# A Survey on LoRaWAN Architecture, Protocol and Technologies
## 2 LoRa & LoRaWAN Technologies
### Physical Layer-LoRa
Higher the SF values (such as \(SF=12\)), higer the frame air time. To evaluate LoRa frame transmission performance we have implemented a testbed environment in our previous work [9]. The testbed includes Semtech SX1272/76 chipsets, a GW and a network server. Mathematical Equation (2) and testbed results are evaluated in terms of frame transmission times in Figure 8. Dashed lines represent the mathematical model where solid lines are real testbed results. Obtained data proves that both testbed and mathematical models are almost identical. We can conclude that this model could be used to simulate LoRa modulation and other LoRa based systems  
Figure 5: LoRa frame air time comparison for CR = 4/5 BW = 125 kHz. Figure 6: LoRa frame air time comparison for CR = 4/5 BW = 250 kHz. Figure 7: LoRa frame air time comparison for CR = 4/5 BW = 500 kHz. Related Work  
Operating at ISM band frequencies, LoRa modulation attracts attention from the academic and industrial community. This led researchers to study different aspects of the LoRa modulations; such as communication range (coverage), interference, link quality, and other performance metrics. Researchers performed LoRa coverage tests in different regions to analyze the boundaries of the modulation. [PERSON] et al. [10] make a LoRa analysis for 433 and 868 MHz using a testbed at Dortmund/Germany to test different frequencies and performance with field tests. [PERSON] et al. [11] test LoRa coverage for Oulu/Finland to range limits of the modulation and aims to find an attenuation model. Results given by the study show that 80% of the frames are received successfully up to 5 km and 60% of the frames are delivered correctly up to 5-10 km. The most of frames sent over 10 km were lost. The above water surface communication range could be up to 30 km. [PERSON] et al. [12] aim to measure the impact of structures for LoRa communication range, the study obtains 5.6 km and 2 km ranges in suburban and urban areas. LoRa and FSK are compared analyzed for IoT applications for smart cities by [13]. The author presents that LoRa performs much better when compared to FSK in most scenarios and highlights of successful transmission ranges up to 10 km in suburban scenarios. Also, other researchers illustrate that LoRa can provide long ranges with different environments [14; 15; 16; 17]. Comparative coverage analysis is also studied and cross-technology comparisons are performed. [PERSON] et al. [18] simulate LoRa link budget using existing 2G, 3G coverage data and compare results with Sigfox, NB-IoT. Also, in the study, a model is presented to estimate uplink probabilities. It is highlighted that LoRa has lower blocking probabilities than Sigfox, however, Sigfox has better uplink performance. Similar cross-technology coverage studies are performed by [PERSON] et al. [19], in Denmark for Sigfox, LoRa, GPRS, and NB-IoT. In the study, all compared LPWAN technologies have less than 1% outage for outdoor deployments. As show from studies from 2 km to 30 km point to point LoRa communication is possible and this results in approximately 12.5 km\({}^{2}\) to 2827.4 km\({}^{2}\) area of coverage. [PERSON] et al. [20] develop an error detection technique for LoRa based sensor nodes and model is implemented on MSP430 processors. A physical layer study for implementing a power amplifier for LoRa [21] and LoRa compatible CMOS design is presented by the authors [22]. Figure 8: LoRa frame air time comparison with testbed and the model. Finding an optimum configuration for the LoRa to increase performance is a challenging task, with the studies carried by [PERSON] and [PERSON] [23] aim to find optimum tx power for nodes to optimize node energy consumption. [PERSON] and [PERSON] [24] performed a LoRa uplink analysis, channel assignment and power allocation issues with a model. Also, similar link analyses addressed by different researchers [25] and evaluated with simulations.