Question 1
Coherence time is dependent on the choice of the algorithm and corresponding rate of convergence.
A. TRUE
B. FALSE
View Answer
Answer: Option A
Explanation:
The choice of algorithm and its corresponding rate of convergence depends on the channel data rate and coherence time. The speed of the mobile unit determines the channel fading rate and the Doppler spread, which is directly related to coherence time of the channel.
Question 2
Computational complexity is a measure of ________
A. Time
B. Number of iterations
C. Number of operations
D. Accuracy
View Answer
Answer: Option C
Explanation:
Computational complexity is the number of operations required to make one complete iteration of the algorithm. It helps in comparing the performance with other algorithms.
Question 3
Convergence rate of LMS is fast.
A. TRUE
B. FALSE
View Answer
Answer: Option B
Explanation:
The convergence rate of the LMS algorithm is slow. It is slow due to the fact that it uses only one parameter i.e. step size that control the adaptation rate.
Question 4
For N symbol inputs, LMS algorithm requires ______ operations per iterations.
A. 2N
B. N+1
C. 2N+1
D. N2
View Answer
Answer: Option C
Explanation:
The LMS algorithm is the simplest algorithm. For N symbol inputs, it requires only 2N+1 operations per iteration.
Question 5
LMS equalizer minimizes __________
A. Computational complexity
B. Cost
C. Mean square error
D. Power density of output signal
View Answer
Answer: Option C
Explanation:
LMS equalizer is a robust equalizer. It is used to minimize mean square error (MSE) between the desired equalizer output and the actual equalizer output.
Question 6
Rate of convergence is defined by __________ of algorithm.
A. Time span
B. Number of iterations
C. Accuracy
D. Complexity
View Answer
Answer: Option B
Explanation:
Rate of convergence is required as number of iterations required for the algorithm to converge close enough to the optimum solution. It enables the algorithm to track statistical variations when operating in non stationary environment.
Question 7
Stochastic gradient algorithm is also called ________
A. Zero forcing algorithm
B. Least mean square algorithm
C. Recursive least square algorithm
D. Mean square error algorithm
View Answer
Answer: Option B
Explanation:
The minimization of the MSE is carried out recursively, and it can be performed by the use of stochastic gradient algorithm. This more commonly called the least mean square (LMS) algorithm.
Question 8
Which of the following algorithm uses simple programming?
A. LMS Gradient DFE
B. FTF algorithm
C. Fast Kalman DFE
D. Gradient Lattice DFE
View Answer
Answer: Option A
Explanation:
Advantages of LMS gradient DFE algorithm are low computational complexity and simple programming. While fast tranversal filter (FTF) algorithm, Fast Kalman DFE and gradient lattice DFE uses complex programming.
Question 9
Which of the following does not hold true for RLS algorithms?
A. Complex
B. Adaptive signal processing
C. Slow convergence rate
D. Powerful
View Answer
Answer: Option C
Explanation:
Recursive least square (RLS) algorithm uses fast convergence rate as opposed to LMS algorithms. They are powerful, albeit complex, adaptive signal processing techniques which significantly improves the convergence of adaptive equalizer.
Question 10
Which of the following factor could not determine the performance of algorithm?
A. Structural properties
B. Rate of convergence
C. Computational complexity
D. Numerical properties
View Answer
Answer: Option A
Explanation:
The performance of an algorithm is determined by various factors. These factors are rate of convergence, computational complexity and numerical properties. The performance of algorithm does not depend on structural properties.
Question 11
Which of the following is a drawback of zero forcing algorithm?
A. Long training sequence
B. Amplification of noise
C. Not suitable for static channels
D. Non zero ISI
View Answer
Answer: Option B
Explanation:
The zero forcing algorithm has the disadvantage that the inverse filter may excessively amplify noise at frequencies where the folded channel spectrum has high attenuation.
Question 12
Which of the following is not an algorithm for equalizer?
A. Zero forcing algorithm
B. Least mean square algorithm
C. Recursive least square algorithm
D. Mean square error algorithm
View Answer
Answer: Option D
Explanation:
Three classic equalizer algorithm are zero forcing (ZF) algorithm, least mean squares (LMS) algorithm and recursive least squares (RLS) algorithm. They offer fundamental insight into algorithm design and operation.
Question 13
Zero forcing algorithm performs well for wireless links.
A. TRUE
B. FALSE
View Answer
Answer: Option B
Explanation:
ZF is not often used in wireless links as it neglects the effect of noise altogether. However, it performs well for static channels with high SNR, such as local wired telephone links.