49 results about "Hidden node problem" patented technology

Devices, softwares and methods reschedule multi-party sessions upon premature termination of a wireless communication session. Upon sensing a premature termination, an access point transmits a rescheduling frame. All sessions are advanced in time, which saves time in the end, without leaving quiet times. In addition, the invention avoids a hidden node problem.

A system and method for identifying potential hidden node problems in a multi-hop wireless ad-hoc communication network, such as an 802.11 network. The system and method evaluates the relationship between the neighbors of each respective node to identify nodes of a wireless ad-hoc communication network whose capabilities of receiving data packets can be adversely affected by hidden node problems in order to avoid selecting paths containing those potentially problem nodes for routing data packets. Specifically, for each node, the system and method generates a node metric identifying the relationship between the neighbors of a node. Each node can then transmit its respective metric with its routing advertisement data, so that other nodes can assess the degree of potential hidden node problem that may be experienced by that node, and can choose to avoid using that potentially problem node for routing data packets to other nodes.

Disclosed are a method and a system for setting a routing path in consideration of hidden nodes and carrier sense interference.

The method of setting a routing path for transmitting a packet from a source node to a destination node in a wireless multi-hop network consisting of plural nodes and plural links for connecting two nodes with each other, comprises: calculating carrier sense interference weights representing carrier sense interference related to the respective links and combining the carrier sense interference weights of the links included in at least one specific path connecting the source node with the destination node; calculating hidden node weights representing hidden node problems related to the respective links and accumulating the hidden node weights of the links included in the path; and calculating a metric value for the specific path by combining the carrier sense interference weights and the hidden node weights, and determining the specific path with the least metric value as the routing path.

Accordingly, in the multi-channel multi-radio wireless mesh network, the path with minimized hidden node problem and carrier sense interference can be selected to improve network performance

In a wireless network using a carrier sense multiple access (CSMA) scheme is provided a method, system, devices and instruction sets for detecting transmission levels and adjusting the transmission levels for both a connection point and mobile stations within the network in order to reduce power consumption in network devices and minimize interference problems while keeping hidden node problems on a controlled level.

The present invention discloses an apparatus, a method and a computer program for resolving a hidden node problem in relation to handshake message transferring e.g. in WLAN networks. In one embodiment of the invention, the apparatus receiving a Clear to Send (CTS) message repeats the message after a Short Interframe Space (SIFS) time period. Stations not directly hearing the original CTS due to a low power are able to receive the repeated CTS and defer their transmissions accordingly. In another embodiment, the apparatus receiving the CTS message indicates in its Ready to Send (RTS) message that the CTS sender station has a low transmitting power. With this knowledge, the other present stations can defer their transmissions until they are sure that the data transfer between the first two stations having the RTS-CTS messaging has not been initiated or is already completed.

Embodiments of the invention provide signaling mechanisms for wireless networks composed of a large number of stations. An example method embodiment comprises: receiving by a wireless terminal device, a first message from an access point, the first message comprising information indicating a plurality of restricted access windows, each allocated for a different group of terminal devices associated to a wireless network managed by the access point; receiving by the terminal device, a second message from the access point, within a restricted access window of the plurality of restricted access windows, the restricted access window allocated to a group of terminal devices of which the terminal device is a member, the second message comprising information indicating that a communications channel is available; and determining by the terminal device, based on the second message, that the communications channel is not occupied by hidden ones of the terminal devices associated to the network.

The invention discloses a method for starting an RTS/CTS mechanism, which comprises the following steps: an AC (AP (Access Point) Controller) receives transmitting terminal information reported by APs in the self district; the AC detects whether hidden nodes exist between APs or not according to the transmitting terminal information reported by the APs; the AC determines STAs (Station) influenced by the hidden nodes according to the transmitting terminal information reported by APs between which the hidden nodes exist, so as to generate controlled information and issue the controlled information to the APs related with the STA; and the APs receive the controlled information, and start the RTS/CTS mechanism when sending data to the STAs according to the controlled information. Accordingly, the invention further discloses a device and system for starting the RTS/CTS mechanism. The method, the device and the system reduce the interference caused by the hidden nodes existing between the APs in the system, the RTS/CTS mechanism is not abused, and the air interface utilization rate and the system access capability are improved.

The invention discloses a visible light full duplex continuous transmission random access method based on a channel reservation mechanism. Different from the CSMA/CA protocol in the existing IEEE802.15.7 standard, after a user executes idle channel estimation and detects that the channel is in an idle state, the user does not directly send a data frame, but firstly sends a RTS frame to reserve the channel, and sends the data frame after successfully reserving the channel. A full duplex visual light access point needs to broadcast busy tone to eliminate the hidden nodes when receiving the RTS frame or the data frame. Moreover, the user can directly execute CCA without executing random evasion again after successfully transmitting the data frame, therefore the conflict of the data frame is prevented, the time slot resources consumed by the random evasion mechanism are reduced, and the throughput and delay performance are improved. By adoption of the visible light full duplex continuous transmission random access method, the visible light hidden node problem is effectively solved, and meanwhile, the throughput and the delay performance of the visible light CSMA/CA protocol is optimized at the same time.

A method of ameliorating the hidden node problem in wireless local area networks employing power control is disclosed. The illustrative embodiments function in a variety of ways that have a common theme: while the Data Frames are transmitted at lesser potency, at least one of the control frames—Request-to-Send, Clear-to-Send, and Acknowledgement—associated with the Data Frame are sent at a greater potency. This causes at least one of the “loud” control frames to be heard and decoded by all of the potentially contending stations. And because the control frames carry duration information for the virtual carrier sense mechanism, their reception suppresses transmissions by potentially-contending stations that cannot sense the “quiet” Data Frames.

The invention provides an auxiliary directional access control method of idle nodes in WLAN. The method comprises the following steps: firstly monitoring a channel by a source node, after the channel is idle, sending a Directional Request To Send (DRTS) information; after an idle neighbor node receives the DRTS, judging whether the DRTS causes interference on communication among other nodes according to an information list, if interference is caused, sending a Neighbor Information Package (NIP) to the source node by the idle neighbor node, and blocking the transmission of the source node; if interference is not caused, updating a Directional Network Allocation Vector (DNAV) value in the DRTS information list according to the DRTS, sending Directional Clear To Send (DCTS) information to the source node by a destination node by using a wave beam in the DRTS direction of a receiving source node, beginning to send data by the source node and confirming successful transmission after the response of the destination node is received, and returning to a monitoring state. The problem of hidden nodes caused by handshaking signal listening missing is avoided, the pair number of parallel transmission nodes is increased, and the channel utilization rate is improved.

The embodiment of the invention relates to the field of wireless communication, and particularly relates to a channel multiplexing method and system, a channel multiplexing device and an access point, and aims at solving a hidden node problem and an exposed node problem existing in the prior art. The channel multiplexing method provided by the embodiment of the invention comprises that: aiming at one target access point, the access point which is adjacent to the logic of the target access point is confirmed, and the access point which is not adjacent to the logic of the target access point is confirmed; the target access point and the access point which is adjacent to the logic of the target access point are arranged to use a same channel to perform data transmission within different time ranges; and the target access point and the access point which is not adjacent to the logic of the target access point are arranged to use the same channel to perform data transmission. The hidden node problem and the exposed node problem existing in the prior art are solved by the embodiment of the invention so that interference is avoided and efficiency in channel multiplexing is enhanced.

Disclosed are a resource reservation method and device, which are applied to a WiFi system. The method includes the following steps: a target node receives a resource reservation request sent by a source node and sends a resource reservation response to the source node, wherein the resource reservation response includes a reservation time, and the resource reservation response is used for enabling other nodes which are capable of monitoring the resource reservation response in the WiFi system to set respective network allocation vectors according to the reservation time; and the target node judges whether data sent by the source node is received in a preset time and if not so, a resource release instruction is sent to the other nodes so as to enable the other nodes to initialize the respective network allocation vectors and re-compete for resources. Therefore, a hidden node problem is solved and at the same time, sufficient and reasonable utilization of network resources are ensured.

A method and a wireless communication device to overcome a hidden node problem in a BSS The method includes detecting that transmitting one or more data frames causing one or more nodes of an unsynchronized wireless communication network to become hidden nodes. The wireless communication device that causes the hidden node problem requests a time allocation for transmitting one or more data frames to at least one node of the unsynchronized wireless communication network and to transmit the one or more data frames using an antenna beam forming technique at the allocated time frame.

Method and system for managing hidden node problem in a communication network. A receiving node in the system, upon receiving a data transmission request from at least one transmitting node, dynamically checks status of the channel between the transmitting node and the receiving node. If the channel is found to be clear for transmission, then the receiving node sends a message that indicates that the channel is clear, to the transmitting node, and the transmitting node starts transmitting the data. Upon receiving a message from the receiving node that the channel is not clear for transmission, then the transmitting node waits for a particular time period and attempts the connection again.

The invention discloses a method for expanding capacity of Ad Hoc network through mitigating interference using multiple antennas MAC (MIMO-MAC) optimization. The method comprises the following step that: each node is provided with a plurality of antennas, and the number of the antennas on each node is the same. Data frames of the MAC layer are synchronized and have four stages: namely a request to send (RTS) competing stage, a clear to send (CTS) emitting stage, a data (DATA) emitting stage and an acknowledgement (ACK) emitting stage, which are closely associated and cannot be separated. RTS signal packets in the method are emitted in a competition manner and CTS signal packets are synchronously emitted so as to shorten interactive time for RTS and CTS. The number of the data packets which can be emitted by each node is derived by a method for bilaterally allocating the data packets, so the problem of node hiding is solved and the capacity of the network is greatly expanded.

The invention discloses a Zigbee hidden conflict resolution method for a wireless sensor network. A hidden node problem is an important factor for the performance degradation of an IEEE802.15.4 protocol. According to the method, a contention free period (CFP) of the IEEE802.15.4 is equally divided into a plurality of timeslots, the address information of hidden nodes is extracted from a partially-damaged frame caused by a hidden conflict, the nodes are dynamically regulated into different competition groups according to a currently acquired hidden relationship, the nodes in the same competition groups competitively transmit messages according to a binary backoff method in the same period, and the nodes in different competition groups transmit the messages in different timeslots, so that the problem of hidden conflict is completely solved. Compared with other hidden conflict resolution methods, a conflict-identification-and-grouping-based hidden conflict avoidance method has the advantages of low additional overhead, dynamic regulation and the like, and a data transmission rate, throughput and an energy utilization rate are remarkably increased.

The invention provides an MAC protocol based on instant forwarding. The protocol is achieved through the self-organization router step and the transmission step. According to the self-organization router step, nodes generate a self-organization router according to a ROUT_REQ frame, a response frame ROUT_ACK and an acknowledgement frame ROUT_CNFM. According to the transmission step, the nodes are classified, the classified nodes acquire target addresses according to the self-organization router, and data packets are sent or received according to the target addresses. According to the MAC protocol based on instant forwarding, through the self-organization router and the improvement of a handshaking mechanism, synchronous check can be carried out through forwarded signals in the forwarding process, dual-way contralateral routing and single-way instant forwarding are supported at the same time, the problem of hidden nodes can be solved, end-to-end delay is lowered, and the throughput rate and full-duplex network performance are improved.

For directional wireless communications, at least one new response to a Request-to-Send (RTS) message has been created to avoid a hidden-node problem that is particular to directional networks. In response to an RTS received during a NAV period, a Denial-to-Send (DTS) may be transmitted to indicate that the responding device cannot currently communicate further because its NAV is currently set, but it will be ready to communicate after expiration of the time period specified in the DTS.