To Know Channels Better: Challenges and Opportunities of Ray Tracing

How to know wireless channels better in a more accurate and efficient way is the motivation and goal of wireless propagation and channel modeling, including but not limited to ray tracing (RT) and stochastic channel models (CMs). Although being called "deterministic channel modeling", the essence of RT is still electromagnetic (EM) calculation. This is dramatically different from the mainstream CMs (short for stochastic CMs in the following text). In order to understand the prospects of these two approaches, we provide insight into the comparison of RT and CMs in terms of essence, usage, and cost (of complexity). In order to enhance the potential of RT, we identify the challenges and contemplate the future research outlook toward breaking through these bottlenecks from the perspectives of the input data, algorithms, and computing power.