Aura Ganz

Lightpath communications: an approach to high bandwidth optical WAN's

An architectural approach that meets high bandwidth requirements by introducing a communication architecture based on lightpaths, optical transmission paths in the network, is introduced. Since lightpaths form the building block of the proposed architecture, its performance hinges on their efficient establishment and management. It is shown that although the problem of optimally establishing lightpaths is NP-complete, simple heuristics provide near optimal substitutes for several of the basic problems motivated by a lightpath-based architecture. >

Packet scheduling for QoS support in IEEE 802.16 broadband wireless access systems

In this paper we introduce a scheduling algorithm and admission control policy for IEEE 802.16 broadband wireless access standard. The proposed solution which is practical and compatible to the IEEE 802.16 standard, provides QoS support to different traffic classes. To the best of our knowledge this is the first such algorithm. The simulation studies show that the proposed solution includes QoS support for all types of traffic classes as defined by the standard. We have shown the relationship between traffic characteristics and its QoS requirements and the network performance. Copyright

Ad hoc QoS on-demand routing (AQOR) in mobile ad hoc networks

We introduce a resource reservation-based routing and signaling algorithm, Ad hoc Qos on-demand routing (AQOR), that provides end-to-end quality of service (QoS) support, in terms of bandwidth and end-to-end delay, in mobile ad hoc networks (MANETs). The increasing use of MANETs for transferring multimedia applications such as voice, video and data, leads to the need to provide QoS support. To perform accurate admission control and resource reservation in AQOR, we have developed detailed computations that allow us to estimate the available bandwidth and end-to-end delay in unsynchronized wireless environment. AQOR also includes efficient mechanisms for QoS maintenance, including temporary reservation and destination-initiated recovery processes. The performance of AQOR is studied in detail by simulation using OPNET Modeler. The results validate that AQOR provides QoS support in ad hoc wireless networks with high reliability and low overhead.

A mobile teletrauma system using 3G networks

This paper introduces a cost-effective portable teletrauma system that assists health-care centers in providing prehospital trauma care. Simultaneous transmission of a patients video, medical images, and electrocardiogram signals, which is required throughout the prehospital procedure, is demonstrated over commercially available 3G wireless cellular data service. Moreover, the physician can remotely control the information sent from the patient side. Such a technology will allow a trauma specialist to be virtually present at the remote location and participate in prehospital care, which improves the quality of trauma care and can potentially reduce mortality and morbidity. To alleviate the limited and fluctuant bandwidth barriers of the wireless cellular link, the system adapts to network conditions through media transformations, data prioritization, and application-level congestion control methods. Experimental evaluation of the system prototype over real network conditions, transmitting different media types between the trauma patient and hospital unit, is encouraging. The teletrauma system reported in this paper is the first of its kind and it provides a basis for future enhancements.

IEEE 802.16 based last mile broadband wireless military networks with quality of service support

Future Department of defense warfighting concepts leverage information superiority and will require vast improvements in information transfer in terms of higher bandwidth, Quality of Service (QoS) support and connection to a high speed backbone. The new IEEE 802.16 broadband wireless access system is a viable alternative that can meet such requirements. In addition, this network can be swiftly deployed to interconnect the military theater, emergency response, and disaster relief operations to the backbone. Due to the diverse multimedia traffic with different priorities and QoS requirements, it is a well know fact that it is imperative to provide QoS support in military networks. However, the IEEE 802.16 provides only signaling mechanisms, but does not specify any scheduling or admission control algorithms that ultimately provide QoS support. In this paper we introduce a new scheduling algorithm for IEEE 802.16 broadband wireless access standard. The proposed solution which is practical and compatible to the IEEE 802.16 standard, provides QoS support to different traffic classes. To the best of our knowledge this is the first such algorithm. The simulation studies show that the proposed solution includes QoS support for all types of traffic classes as defined by the standard. We have shown the relationship between traffic characteristics and its QoS requirements and the network performance. This study will help network architects to decide the system parameters as well as the kind of traffic characteristics for which the network can provide QoS support.

Lightnets: Topologies for High-speed Optical Networks

An inherent problem of conventional point to point WAN architectures is that they cannot translate optical transmis- sion bandwidth into comparable user available throughput due to the limiting electronic processing speed of the switching nodes. This paper presents a solution to WDM based WAN networks that addresses this limitation. The proposed Lightnet architecture trades the ample bandwidth obtained by using multiple wave- length for a reduction in the number of processing stages and a simplification of each switching stage, leading to substantially increased throughputs. The principle of the Lightnet architecture is the construction and use of a virtual topology network in the wavelength domain, embedded in the original network. This paper studies the em- bedding of virtual networks whose topologies are regular, using algorithms which provide bounds on the number of wavelengths, switch sizes, and average number of switching stages per packet transmission. Algorithms for the embedding of alternative regu- lar topologies are presented and their performance is evaluated. It is shown that compared to conventional network architectures, the Lightnets offer substantial performance gains in terms of increased throughput and smaller buffering requirements.

Purely optical networks for terabit communication

Emerging applications require a substantially higher bandwidth than the one offered by current networks. The authors propose a novel architectural approach that meets the high bandwidth requirements by introducing a communication architecture based on lightpaths, which are purely optical transmission paths in the network. Since lightpaths form the building block of the proposed architecture, its performance hinges on their efficient establishment and management. The authors shown that although the problem of optimally establishing lightpaths is NP-complete, distributed heuristics provide near-optimal solutions for several of the basic problems presented by the lightpath architecture.<<ETX>>

On optimal design of multitier wireless cellular systems

We present a general cell-design methodology for the optimal design of a multitier wireless cellular network. Multitier networks are useful when there are a multitude of traffic types with drastically different parameters and/or different requirements, such as different mobility parameters or quality-of-service requirements. In such situations, it may be cost-effective to build a multitude of cellular infrastructures, each serving a particular traffic type. The network resources (e.g., the radio channels) are then partitioned among the multitude of tiers. In general terms, we are interested in quantifying the cost reduction due to the multitier network design, as opposed to a single-tier network. Our study is motivated by the expected proliferation of personal communication services, which will serve different mobility platforms and support multimedia applications through a newly deployed infrastructure based on the multitier approach.

WDM passive star-protocols and performance analysis

A wavelength division multiplexing (WDM) transmissive star network is investigated, in which each node has one tunable transmitter with limited tuning capability and multiple fixed receivers. Two synchronous channel access protocols requiring no pretransmission penalty are considered: random access and fixed transmission scheduling. An efficient approximate analysis with drastically reduced computational complexity is presented. In spite of the reduced complexity, the presented approach produces very accurate results and can serve in producing the most cost-effective system design for given performance requirements.<<ETX>>

Channel allocation protocols in frequency-time controlled high speed networks

In conventional high-speed systems, the high ratio between the end-to-end propagation delay and the message transmission time severely restricts the system performance. Thus, the increase in channel bandwidth may be accompanied by only a marginal increase in actual system capacity. A combined frequency-time division-based control of the high-speed channel that significantly reduces this problem is proposed. The design of protocols subject to the unique channel control penalties of the resulting multichannel system is considered. The allocation of channels on a demand assignment basis is hindered in the multichannel configuration by the time penalty involved in locating an idle channel and by practical limitations on the transmit/receive multichannels mode interface. A new class of fixed allocation protocols is introduced in which the channel access is obtained without the aforementioned penalties. The protocols build on the allocation of source and destination oriented transmission rights, taking into account the implementation aspects of multichannel networks. It is shown that this class of protocols covers the whole range of random-access to fixed-channel-access control policies. An analytic approach for a uniform analytic treatment is introduced, showing the potential for a significant improvement in the system capacity and the average message delay. >