The devices surrounding us become smarter and can autonomously form a network without requiring our intervention. However, our needs can be even better accommodated when the networked devices cooperate and complement each other’s capabilities. One of the initial steps towards achieving a cooperative platform of smart devices is the discovery of resources and capabilities within the network. Today’s operational service discovery protocols carry simple text-based uniform resource identifiers that are not expressive enough. Machines cannot comprehend the meaning of a new service that is not in their knowledge base. In addition to being more expressive, service discovery protocols must compensate the diversity to improve cooperation between the devices that use different application protocols and operate on different communication interfaces. In this paper, we propose the Smart Discovery Protocol (SDP) which outperforms the operational service discovery protocols with three main features: (1) more expressive semantic representation of the services, (2) operating in the network layer to deal with diversity, and (3) unifying existing service discovery protocols. SDP represents services with ontologies as some recently proposed semantic service discovery protocols. It further enhances the success of semantic representations by creating a unified platform that can carry legacy discovery services. In this respect, the novelties of SDP are as follows: firstly, it operates in the network layer and consequently abstracts both the application layer and communication interfaces. Secondly, SDP unifies the legacy service discovery protocols by integrating their simple text-based service representations in one message. The underlying transport mechanism of SDP is designed as an add-on to the Neighbor Discovery Protocol (NDP) of the IPv6 standard. The metadata is carried in the payload of ICMPv6 packets. Simple text-based representations of other service discovery protocols are embedded in type-length-value options of NDP. Authenticity of the devices is ensured by the IPv6 Secure Neighbor Discovery protocol. Unlike previous semantic approaches on service discovery, we have implemented our protocol on real hardware. The results demonstrate the feasibility of carrying semantic representations of the services and integration of other service discovery protocols.@en

Cooperation is the foundation of wireless ad hoc networks with nodes forwarding their neighbors' packets for the common good. However, energy and bandwidth constraints combined with selfish behaviour lead to collapsed networks where all nodes defect. Researchers have tried to incentivize or enforce the nodes for cooperation in various ways. However, these techniques do not consider the heterogeneous networks in which a diverse set of nodes with different cognitive capabilities exist. Furthermore, in ad hoc networks identity is a fuzzy concept. It is easy to forge multiple identities and hide defective behaviour. Moreover, the nature of the wireless medium is always ambiguous due to collisions, interference and asymmetric links. In all this uncertainty, having complete information about the intentions of the nodes and acting on it is not straightforward. Backed by evolutionary game theory and multi-agent systems research, we adapt and modify two meta strategies to embrace this uncertainty. These modified meta strategies, Win Stay Loose Shift and Stochastic Imitate Best Strategy, do not require strict identity information and only depend on nodes' own capabilities. Nodes monitor the traffic in their neighbourhood by using a two-hop overhearing method, and decide whether they should be cooperative or defective. We show that nodes are able to discover and use the best strategy in their locality and protect themselves against the exploitation by free riders who devise Sybil attacks by changing their identities.@en

The 60 GHz technology has a great potential to provide wireless communication at multi-gigabit rates in future home networks. To maintain the network connectivity with 60 GHz links, which are highly susceptible to propagation and penetration losses, is a major challenge. The quality and the robustness of the 60 GHz links can be improved by employing relay nodes in the network. In this paper, the contribution of relaying to the connectivity and the quality of the 60 GHz radio links is studied by modeling three indoor scenarios. It is analytically and through simulations shown that having a relay node in a 60 GHz network decreases the average freespace path loss 33% in the worst case scenario. The effects of relay device position and the obstacle density on the improvement of the average received signal level are investigated with a verified 3D ray tracing tool. A comparative simulation study on the performance of different relay configurations under various network conditions is conducted. The results yield that even a single relay device positioned at the height of other nodes can improve 50% of the links in considerable levels in a 60 GHz indoor network. It is also shown that additional relay nodes do not contribute to 60 GHz indoor connectivity significantly, if there are two properly positioned relay devices in a network which is moderately populated.@en