Code diversity in multiple antenna wireless communication

The standard approach to the design of individual space-time codes is based on optimizing diversity and coding gains. This geometric approach leads to remarkable examples, such as perfect space-time block codes, for which the complexity of Maximum Likelihood (ML) decoding is considerable. Code diversity is an alternative and complementary approach where a small number of feedback bits are used to select from a family of space-time codes. Different codes lead to different induced channels at the receiver, where Channel State Information (CSI) is used to instruct the transmitter how to choose the code. This method of feedback provides gains associated with beamforming while minimizing the number of feedback bits. It complements the standard approach to code design by taking advantage of different (possibly equivalent) realizations of a particular code design. Feedback can be combined with sub-optimal low complexity decoding of the component codes to match ML decoding performance of any individual code in the family. It can also be combined with ML decoding of the component codes to improve performance beyond ML decoding performance of any individual code. One method of implementing code diversity is the use of feedback to adapt the phase of a transmitted signal as shown for 4 by 4 Quasi-Orthogonal Space-Time Block Code (QOSTBC) and multi-user detection using the Alamouti code. Code diversity implemented by selecting from equivalent variants is used to improve ML decoding performance of the Golden code. This paper introduces a family of full rate circulant codes which can be linearly decoded by fourier decomposition of circulant matrices within the code diversity framework. A 3 by 3 circulant code is shown to outperform the Alamouti code at the same transmission rate.Comment: 9 page

On the boundaries between good and evil: Constructing multiple moralities in China

This essay discusses three contrasting versions of the relationship between good and evil in contemporary China: a spirit medium who maneuvers between them, a charismatic Christian group that forges an identity by defending the border between them, and an official state and religious discourse of banal goodness and universal love that that seeks to annihilate evil. Each defines good and evil differently, but more importantly, each imagines the nature of the boundary itself differently – as permeable and negotiable, clear and defensible, or simply intolerable. These varied conceptions help to shape alternate views of empathy, pluralism, and the problem of how to live with otherness

Hydromechanics of low-Reynolds-number flow. Part 5. Motion of a slender torus

In order to elucidate the general Stokes flow characteristics present for slender bodies of finite centre-line curvature the singularity method for Stokes flow has been employed to construct solutions to the flow past a slender torus. The symmetry of the geometry and absence of ends has made a highly accurate analysis possible. The no-slip boundary condition on the body surface is satisfied up to an error term of O(E^2 ln E), where E is the slenderness parameter (ratio of cross-sectional radius to centre-line radius). This degree of accuracy makes it possible to determine the force per unit length experienced by the torus up to a term of O(E^2). A comparison is made between the force coefficients of the slender torus to those of a straight slender body to illustrate the large differences that may occur as a result of the finite centre-line curvature

Photon sputtering of H2O ices: A preliminary report

A preliminary measurement of the total yields of ejected ions and electrons from H2O ices has been carried out using the He I 584 A resonance line as the incident photon beam. The H2O ices were prepared at 77 K in an ultrahigh vacuum system. The total yield of the ejected ion species and electrons was determined to be 8.8x10(exp -5) and 4.2x10(exp -4), respectively