Abstract: The authors outline techniques for dealing with variable propagation conditions for single user channels. They perform comparisons of interference averaging and avoidance multiple access strategies for cellular systems, with capacity as a function of minimum acceptable signal to interference ratio. They discuss some interference suppression methods. Multiple base stations are presented as a means of further increasing capacity. Throughout all of the above, the discussion is centered on connection-oriented traffic such as voice and video, with communication mediated by a network of base stations. The authors then discuss three different personal communication systems being developed at UCLA, illustrating some of the design trade-offs available in achieving low power consumption, high spectral efficiency, and flexible network topology. They conclude with a summary of their perception of the system design choices available at the physical layer. >

Abstract: The present system is split into a physical layer (20), a data link layer, and a network layer (24). The data link layer is further split into three parts, namely, data link control (23), and two medium access control parts (DLC) (21 and 22). The DLC layer (23) is concerned with link establishment, release and maintenance. The lower MAC part (21) may exist in multiple instances, whereas the upper MAC part (22) is unique. Physically, the two MAC parts (21 and 22) are separated on the network side because the upper MAC part resides in a RNC while the lower part exists in each base station. The connectionless packet service (CLPS) entity (25.1) provides the packet radio service to the mobile user and the CLPS entity (25.2) on the netowrk side provides all facilities required for registration and authentication of mobile users, assigning and administrating their VCIs, and interfacing to a packet data network. The CLPS entities (25.1 and 25.2) use the logical link administrators (LLA) (26.x) to initially route messages via a regular dedicated control channel (DCCH) (27.x) to their peer entities. After the MS is attached to the PRCH, all messages exchanged between the CLPS entities (25.x) as well as user data packets are always directed via the respective PRCH (28.x). In this case, the control packets and user data packets are passed through the DLC (29.x) to the packet radio (PR) control entity (30.x). The packets are fragmented and protected with an error control code, e.g. a block code (BC), by a respective unit (31.x) for detecting transmission errors on the receiving side. Then they are convolutionally encoded, interleaved (IL) by the entity (32.x), and transmitted over the PDCH (33). On the receiving side the fragments are reconstructed from the received samples, reassembled to packets, and forwarded to the target CLPS entity (25.2). When the decoder (31.2) detects the receipt of an erroneous packet fragment, an automatic request for repetition (ARQ) scheme provided in the PR control requests its retransmission.

Abstract: To satisfy the needs of wireless data networking, study group 802.11 was formed under IEEE project 802 to recommend an international standard for wireless local area networks (WLANs). A key part of standard are the medium access control (MAC) protocols needed to support asynchronous and time bounded delivery of data frames. We conduct a performance evaluation of the asynchronous data transfer protocols that are a part of the proposed IEEE 802.11 standard taking into account the decentralized nature of communication between stations, the possibility of "capture", and presence of "hidden stations". We compute the system throughput and evaluate the fairness properties of the proposed MAC protocols and evaluate the impact of spatial characteristics on the performance of the system. Further, extensive numerical results are presented.

Abstract: An extender circuit provides a serial communication interface between an ATM layer and a PHY layer. The extender circuit includes a first circuit serially coupled to a second circuit. The first circuit is coupled to the ATM layer and communicates in parallel with the ATM layer. The first circuit is operable to receive a control signal from the ATM layer. The second circuit is coupled to the PHY layer and communicates in parallel with the PHY layer. The first circuit does not transmit the control signal to the second circuit. The second circuit regenerates the control signal at the PHY layer. The first circuit and the second circuit function in like manners. The first circuit receives a control signal generated by the ATM layer. The control signal may comprise a start of cell signal. The first circuit transmits a first sequence of signals to the second circuit. The second circuit detects the occurrence of the first sequence of signals and reproduces the control signal at the PHY layer when the first sequence of signals is not detected. The first sequence of signals may comprise an idle character. In another embodiment, the first circuit transmits a second sequence of signals to the second circuit. The second circuit reproduces the control signal at the PHY layer when the second circuit detects the first sequence of signals followed by the second sequence of signals.

Abstract: Abstmct Rednet provides portable computers with an incxpensivc wireless network connection It is designed to support seamless end-to-end communication using the Asynchronous Transfer Mode (ATM) Rednet uses a Iowpower infrared transceiver operating at 2-5 Mbps over a distance of 4 meters The link layer protocol supports link sharing and transport of ATM cells over the link Ceiling mounted base stalions in each room act as gateways between the infrared link and rhe wired network Rednet is designed to support user mobility, so that users can roam from room to room and access network services in a location independent manner The paper describes our infrared physical layer and link layer protocols, presents an ovcrview of protocols for dynamic address assignment and conncction management, and summarizes the status of the work

Abstract: A plurality of ATM layer receiving blocks to which different applications are allocated are provided for a physical layer receiving part receiving data from an ATM transmission line and carrying out prescribed physical layer processing. The plurality of ATM layer receiving blocks incorporate data from the physical layer receiving allocated thereto are supplied to execute prescribed ATM block only when data utilized by the applications layer processing, for transmitting the processed data to corresponding higher layer processing functional blocks. A plurality of ATM layer transmission blocks responsible for different applications are provided in parallel with each other and coupled to a common ATM layer transmission block for data communication between a terminal and a network data transmission line. Thus implemented is a generic interface between an ATM layer and a physical layer in a terminal-to-network interface unit in a network in which data communication is carried out in an asynchronous transfer mode.

Abstract: A resource model for modelling the resources of a telecommunication network that uses a number of different switching technologies. The resource model comprises three layers, a network layer (13), a node layer (14) and a component layer (15), each layer comprising resource objects (10, 11, 12). The resource objects of the network layer are encapsulated to applications (PSTN, B-ISDN) which use the network. The resource objects of the node layer are encapsulated to the resource objects of the network layer and the resource objects at the component layer are encapsulated to the resource objects of the node layer. The resource model comprises connection handling function (18, 19, 20A-C) for setting up connections in the telecommunication network. The functions are divided into function components. Function components (18) at the network layer operate on resource objects at the network layer only, function components (19) at the node layer operate on resource objects at the node layer only and function components (20A-C) at the component layer operate on resource objects at the component layer.

Abstract: An asynchronous transfer mode (ATM) segmentation and reassembly (SAR) chip is provided for interfacing a host computer with an ATM system having a physical layer (PHY) chip incorporating, for example, a Unified Test and Operations Physical Interface for ATM (UTOPIA) protocol. The PHY chip is capable of operating at both 155 Mbps and 622 Mbps data transmission rates. The UTOPIA protocol requires a clock which is provided by the SAR chip. In an exemplary embodiment described herein, the SAR chip is configured to accommodate both data transmission rates and to synthesize appropriate clock signals for driving the PHY chip which facilitate the clocking out of data and the sampling of data.

Abstract: In an asynchronous transfer mode (ATM) endnode a method is provided by which ATM cells can experience a small delay from the ATM layer to the PHY layer to transmission on the ATM network. Such an arrangement includes providing the endnode with an ATM layer, the ATM layer having a first-in-first-out (FIFO) queue for transmitting transmit ATM traffic, providing the endnode with a PHY layer, the PHY layer having a FIFO queue for receiving the transmit ATM traffic, providing an interface between the FIFO queue of the ATM layer and the FIFO queue of the PHY layer for the flow of the transmit ATM traffic, providing a signal in the ATM endnode, providing a state machine in the ATM endnode, the state machine monitoring the signal in the ATM endnode, stalling the transfer of the transmit ATM traffic from the FIFO of the ATM layer to the FIFO of the PHY layer over the interface when the signal and the state machine indicate that the FIFO of the PHY layer is full, and transmitting the transmit ATM traffic from the FIFO of the ATM layer to the FIFO of the PHY over the interface. By causing the ATM layer to generate/transfer a continuous stream of cells to the PHY layer, the method can provide cell time indications to allow the ATM layer to synchronize itself to the network.

Abstract: In the course of their efforts to upgrade the operating speed of Ethernet from 10 Mbps to 100 Mbps, the members of the IEEE 802.3~ 1OOBASE-T Task Force recognized that it was vital to preserve the media independent nature of Ethernet, but they also recognized that the mechanism by which this was accomplished at 10 Mbps was not up to the task. Thus, they set out to define a new Media Independent Interface (MII) which would allow the development of a family of specifications for operation over various types of network media.

Abstract: Fault-tolerance in fieldbus systems can be accomplished on different OSI layers. Nowadays most fieldbus systems supporting redundancy at the physical layer are based on layer 2 characteristics. Some examples like MIL-STD-1553B, Profibus, CAN, XR-III are presented at the beginning, giving an insight into the state of the art. A new approach for network redundancy is introduced, utilizing inherent fault-tolerance capabilities in the OSI reference model. In more detail we concentrate on Layer-4, the transport layer, which establishes a reliable end to end communication. Detecting duplicate data packets is a service provided in this layer and this service will be the basis for our thoughts about redundancy. An enhanced LONWORKS based network node is presented capable of handling multiple redundant communication media.

Abstract: A general analytical model is proposed to evaluate the performance of a mobile slotted ALOHA network. Near-far effects are incorporated in the model (in an approximate way) by considering a multi-group system. The model approximates the network behavior by an iterative solution between multiple one dimensional Markov chains, one for each group. The model is quite broadly applicable since (1) different physical layer parameters, such as modulation and coding, are abstracted by a set of conditional success probabilities, and (2) different groups can have different link layer parameters, such as the probabilities of packet generation and retransmission. As an example, a 5-group system with fading is used to illustrate the usefulness of the proposed model. The agreement between the analytical and simulation results is good. It is found that the impact of the fading effect on network performance depends on the significance of the near-far effect. The problem of unbalanced throughput between near and far groups is solved by assigning different retransmission probabilities to different groups.

Abstract: A class of multicast multihop lightwave networks (MLNs) is presented. These networks have a two-layered architecture, with the upper "logical layer" implemented electronically, and supported by an underlying "physical layer" implemented as a purely optical network. The unique feature studied is that the logical topology has a regular multicast structure, which is created through the use of optical multicast in the physical layer. It is shown that this type of logical topology yields networks which have significantly superior performance features, when compared with either purely optical networks, or with multihop networks based on point-to-point connections. Special regular logical topologies based on Kautz hypergraphs are used in designing the networks.

Abstract: Introduction to object-oriented programming introduction to layers services and interfaces statement of problem - layers, interfaces and protocols the framework asynchronous programming event sources and scheduling finite state machine implementation the physical layer finite state machines - the data link layer sliding window protocols and flow control error detection and error recovery.

Abstract: In this article, we present an overview of the physical layer specification of the emerging Asynchronous Transfer Mode (ATM) networks. These specifications concern the complete details of how to ship 53-byte ATM cells from Point A to Point B over a physical medium on a Local Area Network (WAN). While the task of defining the interfaces and line coding of the transceivers over different physical media is ongoing, the primary underlying theme has been the leveraging of existing standards and practices to the maximum extent possible.

Abstract: This paper proposes a physical layer structure that supports multiple timeslot operation for high speed packet radio services in the existing TDMA based cellular network, such as GSM/DCS1800. Different channel coding and interleaving schemes in combination with automatic retransmission request (FEC+ARQ) have been studied and the complexity of packet mobile terminals is discussed in terms of multiple timeslot operation and physical layer retransmission timing. The calculation methods and formulas of residual frame error rate (RFER), expected packet throughput and delay estimates of the proposed channel coding with ARQ are presented. Based on computer simulation results and using these formulas, we select the suitable combination of FEC+ARQ scheme.

Abstract: A network terminator with asynchronous mode of transfer to be incorporated into digital networks of integrated services of wideband in order to perform the functions of transmission convergency sublayer of the physical layer of said networks, by simultaneously and continuosly transferring a flow with asynchronous transfer mode to the physical layer of the synchronous digital hierarchy and vice versa, according to recommendations I432, G707, G708 and G709 of CCITT, generating and detecting alarms of physical layer of the route and of section of the synchronous digital hierarchy and of asynchronous transfer mode, providing statistics of service quality of links JDS and ATM.

Abstract: Survivability is an important factor in the evaluation and planning of the current and the future fiber optic based telecommunication network. We analyze the survivability for the telecommunication network by considering a layered network structure, which consists of the service layer, the logical layer, the transmission system layer, and the physical layer. In this study we suggest new network survivability evaluation and improvement models for the physical layer, which consider the capacity of links of the network as well as the topology of the network. The evaluation model is based on the multi-terminal network flow theory and the improvement model is based on decomposition technique.

Abstract: Real-time multimedia communication applications demand performance requirements which differ significantly from conventional data communication applications. Current local area networks (LANs) provide efficient transport for bursty data traffic; however, they cannot necessarily provide quality of service guarantees for real-time communications. In this work we introduce and investigate an experimental priority protocol for supporting real-time communication on Ethernet, a popular implementation of multiple-access broadcast bus LANs. We examine the new protocol, known as Priority Mode-CSMA/CD (PM-CSMA/CD), providing a high priority (HP) class with CSMA/CD employed for standard priority (SP) traffic. PM-CSMA/CD performance is examined through computer simulation of videotelephony workstations operating over the shared bus LAN. Over all observed traffic conditions, the priority protocol provides performance satisfying real-time packet transport requirements of audio and video streams. The primary advantage of our protocol over similar priority schemes is its physical layer compatibility with standard CSMA/CD. The protocol also provides improved channel utilization with increasing high priority load, with no penalty in SP class performance at low to medium network loads.

Abstract: To assure the interoperability, reliability and maintainability of a school district's network, certain standards should be established and followed. This article categorizes these standards and provides a list for designers and implementers. The standards were developed expressly for, and adopted by, the Pittsburgh Public Schools as district policy. The goal of this article is to provide a simple and concise set of standards that school districts can use to facilitate the process of designing and implementing electronic data networks. Such networks are likely to be in increasing demand as new resources and educational applications are developed for the global Internet and as wide area networking increasingly permeates the society at large. In planning the physical connectivity of a school district it is important to develop a broad view of the district's network architecture, including not only the infrastructure of the local area network and Metropolitan Area Network (MAN), but also the set of applications that will initially operate over the network. This ensures that the network will have adequate bandwidth for proposed applications, that these applications will be interoperable, and that sufficient funds will be available for all necessary hardware and software. * The Layered Approach Network design can be greatly simplified if one thinks of the network as a set of levels, with each level isolated from those above and below it, and communication to adjacent levels is through a well-defined interface. This architecture allows one to design elements of the network without having to worry about unexpected interactions, incompatibilities or inefficiencies. The idea of a layered architecture has been carried to a formal extreme in the International Standards Organization's (ISO's) definition of seven layers of network structure. Since the ISO definition is more formal than we need in this article, we simplify it by referring to three layers, each of which represents several ISO layers. The three layers are as follows: * Physical Layer. This refers to the physical medium through which signals are carried, be it copper wire, fiber optic cable or wireless transmissions. * Protocol Layer. This refers to protocols used to encapsulate information and present it to applications running on devices attached to the network. These protocols define a set of rules that enable different entities on the network to communicate with each other. * Application Layer. This refers to programs that run on computers attached to the network and provide specific tools or services to users of the network. * Physical Layer Currently, computer applications that operate on LANs in the school environment can be handled with inexpensive copper wiring. Present technology allows for operation at speeds of 10 million bits per second, and it is possible to install wiring capable of transmitting data at much higher speeds. A prudent recommendation is to use this type of wiring, known as Category 5 Twisted Pair wire. This choice combines economy of hardware and ease of installation with a reasonable allowance for future expansion. The wiring plant should be a structured one, with a central wiring closet to which classroom or office runs return. Large sites will require multiple closets connected by backbones, which can be constructed from either Category 5 copper or fiber optic cable. Sites of intermediate size may also be served economically with coaxial cable runs in some network segments. Each classroom should have a minimum of three network drops. These drops can accommodate three devices, including classroom telephones as needed. Rooms requiring e devices can use fan-out hardware to accommodate as many devices as might be desired. The choice of three drops is a compromise between convenience and cost and is based upon experiences with this wiring architecture in Pittsburgh and elsewhere. …

Abstract: Enhanced Queued Arbitrated (QA) Functions, which can support applications requiring bandwidth guarantees and delay limits on a DQDB subnetwork, are specified. Connection-Oriented Convergence Functions (COCFs) using the enhanced QA Functions, which are necessary to support connection-oriented service, are also specified.

Abstract: Within the European RACE project COBRA, the use of coherent technology in practical network environments is demonstrated. This is done through a number of demonstrator set-ups. Each of these demonstrators can be situated in a specific telecom domain (the core network, the subscriber loop, etc.) and exploits within its domain the benefits of present-day coherent technology. This paper presents one of these demonstrators, the BCPN (Business Customer Premises Network) field demonstration which is setup at the premises of the Dutch PTT in Leidschendam, and describes more specifically its control network and wavelength management system that has been developed at the University of Gent.

Abstract: Binary data is transmitted to a network physical layer from a media access controller (10) as a series of multibit nibbles and is encoded into a multi-level data stream (178) and split among a number of transmission channels (12). The multi-level signal is then translated at a receiver back into a binary data stream. In a specific embodiment, the symbol transmission frequency on each of the transmission channels (12) is at the same frequency as the nibbles transfer rate between the media access controller (10) and the physical layer.

Abstract: In this paper we address the problem of efficiently using the resources in the Digital European Cordless Telephone (DECT) System in multi-rate situations. We consider two type of users: high rate data traffic which needs more that one time slot per time frame and low rate voice traffic needing one time slot per time frame. The physical layer of the DECT system is reviewed as well as the threshold based policies for call admission. The threshold policies were implemented and the performance determined based on a cost function. The results were obtained for heavy, medium and light traffic loads. It was shown that an optimum threshold to minimize the loss function can be found. With the implementation of threshold policies, the system has also became more fair for the users.

Abstract: The requirement for a pan-European digital private mobile radio system has been recognized for some time and has resulted in a standardisation activity at the European Telecommunications Standards Institute (ETSI). The main technical features of the resultant European standard (TETRA) are outlined. The principle physical layer challenges which must be met in the design of terminal equipment are then discussed. >

Abstract: Technology that debuted in the public switched network has been moving, over recent years, into private networks. While there is no need to justify Wavelength Division Multiplexing (WDM) in the public switched network, which makes good use of higher capacity equipment, the cost effectiveness of private WDM networks is not at all clear. In this paper, we investigate of deploying WDM with Asynchronous Transfer Mode (ATM) networks. The WDM networks provide the physical layer; the ATM networks form a logical layer, using light paths from the WDM network. There are 4 different benefits to be derived from such an arrangement, including the possibility of reduced network cost. An algorithm for the design of logical networks is developed. This algorithm has been incorporated in the Intrepid network design tool.

Abstract: PURPOSE: To improve the band width in data transfer by providing a plurality of fiber links respectively having first and second end sections, a frame control circuit connected to a plurality of physical layer controllers, a frame transmission circuit, and a plurality of frame reception circuits connected to a processor. CONSTITUTION: Optical fiber links 142 and 144 transmit data packets to a host interface adapter 52 and optical fiber links 146 and 148 transmit data packets to a data moving device 48. Each of the links 142, 144, 146, and 148 is connected to physical, layer controller having first end sections 138 and 148 and opposed second end sections 174 and 176. A data transfer response is performed by connecting optical pipe frame control circuits 132 and 178, frame transmission circuits 128 and 202, and frame reception circuits 156 and 184 to the physical layer controllers. Therefore, the data transferring band can be improved.

Abstract: PURPOSE: To transmit information elements in the form of cell based on ATM standard on a network concerning a device for measuring the connection performance of ATM type telecommunication network by testing that network. CONSTITUTION: This device is provided with a transmitter equipped with a device for forming a physical layer and a device for forming an ATM transport layer organized into virtual path/virtual channel (VP/VC) and a receiver equipped with a device for processing signals in the physical layer and a device for processing the stream of cells in the ATM transport layer. Therefore, this device is applied to telecommunication in ATM.