KR101471440B1 - MAC frame structure for dynamic Ad Hoc network, and operating method thereof - Google Patents

Abstract

The present invention relates to the MAC frame structure of a dynamic ad hoc network which adapts a virtual time-slot method in response to change in mutual locations of wireless nodes for a multi-control signal and multi-multimedia signals within a signal wireless frequency over time by using a chirp spread spectrum (CSS) physical layer and dynamically allocating a channel using distance measurement data between transmission and reception nodes among the wireless nodes. As a result, according to the present invention, multichannel and multimedia signals can be transmitted to a destination within a predetermined time with a high throughput which is equal to or greater than 75%, so information can be delivered continuously. Therefore, the MAC frame structure of a dynamic ad hoc network can transmit a voice, a video, a real time control signal, etc. in real time instead of a CSMA-CA method recommend in standards.

Description

[0001] The present invention relates to a dynamic ad hoc network MAC frame structure and a dynamic MAC frame structure for dynamic ad hoc network MAC,

The present invention relates to a frame structure and a method of operating a dynamic ad hoc network MAC protocol, and more particularly, to a virtual time slot based MAC protocol frame structure for implementing a dynamic ad hoc network suitable for real time data transmission and a method of operating the same.

IEEE 802.15.4 and IEEE 802.15.4a WPAN standards recommend MAC (Media Access Control) based on Carrier Sense Multiple Access-Collision Avoidance (CSMA-CA) and are suitable for the configuration and application of low-speed sensor networks.

Therefore, in the case of voice, video, and real-time control signals requiring real-time transmission, the generated signal must be continuously transmitted to the destination within a predetermined time. In the CSMA-CA method, It is not suitable for real-time signal transmission.

The average throughput of the CSMA-CA MAC is 36% of the physical layer data rate, and throughput is reduced to less than 30% considering the packet overhead of 15% and the gap of about 7% do.

Therefore, if the actual required transmission rate is determined, if the CSMA-CA MAC is used, there is a burden that the data rate of the physical layer should be about 3.3 times or more than the required transmission data rate.

In the case of voice, video, and real-time control signals requiring real-time transmission, the generated signals must be continuously transmitted to the destination within a predetermined time. In addition, the CSMA- It is premised that a transmission collision may occur in one collision, which is not suitable for transmission of a real-time signal which requires QoS (Quality of Service) guarantee.

KR 10-2010-0012992

The object of the present invention is to provide a real-time (Real-time) control system for voice, video, and real-time control signals in place of the CSMA-CA method recommended by the standard, using a CSS (Chirp Spread Spectrum) physical layer recommended by the IEEE802.15.4a standard, time transmission of multi-channel, multi-media signals with high throughput of more than 75%, it is possible to carry out continuous information transmission to the destination within a certain time, using the improved Virtual Time-Slot method. And to provide a frame structure and a method of operating the dynamic ad hoc network MAC that can efficiently transmit real time wireless data to a destination.

According to an aspect of the present invention, there is provided a dynamic ad hoc network MAC frame structure using a CSS (Chirp Spread Spectrum) physical layer and using distance measurement data between transmission / reception nodes between wireless nodes, By allocating channels dynamically, a Virtual Time-Slot scheme is applied corresponding to the mutual position of the wireless nodes with respect to multiple control signals and multiple multimedia signals in a single radio frequency changes with time .

A control manager for managing the wireless nodes generates a C packet to generate a time reference of the virtual time slot, and each of the wireless nodes receives a C packet according to a time reference of the virtual time slot, The C packet can be retransmitted to the wireless node in the next step after a predetermined time elapses from the completion time.

Each of the wireless nodes measuring a mutual distance value between the wireless nodes using an R packet and measuring a link performance value at the time of exchanging the wireless nodes, Value to a control manager for managing the wireless node through a D packet, and the control manager transmits the value of the mutual distance and the link performance value received via the D packet And transmit the C packet (Control Packet) relay order of the wireless nodes to the wireless nodes through the D packet.

Each of the wireless nodes updates the relay order of its own C packet in accordance with the C packet (Control Packet) relay order transmitted through the D packet, The allocation order of the virtual time slots can be updated.

When the wireless nodes are three and each of the wireless nodes generates multimedia data, each of the frames of the MAC includes three C packet (Control Packet) slots, three R packets (Ranging Packet) slots, three D packets (Data Packet) slot, and 18 V packet slots, and the V packet may be at least one of a video packet and a voice packet.

A moving object 1, a moving object 2, and a moving object 3 on which the three wireless nodes are respectively mounted are sequentially listed, and each of the moving object 1, the moving object 2, and the moving object 3 includes real- When an image camera generating 115.2 Kbps is installed, the frame rate of the MAC frame is 20 msec / frame and 50 MAC frames per second can be generated.

The control manager generates the C packet and sends it out at intervals of 20 msec. The wireless node of the moving object 1 receives the transmitted C packet and relays the received C packet to the wireless node of the moving object 2, 1 to the wireless node of the moving body 3. The C-

The wireless node of the mobile unit 3 generates and transmits the V packet to the wireless node of the mobile unit 2. The wireless node of the mobile unit 2 transmits the generated V packet and the V packet of the mobile unit 3, The wireless node of the mobile unit 1 can transmit the generated V packet and the wireless packet of the mobile unit 2 and the V packet of the wireless unit of the mobile unit 3 to the control manager.

If the payload of the packet is 96 bytes and the V packet is allocated to each channel three times per 20 msec, the data transmission rate may be 115.2 Kbps.

In order to swap the transmission direction of the V-packet, a time slot of a previous time is allocated to a wireless node that generates a packet signal among the wireless nodes, A time slot of the next time can be sequentially allocated.

According to another aspect of the present invention, there is provided a method of operating a frame structure of a dynamic ad hoc network MAC, the method comprising: using a Chirp Spread Spectrum (CSS) physical layer, Allocating channels dynamically using measurement data; And allocating the channel dynamically according to a time-varying mutual position of the wireless nodes with respect to multiple control signals and multiple multimedia signals in a single radio frequency, And a step of applying the method.

A control manager for managing the wireless nodes generates a C packet to generate a time reference of the virtual time slot, and each of the wireless nodes receives a C packet according to a time reference of the virtual time slot, The C packet can be retransmitted to the wireless node in the next step after a predetermined time elapses from the completion time.

Each of the wireless nodes measuring a mutual distance value between the wireless nodes using an R packet and measuring a link performance value at the time of exchanging the wireless nodes, Value to a control manager for managing the wireless node through a D packet, and the control manager transmits the value of the mutual distance and the link performance value received via the D packet And transmit the C packet (Control Packet) relay order of the wireless nodes to the wireless nodes through the D packet.

Each of the wireless nodes updates the relay order of its own C packet in accordance with the C packet (Control Packet) relay order transmitted through the D packet, The allocation order of the virtual time slots can be updated.

Accordingly, the present invention uses CSS (Chirp Spread Spectrum) recommended by the IEEE802.15.4a standard, allocates channels dynamically using distance measurement data between wireless nodes in a virtual time slot, Channel, multi-media (multi-media) communication system by configuring an optimal dynamic ad hoc network that adapts to the mutual position of CSS (Chirp Spread Spectrum) wireless transmit / receive nodes Signals can be transmitted continuously to the destination within a predetermined time with a high throughput of 75% or more, and can be transmitted in real-time such as voice, video, and real-time control signals in place of the CSMA- .

1 is a diagram for explaining a frame structure of a dynamic ad hoc network MAC according to an embodiment of the present invention and a method of operating the same.
2 is a diagram illustrating a configuration example of a 3 HOP transmission path in a frame structure of a dynamic Ad Hoc network MAC according to an embodiment of the present invention.
3 is a view for explaining an example of time slot switching (Swap) of a frame structure of a dynamic Ad Hoc network MAC according to an embodiment of the present invention.
4 is a view for explaining mutual distance measurement between wireless nodes in a multi-frame according to an embodiment of the present invention.
5 is a diagram illustrating various embodiments of the dynamic Ad Hoc network of the present invention.

The present invention will now be described with reference to the accompanying drawings. Hereinafter, a repeated description, a known function that may obscure the gist of the present invention, and a detailed description of the configuration will be omitted. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art. Thus, the shape and size of the elements in the figures may be exaggerated for clarity.

FIG. 1 is a diagram for explaining a frame structure and a method of operation of a dynamic ad hoc network MAC according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a frame structure of a dynamic ad hoc network MAC according to an embodiment of the present invention. 3 HOP transmission path.

The frame structure of the dynamic Ad Hoc network MAC uses a CSS (Chirp Spread Spectrum) physical layer and allocates the channels dynamically using the distance measurement data between the transmitting and receiving nodes between the wireless nodes, A virtual time-slot scheme that implements the dynamic ad hoc network corresponding to the mutual position of wireless nodes with respect to multiple control signals and multiple multimedia signals changes with time can be applied.

 The dynamic Ad Hoc network system illustrated in FIG. 1 may include a control manager 12 and a mobile unit 3. It is assumed that each of the three moving objects is equipped with a wireless node for generating a real time moving picture data of 115.2 Kbps and transmitting data, respectively.

The dynamic ad hoc network system can be listed in the order of the control manager 12, the moving object 1 14, the moving object 2 16, and the moving object 3 18 in this order. An image camera for generating 115.2 Kbps of real-time moving image data may be installed in each of the mobile unit 1 14, the mobile unit 2 16, and the mobile unit 3 18.

A MAC frame structure to which a virtual time slot according to the present embodiment is applied will be described with reference to FIG.

The frame rate of the MAC is 20 msec / frame and 50 frames of MAC per second can be generated. In this case, one MAC frame includes three C packet (control packet) slots, three R packet slots, three D packet data slots, and 18 V packet (multimedia data packet) slots . Here, the V packet (multimedia data packet) may be at least one of video and audio packets.

The control manager 12 can create a C packet at predetermined time intervals, for example, 20 msec time intervals, so as to set a time reference of the virtual time slot. The wireless nodes of the mobile units 14, 16, and 18 retransmit the C packets to the wireless node in the next sequence after a predetermined time from the receipt time of the C packet according to the order set by the control manager 12.

The wireless node of the moving object 1 14 receives the transmitted C packet and relays it to the wireless node of the moving object 2 16 and the wireless node of the moving object 2 14 transmits the C packet relayed from the wireless node of the moving object 1 14 To the wireless node of the moving object 3 (18).

Referring to FIGS. 1 and 2, a C packet is used as a control packet for timing synchronization of all wireless nodes. The C packet has a payload of 16 bytes and is allocated to each channel once every 20 msec. The data rate is 6.4 Kbps (16 * 8/20 * 10 ^-3 = 6400 bps).

The wireless nodes of the mobile units 14, 16, and 18 can start packet retransmission by setting a predetermined time (e.g., 50 usec) from the reception completion time of the received packet.

Accordingly, the frame structure of the dynamic ad hoc network MAC according to the present embodiment can acquire MAC frame synchronization, that is, timing synchronization of the virtual time slot, by all the wireless nodes in the above manner.

Based on the timing synchronization of the virtual time slot obtained above, the wireless node of the moving object 3 18 generates a V packet (Video and / or Voice Packet) and transmits it to the wireless node of the moving object 2 16, Transmits the generated V packet and the V packet of the wireless node of the moving object 3 18 to the wireless node of the moving object 1 14 and the wireless node of the moving object 14 transmits the generated V Packet and the V packet of the wireless node of the moving object 2 (16) and the wireless node of the moving object 3 (18) to the control manager (12).

1, 2, and 3, the V packet is a video packet or a voice packet. V packet has a payload of 96 bytes and is allocated to each channel three times per 20 msec, and the data transmission rate is 115.2 Kbps (96 * 8 * 3/20 * 10 ^-3 = 115200). 3 is a view for explaining an example of time slot switching (Swap) of a frame structure of a dynamic Ad Hoc network MAC according to an embodiment of the present invention.

V packet has a feature of swapping its transmission direction as required, as shown in FIG. 3. In the case of switching directions, a wireless node of a mobile station generating a packet signal transmits a time slot of a previous time And a time slot of the next time is sequentially allocated to the wireless node of the relaying section and the finally delivered mobile object.

Each of the wireless nodes of the control manager 12 and the three moving bodies 14, 16, and 18 measures the physical distance in the mutual space using a CSS (Chirp Spread Spectrum) distance measuring function (Ranging). In most practical applications, the distance between the wireless nodes of the moving object is sufficient once a second, and the number of combinations of all distance values between the control nodes 12 and the wireless nodes of the three moving objects 14, 16, As shown in Fig. 4 is a view for explaining mutual distance measurement between wireless nodes in a multi-frame according to an embodiment of the present invention.

Therefore, it is not necessary to perform all the distance measurements within the MAC frames, and only six frames out of 50 frames per second need to be used as shown in FIG.

That is, the distance between the wireless nodes installed in the mobile object 1 14, the mobile object 2 16, and the mobile object 3 18 can be measured by the CSS distance measurement function using six of the frames of the MAC.

The R packet is a ranging packet, as shown in FIGS. 1 and 2. The C packet has a payload of 16 bytes and is allocated 3 times per 20 msec for each distance measurement.

Each of the wireless nodes of the mobile units 14, 16 and 18 calculates the link performance values such as SNR (Signal to Noise Ratio) and PER (Packet Error Rate) measured at the time of R packet exchange 1 and the D packet (Data Packet) shown in FIG. 2 to the control manager 12.

Based on the distance value and the link performance value between the moving objects received from the wireless nodes of the mobile stations 14, 16 and 18 via the D packet as described above, the control manager 12 transmits the moving objects 14, 16 and 18 ) Optimizes the C-packet relay order of each wireless node and delivers it to the wireless nodes of the mobile units 14, 16, and 18 through the D packet. Thus, the order of real-time data transmission of the wireless nodes can be determined.

Upon receipt of the C packet relay sequence information from the control manager 12 through the D packet, each of the wireless nodes of the mobile units 14, 16, and 18 transmits the relayed C packet in response to the transmitted C packet relay sequence And updates the allocation order of the virtual time slots according to the relay order of the updated C packets.

The dynamic ad hoc network that can be configured by the frame structure of the dynamic ad hoc network MAC according to this embodiment can be implemented in three forms as shown in FIG. 5 is a diagram illustrating various embodiments of the dynamic Ad Hoc network of the present invention.

The dynamic ad hoc network shown in Fig. 5 (a) is configured by the control manager 12, the wireless node of the moving object 1 14, the wireless node of the moving object 2 16 and the wireless node of the moving object 3 18, Are arranged in order. The dynamic ad hoc network shown in FIG. 5 (b) is a network in which the control node 12 and the wireless node of the mobile node 14 are connected and the wireless node of the mobile node 1 (14) 3 (18) are directly connected to each other. The dynamic ad hoc network shown in FIG. 5C is a network in which the control manager 12, the wireless node of the moving object 3 18, the wireless node of the moving object 14 and the wireless node of the moving object 16 sequentially Respectively.

When the connection types of the wireless nodes of the control manager 12 and the mobile bodies 14, 16 and 18 constituting the dynamic Ad Hoc network are changed, the control manager 12 controls the mobile bodies 14, 16 and 18, The communication path is dynamically updated (Dynamic Re-Routing) so that the communication path with the wireless nodes of the communication path is the optimum path (or the shortest path).

Specifically, the update of the communication path described above can be performed by the control manager 12 based on the measured distance value between the moving objects.

When the communication path is updated, the assignment of virtual time slots to each of the wireless nodes of the mobile bodies 14, 16, 18 may also be changed corresponding to the communication path updated above.

Referring to the above description and the timing diagram of FIG. 1, the total data rate required can be calculated according to the following equations (1) and (2).

In this calculation formula, C packet, R packet, and D packet all use 16 bytes. A total of 9 packets are used per frame. A total of 18 packets can be used per frame using 96 bytes of V packets. Packet overhead is 15%, and the minimum interval between packets is 7%.

The data rate of only the payload is 748,800 bps, and the data rate of the physical layer required equivalently requires about 2.47 Mbps when the IEEE standard CSMA-CA type MAC is used, In the case of using the virtual time slot type MAC frame according to the embodiment of the present invention, the required data-rate of the physical layer is 960 Kbps and can be realized by using 1 Mbps, which is the data rate of the physical layer of the IEEE802.15.4a CSS standard method .

In addition, unlike the CSMA-CA method, the dynamic ad hoc network MAC frame structure according to the embodiment of the present invention is time-ordered by a virtual time slot allocation method so that collision between packets does not occur in advance, Quality of Service) can be ensured.

The frame structure and the operation method of the dynamic Ad Hoc network MAC according to an embodiment of the present invention are not limited to the configurations and the methods of the embodiments described above, and all or part of the embodiments may be selectively combined .

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and specific embodiments and drawings. However, it should be understood that the present invention is not limited to the above- And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains.

12: Control Manager
14: mobile 1
16: Mobile 2
18: Mobile 3

Claims (14)

The present invention relates to a frame structure of a dynamic Ad Hoc network MAC,
By using a Chirp Spread Spectrum (CSS) physical layer and dynamically allocating channels using distance measurement data between wireless nodes, it is possible to provide multiple channels for multiple control signals and multiple multimedia signals within a single radio frequency, Wherein a Virtual Time-Slot scheme is applied corresponding to a mutual position of nodes changing with time. The method according to claim 1,
A control manager for managing the wireless nodes generates a C packet (Control Packet) to generate a time reference of the virtual time slot,
Wherein each of the wireless nodes retransmits the C packet to a wireless node in the next sequence after a predetermined time elapses from the reception completion time of the C packet according to the time reference of the virtual time slot. Frame structure. The method according to claim 1,
Each of the wireless nodes measuring a mutual distance value between the wireless nodes using an R packet and measuring a link performance value when exchanging measured mutual distance values of the wireless nodes, A distance value, and a link performance value to a control manager for managing the wireless node through a D packet (Data Packet)
The control manager transmits a C packet (Control Packet) relay order of the wireless nodes to the wireless nodes through the D packet on the basis of the mutual distance value and the link capability value received through the D packet (Data Packet) Wherein the frame structure of the dynamic Ad Hoc network MAC is characterized in that The method of claim 3,
Each of the wireless nodes updates the relay order of its own C packet in accordance with the C packet (Control Packet) relay order transmitted through the D packet, And the allocation order of the virtual time slots is updated according to the allocation order of the virtual time slots. The method according to claim 1,
When the wireless nodes are three and each of the wireless nodes generates multimedia data, each of the frames of the MAC includes three C packet (Control Packet) slots, three R packets (Ranging Packet) slots, three D packets (Data Packet) slot, and 18 V packet slots, and the V packet is at least one of an image packet and a voice packet. 6. The method of claim 5,
A moving object 1, a moving object 2, and a moving object 3 on which the three wireless nodes are respectively mounted are sequentially listed, and each of the moving object 1, the moving object 2, and the moving object 3 includes real- A frame of the MAC frame is 20 msec / frame, and 50 frames of the MAC are generated per second, when a video camera generating 115.2 Kbps is installed. rescue. The method according to claim 6,
The control manager generates the C packets and transmits them at intervals of 20 msec,
The wireless node of the moving object 1 receives the transmitted C packet and relays the received C packet to the wireless node of the moving object 2. The wireless node of the moving object 2 transmits the C packet relayed from the wireless node of the moving object 1 to the wireless node of the moving object 3 A frame structure of a dynamic ad hoc network MAC is characterized in that it relays. 8. The method of claim 7,
The wireless node of the mobile unit 3 generates and transmits the V packet to the wireless node of the mobile unit 2. The wireless node of the mobile unit 2 transmits the generated V packet and the V packet of the mobile unit 3, And transmits the generated V packet to the wireless node of the moving object 1. The wireless node of the moving object 1 transmits the generated V packet and the received wireless node of the moving object 2 and the V packet of the wireless node of the moving object 3 to the control manager Frame structure of Hoc network MAC. 9. The method of claim 8,
Wherein the V-packet has a data payload of 115.2 Kbps when the packet has a payload of 96 bytes and is allocated to each channel three times per 20 msec. 9. The method of claim 8,
In order to swap the transmission direction of the V-packet, a time slot of a previous time is allocated to a wireless node that generates a packet signal among the wireless nodes, And a time slot of a next time is sequentially assigned to the frame of the MAC of the dynamic Ad Hoc network MAC. The present invention relates to a method of operating a frame structure of a dynamic ad hoc network MAC,
Using a Chirp Spread Spectrum (CSS) physical layer and dynamically allocating channels using distance measurement data between wireless nodes; And
The method of claim 1, wherein the step of allocating a channel dynamically allocates a virtual time-slot scheme corresponding to a mutual position of the wireless nodes with respect to multiple control signals and multiple multimedia signals in a single radio frequency with time, The method comprising the steps of: (a) applying a frame structure of a dynamic ad hoc network MAC to a MAC frame; 12. The method of claim 11,
A control manager for managing the wireless nodes generates a C packet (Control Packet) to generate a time reference of the virtual time slot,
Wherein each of the wireless nodes retransmits the C packet to a wireless node in the next sequence after a predetermined time elapses from the reception completion time of the C packet according to the time reference of the virtual time slot. Of the frame structure. 12. The method of claim 11,
Each of the wireless nodes measuring a mutual distance value between the wireless nodes using an R packet and measuring a link performance value when exchanging measured mutual distance values of the wireless nodes, A mutual distance value, and a link performance value to a control manager for managing the wireless node through a D packet (Data Packet)
The control manager transmits a C packet (Control Packet) relay order of the wireless nodes to the wireless nodes through the D packet on the basis of the mutual distance value and the link capability value received through the D packet (Data Packet) Wherein the frame structure of the dynamic ad hoc network MAC frame is configured to perform a frame structure of the dynamic ad hoc network MAC. 13. The method of claim 12,
Each of the wireless nodes updates the relay order of its own C packet in accordance with the C packet (Control Packet) relay order transmitted through a D packet, And the allocation order of the virtual time slots is updated.

Images