7 research outputs found
Service differentiation in OFDM-Based IEEE 802.16 networks
IEEE 802.16 network is widely viewed as a strong candidate solution for broadband wireless access systems. Various flexible mechanisms related to QoS provisioning have been specified for uplink traffic at the medium access control (MAC) layer in the standards. Among the mechanisms, bandwidth request scheme can be used to indicate and request bandwidth demands to the base station for different services. Due to the diverse QoS requirements of the applications, service differentiation (SD) is desirable for the bandwidth request scheme. In this paper, we propose several SD approaches. The approaches are based on the contention-based bandwidth request scheme and achieved by the means of assigning different channel access parameters and/or bandwidth allocation priorities to different services. Additionally, we propose effective analytical model to study the impacts of the SD approaches, which can be used for the configuration and optimization of the SD services. It is observed from simulations that the analytical model has high accuracy. Service can be efficiently differentiated with initial backoff window in terms of throughput and channel access delay. Moreover, the service differentiation can be improved if combined with the bandwidth allocation priority approach without adverse impacts on the overall system throughput
DYBS: A Lightweight Dynamic Slicing Framework for Diagnosing Attacks on x86 Binary Programs
Roll-to-Roll Slot-Die-Printed Polymer Solar Cells by Self-Assembly
Extremely
simplified one-step roll-to-roll slot-die-printed flexible indium
tin oxide (ITO)-free polymer solar cells (PSCs) are demonstrated based
on the ternary blends of electron-donor polymer thieno[3,4-<i>b</i>]thiophene/benzodithiophene, electron-acceptor fullerene
[6,6]-phenyl-C<sub>71</sub>-butyric acid methyl ester, and electron-extracting
polymer poly[(9,9-bis(3′-(<i>N</i>,<i>N</i>-dimethylamino)propyl)-2,7-fluorene)-<i>alt</i>-2,7-(9,9-dioctylfluorene)]
(PFN) at room temperature (RT) in ambient air. The flexible ITO-free
PSC exhibits a comparable power conversion efficiency (PCE) with the
device employing complicated two-step slot-die printing (5.29% vs
5.41%), which indicates that PFN molecules can migrate from the ternary
nanocomposite toward the Ag cathode via vertical self-assembly during
the one-step slot-die printing process in air. To confirm the migration
of PFN, the morphology and elemental analysis as well as charge transport
of different active layers are investigated by the in situ transient
film drying process, transmission electron microscopy, atomic force
microscopy, contact angle and surface energy, X-ray photoelectron
spectroscopy, scanning electron microscopy, impedance spectroscopy,
transient photovoltage and transient photocurrent, and laser-beam-induced
current. Moreover, the good air and mechanical stability of the flexible
device with a decent PCE achieved in 1 cm<sup>2</sup> PSCs at RT in
air suggests the feasibility of energy-saving and time-saving one-step
slot-die printing to large-scale roll-to-roll manufacture in the future