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.
標簽： Telecommunications Processing Signal for
上傳時間： 2020-06-01
上傳用戶：shancjb
In Helsinki during a visiting lecture, an internationally well-known professor in communica- tionssaid,‘Inthecommunicationssocietywehavemanagedtoconvertourproposalsandideas to real products, not like in the control engineering society. They have very nice papers and strong mathematics but most of the real systems still use the old PID controllers!’. As our background is mainly in control as well as communications engineering, we know that this thought is not very accurate. We agree that most of the practical controllers are analog and digital PID controllers, simply because they are very reliable and able to achieve the required control goals successfully. Most of the controllers can be explained in terms of PID. The reasons behind this impressive performance of PID will be explained in Chapter 2.
標簽： Communications Engineering Wireless Systems in
上傳時間： 2020-06-01
上傳用戶：shancjb
The need to develop reliable microelectronic devices capable of operating at high speeds with complex functionality requires a better understanding of the factors that govern the thermal performance of electronics. With an increased demand on system reliability and performance combined with miniaturization of the devices, thermal consideration has become a crucial factor in the design of elec- tronic packages, from chip to system levels.
標簽： Telecommunications Management Equipment Thermal of
上傳時間： 2020-06-01
上傳用戶：shancjb
Having dealt with in-depth analysis of SS#7, GSM and GPRS networks I started to monitor UTRAN interfaces approximately four years ago. Monitoring interfaces means decoding the data captured on the links and analysing how the different data segments and messages are related to each other. In general I wanted to trace all messages belonging to a single call to prove if the network elements and protocol entities involved worked fine or if there had been failures or if any kind of suspicious events had influenced the normal call proceeding or the call’s quality of service. Cases showing normal network behaviour have been documented in Kreher and Ruedebusch (UMTS Signaling. John Wiley & Sons, Ltd, 2005), which provides examples for technical experts investigating call flows and network procedures.
標簽： Performance Measurement Practical Guide UMTS
上傳時間： 2020-06-01
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n the first part of this book, we give an introduction to the basic applications of wireless com- munications, as well as the technical problems inherent in this communication paradigm. After a brief history of wireless, Chapter 1 describes the different types of wireless services, and works out their fundamental differences. The subsequent Section 1.3 looks at the same problem from a different angle: what data rates, ranges, etc., occur in practical systems, and especially, what combination of performance measures are demanded (e.g., what data rates need to be transmitted over short distances; what data rates are required over long distances?) Chapter 2 then describes the technical challenges of communicating without wires, putting special emphasis on fading and co-channel interference. Chapter 3 describes the most elementary problem of designing a wireless system, namely to set up a link budget in either a noise-limited or an interference-limited system. After studying this part of the book, the reader should have an overview of different types of wireless services, and understand the technical challenges involved in each of them. The solutions to those challenges are described in the later parts of this book.
標簽： Communications Wireless Edition 2nd
上傳時間： 2020-06-01
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Electrostatic discharge (ESD) events can have serious detrimental effects on the manufacture and performance of microelectronic devices, the systems that contain them, and the manufacturing facilities used to produce them. Submicron device technologies, high system operating speeds, and factory automation are making ESD control programs a critical factor in the quality and reliability of ESD-sensitive products.
標簽： Management Program ESD
上傳時間： 2020-06-05
上傳用戶：shancjb
Micro-Electro-Mechanical Systems (MEMS) are miniature systems composed ofintegratedelectricalandmechanicalpartstosenseand/orcontrolthingsonaμmscale. The concept of MEMS is attributed to Richard Feynman’s famous talk on December 29th, 1959 [2,3]. Dr. Feynman foresaw many aspects of future MEMS development with his insight in microphysics. In particular, material properties in the μm scale are differentfrombulkpropertiesandthescalingdownofintegratedcircuits(IC)fabrication technology has been a major driving force of MEMS development.
標簽： Performance High MEMS RF
上傳時間： 2020-06-06
上傳用戶：shancjb
In the present era, low observability is one of the critical requirements in aerospace sector, especially related to defense. The stealth technology essentially relates to shaping and usage of radar absorbing materials (RAM) or radar absorbing struc- tures (RAS). The performance of such radar cross section (RCS) reduction tech- niques is limited by the bandwidth constraints, payload requirements, and other structural issues. Moreover, with advancement of materials science, the structure geometry no longer remains key decisive factor toward stealth.
標簽： Fundamentals Design Radar of EM
上傳時間： 2020-06-06
上傳用戶：shancjb
HIS IS THE THIRD —and most likely the last—book in the series on information technology for energy managers and web based energy infor- mation and control systems. This book concentrates on web based enterprise energy and building automation systems, and serves as a capstone volume in this series. The thrust here is that the highest level functions of a building and facility automation system are provided by a web based EIS/ECS system that provides energy management, maintenance management, overall facility operational management, and ties in with the enterprise resource management system for the entire facility or the group of facilities being managed. If there were ever to be a fourth volume in this series, it would follow the logical progression of the first three volumes, and would probably be titled Web Based Enterprise Resource Management Systems.
標簽： Enterprise Energy Based Web
上傳時間： 2020-06-06
上傳用戶：shancjb
For more than a century, overhead lines have been the most commonly used technology for transmitting electrical energy at all voltage levels, especially on the highest levels. However, in recent years, an increase in both the number and length of HVAC cables in the transmission networks of different countries like Denmark, Japan or United Kingdom has been observed. At the same time, the construction of offshore wind farms, which are typically connected to the shore through HVAC cables, increased exponentially.
標簽： Electromagnetic Transients Cables Power in
上傳時間： 2020-06-07
上傳用戶：shancjb
