Distortion exponent with side-information diversity

The joint source-channel coding problem of sending a Gaussian source with minimum average end-to-end distortion over a time-varying fading channel with time-varying correlated side information at the decoder is studied. A block fading model for both the channel and the side information qualities is considered. Perfect state information of the channel and the side information states is assumed at the receiver, while the transmitter has only a statistical knowledge. The performance is measured in terms of the distortion exponent, which quantifies the exponential decay rate of the expected distortion at high SNR. The effects on the distortion exponent of the bandwidth ratio, the side information quality and the side information diversity are analysed. Two upper bounds on the distortion exponent are derived by providing different channel state information to the encoder, and lower bounds are presented based on separate source and channel coding, joint decoding, uncoded transmission and hybrid digital-analog transmission schemes. In particular, the optimal distortion exponent is characterized in certain regimes by showing that hybrid analog-digital transmission or joint decoding schemes meet the optimal performance. \ua9 2013 IEEE

Early warning signs of a mental health tsunami: a coordinated response to gather initial data insights from multiple digital services providers

Introduction: The immediate impact of COVID-19 on morbidity and mortality has raised the need for accurate and real time data monitoring and communication. The aim of this study is to document initial observations from multiple digital services providers during the COVID-19 crisis, especially those related to mental health and wellbeing. Methods: We used email and social media to announce an urgent call for support. Digital mental health services providers (N=46), financial services providers (N=4) and other relevant digital data source providers (N=3) responded with quantitative and/or qualitative data insights. People with lived experience of distress, as service users/consumers, and carers are included as co-authors. Results: This study provides proof-of-concept of the viability for researchers and private companies to work collaboratively towards a common good. Digital services providers reported a diverse range of mental health concerns. A recurring observation is that demand for digital mental health support has risen, and that the nature of this demand has also changed since COVID-19, with an apparent increased presentation of anxiety and loneliness. Conclusion: Following this study, we will continue to work with providers in more in-depth ways to capture follow-up insights at regular time points. We will also onboard new providers to address data representativeness. Looking ahead, we anticipate the need for a rigorous process to interpret insights from an even wider variety of sources in order to monitor and respond to mental health needs