Showing papers on "Physical layer published in 2000"
TL;DR: In this paper, a simple but nevertheless extremely accurate, analytical model to compute the 802.11 DCF throughput, in the assumption of finite number of terminals and ideal channel conditions, is presented.
Abstract: The IEEE has standardized the 802.11 protocol for wireless local area networks. The primary medium access control (MAC) technique of 802.11 is called the distributed coordination function (DCF). The DCF is a carrier sense multiple access with collision avoidance (CSMA/CA) scheme with binary slotted exponential backoff. This paper provides a simple, but nevertheless extremely accurate, analytical model to compute the 802.11 DCF throughput, in the assumption of finite number of terminals and ideal channel conditions. The proposed analysis applies to both the packet transmission schemes employed by DCF, namely, the basic access and the RTS/CTS access mechanisms. In addition, it also applies to a combination of the two schemes, in which packets longer than a given threshold are transmitted according to the RTS/CTS mechanism. By means of the proposed model, we provide an extensive throughput performance evaluation of both access mechanisms of the 802.11 protocol.
8,863 citations
26 Mar 2000
TL;DR: It is demonstrated that even though DSR and AODV share a similar on-demand behavior the differences in the protocol mechanics can lead to significant performance differentials.
Abstract: Ad hoc networks are characterized by multi-hop wireless connectivity, frequently changing network topology and the need for efficient dynamic routing protocols. We compare the performance of two prominent on-demand routing protocols for mobile ad hoc networks - dynamic source routing (DSR) and ad hoc on-demand distance vector routing (AODV). A detailed simulation model with MAC and physical layer models is used to study inter-layer interactions and their performance implications. We demonstrate that even though DSR and AODV share a similar on-demand behavior the differences in the protocol mechanics can lead to significant performance differentials. The performance differentials are analyzed using varying network load, mobility and network size. Based on the observations, we make recommendations about how the performance of either protocol can be improved.
1,989 citations
TL;DR: The network architecture, based on Internet protocols adapted to the mobile environment, is described, followed by a discussion of economic considerations in comparison to cable and DSL services.
Abstract: This article presents an approach to providing very high-data-rate downstream Internet access by nomadic users within the current CDMA physical layer architecture. A means for considerably increasing the throughput by optimizing packet data protocols and by other network and coding techniques are presented and supported by simulations and laboratory measurements. The network architecture, based on Internet protocols adapted to the mobile environment, is described, followed by a discussion of economic considerations in comparison to cable and DSL services.
1,431 citations
TL;DR: In this article, the authors discuss packet data transmission rates of 2-5 Mbps in macrocellular environments and up to 10 Mbps in microcellular and indoor environments as a complementary service to evolving second-and third-generation wireless systems.
Abstract: The rapid growth of wireless voice subscribers, the growth of the Internet, and the increasing use of portable computing devices suggest that wireless Internet access will rise rapidly over the next few years. Rapid progress in digital and RF technology is making possible highly compact and integrated terminal devices, and the introduction of sophisticated wireless data software is making wireless Internet access more user-friendly and providing more value. Transmission rates are currently only about 10 kb/s for large cell systems. Third-generation wireless access such as WCDMA and the evolution of second-generation systems such as TDMA IS-136+, EDGE, and CDMA IS-95 will provide nominal bit rates of 50-384 kb/s in macrocellular systems. This article discusses packet data transmission rates of 2-5 Mb/s in macrocellular environments and up to 10 Mb/s in microcellular and indoor environments as a complementary service to evolving second- and third-generation wireless systems. Dynamic packet assignment for high-efficiency resource management and packet admission; OFDM at the physical layer with interference suppression, space-time coding, and frequency diversity; as well as smart antennas to obtain good power and spectral efficiency are discussed in this proposal. Flexible allocation of both large and small resources also permits provisioning of services for different delay and throughput requirements.
370 citations
TL;DR: A shaping scheme to set the offset, an important system parameter for OBS, between the successive data bursts of a given data stream and their associated control packets results in robust operation of the network and also facilitates traffic engineering.
Abstract: Wavelength-division multiplexing has emerged as an important physical layer technology Optical transmission provides a physical layer capable of carrying bits at the speed at the order of a gigabit per second Optical burst switching is proposed to overcome the shortcomings of conventional WDM deployment, such as lack of fine bandwidth granularity in wavelength routing and electronic speed bottlenecks in SONET/SDH We describe an architecture for IP network over the OBS WDM transmission core The use of MPLS-type technique for forwarding data bursts and the inclusion of a medium access control layer between the optical (WDM) and IP layers are the key ingredients of the proposed architecture In particular, the architecture is based on provisioning MPLS paths, also called label switched paths, of desired quality of service through the OBS WDM transmission core The MAC layer performs various OBS-specific functions, such as burst assembly, burst scheduling, and offset setting/traffic shaping While burst assembly and burst scheduling are relatively straightforward, we point out that the offset setting strategy has significant impact on the performance of IP network operating over OBS WDM core We describe a shaping scheme to set the offset, an important system parameter for OBS, between the successive data bursts of a given data stream (label switched path) and their associated control packets This scheme results in robust operation of the network and also facilitates traffic engineering Guidelines are provided for implementing various IP QoS mechanisms in the optical backbone using OBS
293 citations
TL;DR: Optical CDMA is shown to be competitive with other networking technologies such as WDMA and TDMA, but has the benefit of more flexibility, simpler protocols, and no need for centralized network control.
Abstract: Asynchronous, high-speed multiple-access is proposed as a natural solution to achieving asynchronous, high-speed connectivity in a local area network environment. Optical CDMA is shown to be competitive with other networking technologies such as WDMA and TDMA, but has the benefit of more flexibility, simpler protocols, and no need for centralized network control. The limitations of one-dimensional optical orthogonal codes for CDMA have motivated the idea of spectral spreading in both the temporal and wavelength domains. If the constraints on constant weight in these two-dimensional codes are relaxed, differentiated levels of service at the physical layer become possible. Areas for further research are suggested which may allow quality of service levels to be guaranteed at the physical layer.
210 citations
Book•
11 Oct 2000
TL;DR: Signal Processing Advances in Communication, Volume II brings together research previously scattered across multiple journals worldwide, delivering an unprecedented collection of advanced SP techniques for practicing engineers, researchers, managers, and any professional involved with designing or building state-of-the-art single- or multi-user communications systems.
Abstract: From the Publisher:
Blind synchronization with single- and multi-sensor arrays
Space-time transmit-receive diversity combining systems
New physical layer solutions for CDMA and multicarrier systems
For every engineering professional involved with signal processing for advanced communications
Key advances in signal processing for single-user and multi-user systems.
Signal Processing Advances in Communication, Volume II is the second in a two-volume set that introduces important recent advances in signal processing (SP) tools for wireless and mobile communications, and bringing together contributions by leaders in the field worldwide. This two-volume set covers an exceptionally wide range of technologies and methodologies, including noise and interference cancellation, modem design, mobile Internet services, next-generation audio/video broadcasting, cellular telephony, and wireless multimedia networks.
Volume II focuses on single- and multi-user communication systems, presenting an exceptionally wide range of today's best work on topics such as:
Blind synchronization with single- and multi-sensor arrays
Space-time transmit-receive diversity combining systems
Time-varying channel modeling
Signal separation with constant modulus constraints
Parallel factor analysis tools
New methods for canceling multiuser interference and mitigating multipath effects in CDMA and multicarrier systems at the physical layer
Key signal processing issues at the network layer
This book brings together research previously scattered across multiplejournals worldwide, delivering an unprecedented collection of advanced SP techniques for practicing engineers, researchers, managers, and any professional involved with designing or building state-of-the-art single- or multi-user communications systems.
196 citations
Patent•
28 Jan 2000TL;DR: In this paper, a Data Link Layer (DLL) protocol for direct support of the Internet Protocol (IP) networking in the Universal Mobile Telecommunications System (UMTS) (100), is provided.
Abstract: A Data Link Layer (DLL) (20) protocol for direct support of the Internet
Protocol (IP) networking in the Universal Mobile Telecommunications System
(UMTS) (100), is provided. The disclosed Data Link Layer (20) comprises a
Radio Link Control (RLC) (70) sublayer and a Medium Access Control (MAC)
(80) sublayer. At a transmit end, as well as at a receiving end of the UMTS
wireless system (100), a plurality of Quality of Service (QoS) planes (1...n) are
created according to IP QoS requirements. At the RLC level, each QoS plane
(1...n) comprises a Data-RLC (14-1,..., 14-n) and a Control-RLC (12-1, ..., 12-n).
The QoS planes (1...n) are optimized to handle the QoS requirements of a
corresponding Class of Service (CoS). At the transmitting end, the data
packets received from the upper layers are directed to a QoS plane according
to the particular QoS information they contain, and processed according to
their particular QoS requirement. A Segmentation, Concatenation, and
Reframing module (SCR) is used to generate variable size RLC frames (77;
77'), including multiframing. The variable size RLC frames (77; 77')are
transmitted to the MAC sublayer (80) using logical channels (15). At the MAC
sublayer (80), the RLC frames (77; 77') are multiplexed onto transport
channels (25) based on their QoS requirements and transmitted to the
physical layer for propagation to the receiving end.
190 citations
Patent•
17 Mar 2000
TL;DR: In this paper, a method and device for connecting redundant disk drives to a controller, preferably an intelligent switch, via a network is presented, where disks are controlled by commands transported across the network.
Abstract: The present invention relates to transparent access to a redundant array of inexpensive devices. In particular, it provides a method and device for connecting redundant disk drives to a controller, preferably an intelligent switch, via a network. The disks are controlled by commands transported across the network. Commands may be SCSI, IDE/ATA or other commands. The network may comprise ethernet, fiber channel or other physical layer protocol. Commands can be encapsulated in IP packets and transmitted using either a reliable or unreliable transport protocol. Multicasting of packets from the controller to the multiple disk drives is part of the present invention.
162 citations
23 Sep 2000
TL;DR: It is expected that throughput from 5 GHz IEEE 802.11a products currently in development can be accurately predicted using this model, and a close fit is found between the results for IEEE802.11b obtained from this model and as measured using currently available 2.4 GHz products.
Abstract: The throughput for IEEE 802.11 wireless LANs has been evaluated with respect to various kinds of overhead. The impact of several sources of overhead has been modeled. Sources include gap time, preamble, PHY (physical layer), MAC (medium access layer) and TCP/IP header fields, ACK (acknowledgement) and request frames. After measurement of the net throughput and detailed monitoring of actual exchange of frames, this modeling has been refined. A close fit is found between the results for IEEE 802.11b obtained from this model and as measured using currently available 2.4 GHz products. Therefore, it is expected that throughput from 5 GHz IEEE 802.11a products currently in development can be accurately predicted using this model.
132 citations
Patent•
27 Jul 2000TL;DR: In this paper, a method and system for generating a user interface in a plurality of multiple devices connected to the network system for controlling devices that are currently connected to a network is presented.
Abstract: A method and system for generating a user interface in a plurality of multiple devices connected to the network system for controlling devices that are currently connected to a network. A network system includes: a physical layer, wherein the physical layer provides a communication medium than can be used by devices to communicate with each other; one or more devices connected to the physical layer, each device storing information including device information; a discovery agent in each of one more devices adapted for discovering devices currently connected to the network; a configuration agent in each of one or more devices adapted for configuring devices addresses of the discovered devices connected to the network; and a user interface agent in each of one or more devices, adapted for: obtaining information from discovered devices currently connected to the network, the information including device information, and generating a user interface description in one or more of the devices based at least on the obtained information, the user interface description in each device including at least one reference associated with the device information of each of the devices currently connected to the network.
26 Mar 2000
TL;DR: A novel notion of fairness for wireless links, effort-limited fairness (ELF), which extends WFQ via dynamic weight adjustments, and a practical approximation algorithm, which is evaluated through both trace-driven simulation and measurement of a prototype wireless radio network based on the WaveLAN physical layer.
Abstract: While packet scheduling for wired links is a maturing area, scheduling of wireless links is less mature. A fundamental difference between wired and wireless links is that wireless media can exhibit substantial rates of link errors, resulting in significant and unpredictable loss of link capacity. This capacity loss results in a special challenge for wireless schedulers. For example, a weighted fair queue (WFQ) scheduler assumes an error free link and specifies how flows should share the link capacity. However, this specification is not sufficient to determine the correct outcome when link capacity is sharply reduced, because flows that have been allocated the same weights may differ greatly in their ability to tolerate throughput loss. In this paper, we first describe the wireless scheduling challenge in terms of an effort-outcome disconnection. Next we propose a novel notion of fairness for wireless links, effort-limited fairness (ELF), which extends WFQ via dynamic weight adjustments. ELF guarantees that all flows experiencing an error rate below a per flow threshold receive their expected service, defined as a specified rate for reserved flows or a specified share of best-effort capacity for best effort flows. After motivating and defining ELF, we present a practical approximation algorithm, which we evaluate through both trace-driven simulation and measurement of a prototype wireless radio network based on the WaveLAN physical layer.
Patent•
4 Dec 2000
TL;DR: In this paper, a system and method are provided to simultaneously support a customized multi-priority services that can be used to transmit multipriority data link layer frames to a destination host using a single or multiple communication links.
Abstract: A system and method are provided to simultaneously support a customized multi-priority services that can be used to transmit multi-priority data link layer frames to a destination host using a single or multiple communication links. The scheme does not require to have any pre-assigned bandwidth reservation policy to support multi-priority services on the link(s). The received frames from one or multiple links can be queued into multi-level services as such that the transmitting device, using customized implemented priority schemes, can control the transmission of the outgoing data-link frames on per byte basis. The system processor at the sending device reserves the full control of the link(s) entire bandwidth and has the ability to release and reassign the bandwidth in any byte proportion to the data-link frames of any service at any desired byte boundary. The transmission of any declared low priority data-link frame can be interrupted in real time ‘on the fly’ in order to relinquish the link bandwidth and network resources to any high priority data-link frame ready for transmission. The methodology of the presented scheme is very flexible and can accommodate any number of multi-priority services on multi flavor data link frame environment. Also, the proposed method and system discloses a very unique and innovative technique that can be used to accommodate a diversity of data-link layer protocols simultaneously and concurrently over single or multiple physical layer communication links.
TL;DR: This work proposes an algorithm for locating multiple failures at the physical layer of a WDM network, which is based on a classification and abstraction of the components of the optical layer and of the upper layer, and which handles missing and false alarms.
Abstract: Fault identification and location in optical networks is hampered by a multitude of factors: the redundancy and the lack of coordination (internetworking) of the managements at the different layers (WDM, SDH/SONET, ATM, IP); the large number of alarms a single failure can trigger; the difficulty in detecting some failures; and the resulting need to cope with missing or false alarms. Moreover, the problem of multiple fault location is NP-complete, so that the processing time may become an issue for large meshed optical networks. We propose an algorithm for locating multiple failures at the physical layer of a WDM network. They can be either hard failures, that is, unexpected events that suddenly interrupt the established channels; or soft failures, that is, events that progressively degrade the quality of transmission; or both, hard failures are detected at the WDM layer. Soft failures can sometimes be detected at the optical layer if proper testing equipment is deployed, but often require performance monitoring at a higher layer (SDH, ATM, or IP). Both types of failures, and both types of error monitoring, are incorporated in our algorithm, which is based on a classification and abstraction of the components of the optical layer and of the upper layer. Our algorithm does not rely on timestamps nor on failure probabilities, which are difficult to estimate and to use in practice. Moreover, our algorithm also handles missing and false alarms. The nonpolynomial computational complexity of the problem is pushed ahead into a precomputational phase, which is done off-line, when the optical channels are set up or cleared down. This results in fast on-line location of the failing components upon reception of the ringing alarms.
Patent•
21 Aug 2000
TL;DR: In this article, the authors present a TCP/IP protocol suite for sending and receiving data with reliable communication protocol, which includes a computer at a node having a backplane, a CPU board, software instructions for the CPU, and a special network board plugged into the backplane.
Abstract: A system and method for sending and receiving data with a reliable communication protocol. The system includes a computer at a node having a backplane, a CPU board plugged into the backplane, software instructions for the CPU, and a special network board plugged into the backplane. The CPU board, software, and network card act to implement the TCP/IP protocol suite. The network card or board includes an interface to receive data packets from the physical layer, and circuitry to verify the TCP checksum before de-encapsulation and routing of the TCP segment by the network layer software. It also includes circuitry to automatically prepare the acknowledgement signal to be sent by the receiving computer to the sending computer. It additionally includes circuitry to calculate the error detecting code on outgoing signals from the sending computer to the receiving computer.
Patent•
11 Feb 2000
TL;DR: In this paper, the authors propose an end-to-end encryption algorithm between an originating gateway and an access multiplexor (30) in a virtual neighborhood network (VN) comprising several gateways.
Abstract: A communication system (10) supports the provision of a plurality of dedicated communication resources (50–64), such as copper drops, RF links and optical fibers, to dedicated home-gateway devices (44–48) or distribution points (124). The communication resources (50–64) support broadband interconnection (104) between the dedicated home-gateway devices (44–48) or distribution points (124) and an access multiplexor (30) in a network (12). Each gateway device (44–48) or distribution point (124) generally includes a local RF transceiver (84) and associated control logic (80–82) that allows local communication (86) between gateway devices (44–48) and hence statistically multiplexed access (60–64, 89) to multiple communication resources, thereby providing increased bandwidth in uplink and/or downlink directions. With the control logic (80) operable to provide a routing and prioritisation/arbitration function, each gateway (44–48) is able to selectively engage use of supplemental, non-reserved communication resources usually associated with a dedicated ono-to-one connection between the access network (12) and at least one secondary gateway. Physical layer access to information routed via a secondary gateway within a virtual neighborhood network (90–92) comprising several gateways is restricted through an end-to-end encryption algorithm between an originating gateway and, at least, the access multilpexor (30).
Patent•
29 Nov 2000TL;DR: In this paper, a physical layer interface system for use in a broadband wireless access communication network is provided, which includes a base station, a subscriber station and a wireless communication link for transmitting wireless communication signals upstream and downstream between the base station and the subscriber station.
Abstract: Physical layer interface system for use in a broadband wireless access communication network is provided. The broadband wireless access communication network comprises a base station, a subscriber station and a wireless communication link for transmitting wireless communication signals upstream and downstream between the base station and the subscriber station. The physical interface system comprises a first physical layer interface for the base station for processing the communication signals upstream and downstream between the subscriber station and the base station and a second physical layer interface for the subscriber station for processing the communication signals upstream and downstream between the subscriber station and the base station. The first physical layer interface transmits downstream transmission of communication signals from the base station to the subscriber station in a burst mode.
Patent•
18 Dec 2000TL;DR: In this paper, the authors present a method, system and apparatus for managing data flow over an open system interconnection type network (10) which includes a physical layer (12) and a media access control layer (146).
Abstract: The present invention provides a method, system and apparatus for managing data flow over an open system interconnection type network (10) which includes a physical layer (12) and a media access control layer (146). The invention implements a plurality of operating modules (315) each enabling a respective media access control layer operating function in which at least a portion of the operating modules are implemented in software. The invention further implements a host interface module (305) for communication between a host processor and the media access control layer, a physical layer interface module (310) for communication between the physical layer and media access control layer, and an inter-module programming interface for communications between respective operating modules.
26 Mar 2000
TL;DR: An efficient and general graph-theoretic model (the wavelength-graph (WG) has been proposed which enables solution of the static routing and wavelength assignment (RWA) problems in multihop wavelength routing (WR) wavelength division multiplexing (WDM) networks simultaneously, and-as a unique feature-it optimises the optical layer jointly with the electrical one.
Abstract: An efficient and general graph-theoretic model (the wavelength-graph (WG)) has been proposed which enables solution of the static routing and wavelength assignment (RWA) problems in multihop wavelength routing (WR) wavelength division multiplexing (WDM) networks simultaneously, and-as a unique feature-it optimises the optical layer jointly with the electrical one. Based on the proposed WG model the problem has been formulated as an integer linear program (ILP), solved by stochastic algorithms improved by simple heuristics. The topology of the physical layer, the type of each node (e.g., OADM, OXC or EXC), the number of available wavelengths per link and the capacity of each wavelength-channel are assumed given with the aggregated traffic demand of each node-pair. The output of the optimisation is the system of wavelength paths, light paths and semi-light paths. The objective of the optimisation is to reduce resource usage at upper (electrical) layers, subject to the constrained amount of capacity of each wavelength and a limited number of wavelengths. Although the problem to be solved is NP-hard, all methods proposed give a result in a very short time.
Patent•
3 Apr 2000TL;DR: In this paper, the authors propose a service interface architecture for IEEE 802.3, 10BASE-T, 100BASETX, and Ethernet LAN standards compatible with Ethernet LAN.
Abstract: A method and apparatus for transmitting information compatible with IEEE 802.3, 10BASE-T, 100BASE-TX, and Ethernet LAN standards across a service interface in the Physical Layer which is architected to reduce pin count in multi-port Physical Layer Devices. The service interface architecture allows specification of a four channel PHY device in a PLCC package or a six channel PHY device in a PLCC package and reduces the interface connection requirement of a twelve channel MAC device to 56 pins from a worst case 216 pins for 802.3 standard MII implementations. The interface utilizes a single, constant rate system clock and a single transmission path per channel that operates at constant speed while supporting both 10 Mb/s and 100 Mb/s data rates. The service interface separates the digital gates, in the Physical Layer from the analog functionality to implement a dual speed, 10/100 Mb/s IEEE standards compliant PHY device, with Auto-Negotiation, that optimizes device implementation technology to functional requirements, but does not necessarily adhere to the architectural boundaries and signaling primitives defined in the IEEE 802.3 standard.
Patent•
24 Apr 2000TL;DR: In this article, the authors propose a method for controlling operation of a multi-pair gigabit transceiver consisting of a physical layer control module (PHY Control), a physical coding sublayer module (PCS), and a digital signal processing module (DSP).
Abstract: A method for controlling operation of a multi-pair gigabit transceiver. The multi-pair gigabit transceiver comprises a Physical Layer Control module (PHY Control), a Physical Coding Sublayer module (PCS) and a Digital Signal Processing module (DSP). The PHY Control receives user-defined inputs from the Serial Management module and status signals and diagnostics signals from the DSP and the PCS and generates control signals, responsive to the user-defined inputs, the status signals and diagnostics signals, to the DSP and the PCS.
Patent•
[...]
TL;DR: In this paper, the authors present a method, system and apparatus for managing data flow over an open system interconnection type network, which includes a physical layer (12) and a media access control layer (146).
Abstract: The present invention provides a method, system and apparatus for managing data flow over an open system interconnection type network (10) which includes a physical layer (12) and a media access control layer (146). The invention implements a plurality of operating modules (315) each enabling a respective media access control layer operating function in which at least a portion of the operating modules are implemented in software. The invention further implements a host interface module (305) for communication between a host processor and the media access control layer, a physical layer interface module (310) for communication between the physical layer and media access control layer, and an inter-module programming interface for communications between respective operating modules. The physical layer interface includes an enhanced media independent interface in accordance with some embodiments of the present invention.
19 Oct 2000
TL;DR: An overview of the HIPERLAN/2 standards is presented together with software simulated physical layer performance results for each of the transmission modes defined in the two standards.
Abstract: At present, wireless local area networks (WLANs) supporting broadband multimedia communication are being developed and standardized. Two such standards are HIPERLAN/2, defined by ETSI BRAN and the IEEE's 802.11a. These WLAN standards will provide data rates up to 54 Mbps (in a channel spacing of 20 MHz) in the 5.2 GHz band. In this paper, an overview of the the standards is presented together with software simulated physical layer performance results for each of the transmission modes defined in the two standards. Furthermore, the differences between the standards (protocol data unit-PDU-size, upper protocol layers etc.) and the effects on applications are discussed.
Patent•
11 Dec 2000TL;DR: In this article, a wireless data network architecture supports both centralized mode operation and distributed mode operation, where the data transmission is dynamically switched from one of the nodes to the other as a function of various implementation-specific triggers.
Abstract: A wireless data network architecture supports both centralized mode operation and distributed mode operation. In the centralized mode, all of the Open Systems Interconnection (OSI) reference model data link layer, also known as layer 2, protocol functions are implemented within the radio access network control entity, such as at a base station controller (BSC) or similar network controller, before the data packets are delivered to one or more base station transceiver subsystems (BTSs). In the distributed mode, some of the layer 2 protocol functions are implemented at the BSC or similar network controller, and some of the layer 2 protocol functions are implemented at the BTSs. The data transmission is dynamically switched from one of the nodes to the other as a function of various implementation-specific triggers.
Patent•
6 Oct 2000
TL;DR: In this paper, a medium access control (MAC) layer protocol and a method for contention resolution using the protocol is provided for networks with multiple priority traffic, where a physical layer connected to a transmission medium uses a carrier modulation scheme with multiple frequencies.
Abstract: A Medium Access Control (“MAC”) Layer protocol and a method for contention resolution using the protocol is provided for networks with multiple priority traffic. The protocol is used where a physical layer connected to a transmission medium uses a carrier modulation scheme with multiple frequencies. Stations on the network that desire access to the transmission medium use a carrier modulation scheme with multiple frequencies. Stations that desire access simultaneously transmit a single frequency selected at random from a set of physical layer frequencies during an open-contention-interval. At the same time, the stations listen to a combined frequency signal and analyzes it for frequency content. The station whose own frequency matches the highest frequency signal in the combined signal gains access to a transmission medium. In the event of a collision, a restricted-contention-interval is used only for the colliding stations. The probability of successful contention resolution increases very rapidly using the restricted-contention-interval. By partitioning the set of frequencies in contiguous ranges, multiple priority classes can be used with the contention method and the MAC layer protocol.
Patent•
27 Sep 2000TL;DR: In this article, a medium access control (MAC) layer for a node of a wireless local area network, which may be used in embedded, host and stand-alone applications, includes a hardware layer and a software layer.
Abstract: A medium access control (MAC) layer for a node of a wireless local area network, which may be used in embedded, host and stand-alone applications, includes a hardware layer and a software layer. The hardware layer is configured to perform time-critical tasks and the software layer is configured to perform non-time critical tasks. The software layer includes multiple modules, such as one or more of a host communication agent, a bridging layer, a network management support module, a SBM-to-TAME conversion module, and a rate estimation module. Further, the software layer acts as the source of and the destination of MAC Service Data Units and is configured as a hierarchical structure in which functional unit blocks for associated elements of the hardware layer communicate with an application layer through respective device drivers and managers. Device drivers and managers communicate through a device manager layer.
TL;DR: The European Union ACTS project SONATA will define and demonstrate a cswitchlessn all-optical network to provide a future single-layer, advanced transport architecture on a national scale, providing major transport architecture simplifications and hardware reductions.
Abstract: The European Union ACTS project SONATA will define and demonstrate a cswitchlessn all-optical network to provide a future single-layer, advanced transport architecture on a national scale. The single-hop, shared-access network employs time and wavelength agility (a WDMA/TDMA protocol), using fast tunable transmitters and receivers to route individual customer connections as well as bandwidth pipes through a single wavelength router (suitably replicated for resilience). No electronic switching nodes or cross-connects (telephony, IP, ATM, SDH) are required within the transport network, nor optical cross-connects (save the wavelength routing node), thus providing major transport architecture simplifications and hardware reductions. The network is scalable to 200 Tbit/s throughput over 1, 000 krn, connecting 20 million terminals operating at 622 Mbit/s over 50.000-way split c
26 Mar 2000
TL;DR: A quality of service wireless framework based on the joint design of a packet fair queuing scheduler, demand assignment medium access control (MAC) protocol, and multirate multipath-transparent CDMA-based physical layer is proposed.
Abstract: The traditional layered approach to wireless networks (network, data link, and physical layer) suboptimally utilizes the limited available capacity. We propose a quality of service wireless framework based on the joint design of a packet fair queuing scheduler, demand assignment medium access control (MAC) protocol, and multirate multipath-transparent CDMA-based physical layer. The unique code assignment procedure allows a direct mapping of the packet fair schedule to the physical layer transmission/reception, and supports transmission (service) rates of arbitrarily fine resolution. Judiciously designed user codes combat the harsh time-varying fading environment, and parsimonious code description minimizes overhead in the MAC. Simulations illustrate the merits of our designs.
TL;DR: The article is focused on the physical layer structure and associated procedures of cdma2000 and does not cover the MAC, LAC, radio resource management, or any other signaling protocols in any detail.
Abstract: cdma2000 offers several enhancements as compared to TIA/EIA-95, although it remains fully compatible with TIA/EIA-95 systems and allows for a smooth migration from one to the other. Major new capability include: 1) connectivity to GSM-MAP in addition to IP and IS-41 networks; 2) new layering with new LAC and MAC architectures for improved service multiplexing and QoS management and efficient use of radio resource; 3) new bands and bandwidths of operation in support of various operator needs and constraints, as well as desire for a smooth and progressive migration to cdma2000; and 4) flexible channel structure in support of multiple services with various QoS and variable transmission rates at up to 1 Mbps per channel and 2 Mbps per user. Given the phenomenal success of wireless services and desire for higher rate wireless services, improved spectrum efficiency was a major design goal in the elaboration of cdma2000. Major capacity enhancing features include: 1) turbo coding for data transmission; 2) fast forward link power control; 3) forward link transmit diversity; 4) support of directive antenna transmission techniques; 5) coherent reverse link structure; and 6) enhanced access channel operation. As users increasingly rely on their cell phone at work and at home for voice and data exchange, the stand-by time and operation-time are essential parameters that can influence customer's satisfaction and service utilization. Another major goal of cdma2000 was therefore to enable manufacturers to further optimize power utilization in the terminal. Major battery life enhancing features include: 1) improved reverse link performance (i.e., reduced transmit power per information bit); 2) new common channel structure and operation; 3) quick paging channel operation; 4) reverse link gated transmission; and 5) new MAC states for efficient and ubiquitous idle time operation. This article provides additional details on those enhancements. The intent is not to duplicate the detailed cdma2000 radio access network specification, but rather to provide some background on the new features of cdma2000 and on the qualitative improvements as compared to the TIA/EIA-95 based systems. The article is focused on the physical layer structure and associated procedures. It therefore does not cover the MAC, LAC, radio resource management [1], or any other signaling protocols in any detail. We assume some familiarity with the basic CDMA concepts used in TIA/EIA-95.
Patent•
IBM1
TL;DR: In this paper, a method for determining the physical locations of a plurality of computers in a network is disclosed, which includes providing an additional information physical layer and logic in each of the wall plates.
Abstract: A method for determining the physical locations of a plurality of computers in a network is disclosed. The network includes a plurality of wall plates, each of the wall plates for coupling one of the computers to the network. The method and system comprises providing an additional information physical layer and logic in each of the wall plates. The method and system further comprises capturing and storing the system media access-controller (MAC) address of the connect computer in the additional logic of each of the plurality of wall plates and storing a physical address of the wall plate in the logic of each of the plurality of wall plates. The method and system also comprises providing a command from the network that will cause the system MAC address and the physical address of at least one of the plurality of computers to be provided to an application in the network. A system and method in accordance with the present invention adds a low cost physical layer and logic within an Ethernet wall plate associated with the computer on the network. The logic is designed to respond to a broadcast signal to a UDP (User Datagram Protocol) port. In so doing the physical location of the computer can be determined. In a preferred embodiment, a command is provided from the network that will cause the MAC address and the physical address of at least one of the plurality of computers to be provided to an inventory application in the network, thereby allowing a network administrator to remotely determine the physical location (room, floor, building, etc.) of any and all computers attached to the network.