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A constant-amplitude output signal for the Zadoff-Chu sequence was used for the low complexity MANET transmitter devices to improve safety of autonomous cars. The main goal is to merge the communication block and the obstacle detection block in singular multipurpose device. The article presents the algorithm of using the Zadoff-Chu sequence to establish the initial synchronization for the joint communication...
Multi-replicA decoding using corRelation baSed LocALisAtion (MARSALA) is a recent random access technique designed for satellite return links. It follows the multiple transmission and interference cancellation scheme of Contention Resolution Diversity Slotted Aloha (CRDSA). In addition, at the receiver side, MARSALA uses autocorrelation to localise replicas of a same packet so as to coherently combine...
The superframing option of the recent DVB-S2X standard specifies, for the so-called SF-Pilot fields, the use of the orthogonal set of Walsh-Hadamard (WH) sequences. In order to exploit this orthogonality, waveforms coming from different beams to the k-th User Terminal (UT) should be quasi perfectly aligned in time. While in the downlink part of a terrestrial system this is quite straightforward, in...
Advanced method of inner calibration of individual receive modules of active phased antenna arrays (APAA) in synthetic aperture radar (SAR) is discussed. This method allows fast and accuracy amplitude and phase characterization of every receive modules and uses pseudo-noise sequences as core of calibrating sequences system. Decorrelation method of cancelling mutual interference using simple matrix...
Military communications face increasingly congested environments requiring spectrally efficient approaches capable of contending with many users and interference. We evaluate the over-the-air performance of recently designed minimum total squared correlation (MinTSC) signature sets compared to maximal length pseudorandom binary spreading sequences (m/PN) under a variety of interference conditions...
Super-regenerative receivers (SRR) are known for their ultra-low power (ULP) consumption. However, its wide frequency selectivity seriously degrades performance especially in the presence of interference. An attractive approach to address this problem is by lowering the quench rate of the SRR to the modulation rate. However, this brings in uncertainty due to lack of oversamples and leads to the timing...
ZCZ-CDMA operating under quasi-synchronous timing control and using zero correlation zone (ZCZ) code possesses interference free performance and fast frame acquisition. This paper discusses fast synchronization acquisition methods using a matched filter bank, which simultaneously calculates correlation between a received signal and any sequence in ZCZ code, and the effectiveness is shown from synchronization...
Nowadays, correlator is a crucial part of communication systems. The correlation function has a great practical importance when it is necessary to process a signal in the presence of noise. Use of correlator in modern communication system have more precise frequency and timing synchronization, which improves its ability against interference of multipath and frequency selective fading channels. Even...
This paper describes an informed unipolar spread spectrum (SS) modulation to improve the performance of SS-based watermark extraction with self-synchronization. Compared with bipolar SS, unipolar SS, realized by employing a pair of orthogonal codes to represent the watermark bits, is more robust against the distorted correlation between the received watermarked signal and the reference. The informed...
In this paper, we propose an iterative SSS detection scheme for neighbor cell search in 3GPP LTE systems. The proposed scheme contains three stages for each iteration. At the first stage, SSS is detected without channel information and a candidate cell is selected. Then a coherent detection is utilized with channel response estimated from the candidate's SSCH at the second stage, in which a corresponding...
In LTE system, in order to access the network, user equipment (UE) should detect the primary synchronization signal (PSS) and secondary synchronization signal (SSS) in downlink (DL) signal from the surrounding base stations (BS). This paper presents a novel initial cell search (ICS) scheme in TD-LTE system that contains two steps. In the first step, modified normalization based PSS detection is proposed...
In this paper, new methods has been proposed, that is to construct ZCZ Sequences based on almost perfect sequence. The feasibility of this construction method has been proved, and we get two construction methods, meanwhile, the new methods have solved the deficiency of the construction of ZCZ based on perfect sequence.
The optimal detector for CP (Cyclic Prefix)-OFDM (Orthogonal Frequency Division Multiplexing) signal with inherent periodic pilots in low signal to noise ratio environments relies on perfect time synchronization. In this paper, we modify the optimal detector and propose a new suboptimal sensing scheme based on pilots estimation (SSS-BPE). In the proposed SSS-BPE, the likelihood criterion and periodicity...
The promising spectrum sharing technology used to improve the spectrum usage may cause severe narrowband interference, which seriously degrades the timing synchronization. As noticed that only the auto-correlation based methods have been investigated in the literature, this paper examines the impairment of narrowband interference to the cross-correlation based timing synchronization, to obtain a comprehensive...
Spectrum sharing is promising to improve the efficiency of spectrum usage. However, this technology may incur severe narrow band interference (NBI), which seriously complicates the synchronization problem. This paper investigates the timing synchronization problem in the presence of NBI for the OFDM-based spectrum sharing systems. We consider the cross-correlation based timing synchronization and...
Complementary sequences are well studied in the communication field for their good correlation properties. Besides being used as spreading sequences, they can also be used for channel estimation, synchronization, reduction of peak-to-average power ratio of symbols, preamble design, sequence design, Target detection and so on. A recursive construction of complementary sequences based on orthogonal...
Interference is a performance limiting factor for both reliable data estimation and synchronization, especially at the cell edge of wireless communications systems targeting a frequency reuse factor of one. In this paper we address time synchronization algorithms applicable to the beyond 3G standard 3GPP-LTE. To get rid of the interference problem, multi-link synchronization methods are proposed,...
Robust time and frequency synchronization is an essential requirement for a successful cell search in cellular networks like LTE (Long Term Evolution). High level of co-channel interference experienced in spectrally efficient deployments (Frequency reuse-1) can adversely affect reliable detection of synchronization sequences. Different solutions for the detection of LTE Primary Synchronization Signals...
Cognitive radio is an enabling technology for efficient utilization of radio spectrum. In this paper, an orthogonal frequency division multiple access (OFDMA) based cognitive (opportunistic) network is considered, which co-exists with a macrocell network through utilizing its unused subcarriers. We particularly consider the uplink opportunity detection problem by the opportunistic network, where accurate...
In orthogonal frequency-division multiplexing (OFDM) systems, Cyclic Prefix (CP) is added for multi-path interference protection, which is a copy of the last part of the following OFDM symbol; however, this popular symbol structure may cause a virtual peak problem in some OFDM synchronization process. In order to solve the problem, we propose a new preamble structure to improve the synchronization...
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