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Áp dụng DSP lập trình trong truyền thông di động P14
Existing AM and FM broadcasting have remained relatively unchanged since the 1960s when FM stereo transmission was introduced. Meanwhile, audio recording techniques have undergone tremendous change from traditional analog to high quality digital recording with the introduction of compact disc, and most recently MP3 compressed audio recording to permit music be transmitted via the Internet. Traditional analog broadcasts were originally designed for stationary receivers and suffer from degradation of the received signal when used in a mobile environment with weak signal strength and multipath...
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Áp dụng DSP lập trình trong truyền thông di động P15
In recent years, the technological trend toward high-performance mobile communications devices has caused a burgeoning interest in the field of low-power design. Indeed, with the proliferation of portable devices such as digital cellular phones, pagers and personal digital assistants, designing for low-power with high throughput is becoming increasingly necessary. It is often claimed that a full-custom ASIC will be ‘‘lower power’’ than a programmable approach. This is certainly the case when compared to a general purpose processor, but less apparent when compared to a programmable Digital Signal Processor (DSP) processor [13]....
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Áp dụng DSP lập trình trong truyền thông di động P16
In a variety of scenarios, often the only way to fully observe or monitor a situation is through the use of sensors. Sensors have been used in both civil and military applications, in order to extend the field of view of the end-user. However, most current sensing systems consist of a few large macrosensors, which while being highly accurate are expensive. Macrosensor systems are highly sensitive; the entire system can break down even with one faulty sensor. Trends in sensing applications are shifting towards designing networks of wireless microsensor nodes for reasons such as lower cost, ease of deployment and...
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Áp dụng DSP lập trình trong truyền thông di động P17
The Pleiades Architecture Arthur Abnous, Hui Zhang, Marlene Wan, Varghese George, Vandana Prabhu and Jan Rabaey Rapid advances in portable computing and communication devices require implementations that must not only be highly energy efficient, but they must also be flexible enough to support a variety of multimedia services and communication capabilities. The required flexibility dictates the use of programmable processors in implementing the increasingly sophisticated digital signal processing algorithms that are widely used in portable multimedia terminals....
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Áp dụng DSP lập trình trong truyền thông di động P18
The Need for Instruction Set Extensibility in a Signal Processor In the early 1990s, digital signal processing in wireless terminals mainly covered voice compression as well as channel equalization, coding and decoding techniques (also called ‘‘modem’’ function). Corresponding electronic systems built to optimize these applications tried to make the best trade-off between software and hardware in order to minimize system cost and power consumption. Software was mostly used as an efficient means to allow a quick evolution or on-the-fly correction of signal processing functions. ...
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Áp dụng DSP lập trình trong truyền thông di động P19
Next Generation Wireless Devices Wireless devices stand at a new frontier. Reduction in the cost and size of powerful processors allow handsets, PDAs and digital cameras to advance from single purpose devices to complete multimedia platforms. Broader bandwidth networks allow vastly expanded functionality in these devices. This platform is more than a small television or tiny computer. It is an entirely new medium with its own limitations and advantages. Most importantly it is used in a completely unique way. Exciting opportunities abound for content providers and users of these new devices. ...
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Các tế bào connetion P1
AN INTRODUCTION TO CELLULAR PHONE SYSTEMS The first mobile communications system began in 1921 when the Detroit Police Department installed two-way radios in its cars. The equipment was bulky, awkward, and a drain on automobile batteries, but it proved its worth. Soon police and fire departments throughout the country were installing two-way radio equipment in their fleets. Eventually someone realized that private individuals could also benefit from being able to talk with the outside world from their cars, and the first commercial mobile telephone service was instituted in St. Louis, Missouri, in 1946. Early mobile phone service was more like using...
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Các tế bào connetion P2
CELLULAR PHONE EQUIPMENT There are three parts to a cellular phone system: the cellular telephone, or cellphone; the cell site, which receives and transmits radio signals from and to your phone; and the MSC, or Mobile Switching Center, which links cellphones to established conventional telephone services. The relationship among these is illustrated in Figure 2.1. THE CELLULAR TELEPHONE The standard portable cellular telephone is a one-piece unit that serves as the handset, and includes a dial pad or ‘‘keypad,’’ display, microphone, miniature speaker or earpiece, a miniature radio receiver and transmitter or transceiver, antenna, and a removable, rechargeable battery....
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Các tế bào connetion P3
THE BUSINESS OF CELLULAR PHONES The business of cellular phones is a big one. Although cellular phone companies must make a large initial investment, the potential for an enormous return makes it certain that there will be no shortage of firms to service the cellular user. WHERE CAN YOU GET CELLULAR SERVICE? Cellular service was deployed beginning in 1983 in order of city population, with licenses for the largest cities awarded first. While some potential users have had to wait for service in smaller cities, in 1992 the last tertiary markets established commercial service....
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Các tế bào connetion P4
GETTING CELLULAR SERVICE Cellular phone equipment must meet stringent standards and pass a number of stiff tests, so you are assured of getting a quality product no matter where you buy it. The real deciding factor on where to buy your cellular phone is the human one — the standards, know-how, and customer service capabilities of the dealer. FINDING THE BEST SOURCE OF CELLULAR PHONES AND SERVICE Cellular phones are a hot item. In addition to Yellow Pages advertising, you can look in any newspaper; ads for cellular equipment and services abound. Advertising for cellular service is also found on radio and...
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Các tế bào connetion P5
THE BILL, PLEASE The costs of a cellular phone, of other necessities such as a battery charger, and of installation, are one-time expenses. Once you’ve paid for these items and services, you’re done with them. Fixed costs, though, account for only a part of what it costs to operate a cellular phone. In this chapter we’ll look at the other, more important expenses — what it costs you to use your phone. ONE-TIME (NONRECURRING) EXPENSES Like the price of purchasing equipment, some operating expenses are paid once and never again (unless, for example, you have your phone number taken out of service...
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Các tế bào connetion P6
HELLO, MA? IT’S ME! Using a cellular telephone is not much different from using a conventional one. In fact, it can even be easier because these phones contain their own small computers and have many more special features than regular phones. And the high quality of their audio makes them a pleasure to use. At first glance, the keypad of a cellular phone may appear intimidating. Once you know what everything’s for, though, and how it works, there’s nothing to it. BUTTONS, BUTTONS In addition to the usual twelve buttons found on a home or office Touch-Tone phone, the handset of a...
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Các tế bào connetion P7
ROAMING Using your cellular phone when you’re away from your home cellular service area, traveling in another, is called roaming. Virtually all cellular carriers have made arrangements under which you can simply arrive in a service area other than your own and automatically start to use that carrier’s service. There is a certain mystery surrounding roaming, and a lot of questions have arisen over what roaming is and how it works. This chapter is intended to answer those questions. HOW TO TELL WHEN YOU’RE ROAMING The boundaries that mark the end of one cellular carrier’s domain and the beginning of another’s are...
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Các tế bào connetion P8
MOBILE AND TRANSPORTABLE PHONES To be able to place and receive telephone calls for various wireless applications — a telephone for the construction site, or on a boat, for example — you may want to consider a transportable phone. Vehicleinstalled phones used to be the primary type of cellular phone, and are still important for many users. CAR CELLULAR TELEPHONE COMPONENTS A typical cellular phone installation for an automobile consists of four basic components: the power source, the control head, the transceiver/logic unit, and the antenna (see Figure 8.1). Most problems with installed car phones are a result of poor or improper...
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Các tế bào connetion P9
OPTIONS AND ACCESSORIES Cellular telephones have so many features built into them that it’s difficult to think of anything more that could be added to them. Many of these features have been discussed in previous chapters, but we will explore them further here. BATTERIES A second battery is perhaps the most-requested accessory of any portable cellphone user. It extends the time between charges while on the road, and ensures that there is always a charged battery at hand if you find that the battery in your phone is dead. Since the standard battery is usually a nickel—cadmium (NiCad) battery, users often will...
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Các tế bào connetion P10
DEALING WITH OPERATIONAL DIFFICULTIES Cellular telephones are rugged and reliable. They have to be, since their very nature dictates that they will be banged around and subjected to extremes of heat and cold in briefcases, automobiles, and other places. They rarely fail. Most of any difficulties with your cellphone will arise from the conditions under which it is used and, possibly, from your initial unfamiliarity with the equipment and with cellular systems in general. This chapter will help you to understand some of the difficulties you may encounter in using your cellular phone, and, when possible, will show you what you...
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Các tế bào connetion P11
SAFETY AND SECURITY This chapter concerns safety and security — safety in the sense of maintaining your usual standard of driving while using a cellular phone, how cellular improves safety, and in safeguarding your phone equipment; and security in the sense of guarding the privacy of your conversations. SAFETY Anything that distracts you from driving can be a hazard. A cellular phone, unless it’s used with care, can be just such a distraction. Using a phone at the same time you’re trying to concentrate on the road and traffic conditions can endanger both you and other drivers. For this reason, try not...
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Các tế bào connetion P12
INTO THE FUTURE The technology that permits us to put telephones in our cars and in our pockets continues to evolve and provide us with new and improved services. Because there is no need for utility poles, conduit, or miles of expensive cable, cellular telephones can be located, either permanently or temporarily, wherever they are needed. This versatility gives cellular the crucial economic edge that ensures the rapid growth of this new industry. In this chapter we will look into the future of wireless telecommunications and its applications. ...
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Điện thoại di động vô tuyến điện - Tuyên truyền Channel P1
The history of mobile radio goes back almost to the origins of radio communication itself. The very early work of Hertz in the 1880s showed that electromagnetic wave propagation was possible in free space and hence demonstrated the practicality of radio communications. In 1892, less than ®ve years later, a paper written by the British scientist Sir William Crookes [1] predicted telegraphic communication over long distances using tuned receiving and transmitting apparatus. Although the ®rst radio message appears to have been transmitted by Oliver Lodge in 1894 [2], it was the entrepreneur Marconi [3] who initially demonstrated the potential of...
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Điện thoại di động vô tuyến điện - Tuyên truyền Channel P2
Fundamentals of VHF and UHF Propagation Having established the suitability of the VHF and UHF bands for mobile communications and the need to characterise the radio channel, we can now develop some fundamental relationships between the transmitted and received power, distance (range) and carrier frequency. We begin with a few relevant de®nitions. At frequencies below 1 GHz, antennas normally consist of a wire or wires of a suitable length coupled to the transmitter via a transmission line. At these frequencies it is relatively easy to design an assembly of wire radiators which form an array, in order to beam the...
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Điện thoại di động vô tuyến điện - Tuyên truyền Channel P3
Propagation over Irregular Terrain Land mobile radio systems are used in a wide variety of scenarios. At one extreme, county police and other emergency services operate over fairly large areas using frequencies in the lower part of the VHF band. The service area may be large enough to require several transmitters, operating in a quasi-synchronous mode, and is likely to include rural, suburban and urban areas. At the other extreme, in major cities, individual cells within a 900 or 1800 MHz cellular radio telephone system can be very small in size, possibly less than 1 km in radius, and service...
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Điện thoại di động vô tuyến điện - Tuyên truyền Channel P4
Propagation in Built-up Areas Having looked at how irregular terrain aects VHF and UHF radio wave propagation and the eects of multipath, we are now in a position to discuss propagation in built-up areas. This chapter will deal principally with propagation between base stations and mobiles located at street level; propagation into buildings and totally within buildings will be discussed later. Although losses due to buildings and other man-made obstacles are of major concern, terrain variations also play an important role in many cases. Within built-up areas, the shadowing eects of buildings and the channelling of radio waves along streets make...
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Điện thoại di động vô tuyến điện - Tuyên truyền Channel P5
Characterisation of Multipath Phenomena In Chapter 3 we described some methods for predicting path losses, concentrating on those applicable to mobile communication systems. The discussion centred around techniques that deal principally with radio propagation over irregular terrain; methods of predicting signal strength in urban areas or in other environments, e.g. inside buildings, were deliberately left until Chapter 4. These propagation models are extremely important since the vast majority of mobile communication systems operate in and around centres of population....
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Điện thoại di động vô tuyến điện - Tuyên truyền Channel P6
The mobile radio propagation environment clearly places fundamental limitations on the performance of radio communication systems. Signals arrive at a receiver via a scattering mechanism, and the existence of multiple propagation paths (multipath) with dierent time delays, attenuations and phases gives rise to a highly complex, time-varying transmission channel. In order for systems engineers to determine optimum methods of mitigating the impairments caused by multipath propagation, it is essential that the transmission channel be properly characterised. ...
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Điện thoại di động vô tuyến điện - Tuyên truyền Channel P7
Other Mobile Radio Channels A great deal of attention has been given to propagation in built-up areas, in particular to the situation where the mobile is located in the streets, i.e. when it is outside the buildings. It is apparent, however, that other important scenarios exist. For example, hand-portable equipment can be taken inside buildings, and in recent years there has been a substantial increase in the use of this type of equipment. As a result, interest in characterising the radio communication channel between a base station and a mobile located inside a building has become a priority. Propagation totally...
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Thuyết trình Vận hành và bảo dưỡng NodeB
Thuyết trình Vận hành và bảo dưỡng NodeB gồm 4 phần nhằm giúp bạn nắm bắt các nội dung sau: Hệ thống vận hành và bảo dưỡng, thủ tục vận hành NodeB, thủ tục bảo dưỡng NodeB, quản lý dữ liệu NodeB.
8/29/2018 6:21:23 PM +00:00
Thuyết trình Tổng quan mạng truy nhập vô tuyến WCDMA
Nội dung Thuyết trình Tổng quan mạng truy nhập vô tuyến WCDMA trình bày về tổng quan về 3G, nguyên tắc cơ bản của CDMA, đặc trưng cơ bản của WCDMA. Cùng tham khảo nhé.
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WCDMA UTRAN - Giao diện và thủ tục báo hiệu
Mục tiêu của khoá học: Sau khi hoàn thiện khoá học này, học viên có thế: Hiểu được cấu trúc UTRAN và giao diện UTRAN. Hiểu được định nghĩa về các phần tử mạng UTRAN. Hiểu được thủ tục báo hiệu UTRAN.
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Cấu trúc phần cứng hệ thống DBS3900 WCDMA
DBS3900 là distributed NodeB của Huawei NodeB thế hệ thứ 4. Hệ thống DBS3900 gồm có: BBU3900, RRU3804 hoặc RRU3801E, Hệ thống Antenna và feeder. BBU3900 lắp đặt trong tủ 19-Inch chuẩn: Lợi ích của kiến trúc ứng dụng này: Can reside in any standard 19-inch-wide and 2-U-high cabinet. Có thể lắp đặt trên cột kim loại và gần với antenna.
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Hoà mạng NodeB
Tài liệu này mô tả cách thức cơ bản để hòa mạng NodeB sau khi đã hoàn thành việc lắp đặt phần cứng. Việc hòa mạng này liên quan đến việc nâng cấp phần mềm, tải file cấu hình, kiểm tra việc lắp đặt phần cứng và trạng thái làm việc của NodeB. Hòa mạng cho NodeB (cách 1) : Nâng cấp phần mềm, tải file cấu hình từ ổ đĩa di động USB, và kiểm tra lại trạng thái làm việc của NodeB trên M2000 sau khi hòa mạng NodeB...
8/29/2018 6:21:23 PM +00:00