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With the advent of the 4G broadband wireless communications, the combination of multiple-input multiple-output (MIMO) wireless technology with orthogonal frequency division multiplexing (OFDM) has been recognized as one of the most promising techniques. In particular, coding over space, time and frequency domains provided by MIMO-OFDM enables a much more reliable detection and decoding of the message...
A new method of specifying the performance of a transmitter in a receiver/demodulator agnostic way is proposed. The concept of amplitude and phase error vector magnitude (EVM) is proposed. Experimental results demonstrate that amplitude and phase EVM gives a better characterization of a transmitter than traditional EVM metrics
In this paper, the cooperative diversity with superposition modulation, which has been proposed as an instance of "dirty paper coding", is theoretically analyzed using the outage probability. We investigate the relationship between outage probability and transmission-rate corresponding to the parameter of superposition modulation. Moreover, we extend the modulation of this cooperative transmission...
Crest factor reduction (CFR) techniques aim to solve the high peak-to-average power ratio (PAR) problem encountered in the transmission of modern communication signals such as orthogonal frequency division multiplexing (OFDM). Constrained clipping is a promising CFR technique that is capable of large PAR reductions while guaranteeing that EVM and spectral mask constraints are met. In this paper, we...
Time synchronization is a crucial component of infrastructure for wireless sensor networks (WSN). The design of new synchronization methods for WSNs needs to satisfy the unique requirements and constraints in terms of precision, lifetime, energy, and scope of the synchronization. In this paper we have designed and compared three techniques for achieving synchronization in network centric sensor networks,...
A new wideband 2.4-GHz frequency synthesizer with auto-calibration technique, which is adaptive to process variation, is presented. The monolithic, wideband voltage controlled oscillator (VCO), which has both analog and digital control, has a wide tuning range of 1.98 GHz. The proposed synthesizer with self-calibration block is connected to the on-chip jitter measurement circuit. The control voltage...
Two techniques, i.e. differential and complementary feedbacks, are derived to reduce the feedback overhead for MIMO transmit beamforming. The unitary beamforming matrix is the cumulative product of the fed back unitary matrixes for differential feedback. The fed back matrix depicts the incremental change of the beamforming matrix and it is quantized by small vector codebooks. The overhead can be further...
If the biasing circuit of a class AB radio frequency power amplifier (RF PA) does not present a zero impedance at the envelope frequencies, undesired ac voltages will be added to the dc supply voltage, producing amplitude and phase modulation of the RF output signal. Unfortunately, the sidebands due to this bias modulation fall exactly where the intermodulation distortion (IMD) products occur, producing...
In recently years, with the release of spectral mask by the Federal Communications Commission (FCC), ultra-wideband (UWB) communications by means of impulse-radio (IR) are gaining increasing interest. In order to optimize transmission power spectrum, judicious pulse shaping is required. This paper proposed a modified Hermite function based pulse shaping algorithm and the simulation results show that...
The novel algorithm proposed in this paper is an optimal algorithm, both blind and training data based channel estimation algorithms are described; however, the issue of computationally efficient multiuser detection is not addressed. The multiuser detection is investigated in a long code CDMA system over frequency selective multipath channel. The issue of channel estimation is not addressed here,...
Mobile transmit diversity (MTD) technology can provide beam forming benefit and result in an additional diversity gain on the top of the traditional diversity gain from the multiple antennae. The MTD technology also benefits the network capacity by reducing the interference to the neighboring cells (sectors). In this paper, we present the measurement results of the 42% and 45% increases on the reverse...
In this paper, we present and analyze a novel link layer transmission strategy for wireless networks using multiple input multiple output (MIMO) technology at the physical layer. When the channel state information (CSI) is available at the transmitter (CSIT), we present an adaptation algorithm that selects the proper orthogonal sub-channels of the MIMO link to use in order to increase the link layer...
Radiation characteristics of printed antennas etched on a high permittivity dielectric substrate with a relative dielectric constant of 197 were investigated for the purpose of miniaturization of antennas. At first, the effect of shortening of the wavelength caused by use of the high permittivity dielectric substrate was calculated from the viewpoint of the directive gain performance, and it was obvious...
MIMO wireless transceivers employ multiple antennas and advanced digital signal processing to achieve higher data rates and superior link reliability compared to their single-antenna counterparts. This paper presents a 2times2 MlMO 5 GHz WLAN transceiver implemented in 90 nm CMOS. Crosstalk between the different MIMO channels is shown to have a detrimental effect on MIMO performance. Such crosstalk...
This paper proposes a novel hybrid linear prediction and QR based blind equalization algorithm. The algorithm is more robust to channel order under/over estimation. The algorithm is a data based (as opposed to channel based) algorithms and is also numerically superior. Simulations clearly indicate that our algorithm performs very well under channel order under/over estimation, when LP and QRD based...
This presentation introduces bit interleaved coded multiple beamforming (BICMB). The paper also shows that with the inclusion of BICM to the system, one actually does not need to lose the diversity order with multiple beamforming even when all the subchannels are used. BICMB achieves full diversity order of NM, and full spatial multiplexing order of min(N, M) for a system with N transmit and M receive...
The objective of this work is to develop a handset adaptive antenna for operation at the frequency of 5.8 GHz. This antenna must be compact and have fast convergence. A phased array of switched beam elements is introduced to speed up initialization of CMA. Using dual-feed switched-beam patch antennas, the antenna system can be compact. An array element has dimension of 15.5times15.5 mm2 and the array...
In the uplink multi-user MIMO-OFDM system, usually there are multiple carrier frequency offsets (CFOs) between the users and the base-station. The CFOs destroy the orthogonality among subcarriers and cause inter-carrier interference (ICI) in the received signals, and therefore make the "per-tone" equalization invalid. Since there are multiple different CFOs, the conventional CFO compensation...
In this paper, we propose an indoor location positioning method for non-active objects (that is, objects that do not transmit radio waves) using ultra-wideband radios and a fingerprinting-like algorithm. This proposed method is based on pattern matching of the changes to the multipath intensity profile caused by the object to be located. Experimental results are reported, and the performance of the...
In this paper, the use of fractal elements in miniaturized antenna applications is discussed. Hilbert grounded wires are studied and a simple design routine is outlined. Using commercial software tools, the design of groundless fractals is shown to be simple and fast. We present grounded and groundless Hilbert and Meander antennas for 250 MHz, 400 MHz and 2 GHz applications. Application of Hubert...
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