Underwater Wireless Sensor Networks: A Review of Recent Issues and Challenges

Table 3

Effect of noise, errors, and protocols.

S. No.	Area of research	Findings	Noise effect	Bit error rate	Protocol usage
01	Challenges: Building Scalable and Distributed Underwater Wireless Sensor Networks (UWSNs) for Aquatic Applications,	Time Division Multiple Access (TDMA) is not efficient due to large propagation delays, Frequency Division Multiple Access (FDMA) is not suitable due to the narrow bandwidth and Code Division Multiple Access (CDMA) is suitable for underwater acoustic networks. While contention-based protocols are not appropriate for underwater communications.	N/A	N/A	(TDMA) is not efficient; (FDMA) is not suitable. (CDMA) is suitable
02	Prospects and Problems of Wireless Communication for Underwater Sensor Networks	Acoustic communication also has less attenuation in deep and thermally stable oceans. Shallow water effects acoustic communication by temperature gradients, ambient noises regarding surface and multi-path effect because of reflection and refraction.	Decreases by ambient noises	less attenuation in deep and thermally stable oceans	N/A
03	Analyzing the Performance of Channel in Underwater Wireless Sensor Networks (UWSN)	Multi-path propagation results in fading and phase fluctuations, Doppler Effect is observed due to the movement of both the sender and receiver nods. Speed of sound and underwater noise are other factors that influences the performance of acoustic channel.	Decreases by ambient noises	Fading and phase fluctuations, Doppler Effect	N/A
04	Optimized packet size selection in underwater wireless sensor network communications	Effect of bit error rate, interference, collision, retransmission leading selection of optimal packet size is also considered and achieves improvement in all metric e.g., throughput, energy consumption, resource utilization and packet latency underutilization of optimal packet size selection.	N/A	Less bit errors in small packets	N/A
05	Choosing the packet size in multi-hop underwater networks	Data packets are large enough as compared to the control packets and because of control and data packet collision entire data packet is discarded that causes of huge number of retransmissions and energy dissipation.	N/A	Error due to control and data packet collision entire data packet discarded	CDMA, DACAP
06	Challenges for efficient communication in underwater acoustic sensor networks	A major cause that makes acoustic signal weak is called multi-path effect, that becomes cause of inter-symbol interference also makes acoustic data transmission difficult and erroneous. Vertical acoustic channel is less affected by multi-path effect as compared to horizontal acoustic channel.	N/A	Interference and multi-path effect	N/A
07	Ocean ambient noise: Its measurement and its significance to marine animals	Large number of ships present at large distance from communication system in ocean produce high traffic noise in acoustic communication, if sound propagation is good enough. Ships consider main source of anthropogenic ambient noise.	N/A	Decreases due to ships noise	N/A
08	SEA 6 Technical report: Underwater ambient noise	Turbulence can be defined as surface disturbance due to waves or tides that generates low frequencies that results continuous noise in acoustic communication. Underlying noise is considered as thermal noise in the absence of all other sources of noise, including self-noise. Thermal noise is directly proportional to the frequency which is used for acoustic communication.	surface disturbance of waves or tides generates low frequencies that results in noise in acoustic communication	Errors due to noise	N/A
09	Doppler estimation and correction for shallow underwater acoustic communications	Because of channel flaws, Wireless signals practice a diversity of degradations. For example, electromagnetic signal affects by interference, reflections, and attenuation, acoustic signals regarding underwater are also affected by same kind of factors.	N/A	High BER due to interference, reflections, and attenuation	N/A
10	Study on Doppler effects estimate in underwater acoustic communication	Two types of influences are observed on acoustic channel because of Doppler Effect, first is pulse width that will be compressed or stretched and second is frequency offset as a result of frequency offset compressing or expending of signal time domain occurs.	N/A	Doppler Effect, frequency offset	N/A