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This paper studies the wireless positioning method using digital TV (DTV) signals with orthogonal frequency division multiplex (OFDM) modulation. A novel pseudo range estimation method is proposed, which utilizes the synchronization modules in the data demodulation as the signal acquisition for the coarse time delay estimation and introduces a data-directed delay tracking mechanism for the fine time...
Traditional OFDM systems present some embedded features that may be exploited in order to intercept the wireless transmitted signal. However, such a possibility is not accepted in military applications where security is a very important issue. Cyclic prefix is one of the most obvious OFDM parameters that induce cyclostationarity features. Aiming to suppress these features, some classical solutions...
This paper addresses the problem of indoor location for devices that are connected to WLAN. Nowdays most of the smart terminals: mobile phones, portable computers and tablets are WLAN enabled. Location of these devices is of interest to network security issues as well as employee and company security and reliability. Most of the algorithms on the market use triangulation as a basic rule for location...
Orthogonal Frequency Division Multiplexing (OFDM) is considered as an effective method for overcoming problems such as noise, multi-path propagation and frequency selective fading in low voltage power-line communication (PLC). However, OFDM system is sensitive to the error of synchronization. Accurate symbol timing and carrier frequency offset estimation are crucial to the PLC system based on OFDM...
An overview of the unique challenges in underwater acoustic (UWA) communication in ocean environment is presented. The UWA channel is compared with conventional RF channels. Several design considerations applicable to the physical layer design of a UWA communication system is described based on field measurements. The unique problems in synchronization under high Doppler are described highlighting...
The paper deals with a new frame synchronization scheme for OFDM systems. The scheme is based on the computing of the detection window variance. The variance is computed in two delayed times, so a modified Early-Late loop is used for the frame position detection. The proposed algorithm has good properties regarding the choice of the algorithm's parameters since the parameters may be chosen within...
OFDM signal classification has become an important requirement in many cognitive radios and military systems. Implementing such a requirement under Frequency Selective Rayleigh fading is a challenging task. In this paper, we explore different blind OFDM parameter and channel estimation techniques based on Maximum Likelihood techniques and higher order signal processing to ascertain the reception of...
In this paper, the impact of both time offsets (TOs) and carrier frequency offsets (CFOs) on the average output signal-to-interference-plus-noise ratio (SINR) in a frequency selective channel is investigated with a novel approach. First, TOs are partitioned into five cases based on how they occur. Then the mathematical models for different cases are derived. Considering CFOs and benefiting from the...
Inter carrier interference (ICI) is deemed as a critical issue in orthogonal frequency division multiple access (OFDMA) systems. Though ICI caused by Doppler spread is negligible in femtocell systems, frequent reception of signals over misaligned subcarriers will introduce severe ICI. Successive interference cancellation and decision feedback equalizers are some of the techniques proposed to mitigate...
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...
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...
Orthogonal frequency division multiplexing (OFDM) communication systems require accurate estimation of timing offset and channel impulse response in order to achieve desirable performance. In this paper, we consider the optimal placement of pilot symbols over the OFDM subcarriers in order to minimize a function of the Cramér-Rao bound on these parameters. Previous work has investigated this problem...
This paper gives an introduction to a generic OFDM based testbed for positioning using time difference of arrival (TDoA) measurements. An overview of the transmitter system and receiver system is given. Furthermore an inital access algorithm with interference mitigation for subsample delay estimation is presented and simulation results are shown. The influence of the geographic base station mapping...
For orthogonal frequency division multiplexing (OFDM) systems in multipath channels, the detection of the first path is desirable to avoid inter-symbol-interference (ISI). However, the conventional peak detection of the cyclic prefix (CP) correlation curve can detect the strongest path but not the first path, while the largest slope detection is sensitive to background noise. This paper presents a...
In this paper, a jointed preamble/boundary detection and fractional carrier frequency offset (CFO) estimation design is presented which supports dual SC/HSI modes of IEEE 802.15.3c applications. Based on correlation based algorithms which utilizes the structure of preamble, an efficiency architecture is proposed which realizes synchronization detection with a sequential detection scheme and only single...
This paper presents a novel maximum likelihood (ML) time difference of arrival (TDoA) estimation algorithm for subsample delays. We introduce a new initial acquisition and cell search algorithm with implicit multiple access interference (MAI) cancelation. A joint carrier frequency offset (CFO) estimation and subsample delay estimation is used to compensate Doppler spreads and oscillator drifts. Analytical...
Orthogonal frequency division multiplexing (OFDM) is effective method for transmitting high speed data at frequency selective channel. But OFDM is sensitive to the carrier frequency offset (CFO) and sample timing offset (STO). As these effects, inter-carrier interference (ICI), inter-symbol interference (ISI) and common phase noise error (CPE) occur. And these effects cause degradation of performance...
In this paper, two estimators are proposed for calculating fine timing and channel impulse response (CIR) of a CD-OFDM based communication system. The proposed low complexity algorithms are designed to operate with asynchronous nodes having independent timing and carrier frequency offsets. These algorithms fully exploit the specially designed structure of time domain preamble used for cooperative...
Traditional OFDM based transmission system uses Cyclic Prefix (CP) in an OFDM symbol in order to maintain orthogonality of transmission. Present days' Ultra-Wideband (UWB) systems use Multi-Band OFDM (MB-OFDM) techniques for transmission in application like Wireless Personal Area Network (WPAN). UWB based systems are power limited by the regulation of FCC. CP introduces correlation in the transmitted...
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