Wideband Sequential Spectrum Sensing with Varying Thresholds

In this contribution, time varying threshold sequential detectors are employed for energy detection-based spectrum sensing in low-SNR regimes. Sequential detection is proven to be faster (on average) than any other multi-sample detector for a set of given probabilities of detection and false-alarm. In this report, exact performance of a sequential detector for spectrum sensing is analyzed using the direct method. The theoretical results presented herein are verified with Monte-Carlo simulations. It is shown that for a SNR of −10 dB, among tests with Wald and triangular thresholds with similar probabilities of mis-detection and false-alarm, triangular performs 54% faster in terms of maximum detection time (90 percentile)

Valuation of small and multiple health risks: A critical analysis of SP data applied to food and water safety

This study elicits individual preferences for reducing morbidity and mortality risk in the context of an infectious disease (campylobacter) using choice experiments. Respondents are in the survey asked to choose between different policies that, in addition to the two health risks, also vary with respect to source of disease being targeted (food or water), when the policy takes place (in time), and the monetary cost. Our results in our baseline model are in line with expectations; respondents prefer the benefits of the program sooner than later, programs that reduce both the mortality and morbidity risk, and less costly programs. Moreover, our results suggest that respondents prefer water- compared with food-safety programs. However, a main objective of this study is to examine scope sensitivity of mortality risk reductions using a novel approach. Our results from a split-sample design suggest that the value of the mortality risk reduction, defined as the value of a statistical life, is SEK 3 177 (USD 483 million) and SEK 50 million (USD 8 million), respectively, in our two sub-samples. This result cast doubt on the standard scope sensitivity tests in choice experiments, and the results also cast doubt on the validity and reliability of VSL estimates based on stated preference (and revealed preference) studies in general. This is important due to the large empirical literature on non-market evaluation and the elicited values’ central role in policy making, such as benefit-cost analysis

Frequency Diversity Performance of Coded Multiband-OFDM Systems on IEEE UWB Channels

This paper investigates how convolutional and Reed-Solomon codes can be used to improve the performance of multiband-OFDM by utilizing the inherent frequency diversity of the new IEEE 802.15 UWB channel models. A normalized amplitude autocovariance function of the Fourier transform of the channel impulse response is defined. Then the average coherence bandwidths of CM1, CM2, CM3, and CM4 are estimated to be 31.6, 16.3, 11.0, 5.8 MHz, respectively. Using the central limit theorem, we can expect that the performance of an uncoded OFDM system on CM1-CM4 without shadowing is the same as in a Rayleigh fading channel with uniformly distributed phase. The performance of a convolutional code with rate 1/2 and constraint length 7 on CM2-CM4 without shadowing are up to 0.4 dB worse than that of on an uncorrelated Rayleigh fading channel. The loss for CM1 is around 1 dB. A block interleaver with 32 rows and 24 columns was used. This result is also valid for a convolutional code with rate 1/4 and constraint length 7. For code rates around 2/3, the performance of a punctured convolutional code with soft-decision decoding is much better than that of the Reed-Solomon codes with with 6, 7, and 8 bits per symbol and hard-decision decoding

Valuation of small and multiple health risks: A critical analysis of SP data applied to food and water safety

This study elicits individual preferences for reducing morbidity and mortality risk in the context of an infectious disease (campylobacter) using choice experiments. Respondents are in the survey asked to choose between different policies that, in addition to the two health risks, also vary with respect to source of disease being targeted (food or water), when the policy takes place (in time), and the monetary cost. Our results in our baseline model are in line with expectations; respondents prefer the benefits of the program sooner than later, programs that reduce both the mortality and morbidity risk, and less costly programs. Moreover, our results suggest that respondents prefer water- compared with food-safety programs. However, a main objective of this study is to examine scope sensitivity of mortality risk reductions using a novel approach. Our results from a split-sample design suggest that the value of the mortality risk reduction, defined as the value of a statistical life, is SEK 3 177 (USD 483 million) and SEK 50 million (USD 8 million), respectively, in our two sub-samples. This result cast doubt on the standard scope sensitivity tests in choice experiments, and the results also cast doubt on the validity and reliability of VSL estimates based on stated preference (and revealed preference) studies in general. This is important due to the large empirical literature on non-market evaluation and the elicited values’ central role in policy making, such as benefit-cost analysis

Valuation of small and multiple health risks: A critical analysis of SP data applied to food and water safety

This study elicits individual preferences for reducing morbidity and mortality risk in the context of an infectious disease (campylobacter) using choice experiments. Respondents are in the survey asked to choose between different policies that, in addition to the two health risks, also vary with respect to source of disease being targeted (food or water), when the policy takes place (in time), and the monetary cost. Our results in our baseline model are in line with expectations; respondents prefer the benefits of the program sooner than later, programs that reduce both the mortality and morbidity risk, and less costly programs. Moreover, our results suggest that respondents prefer water- compared with food-safety programs. However, a main objective of this study is to examine scope sensitivity of mortality risk reductions using a novel approach. Our results from a split-sample design suggest that the value of the mortality risk reduction, defined as the value of a statistical life, is SEK 3 177 (USD 483 million) and SEK 50 million (USD 8 million), respectively, in our two sub-samples. This result cast doubt on the standard scope sensitivity tests in choice experiments, and the results also cast doubt on the validity and reliability of VSL estimates based on stated preference (and revealed preference) studies in general. This is important due to the large empirical literature on non-market evaluation and the elicited values’ central role in policy making, such as benefit-cost analysis

Unequal Error Protection in BICM with QAM Constellations: Interleaver and Code Design

In this paper we present a general methodology for the interleaver and code design for QAM-based BICM transmissions. We develop analytical bounds on the bit error rate and we use them to predict the performance of BICM when unequal error protection (UEP) is introduced by the constellation labeling. Based on these bounds, the optimum design of interleaver and code is presented. The improvements obtained reached 2~dB for the analyzed cases, and are obtained without complexity increase. Although previous works noted the influence of the interleaver design and the UEP, to the best of our knowledge, this paper is the first to analyze formally this problem for BICM transmissions