Linköping University

About: Linköping University is a education organization based out in Linköping, Sweden. It is known for research contribution in the topics: Population & Thin film. The organization has 15671 authors who have published 50013 publications receiving 1542189 citations.

Multipair Full-Duplex Relaying With Massive Arrays and Linear Processing

Abstract: We consider a multipair decode-and-forward relay channel, where multiple sources transmit simultaneously their signals to multiple destinations with the help of a full-duplex relay station. We assume that the relay station is equipped with massive arrays, while all sources and destinations have a single antenna. The relay station uses channel estimates obtained from received pilots and zero-forcing (ZF) or maximum-ratio combining/maximum-ratio transmission (MRC/MRT) to process the signals. To significantly reduce the loop interference effect, we propose two techniques: i) using a massive receive antenna array; or ii) using a massive transmit antenna array together with very low transmit power at the relay station. We derive an exact achievable rate expression in closed-form for MRC/MRT processing and an analytical approximation of the achievable rate for ZF processing. This approximation is very tight, particularly for a large number of relay station antennas. These closed-form expressions enable us to determine the regions where the full-duplex mode outperforms the half-duplex mode, as well as to design an optimal power allocation scheme. This optimal power allocation scheme aims to maximize the energy efficiency for a given sum spectral efficiency and under peak power constraints at the relay station and sources. Numerical results verify the effectiveness of the optimal power allocation scheme. Furthermore, we show that, by doubling the number of transmit/receive antennas at the relay station, the transmit power of each source and of the relay station can be reduced by 1.5 dB if the pilot power is equal to the signal power, and by 3 dB if the pilot power is kept fixed, while maintaining a given quality of service.

Measurement of water exchange through skin.

Abstract: A new method for the measurement of the water exchange through the human skin has been developed. The method, based on the estimation of the vapour-pressure gradient immediately adjacent to the surface of the skin, permits the surface investigated to be exposed to normal ambient air during the entire period of measurement. A minimal influence on the humidity and the temperature of the microclimate surrounding the skin is thereby achieved. On the basis of the new method an instrument for measuring small amounts of water evaporated from or absorbed by a surface per unit time and area is described and its accuracy discussed. The instrument, which is intended for use in the temperature range 15–40°C and the atmospheric pressure range 98–104 kPa, has proved to offer a high accuracy and an improved sensitivity in comparison with devices previously employed. It has been used primarily for investigations of the rate of evaporation from the skin surface of newborn infants as well as of thyrotoxic and burned patients. The construction of the instrument, however, makes it well suited for the measurement of evaporation rates in many other fields of application.

On positive real transfer functions and the convergence of some recursive schemes

Abstract: The convergence with probability one of a recently suggested recursive identification method by Landau is investigated. The positive realness of a certain transfer function is shown to play a crucial role, both for the proof of convergence and for convergence itself. A completely analogous analysis can be performed also for the extended least squares method and for the self-tuning regulator of Astrom and Wittenmark. Explicit conditions for convergence of all these schemes are given. A more general structure is also discussed, as well as relations to other recursive algorithms.

Internet-Delivered Psychological Treatments

Abstract: During the past 15 years, much progress has been made in developing and testing Internet-delivered psychological treatments. In particular, therapist-guided Internet treatments have been found to be effective for a wide range of psychiatric and somatic conditions in well over 100 controlled trials. These treatments require (a) a secure web platform, (b) robust assessment procedures, (c) treatment contents that can be text based or offered in other formats, and (d) a therapist role that differs from that in face-to-face therapy. Studies suggest that guided Internet treatments can be as effective as face-to-face treatments, lead to sustained improvements, work in clinically representative conditions, and probably are cost-effective. Despite these research findings, Internet treatment is not yet disseminated in most places, and clinical psychologists should consider using modern information technology and evidence-based treatment programs as a complement to their other services, even though there will always be clients for whom face-to-face treatment is the best option.