Fast Convergence and Reduced Complexity Receiver Design for LDS-OFDM System

Low density signature for OFDM (LDS-OFDM) is able to achieve satisfactory performance in overloaded conditions, but the existing LDS-OFDM has the drawback of slow convergence rate for multiuser detection (MUD) and high receiver complexity. To tackle these problems, we propose a serial schedule for the iterative MUD. By doing so, the convergence rate of MUD is accelerated and the detection iterations can be decreased. Furthermore, in order to exploit the similar sparse structure of LDS-OFDM and LDPC code, we utilize LDPC codes for LDS-OFDM system. Simulations show that compared with existing LDS-OFDM, the LDPC code improves the system performance

On receiver design for low density signature OFDM (LDS-OFDM)

Low density signature orthogonal frequency division multiplexing (LDS-OFDM) is an uplink multi-carrier multiple access scheme that uses low density signatures (LDS) for spreading the symbols in the frequency domain. In this paper, we introduce an effective receiver for the LDS-OFDM scheme. We propose a framework to analyze and design this iterative receiver using extrinsic information transfer (EXIT) charts. Furthermore, a turbo multi-user detector/decoder (MUDD) is proposed for the LDS-OFDM receiver. We show how the turbo MUDD is tuned using EXIT charts analysis. By tuning the turbo-style processing, the turbo MUDD can approach the performance of optimum MUDD with a smaller number of inner iterations. Using the suggested design guidelines in this paper, we show that the proposed structure brings about 2.3 dB performance improvement at a bit error rate (BER) equal to 10-5 over conventional LDS-OFDM while keeping the complexity affordable. Simulations for different scenarios also show that the LDS-OFDM outperforms similar well-known multiple access techniques such as multi-carrier code division multiple access (MC-CDMA) and group-orthogonal MC-CDMA

EXIT chart analysis for turbo LDS-OFDM receivers

In this paper, the mutual information transfer characteristics of turbo Multiuser Detector (MUD) for a novel air interface scheme, called Low Density Signature Orthogonal Frequency Division Multiplexing (LDS-OFDM) are investigated using Extrinsic Information Transfer (EXIT) charts. LDS-OFDM uses Low Density Signature structure for spreading the data symbols in frequency domain. This technique benefits from frequency diversity besides its ability of supporting parallel data streams more than the number of subcarriers (overloaded condition). The turbo MUD couples the data symbols' detector of LDS scheme with users' FEC (Forward Error Correction) decoders through the message passing principle. The effect of overloading on LDS scheme's performance is evaluated using EXIT chart. The results show that at Eb/N0 as low as 0.3, LDS-OFDM can support loads up to 300%

Ticagrelor Plus Aspirin vs Clopidogrel Plus Aspirin In Mild Non-cardioembolic Ischemic Stroke: A Protocol Of a Randomized, Controlled, Active Comparator Arm, Outcome Assessor Blind, Feasibility Study

Background & Objectives: The risk of recurrence after a transient ischemic attack (TIA) or minor stroke is high especially within three months after first event. The aim of study is assessing the efficacy of ticagrelor plus aspirin in reduction of mild non-cardioembolic ischemic stroke or high risk TIA recurrence during first 3 months. Methods: This is a randomized, controlled, active comparator arm, outcome assessor blind, parallel group, feasibility study design on 90 patients with diagnosis of non-cardioembolic minor ischemic stroke or high risk TIA admitted in Bou-Ali Sina Hospital, Sari, Iran. After meeting all inclusion and exclusion criteria, patients will be randomized to ticagrelor 90 mg BID plus aspirin (ASA) 80 mg daily or clopidogrel 75 mg daily plus ASA 80 mg daily (1:1 ratio) until 21 days and then ASA 80 mg daily. Participants will be visited at month one and three. Any adverse events, serious side effects and outcome events will be recorded. The primary outcome is defined as ischemic stroke recurrence. Conclusion: Ticagrelor plus ASA is expected to be effective for prevention of recurrence in mild non-cardioembolic stroke and high risk TIA. Trial Registration: ClinicalTrials.gov: NCT0473809

Effect of Forward Error Correction Codes on the Performance of LDS-OFDM

In this paper, selection criteria of Forward Error Correction (FEC) codes, in particular, the convolutional codes are evaluated for a novel air interface scheme, called Low Density Signature Orthogonal Frequency Division Multiple Access (LDS-OFDM). In this regard, the mutual information transfer characteristics of turbo Multiuser Detector (MUD) are investigated using Extrinsic Information Transfer (EXIT) charts. LDS-OFDM uses Low Density Signature structure for spreading the data symbols in frequency domain. This technique benefits from frequency diversity in addition to its ability of supporting parallel data streams more than the number of subcarriers (overloaded condition). The turbo MUD couples the data symbols' detector of LDS scheme with users' FEC decoders through the message passing principle

Intrinsic Interference Use for FBMC-IOTA Systems

In this paper, the intrinsic interference of filter bank-based multicarrier systems (FBMC) systems with isotropic orthogonal transfer algorithm (IOTA) pulse-shaping is analyzed and used. Such intrinsic interference is treated as a parity symbol, and an iterative soft-in-soft-out (SISO) detector, which is based on message-passing algorithm (MPA), is proposed to exploit the useful information of the intrinsic interference. The performance of the intrinsic interference user (IIU) is investigated

Non-Orthogonal Multiple Access (NOMA) for cellular future radio access

Radio access technologies for cellular mobile communications are typically characterized by multiple access schemes, e.g., frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and OFDMA. In the 4th generation (4G) mobile communication systems such as Long-Term Evolution (LTE) (Au et al., Uplink contention based SCMA for 5G radio access. Globecom Workshops (GC Wkshps), 2014. doi:10.1109/GLOCOMW.2014.7063547) and LTE-Advanced (Baracca et al., IEEE Trans. Commun., 2011. doi:10.1109/TCOMM.2011.121410.090252; Barry et al., Digital Communication, Kluwer, Dordrecht, 2004), standardized by the 3rd Generation Partnership Project (3GPP), orthogonal multiple access based on OFDMA or single carrier (SC)-FDMA is adopted. Orthogonal multiple access was a reasonable choice for achieving good system-level throughput performance with simple single-user detection. However, considering the trend in 5G, achieving significant gains in capacity and system throughput performance is a high priority requirement in view of the recent exponential increase in the volume of mobile traffic. In addition the proposed system should be able to support enhanced delay-sensitive high-volume services such as video streaming and cloud computing. Another high-level target of 5G is reduced cost, higher energy efficiency and robustness against emergencies

Assessing the Conformity of Radiology BSc Curriculum and Job Requirements from the Viewpoint of Radiology Graduates Employed at Medical Imaging Centers

Introduction: Assessing the educational program relevance to job requirements can help identify its weaknesses and foster an opportunity for its improvement. Radiology experts play a vital role in disease diagnosis. The objective of this study was to investigate the viewpoint of radiology graduates about the coordination of the curriculum of Radiology BSc with their professional needs. Methods: This descriptive cross-sectional study was performed on 134 graduates of radiology BSc Working in Medical Imaging centers of Hamedan, Kermanshah, Kurdistan, Ilam, and Lorestan in the academic year 2018. In each province, 20% of the population of radiology technologists was selected via simple random sampling. Data were collected through a questionnaire that included demographic information and survey questions about the application of the main courses in this field in job responsibilities. The data were analyzed using descriptive statistics (mean, standard deviation, frequency, percentage). Results: Based on the job needs, the current curriculum had varying levels of application. The highest application rate was in specialty courses (4.04±0.7), and the lowest rate was in basic courses (3.08±0.9). The results revealed that the appropriate courses are Anatomy 1-3 (4. 6±0.7), and Radiographic positioning and procedures 1-3 (4.6±0.8) in specialty courses, and radiographic positioning and procedure in training units (4.2±0.6). Ultrasound physics and Seminar in specialty courses, and Statics and general mathematics in basic courses had the least conformity with professional needs with 3.15±1.5, 2.7±1.3, 1.8±0.7, and 2. 1±0.9, respectively. According to the results of this study, the graduates of this discipline had an average satisfaction level (3.26) with the contents of their academic program. Conclusion: The findings indicated that the didactic content of radiology BS is somewhat coordinated with the job requirements of this field. However, the curriculum should be revised to improve its applicability for future employees

Estimating Data Symbols from a Filter Bank Multicarrier (FBMC) Signal

Methods and apparatus are disclosed which estimate transmitted data symbols from a received Filter Bank Multicarrier (FBMC) signal by utilizing intrinsic interference as parity information. For each intrinsic interference symbol, a corresponding estimated parity symbol is obtained based on one or more of the received data symbols. The transmitted data symbols are then estimated by identifying a set of data symbols which provide a closer match between the intrinsic interference symbols and estimated parity symbols obtained based on the estimated transmitted data symbols, relative to a match between the intrinsic interference symbols and the estimated parity symbols obtained based on the received data symbols