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Filter bank multicarrier (FBMC) has been taken as a candidate modulation for the 5th generation (5G) mobile network, because it exploits well-shaped prototype filters to reduce the inter-symbol-interference (ISI) and inter-carrier-interference (ICI) in OFDM system. To achieve more flexibility in filter performances, this paper designs nearly perfect reconstruction (NPR) filters by relaxing the Nyquist...
Large peak-to-average power ratio (PAPR) is the major issue in orthogonal frequency-division multiplexing (OFDM) systems. Selective mapping (SLM) has been commonly employed to reduce the PAPR. However, SLM requires side information (SI) which reduce the bandwidth efficiency. A low-complexity cyclic SLM (C-SLM) scheme without SI which uses delay correlation and matched filter, called C-SLM-DC-MF, has...
In this paper, we address the use of multi-layered sliding windows to detect the presence of a wireless network for cognitive radio applications. Although synchronization signals of the Long Term Evolution (LTE) has been used as the reference system, the proposed scheme is generic in principle. Our proposed scheme doesn't require any a priori knowledge of the exact synchronization sequences, so it...
We present an optimal frame timing estimator for OFDM signals that utilizes both cyclic prefix (CP) and pilot-carrier-aided channel estimation. Combining the periodic nature of the embedded pilot signal information with the correlation present in the cyclic prefix allows improved frame timing estimates relative to use of either one. Following a derivation of the ML estimator, a processor diagram is...
Cognitive radio (CR) is an intelligent system for designing modern wireless communication systems. Spectrum sensing is one of the most important issues in CR. This paper presents a semi blind spectrum sensing method which exploits the combination of comb filter and autocorrelator. The proposed method improves the detection performance of blind spectrum sensing in severe noise environments where an...
In recent years, a new communication technology emerged by taking advantage of the high-speed switching capabilities of LED known as VLC (Visible Light Communication) has been getting more attention. On the other hand, OFDM is one of the technology that can efficiently utilize a frequency band. In this paper, our goal is to develop a VLC OFDM system, that is easily operable, and capable of high speed...
Electronic systems are becoming always more complex and consequently more subject to defect. For safety, security and integrity reasons, wire diagnosis is crucial. The emerging of sensor networks and connected objects has created the need for embedded and non invasive fault diagnosis solutions. Actual systems rely on multi-carrier reflectometry to locate upcoming defects on wires, though their precision...
Compressed sensing (CS) based sparse channel estimation which sufficiently exploits the inherent sparsity of channels can achieve desirable performance compared with conventional channel estimation algorithms. However, in channel estimation common recovery algorithms, such as orthogonal matching pursuit (OMP), uses pilots inserted in one individual orthogonal frequency division multiplex (OFDM) symbol...
This paper presents a method for protecting wireless signals through the creation and exploitation of time-varying spectral redundancy. Redundant symbols are multiplexed in both time and frequency in dynamic patterns within multicarrier symbols which creates the spectral redundancy. A novel Frequency Shift (FRESH) filter is developed to exploit this timevarying spectral redundancy. This filter structure...
The existing constructions of Golay complementary sets based on generalized Boolean functions are limited to lengths, which are powers of two. In a recent paper, Chen [3] proposed a new construction of binary and nonbinary complementary sets of non-power-of-two length based on truncated method. In this paper, we proposed a novel construction of ç-ary complementary sets based on the concatenation of...
We present our previous work in [17] in a more generic way to construct q-ary Golay complementary sets and near-complementary sets of size N and sequence length M · Nm by using different seed sequences, where m is an arbitrary non-negative integer, M is the length of seed sequences and N is a power of 2. The boolean functions of these sequences will also be derived with our method. To illustrate it,...
This paper presents a filter for exploiting time-varying cyclostationary statistics. The motivating example is designing redundancies into an OFDM signal to reject in-band, strong, wideband interference. Combining the filter with error correcting codes gives a 10 dB gain over LDPC codes and more than a 1000x reduction in BER. This allows the creation of multicarrier waveforms that are robust, reliable...
It is indispensable to take a low complexity and high accuracy channel estimation algorithm into account under rapidly growth in wireless communication. In this paper, we propose an algorithm for channel estimation using complementary sequence (CS). By utilizing the fantastic autocorrelation property of CS, time domain channel estimation can be easily achieved. We analyzed the complementary sequence,...
The downlink positioning method specified by 3GPP is a part of LTE location service. The method utilizes the time difference of Positioning Reference Signal (PRS) for ranging, therefore time delay estimation of PRS is a fundamental question in the method. A conventional algorithm relies on time correlation however faces challenges in multipath channel. For OFDM signal, Multiple Signal Classification...
Cognitive radio (CR) was proposed in wireless communications to improve spectral efficiency based on the concept of opportunistic spectrum access. Because orthogonal frequency division multiplexing (OFDM) has become the major access technique, an efficient spectrum sensing technique targeted at OFDM-based signals is one of the primary requirements of CR networks. To reduce computational complexity,...
This work proposes a novel authentication method for identifying Unmanned Aerial Vehicles (UAVs) based on a channel-tap power. A ground control station utilized the channel-tap power as a radio-frequency fingerprint (RFF) to directly detect UAVs via physical (PHY) layer. The proposed authentication method uses the Neyman-Pearson test to discriminate between two UAVs, UAVI and UAVA, which are controlled...
This paper proposes an efficient ordering calculation method employing frequency correlation in multiuser multiple-input multiple-output orthogonal frequency division multiplexing (MU-MIMO-OFDM) Tomlinson Harashima Precoding (THP). Although the ordering process is effective to improve the transmission performance of THP, it requires a large amount of computational effort due to sub-carrier-based operation...
A minimum mean square error estimation (MMSE) using a virtual pilot channel estimation scheme was proposed by our researchers for improving the error performance of the IEEE 802.11p. However, compared to the STA channel estimation scheme, the MMSE scheme cannot provide an acceptable error performance in a low SNR region. To alleviate this, we propose an adaptive channel estimation scheme, which selectively...
LTE has several advantages to be investigated as transmitter of opportunity for passive radar in Germany: low carrier frequencies (i.e. low free space attenuation), high bandwidth (i.e. high range resolution) and wide area network (i.e. large availability). Therefore the signal correlation behavior is investigated. Additionally, a signal processing method is proposed for passive radar using LTE. The...
A novel method for distance estimation is introduced, based on an OFDM signal combined with the Zadoff-Chu Sequences. By exploiting the properties of these sequences it is possible to evaluate the distance between a transmitter and a receiver with a very good precision and accuracy. The technique effectiveness is demonstrated in a real operating environment by measuring the distance between two active...
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