## 2 Related Work  
The constant evolution of the IEEE 802.11 standard has transformed the way we access the Internet since its inception, enabling mobility and eliminating reliance on traditional wired connections. The exponential progression of the latest Wi-Fi standards reflects improvements in terms of performance, capacity, and efficiency, addressing the technological challenges that arise with the increasing number of ultra-low-latency industrial services with stringent communication requirements. Due to recent improvements, Wi-Fi networks have emerged as a promising candidate to digitise and automate the industrial sector [5,17]. Therefore, a detailed review of Wi-Fi standards is presented, with a focus on key advancements in IEEE 802.11n (Wi-Fi 4), IEEE 802.11 ac (Wi-Fi 5), IEEE 802.11 ax (Wi-Fi 6/6E) [4,13,18], and the future standard yet to be finalised, IEEE 802.11 be (Wi-Fi 7) [5,19]. In order to contextualise these developments, it is essential to understand the physical-layer fundamentals that enable such performance improvements, especially the role of channel bandwidth and its relationship with spectrum allocation. All modern Wi-Fi standards are fundamentally shaped by how they utilise and aggregate frequency resources across the 2.4 GHz, 5 GHz, and 6 GHz unlicensed bands. Through the concept of channel bonding, IEEE 802.11 systems have moved from narrow 20 MHz channels to broader bandwidths of up to 320 MHz, allowing for increases in peak throughput. This expansion is not arbitrary but rather follows precise spectral structures regulated and engineered to ensure coexistence, efficiency, and backward compatibility. In IEEE 802.11 wireless communication systems, the channel bandwidth is one of the most critical physical-layer parameters that define system throughput and spectral efficiency. With the evolution of user demand and latency-sensitive applications, modern Wi-Fi systems have adopted wider spectral allocations through channel bonding techniques, leading to significant gains in peak data rates [12,20]. Wi-Fi primarily operates in three unlicensed frequency bands: 2.4 GHz, 5 GHz, and 6 GHz. Within these bands, the fundamental spectral unit is the 20 MHz channel, shaped by regulatory guidelines and radio hardware constraints. A 20 MHz channel was originally divided into 64 OFDM subcarriers, spaced at 312.5 kHz [3]. To improve capacity, adjacent 20 MHz channels can be aggregated, forming wider bandwidths according to Equation (1), where \(B\) represents the total channel bandwidth in MHz, and \(N\) is the number of 20 MHz channels being bonded [21]. \[B=20\cdot N\quad\text{(MHz)},\quad N\in\{1,2,4,8,16\} \tag{1}\]  
This hierarchical aggregation of adjacent 20 MHz channels results in wider operational bandwidths: 40 MHz (2 \(\times\) 20 MHz), 80 MHz (4 \(\times\) 20 MHz), 160 MHz (8 \(\times\) 20 MHz, either as a contiguous block or split as 80 + 80 MHz), and up to 320 MHz (16 \(\times\) 20 MHz), the latter introduced with Wi-Fi 7 in the 6 GHz band. This channel bonding approach enables significant increases in data transmission capacity; however, it also requires larger contiguous portions of the spectrum and careful coordination with legacy systems to avoid interference and ensure interoperability [12]. Figure 1 provides a visual reference for how adjacent 20 MHz channels are combined into broader bandwidths to meet increasing data rate demands, illustrating the core principle of channel bonding in modern Wi-Fi systems. The figure covers the 2.4 GHz, 5 GHz and 6 GHz bands, showing the structured allocation of 20, 40, 80, 160, and 320 MHz channels. In the 2.4 GHz band, only three non-overlapping 20 MHz channels are available, which limits the aggregation potential. The 5 GHz band comprises several segments of unlicensed spectrum defined by regulatory entities, ETSI in Europe, and FCC in the United States, with each region imposing specific constraints on transmission power and indoor/and outdoor use.