CN113225291A

CN113225291A - Ad hoc network synchronization system based on OFDM and method thereof

Info

Publication number: CN113225291A
Application number: CN202110401737.4A
Authority: CN
Inventors: 王志刚; 盖平; 丁高泉; 王进帅; 章灵芝; 胡浩瀚; 单宝麟; 张立; 孙亮; 边立云; 张溦
Original assignee: Tianjin Richsoft Electric Power Information Technology Co ltd; State Grid Information and Telecommunication Co Ltd
Current assignee: Tianjin Richsoft Electric Power Information Technology Co ltd; State Grid Information and Telecommunication Co Ltd
Priority date: 2021-04-14
Filing date: 2021-04-14
Publication date: 2021-08-06

Abstract

The invention provides an OFDM-based ad hoc network synchronization system and a method thereof. The ad hoc network synchronization system based on OFDM and the method thereof comprise a radio frequency, an intermediate frequency, a baseband, an operation module and a record storage module, wherein the radio frequency: the function of transmitting signals remotely; intermediate frequency: a signal obtained by frequency-converting a high-frequency signal; baseband: original electrical signal without modulation for sending; an operation module: the sequence used for adjusting the frequency offset of the received baseband signal and the locally generated synchronous sequence is operated to obtain a relevant numerical value; a record storage module: the device is used for recording and storing relevant numerical values, the radio frequency is electrically connected with the intermediate frequency, the intermediate frequency is electrically connected with the baseband, the baseband is electrically connected with the operation module, and the operation module is electrically connected with the recording and storing module. The OFDM-based ad hoc network synchronization system and the method thereof have the advantages of reducing the frequency shift calculation again on the baseband signals, reducing the operation amount and improving the efficiency of synchronous detection.

Description

Ad hoc network synchronization system based on OFDM and method thereof

Technical Field

The invention relates to the technical field of wireless communication, in particular to an OFDM-based ad hoc network synchronization system and a method thereof.

Background

The main idea of OFDM is as follows: the channel is divided into a plurality of orthogonal sub-channels, the high-speed data signal is converted into parallel low-speed sub-data streams, and the parallel low-speed sub-data streams are modulated to be transmitted on each sub-channel. The orthogonal signals may be separated by correlation techniques at the receiving end, which may reduce the mutual interference (ISI) between the subchannels. The signal bandwidth on each subchannel is smaller than the associated bandwidth of the channel, so that flat fading can be seen on each subchannel, thereby eliminating inter-symbol interference, and since the bandwidth of each subchannel is only a small fraction of the original channel bandwidth, channel equalization becomes relatively easy.

The received baseband signal and the sequence adjusted by the frequency offset of the locally generated synchronization sequence cannot be directly operated by the operation module, so that frequency shift calculation needs to be performed on the baseband signal again, the operation amount is increased, and the efficiency of synchronous detection is reduced.

Therefore, there is a need to provide a new OFDM-based ad hoc network synchronization system and method thereof to solve the above technical problems.

Disclosure of Invention

In order to solve the above technical problems, the present invention provides an OFDM-based ad hoc network synchronization system and method that reduces the frequency shift calculation again for baseband signals, reduces the amount of computation, and improves the efficiency of synchronization detection.

The invention provides an OFDM-based ad hoc network synchronization system and a method thereof, wherein the OFDM-based ad hoc network synchronization system comprises: radio frequency, intermediate frequency, baseband, operation module and record storage module, the radio frequency: the function of transmitting signals remotely; intermediate frequency: a signal obtained by frequency-converting a high-frequency signal; baseband: original electrical signal without modulation for sending; an operation module: the sequence used for adjusting the frequency offset of the received baseband signal and the locally generated synchronous sequence is operated to obtain a relevant numerical value; a record storage module: the device is used for recording and storing relevant numerical values, the radio frequency is electrically connected with the intermediate frequency, the intermediate frequency is electrically connected with the baseband, the baseband is electrically connected with the operation module, and the operation module is electrically connected with the recording and storing module.

Preferably, the radio frequency and the intermediate frequency are in one-way electrical connection, the intermediate frequency and the baseband are in one-way electrical connection, and the baseband and the operation module are in one-way electrical connection.

Preferably, the operation module is in bidirectional electrical connection with the record storage module.

Preferably, the recording storage module is further provided with a WIFI module, and the recording storage module is electrically connected with the WIFI module.

A synchronization method of an ad hoc network synchronization system based on OFDM comprises the following steps:

the method comprises the following steps: synchronous sequence design, signal is transmitted on two OFDM symbols with the time domain length of 128, wherein N_ZC139, each sequence length 139,

dividing the generated sequence into two parts, wherein 72 bits of the former part are placed on a first ofdm symbol, 67 bits of the latter part are placed on a second ofdm symbol, and the time domain sending signal is that the time domain data length is 128:

t when the set position is the first ofdm symbol_CPIs 10, L ═ 72; t when the set position is the second ofdm symbol_CPIs 9, L ═ 67;

step two: the frame structure sent by the air interface is shown in fig. 3;

step three: the frame structure of the synchronization, the time domain signal mapping position of the synchronization sequence is shown in fig. 4;

step four: the correlation verification under the current synchronization sequence configuration can obtain better auto-correlation and cross-correlation characteristics by screening proper u values, and the u values are selected as follows: 71113161720212829303334394146485154889198100106108109110111119120122123126, respectively;

using the above selected u values, the correlation characteristics are shown in fig. 5;

step five: when accessing the ad hoc network, the synchronization detection device user needs to detect all synchronization sequences and determine the user resources that can be currently contacted.

Compared with the related technology, the ad hoc network synchronization system and the method thereof based on the OFDM have the following beneficial effects:

1. a synchronous system design based on OFDMA ad hoc network is provided, the device refers to 12 subcarriers and 7 OFDM symbols of LTE to be the most RB resource, and 6RB is the smallest schedulable resource. Each user transmits a synchronization sequence on the 6RB resource of the central frequency point. A maximum of 16 users may be allowed to access the ad hoc network system in the case where the system uses 100 RBs.

2. The synchronous detection device can directly carry out the operation module on the received baseband signal and the sequence of the frequency offset adjustment of the locally generated synchronous sequence, thereby reducing the frequency shift calculation of the baseband signal again, reducing the operation amount and improving the efficiency of synchronous detection.

Drawings

Fig. 1 is a schematic diagram of LTE resource allocation in the present invention;

FIG. 2 is a block diagram of the synchronization detection apparatus of the present invention;

fig. 3 is a block diagram of a frame structure transmitted by the air interface of the present invention;

fig. 4 is a schematic diagram of the time domain signal mapping position of the synchronization sequence according to the present invention.

FIG. 5 is a diagram illustrating the correlation characteristics of the u value according to the present invention.

Detailed Description

The invention is further described with reference to the following figures and embodiments.

Please refer to fig. 1-5, wherein fig. 1 is a schematic diagram illustrating a resource allocation situation of LTE in the present invention; FIG. 2 is a block diagram of the synchronization detection apparatus of the present invention; fig. 3 is a block diagram of a frame structure transmitted by the air interface of the present invention; FIG. 4 is a diagram illustrating the mapping positions of the time domain signals of the synchronization sequence according to the present invention; FIG. 5 is a diagram illustrating the correlation characteristics of the u value according to the present invention. The method comprises the following steps: radio frequency, intermediate frequency, baseband, operation module and record storage module.

In the specific implementation process, as shown in fig. 1 and 2, the radio frequency: the function of transmitting signals remotely; intermediate frequency: a signal obtained by frequency-converting a high-frequency signal; baseband: original electrical signal without modulation for sending; an operation module: the sequence used for adjusting the frequency offset of the received baseband signal and the locally generated synchronous sequence is operated to obtain a relevant numerical value; a record storage module: the device is used for recording and storing relevant numerical values, the radio frequency is electrically connected with the intermediate frequency, the intermediate frequency is electrically connected with the baseband, the baseband is electrically connected with the operation module, and the operation module is electrically connected with the recording and storing module.

The radio frequency and the intermediate frequency are in one-way electric connection, the intermediate frequency and the baseband are in one-way electric connection, the baseband and the operation module are in one-way electric connection, and the one-way electric connection ensures that data are normally transmitted to the next stage.

The operation module is in bidirectional electric connection with the record storage module, the operation module is in bidirectional electric connection, data after operation can be recorded in the record storage module, and the data in the record storage module can be extracted to the operation module to be verified and calculated.

Still install the WIFI module on the record storage module, record storage module is connected with the WIFI module electricity, needs to explain, can transmit information for mobile terminal through the WIFI module mode.

The synchronization method of the ad hoc network synchronization system based on OFDM comprises the following specific steps:

step two: the frame structure sent by the air interface is shown in fig. 3;

The circuits and controls involved in the present invention are prior art and will not be described in detail herein.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. an ad hoc network synchronization system based on OFDM, is characterized in that, comprising: radio frequency, intermediate frequency, baseband, arithmetic module and record storage module, radio frequency: be used for long-distance signal transmission function; A signal obtained by frequency conversion; baseband: used to send out the original electrical signal without modulation; operation module: used to calculate the received baseband signal and the frequency offset adjustment sequence of the locally generated synchronization sequence to obtain Relevant values; record storage module: used to record and store relevant values, the radio frequency is electrically connected to the intermediate frequency, the intermediate frequency is electrically connected to the baseband, the baseband is electrically connected to the operation module, and the operation module is electrically connected to the record storage module.

2. The OFDM-based ad hoc network synchronization system according to claim 1, wherein the radio frequency and the intermediate frequency are one-way electrical connection, the intermediate frequency and the baseband are one-way electrical connection, and the baseband and the arithmetic module are one-way electrical connection. connect.

3 . The OFDM-based ad hoc network synchronization system according to claim 1 , wherein the operation module and the recording storage module are electrically connected bidirectionally. 4 .

4 . The OFDM-based ad hoc network synchronization system according to claim 1 , wherein a WIFI module is further installed on the recording storage module, and the recording storage module is electrically connected to the WIFI module. 5 .

5. The OFDM-based synchronizing method of an ad hoc network in the same system according to any one of claims 1-4, wherein the specific steps are as follows:

Step 1: Synchronization sequence design, the signal is transmitted on two OFDM symbols with a time domain length of 128, where N _ZC is 139, each sequence length is 139,

Divide the generated sequence into two parts. The 72bit of the former part is placed on the first ofdm symbol, and the 67bit of the latter part is placed on the second ofmd symbol. The time domain transmission signal is, and the time domain data length is 128:

When the placement position is the first ofdm symbol, the _TCP is 10, and L=72; when the placement position is the second ofdm symbol, the _TCP is 9, and L=67;

Step 2: The frame structure sent by the air interface is shown in Figure 3;

Step 3: Synchronized frame structure, the time domain signal mapping position of the synchronization sequence is shown in Figure 4;

Step 4: Correlation verification under the current synchronization sequence configuration, better autocorrelation and cross-correlation characteristics can be obtained by screening the appropriate u value. The u value is selected as follows: 7 11 13 16 17 20 21 28 29 30 33 34 39 41 46 4851 54 88 91 98 100 106 108 109 110 111 119 120 122 123 126;

Using the u value selected above, the relevant characteristics are shown in Figure 5;

Step 5: When the user of the synchronization detection device accesses the ad hoc network, all synchronization sequences need to be detected to determine the current user resources that can be contacted.