Hans-Jürgen Reumerman

The application-based clustering concept and requirements for intervehicle networks

A new network clustering concept for foresighted driving applications is introduced, taking into account the specific requirements for highly dynamic intervehicle networks. Considering the initially low system penetration in the market, the concept includes the so-called message relay boxes without backbone network connection for temporary roadside storage of messages. The article differentiates between moving and quasi-stationary applications and explains how clusters tied to specific geographic locations leads to even more complicated mechanisms for topology management in clustered ad hoc networks. A proposed message handling algorithm for cluster establishment shows the complexity needed to guarantee overall data consistency and network reliability as required for safety-relevant cooperative systems.

Evaluation of Communication Distance of Broadcast Messages in a Vehicular Ad-Hoc Network Using IEEE 802.11p

Current research for vehicular communication is largely driven by the allocation of 75MHz spectrum in the 5.9GHz band for dedicate short range communications (DSRC) in North America. The IEEE 802.11p physical (PHY) layer and medium access control (MAC) layer that is currently under standardization aim at communication distances of up to 1000m. In this paper we evaluate the maximum communication distance of an IEEE 802.11p vehicular ad-hoc network including mobility effects and multi-path propagation. Furthermore the communication distance for different path loss exponents is evaluated.

Towards Broadband Vehicular Ad-Hoc Networks - The Vehicular Mesh Network (VMESH) MAC Protocol

The current medium access control (MAC) protocol of the wireless access in vehicular environments (WAVE) system is based on IEEE 802.11 distributed coordination function (DCF) and enhanced distributed channel access (EDCA), which have drawbacks in supporting throughput-sensitive non-safety applications in vehicular ad-hoc network (VANET). In order to address the problem, we propose a novel MAC protocol, namely vehicular MESH network (VMESH), which is specifically designed for the control channel (CCH) and multiple service channels (SCHs) structure of WAVE. A synchronized and distributed beaconing scheme is employed in the VMESH protocol for the purposes of neighborhood awareness and dynamic resource reservation on SCHs. The advantages of the VMESH protocol in supporting the throughput-sensitive non-safety applications in VANET are shown through the theoretical analysis comparing to the current WAVE MAC.

A Novel MAC Protocol for Throughput Sensitive Applications in Vehicular Environments

The current medium access control (MAC) protocol of the wireless access in vehicular environments (WAVE) system is based on IEEE 802.11 distributed coordination function (DCF) and enhanced distributed channel access (EDCA), which have drawbacks in supporting throughput-sensitive applications in high density networks, e.g. future vehicular ad-hoc networks (VANET). In order to address the problem, we propose a novel MAC protocol, namely vehicular MESH network (VMESH), which is specifically designed for the control channel (CCH) and multiple service channels (SCHs) architecture of WAVE system. A synchronized and distributed beaconing scheme is employed by the VMESH protocol for the purposes of neighborhood awareness and dynamic channel resource reservation. In this paper, we present the advantage of VMESH protocol under saturated traffic load condition through theoretical analysis. For more realistic scenarios with mobility and unsaturated traffic loads, through the simulative study, we can also show that the VMESH protocol outperforms the WAVE protocol when the traffic load is heavy.

Wireless local danger warning using inter-vehicle communications in highway scenarios

In this paper we proposed a novel self-organized message dissemination algorithm, namely the cluster-based broadcast (CB), for the emergency electronic brake light (EEBL) application in vehicular ad-hoc networks (VANET). The proposed cluster-based broadcast algorithm converts multihop broadcast message forwarding into multiple of single-hop broadcast clusters, which offers higher reliability, lower channel usage and message propagation delay in comparison with the traditional Directional Flooding (DF). Furthermore, we study the depedence of EEBL application on the market penetration ratio of the VANET wireless communication nodes. An innovative idea of combining the VANET with nomadic devices is proposed in this work to mitigate the slow market penetration rate problem. The results show that the nomadic devices, like portable navigation devices with communication ability, will play an important role when the VANET technology is rolling out in our real life.

Global Communications Newsletter - Paving the way for gigabit networking

Wired LANs soared to the gigabit level some years ago, and terabit networks are in place for wide area networking. However, in terms of data rate, wireless short-range networks tend to lag one generation behind wired LANs. The recent second generation of wireless short-range networks offers transmission rates of up to 54 Mb/s. The third wireless LAN generation is under development and will materialize in the IEEE 802.11n standard in about two years. IEEE 802.11n WLANs will offer a few hundred megabits per second, but the performance gap from wired networks remains. The recently started project Wireless Gigabit with Advanced Multimedia (WIGWAM) aims to close this gap with a heterogeneous 1 Gb/s fourth-generation system based on high-data-rate orthogonal OFDM transmission, MIMO, and efficient MAC protocol techniques.

OFDM-UWB Physical Layer Emulation for Event-Based MAC Simulation

Simulation is one possibility to assess the performance of new medium access protocols for wireless communications. While the new algorithms are usually implemented in a very realistic way, the physical layer is emulated as a simple model. Often, this simplification is invalid in complex scenarios, where interference and non line of sight conditions degrade the signal quality. A complete physical layer implementation including the error correction, modulation, channel equalization and different channel pulse responses is not feasible in a layer two simulator. Hence, its characteristic is mapped onto a computational efficient stochastical model. The presented method differs from other error models in the way it is enriched with data to compute the packet error rates: The physical layer under examination, the WiMedia OFDM ultra wideband physical layer, is simulated in a detailed physical simulator and the error rates are derived then using an error analysis

MIMO Link Modeling for System Level Simulations

MIMO (multiple input - multiple output) systems apply multiple antennas to increase signal to noise ratio (SNR), reduce interference and/or send multiple streams simultaneously over a single channel. Besides increasing the data rate of the physical layer (PHY), benefits can be achieved with cross-layer optimization approach exploiting the layered structure of the channel. In this paper we focus on MIMO schemes with multiplexing and/or diversity gain and present a link model for system level simulations. The model maps total SNR to achievable link level throughput, both per spatial subchannel and cumulative. The model can be combined with an arbitrary coding and modulation scheme and is abstract enough to be applied to any system protocol, fulfilling the given conditions about channel propagation characteristics

An Addressing Scheme to Support Untraceability in Mobile Ad Hoc Networks

The movement of nodes in mobile ad hoc networks can be inferred by inspecting unique addresses embedded into exchanged messages. If these addresses are fixed, tracing a message to a single source is trivial and movement can be easily uncovered by listening to transmissions in the area of interest. The ease in which such traces can be obtained creates a fertile environment for information misuse and privacy violation. In this paper, a scheme based on address randomization is proposed to reduce traceability in mobile ad hoc networks. The novel feature of the scheme consists of producing new addresses without disrupting communication that relies on keeping neighbor state. This feature is obtained by randomizing addresses progressively, bit by bit, until the desired uncorrelation between old and new address is obtained.

A packet switch with bufferless switch cards and partial distribution of VOQ-state information to parallel arbiters

The main problem of bufferless crosspoint switches is the realization of fast arbitration between the input and output ports. Keeping the arbitration simple and fast, a higher throughput can be achieved by using a number of switches in parallel. With increasing port speed the bandwidth needed to report input queue state information to the parallel arbiters poses a second problem. To avoid costly high-speed communication lines or large number of pins on the arbiter, this paper defines three different methods to reduce this bandwidth by informing the arbiters only partially of the states of the input queues. Simulations of these state distribution methods show a similar and under some conditions even better performance than for a reference method in which all arbiters are completely informed.