Random codekey selection using codebook without pre-shared keys for anti-jamming in WBAN

Spread spectrum techniques including Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS) are used widely as a countermeasure against jamming attacks. In recent years, the DSSS based system has been used to achieve the anti-jamming systems without a pre-shared secret key. Delayed Seed-Disclosure DSSS (DSD-DSSS) is one of these systems that uses a random seed to generate multiple spreading codes to spread an original message. However, it discloses the information of a random seed in a way that it is vulnerable to the attacker. In this paper. we propose a new system that mainly focuses on concealing a random seed from the attacker by inserting it at a random position of a spreading message. We develop a new technique to identify the location of a random seed at a receiver by aligning between multiple received messages. Our evaluation and simulation results show that a receiver can obtain the position of a random seed, and then he can recover both a random seed then regenerating the spreading codes used to spread an original message.

This paper presents performance evaluation and comparison analysis of Direct Sequence Spread Spectrum (DSSS) and Frequency Hopping Spread Spectrum (FHSS) systems. The evaluation and analysis are done based on the systems performance against wideband interferences. The interferences are signals with similar spectrum characteristic to the transmitted signals of DSSS and FHSS systems. Bit Error Ratio (BER) is used as evaluation parameter to assess the performance of both systems. Simulation and mathematical analysis are performed to test and verify the performance of both systems. Mathematical analysis also verifies that increasing Spreading Frequency on certain conditions will reduce the BER. This research also points out that FHSS system has a better performance compared to DSSS system indicated by smaller BER.

Deployment of wireless sensor networks (WSNs) with a large number of nodes have reinstated interest in spread spectrum (SS) technologies as they allow to establish multiple access for nodes with simple hardware and limited power budget. Chaotic spreading is one of the still insufficiently explored areas which can lead to higher security and lower multiple access interference (MAI). This research is intended to bring new information about the performance of binary direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS) communication systems which employ chaos-based spreading codes and compare them against classical systems employing m-sequences. Unlike existing research, this investigation is based on the simulation of passband communication systems with up/down-conversion and respective filtering. Performance comparison in terms of bit error ratio (BER) versus signal-to-noise ratio (SNR) at the different number of users and MAI dependence on carrier frequency offset among users in case of additive white Gaussian noise (AWGN) channel are presented. Obtained results highlight several scenarios where chaotic-sequences-based binary DSSS and FHSS systems have advantages over classical solutions.

Due to a world wide surge in the intelligent vehicle highway system (IVHS), the field of automatic vehicle identification (AVI) has been rapidly growing. The use of spread spectrum communications has not yet pervaded the AVI market. However, in the already cramped electromagnetic environment, spread spectrum techniques have gained significant popularity in many growing areas of wireless communication. AVI is perfectly suited to benefit. The fundamental advantage of spread spectrum technology in AVI applications is its invulnerability to interference and its ability to operate alongside narrow band communication systems already in place. The second advantage is the ease of licensing for spread spectrum AVI, since it does not require a dedicated frequency spectrum. It is also possible for several spread spectrum AVI systems to operate simultaneously in the vicinity of each other, using different spreading codes. This article concentrates on architecture as well as applied key signal processing techniques for a proposed direct sequence spread spectrum (DSSS) AVI system. A functional block diagram that outlines the major components of the system is presented. The system consists of three major functional parts: interrogator, transponder, and trigger. Free flow of traffic can be maintained only if the interrogator can isolate each vehicle in a common interrogation zone. DSSS allows this through code division multiple access (CDMA). The triggering system is based on the principles of speed enforcement radar. The proposed digital modulation scheme is BPSK. The DSSS modulator applies a Gold pseudo-random (PN) code to spread the spectrum of the binary signal. Despreading is carried out through the use of a PN matched filter. The antenna is assumed to have a 60/spl deg/ half-power radiation field and is placed on an existing overpass approximately 6 meters above the roadway. With 50 mW antenna transmit power, link budget analysis indicates that sufficient bit energy-to-noise power spectral density ratio is available at the receiver to generate an excellent bit error rate without requiring error control coding.

Based on spread spectrum technique, two wireless video transmission schemes are designed and implemented in this paper, namely direct sequence spread spectrum (DSSS) scheme and multi-code spread spectrum (MCSS) scheme. We use software defined radio (SDR) method for hardware implementation of two schemes, where a XILINX Virtex-4 field programmable gate array (FPGA) for the transmitter and another Virtex-5 FPGA for the receiver. In order to evaluate their performance, we compared the two designed schemes with our previous work on orthogonal frequency division multiplexing (OFDM) scheme. The experimental results show that two schemes of DSSS and MCSS have better anti-jamming performance than OFDM scheme at the cost of spectrum efficiency. Also, DSSS scheme possesses higher power efficiency than MCSS scheme and OFDM scheme due to its lower peak-to-average power ratio.

Investigations into code division multiple access (CDMA) have shown that frequency hopping (FH) possesses many of the advantages claimed by direct sequence (DS) spread spectrum techniques. This paper investigates the theoretical and practical implementation issues associated with designing a FH modem. The criteria which are explored include areas which are specifically associated with the frequency hopping nature of the modem, such as the the hopping synthesizer, hop duration, and hop bin separation. Furthermore, consideration is made of the impact of frequency hopping on more general design issues, such as coding, modulation, and multiple access. Work at the Centre for Communications Research (CCR) in Bristol has been carried out to develop a practical implementation of a prototype frequency hopped modem. The paper includes the modem design, and preliminary performance in an additive white noise channel.

Hybrid spread-spectrum (HSS) systems have recently received considerable interest in commercial, Smart Grid, and military communication systems because they accommodate high data rates with high link integrity, even in the presence of significant multipath effects and interfering signals. A highly useful form of this modulation scheme is the specific code-related combination of standard direct-sequence spread spectrum (DSSS) with fast frequency-hopping (FFH) spread spectrum, denoted hybrid DS/FFH, wherein multiple frequency hops occur within a single data-bit time. In this paper we perform a simulation-based study of the DS/FFH performance as compared to the existing standard DSSS and FHSS wireless networks. The performance metrics are biterror probability and multiple-access capability. The parameter space of DS/FFH, including the DS spreading rate, frequency hopping rate, carrier frequencies, and numbers of users, is explored to show its performance under frequency-selective Rayleigh fading environments and multiuser interference. Direct digital synthesizers to achieve fast hopping speeds are also considered in our study.

Contemporary wireless communication strategies focus on efficient use of bandwidth in order to allow more users to exploit the RF spectrum through techniques like Frequency-hopping spread spectrum (SS) and Direct-sequence SS. In many real-world applications, these methods are implemented for synchronous communication systems. To achieve synchronous communication, two-way handshaking that requires overhead circuitry is performed between the sender and receiver. In order to use spread spectrum methods for certain unconstrained and low-power applications, such as implantable and remote monitoring devices, it is necessary to refine these methods to support asynchronous communication. We have designed and modeled a SS system, which could be integrated with a custom integrated circuit that would provide elementary multi-user communication. The SS logic generates a gold-code based on address and data bits that is then modulated with a carrier to transmit the information. Because the system is asynchronous, we treat each transmitted code as an independent piece of information. The receiver decodes the information using a full correlation with the ideal known gold-codes. For efficiency purposes, the filter is applied in the frequency domain. A threshold is applied to the output of the filter to determine if a particular code is transmitted as well as the point in time/space from which the signal was sent. The method was simulated and evaluated under several scenarios including different carrier frequencies, multiple targets, and various positions relative to the receiver from the simulated receiver. The results demonstrate the utility of asynchronous SS under many different conditions.

Chapter 3 - Security and the Layered Architecture

Direct sequence spread spectrum (DSSS) communication has been extensively adopted in military and civilian fields because of its high processing gain, anti-jamming capability and low probability of interception (LPI). In this paper, non-cooperative interception of DSSS signal in multiple signals environment is presented. The proposed algorithm is based on the fluctuations of autocorrelation, and also banks upon proper thresholding criteria. This methodology comes out to be a robust practical method for blind detection of DSSS signals in a dense multiple signals environment. In the proposed approach, firstly DSSS signals are blindly detected by leveraging the variations in autocorrelation of the received signal. Then, the presence of desired DSSS signal is confirmed when correlation peaks cross the threshold at multiple positions after a fixed period. In a real-time environment, signals other than spread spectrum with much better signal-to-noise ratio (SNR) can also co-exist. Among these multiple signals, the high SNR signals disturb the threshold selection criteria for detection. Consequently, this leads to erroneous or miss detection of the DSSS signal. The proposed scheme aims to reduce the effect of better SNR signals on the blind detection of DSSS signal. In order to validate the proposed algorithm, QPSK and 16-QAM signals are considered to co-exist with the desired DSSS signal. Analytical and numerical analysis signify the efficiency of the proposed algorithm with acceptable computational complexity, making it suitable for real-time practical systems.

Troposcatter radio links may be a low cost alternative for long distance communications, or when the transmitter and the receiver are separated by difficult terrain that prevent from line-of-sight communications. These links permit one to preserve satellite resources in the case of civil applications, so as to overcome geographical barriers (oceans, mountains, desert, etc.). They also can easily and rapidly be installed for emergency situations in both civil and military cases. They represent a good solution in the case of single transhorizon hops of length limited to several hundreds of kilometers. The problem is that the transmission is based on the presence of multipath, whose dispersion is very varying on long periods. Wide-band transmission schemes can be then employed, like OFDM or spread spectrum techniques. The limitations of OFDM in presence of non-linearities of the amplifiers has often led one to prefer spread spectrum techniques in the case of troposcatter links: direct sequence (DS) or frequency hopping (FH). All the more so as other characteristics of spread spectrum are exploited for performance and also discretion purposes, as we are concerned with military tactical transmissions. The implementation of hybrid DS/FH spread spectrum receivers, which realize a maximal ratio combination of the paths (RAKE) is presented. After a description of the channel, we then describe the communication systems involved, and finally estimate the bit error rate.

At present, the blind detection of DSSS (direct sequence spread spectrum) signals is mainly based on the cyclostationarity of the signals and uses the statistics analysis of the second or higher order eigenvalues as a cut-in sticking point for resolving the problem, it is quite easily influenced by the low signal to noise ratio and restricted by the implementation of the algorithm. In order to resolve the problem of the blind detection, the paper proposes a blind spread spectrum pseudo random sequence detection method: multi-chip allied correlation detection, and a blind chip synchronization method: multi-codeword correlation smoothing match. The proposals of the paper resolve the bottleneck problems in the blind detection of DSSS signals: the blind spread spectrum pseudo random sequence estimation and the chip synchronization search in the context of low signal to noise ratio. The proposed methods not only avoid the need of the second or higher order processing of many blind detection methods, reduce the complexity of the blind detection of DSSS signals greatly, but also overcome the shortcoming of many blind detection methods while dealing with the spread spectrum transmission far below the noise level. The paper may be a foundation for achieving the detection of the DSSS signals in non-cooperative context.

Direct sequence spread spectrum (DSSS) signal uses phase coherent signals where the information symbols are multiplied with a code sequence, commonly known as chips. The signals are processed at the receiver using the code sequence as a matched filter to extract the information symbols. Taking advantage of the spread processing gain derived from the matched filter, communications can be carried out at low signal levels, which is the preferred method for high quality underwater acoustic (UWA) communication and remote UWA communication. However, in practical applications, DSSS UWA communication will face lots of interferences including multipath interference, Doppler compression interference and phase fluctuation interference, which will seriously affect the performance of DSSS. This paper first analyzes the interferences that DSSS faces in practical applications based on multiple actual received data collected in different water areas. By calculating the gain of the matched filter loss, one can find that influence of phase fluctuation interference has the most serious impact on DSSS. Secondly, the corresponding receiver processing algorithms are given for these interferences, including the differential energy detector and Doppler estimation method. The performance of differential energy detector under the above interferences is analyzed, which shows that the differential energy detector is insensitive to slow phase fluctuation interference and multipath interference and the differential energy detector combined with Doppler compensation can work well based on moving at-sea data. Finally, the parameter design of DSSS system in practical application is discussed and parameter design of DSSS UWA communication system should comprehensively consider the Doppler compression interference and phase fluctuation interference.

Wireless body area networks (WBANs) are an emerging technology expected to revolutionize mobile healthcare via the real-time monitoring and analysis of medical data. This article describes the generalized WBAN concept and examples of WBAN medical applications for a variety of users and scenarios. The properties of wireless communication channels used in WBANs - specifically the human body communications channel and the 60 GHz Millimeter-wave (mmWave) - highlight the challenges facing modern WBAN development. Several research topics related to WBAN implementation in 5G networks are examined, including simulating extremely high-frequency communications, routing protocols, energy harvesting, tailoring WBANs to individual users, and user satisfaction. Future WBAN developments related to 6G networks and quantum technologies are also explored to demonstrate the potential future of mobile health.

Spread spectrum technique becomes one of the most important communication techniques in the recent decades. It provides high security, in addition to its resistance to the various interference and fading types. One of the most important parameter in the spreading process is the spreading code used in the spreading process, especially in the direct sequence spread spectrum. Recently, many researches focused on the chaotic codes, due to its attractive security properties, in addition to its availability to generate a huge number of spreading codes. This property is very useful in the multi-access applications. However, as the number of the MAI is increased, the performance of the chaotic codes is degraded. This paper presents a new method to generate a set of orthogonal self-balanced chaotic codes. The results show that the presented method generates a set of chaotic codes with correlation properties much better than the traditional chaotic code. The results show also that the BER performance of the presented orthogonal chaotic codes is superior and outperforming the BER performance of the traditional chaotic codes in addition to the PN sequences.