This book is a result of the recent rapid advances in two related technologies: com- munications and computers. Over the past few decades, communication systems have increased in complexity to the point where system design and performance analysis can no longer be conducted without a significant level of computer sup- port. Many of the communication systems of fifty years ago were either power or noise limited. A significant degrading effect in many of these systems was thermal noise, which was modeled using the additive Gaussian noise channel.
标签： Communication Principles Simulation Systems of
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The investigation of the propagation channel is becoming more and more important in mod- ern wireless communication. The demand for spectral efficiency motivates exploitation of all channels that can possibly be used for communications. Nowadays, a common trend for designing physical layer algorithms is to adapt the transceiving strategy, either by maximizing the diversity gains or by utilizing the coherence of the channels to improve the signal-to-noise power ratio.
标签： Characterization Propagation Channel
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The single-carrier frequency division multiple access (SC-FDMA) system is a well-known system that has recently become a preferred choice for mobile uplink channels. This is attributed to its advantages such as the low peak-to-average power ratio (PAPR) and the use of frequency domain equalizers. Low PAPR allows the system to relax the specifications of linearity in the power amplifier of the mobile terminal, which reduces cost and power consumption.
标签： Communications SC-FDMA Mobile for
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This paper presents a Hidden Markov Model (HMM)-based speech enhancement method, aiming at reducing non-stationary noise from speech signals. The system is based on the assumption that the speech and the noise are additive and uncorrelated. Cepstral features are used to extract statistical information from both the speech and the noise. A-priori statistical information is collected from long training sequences into ergodic hidden Markov models. Given the ergodic models for the speech and the noise, a compensated speech-noise model is created by means of parallel model combination, using a log-normal approximation. During the compensation, the mean of every mixture in the speech and noise model is stored. The stored means are then used in the enhancement process to create the most likely speech and noise power spectral distributions using the forward algorithm combined with mixture probability. The distributions are used to generate a Wiener filter for every observation. The paper includes a performance evaluation of the speech enhancer for stationary as well as non-stationary noise environment.
标签： Telecommunications Processing Signal for
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Ultra-wideband (UWB) technology enables high data-rate short-range communica- tion, in excess of hundredmegabit-per-secondsand up to multi-gigabit-per-seconds, over a wide spectrum of frequencies, while keeping power consumption at low lev- els. This low power operation results in a less-interfering co-existence with other existed communication technologies (e.g., UNII bands). In addition to carrying a huge amount of data over a distance of up to 230 feet at very low power (less than 0.5mW), the UWB signal has the ability to penetrate through the doors and other obstacles that tend to reflect signals at more limited bandwidths and higher power densities.
标签： Silicon-Based Front-Ends RF
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Heterogeneous Network (HetNet): A network that consists of a mix of macro cells and low-power nodes, e.g. Pico, Femto, Relay Node (RN) and Remote Radio Head (RRH)
标签： Efficient Spectrum Energy and
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A wireless communication network can be viewed as a collection of nodes, located in some domain, which can in turn be transmitters or receivers (depending on the network considered, nodes may be mobile users, base stations in a cellular network, access points of a WiFi mesh etc.). At a given time, several nodes transmit simultaneously, each toward its own receiver. Each transmitter–receiver pair requires its own wireless link. The signal received from the link transmitter may be jammed by the signals received from the other transmitters. Even in the simplest model where the signal power radiated from a point decays in an isotropic way with Euclidean distance, the geometry of the locations of the nodes plays a key role since it determines the signal to interference and noise ratio (SINR) at each receiver and hence the possibility of establishing simultaneously this collection of links at a given bit rate. The interference seen by a receiver is the sum of the signal powers received from all transmitters, except its own transmitter.
标签： Stochastic Geometry Networks Wireless Volume and II
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The idea for this book was born during one of my project-related trips to the beautiful city of Hangzhou in China, where in the role of Chief Architect I had to guide a team of very young, very smart and extremely dedicated software developers and verification engineers. Soon it became clear that as eager as the team was to jump into the coding, it did not have any experience in system architecture and design and if I did not want to spend all my time in constant travel between San Francisco and Hangzhou, the only option was to groom a number of local junior architects. Logically, one of the first questions being asked by these carefully selected future architects was whether I could recommend a book or other learning material that could speed up the learning cycle. I could not. Of course, there were many books on various related topics, but many of them were too old and most of the updated information was either somewhere on the Internet dispersed between many sites and online magazines, or buried in my brain along with many years of experience of system architecture.
标签： Telecommunication Gateways System Design for
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I love telecommunications. It is powerful and it empowers, with far-reaching consequences. It has demonstrated the potential to transform society and business, and the revolution has only just begun. With the invention of the telephone, human communications and commerce were forever changed: Time and distance began to melt away as a barrier to doing business, keeping in touch with loved ones, and being able to immediately respond to major world events. Through the use of computers and telecommunications networks, humans have been able to extend their powers of thinking, influence, and productivity, just as those in the Industrial Age were able to extend the power of their muscles, or physical self, through use of heavy machinery.
标签： Telecommunications Essentials
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Wireless communications has become a field of enormous scientific and economic interest. Recent success stories include 2G and 3G cellular voice and data services (e.g., GSM and UMTS), wireless local area networks (WiFi/IEEE 802.11x), wireless broadband access (WiMAX/IEEE 802.16x), and digital broadcast systems (DVB, DAB, DRM). On the physical layer side, traditional designs typically assume that the radio channel remains constant for the duration of a data block. However, researchers and system designers are increasingly shifting their attention to channels that may vary within a block. In addition to time dispersion caused by multipath propagation, these rapidly time-varying channels feature frequency dispersion resulting from the Doppler effect. They are, thus, often referred to as being “doubly dispersive.”
标签： Time-Varying Channels
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