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In the last years, the migration from analog to digital terrestrial television systems has favored the deployment of Single Frequency Networks (SFN), more efficient from a spectrum point of view, to provide DVB-T services in larger geographical areas through the reuse of frequencies. However, the planning of a SFN is not a trivial task, since the designer must find a trade-off between the quality...
Channel estimation is a significant component of any receiver implementation. This paper presents a fast non-iterative channel estimation and equalization algorithm for TDS-OFDM systems. The proposed method is a hybrid of CP-OFDM and ZP-OFDM systems. By discarding the initial portion of the PN-sequence that absorbs all the ISI, the channel can be estimated from the remaining PN-sequence by using the...
Realization of transmitter and Receiver architecture for LTE is the major research work being carried out by implementation experts. There are four Control channels available in LTE for both uplink and downlink. The uplink control channel is PUCCH. The downlink control channels are PDCCH, PCFICH and PHICH. The Physical Control Format Indicator Channel(PCFICH) is one among the downlink physical control...
This paper proposes time, frequency and clock synchronization technique for a Q transmit and L receive (Q x L), Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) for Wireless Local Area Network (WLAN) systems. OFDM is a multi-carrier modulation scheme that transmits a large number of closely spaced sub-carriers to be modulated with a conventional modulation technique...
In this paper, we propose a new robust closed-loop extended orthogonal space-time block coding (EO-STBC) scheme for two-way four relay networks over frequency selective fading channels with imperfect synchronization. It is a three time slot scheme where the first one is specified for the two terminals while the other two are specified for amplify-and-forward (AF) relays. An orthogonal frequency division...
Channel estimation in orthogonal frequency division multiplexing (OFDM) systems is required for coherent demodulation. This paper deals with channel estimation in the OFDM based LTE system. In particular, two pilot-aided techniques are presented: the low-pass filter based estimator (LPFE), and the robust minimum mean square error estimator (MMSE). These techniques are characterized by their low complexity...
WiMAX is a Worldwide Interoperability for Microwave Access. The technology is specified by the Institute of Electrical and Electronics Engineers Inc., as the IEEE 802.16 standard that works on development of globally standardized protocols for wireless MAN and it has been commercialized under the name “WiMAX”. 802-16-2004 has often been considered the “fixed standard” or “fixed WiMAX” and 802.16-2005...
Estimation of time-varying and sparse channels is a topic that has attracted considerable interest lately, especially for underwater acoustic communication. In the context of multicarrier transmission, several important questions remain unanswered: i) should pilots be placed in clusters as for time-varying, non-sparse channels, or randomly dispersed between the data as common in the Compressive Sensing...
In this paper, we study the impact of an important RF impairment inside direct-conversion receiver, namely the I/Q imbalance, on the performance of OFDM radio link over frequency-selective Rayleigh fading channel. Closed-form expressions for link performance, in terms of detection error rate, ergodic capacity and outage capacity, under both frequency-selective RX I/Q imbalance and noisy frequency-selective...
The use of distributed space-time codes in cooperative communications promises to increase the rate and reliability of data transmission. These gains were mostly demonstrated for ideal scenarios, where all nodes are perfectly synchronized. Considering a cooperative uplink scenario with asynchronous nodes, the system suffers from two effects: timing errors and individual carrier frequency offsets....
This paper discusses the performance of Golden codes in a hybrid satellite/terrestrial system framework employing dual polarized MIMO-OFDM transmissions. Although the use of Golden codes in satellite and terrestrial scenarios has been studied independently, a realistic performance assessment must involve both components taking into account the relative delay between their reception. In fact, this...
Due to wide coverage and high transmission power of digital television (DTV) transmitters, DTV based wireless positioning is a promising complementary to global positioning system. For Chinese DTV broadcasting network whose key technology is time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM), this paper proposes a time-frequency joint positioning scheme by utilising TDS-OFDM...
In this paper, we present a thorough investigation on the impact of spatial smoothing and forward-backward averaging techniques for subspace-based channel estimation. The spatial smoothing technique requires the selection of a window size, which, if not selected properly, leads to dramatically performance breakdown of the subspace-based methods. We aim to provide an explanation of the performance...
Long Term Evolution (LTE) is considered one of the main candidate to provide wireless broadband access to mobile users. Among main LTE characteristics, flexibility and efficiency can be guaranteed by resorting to suitable resource allocation schemes, in particular by adopting adaptive OFDM schemes. This paper proposes a novel solution to the sub-carrier allocation problem for the LTE downlink that...
To fully exploit frequency diversity in cyclic delay diversity orthogonal frequency division multiplexing (CDD-OFDM) system, accurate channel estimation is crucial. Due to the excessive channel delay spread in CDD, traditional in-band pilot assisted channel estimation with limited frequency resolution fails to track the considerable variation in the frequency domain. Alternatively, increasing pilot...
Spectrum awareness is one of the most challenging requirements in cognitive radio (CR). To adequately adapt to the changing radio environment, it is necessary for the CR to be able to perform joint detection and classification of low signal-to-noise ratio (SNR) signals. In this paper we propose a joint detection and classification algorithm for the mobile Worldwide Interoperability for Microwave Access...
Since the IEEE 802.16 first standard was proposed in 2004 to provide broadband wireless service, the standard has not only been widely studied, but also broadly commercialized. The current IEEE 802.16-2009 standard document specifies five Quality of Service classes. As is typical with most standards, IEEE 802.16 does not require the use of a specific scheduler. In this paper, we first evaluate the...
In this paper, we investigate the impact of the a priori channel state information (CSI) on the orthogonal frequency-division multiplexing (OFDM) system performance. A joint iterative channel estimation, detection and decoding receiver involving the dual diagonal linear-minimum-mean-square-error (DD-LMMSE) algorithm is employed. We show that the discrepancy between the a priori CSI and true CSI has...
This paper presents a novel analytical derivation of the false alarm probability (FAP) and detection probability (DP) for non-line-of-sight (NLOS) detection based on LTE signals. Position estimation in indoor or urban area with cellular wireless communication systems is getting more and more important. However, especially in these environments NLOS propagation causes positioning errors in the order...
Based on differential properties of the received preamble, a novel start of packet (SoP) detection and synchronization approach is developed for the IEEE802.11n MIMO-OFDM WLAN system to obtain better mean and variance of timing estimates and lower missing packet and false alarm rates.
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