Academic literature on the topic 'Pn_ sequence (pseudo-noise sequence)'

У дисертаційній роботі вирішена актуальна науково-технічна задача, яка полягає в новому комплексному підході до забезпечення мінімальної потужності передавача, достатньої для одержання заданої ймовірності помилки приймання сигналу, та покращеної скритності передачі інформації. Проведені дослідження впливу виду модуляції сигналу на потужність передавача радіорелейної станції. Показано, що найкращі результати досягаються при використанні 4-х позиційного фазоманіпульованого сигналу ФМ-4. При даній смузі пропускання радіоканалу пропонується використати амплітудно-маніпульований сигнал з підвищеним рівнем сигналів та їх кількості шляхом автоматичного встановлення максимального рівня вихідної напруги підсилювача. Пропонується спосіб визначення відношення сигнал/шум та рівня сигналу помилки, що дозволяє створити системи автоматичного регулювання потужності передавачів радіорелейних станцій в дуплексній та симплексній системі радіорелейній зв’язку з використанням переданого через канал зворотного зв’язку сигналу помилки.. При розробці телекомунікаційних систем (ТКС) ефективно використання широкосмугового шумоподібного сигналу з великою базою, що забезпечує підвищену завадостійкість систем в умовах дії завад, покращені електромагнітну сумісність систем та скритність передачі інформації. Широкосмуговий сигнал формується з використанням ряду відомих модулюючих псевдовипадкових послідовностей (ПВП) методом прямого розширення спектру, але такі системи не можна вважати захищеними від несанкціонованого доступу. Суттєве підвищення скритності передачі інформації забезпечує створення та використання для створення шумоподібного сигналу ПВП на основі хаосу. Як показали дослідження, слід вважати ефективним використання ПВП з шістьма секретними ключами на основі ПВП із 2-х хаотичних сигналів. Такі системи практично неможливо розкрити зловмисникам на відміну від ТКС з відомими ПВП (m-послідовності, ПВП Голда, Касамі та інш.). При створенні системи з широкосмуговим сигналом з 2-а антенними каналами здійснюється кодове розділення сигналів в приймачі та оптимальна обробка сигналу шляхом використання RAKE- приймачів . Підкреслюється можливість створення в системі каналу зворотного зв’язку для корегування потужності передавача в симплексній та дуплексній радіорелейній системі передачі.<br>В диссертационной работе решена актуальная научно-техническая задача, заключающаяся в новом комплексном подходе к улучшению энергетических характеристик цифровых радиорелейных системах передачи путем использования эффективных методов манипуляции сигнала, адаптивных методов приема с автоматической регулировкой мощности передатчика и обработкой сигнала в приемнике. Кроме того, использование псевдослучайной последовательности на основе хаоса и кодовое разделение сигнала в отдельных каналах обеспечивает улучшенную скрытность передачи информации Проведены исследования влияния вида манипуляции сигнала на мощность передатчика радиорелейной станции. Показано, что наилучшие результаты достигаются при использовании 4-х позиционного фазоманипулированного сигнала ФМ-4. При этом энергоэффективность системы будет на 2,7 дБ выше, чем при использовании сигнала ФМ-2, а тем более других видов манипуляции. Важно, что в данном случае система имеет также лучшую помехоустойчивость. При данной полосе пропускания радиоканала предлагается добиться повышения пропускной способности системы путем увеличения количества позиций амплитудно-манипулированного сигнала та их уровня, что достигается автоматическим регулирования максимального уровня выходного напряжения усилителя. Предлагается способ определения отношения сигнал/шум и уровня сигнала, который позволяет создать системы автоматического регулирования мощности передатчиков радиорелейных станций в дуплексной и симплексной системе радиорелейной связи с использованием канала обратной связи. При этом осуществляется адаптивный прием сигнала в системе с автоматическим регулированием мощности передатчиков с использованием сигнала ошибки, переданного через канал обратной связи. При разработке телекоммуникационных систем (ТКС) эффективно использование широкополосного сигнала с большой базой, что обеспечивает повышенную помехоустойчивость систем в условиях действия узкополосных и широкополосных помех, улучшенные электромагнитную совместимость систем с соседними электронными устройствами и скрытность передачи информации. Широкополосный шумоподобный сигнал формируется с использованием ряда известных модулирующих псевдослучайных последовательностей (ПСП) методом прямого расширения спектра, но такие системы нельзя считать защищенными от несанкционированного доступа. Существенное повышение скрытности передачи информации обеспечивает использование для создания шумоподобных сигналов ПСП на основе хаоса. Как показали исследования, следует считать эффективным использование ПСП с шестью секретными ключами на основе ПСП из 2-х хаотических сигналов с логистическим и квадратичными изображениями. Это в 2 раза повышает уровень криптозащиты систем, которые практически невозможно раскрыть злоумышленникам в отличие от ТКС с известными ПСП (m-последовательности, ПВП Голда, Касами и др.). При создании систем с широкополосным сигналом двумя антенными каналами осуществляется кодовое разделение сигналов в приемнике и оптимальная обработка сигнала путем использования Rake-приемников. Подчеркивается возможность создания в системе канала обратной связи для передачи сигнала ошибки и создания системы автоматического регулирования мощности передатчика в симплексной и дуплексной радиорелейной системе передачи.<br>Actual scientific and technical problem is solved in the thesis, which consists in a new complex approach to provide the minimum transmitter power sufficient to obtain a given probability of signal reception error and improved secrecy of information. Researches of influence of modulation types of a signal are carried out on power of radio relay station transmitter. It is shown that the best results are achieved when using a QPSK modulation type. With the given bandwidth, it is proposed to use AM signal with an increased level of signals and their number by automatically setting the maximum amplifier output voltage. A method is proposed to determine the signal / noise ratio and a level of signal error, enabling to develop a system of automatic power control of radio relay station transmitter for simplex and duplex types using transmitted signal error via a feedback channel. Developing a telecommunication system (TCS), it is efficient to use a broadband signal with a wide base, which provides increased noise immunity for interference, improved electromagnetic compatibility of systems and secrecy of information transmission. Broadband noise-like signal is generated using a number of known modulating pseudo-random sequences (PRS) by direct spread spectrum approach, but such systems cannot be considered protected from unauthorized access. A significant increase of the secrecy of information transmission provides the use of a noise-like signal using PRS based on chaos. Studies have shown that the use of PRS with six secret keys based on PRS with 2 chaotic signals should be considered an effective one. Such systems are significantly protected from unauthorized encoding, in contrast to TCS with known PRS (m-sequences, Gold’s PRS, Kasami’s PRS, etc.). Creating a system with a broadband noise-like signal with 2 antenna channels are used code division of signals in the receiver and optimal signal processing by using Rake type receivers. The possibility of creating a feedback channel in the system to adjust transmitter power of simplex and duplex radio relay system is emphasized.

碩士<br>樹德科技大學<br>電腦與通訊研究所<br>92<br>Abstract This thesis investigates spread spectrum technology in Code Division Multiple Access (CDMA) for wireless communication system, and applies MATLAB Simulink to simulate a part of the operation in CDMA process. In the 2G mobile communication system, the bad control of far and near power over mobile station and base station often causes the bad impression on communication. Besides, the defect in the 2G mobile communication system will cause more critical situation to the users in the high-speed standard of 3G mobile communication system, which is expanded because of the developing of internet and the requisition of communication application. This investigation also employs the features of high security and low interception of multiple encoding technology by combining the Pseudo-Noise sequence and data signal to avoid wiretap by other users in 2G communication system. The power of transmitter data signal will be decided increased or decreased to make sure that base station can receive all the CDMA encoding signal. The demo program in MATLAB Simulink has formed the process as many function blocks to users to edit the CDMA communication system conveniently. But these convenient functions also make the system hard to understand. Therefore, this thesis also contributes to re-edit the function blocks using MATLAB Simulink in order to present the CDMA spread spectrum communication system in an easier way.

Code Division Multiple Access (CDMA) based on Spread Signal (SS) has emerged as one of the most important multiple access technologies for Second Generation (2G) and Third Generation (3G) wireless communication systems by its wide applications in many important mobile cellular standards. CDMA technique relies on spreading codes to separate dierent users or channels and its properties will govern the performance of the system. So many of the problems of communication systems based on CDMA technology stem from the spreading codes/sequences, which includes two sub-categories, one being the orthogonal codes, such as Walsh Hadamard (WH) codes and Orthogonal Variable Spreading Factor (OVSF) codes, and the other being pseudo-noise or Pseudo Random (PN) sequences, such as Gold sequences, Kasami sequences, m-sequences, etc. In this thesis a PN sequence generation based on Residue Arithmetic is investigated with an eort to improve the performance of existing interference-limited CDMA technology for mobile cellular systems. This interference-limited performance is due to the fact that all the existing CDMA codes used in mobile cellular standards does not consider external interferences, multipath propagation, Doppler eect etc. So the non-ideal correlation properties of the pseudo-random CDMA codes results in MAI when used in a multi-user system. The PN codes appear random yet they are completely deterministic in nature with a small set of initial conditions. Consequently this work focuses on CDMA code design approach based on Residue Number System (RNS) which should take into account as many real operational conditions as possible and to maintain a suciently large code set size.First, the thesis reviews RNS, DS-CDMA and CDMA codes that are already implemented in various mobile cellular standards. Then the new PN Sequencegenerator design based on RNS is discussed. Comparison of the generated PN sequence with respect to other standard sequence is done in terms of number of codes and correlation properties. Monte-Carlo simulations with the generated sequence are carried out for performance analysis under multi-path environment. The system has been evaluated in AWGN, Rayleigh Fading channel and dierent Stationary Multipath Channels for dierent cross-correlation threshold. It is known that orthogonal Codes are used to multiplex more than one signal for downlink transmission over cellular networks. This downlink transmission is prone to self interference caused by the loss of orthogonality between spreading codes due to multipath propagation. This issue is investigated in detail with respect to WCDMA standards, which is very good representative for CDMA based 3G mobile cellular systems where the channelization code is OVSF code. The code assignment blocking (CAB) (If a particular code in the tree is used in a cell, then all its parent codes and child codes should not be used in the same cell to maintain orthogonality among the users) problem of OVSF codes restricts the number of available codes for a given cell. Since the 3rd generation WCDMA mobile communication systems apply the same multiple access technique, the generated sequence can also be the channelization code for downlink WCDMA system to mitigate the the same. The performance of the system is compared with Walsh Hadamard code over multipath AWGN and dierent Fading channels. This thesis work shows that RNS based PN sequence has enhanced performance to that of other CDMA codes by comparing the bit error probability in multi- user and multipath environment thus contributing a little towards the evolution of next generation CDMA technology.

博士<br>國立中正大學<br>電機工程研究所<br>87<br>Many code acquisition techniques with different types of searching strategies and detector structures have been proposed, analyzed and employed in practical Direct-Sequence Spread-Spectrum (DS/SS) systems. In this thesis, the noncoherent code acquisition systems with different test methods (fixed dwell-time or sequential) and correlators (active or passive) are investigated for AWGN channels and multipath fading channels. For AWGN channels, a new method is explored to evaluate the performance of the sequential code acquisition systems to any desired accuracy. Starting from Albert''s integral equations, the method evaluates the detection probability, false alarm probability and the moments of the sample number very efficiently and accurately by using polynomial interpolations. Numerical examples show that the new method is much more efficient and/or accurate than the known methods, including the Wald''s approximation. For multipath fading channels, the exact analysis of the code acquisition system becomes extremely difficult because of the channel memory incurred by multipath fading. In this research, we first investigate a code acquisition based on multiple-dwell or sequential linear test with the active correlator on multipath Rayleigh fading channels. By assuming the time between correct cells detections is larger than the channel coherence time, a novel method is developed to evaluate the mean acquisition time of the acquisition systems to any desired accuracy. The effects of multipath fading are evaluated, and comparisons are made between the multiple-dwell and sequential linear tests. Numerical results show that the multipath fading may result in 1-4 dB loss in performance and the sequential linear test can outperform the multiple-dwell test by a margin of 1-2.5dB. The analytical results are verified by computer simulations. In addition, a unified analysis is proposed for accurate evaluation of the acquisition performance on multipath Rayleigh fading channels without imposing the assumption that the time between correct cells detections is larger than the channel coherence time. Since the homogeneous Markov chain model, used to characterize the acquisition process over additive white Gaussian noise (AWGN) channels, is no longer valid due to the correlations between cell detections incurred by fading. The traditional direct and flow-graph approaches for performance evaluation of an acquisition system are not applicable to this fading channel.Hence, some new theory are required in this analysis. This analysis is quite general and can include various search strategies, correlators and test methods with different performance measures: probability mass function (PMF) and/or moments of the acquisition time. Analytical and computer simulation results show that the new method predicts the acquisition performance very accurately.

博士<br>國立中正大學<br>電機工程研究所<br>88<br>Four issues and solutions are investigated in the thesis with regard to the pseudo-noise (PN) code synchronization for single- and multi-carrier direct sequence spread spectrum (DS-SS) systems operating on additive white Gaussian noise (AWGN) and/or multipath fading channels. In the first part, code tracking with code-Doppler compensation for single carrier DS-SS systems on AWGN channels is proposed. Code Doppler compensation is introduced to the traditional noncoherent digital delay lock loop (DLL) in addition to carrier Doppler compensation. Thanks to the code Doppler compensation, the simple-to-implement active correlation with a large correlation length can be employed to improve the loop performance. The code Doppler compensation significantly improve the loop performance with the presence of a large code Doppler. In the second part, new tracking loop analysis with A/D quantization for single carrier DS-SS systems on AWGN channels is considered. In particular, the performance of non-coherent second-order all digital delay lock loops with the presence of Doppler shift is analyzed. A new method based on a regenerative Markov chain modeling of the tracking process is proposed with the loop A/D quantization being taken into account that has been neglected in previous analyses. Numerical results show that A/D quantization has a significant impact on the loop performance, including loop transient responses, lock-in range, mean time to lose lock (MTLL) and mean square error (MSE). In addition, by using saddle point integration for the evaluation of the transition probabilities of the Markov chain, MTLL and MSE is evaluated more accurately than previous methods. In the third part, the code acquisition for multicarrier direct sequence code division multiple access (DS-CDMA) systems on multipath fading channels is investigated. For multipath fading channels, the exact analysis of code acquisition becomes difficult because of the channel memory incurred by multipath fading. In this part, a new analysis is given to accurately evaluate the mean acquisition time performance of the serial search multiple dwell code acquisition for the multicarrier DS-CDMA systems. Our analysis can take the fading correlations into account, the effects of system parameters on the acquisition performance such as carrier and user numbers, fading correlations, dwell''s number, times and thresholds can be easily evaluated, and, therefore, facilitating the design of the acquisition subsystem. Finally, code tacking for multicarrier DS-CDMA systems on multipath fading channels is investigated. In this part, the tracking error performance of the traditional noncoherent DDLL with diversity reception is analyzed for the multicarrier DS-CDMA systems, under the effects of automatic gain control (AGC), multipath fading, and multiple access interference. AGC is used to eliminate the inherent stability problem of a DDLL. And, a new decision-directed noncoherent tracking loop based on a differentially-detected phase detector is proposed and analyzed. The new tracking loop outperforms the traditional DDLL.

Third generation mobile communication systems promise a greater data rate and new services to the mobile subscribers. 3G systems support up to 2 Mbps of data rate to a fixed subscriber and 144 Kbps of data rate to a fully mobile subscriber. Code Division Multiple Access (CDMA) is the air interface access scheme widely used in all the 3G communication systems. This access scheme has many inherent advantages m terms of noise immunity, security, coherent combining of multi path signals etc. But all these advantages come at the expense of higher complexity of the receivers. The receivers form the major portion of the processing involved in a base station. The heart of any CDMA receiver is the RAKE. The RAKE receiver separates the different multi-paths received by the antenna by using the properties of the Pseudo Random sequences. The phase and strength of each of these path signals is measured and are used by the coherent combiner, which de-rotates all the signals to a single reference and coherently combines them In general the Base station receivers make use of the top three multi-path signals ranked in terms of their signal energy Hence four RAKE fingers, each catering to single multi-path are needed for receiving a single code channel (3 for coherent combining and one for scanning). One such channel receiver requires a processing power of 860 MIPS (Mega Instructions Per Second). Some of the CDMA standards support up to 90 code channels at the same time. This means that the total processing power required at the base station is about 80 GIPS. This much of processing power will require large number of high end DSPs, which will be a very costly solution. In the current base station architectures these blocks are implemented using ASICs, which are specific to a particular standard and also the algorithms used for the different operations are fixed at the design time itself. This solution is not flexible and is not amenable for SDR (Software defined Radio) architectures for the Base stations. This thesis proposes a Co-Processor solution, which can be attached to a generic DSP or any other processor. The processor can control the Co-Processor by programming its parameter registers using memory mapped register accesses. This co-processor implements only those blocks, which are compute intensive. This co-processor performs all chip-rate processing functions involved m a RAKE receiver. All the symbol-rate functions are implemented through software in the processor. This provides more choices m selecting the algorithms for timing recovery and scanning. The algorithms can be changed through software even after the base station is installed in the field. All the inputs and outputs of the Co-Processor are passed through dual port RAMs with independent read and write clocks. This allows the Co-Processor and the processor to be running on two independent clocks. This memory scheme also increases the throughput as the reads and writes to these memories can happen simultaneously. This thesis introduces a concept of incorporating programmable PN/Gold code generators as part of the Co-Processor, which significantly reduces the amount of memory required to store the Scrambling and Spreading codes. The polynomial lengths as well as the polynomials of the code generator are programmable. The input signal memory has a bus width equal to 4 times the bus width of the IQ signal bus width (4 * 24 = 96 bits) towards the Co-Processor to meet the huge data bandwidth requirement. This memory is arranged as word interleaved memory banks. This can supply one word per memory bank on each clock cycle as long as the accessed words fall in different memory banks. The number of banks is chosen as more than twice that of the number of Correlators/ Rake fingers. This gives more flexibility in choosing the address offsets to different Correlator inputs. This flexibility allows one to use different timing recovery schemes since the number of allowable address offsets for different Correlators is more. The overall complexity of the solution is comparatively less with respect to the generic DSP based solution and much easier to modify for a different standard, when compared to the rigid ASIC based solution. The proposed solution is significantly different from the conventional way of designing the Base station with fixed ASICs and it clearly outweighs the solutions based on conventional approach in terms of flexibility, design complexity, design time and cost.

Third generation mobile communication systems promise a greater data rate and new services to the mobile subscribers. 3G systems support up to 2 Mbps of data rate to a fixed subscriber and 144 Kbps of data rate to a fully mobile subscriber. Code Division Multiple Access (CDMA) is the air interface access scheme widely used in all the 3G communication systems. This access scheme has many inherent advantages m terms of noise immunity, security, coherent combining of multi path signals etc. But all these advantages come at the expense of higher complexity of the receivers. The receivers form the major portion of the processing involved in a base station. The heart of any CDMA receiver is the RAKE. The RAKE receiver separates the different multi-paths received by the antenna by using the properties of the Pseudo Random sequences. The phase and strength of each of these path signals is measured and are used by the coherent combiner, which de-rotates all the signals to a single reference and coherently combines them In general the Base station receivers make use of the top three multi-path signals ranked in terms of their signal energy Hence four RAKE fingers, each catering to single multi-path are needed for receiving a single code channel (3 for coherent combining and one for scanning). One such channel receiver requires a processing power of 860 MIPS (Mega Instructions Per Second). Some of the CDMA standards support up to 90 code channels at the same time. This means that the total processing power required at the base station is about 80 GIPS. This much of processing power will require large number of high end DSPs, which will be a very costly solution. In the current base station architectures these blocks are implemented using ASICs, which are specific to a particular standard and also the algorithms used for the different operations are fixed at the design time itself. This solution is not flexible and is not amenable for SDR (Software defined Radio) architectures for the Base stations. This thesis proposes a Co-Processor solution, which can be attached to a generic DSP or any other processor. The processor can control the Co-Processor by programming its parameter registers using memory mapped register accesses. This co-processor implements only those blocks, which are compute intensive. This co-processor performs all chip-rate processing functions involved m a RAKE receiver. All the symbol-rate functions are implemented through software in the processor. This provides more choices m selecting the algorithms for timing recovery and scanning. The algorithms can be changed through software even after the base station is installed in the field. All the inputs and outputs of the Co-Processor are passed through dual port RAMs with independent read and write clocks. This allows the Co-Processor and the processor to be running on two independent clocks. This memory scheme also increases the throughput as the reads and writes to these memories can happen simultaneously. This thesis introduces a concept of incorporating programmable PN/Gold code generators as part of the Co-Processor, which significantly reduces the amount of memory required to store the Scrambling and Spreading codes. The polynomial lengths as well as the polynomials of the code generator are programmable. The input signal memory has a bus width equal to 4 times the bus width of the IQ signal bus width (4 * 24 = 96 bits) towards the Co-Processor to meet the huge data bandwidth requirement. This memory is arranged as word interleaved memory banks. This can supply one word per memory bank on each clock cycle as long as the accessed words fall in different memory banks. The number of banks is chosen as more than twice that of the number of Correlators/ Rake fingers. This gives more flexibility in choosing the address offsets to different Correlator inputs. This flexibility allows one to use different timing recovery schemes since the number of allowable address offsets for different Correlators is more. The overall complexity of the solution is comparatively less with respect to the generic DSP based solution and much easier to modify for a different standard, when compared to the rigid ASIC based solution. The proposed solution is significantly different from the conventional way of designing the Base station with fixed ASICs and it clearly outweighs the solutions based on conventional approach in terms of flexibility, design complexity, design time and cost.