# Industrial Internet of Things for a Wirelessly Controlled Water Distribution Network
## 4 Wireless Technologies
### Wi-Fi  
Wi-Fi is a wireless communication technology that allows devices to connect to a local area network. It is based on the (IEEE 802.11) [5], which specify how wireless communication is implemented in various frequency bands such as 2.4 GHz, 5 GHz, and recently 6 GHz for Wi-Fi 6. The (IEEE 802.11) has many variations, but the more recent ones are 802.11n (Wi-Fi 4), 802.11 ac (Wi-Fi 5), and 802.11 ax (Wi-Fi 6). The (IEEE 802.11) operates in the two lowest layers of the OSI (Open Systems Interconnection) model: The physical (PHY) layer is responsible for transmitting and receiving signals, as well as modulation and coding. The media access control (MAC) sublayer in the data link layer coordinates wireless medium access, security, and the structure of data packets [19; 20].  
1. Network Structure: In (IEEE 802.11) [5], a group of devices communicating together are known as the basic service set (BSS). There are three main types of network deployment within these standards. For the infrastructure BSS, or just BSS, in this deployment, the devices are connected in the form of a star topology that connects all devices in the network to a BS known also as an access point AP. Additionally, there are also the ad-hoc BSS, which allows a peer-to-peer communication, and the Extended Service Set (ESS) to connect BSSs together through a backbone network [21].
2. PHY and MAC Layer: For medium access, (IEEE 802.11) include two MAC mechanisms, also known as coordinating functions: The mandatory distributed coordination function (DCF), a contention-based MAC mechanism, is widely used and implemented in most commercial wireless modules. The optional point coordinationfunction (PCF), polling-based and limited only to infrastructure-based networks (BSS), is used in applications that require low-latency and real-time communication [22].  
Furthermore, the newer versions of the (IEEE 802.11) protocol are designed to work well with older versions in the same network. This is possible because the MAC sublayer basic functionalities remain interoperable across versions. Distinctions between versions are primarily introduced at the PHY layer, including modulation techniques, channel utilization, and transmission capabilities [20; 23].  
IEEE 802.11n, also known as (Wi-Fi 4), has a throughput reaching up to 600 Mbps. 802.11n uses an Orthogonal frequency division multiplexing (OFDM) modulation scheme for transmitting the data. It also introduced the multiple inputs multiple outputs (MIMO) technology by increasing the number of antennas at the sender and the receiver, resolving the multipath issue, and reducing bit error [23].  
IEEE 802.11 ac (Wi-Fi 5) builds upon the foundation of (Wi-Fi 4) improve the use of OFDM and MIMO and introduces the Multi-User MIMO, which allows an AP to communicate with multiple stations simultaneously rather than sequentially. These improvements enable 802.11 ac to achieve data rates exceeding 1 Gbps [23].  
IEEE 802.11 ax (Wi-Fi 6) introduces Orthogonal Frequency Division Multiple Access (OFDMA), a key enhancement over the OFDM used in earlier standards. While OFDM efficiently transmits data from a single user across multiple subcarriers, OFDMA subdivides these subcarriers into smaller sub-channels. This allows the simultaneous allocation of bandwidth to multiple users, improving network efficiency, and achieving higher throughput [20; 24].  
Security: Currently, the most used encryption protocols in Wi-Fi are Wi-Fi Protected Access 2 (WPA2) and Wi-Fi Protected Access 3 (WPA3). WPA2 utilizes AES encryption with Counter Mode Cipher Block Chaining Message Authentication Code Protocol (CCMP) for device authentication, and it uses Pre-Shared Keys (PSK) for the personal network. On the other hand, WPA3 improves upon WPA2 by implementing the Simultaneous Authentication of Equals (SAE) instead of the PSK [25].