Channel, Phase Noise, and Frequency Offset in OFDM Systems: Joint Estimation, Data Detection, and Hybrid Cramer-Rao Lower Bound

Oscillator phase noise (PHN) and carrier frequency offset (CFO) can adversely impact the performance of orthogonal frequency division multiplexing (OFDM) systems, since they can result in inter carrier interference and rotation of the signal constellation. In this paper, we propose an expectation conditional maximization (ECM) based algorithm for joint estimation of channel, PHN, and CFO in OFDM systems. We present the signal model for the estimation problem and derive the hybrid Cramer-Rao lower bound (HCRB) for the joint estimation problem. Next, we propose an iterative receiver based on an extended Kalman filter for joint data detection and PHN tracking. Numerical results show that, compared to existing algorithms, the performance of the proposed ECM-based estimator is closer to the derived HCRB and outperforms the existing estimation algorithms at moderate-to-high signal-to-noise ratio (SNR). In addition, the combined estimation algorithm and iterative receiver are more computationally efficient than existing algorithms and result in improved average uncoded and coded bit error rate (BER) performance

Relational properties of weakly orthogonal and orthogonal spherical harmonics in cubed sphere

Numerical computations on the sphere in solving problems defined on the sphere suffer from many difficulties near the poles when using spherical polar coordinate system for the spherical surface. For example, in the computations of global weather prediction models, concentrated grid points near the poles increase the amount of computations in the pole region where quantities of interest are of less important than in other parts of the globe. Such problems are collectively called as the 'pole problems'. Avoiding pole problems have attracted some researches in the recent past. One of the recent development in this direction is to define grid meshes on the sphere which do not contain polar concentrated points. Among these the 'cubed sphere' defined from the surface of a unit cube has been used by some authors for approximating weather prediction models by finite difference and finite element methods. In a recent paper, one of the present authors has constructed weakly orthogonal spherical harmonics in a non-polar spherical co-ordinate system based on the cube sphere concept. This can be used for approximating functions on the sphere by spectral methods without the pole problems. In this work, we establish some Lin ear and recurrence relations between these two sets of spherical harmonics. We also exploit linear relations between harmonic components defined in the six faces of the cubed sphere

A Multiband OFDMA Heterogeneous Network for Millimeter Wave 5G Wireless Applications

Citation: Niknam, S., Nasir, A. A., Mehrpouyan, H., & Natarajan, B. (2016). A Multiband OFDMA Heterogeneous Network for Millimeter Wave 5G Wireless Applications. Ieee Access, 4, 5640-5648. doi:10.1109/access.2016.2604364Emerging fifth generation (5G) wireless networks require massive bandwidth in higher frequency bands, extreme network densities, and flexibility of supporting multiple wireless technologies in order to provide higher data rates and seamless coverage. It is expected that the utilization of the large bandwidth in the millimeter-wave (mmWave) band and deployment of heterogeneous networks (HetNets) will help address the data rate requirements of 5G networks. However, high pathloss and shadowing in the mmWave frequency band, strong interference in the HetNets due to massive network densification, and coordination of various air interfaces are challenges that must be addressed. In this paper, we consider a relay based multiband orthogonal frequency division multiple access HetNet in which mmWave small cells are deployed within the service area of macro cells. In particular, we attempt to exploit the distinct propagation characteristics of mmWave bands (i.e., 60 GHz-the V-band and 70-80 GHz the E-band) and the long term evolution band to maximize overall data rate of the network via efficient resource allocation. The problem is solved using a modified dual decomposition approach and then a low complexity greedy solution based on the iterative activity selection algorithm is presented. Simulation results show that the proposed approach outperforms conventional schemes

Characterization of pathogenic mutations in 21-hydroxylase gene of Pakistani patients with congenital adrenal hyperplasia and their family members--a preliminary report

Objective: To characterize specific mutations within the 21-hydroxylase gene (CYP21-B) using ARMS-PCR assay in patients with congenital adrenal hyperplasia (CAH) and to compare it with that reported in other populations. Subjects and Methods: Five families, having an index case with CAH diagnosed on the basis of clinical and biochemical findings volunteered to give blood samples for analysis. A strategy, based on ARMS-PCR (Amplified Refractory Mutation System) was employed for the detection of mutations in 21-hydroxylase gene. The products of ARMS-PCR were resolved on agarose gels and the PCR products were visualized over ultra violet illumination. Results: Twenty-six specimens were analyzed for common point mutations in the 21-hydroxlase genes at the nucleotide positions 659, 1004 and 1688. Seven samples belonged to index cases with CAH. Of these 7, the assigned sex was male in 5 and female in 2 cases. However, genotypic sex was 3 males and 4 females. The mean age was 8 months in 5 cases while the median 17-OH Progesterone levels was 273.2 ng/ml. Vomiting, precocious puberty and ambiguous genitalia were the presenting features in 2, 1 and 4 cases respectively. Analysis for mutation at 659, 100 and 1688 was performed on 7 index cases and the family members of 5 index cases. The mutation analysis for the family members of index case 6 and 7 was not performed due to non-availability of their blood specimens. Index case No. 1, 4 and 7 showed homozygosity for splice mutations at nucleotide position 659, intron 2 with a sequence change of A to G, while the index case No. 2 and 6 showed heterozygosity for the same mutation. No mutation was found at 659, 1004 or 1688 in index case No. 3 and 4 at the analyzed nucleotide position. Nineteen family members of Case Nos. 1-5 were also analyzed for the same mutations. (Family No. 1, 2, 3, 4 and 5 included 3, 2, 7, 4 and 5 members respectively). These included 8 males and 11 females. All were asymptomatic. Both the parents of index case 1 and 4 were heterozygous at 659 while the father of index case No. 2 was heterozygous at 659 and mother was normal. Conculsion: Our results demonstrated the A to G transition at nucleotide 659 causing aberrant splicing, reported for some other populations as the most commonly identified point mutations. All cases were appropriately assigned to paternal or maternal chromosomes