Showing papers on "Media access control published in 1999"

Application-aware, quality of service (QoS) sensitive, media access control (MAC) layer

Abstract: An application aware, quality of service (QoS) sensitive, media access control (MAC) layer includes an application-aware resource allocator, where the resource allocator allocates bandwidth resource to an application based on an application type. The application type can be based on input from at least one of: a packet header; and an application communication to the MAC layer. The application communication includes: a communication between the application, running on at least one of a subscriber workstation and a host workstation, and the MAC layer, running on at least one of a subscriber CPE station and a wireless base station. The bandwidth resource is wireless bandwidth. The resource allocator schedules bandwidth resource to an IP flow. The IP flow includes at least one of: a transmission control protocol/internet protocol (TCP/IP) IP flow; and a user datagram protocol/internet protocol (UDP/IP) IP flow. The resource allocator in scheduling takes into account resource requirements of at least one of a source application and a destination application of an IP flow. The resource allocator takes into account IP flow identification information extracted from at least one packet header field. The bandwidth resource is wireless bandwidth. The resource allocator allocates switching resource to an application based on an application type. The application type is based on input from at least one of: packet header; and an application communication to the MAC layer. The application communication includes a communication between an application, running on at least one of a subscriber workstation and a host workstation, and the MAC layer, running on at least one of a subscriber CPE station and a wireless base station. The application communication includes a priority class of the IP flow.

A multichannel CSMA MAC protocol for multihop wireless networks

Abstract: We describe a new carrier-sense multiple access (CSMA) protocol for multihop wireless networks, sometimes also called ad hoc networks. The CSMA protocol divides the available bandwidth into several channels and selects an idle channel randomly for packet transmission. It also employs a notion of "soft" channel reservation as it gives preference to the channel that was used for the last successful transmission. We show via simulations that this multichannel CSMA protocol provides a higher throughput compared to its single channel counterpart by reducing the packet loss due to collisions. We also show that the use of channel reservation provides better performance than multichannel CSMA with purely random idle channel selection.

Medium access control protocols for multimedia traffic in wireless networks

Abstract: This article presents a survey on medium access control protocols for multimedia traffic in wireless networks. A basic overview of MAC protocol concepts is presented, and a framework is developed on which to base qualitative comparisons. The MAC protocols covered include third-generation TDMA and CDMA schemes intended for use in a single-hop wireless system. The operation of each protocol is explained, and its advantages and disadvantages ore presented. Finally, a qualitative comparative outline of the discussed protocols is provided, based on multimedia traffic requirements.

Adaptive communication protocol for wireless networks

Abstract: A communication protocol that provides link-level and media access control (MAC) level functions for wireless (e.g., ad-hoc) networks and is robust to mobility or other dynamics, and for scaling to dense networks. In a mobile or otherwise dynamic network, any control-packet collisions will be only temporary and fair. In a dense network, the network performance degrades gracefully, ensuring that only a certain percentage of the common channel is consumed with control packets. The integrated protocol allows packets (e.g., data scheduling control packets) to be scheduled in a collision-free and predictable manner (known to all neighbors), multicast packets can be reliably scheduled, as well as streams of delay- or delay-jitter-sensitive traffic. Further, using an optional network code, the scheduling of control packets can appear to observers to be randomized.

Capture effects of wireless CSMA/CA protocols in Rayleigh and shadow fading channels

Abstract: We investigate the capture effects for a wireless local area network (LAN) system in the presence of multipath, shadowing, and near-far effects The performance of wireless media access control (MAC) protocols with Rayleigh fading, shadowing, and capture effect are analyzed We consider carrier-sense multiple-access/collision-avoidance (CSMA/CA) protocols as the wireless MAC protocols, since CSMA/CA protocols are based on the standard for wireless LAN's IEEE 80211 We analyze and compare the channel throughput and packet delay for three types of CSMA/CA protocols: basic CSMA/CA, stop-and-wait automatic repeat request (SW ARQ) CSMA/CA, and four-way handshake (4-WH) CSMA/CA We calculate the capture probability of an access point (AP) in a channel with Rayleigh fading, shadowing, and near-far effects, and we derive the throughput and packet delay for the various protocols We have found that the performance of CSMA/CA in a radio channel model is 50% less than in an error-free channel model in low-traffic load, while the throughput and packet delay of CSMA/CA in a radio channel model show better performance than in an error-free channel model in high-traffic load We also found that the 4-WH CSMA/CA protocol is superior to the other CSMA/CA protocols in high-traffic load

Medium access control protocol for centralized wireless network communication management

Abstract: A Medium Access Control protocol software architecture which comprises a microcode component providing the protocol implementation level functions and an engine component providing hardware level functions. The Medium Access Control protocol and method for use in a network system allows for centralized management of all MAC-level services by a master device. The Medium Access Control protocol provides an improved protocol message throughput via the sequence retransmission request protocol scheme. The Medium Access Control protocol provides a reduced data transmission latency and provides dynamic allocation of data slots within a Time Division Multiple Access frame definition. The Medium Access Control protocol also provides a set of failure management functions and power control support.

Combining virtual local area networks and load balancing with fault tolerance in a high performance protocol

Abstract: A method to send and receive data packets over a network of computer systems (e.g., a plurality of virtual local area networks [VLANs] compliant with the IEEE 802.1Q standard) using a server computer system adapted to have a plurality of network interface cards (NICs) coupled thereto. An outgoing data packet is addressed using a first media access control (MAC) address, wherein the first MAC address is a virtual MAC address representing the plurality of NICs. A NIC is selected from the plurality of NICs using a load balancing scheme. The functionality of the selected NIC is verified using a fault tolerance scheme. The first MAC address in the outgoing data packet is replaced with a second MAC address, wherein the second MAC address represents the selected NIC. The outgoing data packet is then transmitted using the selected NIC. For an incoming data packet received at one of the plurality of NICs, the existing MAC address in the incoming data packet is replaced with the first MAC address. Thus, the present embodiment of the present invention provides a high performance method that supports multiple VLANs and elegantly combines a load balance scheme and a fault tolerance scheme into a software element implemented on a server computer system.

Method and apparatus for dynamic source routing in ad hoc wireless networks

Abstract: This invention addresses Media Access Control (MAC) routing protocol that accounts for QoS constraints for IP traffic in MANETs. Methods and systems consistent with this example use a decentralized algorithm that is run by the participating nodes with a minimal amount of control packets adding to network overhead. Methods and systems consistent with this invention calculate a maximum available bandwidth (MAB) metric used in the MAC protocol. The MAB, along with other information may be shared among nodes in the MANET. The shared information is also used in computing the traffic loads in other parts of the MANET, and in identifying the available links that could support the QoS requirements. Then, the information concerning available links is used in the MANET routing algorithm.

Fail over with multiple network interface cards

Abstract: A method and system for detecting a non-functioning network interface card (NIC) in a server computer system adapted to have a plurality of network interface cards coupled thereto and communicatively coupled to client computer systems in a network. A directed packet is sent from a first NIC to a second NIC, and a direct packet is also sent from the second NIC to the first NIC. The server computer system monitors the NICs to determine whether the directed packet from the first NIC is received by the second NIC. The server computer system also monitors the first NIC to determine whether the directed packet from the second NIC is received by the first NIC. The server computer system determines whether the first NIC is functioning using the results from the monitoring. When the first NIC is determined to be non-functioning, the functions of the first NIC are automatically switched from the first NIC to one of the plurality of NICs. A broadcast packet is sent from the server computer system to the client computer systems. The broadcast packet contains a media access control (MAC) address for the NIC that replaces the first NIC, and each client computer system replaces the MAC address for the first NIC with the MAC address for the second NIC in its memory cache.

5.8 GHz DSRC packet communication system for ITS services

Abstract: In this paper, we introduce a 5.8 GHz DSRC (dedicated short range communication) packet communication system which has been developed by ETRI. 5.8 GHz DSRC packet communication systems are under deveolpment worldwide and it will be widely applied to ITS (intelligent transportation system) services. We discuss the basic requirements of the DSRC communication system and system design specification to meet the requirements with regard to the physical layer, MAC (media acces control) layer, LLC (logical link layer) layer and application layer. DSRC packet communication systems consist of a micro-processor block, baseband packet modem block and an RF block. The microprocessor block handles MAC and application SW, the baseband packet modem transmits data up to 2.048 Mbps and recovers the received data from the RF block. The RF block has a function for ASK modulation and demodulation. We describe packet frame architecture and packet communication procedures for link setup and normal communication.

Statistical real-time communication over Ethernet for manufacturing automation systems

Abstract: In order to realize real time communication over Ethernet or fast Ethernet, one must be able to bound the medium access time within an acceptable limit. The multiple access nature of an Ethernet makes it impossible to guarantee a deterministic medium access time to individual stations. However one can bound the medium access time statistically by limiting the packet arrival rate at the medium access control (MAC) layer. While focusing on automated manufacturing systems as the main application, the paper considers the connection admission control (CAC) problem for statistically bounding the medium access time of Ethernet. Specifically, a packet is guaranteed to have a medium access time smaller than a predefined bound with a certain probability if the instantaneous packet arrival rate is kept below a certain threshold. Through an analysis, we first derived such a threshold. In order to keep the packet arrival rate under the given threshold, we employ a traffic smoother which: (i) is located between the transport layer and the Ethernet datalink layer and (ii) smooths packet streams between the two layers. The implementation of this traffic smoother requires only a minimal change in the OS kernel without any modification to the current standard of Ethernet MAC protocol or TCP or UDP/IP stack. In order to solve the CAC problem, we derived the probability of transmitting a packet successfully upon each trial by modeling the MAC protocol, 1-persistent CSMA/CD, and the collision resolution protocol, Binary Exponential Backoff, of Ethernet. We implemented a traffic smoother on the Linux OS, demonstrating the effectiveness of our approach in providing real time communication over Ethernet.

Fair media access for wireless LANs

Abstract: This paper addresses load balancing algorithms for the wireless links to solve the fairness problem, where stations are not able to gain access equally to the shared wireless medium. The fairness problem occurs mostly because of the existence of hidden stations and the presumption of a non-fully connected wireless network topology. In this paper, p/sub ij/-persistent carrier sense multiple access based algorithms are proposed in which a fair wireless access for each user is accomplished using a pre-calculated link access probability. Link access probabilities are calculated at the source station in two ways using connection-based and time-based media access methods. Each active user broadcasts information on either the number of logical connections or the average contention time to the stations within the communication reach. Each station reserves a specific priority for its each link to gain access to the shared medium based on the exchanged information. The proposed algorithms are dynamic and sensitive to the changes in the network topology. They are applicable to all CSMA based media access control protocols to provide a degree of fairness.

A real-time medium access control protocol for ad hoc wireless local area networks

Abstract: We develop and analyze a simple, elegant medium access control (MAC) protocol for use in transmitting real-time data in point to point ad hoc wireless local area networks (WLANs). Our enhancement of IEEE 802.11, real-time MAC (RT-MAC), achieves dramatic reductions in mean delay, missed deadlines, and packet collisions by selectively discarding packets and sharing station state information. For example, in a 50 station network with a normalized offered load of 0.7, mean delay is reduced from more than 14 seconds to less than 45 ms, late packets are reduced from 76% to less than 1%, and packet collisions are reduced from 36% to less than 1%. Regression models are developed from simulation data to describe network behavior in terms of throughput, mean delay, ratio of late packets, and ratio of collisions. Stations using RT-MAC are interoperable with stations using IEEE 802.11.

A system and method for link and media access control layer transaction completion procedures

Abstract: A system and method of implementing a radio link protocol and dynamic partial echo management for a transaction oriented packet data communication system. A data backlog is described with a media access control layer controller and transmitting a BEGIN protocol data unit transmitted to a receiver. A media access control layer transaction is initiated in response to the transmitting of the BEGIN frame.

Quality of service support in mobile ad-hoc IP networks

Abstract: Real-time IP applications such as IP telephony, IP video streaming, and transport of time-sensitive information need predictable network resources. Examples of network resources include minimum guaranteed bandwidth, and special processing of certain types of packets at points of congestion, regardless of traffic fluctuations in the network. Support for such applications in mobile ad-hoc networks requires acceptable channel conditions, QoS aware mechanisms for channel access, identification of transit nodes that can sustain the resulting traffic, as well as measures for congestion prevention and management at the nodes. This paper provides a framework for QoS support in mobile ad-hoc IP networks, and discusses methods to enable QoS aware media access control, and routing IP packets with QoS constraints.

System and method for remotely generating, assigning and updating network adapter card in a computing system

Abstract: A system and method for retrieving and assigning a unique media access control (MAC) address to a network adapter card in a computer system that uses the network adapter card to connect to a data network. The computer system includes a communications application for invoking a network connection to a remote server. The remote server includes a MAC address list that stores MAC addresses that have been assigned to network adapter cards according to serial numbers. The remote server includes a web page that requests the user to enter a serial number. The remote server uses the serial number to search for a MAC address in the MAC address list. When the remote server finds the serial number, it stores the corresponding MAC address in a file and sends the file name to the user. The user then requests the remote server to download the file by file name, or by FTP URL. The computer system receives the file and an update program reads the MAC address from the file and sends the MAC address to the network adapter card. The network adapter card then stores the MAC address in non-volatile memory.

Selective back-pressure in switched Ethernet LANs

Abstract: Although switched LANs are usually over-provisioned, their characteristics (short RTT, link speed mismatches) lead to increased burstiness, and thus to the occurrence of transient congestion. In order to fully utilize the potential of large switched LANs, a link layer back-pressure mechanism may be used to complement the end-to-end flow control by handling the short term congestion. A simple such mechanism, as the one specified in IEEE 802.3x, is shown to improve network performance in some situations, but to lead to poor performance in others. We propose selective back-pressure schemes based on the destination MAC address and traffic class information, which overcome the limitations of the simpler scheme. These are shown to provide superior performance for a wide range of situations. The results obtained suggest the need to incorporate these enhancements in the 802.3x standard.

A packet-switched multiple-access network system with distributed fair priority queuing

Abstract: A packet-switched multiple-access network system with a distributed fair priority queuing media access control protocol that provides multiple levels of priority of access and fair collision resolution with improved performance is disclosed. In one embodiment, the system provides high-speed transport of multimedia information on a shared channel. Further, in one embodiment, MAC level side-band signaling that is useful to other levels of the network protocol (e.g., the physical layer) is also provided.

ADAPT: a dynamically self-adjusting media access control protocol for ad hoc-networks

Abstract: This paper presents a dynamically adaptive protocol for transmission (ADAPT) for ad hoc networks that combines, in a novel way, a collision-free allocation based protocol and a contention based protocol while retaining the advantages of each. At low loads, ADAPT uses its contention mechanism to reclaim/reuse bandwidth that would otherwise be wasted by a pure allocation based protocol. At high loads, ADAPT provides bounded delay guarantees by dynamically changing its operation to that of its allocation based protocol, avoiding the fundamental problem of instability associated with pure contention based protocols. Thus, ADAPT self-adjusts its behavior according to the prevailing network conditions. Both analysis and simulation results demonstrate that the two protocols interact in a positive way, showing that it is possible to combine the advantages of two fundamentally different design philosophies without suffering from their drawbacks.

Channel reservation media access control protocol using orthogonal frequency division multiplexing

Abstract: A contention resolution media access control protocol for a local area network (LAN) using orthogonal frequency division multiplexing (OFDM). The protocol takes advantage of OFDM frames available on the channel physical layer. Each LAN node is assigned a LAN-unique node identifier that is the index of a Fast-Fourier transform (FFT) frequency bin or other discrete tone in the free band. The node identifier is played in each contention cycle by each node that has data to transmit. Each contending node can easily determine which nodes are contending for transfer of data over the media channel from the presence of node identifiers within distinct frequency bins. Contention for the media channel is resolved by each contending node being giving access to the media channel in accordance with a preset order in which contending nodes will transmit.

High performance load balancing and fail over support of internet protocol exchange traffic over multiple network interface cards

Abstract: A method for selecting a network interface card (NIC) to be used to send and receive data packets in an Internetwork Protocol Exchange (IPX) environment using a server computer system having a plurality of NICs coupled thereto. An outgoing data packet is addressed using an IPX address and a socket number. A load balancing scheme is executed in order to select a NIC from the plurality of NICs. In one embodiment, the load balancing scheme is a function of the IPX address; in alternate embodiments, the load balancing scheme is a function of the IPX address and either the destination or source socket number. The media access control (MAC) address that represents the selected NIC is inserted in the outgoing data packet. The data packet is then sent using the selected NIC. In one embodiment, the present invention also provides a system and method for fault tolerance and fail over support. The plurality of NICs each include a filter that is adapted to mask a portion of a MAC address in an incoming data packet received at a NIC such that the MAC address in the incoming data packet is equivalent to the MAC address representing the NIC.

Apparatus and method for managing variable-sized data slots within a time division multiple access frame

Abstract: A reliable Medium Access Control layer protocol and method employing centralized management of communication in a Time Division Multiple Access network architecture. The Medium Access Control layer protocol implements Quality of Service guaranties to the layers of the Open Systems Interconnection reference model above the Medium Access Control layer by providing guaranteed bandwidth links within the bandwidth range specified by those layers. The Medium Access Control layer protocol further provides variable data slot requisition, variable data slot allocation, dynamic data slot reallocation, and data slot deallocation.

Upstream channel multicast media access control (MAC) address method for data-over-cable systems

Abstract: A head-end in a data-over-cable system transmits a multicast message in a downstream channel to all the cable modems in a particular MAC layer The message includes an address field that contains an upstream channel multicast MAC address that identifies a particular channel, and is used to send a multicast message for which only cable modems transmitting in the upstream direction in that channel are to respond When the message is received by the cable modems, the cable modems compare the upstream channel multicast MAC address with addresses stored in a memory If a match is found, indicating that the cable modem happens to transmit in the upstream direction in the particular channel, it processes the message If no match is found, the message is discarded The upstream channel multicast MAC address helps noise avoidance or redundancy problems associated with a particular channel to be quickly remedied, and avoids the head-end from having to send out a large number of unicast messages in order to communicate with all the modems sharing a given upstream channel

Efficient and accurate Ethernet simulation

Abstract: The Internet is increasingly being called upon to provide different levels of service to different applications and users. A practical problem in doing so is that although Ethernet is one of the hops for nearby all communication in the Internet, it does not provide any QoS guarantees. A natural question, therefore, is the effect of offered load on Ethernet throughput and delay. In this paper, we present several techniques for accurately and efficiently modeling the behavior of a heavily loaded Ethernet link. We propose an efficient distributed simulation model, called Fast Ethernet Simulation, that empirically models an Ethernet link to quickly and accurately simulate it. By eliminating the implementation of the CSMA/CD protocol, our approach reduces computational complexity drastically while still maintaining desirable accuracy. Performance results show that our techniques not only add very little overhead (less than 5% in our tests) to the basic cost of simulating an Ethernet link, but also closely match real-world measurements. We also present efficient techniques for compressing cumulative distributions using hyperbolic curves and for monitoring the load on a heavily loaded link. Finally, we show applications to illustrate the potential usage of the Fast Ethernet Simulation.

Combined tuning of RF power and medium access control for WLANs

Abstract: Mobile communication systems like handhelds and laptops still suffer from low operation time due to limited battery capacity. We exploit the relative new approach of protocol harmonization to extend the time between battery charges in mobile devices using an IEEE 802.11 network interface. Many known energy saving mechanisms only concentrate on a single protocol layer while others only optimize the receiving phase by on/off switching. We show, that energy saving is also possible while sending. This is achieved by a combined tuning of the data link control and physical layer. In particular harmonized operation of power control and medium access control will lead to reduction of energy consumption. In the course of the paper we show a power and medium access control trade-off. Further on we discuss applications of the results in IEEE 802.11 networks.

System with a plurality of media access control circuits with a shared memory for storing data and synchronizing data from a clock domain to a host clock domain

Abstract: Integrated circuits are disclosed which implement multiple channel media access control devices for controlling network communications. The integrated circuits include multiple channel slices which output data for transmission through the network. Each of the channel data are input to a single data memory, which reduces the size of the integrated circuit. Since only one data memory is used to buffer data from multiple channels, the data are first retimed from individual media access control circuit clock domains to a common host clock domain and then scheduled for output to the host. By retiming the data, integrated circuit signal throughput is enhanced. Deeply embedded transmit and receive FIFOs are provided to receive the channel data and implement shared memory access.

Access priority schemes in UMTS MAC

Abstract: UMTS is a third generation radio access network which supports multimedia-capable mobile communication such as packet data and Internet access. In order to provide end-to-end quality of service (QoS) in the UMTS network, certain features need to be incorporated into the MAC design. One possible way of providing different QoS is via providing priority mechanisms. The priority mechanism can be implemented in terms of access priority, service priority and/or buffer management schemes. In this paper, we three access priority schemes based on the random access channel structure. The three schemes are: random chip delay access (RCDAP), random backoff based access (RBBAP), and variable logical channel based access priority (VLCAP). We discuss scenarios where such access priority schemes may be useful. Via simulations, we evaluated and compared these three access priority schemes, Our results indicate that all three schemes provide delay differentiation. However, only the RBBAP scheme provides delay differentiation among different priority classes over a wide range of access request rates without impacting the throughput of the access requests. The other two schemes may cause the throughput of access requests from the lower priority classes to drop apart from forcing them to have a higher access delay.