2,138 research outputs found
EVM as generic QoS trigger for heterogeneous wieless overlay network
Fourth Generation (4G) Wireless System will integrate heterogeneous wireless
overlay systems i.e. interworking of WLAN/ GSM/ CDMA/ WiMAX/ LTE/ etc with
guaranteed Quality of Service (QoS) and Experience (QoE).QoS(E) vary from
network to network and is application sensitive. User needs an optimal mobility
solution while roaming in Overlaid wireless environment i.e. user could
seamlessly transfer his session/ call to a best available network bearing
guaranteed Quality of Experience. And If this Seamless transfer of session is
executed between two networks having different access standards then it is
called Vertical Handover (VHO). Contemporary VHO decision algorithms are based
on generic QoS metrics viz. SNR, bandwidth, jitter, BER and delay. In this
paper, Error Vector Magnitude (EVM) is proposed to be a generic QoS trigger for
VHO execution. EVM is defined as the deviation of inphase/ quadrature (I/Q)
values from ideal signal states and thus provides a measure of signal quality.
In 4G Interoperable environment, OFDM is the leading Modulation scheme (more
prone to multi-path fading). EVM (modulation error) properly characterises the
wireless link/ channel for accurate VHO decision. EVM depends on the inherent
transmission impairments viz. frequency offset, phase noise,
non-linear-impairment, skewness etc. for a given wireless link. Paper provides
an insight to the analytical aspect of EVM & measures EVM (%) for key
management subframes like association/re-association/disassociation/ probe
request/response frames. EVM relation is explored for different possible
NAV-Network Allocation Vectors (frame duration). Finally EVM is compared with
SNR, BER and investigation concludes EVM as a promising QoS trigger for OFDM
based emerging wireless standards.Comment: 12 pages, 7 figures, IJWMN 2010 august issue vol. 2, no.
Bandwidth extension of planar antennas using embedded slits for reliable multiband RF communications
In this paper a technique is described to extend the impedance bandwidth of patch antennas without compromising their size. This is accomplished by embedding capacitive slits in the rectangular patch with a truncated ground-plane, and exciting the antenna through a meandered strip-line feed. The proposed antenna was fabricated on standard FR-4 substrate with permittivity of 4.6, thickness of 0.8 mm and loss-tangent of 0.001. The performance of the prototype antenna was verified through measurements. Characteristics of the antenna include an impedance bandwidth of 5.25 GHz (800 MHz–6.05 GHz) for VSWR<2 corresponding to a fractional bandwidth of 153.28%, peak gain of 5.35 dBi, radiation efficiency of 84.12% at 4.45 GHz, and low cross-polarization. These attributes make the antenna applicable for stable and reliable multiband applications in the UHF, L, S and major part of C-bands. The antenna offers advantages of low cost, low profile, ease of manufacturing, durability and conformability
Cross-Layer Adaptive Feedback Scheduling of Wireless Control Systems
There is a trend towards using wireless technologies in networked control
systems. However, the adverse properties of the radio channels make it
difficult to design and implement control systems in wireless environments. To
attack the uncertainty in available communication resources in wireless control
systems closed over WLAN, a cross-layer adaptive feedback scheduling (CLAFS)
scheme is developed, which takes advantage of the co-design of control and
wireless communications. By exploiting cross-layer design, CLAFS adjusts the
sampling periods of control systems at the application layer based on
information about deadline miss ratio and transmission rate from the physical
layer. Within the framework of feedback scheduling, the control performance is
maximized through controlling the deadline miss ratio. Key design parameters of
the feedback scheduler are adapted to dynamic changes in the channel condition.
An event-driven invocation mechanism for the feedback scheduler is also
developed. Simulation results show that the proposed approach is efficient in
dealing with channel capacity variations and noise interference, thus providing
an enabling technology for control over WLAN.Comment: 17 pages, 12 figures; Open Access at
http://www.mdpi.org/sensors/papers/s8074265.pd
Systems architecture for the acquisition and preservation of wireless network traffic
Wireless networking provides a ready and cost effective solution for business applications. It has escalated in popularity mainly due to the ability to form computer networks without a wired based infrastructure. However, accompanying the widespread usage also comes the inherent prospect of criminal misuse, including unauthorized application and the launch of system attacks. This paper presents the testing of an innovative Wireless Forensic Model (WFM) system that provides capability for acquisition and preservation of wireless network traffic (802.11) frames by implementing a wireless drone architecture. It is thus a forensic readiness system providing available evidence for forensic investigation. The results show that the tested system has the ability to collect upwards of 90% of all frames, as well as evidence and detection of attacks conducted against the wireless network
Performance Analysis of Bluetooth Network in the Presence of WI-FI System
Many wireless technologies used to build local or personal area network (WLANs or WPANs) operate in the 2.4 GHz ISM band. Due to mutual interference, the coexistence of such devices working at the same time in the same area can be troublesome. This paper reports the result of Bluetooth performance with 802.11b interference in term of BER of Bluetooth network. This study employed Agilent Advance Design system 2011 (ADS 2011) as methodology. The result revealed how Bluetooth network suffered degradation in terms of BER and the IEEE 802.11b interfering power and frequency offset. This study confirm previous finding. Further, the study recommends that the data rate of IEEE 802.11b should be taken into account in the performance evaluation of the Bluetooth network. Keywords: Bluetooth, Performance, and WI-FI syste
A Remote Capacity Utilization Estimator for WLANs
In WLANs, the capacity of a node is not fixed and can vary dramatically due to the shared nature of the medium under the IEEE 802.11 MAC mechanism. There are two main methods of capacity estimation in WLANs: Active methods based upon probing packets that consume the bandwidth of the channel and do not scale well. Passive methods based upon analyzing the transmitted packets that avoid the overhead of transmitting probe packets and perform with greater accuracy. Furthermore, passive methods can be implemented locally or remotely. Local passive methods require an additional dissemination mechanism in order to communicate the capacity information to other network nodes which adds complexity and can be unreliable under adverse network conditions. On the other hand, remote passive methods do not require a dissemination mechanism and so can be simpler to implement and also do not suffer from communication reliability issues. Many applications (e.g. ANDSF etc) can benefit from utilizing this capacity information. Therefore, in this thesis we propose a new remote passive Capacity Utilization estimator performed by neighbour nodes. However, there will be an error associated with the measurements owing to the differences in the wireless medium as observed by the different nodes’ location. The main undertaking of this thesis is to address this issue. An error model is developed to analyse the main sources of error and to determine their impact on the accuracy of the estimator. Arising from this model, a number of modifications are implemented to improve the accuracy of the estimator. The network simulator ns2 is used to investigate the performance of the estimator and the results from a range of different test scenarios indicate its feasibility and accuracy as a passive remote method. Finally, the estimator is deployed in a node saturation detection scheme where it is shown to outperform two other similar schemes based upon queue observation and probing with ping packets
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