Photoplethysmography (PPG) was used to detect changes in the anterior tibial muscle blood flow (MBF) during foot-transmitted vibration in six healthy subjects. A filter was developed for reducing the vibration-induced artefacts in the PPG signal. The vibration applied was random with constant acceleration power density in the range 5-2000 Hz with an acceleration of 16-46 m s(-2) (rms). The application of the filter technique showed a dramatic reduction in the vibration-induced artefacts and distortion of the PPG signal was negligible. The mean ratio and correlation coefficient of MBF originating from filtered and non-filtered PPG signals was [mean (SD)] 0.89 (0.04) and 0.99, respectively. This made it possible to detect a relative increase in MBF of 20% during an acute vibration exposure. The results suggest that the use of the filter enables MBF to be measured by PPG during vibration, thus extending the range of applications of the PPG technique to include ergonomic conditions.

The emerging multiuser transmission techniques for enabling higher data rates in the copper-access network relies upon accurate knowledge of the twisted-pair cables. In particular, the square-magnitude of the crosstalk channels between the transmission lines are of interest for crosstalk-mitigation techniques. Acquiring such information normally requires dedicated apparatus since crosstalk-channel measurement is not included in the current digital subscriber line (DSL) standards. We address this problem by presenting a standard-compliant estimator for the square-magnitude of the frequency-dependent crosstalk channels that uses only functionality existing in today's standards. The proposed estimator is evaluated by laboratory experiments with standard-compliant DSL modems and real copper access network cables. The estimation results are compared with both reference measurements and with a widely used crosstalk model. The results indicate that the proposed estimator obtains an estimate of the square-magnitude of the crosstalk channels with a mean deviation from the reference measurement less than 3 dB for most frequencies.

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Abstract-This paper investigates common-mode propagation in shielded twisted pair cables. The common mode exhibits great potential for improving the throughput in emerging wireline systems. The design of corresponding transmission schemes over multipair copper cables requires accurate knowledge of the channel properties. We present measurement and modeling results and investigate the feasibility of using standard differentialmode models for data fitting in multiconductor transmission-line modelling of common-mode paths.

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This paper describes Sequence Time Domain Reflectometry (STDR) and Spread Spectrum Time Domain Reflectometry (SSTDR), which utilizes concepts from direct sequence spread spectrum communications, as a technique for detecting impedance mismatches in telephone lines (twisted pair). The aim of this paper is to present methodologies for characterizing a subscriber loop, which is used for Digital Subscriber Line (DSL) technology, based on STDR and SSTDR tests. Those tests enable the TDR functionality to be incorporated into a DSL transceiver integrated circuit eliminating the need for costly test equipment. In addition to the cost savings, the characteristics of the STDR and SSTDR offer improved spectral compatibility, interference immunity and fault resolvability.