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The correct option is (d) Could be either ZERO or one

For explanation: The decoder front end produces an integer for each BIT in the DATA stream. This integer is the measure of how likely it is that the bit 0 or 1 and is called as soft bit. It ranges from -127 to 127. Here 0 represents ‘could be either zero or one’.

Correct option is (d) Very likely one

Explanation: The decoder front end produces an integer for each BIT in the data stream. This integer is the MEASURE of how likely it is that the bit 0 or 1 and is called as soft bit. It RANGES from -127 to 127. Here 100 represents very likely one.

Correct CHOICE is (B) Scatter error BURSTS

Explanation: An inter leaver installed between the TWO decoders connected in series is USED to scatter error bursts.

The correct choice is (b) Certainly zero

To explain: The decoder FRONT end produces an INTEGER for each bit in the DATA stream. This integer is the measure of how likely it is that the bit 0 or 1 and is CALLED as soft bit. It ranges from -127 to 127. Here -127 REPRESENTS certainly zero.

The CORRECT answer is (a) True

Explanation: Two elementary decoders are CONNECTED in SERIAL connection for decoding the turbo codes.

Correct choice is (C) Inter leavers & PUNCHING pattern

For explanation: There are many instances of turbo CODES, using different COMPONENT ENCODERS, input/output ratios, inter leavers, punching patterns.

Correct option is (a) Subtracting equivocation from ENTROPY

The explanation is: According to Shannon the average EFFECTIVE INFORMATION is obtained by subtracting the equivocation from the entropy of the source.

Correct ANSWER is (a) Zero

The explanation: For a error free channel conditional probability should be zero, because having RECEIVED Y there is complete CERTAINTY about the MESSAGE X.

Correct option is (c) Rs/2

The explanation: Theoretical minimum nyquist bandwidth NEEDED for the BASEBAND transmission of Rs symbols per second WITHOUT ISI is Rs/2.

The correct answer is (B) ERROR correcting code

To elaborate: Concatenated CODES belong to the class of error correcting codes.

Right option is (b) Parallel concatenation code

For explanation I would say: Turbo codes implemented a parallel concatenation of two CONVOLUTION codes with an INTER leaver and an ITERATIVE DECODER.

Right option is (a) Low error rate

Explanation: A concatenated CODE has low error rate with an overall implementation complexity which is LESS than that would be required for SINGLE level CODING.

The correct option is (b) 2MN-2M+2

For explanation I would say: The inter leaver or De-inter leaver delay is 2MN symbol TIMES. M(N-1)+1memory CELLS needs to be FILLED before TRANSMISSION can begin. Thus the minimum end to end delay is 2MN-2M+2 symbol times, not including any channel propagation delay.

Right answer is (b) Two LEVELS of coding

The best I can explain: A concatenated code is the one that USES two levels of coding, inner code and OUTER code to ACHIEVE DESIRED error performance.

Correct answer is (d) All of the mentioned

To elaborate: A channel that exhibits multi-path FADING where the signal arrives at the receiver over two or more DIFFERENT paths. This channel has MEMORY, exhibits mutually dependent signal TRANSMISSION IMPAIRMENT.

Right OPTION is (c) New samples are added & UNRELIABLE samples are removed

To explain: The function of the INTERPOLATION function is to ADD new samples estimated from the reliable ones in place of unreliable ones.

Correct answer is (a) LARGER, smaller

Easy explanation: There is a trade off between ERROR CORRECTION and erasure correction, the larger the error CORRECTING capability used the smaller will be the erasure correcting capability.

The correct CHOICE is (c) Correction & Concealment

For explanation I would say: The cross interleave REED Solomon error control scheme in the CD system INVOLVES both correction and concealment of errors.

Correct option is (d) All of the mentioned

Easy EXPLANATION: Some of the sources of channel errors are some UNWANTED particles, air bubbles, finger prints, SCRATCHES ETC.

The CORRECT choice is (c) Digital STORAGE & REPRODUCTION of audio SIGNALS

Explanation: Compact DISC digital audio system is used for both digital storage and reproduction of audio signals.

The CORRECT answer is (B) Safety theorem

For explanation I would say: According to safety theorem, if the inversion is performed correctly, the multiplication of ORIGINAL matrix by INVERTED matrix will yield identity matrix.

The CORRECT option is (B) Non zero ELEMENTS

The best explanation: In a primitive polynomial at least one of its roots will be primitive ELEMENT. A primitive elements are those which YIELD non zero elements when raised to a higher order exponent.

Right answer is (b) n-k+1

Easiest explanation: REED Solomon code achieves the largest POSSIBLE code MINIMUM DISTANCE for any linear code and it is given by n-k+1.

Right choice is (a) m+1

The EXPLANATION is: Look ahead LENGTH L is given by m+1 where m is the preselected POSITIVE integer.

Right option is (c) Coding GAIN & Complexity INCREASES

For explanation: On increasing the look AHEAD length the coding gain increases and also increases the decoder implementation complexity.

The correct answer is (c) NON binary & Cyclic

For explanation I would say: Reed Solomon codes are non binary cyclic codes with symbols made up of m BIT SEQUENCES where m is any positive integer with value GREATER than 2.

Right choice is (b) Maximum CORRELATION

To EXPLAIN I WOULD say: While using Euclidean DISTANCE squared METRIC, maximum correlation is desirable rather than minimum distance.

The correct CHOICE is (c) Euclidean distance & distance squared

For explanation: As soft decision DECODING algorithm has limited resolution it cannot USE hamming distance metric. Instead it USES Euclidean and monotonic metric such as Euclidean distance squared.

The correct option is (B) Soft decision decoder

To explain: The soft decision algorithm has LIMITED resolution than hard decision algorithm and thus it cannot use hamming DISTANCE METRIC.

Correct choice is (a) Not have catastrophic ERROR PROPAGATION

The explanation: Generally code’s are selected BASED on the free distance property. The CRITERIA for selecting code is that it should not have catastrophic error propagation and it should have maximum free distance.

The correct option is (b) Finite, infinite

To EXPLAIN I would say: A catastrophic error is DEFINED as an event WHEREBY a finite NUMBER of code symbols error causes an infinite number of decoded data bit errors.

Correct OPTION is (b) MINIMUM DISTANCE

The best I can explain: Minimum distance between all pair of CODE words is related to the error CORRECTING capability of the code.

The CORRECT CHOICE is (a) Beginning of received sequence

The best explanation: Branch word synchronization is the PROCESS of determining the beginning of a branch word in the received sequence. Such synchronization can take place WITHOUT adding new information to the transmitted SYMBOLS.

The correct CHOICE is (B) False

Best explanation: The quantized GAUSSIAN channel is referred to as the soft DECISION channel.

Correct option is (a) True

The best I can explain: A binary symmetric CHANNEL is an EXAMPLE for hard decision channel which means that even though CONTINUOUS values may be received by the DEMODULATOR the BSC only allows firm decisions.

The correct answer is (B) More memory

The best explanation: The PRICE paid for SOFT decision DECODING is an increase in required memory size at the DECODER.

The CORRECT choice is (b) More than 2

Explanation: If the quantization LEVEL of a demodulator output is 2 it is called as HARD decision decoding and if it is greater than 2 it is called as soft decision decoding.