Wi-Fi Transmission Research Articles

802.11g/n Compliant Fully Integrated Wake-Up Receiver With −72-dBm Sensitivity in 14-nm FinFET CMOS

This paper presents an 802.11g/n compliant wake-up radio solution that consists of an innovative on–off keying (OOK) emulating orthogonal frequency division multiplexing (OFDM) modulation scheme, and a fully integrated, highly scaled, ultra-low power wake-up receiver design in 14-nm FinFET CMOS technology requiring only a 32-kHz real-time clock reference. The receiver achieves −72-dBm sensitivity and +20 dBr adjacent channel interference (ACI) rejection at 10−3 bit error rate (BER) while consuming $95~\mu \text{W}$ . This receiver can be utilized along with any legacy Wi-Fi transmitter without changing any hardware.

Stochastic Analysis of Delayed Mobile Offloading in Heterogeneous Networks

Mobile cloud offloading that migrates heavy computation from mobile devices to powerful cloud servers through communication networks can alleviate the hardware limitations of mobile devices thus providing higher performance and saving energy. Different applications usually give different relative importance to response time and energy consumption. If a delay-tolerant job is deferred up to a given deadline, or until a fast and energy-efficient network becomes available, the transmission time will be extended, which can save energy because a more energy-efficient communication channel and a less energy-restricted computation platform may become available. However, if the reduced service time fails to cover the extra waiting time, this policy may not be competitive. In this paper, we investigate two types of delayed offloading policies, the partial offloading model where jobs can leave from the slow phase of the offloading process and be executed locally on the mobile device, and the full offloading model, where jobs can abandon the WiFi Queue and be offloaded via the Cellular Queue . In both models, we minimize the Energy-Response time Weighted Product (ERWP) metric. Not surprisingly, we find that jobs abandon the queue often when the availability of the WiFi network is low. In general, for delay-sensitive applications the partial offloading model is preferred under a suitable reneging rate, while for delay-tolerant applications the full offloading model shows very good results and outperforms the other offloading model when selecting a large deadline. From the perspective of energy consumption, the full offloading model will always be best, even if the deadline must be extremely long. Only if job response time is of high importance an optimal deadline to abort offloading in the partial offloading model or the WiFi transmission in the full offloading model can be found. For reduction of the energy consumption it will always be better to wait longer rather than compute locally or use the cellular network.

Investigation on inkjet printing for electromagnetic compatibility application

The research is focused on the development of inkjet-printed silver grids on flexible films to (I) attenuate electromagnetic waves at 2.45 GHz locally by applying them directly on Wi-Fi or Bluetooth transmitter or to (II) protect electromagnetic compatibility (EMC) sensitive devices close to electromagnetic transmitters. The inkjet printing technology leads to resource, time as well as cost efficient manufacturing and simplifies the adjustment of the pattern design regarding different applications. The research contains a fundamental analysis of the behavior of printed silver patterns on flexible polymer substrates regarding line widths, layer morphology and electrical performance. On that basis the grid pattern for a certain frequency range is simulated. The report shows first simulation results on basis of the given material parameters. The results are the fundamentals for further research on realization of the simulated grid patterns by inkjet printing technology.

Remote Environment Exploration and Measurement Technique via Transmission of Real-Time Video

This study intends to use remote control technology to conduct environment exploration and create a measurement tool that can effectively protect measurement personnel from harm caused by negative environmental factors. In a detected environment, there are various negative environmental factors, such as radioactive rays, gases, or other unknown factors, thus, the safety of traditional manual detection is a concern. This study proposed a mobile exploration tool for solving the above problem. The tool integrates a smart system, a 4G network, WIFI transmission, a radiation sensor circuit, and a wireless IP camera. The concept of remote control cars is used for design and manufacture. After correction, the overall error rate of the system is 4.2%. The proposed tool can realize cross-regional control and provide an unmanned omnibearing tool for preliminary environment exploration and measurement.

Design of Multi-sensor Human Environment Monitoring Equipment

In order to meet the patient's daily monitoring needs, in view of the problems existing in monitoring equipment at home and abroad, such as the single sensing parameter, the loss of data association and 433Mhz, ZigBee and other short wave communication modes are limited by the transmission distance, high power consumption, etc. It uses IEEE 802.11 WIFI transmission protocol, directly connected with the Internet. It integrates a number of high-precision sensors, such as light intensity, temperature, humidity, magnetic field, acceleration, vibration, etc., which can be used to monitor the activities of the environment data in a multi-dimensional way. The experiments show that the real-time, event correlation and reliability of the data are verified. Families and doctors can fully monitor the patient through mobile phones and PC side data, call the police in case of emergency, and the minimum power consumption can reach 59uA.

Opportunistic Mobile Data Offloading with Deadline Constraints

Due to the explosive proliferation of mobile cloud computing applications, much data needs to be transmitted between mobile users and clouds, incurring a huge traffic demand on cellular networks. Mobile offloading is a promising approach to address this challenge. In this paper, we focus on the problem of offloading many deadline-sensitive data items to some WiFi networks with capacity constraints; that is, how to schedule each data item to the WiFi networks, so that we can offload as many data items before their deadlines as possible, while taking the constraints of transmission capacity into consideration. This problem involves a probabilistic combination of multiple 0-1 knapsack constraints, which differs from existing problems. To solve this problem, we propose a greedy oFfline Data Offloading (FDO) algorithm, achieving an approximation ratio of 2. Also, we propose an oNline Data Offloading (NDO) algorithm, which has a competitive ratio of 2. Additionally, we extend our problem to a more general scenario where WiFi transmission costs are heterogeneous. We design a Heterogeneous Data Offloading (HDO) algorithm to solve the extended problem, and give its performance analysis. Finally, we demonstrate the significant performances of our algorithms through extensive simulations based on some real-world and synthetic WiFi datasets.

A Power Processing Circuit for Indoor Wi-Fi Energy Harvesting for Ultra-Low Power Wireless Sensors

This article proposes a complete power processing circuit for an indoor 2.45 GHz Wi-Fi energy harvesting system. The proposed power processing circuit works by using power harvested from indoor Wi-Fi transmitters. The overall system of this work is simplified as an equivalent circuit and analyzed mathematically. A two-port network is analyzed in formulating the relevant equations of the equivalent circuit. The importance of matching the impedance of a harvesting antenna to the rectifier circuit is highlighted by using simulation analysis, and it is shown that the impedance matching for both components has satisfied the conditions for a high sensitivity circuit and radio frequency-to-direct current (RF-to-DC) power conversion. Actual experiments showed that the proposed power processing circuit could operate with an incident power as low as −50 dBm. It has been found that the proposed harvesting system stored 0.11 J in a 200 mF supercapacitor as the storage device in 20 hours of the experimentation periods. Moreover, actual results for the overall energy harvesting system is compared with previous research, and it has been found that the proposed system has advantages over the listed works.

Dynamic Path To Stability in LTE-Unlicensed With User Mobility: A Matching Framework

LTE-Unlicensed has recently captured intense attention from both academic and industrial fields. By integrating the unlicensed spectrum with the licensed spectrum, using carrier aggregation, LTE-Unlicensed users can experience enhanced transmission while maintaining the seamless mobility management and predictable performance. However, due to different transmission regulations, the coordination between LTE and Wi-Fi systems requires careful design. It is especially important to understand how to guarantee the transmission quality for LTE users and reduce Wi-Fi users’ performance degradation, under the impact of the co-channel interference. In other words, how can we solve the unlicensed resource allocation problem under both LTE and Wi-Fi transmission requirements? In this paper, we propose a matching theory framework to tackle this problem. Specifically, the coexistence between LTE and Wi-Fi systems, i.e., the interaction between LTE and Wi-Fi users, is modeled as a stable marriage game. The coexistence constraints are interpreted as the preference lists. Two semi-distributed solutions, namely, the Gale–Shapley and the random path to stability algorithms are proposed. In addition, to address the external effect in matching, the inter-channel cooperation algorithm is introduced. Last but not least, the resource allocation problem is studied with network dynamics and the proposed mechanisms are evaluated under two typical user mobility models.

Operating Massive MIMO in Unlicensed Bands for Enhanced Coexistence and Spatial Reuse

We propose to operate massive multiple-input multiple-output (MIMO) cellular base stations (BSs) in unlicensed bands. We denote such systems as massive MIMO unlicensed (mMIMO-U) ones. We design the key procedures required at a cellular BS to guarantee coexistence with nearby Wi-Fi devices operating in the same band. In particular, spatial reuse is enhanced by actively suppressing interference toward neighboring Wi-Fi devices. Wi-Fi interference rejection is also performed during an enhanced listen-before-talk phase. These operations enable Wi-Fi devices to access the channel as though no cellular BSs were transmitting, and vice versa. Under concurrent Wi-Fi and BS transmissions, the downlink rates attainable by cellular user equipment (UEs) are degraded by the Wi-Fi-generated interference. To mitigate this effect, we select a suitable set of UEs to be served in the unlicensed band accounting for a measure of the Wi-Fi/UE proximity. Our results show that the so-designed mMIMO-U allows simultaneous cellular and Wi-Fi transmissions by keeping their mutual interference below the regulatory threshold. Compared with a system without interference suppression, Wi-Fi devices enjoy a median interference power reduction of between 3 dB with 16 antennas and 18 dB with 128 antennas. With mMIMO-U, cellular BSs can also achieve large data rates without significantly degrading the performance of Wi-Fi networks deployed within their coverage area.

8-5 小型衛星伝送装置を搭載した多機能型取材伝送車の製作(第8部門 放送現業)

8-5 小型衛星伝送装置を搭載した多機能型取材伝送車の製作(第8部門 放送現業)

A 56 Gb/s PAM4 VCSEL-Based LiFi Transmission With Two-Stage Injection-Locked Technique

A 56 Gb/s four-level pulse amplitude modulation (PAM4) light-based WiFi (LiFi) transmission based on a 680-nm/5.4-GHz vertical-cavity surface-emitting laser (VCSEL) with a two-stage injection-locked technique is proposed and demonstrated. Experimentally results show that a 5.4-GHz VCSEL with a two-stage injection-locked technique is effective for 56 Gb/s PAM4 LiFi transmissions. To the authors’ knowledge, it is the first one to adopt a 680-nm VCSEL transmitter with two-stage injection-locked technique in a 56 Gb/s PAM4 LiFi transmission. A pair of doublet lenses is employed in the proposed PAM4 VCSEL-based LiFi transmissions to enhance the free-space link. The link performances of the proposed PAM4 LiFi transmissions have been analyzed in real time. Good bit error rate performance and three independent clear eye diagrams are obtained over a 20-m free-space link. Such a proposed 56 Gb/s PAM4 VCSEL-based LiFi transmission with two-stage injection-locked technique has the potential to play a significant role in future wireless infrastructure for providing high transmission rate and long free-space transmission distance effectively.

PASSIVE WI-FI

Wi-Fi has traditionally been considered a power-consuming communication system and has not been widely adopted in the sensor network and Internet of Things (IoT) space. We introduce Passive Wi-Fi that demonstrates that one can generate 802.11b transmissions using backscatter communication, while consuming 3-4 orders of magnitude lower power than existing Wi-Fi chipsets. Passive Wi-Fi transmissions can be decoded on any Wi-Fi device including routers, mobile phones and tablets. Our experimental evaluation shows that passive Wi-Fi transmissions can be decoded on off-the-shelf smartphones and Wi-Fi chipsets over distances of up to 100 feet. We also design a passive Wi-Fi IC that shows that 1 and 11 Mbps transmissions consume 14.5 and 59.2 ?W respectively. This translates to 10000x lower power than existing Wi-Fi chipsets and 1000x lower power than Bluetooth LE and ZigBee.

Coexistence of Outdoor Wi-Fi and Radar at 3.5 GHz

Coexistence between radar and outdoor wireless fidelity (Wi-Fi) needs thorough study since the IEEE 802.11 working group (WG) opposed the latest rules in 3550–3700 MHz (the 3.5 GHz band) that require “exclusion zones.” This letter proposes a method that suppresses Wi-Fi-to-radar (WtR) interference, in which a Wi-Fi transmitter (TX) is selected to avoid beam angles toward the victim radar. It is distinguished from prior schemes since it ensures that the Wi-Fi remains operable while suppressing the WtR interference.

Evaluation of Wi-Fi and LTE Integrated Channel Performance with Different Hardware Implementation for Moving Objects

Combining Wi-Fi and LTE data transmission technologies we can obtain an integrated solution that provides full end-to-end data transmission channel. This article compares goodputs of two LTE routers, which connect multiple WLAN access points (including Wi-Fi access controller) with the remote FTP server. Handover impact on data channel goodput is measured between wireless access points. Experimental data obtained by taking measurements under field conditions using real hardware, which imitates realistic two rank heterogeneous wireless network. The obtained results are very valuable, as they can be used as source data to develop mathematical network models as well as to tune network simulation software. The article also contains a mathematical model, which allows analyzing the impact on the data channel goodput at several competing vehicles which try to gain access to data channel via wireless access points. Experimental data is used in mathematical model. Obtained results supplement previous research and in this case the results show hardware's impact on channel goodput.

WATCH: WiFi in Active TV Channels

The “white space” model allows TV channels not being used regionally by a TV broadcaster to be re-purposed for secondary access. Unfortunately, populated areas have few unused channels. Nonetheless, Nielsen data show severe <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">under-utilization</i> with vast regions in range of TV transmitters having <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">no active TV receivers</i> even at peak TV viewing time. In this paper, we present the design, implementation, and evaluation of WiFi in active TV channels (WATCH), the first system to enable secondary WiFi transmission in the presence of kilowatt-scale TV transmitters. To protect active TV receivers, WATCH includes a smartphone-based TV remote controller or an Internet-connected TV to inform WATCH controller of TV receivers’ spatial-spectral requirements. To enable WiFi transmission in UHF bands, we design WATCH-interference cancellation and constructive addition transmission to 1) exploit the unique environment of asynchronous WiFi transmission in the presence of a strong streaming interferer, and 2) require no coordination with legacy TV transmitters. With FCC permission to test our implementation, we show that WATCH can provide at least six times the total achievable rate to 4 watt secondary devices compared to current TV white space systems, while limiting the increase in TV channel switching time to less than 5%.

Piconet construction and restructuring mechanisms for interference avoiding in bluetooth PANs

Bluetooth and IEEE 802.11 (Wi-Fi) are two of the most popular communication standards that define physical and MAC layers for wireless transmissions and operate on 2.4GHz industrial scientific medical (ISM) band. To avoid the rich interference existed in ISM band, Bluetooth adopts a time-slotted frequency-hopping spread-spectrum scheme, preventing the Bluetooth device communication from being interfered for a long time on specific channel. However, the coexistence of Bluetooth and Wi-Fi in the neighborhood degrades the performance of both networks because the two wireless technologies cannot negotiate with each other. To improve the throughput of a given piconet, this paper presents two interference aware approaches. First, an interference aware piconet establishment mechanism, called IAPE, is proposed to consider the frequencies occupied by Wi-Fi and then minimize the interference from Wi-Fi transmissions, when Bluetooth and Wi-Fi coexist in the same space. To further improve the throughput of the constructed piconet, an interference aware piconet restructuring mechanism, called IAPR, is proposed. Performance study reveals that the proposed IAPE and IAPR approaches further reduce the interference between Bluetooth and Wi-Fi and thereby save the energy of Bluetooth device, improving the throughput of Bluetooth personal area networks (PANs).

Device-to-device meets LTE-unlicensed

In this article, we look into how the LTE network can efficiently evolve to cater for new data services by utilizing direct communications between mobile devices and extending the direct transmissions to the unlicensed bands, that is, D2D communications in conjunction with LTE-Unlicensed. In doing so, it provides an opportunity to solve the main challenge of mutual interference between D2D and CC transmissions. In this context, we review three interconnected major technical areas of multihop D2D: transmission band selection, routing path selection, and resource management. Traditionally, D2D transmissions are limited to specific regions of a cell's coverage area in order to limit the interference to CC primary links. We show that by allowing D2D to operate in the unlicensed bands with protective fairness measures for WiFi transmissions, D2D is able to operate across the whole coverage area and, in doing so, efficiently scale the overall network capacity while minimizing cross-tier and cross-technology interference.

10 m/25 Gbps LiFi transmission system based on a two-stage injection-locked 680 nm VCSEL transmitter.

A 10 m/25 Gbps light-based WiFi (LiFi) transmission system based on a two-stage injection-locked 680 nm vertical-cavity surface-emitting laser (VCSEL) transmitter is proposed. A LiFi transmission system with a data rate of 25 Gbps is experimentally demonstrated over a 10 m free-space link. To the best of our knowledge, it is the first time a two-stage injection-locked 680 nm VCSEL transmitter in a 10 m/25 Gbps LiFi transmission system has been employed. Impressive bit error rate performance and a clear eye diagram are achieved in the proposed systems. Such a 10 m/25 Gbps LiFi transmission system provides the advantage of a communication link for higher data rates that could accelerate the deployment of visible laser light communication.

BackFi

We present BackFi, a novel communication system that enables high throughput, long range communication between very low power backscatter devices and WiFi APs using ambient WiFi transmissions as the excitation signal. Specifically, we show that it is possible to design devices and WiFi APs such that the WiFi AP in the process of transmitting data to normal WiFi clients can decode backscatter signals which the devices generate by modulating information on to the ambient WiFi transmission. We show via prototypes and experiments that it is possible to achieve communication rates of up to 5 Mbps at a range of 1 m and 1 Mbps at a range of 5 meters. Such performance is an order to three orders of magnitude better than the best known prior WiFi backscatter system [27,25]. BackFi design is energy efficient, as it relies on backscattering alone and needs insignificant power, hence the energy consumed per bit is small.

Parasitic Exploitation of Wi-Fi Signals for Indoor Radar Surveillance

In this paper, we examine the potentiality of passive coherent location (PCL) for indoor area monitoring. In particular, we show that Wi-Fi transmissions can be successfully exploited as waveforms of opportunity to perform moving target detection and localization based on the passive radar principle. Moreover, we investigate the advanced capability to obtain high-resolution cross-range profiles of the observed targets via inverse-synthetic-aperture-radar (ISAR) techniques. To these purposes, appropriate processing techniques are introduced to cope with the limitations resulting from the indoor applications such as the strong returns from the stationary scene and the high density of potential targets. The proposed system concept has been tested against both simulated and real data sets. The reported results clearly show that using few receiving channels connected to properly dislocated antennas allows an accurate target localization and tracking. In addition, reliable and stable profiles are obtained for the targets moving in the surveyed scene, which might fruitfully feed a classification stage. This contributes to the demonstration of the effective applicability of the passive radar concept for improving internal and external security of private/public premises.