Carl Gustafson

On mm-Wave Multipath Clustering and Channel Modeling

Efficient and realistic mm-wave channel models are of vital importance for the development of novel mm-wave wireless technologies. Though many of the current 60 GHz channel models are based on the useful concept of multipath clusters, only a limited number of 60 GHz channel measurements have been reported in the literature for this purpose. Therefore, there is still a need for further measurement based analyses of multipath clustering in the 60 GHz band. This paper presents clustering results for a double-directional 60 GHz MIMO channel model. Based on these results, we derive a model which is validated with measured data. Statistical cluster parameters are evaluated and compared with existing channel models. It is shown that the cluster angular characteristics are closely related to the room geometry and environment, making it infeasible to model the delay and angular domains independently. We also show that when using ray tracing to model the channel, it is insufficient to only consider walls, ceiling, floor and tables; finer structures such as ceiling lamps, chairs and bookshelves need to be taken into account as well.

High-accuracy localization for assisted living: 5G systems will turn multipath channels from foe to friend

Assisted living (AL) technologies, enabled by technical advances such as the advent of the Internet of Things, are increasingly gaining importance in our aging society. This article discusses the potential of future high-accuracy localization systems as a key component of AL applications. Accurate location information can be tremendously useful to realize, e.g., behavioral monitoring, fall detection, and real-time assistance. Such services are expected to provide older adults and people with disabilities with more independence and thus to reduce the cost of caretaking. Total cost of ownership and ease of installation are paramount to make sensor systems for AL viable. In case of a radio-based indoor localization system, this implies that a conventional solution is unlikely to gain widespread adoption because of its requirement to install multiple fixed nodes (anchors) in each room. This article therefore places its focus on 1) discussing radiolocalization methods that reduce the required infrastructure by exploiting information from reflected multipath components (MPCs) and 2) showing that knowledge about the propagation environment enables localization with high accuracy and robustness. It is demonstrated that new millimeter-wave (mm-wave) technology, under investigation for 5G communications systems, will be able to provide centimeter (cm)-accuracy indoor localization in a robust manner, ideally suited for AL.

60 GHz Spatial Radio Transmission: Multiplexing or Beamforming?

This paper compares the capacity improvement capability of spatial multiplexing and beamforming techniques for 60 GHz spatial transmissions in a multi-carrier radio system such as orthogonal frequency division multiplexing. The term beamforming in this paper refers to the conventional gain focusing, for the strongest propagation path, by narrow antenna beams. Our channel capacity metric depends only on the multipath richness of the propagation channel and the antenna aperture size, but is otherwise independent of the realization of antenna elements on the aperture. Our analysis also reveals the spatial degrees-of-freedom (SDoF) of the radio channel, which is the maximum number of antenna elements on the aperture for efficient spatial multiplexing. We evaluate the capacity and SDoF of single-polarized 60 GHz radio channels measured in an office environment. Our results show that the radio channel offers multiple SDoFs both in line-of-sight (LOS) and non-LOS (NLOS) scenarios such that spatial multiplexing can improve the channel capacity, provided that the receive signal-to-noise ratio (SNR) is sufficiently high to utilize them. Under -10 dBm of the transmit power, the high receive SNR is guaranteed when the antenna aperture size is larger than 1λ2 in LOS and 9λ2 in NLOS scenarios, respectively.

Slot-Coupled Millimeter-Wave Dielectric Resonator Antenna for High-Efficiency Monolithic Integration

A readily mass-producible, flip-chip assembled, and slot-coupled III-V compound semiconductor dielectric resonator antenna operating in the millimeter-wave spectrum has been fabricated and characterized. The antenna has a 6.1% relative bandwidth, deduced from its 10 dB return loss over 58.8–62.5 GHz, located around the resonance at 60.5 GHz. Gating in the delay-domain alleviated the analysis of the complex response from the measured structure. The radiation efficiency is better than

Directional Analysis of Measured 60 GHz Indoor Radio Channels Using SAGE

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Methane emission bursts from permafrost environments during autumn freeze‐in: New insights from ground‐penetrating radar

dB in simulations fed from the on-chip coupling-structure, but reduced by 3.7 dB insertion loss through the measurement assembly feed. Antenna gain measurements show distortion in relation to the simulated pattern, which has a maximum gain of 6 dBi, mainly caused by interference from the electrically large connector used in the assembly. Mode degeneration in the utilized quadratic-footprint resonator was not seen to influence the performance of the antenna. The antenna is intended for on-chip integration and the fabrication technology allows scaling of the operation frequency over the complete millimeter-wave spectrum.

Statistical Modeling and Estimation of Censored Pathloss Data

Directional properties of the radio channel are of high importance for the development of reliable wireless systems operating in the 60 GHz frequency band. Using transfer functions measured from 61 to 65 GHz in a conference room we have extracted estimates of the multi-path component parameters using the SAGE algorithm. In the paper we compare results for line-of-sight (LOS) scenarios and the corresponding non-line-of-sight (NLOS) scenarios and present values of the direction spread at the Tx and the Rx.

Spatial Degrees-of-Freedom of 60 GHz Multiple-Antenna Channels

Large amounts of methane (CH4) are known to be emitted from permafrost environments during the autumn freeze-in, but the specific soil conditions leading up to these bursts are unclear. Therefore, we used an ultrawide band ground-penetrating radar in Northeast Greenland in autumn 2009 to estimate the volumetric composition inside the soil through dielectric characterization from 200 to 3200 MHz. Our results suggest a compression of the gas reservoir during the phase transition of soil water, which is accompanied by a peak in surface CH4 emissions. About 1 week thereafter, there seems to be a decompression event, consistent with ground cracking which allows the gas reservoir to expand again. This coincides with the largest CH4 emission, exceeding the summer maximum by a factor of 4. We argue that these complementary measurement techniques are needed to come to an understanding of tundra CH4 bursts connected to soil freezing. (Less)

Estimation of Spherical Wave Coefficients From 3-D Positioner Channel Measurements

Pathloss is typically modeled using a log-distance power law with a large-scale fading term that is log-normal. However, the received signal is affected by the dynamic range and noise floor of the measurement system used to sound the channel, which can cause measurement samples to be truncated or censored. If the information about the censored samples is not included in the estimation method, as in ordinary least squares estimation, it can result in biased estimation of both the pathloss exponent and the large scale fading. This can be solved by applying a Tobit maximum-likelihood estimator, which provides consistent estimates for the pathloss parameters. This letter provides information about the Tobit maximum-likelihood estimator and its asymptotic variance under certain conditions.

Simulations and measurements of 15 and 28 GHz indoor channels with different array configurations

This paper studies the potential of spatial multiplexing for measured 60 GHz radio channels by estimating the number of eigenchannels. It is well-known that the number of available eigenchannels is dependent on a propagation channel condition as well as antenna array conguration. We evaluate a spatial degrees- of-freedom (SDoF) metric that depends on the propagation conditions and the antenna aperture size, but is otherwise independent of the realization of antenna elements on the aperture. The SDoF metric is a measure of the effective number of antenna elements for spatial multiplexing. We evaluate the SDoF for 60 GHz multiple-input multiple-output channels measured in a conference room environment under a line-of- sight (LOS) condition. Our analysis reveals that the SDoF is more than one for a transmit- receive antenna separation of more than 2 m, which indicates that spatial multiplexing can work in such LOS scenarios. Our results indicate that using only 10 antenna elements at each of the transmit and receive antenna aperture is sufficient for effective spatial multiplexing performance in the considered propagation scenario. Furthermore, by using just 5 antennas at each aperture, eigenchannels down to -15 dB relative magnitude can still be captured.