# IEEE 802.11 ah: A Technology to Face the IoT Challenge
## 3 Comparative Analysis of IEEE 802.11 ah with Previous IEEE 802.11 Amendments
### Comparison of IEEE 802.11 Amendments Based on MAC Features
#### 3.2.Throughput and Range Characterization of IEEE 802.11 Amendments  
In order to compare different IEEE 802.11 amendments, we evaluate layer-2 throughput versus coverage range by using different channel bandwidth values, number of Spatial Streams (SS) and MCS. We analyze a scenario defined by a single radio link composed of two stations (transmitter and receiver) where we consider path loss models defined by TGah [11]. The macro deployment model assumes an outdoor scenario with antenna placed at 15 m above rooftop. On the other side, we employ the large indoor open space TGah path loss model with Non-Line-of-Sight (NLoS) conditions, which corresponds to a factory/warehouse type of environment. The macro deployment path loss model follows the next expression:  
\[PL=8+37.6\text{log}10\left(d\right) \tag{1}\]  
where \(d\) corresponds to the distance in meters between transmitter and receiver, and radio frequency carrier is 900 MHz. For other frequencies, a correction factor of \(21\times\text{log}10\left(\frac{f}{900 MHz}\right)\) should be applied. TGah indoor path loss model is modelled by directly scaling down the frequency operations of TGn path loss model. It consists of the free space loss model (slope of 2) up to a breakpoint distance (\(d_{BP}\)), and employs a slope of 3.5 after the breakpoint. We consider the large indoor open space scenario with NLoS conditions (with \(d_{BP}\) of 5 m). This indoor channel model would correspond to a factory/warehouse type of environment:  
\[L\left(d\right)=\left\{ \begin{array}{l}L_{FS}\left(d\right)=20\text{ log}10\left(\frac{4\pi fc}{c}\right)\ d\leq d_{BP}\\ L_{FS}\left(d_{BP}\right)+35\text{log}10\left(\frac{d}{d_{BP}}\right)\ d>d_{BP} \end{array} \right. \tag{2}\]  
where \(d\) corresponds to the distance in meters between transmitter and receiver, \(fc\) is the center carrier frequency in MHz and \(c\) the speed of the light in m/s. Note that the TGah indoor channel propagation loss model was recently amended according to [12] as shown in Equation (2). We consider omnidirectional antennas with 0 dB gain and transmitted power of 30 dBm. The MAC aggregation feature is included in our evaluation, and ideal transmission conditions have been considered for comparison purposes. The throughput expression S in Mbps is as follows, employing DCF MAC access and including the aggregation feature:  
\[S=\frac{L_{data}\times 8\times K}{T_{message}} \tag{3}\]  
where \(K\) is the number of aggregated frames (of equal size), \(L_{data}\) corresponds to the payload size and \(T_{message}\) is computed as:  
\[T_{message}=DIFS+T_{DATA}+SIFS+T_{BA}+T_{BACKOFF}+2\delta \tag{4}\]  
_DIFS_ and _SIFS_ are given in Table 3, \(\delta\) is the propagation delay, \(T_{BA}\) corresponds to the duration of an Block ACK frame and \(T_{DATA}\) represents the transmission time of a data frame, which depends mainly on the size of the payload and on the PHY rate. \(T_{DATA}\) and \(T_{BA}\) computation also depends on the IEEE 802.11 amendment used in the transmission. Under ideal channel conditions, we consider that \(T_{BACKOFF}\) is \(CW_{min}/2\) times the slot time (\(T_{\text{Slot}}\)); \(CW_{min}\) corresponds to the minimum \(CW\) (cf. Table 3). All frame sizes are given in Bytes and frame durations in \(\upmu\)s.