Rapid growth of wireless communication services in recent decades has created a huge demand of radio spectrum. Spectrum scarcity and utilization inefficiency limit the development of wireless networks. Cognitive radio is a promising tech- nology that allows secondary users to reuse the underutilized licensed spectrum of primary users. The major challenge for spectrum sharing is to achieve high spectrum efficiency while making non-intrusive access to the licensed bands. This requires in- formation of availability and quality of channel resources at secondary transmitters, however, is difficult to be obtained perfectly in practice.
標(biāo)簽： Opportunistic Spectrum Sharing
上傳時(shí)間： 2020-05-31
上傳用戶：shancjb
The roots of this book were planted about a decade ago. At that time, I became increasingly convinced that wide-area and metropolitan-area networks, where much of my group’s research has been centered at that time, were in good shape. Although research in these fields was (and still is) needed, that’s not where the networking bottleneck seemed to be. Rather, the bottleneck was (and still is in many places) in the access networks, which choked users’ access to information and services. It was clear to me that the long-term solution to that problem has to involve optical fiber access networks.
標(biāo)簽： Networks Optical Access
上傳時(shí)間： 2020-05-31
上傳用戶：shancjb
Recent decades have shown a tremendous expansion of the Internet. The number of connected terminals has increased by orders of magnitude, traffic has grown exponen- tially, coverage has become ubiquitous and worldwide, and today’s sophisticated Web 2.0 applications are increasingly providing services which hitherto have been the realm of telecommunications, such as Skype and video conferencing. This has even led to the thought that access to the Internet might one day be a universal right of every citizen. This evolution will accelerate in the coming decades.
標(biāo)簽： Networking Personal Networks Wireless
上傳時(shí)間： 2020-05-31
上傳用戶：shancjb
Soon after Samuel Morse’s telegraphing device led to a deployed electri- cal telecommunications system in 1843, waiting lines began to form by those wanting to use the system. At this writing queueing is still a significant factor in designing and operating communications services, whether they are provided over the Internet or by other means, such as circuit switched networks.
標(biāo)簽： Telecommunication Queueing Packet Theory with
上傳時(shí)間： 2020-05-31
上傳用戶：shancjb
One of the prerequisites for the development of telecommunication services is the understanding of the propagation of the waves, either acoustic, electromagnetic, radio or light waves, which are used for the transmission of information. In this work, we shall limit ourselves to the study of radio waves: this term apply to the electromagnetic waves used in radio communications. Their frequency spectrum is very broad, and is divided into the following frequency bands : ELF waves (f < 3 kHz), VLF (3-30 kHz), LF waves (30-300 kHz), MF waves (300-3000 kHz), HF (3-30 MHz), VHF waves (30-300 MHz), UHF waves (300-3000 MHz), SHF waves (3-30 GHz), EHF waves (30-300 GHz) and sub- EHF waves (300-3000 GHz).
標(biāo)簽： Propagation Radio Wave
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
We are currently witnessing an increase in telecommunications norms and standards given the recent advances in this domain. The increasing number of normalized standards paves the way for an increase in the range of offers and services available for each consumer. Moreover, the majority of available radio frequencies have already been allocated.
標(biāo)簽： Allocation Resource Radio
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
Wireless communications and networking technology are advancing at a very rapid pace. Newer technologies and standards are evolving to serve the ever-increasing num- ber of users demanding different types of mobile applications and services. Research and development activities on wireless technology constitute one of the most impor- tant segments of research and development in the telecommunications area today.
標(biāo)簽： Management Resource Radio
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
It is more than a decade since GSM was first commercially available. After some unexpected delay, it seems that finally UMTS is here to stay as a 3G system standardised by 3GPP, at least for another ten years. UMTS will enable multi-service, multi-rate and flexible IP native-based mobile technologies to be used in wide area scenarios and also pave the way for a smooth transition from circuit switched voice networks to mobile packet services.
標(biāo)簽： Management Strategies Resource Radio
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
Commoditization is a serious threat to the telecommunications industry. Most CSPs offer similar services at rates designed to win what has become a price war. As a result, many face decreasing margins and difficulty sustaining differentiation based on prices or products alone. On top of commoditization, CSPs also face competition from OTT providers and an increasingly knowledgeable and demanding customer base. With access to growing amounts of data from an ever-increasing number of sources and devices, today’s empowered, savvy consumers know what they want and expect to get it.
標(biāo)簽： RestoringConnections_IBM_CPL
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
Software Radio (SR) is one of the most important emerging technologies for the future of wireless communication services. By moving radio functionality into software, it promises to give flexible radio systems that are multi-service, multi- standard, multi-band, reconfigurable and reprogrammable by software. Today’s radios are matched to a particular class of signals that are well defined bytheircarrierfrequencies,modulationformatsandbandwidths.Aradiotransmitter today can only up convert signals with well-defined bandwidths over defined center frequencies, while, on the other side of the communication chain, a radio receiver can only down convert well-defined signal bandwidths, transmitted over specified carrier frequencies.
上傳時(shí)間： 2020-06-01
上傳用戶：shancjb
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