CN111384996A - Channel fading suppression method and system based on adaptive frequency hopping mechanism - Google Patents
Channel fading suppression method and system based on adaptive frequency hopping mechanism Download PDFInfo
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- CN111384996A CN111384996A CN202010099548.1A CN202010099548A CN111384996A CN 111384996 A CN111384996 A CN 111384996A CN 202010099548 A CN202010099548 A CN 202010099548A CN 111384996 A CN111384996 A CN 111384996A
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- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/713—Spread spectrum techniques using frequency hopping
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Abstract
The invention provides a channel fading suppression method and a system based on self-adaptive frequency hopping, which comprises the following steps: step 1: in a frequency hopping network, periodically detecting the channel quality of each frequency point, finding out the frequency point subjected to fading and reporting to a root node; step 2: the root node performs fusion processing on the information of the faded frequency points; and step 3: rejecting a frequency hopping set from the faded frequency points and sending the reconstructed frequency hopping set information and switching time to other nodes; and 4, step 4: the entire frequency hopping network is negotiated and the frequency hopping set is switched. The invention does not need to implement channel equalization and diversity measures on each frequency point, and can achieve the communication quality similar to a white noise channel only by removing the faded frequency points and reconstructing a frequency hopping set in the network, thereby reducing the system overhead and improving the communication efficiency.
Description
Technical Field
The present invention relates to the field of wireless communication technologies, and in particular, to a channel fading suppression method and system based on an adaptive frequency hopping mechanism.
Background
The carrier frequency of the traditional frequency hopping radio station is controlled by a pre-agreed pseudo-random code, can jump continuously and randomly, and has certain anti-multipath capability. The frequency hopping system can be divided into two types, slow frequency hopping, which transmits a plurality of symbols within one carrier frequency duration, and fast frequency hopping, which undergoes a plurality of carrier frequency hops within one symbol duration. Due to the general improvement of the code element rate, a slow frequency hopping technology is mostly adopted at present. In this case, when a carrier frequency suffers from deep fading, continuous symbol errors will be caused, and when serious, the whole packet of data will be lost. Therefore, a simple and feasible method with low overhead needs to be found to improve the multipath resistance of the slow frequency hopping system.
The invention does not adopt corresponding anti-fading measures aiming at different channel fading types, and only accepts or rejects the frequency points according to the simple detection result of the channel fading condition of each frequency point. Compared with the traditional channel fading suppression method, the method does not need to consume computing resources on each fading frequency point for channel equalization, simultaneously saves a diversity link, and improves the utilization efficiency of communication resources.
Patent document CN109088708A (application number: 201710447904.2) discloses a method, a device and a computer-readable storage medium for setting physical signals of the internet of things, wherein the method comprises the following steps: setting each RU in the single-tone signal as a set number of transmission durations; according to the scheduling conditions of all subcarriers in NB-IoT, in the range of the subcarriers for transmitting the single-tone signals, the range of subcarrier frequency intervals for transmitting the single-tone signals in adjacent transmission time duration in the RU is preset as a limit, and the subcarrier frequency for transmitting the single-tone signals in each transmission time duration in the RU is determined.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a channel fading suppression method and system based on an adaptive frequency hopping mechanism.
The invention provides a channel fading suppression method based on adaptive frequency hopping, which comprises the following steps:
step 1: in a frequency hopping network, periodically detecting the channel quality of each frequency point, finding out the frequency point subjected to fading and reporting to a root node;
step 2: the root node performs fusion processing on the information of the faded frequency points;
and step 3: rejecting a frequency hopping set from the faded frequency points and sending the reconstructed frequency hopping set information and switching time to other nodes;
and 4, step 4: the entire frequency hopping network is negotiated and the frequency hopping set is switched.
Preferably, each node adds a section of training sequence in the data sent by its own time slot, and other nodes perform channel estimation according to the training sequence to form an instantaneous channel quality grade, and smoothens the instantaneous channel quality grades for many times into an average channel quality grade, and feeds back the average channel quality grade to the original node in their respective service time slot, and when the average channel quality grade of a certain frequency point received for many times continuously has a quantity greater than the quantity not meeting the set grade, the frequency point is listed as a frequency point subject to fading.
Preferably, for a non-root node, if the information of the faded frequency points is from the child nodes, the faded frequency point information is firstly stored until the information of the faded frequency points of all the child nodes is collected, and then the faded frequency point information is fused and reported to the father node of the non-root node until the root node receives the information of the faded frequency points of the whole scheduling tree;
if the child node receives the message only containing the frequency point information of the father node, the message is not processed.
Preferably, for the root node, when the current fusion processing period arrives, the root node fuses the received information of the faded frequency points reported by each scheduling tree, removes the faded frequency points, forms a reconstructed information message of the frequency hopping set, which includes the frequency point information and the TOD information of the switching time, and broadcasts and issues the message to the whole network.
Preferably, the rejected fading frequency points are imprisoned;
the imprisoning time and the current frequency point number form a positive correlation relationship, and release is carried out after imprisoning.
Preferably, if the imprisoned frequency point is determined to be the frequency point subject to fading again, the imprisoning time is extended to the preset upper time limit, if the frequency point subject to fading is received normally, the imprisoned time is released, otherwise, the imprisoned frequency point is imprisoned to the preset upper time limit again.
Preferably, when the frequency points in the whole frequency hopping network are judged to be the frequency points subject to fading, the root node classifies the frequency points according to the channel quality of each frequency point, and selects a plurality of frequency points with the channel quality meeting the preset requirement to form a frequency hopping set.
The channel fading suppression system based on the adaptive frequency hopping provided by the invention comprises:
module M1: in a frequency hopping network, periodically detecting the channel quality of each frequency point, finding out the frequency point subjected to fading and reporting to a root node;
module M2: the root node performs fusion processing on the information of the faded frequency points;
module M3: rejecting a frequency hopping set from the faded frequency points and sending the reconstructed frequency hopping set information and switching time to other nodes;
module M4: the entire frequency hopping network is negotiated and the frequency hopping set is switched.
Compared with the prior art, the invention has the following beneficial effects:
the invention does not need to implement channel equalization and diversity measures on each frequency point, and can achieve the communication quality similar to a white noise channel only by removing the faded frequency points and reconstructing a frequency hopping set in the network, thereby reducing the system overhead and improving the communication efficiency.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is an exemplary diagram of a frequency hopping network architecture;
fig. 2 is a flow chart of processing frequency point information by a root node and a non-root node.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 1, the channel fading suppression method based on adaptive frequency hopping according to the present invention is divided into five aspects, such as channel quality detection of each frequency point, information reporting and fusion of faded frequency points, fading frequency point rejection and frequency hopping set reconstruction, rejected frequency point recovery, and extreme case handling.
The whole frequency hopping network consists of a plurality of scheduling trees taking the network building nodes as tree roots, wherein the network building nodes are also called root nodes and serve as unique time reference sources of the whole network to provide time system information of the whole network; for a non-root node on the scheduling tree, a node upstream of the timing information flow is a parent node, and a node downstream of the timing information flow is a child node.
As shown in FIG. 2, in the frequency hopping network, each node (frequency hopping radio station) periodically detects the channel quality of each frequency point, finds out the frequency points subject to fading, performs step-by-step or fusion processing on the frequency point numbers and reports the frequency point numbers to a root node, performs or fusion processing on the collected information of the frequency points subject to fading of each scheduling tree by the root node, rejects the frequency hopping sets from the frequency points subject to fading, and sends the reconstructed information of the frequency hopping sets and switching time to other nodes in the network, and finally the whole network negotiates and switches the frequency hopping sets consistently. In addition, the contents of rejected frequency point recovery, extreme case treatment and the like are considered.
1. Channel quality detection at each frequency point
When each node sends data in the time slot of the node, a physical prefix is added in front of a data packet, wherein a section of training sequence is arranged; after other nodes receive the sequence, whether the node is the destination of the subsequent data or not, the channel estimation is carried out according to the sequence, and the instantaneous channel quality grade is formed. The channel quality is divided into two levels of 'good' and 'bad'. And other nodes smooth the continuous multiple instantaneous channel quality levels into an average channel quality level, and finally feed back the average channel quality level to the original node in each service time slot.
By the method, each node periodically detects each frequency point channel in the whole frequency hopping set, records the frequency point number with poor channel quality or violent change, and the specific judgment criterion is as follows: when more than M (M < N) "poor" levels exist in the average channel quality levels of a certain frequency point received continuously for N times, the frequency point is listed as a frequency point subject to fading, and the information of the frequency point subject to fading is added.
2. Information reporting and fusion of faded frequency points
For a non-root node, reporting the information of the faded frequency points detected by the node to a father node after the network access is successful.
And then, each non-root node reports the information of the faded frequency points step by step, and the specific process is as follows: if the fading frequency point information comes from the child nodes, the fading frequency point information is stored firstly until the fading frequency point information of all the child nodes is collected, and then OR fusion is carried out and reported to the father node of the user; and repeating the process by the father node until the root node receives the information of the faded frequency points of the whole scheduling tree. In the process, if the child node receives the message only containing the frequency point information of the father node, the message is not processed.
3. Fading frequency point rejection and frequency hopping set reconstruction
For the root node, after the network is successfully established, the available frequency point information and the TOD information of the switching time are issued to the whole network.
And then, when the fusion processing period reaches, the root node performs or fusion on the received information of the faded frequency points reported by each scheduling tree, and rejects the faded frequency points to form a reconstructed information message of the frequency hopping set, wherein the reconstructed information message comprises the information of the available frequency points and the TOD information of the switching time. And the root node sends the frequency hopping set reconstruction information and the switching time TOD information obtained by the fusion processing to the whole network broadcast, and after receiving the information, each node negotiates to switch a new frequency hopping set consistently at the time point indicated by the switching time TOD information.
4. Rejected frequency point recovery
The rejected faded frequency points are not recovered forever, but released after being imprisoned for a period of time (the specific duration and the number of currently usable frequency points form a positive correlation). If the frequency point is judged to be faded again, the imprisoning time is prolonged to the preset time length upper limit, if the frequency point is received normally, the imprisoning time is released, and if not, the imprisoning time is imprisoned again to the preset time length upper limit.
5. Extreme case handling
When the frequency points in the whole frequency hopping table are judged to be faded, the root node can grade the frequency points according to the channel quality of each frequency point, and selects a plurality of frequency points with the best channel quality to form a frequency hopping set, and in an extreme case, the frequency hopping set is degenerated to be frequency-fixed communication on the frequency points with the best channel quality.
Those skilled in the art will appreciate that, in addition to implementing the systems, apparatus, and various modules thereof provided by the present invention in purely computer readable program code, the same procedures can be implemented entirely by logically programming method steps such that the systems, apparatus, and various modules thereof are provided in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system, the device and the modules thereof provided by the present invention can be considered as a hardware component, and the modules included in the system, the device and the modules thereof for implementing various programs can also be considered as structures in the hardware component; modules for performing various functions may also be considered as structures within both software programs and hardware components that perform the methods.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (9)
1. A channel fading suppression method based on adaptive frequency hopping is characterized by comprising the following steps:
step 1: in a frequency hopping network, periodically detecting the channel quality of each frequency point, finding out the frequency point subjected to fading and reporting to a root node;
step 2: the root node performs fusion processing on the information of the faded frequency points;
and step 3: rejecting a frequency hopping set from the faded frequency points and sending the reconstructed frequency hopping set information and switching time to other nodes;
and 4, step 4: the entire frequency hopping network is negotiated and the frequency hopping set is switched.
2. The method for suppressing channel fading based on adaptive frequency hopping according to claim 1, wherein each node adds a training sequence to data transmitted in its own time slot, and other nodes perform channel estimation according to the training sequence to form an instantaneous channel quality level, and smooth the instantaneous channel quality levels of consecutive times into an average channel quality level, and feed back the average channel quality level to the original node in their respective service time slot, and when the average channel quality level of a certain frequency point received consecutively and many times has a number greater than the number of levels that do not meet the setting, the frequency point is listed as a frequency point subject to fading.
3. The method for suppressing channel fading based on adaptive frequency hopping as claimed in claim 1, wherein for non-root nodes, if the information of the faded frequency points comes from the child nodes, the faded frequency point information is stored first until the information of the faded frequency points of all the child nodes is collected, and then the faded frequency point information is fused and reported to the father node of the non-root node until the root node receives the information of the faded frequency points of the whole scheduling tree;
if the child node receives the message only containing the frequency point information of the father node, the message is not processed.
4. The method according to claim 1, wherein for a root node, when the current fusion processing cycle arrives, the root node fuses the received information of the faded frequency points reported by each scheduling tree, and rejects the faded frequency points to form a reconstructed information packet of a frequency hopping set, which includes frequency point information and TOD information of switching time, and broadcasts and transmits the reconstructed information packet to the whole network.
5. The channel fading suppression method based on adaptive frequency hopping as claimed in claim 1, wherein the rejected faded frequency points are imprisoned;
the imprisoning time and the current frequency point number form a positive correlation relationship, and release is carried out after imprisoning.
6. The method for suppressing channel fading based on adaptive frequency hopping as claimed in claim 5, wherein if the trapped frequency point is determined to be a frequency point subject to fading again, the trapping time is extended to a preset upper duration limit, and if the frequency point subject to fading is received normally in the future, the frequency point subject to fading is released, otherwise, the frequency point subject to trapping is trapped again to the preset upper duration limit.
7. The method for suppressing channel fading based on adaptive frequency hopping as claimed in claim 1, wherein when the frequency points in the whole frequency hopping network are all determined to be frequency points subject to fading, the root node ranks the frequency points according to the channel quality of each frequency point, and selects a plurality of frequency points whose channel quality meets the preset quality to form a frequency hopping set.
8. A system for suppressing channel fading based on adaptive frequency hopping, comprising:
module M1: in a frequency hopping network, periodically detecting the channel quality of each frequency point, finding out the frequency point subjected to fading and reporting to a root node;
module M2: the root node performs fusion processing on the information of the faded frequency points;
module M3: rejecting a frequency hopping set from the faded frequency points and sending the reconstructed frequency hopping set information and switching time to other nodes;
module M4: the entire frequency hopping network is negotiated and the frequency hopping set is switched.
9. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 8.
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