2,385 research outputs found
Successive Local and Successive Global Omniscience
This paper considers two generalizations of the cooperative data exchange
problem, referred to as the successive local omniscience (SLO) and the
successive global omniscience (SGO). The users are divided into nested
sub-groups. Each user initially knows a subset of packets in a ground set
of size , and all users wish to learn all packets in . The users exchange
their packets by broadcasting coded or uncoded packets. In SLO or SGO, in the
th () round of transmissions, the th smallest sub-group
of users need to learn all packets they collectively hold or all packets in
, respectively. The problem is to find the minimum sum-rate (i.e., the total
transmission rate by all users) for each round, subject to minimizing the
sum-rate for the previous round. To solve this problem, we use a
linear-programming approach. For the cases in which the packets are randomly
distributed among users, we construct a system of linear equations whose
solution characterizes the minimum sum-rate for each round with high
probability as tends to infinity. Moreover, for the special case of two
nested groups, we derive closed-form expressions, which hold with high
probability as tends to infinity, for the minimum sum-rate for each round.Comment: Accepted for publication in Proc. ISIT 201
A Practical Approach for Successive Omniscience
The system that we study in this paper contains a set of users that observe a
discrete memoryless multiple source and communicate via noise-free channels
with the aim of attaining omniscience, the state that all users recover the
entire multiple source. We adopt the concept of successive omniscience (SO),
i.e., letting the local omniscience in some user subset be attained before the
global omniscience in the entire system, and consider the problem of how to
efficiently attain omniscience in a successive manner. Based on the existing
results on SO, we propose a CompSetSO algorithm for determining a complimentary
set, a user subset in which the local omniscience can be attained first without
increasing the sum-rate, the total number of communications, for the global
omniscience. We also derive a sufficient condition for a user subset to be
complimentary so that running the CompSetSO algorithm only requires a lower
bound, instead of the exact value, of the minimum sum-rate for attaining global
omniscience. The CompSetSO algorithm returns a complimentary user subset in
polynomial time. We show by example how to recursively apply the CompSetSO
algorithm so that the global omniscience can be attained by multi-stages of SO
Cooperative Data Exchange based on MDS Codes
The cooperative data exchange problem is studied for the fully connected
network. In this problem, each node initially only possesses a subset of the
packets making up the file. Nodes make broadcast transmissions that are
received by all other nodes. The goal is for each node to recover the full
file. In this paper, we present a polynomial-time deterministic algorithm to
compute the optimal (i.e., minimal) number of required broadcast transmissions
and to determine the precise transmissions to be made by the nodes. A
particular feature of our approach is that {\it each} of the
transmissions is a linear combination of {\it exactly} packets, and we
show how to optimally choose the value of We also show how the
coefficients of these linear combinations can be chosen by leveraging a
connection to Maximum Distance Separable (MDS) codes. Moreover, we show that
our method can be used to solve cooperative data exchange problems with
weighted cost as well as the so-called successive local omniscience problem.Comment: 21 pages, 1 figur
Compressed Secret Key Agreement: Maximizing Multivariate Mutual Information Per Bit
The multiterminal secret key agreement problem by public discussion is
formulated with an additional source compression step where, prior to the
public discussion phase, users independently compress their private sources to
filter out strongly correlated components for generating a common secret key.
The objective is to maximize the achievable key rate as a function of the joint
entropy of the compressed sources. Since the maximum achievable key rate
captures the total amount of information mutual to the compressed sources, an
optimal compression scheme essentially maximizes the multivariate mutual
information per bit of randomness of the private sources, and can therefore be
viewed more generally as a dimension reduction technique. Single-letter lower
and upper bounds on the maximum achievable key rate are derived for the general
source model, and an explicit polynomial-time computable formula is obtained
for the pairwise independent network model. In particular, the converse results
and the upper bounds are obtained from those of the related secret key
agreement problem with rate-limited discussion. A precise duality is shown for
the two-user case with one-way discussion, and such duality is extended to
obtain the desired converse results in the multi-user case. In addition to
posing new challenges in information processing and dimension reduction, the
compressed secret key agreement problem helps shed new light on resolving the
difficult problem of secret key agreement with rate-limited discussion, by
offering a more structured achieving scheme and some simpler conjectures to
prove
Death on the Freeway: Imaginative resistance as narrator accommodation
We propose to analyze well-known cases of "imaginative resistance" from the philosophical literature (Gendler, Walton, Weatherson) as involving the inference that particular content should be attributed to either: (i) a character rather than the narrator or, (ii) an unreliable, irrational, opinionated, and/or morally deviant "first person" narrator who was originally perceived to be a typical impersonal, omniscient, "effaced" narrator. We model the latter type of attribution in terms of two independently motivated linguistic mechanisms: accommodation of a discourse referent (Lewis, Stalnaker, Kamp) and 'cautious' updating as a model of non-cooperative information exchange (Eckardt)
Investing in Realism: An Interview with Bruce Robbins
No abstract (available)
'Islamic fatalism': life and suffering among Bangladeshi psychiatric patients and their families in London--an interview study 2
An interview study of 44 Bangladeshi patients and relatives in eastern London demonstrated frequent appeals to God and deprecation of personal agency. This paper offers an interpretation of this apparent 'fatalism', which argues for the logical downplaying of human agency and ambition in archaic Arabia, contemporary rural Sylhet and among first generation Sylheti migrants in London
- …