A Summer Training Experience
PRESENTED BY : UNDER THE GUIDANCE OF:
AMBRISH KUMAR SHUKLA PRATIBHA GUPTA
ECE, FINAL YEAR JTO, ALTTC(BSNL)
Advanced Level Telecom Training Centre(ALTTC),
Ghaziabad is the apex training institute of BSNL. ALTTC
was set up as joint venture of ITU, Geneva, UNDP and
the Govt. of India. It imparts excellent training level in
the field of Telecom technology.
The training areas cover vast spectrum of topics
such as Digital Switching; Mobile Communication: GSM,
3G, CDMA; Data communication and Information
Technology: Broadband , Database Administration,
Server Administration; Optical Network and Telecom
TABLE OF CONTENTS
INTRODUCTION OF BROADBAND
NEED OF BROADBAND.
TYPES OF BROADBAND SERVICES.
DIGITAL SUBSCRIBER LINE
TYPES OF DSL SERVICES.
DISCRETE MULTITONE MODULATION.
ADSL FREQUENCY SPECTRUM.
BROADBAND MARKET SHARE
The term BROADBAND refers to high speed internet access. It is non
specific term. In fact there is no specific international definition for
As the Internet market continues to grow, demand for greater BW
and faster connection speed have led to broadband access to all
The rapid growth of distributed business application , e-commerce
and BW intensive application (such as multimedia , video
conferencing and video on-demand ) generate the demand for BW
and access network.
NEED OF BROADBAND
Home based business
Video conferencing among friends and family
•IN INDIA DOT HAS ISSUED A BROADBAND POLICY IN 2004, KEEPING IN
MIND ,BROADBAND CONNECTIVITY IS DEFINED AS-
“A DATA CONNECTION WHICH HAS CAPABILITY OF MINIMUM
DOWNLOAD SPEED OF 256 KBPS IS SAID TO BE BROADBAND.”
•IN 2012 NEW NTP WAS ANNOUNCED AND BROADBAND SPEED WAS
REVISED TO 2 MBPS IN PLACE OF 256 KBPS.
•PRACTICALLY OBTAINED SPEED IS 56 KBPS.
DIGITAL SUBSCRIBER LINE (DSL)
DSL is a family of technology that provides high speed Internet
access by transmitting digital data over the wires of a local
DSL service is delivered simultaneously with wired telephone
service on the same telephone line.
DSL uses higher frequency band for data transmission.
The bit rate of consumer DSL service typically ranges from 256
kbps-40mbps in downstream direction depending on DSL
technology used ,line condition and service level implementation.
WHY USE DSL
Traditional MODEM can provide data rate upto
56 kbps, to achieve high speed internet access
another techniques named DSL was used.
Sampling rate of telephone company =8000
samples /sec . Each sample is represented by 8
bits. One bit is used for control purpose. Hence
each sample is effectively represented by 7 bits.
Data rate =8000*7=56000 bits/sec
i.e 56 kbps.
WHERE DSL IS USED
DSL service is used on a local telephone
line. As telephone line is twisted pair
cable capable of handling BW upto 1.1
MHz. But voice utilizes only 4 KHz BW. So
to enhance the efficiency of cable
pair , a portion of large BW is utilized for
Distance is a limitation for DSL, why it's not also a
limitation for voice telephone calls ?
The answer lies in small amplifiers called loading
coils that the telephone company uses to boost
these loading coils are incompatible with ADSL
signals, so a voice coil in the loop between your
telephone and the telephone company's central
office will disqualify you from receiving ADSL.
TYPES OF DSL SERVICE
SDSL- Symmetric Digital Subscriber Line
ADSL- Asymmetric Digital Subscriber Line
HDSL- High Bit Rate Digital Subscriber Line
VDSL- Very High Bit Rate Digital Subscriber Line
Symmetric DSL (SDSL)
UPLOAD SPEED = DOWNLOAD SPEED
Upstream= 768 kbps
Downstream= 768 kbps
Ex.- Suitable for residential subscriber
who need equal speed in both
Asymmetrical DSL (ADSL)
ADSL is an asymmetric communication
technology designed for residential users; it
is not suitable for businesses.
Downstream data rate is greater than
upstream data rate.
Downstream = 1.5 – 8 Mbps
Upstream = 16 – 640 Kbps
MODULATION TECHNIQUE FOR ADSL
1. The modulation technique that is used for ADSL is Discrete
Multi tone Modulation (DMT). It combines FDM and QAM.
2. In DMT an available BW of 1.104 MHz is divided into 256
parallel stream . Each parallel stream is known as sub
channel or tone or bin or bucket.
3. Each channel uses a BW of 4.312 KHz and can carry
maximum 15 bits.
4. Voice – Channel 0
Upstream = Channel 6 to 30 ( 25 channels)
Downstream = Channel 31 to 255 (255 channels)
DSLAMDigital Subscriber line Access Multiplexer
A DSLAM is a Network Device, usually placed at a Telephone
Company Central Office, That Receives Signals from multiple
customer of DSL Connections and puts the signals on a high-
speed backbone line using Multiplexing Techniques.
DSLAM enables a phone company to offer business or home
users the fastest Phone Line Technology (DSL) with the fastest
backbone Network Technology.