A New Low-Complexity Decodable Rate-5/4 STBC for Four Transmit Antennas with Nonvanishing Determinants

The use of Space-Time Block Codes (STBCs) increases significantly the optimal detection complexity at the receiver unless the low-complexity decodability property is taken into consideration in the STBC design. In this paper we propose a new low-complexity decodable rate-5/4 full-diversity 4 x 4 STBC. We provide an analytical proof that the proposed code has the Non-Vanishing-Determinant (NVD) property, a property that can be exploited through the use of adaptive modulation which changes the transmission rate according to the wireless channel quality. We compare the proposed code to the best existing low-complexity decodable rate-5/4 full-diversity 4 x 4 STBC in terms of performance over quasi-static Rayleigh fading channels, worst- case complexity, average complexity, and Peak-to-Average Power Ratio (PAPR). Our code is found to provide better performance, lower average decoding complexity, and lower PAPR at the expense of a slight increase in worst-case decoding complexity.Comment: 5 pages, 2 figures and 1 table; IEEE Global Telecommunications Conference (GLOBECOM 2011), 201

A Novel Construction of Multi-group Decodable Space-Time Block Codes

Complex Orthogonal Design (COD) codes are known to have the lowest detection complexity among Space-Time Block Codes (STBCs). However, the rate of square COD codes decreases exponentially with the number of transmit antennas. The Quasi-Orthogonal Design (QOD) codes emerged to provide a compromise between rate and complexity as they offer higher rates compared to COD codes at the expense of an increase of decoding complexity through partially relaxing the orthogonality conditions. The QOD codes were then generalized with the so called g-symbol and g-group decodable STBCs where the number of orthogonal groups of symbols is no longer restricted to two as in the QOD case. However, the adopted approach for the construction of such codes is based on sufficient but not necessary conditions which may limit the achievable rates for any number of orthogonal groups. In this paper, we limit ourselves to the case of Unitary Weight (UW)-g-group decodable STBCs for 2^a transmit antennas where the weight matrices are required to be single thread matrices with non-zero entries in {1,-1,j,-j} and address the problem of finding the highest achievable rate for any number of orthogonal groups. This special type of weight matrices guarantees full symbol-wise diversity and subsumes a wide range of existing codes in the literature. We show that in this case an exhaustive search can be applied to find the maximum achievable rates for UW-g-group decodable STBCs with g>1. For this purpose, we extend our previously proposed approach for constructing UW-2-group decodable STBCs based on necessary and sufficient conditions to the case of UW-g-group decodable STBCs in a recursive manner.Comment: 12 pages, and 5 tables, accepted for publication in IEEE transactions on communication

A New Low-Complexity Decodable Rate-1 Full-Diversity 4 x 4 STBC with Nonvanishing Determinants

Space-time coding techniques have become common-place in wireless communication standards as they provide an effective way to mitigate the fading phenomena inherent in wireless channels. However, the use of Space-Time Block Codes (STBCs) increases significantly the optimal detection complexity at the receiver unless the low complexity decodability property is taken into consideration in the STBC design. In this letter we propose a new low-complexity decodable rate-1 full-diversity 4 x 4 STBC. We provide an analytical proof that the proposed code has the Non-Vanishing-Determinant (NVD) property, a property that can be exploited through the use of adaptive modulation which changes the transmission rate according to the wireless channel quality. We compare the proposed code to existing low-complexity decodable rate-1 full-diversity 4 x 4 STBCs in terms of performance over quasi-static Rayleigh fading channels, detection complexity and Peak-to-Average Power Ratio (PAPR). Our code is found to provide the best performance and the smallest PAPR which is that of the used QAM constellation at the expense of a slight increase in detection complexity w.r.t. certain previous codes but this will only penalize the proposed code for high-order QAM constellations.Comment: 5 pages, 3 figures, and 1 table; IEEE Transactions on Wireless Communications, Vol. 10, No. 8, AUGUST 201

Why Are There So Many Divided Senate Delegations?

The last three decades have witnessed a sharp increase in the number of states with spilt Senate delegations, featuring two senators of different parties. In addition, there is evidence that senators of different parties do not cluster in the middle: they are genuinely polarized. We propose a model which explains this phenomenon. Our argument builds upon the fact that when a Senate election is held, there is already a sitting senator. If the voters care about the policy position of their state delegation in each election, they may favor the candidate of the party which is not holding the other seat. We show that, in general: (1) a candidate benefits if the non-running senator is of the opposing parry; (2) the more extreme the position of the non-running senator, the more extreme may be the position of the opposing party candidate. Our 'opposite party advantage' hypothesis is tested on a sample including every Senate race from 1946 to 1986. After controlling for other important factors, such as incumbency advantage, coattails end economic conditions, we find reasonably strong evidence of the 'opposite party advantage.'

The Breakdown of Representation in American Politics

Streaming video requires Flash Player, RealPlayer, or Windows Media Player to view.Morris P. Fiorina is the Wendt Family Professor of Political Science at Stanford University and a senior fellow of the Hoover Institution. Fiorina has written widely on American government and politics, with special emphasis on topics in the study of representation and elections.Ohio State University. Mershon Center for International Security StudiesEvent Web page, streaming video, event photo

Automatic best wireless network selection based on key performance indicators

Introducing cognitive mechanisms at the application layer may lead to the possibility of an automatic selection of the wireless network that can guarantee best perceived experience by the final user. This chapter investigates this approach based on the concept of Quality of Experience (QoE), by introducing the use of application layer parameters, namely Key Performance Indicators (KPIs). KPIs are defined for different traffic types based on experimental data. A model for an ap- plication layer cognitive engine is presented, whose goal is to identify and select, based on KPIs, the best wireless network among available ones. An experimenta- tion for the VoIP case, that foresees the use of the One-way end-to-end delay (OED) and the Mean Opinion Score (MOS) as KPIs is presented. This first implementation of the cognitive engine selects the network that, in that specific instant, offers the best QoE based on real captured data. To our knowledge, this is the first example of a cognitive engine that achieves best QoE in a context of heterogeneous wireless networks

Legislative Choice of Regulatory Forms: Legal Process or Administrative Process?

Perhaps because of the importance and visibility of some regulatory agencies and commissions, numerous observers have come to regard the administrative form of regulation as the “logical“ or “natural“ method of intervening in the economy or society. In fact, however, regulation comes in a variety of forms. The administrative form might seem all pervasive upon first consideration, but a variety of legislative enactments clearly regulatory in effect such as large portions of the tax code, direct government subsidies and so forth suggest that delegation of legislative authority to administrative entities is, not so universal as is often assumed. Moreover, when viewed in historical perspective, choice of bureaucratic implementation of regulatory programs does not obviously emerge as the “logical“ or “natural“ method, at least not in the view of many political actors of the late nineteenth and early twentieth centuries. This paper surveys a heterogeneous body of literature on the subject of regulatory origin in order to identify proposed explanations for legislative choice of administrative forms of regulation in preference to judicial enforcement of legislative enactments. The focus of the survey is on the choices made by legislators and the considerations underlying their choices. Among the latter are (1) beliefs in the inherent superiority of administrative forms, (2) efforts to escape the costs, political and otherwise, of regulating directly, (3) ideologies supportive of delegation to administrators, and (4) uncertainty about the future operation of the regulatory process. These ideas are examined in an exploratory spirit; no firm conclusions are drawn at this time

Legislative Facilitation of Government Growth: Universalism and Reciprocity Practices in Majority Rule Institutions

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