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compatible with the DVB-C system planned to adopt in China. This will inevitably result in a waste of device incompatibility in the future. Therefore, the use of DVB-C QAM modulation, not only improve the network capacity, but also compatible with the future development trend. It is the rational choice of broadband multimedia information system, which is suitable for the expressway of China's national cond
tree + (PVST +) is deployed to achieve uplink load balancing, you can also obtain a high level of stack permanent. Long-distance Ethernet Technology LRE technology uses orthogonal amplitude modulation (QAM ). The QAM amplitude modulation uses the signal amplitude and phase to define each symbol. LRE adopts the most ad
the points, the information extraction will not be affected. The data transmission rate of OFDM is also related to the number of subcarriers. Subcarriers In the OFDM system can select modulation modes based on the channel conditions and switch between modulation modes. The principle of selection and switching is the balance between spectrum utilization and bit error rate. In general communication systems,
a common copper cable U1C and a U1R reference point. VTU-O and VTU-R are the VDSL transceiver located at the local end and the user end, respectively. The service Splitter, including HPF and LPF, separates the VDSL transmitted on the same pair of telephone copper cables from the narrowband service or ADSL. VDSL uses a wide spectrum, up to 12 MHz. The spectrum range can be divided into several downlink DS and uplink US frequencies. Commonly Used frequencies in the world are Plan997 and Plan998,
"slower" sub-channels are then combined into "faster" channels in a multi-worker way. So the rate will be faster than a simple channel.The bandwidth of the working channel in 802.11A is MHZ,OFDM the physical layer to differentiate the spectrum into the operating channel. Each bandwidth 20-mhz channel consists of 52 subcarrier. The sub-carrier asks each other a 0.3125MHz channel number from 26 to 26, of which 4 sub-carriers act as pilot carrier, subcarrier-21,-7, 7, and 21 are designated as guid
, for sudden strong business flow, then choose TDMA mode; (3) The modulation mode of LMDS system is divided into two kinds of orthogonal phase shift keying (QPSK) and orthogonal amplitude modulation (QAM), in which QAM mainly adopts 4-qam, 16-
O-OFDM System Structure 1 is shown. The original binary sequence is mapped to N parallel sub-carrier channels through string/and conversion. At this time, the data cycle of each modulated sub-carrier is expanded to N times that of the original sequence, latency expansion and the numeric ratio of the symbol period are also reduced by N times. After the QAM modulation is performed on the sequence of each sub
At present, China's broadband access network has developed very mature and many new technologies have emerged. Here we introduce the development status of VDSL and analyze some of its problems, I would like to share it with you here and hope it will be useful to you. 1. Technical Standards of VDSL VDSL currently has two major incompatible technical standards: one is DMT discrete multi-audio modulation, and the other is CAP and
channel is still an option, enterprises should consider deploying the 80 MHz channel. It is important for enterprises to evaluate the available channel spectrum before deployment. This evaluation results will affect the results and data transmission speed that enterprises want their networks to achieve. · 256 orthogonal amplitude modulation (QAM): 802.11ac uses 256-QAM
Management Program. After the CM terminal device is started, it must first contact the CMTS. After the CM is started, the front-end CMTS sends a data signal, and the CM will automatically scan and find the data channel, determine the timing synchronization of the QAM modulation, and lock the data channel, CM obtains the downstream data parameters from the downstream data, and obtains the upstream channel d
the analog user access part hinders the development and forms the bottleneck effect. In this case, xDSL technology appears. At present, XDSL mainly refers to three kinds of HDSL, ADSL and VDSL.2.1, HDSL TechnologyDSL (digtal subscriber lines, digital Subscriber line technology) is the product of the late 80, mainly used for ISDN basic rate service, on a twisted pair to obtain Full-duplex transmission, using the technology is time compression multiplexing (TCM) and echo cancellation. However, cr
. First, CCITT V.22 bis (bis stands for "second" in French) is adopted by most modem manufacturers. 16-qam (12 phase angles and orthogonal modulation of four amplitude modulation phases ) Modulation technology achieves the transmission speed of bps. Next, CCITT adopted 32-tcm (Grille encoding
802.11ac has made great strides in improving Wi-Fi performance by using a wider channel, a more efficient modulation mode (by transmitting data in RF waves), and multi-user connections (so-called multi-user MIMO. In fact, this kind of progress will come in a wave in the future. However, the new 2nd wave chip is different from the 1st wave device (please read the hardware upgrade) Remember that not all 802.11ac access points are the same. Many access p
backplane capacity exceeding 1Gbps. CMTS allows cable operators to establish high-density and highly adjustable termination systems for their data-over-cable (DoC) services. The core module of CMTS is cable Access Router, which provides routing connections from the Internet or from the internal backbone data network to the RF (CATV) network. By working in conjunction with the QAM modulator (downlink module), if output can be provided in a 6MHz and MC
a waveform (high-order modulation). So there is a question that I do not know 0 corresponds to what waveform, 1 corresponds to what waveform, is because did not understand the modulation process.after using such as QAM64 modulation, the symbol that comes out is plural., which is also the origin of the plural signal. The general article treats a symbol as an inpu
began in the 1960s. 1964 first passed the first CCITT modem recommended v.21 (1964), a FSK modem with a rate of bps (now the bps), which is still used in the V.34/v.8 handshake protocol. In the 1984, the better performance of the 4-phase (or 2x2-QAM) modulation and the 4x4 QAM V.22bis appeared. In addition, the same year also introduced a new generation of modem
. Because the modulation technology used in MMDS is mainly the phase shift keying PSK (including BPSK, DQPSK, QPSK, etc.) and the orthogonal amplitude modulation QAM modulation technology, it is impossible to achieve the non line-of-sight transmission, which is difficult to be popularized in the present complicated urb
volume is small or there is no business. Multi-line rate bundling is supported, it can achieve a higher data rate. It is worth noting that although the new-generation ADSL technology has introduced the ADSL2 and ADSL2 + standards, the ADSL2 standard only paves the way for the final launch of the ADSL2 + standard, the new-generation ADSL technology will be promoted and applied in the form of ADSL2 + technology. VDSL technology has always been a controversial technology. Its standard trend and it
supports multiple European languages and hybrid display of simple images and texts. Chapter 2 Composition of the DVB System[This article does not describe the hardware structure of the DVB system in detail, but explains in detail the format and Reuse Principle of the TS code stream according to the description in iso13818. (Enough, Enough)]Classification of DVBAccording to the application of different DVB, mainly divided into DVB-S, DVB-C, DVB-T, DVB-H and other specifications. Different Specif
Cable technology and RF technology, therefore, analog TV signals and digital signals are transmitted simultaneously between 5-MHz, and 64QAM (orthogonal Amplitude Modulation) technology with commercial efficiency is used, the downstream channel speed can be up to 30 Mbit/d. The transmission rate of Cable Modem has nothing to do with the distance of transmission, but it is related to the noise of the optical fiber and the number of users of simultaneo
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