Abstract: The broadband wireless access industry, which provides high-rate network connections to stationary sites, has matured to the point at which it now has a standard for second-generation wireless metropolitan area networks. The IEEE standard 802.16, with its WirelessMAN/sup TM/ air interface, sets the stage for widespread and effective deployments worldwide. This article overviews the technical medium access control and physical layer features of this new standard.

Abstract: The design and simulation of coding schemes, medium access control (MAC), and link-layer protocols for future industrial wireless local area networks can be supported by some understanding of the statistical properties of the bit error patterns delivered by a wireless link (which is an ensemble of transmitter, channel, receiver, modems). The authors present results of bit error measurements taken with an IEEE 802.11-compliant radio modem in an industrial environment. In addition to reporting the most important results, they draw some conclusions for the design of MAC and link-layer protocols. Furthermore, they show that the popular Gilbert/Elliot model and a modified version of it are a useful tool for simulating bit errors on a wireless link, despite their simplicity and failure to match certain measured statistics.

Abstract: A modem (104) which includes an application interface for receiving packets to be transmitted on an electrical power network (112), a network interface connecting the modem to the electric power network, at least one media access control (MAC) unit adapted to perform MAC layer tasks in accordance with at least two different MAC protocols (172), on packets received from the application interface, and at least one physical layer unit adapted to transmit packets from the at least one MAC unit onto the electric power network, through the network interface, in a same frequency band.

Abstract: An improved method for packet transmission scheduling and an improved packet transmission scheduling system in mobile telecommunication systems. Both the improved method and the system especially adapted to be used for UMTS systems. A quality of service scheduling of multiple data flows in a mobile telecommunication system is proposed, wherein a priority order of protocol data units (PDU) of multiple data flows with regard to predefined flow's quality of service requirements is determined, a serving of the protocol data units (PDU) is performed by dynamically determining transport blocks (TB) to be transmitted by the physical layer (PHY-layer) with regard to the defined priority order and in dependence of allocated radio resource constraints, by assigning to each transport block (TB) a respective associated transport format (TF), and by creating transport block sets (TBS) with the determined transport blocks (TB) to be transmitted by the physical layer (PHY-layer) by using the respective associated transport format (TF) as assigned.

Abstract: As part of 3GPP Release'5 standardization work on WCDMA/UTRA, a new packet concept has been added to grant high speed downlink packet access (HSDPA). One of the central features of the HSDPA concept is advanced physical layer retransmission scheduling employing soft combining gain, incremental redundancy, and low retransmission delays. Since the average retransmission probability in HSDPA is typically on the order of 10-40%, the retransmission scheduling needs to be accurately simulated and modeled at both link and network level. Based on an extensive simulation campaign, this paper presents methods to map the link level performance of the HSDPA retransmission schemes into a low-complexity representation suitable for network level evaluation. The method accurately predicts the throughput and delay performance within a few percent.

Abstract: A comprehensive book on DWDM network design and implementation solutionsDesign Software Included Study various optical communication principles as well as communication methodologies in an optical fiber Design and evaluate optical components in a DWDM network Learn about the effects of noise in signal propagation, especially from OSNR and BER perspectives Design optical amplifier-based links Learn how to design optical links based on power budget Design optical links based on OSNR Design a real DWDM network with impairment due to OSNR, dispersion, and gain tilt Classify and design DWDM networks based on size and performance Understand and design nodal architectures for different classification of DWDM networks Comprehend different protocols for transport of data over the DWDM layer Learn how to test and measure different parameters in DWDM networks and optical systemsThe demand for Internet bandwidth grows as new applications, new technologies, and increased reliance on the Internet continue to rise. Dense wavelength division multiplexing (DWDM) is one technology that allows networks to gain significant amounts of bandwidth to handle this growing need. DWDM Network Designs and Engineering Solutions shows you how to take advantage of the new technology to satisfy your network's bandwidth needs. It begins by providing an understanding of DWDM technology and then goes on to teach the design, implementation, and maintenance of DWDM in a network. You will gain an understanding of how to analyze designs prior to installation to measure the impact that the technology will have on your bandwidth and network efficiency. This book bridges the gap between physical layer and network layer technologies and helps create solutions that build higher capacity and more resilient networks.Companion CD-ROM The companion CD-ROM contains a complimentary 30-day demo from VPIphotonics™ for VPItransmissionMaker™, the leading design and simulation tool for photonic components, subsystems, and DWDM transmission systems. VPItransmissionMaker contains 200 standard demos, including demos from Chapter 10, that show how to simulate and characterize devices, amplifiers, and systems.

Abstract: This chapter contains sections titled: Introduction Background Physical Layer Link Layer EGPRS Performance Conclusions This chapter contains sections titled: References

Abstract: A reconfigurable multi-media system, method and device provides monitoring and reconfiguration of a plurality of communication layers of a communications stack to dynamically reconfigure the modulation and coding of software defined radio (SDR) .The system includes a software object radio (SWR) library having reconfigurable object specification, design and performance parameters, the SWR is adapted for at least one of transmitting and receiving multi-media content via wireless communication; a controller in communication with the SWR library; a power management device module in communication with said controller; a reconfigurable encoder/decoder in communication with said controller to provide the SWR with dynamic coding information for modulation; a TCP/IP interface in communication with said reconfigurable encoder/decoder and said controller; and an application layer comprising a link layer and a reconfigurable physical layer in communication with each other and said controller, the physical layer adapted for communication with a channel, and the application layer including at least one driver for multimedia delivery. The controller monitors the physical layer and link layer information and the reconfigurable encoder/decoder dynamically reconfigures modulation and coding of multi-media content according to a cross-layer optimization approach.

Abstract: Next-generation mobile/wireless networks are already under preliminary deployment Mobile/wireless all-IP networks are expected to provide a substantially wider and enhanced range of services However, an evolutionary rather than revolutionary approach to the deployment of a global all-IP wireless/mobile network is expected To support global roaming, next-generation networks will require the integration and interoperation of mobility management processes under a worldwide wireless communications infrastructure In this article global roaming is addressed as one of the main issues of next-generation mobile networks Apart from the physical layer connectivity and radio spectrum allocation plans, mobility in a hierarchical structured scheme is discussed An all-IP wireless/mobile network combined with inherited mobility schemes of each network layer and Mobile IP extensions is proposed In this respect the mobility management mechanisms in WLAN, cellular, and satellite networks are analyzed, and an all-IP architecture is described and an enhanced roaming scenario presented

Abstract: We propose a novel cross layer design concept that could improve the network throughput significantly for mobile ad hoc networks. The channel reservation control packets employed at the MAC layer can be utilized at the physical layer for exchanging timely channel estimation information to enable an adaptive selection of a spectrally efficient transmission rate. In particular, the size of a digital constellation can be varied dynamically based on the channel condition estimated at the receiver which can be relayed to the transmitter via the control packets. In addition, this channel adaptive information gathered at the MAC layer can be communicated to the routing layer via different routing metrics for optimal route selection. We have examined the performance improvement at the network layer due to cross layer communications. For this, we present a simple cross layer design implemented with minor modifications on the IEEE 802.11 standard and the dynamic source routing (DSR) protocol. We demonstrate that the network throughput is significantly increased, as much as 50% to 100%, in low mobility scenarios simulated using ns-2.

Abstract: A wireless network is disclosed in which individual wireless stations can be configured to implement any of a plurality of physical configurations including antenna configurations. Such antenna configurations may include, without limitation, multiple input multiple output (MIMO) and single input single output (SISO). Different types of MIMO configurations can also be implemented such as open loop MIMO and closed loop MIMO.

Abstract: In this paper, we demonstrate the energy-efficient point coordination function (PCF) operation of IEEE 802.11a wireless LAN (WLAN) via both transmit power control (TPC) and physical layer (PHY) rate adaptation. First, we derive the energy-consumption performance analytically for uplink data transmissions under the PCF. From the evaluation results, we observe that significant energy savings can be achieved by combining TPC with adaptive PHY rate selection. A key requirement for a transmitter to select the most energy-efficient combination of transmit power level and PHY rate is the knowledge of the path loss between the receiver and itself. We present a novel scheme for accurate path loss estimation in 802.11 WLAN. Results and conclusions presented in this paper can serve as a valuable guidance or reference for the design of future 5 GHz 802.11 WLAN systems.

Abstract: The increasing popularity of wireless broadband access in local and wide area networks is the main expression of the need for flexible and ubiquitous wireless connectivity. In order to satisfy user resource requirements in the presence of volatility of the wireless medium, sophisticated multiple access and adaptation techniques are required, which alleviate channel impairments and increase system throughput. The use of multiple antennas at the base station allows intra-cell channel reuse by multiple spatially separable users through space division multiple access (SDMA) and hence enhances cell capacity. However, the employment of antennas in the physical layer raises significant issues in the medium access control (MAC) layer. We investigate the impact of antenna arrays on MAC layer channel allocation in the context of orthogonal frequency division multiplexing (OFDM), which is the predominantly proposed signaling scheme for wireless broadband access. We propose an algorithm to allocate channels to users based on their spatial separability properties, while appropriately adjusting beamforming weights and transmission rates for each user in a channel. The unified consideration of such adaptive techniques yields significant throughput benefits.

Abstract: From the Publisher: This book gives network managers and 3G workers a select background in spread spectrum technology, empowering them to make real-world design, purchasing, and deployment decisions. Assuming only that W-CDMA is the preferred interface, the authors make a point of grounding 3G technologies in the fundamentals of propagation characteristics, physical layer functionalities, and spectrum requirements, so readers can confidently tackle soft handover, power control, sectorization, and message flows.

Abstract: Dynamic bandwidth allocation (DBA) will play an important role in future broadband wireless networks, including the 3G and 4G WCDMA systems. A code-division generalized processor sharing (CDGPS) fair scheduling DBA scheme is proposed for WCDMA systems. The scheme exploits the capability of the WCDMA physical layer, reduces the computational complexity in the link layer, and allows channel rates to be dynamically and fairly scheduled in response to the variation of traffic rates. Deterministic delay bounds for heterogeneous packet traffic are derived. Simulation results show that the proposed CDGPS scheme is effective in supporting differentiated QoS, while achieving efficient utilization of radio resources.

Abstract: A system and method are disclosed for providing a high speed wireless network. In one embodiment, a network is configured in a star configuration having a single router at the center. A Metropolitan Access Network (MAN) is configured with a plurality of access points that provide a wireless interface using defined physical layer and Media Access Control (MAC) layer. Packet data delivered to and from the access points are connected to the single router using a plurality of layer two links, which may include point to point links and packet switches. All links within the network operate at layer two or below and do not modify the packet data. The single router at the center of the MAN star network uses layer three information to direct packets between Local Area Networks (LANs) or sub-networks connected to different ports on the router.

Abstract: The traditional design of communication networks has rarely been able to focus on the optimization of global network properties. Ultra-wideband (UWB) radio is emerging as an attractive physical layer for wireless communication networks offering new opportunities for the principled design and optimization of network properties. We develop a framework for the principled design of UWB wireless networks based on a flexible cost function that can be tailored and scaled to a wide range of networks and applications, ranging from sensor networks to voice and data wireless networks. The function comprises cost terms associated with transmission, connection setup, interference, and quality-of-service. Multihop routing strategies are associated with admissible paths of minimal cost that are computable in linear time. The cost function together with the overall level of requests determine the dynamics of the connections and the equilibrium topology of the network. We report simulation results in the case of simple ring and square lattice networks.

Abstract: A method and apparatus for handling data during link suspend pulse and the silent line state of a network device operating in a low power link suspend mode is presented. Accordingly, a new generation of network devices capable of operating in both the full power operational mode of prior art network devices, and a low power “link-suspend” operational mode are presented. The low power “link-suspend” (LS) mode reduces the power consumption of a LAN communications link at the physical layer by eliminating the need to continuously transmit standard idles to maintain link between two linked partners. In the LS mode, a low duty cycle “link-suspend-packet” (LSP) is transmitted between periods of silent line state (SLS). During the SLS, which is a non-data transmission period, the transmitter may be turned off to conserve power therefore preventing the receiver from immediately knowing the phase of an incoming data. Thus, in order to prevent loss of data, the LSPs serve to maintain link and provide information necessary to train the receiver loops so that they can quickly lock onto the incoming data. LSPs are specially constructed so that they can serve as part of the data preamble when the network devices are operating in the link suspend mode. Therefore, the nature of the LSPs is that they are compatible with the standard protocol requirements for data transmission.

Abstract: A method for improving the bit error rate of Ethernet packets applies forward error correction (FEC) coding to transmitted packets. The FEC coding is systematic block coding, and is applied so that the coded packets can be interpreted by legacy network devices that are not capable of FEC decoding. The transmit and receive state machines of FEC-capable Ethernet nodes are modified to enable the nodes to encode and/or decode the packets with the FEC code, and to adapt the nodes' respective medium access layer (MAC) and physical layer (PHY) data rates.

Abstract: A base station implementing physical layer automatic repeat request includes a transmitter (38) and a receiver (52). The transmitter has a physical layer transmitter for receiving data, format the received data into packets transmitting the packets and retransmitting packets in response to failure to receive a corresponding acknowledgment for a given packet; an acknowledgment receiver (56) for receiving the corresponding acknowledgment; and an adaptive modulation and coding controller for collecting retransmission statistics and adjusting the particular data encoding/modulation using the collected statistics. The receiver (52) has a physical layer receiver for demodulating the packets; a combiner/decoder (50-1-50-n) for buffering, decoding and detecting packet errors; and an acknowledgment generator for generating an acknowledgment for each packet if that packet has an acceptable error rate.

Abstract: Modern wireless communication standards like HiperLAN/2 or IEEE 802.11a provide a high degree of flexibility on the physical layer (PHY) allowing the data link control (DLC) layer to choose transmission parameters with respect to the currently observed link quality. This possibility of so-called link adaptation (LA) is also a key element for meeting quality of service (QoS) requirements of higher layers. Most LA algorithms take an estimate of the signal-to-noise ratio (SNR) or carrier-to-interference ratio (CIR), respectively, as the only input from the PHY layer. For frequency selective channels, however, the SNR alone does not adequately describe the channel quality. It is shown in this paper that system performance can be significantly improved if the LA scheme is based on a more detailed description of the channel situation. Methods for selecting the PHY mode based on the estimated channel transfer function are presented and compared to conventional algorithms.

Abstract: The invention includes a protocol, systems and methods for operating, administering, and maintaining (OAM) physical links in a network that carries packet switched data. A network control point implementing the protocol assigns addresses to all ports of the network, discovers network topology and capabilities, and initializes remote parameters through OAM frames sent to the ports. The OAM protocol maintains all physical transmission links through the communication of OAM frames with information concerning link errors and the status of ports and boxes. The OAM frame has a preamble that is an inverse of a preamble of a data frame, allowing decoupling of the OAM and data services. The OAM frames are initiated and terminated at the physical layer of the network. Ports of the network may include ASIC integrated circuits that create, transmit, receive, and process the OAM frames at the physical layer of the ports.

Abstract: An apparatus and method for operating a Multiple Input Multiple Output (MIMO)-capable subscriber node are disclosed. In one embodiment, an apparatus includes a MIMO-capable physical layer transceiver and a Medium Access Control (MAC) layer block that measures a received transmission to determine channel conditions. Upon receiving a transmission wherein said channel conditions meet specified conditions, the MAC layer block transmits a message to an access point indicating that the apparatus wants to switch between a non-MIMO mode and a MIMO mode, and upon receiving an acknowledgement, the MAC layer block switches between the non-MIMO mode and the MIMO mode. An apparatus for operating an access node is also disclosed.

Abstract: A distributed cable modem termination system (CMTS) in a hybrid fiber/coaxial (HFC) plant. The distributed CMTS comprises a network layer, at least one media access control layer, and at least one physical layer. The media access control layer implements a media access control chip. The media access control chip interfaces with the physical layer to provide timing to maintain components within the physical layer. The network layer, media access control layer, and physical layer each function as separate modules. The media access control chip provides the packet level media access control functions, and thus, does not require packet level media access control functions to be implemented in the same physical location. The media access control chip also provides a timing offset feature for handling time delays between the media access layer and the physical layer. This enables the network layer, the media access control layer, and the physical layer to each be in separate component locations of the HFC plant, yet physically connected throughout the HFC plant.

Abstract: The present invention discloses a method and an apparatus for reducing power consumption in a network linking system. The apparatus comprises: a network linking interface device, including a media access controller (MAC), a gigabit physical layer (gigabit PHY), and a connector, through which the network linking interface device is coupled to an Ethernet by a network cable; a driving device, for driving and controlling the network linking interface device; and a load monitoring module, for monitoring the load for the network interface device so as to adjust the link speed according to the load. The method comprises steps of: determining the network linking interface device to be in an autonegotiation mode; performing autonegotiation; obtaining settings of a remote-end network linking interface device; linking at the highest usable link speed; enabling the load monitoring module; adjusting the settings of the network linking interface device according to the load of the network linking interface device; and performing autonegotiation again and linking at a proper link speed.

Abstract: A method for handling an application in a communication between a first end and a second end involving an application layer, a transport layer, and a network layer, which method includes steps of: (a) receiving network layer packets from the first end of the communication, which packets contain application information provided using application layer processing; (b) processing the application information using application layer processing; and (c) transmitting network layer packets toward the second end of the communication, which packets contain information resulting from the application layer processing.

Abstract: A system, method and computer program product is provided for mitigating the effects of burst noise on packets transmitted in a communications system. A transmitting device applies an outer code, which may include, for example, a block code, an exclusive OR (XOR) code, or a repetition code, to one or more packets prior to adaptation of the packets for transmission over the physical (PHY) layer of the communications system, wherein the PHY layer adaptation may include FEC encoding of individual packets. The outer coded packets are then separately transmitted over a channel of the communications system. A receiving device receives the outer coded packets, performs PHY level demodulation and optional FEC decoding of the packets, and then applies outer code decoding to the out6r coded packets in order to restore packets that were erased during transmission due to burst noise or other impairments on the channel.

Abstract: Fault identification and localization problems in optical networks have become crucial. Due to network transparency and high data rates, optical networks are vulnerable to sophisticated attacks on the physical infrastructure, and hence require adequate fault monitoring in order to accurately identify and locate network failures. In transparent optical networks, faults may propagate to various parts of the network from the origin, and multiple alarms can be generated for a single failure. In order to reduce the number of redundant alarms, simplify fault localization, as well as lower financial investment in network monitoring equipment, fault monitor placement should be optimized for a given network. In this paper, we formulate a problem on the optimal placement of network monitoring devices and propose a solution approach. We provide a brief summary of available physical-layer monitoring devices, and present a scheme for optimal monitor placement.