Rate-Constrained Wireless Networks with Fading Channels: Interference-Limited and Noise-Limited Regimes

A network of $n$ wireless communication links is considered in a Rayleigh fading environment. It is assumed that each link can be active and transmit with a constant power $P$ or remain silent. The objective is to maximize the number of active links such that each active link can transmit with a constant rate $\lambda$. An upper bound is derived that shows the number of active links scales at most like $\frac{1}{\lambda} \log n$. To obtain a lower bound, a decentralized link activation strategy is described and analyzed. It is shown that for small values of $\lambda$, the number of supported links by this strategy meets the upper bound; however, as $\lambda$ grows, this number becomes far below the upper bound. To shrink the gap between the upper bound and the achievability result, a modified link activation strategy is proposed and analyzed based on some results from random graph theory. It is shown that this modified strategy performs very close to the optimum. Specifically, this strategy is \emph{asymptotically almost surely} optimum when $\lambda$ approaches $\infty$ or 0. It turns out the optimality results are obtained in an interference-limited regime. It is demonstrated that, by proper selection of the algorithm parameters, the proposed scheme also allows the network to operate in a noise-limited regime in which the transmission rates can be adjusted by the transmission powers. The price for this flexibility is a decrease in the throughput scaling law by a multiplicative factor of $\log \log n$.Comment: Submitted to IEEE Trans. Information Theor

Characterization of Rate Region in Interference Channels with Constrained Power

In this paper, an $n$-user Gaussian interference channel, where the power of the transmitters are subject to some upper-bounds is studied. We obtain a closed-form expression for the rate region of such a channel based on the Perron-Frobenius theorem. While the boundary of the rate region for the case of unconstrained power is a well-established result, this is the first result for the case of constrained power. We extend this result to the time-varying channels and obtain a closed-form solution for the rate region of such channels.Comment: 21 Pages, The Conference Version is Submitted to IEEE International Symposium on Information Theory (ISIT2007

On the Throughput Maximization in Dencentralized Wireless Networks

A distributed single-hop wireless network with $K$ links is considered, where the links are partitioned into a fixed number ($M$) of clusters each operating in a subchannel with bandwidth $\frac{W}{M}$. The subchannels are assumed to be orthogonal to each other. A general shadow-fading model, described by parameters $(\alpha,\varpi)$, is considered where $\alpha$ denotes the probability of shadowing and $\varpi$ ($\varpi \leq 1$) represents the average cross-link gains. The main goal of this paper is to find the maximum network throughput in the asymptotic regime of $K \to \infty$, which is achieved by: i) proposing a distributed and non-iterative power allocation strategy, where the objective of each user is to maximize its best estimate (based on its local information, i.e., direct channel gain) of the average network throughput, and ii) choosing the optimum value for $M$. In the first part of the paper, the network hroughput is defined as the \textit{average sum-rate} of the network, which is shown to scale as $\Theta (\log K)$. Moreover, it is proved that in the strong interference scenario, the optimum power allocation strategy for each user is a threshold-based on-off scheme. In the second part, the network throughput is defined as the \textit{guaranteed sum-rate}, when the outage probability approaches zero. In this scenario, it is demonstrated that the on-off power allocation scheme maximizes the throughput, which scales as $\frac{W}{\alpha \varpi} \log K$. Moreover, the optimum spectrum sharing for maximizing the average sum-rate and the guaranteed sum-rate is achieved at M=1.Comment: Submitted to IEEE Transactions on Information Theor

Throughput Scaling Laws for Wireless Networks with Fading Channels

A network of n communication links, operating over a shared wireless channel, is considered. Fading is assumed to be the dominant factor affecting the strength of the channels between transmitter and receiver terminals. It is assumed that each link can be active and transmit with a constant power P or remain silent. The objective is to maximize the throughput over the selection of active links. By deriving an upper bound and a lower bound, it is shown that in the case of Rayleigh fading (i) the maximum throughput scales like $\log n$ (ii) the maximum throughput is achievable in a distributed fashion. The upper bound is obtained using probabilistic methods, where the key point is to upper bound the throughput of any random set of active links by a chi-squared random variable. To obtain the lower bound, a decentralized link activation strategy is proposed and analyzed.Comment: Submitted to IEEE Transactions on Information Theory (Revised

When Environmental Obligations Collide with State Sovereignty: An International and Sharia Law Perspective

This article critically reviews the notion of State sovereignty under international law and argues that to achieve eco-justice as well as sustainable development goals, a restrictive and ecological approach needs to be taken toward the principle of states’ permanent sovereignty over natural resources. Environmental sustainability requires states’ environmental obligations to be identified as erga omnes so they can be addressed toward the international community as a whole and fall within the scope of article 48 of the ILC Articles on States Responsibility. Interestingly, in complete alignment with this progressive interpretation, sustainable utilization of natural resources has a longstanding foundation in Islam. According to some Islamic scholars, the Islamic notion of Al-Anfal implies that the Islamic States cannot own the natural wealth and resources in their territories, but should only manage them for the benefit of all generations in a manner that the origin of the source would be preserved at all times. Therefore, suggested transformation can be acceptable to the Muslim majority countries. This research takes a normative approach and a library research method to the inevitable development that needs to take place in international law

THE PREVALENCE OF CUTANEOUS LEISHMANIASIS IN EAST OF AHVAZ COUNTY, SOUTH-WESTERN IRAN

Objectives: Cutaneous Leishmaniasis (CL) is a zoonotic parasitological disease. This disease cause always important health challenges for the human communities. It is common in many parts of the globe. This research was designed to determine the epidemiology of CL in East of Ahvaz County during 2003- 2013. Methods: This was a descriptive cross-sectional study. The disease was diagnosed based on clinical examination and microscopic observation of the parasite in the ulcer site. The patient's Information such as age, gender, number and sites of ulcer (s) on the body, month and residence area were recorded. Data analysis was performed using SPSS software. Results: Totally, 2287 cases were detected during 2003 – 2013. About 53.4% patients were male and 46.4% female. The highest frequency infected age groups were observed in 10-19 years old (n=550 ,24%). Nearly 37 % of the patients had one and 38.1% had three ulcers. The most common location of ulcers were on hands (n=1022, 44.7%) and then on feet (n=501, 21.9%). Totally 1877 of the patients were infected in rural areas. Based on the appearance of the lesion it was found that 410 cases (17.9%) were of the dry type and 1877 cases (82.1%) were wet type. Concluaions: Such high prevalence and incidence rates are alarming and require control and prevention measures. Further epidemiological studies of CL are suggested. Key words: Epidemiology, Cutaneous Leishmaniasis, Iran

A Study of Swelling Behaviour in a Tunnel Using Finite Element Methods

The aim of this research is to show swelling behaviour in a tunnel excavated through rocks by modeling them and using laboratory results. The engineering challenge is how to design a tunnel which contains swelling rocks such as marl. This aim is achieved through two methods. In the first method, the Field System Solution program (FISS) is calibrated using experimentally obtained laboratory graphs of the saturated rocks around the tunnel, and the parameters are applied to the geometry of the tunnel. Comparing a critical state model with stresses around the tunnel, stability of the rocks was examined. In the second method, stability of the rocks around the tunnel was investigated by using the Nisa-II program, adjusting the laboratory swelling graphs with the creep function to the program and, finally, drawing Von Mises stresses around the tunnel

The Effect of Spiritual and Religious Group Psychotherapy on Suicidal Ideation in Depressed Patients: A Randomized Clinical Trial

Introduction: Suicide is a great economical, social and public health problem. It is prevalent worldwide and has a lot of negative effects on individuals, families and society. Depression is often prelude to Suicide. An important part of the treatment of the mentally ill patients is spiritual-religious psychotherapy which should be done after physical treatment. The aim of this study was to determine the effect of spiritual and religious group psychotherapy on suicidal ideation in depressed patients. Methods: 51 depressed patients with suicidal ideation from Razi hospital (Tabriz, Iran) participated in this clinical trial. To collect Data questionnaire was used which included demographic and Beck Suicide Scale Ideation. Experimental group participated in 10 sessions of group psychotherapy. Each section lasted 1 hour. Two weeks after the last section post test was done. Statistical software SPSS ver 13 was used for data analysis. Results: Results of independent t-test revealed no difference between two groups in terms of suicidal ideation before intervention but after study there is a statistical difference. Also the results of ANCOVA test showed a significant relationship between spiritual group therapy and decrease in suicidal ideation, so that this intervention can make 57% of variance in suicidal ideation of experimental group.Conclusion: Regarding positive effect of spiritual and religious group psychotherapy on decreasing suicidal ideation of depressed patients, we suggest this intervention to be held in Psychiatric Wards and also more study on depression and other psychiatric patients with greater sample size would be helpful

Isolated Retrobulbar Hydatid Cyst: A Case Report

Background: Hydatid cyst is caused by Echinococcus granulosus and human is the accidental host. The most common sites of involvement are the liver and lungs, and involvement of other organs is less common. Ocular involvement of hydatid cyst is one of the most uncommon manifestations of hydatid cyst.Cases Report: The case was a 40-year-old woman with a retrobulbar cystic lesion who was examined for the left eye pain and then proptosis. With the initial diagnosis of retrobulbar tumor, the patient underwent surgery and the removed mass was sent to the pathology laboratory. Since the result indicated the existence of a hydatid cyst, the patient was referred to the infectious service and was treated with albendazole.Conclusion: Although the ocular involvement of hydatid cyst is uncommon, it should be considered as a differential diagnosis in patients with proptosis in the endemic areas