RU2298289C2

RU2298289C2 - Device and method for delivering packets in wireless networks with multiple retranslations

Info

Publication number: RU2298289C2
Application number: RU2003134626/09A
Authority: RU
Inventors: Говиндараджан КРИШНАМУРТИ (US); Говиндараджан КРИШНАМУРТИ; Йил ГУО (US); Йил ГУО
Original assignee: Нокиа, Инк.
Priority date: 2001-06-30
Filing date: 2002-06-26
Publication date: 2007-04-27
Also published as: CN1541466A; RU2003134626A; EP1415424A4; WO2003005629A1; MXPA03010849A; CN100411327C; JP4392033B2; JP2007251991A; JP2004537206A; AU2002311547B2; EP1415424A1; CA2449532A1

Abstract

FIELD: wireless communication systems, in particular, system and method for decreasing losses during data transfer, when damage occurs in communication line or unit.

SUBSTANCE: invention suggests system and method for decreasing data loss in wireless networks, as a result of failures in one or several wireless communication lines or due to damage of intermediate connecting unit, while wireless network contains at least one intermediate unit (15), having internal buffer (71) for continuous buffering of data, transferred from source unit (11) to destination unit (21), and sets up alternative route for bypassing damaged unit. Lost data packets are transferred again in certain position in response to receipt of error message, denoting damaged unit, or in response to repeatedly transferred request, as a result of data failures in wireless communication network, while intermediate units, without such internal buffering, execute transfer of requests and messages to higher positioned units with internal buffering.

EFFECT: decreased data loss.

5 cl, 8 dwg

Description

FIELD OF THE INVENTION

This invention relates to wireless communication systems, in particular to a system and method for reducing data transmission loss when damage occurs on a communication line or node.

State of the art

Wireless mobile relay networks with multiple retransmissions lack infrastructure certainty and, therefore, they experience frequent communication disruptions caused by node mobility and interference in wireless links. This is a problem in providing quality of service (QoS) in such networks. It is essential in this technical field to understand that typical direct relayings (retransmissions) can satisfy a limited time frame for timely packet delivery. In particular, the transmission of multimedia data is an example of an application in which the loss of data packets is unacceptable. Wireless networks with multiple retransmissions can be used, for example, for a user-oriented network in military applications, for taxi networks, for networks in meeting rooms and for emergency situations, including “911 calls”, which coordinate work between groups involved in search and rescue operations, or through a network, establish a connection between the ambulance operators at the scene of the accident and the doctors in the remote hospital.

Accordingly, the network topology of a wireless multiple-relay mobile communication network changes with time, where the network nodes are mobile, and where communication lines are established and then opened. Accidental damage to such wireless links is also more likely than wired networks because wireless links are more susceptible to interference. Therefore, routing is the most difficult problem in such networks, and the route from the source to the receiver (receiver) may not always guarantee the integrity of the communication session.

Several research attempts have been made to optimize routing protocols on multiple relay networks. These routing protocols optimize routes from the source node to the destination node in the presence of damage to the communication lines caused by the mobility of the node or the deterioration of the quality of the communication line due to interference in the transmission. Various criteria have been proposed for establishing communication routes using such optimization procedures. Some of these criteria include saving power for mobile systems and preventing congestion. At the same time, an enhancement to the TCP / UDP protocol was proposed to transmit packets on multiple relay networks.

Earlier research efforts in this area addressed routing problems without considering local retransmissions and packet delivery in accordance with priorities. The protocols discussed in this technical field depend on high-level protocols, such as TCP (Data Transmission Control Protocol), when solving problems with the loss of a data packet. Such approaches depend on direct retransmissions of lost packets and therefore are not applicable in order to guarantee QoS in a wireless network with multiple relayings in which communication line damage occurs frequently, which leads to an unacceptable delay. In addition, such approaches do not provide prioritization of packet delivery, because packets transmitted from the source to the receiver are processed the same way. This is not an optimal technique, since different microflows within a flow may have different delivery deadlines. Priority delivery in wired networks is known in the art, but timely delivery cannot be guaranteed in a wireless network due to the high probability of transmission errors.

An improved method is needed to ensure the timely delivery of packets with high quality of service in wireless multiple-relay mobile networks.

SUMMARY OF THE INVENTION

The present invention follows from the observation that data loss in wireless networks can be reduced by introducing buffering of data packets at the network level in the intermediate nodes on the transmission path, and local retransmission (relay) of the lost data packets. A wireless network formed using one or more intermediate nodes having internal buffers for continuous buffering of data transmitted from the source to the destination nodes establishes an alternative route that allows bypassing the damaged node and retransmits the lost data packets in response to the receipt of an error message. If the connector lacks an internal buffer, an error message is sent to the upstream node that stores buffered data packets that can recover the missing (lost) data.

Brief Description of the Drawings

The invention described below refers to the accompanying drawings, in which:

Figure 1 is a schematic representation of a wireless network, showing communication routes formed by the connecting nodes;

FIG. 2 is a block diagram describing data transmission using the wireless network of FIG. 1;

Figure 3 is a diagram of the communication node of Figure 1, showing an internal buffer for buffering data passing through the node;

FIG. 4 is a diagram of a connecting node of FIG. 1 showing buffers with a high, normal, and low transmission priority level for buffering data passing through a node; FIG.

FIG. 5 is a flowchart describing in more detail the process of transmitting undelivered data packets, as shown in the flowchart of FIG. 2;

6 is a schematic representation of a wireless network including a connecting node without internal buffering;

7 is a schematic representation of a wireless network including a damaged wireless communication line;

FIG. 8 is a block diagram describing data transmission using the wireless network of FIG.

Detailed description disclosing an embodiment of the invention

1 shows a simple wireless network 10 including a source node 11 (S) and a destination node 21 (D). A user of the wireless network 10 can transmit data by establishing an initial communication route between the source node 11 and the destination node 21 through a series of intermediate connecting nodes. The initial communication route may include, for illustration, sections of the route from the source node 11 to the first connecting node or intermediate node 13 (N ₀₁ ), to the second intermediate node 15 (N ₀₂ ), to the third intermediate node 17 (N ₀₃ ), to the fourth the intermediate node 19 (N ₀₄ ), and then to the destination node 21. The initial communication path can be established in a sequential combination: a wireless communication line 31 between the source node 11 and the first intermediate node 13, a wireless communication line 33 between the first intermediate node 13 and the second intermediate node 15, a wireless communication line 35 between the second intermediate node 15 and the third intermediate node 17, a wireless communication line 37 between the third intermediate node 17 and the fourth intermediate node 19 and a wireless communication line 39 between the fourth intermediate node 19 and the destination node 21.

During data transmission on the initial communication path, one or more intermediate nodes 13-19 may fail. Damage can occur, for example, due to the termination of the connection node (for example, equipment damage or power failure), due to the mobile node moving from the coverage area of the corresponding wireless communication line, or due to the unfavorable environment of the signal propagation (for example , precipitation, or storm) in the intermediate node involved. Accordingly, damage to the intermediate connecting node would cause the loss of one or more wireless communication lines 31-39 and, as a result, the initial communication node will be stopped due to loss or failure of data. The detection of a damaged assembly is well known in the art, and, for example, a mechanism based on the expiration of a timeout can be used.

The operation of the present method of the invention can be described by reference to the flowchart of FIG. 2, in which the initial communication route is established by the method known in the art in step 51, and the data packet stream 29 is configured to transmit in accordance with the selected protocol . Since the transmission of the data packet stream 29 to the destination node 21 is initiated via the initial communication path, each of the individual data packets in the data packet stream 29 sequentially passes through each of the intermediate nodes 13-19. At least one intermediate node in the original communication path is configured such that data packets are buffered for possible local retransmission using priority queuing, at step 57, as described in more detail below. If the original communication route remains intact, a node failure is detected, in decision block 59, the system prepares for the next transmission in operation 61, and receives data packets, when necessary, in operation 53.

If the intermediate node becomes unavailable, causing the break of one or more wireless communication lines 31-39 forming the initial communication route, an alternative connecting route is established, at step 63, using a method known in the art, and the remaining undelivered data packets are transmitted to the node 21 destination to complete the transmission of the stream 29 data packets at step 65. Here is an example: if the third intermediate node 17 becomes unavailable, wireless communication lines 35 and 37 are lost As shown in dotted lines in Figure 1, and the initial communication path is thereby interrupted. The second intermediate node 15 is notified (receives a message) of the damage and an alternative route bypassing the damaged third intermediate node 17, and finds the destination node 21. Such an alternative route may include, for example, a first alternative connecting node 23 (N ₁₁ ) and a second alternative connecting node 25 (N ₁₂ ).

A new wireless communication line 41 may be formed between the second intermediate node 15 and the first alternative connecting node 23, another new wireless communication line 43 may be formed between the first alternative connecting node 23 and the second alternative connecting node 25, and a new wireless communication line 45 may be formed between the second alternative connecting node 25 and the fourth intermediate node 19. The remaining undelivered data packets are then transmitted to the destination node 21 during operation 67, as described in more detail below. If the session transfer session was not completed in decision block 61 of FIG. 2, the system returns to operation 53, in which the next part of the data packet stream 29 is configured for transmission.

In a preferred embodiment, each (one or more) of the intermediate nodes 13-19 includes at least one internal buffer for continuously buffering data packets that pass through the corresponding connecting node. So, in the image of the second intermediate node 15, shown in more detail in FIG. 3, an internal buffer 71 is included in order to store a number of data packets. The size of the buffer 71 depends on the amount of backup memory available in the second intermediate node 15 for use under this function, and is determined by one or more factors, including application bandwidth and mobility speed. If sufficient memory is available, the size of the buffer 71 may be increased to operate with relatively higher data rates through the corresponding connection node and accommodate data packets arriving during the alternate route discovery period.

Buffer 71 may be implemented as a “software” buffer including a portion of the permanent memory of the second intermediate node 15, or may be implemented as a component of computer hardware, such as random access memory (RAM), in the second intermediate node 15. Software buffer can be implemented by reconfiguring the host kernel for buffering. That is, kernel reconfiguration allows buffering and transmission of priority packets and responding to packet retransmission requests. Such requests will be analyzed, the packet (s) will be placed in the buffer (s), and the packet (s) will be queued, as is known in the art. Otherwise, the second intermediate node 15 may include an optional processing device 79 for controlling the identification, storage and retransmission of data packets to the buffer 71. For example, the transmitted data packets 29a, 29b, ..., 29n enter the wireless communication line 33 and leave wireless communication line 35, the buffer 71 also buffers the newly transmitted data packets 29a, 29b ..., 29n, respectively, in the memory cells 71a, 71c and 71e. Buffer 71 may follow a first-come-first-out (store-type) protocol. Otherwise, buffering may be based on a single stream in which the data packets of a particular stream are replaced with pre-buffered data packets of the same stream.

In a preferred embodiment, each of the intermediate nodes 13-19 includes three internal buffers, which are shown as buffers 73-77, in the diagram of the fourth intermediate node 19 in figure 4, the buffers include a portion of the available memory or chip (element) with discrete memory. In this configuration, these three buffers 73-77 can be used to separate the received data packets 29a, 29b ..., 29n into different transmission priority classes, for example, providing high priority of buffer 73, normal priority of buffer 75 and low priority of buffer 77. Thus , data packets in a high priority buffer 73 may be queued for transmission in front of data packets in a low priority buffer 77, using a method known in the art.

FIG. 5 is a flowchart providing a more detailed description of the action taken in step 65 of FIG. 2. From step 63, an alternative route between the intermediate nodes 15 and 19 is established, as shown in FIG. 1, for example, by using the connecting nodes 15, 23, 25 and 19 in step 81. The data packets that now arrive on the alternative route are also buffered accordingly in alternative connecting nodes 23 and 25. The fourth intermediate node 19 is reconfigured with the establishment of an alternative transmission route. That is, data packets originally transmitted from the third intermediate node 17 to port 19a before the damage of the third intermediate node 17 are instead transmitted from the second alternative connector 25 to port 19b due to damage to the third intermediate node 17. Those skilled in the art can appreciate that the reconfigurable fourth intermediate node 19 is the first lower node on the new transmission route, which is located both in the original communication route and in the alternative cottages. When the fourth intermediate node 19 receives a routing message for the same stream (i.e., data packet stream 29), the fourth intermediate node 19 recognizes that the third intermediate node 17 is damaged and responds by notification to the second intermediate node 15 from which the data packets were received by the fourth intermediate node 19 in operation 83. This is to avoid double retransmission of data packets.

For example, as shown in FIG. 4, data packets 29a and 29n reached the fourth intermediate node 19, before the third intermediate node 17 was damaged. When the fourth intermediate node 19 recognizes the reconfiguration of the transmission route (i.e., the data packet from the second intermediate node 15 reaches port 19b and does not reach 19a), a notification is sent to the second intermediate node 15 that the data packets 29a and 29n have been received. The second intermediate node 15 then, trying to determine which data packets sent to the third intermediate node 17 were not received by the fourth intermediate node 19, and determines that the data packet 29b was not received by the fourth intermediate node 19.

At operation 85, data packets identified on the initial communication path as missing (missed) are received from the nearest node located upstream, and the receiving (final) node has corresponding buffered (stored in the buffer) data. Data packet 29b depicts the missing data packet, which was then recovered from buffer 71 in the second intermediate node 15 and transmitted to the fourth intermediate node 19 using an alternative route in step 87. The fourth intermediate node 19 transmits data packets 29a, 29b and 29n to the node 21 destination. If the applicable transmission protocol requires the ordered delivery of data packets, the data packet 29n is transmitted to the destination node 21 only after the transmission of the data packet 29a. Otherwise, if the applicable transmission protocol does not require ordered delivery, the data packet 29b, if buffering occurs in the high priority buffer 73, is transmitted before the data packets 29a and 29n that are buffered in the low priority buffer 77. Additionally, the remainder of the data packet stream 29 is transmitted via an alternative route in step 87. The action is then repeated in step 61 of FIG. 2.

In an alternative embodiment of the method according to the invention shown in FIG. 6, the wireless network 10 includes an unbuffered intermediate node 27, and no memory resource has been created for the internal buffer in the intermediate node 27. Therefore, the intermediate node 27 cannot buffer data packets passing along the transmission route. However, the intermediate node 27 is configured to transmit messages up the transmission direction, as well as the ability to search for alternative routes in case of damage to the node or communication line. If the intermediate node is damaged, as discussed above, for example, the third intermediate node 17 retransmits the message 49 received by the intermediate node 27. Since the intermediate node 27 cannot create missing data packets in case of damage to the node, the retransmitted message 49 is sent upward transmitting to the next intermediate node having internal buffers, for example, of the type of the first intermediate node 13. The missing data packet (s), such as the data packet 29b shown in the illustration, is obtained from any one of the buffers 73-77 and provides the requested node, shown here is the fourth intermediate node 19. If the missing data packet 29b is not present in any of the buffers 73-77 of the first intermediate node 13, the message is transmitted to the source node 11. In the network configuration, of which none of the intermediate nodes located between the damaged node and the source node 11 has internal buffers, missing data packets are received from the source node 11 and passed to the requesting node, as described above.

In yet another alternative embodiment, the quality of the wireless link 37 in the wireless network 10 is degraded or else it becomes unreliable due to interference in the transmission medium, for example, as indicated in FIG. 7. As a result, errors can be introduced in the transmission of the packet between the third intermediate node 17 and the fourth intermediate node 19. The corrective action can be described using an additional link to the flowchart of Fig. 8, on which the initial communication route is established at operation 91, and data packets from stream 29, data packets are received at intermediate nodes at step 93, and buffered at step 95.

If there is no receipt of retransmitted messages, in decision block 99, and if the wireless communication lines 31-39 remain operational, the system stops for transmission at step 101. When the wireless communication line 37 becomes unreliable and transmission errors occur, the retransmitted message is received and the third intermediate node 17 searches for internal buffers 73-77 for the corresponding data packet in operation 103. If the data packet is found in one of the buffers 73-77, in decision block 105, the third intermediate node 17 is aligned AET of the queue the data packet for priority retransmission (not shown) at step 97. This scheduled transmission is made in accordance with the data packet transfer priority as described above.

If the required data packet is not found in the internal buffers 73-77 of the third intermediate node 17, in decision block 105, the next upstream node is checked for the required data replacement in step 107. If the required data is found, in decision block 109, the data are transmitted at operation 97. If the required data is not found, in decision block 109, a request is made as to whether the source node 11 was reached in decision block 111. If the source node 11 has not been reached, operation continues at decision block 105. If the source node 11 has been reached, in decision block 111, and if the required data packet is not contained, in decision block 113, an additional error message may be sent to the data initiator in step 115, and the procedure for the next transmission session continues at operation 101. If the required data packet is available, in decision block 113, the data packet is planned and prioritized for transmission to destination node 21 at operation 97.

While the invention has been described with reference to embodiments, it should be understood that the present invention is in no way limited to the features of the devices and methods disclosed and / or shown in the drawings, but also includes any modifications or equivalents within the scope of the formula inventions.

Claims

1. The communication method used in a wireless network to reduce data loss due to damage to the intermediate node during the transmission of data packets from the source node (11) to the destination node (21), which consists in establishing the initial communication route from the source node ( 11) to the destination node (21), wherein the initial communication route contains two or more intermediate nodes, transmit a data packet (29a) from the source node (11) through the first intermediate node (13) as soon as the connection between the source node (11) and the first intermediate node (13) it will be established, characterized in that the data packet (29a) is additionally stored in the first intermediate node (13) as a data packet (29a) that passes through the first intermediate node (13) through the initial communication path, damage to the second intermediate node (17) is detected in response to the transmission of the mentioned data packet, an alternative communication route is established to the destination node (21) without using a second intermediate node (17), bypass the second intermediate node (17) in response to the detection of damage to the second industrial daily node (17), wherein an alternative communication route originates from the first intermediate node (13), and a data packet (29a) stored in the first intermediate node (13) is retransmitted from the first intermediate node (13) to the destination node (21) through an alternative communication route.

2. The communication method according to claim 1, characterized in that at the said storage step, the data packet (29a) is buffered into one selected buffer from a plurality of buffers (71), the selected buffer corresponding to the priority class of the data packet (29a).

3. The communication method according to claim 1, characterized in that it further stores a buffered data packet (29a) in an alternative connection node (23) located on an alternative communication route.

4. The communication method according to claim 1, characterized in that the first intermediate node (13) is additionally notified of data packets received from the second intermediate node (17).

5. The communication method according to claim 1, characterized in that when transmitting the data packet (29a) via an alternative communication route, transmission is planned in accordance with priority classes in the queue.

6. The communication method according to claim 2, characterized in that when transmitting a data packet (29a) buffered in a first intermediate node (13), a data packet (29a) is transmitted that precedes the transmission of a second data packet (29b) buffered in a buffer with a lower priority class in the first intermediate node (13).

7. The communication method according to claim 2, characterized in that when transmitting a data packet (29a) buffered in the first intermediate node (13), a data packet (29a) is transmitted following the transmission of the second data packet (29b) buffered in the buffer with a higher priority class in the first intermediate node (13).

8. The communication method according to claim 4, characterized in that the said notification of the first intermediate node (13) is performed using the node on an alternative communication route.

9. The communication method according to claim 4, characterized in that the initial communication route includes a third intermediate node (15) located between the first and second intermediate nodes, the third intermediate node (15) containing means for relaying the message.

10. The communication method according to claim 1, characterized in that the alternative communication route comprises a third intermediate node (19) located on the initial communication route between the second intermediate node (17) and the destination node (21).

11. The communication method according to claim 10, characterized in that in addition to the third intermediate node (19), said alternative communication route is recognized in response to said transmission of a data packet buffered in the first intermediate node (13).

12. The communication method according to claim 11, characterized in that the first intermediate node (13) is additionally notified in the third intermediate node (13) of data packets received from the second intermediate node (17) in response to recognition of an alternative communication route in the third intermediate node (19).

13. The communication method according to claim 1, characterized in that upon detection of damage to the second intermediate node (17), a retransmitted message is received.

14. The communication method according to claim 1, characterized in that when establishing an alternative communication route, a communication route is established from the first intermediate node (13) to the destination node (21).

15. A wireless communication network used to transfer data from the source node (11) to the destination node (21) when establishing a connection between the source node (11) and the destination node (21), the initial communication route containing two or more intermediate nodes between the original node (11) and node (21) destination, characterized in that the first intermediate node (13) includes a buffer for storing at least a portion of the data that passed through the first intermediate node (13) through the initial communication path, over a period of time which exceeds the amount of time required for at least part of the data to pass through the first intermediate node (13) via the initial communication route.

16. The wireless communication network according to claim 15, wherein said buffer comprises buffers (71) of at least two different priority classes.

17. The wireless communication network according to claim 15, wherein the first intermediate node (13) further comprises a processor (79) for responding to a retransmission request (49).

18. The wireless communication network according to item 15, wherein the second intermediate node (27) includes means for relaying the message.

19. The wireless communication network according to claim 15, wherein the first intermediate node (13) further comprises a processor and memory for loading a kernel configured to buffer part of the data passing through the first intermediate node (13).

20. The communication method used to reduce data loss due to damage to the wireless communication line between the source node (11) and the destination node (21), which consists in establishing the first communication route from the source node (11) to the node (21) destination, and the first communication path contains at least a first intermediate node (13), when a connection is established between the source node (11) and the destination node (21) transmit a data packet from the source node (11) through the first intermediate node (13) through the first communication route, characterized in that further storing the data packet in the first intermediate node (13) as a data packet transmitted on the first communication path, receiving the retransmitted message (49) in the first intermediate node (13) requesting the data packet (29b) identified as missing, and retransmit a data packet (29b) stored in the first intermediate node (13) from the first intermediate node (13) to the destination node (21) by means of a second communication route in response to receiving a retransmitted message (49), the second communication route coming from the first about interstitial node (13).

21. The communication method according to claim 20, characterized in that it is further determined that the stored data packet in the first intermediate node corresponds to a data packet (29b) identified as missing.

22. The communication method according to claim 20, characterized in that, with said storage, a data packet is buffered in one selected buffer from a plurality of local buffers, the selected local buffer corresponding to the priority class of the data packet.

23. The communication method according to claim 20, characterized in that they additionally receive a retransmitted message in the second intermediate node (27) from at least one other intermediate node and the destination node and relay the retransmitted message from the second intermediate node to the first intermediate node ( 13).

24. The communication method according to claim 23, characterized in that it further checks the local buffer in the second intermediate node (27) for the data packet identified as missed in the retransmitted message and determines that the data packet identified as missed is not detected in local buffer of the second intermediate node (27).

25. An intermediate node in a wireless communication network, comprising a processor, a plurality of storage buffers, and a memory for storing computer-readable instructions that, when executed by the processor, enable the intermediate node to perform the steps of receiving a data packet when establishing a connection between the source node and the destination node, storing a data packet in one or more buffers from a plurality of storage buffers for a predetermined period of time, the predetermined period of time exceeding the period of time required dimy for passing the data packet through an intermediate node receiving the retransmitted message requesting the data packet identified as missing data and transmitting the packet stored in said buffer storage in response to receiving the retransmitted message.

26. A computer-readable storage medium storing computer-readable instructions that, when executed by a processor, enable the first intermediate node in the wireless communication network to execute a method that receives a data packet when establishing a connection between the source and destination nodes, stores the data packet in a buffer during a predetermined period of time, and the predetermined period of time exceeds the period of time necessary for the data packet to pass through the first intermediate node give a data packet to the second intermediate node, detect damage to the second intermediate node in response to the transmission of the data packet, establish an alternative communication route originating from the first intermediate node to the destination node bypassing the second intermediate node in response to the damage detection of the second intermediate node, and repeatedly transmitting a data packet stored in the first intermediate node from the first intermediate node via an alternative communication route.