Sparse Reconstruction-based Detection of Spatial Dimension Holes in Cognitive Radio Networks

In this paper, we investigate a spectrum sensing algorithm for detecting spatial dimension holes in Multiple Inputs Multiple Outputs (MIMO) transmissions for OFDM systems using Compressive Sensing (CS) tools. This extends the energy detector to allow for detecting transmission opportunities even if the band is already energy filled. We show that the task described above is not performed efficiently by regular MIMO decoders (such as MMSE decoder) due to possible sparsity in the transmit signal. Since CS reconstruction tools take into account the sparsity order of the signal, they are more efficient in detecting the activity of the users. Building on successful activity detection by the CS detector, we show that the use of a CS-aided MMSE decoders yields better performance rather than using either CS-based or MMSE decoders separately. Simulations are conducted to verify the gains from using CS detector for Primary user activity detection and the performance gain in using CS-aided MMSE decoders for decoding the PU information for future relaying.Comment: accepted for PIMRC 201

On Spatial Multiplexing Using Reconfigurable Intelligent Surfaces

We consider an uplink multi-user scenario and investigate the use of reconfigurable intelligent surfaces (RIS) to optimize spatial multiplexing performance when a linear receiver is used. We study two different formulations of the problem, namely maximizing the effective rank and maximizing the minimum singular value of the RIS-augmented channel. We employ gradient-based optimization to solve the two problems and compare the solutions in terms of the sum-rate achievable when a linear receiver is used. Our results show that the proposed criteria can be used to optimize the RIS to obtain effective channels with favorable properties and drastically improve performance even when the propagation through the RIS contributes a small fraction of the received power.Comment: 5 pages, 4 figures, accepted for publication in IEEE Wireless Communications Letter

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Utilizing Full Duplex Multiple Antenna in Heterogeneous Networks

The next generation networks are required to offer a huge increase in the network's capacity. Therefore, efficient resource allocation schemes are required. Full-duplex (FD) transmission is considered one of the strongest candidates for the 5G networks to increase the spectrum efficiency. Additionally, largely increasing the number of active antennas, i.e., deploying massive MIMO is expected to increase the link reliability due to the high antenna gain and resistivity to the fading channels. In this dissertation, we study the FD transmission in small cell networks. First, we propose a power allocation problem to maximize the downlink capacity and define when the FD transmission outperforms the half-duplex (HD) transmission. Second, we derive theoretical thresholds expressions for the self-interference cancellation, the mutual distance between users and the spatial correlation coefficient between antennas that dominate the switching between the FD transmission and the HD transmission. Third, we study the FD transmission in orthogonal frequency division multiple access (OFDMA) heterogeneous networks. We propose a joint mode selection, user pairing, subcarrier and power allocation problem to maximize the sum capacity. Fourth, we propose a low complexity algorithm to derive the crystallized rate regions in a two-node FD enabled small cell network. Then, we study the FD communication in the massive MIMO networks. First, we propose an optimization problem that determines the optimum users' biasing value that maximizes the sum capacity. Second, we determine the necessary conditions to be satisfied for the FD mode to outperform the HD mode in a massive MIMO setting. Third, we study the trade-off between the DL transmission gain and self-interference cancellation via transmit beamforming. We formulate two rate-maximization problems to optimize both the ratio between transmit and receive antennas as well as the ratio of receive antennas at which the self-interference is cancelled. Finally, In this dissertation, we optimize the performance of the FD communications towards the 5G networks and we validate the performance of the proposed algorithms to define the gains of the FD transmission.Electrical and Computer Engineering, Department o

Crystallized rate regions for full duplex enabled small cell networks

[abstract not available

Users association in small cell networks with massive MIMO

[abstract not available

Full duplex in massive MIMO systems: Analysis and feasibility

[abstract not available

Full-Duplex Meets Multiuser MIMO: Comparisons and Analysis

Efficient utilization of wireless communication resources and increases in the capacity of the communication networks have become very crucial claims for next-generation cellular networks. Full-duplex (FD) is a very promising technique that allows for the efficient use of wireless communication resources, given that the self-interference level can be suppressed to an acceptable level. In this paper, we consider a simple FD communication system, consisting of one FD access point (AP) and two half-duplex (HD) mobile users, and investigate when it is more advantageous for the communication network to operate in FD or HD multiuser multiple-input multiple-output (MIMO) mode. Since FD transmission is degraded by self-interference while HD suffers from spatial correlation between MIMO antennas, which causes rate loss, we study the effect of both the self-interference cancelation parameter at the FD AP and the mutual distance between the HD users on FD performances and the effect of the spatial correlation coefficient on HD MIMO. Afterward, a switching criterion is proposed, which chooses the operation mode that maximizes the downlink channel capacity while maintaining the uplink channel capacity at a certain level. Subsequently, based on our study of the system's parameters that affect the performance of both FD and HD, theoretical thresholds for these parameters are derived. Finally, numerical analysis is presented, verifying the validity of the optimization problem solution and the derived thresholds.National 863 Project [2015AA01A709 5G]; National Natural Science Foundation of China [U1301255, 61461136002]; US NSF [ECCS-1547201, CCF-1456921, CNS-1443917, ECCS-1405121, NSFC61428101]SCI(E)ARTICLE1455-4676

Asymptotic Behavior Analysis and Performance Optimization in Full Duplex Massive MIMO

[abstract not available

Effect of leadership support, work conditions and job security on job satisfaction in a medical college

Background: Faculty members are crucial elements of an educational institution, and their job satisfaction is likely essential for success of the educational process. Leadership support, work conditions and perceived job security could be factors affecting academic job satisfaction. Objective: The aim of the study was to investigate the effect of leadership support, work conditions and perceived job security on the overall academic job satisfaction of faculty. Materials and Methods: A cross-sectional survey, using a structured questionnaire, was conducted to determine the effect of leadership support, work conditions and perceived job security on academic job satisfaction among faculty and teaching staff at the College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia. Multiple regression analysis was performed to examine the significance of these relationships at 95% confidence interval and P < 0.05 level of significance. Results: Leadership support (β = 0.187, t = 2.714, P= 0.007), work conditions (β = 0.199, t = 2.628, P= 0.009) and perceived job security (β = 0.264, t = 3.369, P= 0.001) were found to be significantly associated with overall academic job satisfaction. Conclusion: The results of this study support the hypothesis that faculty and teaching staff working with supportive leaders and favorable work conditions as well as having an optimized sense of perceived job security demonstrate significantly higher levels of overall academic job satisfaction. These findings provide input for policymakers, and their implementation could enhance an institution's vitality and performance, and thus enable it to fulfill its goals