Channel coding for progressive images in a 2-D time-frequency OFDM block with channel estimation errors.

Coding and diversity are very effective techniques for improving transmission reliability in a mobile wireless environment. The use of diversity is particularly important for multimedia communications over fading channels. In this work, we study the transmission of progressive image bitstreams using channel coding in a 2-D time-frequency resource block in an OFDM network, employing time and frequency diversities simultaneously. In particular, in the frequency domain, based on the order of diversity and the correlation of individual subcarriers, we construct symmetric n -channel FEC-based multiple descriptions using channel erasure codes combined with embedded image coding. In the time domain, a concatenation of RCPC codes and CRC codes is employed to protect individual descriptions. We consider the physical channel conditions arising from various coherence bandwidths and coherence times, leading to a range of orders of diversities available in the time and frequency domains. We investigate the effects of different error patterns on the delivered image quality due to various fade rates. We also study the tradeoffs and compare the relative effectiveness associated with the use of erasure codes in the frequency domain and convolutional codes in the time domain under different physical environments. Both the effects of intercarrier interference and channel estimation errors are included in our study. Specifically, the effects of channel estimation errors, frequency selectivity and the rate of the channel variations are taken into consideration for the construction of the 2-D time-frequency block. We provide results showing the gain that the proposed model achieves compared to a system without temporal coding. In one example, for a system experiencing flat fading, low Doppler, and imperfect CSI, we find that the increase in PSNR compared to a system without time diversity is as much as 9.4 dB

Pulsed radiofrequency treatment in interventional pain management: mechanisms and potential indications—a review

Item does not contain fulltextBACKGROUND: The objective of this review is to evaluate the efficacy of Pulsed Radiofrequency (PRF) treatment in chronic pain management in randomized clinical trials (RCTs) and well-designed observational studies. The physics, mechanisms of action, and biological effects are discussed to provide the scientific basis for this promising modality. METHODS: We systematically searched for clinical studies on PRF. We searched the MEDLINE (PubMed) and EMBASE database, using the free text terms: pulsed radiofrequency, radio frequency, radiation, isothermal radiofrequency, and combination of these. We classified the information in two tables, one focusing only on RCTs, and another, containing prospective studies. Date of last electronic search was 30 May 2010. The methodological quality of the presented reports was scored using the original criteria proposed by Jadad et al. FINDINGS: We found six RCTs that evaluated the efficacy of PRF, one against corticosteroid injection, one against sham intervention, and the rest against conventional RF thermocoagulation. Two trials were conducted in patients with lower back pain due to lumbar zygapophyseal joint pain, one in cervical radicular pain, one in lumbosacral radicular pain, one in trigeminal neuralgia, and another in chronic shoulder pain. CONCLUSION: From the available evidence, the use of PRF to the dorsal root ganglion in cervical radicular pain is compelling. With regards to its lumbosacral counterpart, the use of PRF cannot be similarly advocated in view of the methodological quality of the included study. PRF application to the supracapular nerve was found to be as efficacious as intra-articular corticosteroid in patients with chronic shoulder pain. The use of PRF in lumbar facet arthropathy and trigeminal neuralgia was found to be less effective than conventional RF thermocoagulation techniques

Development of cognitive enhancers based on inhibition of insulin-regulated aminopeptidase

The peptides angiotensin IV and LVV-hemorphin 7 were found to enhance memory in a number of memory tasks and reverse the performance deficits in animals with experimentally induced memory loss. These peptides bound specifically to the enzyme insulin-regulated aminopeptidase (IRAP), which is proposed to be the site in the brain that mediates the memory effects of these peptides. However, the mechanism of action is still unknown but may involve inhibition of the aminopeptidase activity of IRAP, since both angiotensin IV and LVV-hemorphin 7 are competitive inhibitors of the enzyme. IRAP also has another functional domain that is thought to regulate the trafficking of the insulin-responsive glucose transporter GLUT4, thereby influencing glucose uptake into cells. Although the exact mechanism by which the peptides enhance memory is yet to be elucidated, IRAP still represents a promising target for the development of a new class of cognitive enhancing agents

Drug Insight: choosing a drug treatment strategy for women with osteoporosis—an evidence-based clinical perspective

Many randomized controlled trials (RCTs) have investigated drug treatment for women at high risk of fracture, with a reduction in fracture risk as their end point. There has also been progress in identifying women at the highest risk of fractures. The most important clinical determinant contributing to the clinical decision of initiating and choosing drug therapy for fracture prevention is a woman's fracture risk, which, in RCTs, was determined by menopausal state, age, bone mineral density, fracture history, fall risks and glucocorticoid use. Women with secondary osteoporosis were excluded, except in studies of glucocorticoid use. A second determinant of drug therapy is the evidence for fracture prevention in terms of spectrum (vertebral, nonvertebral and/or hip fractures), size and speed of effect. In the absence of head-to-head RCTs with fracture risk as the end point, however, the efficacy of antifracture drugs cannot be directly compared. Other determinants include the potential extraskeletal benefits and safety concerns of the drug, patient preferences and reimbursement issues

Subcarrier Assignment and Power Allocation for Device-to-Device Video Transmission in Rayleigh Fading Channels

Subcarrier assignment and power allocation for device-to-device (D2D) video transmission using a filter bank multicarrier waveform in a Rayleigh fading environment are investigated. We analyze the co-channel interference between D2D pairs, and propose a cross-layer algorithm with a subcarrier assignment outer loop and a power allocation inner loop, which aims to optimize the overall video quality. Unlike the non-convexity in physical layer power allocation for maximizing the total throughput, the cross-layer power allocation problem is convex under certain conditions, so a high quality solution for power allocation can be efficiently found. Simulation results demonstrate a higher overall video quality by the proposed cross-layer algorithm compared with baseline algorithms

Optimized spoofing and jamming a cognitive radio

We examine the performance of a cognitive radio system in a hostile environment where an intelligent adversary tries to disrupt communications by minimizing the system throughput. We investigate the optimal strategy for spoofing and jamming a cognitive radio network with a Gaussian noise signal over a Rayleigh fading channel. We analyze a cluster-based network of secondary users (SUs). The adversary may attack during the sensing interval to limit access for SUs by transmitting a spoofing signal. By jamming the network during the transmission interval, the adversary may reduce the rate of successful transmission. We present how the adversary can optimally allocate power across subcarriers during sensing and transmission intervals with knowledge of the system, using a simple optimization approach specific to this problem. We determine a worst-case optimal energy allocation for spoofing and jamming, which gives a lower bound to the overall information throughput of SUs under attack. © 1972-2012 IEEE

Optimized spoofing and jamming a cognitive radio

We examine the performance of a cognitive radio system in a hostile environment where an intelligent adversary tries to disrupt communications by minimizing the system throughput. We investigate the optimal strategy for spoofing and jamming a cognitive radio network with a Gaussian noise signal over a Rayleigh fading channel. We analyze a cluster-based network of secondary users (SUs). The adversary may attack during the sensing interval to limit access for SUs by transmitting a spoofing signal. By jamming the network during the transmission interval, the adversary may reduce the rate of successful transmission. We present how the adversary can optimally allocate power across subcarriers during sensing and transmission intervals with knowledge of the system, using a simple optimization approach specific to this problem. We determine a worst-case optimal energy allocation for spoofing and jamming, which gives a lower bound to the overall information throughput of SUs under attack. © 1972-2012 IEEE

Joint source-channel coding and unequal error protection for video plus depth

We consider the joint source-channel coding (JSCC) problem of 3-D stereo video transmission in video plus depth format over noisy channels. Full resolution and downsampled depth maps are considered. The proposed JSCC scheme yields the optimum color and depth quantization parameters as well as the optimum forward error correction code rates used for unequal error protection (UEP) at the packet level. Different coding scenarios are compared and the UEP gain over equal error protection is quantified for flat Rayleigh fading channels. © 2014 IEEE