Wim Torfs

QoS-enabled Internet-on-train network architecture: inter-working by MMP-SCTP versus MIP

Internet-on-the-train is a rising concept in the last few years. Several trials in different countries have proved the feasibility of offering Internet access to train commuters, but none of them combines broadband access, scalability, seamless handover and quality of service guarantees in one solution. In this paper, we propose a new architecture to satisfy these needs. Using real handover measurement data of several common broadband wireless technologies, we compare two possible inter-working mobility solutions: Mobile Multi-Path SCTP (MMP-SCTP) and Mobile IP (MIP).

An analysis of asynchronism of a neighborhood discovery protocol for cognitive radio networks

Due to the changing network topology and the time and location varying spectrum availability in Cognitive Radio Networks (CRNs), there is a need of on-demand searching for a control traffic channel by CR users in order to be able to initiate a communication. This neighborhood discovery phase, also referred to as a rendezvous (RDV) phase, is challenging due to the dynamics of CRNs. There are a number of different proposed solutions (pseudo-random or systematic approaches such as quorum systems) to tackle this issue, however, not so many elaborate on the asynchronous character of CRNs, and even less taking into account channel heterogeneity in terms of quality. In this study, on the one hand, we propose a novel quorum system-based neighborhood discovery protocol, which operates on channels having different priorities, on the other hand, we perform an analysis of the effect of asynchronism on the proposed protocol. We analyze the behavior of the protocol in terms of rendezvous opportunities, time-to-rendezvous, and the measured error margins for both, for different asynchronous offsets. We show that an asynchronism can bring noticeable profits over the slot synchronized case.

Benefiting from an induced asynchronism in neighborhood discovery in opportunistic cognitive wireless networks

In opportunistic Cognitive Radio Networks (CRNs), which are characterized by changing network topology, the time and location varying spectrum availability, there is a need of on-demand searching for a control traffic channel by cognitive radio (CR) users in order to be able to initiate a communication. Therefore, the neighborhood discovery phase, also referred to as a rendezvous (RDV) phase, is challenging due to the dynamics of such networks. Lately, there has been a proliferation of different rendezvous protocols. However, mostly the proposed protocols have had a narrow focus, which is usually a RDV guarantee in a single cycle. At times there is support for a RDV guarantee on every unoccupied channel in a single cycle, however, very rarely asynchronism is exploited as a main factor, or considering channel heterogeneity in terms of quality. In this study we show how to add and benefit from asynchronism in neighborhood discovery protocols that already guarantee a RDV on each free channel. Thanks to induced asynchronism, the ranking of channels is introduced, allowing nodes to stay longer on better quality channels. We analyze the behavior of three different rendezvous protocols in terms of efficiency and time-to-rendezvous with the measured error margins for different asynchronous offsets. We show that an asynchronism significantly improves the efficiency of all the studied protocols. The goal of this paper is not to proof that one particular protocol is better than another, we aim only to show that the added asynchronism and induced ranking of channels can improve significantly the performance of different rendezvous protocols.

Multimedia multicast performance analysis for 802.11n network cards

The technical evolution of Wi-Fi networks has made it possible to attain very high speeds for delivering content to users. However multicast transmissions never received the same level of attention as unicast transmissions in the IEEE802.11n standard. In this paper, we experimentally assess the viability of employing commercially available IEEE802.11n hardware to multicast real-time multimedia content, requiring high bandwidth and low delay. We verify the performance of the leader based multicast scheme and compare it to the standard multicast scheme.

SCTP as mobility protocol for enhancing internet on the train

Internet-on-the-train is a rising concept in the last few years. Several trials in different countries have proved the feasibility of offering Internet access to train commuters, but none of them combines broadband access, scalability, seamless handover and quality of service guarantees in one solution. In this paper, we look at the features of SCTP and its extensions which could overcome these shortcomings and which were successfully demonstrated.

AND: Asynchronous neighborhood discovery protocols for opportunistic cognitive wireless networks

A neighborhood discovery (ND), also referred to as a rendezvous (RDV), is a challenging and fundamental phase in opportunistic Cognitive Radio Networks (CRNs) due to changing network topology, the time and location varying spectrum availability and different channel qualities. Simplified solutions, such as, a central controller or common control channel are not feasible in opportunistic CRNs. Therefore, in order to be able to initiate a communication, there is a need of on-demand searching for a control traffic channel by cognitive radio (CR) users, usually working in an asynchronous manner. To meet these challenges we propose an asynchronous neighborhood discovery (AND) for opportunistic CRNs, which takes into account the asynchronous character of CRs, different channel ranks, as well as heterogeneous channel availability.

Binary TDMA scheduler by means of egyptian fractions for real-time WSNs on TMotes

In Wireless Sensor Networks (WSNs), the user should not be bothered with configuring the network, depending on the kind of sensors that he/she is using. It should only be a matter of deploying the sensors and they should do the necessary effort to construct a network. Since most of these networks use low power devices, the energy consumption is vital. The most suited medium access method in order to waste as few energy as possible, is Time Division Multiple Access (TDMA). TDMA has however the reputation of being a rigid access method. In this paper, we present a TDMA access method for passive sensors, i.e. sensors are constant bitrate sources. The presented protocol does not only take into account the energy, but it also ensures that every sensor gets its data on time at the sink and this in a fair fashion. Even more, the latency of the transmission is deterministic. We could say that real-time communication is possible. The protocol is developed keeping in mind the practical limitations of actual hardware by limiting the memory usage and the communication overhead. The schedule that determines which sensor can send when, which can be encoded in a very small footprint, and needs to be sent only once. To prove our statement, we implemented our scheduling protocol on TMotes.

WBAN Implementation on Magnetic Induction Radio IC for Medical Remote Monitoring

The medical service environment is changing. There is a need for automatization of collecting medical data remotely from the patient. Telecare is the continuous remote monitoring of the health of the patient. The IM3 (interactive mobile medical monitoring) project focuses on developing and implementing such end-to-end service. We implemented the WBAN (wireless body area network) protocol on the magnetic induction radio IC (integrated circuit), which is designed by NXP Semiconductors. We show in this paper that we have a working setup, where nodes form autonomously the network and send ECG data to the sink.

How to be an efficient asynchronous neighbourhood discovery protocol in opportunistic cognitive wireless networks

In opportunistic cognitive radio networks CRNs there is a need of on-demand searching for a control traffic channel by cognitive radio CR users in order to be able to initiate a communication. The neighbourhood discovery ND phase is challenging due to the dynamics of such networks. Lately, there has been a proliferation of different RDV protocols. However, most protocols have a narrow focus, which is usually a RDV guarantee in a single cycle. Very rarely asynchronism is exploited as a main factor, or considering channel heterogeneity in terms of quality. In this study we show how to add and benefit from an asynchronous RDV extension and its enhancement. Thanks to induced asynchronism, the ranking of channels is introduced, allowing nodes to stay longer on better quality channels. We analyse the behaviour of different selected ND protocols in terms of time-to-rendezvous and normalised RDV. We show that an asynchronism significantly improves the efficiency of the studied protocols.

Analysis of TDMA scheduling by means of Egyptian Fractions for real-time WSNs

In Wireless Sensor Networks (WSNs), Time Division Multiple Access (TDMA) is a well-studied subject. TDMA has, however, the reputation of being a rigid access method and many TDMA protocols have issues regarding the entering or leaving of sensors or have a predetermined upper limit on the number of nodes in the network. In this article, we present a flexible TDMA access method for passive sensors, that is, sensors that are constant bitrate sources. The presented protocol poses no bounds on the number of nodes, yet provides a stable framing that ensures proper operation, while it fosters that every sensor gets its data on time at the sink and this in a fair fashion. Even more, the latency of the transmission is deterministic and thereby enabling real-time communication. The protocol is developed, keeping in mind the practical limitations of actual hardware, limiting the memory usage and the communication overhead. The schedule that determines when a sensor can send can be encoded in a very small footprint and needs to be sent only once. As soon as the sensor has received its schedule, it can calculate for the rest of its lifetime when it is allowed to send.