## 1 Introduction  
Wireless broadband has become an integral part of work, as well as daily life, because of the challenge of dealing with large amounts of Internet data. Although broadband access is very common on the land, maritime networks still need attention in this area. Due to their heterogeneous, low bandwidth and dynamic connectivity, maritime networks are difficult to manage [1]. Nowadays, communication systems based on narrow ultra-high frequency band (UHF, 300 MHz-3 GHz) and very high frequency band (VHF, 30-300 MHz) are used for close water ports' ship-to-shore communication. On the other hand, satellite communication is used for long range ship-to-shore and ship-to-ship communication [2]. Satellite links are very expensive for voice calls and Internet access, to and from the ship, when compared to land communication. Improvements in existing techniques, as well as new research, are required in order to reduce the cost of communication and provide high speed data rates at sea. Using a dedicated spectrum in maritime networks is difficult, due to congested bandwidth allocation [3]. The network devices on the shore may need to coexist with other radio devices installed on the land. Moreover, it is also necessary to synchronize the frequency bands around the world, as ships may travel between different countries and continents. [PERSON] _et al_. showed that spectrum issues in maritime networks can be alleviated by incorporating cognitive radio (CR) technology [3]. In this regard, they have also found that much of the spectrum is underutilized at sea. CR is a key technology that can help to mitigate the scarcity of the spectrum by using licensed spectrum bands opportunistically for unlicensed users. CR's advantages associated with the opportunistic access of unused the licensed band are the alleviation of spectrum scarcity, the large bandwidth, long-range communication using TV band and reduced cost for communication. The most essential task for CR is the detection of the licensed/primary user (PU), which is achieved by sensing the radio environment. This process is called spectrum sensing. If the PU is absent, its spectrum is available for a cognitive radio/secondary user (SU) and is called the spectrum hole/white space. The spectrum sensing requirements for maritime cognitive radio networks (MCRN) have to face unique challenges in the sea environment because of the following reasons: (1) radio wave propagation over water; (2) surface reflection; and (3) wave occlusions. Therefore, to achieve a higher detection probability, CR may need a longer sensing time or some advances in the existing spectrum sensing schemes. In cooperative spectrum sensing, the local decision of multiple SUs is fused to get the final decision. Cooperative spectrum sensing seems to be an effective method to improve detection performance and to mitigate the impact of the unique challenges mentioned earlier. Researchers have been focused on improving the sensing accuracy with minimum sensing time to avoid interference. The most renowned local spectrum sensing schemes are energy detection, entropy detector, matched filter and cyclostationary feature detection [4]. There are many improved local sensing schemes [5,6] and advanced cooperative spectrum sensing schemes [7,8] proposed in the literature. However, none of them has been effective at overcoming the unique challenges associated with MCRN, which includes radio wave propagation over water, surface reflection and wave occlusions. Entropy is the measure of uncertainty in random variables [9]. Under a fixed-dimension probability space, the entropy of a signal is independent of noise power. Therefore, entropy-based detection can beused to cancel out the effect of noise uncertainty in MCRN. Entropy-based spectrum sensing can be used to counteract the unique challenges associated with the MCRN. In this paper, we investigated entropy-based detection to counteract sea state effects.