Spread Spectrum Communications and Jamming

A spread spectrum communication system deliberately spreads the spectrum of the signal beyond the required bandwidth needed for information transmission to achieve resilience against hostile jamming, low probability of intercept resulting detectability to be almost impossible as compared to non-spread signals, inherent message privacy and security, good rejection of multipath signals, high degree of ranging precision (due to the large bandwidth involved), and compatibility with code division multiple access (CDMA) capability. Originally adopted in military networks as a means of ensuring secure communication when confronted with the threats of jamming and interception, spread spectrum systems are now the core of commercial applications such as mobile cellular and satellite communications. The Global Positioning System (GPS) is the first commercial communication system that uses spread spectrum signals enabling ranging, jamming protection, multipath protection and high degree of range precision. In today’s world, there are more applications of spread spectrum on the commercial side than on the military side. CDMA is a popular multiple access scheme where several users share the same physical medium, that is, the same frequency at the same time. CDMA is based on spread spectrum technique where the spectral band is spread by multiplying each user’s signal by unique orthogonal pseudorandom sequence. Orthogonality of the codes ensures the retrieval of information without interference from each other where spreading allows the receiver to take benefit from multipath properties of the mobile radio channel. Over the years, the most successful implementation of spread spectrum communication in commercial world lies in cdma 2000, WCDMA and UMTS, a 3G mobile communication system, WLAN, Ultra Wideband Communications (UWB), Body Area Networks, and energy efficient Radio Architecture design for future generation Millimeter Wave (mmWave) communications. The common cordless phone utilizes spread spectrum technology to provide a telephonic interference-rejecting communication link in both 900 MHz and 2.4 GHz bands. In addition, spread spectrum communication methods have been considered an alternative to hard wiring for indoor private branch offices, laboratories, or factories where the transmission medium involves severe multipath fading.

The present course introduces basic principle of spread spectrum techniques, key concept of code designing supported by Galois field mathematics, understanding Jamming environment and interference handling mechanisms. The theoretical principles are tempered with their practical significance to cope up with the interest to both researchers and system designers. Learning is facilitated by streamlined derivations, tutorials, and assignments. Several systems examples help students understand the concept and tutorials offer quick practice. After an in–depth exposure to spread spectrum techniques and wireless cellular environment the course takes a thorough tour of training on wireless multiuser system design with spread spectrum technique in MATLAB platform. The course ends with an expose to cdma2000 and WCDMA protocol structure and brief introduction to low probability of intercept methods.

INTENDED AUDIENCE : Practicing engineers, Technical and Non-technical managers of telecomm companies, Students preparing for competitive exams with Signals and Systems subject

PREREQUISITES : Digital Communication, Fundamentals of Wireless Communications

INDUSTRY SUPPORT : Spread Spectrum Communications is the core technology for secured Defence Communication Systems. It is also applied to several modern commercial communication systems e.g. CDMA in 3G, and upcoming Millimeter Wave Communications. Hence all Defence R&D labs under Ministry of Defence will be in need of the course.