# Autonomic Network Management and Cross-Layer Optimization in Software Defined Radio Environments
## 3 Autonomic Framework for Network Management and Cross-Layer Optimization in SDR  
### Conceptual Framework of ANMO-SDR  
We propose a framework for autonomic network management and cross-layer optimization in SDR environments, namely ANMO-SDR, which combines for the first time the ANM and SDR/SDN/NFV concepts. To the best of our knowledge, there are no previous works that combine ANM with SDN, SDR and NVF, as it is proposed in the current paper. The ANMO-SDR functionality focuses especially on D2D communication in SDR environments, uniquely addressing the objective of QoS-aware ubiquitous connectivity and efficient use of resources. The emergent D2D communication approach utilizes the concept developed in SDR based CRNs involving communication between the SUs, signifying direct communication between mobile devices without the inter-mediation of a Base Station (BS) or an Access Point (AP), which can potentially offer faster and more resource efficient ubiquitous connectivity. The CRN architecture comprises of Primary Users, who have (purchased exclusive) rights to operate at certain channels, and Secondary (or Cognitive) Users, i.e., users who do not have assigned bands. Specifically, CRNs enable the reuse of the under-utilized licensed spectrum, i.e., opportunistic access by the SUs, when no interference is caused to licensed users [28]. The ANMO-SDR approach provides a more general framework adopting these principles that can be applied to any D2D type of communications and it can address various problems such as that of spectrum scarcity. In the rest of this section, we provide the architectural components, the interactions between them and the generic ANMO-SDR functionality, which focuses on a number of performance objectives, utilizing the ANM attributes. The goal of the proposed framework is twofold: first, to implement spectrum management for the SUs, and second, their operation to be transparent to the PUs. The management and the orchestration of all network operations is provided by the ANM components, which encapsulate ACLs, implemented by the autonomic MNs. Specifically, ANMO-SDR implements decentralized cooperative spectrum sensing in CRNs, utilizing a number of ANM attributes, such as awareness--as it monitors channel availability information including interference (such as transmission frequency, bandwidth, power, modulation, etc. )-adaptivity/flexibility--as it adapts the channel assignment process according to preferences and QoS requirements, adjusting the transmission or reception parameters without any modification in hardware components, while it can operate under different/dynamic topologies--as well as, pro-activity, as it prevents collisions. More precisely, the proposed framework's functionality, related to ACL components can be specified as follows:  
* _Information Collection_: Sense the spectrum in order to identify the channels allocated to the licensed users and detect empty spectrum (spectrum holes or white space). * _Decision Making_: Analyze the collected information and select the best available channel, i.e., the channel that best meets the QoS requirements. Plan transmission power among CRN users. Maintain the QoS of the SUs without causing interference to the PUs. Plan reconfiguration actions, when PU (re)appears, i.e., vacate the respective spectrum and select another channel. * _Execute and Observe_: In order to provide seamless operation, transfer the ongoing communication to another vacant channel that can maintain the QoS requirements (spectrum hand-off). In Figure 2, the conceptual diagram of the combination of ANM with SDN/SDR/NVF is provided. It is noted that the novelty of the proposed approach lies on the combination of the four emerging concepts to a single solution, which has not been introduced previously. Particularly, the role of each component within the proposed architecture is highlighted. ANMO-SDR follows the cross layer SDN/SDR perspective that decouples control plane from the data plane, maintaining modularity, following the directions proposed in [20].