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.     

Continuous TDEV calculation for in-situ synchronisation monitoring in SONET/SDH networks

C-TDEV is proposed to adapt the block TDEV stability measure from atomic clock metrology to continuous in-situ network synchronisation monitoring. C-TDEV processes TIE samples serially and detects stability fluctuations in the real-time scale of the fluctuations themselves. It yields constant statistical confidence for all observation intervals and requires much less storage than the block calculation.<>     

An analytical calculation of power delay profile and delay spread with experimental verification

Realistic system and link level simulations require specific information about the radio channel. A key role is played by the power delay profile which is widely agreed to be a negative exponential characterized by the delay spread. Since this finding is based on empirical evidence only, the delay spread must be derived from measured data. The power delay profile is rigorously derived by combining ray optical and statistical properties of wave propagation in a single room. We show that the power delay profile is indeed a negative exponential and provide a decay constant which serves as an analytical upper bound for experimentally obtained delay spreads of indoor environments. To the best knowledge of the author, this is the first derivation of the power delay profile from first principles.     

Power estimation method for highly correlated input sequences underrealistic delay model

A new power estimation method is presented which considers spatio-temporal correlations among the primary inputs as well as the glitch effect under a realistic delay model. To deal with the glitch effect, the symbolic simulation technique is employed, and to take the correlations among the primary inputs into account, the authors employ a new technique which transforms correlation information into a logic structure, called `pre-logic'. Experimental results show that the estimation error of the proposed method is ~4% under a realistic delay model with highly correlated input streams     

Improvement of delay spread immunity by using symbol timing synchronisation based on maximum likelihood estimation for 16 QAM/TDMA diversity receivers

Symbol timing synchronisation (STSYNC) based on maximum likelihood estimation and a receiver configuration in which each branch independently estimates optimum STSYNC timing are proposed to improve delay spread immunity for I6 QAM/TDMA diversity receivers. Computer simulation confirms that the proposed STSYNC and receiver configuration can improve delay spread immunity by approximately 30%.<>     

New technique for channel synchronisation in time division multiplexing

A channel synchronisation technique is described for t.d.m. systems carrying voice or teletype signals. According to this method, no extra sync signal is transmitted and synchronisation is extracted from the information signal. Furthermore, some encryption of the signal is achieved in this way. Tests had quite satisfactory results.     

Markov-chain modeling for multicast signaling delay analysis

Feedback signaling plays a key role in flow control because the traffic source relies on the signaling information to make correct and timely flow-control decisions. However, it is difficult to design an efficient signaling algorithm since a signaling message can tolerate neither error nor latency. Multicast flow-control signaling imposes two additional challenges: scalability and feedback synchronization. Previous research on multicast signaling has mainly focused on the development of algorithms without analyzing their delay performance. To remedy this deficiency, we have previously developed a binary-tree model and an independent-marking statistical model for multicast-signaling delay analysis. This paper considers a general scenario where the congestion markings at different links are dependent - a more accurate but complex case. Specifically, we develop a Markov-chain model defined by the link-marking state on each path in the multicast tree. The Markov chain can not only capture link-marking dependencies, but also yield a tractable analytical model. We also develop a Markov-chain dependency-degree model to evaluate all possible Markov-chain dependency degrees without any prior knowledge of them. Using the above two models, we derive the general probability distributions of each path becoming the multicast-tree bottleneck. Also derived are the first and second moments of multicast signaling delays. The proposed Markov chain is also shown to asymptotically reach an equilibrium, and its limiting distribution converges to the marginal link-marking probabilities when the Markov chain is irreducible. Applying the two models, we analyze and contrast the delay scalability of two representative multicast signaling protocols: Soft-Synchronization Protocol (SSP) and Hop-By-Hop (HBH) algorithms.     

Series resistance calculation for source/drain extension regionsusing 2-D device simulation

Series resistance in the source/drain region is becoming a bottleneck for MOS device performance. A rigorous, simulation-based method for calculating resistance components that correctly accounts for current spreading is presented. Resistance calculation strategies used to project lateral abruptness requirements for future scaling, based on partitioning the device into vertical strips, are shown to cause substantial errors when current spreading occurs. This can result in an overestimate of the benefits of abrupt junctions. The physical resistances obtained from simulated devices are compared with the extracted resistances from the shift-and-ratio method. Discrepancies can be explained based on violation of the basic assumptions of the shift-and-ratio method: that series resistance is bias independent and the channel resistance is directly proportional to the channel length. A new extraction method that relaxes these assumptions is presented and used to provide deeper understanding in the application of the shift-and-ratio method to deep submicron devices     

时滞和相关性观测条件下的红外目标状态估计方法

着重对红外跟踪系统目标状态估计过程中存在的观测量滞后和相关性问题进行研究。在目标跟踪过程中,脱靶量信号的滞后导致目标量测位置和真实值间是有误差的,进而通过状态估计得到的目标参数也是不准确的,另外观测量的相关性也降低了估计效果的准确性。对于以上问题,首先利用观测重组技术对时滞观测序列进行重组,将其转化为变结构无时滞观测系统,并在此基础上提出了一种时滞椭球集员估计算法(Delayed ellipsoidal set filter,DESF)。仿真实验结果表明,DESF算法可以有效克服观测序列相关性的影响,同时系统跟踪性能较不考虑观测延迟的情况也有显著提高。     

Message delay analysis for TDMA schemes using contiguous-slotassignments

Under a TDMA (time-division multiple-access) scheme, a station shares a multiple-access communications channel by transmitting its messages during its dedicated time slots. An exact result concerning the queue-sizer and message delay analysis of TDMA systems in which a station is allocated multiple consecutive slots per frame is presented. The generating function of the system queue-size for a general independent arrival message process is obtained. Messages consist of a random number of packets, following a geometric distribution. An exact result for the generating function of the message delay for various common message arrival processes and light bounds for the mean message queue-size and delay are then derived. The results are compared to previously derived approximations. It is also proved that a slot allocation scheme which distributes station slots uniformly over the frame yields a message-delay lower bound. The results also apply to the analysis of time-shared reservation schemes     

Message delay and queue-size analysis for circuit-switched TDMAsystems

A multiple-access communications channel which is shared among network stations using a circuit-switched time-division multiple-access (CS-TDMA) scheme is examined. Each station is allocated a fixed number of slots (N) during each frame. The authors carry out queue-size message delay analysis for CS-TDMA systems. They derive the generating function of the queue size and of the waiting time distribution for a discrete-time Geom^[x]/Geom/N queuing system. This result is used to obtain the generating function of the system size for the CS-TDMA scheme. The associated computation requires the solution of (N+1)2^N linear equations. To derive a more computationally effective procedure, tight lower and upper bounds are obtained, requiring the solution of at most 3N linear equations. The authors prove that a slot allocation scheme which distributes station slots uniformly over the frame yields a message delay lower bound. The application of the results to the analysis of demand-assigned CS-TDMA systems is also discussed     

Crosstalk-affected delay analysis in nanometer technologies

This article presents a detailed analysis of the crosstalk-affected delay of coupled interconnects considering process variations. We utilise a distributed RC-π model of the interconnections to accurately model process variations. In particular, we perform a detailed investigation of various crosstalk scenarios and study the impact of different parameters on crosstalk delay. Although accounting for the effect of correlations among parameters of the neighbouring wire segments, statistical properties of the crosstalk-affected propagation delays are characterised and discussed. Monte Carlo-based simulations using Spice demonstrate the effectiveness of the proposed approach in accurately modeling the correlation-aware process variations and their impact on interconnect delay in the presence of crosstalk.     

Long transition analysis for digital video sequences

Video indexing is a technique used to extract objects within a video sequence and index them so that they can be used for future retrieval. In many video sequences, special effects such as fade and wipe are incorporated, and in some cases, it is desirable to be able to include objects within such effects for indexing. In this paper, we introduce an automatic process that determines the type of transition and extracts information from it, so that this information can be used in object extraction. Such a process consists of four stages: shot boundary refinement, shot type determination, frame reconstruction for soft transitions, and shot classification for hard transitions. In this paper, we will give the implementation, timing, and performance analysis for each stage. Long transition analysis bridges the gap between shot boundary detection and object tracking and smoothes the process of automatic video indexing for video databases.     

Covariance analysis of time delay estimates for strained signals

Estimates of time-varying delays from the ultrasonic echo signals of compressed biological media are the basis of a new type of medical imaging known as elastography. This paper is focused on predicting the covariance between time delays estimated from sequential Gaussian-weighted echo segments that overlap. The accuracy of the analysis was tested and improved by comparisons with measurements involving ultrasonic waveforms simulated from independent band-limited Gaussian signal and noise spectra. Data were generated to explore the dependence of time delay covariance on ultrasonic signal-to-noise ratio, time-bandwidth product W, fractional bandwidth, window separation, and the amount of strain (a is the time rate of change in delay). The relationship between a and other experimental parameters was crucial for understanding how signal decorrelation affects time delay error and, ultimately, elastographic noise. For echo waveforms without strain (a=0), delay variance was found to decrease with W. However, when waveform segments were strained (a≠0) a minimum was found in the plot of time delay variance versus W, where delay errors from additive noise equaled those from signal decorrelation caused by strain. Delay covariance decreased monotonically with increasing window separation (less overlap) when a=0. When a≠0, however, the covariance became negative for large separations. Properties of strain image noise were predicted from knowledge of the experimental parameters and time delay errors     

Triple correlation analysis of binary sequences for codeworddetection

It is well known that multiple correlations of deterministic signals allow information about those signals to be extracted. The paper describes the application of triple correlation techniques to identify characteristics of several binary cyclic sequences commonly used in communications systems, especially those used in spread-spectrum systems. It is shown that the feedback function for a linear feedback shift register which generates an m-sequence can be found through the use of triple correlation. Examples of how to identify the feedback function when noise and data are present on the spread-spectrum signal are given     

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.     

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.<>     

A packet delay analysis for cellular digital packet data

We formulate and analyze a model of voice and data burst traffic for cellular digital packet data (CDPD). To develop a tractible model, we make some reasonable simplifying assumptions to model the voice traffic and one of the logical CDPD channels as an M/M/1 queue in a random environment. Rather than explicitly solve the resulting matrix quadratic equation, we develop an asymptotic analysis that gives us simple approximate formulas (with error bounds) for many performance measures of interest. In particular, one metric that we highlight comes from using our approximate mean data burst delay formula to characterize the performance of a set of interacting logical CDPD channels. We do so by describing it in terms of an equivalent number of independent, dedicated CDPD channels, We can use this metric to suggest what the optimal number of logical CDPD channels for a given system should be     

Design of optimum sync and detection patterns for frame synchronisation

Frame synchronisation for a packet transmission system, in which the sync pattern is preceded by a known preamble, is considered. The correlation receiver uses an extended (or shortened) version of the sync pattern, which is called the detection pattern. This leads to a new criterion for designing optimum pairs of sync and detection patterns. The obtained patterns result in a normalised improvement of up to 3.91 dB over the known optimum patterns.     

A unified delay analysis framework for opportunistic data collection

Wireless Networks - The opportunistic data collection paradigm leverages human mobility to improve sensing coverage and data transmission for collecting data from a number of Points of Interest...