Camillo Gentile

Robust location using system dynamics and motion constraints

To our knowledge, the indoor location system which currently achieves the best performance using inexpensive off-the-shelf equipment locates a mobile within 1.5 meters with probability 77% in hallways. Even while maintaining this accuracy, the system often reports logical errors such as the mobile in the wrong cubicle of an office or even on the wrong side of a wall when broadening the domain of application to within rooms. We propose an extension of the work using the same Markov localization framework, however incorporating system dynamics (necessitating no post-processing of the output) and motion constraints which implicitly encode the physical properties of the survey area. Our system retains the advantages of its predecessor of low cost, wireless LAN connectivity and security, and large-scale deployment, however extending the survey area from simple hallways to the whole office environment, while maintaining the same precision without logical errors.

A Methodology to Evaluate Wireless Technologies for the Smart Grid

This paper presents a methodology for assessing the suitability of various wireless technologies for meeting the communication requirements of Smart Grid applications. It describes an approach for translating application requirements to link traffic characteristics, determining the transmission range or coverage area of a wireless technology, and modeling the link layer to obtain performance measures such as message reliability, delay, and throughput. To illustrate the use of this approach, we analyze the performance of three representative application use cases over an IEEE 802.11 link.

A comprehensive evaluation of indoor ranging using ultra-wideband technology

Ultra-wideband technology shows promise for precision ranging due to its fine time resolution to resolve multipath fading and the presence of lower frequencies in the baseband to penetrate walls. While a concerted effort has been conducted in the extensive modeling of the indoor UWB channel in recent years, to our knowledge only two papers have reported ranging performance, but for limited range and fixed bandwidth and center frequency. In principle, boosting power can guarantee connectivity between transmitter and receiver, but not precision due to the distorting effects of walls and other objects in the direct path. In order to gauge the limits of UWB ranging, we carry out 5000 measurements up to an unprecedented 45 m in non-line-of-sight conditions in four separate buildings with dominant wall material varying from sheet rock to steel. In addition, we report performance for varying bandwidth and center frequency of the system.

WLC28-4: An Evaluation of Ultra Wideband Technology for Indoor Ranging

Ultra wideband technology shows promise for precision ranging due to its fine time resolution to resolve multipath fading and the presence of lower frequencies in the baseband to penetrate walls. While a concerted effort has been conducted in the extensive modeling of the indoor UWB channel in recent years, to our knowledge only two papers have reported ranging performance, but for limited range and fixed bandwidth and center frequency. In principle boosting power can guarantee connectivity between transmitter and receiver, but not precision due to the distorting effects of walls and other objects in the direct path. In order to gauge the limits of UWB ranging, we carry out 5000 measurements up to an unprecedented 45 m in non line-of- sight conditions in four separate buildings with dominant wall material varying from sheet rock to steel. In addition, we report performance for varying bandwidth and center frequency of the system.

Sensor location through linear programming with triangle inequality constraints

Interest in dense sensor networks due to falling price and reduced size has motivated research in sensor location in recent years. While many algorithms can be found in the literature, no benchmark exists and most papers fail to compare their results to other competing algorithms. To our knowledge, the algorithm which achieves the best performance in sensor location uses semidefinite relaxation of a quadratic program to solve for sensor location. We propose solving the same program, however without relaxing the constraints, but rather transforming them into linear triangle inequality constraints. Our linear program ensures a tighter solution to the problem. We benchmark ours against the competing algorithm, and provide extensive experimentation to substantiate the robustness of our algorithm even in the presence of high levels of noise.

A Radio Channel Sounder for Mobile Millimeter-Wave Communications: System Implementation and Measurement Assessment

We describe a state-of-the-art channel sounder to support channel-model development for mobile millimeterwave (mm-wave) communications. The system can measure the complex amplitude, delay, and angle of arrival of the multipath components of indoor and outdoor channels. Specifically, a custom multiplexer (MUX) records the channel impulse response across a 16-element receive (RX) antenna array in 65.5 μs, while the channel is static. The delay resolution of the system is 1 ns and, because the elements are oriented in a 3-D space, both azimuth and elevation angles can be extracted. The robust link budget, comprising high-gain directional RX antennas, enables indoor link measurement beyond 150 m in line-of-sight and 20 m in non-line-of-sight conditions. The RX array is mounted on a location-aware robot, which is battery operated. Combined with the speed of the MUX, untethered acquisition of mobile-channel data is possible. To the best of our knowledge, this paper contributes the first sounder that is capable of mobile measurements at mm-wave frequencies. The hardware implementation of a functional 83.5-GHz system is described in this paper, and some illustrative results, including small-scale statistics and Doppler, are presented.

A comprehensive evaluation of joint range and angle estimation in indoor ultrawideband location systems

Fine time resolution enables ultrawideband (UWB) ranging systems to extract the first multipath arrival corresponding to the range between a transmitter and receiver, even when attenuated in strength compared to later arrivals. Bearing systems alone lack any notion of time and in general select the strongest arrival which is rarely the first one in nonline-of-sight conditions. Complementing UWB ranging systems with bearing capabilities allows indexing the arrivals as a function of both time and angle in order to isolate the first, providing precision range and angle. However, that precision degrades with the increasing presence of walls and other objects which distort the properties of the first arrival. In order to gauge the physical limits of the joint UWB system, we design and assemble a spatial-temporal channel sounder using a vector network analyzer coupled to a virtual antenna array, and conduct 200 experiments to measure the time- and angle-of-flight. The experiments are carried out in both line-of-sight and nonline-of-sight conditions up to an unprecedented 45 meters throughout four separate buildings with dominant wall material varying from sheet rock to steel. In addition, we report performance for varying bandwidth and center frequency of the system. We find that operating at a bandwidth of 4 GHz suffices in resolving multipath in most buildings and in excess shows virtually no improvement. While the range error decreases at lower center frequencies, the higher frequencies offer better angular resolution and so smaller angle error.

A Comprehensive Spatial-Temporal Channel Propagation Model for the Ultrawideband Spectrum 2–8 GHz

Despite the potential for high-speed communications, stringent regulatory mandates on ultrawideband (UWB) emission have hindered its commercial success. By combining resolvable UWB multipath from different directions, multiple-input multiple-output (MIMO) technology can drastically improve link robustness or range. In fact, a plethora of algorithms and coding schemes already exist for UWB-MIMO systems, however these papers use simplistic channel models in simulation and testing. While the temporal characteristics of the UWB propagation channel have been well documented, surprisingly there currently exists but a handful of spatial-temporal models to our knowledge, and only two for bandwidths in excess of 500 MHz. This paper proposes a comprehensive spatial-temporal channel propagation model for the frequency spectrum 2-8 GHz, featuring a host of novel parameters. In order to extract the parameters, we conduct an extensive measurement campaign using a vector network analyzer coupled to a virtual circular antenna array. The campaign includes 160 experiments up to a non line-of-sight range of 35 meters in four buildings with construction material varying from sheetrock to steel.

A raytracing model for wireless propagation in tunnels with varying cross section

Mandated by the 2006 United States Miner Act, reliable two-way communications in mines has drawn the interest of network engineers in recent years. Critical to the design of these systems is an accurate channel propagation model. Given the elementary geometry seen in most tunnels, models that approximate them as a rectangular waveguide have been developed. These models are extremely accurate in vehicular tunnels because - since the tunnel is typically cast from concrete - the cross section is uniform throughout and the surface roughness is negligible. Mines, however, do not conform to these two conditions. In this paper, we extend the waveguide model to tunnels with varying cross section and measurable surface roughness. The effectiveness of the proposed model is validated through in-house field measurements collected in a vehicular tunnel and in a coal mine. We show that while the original model performs well in the former, it falters in the latter. The extended model, however, predicts reliably in the mine as well.

Radio channel sounders for modeling mobile communications at 28 GHz, 60 GHz and 83 GHz

NIST has developed a new channel sounder design specifically to support radio-channel model development for 5G millimeter-wave mobile communications. Design elements include 40 GB/s real-time sampling; an electronically switched, high-gain, directional receive antenna array covering the upper hemisphere; and automated mobile operations. These features allow measurement of calibrated received signal strength and the spatio-temporal channel response for both indoor and outdoor environments under mobile conditions. An 83 GHz system is described in this paper while 28 GHz and 60 GHz systems, in process, have similar capabilities. To our knowledge, this work contributes the first channel sounder which is capable of broadband, 3D, mobile measurements at millimeter-wave frequencies.