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MIMO - 802.11ac

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Reference https://www.youtube.com/watch?v=0fpyfPUyfic Multipath:  A signal from the transmitter may travel through different paths due to reflections from obstacles along the path. These signals arrive at different times and different angles  at the receiver and  interfere with signal from direct line of sight. This causes distortion of signal at the receiver. Prior to 802.11n this multi-path had a adverse effect. But from 802.11n , the multi path effect has been used constructively,  1.  Using spatial multiplexing, different data streams are transmitted from different antennas  2.  Transmit diversity, where the same data is sent through different transmitter radio chain and processed at the receiver 3. Multiple  identical data streams  received at the the receiver by different radio chains can be processed using MRC algorithms Multi path is a requirement for sending multiple streams. If multipath effect is not there , multiple spatial streams cannot be sent. For example in the outdoor
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WPA3

  1) Basic security enhancements in WPA3 vs. WPA2 WPA2 flaws - susceptible to brute force and offline dictionary attacks where passwords can be recovered offline dictionary attack : 4 way hand shake can be captured and passwords can be recovered. The attacker can capture the 4 way handshake. Make a guess of password from a dictionary list Run  the password through know function/algorithm(PBKDF2) that is defined in the standard to get the PMK/PSK .  From the captured message compute the PTK using          Anonce, Snonce, Cl Mac addr and AP Mac Address are known from the 4 way              handshake          Computed PMK from guessed passphrase          Compute MIC If the MIC matches with that in the captured message, PTK keys is correct ad password is cracked. In WPA3, even if password can be guessed, the PMK cannot be hacked because of the way the key is derived.( dragon fly protocol)   2) S ecurity enhancements of encryption and integrity in WPA3 OWE :
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Authentication and Security in Wireless LANs

References https://www.youtube.com/watch?v=hLQ5rYNUwNg https://www.youtube.com/watch?v=ntGA6V5EciE&t=396s Data frames in wireless medium should be protected in order to ensure that data has not been tampered with while transmission in air.  Any wireless device or radio capable of receiving and decoding 802.11 frames can have access to the  data. So data has to be protected by proper encryption methods. WEP ( Wired Equivalent Privacy) and WPA ( Wifi Protected Access ) are security protocols used to secure wireless networks by properly encrypting the data before transmission. WEP uses the same static key configured on on devices to encrypt the data. WPA generates different encryption keys for different devices using  4 way handshake. WPA uses TKIP to encrypt data while WPA2 uses AES-CCMP to encrypt data Data Confidentiality is maintained by encrypting frame body of the data. A Message Integrity check is added as part of data. Receives validate the received data against this MIC to en
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Protection Mechanism in 802.11n

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References: https://www.cwnp.com/802-11n-protection-mechanisms-part-2/ https://mrncciew.com/2014/11/04/cwap-ht-operations-ie/ 802.11n survival guide - Mathew Gast When ever a new wireless standard is introduced, the new devices' transmissions cannot be decoded by the older devices. When 802.11g came into existence, the OFDM transmissions by 802.11g devices cannot be decoded by the older 802.11b /802.11devices.  Hence in order to protect the newer 802.11g devices from older 802.11b devices,  protection mechanisms were introduced in 802.11g 's standard. In a ERP BSS where 802.11/802.11b coexist, protection mechanism has to be enabled.  This is indicated by setting the bits ' Use Protection ' and 'non Erp Present ' bits in the ERP information element of the beacon. ERP stations know that they need to use the protection frames prior to sending OFDM frames based on this. In the case of 802.11n, HT transmissions needs to be protected if there  are older stations ( b/a
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Protection Mechansims in 802.11g

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Need for Protection  In a WLan BSS with both 802.11b and 802.11g devices,  the AP ( 802.11g)  has to serve both 802.11g and 802.11b clients. Due the difference in chipset implementations of 802.11b and 802.11g devices, a 802.11b device cannot decode  high rate  transmissions from a 802.11g device.  Unaware of a 802.11g device's transmission, if a 802.11b client transmits at the same time, it will cause interference to 802.11g's transmission.  So 802.11g specifies certain protection mechanisms to ensure that 802.11g's transmissions are not interrupted by the legacy devices. These protection mechanisms  are there to make sure that the legacy devices are  aware when a 802.11g device is transmitting so that , legacy devices can defer their transmission. Types of Protection Mechanisms in 802.11g 802.11g specifies two types of protection mechanism.  1) cts-to-self protection mechanism: In this , when ever a 802.11g station has a ofdm data frame to send, it sends a CTS-TO-SELF fra
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