A Generic Framework for Heterogeneous Wireless Network Virtualization: Virtual MAC Design Bo Fan, Hui Tian, Xiao Yan
[email protected],
[email protected],
[email protected] State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications, Beijing 100876, China Abstract—Virtualization is a promising technique to solve the ossification of current wireless networks and meet the ever-increasing mobile data volume. This paper analyses the requirements in wireless network virtualization and proposes a generalized virtualization framework to overcome these challenges. A novel VMAC (virtual medium access control) concept is devised to perform resource virtualization and management, and the functionalities of VMAC are presented in detail, including user plane as well as data control plane. Through VMAC, heterogeneous RANs (radio access networks) can be aggregated with a unified protocol stack, packaged in the form of a service, reconfigured to provide end-to-end user services. The paper is concluded by identifying important open issues to be studied in future research.
I. I NTRODUCTION Mobile communication is witnessing an explosion in the number and category of applications and services demanded by users. Moreover, as mobile networks evolve from one generation to another, multiple radio access techniques (RATs) begin to accelerate in the same domain. However, current networks lack an efficient methodology for coordinating these RATs while the fulfillment of mobile users’ demand is desired. To cope with this situation, virtualization technique is introduced to revolutionize the 5G mobile network [1]. Different research works have investigated and exemplified the implementation of virtualization to radio access networks (RANs). Two RAN virtualization scenarios are proposed in the Third Generation Partnership Project (3GPP) specification where RANs can be respectively shared by spectrum-split and geography-split network operators [2]. However, in both cases, operators will be limited to using their own dedicated RAN resources. To take a step further, Centralized RAN (C-RAN) has drawn researchers’ attention as one possible way to achieve full RAN centralization [3]. In C-RAN, baseband signals are centrally processed in a cloud-based center unit (CU), with radio units (RUs) providing coverage to end users. Although the flexibility of signal processing and resource utilization is theoretically maximized, fronthaul (the link between RU and CU) capacity limitation is known to impose a formidable bottleneck to C-RAN. As a tradeoff between full centralization (C-RAN) and decentralization (3GPP RAN sharing), the underlying concepts of partially RAN centralization are identified This work is supported by the National High Technology Research and Development Program of China (863 Program) (No. 2015AA015701) and Funds for Creative Research Groups of China (No. 61421061).
by P. Rost et al. [4]. However, there remain several specific problems unsolved: at which network layer (to what degree) should the virtualization (partially centralization) be realized? What changes will the virtualization bring about to existing network protocols? Motivated by these problems, in this paper, we focus on the architecture and protocol design for RAN virtualiztion. A novel ‘VMAC’ (virtual medium access control) concept is proposed, compromising flexibility and compatibility of the virtualization framework. VMAC resides right above the network MAC layer, but below IP layer. Through VMAC, heterogeneous RANs can be coupled within a unified protocol stack, forming the functionality for service providers (SPs) to manage and operate their own virtualized networks. In detail, functionalities of VMAC are presented, including resource abstraction, virtual resource allocation, mobility management, etc. As a conclusion, VMAC provides a generalized methodology for aggregating and virtualizing heterogeneous RANs, realizing the novel RAN as a Service (RANaaS) concept, paving the way for solving the ossification of today’s mobile network paradigm. Finally, several challenges are presented for the proceeding research of RAN virtualization. The rest of the paper is organized as follows. We start by summarizing the motivations and requirements in the wireless network virtualization. The proposed virtualization framework is presented in detail in Section III. Section IV provides some open research issues within the generalized virtualization paradigm. The paper is concluded in Section V. II. M OTIVATIONS AND R EQUIREMENTS As a result of explosive growth in wireless network volume, there have already been a variety of radio access technologies (RATs) coexisting in the same area, deployed by different cellular operators. However, these networks are managed individually, causing the following problems. First, RATs cannot respond quickly to subscriber mobility, which leads to frequent service disruptions. This is because today’s cellular operators do not have common protocols for controlling forwarding across different RATs (e.g., UMTS, LTE, WiMax, WLAN, etc). As a result, handoff across technologies involving complex procedures will result in longer delays and higher packet loss rates. Second, the ability for operators to offer fine-grained end-toend traffic services is ossified. For example, cellular providers
([HFXWHGDW%6
&HQWUDOO\ H[HFXWHG
&RQYHQWLRQDO5$7 LPSOHPHQWDWLRQ
3URWRFROIXQFWLRQVSOLW S )LQHJUDLQHGYLUWXDOL]DWLRQ )LQHJUDLQHG YLUWXDOL]DWLRQ
&5$1 LPSOHPHQWDWLRQ
1HWZRUN PDQDJHPHQW
1HWZRUN PDQDJHPHQW
$GPFRQJ FRQWURO
$GPFRQJ FRQWURO
550
550
0$&
9LUWXDOL]HG0$& WKH SURSRVHGVROXWLRQ
&HQWUDOO\H[HFXWHG
0$&
3+
