CN106454873A - Self-organized terahertz network-orientated auxiliary type directed communication method and network architecture thereof - Google Patents

Abstract

Auxiliary directed communication method for self-organizing terahertz networks, including: ordinary nodes obtain their own location information through omnidirectional communication with anchor nodes; when the sending node needs to send data, it first retreats a distributed inter-frame Listen to the low-frequency channel used, if the channel is occupied, back off until the channel is free; the sending node first sends an extended request to send the frame to the receiving node through the low-frequency omni-directional antenna, and the receiving node returns a message carrying its own location information and antenna information Clear the sending frame to the sending node; the two nodes get the direction and beam width of the antenna after calculation; the sending node waits for an antenna switching time, and then sends a test frame to the receiving node through the directional terahertz antenna; after sending data, The receiving node returns an ACK again, and if the sending node receives it successfully, the entire sending process ends. The invention also includes a network framework for implementing the inventive method.

Description

Auxiliary directed communication method and network architecture for self-organizing terahertz network

technical field

The invention belongs to the technical field of terahertz (THz) network data exchange, and in particular relates to a self-organized terahertz network-oriented auxiliary directional communication technology to improve the transmission distance and transmission performance of nodes, and is aimed at the formation of mobile network nodes The self-organizing terahertz network architecture uses omnidirectional low-frequency communication technology to assist in solving the problem of directional antenna matching between nodes, so as to realize the proposed efficient, energy-saving, and high-speed auxiliary directional communication method.

Background technique

With the development of Internet technology and technology, a large amount of data needs to be exchanged and transmitted in daily life. In the past few decades, the wireless data transmission rate has doubled every eighteen months to meet the explosive growth of data. According to this trend, in the near future, the wireless transmission speed needs to reach terabits per second (Terabyte, TB) to meet the needs of use. However, this speed far exceeds the maximum speed that can be achieved by traditional wireless communication frequencies (2.4GHz and 5GHz), and even exceeds the maximum speed of millimeter wave communication (30-300GHz), a hotspot of recent research. Therefore, researchers are urged to continuously explore higher frequency, higher rate communication frequency bands and corresponding solutions. In this context, the terahertz frequency band has been proposed to be used in ultra-high-speed wireless communication technology because of its high frequency, low energy consumption, and good directivity.

With the development of terahertz technology and related software and hardware technologies, terahertz communication will soon become a possibility. However, some characteristics in the terahertz frequency band lead to a very limited transmission distance. On the one hand, because the frequency of the terahertz frequency band is extremely high, the propagation loss is relatively large during the propagation process, and the signal attenuation will gradually increase as the distance increases. ; On the other hand, the terahertz frequency band is greatly affected by the molecular absorption in the air, especially the absorption of water molecules to the terahertz frequency band is relatively strong, resulting in a large terahertz path loss. In order to solve this problem, a directional antenna with high gain and high directivity is applied to the terahertz node. The directional antenna can help enhance the terahertz transmission signal and increase the transmission distance.

In traditional low-frequency communication systems, there are already examples of directional antenna applications, and related researchers have designed corresponding media access control layer (Media Access Control, MAC) communication methods, but these methods are not suitable for terahertz networks Among them, the main reason is that the traditional directional transmission technology and communication method are all based on the link signal covering at least one node. However, in the terahertz network, due to the high path loss of the terahertz frequency band and the high directivity of the directional antenna, the transmission distance of nodes may be insufficient and communication matching between nodes may not be completed. Related studies have proposed that in a centralized network, ordinary nodes solve the problem of node communication matching through a "rotating" antenna and transmitting information to the central node through a handshake protocol. However, in the self-organizing network, the nodes have mobility and there is no central node, so the method of "rotating" the antenna is very limited in the self-organizing network, so a new method is urgently needed to realize the communication between terahertz nodes. High-speed information transmission.

Due to the high path loss of the terahertz frequency band, the node transmission distance is short and communication is difficult, so it is necessary to use a high-gain beamforming directional antenna to assist in communication. However, terahertz network nodes equipped with directional antennas cannot solve the problem of sending nodes adjusting their antenna direction in time according to the receiving node's position and its antenna direction to perform pairing; at the same time, nodes in ordinary network architectures cannot obtain their own position well The problem of designing an auxiliary directed communication method and its network architecture for self-organizing terahertz networks.

Contents of the invention

The present invention overcomes the above-mentioned problems of the prior art, and provides an auxiliary directed communication method and a network framework thereof for self-organizing terahertz networks.

The network architecture described is an ad hoc network, as shown in Figure 1 , which shows the network architecture for implementing the method of the present invention, and the network includes anchor nodes and ordinary nodes. As a positioning auxiliary node, the anchor node is uniformly distributed in a certain area. It obtains its own location information by being equipped with a GPS module or manual setting, and helps ordinary nodes realize positioning and adjustment of the beam width and direction of the directional antenna through omnidirectional low-frequency communication technology. Ordinary nodes are randomly distributed in a certain area, using low-frequency omnidirectional communication technology to exchange control information, and establish communication between nodes, using directional terahertz antennas for high-speed information transmission.

Preferably, the frequency of the low frequency band is used but not limited to 2.4GHz and 5GHz; the frequency of the terahertz frequency band includes but not limited to 0.1-10THz.

Preferably, under the condition that anchor nodes can cover all common nodes, the number of anchor nodes used for auxiliary positioning in a two-dimensional planar environment cannot be less than three, and the number of anchor nodes in a three-dimensional environment cannot be less than four.

The auxiliary directed communication method for ad hoc terahertz network of the present invention comprises the following steps:

Step 1.1: Ordinary nodes obtain their own location information through omnidirectional communication with anchor nodes;

Step 1.2: When the sending node needs to send data, first back off a distributed inter-frame space, and then start listening to the low-frequency channel used, if the channel is occupied, back off until the channel is free;

Step 1.3: The sending node first sends an extended request to send frame (Request to Send of Node Information, RTS-NI) to the receiving node through the low-frequency omnidirectional antenna, which contains the location information of the sending node and its directional terahertz antenna Direction, the specific frame format is shown in Figure 2. After the receiving node receives the RTS-NI frame, it returns an extended Clear to Send of Node Information (CTS-NI) frame to the sending node. The CTS-NI frame contains the location information of the receiving node and its directional terahertz information. the direction of the antenna;

Step 1.4: The two nodes obtain the direction and beam width of the antenna after calculation, and the power reaching the receiving node must satisfy the following formula:

where d is the distance between two nodes, c is the speed of light, is the noise power, SNR _min is the minimum signal-to-noise ratio threshold, S _t (f) is the power spectral density of the sending node, and k _abs (f) is the molecular absorption factor. Define the fixed beam angle of the antenna array as Ω _A , and the directivity of the directional antenna can be expressed as:

where θ _h and φ _h are the horizontal and elevation angles of the half-power beamwidth, respectively.

Step 1.5: The sending node waits for an antenna switching time, and then sends a test frame (Test to Send, TTS) to the receiving node through the directional terahertz antenna. If the receiving node does not return an acknowledgment frame (Acknowledgment, ACK) or the sending node does not Successfully receiving the returned ACK frame indicates that the connection failed, and repeat step 1.1 until the upper limit of the number of connection establishments is reached; otherwise, the sending node starts to send data through the directional terahertz antenna.

Step 1.6: After sending the data, the receiving node returns an ACK again. If the sending node receives it successfully, the entire sending process ends. If the receiving node does not return an ACK or the sending node does not receive the ACK, the data will be resent until the retransmission is reached. The upper limit of the number of times, Figure 3 shows the main process of two steps.

Preferably, the common node communicates with the anchor node at regular intervals through the low-frequency omni-directional antenna to update its own location information and ensure the accuracy of the location before the next communication.

Preferably, the distributed inter-frame interval is set to 34 μs, which can be adjusted according to the frequency and information rate adopted by the antenna.

Preferably, before the node sends data, it needs to detect whether the low-frequency channel is occupied, and if it is occupied, a backoff time needs to be enabled. The backoff time mechanism uses a binary backoff algorithm, but is not limited thereto.

Preferably, common nodes use the same directional terahertz antenna, but it can be adjusted according to actual conditions.

Preferably, the request to send frame RTS-NI and the clear to send frame CTS-NI include information such as frame control, duration, source address and destination address information, sequence control, node location information, antenna information and frame check sequence, but not only limited to this.

Preferably, if two or more sending nodes send requests to the same receiving node at the same time, the multiple sending nodes will obtain the sending right through competition, and the node that fails the competition will randomly wait for a backoff time before resending.

The present invention provides an auxiliary directional communication method oriented to an ad hoc terahertz network and a network architecture thereof. The network architecture is an ad hoc network architecture, and uses low-frequency band omnidirectional communication technology and directional terahertz communication technology at the same time. The network contains anchor nodes and ordinary nodes, among which the anchor node is used as a positioning auxiliary node to help ordinary nodes achieve positioning and adjust the beam width and direction of the directional antenna through omnidirectional low-frequency communication technology; ordinary nodes use low-frequency omnidirectional communication technology and Other nodes exchange control information, establish communication between nodes, and use directional terahertz antennas for high-speed information transmission. Compared with ordinary antennas, the directional antenna has good directivity and high gain, which can make the transmission of terahertz signals more stable and the transmission distance longer. However, due to the high directivity of the directional antenna, it is difficult for nodes to pair, so the design of Use low-frequency omni-directional antennas as a method of aiding positioning. The low-frequency omnidirectional antenna is used to transmit the position of the node and antenna control information to solve the problem of antenna pairing, and realize high-speed communication between nodes through a reasonable communication mechanism.

The invention has the advantages that: on the one hand, it solves the problems of short terahertz transmission distance, difficult matching of directed node communication, and poor scalability; on the other hand, it significantly improves the terahertz channel utilization rate and network throughput.

Description of drawings

FIG. 1 is a schematic diagram of a terahertz communication ad hoc network architecture of the present invention.

FIG. 2 is a schematic diagram of the format of each data frame in the present invention.

Fig. 3 is a flow chart of the method of the present invention.

detailed description

The present invention will be described in further detail below in conjunction with the examples, but the protection scope of the present invention is not limited thereto.

The network architecture shown in Figure 1 includes ordinary nodes and anchor nodes, where ordinary nodes have low-frequency omnidirectional antennas and directional terahertz antennas, anchor nodes only have low-frequency omnidirectional antennas, and ordinary nodes obtain location information through anchor nodes. It communicates with other nodes in a self-organizing manner, and obtains the position of the other party and the direction information of the directional antenna through omnidirectional communication with other nodes, and transmits data through the directional terahertz antenna.

The header and tail of each frame shown in Figure 2 are unified. The header is mainly composed of frame control, duration, address information, and sequence control. The frame control information determines the type of data frame, and the duration indicates the data frame. During the survival time in the network, the address information includes the unique identity code of the sending node and the receiving node in the network, and the sequence control controls the sequence of data frames. The frame check sequence at the end contains a 32-bit CRC check code to check whether the received data frame is correct. The RTS-NI and CTS-NI frame formats are basically the same, carrying the location information and antenna information of the sending node and the receiving node respectively, and the TTS frame only carries random test data.

In the data frame, the frame control occupies 2 bytes, the duration occupies 2 bytes, the address information occupies 6 to 12 bytes as needed, the sequence control occupies 2 bytes, and the frame check sequence occupies 4 bytes . Each space coordinate of RTS-NI and CTS-NI occupies 2 bytes respectively, and antenna information occupies 4 bytes. The test data in the TTS frame occupies 4 bytes.

The entire communication process shown in Figure 3 is divided into two stages. Stage 1 is the exchange of control information in the low frequency band, and stage 2 is data transmission in the terahertz frequency band. Among them, T _DIFS and T _SIFS are the distributed inter-frame gap and the shortest inter-frame interval time, T _BF is the backoff time, T _RTS-NI is the time required to propagate a frame of RTS-NI frame, and T _prop is the sending node and the receiving node The propagation delay between T _CTS-NI is the time required to propagate a CTS-NI frame, T _switch is the time required for the node to switch to terahertz communication, T _TTS is the time required to propagate a TTS frame, T _proc It is the time required for the receiving node to process the received data, T _ACK is the time required to transmit an ACK frame, and T _DATA is the time required to transmit all data.

Preferably, in the auxiliary directional communication method, the distributed inter-frame interval T _DIFS is 34 μs, the shortest inter-frame interval T _SIFS is 16 μs, the antenna switching time T _switch is 10 ns, the data processing time T _proc is 10 ns, and other The time is adjusted according to the size of the data being transferred.

The present invention relates to an auxiliary directional communication method and its network architecture for a self-organizing terahertz network. The network architecture is an ad hoc network architecture, and the designed communication method uses a low-frequency omnidirectional antenna and a directional terahertz antenna at the same time. To complete the purpose of high-speed data transmission, the communication is mainly carried out through the following steps:

Step 1.1: Ordinary nodes obtain their own location information through omnidirectional communication with anchor nodes;

Step 1.2: When the sending node needs to send data, first back off a distributed inter-frame space, and then start listening to the low-frequency channel used, if the channel is occupied, back off until the channel is free;

Step 1.3: The sending node first sends an extended request to send frame (Request to Send of Node Information, RTS-NI) to the receiving node through the low-frequency omnidirectional antenna, which contains the location information of the sending node and its directional terahertz antenna The specific frame format is shown in Figure 2. After the receiving node receives the RTS-NI frame, it returns an extended Clear to Send of Node Information (CTS-NI) frame to the sending node. The CTS-NI frame contains the location information of the receiving node and its directional terahertz information. the direction of the antenna;

Step 1.4: The two nodes obtain the direction and beam width of the antenna after calculation, and the power reaching the receiving node must satisfy the following formula:

where d is the distance between two nodes, c is the speed of light, is the noise power, SNR _min is the minimum signal-to-noise ratio threshold, S _t (f) is the power spectral density of the sending node, and k _abs (f) is the molecular absorption factor. Define the fixed beam angle of the antenna array as Ω _A , and the directivity of the directional antenna can be expressed as:

where θ _h and φ _h are the horizontal and elevation angles of the half-power beamwidth, respectively.

According to the process of the above steps, the delay of the whole process can be obtained as:

T _total1 ＝T _DIFS +T _SIFS +2T _NI +T _BF +2T _prop ⑸

The backoff time T _BF can be obtained by the following formula:

T _BF ＝[Rnd(·)×(2 ^CW -1)]·2τ ⑹

Among them, Rnd(·) is a random number between 0 and 1, CW is a smaller value between the number of retransmissions and 10, and square brackets indicate rounding.

Step 1.5: The sending node waits for an antenna switching time, and then sends a test frame (Test to Send, TTS) to the receiving node through the directional terahertz antenna. If the receiving node does not return an acknowledgment frame (Acknowledgment, ACK) or the sending node does not Successfully receiving the returned ACK frame indicates that the connection failed, and repeat step 1.1 until the upper limit of the number of connection establishments is reached; otherwise, the sending node starts to send data through the directional terahertz antenna.

Step 1.6: After sending the data, the receiving node returns an ACK again. If the sending node receives it successfully, the entire sending process ends. If the receiving node does not return an ACK or the sending node does not receive the ACK, the data will be resent until the retransmission is reached. Figure 3 shows the main process of two steps.

According to the above steps, the main delay can be obtained as:

T _total2 = T _test + T _DATA ⑺

Where T _test is the time to send the test packet, which can be expressed as:

T _test ＝T _switch +T _TTS +T _ACK +T _proc +2T _prop ⑻

Among them, T _DATA is the time required to transmit data, which can be expressed as:

The network architecture for implementing the method of the present invention belongs to the self-organizing terahertz network architecture. In this network architecture, ordinary nodes communicate through self-organization. The ordinary nodes have low-frequency omnidirectional antennas to exchange control information with other nodes, and use high-frequency A directional terahertz antenna for data transmission. The anchor node obtains the geographic location through the equipped GPS module or manual setting, and assists the ordinary node to locate through the omnidirectional communication technology.

The directional antenna can adjust the gain by adjusting its own beam width, and can also adjust its own beam direction to perform pairing between nodes to achieve the purpose of communication.

Before sending data, the sending node needs to detect whether the low-frequency channel is occupied. If it is occupied, a backoff time needs to be enabled. The backoff time is preferably adjusted according to the binary backoff algorithm, but not limited to the binary backoff algorithm.

If two or more sending nodes send requests to the same receiving node, the multiple sending nodes will compete to obtain the right to send, and the node that fails the competition will wait for a random backoff time before resending.

Aiming at the problems of short terahertz communication distance and large path loss in the self-organized terahertz network, the present invention introduces a directional terahertz antenna with high directivity and high gain. And aiming at the problem that terahertz network nodes using directional antennas may encounter problems that cannot be matched for communication, a low-band omnidirectional antenna is introduced for node positioning and control information transmission, helping nodes adjust the beam width and direction of the antenna. At the same time, a reasonable directional communication method is designed, which is mainly divided into two stages: In stage 1, the nodes exchange the corresponding position information and antenna information through the omnidirectional antenna in the low frequency band, and the directional communication method is obtained after calculation. The beam width and beam direction of the Hertzian antenna are used to complete the communication matching problem between the two nodes; in phase 2, the sending node first sends a test frame TTS to the receiving node, and the receiving node returns the confirmation frame ACK to start data transmission. After the node sends the data, the receiving node will return an acknowledgment frame ACK to indicate that the data has been received. Through the method of the present invention, on the one hand, the problems of short terahertz transmission distance, difficult matching of directional node communication, and poor scalability are solved; on the other hand, the terahertz channel utilization rate and network throughput are significantly improved.

Claims (4)

1. a kind of oriented communication means of assist type of self-organizing Terahertz (THz) network, has steps of：

Step 1.1：Ordinary node by obtaining the positional information of itself with anchor node directional communication；

Step 1.2：When sending node needs to send data, keep out of the way a distributed inter-frame space first, then begin to intercept The low frequency channel being adopted, if channel is occupied, is kept out of the way until channel idle；

Step 1.3：Sending node first passes through request to send frame RTS-NI that low frequency omni-directional antenna sends an extension (Request To Send of Node Information) gives receiving node, includes the position letter of sending node in this frame Breath and its direction of oriented Terahertz antenna.After receiving node receives RTS-NI frame, return the Clear to Send frame of an extension CTS-NI (Clear To Send of Node Information) gives sending node, comprises receiving node in CTS-NI frame Positional information and its direction of oriented Terahertz antenna；

Step 1.4：Two nodes obtain direction and the beam angle of antenna after calculating, and wherein reach the power of receiving node Size must is fulfilled for below equation：

$P_r={\∫}_B{S}_t\left(f\right)\frac{c^2}{{\left(4\mathrm{\π}fd\right)}^2}{G}_t{G}_r{e}^{-k_{abs}\left(f\right)d}df\≥P_{N_0}{\mathrm{SNR}}_{min}---\left(1\right)$

Wherein d is the distance between two nodes, and c is the light velocity,For noise power, SNR_minFor minimum signal-noise ratio threshold value, S_t F () is the power spectral density of sending node, k_absF () is the molecule absorption factor.Defining the fixing beam angle of aerial array is Ω_A, the directivity of oriented antenna is represented by：

$D_0=\frac{4\mathrm{\π}}{{\mathrm{\Ω}}_A}=\frac{4\mathrm{\π}}{{\mathrm{\θ}}_h{\mathrm{\φ}}_h}\≥G---\left(2\right)$

Wherein θ_hAnd φ_hIt is respectively horizontal angle and the elevation angle of half-power beam width.

According to the process of above step, the time delay T of all stage 1 can be obtained_total1For：

T_total1=T_DIFS+T_SIFS+T_RTS-NI+T_CTS-NI+T_BF+2T_prop⑸

Wherein T_DIFSAnd T_SIFSIt is respectively distributed inter-frame space and short interFrameGap time, T_RTS-NIAnd T_CTS-NIIt is to pass respectively The time that defeated frame RTS-NI and CTS-NI needs, T_propFor the propagation delay between sending node and receiving node, T_BFFor one Secondary back off time, can be obtained by the following formula：

T_BF=[Rnd () × (2^CW-1)]·2τ ⑹

Wherein Rnd () is the random number between 0 to 1, and CW is smaller value between number of retransmissions and 10, and square brackets represent and take Whole, τ is minimum time interval.

Step 1.5：Sending node waits an antenna conversion time, subsequently passes through oriented Terahertz antenna and sends a frame test frame (Test to Send, TTS) give receiving node, if receiving node do not return acknowledgement frame (Acknowledgment, ACK) or The ACK frame that person's sending node is not properly received return then represents connection failure, and repeat step 1.1, until reaching the company of foundation Connect the upper limit of number of times；Conversely, then sending node begin through oriented Terahertz antenna start send data.

Step 1.6：After sending ED, receiving node again returns to an ACK, if sending node is properly received, whole Transmission process terminates, if receiving node does not return ACK or sending node does not receive ACK, carries out data re-transmitting, directly Reach the number of retransmissions upper limit.

According to above step, the time delay T in stage 2 can be obtained_total2For：

T_total2=T_test+T_DATA⑺

Wherein T_testFor sending the time of test bag, it is represented by：

T_test=T_switch+T_TTS+T_ACK+T_proc+2T_prop⑻

Wherein T_switchIt is the time that antenna is converted to from low frequency omni-directional antenna oriented Terahertz antenna, T_TTSFor sending TTS frame Time, T_ACKFor sending the time of ACK acknowledgement frame, T_procIt is the process time to Frame, wherein T_DATANeed for transmission data The time wanted, it is represented by：

Wherein L_dataFor total data volume needing to send, L_oneFor the restriction size of a packet, r_THzFor Terahertz frequency range number According to transfer rate,Expression rounds up.

2. a kind of self-organizing Terahertz network according to claim 1 the oriented communication means of assist type it is characterised in that： Ordinary node is communicated with anchor node at set intervals by low frequency omni-directional antenna, to update the positional information of itself, protects The accuracy in the front position of upper once communication for the card；The frequency that the length of described distributed inter-frame space adopts according to omnidirectional antenna Determine with information rate；Before node sends data, whether occupied, if occupied, need if needing first to intercept low frequency channel Enable a back off time；Ordinary node passes through low frequency omni-directional aerial exchanging node location information and control information, by terahertz Hereby the oriented antenna of frequency range carries out data transmission；Request to send frame RTS-NI and Clear to Send frame CTS-NI, include frame control, The letter of persistent period, source address and destination address information, sequence control, node location information, aerial information and Frame Check Sequence Breath；Described node adopts identical oriented Terahertz antenna.

3. a kind of self-organizing Terahertz network according to claim 2 the oriented communication means of assist type it is characterised in that： Send request if there are two and above sending node to same receiving node, then this multiple sending node is by competing simultaneously The mode striven obtains transmission route, and random wait is resend after a back off time by the node of competition failure.

4. realize a kind of network rack of the oriented communication means of assist type of self-organizing Terahertz network as claimed in claim 1 Structure it is characterised in that:Possess two kinds of different nodes, a kind of is ordinary node, is randomly dispersed in certain region, node can To move, and form the network of self-organizing by mutual communication；A kind of is anchor node, and univesral distribution is in certain area In domain, anchor node obtains own location information by being equipped with GPS module or the mode that manually sets, simultaneously by entering with ordinary node Row directional communication assists it to be positioned；

Described ordinary node and anchor node are equipped with low frequency omni-directional antenna, and the frequency of described low frequency includes 2.4GHz and 5GHz；General Logical node is equipped with the information transfer that the oriented antenna of Terahertz frequency range is used between node, the Terahertz frequency range orientation of ordinary node Antenna can adjust beam angle and the beam direction of antenna according to the geographical position of sending node and receiving node, and anchor node is not It is equipped with the beam antenna of Terahertz frequency range, the frequency of described Terahertz frequency range includes 0.1-10THz；

In described network, in the case of ensureing that anchor node can cover all ordinary nodes, it is used in two dimensional surface environment The anchor node quantity of auxiliary positioning can not be less than 3, and in three-dimensional environment, anchor node number can not be less than 4.