Using HARQ is an efficient mean of adding diversity to communications systems without using unnecessary resources, and when properly tuned, it can be beneficial even for URLLC applications. We have shown how properly designing the scheme can lead to important reductions in the maximum EMF radiation being output by the communication system. In the context of URLLC, several suboptimal aspects of HARQ have to be improved and fine-tuned with latency in mind. However, even in those cases, clever engineering and design can overcome possible added latencies and harvest the efficient resource usage of HARQ. This efficient use of resources is relevant as it enables devices to communicate using less energy and therefore reduces the EMF emission, which is particularly relevant when considering the massive scale of deployments foreseen for the near future.

Chapter Contents:

• 10.1 Hybrid automatic repeat request
• 10.2 Reducing EMF emission
• 10.2.1 Health concerns from EMF exposure
• 10.2.2 Reducing EMF radiation in URLLC applications
• 10.2.2.1 Early feedback
• 10.2.2.2 Code design
• 10.2.2.3 Optimizing the number of transmission attempts
• 10.3 Conclusion
• References

Inspec keywords: electromagnetic fields; automatic repeat request

Other keywords: ultra-reliable low-latency communications; URLLC applications; maximum EMF radiation; EMF emission reduction; HARQ

Subjects: Protocols; Electric and magnetic fields