## 5 Smart-BEEM For IoT Systems in 5G Scenarios
### Smart-BEEM Algorithm Design  
The two main objectives of Smart-BEEM are to (1) improve QoE and (2) reduce power consumption for IoT systems. Unfortunately, in most scenarios, those two objectives cannot be achieved simultaneously. In this paper, Smart-BEEM currently is designed to take QoE as the highest prioritised task. Meanwhile if possible, it will also try to reduce power consumption. For example, if a node aims to transmit temperature data back to the BS, it currently can communicate with one CH through Zigbee and another CH located further with Direct-WiFi. Since the bandwidth values for Zigbee and Direct-WiFi are both enough for temperature data, choosing Zigbee can significantly reduce energy consumption for communication. On the other hand, if the node aims to transmit video stream back to the BS and currently Direct-WiFi and Zigbee are both available, even though using Direct-WiFi will consume more energy, it will still be prioritised over Zigbee due to QoE concerns.  
Each node will rank the available communication interfaces by its own preference. The ranking algorithm is described as below. If transmitting simple data, all communication interfaces are allowed. If transmitting video stream, only interfaces with NAI\({}_{i}^{r}>x^{r}\) are allowed, where NAI\({}_{i}^{r}\) is transmission data rate for the \(i_{th}\) Network Access Interface (NAI) and \(x^{r}\) is the data rate requirement from the application running on Node \(x\). Then the preferred interfaces can be ranked by dividing the square of energy consumption.  
\[Ranking_{i}=\frac{NAI_{i}^{r}}{\left(NAI_{i}^{r}\right)^{2}} \tag{4}\]  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \begin{tabular}{c} **Communication** \\ **Means** \\ \end{tabular} & **Bandwidth** & **Data Rate** & \begin{tabular}{c} **Transmission** \\ **Range** \\ \end{tabular} & \begin{tabular}{c} **Energy** \\ **Consumption** \\ \end{tabular} \\ \hline WiFi (802.11a) & 2.4 GHz; 5 GHz & 54 Mbps & 30 m & Medium 15–20 dBm \\ \hline Bluetooth & 2.4–2.5 GHz & 1 Mbps & 10 m & Low Days \\ \hline Zigbee & 868–915 MHz; 2.4 GHz & 250 kbps & 10–100 m & Low Years \\ \hline LTE & 2.6 GHz & \
\begin{tabular}{c} Uplink: 5 Mbps \\ Downlink: 10 Mbps \\ \end{tabular} & \textless{}15 km & 23 dBm \\ \hline NB-LTE & 180 kHz &
\begin{tabular}{c} Uplink: 250 kbps \\ Downlink: 170 kbps \\ \end{tabular} & \textless{}15 km & 20–23 dBm \\ \hline \hline \end{tabular}
\end{table}
Table 4: Documented Characteristics for Different Communication Interfaces.  
\(NAI_{i}\)\({}^{e}\) is the energy consumption for \(NAI_{i}\) over one unit transmission distance. The ranking for interface NAI\({}_{i}\) is \(ranking_{i}\). Supposedly Node \(x\) can receive CH information from \(m\) CHs. Then it can construct a communication table as below in Table 5:  
The QoE for communication between Node \(x\) and connect CH\({}_{j}\) through network interface NAI\({}_{i}\) is defined as below:  
\[QoE_{i,j}=\begin{cases}0&\text{if $Node~{}x$ cannot communication with $CH_{j}$ by $NAI_{i}$}\\ \frac{ranking_{i}}{distance_{x,j}}&\text{otherwise}\end{cases} \tag{5}\]  
where \(distance_{x,j}\) is the distance between Node \(x\) and CH\({}_{j}\). By checking this table, node \(x\) will pick the pair of NAI and CH with the highest value of QoE\({}_{i,j}\).  
In order to perform this algorithm, we need to do a normalisation on the features of the communication interfaces. Taking Table 4 as an example, the data rate will be classified into Low (value = 1) or High (value = 2). The energy consumption will be rated as High (value = 3), Medium (value = 2) or Low (value = 1). Any available network accessing interface in 5G communication can be added into this normalisation table.