# A Review of DSP-Based Enabling Technologies for Cloud Access Networks
## 1 Introduction  
Today's communication networks are increasingly struggling to support the growing demands of emerging network services and traffic, such as the higher data rates, drastically increased the number of connections and ultra-low latency requirements of 5G. Traditionally networks have been designed with an essentially static architecture [1; 2] which provides end users with fixed capacity internet connections. If end users require a change to their connection speed this can require manual operator intervention and can take significant time to implement as potentially physical hardware must be replaced, thus bandwidth provision is fundamentally static in nature. As internet connection speeds started to steadily increase, operators have been able to increase subscription rates to maintain a viable business model based on the fixed capacity provision. However, it is predicted, that to meet traffic growth demands in the future, operators must offer multi-Gb/s internet connection speeds [3], but provision of multi-Gb/s connections is highly challenging to achieve in a cost-effective manner as subscribers arenot prepared to pay significantly increased subscription rates, thus operators are facing the dilemma of the decoupling effect between traffic growth and revenue growth. Networks must, therefore, evolve to offer advanced, highly agile, dynamically reconfigurable architectures that support features, such as elastic bandwidth allocation, network slicing and SDN control. These dynamic networks [4; 5] would thus allow operators to instantly respond to changing traffic demands, offering network features, such as elastic connectivity tailored to the end users' prevailing needs, automatic network reconfiguration based on identified traffic patterns and provision of dedicated virtual networks with service critical characteristics, such as security and latency. These new dynamic network architectures can, therefore, be cost-effective and commercially viable as highly efficient use of the available network resources is achieved and operators can also decouple their revenue from pure data capacity provision and link it more to on-demand network service provision.  
To realise highly dynamic networks at the physical layer, we have proposed Cloud Access Networks (CANs) [6; 7] which employ flexible, adaptive and reconfigurable networks elements. By exploiting optical transceiver-embedded digital signal processing (DSP) we have proposed a digital orthogonal filter-based multiplexing technique to implement CANs with multiplexed, independent optical channels at the wavelength, sub-wavelength (Sub-\(\lambda\)) and orthogonal sub-band (Sub-B) levels [8; 9]. The objective of this paper is to review our recent work on DSP-based technologies for enabling CANs, thus it provides a unique insight into the overall capabilities of a CAN, facilitated by the various complementary technologies. The overall CAN concept is presented in Section 2, and Section 3 presents the operating principles of the various DSP-based CAN network elements, along with an overview of our associated real-time DSP-based research work. Finally, Section 4 concludes the paper.