An efficient hexagonal switched beam antenna structure based on Fabry-Perot cavity leaky-wave antenna

Wireless local area network (WLAN) systems are typically designed to provide fixed or nomadic access. Using WLAN systems for military purposes raises the question of how WLAN terminals can be utilized in a fully mobile outdoor environment. In these environments, there typically exists multipath propagation with a large delay spread in the radio channel. This paper investigates the effect of terminal movement on the physical layer performance and capacity of IEEE 802.11b WLAN systems in a realistic outdoor mobile environment. Several wireless network interface cards are measured in laboratory conditions using a simulated radio channel. The measurement results indicate that WLAN systems can operate in mobile outdoor environment up to a certain mobile speed, and there are significant differences between equipment from product vendors

In wireless data communication, an advanced nonlinear distortion analysis is required in order to see its effect to the performance of a Radio Frequency (RF) front-end system. This technical paper therefore, reports the effect of third order intermodulation (IM3) distortion on the constellation error (a key measure of modulation quality) in RF transmitter of IEEE 802.11a wireless local area network (WLAN) system. The selected RF transmitter architecture is based on the off-the-shelf components. Advanced Design System (ADS) software has been used for RF transmitter modeling and simulation. The constellation error simulation is based on the IEEE 802.11a standard. As results, two observations have been obtained. First, it is shown that the IM3 distortion in the RF transmitter for IEEE 802.11a WLAN system must be kept in minimum level in order to get lower constellation error. Second, with the same IM3 distortion level, the constellation error is very sensitive to the IM3 distortion at higher data rate (e.g. 54 Mbps) compared to lower data rate (e.g. 6 Mbps).

The authors have analyzed and compared performances of PN (pseudo noise) codes to find optimal PN codes which can be used in a DS/SS (direct sequence/spread spectrum) wireless LAN (local area network) system over a multipath fading channel. A wireless LAN system is susceptible to multipath fading that gives rise to intersymbol interference. The authors have analyzed and compared performances of Barker sequences with those of Gold sequences. As results, Barker sequences are better than Gold sequences for DS/SS wireless LAN systems, from the SNR and BER points of view.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In recent years, advances in wireless local area network (WLAN) systems have led to large increases in the transmission speed. The IEEE 802.11ac standard allows for very high transmissions by using multi-user multiple input multiple output (MU-MIMO) techniques in the physical (PHY) layer. However, the transmission efficiency is decreased by the channel state information (CSI) estimation algorithm in the medium access control (MAC) sub-layer. Massive MIMO transmission has attracted attention as a new technology for wireless communication in 5th-generation mobile communication systems (5G). We propose a novel access control scheme for multi-beam massive MIMO technology called overhead-less access control. The proposed scheme allows random access control without CSI estimation for massive MIMO technology. Thus, it greatly reduces the overhead of the MAC sub-layer and improves the transmission efficiency. The proposed scheme can be used to control new massive MIMO systems. We evaluated our proposed overhead-less access control scheme for multi-beam massive MIMO transmission in WLAN systems.

Dual home agent (DHA)-based location management scheme in integrated cellular–WLAN networks

The recent developments in wireless communication systems in indoor environments require high data rates and high transmission qualities especially for multimedia applications in WLAN (Wireless Local Area Network) systems. The support of high data rate MIMO spatial-multiplexing communication in OFDM-WLAN systems conforming to IEEE802.11n standard requires the use of compact antennas with low correlation ports. In this paper, higher-order space-multimode diversity stacked circular microstrip patch uniform linear arrays (SCP-ULAs) are proposed for use in WLAN systems. The performance analysis of higher-order modal SCP-ULA is presented in terms of modal correlation, ergodic spectral efficiency and average BER by using both maximum-likelihood (ML) and suboptimal zero-forcing (ZF) and minimum mean-squared error (MMSE) MIMO detectors.

This paper presents the design and analysis of general packet radio service (GPRS)-wireless local area network (WLAN) mobility gateway (GWMG) for the integration of GPRS and WLANs. The interworking between GPRS and WLANs is achieved by the GWMG that resides on the border of GPRS and WLAN systems. The design goal is to minimize the modifications in GPRS and WLANs as both systems are already widely available. By deploying the GWMG, users can seamlessly roam among the two systems. Unlike other related work, the proposed GWMG could be used when either the GPRS or WLAN is a user's home network. Both mathematical analysis and simulation are developed to analyze the performance. The proposed GWMG has also been implemented in a testbed comprising a commercial GPRS system. The results show that the GWMG could achieve a design goal that will effectively integrate GPRS and WLANs.

The increase in demand for proper and fast access to network infrastructure around the University environment by staff, students, and visitors in the quest to carry out daily tasks or keeping up with trends/innovations around the globe is a daily experience resulting in some challenges. But these challenges are not unexpected. The access to network infrastructure around the environment encourages proper development. This paper presents an empirical observation of transmission control protocol upstream throughput (TCPupT) and downstream throughput (TCPdownT) performance for an IEEE 802.11g wireless local area network (WLAN) installed at a corridor space of University of Nigeria, Nsukka campus. This work measured the TCP upstream and downstream throughput values for single, double, and multiple users (several Users) accessing an installed WLAN access point. The paper adopted basic WLAN system setup approach while observing the TCP performance in relation to SNR. Data collected for each environment were statistically analyzed, equations and results were also presented. The observed TCP throughput values vary as users increase thereby affecting the observed round-trip time (RTT). The generated equations were also used to predict TCP throughput which would aid network engineers in the deployment of IEEE 802.11g WLAN systems especially around the university environment. It is now clear that the generated model equations can be used for predicting the expected performance of IEEE 802.11g WLAN systems during deployment. This work gives WLAN engineers, researchers and users an apparatus to rapidly estimate the TCP upstream and downstream throughput, by monitoring the received SNR for IEEE 802.11g systems.

An integrated design of antennas and diplexers for dual-band wireless local area network (WLAN) systems for the purpose of reducing the component count is reported in this paper. Two antenna structures are used in this design. One is the sleeve monopole antenna, and the other is a novel tapered bent folded monopole. The novel tapered bent folded monopole has a bandwidth of 12.5% in the 2.4 GHz WLAN band and 32.4% in the 5 GHz WLAN band. The proposed integrated structures of antennas and diplexers can meet the requirements of the 2.4 GHz and 5 GHz WLAN systems.

In this paper, we introduce a design for a compact low cost dual polarized adaptive planar phased array for Wireless Local Area Networks (WLAN). The uniqueness of the design is that a wide variety of beam shapes can be electronically selected from a large set of possible patterns while maintaining compact size low cost with reasonable efficiency and having independent dual diversity ports. An important application of the array is in WLAN systems where compact and low cost adaptable antennas promise increases in capacity and coverage. The array design makes use of key innovations in the antenna element and feed network, along with improved low cost phase shifting circuits with low loss performance. The compact antenna element we propose exhibits low mutual coupling between elements with good bandwidth and dual polarized diversity feeds. The feed network is designed to minimize coupling between ports while the phase shifters are low cost but allow flexible control of the antenna patterns. The design is verified both through numerical simulations and also measurements of an experimental prototype and these confirm the good performance of the antenna system and suitability for use in WLAN systems.

A novel compact triple-band monopole microstrip antenna for WLAN applications is proposed. The proposed antenna is made up of two one-quarter wavelength resonating components, fed by a 50ohmic microstrip line. The configuration is simple. The resonating frequencies of the proposed antenna are 2.5GHz and 4.8GHz, respectively, the bandwidth is about 500MHz (2.25~2.75GHz) and 2.63GHz (3.82~6.45GHz) (return loss less than -10dB), covering the triple bands of WLAN system. The lower and higher resonant frequencies can be easily tuned by adjusting a few parameters of the presented antenna. This antenna satisfies the requirements of wireless local area network(WLAN) 802.11(2.4~2.484GHz, 5.15~5.35GHz, 5.725~5.825GHz) applications. The softwares of Ansoft HFSS11 and CST Microwave Studio are used to simulate and optimize the antenna.

Wireless Local Area Network (WLAN) offloading is an important approach to address the data traffic challenge faced by Long Term Evolution (LTE) network. Legacy offloading solutions based on the core network suffer from the limitations of load unbalance and user experience degradation. To solve this problem, 3GPP has recently proposed a radio access network (RAN) assisted WLAN offloading scheme. In this article, we thoroughly analyze the performance of this new scheme, with emphasis on the RAN auxiliary parameters and control rules defined in it. Furthermore, two kinds of offloading algorithms based on this scheme are proposed and compared with the traditional solutions by simulation. Results show that the RAN-assisted offloading scheme can increase average user throughput and leverage resources available in both LTE and WLAN systems.

This paper presents a novel medium access control (MAC) mechanism for wireless local area network (WLAN) systems, called visual recognition based medium access control (VRMAC) mechanism. VRMAC exploits Wi-Fi and visible light communications techniques, using LEDs and a camera to facilitate collision-less medium access with low overhead. In VRMAC, stations (STAs) equipped with LEDs send medium-access request messages by blinking their LEDs and an access point (AP) equipped with a camera receives the messages via the camera. In this paper, we introduce the fundamentals of the mechanism and present an example protocol. Our simulation results indicate that the mechanism improves WLAN throughput over that of the conventional MAC mechanism in WLANs.

A Compact dual slot ultra-wide band (UWB) Antenna for WLAN and X-Band applications is proposed. The projected antenna is designed for the planar ultra-wide band (UWB) antenna and ultra-wide band (UWB) with two band dismissals. The proposed antenna overall size is 30x40x1.6. The antenna comprises of Rectangular patch imprinted on the Flame Resistant (FR4) substrate with 50Ω input impedance. FR-4 is a composite material made out of fiberglass fabric woven with an epoxy pitch cover that is fire safe (self-dousing). "FR" implies fire resistant, and means that the material meets the standard. This patch consists of dual slot one for WLAN and one for X-band Satellite Communication System. The antenna intended with return loss (RL) &gt;= 10db and frequency ranges between 3.1 to 10.6 GHz with VSWR&lt;2. The antenna works for the applications of wireless local area network (WLAN) system (5.15 – 5.825 GHz), X-band downlink (7.25 - 7.75). The ultra-wide band frequency range for these wireless systems causes interference. To reduce the interference, band notching is done. The WLAN and X-Band satellite communication system bands are forbidden by inserting slots in the patch. The proposed antenna is having high gain at the pass bands while a sharp drop at the forbidden bands.

In this paper, we introduce a technique to reduce the authentication overhead for handoff process in wireless local area networks (WLAN). It is based on user mobility prediction to reduce the network scanning area during the handoff procedure. The central server facilitates an intelligent mobility prediction mechanism to identify the next possible mobile access points for mobile subscriber. The predicted information is managed by an event log table, and it helps to reduce the authorisation overheads for cellular networks. It follows the reserve channel scheme to maintain the QoS for users during the call and handoff procedure and the handover-call has higher priority over local initiated call. The analytical model shows the effectiveness and efficiency of proposed work, we apply the Markov random walk model and M/M/1 queuing model to formulate our work. It is compared with the tradition technique, and has 40% better result than legacy techniques.