Media-Based MIMO: A New Frontier in Wireless Communications

The idea of Media-based Modulation (MBM), is based on embedding information in the variations of the transmission media (channel state). This is in contrast to legacy wireless systems where data is embedded in a Radio Frequency (RF) source prior to the transmit antenna. MBM offers several advantages vs. legacy systems, including "additivity of information over multiple receive antennas", and "inherent diversity over a static fading channel". MBM is particularly suitable for transmitting high data rates using a single transmit and multiple receive antennas (Single Input-Multiple Output Media-Based Modulation, or SIMO-MBM). However, complexity issues limit the amount of data that can be embedded in the channel state using a single transmit unit. To address this shortcoming, the current article introduces the idea of Layered Multiple Input-Multiple Output Media-Based Modulation (LMIMO-MBM). Relying on a layered structure, LMIMO-MBM can significantly reduce both hardware and algorithmic complexities, as well as the training overhead, vs. SIMO-MBM. Simulation results show excellent performance in terms of Symbol Error Rate (SER) vs. Signal-to-Noise Ratio (SNR). For example, a $4\times 16$ LMIMO-MBM is capable of transmitting $32$ bits of information per (complex) channel-use, with SER $\simeq 10^{-5}$ at $E_b/N_0\simeq -3.5$dB (or SER $\simeq 10^{-4}$ at $E_b/N_0=-4.5$dB). This performance is achieved using a single transmission and without adding any redundancy for Forward-Error-Correction (FEC). This means, in addition to its excellent SER vs. energy/rate performance, MBM relaxes the need for complex FEC structures, and thereby minimizes the transmission delay. Overall, LMIMO-MBM provides a promising alternative to MIMO and Massive MIMO for the realization of 5G wireless networks.Comment: 26 pages, 11 figures, additional examples are given to further explain the idea of Media-Based Modulation. Capacity figure adde

Sampling Time Jitter

Electrical systems which use voltage transitions to represent timing information suffer from a degrading phenomenon called timing jitter. Sampling time jitter is the deviation of sampling clock from its ideal position. As transmission rates raise above couple of GHz, deviations become significant comparing to signalling interval, jitter becomes a fundamental performance bottleneck. Especially in band-limited communication systems that imperfect sampling times result in Inter-Symbol Interference (ISI) jitter is a very limiting factor to decode correct transmitted data. In this case, jitter timing error translates into amplitude error. At first, the effect of sampling time jitter at the received signal is modelled as an additive noise .This additive noise signal which we call it jitter noise is a coloured noise that also depends on input signal. Expressions for jitter noise correlation factors, its cross- correlation with input signal are derived. These correlations depend on input spectral density, timing jitter characteristic function (Fourier transform of jitter probability density function) and whether timing jitter is white or coloured. In case of first order Gauss-Markov process for sampling time jitter it is observed that in high memory regime (highly correlated timing jitter) the spectral density of additive jitter noise is concentrated around higher frequencies. Exploiting this quality, a spectral shaping scheme is used to improve the performance in terms of Bit Error Rate (BER) for an AWGN channel with discrete input corrupted by sampling time jitter. Simulation results comparing the proposed scheme performance with a minimum distance decoder are provided. As another approach the well-known Viterbi Algorithm is used for decoding same AWGN channel suffering from ISI terms due to sampling jitter. The Viterbi algorithm, which basically is a dynamic programming algorithm, finds the most likely input data and jitter times based on observed output sequence. A quantized version of jitter times is used to be able to work with a finite state trellis and to find likelihoods along the paths of the diagram. Then Bit Error Rate curves for different jitter quantization levels and different impulse response lengths of channel are presented

Denoising and despiking ADV velocity and salinity concentration data in turbulent stratified flows

Due to the presence of noise and spikes in velocity measurements of turbulent flow fields, understanding the flow pattern may be seriously affected by the spurious values for zones where certain flow behaviour is not necessarily expected. In a series of laboratory experiments the velocity data recorded, using Acoustic Doppler Velocity meters (ADVs), and the salinity measurements were noticeably noisy. In despiking and denoising the velocity data a linear correlation algorithm was established, which successfully lowered the noise levels and removed the spikes. For the assessment of the method, an autoregressive model was used to generate a clean velocity signal. The spikes were generated with a uniformly random time index and a Gaussian distributed value, where White Gaussian noise was added to this simulated signal. Assessment was also undertaken on the signals generated using a three-dimensional numerical model. To enhance the comprehension of the flow field, an interpolation method for producing the missing data has also been developed, which may be deployed to increase the sampling frequency, or to produce data for the spatial domain at locations which are not included in the measurements. For salinity a different strategy was applied where a moving average procedure was carried out, as the data did not suffer from spikes and exhibited almost a constant band of noisy fluctuations

Media-Based Modulation for Next-Generation Wireless: Latest Progress and New Applications

Media-based modulation (MBM) is a novel technique for embedding information in the channel states via intentional perturbations of the transmission media. This article provides an overview of MBM and its benefits while highlighting relevant challenges and future research directions. We explain how MBM differs from source-based modulation and how it addresses issues in legacy multiple-input multipleoutput (MIMO) systems, such as deep fades and MIMO diversity-multiplexing trade-off. We demonstrate how MBM works in harmony with other index modulations and improves upon them by providing similar advantages with a more compact transmitter. Numerical results (simulation and analytical) support these claims and include outage comparison with legacy MIMO systems, comparisons with other state-of-the-art modulation schemes, and a performance example showcasing transmitting 32 bits of information in a single channel use with an excellent symbol error rate of SER ~ 1e-5  at “energy per bit to noise power spectral density ratio” of Eb=N0 ~ 3:5 dB. The article continues with methods to address the issues of receiver training and decoding for large constellation sets. A number of other research questions, such as pulse shaping to limit bandwidth expansion due to the time-varying nature of MBM and the effect of forward error correcting codes on MBM diversity order are discussed. We present an RF transceiver structure that generates independent propagation paths for embedding information. Fabrication and testing of the transceiver structure show close agreement between simulation and measurement. There are inherent connections between MBM and intelligent reflecting surface (IRS). These connections, including the application of MBM in beamforming, are discussed. We present a solution that involves the integration of a filtering radiating patch within the MBM walls to restrict bandwidth expansion. Lastly, we delve into several specific application domains for MBM.</p

Analysis of Hip Joint Dose in Prostate Cancer Radiation Therapy: A Dosimetric Comparison of Treatment Plans

Background and purpose: Radiation therapy as a part of cancer treatment is used in almost 50-60% of involved cases. In prostate cancer radiation therapy, a large volume of pelvis is irradiated, so, it is necessary to preserve sensitive organs around the treatment area, especially rectum and bladder. In this study, some dosimetric parameters such as minimum dose (Dmin), maximum dose (Dmax), mean dose (Dmean) to target (PTV) and organs at risk (OAR), Integral dose, Homogeneity Index and Conformity Index were compared between two techniques. Materials and methods: In this analytical study, computed tomography scans of 50 patients (mean age: 52 years) attending Sari Imam Khomeini Hospital were acquired and transferred to the 3D treatment planning system (TPS). For each patient, a conventional plan (Box Fields) and modified oblique four-field (MOFF) plan were prepared using TPS for 15 MV photon energy. A total dose of 7200 cGy was prescribed for each patient. Data analysis was carried out in SPSS applying paired-t-test. Results: In current study, 15-MV energies for radiation of pelvis and bladder using box radiation fields (routine plan) lead to maximum uniformity and homogeneity of dose in irradiated tumor tissue. The results also showed that 15-MV energies for radiation of pelvis and bladder and the new plan could decrease the average integrated dose in femur heads. Conclusion: We observed a significant effect of the geometrics of radiation fields on distribution of dose in tumor tissue and also the amount of dose received by organs at risk in radiotherapy of patients with prostate cancer

Characteristics, distribution and sources of polychlorinated biphenyls (PCBs) in coastal sediments from the heavily industrialized area of Asalouyeh, Iran

In this research, the levels of polychlorinated biphenyls (PCBs) were investigated in the marine sediments of Asaluyeh harbor, in the Persian Gulf. The samples were taken from industrial, semi-industrial and urban regions. The mean concentration levels of total (Σ) 18 detected PCBs were 514.32, 144.67 and 31.6 pg/g dw for the industrial, semi-industrial and urban sampling stations, respectively. Based on a multivariate statistical analysis, it was found that high contamination levels of PCBs in sediments collected along the Persian Gulf were associated with releases from local industries. Total organic carbon (TOC) content was significantly and positively correlated with the concentrations of PCB congeners. World Health Organization toxic equivalents (TEQs) for PCBs ranged from 0.04 to 2.66 pg TEQ/g dry weight (dw) in the coastal sediments. The TEQ values in this study were higher than many reported worldwide in the literature for sediments. This suggests that there are high levels of contamination in the area due to industrial and other human activities

Evaluation of Lung Dose in Esophageal Cancer Radiotherapy Using Monte Carlo Simulation

Background and purpose: Radiation therapy make an important contribution in the control and treatment of cancers. Lungs are the main organs at risk in esophageal cancer radiotherapy. Difference between the dose distribution due to the treatment planning system (TPS) and the patient's body dose is dependent on the calculation of the treatment planning system algorithm, which is more pronounced in heterogeneities such as the lung. In this study, the dose distribution of treatment planning system was compared with Monte Carlo calculations in both homogeneous and heterogeneous tissues. Materials and methods: Three dimensional planning composed of four fields were done on the CT images using the CorPLAN TPS of a SIEMENS PRIMUS linac. EGSnrc Monte Carlo simulation code was used for the same conditions. The dose distributions obtained from Monte Carlo simulation and the TPS were compared using PDD curve and Dose Difference Percentage index obtained from the two modes. Results: According to the findings, the error rate from the TPS was less than 3% in the homogeneous tissue, whereas the error in the heterogeneous tissue was higher than the standard value (more than 5%). Conclusion: The accuracy of CorPLAN TPS at homogeneous tissue is more than that in the heterogeneous tissue and this should be considered in the clinic. This study suggests that the Monte Carlo code can be used to simulate and estimate the dose distribution in radiotherapy, and in cases where the practical measurement of some dosimetric parameters is impossible or difficult, this code can be used for prediction and optimization of treatment plans

Assessment of Dose Delivery to Supraclavicular and Axillary Lymph Nodes in Adjuvant Breast Cancer Radiotherapy, with or without Posterior Axillary Boost in Relation to BMI

Background: The axillary and supraclavicular nodal volume treatment results in improvement of local control and survival after breast conserving surgery (BCS) or modified radical mastectomy (MRM). Studies on the depth of these nodes have questioned the consistent use of standard fields for all patients. This study was done to assess the dose delivery to these lymph nodes with conventional treatment techniques according to body mass index (BMI). Methods: Twenty six patients with breast cancer undergoing breast surgery were included and computed tomography (CT) simulation was done. Their axillary and supraclavicular nodal volumes were contoured for planning target volume (PTV). Supraclavicular and posterior axillary fields were generated for each patient with digital reconstruction radiography (DRR) technique. Then the dose distribution of the two conventional methods - anterior-posterior field (AP), and anterior field with posterior boost (AP+PA boost) - for total dose of 5000 cGy, was examined with radiotherapy dose plan program. An AP planned field suitable for PTV, was designed and compared to AP+PA boost. The diameter of axilla was measured at the center of AP field in CT scan. Data were analyzed in relationship to BMI. Results: PTV coverage and excessively irradiating normal tissues (hot points), proved to have significant differences in each method (p < 0.001 to 0.01). Axillary and supraclavicular LNs were in 1.6 to 10 and 0.5 to 6.3 cm depth, respectively. Depth of the prescribed dose, which was gained from planned field, had a significant statistical association with BMI (p < 0.05). Conclusions: Current standard fields are not appropriate for all patients, because of poor coverage of PTV. To sum up, 3D CT planning is strongly recommended for patients with high BMI

Salivary VEGF-R3, TNF-α, TGF-β and IL-17A/F Levels in Patients with Minor Aphthous

Background : Recurrent aphthous stomatitis (RAS) is one of the most common mucosal ulcerative of oral cavity. Role of immune system, especially cytokines in immunopathogenesis of aphthous stomatitis was not highly considered. The aim of this study was to evaluate the levels of salivary cytokines, including VEGF-R3, TGF-&beta1, TNF-&alpha, and IL-17A/F in patients with RAS in two clinical stages, ulcerative and healing period. Material and Methods: In this case &ndash;control study, 18 patients with RAS (case group) and 18 healthy individuals (control groups) who were matched for age and sex, were selected. In both ulcerative and healing stages, unstimulated saliva of patients with RAS and healthy controls were collected. Levels of salivary cytokines, including VEGF-R3, TGF-&beta, TNF-&alpha, and IL-17A/F at each stage was determined by ELISA procedure and result were compared with the control group. Results: The levels of salivary VEGF-R3 in the ulcerative (5.92 1.87ng/ml) and healing (7.14 &plusmn;3.1 ng/ml) stages significantly decreased comparing with control group ( 9.71&plusmn;2.24 ng/ml). Moreover, the level of salivary TGF-&beta1 in ulcerative (142.21&plusmn;18.7 pg/ml) and healing (167.02&plusmn;28.1 pg/ml) stages significantly reduced comparing with control group (178.35&plusmn;55.67 pg/ml). In addition, our finding showed that both inflammatory cytokines including TNF-&alpha and IL-17 A/F significantly increased comparing to control group. The level of salivary TNF-&alpha in ulcerative (34.9&plusmn;11.35pg/ml) and healing (28.09&plusmn;9.07pg/ml) stages significantly increased comparing with control group (10.76&plusmn;1.83 pg/ml). Also, the IL-17 A/F level in the ulcerative &nbsp;(96.44&plusmn;25.74 pg/ml) and healing (79.17&plusmn;24.96 pg/ml) stages significantly increased comparing to the control group (53.47&plusmn;13 pg/ml). Conclusion: Our finding in this study showed that the reduction of VEGF-R3 and TGF-&beta1 cytokines and increasing of inflammatory cytokines such as TNF-&alpha and IL-17 A/F are effective in the pathogenesis of minor aphthous particularly in ulcerative stage.