# Research Progress on Carrier-Free Phase-Retrieval Receivers
## 3 Modified CF-PR Receiver Scheme
### Improve the Performance of the CF-PR with a Reduced Number of Iterations and Better Steady Accuracy
#### 3.1.2 Enhanced CF-PR Algorithms
For example, the transmission impairments induced from the transceiver such as bandwidth constraint and in-phase/quadrature imbalance degrade the PR performance significantly, which can be reflected by a relatively large BER, above the 7% FEC threshold, in experiments. Additionally, the required number of iterations to guarantee a full PR convergency is still high in terms of practical implementation, and we believe that the utilization of machine learning techniques would play a vital role in further reducing the iteration number because of its strong fitting capability. Finally, the comparison between CF-PR receivers and other self-coherent receivers in terms of performance and hardware configuration requirement is worthy studying. Conceptualization, Y.M., X.G. and M.X. ; methodology, M.X. and S.F. ; software, Y.M. and M.X. ; validation, Y.M. and M.X. ; formal analysis, C.W., W.C., J.L. ([PERSON]), J.L. ([PERSON]) and G.Z. ; investigation, Y.M., M.X. and S.F. ; resources, M.X. ; data curation, W.C. and M.X. ; writing--original draft preparation, Y.M. ; writing--review and editing, X.G., Y.Q. and S.F. ; supervision, C.W. ; project administration, X.G. ; funding acquisition, M.X. All authors have read and agreed to the published version of the manuscript. This work was partially supported by the National Key Research and Development Program of China (2021 YFB2900702), the National Natural Science Foundation of China (62075046, U21A20506), and the Guangdong Introducing Innovative and Entrepreneurial Teams of \"The Pearl River Talent Recruitment Program\" (2021 ZT09X044). Not applicable. Data Availability Statement: Data underlying the results presented in this paper are not publicly available at this time, but may be obtained from the authors upon reasonable request. The authors declare no conflicts of interest. ## References

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