Kasturi Vasudevan

Indian Institute of Technology Kanpur | IIT Kanpur · Advanced Centre for Electronic Systems (ACES)

Achieving high bit rates is the main goal of wireless technologies like 5G and beyond. This translates to obtaining high spectral efficiencies using large number of antennas at the transmitter and receiver (single user massive multiple input multiple output or SU-MMIMO). It is possible to have a large number of antennas in the mobile handset at mm-...

Achieving high bit rates is the main goal of wireless technologies like 5G and beyond. This translates to obtaining high spectral efficiencies using large number of antennas at the transmitter and receiver (single user massive multiple input multiple output or SU-MMIMO). It is possible to have a large number of antennas in the mobile handset at mm-...

In Fig. 3.1, the magnitude of the phasor voltages Voltagephasor|textit across L and C are 5 V and 4 V, respectively.

Solution: Refer to Fig. 1.1. Assuming that a voltage drop is negative and a voltage rise is positive.

Draw Vo versus Vi for the circuit in . Assume ideal diode.

Solution: Consider Fig. 6.1. We have the following situations:

In Fig. 2.1, the switch \(S_1\) is closed for \(0\le t < \infty \) and \(S_2\) is closed for \(0 \le t \le 1\) s. \(S_2\) is opened at \(t=1\) s. Find i(t) for \(0 \le t < \infty \). It is given that \(i(0)=0\) A.

Determine the transfer function \(H(\omega )=\vec V_o/\vec V_s\) in Fig. 7.1. Assume ideal op amp.

In Fig. 4.1, find the input impedance Z→in at resonance and the resonant frequency Frequencyresonant|textit in rad/s.

The International Telecommunication Union (ITU) has recently announced the detailed 5G specifications for International Mobile Telecommunications (IMT-2020). A number of candidate Radio Interface Technologies (RITs) were being evaluated by the independent evaluation groups of the ITU. Meanwhile, the roll out of 5G is going on, and 5G is available i...

This work deals with turbo coded single user massive multiple input multiple output (SU-MMIMO) systems, with and without precoding. SU-MMIMO has a much higher spectral efficiency compared to multi-user massive MIMO (MU-MMIMO) since independent signals are transmitted from each of the antenna elements (spatial multiplexing). MU-MMIMO that uses beamf...

In this paper, a printed low-profile antenna with frequency and pattern reconfigurable functionality is designed in three modes. Each mode operates at different frequency bands and has several options available for pattern reconfiguration in these bands. The proposed antenna consists of eight pin-diode switches (S1 to S8). The switches S1 and S2, i...

A speech signal has a total duration of 10 s. It is sampled at a rate of 8 kHz and then encoded. The \(\text{ SNR}_Q\) must be greater than 40 dB. Calculate the minimum storage capacity required to accommodate this digitized speech signal.

For the transmit filter with impulse response given in Fig. 7.1, draw the output of the matched filter.

Show that the magnitude of the correlation coefficient \(|\rho |\) is always less than or equal to unity.

In a frequency-modulated radar, the instantaneous frequency of the transmitted carrier \(f_t(t)\) is varied as given in Fig. 4.1. The instantaneous frequency of the received echo \(f_r(t)\) is also shown, where \(\tau \) is the round-trip delay time.

This textbook covers the fundamental concepts of analog communications with a Q&A approach. It is a comprehensive compilation of numerical problems and solutions covering all the topics in analog communications. Richly illustrated with figures, this book covers the important topics of signals and systems, random variables and random processes, ampl...

The initial solution of a massive multiple-input multiple-output (M-MIMO) detector for uplink (UL) is greatly influence the balance between the bit error rate (BER) performance and the computational complexity. Although the maximum likelihood (ML) detector obtains the best BER performance, it has an extremely high computational complexity. Iterativ...

Precoding is a method of compensating the channel at the transmitter. This work presents a novel method of data detection in turbo coded single user massive multiple input multiple output (MIMO) systems using precoding. We show via computer simulations that, when precoding is used, re-transmitting the data does not result in significant reduction i...

This study investigates the uplink performance of offset quadrature amplitude modulation (OQAM)‐based orthogonal frequency division multiplexing (OFDM) waveform in single‐cell multi‐user massive multiple‐input multiple‐output (MIMO) systems over Ricean fading. An uplink training‐based minimum mean square error (MMSE) channel estimation by exploitin...

Detecting the presence of a valid signal is an important task of a telecommunication receiver. When the receiver is unable to detect the presence of a valid signal, due to noise and fading, it is referred to as an erasure. This work deals with the probability of erasure computation for orthogonal frequency division multiplexed (OFDM) signals used b...

Detecting the presence of a valid signal is an important task of a telecommunication receiver. When the receiver is unable to detect the presence of a valid signal, due to noise and fading, it is referred to as an erasure. This work deals with the probability of erasure computation for orthogonal frequency division multiplexed (OFDM) signals used b...

We consider vertical Bell laboratories layered space-time architecture for offset quadrature amplitude modulation based filter bank multicarrier (FBMC) systems, and propose two different receivers. We first investigate a low-complexity QR decomposition (QRD) based conventional minimum mean square error (MMSE) successive interference cancellation (C...

This work addresses frequency synchronization and channel estimation for highly frequency-selective orthogonal frequency division multiplexed systems with offset quadrature amplitude modulation. A two-step approach is proposed, wherein a coarse carrier frequency offset (CFO) estimator, which does not require channel knowledge, is designed in the fi...

Welcome to the inaugral issue of Semiconductor Science and Information Devices. It is expected that future telecommunication networks (5G and beyond) will host not only humans but also machines in the form of Internet of Things (IoT). Therefore, there is a growing demand for increased data rates, of the order of tens of gigabits per second for each...

This paper analyses the performance of filter bank multicarrier (FBMC) signaling in conjunction with offset quadrature amplitude modulation (OQAM) in multi-user (MU) massive multiple-input multiple-output (MIMO) systems. Initially, closed form expressions are derived for tight lower bounds corresponding to the achievable uplink sum-rates for FBMC-b...

In this paper, a general preamble-based time domain channel estimation model for multiple-input multiple-output (MIMO)-filter bank multicarrier (FBMC) system based on offset quadrature amplitude modulation (OQAM) is derived. In contrast to the conventional frequency domain interference approximation method (IAM)-based channel estimation model, the...

This work considers and analyzes the performance of semi-blind, training and data-aided channel estimation schemes for multiple-input multiple-output (MIMO) filter bank multicarrier (FBMC) systems with offset quadrature amplitude modulation (OQAM). A semi-blind MIMO-FBMC (SB-MF) channel estimator is developed that exploits both the training symbols...

This paper presents and analyses the performance of training-based least squares (LS) and minimum mean square error (MMSE) channel estimation schemes for multiple input multiple output (MIMO) filter bank multicarrier (FBMC) systems based on the offset quadrature amplitude modulation (OQAM) in the presence of limited, and imperfect knowledge of the...

This work calculates closed-form symbol error rate (SER) expression for minimum mean square error (MMSE) detection in low frequency selective multiple-input multiple-output (MIMO) filter bank multicarrier (FBMC) systems with offset quadrature amplitude modulation (OQAM). To achieve this aim, we first derive, by assuming perfect receive channel stat...

Background Single user Massive Multiple Input Multiple Output (MIMO) can be used to increase the spectral efficiency since the data is transmitted simultaneously from a large number of antennas located at both the base station and mobile. It is feasible to have a large number of antennas in the mobile, in the millimeter wave frequencies. However, t...

This paper analyzes the performance of filter bank multicarrier (FBMC) signaling in conjunction with offset quadrature amplitude modulation (OQAM) in multi-user (MU) massive multiple-input multiple-output (MIMO) systems. Initially, closed form expressions are derived for tight lower bounds corresponding to the achievable uplink sum-rates for FBMC-b...

We derive post-processing signal-to-noise-plusinterference-ratio (PP-SINR) for minimum mean square error (MMSE) combining in multiple-input multiple-output (MIMO) filter bank multi-carrier (FBMC) systems based on offset quadrature amplitude modulation (OQAM). We show that the PP-SNR, derived by assuming imperfect receive channel state information,...

Single user massive multiple input multiple output (MIMO) can be used to increase the spectral efficiency, since the data is transmitted simultaneously from a large number of antennas located at both the base station and mobile. It is feasible to have a large number of antennas in the mobile, in the millimeter wave frequencies. However, the major d...

This letter estimates carrier frequency offset (CFO) and channel in multiple-input multiple-output (MIMO) filter bank multi-carrier systems based on offset quadrature amplitude modulation. A two-step preamble-based approach is proposed using a novel frame structure. For the first step, we develop a coarse CFO estimator, which does not require chann...

We consider two-way amplify-and-forward (AF) relaying, where multiple full-duplex user pairs exchange information via a shared full-duplex massive multiple-input multipleoutput (MIMO) relay. Most of the previous massive MIMO relaying works maximize the spectral efficiency (SE). By contrast, we maximize the non-convex energy efficiency (EE) metric b...

Precoded orthogonal frequency division multiplexed (OFDM) systems have low bit error rate (BER) performance compared to conventional OFDM systems. In this work, we have proposed a new buffer-interleaver based system architecture. The proposed system is found to have a better BER performance than the conventional precoded OFDM system when minimum me...

An approach for the linear prediction-based detection of serially concatenated turbo coded differential quaternary phase shift keyed signals, is presented for SIMO-OFDM systems. The proposed method exploits the high degree of correlation in the channel frequency response, when the channel impulse response is much smaller than the FFT length. A pred...

We consider two-way amplify and forward relaying, where multiple full-duplex user pairs exchange information via a shared full-duplex massive multiple-input multiple-output (MIMO) relay. We derive closed-form lower bound for the spectral efficiency with zero-forcing processing at the relay, by using minimum mean squared error channel estimation. Th...

Superimposed training (ST) is used to estimate channel in orthogonal frequency division multiplexing (OFDM) systems which results in higher throughput than the time/frequency multiplexed training schemes. Orthogonal affine precoders (OAP) are used in ST-based SISO/MIMO-OFDM system to cancel the interference caused due to simultaneous data transmiss...

The minimum average signal-to-noise ratio (SNR) per bit required for error-free transmission over a fading channel is derived, and is shown to be equal to that of the additive white Gaussian noise (AWGN) channel, which is −1.6 dB. Discrete-time algorithms are presented for timing and carrier synchronization, as well as channel estimation, for turbo...

We consider multi-pair two-way amplify and forward (AF) relaying, where multiple full-duplex source-node pairs exchange information via a shared full-duplex massive multiple-input multiple-output (MIMO) relay. Most of the previous massive MIMO relay works maximize spectral efficiency (SE). We maximize global energy efficiency (GEE) with quality-of-...

Noncoherent detection of differential quaternary phase shift keying (DQPSK) signals in OFDM systems is efficiently implemented using a predictive Viterbi algorithm (VA) operating on a trellis with just S T = MP−1 states instead of M P states, where M denotes an M-ary PSK constellation and P denotes the order of the prediction filter. The prediction...

Precoder matrices are used in various contexts in the MIMO-OFDM systems. In particular, orthogonal affine precoder (OAP) is used in superimposed training (ST) based MIMO-OFDM system to nullify the data training interference. Precoders are also used to reduce the peak to average power ratio (PAPR) of MIMO-OFDM. In general, the OAP does not reduce th...

The Twelfth International Conference on Wireless and Mobile Communications (ICWMC 2016), held between November 13-17, 2016 - Barcelona, Spain, followed on the previous events on advanced wireless technologies, wireless networking, and wireless applications. ICWMC 2016 addressed wireless related topics concerning integration of latest technological...

In this paper, a preamble aided integer frequency offset (IFO) estimation scheme is proposed. The proposed algorithm estimates the IFO by using cross correlation with extended correlation length. The performance is investigated by means of probability of failure to detect IFO with the existing integer frequency synchronization methods in multipath...

In this paper a channel independent precoder is proposed for orthogonal frequency division multiplexed (OFDM) signals which reduces the peak to average power ratio (PAPR) and also achieves optimal BER performance in frequency selective Rayleigh fading channels. The complexity of the proposed system is lower than the Zadoff-Chu transform based preco...

In this study, the design of a superimposed training (ST) for an interference-limited spatially correlated multipleinput- multiple-output (MIMO) system is addressed and a closed-form solution for designing the training signal is proposed in a sub-optimal way. Earlier papers have considered noise limited MIMO systems. The authors also propose random...

In this work, we discuss techniques for coherently detecting turbo coded orthogonal frequency division multiplexed (OFDM) signals, transmitted through frequency selective Rayleigh (the magnitude of each channel tap is Rayleigh distributed) fading channels having a uniform power delay profile. The channel output is further distorted by a carrier fre...

In this paper, bandwidth efficient turbo codes, commonly known as turbo trellis coded modulation (TTCM) is used in orthogonal frequency division multiplexed (OFDM) systems. It improves the error performance and spectral efficiency simultaneously, which are the major requirements for modern communication systems. The throughput can be improved by pu...

This work addresses the problem of coherently detecting turbo coded orthogonal frequency division multiplexed (OFDM) signals, transmitted through frequency selective Rayleigh fading channels. A single transmit and receive antenna is assumed. The channel output is distorted by a carrier frequency and phase offset, besides additive white Gaussian noi...

In this paper, channel estimation methods based on pilot patterns are investigated. LS and MMSE techniques are used for estimating channel at pilot subcarriers in block type and comb type methods. Channel estimation at data subcarriers is done using interpolation methods like linear interpolation, spline interpolation, low-pass interpolation, time...

In recent years, there has been an upsurge of research interest in cooperative wireless communications in both academia and industry. This article presents a simple overview of the pivotal topics in both mobile station (MS)- and base station (BS)- assisted cooperation in the context of cellular radio systems. Owing to the ever-increasing amount of...

codes are family of forward error correcting codes, whose performance is near Shannon limit. Turbo decoding is based on the maximum a-posterior algorithm (MAP) algorithm. In this paper, the problem of turbo decoding in ISI channel is studied. A Super-trellis structure method has been presented and modified turbo decoding is suggested. Two methods h...

Viterbi Algorithm is the optimum technique for detection of coded signals in white noise. However in many practical situations noise is coloured or correlated. The optimum detection techniques for both uncoded and coded (Trellis coded) signals in additive coloured Gaussian noise (ACGN) have been derived earlier in the literature. For detection of c...

Turbo codes are family of forward error correcting codes, whose performance is near Shannon limit. Turbo decoding is based on the maximum a-posterior algorithm (MAP) algorithm. In this paper, the problem of turbo decoding in ISI channel is studied. A Super-trellis structure method has been presented and modified turbo decoding is suggested. Two met...

The key contribution of this paper is to develop transmitter and receiver algorithms in discrete-time for turbo-coded offset QPSK signals. The procedure for simulating a clock offset between the transmitter and receiver is described. Due to the use of up-sampling, matched filtering and a differential correlation approach at the receiver, the time r...

This paper deals with the problem of synchronization of bursty offset QPSK signals in the presence of frequency offset and additive white Gaussian noise. The main tasks of the receiver are to detect a burst (a frame of data) with a low acquisition time, to estimate and cancel the frequency and phase offset (carrier recovery), perform timing recover...

The additional topics covered in the second edition are: 1. Computing the average probability of error for constellations having nonequiprobable symbols (Chapter 1). 2. Performance analysis of differential detectors in Rayleigh flat fading channels (Chapter 1). 3.Synchronization techniques for linearly modulated signals (Chapter 4). The additional...

The desire to reduce complexity at mobile unit in cellular system has led to the investigation of signal processing techniques that move the complexity from the mobile unit to the base station. Transmitter precoding is one such technique and it represents a linear transformation of transmitted signals, such that mean squared error at all receivers...

First Page of the Article

This paper addresses the problem of iterative decoding in the presence of coloured noise. Although most of the current literature deals with iterative decoding in additive white Gaussian noise (AWGN), in many practical situa-tions, the noise is correlated. This correlation is usually due to the use of a linear equalizer to remove ISI. In this pa-pe...

We address the problem of optimally detecting signals in correlated noise using a predictive Viterbi algorithm (PVA). We derive expressions for the probability of error for uncoded systems employing the PVA, which are corrupted by coloured noise. As an application, the PVA is used in conjunction with a fractionally-spaced linear equalizer (LE-PVA),...

It is well known that the optimum detector based on linear prediction, for frequency-nonselective (flat) fading channels, requires states for M-ary signalling, where is the order of the prediction filter required to decorrelate the received signal. In this paper, we first derive a suboptimal linear predictive-based (SLP) detector for M-ary PSK by m...

This paper addresses the recovery of multilevel signals in the presence of frequency nonselective fading and additive white Gaussian noise. We first propose a novel detector which performs approximate noncoherent maximum likelihood estimation for slowly fading channels, where the channel gain and phase remain constant over several symbol durations....

This paper deals with the differential detection of circular QAM-type signal constellations, transmitted through frequency nonselective (flat) Rayleigh fading channels. We propose three schemes, namely (i) symbol-by-symbol differential detector for multilevel signals (SSDD-M), (ii) multiple symbol differential detector using Viterbi algorithm (VA)...

This paper addresses the issue of recovering multilevel signals in the presence of slow, frequency nonselective fading and additive white Gaussian noise (AWGN). First, we present a novel noncoherent detector which performs approximate maximum likelihood detection in unknown amplitude and phase (ML-UAP). This ML-UAP detector is implemented using the...

The authors propose an efficient method of implementing the Viterbi algorithm at Nyquist-rate, for linearly modulated signals corrupted by ISI and AWGN. When signalling is M-ary and ISI extends over L-1 symbols, this scheme results in M+CL (complex multiplications, C is the number of samples per symbol), whereas the whitened-matched-filter based Vi...