Proposing an Effective Retransmission Using the Relaying Nodes for Multihop Networks

Coop MAC has been recently proposed as a possible implementation of cooperation protocols in the medium access control (MAC) layer of a wireless network. However, some nodes may refrain from cooperation for selfish purposes, e.g. in order to save energy, in what is called selfish behavior or misbehavior. This protocol violation worsens other nodes’ performance and can be avoided if other nodes detect and punish (e.g. banning from the network) misbehaving nodes. However, fading and interference may prevent nodes from cooperating even if they are willing, therefore it is not trivial to identify misbehaving nodes. In a fading scenario where an automatic repeat request (ARQ) protocol is used, we propose a mechanism that allows detecting misbehaving nodes. Two approaches, either based on the uniformly most powerful (UMP) test or on the sequential probability ratio test (SPRT) are considered. The two techniques are characterized and compared in terms of their average detection delay and resulting network performance. Index Terms: Ad-hoc networks, cooperative diversity, medium access control, MIMO systems, security, privacy, and authentication

Virtual mobility to improve cooperation in mobile ad hoc networks

We study the impact of mobility on the level of cooperation between mobile nodes in a mobile ad hoc network. In a mobile ad hoc network, if the nodes are static or have a reduced mobility and if some nodes adopt a selfish behaviour, the performance of the network is affected. This is because the same nodes that are relaying the packets. On the other hand, nodes with a significant mobility affect the network topology, hence the traffic often changes routes and the probability that nodes that are not selfish relay packets is better. We exploit the advantage that the mobility provides on cooperation to propose a solution with mechanisms that generate virtual mobility in a static network or with a reduced mobility, so it seems like a dynamic network

Distributed Relay Selection and Power Allocation Using Stackelberg and Auction Games in Multi-user Multi-relay Networks

This paper focuses on the problem of distributed relay selection and power allocation problem in a multi-user multi-relay network, aims to maximize users’ achievable rate while consume less power of relays which are selected for helping users transmit information. At first, we use the auction game theory to choose the relays for each user preliminarily, then for each user and the selected relays, we model the interaction between them as a two-level Stackelberg game, the relays modeled as the service provider and the users modeled as customers who will buy power from the providers. Based on this game model, we get the relays at relatively better locations for each user and the optimal power need to buy from them. Otherwise, as the users will not exchange information between themselves, we recalculate the power allocated to each user for relays the power users buy from it exceeds the maximizing transmit power. Simulation results show the effectiveness of our proposed scheme

Performance analysis of collaborative hybrid-arq protocols over fading channels

Impairments due to multipath signal propagation on the performance of wireless communications systems can be efficiently mitigated with time, frequency or spatial diversity. To exploit spatial diversity, multiple-antenna technology has been thoroughly investigated and emerged as one of the most mature communications areas. However, the need for smaller user terminals, which results in insufficient spacing for antenna collocation, tends to limit the practical implementation of this technology. Without compromising terminal dimensions, future wireless networks will therefore have to exploit their broadcast nature and rely on collaboration between single-antenna terminals for exploiting spatial diversity. Among cooperative schemes, Collaborative ARQ transmission protocols, prescribing cooperation only when needed, i.e., upon erroneous decoding by the destination, emerge as an interesting solution in terms of achievable spectral efficiency. In this thesis, an information theoretical approach is presented for assessing the performance of Collaborative Hybrid-ARQ protocols based on Space-Time Block Coding. The expected number of retransmissions and the average throughput for Collaborative Hybrid-ARQ Type I and Chase Combining are derived in explicit form, while lower and upper bound are investigated for Collaborative Hybrid-ARQ Incremental Redundancy protocol, for any number of relays. Numerical results are presented to supplement the analysis and give insight into the performance of the considered scheme. Moreover, the issue of practical implementation of Space-Time Block Coding is investigated

Content Discovery and Caching in Mobile Networks with Infrastructure

We address content discovery in wireless networks with infrastructure, where mobile nodes store, advertise, and consume content while Broker entities running on infrastructure devices let demand and offer meet. We refer to this paradigm as match-making, highlighting its features within the confines of the standard publish-and-subscribe paradigm. We study its performance in terms of success probability of a content query, a parameter that we strive to increase by acting as follows: 1) We design a credit-based scheme that makes it convenient for rational users to provide their content (thus discouraging free-riding behavior), and it guarantees them a fair treatment. 2) We increase the availability of either popular or rare content, through an efficient caching scheme. 3) We counter malicious nodes whose objective is to disrupt the system performance by not providing the content they advertise. To counter the latter as well as free riders, we introduce a feedback mechanism that enables a Broker to tell apart well- and misbehaving nodes in a very reliable manner, and to ban the latter. The properties of our match-making scheme are analyzed through game theory. Furthermore, via ns-3 simulations, we show its resilience to different attacks by malicious users and its good performance with respect to other existing solution

Cooperative Energy-efficient Management of Federated WiFi Networks

The proliferation of overlapping, always-on IEEE 802.11 access points (APs) in urban areas, can cause inefficient bandwidth usage and energy waste. Cooperation among APs could address these problems by allowing underused devices to hand over their wireless stations to nearby APs and temporarily switch off, while avoiding to overload a BSS and thus offloading congested APs. The federated house model provides an appealing backdrop to implement cooperation among APs. In this paper, we outline a distributed framework that assumes the presence of a multipurpose gateway with AP capabilities in every household. Our framework allows cooperation through the monitoring of local wireless resources and the triggering of offloading requests toward other federated gateways. Our simulation results show that, in realistic residential settings, the proposed framework yields an energy saving between 45 and 86 percent under typical usage patterns, while avoiding congestion and meeting user expectations in terms of throughput. Furthermore, we show the feasibility and the benefits of our framework with a real test-bed deployed on commodity hardware