LTE SFBC MIMO Transmitter Modelling and Performance Evaluation

High data rates are one of the most prevalent requirements in current mobile communications. To cover this and other high standards regarding performance, increasing coverage, capacity, and reliability, numerous works have proposed the development of systems employing the combination of several techniques such as Multiple Input Multiple Output (MIMO) wireless technologies with Orthogonal Frequency Division Multiplexing (OFDM) in the evolving 4G wireless communications. Our proposed system is based on the 2x2 MIMO antenna technique, which is defined to enhance the performance of radio communication systems in terms of capacity and spectral efficiency, and the OFDM technique, which can be implemented using two types of sub-carrier mapping modes: Space-Time Block Coding and Space Frequency Block Code. SFBC has been considered in our developed model. The main advantage of SFBC over STBC is that SFBC encodes two modulated symbols over two subcarriers of the same OFDM symbol, whereas STBC encodes two modulated symbols over two subcarriers of the same OFDM symbol; thus, the coding is performed in the frequency domain. Our solution aims to demonstrate the performance analysis of the Space Frequency Block Codes scheme, increasing the Signal Noise Ratio (SNR) at the receiver and decreasing the Bit Error Rate (BER) through the use of 4 QAM, 16 QAM and 64QAM modulation over a 2x2 MIMO channel for an LTE downlink transmission, in different channel radio environments. In this work, an analytical tool to evaluate the performance of SFBC - Orthogonal Frequency Division Multiplexing, using two transmit antennas and two receive antennas has been implemented, and the analysis using the average SNR has been considered as a sufficient statistic to describe the performance of SFBC in the 3GPP Long Term Evolution system over Multiple Input Multiple Output channels.Comment: 11 pages, 20 figures, 5 table

Differential orientation effect in the neural response to interacting biological motion of two agents

<p>Abstract</p> <p>Background</p> <p>A recent behavioral study demonstrated that the meaningful interaction of two agents enhances the detection sensitivity of biological motion (BM), however, it remains unclear when and how the 'interaction' information of two agents is represented in our neural system. To clarify this point, we used magnetoencephalography and introduced a novel experimental technique to extract a neuromagnetic response relating to two-agent BM perception. We then investigated how this response was modulated by the interaction of two agents. In the present experiment, we presented two kinds of visual stimuli (interacting and non-interacting BM) with two orientations (upright and inverted).</p> <p>Results</p> <p>We found a neuromagnetic response in the bilateral occipitotemporal region, on average 300 – 400 ms after the onset of a two-agent BM stimulus. This result showed that interhemispheric differences were apparent for the peak amplitudes. For the left hemisphere, the orientation effect was manifest when the two agents were made to interact, and the interaction effect was manifest when the stimulus was inverted. In the right hemisphere, the main effects of both orientation and interaction were significant, suggesting that the peak amplitude was attenuated when the visual stimulus was inverted or made to interact.</p> <p>Conclusion</p> <p>These results demonstrate that the 'interaction' information of two agents can affect the neural activities in the bilateral occipitotemporal region, on average 300 – 400 ms after the onset of a two-agent BM stimulus, however, the modulation was different between hemispheres: the left hemisphere is more concerned with dynamics, whereas the right hemisphere is more concerned with form information.</p

Space-Division Multiplexing in Data Center Networks: On Multi-Core Fiber Solutions and Crosstalk-Suppressed Resource Allocation

The rapid growth of traffic inside data centers caused by the increasing adoption of cloud services necessitates a scalable and cost-efficient networking infrastructure. Space-division multiplexing (SDM) is considered as a promising solution to overcome the optical network capacity crunch and support cost-effective network capacity scaling. Multi-core fiber (MCF) is regarded as the most feasible and efficient way to realize SDM networks, and its deployment inside data centers seems very likely as the issue of inter-core crosstalk (XT) is not severe over short link spans (<1  km ) compared to that in long-haul transmission. However, XT can still have a considerable effect in MCF over short distances, which can limit the transmission reach and in turn the data center’s size. XT can be further reduced by bi-directional transmission of optical signals in adjacent MCF cores. This paper evaluates the benefits of MCF-based SDM solutions in terms of maximizing the capacity and spatial efficiency of data center networks. To this end, we present an analytical model for XT in bi-directional normal step-index and trench-assisted MCFs and propose corresponding XT-aware core prioritization schemes. We further develop XT-aware spectrum resource allocation strategies aimed at relieving the complexity of online XT computation. These strategies divide the available spectrum into disjoint bands and incrementally add them to the pool of accessible resources based on the network conditions. Several combinations of core mapping and spectrum resource allocation algorithms are investigated for eight types of homogeneous MCFs comprising 7–61 cores, three different multiplexing schemes, and three data center network topologies with two traffic scenarios. Extensive simulation results show that combining bi-directional transmission in dense core fibers with tailored resource allocation schemes significantly increases the network capacity. Moreover, a multiplexing scheme that combines SDM and WDM can achieve up to 33 times higher link spatial efficiency and up to 300 times greater capacity compared to a WDM solution

Basis Function Selection of Frequency-Domain Hammerstein Self-Interference Canceller for In-Band Full-Duplex Wireless Communications

This paper presents a basis function selection technique of a frequency-domain Hammerstein digital selfinterference canceller for in-band full-duplex communications. The power spectral density (PSD) of the nonlinear selfinterference signal is theoretically analyzed in detail, and a nonlinear self-interference PSD estimation method is developed. The proposed selection technique decides on the basis functions necessary for cancellation and relaxes the computational cost of the frequency-domain Hammerstein canceller based on the estimated PSD of the self-interference of each basis function. Furthermore, the convergence performance of the canceller is improved by the proposed selection technique. Simulation results are then presented, showing that the proposed technique can achieve similar cancellation performance compared with the original frequency-domain Hammerstein canceller and a time-domain nonlinear canceller. Additionally, it is shown that the proposed technique improves the computational cost and the convergence performance of the original frequency-domain Hammerstein canceller

Multiple Signal Classification for Determining Direction of Arrival of Frequency Hopping Spread Spectrum Signals

This research extends a MUSIC algorithm to determine DOA of FHSS signals. All incident FHSS signals have unknown DOA and use PSK. Conventional MUSIC algorithm involves multiple MUSIC estimation for all frequency bins. On the other hand, the extended development is meant to execute a single MUSIC algorithm of observations on multiple frequency bins or hops. The new extension shows better performance compared to the conventional MUSIC execution at different SNR levels. Both have the same power accumulation at the true angles of arrival. However, the new development has lower side lobes and hence helps avoid false detections. In addition, the new development has lower side lobes variance resulting in lower error of false detections compared to the normal execution. Simulation results show that the new extension is sensitive to the SNR values and number of samples taken at each frequency bin. However, it is less sensitive to the possible number of frequency hops or hop set and number of array sensors

Uncoded space-time labelling diversity : data rate & reliability enhancements and application to real-world satellite broadcasting.

Doctoral Degree. University of KwaZulu-Natal, Durban.Abstract available in PDF