Showing papers on "Media access control published in 2002"

Measurements of a wireless link in an industrial environment using an IEEE 802.11-compliant physical layer

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.

Reliable MAC layer multicast in IEEE 802.11 wireless networks

Abstract: Multicast/broadcast is an important service primitive in networks. The IEEE 802.11 multicast/broadcast protocol is based on the basic access procedure of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). This protocol does not provide any media access control (MAC) layer recovery on multicast/broadcast frames. As a result, the reliability of the multicast/broadcast service is reduced due to the increased probability of lost frames resulting from interference or collisions. In this paper, we propose a reliable Batch Mode Multicast MAC protocol, BMMM, which substentially reduces the number of contention phases, thus considerably reduces the time required for a multicast/broadcast. We then propose a Location Aware Multicast MAC protocol, LAMM, that uses station location information to further improve upon BMMM. Extensive analysis and simulation results validate the reliability and efficiency of our multicast MAC protocols.

Dual purpose power line modem

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.

Hybrid automatic repeat request (harq) scheme with in-sequence delivery of packets

Abstract: A method, along with corresponding devices (11, 12) and a system (11, 12), by which in-sequence delivery of data blocks, sent wirelessly by a sending terminal (11), is provided to a radio link control layer (12a) of a receiving terminal (12) by a media access control layer service (12b) of the receiving terminal (12), where the data blocks are communicated according to a protocol, such as WCDMA, in which a media access control layer (11b) of the sending terminal (11) includes as a service the transmission of the data blocks and possible retransmission of the same data blocks in response to ACK/NAK signaling by a corresponding service included in a media access control layer of the receiving terminal. No data block sequence number is used in the ACK/NAK signaling.

Highly integrated media access control

Abstract: A supervisory communications device, such as a headend device within a communications network, monitors and controls communications with a plurality of remote communications devices throughout a widely distributed network. The supervisory device allocates bandwidth on the upstream channels by sending MAP messages over its downstream channel. A highly integrated media access controller integrated circuit (MAC IC) operates within the headend to provide lower level processing on signals exchanged with the remote devices. The enhanced functionality of the MAC IC relieves the processing burden on the headend CPU and increases packet throughput. The enhanced functionality includes header suppression and expansion, DES encryption and decryption, fragment reassembly, concatenation, and DMA operations

Method and system for dynamic bandwidth allocation in an optical access network

Abstract: An optical access network (202) and method for transmitting optical data in the network (202) utilizes an interleaved polling scheme to efficiently use the available bandwidth of the network (202). The use of the interleaved polling scheme allows a central terminal (204) of the network (202) to dynamically allocate upstream bandwidth from remote terminals (206, 208, 210) of the network (202) to the central terminal (204) in response to the amount of data that is waiting at the remote terminals (206, 208, 210) to be transmitted to the OLT (204). In one embodiment, the optical access network (202) is based on Passive Optical Network (PON) technology. In another embodiment, the optical access network (202) utilizes Ethernet protocol to encapsulate data in Ethernet frames for transmission. Thus, in these embodiments, the optical access network (202) includes all of the advantages associated with the PON technology and/or the Ethernet protocol.

Adaptive resource allocation in SDMA-based wireless broadband networks with OFDM signaling

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.

Method of setting network configuration and device and system thereof

Abstract: A method of setting network configuration, and the device and system implemented in a virtual LAN are disclosed. By utilizing the present invention, a network device, such as switch, which supports VLAN, can set and adjust the VLAN configuration information record dynamically according to the media access control (MAC) addresses of other network devices connected to the ports of the network device, and by detecting the plug and play signal on each port of the network device, in order to maintain and manage the VLAN conveniently.

Wireless metropolitan area network system and method

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.

Optical CSMA/CD media access scheme for Ethernet over passive optical network

Abstract: In this letter, we propose and demonstrate a novel implementation of optical carrier-sense multiple access with collision detection to efficiently transport Ethernet frames over a star coupler (SC) based passive optical network. We introduce a redirection mechanism at the SC to achieve high channel efficiency.

A highly reliable broadcast scheme for IEEE 802.11 multi-hop ad hoc networks

Abstract: In wired networks, the broadcast data packets can be easily and safely delivered to destinations. Nevertheless, it is a big challenge to transfer the broadcast frames over the IEEE 802.11 based multi-hop ad hoc wireless networks due to the high bit error rate, the high collision probability, and the lake of acknowledgement (ACK). Unfortunately, most of routing protocols need the broadcast function to exchange important information between nodes. From our observations, the efficiency of the routing protocol, such as dynamic source routing (DSR) and ad-hoc on-demand distance vector (AODV), finding the path from source to destination is strongly depending on the supported broadcast scheme in the underlying media access control (MAC) protocol. In this paper, we first investigate the uncertain broadcast problem in the IEEE 802.11 MAC protocol while delivering the necessary broadcast frames. Since no acknowledgement will be sent by any recipient of the broadcast frame in IEEE 802.11 MAC protocol, we propose a highly reliable broadcast scheme to solve such uncertain problem. The proposed scheme, which is still compatible with standard, can efficiently minimize bandwidth consumption as well as propagation delay.

Media access control for MIMO wireless network

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.

A distributed cable modem termination system (CMTS) architecture implementing a media access control chip

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.

Method for dynamically allocating bandwidth in ATM passive optical network

Abstract: The present invention relates to a method for dynamically allocating bandwidth under a media access control (MAC) protocol between an optical line termination (OLT) and a group including a plurality of optical network units (ONUs) in an ATM-PON. In order to meet quality of service (QoS) requirement, the dynamic bandwidth allocation method is capable of determining bandwidth to be allocated to each of the ONUs on the basis of information about traffic indicators of connections established to each of the ONUs and about the number of non-real time cells waiting in each of the ONUs, resulting in an enhancement in utilization efficiency of an upstream transmission channel and enabling an effective transmission.

Sharing network adapter among multiple logical partitions in a data processing system

Abstract: A data processing system comprising a set of logical partitions and at least one hardware resource that is shared by two or more of the partitions is disclosed. The hardware resource is typically a network communication device such as a conventional network adapter. A first logical partition will generally take control or ownership of the resource through resource driver software that is part of the first partition. The other partitions that want to share the resource typically then register themselves with the first partition. In one embodiment, the registration of each subsequent partition is achieved by registering a set of low level network identifiers with the resource driver software. In one embodiment, a Media Access Control (MAC) address is assigned to each logical partition and the logical partition registers this address with the resource driver to identify itself from other logical partitions. The first partition will then typically configured the resource to prevent any hardware filtering of packets or other information that the resource might otherwise engage in. Once the hardware filtering is deactivated, the resource can receive and accept any and all packets on the connected medium. The driver software can then compare the destination MAC address against the list of registered MAC addresses and forward the packet to the appropriate LPAR if a match is detected. The driver can typically also accommodate broadcast packets that are intended to be delivered to every node on the network.

Quality of service based media access control for mobile ad hoc networks

Abstract: A manager node (105) controls access to a shared network communication medium by a number of nodes. A first node (101) transmits a request to the manager node (105). The request includes information indicating that the first node (101) requires a QoS link to a second node. The manager node (105) determines whether the QoS link from the first node (101) to the second node can be supported and sends an accept message to the first node (101) when the QoS link can be supported. Prioritized media access control may also be used in a distributed network without using a manager node to control access to a shared communication medium. A node with high priority data may reduce the duration of its contention window so that it will have a better chance of gaining control of the shared communication medium than a node with low priority data.

IEEE 802.11 optimal performances: RTS/CTS mechanism vs. basic access

Abstract: We address the throughput analysis of high-speed IEEE 802.11b WLANs from both an analytical and a simulative perspective. Specifically, we derive the throughput formula for the RTS/CTS access method of the p-persistent IEEE 802.11b MAC protocol. The accuracy of the proposed model is exhaustively validated via simulation results. By exploiting our formulas, we derive the theoretical upper bound for the throughput performance of the IEEE 802.11b protocol. Our analytical and simulative results indicated that the RTS/CTS mechanism produces very limited advantages in the standard IEEE 802.11 networks with respect to the basic access when no hidden stations are present. Finally, we extend a distributed backoff-tuning strategy firstly proposed for the basic access method, and we validate its effectiveness to approach closely the throughput limit of the IEEE 802.11b protocol.

Gigabit ethernet passive optical network system and media access control method for the same

Abstract: A GE-PON (Gigabit Ethernet Passive Optical Network) system and media access control method for the same are disclosed. In the GE-PON system, by employing MAC attributes of the gigabit Ethernet frames, an OLT (Optical Line Termination) transmits a downstream window containing both a control frame having timeslot position and size information in association with at least two ONUs and Ethernet frames to an ODN (Optical Distribution Network). The OLT analyzes contents of RAUs in an upstream window transmitted from the ONUs in a TDMA method and received from the ODN, and permits timeslot position and size corresponding to each of the ONUs. A plurality of ONUs, connected to the ODN, have their respective timeslot position and size allocated in response to their respective information contained in the control frame of the downstream window. RAU frames are transmitted having queue information and Ethernet frames associated with the allocated timeslots. As a result, by the above MAC structure of the GE-PON system, the OLT can be quickly intercommunicated with a plurality of ONUs.

Time bounded medium access control for ad hoc networks

Abstract: Most previous work on medium access control (MAC) protocols for wireless ad hoc networks has focused on the twin goals of maximising throughput and minimising average packet delay as required for general-purpose applications.In this paper we describe a new MAC protocol for use in multi-hop ad hoc networks whose goal is to provide, with high probability, time-bounded access to the wireless medium for applications with guaranteed response time requirements.The Time-Bounded Medium Access Control (TBMAC) protocol is based on time-division multiple access with dynamic but predictable slot allocation. TBMAC uses a light-weight atomic multicast protocol to achieve distributed agreement on slot allocation and employs location information to minimise contention for slots.TBMAC is the first time-bounded MAC protocol for multi-hop wireless ad hoc networks. In this paper we describe the protocol and provide a number of time bounds for the transmission of messages.

Method for supporting ethernet mac circuits

Abstract: An Ethernet MAC sublayer is provided for supporting Ethernet MAC circuits in an Ethernet Network. In accordance with one embodiment, an Ethernet MAC sublayer is provided for processing and setting up circuits. The MAC sublayer provides support for higher level signaling (112, 122, 132) and routing (114, 124, 134) applications to implement Ethernet MAC circuit functionality. The MAC sublayer provides interrupts for WAN learning and circuit setup. The MAC sublayer also provides address table entry extension (2102, 2202, 2302) to allow for usage of multiple links between nodes (2100, 2200, 2300). The routing application is used to manage routing information, maintain a MAC to port mapping database, and manage port resources. The signaling application is used to set up and manage circuits. In accordance to various embodiments, circuits of various types and properties can be managed in the Ethernet Network.

System and method for traffic accounting and route customization of network services

Abstract: Traffic accounting and route customization of network services is described. According to one embodiment of the invention, a route customization server selects one or more network service providers to provide network services for one of a plurality of network users. The selection is based on a change request being provided by the one of the plurality of users. In another embodiment of the invention, a traffic accounting server provides billing information to the one of the plurality of users based on one or more media access control (MAC) addresses included in the network traffic of the one of the plurality of users.

System and method for trans-medium address resolution on an ad-hoc network with at least one highly disconnected medium having multiple access points to other media

Abstract: A system and method for providing a mechanism for trans-medium address resolution on a network with at least one highly disconnected medium having multiple access points to other media. The system and method provides a “unique” media access control (MAC) address in address resolution protocol (ARP) for mobile nodes in an ad-hoc network, correctly identifying the optimum intelligent access point (IAP) for node communication where the optimum IAP changes more rapidly than traditional address updating may be able to accommodate. Medium layer routing protocols recognize medium frames addressed with this unique MAC address should be routed to the currently associated IAP, whichever IAP that might be at the moment the frame is sent.

Controlling reverse channel activity in a wireless communications system

Abstract: A wireless communications system includes access networks and access terminals Within each cell or cell sector, reverse links and forward links are defined between an access network and multiple access terminals in the cell or cell sector Based on a reverse data rate threshold value calculated from noise measurements, the access network indicates to access terminals within its cell or cell sector whether activity on reverse links are to be increased or decreased

Wireless communication terminal, wireless communication module, program, recording medium, wireless communication network, and communication control method

Abstract: PROBLEM TO BE SOLVED: To enhance the security function of a wireless communication terminal. SOLUTION: A communication terminal 40 decodes the SSID (Service Set IDentification) and a MAC (Media Access Control) address of a base station 30 included in a received beacon and authenticates the base station 30 by discriminating whether the SSID obtained by decoding the beacon is coincident with the SSID stored in an SSID storage area 408a and whether the MAC address obtained by decoding the beacon is matched with any MAC address in a base station address storage table 408b. Further, the communication terminal 40 measures a radio wave reception strength of the beacon received from each base station 30 when the communication terminal 40 is present in an area wherein a plurality of basic service areas are overlapping and authenticates the base station 30 in the order of stronger radio wave reception strength. COPYRIGHT: (C)2003,JPO

Communication system, communication device, and communication method

Abstract: A hands-free device includes a communication unit that obtains a Media Access Control (MAC) address of a portable terminal device from the portable terminal device, and an address storing unit that registers one of the MAC addresses that is obtained by the communication unit into the address storing unit itself in response to a registration trigger signal The hands-free device also includes a control unit that reads the registered MAC address from the address storing unit and specifies a portable terminal device having the read registered address as a communication target device in response to a search trigger signal

The road to an end-to-end deterministic Ethernet

Abstract: In recent years we have witnessed that switched Ethernet is on the way to get a predominant position in the automation world. From a communication point of view the introduction of the IEEE 802.1p traffic prioritization standard is an important milestone on the road towards deterministic Ethernet, that has made it possible to predict worst case latency over a switched Ethernet infrastructure. However, the missing link with respect to achieving an application-to-application predictable transfer time has been the ability to control the latency behavior within the end-nodes that may cause severe jitter. We present a generic concept for introducing also a prioritization mechanism into the protocol stacks and give arguments for applying these mechanisms within automation networks in order to obtain deterministic Ethernet node-to-node. The argumentation is followed by real-world measurements showing promising results.

IEEE 802.11e MAC-level FEC performance evaluation and enhancement

Abstract: We evaluate and enhance the performance of the Forward Error Correction (FEC) scheme being defined in the upcoming IEEE 802.11e Medium Access Control (MAC) protocol. A novel retransmission-combining technique is proposed to enhance the performance of the MAC-level FEC scheme. We also identify a problem with the IEEE 802.11a physical (PHY) layer when it is used with the MAC-level FEC. A new PHY frame format, backward compatible with the original format, is proposed to resolve the problem. Finally, we analytically evaluate the error performance of the MAC-level FEC, and its enhanced performance via retransmission-combining and new 802.11a PHY frame format.

Performance analysis of predictive p-persistent CSMA protocol for control networks

Abstract: Performance analysis of predictive p-persistent CSMA algorithm, employed in the MAC sublayer of the LonTalk protocol (ANSI/EIA 709.1, ENV 13154-2), designed for local operating networks (LonWorks) has been developed. The simulation approach based on the channel-centric discrete-event method has been chosen. The performance is evaluated on the basis of the most important measures used in random access networks: the channel throughput, the channel capacity, the collision rate and the mean packet delay versus the offered load. The simulation results for collision rate under heavy steady-state load condition confirm the analytical solution based on a probabilistic calculation.

A time space division multiple access (TSDMA) protocol for multihop wireless networks with access points

Abstract: We propose time division multiple access with circular reservation (TDMA/CR), a time/space division multiple access (TSDMA)-based medium access control (MAC) protocol for wireless mobile networks with control units, including wireless LANs, cellular networks with ad hoc relaying capability, and ad hoc networks with access points or clusterheads. Different from the MAC protocol of IEEE 802.11, TDMA/CR is centralized and can utilize the computation capability of base stations or access points to increase network throughput, reduce latency, and provide QoS guarantees. We evaluate the performance of TDMA/CR and show that the utilization achievable by the wireless-tree (or splitting) channel access mechanisms of TDMA/CR is about 40% to 46% and the channel access delay is small and bounded. Moreover, TDMA/CR can achieve considerably higher throughput (e.g., by a factor of about 3 or higher) due to its support for variable-radius transmissions in ad hoc wireless networks.