All-Planar RF Integration Approach to Millimeter-Wave Wireless Front-Ends

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 ability to estimate the location of wireless device users has led to many applications that use location information to provide users and service providers with commercially valuable real time information. In this paper, we propose a low-complexity method for location estimation in an indoor wireless local area network (WLAN) deployment. The proposed method relies on measurements of signal strength (SS) of multiple access-points (APs) in a WLAN and is based on a piecewise-linear model that represents distances from APs in terms of SS measurements. The proposed scheme has significantly lower computational and storage requirements as compared to conventional location estimation methods.

In wireless local area networks (WLANs), link-layer multicast is a promising technology for many multimedia applications, e.g., video conference, as multicast frames can reach multiple clients simultaneously. However, the efficiency of multicast in WLANs is unsatisfactory since multicast frames are transmitted at low data rates to reach clients with poor channel quality. Moreover, the reliability of multicast cannot be guaranteed either, as multicast transmissions are not acknowledged. Some recent works have utilized smart antennas to improve multicast performance. But most of them require customized hardware and are not designed for the latest IEEE 802.11 standard, 802.11n WLANs. In this paper, we consider link-layer multicast in 802.11n WLANs with smart antennas. We partition clients into several groups, then select an antenna pattern from smart antennas and a multicast rate for each group, and transmit the same frame to each group. We first examine the gain of smart antennas and reliability of various 802.11n data rates for multicast in indoor WLANs via experiments. We then present the system model for multicast over smart antennas and formulate the problem into a mixed integer program. After that, we propose an optimal algorithm for the mixed integer program, under the condition that the packet reception ratio (PRR) of all antenna patterns and data rates is known for every client. As clients join and leave the network frequently and the wireless channel is time varying, we also propose an on-line algorithm that is able to adapt the partition of clients, antenna pattern and multicast rate for each group dynamically, based on PRR reports from clients. We have implemented the on-line algorithm on off-the-shelf WLAN products and conducted extensive experiments to evaluate the performance. The results show that the proposed algorithm can significantly improve multicast throughput compared to other strategies, and at the same time guarantee high PRR for all clients.

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.

The IEEE 802.11a OFDM wireless local area network (WLAN) system aims to achieve code diversity in quasi-static frequency-selective fading channels by employing bit interleaved coded modulation (BICM). Since the time variation of the channel during a WLAN packet transmission is small and its frequency selectivity finite, the code diversity is limited by both the degree of the channel variation as well as by the code properties. This paper experimentally investigates the impact of channel frequency selectivity on the code-diversity performance of BICM, with and without 2/spl times/1 Alamouti transmit diversity. Using a simplified model of the finite frequency selectivity, we develop a mathematical framework to show that the code diversity is only probabilistically achieved. Our results indicate that for the frequency selectivity typically seen in indoor WLAN channels, using a channel code with larger d/sub free/ does not improve the packet error rate (PER) performance.

The procedure of attaining a compact bandpass filter (BPF) with dual band‐notch function for ultra‐wideband (UWB) applications is presented and discussed. In the proposed BPF, defected ground structure is used in order to improve the out‐of‐band performance of the filter. Also, four short‐circuited bent stubs are employed in order to improve the selectivity of the filter at its cutoff frequencies. Dual band‐notch function is added to the performance of the filter by coupling two short‐circuited inverted T‐shaped stubs to the filter main resonator. The fabricated filter satisfies well the demands of the Federal Communications Committee with two narrow band‐notch functions at 5.5 and 8 GHz, which eliminates the interference of the UWB system with wireless local area network (WLAN) and satellite communication systems, respectively. The improved upper stop‐band of the proposed filter with more than 20 dB attenuation level extends up to 20 GHz.

High-performance radio frequency (RF) modules are required in transmitter and reception devices due to the recent expansion of wireless technology. The power amplifier, low-noise amplifier, filter, and mixer are the most crucial components in the RF transmitter/receiver chain. This work presents the design and analysis of a dual-band bandpass filter (BPF) for wireless local area network (WLAN) and C-band satellite applications. Stubs of the proper electrical length that are open and short-circuited are used to implement the filter. The low pass performance is generated by the open-circuited stubs. Short-circuited stubs achieve high-pass performance, while the combination of open and short-circuited stubs achieves bandpass performance. We confirm the filter's behaviour using the advanced design system 2022 simulation tool. The findings of return loss and insertion loss confirm the simulation-level performance analysis of the filter. The result demonstrates the suggested BPF's dual-band behaviour at 4 GHz and 6 GHz.

Wireless Local Area Network is one of the important technologies of computer networking. An emerging Wireless Local Area Network standard given by IEEE is 802.11ac. 802.11 ac is exclusively a 5GHz technology. It is faster compared to 802.11n. Huge number of Personal Computers like 2-in-1s, desktops, and laptops are equipped with Wireless-AC adapters. Empirical study is conducted to form a path-loss model in the Faraday Chamber, the path-loss exponent determined from this empirical study improves the accuracy in relationship between distance and Received Signal Strength Indicator of the Wireless Local Area Network.

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.

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.

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.