# LoRa Resource Allocation Algorithm for Higher Data Rates
## 3 LRA Algorithm Framework
### Resource Allocation Algorithm
\[\varphi=1-\frac{ToA_{n}-t_{u}}{T_{tx}}\approx 1-\frac{ToA_{1}-t_{u}}{T_{tx}} \tag{12}\]

\[BR_{LRA}=(1-\varphi)\frac{PL}{T_{tx}} \tag{13}\]

### Energy Consumption Model

The energy consumption of the LRA algorithm can be modeled by the total energy consumed by DEDs. This total energy can be determined by calculating the energy needed for transmitting on each radio (specific SF and BW), the energy spent in standby mode to allow packet reception and processing at the receiver, and the energy required for receiving and processing packets. Equation (14) shows the total energy dissipated across all nodes. As shown in Equations (15) and (16), \(E_{tx}\) is the energy required for burst data transmission, where \(P_{tx}\) and \(P_{s}\) are the LoRa transmit and standby power, respectively. \(T_{u}\) is the sum of packet processing times during which the nodes are in standby mode. Equations (17) and (18) present the energy required for packet reception and processing, \(E_{rx}\). The power required for the LoRa transceiver (such as SX1276) to transmit and receive is the same for all BWs and SFs. Therefore, \(P_{tx}\) and \(P_{rx}\) can be replaced with \(P_{0}^{tx}\) and \(P_{0}^{rx}\). These values are set as follows: \(P_{0}^{tx}=287.1\) mW, \(P_{0}^{rx}=37.95\) mW, and \(P_{s}=5.28\) mW [24]. The total energy consumed can be represented as (19). \[E_{total}=E_{tx}+E_{rx} \tag{14}\]

\[E_{tx}=P_{tx}T_{0}A_{tx}+P_{s}T_{u} \tag{15}\]

Figure 5:0

Figure 5:1

Figure 5:2

Figure 5:3

## 4 Experimental Study and Results

At the time of the writing of this manuscript, no LoRa modules capable of parallel transmission were found. The experimental study is organized in two phases. In the first phase, the functionality of our DED and resource allocation algorithm is investigated by conducting three distinct experiments using some small bytes as pilot data. Once the optimal set of parameters is found, the second phase is performed by sending image data and reporting the \(T_{tx}\), BR, BER, consumed energy, and received image quality. ### Phase I

In these experiments we have investigated parallel transmission of the pilot data using:

1. Different radio channels with the same BW and SF;
2. Different BWs with the same radio channel and SF;
3. Different SFs with the same BW and radio channel. Since the third experiment with different SFs has already been thoroughly investigated in the literature (such as [26; 27]), we chose not to present the analysis results for it to avoid redundancy. While varying the experimental parameters as required during the experiment, the remaining LoRa parameters were kept constant. The radio spectrum is monitored via a Software Defined Radio (SDR) receiver. The received data quality, RSSI and SNR of the transmitted signal were monitored using another DED, identical to the one at the transmitter, configured for specific SF, BW, and radio channels. The experimental setup is shown in Figure 5:4

#### 4.1.1 Different Radio Channels

Inter-radio channel interference was monitored to determine the best radio channels for parallel data transmission. In this experiment, the receiver was configured with SF = 7, BW = 250 kHz, and the radio channel frequency of 915 MHz. The transmitter was configured with different radio channel frequencies ranging from 900 MHz to 940 MHz; BWs of 125 kHz, 250 kHz and 500 kHz; and SF values from 7 to 12. The radio channel was monitored using the spectrum analyzer, which showed more than one reflected channel other than the transmitted channel. This caused interference with the configured radio channel. Figure 8 shows a reflected radio channel at 916 MHz for the transmitted signal using a 915 MHz radio channel with BW = 250 kHz and SF = 7. Although the reflected channel signal level was lower compared to the actual channel, the receiver configured for the reflected channel received 5-10% of the packets with 20% data-bit loss. Therefore, it was determined that multiple LCs with different radio frequencies could not be used for parallel transmission.