WiFi Concepts

WiFi Concepts DR ADNAN HAIDER  WiFi Generations Radio Maximum IEEE...

WiFi Concepts DR ADNAN HAIDER  WiFi Generations Radio Maximum IEEE Frequenc Generation Adopted Linkrate Standard y (Mbit/s) (GHz) 1376 to Wi-Fi 7 802.11be (2024) 2.4/5/6 46120 Wi-Fi 6E 2020 6 802.11ax 574 to 9608 Wi-Fi 6 2019 2.4/5 Wi-Fi 5 802.11ac 2014 433 to 6933 5 Wi-Fi 4 802.11n 2008 72 to 600 2.4/5 (Wi-Fi 3)* 802.11g 2003 6 to 54 2.4 (Wi-Fi 2)* 802.11a 1999 6 to 54 5 (Wi-Fi 1)* 802.11b 1999 1 to 11 2.4 (Wi-Fi 0)* 802.11 1997 1 to 2 2.4 *(Wi-Fi 0, 1, 2, 3, are unbranded common usage) What are the techniques used to cause all improvements in data rates? Signal to Noise Ratio (SNR), Coverage, and Data Rate Which has longer coverage and why? Why 5G is better than 2.4G  Co-Channel Interference (CCI), ocure when 2 or more AP’s that are in the same area are operating on the same channel. This essentially turns both cells (a cell is the coverage area for an AP) into one big cell.  This means that any STA that has anything to transmit now must wait for not only the other STAs associated to the same AP, but also all the STAs associated to the other AP on the same channel.  While not as damaging as ACI, CCI will also degrade performance. This is caused by more devices trying to gain access to the wireless medium on the same channel, making STAs wait longer for their chance to transmit. How Many APs can be Installed in One place  2.4G WiFi (3 APs with overlapping coverages of nonoverlapping channels)  WiFi ‫انقر فوق األيقونة إلضافة صورة‬ Non- Overlapping Channel Design Frequency Reuse Number of WiFi Clients  It depends on:  AP model  WiFi Generation (max Speed) 5 GHz Channel Allocations 5 GHz Considerations | DFS (802.11h)  Some of the 5 GHz band may be affected by radar activity, called DFS (Dynamic Frequency Selection)  Out of 25 available 5 GHz channels in the US and EU, only 9 single 20MHz wide channels (UNII-1 and UNII-3) are unaffected by it.  Dynamic Frequency Selection (DFS) is a channel allocation scheme, specified for wireless LAN, designed to prevent electromagnetic interference by avoiding co-channel operation with systems that predated Wi-Fi, such as military radar, satellite communication, and weather radar. 5 GHz Considerations | DFS (802.11h) In order to not interfere with licensed band users – the requirement is pretty straightforward:  The Wi-Fi equipment must be able to detect radar and satellite emissions  Before using a channel in this range – a “channel primary” (an Infrastructure AP) must first listen for 60 seconds and determine that the channel is clear of Radar  If a radar signal is detected, the Wi-Fi channel primary – and all the clients associated to it have to abandon the channel immediately and not return to it for 30 minutes at which time it can be cleared again for Wi-Fi use if no radar emissions are detected. Wireless Networks | Types and Scopes 802.11 Duplex  Channel is shared among all clients  802.11 networks are half duplex  802.11 implement CSMA/CA to allow clients to send/receive using wireless shared medium Basic Service Set (BSS)  BSS is the building block (a fundamental unit) of wireless network  BSS components  Access Point (AP)  Stations (STA)  BSSID  SSID  BSS Types  Infrastructure BSS (uses APs)  Independent BSS or Ad hoc mode BSSID and SSID  BSSID is a unique 48-bit MAC address that identifies a specific Wi-Fi network  SSID is a name used to identify a wireless network to the clients  It can be up to 32 characters long and is case-sensitive BSS | Traffic Flow Distribution System  The 802.11 standard refers to the upstream wired Ethernet as the distribution system (DS) for the wireless BSS. Extended Service Set (ESS)  WiFi Service coverage is extended using 802.11 Extended Service Set`  ESS is a network architecture that allows multiple wireless access points (APs) to work together to create a single, seamless wireless network.  ESS provide  Extended coverage  Roaming capabilities  Load balancing: ESS can distribute the load of connected devices across different APs. SSID vs BSSID vs ESSID  Each radio has 32 MAC addresses and supports up to 32 service set identifiers (SSIDs), with one MAC address assigned to each SSID as a basic service set identification (BSSID).  Similar ESSID provide Roaming  SSID can be from 0/2 to 32 octets. IBSS (Independent Basic Service Set)  IBSS or ad-hoc wireless network is composed of 2 or more wireless clients communicating directly.  In IBSS, one device must take the lead and advertise a network name and its necessary parameters Modes  AP  Client  Client Bridged  Repeater  Repeater Bridged (DD WRT routers)  Ad-hoc  WDS  WDS with AP AP mode  Also called Infrastructure mode  AP connects a group of wireless devices to an adjacent wired LAN.  Client Mode (Client Router)  The AP will be used as a radio interface.  A Client Mode router connects to a Wireless Access Point (WAP) wireless connection as the WAN interface, and shares the internet connection only to the LAN ports, or a separate WAP for multi-radio routers.  It is not seen as a WAP, nor accepts wireless connections by other client devices.  NAT or routing are performed between WAN and LAN, like in "normal" gateway or router mode.  Use this mode, e.g., if your internet connection is provided by a remote access point, and you want to connect a subnet of your own to it. Client Bridged  The radio interface is used to connect the LAN side of the router to a remote access point  The LAN and the remote AP will be in the same subnet  Called a "bridge" between two network segments  WAN side of the router is unused  Can be disabled.  Use this mode, e.g., to make the router act as a "WLAN adapter" for a device connected to one of its LAN Ethernet ports Repeater Mode  A repeater simply regenerates a network signal in order to extend the range of the existing network infrastructure  A WLAN repeater does not physically connect by wire to any part of the network  Instead, it receives radio signals ( frames) from an access point, end user device, or another repeater and retransmits the frames  Makes it possible for a repeater located in between an access point and distant user to act as a relay for frames traveling back and forth between the user and the access point  Wireless throughput is reduced by at least 50%  WDS (Wireless Distribution System)  WDS may provide two modes of access point-to-access point (AP-to-AP) connectivity  Wireless bridging, in which WDS APs (AP-to-AP on local routers AP) communicate only with each other and don't allow wireless stations (STA, also known as wireless clients) to access them  Wireless repeating, in which APs (WDS on local routers) communicate with each other and with wireless STAs Dynamically assigned and rotated encryption keys are usually not supported in a WDS connection Why WDS+AP (WDS repeater) mode does halve the WiFi WDS repeater  Also called WDS+AP  Repeater Bridge  DD-WRT's repeater bridge mode tries to provide the same basic capability as WDS without requiring any special support from the remote AP. Essentially, it pretends to be a wireless client of the existing AP for every device connected to it, whether wired or wireless. This convinces the existing AP that all those devices are connected directly to it, and it "just works".  Mesh Network  Provide wireless coverage over large area where running ethernet cables to each AP is impossible or impractical.  Mesh network can run static or dynamic routing protocols.  Mesh APs can leverage two dual radio. (one for clients and the other for AP-to-AP connection as a backhaul network) Access Point (AP)  AP connects a group of wireless devices to an adjacent wired LAN. 2.4 vs 5.0 GHz | Propagation Distance Packet Airtime | Speed & Size