Synchronisation-burst spectra for the switching satellite

Synchronisation of Earth stations to a switching communications satellite is achieved by transmitting synchronisation-burst signals. When more than one synchronisation-burst passes through the synchronisation window, mutual interference is generated by the frequency sidelobes. This interference can be reduced, however, by amplitude modulation of the synchronisation-burst signals.     

Time synchronisation without specific symbols for OFDM

A time synchronisation method without specific symbols for an orthogonal frequency division multiplexing (OFDM) system is investigated. The coarse time synchronisation and the fine time synchronisation algorithms are described. The problem of the time synchronisation of a coded OFDM terrestrial digital video broadcasting receiver in the presence of long echoes and pre-echoes is then analysed and worked out by an optimum use of both algorithms, which prove complementary     

System design of a mutually synchronised system

Feasibility of overall synchronisation in a p.c.m. integrated communication system based on the mutual-synchronisation principle is described. Considerations are made of the basic design problem, which is to establish synchronisation in frequency as well as phase. An experimental system based on these considerations is described which is constructed to demonstrate the realisability of the principle.     

Frame synchronisation using two frame alignment words

The use of two frame alignment words (FAWs) in a frame synchronisation system is investigated. This has the advantage of reducing the overhead when compared to conventional single FAW schemes. The scheme is of benefit when fast synchronisation and low overhead are important.<>     

Improved masking algorithm for chaotic communications systems

A method is proposed for robust synchronisation of the transmitter and receiver in chaotic communications schemes. It is verified in a modified Lorenz system. Simulations and theoretical analysis show that synchronisation robustness greatly improves under the method. Multiple chaotic systems communicating through a single channel can also be synchronised. Synchronisation of each user is independent, allowing multiple access chaotic communications     

Analysis and Comparison of Multimedia Inter-stream and Group Synchronisation Algorithms

In this paper an analysis and comparison of multimedia synchronisation algorithms is presented. After presenting the three types of multimedia synchronisation (intra-stream, inter-stream and group synchronisation), only inter-stream and group synchronisation algorithms are considered. The main synchronisation techniques included in most of the analysed algorithms have also been classified. Finally, a table is presented with the main characteristics of each algorithm according to the techniques included and other critical parameters such as the use of global or locally available clocks, the suitability for stored contents or live contents, the synchronisation information added to the data packets, the use of Real Time Transport Protocol, etc. This work provides a good starting point to all the new researchers interested in multimedia synchronisation and multimedia systems.     

Optimisation chaotic synchronisation of length-limited noisy Chua'scircuit signal

A new approach to synchronisation of Chua's circuit is presented. It effectively combines the interior penalty method of optimisation and chaotic synchronisation. Even under unfavourable, noisy conditions, the approach shows attractive lower variance results compared with conventional chaotic synchronisation in realising the synchronisation of length-limited noisy chaotic signals     

Reference node selection in dynamic tree

The reference node (RN) is a central node that has minimum distance/hop count to all other nodes in the network. This central node can play several critical roles such as being the time reference in order to synchronise computer nodes. For synchronisation, the main goal is to minimise the sum of synchronisation errors. The time synchronisation error, known for each link between two nodes, accumulates for each hop along the path used for synchronisation between two nodes. In such a context, the best RN is defined as having the minimal sum of time synchronisation errors between itself and every other node. Thus, the first step for error minimisation is to select a minimum spanning tree (MST), formed by the links with minimum synchronisation error, as synchronisation path. The second step is to select an RN, which minimises the sum of synchronisation errors to all nodes in the MST, as time reference for synchronisation. In a dynamic network, where communication links appear and disappear, and synchronisation accuracy improves as more packets are exchanged, a static RN would entail suboptimal synchronisation accuracy. All existing models in this area are limited to static RNs because of the computing cost of updating the RN, yielding a suboptimal total synchronisation error over time and causing problems if the selected node is removed from the dynamic network. This paper presents a novel and efficient method for dynamic RN selection in dynamic networks. The approach proposed in this paper improves the performance of RN computation and update in live mode for dynamic networks. This new method concentrates on the altered path with respect to the RN, each time the MST is updated. This provides an efficient way to find and maintain a RN incrementally in an average time complexity of O(log n) per update, which n is the total number of nodes in the network. The proposed approach was tested with a huge dynamic network containing 60 000 simulated nodes, in a number of different situations. The proposed approach achieves excellent running time while minimising synchronisation error. Although this work is currently used for time synchronisation purposes, several dynamic network tools can benefit from an efficient incremental algorithm to calculate hop counts and select a central point for the network. Copyright © 2014 John Wiley & Sons, Ltd     

Efficient transmit diversity scheme for synchronisation channel in OFDM cellular systems

Transmit diversity is a well-known technique that improves receiving performance by mitigating the amplitude variation of received signal. A number of diversity techniques have been investigated for data and control channels in OFDM cellular systems [1]. However, the diversity schemes for the synchronisation channel have not yet been fully investigated. Because of the inherent characteristics of a synchronisation channel, FSTD and TSTD can be considered as diversity schemes [2]. For data and control channels, it is important to increase the average detection probability for reliable system operation. For the synchronisation channel, however, the searching time is more important than the average detection probability. It implies that the transmission scheme increasing the average detection probability after multiple detection trials can be more beneficial even if it degrades the average detection performance at a first detection trial.     

Robust frequency hop synchronisation algorithm

The performance of conventional frequency hop (FH) synchronisation algorithms degrades in the presence of fading. Recovery times can be quite long for these classical synchronisation techniques. The authors describe a novel algorithm that makes use of past state information about the synchronisation to maintain FH synchronisation even in the presence of fading, narrowband interference and other channel distortion     

Implementation of secure digital communication by hyperchaoticsynchronisation

By active-passive-decomposition synchronisation, the application of the one-way coupled ring map lattice hyperchaotic system in secure digital speech communication is demonstrated. Synchronisation guarantees strong security and recovery without error     

Feedback scheme for frame synchronisation in photonic network of time-multiplexed space switches

A method for frame synchronisation in a photonic network of time-multiplexed space switches is presented. The proposed method, which is based on a feedback scheme, provides a mechanism for frame synchronisation to be achieved initially, without the need for accurate transmission time measurements, and allows synchronisation to be maintained within very tight bounds.<>     

Efficient synchronisation signal for the switched satellite

An efficient synchronisation signal for the s.d.m.a./s.s-t.d.m.a. satellite is described, which achieves accurate synchronisation in one round-trip time, thus eliminating the need for repeated transmissions of synchronisation bursts. An added feature is the direct measurement of variations in path-length time delay, which may be used to track satellite motion.     

Detection technique for a serial DS-SS code synchronisation in afading mobile channel

A performance analysis of the threshold decision technique for direct-sequence spread-spectrum (DS-SS) code synchronisation is presented. The proposed serial acquisition system is compared to the conventional serial acquisition system, and a significant improvement in performance is shown in terms of the mean acquisition time     

New synchronisation method for satellite-switched time-division multiple-access systems

A new synchronisation method for satellite-switched time-division multiple-access systems is described. It is shown that this method has some significant system benefits, and involves a small increase in satellite hardware complexity.     

Signal processing hardware in a radio LAN demonstrator

In order to demonstrate the practicality of high speed radio LANs, such as HIPERLAN, a hardware demonstrator has been built. To overcome the inter-symbol interference caused by the dispersive nature of the indoor radio channel, a decision feedback equaliser has been included in the system. No central synchronisation is provided in a network and a node must be able to derive all synchronisation from a received packet. This paper describes all of the signal processing hardware built for the demonstrator. The demonstrator is not standards compliant but the physical layer parameters are very similar and the signal processing required in HIPERLAN equipment will be very similar to that in the demonstrator.     

Optimised cross-layer synchronisation schemes for wireless sensor networks

This paper aims at synchronisation between the sensor nodes. Indeed, in the context of wireless sensor networks, it is necessary to take into consideration the energy cost induced by the synchronisation, which can represent the majority of the energy consumed. On communication, an already identified hard point consists in imagining a fine synchronisation protocol which must be sufficiently robust to the intermittent energy in the sensors. Hence, this paper worked on aspects of performance and energy saving, in particular on the optimisation of the synchronisation protocol using cross-layer design method such as synchronisation between layers. Our approach consists in balancing the energy consumption between the sensors and choosing the cluster head with the highest residual energy in order to guarantee the reliability, integrity and continuity of communication (i.e. maximising the network lifetime).     

Binary frame synchronisation sequences for packet radio

Frame synchronisation sequences with the smallest possible correlation sidelobes are determined by exhaustive search for the case when the frame synchronisation word is preceded by specific bit synchronisation patterns. For a given length these new sequences have significantly lower sidelobes than the optimum autocorrelation sequences.     

WCDMA系统中匹配滤波器的FPGA实现

WCDMA中规定了小区搜索的时隙同步过程采用匹配滤波器的方法实现,本论文主要研究匹配滤波器原理及FPGA实现结构。     

Design of electrode layout for motor imagery based brain?computer interface

A simple electroencephalogram (EEG) electrode layout is proposed to implement a motor imagery based brain-computer interface (BCI). The design was derived from investigation of EEG synchronisation in the motor cortex. A significant improvement in BCI performance was obtained in the new system