Raveendra Kolarramakrishna Rao

In the recent literature, Saci et al. [1] proposed a novel blind channel estimator for Orthogonal Frequency Division Multiplexing (OFDM) systems, denoted as One Shot Blind Channel Estimator (OSBCE). However, the OSBCE is designed and its performance is analyzed for Single-Input Single-Output OFDM (SISO-OFDM). Therefore, of aim of this work is to extend the design and performance evaluation of the OSBCE, to the multiple receiving antenna case, i.e., Single-Input Multiple-Output OFDM (SIMO-OFDM) systems, where we show that SIMO OSBCE can be designed in different variations based on the channel behavior as a function of the Euclidean distance between the symbols used in the OSBCE structure. The mean-squared error (MSE) performance of the OSBCE for SIMO-OFDM is evaluated for different design structures and compared against the pilot-based OFDM system. Moreover, degradation in the system performance as the Euclidean distance between the OSBCE system-related symbols is presented and discussed. The obtained results show that the OSBCE for SIMO-OFDM can achieve reliable estimates, which are equivalent to pilot-based systems, yet with the gain of improved spectral efficiency. Moreover, the OSBCE achieves those reliable estimates with an equivalent complexity to that of the pilot-based scheme for particular OSBCE structures.

Millimeter wave (mmWave) spectrum has been proposed for use in commercial cellular networks to relieve the already severely congested microwave spectrum. Thus, the design of an efficient mmWave cellular network has gained considerable importance and has to take into account regulations imposed by government agencies with regard to global warming and sustainable development. In this paper, a dense mmWave hexagonal cellular network with each cell consisting of a number of smaller cells with their own Base Stations (BSs) is presented as a solution to meet the increasing demand for a variety of high data rate services and growing number of users of cellular networks. Since spectrum and power are critical resources in the design of such a network, a framework is presented that addresses efficient utilization of these resources in mmWave cellular networks in the 28 and 73 GHz bands. These bands are already an integral part of well‐known standards such as IEEE 802.15.3c, IEEE 802.11ad, and IEEE 802.16.1. In the analysis, a well‐known accurate mmWave channel model for Line of Sight (LOS) and Non‐Line of Sight (NLOS) links is used. The cellular network is analyzed in terms of spectral efficiency, bit/s, energy efficiency, bit/J, area spectral efficiency, bit/s/m², area energy efficiency, bit/J/m², and network latency, s/bit. These efficiency metrics are illustrated, using Monte Carlo simulation, as a function of Signal‐to‐Noise Ratio (SNR), channel model parameters, user distance from BS, and BS transmission power. The efficiency metrics for optimum deployment of cellular networks in 28 and 73 GHz bands are identified. Results show that 73 GHz band achieves better spectrum efficiency and the 28 GHz band is superior in terms of energy efficiency. It is observed that while the latter band is expedient for indoor networks, the former band is appropriate for outdoor networks.

In this paper, we investigate an interpolation technique for pilot-symbol assisted channel estimation in Long Term Evolution-Advanced (LTE-A) Orthogonal Frequency Division Multiplexing (OFDM). The studied interpolation method is a two one-dimensional (2 × 1-D) Fast Fourier Transform (FFT) interpolator. The performance of such interpolator in estimating LTE-A Cell-specific Reference Signals (C-RS) is reported and compared to different variations of Wiener and moving average filters, with different interpolation techniques. Moreover, degradation in LTE-A OFDM performance for high mobility channels is presented and discussed. It is shown that Wiener/2 × 1-D FFT/IFFT as a full system does not require setting a window size and provides better performance compared to Equal Weight Averaging (EWA)/Spline variations.

Multi-h CPFSK mapper in an OFDM system can offer significant gain in both PAPR and bit error rate probability. The OFDM PAPR problem is addressed and investigated using SLM reduction technique. Next, an OFDM system with a multi-h CPFSK mapper is considered and its performance is evaluated in terms of the upper and lower bounds on bit error rate probability, and a closed form expression is obtained. Also, the system performance is examined over Rayleigh and Nakagami-m fading channels. The simulation and analytical results show that the performance of the system is superior than the OFDM system with BPSK and single-h CPFSK mappers.

The performance of a low-complexity detection technique for OFDM-IM over the Nakagami-m fading channel has been analyzed. The orthogonal frequency-division multiplexing with index modulation (OFDM-IM) has recently been used in conjunction with the subcarriers using on-off keying modulation. The result shows improved performance in comparison with the conventional OFDM. The closed-form expression for the average pairwise error probability (PEP) over the Nakagami-m fading channel is derived.