The comparison of energy consumptions for OOK and BPSK modulationsin wireless sensor networks

Given that the majority of sensor nodes in wireless sensor networks (WSNs) are battery-powered and have limited energy resources, energy efficiency is a crucial consideration. By putting appropriate strategies into practice, the energy efficiency of WSNs might be significantly increased and thus provided a longer network lifespan, lower maintenance costs, and better performance. The energy efficiency of wireless sensor networks is significantly impacted by modulation. To achieve the optimal balance between energy economy and performance, the modulation method for a given WSN application relies on variables including energy consumption, transmission distance, interference, noise and bandwidth efficiency. BPSK (Binary Phase Shift Keying) and OOK (On-Off Keying) are two digital modulation methods used in WSNs. For low-power wireless communication systems like WSNs, OOK modulation is a straightforward and effective modulation technique. It is a desirable alternative for WSNs thanks to its interoperability, affordability, and simplicity. OOK is a digital modulation method that sends binary data by switching the carrier signal on and off. Either the entire strength (ON) of the carrier signal is carried, or it is not transmitted at all (OFF). A binary 0 in OOK modulation is represented by the carrier signal being off, whereas a binary 1 is represented by the carrier signal being on. OOK is easy to use and effective in utilizing bandwidth, although it is sensitive to noise and interference and has a short range of transmission. BPSK is another digital modulation method that transmits binary data using phase shift keying. A single bit is used in BPSK, a kind of Phase Shift Keying (PSK) modulation, to indicate two distinct carrier signal phases. A binary 0 in BPSK is represented by no phase shift, whereas a binary 1 is represented by a 180-degree phase shift of the carrier signal. Thanks to its simplicity and low energy consumption, it is preferred to be used in WSNs. In comparison to OOK, BPSK has a larger transmission range and is less vulnerable to noise and interference. It does, however, use more bandwidth than OOK. In WSNs, OOK and BPSK are both often used depending on the application and particular requirements. OOK, for instance, may be employed in situations where energy efficiency is important, such in low-power gadgets with short battery lives. The usage of BPSK, on the other hand, may be appropriate in situations when a greater transmission distance is required, such as in extensive industrial monitoring systems. In this thesis, the energy model of WSNs for BPSK and OOK modulation was reviewed, underlining how crucial they are for lowering power usage. The energy consumptions per bit (Ebit) of OOK and BPSK modulations were investigated for narrow bandwidth (< 50 kHz) and low data rate (< 50 kbps) WSNs with the propagation distance (d) no more than 150 meters in this study. For this purpose, the mathematical formulas and parameters which were previously published in the literature were utilized. The energy consumption per bit (Ebit) versus propagation distance (d) graphs were obtained for three distinct bandwidth (BW) values (10 kHz, 25 kHz and 50 kHz) in the OOK and BPSK modulation schemes. From the comparisons of results, it was observed that BPSK became more energy efficient than OOK with the increase of the propagation distance. Then the critical propagation distance (dcritical) at which BPSK started to become superior to OOK in terms of energy consumption per bit was defined and derived mathematically. The contribution of this thesis is to propose a new concept defined as the the critical propagation distance (dcritical) at which BPSK starts to become more energy efficient than OOK and present a mathematical expression to determine dcritical for any given bandwidth without any simulation requirement.