KEYWORDS: Networks, Telecommunications, Data modeling, Data transmission, Data communications, Wireless communications, Performance modeling, Internet, Transmitters
Recent and future communications networks have to provide QoS guarantees for a rapidly growing number of various telecommunications services. Therefore, various communications systems, such as wireless and fixed access networks, apply reservation MAC protocols, providing a good network utilization, which is particularly important access networks with typically limited data rates, and ensuring realization of different QoS guarantees for various telecommunications services. This is important because of a hard competition among communications technologies applied in the access area. The considered MAC protocols apply a per-packet reservation method to avoid the transmission gaps caused by per-burst reservation, and accordingly to achieve a better network utilization. However, the per-packet reservation increases the network load caused by the signaling, which calls for an efficient resource sharing strategy in the signaling channel. There are two basic solutions for capacity sharing in the signaling channel: random access, usually using slotted ALOHA, and dedicated access, realized by a polling method. Performance improvement of basic protocols can be carried out in different ways; by protocol extensions, a combination of different protocol solutions, and the application of adaptive protocols providing a change of access parameters according to the current network status. The best network performance is achieved by application of two-step reservation protocol, which combined with additional features, such as appropriate signaling procedure, priority and fairness mechanisms, and combined reservation domains, can fulfill requirements of services with high QoS demands.
KEYWORDS: Networks, Data modeling, Internet, Telecommunications, Data transmission, Performance modeling, Wireless communications, Automatic repeat request, Data analysis, Data communications
Recent and future communications networks have to provide QoS guarantees for a rapidly growing number of various telecommunication services, which can be ensured by application of an efficient MAC layer. Particularly, per-packet reservation MAC protocols are efficient ensuring a good network utilization and realization of QoS for various telecommunications services. However, per-packet reservation protocols suffers from an unfairness because network stations achieve different relative data throughput depending on the traffic characteristics of used services. A fair scheduling between network stations can be ensured if offered data rate per station is known, which is unfortunately not the case. In this investigation it is shown that the offered data rate can be successfully estimated by calculation of so-called effective requesting period per network station, which can be used for implementation of a fair scheduling mechanism. The results show a significant improvement of the fairness behavior in the network if the fair scheduling is applied.
Recent and future communications networks have to provide QoS guarantees for a rapidly growing number of various telecommunication services, which can be ensured by application of an efficient MAC layer. Various communication technologies, such as cellular networks and PLC (PowerLine Communications) access networks, apply reservation MAC protocols, providing a good network utilization and realization of different QoS guarantees. In this investigation, we analyze possibilities for provision of QoS guarantees for various telecommunications services with a two-step reservation MAC protocol using per-packet reservation principle, which is proposed for application in broadband PLC access networks. Particularly, performance of the reservation procedure is analyzed to provide priority mechanisms which are necessary for realization of various telecommunications services ensuring the required QoS guarantees. Since the telephony, realized by the packet voice service, has the strongest QoS requirements among various telecommunications services, we analyze possibility for its realization within the two-step MAC protocol. It can be concluded that the packet voice can be efficiently implemented. However, with application of a combined reservation domains for various service classes, network performance could be further improved.
Recent and future communications networks have to provide QoS guarantees for a rapidly growing number of various telecommunications services. This can be ensured by application of an efficient MAC layer. Various communications technologies, such as cellular networks and PLC access networks, apply reservation MAC protocols, providing a good network utilization, which is important for networks with limited data rate, and ensuring realization of different QoS guarantees. In this investigation, we compare the performance of so-called one-step reservation protocols, represented by slotted ALOHA and active polling, with a hybrid two-step reservation protocol. The protocols are investigated in their extended variants, including piggybacking, signaling over data channels and dynamic backoff mechanism. The protocols are implemented within a simulation model representing an OFDMA/TDMA scheme, which is outlined as a suitable solution for the PLC networks. Nevertheless, the achieved results can be generalized and interpreted for any other multiple access schemes, as well as for other communications technologies. To observe networks with different subscriber behavior, we define a traffic mix representing internet based data traffic, which is mainly expected in the access networks, such as PLC. As expected, the two-step protocol achieves always the best performance, compared with both one-step protocols. On the other hand, the fairness between the subscribers belonging to the same traffic class is ensured in all three investigated MAC protocols. However, a performance variation can be observed between different traffic classes.
We study the error handling methods and their integration with the MAC layer to be applied to a broadband powerline communications (PLC) access network. Because of the expected unfavorable noise influence in PLC systems, various error handling mechanisms have to be applied in different network layers. On the other hand, PLC networks have to provide various telecommunication services and to ensure sufficient QoS, which is important for the competition with other communication technologies used in the access area. Therefore, we propose application of efficient reservation MAC protocols ensuring realization of QoS guarantees and providing a good utilization of a shared medium with limited transmission capacity like in PLC networks. We consider several error protection methods against disturbances for data transmission and implement them within an extended two-step reservation MAC protocol with active polling. Simulation results show that application of a fast —re-signaling procedure reduces signaling delay in disturbed networks. On the other hand, application of ARQ mechanisms improves the network utilization and data throughput significantly and reduces the packet transmission delays. However, the combination of ARQ mechanisms and a per-packet reservation MAC protocols causes so-called transmission gaps (unused portions ofthe network capacity). Therefore, we implement an ARQ-plus mechanism which avoids the transmission gaps and improves furthermore the network performances.
We study the MAC layer of powerline communications (PLC) transmission systems applied to telecommunication access networks. PLC networks have to operate with a limited signal power which makes them more sensitive to disturbances from the electrical power supply grid and from the network environment. Well-known error handling mechanisms can be applied to the PLC systems to solve the problem of transmission errors caused by the disturbances (e.g. FEC and ARQ). However, the use of this mechanisms consumes a part of the transmission capacity and therefore decreases the already limited net data rate of the PLC systems. Because of the limited bandwidth, PLC networks have to provide a very good network utilization. Also a sufficient QoS is required, which can be reached by usage of efficient methods for the network capacity sharing - MAC protocols. The impulsive noise influences very much the error-free transmission. Therefore, this investigation includes modeling of several disturbance scenarios, too. We propose the reservation MAC protocols to be applied to the PLC access networks, because they are suitable to carry hybrid traffic with variable data rates ensuring a high network utilization. The analysis of the basic reservation protocols shows that the ALOHA random protocol can not deal with frequent transmission demands but it is more robust against disturbances than the polling based access protocol. The ALOHA protocol can be improved by the piggybacking method which degrades the collision probability and accordingly, shorts access delay. The polling protocol is extended with insertion of a contention component building a hybrid access method, which makes the access delays shorter, if there is a small number of stations in the network. Generally, the problems caused by the frequent transmission requests remain in all investigated access methods. However, the ALOHA based protocols show worst behavior in this case.
KEYWORDS: Networks, Photonic integrated circuits, Telecommunications, Data transmission, Data modeling, Orthogonal frequency division multiplexing, Internet, Power supplies, Signal to noise ratio, Performance modeling
The usage of electrical power distribution networks for voice and data transmission, called Powerline Communications, becomes nowadays more and more attractive, particularly in the telecommunication access area. The most important reasons for that are the deregulation of the telecommunication market and a fact that the access networks are still property of former monopolistic companies. In this work, first we analyze a PLC network and system structure as well as a disturbance scenario in powerline networks. After that, we define a logical structure of the powerline MAC layer and propose the reservation MAC protocols for the usage in the PLC network which provides collision free data transmission. This makes possible better network utilization and realization of QoS guarantees which can make PLC networks competitive to other access technologies.
KEYWORDS: Asynchronous transfer mode, Switches, Local area networks, Networks, Systems modeling, Virtual colonoscopy, Computer simulations, Multiplexing, Control systems, Receivers
Future high-speed networks will be very complex and use many sophisticated traffic control mechanisms. This paper investigates the performance of interactive TCP services over large scale ATM networks with many TCP connections by means of simulation. A simulation environment has been developed, which allows the automatic creation of large simulation scenarios on the basis of a tabular description.
KEYWORDS: Transmitters, Receivers, Networks, Local area networks, Data modeling, Instrument modeling, Systems modeling, Chlorine, Computer simulations, Multiplexers
We present a simulation study of WWW traffic over a DQDB network running the TCP/IP protocol stack. All network and protocol elements have been implemented in detail. A realistic DQDB network with 12 nodes and 24 access units is studied. QoS parameters of 552 TCP connections between end users are analyzed. Our traffic source model and its parameters has been chosen according to the characteristics of typical WWW traffic. We have analyzed several network models with different kinds of buffer management in the DQDB access unit. The influence of the buffer management on QoS parameters and transmission performance has been examined. In this paper we describe and compare the results of our investigations for two types of the access unit; with separate buffer management and with shared buffer management. Simulation results for the throughput of the DQDB busses and the loss of IP packets in the DQDB network are given. TCP throughput and transmission times at two protocol levels are measured. Our results show a good utilization of the DQDB network for both types of access units studied.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.