File Name: spread spectrum and its types .zip
UMTS pp Cite as. In this chapter we will present the basic idea behind spread spectrum systems together with some of the most important issues regarding their design and implementation. We will start with a definition of spread spectrum systems and consider their advantages as well as their disadvantages, after which the different types will be described. The direct sequence spread spectrum principle will be covered into more detail including a short mathematical representation and the derivation of the optimum receiver, since UMTS relies on this technique.
This lecture covers the fundamentals of spread spectrum modulation, which can be defined as any modulation technique that requires a transmission bandwidth much greater than the modulating signal bandwidth, independently of the bandwidth of the modulating signal. After reviewing basic digital modulation techniques, the principal forms of spread spectrum modulation are described. One of the most important components of a spread spectrum system is the spreading code, and several types and their characteristics are described. The most essential operation required at the receiver in a spread spectrum system is the code synchronization, which is usually broken down into the operations of acquisition and tracking. Means for performing these operations are discussed next.
A means of communicating by purposely spreading the spectrum frequency extent or bandwidth of the communication signal well beyond the bandwidth of the unspread bandwidth. Spread spectrum signals are typically transmitted by electromagnetic waves in free space with usage in both no military and military systems. Chirp Modulation : This is an older spread spectrum method that was developed for radar use. The frequency-modulated signal returned from the target passes through a filter in the receiver at a velocity of propagation proportional to frequency. The result is a pulse that is much shorter in time duration than the transmitted pulse with a larger peak power content. Unchirped pulses such as interference or jamming pulses do not "compress" at the receiver, so that this method yields a processing gain or advantage for the chirpped signal. Time Hopping : Not normally used alone, is a method in which the transmitted pulse occurs in a manner determined by a pseudorandom code which places the pulse in one of n possible positions per frame.
Metrics details. In recent years, there has been great interest in using hybrid spread-spectrum HSS techniques for commercial applications, particularly in the Smart Grid, in addition to their inherent uses in military communications. This is because HSS can accommodate high data rates with high link integrity, even in the presence of significant multipath effects and interfering signals. The optimization objective function is non-convex and can be solved by applying the Karush-Kuhn-Tucker conditions. Numerical and experimental results are presented under widely varying design parameters to demonstrate the adaptability of the waveform for varied harsh smart grid RF signal environments.
A collective class of signaling techniques are employed before transmitting a signal to provide a secure communication, known as the Spread Spectrum Modulation. The signals modulated with these techniques are hard to interfere and cannot be jammed. An intruder with no official access is never allowed to crack them. Hence, these techniques are used for military purposes. These spread spectrum signals transmit at low power density and has a wide spread of signals. A coded sequence of 1s and 0s with certain auto-correlation properties, called as Pseudo-Noise coding sequence is used in spread spectrum techniques. It is a maximum-length sequence, which is a type of cyclic code.
Each bit is represented by multiple bits in transmitted Spread Spectrum Concept M is the number of different signal elements, frequencies to encode data.
Search this site. Methodius PDF. Hildegard of Bingen PDF. Access To The Throne! Address Book PDF.
Тот вскрикнул и испуганно посмотрел на Беккера.
- Он нахмурился, глаза его сузились. - Сегодня суббота. Чем мы обязаны. Хейл невинно улыбнулся: - Просто хотел убедиться, что ноги меня еще носят. - Понимаю. - Стратмор хмыкнул, раздумывая, как поступить, потом, по-видимому, также решил не раскачивать лодку и произнес: - Мисс Флетчер, можно поговорить с вами минутку.
Поссорились. На мгновение Беккер задумался. Потом изобразил смущенную улыбку. - Неужели это так заметно. - Как ее зовут? - Женщина лукаво подмигнула.
Металлический голос Джаббы заполнил комнату: - Мидж, я в главном банке данных. У нас тут творятся довольно странные вещи.
On receiving end, digit sequence is used to demodulate the o Immunity from various kinds of noise and multipath Frequency Hoping Spread Spectrum.Reply