Wireless Local Area Network Transmission Research Articles

Mobile Phone Signals Interference Cancellation With Improved WLAN Transmission and Thermal Insulation of Buildings Using FSS and RC Film

For macro-femto network, intratier and cross-tier interference (CI) must be canceled to achieve the quality of service, better indoor coverage, and higher data rates. Moreover, for better wireless local area network (WLAN) and mobile communication services while ensuring WLAN security, appropriate temperature in modern buildings with reduced energy cost is also required. To address these issues, RadioClear (RC) film can be pasted on an ordinary glass and installed in different sections to cancel the intratier interference between the femto network as well as CI between the femto and macro network. Moreover, this technique can also ensure enhanced WLAN security and thermal insulation in modern buildings. For WLAN transmission, a fractal dual bandpass frequency selective surface (FSS) designed in the RC sheet can be used to improve the WLAN communication in a situation where two or more than two rooms are served through a single WLAN router. Theoretical results are presented which are further verified through the experimental results.

Accurate bus occupancy estimation for WLAN probing utilising probabilistic models

This paper obtains an enhanced estimator of the number of people on buses using probabilistic models and wireless local area network (WLAN)-based device counts. The improved estimator exploits probabilistic models of false positives and false negatives of a previously presented baseline estimator. False positives of the baseline estimator result from devices on the roadside outside the bus that fail to be filtered out by the used threshold approaches. False negatives may be caused by low probe emission frequency, message losses due to collisions of the WLAN transmissions, medium access control (MAC) address randomisation, WLAN channel selection, and occur in particular when passengers stay on the bus only for short duration of time. The extensions of the baseline model by probabilistic models for false positives and false negatives enables to apply maximum likelihood estimation. Distribution parameters for false positives and false negatives are found from measurements. Field tests on buses in a Danish town are used to validate and quantify the gain of the enhanced estimator.

LWA Rate Adaption by Enhanced Event-Triggered Reporting

Unlicensed spectrum has been utilized to open up additional capacity to support long-term evolution (LTE) service. LTE and wireless local area network (WLAN) Aggregation (LWA) is a perfect solution that satisfies this need. In 2017, Taiwan has deployed the first commercial LWA service. The deployed LWA network reuses and is nicely merged with the existing individual LTE and WLAN networks. To provide appropriate WLAN transmission bandwidth, the user equipment periodically measures the WLAN quality and reports the results to the eNB (the LTE base station). The eNB then decides if the transmission rate should be adapted. We investigate the performance of periodical reporting and then propose the enhanced event-triggered reporting to improve the performance of WLAN transmission rate adaption. We suggest how to select appropriate frequency to minimize the network traffic of periodical reporting. We also show that enhanced event-triggered reporting outperforms periodical reporting. Our solution utilizes the standard 3GPP protocols and does not modify the mobile phone's software.

An Adaptive WLAN Interference Mitigation Scheme for ZigBee Sensor Networks

We propose an adaptive interference avoidance scheme that enhances the performance of ZigBee networks by adapting ZigBees' transmissions to measured wireless local area network (WLAN) interference. Our proposed algorithm is based on a stochastic analysis of ZigBee operation that is interfered with by WLAN transmission, given ZigBee and WLAN channels are overlaid in the industrial, scientific, and medical (ISM) band. We assume that WLAN devices have higher transmission power than ZigBee devices. Then, the high transmission power of WLAN devices causes the capture effect when WLAN and ZigBee transmit simultaneously. On the other hand, ZigBee performs backoff during clear channel assessment (CCA) operation if the WLAN is transmitting its frames on the channel. We adopt a widely used WLAN queueing/transmission model that is based on a Markov chain concept. We model a ZigBee device's operation using the Markov chain that includes WLAN interference statistically derived from the WLAN queueing/transmission model. Our proposed algorithm is evaluated in a simulated ZigBee network in the presence of varying WLAN interference. Numerical results show that our WLAN interference mitigation scheme finds the ZigBee control parameters, among a candidate set, which enhances ZigBee network performance compared to the conventional ZigBee operation.

Cognitive beamforming based smart metering for coexistence with wireless local area networks

The ZigBee network has been considered to monitor electricity usage of home appliances in the smart grid network. Zig-Bee, however, may suffer from a coexistence problem with wireless local area network (WLAN). In this paper, to resolve the coexistence problem between ZigBee network and WLAN, we propose a new protocol constructing a cognitive smart grid network for supporting monitoring of home appliances. In the proposed protocol, home appliances first estimates the transmission timing and channel information of WLAN by reading request to send/clear to send (RTS/CTS) frames of WLAN. Next, based on the estimated information, home appliances transmit a data at the same time as WLAN transmission. To manage the interference between WLAN and smart grid network, we propose a cognitive beamforming algorithm. The beamforming algorithm is designed to guaranteeing zero interference to WLAN while satisfying a required rate for smart metering. We also propose an energy efficient rate adaptation algorithm. By slowing down the transmission rate while satisfying an imperceptible impact of quality of service (QoS) of the receiver, the home appliance can significantly save transmit power. Numerical results show that the proposed multiple antenna technique provides reliable communications for smart metering with reduced power comparing to the simple transmission technique.

Millimeter-Wave Wireless Local Area Network Over Multimode Fiber System Demonstration

A radio over fiber system using millimeter-wave for downlink (DL) and intermediate frequency for uplink (UL) transmission, that includes a wireless path and uses multimode fiber (MMF), is investigated by throughput measurements. Live wireless local area network transmissions (IEEE 802.11g, 54 Mbps), are upconverted to 25.2 GHz for the DL by using an optical phase modulator and optical filter millimeter-wave generation approach. Both DL and UL data were successfully transmitted between a mobile unit (MU) and commercial access point (AP), via a remote antenna unit connected to the AP by a 300-m MMF link. The measurements, for the full link using omni-directional antennas at the MUs, demonstrate good signal coverage throughout an office area of 12.8 × 7.2 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and indicate that a coverage area four times this size would be possible if the antenna were placed in the center of a room.

Minimal optimization technique for radio over fiber WLAN transmission in IM‐DD optical link

AbstractAn optimization technique is presented for the radio over fiber (ROF) wireless local area network (WLAN) transmission in IM/DD optical link. The results show that with minimal optimization, directly modulated ROF WLAN 802.11g signal at 2.4 GHz and externally modulated 1.25 Gbps baseband signal can coexist in the 2 km IM/DD optical link with a power penalty of 3 dB. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:812–815, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25029

An Integrated Solution for Suppressing WLAN Signals in UWB Receivers

A fully integrated solution for rejecting the interference caused by wireless local area network transmissions in the 4.9-5.825-GHz band for ultra-wide-band (UWB) receivers is presented. Front-end prototypes implemented in a low cost 0.35-m SiGe BiCMOS technology are used as a test vehicle to assess the effectiveness of the presented approach. The proposed blocker filtering technique mitigates the gain desensitization, third-order intermodulation distortion and second-order intermodulation distortion by as much as 9.8, 7.9, and 6 dB, respectively. At a power consumption of only 49.2 mW, the receiver conversion gain ranges from 22-19 dB while the double side-band measured at the PCB connectors ranges from 5.5-8 dB in the 3.6-7.4-GHz frequency range.