Optimization of Heterogeneous MSN Architecture
In this chapter, we discuss the modeling and optimization for heterogeneous MSN architecture to deliver social contents. With the small cells and macro cells, we present a heterogeneous architecture where the content can be managed in a content-centric mode. Based on the availability of cached replicas in the content store of content centric nodes, a novel caching algorithm is proposed to replace replicas in order to efficiently use the cache capacity of the content store. In addition, simulation results show the efficiency of the proposed scheme.
Network Architecture for Heterogeneous MSNs
With the advance of network technologies and the innovation of mobile services [1-3], many efforts have been given by both academia and industry to design the fifth generation (5G) mobile networks [4, 5]. Some related projects such as 5GNOW  and 20BAH  are carried out in academia, and there are also many standardization activities in industry.
Among these research activities, MSNs keep attracting much attention , where the MSNs have been developed rapidly and millions of users can interact with each other to exchange content [9-12]. Besides, since 5G can make it possible for users to experience more emerging multimedia services including wearable mobile communications, augmented reality applications, etc., it can be predicted that MSNs will be one of the most important network paradigms in 5G.
However, compared with other conventional networks, MSNs pose some new challenges for development in 5G. First, the amount of content requests in MSNs is greater than others such that a higher delay is caused and it is hard to satisfy the requirements in 5G. Second, the replicas of one content may be stored at different sites. As these replicas are managed according to their different locations in the current networks, the overhead to manage these replicas on different sites incurs huge operating costs. In addition, with the rapid development of the Internet of things (IoT), connected vehicles, etc., various types of content need to be delivered
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efficiently while users are in motion . New consideration to mobility should be given when designing MSNs in 5G.
In this chapter, we propose content centric based mobile social networks to resolve the above problems. First, in the content centric networks (CCNs) , content is delivered based on the interest in it instead of sending the conventional requesting message. In MSNs, the communities are organized by users with common interests. If the content is delivered by interest, delivering one content in a community may satisfy multiple users who have the same interest. Therefore, the total number of requesting messages in MSNs can be reduced. Second, in CCNs replicas are not controlled by their locations specified by IP addresses. Instead, the content is recognized by its content ID. This makes it possible to manage different replicas of the same content with the ID of the original content, and so the overhead to control these replicas can be reduced at the same time. Third, there are some CCN nodes in CCNs that cache some replicas of frequently used content within the coverage area of small cells. Therefore, when users keep moving through the coverage area of different cells, they can obtain the interested contents from the replicas cached in CCN nodes in small cells, without contacting the far away server.
To realize the above content-centric MSNs both content distribution using virtualization and related standardization are needed. On one hand, the construction of virtual CCNs has been studied for content distribution . However, the network architecture and process of mobile social content delivery have not been mentioned. On the other hand, the IETF has carried out standardization activities to discuss the protocol for CCNs . Although there are some standardized approaches such as the structure of the identifier and the status of the path, the related analytical models and algorithms need to be studied further, especially for content centric mobile social networks.
Therefore, in this chapter, we outline the delivery of mobile content based on content centric mechanism in MSNs. First, we present a heterogeneous network structure of content centric MSNs, which consist of users, communities, CCN nodes, small cells, and macro cells. Then, the process of content delivery based on the interest in content among users in communities is shown. Next, according to the availability of cached replicas in the content store of CCN nodes, we propose a novel caching scheme algorithm to replace replicas to efficiently use the cache capacity of the content store. In addition, experiment results are given to verify the proposed scheme.