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CS601 Assignment No. 4 Semester Fall 2012 Data Communication Due Date: 29-01-2013 Please share your ideas here

Assignment No. 4
Semester Fall 2012
Data Communication - CS601


Total Marks: 30


Due Date: 29-01-2013


Objective: Understanding the T & E lines and Error detection method.


Please read the following instructions carefully before solving & submitting assignment:

Assignment should be in your own wordings not copied from net, handouts or books.

It should be clear that your assignment will not get any credit (marks) if:


  • The assignment is submitted after due date.
  • The submitted assignment does not open or file is corrupt.
  • The assignment is copied (from other student or copied from handouts or internet).


For any query about the assignment, contact at






Q. 1. Telephone Companies use a hierarchy of Digital Signals Service (DS) which have different levels as DS-0, DS-1, DS-2, DS-3 and DS-4. All these levels have different data rates and are implemented through different types of T lines (from T-1 to T-4) or E lines (from E-1 to E-4) on the basis of data rate in each level.

Now you are required to fill  the columns of the given table according to following  instructions:

  1. Calculate the corresponding data rate against each number of given voice channels.
  2. Write the best suitable type of line (form T-1 to T-4 or from E-1 to E-4 line) with total number of T or E lines corresponding to calculated data rate. [15 Marks]


Note: Type of line (form T-1 to T-4 or from E-1 to E-4 line) and total number of T or E lines must be selected on the basis of calculated data rate having minimum wastage of capacity of the line. Only optimal solution is required for these columns.


No. of Voice Channels

Data Rate in Mbps

Type of T/E line used

Total No. of T/E lines
























Q. 2.  Using Modulo-2 Division and Polynomial x4 + x3 + x + 1, perform the complete process of Cyclic Redundancy Check (CRC) on the given message by writing all steps for both sender and receiver end.

 Assume that the message has been received by the receiver without any error. [15 Marks]






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Replies to This Discussion


DS 0 ke liye to koi t line nai hoti i mean ke wo to sirf base banta hai then aap ne DS0 ke liye T1 line kyun select ki??


what is meant by "

total number of T or E lines must be selected on the basis of calculated data rate having minimum wastage of capacity of the line. Only optimal solution is required for these columns."explain please

According to me solution:


total chanel * cahanel capcty = data rate


total chanel = 50

chanel capcty = 64kbps

50*64kbps= 3200

ye confusion hy k mbps men cnvrt krny k liey 1024 se divid krain gy ya 1000 se lkn jo file men ne sbmit ki hy us men men ne 1000 se divid kia hy


3200/1000 = 3.2mbps

according to data rate hmen T ya E lines ko select krna hy hm 1 se ziada lines b use kr skty hen ta k wastage kam se km ho


data rate=32mbps

if we combine 2 E-1 lines we can get the data rate 4.096mbps agr hm isy use krain to hmra wastag  hoga 0.896

lkn agr ham koi r conbination bnain to phir hmari wastag ziada ho gi

isis trha baqi ka q b solv krain


yahn hmen (CRC) ka proces btana hy. hmen Polynomial dia gya hy us se ham divisor nikalain gy r jitni bits divisor ki hon gi us se 1 bit kam 0's ham real data ka sath atach kr k usy binry division use krty hwy devide krain gy jo remainder ho ga woh hmara CRC ho ga usy ham real data k sath atach kr k send kr dain gy reciver phir uski division kry ga r agr remainder 0 ho to woh data accept kr lay ga warna wapis snd kr day ga yahan q k hmara data without error recive ho gya hy to reciver sidee py hmara remainder 0 hna chahey

Thanks this information is very helpful.

Digital Signal Service 0 (DS0)

Digital Signal 0 (DS0) is a basic digital signaling rate of 64 kbit/s, corresponding to the capacity of one voice-frequency-equivalent channel.[1] The DS0 rate, and its equivalents E0 and J0, form the basis for the digital multiplex transmission hierarchy in telecommunications systems used in North America, Europe, Japan, and the rest of the world, for both the early plesiochronous systems such as T-carrier and for modern synchronous systems such as SDH/SONET.
The DS0 rate was introduced to carry a single digitized voice call. For a typical phone call, the audio sound is digitized at an 8 kHz sample rate using 8-bit pulse-code modulation for each of the 8000 samples per second. This resulted in a data rate of 64 kbit/s.
Because of its fundamental role in carrying a single phone call, the DS0 rate forms the basis for the digital multiplex transmission hierarchy in telecommunications systems used in North America. To limit the number of wires required between two involved in exchanging voice calls, a system was built in which multiple DS0s are multiplexed together on higher capacity circuits. In this system, twenty-four (24) DS0s are multiplexed into a DS1 signal. Twenty-eight (28) DS1s are multiplexed into a DS3. When carried over copper wire, this is the well-known T-carrier system, with T1 and T3 corresponding to DS1 and DS3, respectively.
Besides its use for voice communications, the DS0 rate may support twenty 2.4 kbit/s channels, ten 4.8 kbit/s channels, five 9.67 kbit/s channels, one 56 kbit/s channel, or one 64 kbit/s clear channel.
E0 (standardized as ITU G.703) is the European equivalent of the North American DS0 for carrying . However, there are some subtle differences in implementation. Voice signals are encoded for carriage over E0 according to ITU G.711. Note that when a T-carrier system is used as in North America, robbed bit signaling can mean that a DS0 channel carried over that system is not an error-free bit-stream. The out-of-band signaling used in the European E-carrier system avoids this.

The United States Bell System activated the first commercial digital carrier system in 1962 in Chicago, Illinois, where electrical noise from high-tension lines and automotive ignitions interfered with analog systems. The system was designated T1, with the T standing for Terrestrial to distinguish the land transmission from satellite transmission. (Bell Laboratories also launched Telstar I, the first communications satellite, in 1962.) T-carrier was designed for a four-wire twisted-pair circuit, although the DSX-1 interface is medium-independent, i.e., can be provisioned over any of the transmission media, at least at the T1 rate of 1.544 Mbps. At the T3 rate of 44.736 Mbps, twisted pair is unsuitable over distances greater than 50 feet due to issues of signal attenuation. As the first digital carrier system,T-carrier set the standards for digital transmission and switching, including the use of pulse code modulation (PCM) for digitizing analog voice signals. (Note: T-carrier uses the µ-law (mu-law) companding technique for PCM.) T-carrier not only set the basis for the North American digital hierarchy, but also led to the development of E-carrier in Europe and J-carrier in Japan.The fundamental building block of T-carrier is a 64-kbps channel, referred to as DS-0 (Digital Signal level Zero). Through time-division multiplexing (TDM), T-carrier interleaves DS-0 channels at various signaling rates to create the services that comprise the North American digital hierarchy, as detailed in Table T-1.

Table T-1: North American Digital Hierarchy: T-carrier
Digital Signal (DS) Level Data Rate 64-Kbps Channels (DS-0s) Equivalent T1s
DS-0 64 Kbps 1 1/24
DS-1 (T1) 1.544 Mbps 24 1
DS-1C (T1C) 3.152 Mbps 48 2
DS-2 (T2) 6.312 Mbps 96 4
DS-3 (T3) 44.736 Mbps 672 28
DS-4 (T4) 274.176 Mbps 4,032 168
DS-5 (T5) 400.352 Mbps 5,760 250

cyclic redundancy checking

Cyclic redundancy checking is a method of checking for errors in data that has been transmitted on a communications link. A sending device applies a 16- or 32-bit polynomial to a block of data that is to be transmitted and appends the resulting cyclic redundancy code (CRC) to the block. The receiving end applies the same polynomial to the data and compares its result with the result appended by the sender. If they agree, the data has been received successfully. If not, the sender can be notified to resend the block of data.

The ITU-TS (CCITT) has a standard for a 16-bit polynomial to be used to obtain the cyclic redundancy code (CRC) that is appended. IBM's Synchronous Data Link Control and other protocols use CRC-16, another 16-bit polynomial. A 16-bit cyclic redundancy code detects all single and double-bit errors and ensures detection of 99.998% of all possible errors. This level of detection assurance is considered sufficient for data transmission blocks of 4 kilobytes or less. For larger transmissions, a 32-bit CRC is used. The Ethernet and token ring local area network protocols both used a 32-bit CRC.

In Europe, CRC-4 is a multiframe system of cyclic redundancy checking that is required for switches on E-1 lines.

A less complicated but less capable error detection method is the checksum method. See modem error-correcting protocols for a list of protocols that use either of these methods.


Tauqeer bhai wala same question mera bhe hia

Data rate k bad wala part T/E es k smjh nae a rahi 

ye to pta lg gia k mbps kese aye ga ab type of t and e line and their total no kese nikala jae

or koi 2nd q b upload kre


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