Open Radio Access Networks (O-RAN) enhance RAN flexibility, interoperability, and intelligence by introducing open interfaces, disaggregation of RAN components, and data-driven control. This flexibility has the potential to significantly reduce capital and operating expenses (CAPEX/OPEX) by en-hancing efficiencies in network energy consumption. Advanced Sleep Modes (ASMs) are an advantageous energy-saving technique for 5G base stations (BS), with a set of sleep depths that progressively deactivate different RAN components. The deploy-ment and effectiveness of ASMs in O-RAN raises a number of challenges that have yet to be investigated. This paper surveys and critically reviews RAN ASMs, as well as other energy-enhancing techniques applied in O-RAN. It presents the first granular, per-component O-RAN Radio Unit (O-RU) power model, that will enable researchers to quantify the power savings gained from deploying ASMs. A calculation of the energy savings achieved at each ASM level per O-RU component for different 3GPP functional splits is provided. The power consumption of O-RU sub-components for functional splits 6, 7.2x, and 8 is shown. The default 3GPP functional split 7.2x as adopted by O-RAN shows that substantial power savings can be achieved by applying ASMs to the O-RU, achieving a minimum of 80% savings depending on the choice of SM as compared to power consumption at full load. Finally, a discussion of the open research challenges and opportunities in deploying ASMs in O-RAN is provided.

The concept of open radio access networks (RAN) creates numerous opportunities for developing new technology and economy branches. At the same time, a flexible and modular approach in the disaggregated RAN entails the need for careful design of the overall RAN architecture and the implementation and deployment process of new applications. It is assumed that dedicated and specialized software companies may deliver the latter. A joint effort must be guaranteed among different sectors (industry, academia, and standardization bodies) to make the whole process efficient, safe, and reliable. Here, one of the critical driving forces origins from the open-source community that often stimulates the development of a specific technology. In this paper, we address the challenges that have to be faced by third-party application developers in the context of Open RAN. Based on many implemented applications (called xApps or rApps), we compare various available solutions. We pose the most critical issues that must be tackled in the near future to stimulate the progress in open RAN development further. In particular, we compare available open platforms for xApp development and testing. We present the details of implementing four selected applications describing the problems encountered. The paper is split into two logical parts - first, we identify the key ambiguities related to the development of new xApps, which address more complicated use cases like beam management. In the second part, we present the challenges associated with detailed software implementation in existing open platforms. In the first case, we show that dedicated beam mobility management xApp can reduce beam switches and keep beam failures low. However, it requires access to detailed localization information. Similarly, the signaling storm detection xApp provides expected performance under the assumption that there is access to detailed information on, e.g., time advance resolution parameter. We conclude here that several aspects still need to be well-defined to allow smooth software implementation; these include the rules for data reporting in time, parameters available in service models, and localization features. Concerning the second logical part, related to low-level implementation, we compare the numerical results of the traffic steering and quality-of-service-based resource allocation xApps and draw conclusions related to implementation and testing. In particular, we point out problems associated with the simulator, the software, and conflicts inside. Finally, we identify the key challenges which should be treated as incentives for joint academia-industry cooperation in the field of Open RAN. Thus, the paper presents the lesson learned during the first years of xApp development.

In this paper, we concentrate on modeling and simulation aspects of the Open Radio Access Networks (O-RAN). In detail, we present the solution in the form of an xApp considering the Quality-of-Service (QoS) Based Resource Optimization Use Case (QBRO-UC) within the O-RAN system. The xApp has been developed for the μONOS RAN Intelligent Controller (RIC) contained in the SD-RAN software platform designed by the Open Networking Foundation (ONF). The paper focuses on the mechanisms of Radio Resource Management (RRM) controlled by O-RAN-compliant policies. The paper highlights the capabilities of the proposed Physical Resource Block (PRB) allocation and discusses the limitations of the whole modeling framework.

Dynamic spectrum sharing can provide many benefits to wireless networks operators. However, its efficiency requires sophisticated control mechanisms. The more context information is used by it, the higher performance of networks is expected. A facility for collecting this information, processing it, and controlling base stations managed by various network operators is a so‐called Radio Environment Map (REM) subsystem. This paper proposes REM‐based schemes for the allocation of base stations power levels in 4G/5G networks, while considering interference generated to a licensed network. It is assumed that both networks have different profiles of served users, e.g., area of their positions and movement, which opens opportunities for spectrum sharing. The proposed schemes have been evaluated by means of extensive system‐level simulations and compared with two widely adopted policy‐based spectrum sharing reference schemes. Simulation results show that dynamic schemes utilizing rich context information outperforms static, policy‐based spectrum sharing schemes.

LTE and LTE-Advanced have been optimized to deliver high bandwidth pipes to wireless users. The transport mechanisms have been tailored to maximize single cell performance by enforcing strict synchronism and orthogonality within a single cell and within a single contiguous frequency band. Various emerging trends reveal major shortcomings of those design criteria: (1) The fraction of machine-type-communications (MTC) is growing fast. Transmissions of this kind are suffering from the bulky procedures necessary to ensure strict synchronism. (2) Collaborative schemes have been introduced to boost capacity and coverage (CoMP), and wireless networks are becoming more and more heterogeneous following the non-uniform distribution of users. Tremendous efforts must be spent to collect the gains and to manage such systems under the premise of strict synchronism and orthogonality. (3) The advent of the Digital Agenda and the introduction of carrier aggregation are forcing the transmission systems to deal with fragmented spectrum. 5GNOW will question the design targets of LTE and LTE-Advanced having these shortcomings in mind. The obedience of LTE and LTE-Advanced to strict synchronism and orthogonality will be challenged. It will develop new PHY and MAC layer concepts being better suited to meet the upcoming needs with respect to service variety and heterogeneous transmission setups. A demonstrator will be built as Proof-of-Concept relying upon continuously growing capabilities of silicon based processing. Wireless transmission networks following the outcomes of 5GNOW will be better suited to meet the manifoldness of services, device classes and transmission setups being present in envisioned future scenarios like smart cities. The integration of systems relying heavily on MTC, e.g. sensor networks, into the communication network will be eased. The per-user experience will be more uniform and satisfying. To ensure this 5GNOW will contribute to upcoming 5G standardization.