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WO2011128475A1 - Procédé et système de formation de faisceau distribué en réseaux de nœuds sans fil, et nœud sans fil applicable à un tel système - Google Patents

Procédé et système de formation de faisceau distribué en réseaux de nœuds sans fil, et nœud sans fil applicable à un tel système Download PDF

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Publication number
WO2011128475A1
WO2011128475A1 PCT/ES2011/000128 ES2011000128W WO2011128475A1 WO 2011128475 A1 WO2011128475 A1 WO 2011128475A1 ES 2011000128 W ES2011000128 W ES 2011000128W WO 2011128475 A1 WO2011128475 A1 WO 2011128475A1
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WIPO (PCT)
Prior art keywords
node
nodes
network
stage
time
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PCT/ES2011/000128
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English (en)
Spanish (es)
Inventor
Marti MAÑOSAS CABALLÚ
Gonzalo Seco Granados
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Universitat Autonoma de Barcelona UAB
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Universitat Autonoma de Barcelona UAB
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Priority to ES201290075A priority Critical patent/ES2396766B1/es
Publication of WO2011128475A1 publication Critical patent/WO2011128475A1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/04—Scheduled access
    • H04W74/06—Scheduled access using polling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/001—Synchronization between nodes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/24—Cell structures
    • H04W16/28—Cell structures using beam steering

Definitions

  • the present invention concerns, in a first aspect, a distributed beam forming method in wireless node networks, and more particularly a method that allows to continue with an initiated synchronization cycle, even if one or more of the cancellation occurs said wireless nodes.
  • the present invention concerns a system intended to implement the method proposed by the first aspect.
  • a third aspect of the invention concerns a wireless node intended to constitute, together with other similar or similar wireless nodes, the system proposed by the second aspect of the invention.
  • a fundamental problem in ad-hoc wireless networks and wireless sensor networks is to achieve energy efficient communication.
  • one of the current challenges lies in sending a common message to a distant base station by a group of distributed nodes or sensors with power restrictions.
  • a solution to this problem is known as distributed beam shaping or distributed beamforming.
  • Beam shaping is a technique that allows a transmitter equipped with more than one antenna to focus its signal in a certain direction, obtaining clear energy benefits.
  • each transmitter is equipped with a single antenna.
  • cooperatively working the transmitters can emulate a cluster of antennas and behave like a "distributed beam shaper".
  • the signals arrive at reception coherently, that is, forming a constructive interference of the information sent by the different sensors.
  • the gain measured as the increase in signal to noise ratio for the same total transmitted power, is equal to the number of sensors that make up the network.
  • Ensuring simultaneity at the destination offers a greater degree of freedom: it allows to use codes with high transmission rates as there is no mismatch between symbols of the different signals at the destination. If a protocol does not offer simultaneity, then small mismatches can occur between signals at the destination, resulting in an imperfect sum of the symbols in reception. This decoupling between symbols worsens for high transmission rates.
  • the sensors can disappear without any kind of prior warning, as for example it is the case that a sensor breaks down and, therefore, does not have the capacity to send a prior notice of disconnection, so that the rest of the network components are aware of their cancellation and act accordingly.
  • the present invention offers a solution to the objective technical problem posed, for which it concerns, in a first and second aspects, a method and a beam shaping system distributed in wireless node networks that allows smooth operation regardless of the disappearance of some nodes in the network, that is, it is planned to work dynamically, determining possible node cancellations and preventing them from interrupting the indicated synchronization process, which makes it a much more flexible proposal than those described in the aforementioned background, which allows the nodes to be able to disconnect voluntarily at any time.
  • the present invention concerns, in a first aspect, a method of forming a distributed beam in wireless node networks, which comprises performing the following steps.
  • b) performing a first synchronization stage comprising sending, sequentially, each of said wireless nodes, after receiving said beacon signal, a respective time reference signal to at least one consecutive node, or closer, according to a first sense in a cycle of ascent, starting with a first node of said network;
  • c) performing a second synchronization step comprising sequentially sending each of said wireless nodes, a respective temporary reference signal to at least one consecutive node, or closer, according to a second direction, opposite to said first direction, in a down cycle, starting with the last node of said network.
  • At least steps a), b) and c) are carried out in order to carry out a stage d) comprising sending, after said stage c), by each of the wireless nodes, a respective signal containing a message common, distributed, to the base station, in a synchronized phase, frequency and arrival time (such as a symbol synchronization), so that all the signals received in a constructive way can be added to it.
  • the method proposed by the first aspect of the invention comprises determining that at least one of the wireless nodes has caused the network to drop if at least its respective consecutive node has not received the respective time reference signal from it, in step b) or stage c), after a predetermined waiting time, and sending, after said determination, by said consecutive node, its respective temporary reference signal to the next node, in said cycle of rising of said stage b) or in said descent cycle of said stage c).
  • said predetermined waiting time is substantially equal to 2-tp for each node that has caused a low, and of m-2-tp for m consecutive nodes that have caused a low, if applicable, tp being a time estimated maximum propagation between any two nodes of the network, which is given by the maximum distance between the nodes and the speed of propagation of the signal.
  • this is, in general, a logical position known by the respective node, said first and last nodes having the first and last logical positions, respectively.
  • each node will be used to indicate whether a node is inferior or superior to another, regardless of whether the up or down cycle is being performed.
  • the method comprises broadcasting the time reference signals in steps b) and c), so that these are also received by the other nodes of the network, in addition from by the consecutive node to which they are explicitly addressed, in which case the method comprises carrying out the determination that at least one node has caused the addition in addition to said consecutive node, also in each of the other nodes of the network, if upon receipt (at each node of the network) of the temporary reference signal broadcast by the previous node to which it may, or to those who may have caused cancellation, said predetermined waiting time elapses without receiving another temporary reference signal.
  • the method comprises, for an exemplary embodiment, after said determination of the withdrawal of at least one sensor, updating the network composition in each of the nodes of the network that has not caused cancellation, at least as regards the total number of live nodes and status of each of the nodes, and also update its new logical position in the network, only for the superior nodes with respect to which it has caused cancellation, in any of said first and second senses, that is to say for the nodes with a logical position higher than the one that caused cancellation.
  • the method proposed by the present invention comprises counting, by means of an internal counter of each node, the number of received signals, including the signal of beacon broadcast by the base station and the temporary reference signals broadcast by the other nodes, to know, each node, taking into account at least its logical position, when it is your turn to consider that the received temporary reference signal is explicitly addressed to it and to carry out the subsequent sending of its temporary reference signal in said stage b) and / or in said stage c).
  • the method comprises that the penultimate node take the role of said last node and should only send a temporary reference signal, the already sent in the ascent cycle, and when the last to last node determines said termination of the last node, produced in the ascent cycle of stage b), the method comprises considering, by said second to last node, that the temporal reference signal broadcast by the penultimate node in stage b) it is part of the sending of the descent cycle of stage c) and is directed to said second to last node.
  • step b) If the determination of the cancellation of one or more nodes is carried out in step b), that is, during the upload cycle, the method comprises carrying out step d) of sending the common message in a distributed manner, by means of all the nodes that do not They have caused low.
  • step c) if the determination of the cancellation or cancellation of nodes is carried out in step c), that is to say in the descent cycle, the method comprises canceling the realization of stage d) at least as regards the subsequent nodes ( with a lower logical position) than the one that caused the loss, according to said second direction.
  • the method comprises using, in steps b) and c), time reference signals dependent on the beacon signal broadcast by the base station, as is the case of the proposal made in [Br008], for a more preferred embodiment, the method comprises using, in steps b) and c), time reference signals independent of the beacon signal, in order to improve, in comparison with [Br008], time synchronization of arrival, or symbol, of the signals containing the common message sent in a distributed way to the base station, each node making an estimate of the initial phase and the frequency of the beacon sent by the base station in step a), and using both values to generate its carrier during the distributed beam conformation stage, to perform the phase and frequency synchronization, in stage d), of the respective signals containing the common message sent by each of the nodes, distributed, to the base station.
  • said temporal reference signals contain at least one pulse or one pulse, unlike those used by [Br008] which are sinusoidal in nature.
  • the method comprises using the temporary reference signals sent by the nodes to perform the synchronization in the three indicated signal characteristics, but these are especially used to perform the synchronization at the time of arrival at the base station of the respective containing signals of the common message sent, in step d), by each of the nodes, which is carried out, in general, by determining the time at which each node must send its respective containing signal of the common message in step d), without any communication from the nodes to the base station.
  • the method comprises making a preliminary calculation, in each node, of a delay that goes from the end of the reception of the beacon signal from the base station until the end of the reception of the temporary reference signal sent by the immediately previous node, in step b), if it has not caused cancellation, determining that said moment of sending the common message is equal to the time in which the node in question has finished sending its respective temporal reference signal, in step c), plus said calculated delay r.
  • the method comprises determining that said moment in which each node must send its respective signal containing the common message is the same, if at least a node with a lower logical position has caused a drop in stage b), while the node in question has finished sending its respective time reference signal, in step c), plus a corrected delay ⁇ resulting from subtracting a value of temporary error e, at a delay of 7 "that goes from the end of the reception of the beacon signal until the end of the reception of the temporary reference signal sent by a node that has not caused cancellation in step b) with a logical position lower immediately before the node in question but higher than the one that caused the cancellation.
  • said temporary error value e it is substantially equal to m-2tp, with tp in general being an estimated propagation time between two nodes, and m the number of consecutive nodes that have caused low, although for an embodiment example for which the signals sent have a frequency in the range of the THz, each node generates its own tp on its own time scale.
  • Such delay correction is valid for each node after at least one "live” node, that is to say that it has not caused termination, arranged between the "dead” node, which has caused termination, and the node in question or later, since when it receives the temporary reference signal sent by said intermediate "live” node, in the calculation of the delay f the predetermined waiting time required to determine the withdrawal of one or more nodes is accumulated.
  • the method comprises determining that said moment at which each node must send its respective signal containing the common message is the same, if at least one node with a lower logical position and immediately prior to the node in question it has caused the cancellation in stage b), at the time in which the node in question has finished sending its respective temporal reference signal, in said stage c), plus a corrected delay ⁇ resulting from subtracting a temporary error value e ⁇ At a delay f that goes from the end of the reception of the beacon signal to the end of the course of said predetermined waiting time without receiving a temporary reference signal.
  • a double objective is achieved, a first objective related to correctly performing the interchange of temporal reference signals between nodes, that is, in preventing the system from being blocked and in updating the vision of the network of each node, and a second objective that lies in correcting the values of temporary delays that are deduced during the synchronization process, in the case where nodes disappear.
  • the method proposed by the first aspect of the invention allows for beam shaping distributed in a network with power restrictions and unknown topology. It is important to note that communication from the nodes to the base station is not necessary at any time during the synchronization stages, until the sending of the common message.
  • a second aspect of the invention concerns a distributed beam shaping system in wireless node networks, comprising:
  • Y a base station intended to broadcast a beacon signal by one or more omnidirectional antennas
  • each of said wireless nodes being provided to receive said beacon signal and to send a respective signal containing a common message, distributed, to the base station, in a synchronized manner in phase, in frequency and at the time of arrival, so that in it all the signals received in a constructive way are added.
  • the system proposed by the second aspect of the invention is configured to implement the method proposed by the first aspect of the invention.
  • each of the wireless nodes comprises an omnidirectional antenna through which to send the steps of stages b) and c), and at least one processing unit provided for as minimum determine that one or more wireless nodes have caused low, said processing unit having access to a memory, and ability to register in said memory data referring to the total number of nodes that make up the network, the state of the same, by For example, a vector of states, and to the logical position that the node in question occupies in the network, the processing unit also being provided to update said data after the determination that one or more nodes have caused cancellation.
  • the processing unit of each of the nodes is also provided, for an exemplary embodiment, to determine the moment in which the node must send its respective signal containing the common message in step d), performing all the necessary calculations, for ensure said synchronization at the time of arrival at the base station of the respective signals containing the common message sent, in step d), by each of the nodes.
  • Both the acquisition of said data referring to the total number of nodes that make up the network, their status, and the logical position, and their update if necessary, such calculations that determine when the node should send its respective signal containing the common message, are carried out by using one or more algorithms implemented in the processing unit of each node, some of which will be described in detail in a later section of this description.
  • the wireless nodes are mobile and / or are wireless sensors, in which case the wireless network is an ad hoc network containing an arbitrary number of wireless sensors.
  • a third aspect of the invention concerns a wireless node applicable to a distributed beam shaping system in wireless node networks, and which is intended to constitute, together with other similar or similar wireless nodes, the system proposed by the second aspect of the invention.
  • Fig. 1 is a schematic diagram illustrating, by means of three corresponding views, steps a), b) and c) of the method proposed by the first aspect of the invention, for an exemplary embodiment, using a base station and wireless nodes of the system proposed by the second aspect of the invention;
  • Fig. 2 shows a temporal scheme of the tasks performed in each time interval or timeslot in steps a) to d) of the method proposed by the first aspect of the invention
  • Fig. 3 is a flow chart of the actions to be performed by any node of the system network proposed by the second aspect of the invention, in case of not contemplating casualties in the system;
  • Fig. 4 shows a flow chart of the actions to be performed by any node of the network each time a beacon is received, for an example of embodiment of the method proposed by the present invention
  • Fig. 5 shows another flow chart, in this case of the actions to be performed by any node of the network every time a predetermined waiting time is exceeded without receiving beacons.
  • Fig. 1 shows a series of wireless nodes, in particular sensors, indicated as Si, S 2 ... Sj ... S N , and a base station D 0 , all of them forming part of the system proposed by the second aspect of the invention, and by which the method proposed by the first aspect of the invention is implemented.
  • step a) of the method is illustrated in the left view of Fig. 1, in which the base station D 0 broadcasts a beacon signal to the wireless sensors S 1 f S 2 ... S j .. .S N , in the central and right views, steps b) and c), respectively, corresponding to the time reference signal sendings in respectively, an up and down cycle are illustrated respectively.
  • each temporary reference signal sending has been illustrated by a single arrow directed to the next node, as explained in a previous section, for a preferred embodiment the signal sent by each one of the nodes is received by all the nodes Yes, S 2 ... Sj ... S N of the network, since it is transmitted by broadcasting.
  • beacons will be referred to both the beacon signal broadcast by the base station D 0 and the time reference signals exchanged, by broadcasting, between the sensors S ⁇ S 2 ... S j ... S N.
  • Fig. 2 the different signals sent in steps a) to d) and their order are illustrated by means of a time scheme formed by respective intervals or time slots, indicated by the steps of the method in which They find included.
  • a beacon is sent, starting with the one sent by the base station in TS 0 , and in the last Time interval, TS BEAM , the information is sent to the destination as a distributed beam shaper, in step d).
  • the ascent cycle which is carried out from TS 0 to TS N-1 , that is during stage b
  • the descent cycle which is carried out from TS N to TS 2N-2 , that is during stage c).
  • each sensor S ⁇ S 2 ... S j ... S N calculates the time delay previously referred to as r, which added to the time at which each sensor has finished sending its respective beacon, in step c), determines the moment in which the sensor in question must send the signal containing the common message to the base station D 0 .
  • FIG. 3 A flowchart of the actions to be followed by each node or sensor of the network is shown in Fig. 3 when there are no casualties, which are described below, from the box labeled "Start" in the diagram of Fig. 3.
  • A1 In this box the node checks whether or not it has received a beacon (either from the base station or any other node). If the answer is yes, go to box A2, and if it is negative, the action indicated by this box is executed over and over again, until it offers an affirmative answer.
  • a beacon either from the base station or any other node.
  • A2 In this box the node questions whether the received beacon is the first, that is, the one coming from the base station. If so, go to box A3, and if the answer is negative, turn to A4.
  • A3 The action carried out in this box by the node is to initiate the time count that will allow the calculation of the delay r, as described above, and move on to box A4, that is, continue With the protocol.
  • A4 The dilemma represented by this box raises the question of whether it is the first turn of the node in question. If so, go to box A5, and if not, the AIO.
  • A5 In this box the node for the time account initiated in A3, assigning to delay r the value indicated by said account that, as indicated above, the node will wait to send the signal containing the common message, since send your beacon in the descent cycle, or second cycle.
  • A6 This box is used to check if the node is the last one or not. If yes, go to box A7, and if not, to A9.
  • A7 In this box the node sends a beacon that, being the last node will correspond to the descent cycle.
  • A8 The node sends, in this box, its signal containing the common message to the base station after waiting for the delay ⁇ after sending A7.
  • A9 The node is executing the action corresponding to this box, because it is not the last one, taking into account its logical position, so that action consists of sending the beacon in the upload cycle, after which the actions to perform, that is, go to the "end" box.
  • A10 After checking that it is not the first turn of the node, the dilemma is reached represented by this box, which raises the question of whether the node is the last node. If yes, it ends its actions, and if not, it goes to box A11.
  • the method comprises being carried out by means of a flow chart like that of Fig. 3 but without the box A10, which has been preserved in the embodiment example of Fig. 3 for the reasons stated regarding its implementation in programming code.
  • A1 1 In this box the node, which is not in its first cycle or occupies the last logical position, wonders if it is its second turn. If not, it ends its actions, and if the answer is affirmative, it goes to box A12 .
  • A12 This box is used to check if the node is the first one or not. If yes, go to box A13, and if not, to A14.
  • A13 In this box the node sends its signal containing the common message to the base station without waiting for the delay r, since theoretically it should be zero when it is the first node.
  • A14 In this box the node sends its beacon in the descent cycle.
  • A15 In this box the node sends its signal containing the common message to the base station after waiting for delay r after sending A14, which delay will have been calculated in its first cycle, that is, when a previous execution of the flow chart has taken to box A5. After this box the node ends its actions.
  • Fig. 3 The flowchart of Fig. 3 just described does not take account of node cancellations, so it is representative of the system proposed by the second aspect of the invention that, although adapted to implement the method proposed by the first aspect, is also capable of implementing the most basic actions illustrated by Fig. 3, when node casualties occur. Also this Fig. 3 and its corresponding description is representative of an example of embodiment of the preferred case mentioned in the explanation section of the invention, related to the improvement of the efficiency in the synchronization of phase, frequency and time of arrival at the station base of the signals containing a common message sent by each of the wireless nodes, in a distributed manner, regardless of whether or not the sensor is low.
  • each sensor must have an internal counter that increases its value at the end of the reading of a received beacon. Thanks to this counter, a sensor can know how many beacons have been sent and can deduct the turn of each sensor in the network. The actions of the flowchart in Figure 4 begin each time the counter increases its value.
  • each of the variables or elements referred to in said flow diagrams should be clarified, starting with the state vector, which specifies, for each node, whether it is alive or not. If there are N nodes in the network the state vector has N positions, and in each of them a 1 or a 0 appears depending on whether the node is alive or not.
  • the variable that counts the number of nodes in the network only specifies how many nodes are alive, and depending on this value the state vector goes changing its size when it's your turn.
  • the logical position variable of a node attributes a logical position to the node. When nodes with higher position die this variable does not change. But when nodes with lower position die, all nodes positioned above reduce their logical position so that there is no gap between two live nodes.
  • each sensor has different variables to count time.
  • One variable is essential to count delays ⁇ and r ", and another to count the elapsed time At since the reception of the last beacon.
  • the actions of the flowchart in Fig. 5 begin each time the variable At exceeds integer multiples of 2 -tp.
  • beacon or temporary reference signal Each time a node receives a beacon or temporary reference signal, this algorithm is activated, since said reception indicates that there is a live node sending it and thus serves to update the system casualties, in addition to performing the actions of the diagram in Fig. 3 in case there are no casualties.
  • beacon and temporal reference signal since it is not necessary that both types of signals have different shapes, although this is configured to work whatever the forms of the temporary reference signals and the signals of beacon sent by the base station.
  • beacon from the base station
  • start of the protocol represented by said flow diagram also called dynamic synchronization protocol.
  • temporary reference signals allow the network update and protocol monitoring.
  • B1 In this box the node checks whether or not it has received a beacon (either from the base station or any other node). If the answer is yes, go to box B2, and if it is negative, the action indicated by this box is executed over and over again, until it offers an answer affirmative.
  • a beacon either from the base station or any other node.
  • B2 In this box the node for the At time count to count dead nodes, since it has received a beacon from a live node.
  • B3 The action carried out in this box by the node is to check whether the beacon received is the first or not. If it is the first beacon then just start the synchronization protocol and start, in B4, the ⁇ account because it is the beacon of the base station. If not, what happens is that the received beacon is a temporary reference signal and means that the protocol is already in full execution.
  • B5 The node checks if it is in the upload cycle and if the turn is of a node with a lower logical position. If you are in the upload cycle and it is up to a lower node, you will go to box B6 to perform the corresponding actions in this case.
  • B6 In this box it is checked whether there have been any node cancellations, in this case for nodes with lower logical positions than the one that sent the beacon, by checking the value of At whose account has been stopped at B2. If there are one or more dead nodes, go to box B7, and if not, directly to B8.
  • B9 The node checks if it is its first turn, in which case it goes to box B10. If not, go to box B19.
  • the node When the node has received a beacon explicitly addressed to it, either from the immediately preceding node, that is to say with a lower logical position, or that of the base station in the case of being the first node, that is to say its first turn, or turn of the climb cycle, this, the node for the time count that will allow the calculation of the delay r B11: Here the node checks if it is the last node. If so, it should be taken into account that the node will only send a beacon and that therefore the instant it is sent is the reference time that the node has to start counting the previously calculated time until the message is sent to the base station (beamforming). If it is not the last node, it is not necessary to comment, and therefore it jumps to box B17.
  • B12 In this box the node checks if, in addition to being the last one, it is also the first node, that is to say that it is the only node, because all the others have disappeared in some synchronization cycle.
  • B13 Having verified the node that is the only live node, here it proceeds to send the signal containing the common message to the base station, after which it terminates its actions.
  • B14 Being the last but not the only node, in this box it proceeds to broadcast the only beacon to be sent because it is the last node, already in the descent cycle.
  • the method comprises being carried out by means of a flow chart such as that of Fig. 4 but without the boxes B19 to B24, which have been preserved in the embodiment example of Fig. 4 for the reasons stated regarding its implementation in programming code.
  • B20 In this box the node checks if it is in the descent cycle and the turn is of a lower node. If not, the node ends its actions. If yes, it goes to box B21. In fact, the answer will always be affirmative because there are no more options, but adding the condition makes everything more schematic.
  • B21 Here the node checks if there have been casualties in the network, in this case for nodes with higher logical positions than the one that sent the beacon, by checking the value of M whose account has been stopped at B2. If there have been, go to box B22 and if not, directly to B23.
  • B23 Here the node checks if the received beacon is from node 2. In this case, once the node variables have been updated, if necessary, it is necessary to see if the At time count should be started or not. If the beacon comes from node 2 then it is no longer necessary to start the At time count because node 1 does not resend no beacon, but instead sends the message to the base station (beamforming). In this case the node ends its actions.
  • B24 If the beacon does not come from node 2 then the node expects more beacons and that is why here the node starts the At time count, because it had received a beacon and is waiting for another to update its vision of the network, after which it ends its actions along this path.
  • B26 Here the node checks if there have been any node cancellations in the network, in this case for nodes with lower logical positions than the one that sent the beacon, by checking the value of At whose account has been stopped at B2 .
  • B28 Here the node starts the At time count, because it had received a beacon and is waiting for another to update its network vision, after which it ends its actions along this path.
  • B29 In this box the node checks if it is in the descent cycle and the turn is of some superior node. If yes, go to box B30, and if not, B34.
  • B30 Here the node checks if there has been any node cancellation in the network, in this case for nodes with higher logical positions than the one that sent the beacon, by checking the value of At whose account has been stopped at B2 . If there are one or more dead nodes, go to box B31, and if not, directly to B33.
  • the node deactivates, here, the sending of the signal containing the common message to the base station, since as there have been node cancellations in the descent cycle, it is not possible to correct the delay r. And since the casualties have been of nodes with a logical position superior to that of the node that is executing the algorithm, it is still time to deactivate said sending, since it has not begun.
  • a node deactivates the sending it is deactivated during the entire synchronization cycle. I mean once deactivated, said node will not be able to send even if requested in any of the flowchart boxes.
  • B33 Here the node starts the At time count, because it had received a beacon and is waiting for another to update its network vision, after which it ends its actions along this path.
  • B34 The node checks if it is its second turn. If yes, go to box B35, and if not, B40.
  • B35 The node checks in this box if it is the first node.
  • B36 Here the node that has verified that it is the first, proceeds to send the signal containing the common message to the base station, after which it terminates its actions.
  • B39 The node starts the At time count again, because it had received a beacon and is waiting for another to update its network vision, after which it ends its actions along this path.
  • B40 In this box the node checks if it is in the descent cycle and the turn is of a lower node. If not, the node ends its actions. If yes, it goes to box B41. In fact, the answer will always be affirmative because there are no more options, but by adding the condition everything is more schematized).
  • B41 Here the node checks if there have been casualties in the network, in this case for nodes with higher logical positions than the one that sent the beacon, by checking the value of At whose account has been stopped at B2. If there have been, go to box B42 and if not, directly to B43.
  • B43 Here the node checks if the received beacon is from node 2. If the beacon comes from node 2 then it is no longer necessary to start the time count ⁇ because node 1 does not send any beacon again, but instead sends the message towards the base station (beamforming). In this case the node ends its actions.
  • B44 If the beacon does not come from node 2 then the node expects more beacons and that is why here the node begins the At time count, because it had received a beacon and is waiting for another to update its vision of the network, after which it ends its actions along this path.
  • this algorithm is intended to address only very specific cases of disappearances of nodes that influence negatively in the operation of the protocol if its consequences are not taken into account. These cases are the disappearance of node 2 during the second synchronization cycle and the disappearance of the last node.
  • C2 The node begins by increasing the unit that counts the dead nodes by one unit, since the limit wait has been exceeded and therefore it has been determined that one or more nodes have been dropped.
  • C5 Here the node checks if it is the first live node since the last one that sent a beacon, in which case it performs the actions that begin with box C6. If this is not the case, no other update is necessary or the protocol must be followed, since it must be done by another node with a turn before the one that is executing the algorithm, so the node ends the actions to be performed here.
  • C6 As the node is the first live, it becomes its first turn, so it is as if it has just received the beacon of the previous node during the upload cycle and therefore has to stop, at this point, the account of time that will allow the calculation of the delay
  • C7 Since it is the first live node and is in the first cycle, it no longer expects more nodes to die before its turn, and updates the temporary error that can be used to obtain the corrected delay r. As a node with a lower position has died, and by not waiting for more nodes to die before its turn, the node updates its new logical position, which will be reduced, in addition to the number of nodes in the network.
  • the node After the indicated updates, here the node checks if it is the last one, in which case it must be taken into account that you only have to send a beacon, and therefore the moment of sending it is your reference time to start counting the previously calculated time r, until the signal containing the common message is sent to the base station. If it is not the last sensor, it is not necessary to comment.
  • C9 The node checks at this point if it is the one that occupies the first logical position in the network, that is, if it is the only node left alive, because all the others have disappeared in some synchronization cycle.
  • C12 Here the node sends, by broadcasting, the only beacon to be sent, as it is the last node, which corresponds to the descent cycle.
  • C1 The node restarts the At time count at this point because it has already made all the updates corresponding to the missing node / nodes, and has just sent a beacon, so it has to start counting dead nodes again.
  • C15 Since arriving at this box means that it is the first turn of the node, it proceeds to broadcast the first beacon of the synchronization protocol, the one corresponding to the upload cycle.
  • C16 Here the node restarts the At time count because it has already made all the updates corresponding to the missing node / nodes, and has just sent a beacon, so it has to start counting dead nodes again.
  • the method comprises being carried out by means of a flow chart like that of Fig. 5 but without boxes C18 to C22.
  • C19 As a node has disappeared, the node that executes the algorithm updates the state vector.
  • C26 As a node with a higher position has died, and not expecting more nodes to die before its turn, the node updates only the number of nodes in the network.
  • C27 Here the node checks if, in addition to the last one, it is also the first node, that is, the only one left alive because all the others have disappeared in some synchronization cycle.
  • C30 At this point, which is reached because the node is not the only one left alive, it sends the message to the base station after a time ⁇ corrected according to the casualties. As the node is the last one, it must be taken into account that it only sends a beacon, and in this case it has already been sent in the upload cycle. Therefore, the instant it is sent is the reference time used by the node to start counting the previously calculated time r, until the message is sent to the base station.
  • C31 The node restarts the At time count here because it has already made all the updates corresponding to the missing node / nodes, and it is as if it had just sent a beacon. You have to start counting dead nodes again. After that, he ends his actions along this path.
  • C32 The node checks at this point if the last node disappears it has become the penultimate live node. If so, perform the corresponding actions in this case, starting with the one associated with box C33. If this is not the case, other possible critical cases are analyzed within this branch which has been entered by point C23. If the node has determined that it is the penultimate live node, it must be taken into account that the now last one has already sent a beacon, and that therefore it is now the turn of the node that executes the algorithm.
  • C33 As a node with a higher position has died, and not expecting more nodes to die before the turn of the node executing the algorithm, it updates only the number of nodes in the network.
  • C34 The node checks if, in addition to the penultimate, it is the first node, if so it goes to box C35, and if not, to C37.
  • the node Being its second turn, the node sends the message to the base station after a time corrected according to the casualties.
  • C39 The node here restarts the At time count because it has already made all the updates corresponding to the missing node / nodes, and has just sent a beacon. You have to start counting dead nodes again. After that, he ends his actions along this path.
  • C40 The node checks in this box if the last node has disappeared but it is neither the last nor the penultimate live node. If so, it is necessary to update to protect the case in which the penultimate also disappears during the descent cycle. The discharge of the penultimate node would mean that, when no beacon was received from it, the first algorithm, that of Fig. 4, was not activated and the number of nodes in the network was not updated. If the cancellation does not correspond to the last node, no further updates are necessary and the execution of actions by the node is completed here.
  • C41 As the last node has died, and when more nodes can disappear before the turn of the node that executes the algorithm, it updates only the number of nodes in the network.
  • no other update is necessary or follow the protocol, since it must be done by another node with a turn prior to yours (with a higher logical position). Since the node does not send any other beacon at the moment because there are live nodes between its position and that of the last node (which has died), it does not restart the At account and let it continue counting.
  • C42 Here the node checks if it is in the descent cycle and the turn was of some superior node. If the answer is yes, go to box C43 and if not, to C51.
  • C44 The node checks here if it is the first live node since the last one that sent a beacon. If so, proceed to box C45, and if not, no other update is necessary or follow the protocol, since it must be done by another node with a turn prior to yours, so the node ends its actions.
  • C45 Since the node is the first one alive, it deactivates the sending of the message to the base station since, as there have been nodes withdrawals in the descent cycle, the node is not able to correct the delay r. And as the casualties have been of nodes with a logical position superior to that of the node that executes the algorithm, it is still time to deactivate the sending, because it has not started.
  • C46 As a node with a higher position has died, and not expecting more nodes to die before the turn of the node executing the algorithm, it updates only the number of nodes in the network.
  • C49 As it is the second turn of the node, it broadcasts the second beacon of the synchronization protocol, the one corresponding to the descent cycle.
  • C50 The node here restarts the At time count because it has already made all the updates corresponding to the missing node / nodes, and has just sent a beacon. You have to start counting dead nodes again. After that, he ends his actions along this path.
  • C51 The node checks at this point if it is in the descent cycle and the turn was of a lower node. If so, the node performs the corresponding actions in this case, starting with point C52. If not, it does nothing. In fact, the answer will always be affirmative because there are no more options, but adding the condition makes everything more schematic.
  • C53 The node checks if the cancellation corresponds to node 2. If so, it goes to box C54, and if not, no further updates are necessary and the node ends its actions here.
  • C55 In this box the node for the At time count because it no longer has to receive any other beacon, after which it ends its actions.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un procédé et un système de formation de faisceau distribué en réseaux de nœuds sans fil, et un nœud sans fil applicable à un tel système. Le procédé consiste : -à radiodiffuser, à partir d'une station de base, un signal de balise à des nœuds sans fil d'un réseau; -à réaliser des étapes de synchronisation qui consistent à échanger entre les nœuds d'un réseau des signaux respectifs de référence temporelle; - à déterminer qu'un nœud a entraîné une baisse si le nœud respectif n'a pas reçu le signal respectif de référence temporel de celui-ci après un temps prédéfini, et à envoyer après cette détermination, par le nœud consécutif, le signal de référence temporel respectif au nœud suivant; et - à envoyer, à chaque nœud, un signal respectif contenant un message commun, de manière répartie, à la station de base, de manière synchronisée; le système est prévu pour mettre en œuvre le procédé, et le nœud pour faire partie du système.
PCT/ES2011/000128 2010-04-14 2011-04-14 Procédé et système de formation de faisceau distribué en réseaux de nœuds sans fil, et nœud sans fil applicable à un tel système Ceased WO2011128475A1 (fr)

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ES201290075A ES2396766B1 (es) 2011-04-14 2011-04-14 Método y sistema de conformación de haz distribuida en redes de nodos inalámbricos, y nodo inalámbrico aplicable a tal sistema

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008003022A2 (fr) * 2006-06-29 2008-01-03 Intel Corporation Systèmes d'étalonnage et techniques pour une formation de faisceau distribuée
US20100039933A1 (en) * 2008-08-12 2010-02-18 General Atomics Method and system for network setup and maintenance and medium access control for a wireless sensor network

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008003022A2 (fr) * 2006-06-29 2008-01-03 Intel Corporation Systèmes d'étalonnage et techniques pour une formation de faisceau distribuée
US20100039933A1 (en) * 2008-08-12 2010-02-18 General Atomics Method and system for network setup and maintenance and medium access control for a wireless sensor network

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
BROWN, D.R. ET AL.: "Time-Slotted Round-Trip Carrier Synchronization for Distributed Beamforming", IEEE TRANSACTIONS ON SIGNAL PROCESSING, vol. 56, no. 11, November 2008 (2008-11-01), pages 5630 - 5643, XP011227928, DOI: doi:10.1109/TSP.2008.927073 *

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