Substitutability of Spectrum and Cloud-Based Antennas in Virtualized Wireless Networks

Some of the new trends emerging in future wireless networks enable a vastly increased fluidity in accessing a wide range of resources, thus supporting flexible network composition and dynamic allocation of resources to VNOs. In this work we study a new resource allocation opportunity that is enabled by the cloud radio access network architecture. In particular, we investigate the relationship between cloud-based antennas and spectrum as two important resources in virtualized wireless networks. We analyze the interplay between spectrum and antennas in the context of an auction-based allocation mechanism through which VNOs can bid for a combination of the two types of resources. Our analysis shows that the complementarity and partial substitutability of the two resources significantly impact the results of the allocation of those resources and uncovers the possibility of divergent interests between the spectrum and the infrastructure providers

Dynamic resource allocation for virtualized wireless networks in massive-MIMO-aided and Front-haul-Limited C-RAN

This work considers the uplink dynamic resource allocation in a cloud radio access network (C-RAN) serving users belonging to different service providers (called slices) to form virtualized wireless networks (VWN). In particular, the C-RAN supports a pool of base-station (BS) baseband units (BBUs), which are connected to BS radio remote heads (RRHs) equipped with massive MIMO, via fronthaul links with limited capacity. Assuming that each user can be assigned to a single RRH-BBU pair, we formulate a resource allocation problem aiming to maximize the total system rate, constrained on the minimum rates required by the slices and the maximum number of antennas and power allocated to each user. The effects of pilot contamination error on the VWN performance are investigated and pilot duration is considered as a new optimization variable in resource allocation. This problem is inherently non-convex, NP-hard and thus computationally inefficient. By applying the successive convex approximation (SCA) and complementary geometric programming (CGP) approach, we propose a twostep iterative algorithm: one to adjust the RRH, BBU, and fronthaul parameters, and the other for power and antenna allocation to users. Simulation results illustrate the performance of the developed algorithm for VWNs in a massive-MIMO-aided and fronthaul-limited C-RAN, and demonstrate the effects of imperfect CSI estimation due to pilot contamination error, and the optimal pilot duration

Defining and Surveying Wireless Link Virtualization and Wireless Network Virtualization

Virtualization is a topic of great interest in the area of mobile and wireless communication systems. However, the term virtualization is used in an inexact manner which makes it difficult to compare and contrast work that has been carried out to date. The purpose of this paper is twofold. In the first place, this paper develops a formal theory for defining virtualization. In the second instance, this theory is used as a way of surveying a body of work in the field of wireless link virtualization, a subspace of wireless network virtualization. The formal theory provides a means for distinguishing work that should be classed as resource allocation as distinct from virtualization. It also facilitates a further classification of the representation level at which the virtualization occurs, which makes comparison of work more meaningful. This paper provides a comprehensive survey and highlights gaps in the research that make for fruitful future work

Spectrum Valuation: implications for sharing and secondary markets

How much is electromagnetic spectrum worth? Appropriate metrics and methodologies for valuing spectrum help policymakers, network operators, service providers, and end-users in planning wireless-related investment and in ensuring that spectrum resources are used efficiently. Secondary markets have often served to provide publicly observable, market-based valuation metrics, but in the case of spectrum, these are under-developed and segmented, limiting the availability and comparability of market transactions as indicators of spectrum value. Furthermore, the continued growth in wireless services and networks of all types and further advances in wireless technologies enabling more dynamic and granular spectrum sharing are transforming the supply and demand conditions for RF spectrum. Today, the most common metric for valuing spectrum resources is /MHz-POP, derived from dividing the value of a spectrum transaction by the total population in the coverage area of the license times the bandwidth (in MHz). Traditionally, spectrum value has been observed in spectrum auctions, M&A transactions involving the transfer of spectrum usage rights, or from infrequent secondary market activity. This was a viable approach when the fungibility of spectrum resources was limited by technical, market, and regulatory factors that constrained the commodification of highly differentiated spectrum resources and limited the potential for dynamically reallocating, substituting and transferring spectrum rights via markets. With increased opportunities for spectrum sharing, the transition to 5G, smaller cell architectures, and the emergence of IoT, new spectrum usage patterns are arising and enabling more granular, multi-dimensional, virtualized spectrum management (in terms of frequency, location, time, etc.). In a world of increasing spectrum sharing, dynamic spectrum access, and commercial applications of higher frequencies for wireless service, /MHz-POP may be an increasingly noisy indicator of spectrum value. In this paper, we consider how changing technology, markets and policy are enabling the commoditization of spectrum resources and explore what that implies for traditional spectrum value metrics that are used to project auction proceeds and value spectrum transactions

Standardized Exclusion: A Theory of Barrier Lock-In

The United States has relaxed antitrust scrutiny of private standard-setting organizations in recognition of their potential procompetitive benefits. In the meantime, however, the growing importance of network industries—and the coinciding move toward vendor-led standards consortia—has welcomed new, insidious anticompetitive risks. This Note proffers one such risk: barrier lock-in. A theory of barrier lock-in recognizes that dominant vendors can capture and control standards consortia to keep standardized equipment complex and costly. These practices are exclusionary. This Note situates barrier lock-in within the existing antitrust literature and jurisprudence, provides a potential example of barrier lock-in in the 5G network equipment standardization process, and proposes two solutions for future legislative, executive, and judicial action against misbehaving standard-setters

Improving Liquidity in Secondary Spectrum Markets: Virtualizing Spectrum for Fungibility

Pricing mechanisms in the form of auctions have been the main method for spectrum assignment in the U.S. for over 20 years. The spectrum auctions carried out by the Federal Communications Commission (FCC) constitute a primary market for spectrum and have been affected by lack of flexibility which has resulted in inefficiencies in spectrum assignment, especially in environments where spectrum is considered scarce. In recent years, we have observed significant efforts to increase efficiency in spectrum assignment and use. Among those efforts is the design and adoption of secondary markets. Secondary markets have the potential to address inefficiencies arising in primary markets over time or those that occur through features of auction mechanisms by enabling spectrum to be assigned to users who value it the most. Furthermore, liquid secondary markets have enabled the explicit management of risk in other markets, such as agriculture and commodities, through futures and options trading. In this paper, we advance the study of liquidity in secondary markets that was begun in our previous work. We explore (i) the reasons that may have hindered the emergence of liquid secondary markets for radio spectrum and (ii) what we might change to promote secondary markets. With these objectives in mind, we study various configurations for the design of secondary markets, which account for the physical constraints inherent to electromagnetic spectrum. In addition, we study technical alternatives that would permit us to develop an appropriate, tradeable, spectrum-related commodity. The results of our analysis show that lack of fungibility has an adverse impact on secondary market liquidity. To address this outcome, we propose virtualization of spectrum resources into fungible chunks and show that this improves market liquidity by yielding viable market outcomes in all the scenarios we tested

On the Road to 6G: Visions, Requirements, Key Technologies and Testbeds

Fifth generation (5G) mobile communication systems have entered the stage of commercial development, providing users with new services and improved user experiences as well as offering a host of novel opportunities to various industries. However, 5G still faces many challenges. To address these challenges, international industrial, academic, and standards organizations have commenced research on sixth generation (6G) wireless communication systems. A series of white papers and survey papers have been published, which aim to define 6G in terms of requirements, application scenarios, key technologies, etc. Although ITU-R has been working on the 6G vision and it is expected to reach a consensus on what 6G will be by mid-2023, the related global discussions are still wide open and the existing literature has identified numerous open issues. This paper first provides a comprehensive portrayal of the 6G vision, technical requirements, and application scenarios, covering the current common understanding of 6G. Then, a critical appraisal of the 6G network architecture and key technologies is presented. Furthermore, existing testbeds and advanced 6G verification platforms are detailed for the first time. In addition, future research directions and open challenges are identified for stimulating the on-going global debate. Finally, lessons learned to date concerning 6G networks are discussed