Geometric Capacity Studies for DTV Transmitter Identification By Using Kasami Sequences

A transmitter identification system for DTV distributed transmission network using embedded pseudo random sequences is investigated. Different orthogonal pseudo random sequences and their suitability for transmitter identification are discussed. Code generators are developed to study the auto-correlation and cross-correlation properties of the Kasami sequences. To speed up the identification process, the embedded pseudo random sequence is preferred to be time-synchronized with the DTV frame structure. Therefore, the length of the identification code has to be truncated before it is fitted into each field of the ATSC DTV signal. The impact of truncation noise and in-band DTV interference on transmitter identification is also investigated. It is shown that the auto-correlation and cross-correlation properties are only slightly affected by truncation. It is also found that the dominant interference to the transmitter identification is the in-band DTV signal. The signal to truncation noise ratio and signal to DTV interference ratio in the correlation output are derived, and verified via simulation. It is further recognized that in-band DTV interference can only be mitigated by increasing the code length or by time-domain averaging technique to smoothen out the in-band interference.

In a Single Frequency Network (SFN) for Advanced Television Systems Committee (ATSC) terrestrial digital television (DTV) system, the interferences induced by the multiple transmitters and/or repeaters using same frequency are unavoidable. To ease the interference handing in the SFN for ATSC DTV system, transmitter identification (TxID) signal is recommended in the ATSC terrestrial DTV system. The TxID signal is embedded in the ATSC DTV signal and transmitted from each transmitter and repeater within the SFN and in ATSC recommended practice (RP) A/111, Kasami sequence is recommended as the TxID signal. In this paper, we propose an additional data transmission scheme using the TxID signal. In the proposed scheme, the Kasami sequence not only acts as the conventional TxID of the SFN for ATSC terrestrial DTV system but also carriers the additional data bits on its polarity and the code phase.

Transform domain communication system (TDCS) and wavelet domain communication system (WDCS) have been reported to have interference avoiding capability under adverse environmental conditions. These systems achieve low probability of intercept (LPI) and orthogonality simultaneously by using the pseudorandom (PR) sequences for generating the phase vector of the basic function. Conventionally, the PR phase vectors in TDCS and WDCS were generated by a maximal length binary PR sequence (m-sequence), which allows only a relatively small number of users in the systems. This paper reports a method to increase the user capacity of TDCS and WDCS by applying Gold sequence to generate the PR phase vector of the basic function. The increased user capacity of the systems based on Gold sequence is tabulated. Simulation results also demonstrate that by using Gold sequences for the PR phase generation, both TDCS and WDCS can provide a comparable interference avoiding capability with a larger user capacity, compared to those of the systems based on m-sequences in multiple access environments.

In this paper, a binary direct-sequence spread-spectrum multiple-access (DS/SSMA) communication system with an additive white Gaussian noise channel and a correlation receiver are considered. The signature sequences are m-sequences or random sequences when the number of users is small and are random sequences, Gold sequences, or Kasami sequences when the number of users is large. Simulation results are obtained to verify a variety of bounds provided in other literature and to compare system performance when employing different signature sequences. >

The ATSC A/110 standard specifies a transmitter identification (TxID) system using RF water-mark. The system, using a 16-bit Kasami sequence, can identify up to 16 millions DTV Transmitters. With the recent development of the ATSC Mobile DTV (M/H), the implementation of transmitter identification will enable new capabilities to receivers in mobile environment. In this paper, we investigate the TxID reception over mobile channels with Doppler fading, dynamic multipath, carrier offset and clock offset, etc. Our simulation results have confirmed the validity of TxID scheme in mobile environment.

In this paper, we propose a novel transmitter identification (TxID) technique for use in distributed 8VSB DTV systems. Channel information (CI) is obtained by utilizing the properties of training sequence (TS). Channel applied data (CAD) is obtained by applying the detected DTV data to the estimated CI. Thereby, the CAD becomes similar to the received signal except for the embedded watermark. Since the in-band DTV signal can be eliminated efficiently from the received signal when the CAD is used, the proposed method will provide a large dynamic range and fast acquisition of TxID as well as high signal to interference and noise ratio (SINR).

This paper presents new binary spreading sequences, obtained by tabu search. These sequences exhibit odd correlation properties concerning the minimax criterion better than those of the classical sequence families, such as the well known Kasami and Gold sequences. In particular, the design process takes into account both odd and even correlation properties which means that global performance is compromised. These new sequences also have same mean-square correlation performance as classical ones.

In this contribution, we propose a novel scheme for time and frequency synchronization in OFDM systems. A differential modulation is indeed used to design two training symbols with appropriate properties used as a preamble for the detection of the frame start and for the recovery of the integral carrier frequency offset. The new scheme is compared to the well known algorithm of Cox and Schmidl, also using two training symbols, and found to outperform it especially in timing acquisition for both AWGN and Rayleigh channels. As a byproduct, an estimator for the channel power profile is obtained. All the derived estimators performance depend on the choice of the symbols involved in training. We here discuss the properties for optimal performance and compare the results for a set of Gold, Kasami and Zadoff-Chu sequences.

The closed-loop brain stimulation system can adjust stimulation parameters based on neural activity feedback, so as to provide precise and personalized treatment for neurological and neuropsychiatric diseases. The design of a model-based closed-loop system requires the choice of a suitable system identification framework to learn a dynamic mapping from input and output data to quantify the effect of input stimulation on output neural activity, and design the controller with the identification model. We first designed a control-theory system identification framework to build a dynamic input-output (IO) model of neural activity suitable for closed-loop control design. To achieve effective model-based control, we use a linear state space model (LSSM), which uses low-dimensional hidden neural states to characterize the effect of inputs on neural activity. Secondly, in order to train the model parameters, we choose a pulse sequence with independent modulation of parameters by pseudo-random sequence (PRS), and proved that this is the best choice for collecting informational IO data sets in system identification. The input waveform can be used as a deep brain stimulation (DBS) for treating neuropsychiatric diseases while meeting clinical safety requirements. Thirdly, we take the beta frequency band of the local field potential (LFP) as a biomarker of Parkinson's disease (PD) and system feedback signal to identify the system and design a closed-loop controller. The simulation results show that the closed-loop controller designed based on the LSSM model identified by the PRS modulation waveform can achieve the ideal control effect, and the performance of the model is similar to that of a real physiological IO model describing neural activity. The new PRS modulation waveform and system identification framework can help develop future model-based closed-loop stimulation systems, which is of great significance for the treatment of neuropsychiatric diseases.

System identification techniques have been applied to model human sensorimotor systems for research and diagnostic purposes. Accurate human modeling via system identification requires informative experimental data, which further require informative perturbations applied to the human. Previously, designing ideal perturbations for system identification has been extensively studied. On the other hand, the physical realization of perturbations often produces distorted perturbations, resulting in less accurate system identification and incorrect conclusions about the target dynamic system. However, such issues associated with an uncompensated physical realization process have not been fully resolved in the literature. A notable application is the design and use of the pseudorandom sequence (PRS). This article considers the physical realization of PRS perturbations. The impact of zero-order-hold (ZOH) on perturbation quality in terms of the previously proposed band-limited spectral flatness measure (SFM) is identified. To compensate for the spectral flatness degradation due to ZOH, a reference prefilter designed by the Parks–McClellan algorithm is incorporated into the motion control design. A relationship between the prefilter performance and band-limited SFM is established, based on which a prefilter design procedure that guarantees an SFM lower bound of the physically realized perturbations is proposed. Experimental results demonstrated that the proposed prefilter design method effectively improves the SFM of the physical perturbations.

The evolution of the computer-based data collection and analysis systems has lead to significant advancements in the application of modern system identification techniques to paper machine model development. Process data obtained from paper machines excited with pseudo-random binary sequences (PRBS) can be used to determine process dynamics, isolate multivariable process interactions and develop advanced computer models to evaluate existing and new control strategies. This paper examines some of the traditional parametric identification techniques such as least squares, maximum likelihood or instrumental variable methods applied to data collected from a paper machine. The resulting paper machine model includes the process dynamics, the shape of the responses in a cross machine direction sense and defines the interactions between the machine direction and cross machine direction control elements. Finally, the paper illustrates the application of the models to minimum variance methods of coordinating multiple actuators to reduce overall finished paper variability. >

Based on the analysis of the structures of isomorphic multiplicative groups of extended Galois fields, it is established that any cyclic shift of a pseudo-random Gold sequence can be transformed into a function belonging to the complete set of analogues of Rademacher functions of the corresponding dimension. This made it possible to develop a new algorithm for fast synchronization of Gold sequences based on the calculation of their discrete convolution using fast spectral transformation in a truncated basis of Walsh–Hadamard functions. The gain of the developed algorithm in terms of the number of arithmetic operations compared to the traditional method of calculating discrete convolution increases with increasing sequence length N and for N=511.1023 is approximately 3.4 times.

In this paper a completely new analytical approach to the performance evaluation of turbulence induced fading on free space optical (FSO) CDMA communication system is presented. The current analysis develops an expression of average SINR of FSO CDMA system using switched inversed keyed(SIK) correlator transmitter in presence of turbulence induced fading and multiple access interference(MAI). Link performance is evaluated in terms of average bit error rate which is numerically computed. The performance improvement over atmospheric turbulence fading channel is proposed by means of applying diversity using rake correlation receiver and output of rake receiver is combined using maximal ratio combining (MRC) scheme. It has been shown in numerical evaluation that BER gets improved in diversity reception than only line of sight (LOS) reception. Numerical result also shows that, applying path diversity mitigates multiple access interference with less received power. Finally, the performance is evaluated using two different sequences (Gold and Kasami ) and from performance evaluation, it is shown that KASAMI sequence exhibits less bit error performance than GOLD sequence.

Combining evolutionary and stochastic gradient techniques for system identification

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