CN113972968A - Periodic short message transmission method and system based on active delay spread spectrum Aloha protocol - Google Patents
Periodic short message transmission method and system based on active delay spread spectrum Aloha protocol Download PDFInfo
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- CN113972968A CN113972968A CN202111399531.9A CN202111399531A CN113972968A CN 113972968 A CN113972968 A CN 113972968A CN 202111399531 A CN202111399531 A CN 202111399531A CN 113972968 A CN113972968 A CN 113972968A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1812—Hybrid protocols; Hybrid automatic repeat request [HARQ]
- H04L1/1819—Hybrid protocols; Hybrid automatic repeat request [HARQ] with retransmission of additional or different redundancy
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
- H04B7/18513—Transmission in a satellite or space-based system
Abstract
The invention discloses a periodic short message transmission method and a periodic short message transmission system based on an active delay spread spectrum Aloha protocol, which belong to the technical field of satellite communication and comprise the following steps: each user generates original short message data, and each user uses the same PN code to spread the frequency of the short message; after generating short message data and spreading, each user actively delays and then transmits the short message data; the receiving end configures a local receiver according to the PN code of the transmitting end, and when the short message of the user reaches the receiving end, the local receiver captures the short message according to the spread spectrum code of the transmitting end. Through the active delay of the sending end, even if the current short message conflicts, the next sending does not conflict, so that the system performance is improved, the method can be applied to scenes such as periodic short messages of a surface sensor, periodic telemetering of the state of a low-orbit spacecraft and the like, and is worthy of popularization and application.
Description
Technical Field
The invention relates to the technical field of satellite communication, in particular to a periodic short message transmission method and a periodic short message transmission system based on an active delay spread spectrum Aloha protocol.
Background
In a satellite network, short message service has short duration, small occupied resources and large user capacity, so that the short message service becomes an important service type. The user can transmit own state information, application information or access information through the short message. In the conventional short message transmission protocol of the satellite network, random multiple access protocols mainly comprise pure Aloha, time slot Aloha, reserved Aloha, spread spectrum Aloha and the like.
In the pure Aloha protocol, a plurality of user terminals seize a channel in a mode of sending short messages to a public channel at any time according to needs, and resend the short messages if the users collide. Each user terminal works on the same carrier frequency band, timing and synchronization are not needed, and the user sending time is random. When users send packet information at the same time, collision occurs, a receiving end cannot correctly receive or solve the information, and at the moment, the users need to randomly delay a certain time to resend the information. The highest channel utilization of a pure Aloha system is 18%, so slotted Aloha is an improvement on this basis, the system divides the time axis into a number of equally spaced slots with the time of arrival of the signal at the transponder entrance as a reference point, and sets a uniform time-clock, and the data packets of each station must fall within the specified slots, typically each packet having a duration substantially equal to one slot length. The probability of packet collision is smaller than that of the pure Aloha technology, and the channel utilization rate can be improved to 36%. The Reservation Aloha is called Reservation-Aloha, and is an improved version of the Reservation-Aloha based on pure Aloha in consideration of uneven service of each user terminal. If the length of the transmitted message is long, if a pure Aloha or S-Aloha mode is adopted, the message is divided into a plurality of data segments to be transmitted, and considering factors such as collision retransmission and the like, a complete message can be received in a long time, so that an R-Aloha mode is provided. When a user terminal sends a long message inch, reservation is required, and a section of time slot is applied for continuously sending a batch of data; if the short message is sent, the transmission is carried out according to an S-ALOHA mode without reservation, the highest channel utilization rate of the mode can reach 83%, and a new transmission delay is added by a reservation mechanism. The spread-spectrum ALOHA technology is a combination of the CDMA technology and the ALOHA technology, a plurality of users can perform spread-spectrum modulation on data by using a common pseudo-random code, two or more data packets may have overlapping parts on a time axis, namely, collision occurs in a channel, but the collided data packets are not necessarily all destroyed, and as long as the time difference of the data packets reaching the ground meets a certain condition (inherent delay capture characteristic of spread spectrum), the data packets can be successfully received by a ground station.
In the spread spectrum Aloha system, short messages of a plurality of users can be randomly sent on the same spread spectrum code channel, and due to the good autocorrelation characteristic of the spread spectrum code, the receiver can distinguish signals of different users as long as the time when the signals of the plurality of users reach the receiving end theoretically exceeds 2 chips. The system does not need synchronization among users, and only one spread spectrum code capture module is configured at a receiving end to receive signals of different users, so the system is simple to realize and is widely applied to an actual system.
However, when the number of users increases, the difference in arrival time of signals of different users may still fall within 2 chips, resulting in short message collision. In some scenes of periodically sending short messages, for example, the earth surface sensor reports the state of the earth surface sensor according to a fixed period, in these scenes, if different users happen to have conflicts, the short messages are sent according to the fixed period, and the future short messages can always conflict. Therefore, a periodic short message transmission method and a periodic short message transmission method based on an active delay spread spectrum Aloha protocol are provided.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: how to solve the problem that different users happen to have conflicts in the scene of periodically sending short messages, and the short messages are sent according to a fixed period and can always conflict in the future, and provides a periodic short message transmission method based on an active delay spread spectrum Aloha protocol.
The invention solves the technical problems through the following technical scheme, and the invention comprises the following steps:
s1: spreading short messages
Each user generates original short message data, and each user uses the same PN code to spread the frequency of the short message;
s2: active delay transmission
After generating short message data and spreading, each user actively delays and then transmits the short message data;
s3: short message capture demodulation
The receiving end configures a local receiver according to the PN code of the transmitting end, and when the short message of the user reaches the receiving end, the local receiver captures the short message according to the spread spectrum code of the transmitting end.
Further, in the step S1, the user periodically generates the original short message data.
Further, in step S1, the spreading codes of all the user short message data are the same, and a coherent spreading mode is adopted, that is, 1 bit is spread by using 1 periodic PN code.
Furthermore, in step S2, time synchronization is not performed between multiple short message users, and each short message user can send a short message when a short message service arrives.
Further, in the step S2, each user records the generation time T0 of the current short message during transmission, and the actual transmission time is randomly selected within the range of (T0- Δ T, T0+ Δ T), where Δ T is the delay.
Further, in step S3, when the short message of the user arrives at the receiving end, if the time difference between the short messages of different users arriving at the receiving end is greater than 2 chips, the local receiver can capture and demodulate the user signal, and if the time difference between the short messages of different users arriving at the receiving end is less than 2 chips, the local receiver directly enters the next short message sending cycle.
The invention also provides a periodic short message transmission system based on the active delay spread spectrum Aloha protocol, which adopts the transmission method to transmit the periodic short message and comprises the following steps:
the spread spectrum module is used for spreading the spectrum of the short message by using the same PN code for each user after each user generates the original short message data;
the delay sending module is used for actively delaying and then sending short message data generated by each user after the short message data is spread;
the acquisition demodulation module is used for configuring a local receiver at a receiving end according to the PN code of the transmitting end, and when a user short message reaches the receiving end, the local receiver acquires the short message according to the spread spectrum code of the transmitting end;
the control processing module is used for sending instructions to other modules to complete related actions;
the spread spectrum module, the delay sending module, the capturing and demodulating module and the log module are all electrically connected with the control processing module.
Compared with the prior art, the invention has the following advantages: according to the periodic short message transmission method based on the active delay spread spectrum Aloha protocol, even if the current short message conflicts, the current short message does not conflict with the current short message at the next transmission time through the active delay of the transmitting end, so that the performance of the system is improved, the method can be applied to scenes such as periodic short messages of an earth surface sensor, periodic telemetering of the state of a low-orbit spacecraft and the like, and is worthy of popularization and application.
Drawings
FIG. 1 is a flow chart of a system according to a first embodiment of the present invention;
FIG. 2 is a schematic illustration of a spread-spectrum Aloha in a second embodiment of the present invention;
FIG. 3 is a diagram of coherent spreading according to a second embodiment of the present invention;
fig. 4 is a schematic diagram of the actual time of user transmission in the second embodiment of the present invention;
fig. 5 is a schematic diagram of collision determination in the second embodiment of the present invention.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
Example one
As shown in fig. 1, the present embodiment provides a technical solution: the periodic short message transmission method based on the active delay spread spectrum Aloha protocol comprises the following steps:
(1) each user generates original short message data, and each user uses the same PN code to spread the short message data. All the short message spread spectrum codes of the users are the same, and a coherent spread spectrum method is adopted, namely 1 bit adopts 1 periodic PN code spread spectrum.
(2) The time synchronization is not needed among different short message users, and each user can send the short message when the short message service arrives, specifically: each user records the generation time T0 of the current short message, and the actual sending time is randomly selected within the range of (T0-delta T, T0+ delta T), wherein delta T is delay. If the different users happen to have conflicts, the messages are sent according to a fixed period, and the future short messages can always conflict. In order to solve the problem, the invention adds a random delay delta T to the sending time T0, so that even if the current short message collides, the next sending time does not necessarily collide, thereby improving the performance of the system.
(3) When the short message of the user reaches the receiving end, if the time of the short message of different users reaching the receiving end is more than 2 chips, the local receiver considers that the user signal can be captured and demodulated, if the time of the short message reaching the receiving end is less than 2 chips, the local receiver considers that the conflict occurs, and then the local receiver directly enters the next short message sending period.
Example two
(1) As shown in fig. 2, each user generates original short message data, and each user uses the same PN code to spread the short message data. The specific spreading mode is shown in fig. 3, where each user short message information contains 690 bits, and each bit is spread by using an m sequence 1023 long. The short message information rate before spreading is 3kbps, and the chip rate after spreading is 3.069 cps.
(2) The time synchronization is not needed among different short message users, and each user can send the short message when the short message service arrives, specifically: each user records the generation time T0 of the current short message, and the actual sending time is randomly selected within the range of (T0-delta T, T0+ delta T) (namely, one time with equal probability is selected within the time range), wherein delta T is delay. If the different users happen to have conflicts, the messages are sent according to a fixed period, and the future short messages can always conflict. In order to solve the problem, the invention adds a random delay delta T to the sending time T0, so that even if the current short message collides, the next sending time does not necessarily collide, thereby improving the performance of the system.
As shown in fig. 4, the system has 3 users in total, time synchronization is not required between each user, the basic period of short message transmission of each user is 10s, and a random delay with a maximum value of ± 1s is superimposed at the time of generating each short message, see fig. 4, the time of transmitting the first 5 short messages of user 1 is 0s,9.8s,19.6s,30.2s, and 39.8 s; the sending time of the first 5 short messages of the user 2 is 0.2s,9.8s,19.4s,30.1s and 39.7 s; the sending time of the first 5 short messages of the user 3 is 0.3s,10.1s,20.1s,29.8s and 40.1 s. It can be known from the sending time that the sending time of the second short message of the user 1 and the second short message of the user 2 are both 9.8s, and the two short messages collide. However, because the invention superposes a random delay with the maximum value of +/-1 s at each short message sending time, the following short messages do not collide.
(3) The receiving end configures the local receiver according to the PN code of the transmitting end, which is specifically shown in fig. 5. When the user short message reaches the receiving end, because the length of each short message is 690 bits, each short message has 690 collision windows in total. If the time difference between the two short messages reaching the receiving end is less than 2 chips, the system determines that a conflict occurs, and directly enters the next short message sending period, for example, the short messages 1 and 2 in the figure have a conflict, and the system determines that the short message transmission fails; if the time difference between the two short messages reaching the receiving end is greater than 2 chips, the local receiver considers that the user signal can be captured and demodulated, and the short message 3 in the figure can be successfully transmitted.
In summary, according to the periodic short message transmission method based on the active delay spread-spectrum Aloha protocol in the embodiment, even if the current short message collides through the active delay of the sending end, the current short message does not collide with the sending end at the next time, so that the performance of the system is improved.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (7)
1. The periodic short message transmission method based on the active delay spread spectrum Aloha protocol is characterized by comprising the following steps of:
s1: spreading short messages
Each user generates original short message data, and each user uses the same PN code to spread the frequency of the short message;
s2: active delay transmission
After generating short message data and spreading, each user actively delays and then transmits the short message data;
s3: short message capture demodulation
The receiving end configures a local receiver according to the PN code of the transmitting end, and when the short message of the user reaches the receiving end, the local receiver captures the short message according to the spread spectrum code of the transmitting end.
2. The periodic short message transmission method based on the active delay spread spectrum Aloha protocol according to claim 1, characterized in that: in step S1, the user periodically generates original short message data.
3. The periodic short message transmission method based on the active delay spread spectrum Aloha protocol according to claim 1, characterized in that: in step S1, the spreading codes of all the user short message data are the same, and a coherent spreading mode is adopted, that is, 1 bit is spread by using 1 periodic PN code.
4. The periodic short message transmission method based on the active delay spread spectrum Aloha protocol according to claim 1, characterized in that: in step S2, time synchronization is not performed between multiple short message users, and each user can send a short message when a short message service arrives.
5. The periodic short message transmission method based on the active delay spread spectrum Aloha protocol according to claim 1, characterized in that: in the step S2, each user records the generation time T0 of the current short message during transmission, and the actual transmission time is randomly selected within the range of (T0- Δ T, T0+ Δ T), where Δ T is the delay.
6. The periodic short message transmission method based on the active delay spread spectrum Aloha protocol according to claim 1, characterized in that: in step S3, when the short message of the user arrives at the receiving end, if the time difference between the short messages of different users arriving at the receiving end is greater than 2 chips, the local receiver can capture and demodulate the user signal, and if the time difference between the short messages of different users arriving at the receiving end is less than 2 chips, the local receiver directly enters the next short message sending period.
7. A periodic short message transmission system based on an active delay spread spectrum Aloha protocol, wherein the transmission method according to any one of claims 1 to 6 is adopted to transmit the periodic short message, and the method comprises the following steps:
the spread spectrum module is used for spreading the spectrum of the short message by using the same PN code for each user after each user generates the original short message data;
the delay sending module is used for actively delaying and then sending short message data generated by each user after the short message data is spread;
the acquisition demodulation module is used for configuring a local receiver at a receiving end according to the PN code of the transmitting end, and when a user short message reaches the receiving end, the local receiver acquires the short message according to the spread spectrum code of the transmitting end;
the control processing module is used for sending instructions to other modules to complete related actions;
the spread spectrum module, the delay sending module, the capturing and demodulating module and the log module are all electrically connected with the control processing module.
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Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5287384A (en) * | 1992-10-15 | 1994-02-15 | Lxe Inc. | Frequency hopping spread spectrum data communications system |
| US5537397A (en) * | 1994-06-07 | 1996-07-16 | Aloha Networks, Inc. | Spread aloha CDMA data communications |
| US20100054131A1 (en) * | 2008-08-26 | 2010-03-04 | Agence Spatiale Europeenne | Methods, apparatuses and system for asynchronous spread-spectrum communication |
| CN101854729A (en) * | 2010-03-30 | 2010-10-06 | 中国人民解放军信息工程大学 | Random access method for satellite communication system |
| CN104756408A (en) * | 2012-10-18 | 2015-07-01 | 三菱电机株式会社 | Communication terminal, communication method, program, and communication system |
| CN107509247A (en) * | 2017-07-21 | 2017-12-22 | 哈尔滨工业大学深圳研究生院 | The multiple access method and system of spatial data transmission |
| CN108900459A (en) * | 2018-05-25 | 2018-11-27 | 西南电子技术研究所（中国电子科技集团公司第十研究所） | GFDM/CDMA mixing multiple access radio switch-in method |
| CN109257737A (en) * | 2018-11-07 | 2019-01-22 | 北京天海达科技有限公司 | A kind of Beidou long message sending device and method |
| CN112398672A (en) * | 2019-08-16 | 2021-02-23 | 北京新能源汽车股份有限公司 | Message detection method and device |
-
2021
- 2021-11-19 CN CN202111399531.9A patent/CN113972968A/en active Pending
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5287384A (en) * | 1992-10-15 | 1994-02-15 | Lxe Inc. | Frequency hopping spread spectrum data communications system |
| US5537397A (en) * | 1994-06-07 | 1996-07-16 | Aloha Networks, Inc. | Spread aloha CDMA data communications |
| US20100054131A1 (en) * | 2008-08-26 | 2010-03-04 | Agence Spatiale Europeenne | Methods, apparatuses and system for asynchronous spread-spectrum communication |
| CN101854729A (en) * | 2010-03-30 | 2010-10-06 | 中国人民解放军信息工程大学 | Random access method for satellite communication system |
| CN104756408A (en) * | 2012-10-18 | 2015-07-01 | 三菱电机株式会社 | Communication terminal, communication method, program, and communication system |
| CN107509247A (en) * | 2017-07-21 | 2017-12-22 | 哈尔滨工业大学深圳研究生院 | The multiple access method and system of spatial data transmission |
| CN108900459A (en) * | 2018-05-25 | 2018-11-27 | 西南电子技术研究所（中国电子科技集团公司第十研究所） | GFDM/CDMA mixing multiple access radio switch-in method |
| CN109257737A (en) * | 2018-11-07 | 2019-01-22 | 北京天海达科技有限公司 | A kind of Beidou long message sending device and method |
| CN112398672A (en) * | 2019-08-16 | 2021-02-23 | 北京新能源汽车股份有限公司 | Message detection method and device |
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