# Use of Wireless Sensor Networks for Area-Based Speed Control and Traffic Monitoring
## 3 LoRa/LoRaWAN Standard
### LoRa Radio Interface  
The strength and popularity of LoRa technology stem, among other factors, from the fact that its transmission is based on the following unlicensed ISM (Industrial, Scientific, Medical) megahertz bands:  
* 169 MHz (Asia);
* 433 MHz (Asia);
* 868 MHz (Europe);
* 915 MHz (North America). The transmission distances between communicating devices can reach several kilometers, depending, of course, on the terrain, land type, and the type and location of the antennas. However, achieving such coverage comes at a cost, specifically the small data transmission volume, which varies depending on modern configuration, ranging from kilometres to single bytes per second. Despite this limitation, achieving such long distances with minimal power consumption would be impossible without the application of appropriate radio signal modulation. LoRa uses CSS (Chirp Spread Spectrum) modulation for this purpose, which involves modulating the data stream with a linearly increasing frequency signal [44; 53; 54]. The implementation of the CSS signal modulation process depends on three main parameters:  
* BW (modulation bandwidth) describes the extent of modulation frequency variation;
* SF (spread factor) determines the rate of modulation frequency variation;
* CR (code rate) introduces redundancy while correcting errors that arise during transmission. These parameters impact the maximum coverage and throughput of a LoRa link and are described by Relationship (1):  
\[R_{b}[b/s]=SF*\frac{CR*BW[Hz]}{2^{SF}} \tag{1}\]  
where the individual parameters can take the following values [44; 54]:  
* BW [7.8 kHz, 10.4 kHz, 15.6 kHz, 20.8 kHz, 31.25 kHz, 41.7 kHz, 62.5 kHz, 125 kHz, 250 kHz, 500 kHz];
* SF [6, 7, 8, 9, 10, 11, 12];
* CR [4/5, 4/6, 4/7, 4/8]. In LoRa technology, the possible combinations of SF (spreading factor), CR (coding rate), and BW (bandwidth) depend on the specifications and hardware capabilities of specific devices, as well as the regulatory requirements for the use of frequency bands in a given region. Examples of combinations of SF, CR, and BW values and their impact on coverage and airtime are shown in the table [55]. When performing calculations based on Relationship (1), the term \"small data volume\" can be quantified, with a determined minimum and maximum data transfer ranging from just 11.5 b/s to 37.5 kb/s. This includes not only user data but also control and monitoring data. In the LoRaWAN standard, key technical parameters (SF, CR, and BW) significantly affect communication performance, including range, throughput, reliability, and energy consumption. A higher SF results in lower data transmission speeds, as the longer transmission time means that fewer data can be sent in a given period. In comparison, lower SF values (e.g., SF7) offer higher throughput but reduce range and resilience to interference. In practice, selecting an SF value is a trade-off between range and transmission speed. The error correction rate (CR) can range from 4/5 to 4/8, with higher CR values adding more control bits, increasing error resistance but reducing effective data transmission speed. A higher CR improves connection reliability in challenging transmission environments, such as those with significant signal interference, but it also increases transmission time and energy consumption. Thus, choosing a CR involves balancing reliability needs with bandwidth and battery life requirements. A smaller bandwidth (BW) (e.g., 125 kHz) makes the signal more concentrated, enhancing resistance to noise and allowing longer transmission distances, though at the cost of reduced throughput. Conversely, a larger bandwidth (e.g., 500 kHz) increases throughput, enabling faster data transmission, but shortens the range and makes the signal more susceptible to interference. In practice, bandwidth selection depends on whether the priority is greater range or faster data transmission. All of these parameters--SF, CR, and BW--are interrelated and collectively impact communication performance in a LoRaWAN network.