With the ever-growing of mobile Internet and the explosion of its applications, users are experiencing abundant services from different content providers via different network service providers in the heterogeneous network (HetNet). Information-centric network (ICN) advocates to get rid of the current host-centric network protocol for the fact that the information dissemination rather than the endto-end communication contributes to the majority of today's network traffic. Furthermore, it is better for network entities to converge as a whole in order to take advantage of the open, scalability, and smart traffic transmissions. Cloud radio access network (C-RAN) is one of the emerging architecture evolutions in the wireless side for easier infrastructure deployment and network management. Therefore, when ICN meets C-RAN in the HetNet, it is worthwhile and consequential to integrate ICN protocol with the C-RAN architecture to achieve more efficient communication and information management. Moreover, software defined networking (SDN) has been recognized as another promising architecture evolution to achieve the flexibility and reconfigurability of dense HetNets, whose inherent advantage yet lies in the global uniform control of the wired network. Thus any of ICN, C-RAN and SDN is the complementary to the others. In this paper, we contribute to novelly proposing and elaborating the integration of the ICN, C-RAN and SDN for the HetNet to achieve win-win situation. The vision of the proposed system is demonstrated, followed by the advantages and challenges. We further present the hybrid system with a large-scale wireless heterogeneous campus network. This work has been accepted by IEEE Communications Magazine. C. Yang, Z. Chen, and B. Xia (corresponding author) are with the Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai, P. R. China. J. Wang is with School of Engineering and Digital Arts, University of Kent, United Kingdom. To meet with the thousand-fold growth of mobile data traffic, a promising way is embedding mass of small cells into the cellular network, i.e. the heterogeneous network (HetNet) [1] . Heterogeneity will be an essential feature of the future radio access network (RAN) consisting of different kinds of devices. For the highly flexible interfaces among different devices, software defined networking (SDN) has been recognized as a basic enabler to achieve the flexibility and reconfigurability of dense HetNets [2] . Furthermore, under the pressure of inter-/intra-cell coordination and tremendous deployment cost in the large-scale HetNet, Cloud RAN (C-RAN) emerges [3] . C-RAN is widely regarded as a green radio architecture to cope with the increasing network data traffic without incurring significantly additional capital and operational expenses. In addition to the evolution of the network architecture, the human behavior and the service property have been widely concerned to unleash the ultimate potential of networks, e.g., the cache-enabled Information-centric network (ICN) [4] . The state of the art will be elaborated in the following in the perspective of network architecture and network protocol, respectively. The HetNet is the expansion of the existing network in terms of the size and the type: Compared with the the fourth Generation/long term evolution (4G/LTE) network, the fifth Generation (5G) network is expected to attain a 1000-fold capacity increase measured in bit/s/Hz/m 2 , 5 times reduced latency and 10 times longer battery life [5] . Motivated by the everincreasing pressure to enhance the network capacity, cellular networks are overlaid by a wide variety of proliferative infrastructure layers including outdoor pico/indoor femto base stations (BS), relays, distributed antennas [6], WiFi and device to device (D2D) nodes [7] . Heterogeneity will be a key attribute of the future networks. HetNets bring the cell site closer to the users and shorten the radio transmission distance, yielding significant cost reduction and capacity enhancement. Furthermore, the small cells are deployed as the complementary of the macro cellular networks for the seamless coverage and intentionally offload the traffic of the macro cell. Besides, advanced technologies such as highorder spatial multiplexing multiple-input multiple-output (MIMO) come along with higher spectral efficiency (SE) in the HetNet. However, there are still problems: 3 • The resource management and load balancing are two important issues for the successful deployment of HetNets. The inter-/intra-cell coordination and convergence are non-trivial operations in this distributed and large-scale environment. • HetNets enable more flexible and economical deployments of new infrastructure instead of tower-mounted macro systems, but it is not sufficient to achieve the flexibility and reconfigurability of the networks due to the nonuniform and curable device interfaces. • The increasing demands on the backhaul network needs to be evaluated when deploying more small cell sites. The trivial expansion of the size and type of the exiting network can temporarily relieve the pressure, but disruptive evolutions of the network architecture are urgent for the further capacity extension. However, SDN is originally designed for wired networks. There are inherent weaknesses to achieve the SDN ideas in the wireless networks due to vary challenges. Software defined wireless networks (SDWN) needs to define slices which requires to isolate wireless channels so as to provide non-interfering networks to different coordinators. Handoff situations should be considered for the wireless HetNet with smaller cells and richer access technologies. The status and locations of the whole network entities should be reported to SDN in real time only based on which controllers take decisions efficiently. These challenges are no-trivial operations for the wireless medium. There is a long way for the wired and wireless sides to be seamlessly integrated as a whole in the SDN system. C-RAN is ICN provides the new basis on how information can be labeled and distributed across networks: Despite of the tremendously amount of data traffic in the network, only a few contents are frequently accessed by user ends [9] . A small portion of the popular contents contribute to the majority of the traffic during a period of time [10] . Furthermore, Today's network is increasingly occupied by information dissemination, rather than by the end-to-end communications. Thus caching the most popular contents in the RAN or the evolved packet core (EPC) can reduce the 5 redundant access and the duplicated transmission [11] . The pivotal role the caching technology can play for the 5G wireless network is elaborated in [11] and [12]. ICN emerges as a promising candidate for full use of in-network caching and multicast mechanisms [13] . Different in the exiting host-centric networks where users have to transmit/receive information to/from a particular computing entity (host or server), they are increasingly interested in transmitting/receiving information wherever they may be located. The ICN decouples information from its location and sources by defining the named data objects (NDO). Widespread caching and broadcasting allow users to get the information from the optimal node based on the name and/or the location of the information. Providers and requesters are no longer connected in the traditional pair-wise and time-synchronized mode, they are decoupled in terms of time and space. There is no need for them to know each other's location or to be online at the same time. As mentioned above, the widespread in-networking caching of ICN brings great opportunities of cooperative communication among entities in the high-density wireless HetNet, while C-RAN is emerging for easier infrastructure deployment and system management. Then integrating ICN protocol into the C-RAN architecture can achieve better communication with efficient distribution of information via ubiquitous cache-enabled devices. At the same time, the burden of the upper layer (e.g., the CN) will be significantly reduced when user requests can be responded immediately by the entity (e.g., the BBU) who has cached the copy of the requested information. However, C-RAN solely focus on the radio air interface regardless of the states of upper layers. Coincidentally, SDN is born with the original purpose of dealing with wired networks but it will meet more difficulties to introduce concepts of SDN to wireless networks. Moreover, the ICN protocol is available to the SDN as well. Therefore, appropriate combination of ICN, CRAN and SDN is a promising way to achieve mutual benefit and complementary. We organize the reminder of this paper as follows: In Section II, we describe our vision of the coexisting system of the SDN, ICN and H-CRAN. The advantages and main challenges are elaborated. In Section III, a large-scale exemplary campus network is presented. IV gives a brief summary of this article. The Information-centric concept is better suited to today's use which mainly consists of information distribution rather than host-centric communications. For the long tail style of the user request statistical property, in-network caching and multiparty communication can be fully leveraged via replication and cooperative models. We propose to achieve the information-centric approache on the SDN architecture to unleash the ultimate potential of the network, and C-RAN undertakes the role and task of SDN in the wireless side. Few of existing studies has considered the coexisting network and we will give an integrate sight of them. A high-level view of information-centric SDN architecture is shown in Fig. 1 The role that each plane plays in the network is : 7 Content information, SLA, negotiation protocol, ...
The work in REF proposes to combine ICN, C-RAN and SDN in heterogeneous networks.
When ICN Meets C-RAN for HetNets: An SDN Approach
IEEE Communications Magazine
IEEE Communications Magazine
Computer Science Mathematics