ofdm modulation

. What are the characteristics of 802.11ax? What does it bring to wireless? 802.11ax accelerates wireless connections, which many people think. Indeed, 802.11ax delivers a higher transmission rate. It introduces a higher-order modulation and encoding scheme 1024QAM. Compared with the highest 256QAM in 802.11ac, the encoding and modulation efficiency is higher. The association rate of each 80 Mbps bandwidth

, digital data is sent by analog signal-modulation information interaction: Single-order communication, half-duplex: bidirectional alternate communication, full-duplex: the transmission rate of two-way simultaneous communication code element is limited by the nes' criterion. The information transmission rate is limited by the Shannon formula. Porter is the transmission rate unit of the code element (How many code elements are transmitted per second ).

detect and correct errors is called forward correction (FEC). Now the network uses cyclic redundancy detection (CRC) encoding, also known as polynomial encoding. ----------- Broadcast link ---------- there are two types of network links: point-to-point link and broadcast link. The broadcast link requires multi-channel access, that is, to figure and coordinate multiple sending and receiving nodes to access a shared broadcast channel. If two nodes transmit frames at the same time and the frames c

improve system throughput. The combined use of the above technologies not only ensures the stability and reliability of wireless coverage, but also increases bandwidth and coverage capabilities, making the development of wireless networks more economical. In the context of high bandwidth application speed, rural villages and towns with huge network access needs are experiencing a wave of rapid advances in wireless access applications. At present, the rural wireless coverage application product

to achieve global seamless roaming; B The voice is transmitted on the infrastructure inherited from 2G, not on the IP network structure; C) video transmission does not meet the requirements of high definition; D the data rate, although improved, can be difficult to quickly transfer large text and large e-mail attachments. 2 ITU's vision for the post-3G Considering the deficiencies of the 3G system, the ITU has proposed some enhancements to the current 3G system (which can be said to be 3G-

A comparative summary of 802.11 abgn AC 802.11B Standard released at 1999 2.4GHz Maximum rate 11mbps distance 100m~300m business data image and data physical layer CCK and DSSS 802.11G Standard released at 2003 2.4GHZ Maximum rate 54mbps distance 150m service data voice image data physical layer CCK OFDM PBCC 802.11n Standard released at 2.4g5ghz highest rate 300mbps distance almost business data voice image data physical layer MIMO

Baseband signal is the digital signal 1 or 0 directly using two different voltage to express, and then sent to the line to transmit. The wideband signal is a frequency division multiplexing analog signal which is modulated by the baseband signal. The basic principle of multiplexing technology is: Before entering the same wired or wireless transmission medium, each signal is modulated into a modulated signal which is not confused with each other, then enters the transmission medium to transmit to

: one is ieee802.11a, working in the 5GHz band, using OFDM modulation, transmission rate of 6-54mbit/s or 11mbit/s.WLAN uses conventional LANs (such as 10/100/1000mbit/s Ethernet) and its Interconnect devices (routers) to form backbone support networks, using wireless access points (APs) and wireless Access server (was) to enable mobile Terminal (MT) movement and roaming. The function of wireless access ser

In electronic circuits, power supply, amplification, oscillation, and Modulation circuits are called Analog Electronic Circuits because they process and process continuously changing analog signals. 1. Feedback Feedback refers to sending output changes to the input end in some way as part of the input. If the return part and the original input part are subtracted, It is negative feedback. 2. Coupling An amplifier usually has several levels, and the as

sharing, network security, and network management. The common feature of the two modes is that the existing network infrastructure is used. Their common disadvantage is that the bandwidth expansion capability is limited. 4) PLC access method Power Line Communication Technology (PLC) is a communication method that uses power lines to transmit data and voice signals. The technology is to load the high frequency of information contained in the current, and then transmit it using a wire. the modem

). IEEE implements high-speed expansion of the 802.11 standard. Two high-speed extensions are available: IEEE802.11a, which operates in the 5 GHz band and uses OFDM modulation. The transmission rate is 6-54Mbit/s or 11 Mbit/s. WLAN uses a conventional LAN, such as 10/100/1000 Mbit/s Ethernet) and its interconnected equipment routers, to form a backbone support network, using wireless access point AP) and W

PrefaceWith the development of information technology and the increasing demand of users, mobile communication technology has been known as the most development potential in the field of modern communication, and the most popular research hotspot in the market foreground. At present, mobile communication technology has undergone several generations of development.One, the first generation of mobile communication technology (1G)--Analog mobile communicationOriginated in the 1980s, mainly using an

Communication (Addison-Wesley Wireless Communications) by Andrew J. Viterbi11. National Research councel, The Evolution of Untethered Communications, National Emy Press, 1997.12. Bernard Sklar, Digital Communications: Fundamentals Applications (With CD-ROM), Prentice Hall, 2001.13. Andrea Goldsmith, Wireless Communications, Cambridge University Press, 2005.14. Digital Communication over Fading Channels, by Simon and Alouini (Wiley Series)15. Digital Signal Processing-a computer based approach,

one hand, we need multiple receiving antennas on the hardware and channel estimation and other communication algorithms. Speaking of the above two technologies is actually miso (multiple-input single-output) method, but also want to prove from another aspect, the antenna is too much does not mean they can work together. 100 years ago, people knew that the more the antenna the better the better, but the genius of the Alamouti code 1998 years before the multi-antenna technology 802.11n protocol

router is now priced to replace the average broadband router, therefore, we recommend the purchase of wireless router as the "core equipment" of this network, it is a broadband router, wireless AP, small switch, firewall in one of the Tetraena equipment, in the home has a very high availability. Based on the Web interface Setup Way at a glance, a little simple network knowledge can be easily set up applications. D-link DI 624 802.11g/2.4ghz Wireless 108Mbps Wireless router (Figure 5) The D-lin

converter, it determines that it must occupy a certain amount of space and consume a certain amount of power in the system. Therefore, in system solutions that require convenient portability, the static D/A converter has to be replaced with [1].So people choose the so-called "Digital basis" D/A converter. There are two methods for digital D/A conversion: PWM (P Ulse Width Modulation) Pulse Width Modulation

needs of multiple types of users in the system. (6) integration of multiple businesses. The 4G mobile communication system supports a wider range of mobile services, including high-definition image services, conference and television services, and virtual reality services, allowing users to access any required information services anywhere. It integrates personal communication, information systems, broadcast and entertainment industries into a whole to provide users with a wider range of servic

in WCDMA, it is not implemented. PDCP is dispensable. In LTE, PDCP becomes a required sub-layer. To understand the PDCP, you need to check the control plane and the user plane separately. The PDCP on the control plane performs encryption and Integrity protection. User-side PDCP supports encryption, packet header compression, and switching (that is, Sequential transmission and repetitive checks ). RLCThe RLC of LTE is similar to that of WCDMA: there are also three working modes: TM, UM, and AM.

rate. It also uses the built-in error correction function to make up for noise and other interference. VDSL is suitable for short-distance transmission. Currently, we recommend that you use four types of VDSL encoding: CAP and DMT.), DWMT, and SLC. DWMT (Discrete Wavelet Multitone) is a multi-carrier modulation system that uses a single-carrier Wavelet transform. SLC (Simple Line Code) is a baseband signaling version that filters the baseband and res

meet the requirements of data transmission in Multi-Point media, the transmitter signal is not too weak, and the signal transmission requirements are not met in signal attenuation; or Excessive signals lead to Circuit overload and generate harmonic and other false signals. Therefore, for systems with N sites, to meet the preceding requirements, consider N * (n-1)/Two arrays. (4) Two transmission technologies: baseband transmission (full-frequency transmission of two-way digital signal transmiss