# A Review of DSP-Based Enabling Technologies for Cloud Access Networks
## 4 Conclusions  
This review paper has provided an overview of the general CAN concept and a summary of the recent DSP-based research work relating to the proposed CAN technology. The CAN is shown to exploit both DSP-based and DSP-enabled networking devices, to achieve a dynamically reconfigurable network with fine granularity, elastic bandwidth channels that can be multiplexed at the wavelength, sub-wavelength and orthogonal sub-band levels. The CAN realises a dynamic network that can seamlessly integrate Metro-networks, fixed access networks and 4G/5G mobile fronthaul and backhaul networks, thus significantly reducing the cost of network ownership. The adaptive characteristics of the CAN networks provide a cost-effective solution to the relentless growth in demand for data capacity by dynamically sharing and allocating network capacity on-demand to meet the prevailing network traffic requirements. Thus, by fully utilising the available network resources, the CAN removes the need to over provision fixed resources to meet the worst-case traffic scenarios. The CAN also fully supports SDN for efficient control and management of the whole network configuration, including the physical layer. Key DSP-based/enabled network devices that enable the CANs have been presented in terms of operating principles and experimental demonstrations, these network devices are DSP-based reconfigurable optical transceivers, DSP-enable soft-ROADMS and DSP-enabled spectral converters, all of which have been successfully demonstrated in proof-of-principle experiments, which confirms their technical viability.  
To further develop and assess the presented CAN technologies our future research work will focus on aspects, such as, the practical real-time demonstration of CANs with increased channel count and increased aggregate bandwidth, demonstration of the CAN's transparency to signal characteristics, such as modulation format, the impact of cascaded soft-ROADMs on CAN performance and DSP-based techniques to improve CANs in terms of reconfigurability, flexibility and transmission performance.  
**Author Contributions:** [PERSON] supervised the work, provided technical guidance for the DSP design/implementation and wrote the paper; [PERSON] undertook all DSP-design and experimental work relating to reconfigurable optical transceivers; [PERSON]-[PERSON] undertook all DSP-design and experimental work relating to soft-ROADMs; [PERSON] undertook all simulation and experimental work relating to spectral converters.  
**Funding:** The work on reconfigurable optical transceivers was supported by PIANO + under the European Commission's ERA-NET Plus scheme within the project OCEAN under Grant agreement 620029. The work on soft-ROADMs was supported by The Ser Cymru National Research Network in Advanced Engineering and Materials (NRN024) and by the IRAQI Ministry of Higher Education and Scientific Research (MOHESR). The work on spectral converters was supported by The Ser Cymru National Research Network in Advanced Engineering and Materials (NRN024 and NRN147) and by the National Natural Science Foundation of China (Project No. 61132004, 61275073, and 61420106011).  
**Conflicts of Interest:** The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.