METHOD FOR AN ENHANCED TIME OF ARRIVAL POSITIONING SYSTEM

Abstract

Method, node, computer program, and computer program product in a wireless communication network, comprising a network communication unit with a data link sub-layer, said node configured to calculate the Time of Arrival and/or Time of Flight based on a counted time from transmission of a response request message in the medium access control layer of said node to the corresponding arrival of a response to said response request message in the data link sub-layer of said node.

Claims

1. Method in a first node of a wireless positioning system wherein the first node is adapted for determining a distance between said first node and a second node, wherein said nodes comprise at least a network communication unit with a data link sub-layer and a central processing unit, wherein the first node performs a method comprising: transmitting a response request message to the second node, starting a first counter at initiation of the transmission of said response request message by the central processing unit in said first node, receiving a response to said response request message from the second node, stopping the counter at registration of the reception of the response to said response request message in the central processing unit of the first node, determining based on the counter result and a known time between reception and response in the data link sub-layer of the second node the distance between said first and second node, wherein the response to said response request message is a response received directly from the data link-sub layer of the second node without being processed in the central processing unit of said second node.

2. The method according to claim 1 wherein said response request message is a Request-To-Send (RTS) message and said response is a Clear-To-Send (CTS) message.

3. The method according to claim 1 wherein, said first node comprises sound means to receive and transmit acoustic or digital sound signals, wherein after determining the distance between said first and second nodes, said first node performs a method comprising: transmitting a first acoustic or digital sound signal (S.sub.A), starting a counter (T.sub.X) at transmission of the acoustic or digital sound signal (S.sub.A), receiving a second acoustic or digital sound signal (S.sub.B), stopping the counter (T.sub.X) at reception of the second acoustic or digital sound signal (S.sub.B), determining based on the counter result (T.sub.X) the distance between said first and second node.

4. The method according to claim 1 wherein, said first node comprises sound means to receive and transmit acoustic or digital sound signals, wherein after determining the distance between said first and second nodes, said first node performs a method comprising: transmitting a first acoustic or digital sound signal (S.sub.A), starting a counter (T.sub.X) at transmission of the acoustic or digital sound signal (S.sub.A), receiving a second acoustic or digital sound signal (S.sub.B), stopping the counter (T.sub.X) at reception of the second acoustic or digital sound signal (S.sub.B), receiving a determined processing time (T.sub.Y) over said wireless communication network, determining the average Time of Flight=(T.sub.XT.sub.Y)/2, and determining based on the average Time of Flight the distance between said first and second node.

5. The method according to claim 3 wherein said first node prior to transmitting said first acoustic or digital sound signal performs the method of: transmitting, over said wireless communication network, a request to start transmitting and receiving acoustic or digital sound signals, and receiving, over said wireless communication network, a confirmation to start transmitting and receiving acoustic or digital sound signals.

6. The method according to claim 3 wherein, at least one of said acoustic or digital sound signals utilizes chirp.

7. The method according to claim 1, wherein the method is performed more than once and said first node performs the additional method of: collecting multiple determined distances, using the multiple determined distances to determine an average error, using the average error to determine the distance between said first and second nodes.

8. Method in a second node of a wireless positioning system wherein the second node is adapted to enable a first node to determining the distance between said first and second node in a wireless communication network, wherein said nodes comprises at least a network communication unit with a data link sub-layer and a central processing unit, wherein the second node performs a method comprising: receiving a response request message from said first node, transmitting a response to said response request message, wherein the aforementioned method is performed in the data link sub-layer of said second node network communication unit without the response being processed by the central processing unit of the second node.

9. The method according to claim 8 wherein said response request message is a Request-To-Send (RTS) message and said response is a Clear-To-Send (CTS) message.

10. The method according to claim 8 wherein, said second node comprises sound means to receive and transmit acoustic or digital sound signals, wherein, after performing the method of claim 8, said second node performs a method comprising: receiving a first acoustic or digital sound signal (S.sub.A), and transmitting a second acoustic or digital sound signal (S.sub.B).

11. The method according to claim 8 wherein, said second node comprises sound means to receive and transmit acoustic or digital sound signals, wherein after performing the method of claim 8, said second node performs a method comprising: receiving a first acoustic or digital sound signal (S.sub.A), starting a second counter (T.sub.Y) at receipt of said first acoustic or digital sound signal (S.sub.A), transmitting a second acoustic or digital sound signal (S.sub.B), stopping the counter (T.sub.Y) at transmission of said second acoustic or digital sound signal (S.sub.B), transmitting the counter result (T.sub.Y) over said wireless communication network.

12. The method according to claim 10 wherein said second node prior to receiving said first acoustic or digital sound signal performs method of: receiving, over said wireless communication network, a request to start transmitting and receiving acoustic or digital sound signals, and transmitting, over said wireless communication network, a confirmation to start transmitting and receiving acoustic or digital sound signals.

13. The method according to claim 1 wherein, a second wireless communication network is used to wake said first wireless communication network.

14. Computer program product, comprising non-transitory computer readable medium and a computer program which when ran in a node in a wireless communication network, causes the node to perform the corresponding method of claim 1, wherein the computer program is stored on the computer readable medium.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0112] The solution is now described, by way of example, with reference to the accompanying drawings, in which:

[0113] FIG. 1 illustrates RTT as known in the prior art.

[0114] FIG. 2 illustrates the solution with Time of Flight/Time of Arrival.

[0115] FIG. 3 illustrates a schematic drawing of the prior art.

[0116] FIG. 4 illustrates a schematic drawing of the solution.

[0117] FIG. 5 illustrates a typical transmit pattern for nodes in a wireless communication network.

[0118] FIG. 6 illustrates a method for Time of Flight/Time of Arrival determination.

[0119] FIG. 7 illustrates an alternative aspect of a method for Time of Flight/Time of Arrival determination.

[0120] FIG. 8 illustrates a first node, Node A.

[0121] FIG. 9 illustrates a second node, Node B.

[0122] FIG. 10 illustrates a schematic drawing of an enhanced distance determining system using both wireless communication and sound means for determining distance between two nodes.

DESCRIPTION OF EMBODIMENTS

[0123] In the following, a detailed description of the different embodiments of the solution is disclosed under reference to the accompanying drawings. All examples herein should be seen as part of the general description and are therefore possible to combine in any way in general terms. Individual features of the various embodiments and methods may be combined or exchanged unless such combination or exchange is clearly contradictory to the overall function.

[0124] In FIG. 1 an illustration of round trip time (RTT) as known by the prior art is shown. Each node 1, 2, comprise a central processing unit (CPU) 3, 7, a network communication unit (NCU) 5, 8 and one media access layer (MAC-Layer) 6, 9 each. The first node 1 further comprises a counter 4. A RTT message RTT.sub.n is shown in different stages of transmission RTT.sub.1, RTT.sub.2, RTT.sub.3, RTT.sub.4, RTT.sub.5, RTT.sub.6 illustrating the path a RTT message travels. FIG. 1 further shows a simplified sketch of a first node 1, also indicated as Node A and second node 2, also indicated as Node B, wherein said first node 1 comprise a CPU 3 with a first counter 4 and a NCU 5 with a MAC-Layer 6. The second node 2 comprises a CPU 7 and a NCU 8 with a MAC-Layer 9.

[0125] FIG. 1 further illustrates how to determine the distance between a first node 1 and a second node 2 in a wireless communication network with RTT. A RTT message RTT.sub.n is sent from the CPU 3 of the first node 1 and the counter 4 is started with a start signal C.sub.1 at the first transmission step RTT.sub.1. The transmission passes the NCU 5 and the MAC-Layer 6 of said first node 1 in the second transmission step RTT.sub.2 and reaches the MAC-layer 9 of said second node 2. The MAC-layer 9 is a part of the NCU 8 and the transmission is further passed on to the CPU 7 of said second node 2 in transmission step RTT.sub.3. The CPU 7 processes the transmission and creates a response which is transferred back to the NCU 8 through the fourth transmission step RTT.sub.4. The transmission is further passed on through the MAC-Layer 9 of the second node 2 and transferred back to the MAC-Layer 6 of said first node 1 through the fifth transmission step RTT.sub.5. Finally the transmission reaches the CPU 3 of said first node 1 through transmission step six RTT.sub.6 and the counter 4 is stopped through a stop signal C.sub.2.

[0126] In additional to processing times the accuracy of positioning systems in network communication systems, such as Wi-Fi, presents additional problems. The Wi-Fi standard is developed for network communication and is not by default adapted for positioning systems or distance determination. The Wi-Fi standard for example comprises a timer with a clock frequency of 1 MHz, a resolution allowing for time determination in terms of micro seconds. The ability to determine a position or distance is directly related to the resolution of which time can be measured in a RTT system. The resolution of micro seconds thereby makes those systems undesirably inaccurate.

[0127] FIG. 2 illustrates a first embodiment of the solution wherein the transmission for determining the distance between a first node 1, also indicated as Node A, and a second node 2, also indicated as Node B, utilizes Time of Arrival/Time of Flight instead of round trip time. FIG. 2 also illustrates how the transmission used to determine the distance between said first node 1 and said second node 2 is handled in the Mac-Layers 6, 9 of the nodes 1, 2. A response request message RTT.sub.n, is transmitted from the CPU 3 of the first node 1 and the counter is started with a start signal C.sub.1. The response request message is further transferred through the NCU (Network Communication Unit) 5 and the MAC-Layer 6 and finally transmitted to the second node 2. An example of a NCU is a PHY-type of chip, not limiting to other types of components. The NCU and the MAC may be integrated or collocated into the same physical component. The NCU may in different embodiments comprise various functions or components, such as radio frequency functions, signal mixing functions, transceiver functions, digital baseband functions, digital signal processing functions, communication algorithm functions, not limiting to other functions or physical components. The second node 2 handles the response request message RTT.sub.n and returns the reply RTT.sub.5 directly in the MAC-Layer 9 eliminating any steps involving the CPU 7 of the second node 2. The response is transferred to the CPU 3 of the first node 1 and the counter 4 is stopped by the stop signal C.sub.2. Thereby, any unknown processing time in the second node 2 can be eliminated. This can further be improved with the use of RTS and CTS messages in standards supporting such messages. For example, in IEEE 802.11x, the MAC-Layers 6, 9 supports RTS and CTS messages that are sent prior to any data transmission. This is further illustrated in FIG. 5.

[0128] FIG. 3 illustrates a schematic drawing of the prior art showing how a response request message is handled in the illustrated embodiment of FIG. 1.

[0129] FIG. 4 illustrates a schematic drawing of present solution where the processing time in the CPU of FIG. 3 may be limited or eliminated in accordance with an embodiment of the present solution.

[0130] FIG. 5 illustrates a transmit pattern for wireless communication networks, such as for IEEE 802.11x, wherein a first node 1 transmit a Request-to-Send message (RTS) and a second node 2 response with a Clear-to-Send messages (CTS) before any data is transferred. The RTS and CTS messages may be handled in the MAC-Layers of both the first node 1 and the second node 2 and may be thereby not affected of processing times in the CPUs of the nodes 1, 2.

[0131] FIG. 6 illustrates a method of determining the distance between a first and second node. The first node 1 may transmit a first acoustic or digital sound signal S.sub.A and at transmission of the acoustic or digital sound signal S.sub.A starts a counter T.sub.X adapted to measure the Time of Flight of an acoustic or digital sound signal. The acoustic or digital sound signal S.sub.A may be received by the second node 2 and a second counter T.sub.Y adapted to count the time between receipt of said first signal S.sub.A and transmission of a response signal S.sub.B starts. The second node 2 may transmit a response signal S.sub.B and the counter T.sub.Y is stopped. The first node receives the response signal S.sub.B and stops the counter T.sub.X. The Time of Flight is thereafter determined by subtracting the two times determined by the counters and thereby determining the average Time of Flight indicated by (T.sub.XT.sub.Y)/2.

[0132] In an embodiment the determination of Time of Flight may be designated to one of the nodes. For example, in an embodiment the Time of Flight may be determined by the first node 1 after reception of a determined processing time T.sub.Y which corresponds to the value of the counter T.sub.Y of the second node 2.

[0133] FIG. 7 illustrates another embodiment of the present solution wherein a first node 1 and a second node 2 may communicate prior to transmission of any acoustic or digital sound signals and may create a handshake wherein both nodes 1, 2 are aware of an inbound acoustic or digital sound signal. By means of such a handshake action the total transmission time counted by the counter T.sub.X of the first node may be decreased while the average time of flight T.sub.P still can be determined. In an embodiment the determined processing time T.sub.Y counted by the second node could thereby be negative.

[0134] The handshake is in an embodiment conducted over a wireless communication network.

[0135] FIG. 8 illustrates a first node 1, also called Node A, comprising a central processing unit 3 (CPU), a counter 4, a memory or computer readable medium 10, a network communication unit 5 (NCU) comprising a media access layer 6 (MAC-Layer), and sound means 12, 13.

[0136] FIG. 9 illustrates a second node 2, also called Node B, comprising a central processing unit 7 (CPU), a memory or computer readable medium 11, a network communication unit 8 (NCU) comprising a media access layer 9 (MAC-Layer), and sound means 12, 13.

[0137] FIG. 10 illustrates a schematic drawing of an enhanced distance determining system using both wireless communication and acoustic or digital sound means 12, 13 for determining the distance between two nodes. Determination of distance with the use of wireless communication networks has an accuracy which is not always adequate for the desired application area. In order to further enhance the precision of such systems additional means, such acoustic or digital sound means 12, 13 can be added in one embodiment of the present solution.

[0138] In an embodiment of the present solution the distance between two nodes may be first determined with means of Time of Arrival/Time of Flight over the wireless communication network. As a second step the distance determination may be improved by usage of a sound in order to determine a close range distance. The wireless technology may be a complement to the sound distance determination technology due to their different characteristics, for example such as range accuracy. Furthermore, the wireless communication network can further be utilized in combination with said sound distance determination technology by transmitting information, such as counted Time of Flight for the sound, between the two nodes over the wireless communication network.

[0139] In an embodiment of the present solution an additional clock may be added to at least one node in a wireless communication network that uses a higher clock frequency than the standard clock. For example, in an IEEE 802.11x wireless communication network system the 1 MHz clock frequency may be complemented with an additional clock that provides better resolution for distance determination. In a preferred embodiment is such a complementary clock arranged with a frequency at 30-50 MHz, 30-300 MHz, 100 MHz or higher, or approximately 40 MHz.

[0140] An advantage with higher frequencies, such as for example 30-300 MHz is that it is possible to in the lower range reach distance accuracy down to meters and in the higher range accuracy down to centimeters which is a significant improvement over previously known art.

[0141] In one additional embodiment of the present solution the increasing or decreasing frequency of a chirp signal can be used as a part of the distance determination method and device.

[0142] It should be noted that in the detailed description above any embodiment, aspect, or feature of an embodiment are only examples and could be combined in any way if such combination is not clearly contradictory.