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--- networking:wireless_topic:wi-fi_6:wi-fi_6 [2023/11/06 18:18] – aperez
+++ networking:wireless_topic:wi-fi_6:wi-fi_6 [2024/04/16 19:24] (current) – aperez
@@ Line 14: / Line 14: @@
   * **Minimum SNR and RSSI** Determines the minimum SNR and RSSI required for a specific MSC index.
   * **OFDMA is essentially a type of OFDM for multiple users**. It allocates in both the time domain and the frequency domain, allowing for multiple users—even those with widely varying use patterns or data loads. By comparison, OFDM can allocate only sequentially.
+----
+**What are the key differences between OFDM and OFDMA for multiple access?**
+If you are interested in wireless communication technologies, you may have heard of OFDM and OFDMA. These are two methods of dividing a radio channel into multiple subcarriers, each carrying a part of the data. But what are the key differences between them, and why do they matter for multiple access? In this article, you will learn the basics of OFDM and OFDMA, and how they enable efficient and flexible transmission of data over wireless networks.
+**What is OFDM?**
+OFDM stands for orthogonal frequency division multiplexing. It is a technique that splits a high-bandwidth channel into many narrow-band subcarriers, each with a different frequency. The subcarriers are orthogonal, meaning they do not interfere with each other. This allows OFDM to use the channel more efficiently and avoid inter-symbol interference, which is a common problem in wireless communication. OFDM also supports modulation schemes such as QAM and PSK, which can increase the data rate and robustness of the transmission.
+**What is OFDMA?**
+OFDMA stands for orthogonal frequency division multiple access. It is an extension of OFDM that allows multiple users to share the same channel by assigning different subcarriers to different users. For example, user A may use subcarriers 1, 2, and 3, while user B may use subcarriers 4, 5, and 6. This way, OFDMA can support multiple access without causing collisions or wasting bandwidth. OFDMA also enables dynamic allocation of subcarriers based on the channel conditions and user demands, which can improve the performance and fairness of the network.
+**How do OFDM and OFDMA differ?**
+The main difference between OFDM and OFDMA is that OFDM is a single-user technique, while OFDMA is a multi-user technique. This means that OFDM can only transmit data from one transmitter to one receiver at a time, while OFDMA can transmit data from multiple transmitters to multiple receivers simultaneously. Another difference is that OFDM uses a fixed set of subcarriers for each transmission, while OFDMA can vary the number and size of subcarriers for each user. This gives OFDMA more flexibility and adaptability to the channel variations and user requirements.
+**What are the advantages of OFDM and OFDMA?**
+OFDM and OFDMA have several advantages over other wireless communication techniques, such as the ability to achieve high data rates and spectral efficiency by using multiple subcarriers and modulation schemes, reduce inter-symbol interference and fading by using short symbols and guard intervals, simplify the receiver design by using FFT and IFFT operations to convert between the time and frequency domains, and support multiple antennas and spatial diversity by using MIMO and beamforming techniques. OFDMA specifically can support multiple access and increase the network capacity by allowing multiple users to share the same channel, improve the quality of service and user satisfaction by allocating subcarriers according to user needs and channel conditions, as well as reduce power consumption and interference by using subcarrier grouping and power control techniques.
+**What are the challenges of OFDM and OFDMA?**
+Despite their advantages, OFDM and OFDMA also face some challenges and limitations in wireless communication. These include sensitivity to frequency offset and phase noise, which can degrade the signal quality, as well as the need for accurate synchronization and channel estimation, which can increase the complexity and overhead of the transmission. Furthermore, they are vulnerable to peak-to-average power ratio (PAPR) problems, reducing power efficiency and causing distortion in the amplifier. Specific challenges of OFDMA include the need for coordination and feedback between the transmitter and receiver, which can increase signaling and latency, as well as potential inter-user interference and unfairness that can affect network performance and stability.
+**What are the applications of OFDM and OFDMA?**
+OFDM and OFDMA are widely used in various wireless communication standards and applications, such as Wi-Fi (IEEE 802.11a/g/n/ac/ax), WiMAX (IEEE 802.16e/d), LTE (3GPP Long Term Evolution), and 5G (the fifth generation of mobile networks). These technologies provide high-speed wireless LAN services, broadband wireless access services, mobile cellular services, and enhanced mobile broadband, massive machine-type communication, and ultra-reliable low-latency communication respectively.
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 {{ :networking:wireless_topic:wi-fi_6:wifi_gen.jpg?600 |}}
+{{ :networking:wireless_topic:wi-fi_6:wifi_matrix_1.png?600 |}}
+{{ :networking:wireless_topic:wi-fi_6:wifi_matrix_4.png?600 |}}
+{{ :networking:wireless_topic:wi-fi_6:wi-fi_matrix_4.jpg?600 |}}
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 {{pdfjs 46em >:networking:wireless_topic:wi-fi_6:wi-fi-7-reference-card.pdf}}
+{{ :networking:wireless_topic:wi-fi_6:ed_laird_wi-fi_6e_ebook.pdf |}}
+{{pdfjs 46em >:networking:wireless_topic:wi-fi_6:ed_laird_wi-fi_6e_ebook.pdf}}
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   -   Distance between two APs should be approximately **30 to 70 feet (9.144 to 21.336 m) for Wi-Fi 5**.
   -   However, devices with **WiFi 6 (802.11ax)** have a greater range thanks to making modulation modifications. Reaching, for example, **up to 70 meters indoors and 250 meters outdoors in 2.4 GHz**.
+^ Fuerza   ^ Resumen    ^ Calidad esperada         ^ Requerido para         ^
+| -30 dBm   | Increíble    | Intensidad de señal mínima para aplicaciones que requieren una entrega muy fiable y oportuna de paquetes de datos.       |N/A       |
+| -67 dBm   | Grandioso    | La máxima intensidad de señal que se puede conseguir en condiciones controladas.       |Voz sobre IP y streaming de vídeo en tiempo real       |
+| -70 dBm   | Normal       | Minimum signal strength for reliable packet delivery and tasks such as email.       |Email and light web browsing       |
+| -80 dBm   | Pobre        | Intensidad mínima de la señal para la conectividad básica, como la conexión a la red.       |Conexión a la red      |
+| -90 dBm   | Inutilizable | Intensidad de señal extremadamente baja que hace que cualquier funcionalidad, incluida la conexión a la red, sea muy improbable.       |N/A       |
+{{ :networking:wireless_topic:intsig3.png?400 |}}
+----
+**PoE**
+{{ :networking:wireless_topic:wi-fi_6:poe.jpeg?600 |}}
+{{ :networking:wireless_topic:wi-fi_6:poe_class_level.jpg?600 |}}
+{{ :networking:wireless_topic:wi-fi_6:ap_matrix.jpg?1000 |}}
+{{ :networking:wireless_topic:wi-fi_6:ap_switch_matrix.jpg?1000 |}}
+----
+**WLAN Test**
+{{ :networking:wireless_topic:wi-fi_6:wlan_test.pdf |}}
+{{pdfjs 46em >:networking:wireless_topic:wi-fi_6:wlan_test.pdf}}
+----
+**What steps do you follow when troubleshooting a network issue?**
+  - Clearly understand the user experience regarding support
+  - Separate the support metric between the Internet service and the WLAN connectivity by the user.
+  - Verification of the user's Wi-Fi card.
+  - Verification of the channel and connection frequency by the user and/or the WLAN system per AP, which is complying with the rules of non-overlapping and non-activation of the DFS UNII 2 ext channels.
+  - Comparative performance calculation, compared to the characterization of the AP to which the user is connected.
+  - Analysis of materials that focus on absorption and dispersion of photons between wavelengths of 5 cm, 6 cm and 12.5 cm.
+  - Roaming analysis, power, sensors and channels.
+  - Verification of 802.1x/AAA service functionality; certificates, auto-vlan-qos, dictionaries, others.
+  - DNS, DHCP scope service, static ip, local firewall, local EDR, perimeter firewall rules, perimeter DPI, perimeter ACL/WCF, return routes on the side of the UTM or the operator's router, opening of the minimum management ports of the CMS - C/PANEL (2083, 443, other udp) for the management of APs.
+  - Verification of the configuration of the Ethernet ports of the AP or devices that intervene in the verification process, which comply with the minimum traffic rules (802.1Q/802.1D, 802.1P, QoS, DSCP, LLDP, ACL, Broadcast storm control, others)
+----