6,935 research outputs found
Rate-adaptive modulation for square OSTBCs in arbitrarily correlated Rayleigh fading with imperfect channel estimation
No full textMultiple-input multiple-output (MIMO) systems employing adaptive modulation have been widely used for their potential to optimize the spectral efficiency while keeping the bit error probability (BEP) under a certain target level. In this paper, we examine a MIMO system using square orthogonal spacetime block codes (OSTBCs) with rate-adaptive M-QAM and operating over arbitrarily correlated Rayleigh fading channels with imperfect channel estimation. Assuming finite-rate feedback without delay, we derive accurate closed-form expressions for the average BEP, spectral efficiency and bit error outage of our system. The presented expressions allow to easily study the impact of channel estimation errors and fading correlation on the performance of rate-adaptive MIMO OSTBC systems
The Future of Canadian Climate Policy — with Marc Lee
No full textMarc Lee is a Senior Economist at the Canadian Centre for Policy Alternatives\u27 BC Office. In addition to tracking federal and provincial budgets and economic trends, Marc has published on a range of topics from poverty and inequality to globalization and international trade to public services and regulation. Marc is the Co-Director of the Climate Justice Project, a research partnership with UBC\u27s School of Community and Regional Planning that examines the links between climate change policies and social justice.Resources:Climate Justice Project: www.policyalternatives.ca/projects/cli…tice-projectMarc Lee\u27s Posts on Policy Note: www.policynote.ca/author/marclee/Canadian Centre for Policy Alternatives: www.policyalternatives.ca/Marc\u27s Twitter: twitter.com/MarcLeeCCPA International Panel on Climate Change, 2021 report: www.ipcc.ch/report/ar6/wg1
Climate Justice & Inequality: The Future of Canadian Climate Policy — with Marc Lee
No full textMarc Lee is a Senior Economist at the Canadian Centre for Policy Alternatives\u27 BC Office. In addition to tracking federal and provincial budgets and economic trends, Marc has published on a range of topics from poverty and inequality to globalization and international trade to public services and regulation. Marc is the Co-Director of the Climate Justice Project, a research partnership with UBC\u27s School of Community and Regional Planning that examines the links between climate change policies and social justice.Resources: Climate Justice Project: https://www.policyalternatives.ca/projects/climate-justice-projectMarc Lee\u27s Posts on Policy Note: https://www.policynote.ca/author/marclee/Canadian Centre for Policy Alternatives: https://www.policyalternatives.ca/Marc\u27s Twitter: https://twitter.com/MarcLeeCCPA International Panel on Climate Change, 2021 report: https://www.ipcc.ch/report/ar6/wg1
Comparison of Reed-Solomon and Raptor codes for the protection of Video On-Demand on the erasure channel
No full textStreaming on-demand video services can be provided to an end user by transmitting video data as a sequence of Internet Protocol (IP) packets over the network. In order to maintain a sufficient video quality at the end user, video packets must be protected against erasures by means of a suitable form of error control. In this contribution we make a comparison of 2 classes of Forward Error Correction (FEC) codes: the Reed-Solomon (RS) codes and the Raptor codes. We present the decoding complexity analysis of these codes and compare their erasure decoding performance. For a given decoding complexity, the codewords of the Raptor code can be taken much longer than those of the RS code, because the decoding of the former code involves only XOR operations. For a performance target of less than one decoding error event in 4 hours, a video bitrate of 7.3 Mbit/s, a latency constraint of 10 seconds and a transmission overhead of 20%, equal erasure probabilities at the decoder input are allowed for the RS(254,212) code and for the Raptor code of size (8760,7300), whereas this RS code has a 12 times higher decoding complexit
UKMARC AMC: Draft Rev 4.0: UK MARC format for archives and manuscripts control (UK MARC AMC)
No full textThis draft is the first attempt to establish a UK MARC specifically for Archives and Manuscripts Control since the British Library indicated that it would countenance such extensions to the national UK MARC format. In order to keep consistency with the general UK MARC format, standard UK MARC subject fields are not included in this document, since they should be taken from the latest version of the UK MARC manual. {A note of them should perhaps be included in UK MARC AMC.} {NB Text in braces is intended to be explanatory material for readers of this draft}. Certain other fields have not been included that might occasionally be used in the cataloguing of archival materials but would generally only be used for such materials in organizations which were combining archive
databases with library databases. This MARC version is intended for use with descriptions of archive or anuscript material that follow, or fit, the traditional style of cataloguing: we assume that these will normally relate
to paper or parchment originals. It is not intended for use with descriptions of other kinds of material. For these, fields may be drawn from the appropriate UK MARC document. MARC versions for use with archives in special formats should be developed, in order to complete the full range of facilities available to archivists and curators
MARC 21 para recursos contínuos
No full textTranslation and adaptation of the MARC 21 Format for Bibliographic Data, and MARC 21 Format for Holdings Data, Network Development and MARC Standards Office, Library of Congress, USA, by Angela Salles. Rio de Janeiro, 2010. 2 v. V.1 MARC 21 format for bibliographic data (updated until October 2010). V.2 MARC 21 format for data collection (Holdings) (updated until October 2008)
Outage probability minimization for cooperative cognitive radio with best-relay selection under an average interference power constraint
No full textIn this contribution, a cognitive radio scenario is considered, where a secondary user (SU) cooperative network is allowed to transmit concurrently with a primary user (PU), provided that the resulting average interference power at the PU receiver is kept below a certain threshold. The SU network uses a selection amplify-and-forward protocol. An optimum and a low-complexity suboptimum dynamic energy allocation strategy are proposed, that minimize the link outage probability between the source node and the destination node of the SU network under an average interference power constraint. Because the interference channels from the SU nodes to the PU are affected by fast fading, the realistic assumption is made that each SU node has access to the root mean-square value (rather than the instantaneous value) of the gain of its own interference channel to the PU. We show that both dynamic allocation strategies considerably outperform the optimum static allocation strategy, and that the low-complexity dynamic allocation performs nearly as well as the optimum dynamic allocation. Finally, we confirm that our dynamic algorithms show a significant performance improvement as compared to the optimal dynamic algorithm under a peak interference power constraint
MARC 21 para recursos contínuos.
No full textTradução e adaptação de MARC 21 Format for Bibliographic Data e MARC 21 Format for Holdings Data, da Network Development and MARC Standards Office, da Library of Congress, USA, por Angela Salles
Friends of the Greenwood Library Presents Marc Leepson
No full textOn Tuesday, September 11, 2012 the Friends of the Janet D. Greenwood Library hosted its fall event, which featured an evening with Marc Leepson. Leepson is a journalist, historian and the author of seven books, including Lafayette: Lessons in Leadership from the Idealist General (Palgrave/Macmillan, 2011), a concise biography of the famed Marquis de Lafayette
Analysis of challenge-response authentication with reconfigurable intelligent surfaces
No full textPhysical-layer authentication (PLA) mechanisms exploit
signals exchanged at the physical layer of communication
systems to confirm the sender of a received message. In this
paper, we propose a novel challenge-response PLA (CR-PLA)
mechanism for a cellular system that leverages the reconfigurability
property of a reconfigurable intelligent surface (RIS) (under
the control of the verifier) in an authentication mechanism. In
CR-PLA, the verifier base station (BS) sets a random RIS configuration,
which remains secret to the intruder, and then checks
that the resulting estimated channel is modified correspondingly.
In fact, for a message sent by an attacker in a different location
than the legitimate user equipment (UE), the BS will estimate a
different channel and the message will be rejected as fake. Such a
solution reduces the communication and computational overhead
with respect to higher-layer cryptographic authentication. We
derive the maximum a-posteriori attack when the attacker
observes a correlated channel and the reconfigurable intelligent
surface (RIS) has many elements, and the attacker transmits
to Bob either directly or through the RIS. Using a generalized
likelihood ratio test to test the authenticity at the base station
(BS), we derive approximate expressions of the false alarm
and misdetection probabilities when both the BS and the UE
have a single antenna each, while the RIS has a large number
of elements. We also evaluate the trade-off between security
and communication performance, since choosing a random RIS
configuration reduces the data rate. Moreover, we investigate
the impact of various parameters (e.g., the RIS randomness, the
number of RIS elements, and the operating signal-to-noise ratio)
on security and communication performance
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