46 results about "Distribute coordination function" patented technology

A method and system for increasing the overall network throughput over a wireless local area network (WLAN). Specifically, in one embodiment of the present invention, the dynamic switching between the Distributed Coordination Function (DCF) and Point Coordination Function IEEE 802.11 access modes is determined according to the load conditions over the WLAN in a method and system. Stations and access points within a WLAN monitor conditions within the network to determine which access mechanism is most optimum for the current load conditions. Some factors to consider in determining the load conditions include but are not limited to the number of transmissions, number of receptions, and number of collisions.

The invention can establish a default retransmission algorithm and an interference retransmission algorithm. The default retransmission algorithm can be a Distributed Coordination Function (DCF) based algorithm implemented in a MAC layer in conformance with an IEEE 802.11 based standard. The minimum cumulative back-off time for the default transmission algorithm can be less a minimum cumulative back-off time for the interference retransmission algorithm. The minimum cumulative back-off time for the interference retransmission algorithm can be greater than an on-cycle of the PII and less than a sum of the one and off-cycles of the PII (e.g., between ˜8.3 ms and ˜16.7 ms for microwave oven generated PII). A determination can be made whether periodic intermittent interference is present. If so, the default retransmission algorithm can be automatically utilized for wireless data conveyances. When PII is present, the interference retransmission algorithm can be automatically utilized.

An access point transmits a preemptive peg packet when it has no data to transmit in order to maintain the contiguity of its transmission timing position with respect to the timing position of other contention-free sessions (CFS) transmitted by other access points in an existing, periodic sequence. The cyclic prioritized multiple access (CPMA) method establishes the transmission timing position of contention-free sessions (CFS) between overlapping first and second wireless LAN cells contending for the same medium. Each cell includes a respective plurality of member stations. If an access point has no traffic, it will transmit a short, preemptive pegging packet and reset its backoff timer. In this manner, no gaps longer than the distributed coordination function (DCF) Interframe Space (DIFS) are left idle. This prevents other stations from using DCF contention to seize the channel, until all access points have completed one contention-free session (CFS) per periodic cycle.

A method for providing a priority-based, low-collision distributed coordination function (DCF) in a wireless network is provided. The network includes an access point and a plurality of stations. The method includes receiving at a first station a super-frame from the access point. The super-frame is operable to define a service period for each of the stations. A priority for the first station is determined based on the super-frame. A back-off time is selected for the first station based on the priority.

A medium access control method of a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) based wireless LAN (Local Area Network) provides contention-free medium access authority to a station or access point receiving a request signal by: transmitting a request signal frame from an arbitrary station to another arbitrary station or to an access point via a medium occupied in transmission contention with a CSMA/CA algorithm using a DCF (Distributed Coordination Function) interframe space; and transmitting an acknowledgment signal frame from the station or the access point receiving the request signal frame to the station transmitting the request signal frame via an occupied medium using a short interframe space.

The present invention seeks to improve data exchange in a communications system that is especially standardized according to IEEE 802.11a. For this purpose, when the transmission medium, preferably an IEEE 802.11 system with a distributed coordination function (DCF) is accessed in a decentralized manner, pilot signals are transmitted from the transmitter to the recipients using a number of transmission modes and then an allocation table regarding the transmission modes is calculated by the recipient on the basis of the pilot symbols received. The recipient transmits the allocation table to the transmitter so that the subsequent data exchange can proceed on the basis of the allocation table. In the case of centralized access, preferably an IEEE 802.11 system with a point coordination function (PCF), data exchange is improved in that the subsequent data are adaptively modulated already when the allocation table is transmitted.

The invention discloses a distributed media access method used in a wireless local area network. According to the method, on the basis of a distributed coordination function (DCF)-based media access method specified in the conventional standard, the time length of DCF inter-frame space (DIFS) is set by randomizing: namely, a random time length deltaDIFS is added on the basis of the set time length of the DIFS specified in a protocol; moreover, in order not to add excessive channel overhead, the time length deltaDIFS is recommended to be set within a set time slot length, namely, delta DIFS=random (0, Slot_time); the time length of the DIFS is used for avoiding a phenomenon that different users synchronously enter a random backoff window wait state because of selecting contention windows (CWs) with the same time length, so that data collision probability and retransmission numbers among different users are reduced; channel utilization rate is improved; and system throughput is increased. Because only the time length of the DIFS is modified (namely the time length of the DIFS is subjected to randomization processing), the method is simple in operation and easy to develop, cannot increase system complexity, and does not need to update conventional sites; and new sites are compatible with old sites mutually, so that the application range of the method is enlarged, and the method has very good popularization and application prospect.

The present disclosure proposes a method for minor modifications to the Distributed Coordination Function (DCF) channel access mechanism in order to enable a greater number of concurrent communications in a unit area in compliance with the current protocol design. The method comprises equipping nodes with wider neighborhood information than what is obtained with IEEE 802.11, and with a device calibration that equips the device with the knowledge of its performance in the presence of interference. The present disclosure medium access mechanism increases the aggregate throughput with every additional concurrent communication that is enabled in the shared medium. Cocktail Party-capable devices can fairly coexist with 802.11 legacy DCF devices, and co-operate with these devices in the same network without changes to those devices or to the standard. The same or similar mechanisms can be applied to other systems and standards in order to enable concurrent communications in the same contention area.

The invention discloses a resource competition method and a station. The resource competition method comprises the following steps that: during multi-user multiple input multiple output (MU-MIMO) data downlink transmission, a source station selects a target station from a group of target stations according to a predetermined rule, wherein a parameter which corresponds to the selected target station is taken as a parameter of distributed coordination function (DCF) or enhanced distributed channel access (EDCA) resource competition; and the source station competes against other source stations for resources by using the DCF resource competition parameter or the EDCA resource competition parameter.

The present invention provides a multi-channel multiple access method based on a reliable multi-step channel reservation mechanism. The method mainly comprises control channel reservation and data channel reservation. When a node competes successfully in a common control channel according to a distributed coordination function mechanism, a sending node and a receiving node exchange requests on a control channel to send information, and the selection of a data channel, the reservation on the control channel and the reservation on the data channel are completed. According to the method, the multichannel hidden terminal problem is solved by using the control channel reservation, through using multi-step data channel reservation, the data packet transmission without a conflict can be realized with only one control handshake, the control channel congestion is effectively alleviated and the MAC efficiency is improved, and the system performance is greatly improved, which means that the network throughput is improved and the average packet delay is reduced. According to the method, only one set of transceiver is needed, the realization is simple, a central control nodes and entire network synchronization are not needed, and the realization cost and complexity are reduced.

The invention provides a method for designing a WLAN (wireless local area network) MAC (medium access control) layer protocol based on cooperative communication. According to the method, the design work of a network coding based cooperative communication MAC protocol is mainly completed. Mechanisms involved in the whole protocol comprise a network coding mechanism, frame format design and a competition-based DCF (distributed coordination function) channel access mechanism. The invention provides a novel network coding based cooperative communication MAC protocol, the complexity of the access mechanism is reduced, introduction of a large quantity of control frames is avoided, the protocol is well compatible with an existing protocol, meanwhile, the network performance is effectively improved, and the error code rate is reduced.

The invention discloses a powerline communications (PLC) network routing method and system. The method comprises the following steps: step A, a transmitting node transmits a frame of Request To Send (RTS) in a Distributed Coordination Function (DCF) protocol to each neighboring node in a broadcasting manner; step B, each neighboring node calculates own forwarding delay time TCTS_REQ, and the neighboring node having the minimal TCTS_REQ replies to the transmitting node with a frame of Control To Send (CTS); step C, the transmitting node forwards a data packet to the neighboring node having the minimal TCTS_REQ; step D, if the transmitting node receives an acknowledgement character (ACK) returned by the neighboring node having the minimal TCTS_REQ, the transmission is successful; and step E, each node receiving the data packet orderly repeats the steps A to D until the data reaches a target node.

Methods, systems, and devices are described for power management in wireless devices. Power saving for a device of a wireless network may be improved by appropriately setting an inactivity timeout (ITO), and thus the amount of time, after a last transmission or reception of data traffic, that the device remains in an awake mode listening for more data traffic before the device enters a sleep mode. Distributed coordinated function (DCF) information may be used for determining the ITO. For example, the DCF information may be used to determine a channel congestion metric, which may be used to set the ITO for the device.

The invention discloses a resource competition method and a station. The method comprises the following steps that: during multi-user multiple input multiple output (MU-MIMO) data are in downlink transmission, a source station judges minimum back-off time in back-off time which corresponds to an MU-MIMO physical frame, and takes the minimum back-off time as a parameter of distributed coordination function (DCF) or enhanced distributed channel access (EDCA) resource competition; and the source station competes against other source stations for resources by using the DCF resource competition parameter or the EDCA resource competition parameter.

Transmitting multimedia data over a wireless local area network (WLAN), guaranteeing the full length of a multimedia point coordination function (mPCF) period in a WLAN, and dynamically allotting a length of the mPCF period, by receiving a request for multimedia resource from a predetermined device connected to the WLAN, during a distributed coordination function (DCF) period when a right to use a channel is distributed through contention and unilaterally transmitting the requested multimedia resource to the predetermined device during the mPCF period when the right to use a channel is distributed in a centralized manner.

A system and method for prioritizing the transmission of packets in a wireless local area network. A station selects a packet from local priority queuing and identifies the priority bits of the packet. The station declares the priority of the selected packet based on the binary value of the priority bits. If the station detects that another station has selected a packet with a higher priority, then the station ceases to contend for transmission during the current transmission cycle.

The invention provides a bandwidth control method, a bandwidth control device and a network bridge. The invention provides a bandwidth control method based on point-to-multipoint network bridge. The method comprises the following steps that: the beacon cycle with the scheduled length is divided into a distributed coordination function cycle and a point coordination function cycle; based on the scheduled unit bandwidth, the size of the scheduled unit pocket and the point coordination function cycle, minor time slice units comprising a plurality of minor time slices are judged; in the distribution type coordination function cycle, when a registration request message of terminal access equipment is received, the number of the minor time slice units distributed for the bandwidth is calculated according to the bandwidth of the thermal access equipment, and a mark comprising the terminal access equipment and the information item of the number of the minor time slice units are written in the current registration terminal list, and a registration response message is constructed and transmitted; in the point coordination function cycle, taking the minor time slices as a unit, according to the scheduled scheduling algorithm, the terminal access equipment indicated by the mark of the terminal access equipment of each information item in the current registration terminal list is polled.

A wireless network (1) comprises basic service sets (6, 7) and a distribution system (8). Each of the basic service sets (6, 7) comprises stations (2, 3) and stations (4, 5), respectively. Thereby, data is moved between their basic service sets (6, 7) and said distribution system (8) via access points (10, 11), which are also stations (3, 4). A medium access control architecture incorporating a distributed coordination function as an access method is provided. Thereby, a normal mode and a mesh mode are provided. Thereby, normal mode is used to transmit data between stations (2, 3; 4, 5) within each of the basic service sets (6; 7). In mesh mode, data is transmitted between the access points (10, 11). To priorize transmission within the distribution system (8) the stations (2, 5), which are not mesh devices, are silence during mesh mode. Therefor, one of the access points (10, 11) sends a request to send in which the address of the access point (10, 11) is used as both the transmitter address and the receiver address of this request to send.

The invention discloses wireless medium access methods for a DCF (distributed coordination function)/a PCF (point coordination function) on the basis of residual delays. Local residual delay values are computed according to the end-to-end residual delays of data packets and routing states of the data packets in the methods, and positions of the data packets in buffer queues are determined according to the local residual delay values of the data packets. The wireless medium access method for the DCF includes comparing the local residual delays of the next to-be-transmitted data packets of various websites to determine competition windows and interframe spaces of the various data packets so that the probability that the certain data packet with the small local residual delay value can preferably access a channel is high. The wireless medium access method for the PCF includes comparing the local residual delays of the next to-be-transmitted data packets of the various websites to obtain a polling list and polling sequences of the websites in each competition-free period so that the certain data packet with the minimum local residual delay value can preferably access the channel. The methods have the advantages that the certain website with the small local residual delay can assuredly preferably access the channel, and the end-to-end service quality of networks can be improved.

According to the present invention, collision and a back-off slot in a competition by means of DCF can be significantly reduced, and a throughput higher than conventional DCFs can be provided. Also, overhead due to additional control messages is eliminated by reverse order implied information operating in a distributed manner in terminals, and communication with conventional terminals is enabled even in a wireless network using Aps or the DCF.