The Uplink Capacity Evaluation of Wireless Networks: Spectral Analysis Approach

In this paper we study the capacity of wireless cellular network, in particular the uplink of WCDMA system by using the two dimensional continuous-time Markov chain (CTMC) technique. Considering two types of calls: real-time (RT) calls that characterized by a quasi fixed transmission rate, and best-effort (BE) calls which do not require strict demand but need some reliability conditions. We develop an approach based on the spectral analysis for evaluating the cell capacity. We explicitly obtain the simultaneous distribution of the number of RT connections and the number of BE connections in the steady-state. This analysis allows us to simplify the computation of the performance measures including expected delay and throughput of BE traffic. These performances are obtained explicitly in both cases (finite and infinite) of BE calls as function of system parameters like arrival rate of BE and RT calls, service rate of BE and RT calls. These results allow the operator to evaluate the cell capacity by varying these parameters independently of the number of BE calls according to its policy to manage the network. Note that this analysis can be applied to various systems such as WiMAX/HSPA, and for both uplink and downlink scenarios, so our spectral analysis approach is not only applicable to the uplink of WCDMA system. We further propose some CAC (Call admission control) policies for BE traffic. We finally conclude this work by some numerical and simulation results. The simulation results obtained by the network simulator (NS2) are closely to the numerical results of our analytical results which validate our theoretical model

A Unified NET-MAC-PHY Cross-layer Framework for Performance Evaluation of Multi-hop Ad hoc WLANs

Most of the existing works have been evaluated the performance of 802.11 multihop networks by considering the MAC layer or network layer separately. Knowing the nature of the multi-hop ad hoc networks, many factors in different layers are crucial for study the performance of MANET. In this paper we present a new analytic model for evaluating average end-to-end throughput in IEEE 802.11e multihop wireless networks. In particular, we investigate an intricate interaction among PHY, MAC and Network layers. For instance, we incorporate carrier sense threshold, transmission power, contention window size, retransmissions retry limit, multi rates, routing protocols and network topology together. We build a general cross-layered framework to represent multi-hop ad hoc networks with asymmetric topology and asymmetric traffic. We develop an analytical model to predict throughput of each connection as well as stability of forwarding queues at intermediate nodes in saturated networks. To the best of our knowledge, it seems that our work is the first wherein general topology and asymmetric parameters setup are considered in PHY/MAC/Network layers. Performance of such a system is also evaluated through simulation. We show that performance measures of the MAC layer are affected by the traffic intensity of flows to be forwarded. More precisely, attempt rate and collision probability are dependent on traffic flows, topology and routing

Bimodal functionality in a porous covalent triazine framework by rational integration of an electron-rich and -deficient pore surface

A porous Covalent Triazine Framework (CTF) consisting of both an electron-deficient central triazine core and electron-rich aromatic building blocks is reported. Taking advantage of the dual nature of the pore surface, bimodal functionality has been achieved. The electron deficiency in the central core has been utilized to address one of the pertinent problems in chemical industries, namely separation of benzene from its cyclic saturated congener, that is, cyclohexane. Also, by virtue of the electron-rich aromatic rings with Lewis basic sites, aqueous-phase chemical sensing of a nitroaromatic compound of highly explosive nature (2, 4, 6-trinitrophenol; TNP) has been achieved. The present compound supersedes the performance of previously reported COFs in both the aspects. Notably, this reports the first example of pore-surface engineering leading to bimodal functionality in CTFs

Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

Elucidation of the photophysical and biochemical properties of small molecules can facilitate their applications as prospective therapeutic imaging (theragnostic) agents. Herein, we demonstrate the luminescence behavior of a strategically designed potential therapeutic thiosemicarbazone derivative, (E)-1-(4-(diethylamino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide (DAHTS), accompanied by the illustration of its solvation and solvation dynamics using spectroscopic techniques and exploring its promising antitumor activities by adopting the necessary biochemical assays. Solvent-dependent photophysical properties, namely UV–vis absorption, fluorescence emission, and excitation profiles, concentration-dependent studies, and time-resolved fluorescence decays, serve as footprints to explain the existence of DAHTS monomers, its excited-state intramolecular proton transfer (ESIPT) product, and dimeric and aggregated forms. The emission intensity progressively intensifies with increasing polarity and proticity of the solvents up to MeOH, but in water, a sudden dip is seen. Solvent polarity and H-bonding modulate the fluorescence behavior of the primary emission peak and significantly influence the formation of the dimer and DAHTS aggregates. The designed luminophore (DAHTS) exhibits significant antiproliferative activity against the human lung cancer (A549) cell lines with inhibitory concentrations (IC50) of 16.88 and 11.92 μM for 24 and 48 h, respectively. DAHTS effectively reduces the cell viability and induces cytotoxicity with extensive morphological changes in A549 cells in the form of spikes when compared to the normal HEK cell lines. More importantly, it increases the p53 expression at the mRNA level that consolidates its potential therapeutic activity. The effect of DAHTS on apoptotic pathways against the A549 cell line has been investigated to determine its probable mechanism of cell death. Thus, the all-inclusive understanding of the photophysical properties and the necessary biochemical assays put forward important steps toward tailoring the thiosemicarbazone core structure for favorable cancer theragnostic applications in academic and pharmaceutical research