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The following topics are dealt with: VLSI; OFDM; embedded systems; filters; MIMO; cellular and integrated systems; media processing; Internet; image processing; network routing; QoS and resource allocation; network management; channel modelling and equalization; ad hoc networks; communication signal processing; WSN; channel estimation; WLAN and WWAN; coding and detection; security; UWB; cognitive...
This paper presents a quadrature voltage-controlled oscillator (QVCO) based on the coupling of two LC-tank VCOs. The QVCO could be tuned between 2.41 and 2.64 GHz, and showed a phase noise of -139 dBc/Hz at 1 MHz offset frequency from the carrier across the whole tuning range, for a current consumption of 20 mA with 2.5-V power supply. A figure-of-merit of -190 dBc/Hz is observed.
A method for time synchronization is proposed for OFDM based WLAN systems. The proposed method has a comparable performance as an existing approach, but requires less computation. The first half of the long-symbol guard interval needs to be zero padded for the development of the new method.
This paper presents the results of dynamic channel capacity measurements for a multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system in two populated indoor environments with and without line-of-sight (LoS). The experiment used 4 sending and 4 receiving antennas and 114 sub-carriers at 5 GHz as per draft IEEE 802.11n. MIMO-OFDM channel capacity is analysed both...
An aperture coupled patch antenna suitable for IEEE 802.11b/g WLAN applications is described. The antenna system enables the polarization of the device to be dynamically reconfigured, where the reconfiguration is actuated by an RF microelectromechanical system (MEMS) single-pole double-throw (SPDT) switch. An equivalent circuit model of the RF MEMS switch is used in the electromagnetic simulations...
IEEE802.11, which is the most widely used wireless LAN standard protocol, employs Binary Exponential Back-off (BEB) for reducing packet collisions. Although the BEB can effectively avoid packet collision by a simple mechanism, transmission unfairness arises under high traffic environment. Then, a large number of algorithms aimed at reducing unfairness on BEB have been reported. Most of those algorithms...
Wireless mesh networks have an advantage of building backbone infrastructure easily, where access points, which have been conventionally connected by wired LANs, are connected by an ad-hoc network using wireless LANs. However, the wireless mesh network still has various problems such as the realization of a seamless handover, the securing of a communication bandwidth, and the selection of the most...
Most of the routing protocols designed for ad hoc networks assume that IEEE 802.11b is used for lowest-layer communications. In IEEE 802.11 ad hoc mode, the DCF is the basic medium access protocol. In this paper we consider voice calls over mobile ad hoc network based on 802.11b MAC. A new routing metric for searching a stable routing in ad hoc network based on an extended AODV protocol is proposed...
Location-based digital rights management (DRM) refers to a system allowing the owner of an electronic file to specify not only the actions a user is allowed to perform regarding the content, but also restrict the actions to a specified geographical area. A method for retrieving location information is required. One such method is to place wireless access points in areas of interest, requiring a device...
In the paper, an integrated synchronization system for IEEE802.11 multimode wireless LAN (WLAN) has been developed, simulated, and synthesized. A symbol timing recovery for 802.11a/g OFDM systems and a maximum likelihood (ML) matched filter for 802.11 and 802.11b systems are implemented and integrated into a single processor. All of the operation modes are mapped onto a shared, regular, data path...
Existing 802.11 direct link setup (DLS) protocol specifies procedures for direct communication between a pair of stations within the same basic service set (BSS). This eliminates the unnecessary triangular traffic route through an access point and increases the overall effective throughput within the BSS. In this paper, an inter-BSS direct link setup (iDLS) protocol is proposed to facilitate direct...
In this paper, a novel Smart-DCF scheme is proposed for high-speed WLANs. The proposed Smart-DCF scheme may be viewed as a merger of the IEEE 802.11 DCF and PCF schemes. It can achieve a virtually collision-free WLAN environment and efficiently support a desirable quality-of-service requirement as in PCF while maintaining simplicity of medium access with the CSMA mechanism as in DCF. The Smart-DCF...
Local positioning, particularly in indoor environments, poses challenges that are not faced by global and terrestrial positioning systems. Many a times, it is cost effective to build these localization schemes on the existing wireless local area networks (WLANs). In that direction, a time-of-arrival (TOA) estimation based on the "distorted template", which is obtained by convolving the clean...
In this paper, we analyze the operation of ZigBee devices under the presence of WLAN interference and formulate a mathematical model for evaluating the performance of ZigBee devices. Our proposed mathematical model for ZigBee devices is based on a Markov chain concept. We here utilize the fact that the transmission power of WLAN devices is set hundred to thousand times higher than that of ZigBee devices...
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