Effect Of Transmission Characteristics Research Articles

Tele-Assessment of the Berg Balance Scale: Effects of Transmission Characteristics

ObjectiveTo compare Berg Balance Scale (BBS) rating using videos with differing transmission characteristics with direct in-person rating. DesignRepeated-measures study for the assessment of the BBS in 8 configurations: in person, high-definition video with slow motion review, standard-definition videos with varying bandwidths and frame rates (768 kilobytes per second [kbps] videos at 8, 15, and 30 frames per second [fps], 30 fps videos at 128, 384, and 768 kbps). SettingMedical center. ParticipantsPatients with limitations (N=45) in ≥1 of 3 specific aspects of motor function: fine motor coordination, gross motor coordination, and gait and balance. InterventionsNot applicable. Main Outcomes MeasuresAbility to rate the BBS in person and using videos with differing bandwidths and frame rates in frontal and lateral views. ResultsCompared with in-person rating (7%), 18% (P=.29) of high-definition videos and 37% (P=.03) of standard-definition videos could not be rated. Interrater reliability for the high-definition videos was .96 (95% confidence interval, .94–.97). Rating failure proportions increased from 20% in videos with the highest bandwidth to 60% (P<.001) in videos with the lowest bandwidth, with no significant differences in proportions across frame rate categories. Both frontal and lateral views were critical for successful rating using videos, with 60% to 70% (P<.001) of videos unable to be rated on a single view. ConclusionsAlthough there is some loss of information when using videos to rate the BBS compared to in-person ratings, it is feasible to reliably rate the BBS remotely in standard clinical spaces. However, optimal video rating requires frontal and lateral views for each assessment, high-definition video with high bandwidth, and the ability to carry out slow motion review.

Change of transmission characteristics of FSSs in hybrid composites due to residual stresses

The frequency selective surface (FSS) embedded hybrid composite materials have been developed to provide excellent mechanical and specific electromagnetic properties. Radar absorbing structures (RASs) are an example material that provides both radar absorbing properties and structural characteristics. The absorbing efficiency of an RAS can be improved using selected materials having special absorptive properties and structural characteristics and can be in the form of multi-layers or have a certain stacking sequence. However, residual stresses occur in FSS embedded composite structures after co-curing due to a mismatch between the coefficients of thermal expansion of the FSS and the composite material. In this study, to develop an RAS, the thermal residual stresses of FSS embedded composite structures were analyzed using finite element analysis, considering the effect of stacking sequence of composite laminates with square loop (SL) and double square loop (DSL) FSS patterns. The FSS radar absorbing efficiency was measured in the K-band frequency range of 21.6 GHz. Residual stress leads to a change in the deformation of the FSS pattern. Using these results, the effect of transmission characteristics with respect to the deformation on FSS pattern was analyzed using an FSS Simulator.

Transmission Errors and Forward Error Correction in Embedded Differential Pulse Code Modulation

We have derived formulas for the combined effects of quantization and transmission errors on the performance of embedded Differential Pulse Code Modulation (DPCM), a source code that can be used for variable-bit-rate speech transmission. Our analysis is more general and more precise than previous work on transmission errors in digital communication of analog signals. Special cases include conventional DPCM and Pulse Code Modulation (PCM). Our main result is a signal-to-noise ratio formula in which the effects of source characteristics (input signal, codec design parameters) and the effects of transmission characteristics (modulation, channel, forward error correction) are clearly distinguishable. We also present, in computationally convenient forms, specialized formulas that apply to uncoded transmission through a random-error channel, transmission through a slowly fading channel, and transmission with part or all of the DPCM signal protected by an error-correcting code. Numerical results show how channel coding can have different effects on conventional and embedded DPCM. They also show how the binary-number representation of quantizer outputs influences performance.