40+ Starmark Interview Questions and Answers

The choice of scheduling strategy in real-time operating systems depends on the system requirements and constraints.

• Priority-based scheduling is commonly used in real-time operating systems.

• Earliest Deadline First (EDF) scheduling is suitable for systems with strict deadlines.

• Rate Monotonic Scheduling (RMS) is appropriate for systems with periodic tasks.

• Shortest Job First (SJF) scheduling can be used for systems with non-periodic tasks.

• The choice of scheduling strategy should...read more

Use a hash table to store the strings with their associated integers.

• Create a hash table with the integers as keys and the strings as values.

• Use a hash function to map the integers to their corresponding buckets in the table.

• To search for a string, compute the hash of its associated integer and look it up in the table.

Two modes of execution in operating systems are user mode and kernel mode.

• User mode is a restricted mode where user applications run.

• Kernel mode is a privileged mode where the operating system kernel runs.

• User mode has limited access to hardware and system resources.

• Kernel mode has full access to hardware and system resources.

• Switching between modes requires a system call or interrupt.

• Examples of system calls include opening a file or creating a process.

• Kernel mode is more po...read more

The number of parallelograms in a grid of mxn parallel lines can be calculated using a formula involving combinations.

• The formula to calculate the number of parallelograms is (m * (m + 1) * n * (n + 1)) / 4

• For example, in a 2x3 grid, there are (2 * 3 * 3 * 4) / 4 = 18 parallelograms

• The formula is derived by considering all possible combinations of 4 points on the grid to form a parallelogram

Negating alternate samples in time domain results in spectral inversion.

• Negating alternate samples in time domain is equivalent to multiplying the signal by a square wave with alternating values of +1 and -1.

• This multiplication in time domain results in spectral convolution in frequency domain.

• The frequency spectrum is inverted around the Nyquist frequency due to the spectral convolution.

• This technique is used in some audio effects like flangers and phasers.

• It can also be use...read more

To construct a 4x16 decoder from 2x4 decoders with enable pins, you can use the enable pins of the 2x4 decoders to control the output of the 4x16 decoder.

• Use one 2x4 decoder to decode the first 2 bits of the input and the other 2x4 decoder to decode the last 2 bits of the input.

• Connect the enable pins of the 2x4 decoders to the same control signal, which will act as the enable pin for the 4x16 decoder.

• Combine the outputs of the 2x4 decoders to form the 16 outputs of the 4x16 ...read more

My LAB has a star topology because it provides centralized control and easy troubleshooting.

• Star topology has a central hub that connects all devices

• All communication goes through the hub

• Easy to add or remove devices without affecting the rest of the network

• Commonly used in LANs

• Examples: Home networks, small businesses

The product of N normal RVs is a non-central chi-squared distribution with N degrees of freedom.

• The distribution is non-central chi-squared with N degrees of freedom

• The non-centrality parameter is the product of the means of the RVs

• The variance of the distribution is the product of the variances of the RVs

• This distribution is commonly used in signal processing and communication systems

Sort a linked list with minimum time complexity

• Use merge sort or quick sort for O(n log n) time complexity

• Implement the sorting algorithm recursively

• Use a temporary linked list to merge the sorted sub-lists

• Consider edge cases like empty list or list with only one element

Code to print all connected components in a graph.

• Implement Depth First Search (DFS) algorithm to traverse the graph.

• Maintain a visited array to keep track of visited nodes.

• For each unvisited node, perform DFS and add all visited nodes to a connected component.

• Repeat until all nodes are visited.

• Print all connected components.

Pdf of sum and max of two iid uniform rvs in the range 0 to 1

• The sum of two uniform random variables is a triangular distribution

• The maximum of two uniform random variables is also a uniform distribution

• The joint pdf can be derived using convolution and differentiation

• The resulting pdf will have piecewise functions

The impulse response of a system can be found by applying a short impulse input and measuring the output.

• Apply a short impulse input to the system

• Measure the output of the system

• Take the Fourier transform of the input and output signals

• Divide the output Fourier transform by the input Fourier transform to get the transfer function

• Take the inverse Fourier transform of the transfer function to get the impulse response

Rayleigh fading is a statistical model for the effect of a propagation environment on a radio signal.

• Rayleigh fading is a common model for wireless channels because it accurately represents the random fluctuations in signal strength caused by multipath propagation.

• It assumes that the signal is scattered by many objects in the environment, resulting in a large number of reflected signals arriving at the receiver with different phases and amplitudes.

• This randomness is modeled b...read more

Topology deals with the study of properties of space that are preserved under continuous transformations.

• Classification of surfaces

• Homotopy theory

• Fundamental group

• Manifolds

• Knot theory

Coherence time is the time duration over which a signal remains correlated. Coherence bandwidth is the frequency range over which a signal remains correlated. Delay spread is the time difference between the arrival of the first and last multipath components. Doppler spread is the frequency difference between the maximum and minimum Doppler shifts.

• Coherence time and coherence bandwidth are important parameters in wireless communication systems.

• Delay spread is a measure of the ...read more

Coherence time and subcarrier spacing are inversely proportional.

• Coherence time is the time duration over which a wireless channel remains constant.

• Subcarrier spacing is the frequency difference between adjacent subcarriers in an OFDM system.

• The coherence time and subcarrier spacing are inversely proportional to each other.

• If the subcarrier spacing is decreased, the coherence time increases and vice versa.

• This relationship is important in designing OFDM systems for wireless c...read more

The Fourier transform of x1,0,x2,0,x3,0 is X(f) + X(-f)

• The Fourier transform of a shifted signal is the original transform multiplied by a complex exponential

• The Fourier transform of x1,0,x2,0,x3,0 is the sum of the Fourier transforms of x1,x2,x3 shifted by 0

• The Fourier transform of a real signal is symmetric about the origin

• Therefore, the Fourier transform of x1,0,x2,0,x3,0 is X(f) + X(-f)

A symbolic link is a file that acts as a pointer to another file or directory.

• Symbolic links are similar to shortcuts in Windows.

• They allow for easy access to files and directories located in different parts of the file system.

• Symbolic links can be created using the 'ln -s' command in Unix-based systems.

• They can be identified by the 'l' flag in the output of the 'ls -l' command.

• Symbolic links can be used to create a backup of a file or directory without duplicating the data.

Cramer Rao's bound is a lower bound on the variance of any unbiased estimator of a parameter.

• It is used in statistical signal processing to determine the accuracy of parameter estimation.

• It is based on the Fisher information matrix, which measures the amount of information a random variable carries about a parameter.

• The bound is tight when the estimator is efficient, meaning it achieves the minimum variance possible.

• It is useful for comparing the performance of different esti...read more

The Nyquist frequency for unsymmetrical signals can be found using the sampling theorem.

• The Nyquist frequency is half of the sampling rate.

• For unsymmetrical signals, the highest frequency component should be considered when determining the Nyquist frequency.

• Nyquist frequency = 0.5 * highest frequency component

The number of parallelograms in an mXn set of parallel lines can be calculated using a formula.

• Use the formula: (m * (m + 1) * n * (n + 1)) / 4

• For example, in a 2x3 set of parallel lines, there are 18 parallelograms

Optimal threshold for BPSK detection can be derived using the likelihood ratio test.

• The threshold should be set such that the probability of false alarm is equal to the probability of detection.

• The threshold can be derived by finding the point where the likelihood ratio crosses a certain threshold value.

• The threshold can also be derived by maximizing the signal-to-noise ratio.

• Simulation and testing can be done to verify the performance of the threshold.

Computer networking is the practice of connecting devices together to share resources and information.

• It involves the use of hardware and software to create and manage networks

• Networking protocols such as TCP/IP are used to facilitate communication between devices

• Examples of computer networks include LANs, WANs, and the internet

• Networking allows for sharing of resources such as printers and files

• Security measures such as firewalls and encryption are used to protect networks a...read more

A wireless communication channel is an example of a linear time variant system.

• Wireless communication channels experience time-varying fading due to changes in the environment.

• The channel impulse response changes over time, making it a linear time variant system.

• Examples of wireless communication channels include Wi-Fi, cellular networks, and satellite communication.

• The channel can be modeled as a linear time variant system using techniques such as channel estimation and equa...read more

Design an OFDM system for a given scenario.

• Determine the bandwidth and carrier frequency

• Choose the number of subcarriers and their spacing

• Select a suitable cyclic prefix length

• Implement modulation scheme and error correction coding

• Optimize system performance through simulation and testing

Linear time invariant systems are systems whose output is proportional to the input and is not affected by time.

• Linear time invariant systems have constant coefficients and do not change over time.

• The output of the system is a scaled version of the input signal.

• Examples of LTI systems include RC circuits, mass-spring-damper systems, and filters.

• LTI systems are important in signal processing and control theory.

• They can be analyzed using techniques such as Laplace transforms an...read more

Call by value passes a copy of the value while call by reference passes a reference to the value.

• Call by value creates a new copy of the value being passed, while call by reference passes a reference to the original value.

• In call by value, changes made to the parameter inside the function do not affect the original value, while in call by reference, changes made to the parameter inside the function affect the original value.

• Call by value is used for simple data types like int...read more

Qualcomm is a leading technology company with a strong focus on innovation and cutting-edge solutions.

• Qualcomm is a leader in the mobile technology industry

• The company has a strong reputation for innovation and research

• Qualcomm's products and solutions are used by millions of people worldwide

• The company has a diverse portfolio of products, including processors, modems, and wireless technologies

• Qualcomm is committed to sustainability and social responsibility

Trailing zero problem in factorials

• Trailing zeros in a factorial are the number of zeros at the end of the factorial's decimal representation

• The number of trailing zeros is equal to the number of times 10 can be divided from the factorial

• To find the number of trailing zeros, divide the number by 5 and add the quotient to the result of dividing the quotient by 5, and so on

• For example, the factorial of 10 has 2 trailing zeros, while the factorial of 25 has 6 trailing zeros

OFDM is a modulation technique that divides a high-speed data stream into multiple subcarriers. CP is added to prevent inter-symbol interference.

• OFDM stands for Orthogonal Frequency Division Multiplexing

• It is used in high-speed data transmission over wireless and wired networks

• OFDM divides the data stream into multiple subcarriers that are orthogonal to each other

• CP or Cyclic Prefix is added to each OFDM symbol to prevent inter-symbol interference

• CP is a copy of the end of th...read more

Relocation problems can be challenging but can also offer new opportunities.

• Adjusting to a new environment can be difficult

• Finding new housing and schools can be stressful

• Making new friends and building a support system takes time

• Exploring a new city can be exciting and offer new experiences

• Relocation can offer career advancement and new opportunities

Design a 4:16 decoder using 2:4 decoders

• Use two 2:4 decoders to decode the 4 input bits into 16 output bits

• Connect the enable input of each 2:4 decoder to the complement of the other decoder's enable input

• Connect the outputs of the two 2:4 decoders to form the 16 output bits

Nyquist sampling theorem states that a signal must be sampled at least twice its highest frequency component to be accurately reconstructed.

• The theorem is named after Harry Nyquist.

• It is used in digital signal processing and communication systems.

• Sampling rate must be greater than or equal to 2 times the highest frequency component.

• If the sampling rate is less than 2 times the highest frequency component, aliasing occurs.

• Aliasing can be avoided by using a low-pass filter befo...read more

Qualcomm is a leading semiconductor and telecommunications equipment company with a strong focus on innovation.

• Qualcomm is a leader in 5G technology and has been instrumental in the development of this technology.

• The company has a strong patent portfolio and is known for its innovative products.

• Qualcomm has partnerships with many major technology companies, including Apple and Samsung.

• The company has a strong commitment to sustainability and has set ambitious goals for reduci...read more

A CMOS inverter consists of a PMOS and an NMOS transistor connected in series.

• The PMOS and NMOS transistors are connected in series with their gates connected together.

• The output is taken from the connection between the two transistors.

• The input is applied to the gate of the NMOS transistor.

• The PMOS transistor is connected to VDD and the NMOS transistor is connected to GND.

• The layout consists of two complementary transistors and their interconnects.

• The layout is designed to m...read more

RC circuits with diodes involve the combination of resistors, capacitors, and diodes to control the flow of current.

• RC circuits with diodes are commonly used in electronic circuits to control the flow of current and voltage.

• The diode in the circuit allows current to flow in only one direction, preventing reverse current flow.

• The time constant of the circuit is determined by the values of the resistor and capacitor, affecting the charging and discharging of the capacitor.

• Examp...read more

An LTI system is a linear time-invariant system that produces an output signal from an input signal.

• LTI systems have constant parameters that do not change over time

• The output of an LTI system is a linear combination of the input signal and the system's impulse response

• Examples of LTI systems include electronic filters, audio equalizers, and control systems

The sampling theorem states that in order to accurately reconstruct a continuous signal from its samples, the sampling frequency must be at least twice the highest frequency component of the signal.

• The sampling theorem, also known as Nyquist-Shannon theorem, was developed by Claude Shannon and Harry Nyquist in the 1940s.

• It states that in order to accurately reconstruct a continuous signal from its samples, the sampling frequency must be at least twice the highest frequency co...read more

CTFT of a periodic signal involves decomposing the signal into its frequency components.

• CTFT stands for Continuous-Time Fourier Transform

• Periodic signals have discrete frequency components

• CTFT of a periodic signal results in a frequency spectrum with Dirac delta functions at the harmonic frequencies

Convolution equation states that the output of a linear time-invariant system is the convolution of the input and impulse response.

• Convolution is a mathematical operation that combines two functions to produce a third function.

• The convolution of two functions f and g is denoted by (f * g).

• The convolution equation is given by y(t) = x(t) * h(t), where x(t) is the input signal, h(t) is the impulse response, and y(t) is the output signal.

• Convolution is used in signal processing,...read more

The sampling theorem states that a continuous signal can be perfectly reconstructed from its samples if the sampling rate is at least twice the highest frequency component of the signal.

• The sampling theorem, also known as Nyquist-Shannon sampling theorem, is a fundamental concept in signal processing.

• It states that in order to accurately reconstruct a continuous signal from its samples, the sampling rate must be at least twice the highest frequency component of the signal.

• For...read more

DTFT of a signal is a continuous function that represents the frequency content of the signal.

• DTFT stands for Discrete-Time Fourier Transform

• It is used to analyze the frequency content of a discrete-time signal

• The DTFT of a signal x[n] is defined as X(e^jw) = Σ x[n]e^(-jwn)

• Example: DTFT of a rectangular pulse signal