Tài liệu miễn phí Kĩ thuật Viễn thông
Download Tài liệu học tập miễn phí Kĩ thuật Viễn thông
Điện thoại di động băng thông rộng không dây P1
Summary and Introduction Broadband wireless communications have gained an increased interest during the last few years. This has been fuelled by a large demand on high frequency utilisation as well as a large number of users requiring simultaneous high data rate access for the applications of wireless mobile Internet and e-commerce. The convergence of wireless mobile and access will be the next storm in the wireless communications, which will use a new network architecture to deliver broadband services in a more generic configuration to wireless customers and supports value-added services and emerging interactive multimedia communications....
8/29/2018 6:09:49 PM +00:00
Điện thoại di động băng thông rộng không dây P2
Universal Personal Communications (UPC) establishes the new concept of personal mobility and personal numbering [1]. In the UPC environment the fixed association between terminal and user identification is removed. This establishes the basis for personal mobility. Personal communications involves providing an essentially transparent connection so that a practical range of services can be automatically provided to people on the move [2]. Both wired and wireless access can, and should be involved, with existing infrastructures forming the basis of service delivery to a person rather than to a place....
8/29/2018 6:09:49 PM +00:00
Điện thoại di động băng thông rộng không dây P3
UTRAN side MAC architecture. 3GPP TSs and TRs are the property of ARIB, CWTS, ETSI, T1, TTA and TTC who jointly own copyright in them. They are subject to further modification and are therefore provided to you ‘as is’ for information purposes only. Further use is strictly prohibited.
8/29/2018 6:09:49 PM +00:00
Điện thoại di động băng thông rộng không dây P4
The successful deployment and worldwide acceptance of the second-generation (2G) mobile telecommunication systems combined with the need for more advanced and ubiquitous mobile services have paved the way to the initiative of the so-called third-generation (3G) mobile telecommunication systems. In this chapter, we will discuss the network architecture of 3G systems, i.e. we will describe how the network is built, what functional elements exist, what overall functionality is provided, etc.
8/29/2018 6:09:49 PM +00:00
Điện thoại di động băng thông rộng không dây P5
Network Architecture value is 500 octets, then IP datagrams of 1500 octets will be segmented into three SNDCP data units. Each one will be transmitted separately and reassembled by the receiving SNDCP layer. A PDP Context essentially represents a virtual connection between an MS and an external PDN. The PDP Context multiplexing is a function that:
8/29/2018 6:09:49 PM +00:00
Bảng so sánh tính năng WRT120N và WAP4410N
Đặc điểm chính của WAP4410N: Sử dụng công nghệ không dây chuẩn N, với công nghệ MIMO giúp mở rộng vùng phủ sóng; Có thể sử dùng POE hoặc nguồn ngoài; Hỗ trợ Multiple BSSIDs và SSID mapping tới 4 SSID Vlans; Hỗ trợ WMM QoS cho mạng không dây; Cho phép ghi lại Syslog, mail, local log…
8/29/2018 6:09:37 PM +00:00
ANTEN & TRUYỀN SÓNG_Dương Hiển Thuận
Mục đích: Tìmhiểu các đặc điểm, tính chất cũng như ảnh hưởng của môi trường vô tuyến đối với các mạng không dây (wireless), bản chất và các thông số cơ bản của anten. Nội dung: Truyền sóng: các khái niệm, công thức cơ bản trong truyền sóng, đặc điểm của sóng truyền lan trong môi trường tầng đối lưu và tầng điện ly. Anten : nguyên lý bức xạ, các thông số và đặc tính cơ bản của anten, một số anten thường gặp và anten thông minh...
8/29/2018 6:09:36 PM +00:00
Truyền sóng trong tầng điện ly
Các lớp cực đại điện tích: Do mật độ chất khí thay đổi theo độ cao; Do phần trămcác chất khí không giống nhau theo độ cao; Năng lượng ion hóa không giống nhau theo độ cao. Khi bỏ qua va trạm của electron với các hạt nặng. Giả thiết sóng phẳng phân cực tuyến tính truyền vào tầng điện đồng nhất với mật độ N. Nếu có một điện trường ngoài thì các ion và electron sẽ chuyển động có hướng và tạo thành mật độ dòng điện dẫn...
8/29/2018 6:09:36 PM +00:00
LÝ THUYẾT CHUNG VỀ ANTEN
Sóng điện từ có thể truyền dẫn bằng hai phương pháp: Truyền dẫn trong các thiết bị định hướng như đường dây song hành, cáp đồng trục, ống dẫn sang, cáp sợi quang... Khi truyền lan trong các hệ thống này sóng điện từ bị giới hạn trong khoảng không gian của thiết bị và được gọi là sóng điện từ ràng buộc. Bức xạ sóng ra không gian để sóng truyền đi trong các môi trường thực và được gọi là sóng điện từ tự do. Thiết bị dùng để chuyển đổi sóng điện từ ràng buộc thành sóng điện từ tự do và...
8/29/2018 6:09:36 PM +00:00
CHƯƠNG VIII: LÝ THUYẾT VỀ ANTEN PHÁT HÌNH
Tham khảo tài liệu 'chương viii: lý thuyết về anten phát hình', kỹ thuật - công nghệ, kĩ thuật viễn thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả
8/29/2018 6:09:36 PM +00:00
Hệ thống 3G và mạng không dây thông minh P1
Although the number of cellular subscribers continues to grow worldwide [27], the predominantly speech-, data- and e-mail-oriented services are expected to be enriched by a whole host of new services in the near future. Thus the performance of the recently standardised Code Division Multiple Access (CDMA)third-generation (3G) mobile systems is expected to become comparableto, if not better than, that of their wired counterparts.
8/29/2018 6:09:35 PM +00:00
Hệ thống 3G và mạng không dây thông minh P2
In recent years the concept of intelligent multi-mode, multimedia transceivers (IMMT) has emerged in the context of wireless systems [67a,150-1521 and the range of various existing solutions that have found favourin existing standard systems was summarised in the excellent overview by Nanda et al. [153].
8/29/2018 6:09:35 PM +00:00
Hệ thống 3G và mạng không dây thông minh P3
Adaptive beamforming wasinitially developed in the 1960s for the military applications of sonar andradar, in order to remove unwanted noise and jamming from output. The related the literature of the past 40 years is extremely rich [201-2371 and since this book is mainly concerned with the networking aspects of wireless systems, rather than with specific antenna array designs, here we will restrict our discussionson the topic to a rudimentaryoverview.
8/29/2018 6:09:35 PM +00:00
Hệ thống 3G và mạng không dây thông minh P4
Cellular networks are typically interference limited, with co-channel interference arising from cellular frequency reuse, ultimately limiting the quality and capacity of wireless networks [280,281]. However, Adaptive Antenna Arrays (AAAs) capable of exploiting the are spatial dimension in order to mitigate this co-channel interference and thus to increase the achievable network capacity [3,6,38,242,250,282].
8/29/2018 6:09:35 PM +00:00
Hệ thống 3G và mạng không dây thông minh P5
In January 1998, the European standardisation body for third generation mobile radio systems, the European Telecommunications StandardsInstitute - Special Mobile Group (ETSI SMG), agreedupon a radio access schemefor third generation mobile radio systems, referred to as the Universal Mobile Telecommunication System (UMTS) [ 11,321.
8/29/2018 6:09:35 PM +00:00
Hệ thống 3G và mạng không dây thông minh P6
In this book we have discussed the performance implications adaptive antenna arrays of and adaptive modulation techniques both FDMARDMA and CDMA cellular mobile commuin nications networks. In Chapter 3 we investigated antenna arrays and adaptive beamforming algorithms.We commenced, in Section 3.2.2,by considering the possible applications antenna arraysand of their related benefits.
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P1
In recent years the concept of intelligent multi-mode, multimedia transceivers (IMMT) has emerged in the context of wireless systems [l-61. The range of various existing solutions that have found favour in already operational standard systems was summarised in the excellent overview by Nanda et al. [3]. The aim of these adaptive transceivers is to provide mobile users with the best possible compromise amongst a number of contradicting design factors, such as the power consumption of the hand-held portable station (PS), robustness against transmission errors, spectral eficiency, teletrafic capacity, audiohideo quality and so forth [2]....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P2
In most digital data transmission systems the dispersive linear channel encountered exhibits amplitude and phase distortion. As a result, the received signal is contaminatedby Intersymbo1 Interference (ISI). In a system, which transmits a sequenceof pulse-shaped information symbols, the time domain full response signalling pulses are smeared hostile dispersive by the channel, resulting in intersymbol interference. At the receiver, the linearly distorted signal has to be equalized in order torecover the information....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P3
In Chapter 2 the equalizers operated under the assumption of perfect channel estimation, where the receiver always had perfect knowledge of the CIR. However, the CIR is typically time variant and consequently the receiver has to estimate the CIR or the coefficients of the equalizer, in order to compensate the IS1 induced by the channel. for Algorithms have been developed in order to automatically adapt the coefficients of the equalizer directly [ l 181 or by utilizing the estimated CIR [124,125]....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P4
In this chapter, the conceptof Adaptive Quadrature AmplitudeModulation (AQAM) is introduced, whereby the modulation mode is adapted at the transmitter on a burst by burst basis. This adaptation is implemented based on thereceiver’s perceived channel qualityand its main BER. motivation is to maximise the transmission throughput at a given target In our investigations AQAM is initially applied in a narrow-band environment in conjunction with power control, where the transmitted power is only varied near the modem mode switching thresholds of the AQAM scheme. Subsequently, AQAM is investigated in a wideband channel in conjunction with a DE-assisted receiver....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P5
In the previous chapter, introduced the joint Adaptive Quadrature Amplitude Modulation we (AQAM) and equalization scheme, where the pseudo-SNR outputof the DFE was used at the as the modulation mode switching metric in order to mitigate the effectsa wideband fading of AQAM scheme is extended to incorporate benefits the channel. In this chapter, the wideband of channel coding. The general motivation for using channel coding is to exploit the error correction and the error detection capability the channel codes order to improve the of in BER of and throughput performance the wideband AQAM scheme....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P6
Mobile communications channelstypically exhibit time-variant channel quality fluctuations [ 131 and hence conventional fixed-mode modems suffer from bursts of transmission errors, even if the system was designed to provide a high link margin. As argued throughout this monograph, an efficient approach of mitigating these detrimental effects is to adaptively adjust the transmission format based on the near-instantaneous channel quality information perceived by the receiver, which is fed back to the transmitter with the aid of a feedback channel [ 151....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P7
Practical Considerationsof Wideband AQAM In deriving the upper bound performance of wideband AQAM portrayed in Figure 4.21(b), various assumptions were made and stated in Section 4.3.1. However, in order to provide a more accurate comparison between AQAM and constituent fixed modulation modes, those its assumptions must be justified and their effects have to be investigated. Specifically, perfect, i.e. error-free feedback was assumed for the DFE, while in practice erroneous decision can be fed back, which results in error propagation....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P8
Neural Network Based Equalization In this chapter, we will give an overview of neural network based equalization. Channel equalization can be viewed as a classification problem. The optimal solution to this classification problem is inherentlynonlinear. Hence we will discuss, how the nonlinear structureof the artificial neural network can enhancethe performance of conventional channel equalizers as and examinevarious neural network designs amenable channel equalization, such the soto called multilayer perceptron network [236-2401, polynomial perceptron network 1241-2441 and radial basis function network 185,245-2471....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P9
RBF-Equalized Adaptive Modulation Having considered the concepts of RBF-assisted channel equalization in Chapter 8, we are now ready to amalgamate these concepts with the AQAM philosophy detailed in Part I of the book. Although it is advantageous for the reader to consult Part I of the book, before delving into Part I1 dedicated to RBF-assisted arrangements, there is sufficient background information in this part of the book for the reader to be able to dispense with reading Part I.
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P10
RBF Equalization UsingTurbo Codes In this chapter, the wideband AQAM scheme explored in the previous chapter is extended to incorporate the benefits of channel coding. Channel coding, with its error correction and detection capability, is capable of improving the BER and throughput performance of the wideband AQAM scheme. Since the wideband AQAM scheme always attempts to invoke the appropriate modulation mode in order to combat the wideband channel effects, probabilthe ity of encountering a received transmitted burst with a high instantaneous BER is low, when is advantageous, compared to the constituent fixed modulation modes. ...
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P11
RBF Turbo Equalization This chapter presents novel turbo equalization scheme, a which employs a RBF equaliser instead of the conventional trellis-based equaliserDouillard et al. [ 1.531. The basic principles of of turbo equalization will be highlighted. Structural, computational cost and performance comparisons of the RBF-based and trellis-based turbo equalisers areprovided. A novel element of our design isthat in order to reduce the computational complexity the RBF turbo of equaliser (TEQ), we propose invoking further iterations only, if the decoded symbol has a high error probability....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P12
As argued throughout the previous chapters the book, mobile propagation channels exhibit of time-variant propagation properties [ 131. Although apart from simple cordless telephone schemes most mobile radio systems employ power control for mitigating the effects of received power fluctuations, rapid channel quality fluctuations cannot be compensated by practical, finite reaction-time power control schemes.
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P13
High data rate communications are limited not only by noise, --butespecially with increas(ISI) ing symbolrates -often more significantly by the Inter Symbol Interference due to the memory of the dispersive wireless communications channel [317]. Explicitly, this channel memory is caused by the dispersive channel impulse response (CIR) due to the differentlength propagation paths between the transmitting and the receiving antennae. This dispersion effect could theoretically be measured by transmitting an infinitely short impulse and “receiving” the CIR itself....
8/29/2018 6:09:35 PM +00:00
Adaptive thu phát không dây P14
In [515] the encoding and decoding processes as well as the various design trade-offs of space-time block codes [7,2 18,5 were reviewed. More explicitly, various previously pro161 posed space-time block codes [218,5 161 have been discussed and their performance was investigated over perfectly interleaved, non-dispersive Rayleigh fading channels. A range of systems consisting of space-time block codes and different channel codecs were investigated. The performance versus estimated complexity trade-off of the different systems was investigated and compared....
8/29/2018 6:09:35 PM +00:00