Spread Spectrum Research Articles

SENECAN: Secure KEy DistributioN OvEr CAN Through Watermarking and Jamming

The Control Area Network (CAN) represents the standard bus for intra-vehicular networks communication. Unfortunately, CAN was not designed to be a secure protocol. Communications over CAN do not take advantage of any security feature (e.g., cryptography and authentication), raising different vulnerabilities in critical applications. This lack of security is even more emphasized in recent CAN networks, which integrate remote connection capabilities (e.g., Bluetooth and WiFi). This insecurity-by-design led to the development of specific mechanisms to patch CAN vulnerabilities. Many proposed solutions rely on implementing optimized cryptographic primitives and assume that the cryptographic keys were previously shared among the different nodes during the production phase, omitting the issue related to keys distribution and update. We propose SENECAN, a solution that combines watermarking and wired jamming to secure the CAN bus's key distribution. Our solution leverages intentional interference and spread spectrum watermarking to achieve security properties such as confidentiality, integrity, authentication, and anti-replay. Compared to other works, SENECAN does not require any modification of the CAN protocol and system architecture. Instead, it requires an additional CAN transceiver and an initial transmission overhead. Finally, we tested the effectiveness and functioning of the SENECAN distribution schema in a real CAN environment.

АНАЛИЗ ИСПОЛЬЗОВАНИЯ ФИЛЬТРА КАЛМАНА В ПРОЦЕДУРЕ ДЕТЕКТИРОВАНИЯ СИГНАЛА В СИСТЕМЕ С MIMO И ПРИЕМНИКОМ ПРЯМОГО ПРЕОБРАЗОВАНИЯ

Introduction: The procedure for detecting a quadrature amplitude modulation (QAM) signal in a communication system with multiple transmitting and receiving antennas (MIMO) is considered, which consists of two stages: obtaining soft solutions using the recurrent Kalman filtering algorithm, finding hard solutions by criterion of minimum distance between soft decision vectors and possible information symbols on each receiving antenna. The Kalman algorithm evaluates symbols at i-th time point in iterations. A comparison is made of noise immunity of QAM signal reception obtained using the Zero Forcing methods, the minimum mean square error (RMS), and recurrent Kalman procedure. Signal processing takes place under channel conditions with Rayleigh fading and Doppler spread spectrum. Cases are considered when the channel matrix is known exactly and when it is estimated by least squares method (LSM) using a first-order polynomial approximation for channel matrix elements. The channel matrix takes into account not only signal distortions due to the propagation medium, but also distortions obtained in the direct conversion receiver, such as amplitude and phase imbalance between signal quadratures, frequency shift due to non-ideal demodulation procedure, as well as DC drift. Result: The computational complexity of the detector based on Kalman algorithm is analyzede.

Acquisition of Time and Doppler Shift in WFRFT Encrypted Chaotic Direct Sequence Spread Spectrum System

Weighted fractional Fourier transform encrypted chaotic direct sequence spread spectrum (WFRFT-CD3S) signal is aperiodic and complex Gaussian distributed. The aperiodicity and complex Gaussian distribution are conducive to the covert transmission of information but also make it difficult to acquire the WFRFT-CD3S signal. An acquisition method implemented in two steps is proposed to acquire the Doppler-shifted WFRFT-CD3S signal. First, a bidirectional correlation search method is proposed to align the received signal with the local spreading sequence in the time domain. The correlation peak attenuation caused by the Doppler frequency shift is eliminated by differential. Second, the accumulated phase angle caused by the Doppler frequency shift is obtained by the differential correlation value between the aligned received signal and the local spreading sequence. Then, the Doppler frequency shift is estimated by the accumulated phase angle. The detection probability, the false alarm probability, and the root mean square error (RMSE) of the Doppler shift estimation are analyzed theoretically and simulated. The theoretical results are verified by simulation. Theoretical results and simulations show that the detection probability is higher than 0.999, the false alarm probability is less than 0.001, and the RMSE of Doppler shift estimation is lower than 63 Hz when the signal-to-noise ratio is higher than -7.3 dB.

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Communication and ranging composite system based on parallel combinatory spread spectrum technology

First Flight-Testing of LoRa Modulation in Satellite Radio Communications in Low-Earth Orbit

At present, the use of LoRa modulation in satellite radio communications and the construction of a CubeSat constellation for the satellite Internet of Things based on LoRa technology has already begun. However, the limits of applicability of LoRa modulation in low-Earth orbits have not yet been established. This paper presents the results of the first flight tests of LoRa modulation for robustness against the Doppler effect in the satellite-to-Earth radio channel, carried out using a NORBY CubeSat operating at 560 km. Flight tests confirmed the very high immunity of LoRa modulation to the Doppler effect for modes with spreading factor <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SF</i> ≤ 11 and spread spectrum modulation bandwidth <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BW</i> >31.25 kHz. LoRa modulation in these modes can be used in satellite communication without any limitations caused by the Doppler effect. For <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BW</i> = 31.25 kHz, the LoRa radio channel is affected by the static Doppler effect. Communication with the satellite is possible in this case only at high elevation angles. For <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SF</i> = 12, the dynamic Doppler effect becomes significant, and communication is possible only at low satellite elevation angles, which leads to the formation of a “hole” in the center of the coverage area directly below the satellite. In both cases, the duration of the communication session is significantly reduced because of the Doppler effect. In the case of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SF</i> = 11 and 12 at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BW</i> = 31.25 kHz, both static and dynamic Doppler effect catastrophically affect the LoRa radio channel, so that communication with the satellite becomes impossible.

Technical Theme Topics

Spread Spectrum modulation techniques have been widely used for many years in power converters and digital circuits to spread EMI emissions and comply with EMC regulations. However, many researchers are questioning the actual impact of these techniques in terms of coexistence with modern communication systems, which necessarily involve a reflection on the adequacy of the measurement methods specified by standards in the presence of these modulations. In these two articles, the authors share their experience and reflections on the subject by providing interesting food for thought for further analyses and future standardization. As a regular reader of this column, and I am sure I can speak on behalf of all readers of the EMC Magazine, I would like to take this opportunity to thank Prof. Christos Christopoulos for the unique and special impression he has given to this column, and for the outstanding work he did for years in providing us with the opportunity to approach relevant EMC topics that were often quite complex, in an easy to understand way. For me it is a big honor, and yet a challenge at the same time, to be the Associate Editor for this column following his outstanding effort. I truly hope to be able to provide the readers of the EMC Magazine with several interesting themes as Christos did for many years.

Корреляционный прием частотно-манипулированных сигналов в режиме с псевдослучайной перестройкой рабочей частоты

Proposals are presented on the use of signals generated on the basis of the three-element Barker sequence for the mode of frequency-hopping spread spectrum (FHSS). The conditions for the application of the frequency hopping mode are considered. An algorithm for synthesizing signals with a simultaneous change in their frequency and phase structure has been developed. An analysis of the properties of the developed signals was carried out. The positive and negative aspects of the implementation of the developed approach are shown. Proposals for their practical application are formulated. The frequency-hopping spread spectrum is actively used in many telecommunication standards and technologies in order to increase the noise immunity of transmissions in a multipath channel. As a result, due to the short stay of the signal at the carrier frequency, the probability of long-term operation in a channel with deep fading is reduced. Since the structure of the signal and frequency-hopping spread spectrum parameters are determined by known protocols and standards, this makes it possible to evaluate its capabilities in practical applications. In order to reduce the negative consequences caused by the considered collisions, it is proposed to generate signals for the slow frequency-hopping spread spectrum based on the three-element Barker sequence. Features of the implementation of this approach are considered in this article.

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Uplink Transmission Policies for LoRa-Based Direct-to-Satellite IoT

Direct-to-Satellite IoT (DtS-IoT) is a promising approach to deliver data transfer services to IoT devices in remote areas where deploying terrestrial infrastructure is not appealing or feasible. In this context, low-Earth orbit (LEO) satellites can serve as passing-by IoT gateways to which devices can offload buffered data to. However, transmission distances and channel dynamics, combined with highly constrained devices on the ground makes of DtS-IoT a very challenging problem. Here, we present LoRa-based approaches to realize scalable and energy-efficient DtS-IoT. Our study includes the Long Range-Frequency Hopping Spread Spectrum (LR-FHSS) physical layer, currently on the roadmap of future space IoT projects. Specifically, we propose uplink transmission policies that exploit satellite trajectory information. These schemes are framed with a theoretical Mixed Integer Linear Programming (MILP) model providing an upper bound on performance as well as inspiration for scheduled DtS-IoT solutions. Simulation results provide compelling evidence that trajectory based policies can duplicate the amount of IoT nodes, while specific variants can further boost the scalability by 30% without incurring energy penalties. We also quantify that LR-FHSS can improve the deployment scalability by a factor of 75x at the expenses of 30% higher device&#x2019;s power consumption compared to the legacy LoRa modulation.

EVALUATION OF THE FUNCTIONING EFFICIENCY OF RADIOLINES WITH A PSEUDORANDOM ADJUSTABLE OPERATING FREQUENCY

The need for constant improvement of radio communications arises from the growing need for voice and data transmission with high survivability and bandwidth of channels in radio links, providing information exchange between military command and control bodies, units, weapons systems and individual military personnel.The radio stations can operate both at a fixed frequency and in the frequency-hopping spread spectrum (FHSS). In the absence of organized radio interference, the mode of operation of the radio link at a fixed frequency is established. When using electronic suppression (ES) by the enemy, as well as in a complex jamming environment, the main means of protection against suppression of the communication FHSS.The technical implementation of the FHSS mode is a rather complex and costly process, so its choice can be due only to the increased requirements for noise protection. In addition, FHSS systems do not allow high data rates to be achieved due to a number of difficulties associated with coherent frequency synthesizers.The effectiveness of radio communication systems (RCS) is determined by many factors of different nature, it can be conditionally divided into three groups: the quality of the RCS, the conditions for the operation of the SRZ, the ways of using (using) the RCS.The characteristic features of the creation, deployment and operation of radio communication systems at the tactical level of control are a high degree of uncertainty in the characteristics of their functioning in the dynamics of an armed conflict, which necessitates constant improvement of approaches to justifying the choice of directions for the development of RCS.Analysis of noise protection measures by introducing FHSS mode into the radio station dictates the need for rational choice of time characteristics of the process of analog-to-digital conversion of signals (speech and data) and the process of packing the converted information into packets with pauses needed to adjust the operating frequency.The article reflects the views of the authors and proposes proposals for the approach to justify the effectiveness of RCS with FHSS on a generalized indicator of the probability of timely and reliable delivery of messages (services), which will set requirements for the criteria of technical characteristics of RCS.

On the LoRa Chirp Spread Spectrum Modulation: Signal Properties and Their Impact on Transmitter and Receiver Architectures

The LoRa modulation scheme is arousing a growing interest in the Internet of Things community as it is adopted by the emerging LoRaWAN technology. In this paper, we firstly analyse the baseband processing for the generation of LoRa signals at the transmitter side, providing a simple algorithm that leverages digital signal processing techniques to reduce the modulator complexity. Secondly, we analytically investigate the signal demodulation technique. Quite surprisingly, we found that its effectiveness depends on the particular choice of the sampling frequency at the receiver side, which purposely does not meet the sampling theorem requirement. Finally, we consider the actual architecture of digital receivers investigating the trade-off between the selectivity of receive digital filters, which impacts on the required computational effort and power consumption, and the receiver performance.

Aggregated CDMA Crossbar With Hybrid ARQ for NoCs

Network-on-chips (NoCs) are the dominant interconnection technique in modern system-on-chips (SoCs). The medium access technique used in the physical layer of NoC routers profoundly impacts the performance and footprint of the router. Code division multiple access (CDMA) is a medium access technique widely deployed in various wireless communication systems, and it has recently been proposed as a prominent switching method for NoC routers. In a CDMA crossbar, several processing elements (PEs) can communicate simultaneously over a single communication channel by applying the direct-sequence spread spectrum technique to digital interconnects. However, existing CDMA switches are bit-wise architectures in which a binary data bit is spread and serially communicated on an exclusive digital channel while replicating this configuration to communicate multiple data bits, which increases the crossbar area and wiring density. In this work, we propose aggregated CDMA (ACDMA) to improve the area, throughput, and power consumption of existing CDMA NoC routers. ACDMA exploits the static nature and relative noise immunity of on-chip interconnects to aggregate transmission of multiple data bits into M-ary symbols on a single digital communication channel, which significantly reduces the wiring density and area overhead of the crossbar. Serial and parallel variants of the ACDMA crossbar offering a wide range of area-speed trade-offs are implemented in the ASIC <inline-formula> <tex-math notation="LaTeX">$65~nm$ </tex-math></inline-formula> standard cell technology. The implementation results show that the throughput-per-area (TPA) of the serial and parallel ACDMA crossbars is improved by 96.3&#x0025;, 18.2&#x0025;, and 118.6&#x0025;; and 400&#x0025;, 255.3&#x0025;, and 184.2&#x0025; compared to the serial and parallel counterparts of the Walsh Basis (WB), Standard Basis (SB), and Overloaded CDMA Interconnect (OCI) crossbars, respectively. A 65-node ACDMA NoC router is fully realized and compared to the state-of-the-art CDMA and CONNECT NoC routers under multiple synthetic workloads. Communication reliability of the ACDMA NoC router subject to noise is investigated and a hybrid ARQ approach is proposed to improve the interconnect reliability.

Asymptotically Guaranteed Anti-Jamming Spread Spectrum Random Access Without Pre-Shared Secret

Our main contribution is the design of a spread spectrum random access scheme without pre-shared secret with asymptotically guaranteed availability against electronic/cyber-based jamming attacks. In order to establish asymptotic anti-jamming guarantees, first we develop the system model and show that for reactive jamming (only limited by the laws of physical propagation), the required location for a successful attack can be controlled by design. Then, for non-reactive protocol-aware jamming, we map a random selection of (publicly known) spreading codes to the computational birthday problem. Differently to the related literature, we formulate the birthday problem using entropic measures (R&#x00E9;nyi entropy), which allows to obtain the optimal spreading code set sizes that guarantee asymptotically zero collision probability. Accordingly, the birthday attack is the best strategy to optimize the (trial and error) blind acquisition at the legitimate detector. We obtain numerical results that illustrate how to use our entropic method as a system design degree of freedom to identify realistic spreading code set sizes. We also derive an upper bound of the detection latency. Finally, we show that the resulting anti-jamming throughput is higher than the throughput under conventional operation (i.e. without anti-jamming guarantees) due to the control of collision probability by-design.

Blind Estimation of Self-Synchronous Scrambler Using Orthogonal Complement Space in DSSS Systems

In a non-cooperative context, a receiver has to estimate the communication parameters without any prior knowledge of the transmitter, which is highly demanding. Estimating a self-synchronous scrambler is even more challenging because the scrambling sequence of the self-synchronous scrambler is affected by the input sequence. This paper proposes an improved algorithm for blind estimation of a self-synchronous scrambler using the orthogonal property without any bias condition of the received signals in direct sequence spread spectrum (DSSS) systems. We first examine the linear relation of a scrambling sequence using the repetitive property of the spreading code used in a DSSS system. Using the obtained linear relation and the basis of the orthogonal complement space, we then acquire the feedback polynomial candidates of the scrambler. Finally, by calculating the greatest common divisor polynomial of the feedback polynomial candidates, we estimate the correct feedback polynomial. Through computer simulations, we verify that the proposed method achieves superior estimation performance compared to the existing method. Furthermore, we show that the proposed method has practically acceptable computational complexity. For these reasons, it is expected that the proposed method can be applied to blind estimation of a self-synchronous scrambler in a practical non-cooperative system.

Experimental test and performance of RSSI-based indoor localization in LoRa Networks

LoRa (Long Range) is a wireless communication technology, which has established itself in recent years as one of the most widely used LPWAN (Low-Power Wide-Area Network) technologies in various IoT (Internet of things) applications. It is based on Chirp spread spectrum modulation (CSS) in which the number of bits per symbol depends on the spreading factor used, that varies from 7 to 12. In this paper, we have considered the RSSI (Received Signal Strength Indicator) parameter in the indoor environment. For LoRa, we use the LoRa transceiver based on two HTCC AB01 modules for their ability to modify the spreading factor (SF). In our work, we transmit in the 868MHz frequency band, and we use a bandwidth 125 KHz and three spreading factors SF7, 9 and 12. Subsequently, we tried to measure RSSI in an indoor environment with a short distance under LOS and NLOS conditions for three spreading factors. We sent the temperature measured by the DHT11 sensor from the transmitter to the receiver to measure the RSSI for each distance and for each spreading factor. The experimental results show that LoRa can be used in an indoor context, and that the spreading factor improve the performance of this technology in terms of RSSI. Moreover, the power losses of the received signal are more important in the NLOS conditions compared to those observed in the LOS conditions.

Construction and Assignment of Orthogonal Sequences and Zero Correlation Zone Sequences Over GF(p)

Orthogonal sequences can be assigned to a regular tessellation of hexagonal cells, typical for synchronised code-division multiple-access (S-CDMA) systems. The sequences within any cell should both be orthogonal in the adjacent cells and require a sufficient number of users in each cell. However, for binary sequences, the capacity of communication system is limited. So, a new family of non-binary orthogonal sequences is constructed, which has more sequences per cell than binary sequences in the network. Next, an efficient assignment of these orthogonal sequence sets to a regular tessellation of hexagonal cells is given, and also the sequence sets have large re-use distance. Finally, based on above the construction, we construct a family of orthogonal sequences with zero correlation zone (ZCZ) property which can reduce the interference among users in a multi-path environment. The constructed ZCZ sequences can be applied to the quasi-synchronous CDMA (QS-CMDA) spread spectrum systems. And the assignment of sequences has the same re-use distance.

A novel spread spectrum underwater acoustic communication system for the inter-symbol interference reduction

A novel spread spectrum underwater acoustic communication system for the inter-symbol interference reduction

Real-Valued Spreading Sequences for PSSS Based High-Speed Wireless Systems

In past years, Parallel Sequence Spread Spectrum (PSSS) has attracted significant attention as a modulation technique for wireless communication systems targeting data rates of 100 Gb/s and beyond. PSSS allows designing high-speed baseband processors, which can be partially implemented in the analog domain. It uses multiple analog-to-digital converters (ADCs) to sample the received baseband signal in parallel, significantly relaxing the sampling rate and ADC complexity. However, due to the sidelobe effects of bipolar <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> -sequences, PSSS shows lower performance than standard digital modulation schemes. This paper proposes real-valued PSSS spreading sequences with attenuated autocorrelation sidelobes. Such sequences show excellent bit error rate (BER) performance. Moreover, our sequences do not have length restrictions of 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sup> – 1, like in the case of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> -sequences, and reduce the chip area required to implement PSSS transceiver. The proposed sequences also reduce the peak-to-average power ratio (PAPR) of PSSS.

Research and Application of Third-Order Cumulants in Delay Estimation of Chaotic Spread Spectrum

Research and Application of Third-Order Cumulants in Delay Estimation of Chaotic Spread Spectrum

Compressive Sampling of Color Retinal Image Using Spread Spectrum Fourier Sampling and Total Variant

In medical imaging, the application of retinal images demands a lot of retinal photos to analyze and requires efficient compression techniques for retinal image storage. Retinal images must meet stringent quality requirements for clinical data to be accurate and dependable. This paper proposes a compressive sampling (CS) framework for color retinal image (CRI) compression, which relies on spread spectrum Fourier sampling (SSFS) and total variant (TV)-based reconstruction method with three loops of RGB color space, referred to as RGB-TV. In CS, two procedures are performed, i.e., compression and CS reconstruction. In compression steps, SFFS is performed to get a compressed signal from the original CRI with a high compression ratio (CR). While in CS reconstruction, TV-norm and TV proximal operator are exploited for problem optimization to recover original CRI from a compressed signal. In addition, signal-to-noise ratio (SNR), structural similarity (SSIM), and reconstruction time are investigated for the performance metrics of the proposed RGB-TV. The computer simulation result shows that the proposed RGB-TV with a set of CRI of size 512 by 512 pixels can compress until CR = 10 which obtains mean SNR of 22 dB, SSIM 0.84, and reconstruction time of 2.2 seconds.