What is prefix coding? Prefix coding is variable length coding algorithm. In assigns binary digits to the messages as per their probabilities of occurrence. Prefix of the codeword means any sequence which is initial part of the codeword. In prefix code, no codeword is the prefix of any other codeword.

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What is prefix coding? Prefix coding is variable length coding algorithm. In assigns binary digits to the messages as per their probabilities of occurrence. Prefix of the codeword means any sequence which is initial part of the codeword. In prefix code, no codeword is the prefix of any other codeword. State the channel coding theorem for a discrete memoryless channel. Given channel with capacity C.

Explain channel capacity theorem. The channel capacity of the discrete memory less channel is given as maximum average mutual information. Define channel capacity of the discrete memoryless channel. The channel capacity of the discrete memoryless channel is given as maximum average mutual information. Define mutual information.

The mutual information is defined as the amount of information transferred when xi is transmitted and yi is received. Define efficiency of the source encoder.

Define code redundancy. It is the measure of redundancy of bits in the encoded message sequence. Define rate of information transmission across the channel. Define bandwidth efficiency. What is the capacity of the channel having infinite bandwidth? Define a discrete memoryless channel. For the discrete memoryless channels, input and output, both are discrete random variables. The current output depends only upon current input for such channel. Find entropy.

What is entropy? Define code variance. Define Nyquist rate. What is meant by aliasing effect? Aliasing effect takes place when sampling frequency is less than nyquist rate. Under such condition, the spectrum of the sampled signal overlaps with itself. Hence higher frequencies take the form of lower frequencies. This interference of the frequency components is called aliasing effect. What is PWM refers. PWM is basically pulse width modulation. Width of the pulse changes according to amplitude of the modulating signal, it is also referred as pulse duration modulation or PDM.

State sampling theorem. Mention two merits of DPCM. DM encodes the input sample by only one bit. Step rise or fall. DPCM can have more than one bit for encoding the sample, it sends the information about difference between actual sample value and predicted sample value. How the message can be recovered from PAM?

The reconstruction filter integrates amplitudes of PAM pulses. Amplitude smoothing of the reconstructed signal is done to remove amplitude discontinuities due to pulses. Write an expressing for bandwidth of binary PCM with N message each with a maximum frequency of f m Hz. The PDM signal is given as a clock signal to monostable multivibrator. The multivibrator triggers on falling edge. PDM represents the input signal amplitude in the form of width of the pulse.

In other words, the position of the PPM pulse depends upon input signal amplitude. Mention the use of adaptive quantizer in adaptive digital waveform coding schemes. Adaptive quenatizer changes its step size accordion to variance of the input signal. Hence quantization error is significantly reduces due to adaptive quantization.

ADPCM uses adaptive quantization. The bit rate of such schemes is reduces due to adaptive quantization. What do you understand from adaptive coding?

In adaptive coding, the quantization step size and prediction filter coefficients are changed as per properties of input signal. This reduces the quantization error and number of bits used to represent the sample value.

Adaptive coding is used for speech coding at low bit rates. What is meant by quantization? While converting the signal value from analog to digital, quantization is performed.

The analog value is assigned to the nearest digital level. This is called quantization. The quantized value is then converted to equivalent binary value. The quantization levels are fixed depending upon the number of bits. Quantization is performed in every analog to digital conversion.

Hence signal to quantization noise ration in PCM depends upon number of bits or quantization levels. For the transmission of normal speech signal in the PCM channel needs the B.

Speech signals have the maximum frequency of 3. Normally 8 bits PCM is used for speed. It is required to transmit speech over PCM channel with 8-bit accuracy.

Assume the speech in baseband limited to 3. Determine the bit rate? What is meant by adaptive delta modulation? In adaptive delta modulation, the step size is adjusted as per the slope of the input signal.

Step size is made high if slope of the input signal is high. This avoids slope overload distortion. Delta modulation of delta modulation over pulse modulation schemes? Delta modulation encodes one bit per sample. Hence signaling rate is reduced in DM. What should be the minimum bandwidth required to transmit a PCM channel? W is the maximum signal frequency.

What is the advantage of delta modulation over PCM? Delta modulation uses one bit to encode one bit to encode one sample. Hence bit rate of delta modulation is low compared to PCM. How distortions are overcome in AXM? What is hamming distance?

The hamming distance between the two code vectors is equal to the number of elements in which they differ. Therefore the banning distance between X and Y is two.

Define code efficiency? The code efficiency is the ratio of message bits in a block to the transmitted bits for that block by the encoder ie. What is meant by systematic and non systematic codes? In a systematic block code, message bits appear first and then check bits. In the nonsystematic code, message and check bits cannot be identified in the code vector. What is meant by linear code? A code is linear if modulo-2 sum of any two code vectors produces another code vector.

This means any code vector can be expressed as linear combination of other code vectors. What are the error detection and correction capabilities of Hamming codes? Hence it can be used to detect double errors or correct single errors.

What is meant by cyclic code? Cyclic codes are the subclass of linear block codes. They have the properly that a cyclic shift of one codeword produces another code word.

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## IT2302-Information Theory and Coding

Descubra todo lo que Scribd tiene para ofrecer, incluyendo libros y audiolibros de importantes editoriales. SRM Nagar, Kattankulathur. Name of the Staffs. UNIT — 1.

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## IT2302 Information Theory and coding Important Questions for Nov/Dec 2012 Examinations

SRM Nagar, Kattankulathur. Name of the Staffs. UNIT — 1. State source coding theorem. State channel capacity theorem. State channel coding theorem for a discrete memory less channel.

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Anna University Department of Information Technology. Find a codebook for this four letter alphabet that satisfies source coding theorem 4. A discrete memory less source has an alphabet of five symbols whose probabilities of occurrence are as described here. Compare the Huffman code for this source. Also calculates the efficiency of the source encoder 8. A discrete memory less source has an alphabet of seven symbols whose probabilities of occurrence are as described below. Use the Lempel — Ziv algorithm to encode this sequence.