QAP: A QoS supportive adaptive polling protocol for wireless LANs

A QoS supportive adaptive polling (QAP) protocol for wireless LANs is introduced. QAP operates under an infrastructure wireless LAN, where an access point (AP) polls the wireless nodes in order to grant them permission to transmit. The polled node sends data directly to the destination node. We consider bursty traffic conditions, under which the protocol operates efficiently. The polling scheme is based on an adaptive algorithm according to which it is most likely that an active node is polled. Also, QAP takes into account packet priorities, so it supports QoS by means of the Highest Priority First packet buffer discipline and the priority distinctive polling scheme. Lastly, the protocol combines efficiency and fairness, since it prohibits a single node to dominate the medium permanently. QAP is compared to the efficient learning automata-based polling (LEAP) protocol, and is shown to have superior performance. © 2005 Elsevier B.V. All rights reserved

HIPERSIM: A Sense Range Distinctive Simulation Environment for HiperLAN Systems

This paper presents the simulator “HIPERSIM” which was developed and used to examine the behavior of HIPERLAN (Type 1). HIPERSIM simulates the HIPERLAN network under various conditions, assuming that the communication range and the sense range (signal detection range) of a node are different. In a wireless LAN, like HIPERLAN, the medium access protocol, the hidden nodes, the packet forwarding and the power saving mechanism are important issues that significantly affect the overall performance. The intention is to provide a HIPERLAN specialized tool (HIPERSIM) which can simulate most of the features of this WLAN protocol, in order to examine the performance of HIPER-LAN. The main focus is to simulate the channel access mechanism accurately, so as to examine the effectiveness of the EY-NPMA protocol, and underline its advantages and the elements that need improvement. Also, in HIPERSIM, there is emphasis on the “hidden nodes” issue. More specifically, we distinguish between the communication range and the signal detection range of a node, since this is a characteristic of the wireless nature and it affects the network operation. The simulation results show that EY-NPMA is effective and suitable for WLANs. Probably there could be some improvement in order to avert the collisions close to the receiver. © 2003, SAGE Publications. All rights reserved

SQAP: A simple QoS supportive adaptive polling protocol for wireless LANs

A Simple QoS supportive Adaptive Polling (SQAP) protocol for wireless LANs is introduced. SQAP operates under an infrastructure wireless LAN, where an Access Point (AP) polls the wireless nodes in order to grant them permission to transmit. The polled node sends data directly to the destination node. We consider bursty traffic conditions, under which the protocol operates efficiently. The polling scheme is based on an adaptive algorithm according to which it is most likely that an active node is polled. Also, SQAP takes into account packet priorities, so it supports QoS by means of the Highest Priority First packet buffer discipline and the priority distinctive polling scheme. Lastly, the protocol combines efficiency and fairness, since it prohibits a singe node to dominate the medium permanently. SQAP is compared to the efficient learning automata-based polling (LEAP) protocol, and is shown to have superior performance. © 2005 Elsevier B.V. All rights reserved

A Novel Method of Serving Multimedia and Background Traffic in Wireless LANs.

Wireless local area networks (LANs) require the efficient integration of multimedia and traditional data traffic. This paper proposes the priority-oriented adaptive polling (POAP) protocol that could be used in place of the enhanced distributed channel access (EDCA) part of the IEEE 802.11e access scheme. EDCA seems capable of differentiating traffic; however, it exhibits great overhead that limits the available bandwidth and degrades performance. POAP is collision free, prioritizes the different kinds of traffic, and is able to provide quality of service (QoS) for all types of multimedia network applications while efficiently supporting background data traffic. POAP, compared to EDCA, provides higher channel utilization, distributes resources to the stations adapting to their real needs, and generally exhibits superior performance

Measurement of the azimuthal anisotropy of Y(1S) and Y(2S) mesons in PbPb collisions at √S^{S}NN = 5.02 TeV

The second-order Fourier coefficients (υ$_{2}$) characterizing the azimuthal distributions of Υ(1S) and Υ(2S) mesons produced in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV are studied. The Υmesons are reconstructed in their dimuon decay channel, as measured by the CMS detector. The collected data set corresponds to an integrated luminosity of 1.7 nb$^{-1}$. The scalar product method is used to extract the υ$_{2}$ coefficients of the azimuthal distributions. Results are reported for the rapidity range |y| < 2.4, in the transverse momentum interval 0 < p$_{T}$ < 50 GeV/c, and in three centrality ranges of 10–30%, 30–50% and 50–90%. In contrast to the J/ψ mesons, the measured υ$_{2}$ values for the Υ mesons are found to be consistent with zero

Measurement of prompt D0^{0} and D‾\overline{D}0^{0} meson azimuthal anisotropy and search for strong electric fields in PbPb collisions at root SNN\sqrt{S_{NN}} = 5.02 TeV

The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapiditydependent difference (Av2) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, v2) between D0 (uc) and D0 (uc) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of Av2. The rapidity-averaged value is found to be (Av2) = 0.001 ? 0.001 (stat)? 0.003 (syst) in PbPb collisions at ?sNN = 5.02 TeV. In addition, the influence of the collision geometry is explored by measuring the D0 and D0mesons v2 and triangular flow coefficient (v3) as functions of rapidity, transverse momentum (pT), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt D0 meson v2 values is observed, while the v3 is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry. ? 2021 The Author. Published by Elsevier B.V. This is an open access article under the CC BY licens

Measurements of production cross sections of the Higgs boson in the four-lepton final state in proton–proton collisions at S\sqrt{S} = 13 TeV

Production cross sections of the Higgs boson are measured in the H -> ZZ -> 4l (l = e, mu) decay channel. A data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS detector at the LHC and corresponding to an integrated luminosity of 137 fb(-1) is used. The signal strength modifier mu, defined as the ratio of the Higgs boson production rate in the 4l channel to the standard model (SM) expectation, is measured to be mu = 0.94 +/- 0.07 (stat)(-0.08)(+0.09) (syst) at a fixed value of m(H) = 125.38 GeV. The signal strength modifiers for the individual Higgs boson production modes are also reported. The inclusive fiducial cross section for the H -> 4l process is measured to be 2.84(-0.22)(+0.23) (stat)(-0.21)(+0.26) (syst) fb, which is compatible with the SM prediction of 2.84 +/- 0.15 fb for the same fiducial region. Differential cross sections as a function of the transverse momentum and rapidity of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet are measured. A new set of cross section measurements in mutually exclusive categories targeted to identify production mechanisms and kinematical features of the events is presented. The results are in agreement with the SM predictions

Measurement of the tt̄bb̅ production cross section in the all-jet final state in pp collisions at √s = 13 TeV

A measurement of the production cross section of top quark pairs in association with two b jets (tt̄bb̅) is presented using data collected in proton-proton collisions at √s = 13 TeV by the CMS detector at the LHC corresponding to an integrated luminosity of 35.9 fb⁻¹. The cross section is measured in the all-jet decay channel of the top quark pair by selecting events containing at least eight jets, of which at least two are identified as originating from the hadronization of b quarks. A combination of multivariate analysis techniques is used to reduce the large background from multijet events not containing a top quark pair, and to help discriminate between jets originating from top quark decays and other additional jets. The cross section is determined for the total phase space to be 5.5±0.3(stat)^(+1.6)_(-1.3)(syst)pb and also measured for two fiducial tt̄bb̅ definitions. The measured cross sections are found to be larger than theoretical predictions by a factor of 1.5–2.4, corresponding to 1–2 standard deviations