Mohsen Karimzadeh Kiskani

Effect of Social Groups on the Capacity of Wireless Networks

In this paper, we study the effects of social interactions among nodes on the capacity of wireless networks. We consider three scenarios. In the first scenario, the size of the social group for all nodes is fixed while the frequency of communication within members of a social group follows power law distribution. In the second scenario, scale-free networks are studied where the size of the social group differs from node to node, and the destination in each group is selected uniformly among the members of that group. Further investigation in the second scenario reveals that traditional transport capacity definition provides misleading conclusions for such network models. We show that nodes with different social status impact the capacity differently. By separating nodes with different social status and allocating separate bandwidth to them, it is shown that majority of nodes scale in this network. In the third scenario, both the size of the social groups and the destination in each group are selected according to power law distributions. Our simulation results corroborate the analytical results. Further, we observe consistently that social interaction improves the capacity of wireless networks, which implies that the Gupta-Kumar results were pessimistic for practical networks.

Capacity of Cellular Networks with Femtocache

The capacity of next generation of cellular networks using femtocaches is studied when multihop communications and decentralized cache placement are considered. We show that the storage capability of future network User Terminals (UT) can be effectively used to increase the capacity in random decentralized uncoded caching. We further propose a random decentralized coded caching scheme which achieves higher capacity results than the random decentralized uncoded caching. The result shows that coded caching which is suitable for systems with limited storage capabilities can improve the capacity of cellular networks by a factor of log(n) where n is the number of nodes served by the femtocache.

Social interaction increases capacity of wireless networks

A network model with both social and communication characteristics is considered. Different capacity regions are computed as a function of the social network size for each node. It has been shown that as the social connectivity among nodes improves, the likelihood of finding shorter path between source-destination pairs in the network increases which results in increase in the capacity compared to the original results by Gupta and Kumar [3].

Multihop Caching-Aided Coded Multicasting for the Next Generation of Cellular Networks

The next generation of cellular networks deploying wireless distributed femtocaching infrastructure proposed by Golrezaei et al. is studied. By taking advantage of multihop communications in each cell, the number of required femtocaching helpers is significantly reduced. This reduction is achieved by using underutilized storage and communication capabilities in user terminals, which results in reducing the deployment costs of distributed femtocaches. A multihop index coding technique is proposed to code the cached contents in helpers to achieve order-optimal capacity gains. As an example, we consider a wireless cellular system in which contents have a popularity distribution and demonstrate that our approach can replace many unicast communications with multicast communication. We will prove that simple heuristic linear index code algorithms based on graph coloring can achieve order-optimal capacity under Zipfian content popularity distribution.

A Secure Approach for Caching Contents in Wireless Ad Hoc Networks

Caching aims to store data locally in some nodes within the network to be able to retrieve the contents in shorter time periods. However, caching in the network did not always consider secure storage (due to the compromise between time performance and security). In this paper, a novel decentralized secure coded caching approach is proposed. In this solution, nodes only transmit coded files to avoid eavesdropper wiretappings and protect the user contents. In this technique random vectors are used to combine the contents using XOR operation. We modeled the proposed coded caching scheme by a Shannon cipher system to show that coded caching achieves asymptotic perfect secrecy. The proposed coded caching scheme significantly simplifies the routing protocol in cached networks while it reduces overcaching and achieves a higher throughput capacity compared to uncoded caching in reactive routing. It is shown that with the proposed coded caching scheme any content can be retrieved by selecting a random path while achieving asymptotic optimum solution. We have also studied the cache hit probability and shown that the coded cache hit probability is significantly higher than uncoded caching. A secure caching update algorithm is also presented.

Opportunistic interference management: a new approach for multiantenna downlink cellular networks

A new approach for multiantenna broadcast channels in cellular networks based on multiuser diversity concept is introduced. The technique called opportunistic interference management achieves dirty paper coding capacity asymptotically with minimum feedback required. When there are K antennas at the base station with M mobile users in the cell, the proposed technique only requires K integer numbers related to channel state information between mobile users and base station. The encoding and decoding complexity of this scheme is the same as that of point-to-point communications, which makes the implementation of this technique easy. An antenna selection scheme is proposed at the base station to reduce the minimum required mobile users significantly at the expense of reasonable increase in feedback. In order to guarantee fairness, a new algorithm is presented that incorporates opportunistic interference management into existing Global System for Mobile communications GSM standard. Copyright

Secure coded caching in wireless ad hoc networks

A decentralized coded caching technique is introduced for wireless ad hoc networks in which all the existing contents are randomly combined and cached. The scaling behavior of the network is studied in terms of both capacity and security. Proactive and reactive routing techniques for coded caching are presented and the scaling capacity of the network for each case is derived. It has been shown that by using reactive routing, any content can be retrieved by selecting a random path while providing asymptotic optimum solution. The proposed coded caching significantly simplifies the routing protocol in cached networks. We further prove that asymptotic perfect secrecy can be achieved using proposed coded caching scheme.

Application of index coding in information-centric networks

The index coding problem relates to transmission policies when the source node broadcasts encoded data to users with side information. This paper extends the index coding problem to cases when the source node can reach users through multihop communications. The new approach is called Modified Index Coding (MIC) which can be applied to both wireless and wired networks. We demonstrate the benefits of our approach by applying MIC to Information-Centric Networks (ICN). We demonstrate that the combination of ICN and MIC requires a hybrid caching scheme that includes both central and distributed caching to support two different goals. The approach results in a combination of conventional caching in ICN and a new distributed caching scheme across nodes in the network. Our analysis demonstrates that capacity improvement can be achieved by the new architecture. Simulation results compare the capacity improvement to traditional ICN architecture.