Radio-based passive-object sensing can enable a new form of pervasive user-computer interface. Prior work has employed various wireless signal features to sense objects under set predefined, coarse motion patterns. But an operational UI, like trackpad, often needs identify fine-grained, arbitrary motion. This paper explores the feasibility tracking passive writing object (e.g., pen) at sub-centimeter precision. We approach this goal through practical design, mTrack, which uses...

5G, as a monumental shift in cellular communication technology, holds tremendous potential for spurring innovations across many vertical industries, with its promised multi-Gbps speed, sub-10 ms low latency, and massive connectivity. On the other hand, 5G has been deployed only few months, it is unclear how well whether can eventually meet prospects. In this paper, we demystify operational networks through first-of-its-kind cross-layer measurement study. Our focuses on four major...

60 GHz technology holds tremendous potential to upgrade wireless link throughput Gbps level. To overcome inherent vulnerability attenuation, radios communicate by forming highly-directional electronically-steerable beams. Standards like IEEE 802.11ad have tailored MAC/PHY protocols such flexible-beam networks. However, lack of a reconfigurable platform has thwarted realistic proof-of-concept evaluation. In this paper, we conduct an in-depth measurement indoor networks using first-of-its-kind...

Full-duplex has emerged as a new communication paradigm and is anticipated to double wireless capacity. Existing studies of full-duplex mainly focused on its PHY layer design, which enables bidirectional transmission between single pair nodes. In this paper, we establish an analytical framework quantify the network-level capacity gain over half-duplex. Our analysis reveals that inter-link interference spatial reuse substantially reduces gain, rendering it well below 2 in common cases. More...

The ISM spectrum is becoming increasingly populated by emerging wireless networks. Spectrum sharing among the same network of devices can be arbitrated MAC protocols (e.g., CSMA), but coexistence between heterogeneous networks remains a challenge. disparate power levels, asynchronous time slots, and incompatible PHY layers severely degrade effectiveness traditional MAC. In this paper, we propose new mechanism, called Cooperative Busy Tone (CBT), that enables reliable two such networks,...

3D orientation tracking is an essential ingredient for many Internet-of-Things applications. Yet existing systems commonly require motion sensors that are only available on battery-powered devices. In this paper, we propose Tagyro, which attaches array of passive RFID tags as everyday objects. Tagyro uses a closed-form model to transform the run-time phase offsets between into angle. To enable in space, found key challenge lies imperfect radiation pattern practical tags, caused by antenna...

Despite years of innovative research and development, gigabit-speed 60 GHz wireless networks are still not mainstream. The main concern for network operators vendors is the unfavorable propagation characteristics due to short wavelength high directionality, which renders links highly vulnerable blockage mobility. However, advent multi-band chipsets opens possibility leveraging more robust WiFi technology assist in order provide seamless, Gbps connectivity. In this paper, we design implement...

Owing to dense deployment of light fixtures and multipath-free propagation, visible localization technology holds potential overcome the reliability issue radio localization. However, existing systems require customized hardware, which increases cost hinders near term adoption. In this paper, we propose LiTell, a simple robust scheme that employs unmodified fluorescent lights (FLs) as location landmarks commodity smartphones sensors. LiTell builds on key observation each FL has an inherent...

WiFi interface is known to be a primary energy consumer in mobile devices, and idle listening (IL) the dominant source of consumption WiFi. Most existing protocols, such as 802.11 power-saving mode (PSM), attempt reduce time spent IL by sleep scheduling. However, through an extensive analysis real-world traffic, we found more than 60 percent consumed IL, even with PSM enabled. To remedy this problem, propose Energy-Minimizing Listening (E-MiLi) that reduces power given has already been...

Coordination of co-located wireless devices is a fundamental function/requirement for reducing interference. However, different cannot directly coordinate with one another as they often use incompatible modulation schemes. Even the same type (e.g., WiFi) devices, their coordination infeasible when neighboring transmitters adopt spectrum widths. Such an incompatibility between heterogeneous may severely degrade network performance. In this paper, we introduce Gap Sense (GSense), novel...

A well-known bottleneck of contemporary mobile devices is the inefficient and error-prone touchscreen keyboard. In this paper, we propose UbiK, an alternative portable text-entry method that allows user to make keystrokes on conventional surfaces, e.g., wood desktop. UbiK enables text-input experience similar a physical keyboard, but it only requires keyboard outline printed surface or piece paper atop. The core idea leverage microphone device accurately localize keystrokes. To achieve...

Recent works have considered the feasibility of full duplex (FD) wireless communications in practice. While first FD system by Choi et.al. relied on a specific antenna cancellation technique to achieve significant portion self-interference cancellation, various limitations this prompted latter move away from and rely analog achieved through channel estimation. However, systems turn require use variable attenuator delay elements that need be automatically tuned compensate for channel. This...

This paper presents a recognition scheme for fine-grain gestures. The leverages directional antenna and short-range wireless propagation properties to recognize vocabulary of action-oriented gestures from the American Sign Language. Since only relies on commonly available features such as Received Signal Strength (RSS), signal phase differences, frequency subband selection, it is readily deployable commercial-off-the-shelf IEEE 802.11 devices. We have implemented proposed evaluated in two...

Adaptive HTTP video streaming over LTE has been gaining popularity due to LTE's high capacity. Quality of adaptive depends highly on the accuracy client's estimation end-to-end network bandwidth, which is challenging link dynamics. In this paper, we present piStream, that allows a client efficiently monitor basestation's PHY-layer resource allocation, and then map such information an available bandwidth. Given PHY-informed bandwidth estimation, piStream uses probabilistic algorithm balance...

Smart devices bring us the ubiquitous mobile accessing to Internet, making Internet grow rapidly. Using traffic data collected at core metropolitan 2G and 3G networks of China over a week, this paper studies user behavior from three aspects: 1) usage; 2) mobility pattern; 3) application usage. We classify users into different groups study resource consumption in Internet. observe that heavy high tend consume massive radio resources simultaneously. Both usage pattern are closely related...

Loudspeakers are widely used in conferencing and infotainment systems. Private information leakage from loudspeaker sound is often assumed to be preventable using sound-proof isolators like walls. In this paper, we explore a new acoustic eavesdropping attack that can subvert such protectors radio devices. Our basic idea lies an acoustic-radio transformation (ART) algorithm, which recovers by inspecting the subtle disturbance it causes signals generated adversary or its co-located WiFi...

The unlicensed ISM spectrum is getting crowded by wireless local area network (WLAN) and personal (WPAN) users devices. Spectrum sharing within the same of devices can be arbitrated existing MAC protocols, but coexistence between WPAN WLAN (e.g., ZigBee WiFi) remains a challenging problem. traditional protocols are ineffective in dealing with disparate transmit-power levels, asynchronous time-slots, incompatible PHY layers such heterogeneous networks. Recent measurement studies have shown...

Mobile devices are shrinking their form factors for portability, but user-mobile interaction is becoming increasingly challenging. In this paper, we propose a novel system called Okuli to meet challenge. compact, low-cost that can augment mobile device and extend its workspace any nearby surface area. piggybacks on visible light communication modules, uses low-power LED two sensors locate user's finger within the workspace. It built propagation/reflection model achieves around one-centimeter...

The past decade's research in visible light positioning (VLP) has led to technologies with high location precision. However, existing VLP systems either require specialized LEDs which hinder large-scale deployment, or need cameras preclude continuous localization because of power consumption and short coverage. In this paper, we propose Pulsar, uses a compact photodiode sensor, readily fit into mobile device, discriminate ceiling lights---either fluorescent lights conventional LEDs---based...

For over one decade, research in visible light positioning has focused on using modulated LEDs as location landmarks. But the need for specialized LED fixtures, and associated retrofitting cost, been hindering adoption of VLP. In this paper, we forgo approach design iLAMP to enable reliable, high-precision VLP conventional fluorescent lamps inside today's buildings. Our key observation is that these intrinsically possess hidden visual features, which are imperceptible human eyes, but can be...

Multi-User MIMO, the hallmark of IEEE 802.11ac and upcoming 802.11ax, promises significant throughput gains by supporting multiple concurrent data streams to a group users. However, identifying best-throughput MU-MIMO groups in commodity networks poses three major challenges: a) Commodity users do not provide full CSI feedback, which has been widely used for grouping. b) Heterogeneous channel bandwidth limit grouping opportunities. c) Limited-resource on APs cannot support computationally...

Machine learning models, particularly reinforcement (RL), have demonstrated great potential in optimizing video streaming applications. However, the state-of-the-art solutions are limited to an "offline learning" paradigm, i.e., RL models trained simulators and then operated real networks. As a result, they inevitably suffer from simulation-to-reality gap, showing far less satisfactory performance under conditions compared with simulated environment. In this work, we close gap by proposing...

MIMO beamforming technology can scale wireless data rate proportionally with the number of antennas. However, overhead induced by receivers' CSI (channel state information) feedback scales at a higher rate. In this paper, we address fundamental tradeoff Adaptive Feedback Compression (AFC). AFC quantizes or compresses from 3 dimensions --- time, frequency and numerical values, adapts intensity compression according to channel profile. This simple principle faces many practical challenges,...

WiFi interface is known to be a primary energy consumer in mobile devices, and idle listening (IL) the dominant source of consumption WiFi. Most existing protocols, such as 802.11 power-saving mode (PSM), attempt reduce time spent IL by sleep scheduling. However, through an extensive analysis real-world traffic, we found more than 60% consumed IL, even with PSM enabled. To remedy this problem, propose E-MiLi (Energy-Minimizing Listening) that reduces power given has already been optimized...