e3-e4 (e &ws) radio modemtraining.bsnl.co.in/digital_library_source... · convertors have been...

E3-E4 (E &WS)

Radio Modem

18-03-2011 For internal circulation of BSNL only 1

WELCOME

• This is a presentation for the E3-E4 (E &WS) technical

Module for the Topic: Radio Modem .

• Eligibility: Those who have got the Upgradation to from

E3 to E4.

• This presentation is last updated on 18-3-2011.

• You can also visit the Digital library of BSNL to see this

topic.


AGENDA

Introduction

Features and advantages of RM

Technical specification

Function of technical requirement of RM equipment

Modulation schemes used

Transmitter parameters


Introduction

As a practice in the industry, radio connectivity is used in last mile

for maintaining the speed.

– BSNL is providing long distance connectivity to medium and large

enterprise customers to establish their private networks

– As more and more enterprises are using IT and applications like

ERP for their operations, the need for such private networks and

virtual private networks has increased many fold.

– BSNL has been providing such service to its customers across India,

for urban, semi urban and rural locations. Customers look towards

BSNL for their remote locations where only BSNL has the needed

infrastructure.


– Such links have three parts- local lead at ‘A’ end , long distance

media (on OFC), and local lead at ‘B’ end.

– Conventionally , the need was for speed of 64 kbps, 128 kbps,

upto 2 Mbps, and very rarely higher than 2 Mbps. Now the speed

requirement has gone up for most customers, and this is posing

a challenge on the local lead.

– Secondly, many factories etc are located in sub urban locations

which are far away from the nearest exchange or BTS location of

BSNL. Copper cable has severe speed and distance limitations.

– Thirdly, all local leads working on copper are prone to faults

resulting in loss of business to customers.

Introduction


Features of radio modem used in BSNL:

• Frequency band: 2 GHz (free band)

• Data transmission: Data is transmitted in the form of ethernet on

the system.

• Interface required for interconnection: Converters are used to

connect data into the system from user side. V35 to Ethernet

convertors have been used in the systems deployed.

• Data speeds: it supports speeds upto 10 Mbps, however, it has been

used for data rates upto 4 Mbps in our applications so far.

• Distance range: upto 10 kms, but extendable.

• In the systems commissioned so far, speed upto 4 Mbps is working

over distances in the range of 10-12 km.


Antenna height:

• BSNL end: either exchange or BTS tower is used to give maximum

height as per need. The needed height is decided by survey

calculations. It also depends on the height of antenna at customer

site. This varies from case to case.

• Customer end: Antenna at customer end is fixed on roof top or any

structure available. If height needed is more and no structure is

available, a tripod type mast is erected for the antenna. It is

available in lengths upto 20 metres. Normally the antenna height at

customer end varies from 3m to 20m


Advantages

• Overcomes limitations of copper lead

• Offers attractive speeds upto several MBPS

• Gives a fantastic distance range beyond 20 km

• Reliability is far more than copper counterpart. Not

affected by factors like road cuts, monsoons, man made

factors etc.


Technical Specifications of radio Modems allowed for

use in BSNL Network

• Hop distance: It shall depend upon the TX power, RX sensitivity,

size of the antenna and tower height. The typical range of

operation as per the GR is about 40 km. however, the links may

be planned up to 25 kms in 2.4 GHz band and upto 20 kms in 5.7

GHz band.

• Safe Separation between the links: It shall depend on the

frequency separation, azimuth angle of the links and antenna

discrimination and can therefore de decided on link to link basis.

• Size of the antenna: The maximum EIRP is 30 dBm. The links

may be planned accordingly.


• Choice of frequency band: This depends upon a) hop distance b)

Intersystem Interference etc.

• Input power supply: The radio modem equipment is capable of

working on 230 V AC.

• Cost of the Radio modem link: Approximate cost of a radio

modem link is about 1.5 lakhs.


Functional & Technical Requirements of Radio

Modem Equipment

Modem

• Data Rates

The modem shall support one or more of the following data rates.

• 64 Kbps

• 128 Kbps

• 256 Kbps

• 512 Kbps

• 2048 Kbps (E1)

• 2 *2048 Kbps (2xE1)

• 4 *2048 Kbps (4xE1)

• 8 *2048 Kbps (8xE1)


Digital Line Interface:

• The modem interface shall be either hardware

configurable (e.g. DIP Switches) or software

configurable (e.g. AT commands) to act as Data

Communication Equipment (DCE) or Data Terminal

Equipment (DTE) as per the requirements. The

following digital interfaces shall be supported on

Subscriber End Equipment (SEE) and Exchange End

Equipment (EEE).


Digital Interfaces on Subscriber End Equipment (SEE):

Physical interfaces for Subscriber End Equipment (SEE)

• V.35 / V.36 ISO – 2593 physical connector (34 pin, female type)

with provision for holding the corresponding cable using standard

screw-type arrangement.

• V.11 ISO – 4902 physical connector (37 pin, female type) with

provision for holding the corresponding cable using standard


• V.36/V.35/V.II ISO – 2110 physical connector (25 pin, female type)

with provision for holding corresponding cable using standard



• G.703 Co-directional interface at 64 Kbps with ISO-2110 connector

(Female type)

• G.703 physical interface with ISO 2110 connector (female type) with

120 Ohm balanced for 2048 Kbps.


Digital Interfaces on Exchange End Equipment (EEE):

Physical interfaces for Exchange End Equipment (EEE)

• V.II ISO-4902 connector (37 pin, female type) with

provision for holding corresponding cable using

standard screw-type arrangement.

• V.36/V.35 ISO-2110 connector (25 pin, female type)

with provision for holding the corresponding cable using


• G.703 Co-directional interface at 64 Kbps


Digital Interfaces on Exchange End Equipment (EEE):

V.II ISO-4902 connector (37 pin, female type) with

provision for holding corresponding cable using


• V.36/V.35 ISO-2110 connector (25 pin, female type)

with provision for holding the corresponding cable using


• G.703 Co-directional interface at 64 Kbps with ISO-

2110 connector (Female type)


Modulation

The radio modems shall conform to one of the following

modulation:

• Frequency Hopping Spread Spectrum (FHSS)

• Direct Sequence Spread Spectrum (DSSS)


Frequency Hopping Spread Spectrum (FHSS)

modulation:

• FHSS modulation is a form of modulation in which

transmitter signal occupies a number of frequency in

time, each for some period of time, referred to as dwell

time.

• FHSS modulation shall make use of at least 75 well

defined, non-overlapping channels of hopping positions

separated by the channel bandwidth as measured at 20

dB below peak power.


Modulation

• The maximum 20 dB bandwidth of hopping channel is 1

MHz. The average time of occupancy on any frequency

shall not be greater than 0.4 seconds within a 30

seconds period.

• Radio modem is operating each channel of the hopping

sequence shall be occupied at least once during a

period not exceeding four times the product of the

dwell time per hop and the number of channels.


Direct Sequence Spread Spectrum (DSSS) and other

forms of modulation

• DSSS modulation is a form of modulation in which both

data to be transmitted and known code sequence are

combinedly used to directly modulate a carrier.

• Systems using the other forms of modulation shall be

tested according to the requirements for DSSS

modulation. The minimum 6 dB bandwidth shall be at

least 500 kHz.


Transmitter parameter limits

• Effective radiated power

• Peak power density

• Processing Gain

• Hybrid systems


Frequency range

• The frequency range of the radio modem is determined

by the lowest and highest frequencies occupied by the

power envelope.

• FH is the highest frequency of the power envelop: it is

the frequency furthest above the frequency of

maximum power where the output power drops below

the level equivalent to -80dBm/Hz e.i.r.p spectral power

density (-30 dBm if measured in a 100 kHz bandwidth).


• FL is the lowest frequency of the power envelop: it is

the frequency furthest below the frequency of

maximum power where the output power drops below

the level equivalent to -80dBm/Hz e.i.r.p spectral power

density (-30 dBm if measured in a 100 kHz bandwidth).

– The frequency range of the radio modem shall lie within one of

the following band: i) 2400 MHz to 2483.5 MSHz (FL>2400

MHz and FH < 2483.5 MHz)

– ii) 5725 MHz to 5825 MHz (FL>5725 MHz and FH < 5825

MHz)


Field Strength

• Field strength limits are specified at a distance of 3

meters. Emissions radiated outside of the specified

frequency bands, except for harmonics, shall be

attenuated by at least 50 dB below the level of the

fundamental


Spurious emissions

• Spurious emissions are emissions outside the frequency range (s)

of the radio modem as defined in sub clause 2.2.2.4.

• The level of spurious emissions shall be measured as:

Either

• (i) Its power in a specified load (conducted spurious emissions);

and

• (ii) Its effective radiated power when radiated by the cabinet

or Structure of the radio modem (cabinet radiation);

Or

• Its effective radiated power when radiated by cabinet and antenna.


Power supply


The modem shall operate on AC

power supply of 230+ 10% to -15%

and frequency 50 HZ +-2Hz

Alarm Indications


• Transmit power failure• Receive power below threshold

• Radio sync loss• Power up

• DTE input loss

Safety requirements

• The operating personnel should be protected against shock hazards as

per IS 8437 {1993} “Guide on the effects of current passing through

the human body” [equivalent to IEC publication 479-1 {1894}].

• The radio modem shall conform to IS 13252 (1992) “Safety of

information technology equipment including electrical business

equipment” {equivalent to IEC Publication 950 (1986)} and IEC 215

{1987} “Safety requirements of radio transmitting equipments” {for

Radio Equipments only}.

• The radio modem should follow proper construction practice to

minimize unintended radiations due to leakage from any gap or

monitoring points. All unused if/rf ports and monitoring points should

be terminated. The power flux density shall not exceed 1 mW/cm2 at

a distance of 2.5 cms.


Diagnostics

• Local loop back test

• Remote loop back test

• Loop back to remove end

• Receive power level determination

• Receive power signal quality determination

• Quasi random sequence generator

• Data output failure

• System log capability for alarms and test results

• Local & remote monitoring


For internal circulation of BSNLonly

e3-e4 (e &ws) radio modemtraining.bsnl.co.in/digital_library_source... · convertors have been...

Documents