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— Given a multiple-antenna source and a multiple-antenna destination, a multiple-antenna relay between the source and the destination is desirable under useful circumstances. A non-regenerative multiple-antenna relay, also called non-regenerative MIMO (multi-input multi-output) relay, is designed to optimize the capacity between the source and the(More)
—The focus of this paper is an information-theoretic study of retransmission protocols for reliable packet communication under a secrecy constraint. The hybrid automatic retransmission request (HARQ) protocol is revisited for a block-fading wire-tap channel. Here, two legitimate users communicate over a block-fading channel in the presence of a passive(More)
—In this paper, we develop a unified framework for linear nonregenerative multicarrier multiple-input multiple output (MIMO) relay communications in the absence of the direct source–destination link. This unified framework classifies most commonly used design objectives such as the minimal mean-square error and the maximal mutual information into two(More)
Wireless communication is susceptible to eavesdropping attacks because of its broadcast nature. This paper illustrates how interference can be used to counter eavesdropping and assist secrecy. In particular, a wire-tap channel with a helping interferer (WT-HI) is considered. Here, a transmitter sends a confidential message to its intended receiver in the(More)
— Due to the broadcast nature of the wireless medium, wireless communication is susceptible to adversarial eavesdropping. This paper describes how eavesdropping can potentially be defeated by exploiting the superposition nature of the wireless medium. A Gaussian wire-tap channel with a helping interferer (WTC-HI) is considered in which a transmitter sends(More)
— This paper considers the problem of secret communication over a multiple access channel with generalized feedback. Two trusted users send independent confidential messages to an intended receiver, in the presence of a passive eavesdropper. In this setting, an active cooperation between two trusted users is enabled through using channel feedback in order(More)
BACKGROUND In China, the New Co-operative Medical System (NCMS), a rural health insurance system, has expanded nationwide since 2003. This study aims to describe prenatal care use, content and costs of care in one county where prenatal care is included in the NCMS and two counties where it is not. It also explores the perceptions of stakeholders of the(More)
— We study the block fading wire-tap channel, where a transmitter sends confidential messages to a legitimate receiver over a block fading channel in the presence of an eavesdropper, which listens to the transmission through another independent block fading channel. We assume that the transmitter has no channel state information (CSI) available from either(More)
if x 1 = 1 then for i from 1 to b(M + 2)=4c swap(y 4i03 ; y 4i02) if x 2 = 1 then for i from 1 to bM=4c swap(y 4i01 ; y 4i) for i from 1 to L 0 1 for j from 1 to 2 i if j M 0 2 i then if x j+2 = 1 then for k from 1 to b(M 0 j + 2 i)=2 i+1 c p = j + 2 i+1 (k 0 1) swap(yp; y p+2) end. This algorithm then produces mappings with the same jEj values as those(More)