Spherical harmonic based noise rejection and neuronal sampling with multi-axis OPMs

In this study we explore the interference rejection and spatial sampling properties of multi-axis Optically Pumped Magnetometer (OPM) data. We use both vector spherical harmonics and eigenspectra to quantify how well an array can separate neuronal signal from environmental interference while adequately sampling the entire cortex. We found that triaxial OPMs have superb noise rejection properties allowing for very high orders of interference (L=6) to be accounted for while minimally affecting the neural space (2dB attenuation for a 60-sensor triaxial system). To adequately model the signals arising from the cortex, we show that at least 11th order (143 spatial degrees of freedom) irregular solid harmonics or 95 eigenvectors of the lead field are needed to model the neural space for OPM data (regardless of number of axes measured). This can be adequately sampled with 75-100 equidistant triaxial sensors (225-300 channels) or 200 equidistant radial channels. In other words, ordering the same number of channels in triaxial (rather than purely radial) configuration gives significant advantages not only in terms of external noise rejection but also minimizes cost, weight and cross-talk.

Interference Rejection Combining Approach in Vehicle Communication Systems for Throughput Enhancement

In this paper, we present interference rejection combining scheme for interference suppression in wireless access in vehicular environments (WAVE) system. WAVE system performances depend on interference traffic since various signals and noises are present due to various vehicles on the road. The IRC scheme can minimize the interference presence from the received signal within the massive interference condition, resulting in the substantial gain of signal-to-interference and noise ratios (SINR) and performance. Based on the experiment of our proposed scheme, given the vehicle speed, SINR and different channel condition, our proposed scheme for interference suppression achieved significant improvements by 2 dB SINR performance gain in the low speed condition and above 0.5 dB performance gain at the high speed case. To extend our scheme for the comprehensive analysis, we also produced the vehicle speed and SINR performance map, which showed the performance pattern over vehicle speed and SINR of our scheme.

Walsh–Hadamard Transform Based Non-Orthogonal Multiple Access (NOMA) and Interference Rejection Combining in Next-Generation HetNets

In heterogeneous networks (HetNets), non-orthogonal multiple access (NOMA) has recently been proposed for hybrid-access small-cells, promising a manifold network capacity compared to OMA. One of the major issues with the installation of a hybrid-access mechanism in small-cells is the cross-tier interference (intercell interference (ICI)) caused by the macrocell users (MUs) that are unable to establish a connection to the small-cell base station (SBS). In this paper, a joint strategy is proposed for hybrid-access small-cells using the Walsh–Hadamard transform (WHT) with NOMA and interference rejection combining (IRC) to achieve high performance gains and mitigate intercell interference (ICI), respectively. WHT is applied mathematically as an orthogonal variable spreading factor (OVSF) to achieve diversity in communication systems. When applied jointly with NOMA, it ensures better performance gains than the conventional NOMA. It reduces the bit error rate (BER) and enhances subsequent throughput performance of the system. IRC is used at the receiver side for managing the cross-tier interference caused by MUs that are unable to connect to the small-cell base station (SBS) for hybrid-access. The work considers both ideal and nonideal successive interference cancellation (SIC) conditions for NOMA. Mathematical modeling is provided for the proposed joint strategy for HetNets and the results validate it in terms of BER and subsequent user throughput performance, compared to the conventional NOMA approach.

UL-DMRS Based NB-IoT Uplink System and its Performance Analysis Toward 5G Machine Type Communications

As we know, world is moving into the era of modern digital technology and looking forward tomassive machine type communications (mMTC), whichis an integral part of Internet of Things (IoT). The current technologysupporting mMTC market are not standardized; therefore, there are many short comings from physical layer which includes complexity in deployment, poor reliability, lesser flexibility, security threats and high maintenance cost. To address all these challenges in 5G machine type communication (MTC), the 3rdGeneration Partnership Project (3GPP) in release 13has standardizedNarrowband Internet of Things (NB-IoT) as a better choice in deployment of 5G MTC. NB-IoT has been recommended by ITU as a 5G standard and this recognition of NB-IoT as a core technology in massive machine type communication will impact the telecommunication industry. NB-IoT mainly works on low power wide area networks (LPWAN), which isconsidered as a major technology driver in 5G wireless technologies. Initially,we have compared a spectrum power of NB-IoT with W-Fi ac considering their own bandwidthand specificationsas per 3GPP and IEEE 802.11,respectively.As per analysis, we found many advantages of deploying NB-IoT in 5thgeneration wireless technology including ubiquitous coverage, low power consumption, less transmission power and better interference rejection. Considering thisfact of NB-IoT, we proposedand design a NB-IoT uplink systemusing NPUSCH, UL-SCH and UL-DMRS as per 3GPP 5G specificationsand performance analysis has been carried out