Additional Information Bits Research Articles

On beamforming with finite rate feedback in multiple-antenna systems

We study a multiple-antenna system where the transmitter is equipped with quantized information about instantaneous channel realizations. Assuming that the transmitter uses the quantized information for beamforming, we derive a universal lower bound on the outage probability for any finite set of beamformers. The universal lower bound provides a concise characterization of the gain with each additional bit of feedback information regarding the channel. Using the bound, it is shown that finite information systems approach the perfect information case as (t-1)2/sup -B/t-1/, where B is the number of feedback bits and t is the number of transmit antennas. The geometrical bounding technique, used in the proof of the lower bound, also leads to a design criterion for good beamformers, whose outage performance approaches the lower bound. The design criterion minimizes the maximum inner product between any two beamforming vectors in the beamformer codebook, and is equivalent to the problem of designing unitary space-time codes under certain conditions. Finally, we show that good beamformers are good packings of two-dimensional subspaces in a 2t-dimensional real Grassmannian manifold with chordal distance as the metric.

Reducing peak-to-average power ratio using simple transformed CDMA/OFDM signals

A simple peak-to-average power ratio (PAR) reduction scheme using a symbol transform in CDMA/OFDM based transmission systems is presented. This approach is very simple because there is no additional complexity and works with arbitrary numbers of subcarriers and without restriction on the allocation of spreading code, maintaining the original transmission efficiency. Further PAR reduction can be explored by modifying the selective mapping approach at the expense of additional side information bits, which gives nearly same transmitter complexity.

On the value of information in multi-agent decision theory

Several agents, each with his own opinion (probability measure), make decisions in order to maximize their expected utility. A super partes person, ‘the chief’, releases information with the goal of maximizing a social expected utility, which is an increasing function of the agents' utilities. Additional bits of information are individually beneficial to each agent, but might be socially detrimental if the social utility is concave and therefore diversification is valuable. In this paper, information is modeled by filtrations on a suitable probability space, and the problem of establishing how much information ought to be released is tackled. Two situations are examined, in which the chief either updates or does not update her opinion.

Evidence for an attentional model of human intelligence using the competing task paradigm

The present study examined competing task performance within an information theory framework. In the first experiment, 72 subjects performed a card-sorting task at four levels of task difficulty (0-bit, 1-bit, 2-bit and 3-bit levels) under both single and competing task conditions. Output per 60 sec was measured for each task. In the second experiment, estimates of fluid and crystalized ability, as well as short-term acquisition and retrieval, were obtained from 68 subjects who performed the same tasks as the subjects in Experiment 1. The results of the first experiment suggested the rate of processing remains invariant under both single and competing task conditions with the latter condition being readily interpreted as introducing an additional bit of information. The introduction of the competing condition also led to higher correlation between processing parameters and G f (but not G c or SAR) marker tests. The implication of these findings for cognitive models of human ability is discussed.

Forensic demography and civil rights

In the summer of 1965, the legislature of the state of Mississippi passed a law which required children whose parents were living in another state to pay up to $350 tuition in order to attend public school. On the belief that this law discriminated against Negroes and was therefore unconstitutional, the Department of Justice began litigation procedures to repeal it. But evidence was needed to prove that the law was in fact discriminatory. The lawyers contacted demographers at the Bureau of the Census to provide data to determine if the majority of persons affected were Negro and too poor to pay the tuition. They sought information which could tell them, ideally, how many parents of children in Mississippi had left the state and what the economic position and racial characteristics of the children were.An attempt was made to get this information from already published sources, such as census reports and other research findings. These could give a hurried impression of the situation but could not deal directly with the issue of the whereabouts of parents not living with their children, since such a question had not been asked in the 1960 Census. An additional bit of information was obtained from the NAAGP Legal Defense and Education Fund in Jackson, Mississippi, from forms showing characteristics of persons actually affected by the law. But this limited sample did not provide evidence solid enough upon which to build a case.It was decided to rely on a retabulation of 1960 Census records to describe accurately the base population from which children with parents out of state would be drawn-namely, the children not living with either parent. This showed that of all school-age children living without either parent, 82 percent are Negro. The average Negro household, which contains at least one "parentless" child, houses 6.8 persons and has an annual income of $1,429. This allows less than $250 annually per person. Tuition for just one child eats up more than one person's yearly allotment. These data showed that the law, in fact, did discriminate racially, since most of the persons affected were Negro and too poor to pay tuition.This was one instance in which demographers were able to use their special skills in implementing public policy-notably, the law.

Studies on Picasso, 1902-1905

The documentation on the early years of Picasso in Paris is still quite sparse, and additional bits of information are always welcome. We have come across several reviews of expositions in 1902 and 1905 which have apparently escaped the eyes of the biographers and which help in a modest way to fill the gaps in our knowledge of the beginning and the end of the Blue Period. The standard works on Picasso suggest that between the review by Felicien Fagus of the first, 1901 show at Vollard's (“L'Invasion espagnole: Picasso,” La Revue blanche, 15 July, 1901)1 and Apollinaire's essay in 1905 (“Les jeunes: Picasso peintre,” La Plume, 15 May, 1905) four years of total silence elapsed in Paris, whereas the studies which we present bring to light not only a greater number of expositions but also a more widespread interest in the young painter than one would have dared to assume.