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In downlink relay systems, the conventional straightforward relaying scheme named decode-and-forward (DF) protocol is used at relay station (RS) to decode the data received from base station (BS) and forward the decoded data to the mobile station (MS) to improve the spatial diversity gain. However, conventional DF mode is spectral inefficient and not capacity optimal since the wireless channels in...
For distributed antennas based communications, the received signal from different sources can be asynchronous due to the propagation or processing delays. This can destroy the space time block code properties designed initially for synchronous case. In this paper, we introduce the delay-diversity tradeoff showing that it is possible to preserve the maximum diversity of a code without reducing its...
Network coding in cooperative relaying can improve the performance of both users and provide improved efficiency as compared to the conventional relaying. This paper considers different detection schemes for cooperative relaying with network coding. Analytical upper bounds on the bit error probability are derived and used to assess the performance of the different schemes. The obtained results show...
Tight bounds for the Shannon capacity of amplify-and-forward cooperative diversity networks are derived for three different adaptive source transmission policies in a myriad of fading environments: (i) constant power with optimal rate adaptation (ORA); (ii) optimal joint power and rate adaptation (OPRA); and (iii) fixed rate with truncated channel inversion (TCIFR). Our unified framework based on...
Distributed multi-antenna relaying is analyzed in nonregenerative cooperative networks with unbalanced hops and independent but not necessarily identically distributed Rayleigh fading. Exact closed-form expressions are derived for the moment generating function of the end-to-end signal-to-noise ratio (SNR) at the destination. Our analysis applies to arbitrary N number of antennas at the relay and...
This paper is focused on the study of layered space-time-frequency (LSTF) architectures with channel coding for orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) multiplexing systems for high speed wireless communications over a frequency-selective fading channel. In order to achieve the available spatial, temporal and frequency diversities, and also make the...
In orthogonal frequency division multiplexing (OFDM) based cellular systems, co-channel interference (CCI) from adjacent interfering base stations (BSs) would greatly degrade the bit error rate (BER) performance of cell-border users. In the previous work, a blind single antenna interference cancellation (SAIC) algorithm named least mean square-blind joint maximum likelihood sequence estimation (LMS-BJMLSE)...
A new partial transmit sequence (PTS) technique for orthogonal frequency division multiplexing (OFDM) signals which does not require side information, is proposed. In the proposed method, the transmitter applies PTS to reduce the peak-to-average power ratio (PAPR) and does not send the side information on the PTS phase factors to the receiver. Based on the OFDM symbol structure having pilot subcarriers,...
In this paper, a new joint symbol detection and channel tracking algorithm is proposed for the coded MIMO-OFDM systems over time-varying frequency-selective fading channels. The iterative detection/decoding and channel estimation are iteratively employed based on the Variational Bayes expectation-maximization (VBEM) algorithm to improve the system performance. A modified list sphere decoder (LSD)...
Bit-Power Loading (BPL) algorithms are proposed based on Effective SINR Mapping (ESM) techniques. The ESM techniques used are the Exponential ESM (EESM) as well as the Mean Mutual Information per Bit (MMIB). The algorithms are based on proper usage and modifications of algorithms already proposed in the literature, applied to ESM compatible link-level performance models. The performance gain when...
In this paper we analyze the Ricean K-factor for vehicle-to-vehicle (V2V) communications in a typical open sub-urban street crossing. The channel conditions vary from non line-of sight (NLOS) to line-of-sight (LOS). The antenna arrays used for recording the radio channels consist of 4 elements with directional radiation patterns. We measured 16 individual single-input single-output channels, with...
Polarized MIMO systems are an efficient solution for reducing inter-antenna correlation while maintaining compact terminal size. In this paper, a time-variant statistical channel model is proposed for tri-polarized antenna systems. The model is based on a coherent and a scattered component, where each component includes inter-channel correlation and cross-polar discriminations. The temporal variations...
In this paper, the results of outdoor-to-indoor multiple-input multiple-output (MIMO) channel measurements at 780 MHz are presented. The motivation for these measurements was to provide actual measurement data needed to extend the International Mobile Telecommunications -Advanced (IMT-A) channel models to the frequencies around 400 - 900 MHz. There are publications reporting measurement results for...
The channel capacity of a MIMO telecommunication system depends on different parameters such as the signal-to-noise ratio, the space-time characteristics of the propagation channel, the antenna array geometry and the antenna pattern. However, the propagation channel remains the strongest constraint imposed on designers of new radio air interfaces. Using a MIMO channel model, computer simulations are...
This paper presents an unified and empirical propagation model to obtain the received power in mixed scenarios, with outdoor and indoor environments, or in a scenario with only one kind of environment, either for an urban, sub-urban or rural scenario, with or without vegetation. This unified model is called the Lisbon University Institute (LUI) one and can be included into planning tools for wireless...
This paper presents the validation of the unified propagation model, the Lisbon University Institute (LUI) model, which is valid for three wireless technologies: Wireless Fidelity, Universal Mobile Telecommunications System and Worldwide Interoperability for Microwave Access. With this purpose in mind, several experimental trials for those technologies were performed in different scenarios, where...
In many wireless systems, the energy consumed by the receiver is significantly larger than the energy consumed by transmitter, possibly even by orders of magnitudes. This paper derives an analytical solution to maximize the throughput per unit of available receiver circuit power. Adaptive control of the IP3, to handle the time-varying adjacent channel interference level, can substantially improve...
Spectrally Efficient Frequency Division Multiplexing (SEFDM) system proposes enhanced spectrum utilization in contrast to Orthogonal Frequency Division Multiplexing system (OFDM). Spectral efficiency is increased by relaxing the orthogonality condition while maintaining the same transmission rate per individual channel, hence, for the same bandwidth allocation SEFDM offers higher throughput than OFDM...
In this paper we propose a method to reduce the Peak-to-Average Power Ratio (PAPR) in the developmental Wavelet Packet Multi-carrier Modulation (WPM) system. The method works on the principle that the PAPR of a multicarrier system can be adjusted by varying the phase-shifts of the subcarriers. Hence different PAPR values for the same information can be obtained by randomly altering the phases of the...
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