Fig 5. Architecture of Soft-Air
The main contribution of the proposed Soft-Air architecture can be categorized as five main properties:
First, programmability, such that SDN nodes (SD-BSs and SD-switches) can be reprogrammed dynamically associating with different network resources.
Second, cooperativeness, such that SDN nodes can be implemented and linked at data centers for joint control and optimization for improving the general network performance
Third, virtualizability, such that several virtual wireless networks can be implemented on a single Soft-Air platform, while each operates regarding its own protocols customizes and interacts with allocated network resources without interfering with other service provider.
Forth, openness, such that data plane elements (SD BSs and switches) have common data/control interface protocols, regardless of the different data forwarding technologies provided by different vendors, such as: CPRI and OpenFlow, thus the data plane monitoring and management can be simplified.
Fifth, visibility, such that controllers are able to have an overall view over the whole network collected from data plane elements.
To sum it up, Soft-Air tries to design a high flexible architecture providing
maximum spectrum efficiency exploiting benefits of cloudification and virtualization processing; also, advance steady convergence for different network elements by different independent virtual interfaces, and enhance energy efficiency by scaling the computing capacity of data plane elements.
Fig 6. Controller/data plan scheme of Soft-Air
Another method proposes a new multi-tried controller scheme and event processing mechanism for Software Defined Wireless Network (SDWN) architecture for the 5G network toward Openflow standard which results in a user-centric and service-oriented architecture. To provide the proper radio environment required for 5G wireless communication, SDN along with NFV architecture is a promising technique to overcome the isolation of heterogeneous
radio access networks such as LTE, Wi-Fi and W-CDMA. Mainly, because the spectrum efficiency of LTE has achieved very close to the Shannon’s capacity limit. Hence, this article declares that an efficient way to decrease traffic for the networks in the 5G is improving the heterogeneous radio access.
Another important challenge for the future user-centric and the service oriented 5G mobile communication system is the quality of user experience (QoE). The 5G will face with tremendous number of devices that have wide rages of different patterns for the modeling the information with different protocols. However, the legacy needs for quality of service and different specific application requirements are the main determiner for accepting more and more applications, besides to the system capacity. Some of the future applications
require few milliseconds end-to-end delay. In this way, the varying throughput, latency and jitter requirements of application enhance the complexity of state and resource provisioning.
Another significant part of the proposal method is designing a layered cloud net scheme for the multiple controller with two parts: Edge Controller (EC) and Global Controller (GC). The main logic behind this design is to reduce the response latency and balance the network load for the cloud of controller. The EC processes the event within a single RAN domain, and the GC takes events across various RANs into account. Controller architecture is as Fig 7.
Fig 7. Virtualization architecture of the cloud controller
Based on the fact that the 5G technology spectrum and bandwidth will face unavoidable challenges in the future for the huge number
of different and unpredictable clients, integration between the frequency spectrum, and bandwidth will be an inevitable topic. Combining software defined radio (SDR) and software defined networks (SDN) would be the best tool for this integration. However, they are difficult to exchange the information because they belong to different layers. Therefore, we sould design a cross-layer integration mechanism to combine the benefits of integrating SDN and SDR. Researches declares that the co-existence of SDR and SDN is crucial, and the best performance can be achieved only by mutual cooperation. The architecture combing these two layers has been shown in Fig 8.
Fig 8. Hybrid architecture of SDN and SDR
The main component of the proposed architecture is the cross layer controller, which has administration rules to supervising and making proper decisions. Also, the scheme exploits a unit in controller, which makes decisions based on the trade-off between received information from the two layers as shown in Fig. 9. Any time that users want to access spectrum resources, users should request the cross layer controller about accessibility of the band. After the confirmation of the user authorization, the cross layer controller investigates the flow traffic information of the requested band, and allows the access or suggests switching to a better band. Moreover, based on the dynamic network environment, the controller can adapt itself based on spectrum usage and overall network conditions. Therefore, cooperation of the two layers can result in better planning and performance.
Fig 8. Network configuration
The basic properties of a secure communications in a network includes: confidentiality, integrity, availability of information/data or resources, authentication and non-repudiation. In order to provide a secure network, security professionals must secure the data, the network assets (e.g. devices) and the communication transactions across the network at all times. The alterations to the network architecture introduced by SDN along with 5G or other technologies must be assessed to ensure that network security is sustained. One of the network features of 5G technologies is heterogenous access, which only allow use of different access technologies such as Wi-Fi or LTE, but also support multi-network environment. That means that the access network architecture of different networks are different, so security designers of 5G technology must ensure that they are building the suitable security architecture for different access technologies.
In this section, we are going to review some important security challenges briefly.
Risk at Southbound API’s
Due to the lack of intelligence at the southbound APIs, they are susceptible to attack via false and forged flow table entries. The attacker may send false data stream with slightly different header information to overflow the flow table, as a result the legitimate flows cannot be updated on time. The security of the whole network could be compromised by unsecure implementation of the southbound protocols.
Risk due to End Terminals/Devices
End terminals may possess various threats including misuse or downloading of application, trojans or viruses etc. These mobile devices should also the area of focus, as any vulnerable devices may lead to vulnerability in the entire infrastructure. The terminals usually lack an effective security tools such as intrusion detection system, antivirus software, endpoint firewalls, spam blocking and so on. These end terminals/devices possess huge security risk, if not properly secured.
Risk at Communication layer
The 5G network support wide variety of mobile devices that might host vulnerable applications which can also be the source of attack. Hence, the application layer hosting various applications might be vulnerable, as it can cause fault information flow to the controller or inject deceptive rules into the network. A successful attack at this risk layer could gain control of the networking infrastructure. To provide security at this layer, we must focus on preventing unauthorized applications and users from exploiting the controller.
Risk at Controller layer
SDN controller when implemented in 5G provides management and router selection for all radio access network (RAN) to core network connection. But it also provides single point of failure, and if it is compromised the whole network can be under the controller of the attackers. SDN-controller is the high-value target that needs a high level of protection. The controller can also be prone to DDoS attack, if the controller is hijacked, the attacker can take over the whole network, flows and policies. Hence, SDN controller must have strong security policy so as to avoid it from any vulnerability.
In this article, we discussed about different methods and architecture which are trying to provide faster and reliable base for 5G network. SDN as the main component of providing the virtualization, gained increasingly attraction and the main goal of each technique to improve different parts of this scheme has been reviewed. However, there can be more ways to develop these scheme, as the 5G is still at the middle stages of researches.
Also, we reviewed some security challenges briefly.