On the Peak-to-Mean Envelope Power Ratio of Phase-Shifted Binary Codes

The peak-to-mean envelope power ratio (PMEPR) of a code employed in orthogonal frequency-division multiplexing (OFDM) systems can be reduced by permuting its coordinates and by rotating each coordinate by a fixed phase shift. Motivated by some previous designs of phase shifts using suboptimal methods, the following question is considered in this paper. For a given binary code, how much PMEPR reduction can be achieved when the phase shifts are taken from a 2^h-ary phase-shift keying (2^h-PSK) constellation? A lower bound on the achievable PMEPR is established, which is related to the covering radius of the binary code. Generally speaking, the achievable region of the PMEPR shrinks as the covering radius of the binary code decreases. The bound is then applied to some well understood codes, including nonredundant BPSK signaling, BCH codes and their duals, Reed-Muller codes, and convolutional codes. It is demonstrated that most (presumably not optimal) phase-shift designs from the literature attain or approach our bound.Comment: minor revisions, accepted for IEEE Trans. Commun

Multi-Moji: Combining Thermal, Vibrotactile and Visual Stimuli to Expand the Affective Range of Feedback

This paper explores the combination of multiple concurrent modalities for conveying emotional information in HCI: temperature, vibration and abstract visual displays. Each modality has been studied individually, but can only convey a limited range of emotions within two-dimensional valencearousal space. This paper is the first to systematically combine multiple modalities to expand the available affective range. Three studies were conducted: Study 1 measured the emotionality of vibrotactile feedback by itself; Study 2 measured the perceived emotional content of three bimodal combinations: vibrotactile + thermal, vibrotactile + visual and visual + thermal. Study 3 then combined all three modalities. Results show that combining modalities increases the available range of emotional states, particularly in the problematic top-right and bottom-left quadrants of the dimensional model. We also provide a novel lookup resource for designers to identify stimuli to convey a range of emotions

Knowledge management in the voluntary sector: A focus on sharing project know-how and expertise

Voluntary sector organisations are operated principally by volunteers who are not obliged to share their knowledge, as might be expected in a for profit company, with a greater consequent loss of knowledge should individuals leave. This research examines how a volunteer-led organisation, the Campaign for Real Ale (CAMRA), acquires, stores and shares its project knowledge in the context of event management. Three annual CAMRA festivals of different sizes and maturity were selected to see how volunteers' knowledge is managed in the process of organising their festivals. Key festival officers were interviewed and focus groups, comprising of festival volunteers, were conducted. While the maturity of a festival and its size seemed to influence the ways in which knowledge was managed there were some commonalities between festivals. Evident was a strong master-apprentice model of learning with little formal training or record keeping except, that is, where legislation and accountability in treasury and health and safety functions were necessary. Trust between volunteers and their need to know and to share information appeared to be dependent, in part, on their perception and confidence in the success of the overarching project organisation, and this helped shape volunteers' knowledge sharing practices. Whilst there was evidence of a laissez-faire approach to codification and the sharing of knowledge, this was less so when volunteers recognised a genuine lack of knowledge which would hinder the success of their festival. The analysis also highlighted factors related to the sharing of knowledge that, it is suggested, have not been identified in the for-profit sector