Michael N. Koukias

An ON-OFF Multi-Rate Loss Model of Finite Sources

Bursty traffic is dominant in modem communication networks and keeps the call-level QoS assessment an open issue. ON-OFF traffic models are commonly used to describe bursty traffic. We propose an ON-OFF traffic model of a single link which accommodates service-classes of finite population (f-ON-OFF). Calls compete for the available link bandwidth under the complete sharing policy. Accepted calls enter the system via state ON and then may alternate between ON-OFF states. When a call is transferred to state OFF it releases the bandwidth held in state ON, while when a call tries to return to state ON, it re-requests its bandwidth. If it is available a new ON-period (burst) begins; otherwise the call remains in state OFF (burst blocking). We prove that the proposed f-ON-OFF model has a product form solution, and we provide an accurate recursive formula for the call blocking probabilities calculation. For the burst blocking probabilities calculation we propose an approximate but robust formula. In addition, we show the relation between the f-ON-OFF model and other call-level loss models. Furthermore, we generalize the f-ON-OFF model to include service-classes of both finite and infinite population. Simulation results validate our analytical methodology.

e-SCP-ECG+ protocol: an expansion on SCP-ECG protocol for health telemonitoring—pilot implementation

Standard Communication Protocol for Computer-assisted Electrocardiography (SCP-ECG) provides standardized communication among different ECG devices and medical information systems. This paper extends the use of this protocol in order to be included in health monitoring systems. It introduces new sections into SCP-ECG structure for transferring data for positioning, allergies, and five additional biosignals: noninvasive blood pressure (NiBP), body temperature (Temp), Carbon dioxide (CO2), blood oxygen saturation (SPO2), and pulse rate. It also introduces new tags in existing sections for transferring comprehensive demographic data. The proposed enhanced version is referred to as e-SCP-ECG+ protocol. This paper also considers the pilot implementation of the new protocol as a software component in a Health Telemonitoring System.

ATM switch with multimedia traffic priority control

In this paper, a novel ATM switch with a dynamic multimedia traffic priority control scheme (HQMS: Hybrid combination of Queue Length Threshold and Minimum Laxity Threshold Scheme) is proposed. The ATM switch has the same basic topology as the Knockout switch, but employs a simpler N x L concentration scheme, which takes into account cells belonging to different priority levels. The structure of the switch supports two priority mechanisms. The first one is called priority discarding and acts as a local congestion control scheme within the switch fabric satisfying different cell loss requirements of different ATM traffic classes. The second one is called priority scheduling and uses two priority methods: a space priority method used for the control of the buffer space when an overflow condition occurs and/or when the expiration of the maximum admissible delay of the delay sensitive cells takes place and the service priority method which assigns transmission priorities to the buffered cells. A hardware implementation of the two priority mechanisms of the HQMS is presented. The performance of the switch has been studied by simulation, considering three ATM classes (video, data, voice) with different source models. The results have shown that for a large range of traffic load, the proposed HQMS satisfies the loss and delay requirements of the three classes.

Structuring the e-SCP-ECG+ protocol for multi vital-sign handling

Standard Communication Protocol for Computer-assisted Electrocardiography (SCP-ECG) has been standardized in order different ECG devices to be able to communicate with computers through the same language. This paper proposes specific extensions on SCP-ECG protocol structure and introduces the enhanced SCP-ECG+ (e-SCP-ECG+) protocol. e-SCP-ECG+ is backward compatible to the SCP-ECG protocol while it is able to handle more vital sign and demographic data. It also overrides some limits of the original protocol. The proposed extension has been implemented both as new tags in existing sections and as new sections of the SCP-ECG protocol appended to the original file format.

An ON-OFF multi-rate loss model with a mixture of service-classes of finite and infinite number of sources

We consider an ON-OFF traffic model of a single link which accommodates service-classes of finite population. Calls arrive according to a quasi-random process and, if accepted, enter the system via state ON; then calls may alternate between ON-OFF states. When a call is transferred to state OFF, it releases the bandwidth held in state ON, while when it tries to return to state ON it re-requests its bandwidth. If it is available a new ON-period (burst) begins; otherwise burst blocking occurs and the call remains in state OFF. We prove that the proposed finite source ON-OFF model (f-ON-OFF) has a product form solution and provide an accurate recursive formula for the call blocking probabilities calculation. For the burst blocking probabilities calculation we propose an approximate formula. Finally, we generalize the f-ON-OFF model to include a mixture of service-classes of finite and infinite number of sources. Simulation results validate our analytical methodology.

A novel dynamic priority scheduling method for multiple classes of ATM traffic in an ATM statistical multiplexer

The purpose of this paper is to propose a new priority scheduling method that dynamically manages four classes of ATM traffic and assigns different priority levels according to the QoS requirements of each class. Its performance has been studied by simulation under the application on an ATM statistical multiplexer. The results have shown that this scheme satisfies the loss and delay requirements of the ATM classes for a large range of traffic load.

Upgrading of cable line concentrators to accept ISDN subscribers

The upgrading of already installed μP-controlled Cable Line Concentrators (CLC) in order to accept N-ISDN subscribers is presented. The CLC is inserted in the Digital Transmision System (DTS) part of the ISDN subscriber access in such a way that no changes on the ISDN equipment are required. The necessary modifications of the CLC are limited to the replacement of the subscriber line interface modules and to the adaptation of the central control unit software in order to recognize and invoke specific wake-up signals. The proposed upgrading has been applied to a recently developed CLC for ISDN subscriber lines using the DTS 2B1Q.

The erlang multirate loss model under the threshold and Bandwidth Reservation policies

We consider a multirate loss model of a link that accommodates Poisson calls. Calls compete for the available link bandwidth under the combination of the Threshold (TH) and the Bandwidth Reservation (BR) policies. The TH policy limits calls of each service-class up to a threshold, which can be different for each service-class. The BR policy reserves part of the available link bandwidth to benefit calls of high bandwidth requirements. In the proposed model, the calculation of call blocking probabilities and link utilization is based on approximate, recursive formulas whose accuracy is verified through simulation and found to be quite satisfactory.