Energy Efficiency in Cache Enabled Small Cell Networks With Adaptive User Clustering

Using a network of cache enabled small cells, traffic during peak hours can be reduced considerably through proactively fetching the content that is most probable to be requested. In this paper, we aim at exploring the impact of proactive caching on an important metric for future generation networks, namely, energy efficiency (EE). We argue that, exploiting the correlation in user content popularity profiles in addition to the spatial repartitions of users with comparable request patterns, can result in considerably improving the achievable energy efficiency of the network. In this paper, the problem of optimizing EE is decoupled into two related subproblems. The first one addresses the issue of content popularity modeling. While most existing works assume similar popularity profiles for all users in the network, we consider an alternative caching framework in which, users are clustered according to their content popularity profiles. In order to showcase the utility of the proposed clustering scheme, we use a statistical model selection criterion, namely Akaike information criterion (AIC). Using stochastic geometry, we derive a closed-form expression of the achievable EE and we find the optimal active small cell density vector that maximizes it. The second subproblem investigates the impact of exploiting the spatial repartitions of users with comparable request patterns. After considering a snapshot of the network, we formulate a combinatorial optimization problem that enables to optimize content placement such that the used transmission power is minimized. Numerical results show that the clustering scheme enable to considerably improve the cache hit probability and consequently the EE compared with an unclustered approach. Simulations also show that the small base station allocation algorithm results in improving the energy efficiency and hit probability.Comment: 30 pages, 5 figures, submitted to Transactions on Wireless Communications (15-Dec-2016

Caching Improvement Using Adaptive User Clustering

In this article we explore one of the most promising technologies for 5G wireless networks using an underlay small cell network, namely proactive caching. Using the increase in storage technologies and through studying the users behavior, peak traffic can be reduced through proactive caching of the content that is most probable to be requested. We propose a new method, in which, instead of caching the most popular content, the users within the network are clustered according to their content popularity and the caching is done accordingly. We present also a method for estimating the number of clusters within the network based on the Akaike information criterion. We analytically derive a closed form expression of the hit probability and we propose an optimization problem in which the small base stations association with clusters is optimized

An Exclusion zone for Massive MIMO With Underlay D2D Communication

Fifth generation networks will incorporate a variety of new features in wireless networks such as data offloading, D2D communication, and Massive MIMO. Massive MIMO is specially appealing since it achieves huge gains while enabling simple processing like MRC receivers. It suffers, though, from a major shortcoming refereed to as pilot contamination. In this paper we propose a frame-work in which, a D2D underlaid Massive MIMO system is implemented and we will prove that this scheme can reduce the pilot contamination problem while enabling an optimization of the system spectral efficiency. The D2D communication will help maintain the network coverage while allowing a better channel estimation to be performed

Enhancing massive MIMO: A new approach for Uplink training based on heterogeneous coherence time

Massive multiple-input multiple-output (MIMO) is one of the key technologies in future generation networks. Owing to their considerable spectral and energy efficiency gains, massive MIMO systems provide the needed performance to cope with the ever increasing wireless capacity demand. Nevertheless, the number of scheduled users stays limited in massive MIMO both in time division duplexing (TDD) and frequency division duplexing (FDD) systems. This is due to the limited coherence time, in TDD systems, and to limited feedback capacity, in FDD mode. In current systems, the time slot duration in TDD mode is the same for all users. This is a suboptimal approach since users are subject to heterogeneous Doppler spreads and, consequently, different coherence times. In this paper, we investigate a massive MIMO system operating in TDD mode in which, the frequency of uplink training differs among users based on their actual channel coherence times. We argue that optimizing uplink training by exploiting this diversity can lead to considerable spectral efficiency gain. We then provide a user scheduling algorithm that exploits a coherence interval based grouping in order to maximize the achievable weighted sum rate

Nuclear genetic transformation and a restriction fragment length polymorphism analysis of soybean [Glycine max (L) Merr] mitochondrial genetics

Agrobacterium-mediated transformation was used to introduce the maize transposable element Ac into soybean cotyledons by inoculating the cotyledon at the point of embryo axis attachment with Agrobacterium tumefaciens harboring the binary vectors PZAC1, PZAC1/R, and PZAC3. A new method of transformation was applied which requires no intermediate callus formation. Inoculation at the point of embryo axis attachment with A. tumefaciens causes the proliferation of multiple shoots which later develop into whole plants. The Ac element was detected in R0 plants by PCR and Southern blot hybridization. A transformation frequency of 24% and 10% was obtained when PZAC1 and PZAC1/R vectors were used for inoculation, respectively. The element proved to be transmitted sexually to R1 plants. The Ac element follows a Mendelian pattern of inheritance in R1 plants;Restriction fragment length polymorphism analysis of soybean mitochondrial DNA was conducted. A collection of germ plasms containing accessions of three Glycine species: max, soja, and gracilis were analyzed. The Plant Introductions and cultivars used in the RFLP screen for cytoplasmic diversity were used in the construction of isocytoplasmic lines. The cytoplasm was transferred into 2 different nuclear backgrounds of cultivars Clark 63 and Harosoy 63. Based on maize mitochondrial cloned genes and a cosmid library of Phaseolus mitochondrial genomes, the germ plasms were grouped into 6 RFLP groups;The mitochondrial-based RFLP analysis was able to detect variability within the same chloroplast RFLP groups. There was evidence for involvement of the nuclear genome in controlling the physical organization of the mitochondrial genome

Power Control in Massive MIMO with Dynamic User Population

This paper considers the problem of power control in Massive MIMO systems taking into account the pilot contamination issue and the arrivals and departures of users in the network. Contrary to most of existing work in MIMO systems that focuses on the physical layer with fixed number of users, we consider in this work that the users arrive dynamically and leave the network once they are served. We provide a power control strategy, having a polynomial complexity, and prove that this policy stabilizes the network whenever possible. We then provide a distributed implementation of the power control policy requiring low information exchange between the BSs and show that it achieves the same stability region as the centralized policy.Comment: conference paper, submitte

Bacterial osteomyelitis versus diffuse sclerosing osteomyelitis of the jaw, similar nomenclature, different disease entity

Introduction: Osteomyelitis (OM) of the jaw is considered one of the most challenging problems for dental clinicians. Many classifications of OM have been developed based on several characteristics including the clinical progression and pathogenesis of the disease. A particularly informative classification discriminates between bacterial osteomyelitis (B-OM) and non-bacterial osteomyelitis (NB-OM), presenting as diffuse sclerosing osteomyelitis (DSO). Aim: To draw on our experience and observations of osteomyelitis of the jaw to differentiate between B-OM and NB-OM with respect to clinical, radiographic and microbiological findings, as well as discussing the treatment strategies of each type of OM. Methods: The medical records of 175 patients were screened retrospectively, of which, a total of 67 patients were diagnosed with OM and treated surgically or conservatively at a single institution between January 2003 to December 2012. Demographic-, anamnesis-, clinical-, and radiological data were collected and evaluated. The patients were allocated into two groups depending on their aetiology, clinical and radiological features. Patients with history of radiation and bisphosphonate intake prior to OM diagnosis were excluded. Results: The mean age of patients diagnosed with OM was 52 years and the mandible was the most commonly affected site. Moreover, behavioural risk, such as smoking and alcohol abuse, were commonly associated with OM. Notably, surgical procedures were significantly more frequent in the treatment of the B-OM group (50 cases; 96.2%) than in the treatment of the NB-OM group (4 cases; 26.7%). Conclusion: Diffuse sclerosing osteomyelitis is distinct to other forms of osteomyelitis and the use of misleading terminology to describe DSO leads to confusion and misunderstanding of this disease

Atomistic investigation on the effect of temperature on mechanical properties of diffusion-welded Aluminium-Nickel

Atomistic investigation of diffusion welding between Aluminium and Nickel has been investigated, by means of Molecular Dynamics (MD) simulation. This study focuses on examining the effect of temperature on diffusion welding between Al-Ni for which it is still lacking. Employing several different temperatures, this study aims to examine the influence of temperature on the mechanical properties of diffusion-welded Al-Ni. The results have shown that the structural evolution significantly affected by the temperature. Better bonding structure is achieved as the temperature is increased which indicated by the wider interfacial region thickness on concentration profiles. However, as the temperature is increased lower ultimate tensile strength is obtained. Therefore, precisely estimates the temperature for particular materials in diffusion welding is a critical point. In this study, the optimum condition that fitsA on the diffusion welding process is when the temperature set on 500 K