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Abstract — In future deployments of Vehicular Ad hoc Networks (VANETs) safety-related applications such as local danger warning (LDW) will use broadcast-based communication schemes to transmit information to other vehicles within the network. The unlimited flooding of a message throughout the whole network however, is neither feasible nor intended. The high resulting traffic load would congest the shared wireless medium and prevent other, potentially highly relevant and time-critical messages from getting access to the medium. Existing strategies to limit redundant packet retransmissions manage to make broadcast-based data packet dissemination more efficient and reliable. However, they do not take into account the individual network’s nodes interest in information. In fact, the static mechanisms proposed are not adequate to leverage the limited network resources as efficiently as possible in varying network conditions and to transport information to where it is needed as fast as possible. Therefore, we propose an altruistic communication scheme which differentiates data traffic according to the benefit it is likely to provide to potential recipients. A system for calculating and leveraging message benefit and two different node architectures are presented. With the help of a comprehensive simulation environment, the performance of our concept is analyzed. Comparative simulative studies show that an improvement of the benefit provided to all the participants in a VANET is also possible with the help of the readily available IEEE 802.11e standard, but to a lower extent. I.

This paper presents EARA-QoS, a improved version of swarm-intelligence inspired ad hoc routing algorithm EARA introduced in [11]. In this algorithm, we use the principle of swarm intelligence to evolutionally maintain routing information. The biological concept of stigmergy is used to reduce the amount of control traffic. A light-weight QoS scheme is proposed to provide service-classified traffic control. The simulation results show that this novel routing algorithm performs well in a variety of network conditions. 1

This paper examines a new mechanism for distributed resource reservation that offers support for applications with QoS requirements in a wireless multi-hop network. This mechanism is based on IEEE 802.11 DCF and includes end-to-end reservations of time slots and distribution of reservation information to mobile nodes unaware of the reservation, piggy-backed on existing medium access control messages.

The needs for run-time data storage in modern wired and wireless network applications are increasing. Additionally, the nature of these applications is very dynamic, resulting in heavy reliance on dynamic memory allocation. The most significant problem in dynamic memory allocation is fragmentation, which can cause the system to run out of memory and crash, if it is left unchecked. The available dynamic memory allocation solutions are provided by the real time Operating Systems used in embedded or general-purpose systems. These state-of-the-art dynamic memory allocators are designed to satisfy the run-time memory requests of a wide range of applications. Contrary to most applications, network applications need to allocate too many different memory sizes (e.g. hundreds different sizes for packets) and have an extremely dynamic allocation and de-allocation behavior (e.g. unpredictable webbrowsing activity). Therefore, the performance and the de-fragmentation efficiency of these allocators is limited. In this paper, we analyze all the important issues of fragmentation and the ways to reduce it in network applications, while keeping the

Abstract — Disaster areas are a typical usage scenario for mobile wireless communication systems (e.g. ad-hoc networks). Performance evaluation in mobile wireless communication systems is mainly done using simulation. Simulation results strongly depend on the traffic models used. Today, the traffic mainly used in disaster areas is voice traffic. In this paper, we present measurements of voice traffic done in a disaster area maneuver. Based on these measurements, we perform a statistical analysis of channel holding and interarrival times. We show that the traffic in disaster area scenarios has characteristics different from public mobile telephony systems. Thus, when simulating disaster area networks, different traffic characteristics should be assumed. With the results presented in this paper, it is possible to reach a realistic traffic for disaster area scenarios. I.

This paper deals with the characteristics of multicast push to talk voice traffic sources for disaster area scenarios. The goal is to design models that can be used to assign voice traffic sources to nodes. The modelling is based on an analysis of real-life measurements during a catastrophe maneuver. The analysis shows that about half of all calls originate from the communication head of a talk group. Based on this characteristic, different models are considered. Synthetic distributions of traffic sources for the different models are generated and evaluated by statistical analysis. Finally, the impact of the different models is evaluated in an exemplary simulative network performance analysis. 1

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