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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P9
A routing algorithm constructs routing tables to forward communication packets based on network status information. Rapid inflation of the Internet increases demand for scalable and adaptive network routing algorithms. Conventional protocols such as the Routing Information Protocol (RIP) (Hedrick, 1988) and the Open Shortest-Path First protocol (OSPF) (Comer, 1995) are not adaptive algorithms; they because they only rely on hop count metrics to calculate shortest paths. In large networks, it is difficult to realize an adaptive algorithm based on conventional approaches. ...
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P10
All point-to-point communication networks have a means of directing traffic from a source to a destination via intermediate nodes. This routing function must be performed efficiently as it affects all aspects of network communications including jitter, latency and total bandwidth requirement. Other issues related to routing, such as policing and traffic control are not dealt with in this chapter. There are two distinct approaches to ‘routing’ traffic, namely connection-oriented and connectionless. ...
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P11
Computer networks are gaining increasing importance as they penetrate business and everyday life. Technological evolution results in increased computational power and transmission capacity. These phenomena open the way to the development and exploitation of new applications (e.g. video conferencing) which require demanding services from the network. As a result, computer networks are in continuous evolution and the protocols regulating their operation must be assessed for their suitability to new technologies and ability to support the new applications. ...
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P12
The explosive growth of distributed computing has been fuelled by many factors. Applications such as video conferencing, teleoperation and most notably the World Wide Web are placing ever more demanding requirements on their underlying communication systems. Having never been designed to support such diverse communication patterns these systems are failing to provide appropriate services to individual applications. Artificial neural networks have been used in areas of communication systems including signal processing and call management (Kartalopolus, 1994)....
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P13
As Internet connectivity is reaching the global community, information systems are becoming more and more distributed. Inevitably, this overnight exponential growth has also caused traffic overload at various places in the network. Until recently, it was believed that scaling the Internet was simply an issue of adding more resources, i.e. bandwidth and processing power could be brought to where they were needed.
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P14
Many of today’s data intensive applications have the common need to access exceedingly large databases in a shared fashion, simultaneously with many other copies of themselves or similar applications. Often these multiple instantiations of the client application are geographically distributed, and therefore access the database over wide area networks. As the size of these ‘industrial strength’ databases continue to rise, particularly in the arena of Internet, Intranet and Multimedia servers, performance problems due to poor scalabilty are commonplace. ...
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P15
The software crisis is usually defined in terms of projects running over budget and over schedule, though an equally important aspect is the poor quality of software measured in terms of its correctness, reliability and performance. The consequences of releasing faulty software into service may be devastating in safety-related applications, telecommunications and other areas. When the USA telecommunications system failed and half of the nation was isolated, lives and property were clearly put at risk....
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P16
Today an ever increasing number of social and financial services can be provided over data networks. Individuals and businesses alike initiate and complete a large number of commercial transactions over the Internet or other specially constructed networks. Home banking, home shopping, video on demand, buying and selling of stocks and other financial securities can now be undertaken from almost any part of the world where an access to a local network can be achieved.
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P17
In recent years, flow control and network management in high speed networks have drawn much attention by researchers in the telecommunications field. In large-scale network environments with high complexity, decentralized control and decision making are required. Many research papers concerned with multidisciplinary approaches to modeling, controlling and managing networks from a computational intelligence point of view appear in the key telecommunication journals every year.
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P18
In the last two decades, wireless communication systems such as cordless phones, paging systems, wireless data networks, satellite-based and cellular mobile systems have been steadily increasing in both popular importance and technological sophistication. The firstgeneration wireless systems were developed in the late 1970s and 1980s and were based on analog technology (such as the Advance Mobile Phone Service (AMPS) by AT&T and Nordic Mobile Telephone (NMT) by Ericsson).
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Tối ưu hóa viễn thông và thích nghi Kỹ thuật Heuristic P19
Channel Assignment Problems (CAPs) occur in the design of cellular mobile telecommunication systems (Jordan, 1996; Katzela and Naghshineh, 1996; MacDonald, 1979); such systems typically divide the geographical region to be serviced into a set of cells, each containing a base station. The available radio frequency spectrum is divided into a set of disjoint channels; these must be assigned to the base stations to meet the expected demand of each cell and to avoid electromagnetic interference during calls....
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Kiến trúc phần mềm Radio P1
Tham khảo tài liệu 'kiến trúc phần mềm radio p1', kỹ thuật - công nghệ, kĩ thuật viễn thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả
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Kiến trúc phần mềm Radio P2
Architecture Evolution This chapter will convey a deeper understanding of the roots of the software radio. This includes the technical evolution that has resulted in today’s emphasis on SDR. And it includes the management motivations toward realizing appropriately tailored implementations. The chapter begins with an introduction to technology-demographics, a method for studying architecture.
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Kiến trúc phần mềm Radio P3
The Radio Spectrum and RF Environment Radio is the penultimate medium for mobile communications, but it has also been used for many fixed-site applications such as AM/FM broadcast, satellite trunking, point-to-point microwave telephony, and digital TV. Although there are radio applications in very low frequencies (VLF) and extremely low frequencies (ELF), these bands require extensive fixed-site infrastructure whose size and cost is dominated by the mile-long antennas and megawatt-power handling requirements. SDR insertion opportunities in these bands are limited. ...
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Kiến trúc phần mềm Radio P4
Systems-Level Architecture Analysis The objective of this chapter is to give the reader practice in addressing software-radio architecture issues at the systems level. The study of systemslevel software-radio architecture is first motivated with a realistic case study. The case study includes the critical parameters of most radio architectures. The analysis focuses on those aspects that are significant for software-radio architecture. The balance of the chapter develops the issues raised in the case study. I. DISASTER-RELIEF CASE STUDY This case study considers a mobile communications capability for disaster relief....
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Kiến trúc phần mềm Radio P5
Node-Level Architecture Analysis This chapter analyzes node-level software radio architecture. Attention turns to the internal functions, components, and design rules within a radio node. The canonical node architecture partitions software-radio functions into segments within which functions are functionally cohesive, and between which the segments are data-coupled. This approach conforms to well-established principles of structured design [183, 184]. SD has been superseded in contemporary practice by object-oriented technology (OOT) [185]....
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Kiến trúc phần mềm Radio P6
Segment Design Tradeoffs I. OVERVIEW The six steps in the systems-level design process associated with the software radio are illustrated in Figure 6-1. The tradeoffs proceed from front end to back end. The choice of antennas (step 1 in the figure) determines the number and bandwidth of RF channels (step 2). This, in turn, constrains the numbers and bandwidths of ADCs (step 3). Some waveforms may require dedicated ASICs (e.g., W-CDMA despreaders) in front of the ADCs. Additional parallel IF processing and ADC paths may be necessary to support multiple-service bands simultaneously....
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Kiến trúc phần mềm Radio P7
Antenna Segment Tradeoffs The antenna segment establishes the available RF bands. Although much research has been applied toward creating an “all-band” antenna, multiband radios generally require at least one antenna per decade of RF band (e.g., HF, VHF, UHF, SHF, etc.). In addition, the antenna determines the directional properties of the receiving system. Sectorized antennas, static beamforming arrays, and adaptive beamforming arrays (smart antennas) each have different spatial and temporal properties, the most significant of which is the pattern of transmit and/or receive gain....
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Kiến trúc phần mềm Radio P8
RF/IF Conversion Segment Tradeoffs This chapter introduces the system-level design tradeoffs of the RF conversion segment. Software radios require wideband RF/IF conversion, large dynamic range, and programmable analog signal processing parameters. In addition, a high-quality SDR architecture includes specific measures to mitigate the interference readily generated by SDR operation. I. RF CONVERSION ARCHITECTURES The RF conversion segment of the canonical software radio is illustrated in Figure 8-1. The antenna segment may provide a single element for both transmission and reception....
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Kiến trúc phần mềm Radio P9
ADC and DAC Tradeoffs This chapter introduces the relationship between ADCs, DACs, and software radios. Uniform sampling is the process of estimating signal amplitude once each T seconds, sampling at a consistent frequency of fs = 1=T Hz. Although s s there are other types of sampling, SDRs employ uniform-sampling ADCs.
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Kiến trúc phần mềm Radio P10
Digital Processing Tradeoffs This chapter addresses digital hardware architectures for SDRs. A digital hardware design is a configuration of digital building blocks. These include ASICs, FPGAs, ADCs, DACs, digital interconnect, digital filters, DSPs, memory, bulk storage, I/O channels, and/or general-purpose processors. A digital hardware architecture may be characterized via a reference platform, the minimum set of characteristics necessary to define a consistent family of designs of SDR hardware....
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Kiến trúc phần mềm Radio P11
Software Architecture Tradeoffs This chapter addresses software design for SDR nodes. This includes software functions, hardware-software interactions, object-oriented design, and software architecture. It also addresses the evolution of the software components of SDR designs. Architecture tradeoffs addressed include the partitioning of software into objects. The boundaries of functional-interfaces and levels of abstraction determine the potential for reuse. These boundaries also determine the ease with which software products from different development teams will integrate into a multi-mode SDR....
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Kiến trúc phần mềm Radio P12
Software Component Characteristics This chapter addresses the structure and function of low-level software components. These include algorithms, modules (e.g., Ada packages, C++ objects), and APIs. The perspective is bottom-up, with the emphasis on computational complexity. Low-level algorithms may be simple at first, but complexity can increase over time. The increases in complexity can occur with research advances. Measures taken to compensate for a performance problem in one area (e.g., noisy voice channel) can increase complexity of an algorithm (e.g., dithering the digital LO to spread homodyne artifacts over the voice band, improving voice SNR)....
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Kiến trúc phần mềm Radio P13
Performance Management The material covered in this chapter can reduce DSP hardware costs by a factor of 2 : 1 or more. Thus it is pivotal and in some sense the culmination of the SDR design aspects of this text. I. OVERVIEW OF PERFORMANCE MANAGEMENT Resources critical to software radio architecture include I/O bandwidth, memory, and processing capacity.
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Kiến trúc phần mềm Radio P14
Smart Antennas Smart antennas are an important application of SDR technology [381]. An in-depth treatment is beyond the scope of this chapter. The objective is to introduce the topic to identify the implications of smart antennas for softwareradio architecture. The smart antenna is a logical extension of antenna diversity described above [382]. Smart antenna arrays integrate the contributions of spatially distributed antenna elements to provide wireless communication systems with larger capacity and higher link quality through frequency reuse and cochannel interference suppression [383, 384]....
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Kiến trúc phần mềm Radio P15
This chapter develops illustrative applications, including the design of a contemporary SDR infrastructure product, the disaster-relief system. I. THE DESIGN PROCESS The implementation of SDR applications can be structured into an SDR design process. This process begins with the definition of a concept of operations (CONOPS), in which functions of the product are identified. The next stage, system definition, includes rapid prototyping and benchmarking. The third stage, system development, includes the implementation of hardware-software components. ...
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Kiến trúc phần mềm Radio P16
Reference Architecture This chapter provides a consolidated view of the software-radio architecture models developed throughout the text for convenient reference. This consists of a radio platform view (Figure 16-1) and a software components view
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Cấu trúc sóng chức năng trong điện lý thuyết P1
Spheroidal wave functions are special functions in mathematical physics which have found many important and practical applications in science and engineering where the prolate or the oblate spheroidal coordinate system is used. In the evaluation of electromagnetic (EM) fields in spheroidal structures, spheroidal wave functions are frequently encountered, especially when boundary value problems in spheroidal structures are solved using full-wave analysis.
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Cấu trúc sóng chức năng trong điện lý thuyết P2
Spheroidal Coordinates and Wave Functions 2.1 SPHEROIDAL COORDINATE SYSTEMS Prolate and oblate spheroidal coordinate systems are formed by rotating the two-dimensional elliptic coordinate system, consisting of confocal ellipses and hyperbolas, about the major and minor axes of the ellipses, respectively [l] (shown in Figs. 2.1 and 2.2, where d is the interfocal distance).
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Cấu trúc sóng chức năng trong điện lý thuyết P3
Dyadic Green’s Functions in Spheroidal Systems 3.1 DYADIC GREEN’S FUNCTIONS To analyze the electromagnetic radiation from an arbitrary current distribution located in a layered inhomogeneous medium, the dyadic Green’s function (DGF) technique is usually adopted. If the geometry involved in the radiation problem is spheroidal, the representation of dyadic Green’s functions under the spheroidal coordinates system should be most convenient. If the source current distribution is known, the electromagnetic fields can be integrated directly from where the DGF plays an important role as the response function of multilayered dielectric media....
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