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—The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last decade-both in academia and industry. Multiple antennas can be utilized in order to accomplish a multiplexing gain, a diversity gain, or an antenna gain, thus enhancing the bit rate, the error performance, or the(More)
The probabilistic data association (PDA) decoder is investigated for use in coded multiple-input multiple-output (MIMO) systems and its strengths and weaknesses are determined. The conventional PDA decoder includes two approximations. The received symbols are assumed to be statistically independent and a Gaussian approximation is applied for the(More)
— The application of distributed space-time coding schemes in a simulcast network is considered, and a key challenge is addressed which arises in the downlink: Since the local oscilla-tors employed at the individual transmitting nodes may independently differ from the nominal carrier frequency, frequency offsets will occur between the individual(More)
—In this paper, we propose two novel pre–equalization schemes for multiple–input single–output (MISO) direct– sequence ultra–wideband (DS–UWB) systems with pre–Rake combining and symbol–by–symbol detection. The first scheme employs one pre–equalization filter (PEF) per transmit antenna, whereas in the second scheme, the simplified PEF (S–PEF) scheme, all(More)
—We address the issue of optimal transmit power allocation in relay-assisted cognitive-radio (CR) systems. In particular , we assume that the frequency band chosen for unlicensed spectrum usage is not completely unoccupied, but contains one or more licensed narrowband users. For such a setting, we develop distributed transmit power allocation schemes, which(More)
THE USE OF multiple antennas in wireless communication systems has gained much attention during the last decade. It was shown that multiple-antenna systems, called multiple-input multiple-output (MIMO) systems, offer huge advantages over single-antenna systems, both with regard to capacity and error performance. Typically, quite restrictive assumptions are(More)
— In this paper, we consider a relay-assisted wideband cognitive-radio (CR) system under the assumption that the frequency band chosen by the CR relay network for unlicensed spectrum usage overlaps with one or more bands dedicated to primary (e.g., licensed) narrowband links. Our objective is to optimize the performance of the CR system while limiting the(More)
— The generalized K–fading model, characterized by two parameters, k and m, is a very versatile model and was recently shown to accurately capture the effects of composite shadowing and multipath fading in wireless communication systems. Furthermore, it can be used to model cascade multipath fading, which is relevant in, e.g., mobile–to–mobile communication(More)
Analysis of the expected error performance of cooperative wireless networks employing distributed space-time codes, " in Proc. Abstract— In this paper, typical uplink scenarios in a cellular system are considered, where two cooperating mobile stations (serving, for example, as mobile relays) are transmitting the same information to a base station by using a(More)
EXTENDED ABSTRACT Space-time codes (STC) are wireless transmission techniques utilizing multiple transmit antennas (and optionally multiple receive antennas) and have recently gained much interest. The efficiency of STC in fading environments is based on a diversity gain: Given sufficient antenna spacing, the ÒÌ ÒÊ transmission paths from the ÒÌ transmit(More)