Multiuser dual-hop relaying over hybrid RF/FSO links

The performance of multiuser dual-hop relaying over mixed radio frequency/free-space optical (RF/FSO) links is investigated. RF links are used for the simultaneous data transmission from m single-antenna sources to the relay, which is equipped with n ≥ m receive antennas and a photo-aperture transmitter. The relay operates under the decode-and-forward protocol and utilizes the popular ordered V-BLAST technique to successively decode each user's transmitted stream. A common norm-based ordering approach is adopted, where the streams are decoded in an ascending order. After the V-BLAST decoding, the relay retransmits the initial information to the destination, which is equipped with a photo-detector, via a point-to-point FSO link in m consecutive timeslots. Analytical expressions for the end-to-end outage probability and average symbol error probability of each user are derived. Some engineering insights are manifested, such as the diversity order, the impact of the pointing error displacement on the FSO link and the severity on the turbulence-induced channel fading.

Finding a Scientific Voice: Performing Science, Space and Speech in the Nineteenth Century

Taking as a point of departure recent scholarly interest in the geographies of spoken communication, this paper situates the cultivation of a scientific voice in a range of nineteenth-century contexts and locations. An examination of two of the century’s most celebrated science lecturers, Michael Faraday and Thomas Henry Huxley, offers a basis for more general claims about historical relations between science, speech and space. The paper begins with a survey of the ‘ecologies’ of public speaking in which advocates of science sought to carve out an effective niche. It then turns to a reconstruction of the varying and variously interpreted assumptions about authoritative and authentic speech that shaped how the platform performances of Faraday and Huxley were constructed, contested and remediated in print. Particular attention is paid to sometimes clashing ideals of vocal performance and paralinguistic communication. This signals an interest in the performative 2 dimensions of science lectures rather more than their specific cognitive content. In exploring these concerns, the paper argues that ‘finding a scientific voice’ was a fundamentally geographical enterprise driven by attempts to make science resonate with a wider oratorical culture without losing distinctive appeal and special authority