Cognitive ultra wideband radio spectrum sensing window length optimization algorithm

A critical objective of cognitive radio (CR) system is to enhance the spectrum efficiency, and one of the key factors that can determine the spectrum efficiency is the system spectrum sensing performance with respect to sensing window length. For non-coherent detection-based sensing technique, the length of the sensing window required to meet the detection criteria is inversely proportional to the detected signal-to-noise ratio (SNR) of the primary users (PUs). This fact may result in an inadequate use of the white or gray space for the conventional CR system whose transmission and sensing window length are both fixed because a high detected PUs SNR can lead to an excessive long fixed sensing window which occupies the potential CR transmission opportunities while a low received PUs SNR can result in an insufficient sensing window length which degrades the CR detection criteria. In this paper, to improve the spectrum efficiency compared with the fixed sensing/transmission window length-based CR system, we propose an adaptive spectrum sensing window length optimization algorithm. We design the algorithm based on the ultra wideband (UWB) system which is an ideal candidate for the implementation of the CR technology. Based on the analysis of the CR-UWB’s spectrum sensing technique in terms of the factors such as spectrum efficiency, spectrum sensing length, PUs SNR, detection criteria etc., we formulate the optimization problem into a convex problem, which enables the proposed algorithm to find the optimal trade-off with low computational complexity between the sensing window length and the desired detection probabilities for the CR-UWB system. Compared with the conventional fixed length spectrum sensing techniques, the proposed algorithm is verified to be able to adapt the length of the CR-UWB’s transmission window according to the PUs SNR to optimize the use of the available spectrum while guaranteeing the PUs from being interfered

Group A Streptococcus strains and plasmids used in this study.

<p>Group A Streptococcus strains and plasmids used in this study.</p

MGAS315 <i>covS</i>^wt and MGAS315 Δ<i>covS</i> have higher skin invasion than MGAS6180 and MGAS6180 Δ<i>covS</i>, respectively.

<p>(A) Relative levels of <i>hasA</i>, <i>spyCEP</i>, <i>sse</i>, and <i>emm</i> transcripts in MGAS315, MGAS315 Δ<i>covS</i>, MGAS6180, and MGAS6180 Δ<i>covS</i>, MGAS6180/pDCBB-<i>covS</i>^wt, and MGAS6180/pDCBB. All the mRNA levels were normalized first to that of <i>gyrA</i> and then to that of each gene transcript in MGAS315. (B) Lesion sizes in subcutaneous infections of mice at 24 h after inoculation after inoculation with 1.3 x 10⁸ cfu MGAS315 <i>covS</i>^wt, 1.2 x 10⁸ cfu MGAS315 Δ<i>covS</i>, 1.4 x 10⁸ cfu MGAS6180, and 1.3 x 10⁸ cfu MGAS6180 Δ<i>covS</i>. Statistical analysis with the One-way ANOVA Newman-Keuls Multiple Comparison Test in panel B: **, P < 0.01 and ***, P < 0.001.</p

IC₅₀ of different extracts of CK for various antioxidant systems.

<p>Each value in the table is represented as Mean ± SD (n = 3). Means not sharing the same letter are significantly different at P<0.05 probability level in each column.</p

Replacement of <i>covS</i>^1370T with <i>covS</i>^wt in MGAS315 reduces skin invasion and virulence and enhances neutrophil recruitment in subcutaneous infection of mice.

<p>(A) Neutrophil levels and skin lesion sizes in MGAS315 and MGAS315<i>covS</i>^wt infections. (B) Survival rates of mice infected with MGAS315 and MGAS315<i>covS</i>^wt. Inoculum: 1.3 x 10⁸ cfu MGAS315 and 1.4 x 10⁸ cfu MGAS315 <i>covS</i>^wt.</p

Effect of BF on the level of hepatic MDA and SOD activity in mice treated with CCl₄.

<p>Each value in the table is represented as Mean ± SD (n = 8). Means not sharing the same letter are significantly different at P<0.05 probability level in each column.</p

MGAS315 inhibits TNF-α production at skin infection sites.

<p>Presented are the levels of TNF-α (A), INF-γ (B), IL-6 (C), and IL-1β (D) at skin infection sites and levels of IL-6 and TNF-α (E) and INF-γ (F) in sera at the indicated time points after subcutaneous inoculation of 2.1 x 10⁸ cfu MGAS315 and 2.7 x 10⁸ cfu MGAS6180. Statistical analyses with the two-tailed Mann-Whitney <i>t</i> test for the cytokine levels between MGAS315 and MGAS6180 infections: ns, not significant; ***, P < 0.001; **, P < 0.01; and *, P < 0.05.</p

Comparison between MGAS315 and MGAS6180 in innate immune evasion.

<p>(A) Levels of neutrophils at skin infection sites in subcutaneous infections with 1.1 x 10⁸ cfu MGAS315 and 1.4 x 10⁸ cfu MGAS6180. (B-F) Data in the cytospin analysis of neutrophils infiltration in air sac infections with 6.6 x 10⁷ MGAS315 and 1.1 x 10⁸ cfu MGAS6180: Mean numbers ± error of viable neutrophils in the air sac lavages at the indicated times after GAS inoculation (B) and representative pictures of cytospin slides (C, no dilution of the lavage sample for cytospin; D-F, 2x dilution of the lavage samples for cytospin) comparing relative amounts of intact neutrophils versus cell debris at 4 h and 12 h in MGAS315 and MGAS6180 infections. *, P < 0.05, and **, P < 0.01, for the difference in neutrophil numbers between MGAS315 and MGAS6180 infections at 8 and 12 h, respectively.</p

Identification of 13 compounds from CK by developed HPLC–DAD–ESI-Trap MS method.

<p>Identification of 13 compounds from CK by developed HPLC–DAD–ESI-Trap MS method.</p