<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In many engineering applications we deal with constrained optimization problems respect to complex-valued matrices. This paper proposes a Riemannian geometry approach for of real-valued cost function <formula formulatype="inline"><tex>${\cal J}$</tex></formula> matrix argument formulatype="inline"><tex>${\bf W}$</tex></formula>, under the constraint that W}$</tex></formula> is an...

Among the key differentiators of 6G compared to 5G will be increased emphasis on radio-based positioning and sensing. These utilized not only for conventional location-aware services enhancing communication performance but also support new use case families with extreme requirements. This article presents a unified vision from stakeholders across value chain in terms both opportunities challenges sensing as well cases, requirements, gap analysis. Combined, this motivates technical advances...

We address the problem of localization in vehicular ad hoc networks. Our goal is to leverage vehicle communications and smartphone sensors improve overall performance. Assuming vehicles are equipped with IEEE 802.11p wireless interfaces, we employ a two-stage Bayesian filter track vehicle's position: an unscented Kalman for heading estimation using inertial sensors, particle that fuses vehicle-to-vehicle signal strength measurements received from mobile anchors whose positions uncertain,...

Localization is a research area that, due to its overarching importance as an enabler for higher level services, has attracted vast amount of and commercial interest. For the most part, it can be claimed that GPS provides unparalleled solution outdoor tracking navigation. However, same cannot yet said about positioning in GPS-denied or challenged environments, such indoor where obstructions floors walls heavily attenuate reflect high-frequency radio signals. This led plethora competing...

In this paper, we analyze the effect of different underground materials on very-low and low-frequency magnetic fields used in contexts magneto-inductive localization communication applications, respectively. We calculate attenuation that these are subject to while passing through most common rocks minerals. Knowing properties is crucial design systems. addition, provide means predict distortions field impair The proposed work offers basic guidelines for systems terms channel path loss,...

6G will be characterized by extreme use cases, not only for communication, but also localization, and sensing. The cases can directly mapped to requirements in terms of standard key performance indicators (KPIs), such as data rate, latency, or localization accuracy. goal this paper is go one step further map these KPIs on signals, hardware architectures, deployments. Based this, system solutions identified that support several simultaneously. Since there are ways meet the KPIs, no unique...

Underground mines are characterized by a network of intersecting tunnels and sharp turns, an environment which is particularly challenging for radiofrequency based positioning systems due to extreme multipath, non-line-of-sight propagation, poor anchor geometry. Such typically require dense grid devices enable 3-D positioning. Moreover, the precise position each node needs be precisely surveyed, task in underground environments. Magneto-inductive (MI) positioning, provides orientation from...

In this paper, we propose a new two-way time synchronization (TS) method for orthogonal frequency division multiplexing (OFDM)-based wireless systems. It relies on the time-reversal (TR) technique to remove effect of channel phase after signal round-trip. Thus, is named TR-TS. TR yields linear rotation across subcarriers, regardless whether minimum, maximum, or mixed phase. This proportional difference OFDM symbol-timing errors at two receivers. clock-offset between radios determined using...

Despite the large literature on localization, there is no solution yet to localize a commercial off-the-shelf smartphone device using radio measurements from single WiFi AP. We present SPRING, Smartphone Positioning with Radio sINGle wifi access point. SPRING exploits Fine Time Measurements (FTM) and Angle of Arrival (AOA) extracted chipsets exploiting specifications recent 802.11-2016 802.11ac amendment combine distance direction AP client for positioning. Our system has potential bring...

Emotional stress is commonly experienced while speaking in public, producing changes to the various speech productions subsystems, affecting signal predictable ways and being easily conveyed listeners. Speech indicators, however, are typically studied under laboratory settings, allowing little generalization real life settings. To bridge this gap, we propose an interdisciplinary approach assess during public events, based on a platform that records simultaneously annotated with physiological...

Many wireless applications require a propagation model that describes the attenuation of transmitted signal as function distance between devices. Such channel models are derived commonly from strength measurements, and assume true distances terminals known. In practice, however, may be unavailable or difficult to obtain, for instance in mobile scenarios absence line-of-sight. These conditions typically occur forested environments, urban areas, etc. This paper addresses problem path loss...

Ferrous and highly conductive materials distort low-frequency magnetic fields can significantly increase magnetoinductive positioning errors. In this paper, we use the image theory in order to formulate an analytical channel model for field of a quasi-static dipole positioned above perfectly conducting half-space. The proposed be used compensate distorting effects that metallic reinforcement bars (rebars) within floor impose on transmitter node indoor single-story environment. Good agreement...

The continuously increasing bandwidth and antenna aperture available in wireless networks laid the foundation for developing competitive positioning solutions relying on communications standards hardware. However, poor propagation conditions such as non-line of sight (NLOS) rich multipath still pose many challenges due to outlier measurements that significantly degrade performance.In this work, we introduce an iterative method reweights time arrival (ToA) angle (AoA) originating from...

Teams of mobile cooperative robots are ideal candidates for applications where the presence humans is impossible or should be avoided. Knowing positions in crucial such scenarios. A possible solution to derive relative from local communication. In this work, we propose an anchor-free online channel estimation method aimed at small multi-robot teams. By combining both Time-of-Flight (ToF) and Received Signal Strength Indicator (RSSI) ranging, provided by nanoLoc devices, perform indoor...

Wireless connectivity will soon enable people to consume augmented and virtual reality content anywhere cloud-connected mobile robots perform complex tasks collaboratively. This come enterprises, factory floors digital homes first, powered by indoor networks that offer much higher data rates, greater reliability, lower latency than today's networks. In addition providing traditional communication capabilities, the future network have a "sixth sense" enables it provide sensory information...

Localization is envisioned as a key enabler to satisfy the requirements of communications and context-aware services in fifth/sixth generation (5G/6G) communication systems. User localization can be achieved based on delay angle estimation using uplink/downlink pilot signals. However, hardware impairments (HWIs) (such phase noise mutual coupling) distort signals at both transmitter receiver sides thus affect performance. While this impact ignored lower frequencies with less severe HWIs,...

In this paper, we study probabilistic time-of-arrival (ToA) and angle-of-arrival (AoA) joint localization in real indoor environments. To mitigate the effects of multipath propagation, algorithm incorporates into likelihood function Gaussian mixture models (GMM) Von Mises-Fisher distribution to model time bias errors angular uncertainty, respectively. We evaluate performance using a proprietary prototype deployed an factory environment with infrastructure receivers each four corners at...

This correspondence deals with the construction of minimum Euclidean distance precoders for multiple-input multiple-output (MIMO) systems up to four transmit antennas. By making use a state-of-the-art technique optimization over unitary group, we can numerically optimize MIMO precoders. The then proceeds by identifying obtained as well-known lattices (square <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex...

Magneto-inductive navigation is an inexpensive and easily deployable solution to many of today's problems. By utilizing very low frequency magnetic fields, magneto-inductive technology circumvents the problems with attenuation multipath that often plague competing modalities. Using triaxial transmitter receiver coils, it possible compute position orientation estimates in three dimensions. However, situations, additional information available constrains set solutions. For example, may be...

Ferrous objects distort magnetic fields and can significantly increase magneto-inductive positioning errors in indoor environments. In this work, we use image theory order to formulate an analytical channel model for the field of a quasi-static dipole positioned above perfectly conducting half-space. The proposed be used compensate distorting effects that metallic reinforcement bars (rebars) impose on transmitter node environment. Good agreement is observed between solution numerical...

In this paper we propose practical algorithms for optimization under unitary matrix constraint. This type of constrained is needed in many signal processing applications. Steepest descent and conjugate gradient on the Lie group matrices are introduced. They exploit properties order to reduce computational cost. Simulation examples separation MIMO systems demonstrate fast convergence ability satisfy constraint with high fidelity.