself, the company you

represent and clearly describe the problem you are having. Do not contact

a NOC if you are a customer of the company unless that is your direct

support mechanism. This can lead to the lack of tracking of your problem

and inability to obtain credits under your SLA or other support problems.

One should also not become abusive when talking to NOC staff. Their jobs

can be extremely stressful especially during late-night shifts where staffing

tends to be minimal. (00:00-8:30 local time to your NOC)

6.4 Satellite hub

Satellite hub or hub earth station, more about this has been discussed in

section 2.4.1.

6.5 Costumer location (VSAT)

Costumer location can be anywhere on the earth, might be in the middle of

a see also, communication will be established as the same on entire earth.

VSAT’s are used in the costumer location.

VSAT stands for "Very Small Aperture Terminal;" it refers to

receive/transmit terminals, installed at dispersed sites and connecting to a

central hub via satellite using small diameter antenna dishes (0.6 to 3.8

meter).

VSAT technology represents a cost effective solution for users seeking an

independent communications network connecting a large number of

geographically dispersed sites. VSAT networks offer value-added satellite-

based services capable of supporting the Internet, data, LAN, and voice/fax

communications, and can provide powerful, dependable private and public

network communications solutions.

Overview of Technology

The most common VSAT configuration is the TDM/TDMA star network.

These have a high bit rate outbound carrier (TDM) from the hub to the

remote earth stations, and one or more low or medium bit rate Time

Division Multiple Access (TDMA) inbound carriers.

With its star configuration network architecture, interactive VSAT

technology is appropriate for any organization with centralized

management and data processing.

This configuration has been developed to minimize overall lifetime costs

for the complete network including satellite transmission costs. The use of

a single high performance hub allows the use of low cost remote VSAT

terminals and optimizes use of satellite capacity. Even so, in most VSAT

networks, the cost of the VSAT terminals usually far exceeds the cost of the

hub (typically a VSAT terminal is 0.1 to 0.2% of the price of the hub).

In a typical VSAT network, remote user sites have a number of personal

computers, dumb terminals and printers connected to the VSAT terminal

which connects them to a centralized host computer either at the

organization’s head office or data processing centre. Data sent to the VSAT

terminal from the DTEs is buffered and transmitted to the hub in packets.

Note: See (Fig - 1) in block diagram

This is how a star data, TDM/TDMA VSAT network works using a hub

station, usually six meters or more in size and small VSAT antennas

(between 75 centimeters and 2.4 meters). All the channels are shared and

the remote terminals are online, offering fast response times.

However, mesh networks which use capacity on a demand assigned

multiple access (DAMA) basis take a different approach. The master control

station merely acts as a controller and facilitator rather than a hub through

which traffic passes as in a star network. However, these connections take a

little time to set-up and thus, mesh/DAMA systems are often equated to a

terrestrial dial-up connection.

There are also mesh systems which use a TDMA access scheme where

all of the terminals in a network receive and transmit to the same channel,

selecting different time slots because each terminal is aware of what the

others have reserved. In the past this type of system has been costly and

therefore, reserved for large scale trunking applications, but, more

recently, costs have come down considerably and now they can be cost

competitive with SCPC/DAMA systems for thin route applications as well.

Point-to-point SCPC (single channel per carrier) links are the

satellite equivalent of a terrestrial leased line connection. They are usually

set-up on a permanent, 24 hour basis and are thus more costly in satellite

capacity and less efficient if not used all the time. However, they do support

high bandwidths (typically from 9.6 kbps to 2 Mbps) and can easily be used

to carry data, voice and even video traffic.

All other systems are usually a variation on one of the themes

described above, either in a star, mesh or hybrid (star and mesh)

configuration. Most of the TDM/TDMA manufacturers also offer a mesh

product which can be deployed in a hybrid-ized configuration, sharing

common components such as antennas and RF units, at a remote site.

6.6 Satellite modem & Router

They are used for establishing data transfer between communication

satellites and networked workstations.

In the conventional system a satellite modem is used to modulate and

demodulate the radio signals in to binary format and vice versa. This can be

replaced by the software defined radio developed using matlab. All the data

modulations and demodulations are done in the software only.

A Router is used to redirect the data from the modem to the requested

workstations with a specific IP address.

6.7 Networked workstations

This might be any LAN network inside a firm.

In Indian railways this will be the Computers connected in LAN inside the

individual railway stations. The data from the router will be connected to

the requested computer.

6.8 Software defined Radio using MATLAB for Indian Railways

By using Floating point MSK modulation and demodulation

technique we developed software defined radio for VSAT network in Indian

railways.

6.8.1 AWGN:

The AWGN Channel block adds white Gaussian noise to a real or complex

input signal. When the input signal is real, this block adds real Gaussian

noise and produces a real output signal. When the input signal is complex,

this block adds complex Gaussian noise and produces a complex output

signal. This block inherits its sample time from the input signal.

This block uses the Signal Processing Blockset™ Random Source block to

generate the noise. Random numbers are generated using the Ziggurat

method. The Initial seed parameter in this block initializes the noise

generator. Initial seed can be either a scalar or a vector whose length

matches the number of channels in the input signal. For details on Initial

seed, see the Random Source block reference page in the Signal Processing

Blockset documentation set.

This block accepts a scalar-valued, vector, or matrix input signal with a data

type of type single or double. The output signal inherits port data types

from the signals that drive the block.

Note: All values of power assume a nominal impedance of 1 ohm.

Signal Processing and Input Dimensions

This block can process multichannel signals. When you set the Input

Processing parameter to Columns as channels (frame based), the block

accepts an M-by-N input signal. M specifies the number of samples per

channel and N specifies the number of channels. Both M and N can be equal

to 1. The block adds frames of length-M Gaussian noise to each of the N

channels, using a distinct random distribution per channel.

Function Block Parameters:

Input processing

Specify how the block processes the input signal. You can set this

parameter to one of the following options:

Columns as channels (frame based) — When you select this

option, the block treats each column of the input as a separate

channel.

Note   The Inherited (this choice will be removed - see release

notes) option will be removed in a future release. See Frame-

Based Processing in the Communications Blockset Release Notes

for more information.

Initial seed

The seed for the Gaussian noise generator.

Mode

The mode by which you specify the noise variance: Signal to noise

ratio (Eb/No), Signal to noise ratio (Es/No), Signal to noise

ratio (SNR), Variance from mask, or Variance from port.

Eb/No (dB)

The ratio of bit energy per symbol to noise power spectral density, in

decibels. This field appears only if Mode is set to Eb/No.

Number of bits per symbol

The number of bits in each input symbol. This field appears only if

Mode is set to Eb/No.

Input signal power, referenced to 1 ohm (watts)

The mean square power of the input symbols (if Mode is Eb/No or

Es/No) or input samples (if Mode is SNR), in watts. This field appears

only if Mode is set to Eb/No, Es/No, or SNR.

Symbol period (s)

The duration of a channel symbol, in seconds. This field appears only

if Mode is set to Eb/No or Es/No.

Variance

The variance of the white Gaussian noise. This field appears only if

Mode is set to Variance from mask.

6.8.2 Transmitter Subsystem1

a) Bernoulli Binary Generator

The Bernoulli Binary Generator block generates random binary

numbers using a Bernoulli distribution. The Bernoulli

distribution with parameter p produces zero with probability p

and one with probability 1-p. The Bernoulli distribution has

mean value 1-p and variance p(1-p). The Probability of a zero

parameter specifies p, and can be any real number between

zero and one.

Attributes of Output Signal

The output signal can be a frame-based matrix, a sample-based

row or column vector, or a sample-based one-dimensional

array. These attributes are controlled by the Frame-based

outputs, Samples per frame, and Interpret vector parameters

as 1-D parameters. See Signal Attribute Parameters for

Random Sources in Communications Blockset User's Guide for

more details.

The number of elements in the Initial seed and Probability of a

zero parameters becomes the number of columns in a frame-

based output or the number of elements in a sample-based

vector output. Also, the shape (row or column) of the Initial

seed and Probability of a zero parameters becomes the shape

of a sample-based two-dimensional output signal.

Source Block Parameters

Probability of a zero

The probability with which a zero output occurs.

Initial seed

The initial seed value for the random number generator.

The seed can be either a vector of the same length as the

Probability of a zero parameter, or a scalar.

Sample time

The period of each sample-based vector or each row of a

frame-based matrix.

Frame-based outputs

Determines whether the output is frame-based or

sample-based. This box is active only if Interpret vector

parameters as 1-D are unchecked.

Samples per frame

The number of samples in each column of a frame-

based output signal. This field is active only if Frame-based

outputs is checked.

Interpret vector parameters as 1-D

If this box is checked, then the output is a one-

dimensional signal. Otherwise, the output is a two-dimensional

signal. This box is active only if Frame-based outputs is

unchecked.

Output data type

The output type of the block can be specified as a

boolean, int8, uint8, int16, uint16, int32, uint32, single, or

double. By default, the block sets this to double. Single outputs

may lead to different results when compared with double

outputs for the same set of parameters.

b) MSK Modulator

The MSK Modulator Baseband block modulates using the

minimum shift keying method. The output is a baseband

representation of the modulated signal.

This block accepts a scalar-valued or column vector input

signal. For a column vector input signal, the width of the output

equals the product of the number of symbols and the value for

the Samples per symbol parameter.

Integer-Valued Signals and Binary-Valued Signals

When you set the Input type parameter to Integer, then the

block accepts values of 1 and -1.

When you set the Input type parameter to Bit, then the block

accepts values of 0 and 1.

Function Block Parameters:

Input type

Indicates whether the input consists of bipolar or

binary values.

Phase offset (rad)

The initial phase of the output waveform,

measured in radians.

Samples per symbol

The number of output samples that the block

produces for each integer or binary word in the input,

which must be a positive integer. For all non-binary

schemes, as defined by the pulse shapes, this value must

be greater than 1.

Output data type

Specify the block output data type as double and single. By default, the

block sets this to double.

MSK Modulator Subsystem1:

MSK Modulator Subsystem2:

6.8.3 Receiver Subsystem1

The MSK Demodulator Baseband block demodulates a signal

that was modulated using the minimum shift keying method. The

input signal is a baseband representation of the modulated signal.

The Phase offset parameter represents the initial phase of the

modulated waveform.

Integer-Valued Signals and Binary-Valued Signals

This block accepts a scalar-valued or column vector input

signal with a data type of single or double. If you set the Output type

parameter to Integer, then the block produces values of 1 and -1. If

you set the Output type parameter to Bit, then the block produces

values of 0 and 1

Function block Parameters

Output type

Determines whether the output consists of bipolar or binary

values.

Phase offset (rad)

The initial phase of the modulated waveform.

Samples per symbol

The number of input samples that represent each modulated

symbol, which must be a positive integer. For more

information, see Upsampled Signals and Rate Changes in

Communications Blockset User's Guide.

Rate options

Select the rate processing method for the block.

Enforce single-rate processing — When you select this