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Basic Concept of CCIE Wireless 802.11n in-depth analysis

The new CCIE wireless version will be launched soon, and the new technology will be updated faster and faster. The wireless CCIE version of IELAB has already been prepared. Today we will learn about the basics of wireless 802.11n

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802.11n is a technology developed on the basis of 802.11g and 802.11a. The biggest feature is the speed increase. The theoretical speed can reach up to 600Mbps (currently the industry mainstream is 300Mbps). 802.11n can work in two frequency bands of 2.4GHz and 5GHz.

 IEEE 802.11ac, is an 802.11 wireless local area network (WLAN) communication standard, which communicates through the 5GHz band (also the reason for its name). Theoretically, it can provide up to 1Gbps bandwidth for multi-station wireless LAN communication, or a single connection transmission bandwidth of at least 500Mbps.

  802.11ac is the successor of 802.11n. It adopts and extends the concept of air interface derived from 802.11n, including: wider RF bandwidth (increased to 160MHz), more MIMO spatial streams (increased to 8), multi-user MIMO, and higher order modulation (modulaTIon) (up to 256QAM).

 802.11n mainly combines the optimization of the physical layer and MAC layer to fully improve the throughput of WLAN technology. The main physical layer technology involves MIMO, MIMO-OFDM, 40MHz, Short GI and other technologies, thereby increasing the physical layer throughput to 600Mbps. If only the rate of the physical layer is increased without the optimization of the MAC protocol layer such as air interface access, the physical layer optimization of 802.11n will be impossible. It is like even if a very wide road is built, but if the traffic flow management cannot keep up, there will still be congestion and inefficiency. Therefore, 802.11n adopts Block confirmation, frame aggregation and other technologies for MAC, which greatly improves the efficiency of the MAC layer.

 The so-called MIMO, literally seen, is the abbreviation of Multiple Input Multiple Output. Most of the statements you have seen refer to the wireless network signal being synchronously sent and received through multiple antennas, so the data transmission rate can be increased. However, the more correct explanation should be that after the network resources are cut through multiple times, they are transmitted through multiple antennas simultaneously. Because wireless signals are transmitted during the transmission process, in order to avoid interference, they will take different reflection or penetration paths, so The time to reach the receiving end will be inconsistent. In order to avoid data inconsistency that cannot be recombined, the receiver will have multiple antennas at the same time, and then use the DSP recalculation method to recombine the separate data according to the time difference, and then send out the correct and fast data stream.

OFDM (Orthogonal Frequency Division Multiplexing) is orthogonal frequency division multiplexing technology. It is a high-speed transmission technology in a wireless environment. The frequency response curve of the wireless channel is mostly non-flat, and the main idea of ​​the OFDM technology is to divide a given channel into many orthogonal sub-channels in the frequency domain, each sub-channel is modulated with a sub-carrier, and each sub-carrier is transmitted in parallel . In this way, although the total channel is non-flat and frequency selective, each sub-channel is relatively flat, and narrow-band transmission is performed on each sub-channel, and the signal bandwidth is smaller than the corresponding bandwidth of the channel, so the signal waveform can be greatly eliminated Interference. In the OFDM system, the carriers of each sub-channel are orthogonal to each other, so their spectrums overlap each other, which not only reduces the mutual interference between sub-carriers, but also improves the spectrum utilization rate.

802.11n RF rate:

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The configuration of the radio frequency rate is realized by MCS (Modulation and Coding Scheme, modulation and coding strategy) index value. MCS modulation coding table is a representation form proposed by 802.11n to characterize the communication rate of WLAN. MCS takes the factors that affect the communication rate as the column of the table and uses the MCS index as the row to form a rate table. Therefore, each MCS index actually corresponds to the physical transmission rate under a set of parameters.

Basic concept of wireless CCIE 802.11n in-depth analysis and exam dynamics

Typical networking application of 802.11n:

Network deployment is carried out through the cooperation of an AP with 802.11n function and an AC. The AC acts as a wireless data control and forwarding center and is placed in the central computer room. The AP is deployed in various indoor and outdoor places. The AP and AC can be in the same network segment or not in the same network segment. A tunnel is automatically established between them through the CAPWAP protocol. The AC performs centralized management of all APs connected to it. Adopt wireless access based on 802.11n technology to provide end users with higher rate broadband services than traditional 802.11a/b/g.

  802.11n can realize the deployment of multi-required mobile applications. At the same time, it is also a mature milestone. Many customers are willing to deploy wireless networks on a large scale and even replace Ethernet. This expansion has greatly increased the importance of wireless security and wireless security services to the business. VAR (value-added resellers) and system integrators can make good use of this market demand by providing more effective and larger-scale WLAN security solutions, including cloud-based services.

  The wireless CCIE written test and EI CCIE are merged into a 350-401 exam,with a score of 900+ stable pass. The current CCIE written can be tested online except for China and Japan. IELAB provides network engineers worldwide with preferential policies for all Cisco written dumps.

IE-LAB provides valid materials(accurate dumps) to help you pass your CCIE. For the written, we have valid workbooks that cover all real exam questions. You can easily pass the exam, usually 7 days’ preparation in enough. For the Lab exam, we will offer valid workbooks(real exam), rack which is the same as real exam, one to one support, professional tutor and timely update.

This article is exclusively published by James from IELAB.NETWORK and cannot be reproduced without permission.

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