CN113873677A - Satellite communication random access method based on spread spectrum - Google Patents
Satellite communication random access method based on spread spectrum Download PDFInfo
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Abstract
The invention discloses a satellite communication random access method based on spread spectrum, belonging to the technical field of communication, and comprising the following steps of dividing the condition that a user accesses a satellite communication system into two types: the method comprises the steps that under a hopping beam satellite communication system with uniformly distributed users, the users access the satellite by adopting an SSA random access protocol, and under the second condition, under a hopping beam satellite communication system with non-uniformly distributed users, the users perform beam scheduling and access the satellite in batches, so that a random access method for simultaneously accommodating a plurality of users to access is realized, and the collision-tolerant performance of the system is improved; meanwhile, the problem of uneven user distribution is solved by combining beam scheduling, the technical problem of throughput of a beam hopping satellite communication system is further improved, the invention realizes collision tolerance random access of massive users and flexible scheduling of resources, does not cause loss of user information, and can avoid the occurrence of the condition that a reverse link is blocked even when collision is serious.
Description
Technical Field
The invention belongs to the technical field of communication, and relates to a satellite communication random access method based on spread spectrum.
Background
The satellite communication system has wide area coverage characteristics, can support Multiple Access of Multiple users, and a Multiple Access Control (MAC) Protocol mainly solves the problem of how users in a beam share an uplink channel, and the problem includes two aspects of Multiple Access and radio resource management: the multiple access mainly defines how a user accesses a system, including multiple access modes such as FDMA, TDMA, CDMA, Aloha, etc., and the radio resource management includes application, allocation and scheduling of radio resources, which have certain differences in resources, including frequency band, time slot, code word, space, etc., according to the difference of the multiple access modes.
In a satellite communication system, multiple access protocols are classified into connection-oriented multiple access and random multiple access, and connection-oriented multiple access is further classified into orthogonal multiple access and non-orthogonal multiple access. The orthogonal multiple access mode comprises common FDMA, TDMA, CDMA and the like, and the non-orthogonal multiple access mode comprises interleaving multiple access (IDMA), low-density signature multiple access (LDS), Sparse Code Multiple Access (SCMA), non-orthogonal multiple access (NOMA) and the like. The limited number of orthogonal resources exists in the orthogonal multiple access, which is not beneficial to simultaneously supporting large-scale connection, and the resource allocation process can introduce larger signaling overhead, which can affect the system efficiency in the network mainly comprising short data packet service; the novel non-orthogonal multiple access mode breaks through the limitation of orthogonal resource allocation, improves the system connection number and the network capacity, but brings larger overhead, reduces the flexibility of the system to a certain extent, and the connection-oriented multiple access mode can send data after connection is established, wastes time to a certain extent and causes serious time delay.
The random access mechanism was the first multiple access protocol proposed for packet radio transmission, proposed in 1970 by university of hawaii. In the random access mechanism, all time slots are available to all users. Each user can transmit his own data at any randomly selected time slot without any request. If a collision occurs, the data will be corrupted and need to be retransmitted. The traditional random access mode mainly comprises an ALOHA protocol, a time slot ALOHA protocol, a spread spectrum ALOHA protocol and the like. The random access method finally results in uncertain time delay, and under the condition of low load, the time delay is small, and under the condition of high load, the time delay is very large, so that the time delay requirement and the service quality can not be ensured, and the throughput is low.
In order to overcome the above problems, the industry improves the conventional random access method, and generates various new random access protocols such as Diversity Slot ALOHA (DSA), Contention Resolution Diversity Slot ALOHA (CRDSA), Irregular Retransmission Slot ALOHA (IRSA), and Coded Slot ALOHA (CSA).
Although the random access protocol improves the throughput, the premise is that the collision probability is not high, the types and the number of user terminals in a future beam-hopping satellite communication system are various and large, the collision probability of the user access system is very high, and the protocol fails or has higher processing difficulty. In order to adapt to the strong collision situation of user access of the future beam hopping satellite communication system, a random access protocol and a mechanism which are tolerant to collision are provided on the basis of the above protocol.
When satellite communication multi-user random access is carried out, a user terminal randomly selects a time slot to send information to a satellite, when the number of users is large, multiple users may select the same time slot, and at the moment, signals of the users collide to form interference, so that the difficulty in information interpretation is increased. The random access protocol has no corresponding collision tolerance mechanism, so that the user information is lost, and even the reverse link is blocked when the collision is serious.
In the existing beam hopping satellite communication system, collision problems exist in random access of a large number of users, and the weak proportion of beams to wave positions limits the service capacity of each wave position user, so that the probability that a large number of users in the same wave position send random messages in the same time period is increased sharply, data presents strong collision and weak synchronization characteristics, and the system throughput is reduced seriously. And the collision is further aggravated by the large concentration of part of wave position users due to the uneven distribution of the users.
Disclosure of Invention
The invention aims to provide a satellite communication random access method based on spread spectrum, which solves the problem of simultaneously accommodating a random access method for accessing a plurality of users and improves the collision-tolerant performance of a system; meanwhile, the problem of uneven user distribution is solved by combining beam scheduling, and the technical problem of throughput of the beam hopping satellite communication system is further improved.
In order to achieve the purpose, the invention adopts the following technical scheme: a satellite communication random access method based on spread spectrum comprises the following steps:
step 1: the access of users to satellite communication systems is divided into two categories: in the first case, under a hopping beam satellite communication system with uniformly distributed users, the users access the satellite by adopting an SSA random access protocol, and the specific method executes the step 2; in the second case, under the beam hopping satellite communication system with non-uniform distribution of users, the users perform beam scheduling and access to the satellite in batches, and the specific method executes step 3;
step 2: under a hopping beam satellite communication system with uniformly distributed users, the users access a satellite by adopting an SSA random access protocol, and the method specifically comprises the following steps:
step S2-1: the user carries out system time synchronization according to the system time broadcast message to acquire hopping beam pattern information;
step S2-2: the user determines the time of the wave beam reaching the wave position of the user according to the wave beam hopping pattern information;
step S2-3: in the beam hopping period, if a user has a service, the user encodes and frames service data;
step S2-4: carrying out spread spectrum on the user information subjected to coding framing by using a preset PN sequence to obtain sending chip data;
step S2-5: calculating to obtain the time range of the head chip according to the arrival wave position time of the wave beam;
step S2-6: randomly selecting a sending time t within the time range of the head chip;
step S2-7: waiting for the arrival of the beam, and executing the step S2-8 after the arrival of the beam;
step S2-8: after the wave beam arrives, the chip sequence after the spread spectrum is modulated, frequency-converted and amplified;
step S2-9: sending information to the satellite at fixed time according to the sending time t;
step S2-10: the information transmitted in step S2-9 reaches the satellite receiving antenna through the user uplink;
step S2-11: the satellite receives information sent by a plurality of users, and performs low-noise amplification, filtering, frequency conversion and demodulation processing on all the information to obtain chip data of each information before despreading;
step S2-12: despreading by using a corresponding PN sequence, and acquiring a data frame of a specific user from information sent by all users;
step S2-13: de-framing and decoding the de-spread data to obtain the original data of each user;
step S2-14: under a beam hopping satellite communication system with uniformly distributed users, the process that the users access the satellite by adopting an SSA random access protocol is ended;
and step 3: in a beam hopping satellite communication system with non-uniform distribution of users, the users perform beam scheduling and access to the satellite in batches, and the method specifically comprises the following steps:
step S3-1: the user carries out system time synchronization according to the system time broadcast message and acquires hopping beam pattern information;
step S3-2: the user determines the time when the wave position b is lighted and the number N of times that the wave position b is lighted according to the information of the beam hopping patternb；
Step (ii) ofS3-3: the number N of times that the user is lighted according to the position of the wavebAccording to probability
Selecting a hopping wave beam interval for access;
step S3-4: in the beam hopping period, if a user has a service, the user encodes and frames service data;
step S3-5: for the user information after the coding framing is finished, a preset PN sequence is used for carrying out spread spectrum to obtain sending chip data;
step S3-6: the user calculates the time range of the head chip according to the selected wave beam hopping interval and the time of the wave beam reaching the wave position;
step S3-7: randomly selecting a sending time t1 in the time of the head chip;
step S3-8: waiting for the arrival of the beam, and executing the step S3-9 after the arrival of the beam;
step S3-9: when the wave beam arrives, the chip sequence after the spread spectrum is modulated, frequency-converted and amplified;
step S3-10: according to the sending time t1, information is sent to the satellite in a timed mode;
step S3-11: the information transmitted in step S3-10 reaches the satellite receiving antenna through the user uplink;
step S3-12: the satellite receives information sent by a plurality of users, and performs low-noise amplification, filtering, frequency conversion and demodulation processing on all the information to obtain chip data of each information before despreading;
step S3-13: despreading by using a corresponding PN sequence, and acquiring a data frame of a specific user from information sent by all users;
step S3-14: de-framing and decoding the de-spread data to obtain the original data of each user;
step S3-15: and under the beam hopping satellite communication system with the non-uniform distribution of the users, the process that the users carry out beam scheduling and access the satellite in batches is finished.
Preferably, the time range of the head chip is the time range of the access information transmission that can be selected by the user after the beam reaches the beam position of the user set by the system.
Preferably, in the step S2-4 and the step S3-5, the spreading is performed by using a predetermined PN sequence, specifically, by using a spread spectrum Aloha protocol.
Preferably, in step S3-3, the users in the wave position access the satellite in batches according to the number of the wave positions lighted by the wave beam in each wave beam jumping period, i.e. the users in the wave position are divided into NbAnd (4) accessing each batch.
The invention has the beneficial effects that:
the satellite communication random access method based on the spread spectrum solves the problem of a random access method for simultaneously accommodating a plurality of users to access, and improves the collision-tolerant performance of the system; meanwhile, the problem of uneven user distribution is solved by combining beam scheduling, the technical problem of throughput of a beam hopping satellite communication system is further improved, the invention realizes collision tolerance random access of massive users and flexible scheduling of resources, does not cause loss of user information, and can avoid the occurrence of the condition that a reverse link is blocked even when collision is serious.
Drawings
FIG. 1 is a flow chart of step 2 of the present invention;
FIG. 2 is a flow chart of step 3 of the present invention;
FIG. 3 is an exemplary diagram of SSA protocol features of the present invention;
FIG. 4 is a simulation diagram of bit error rate and number of users under different SNR conditions for SSA protocol of the present invention;
fig. 5 is a relationship between throughput and header chips obtained by poisson distribution simulation under the condition of a single beam in the present invention, when the number of users is 40 (the number of users included in each wave position under uniform distribution), and Eb/No =12dB (assuming that 30 users can be accommodated for simultaneous access at most);
fig. 6 is a relationship between collision probability and header chips obtained by poisson distribution simulation under the single beam condition of the present invention, when the number of users is 40 (the number of users included in each wave position under uniform distribution), and Eb/No =12dB (assuming that 30 users can be accommodated for simultaneous access at most);
FIG. 7 is a graph of the relationship between throughput and the number of header chips in a superframe period for the case of non-uniform distribution of beam scheduling and no beam among users according to the present invention;
fig. 8 is a relationship between collision probability and number of header chips in one superframe period in case of non-uniform distribution of beam scheduling and no beam for users of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A spread spectrum-based satellite communication random access method as shown in fig. 1-8 includes the following steps:
step 1: the access of users to satellite communication systems is divided into two categories: in the first case, under a hopping beam satellite communication system with uniformly distributed users, the users access the satellite by adopting an SSA random access protocol, and the specific method executes the step 2; in the second case, under the beam hopping satellite communication system with non-uniform distribution of users, the users perform beam scheduling and access to the satellite in batches, and the specific method executes step 3;
step 2: under a hopping beam satellite communication system with uniformly distributed users, the users access a satellite by adopting an SSA random access protocol, and the method specifically comprises the following steps:
step S2-1: the user carries out system time synchronization according to the system time broadcast message to acquire hopping beam pattern information;
step S2-2: the user determines the time of the wave beam reaching the wave position of the user according to the wave beam hopping pattern information;
step S2-3: in the beam hopping period, if a user has a service, the user encodes and frames service data;
step S2-4: carrying out spread spectrum on the user information subjected to coding framing by using a preset PN sequence to obtain sending chip data;
step S2-5: calculating to obtain the time range of the head chip according to the arrival wave position time of the wave beam;
step S2-6: randomly selecting a sending time t within the time range of the head chip;
step S2-7: waiting for the arrival of the beam, and executing the step S2-8 after the arrival of the beam;
step S2-8: after the wave beam arrives, the chip sequence after the spread spectrum is modulated, frequency-converted and amplified;
step S2-9: sending information to the satellite at fixed time according to the sending time t;
step S2-10: the information transmitted in step S2-9 reaches the satellite receiving antenna through the user uplink;
step S2-11: the satellite receives information sent by a plurality of users, and performs low-noise amplification, filtering, frequency conversion and demodulation processing on all the information to obtain chip data of each information before despreading;
step S2-12: despreading by using a corresponding PN sequence, and acquiring a data frame of a specific user from information sent by all users;
step S2-13: de-framing and decoding the de-spread data to obtain the original data of each user;
step S2-14: under a beam hopping satellite communication system with uniformly distributed users, the process that the users access the satellite by adopting an SSA random access protocol is ended;
fig. 3 shows an example of a spread spectrum Aloha protocol, where users 1-7 in a wave slot have traffic arriving during a hop beam period, assuming a beam arrival time of 0 and a header set to 0 to NpreOne chip duration, assuming one chip time tchipThen the head time is 0-Npretchip. Each user is in the range of 0-NpreThe transmission time is selected on a chip time basis. According to the principle of spread spectrum communication, when two users adopt different PN sequences to carry out spread spectrum, the transmission time of the two users is separated by 2 chips or more, and the two users can be better connectedThe receiving end recovers respective information.
In this embodiment, according to the feature of the SSA protocol, the access capability of the random access protocol based on the SSA is first simulated. Unlike the traditional managed and controlled beam, the SSA access protocol is simulated by adopting a multi-user cooperative reception strategy. As shown in fig. 4, a simulation curve of the bit error rate of the protocol under different signal-to-noise ratios and different numbers of users is given, so as to guide subsequent simulation calculation.
As can be seen from fig. 4, at a bit error rate of 10-7When Eb/No =8dB, at the same time, at most 18 users can be accommodated; Eb/No =12, a maximum of about 30 users can be accommodated.
Due to the difference of the EIRP transmitted by the users, the Eb/No of part of the users can be higher, and the number of the users can be more.
And step 3: in a beam hopping satellite communication system with non-uniform distribution of users, the users perform beam scheduling and access to the satellite in batches, and the method specifically comprises the following steps:
step S3-1: the user carries out system time synchronization according to the system time broadcast message and acquires hopping beam pattern information;
step S3-2: the user determines the time when the wave position b is lighted and the number N of times that the wave position b is lighted according to the information of the beam hopping patternb；
Step S3-3: the number N of times that the user is lighted according to the position of the wavebAccording to probability
Selecting a hopping wave beam interval for access;
step S3-4: in the beam hopping period, if a user has a service, the user encodes and frames service data;
step S3-5: for the user information after the coding framing is finished, a preset PN sequence is used for carrying out spread spectrum to obtain sending chip data;
step S3-6: the user calculates the time range of the head chip according to the selected wave beam hopping interval and the time of the wave beam reaching the wave position;
step S3-7: randomly selecting a sending time t1 in the time of the head chip;
step S3-8: waiting for the arrival of the beam, and executing the step S3-9 after the arrival of the beam;
step S3-9: when the wave beam arrives, the chip sequence after the spread spectrum is modulated, frequency-converted and amplified;
step S3-10: according to the sending time t1, information is sent to the satellite in a timed mode;
step S3-11: the information transmitted in step S3-10 reaches the satellite receiving antenna through the user uplink;
step S3-12: the satellite receives information sent by a plurality of users, and performs low-noise amplification, filtering, frequency conversion and demodulation processing on all the information to obtain chip data of each information before despreading;
step S3-13: despreading by using a corresponding PN sequence, and acquiring a data frame of a specific user from information sent by all users;
step S3-14: de-framing and decoding the de-spread data to obtain the original data of each user;
step S3-15: and under the beam hopping satellite communication system with the non-uniform distribution of the users, the process that the users carry out beam scheduling and access the satellite in batches is finished.
Fig. 5 and 6 show the relationship between the throughput and collision probability obtained by using poisson distribution simulation and the header chips under the single beam condition, when the number of users is 40 (the number of users contained in each wave position under uniform distribution), Eb/No =12dB (assuming that 30 users can be simultaneously accessed at most). As can be seen from the figure, when λ =0.5, the average number of users with traffic arriving is 20, and the throughput is larger. The present embodiment derives from subsequent simulation and analysis that the maximum throughput can be obtained when =0.7 or so, and the average number of users with traffic arriving approaches 30. The collision probability decreases with the increase of the number of the head chips and gradually approaches to a fixed value, and the gain effect of continuously increasing the number of the head chips on the throughput is not obvious.
Under the influence of geographic conditions, urban and rural distribution, industrial distribution and other factors, users of a beam hopping satellite communication system are not uniformly distributed under normal conditions, and the number of users owned by each wave position is greatly different. Under the condition that the satellite receiving capability is limited, more beam hopping time slots are allocated to wave positions in a user distribution set through beam scheduling, and less beam hopping time slots are allocated to wave positions in a user distribution set to optimize beam hopping, wherein a beam scheduling algorithm is as follows:
the algorithm is as follows: and (4) a beam scheduling algorithm.
Inputting: user distribution, number of beams NbeamsNumber of beam hopping slots Nslots。
And (3) outputting: the illuminated wave position and the allocated wave beam of each wave beam hopping time slot.
1) Acquiring the number of each wave bit user according to the user position and the access request sent by the user, and generating a wave bit service volume set i;
2) calculating the proportion of the number of the service arrival users of each wave bit to the total number of the service arrival users;
3) For i in Nslots
4) 
i_temp= 
i；
5) For j in Nbeams
6) While 
i_tempremaining time slot>0
7) Randomly selecting a wave position b from wave positions of users;
8) if wave bit b is allocated time slot not more than proportion and number of users in wave bit is >0
9) There is no interference between If wave bit b and other wave bits allocated in time slot i
10) Allocating a time slot i and a beam j to a wave bit b;
11) will wave bit b from
i_tempDeleting or setting the number of the users to be 0;
12) updating based on user service conditions
iThe number of users of the medium wave position b;
13) Break;
14) Else
15) will be provided with
i_tempThe traffic volume of the medium wave position b is set to be 0;
16) EndIf
17) Else
18) will wave bit b from
i_tempDeleting the data or setting the traffic volume of the data to be 0;
19) EndIf
20) EndWhile
21) EndFor
22) EndFor
in order to avoid that the collision probability is too high due to the fact that the number of users in a wave position accessing a satellite is too large in each wave beam jumping interval time, the users in the wave position need to access the satellite in batches according to the number of the wave positions which are lightened by the wave beams in each wave beam jumping period, and suppose that the wave position b is lightened by N within one wave beam jumping periodbThen, the users in the wave position will be
Probability selects a hopping wave beam interval to access the satellite, namely dividing users in wave positions into NbAnd (4) accessing each batch.
The relationship between the throughput and collision probability and the number of header chips in one superframe period in the case where the users are non-uniformly distributed with beam scheduling and no beam is given as shown in fig. 7 and 8.
As can be seen from fig. 7 and 8, with beam scheduling, throughput is greatly improved compared with that without beam scheduling, and collision probability is greatly reduced, especially when the number of header chips is large, the performance is more obvious. Therefore, in the case of scheduling, the number of header chips is inversely a bottleneck that restricts throughput. And the system throughput of beam scheduling and user batch access is close to the system throughput under the condition of uniform distribution under the condition of non-uniform distribution, which is obtained from subsequent analysis and simulation results.
Preferably, the time range of the head chip is the time range of the access information transmission that can be selected by the user after the beam reaches the beam position of the user set by the system.
Preferably, in the step S2-4 and the step S3-5, the spreading is performed by using a predetermined PN sequence, specifically, by using a spread spectrum Aloha protocol.
Preferably, in step S3-3, the users in the wave position access the satellite in batches according to the number of the wave positions lighted by the wave beam in each wave beam jumping period, i.e. the users in the wave position are divided into NbAnd (4) accessing each batch.
The satellite communication random access method based on the spread spectrum solves the problem of a random access method for simultaneously accommodating a plurality of users to access, and improves the collision-tolerant performance of the system; meanwhile, the problem of uneven user distribution is solved by combining beam scheduling, the technical problem of throughput of a beam hopping satellite communication system is further improved, the invention realizes collision tolerance random access of massive users and flexible scheduling of resources, does not cause loss of user information, and can avoid the occurrence of the condition that a reverse link is blocked even when collision is serious.
Claims (4)
1. A satellite communication random access method based on spread spectrum is characterized in that: the method comprises the following steps:
step 1: the access of users to satellite communication systems is divided into two categories: in the first case, under a hopping beam satellite communication system with uniformly distributed users, the users access the satellite by adopting an SSA random access protocol, and the specific method executes the step 2; in the second case, under the beam hopping satellite communication system with non-uniform distribution of users, the users perform beam scheduling and access to the satellite in batches, and the specific method executes step 3;
step 2: under a hopping beam satellite communication system with uniformly distributed users, the users access a satellite by adopting an SSA random access protocol, and the method specifically comprises the following steps:
step S2-1: the user carries out system time synchronization according to the system time broadcast message to acquire hopping beam pattern information;
step S2-2: the user determines the time of the wave beam reaching the wave position of the user according to the wave beam hopping pattern information;
step S2-3: in the beam hopping period, if a user has a service, the user encodes and frames service data;
step S2-4: carrying out spread spectrum on the user information subjected to coding framing by using a preset PN sequence to obtain sending chip data;
step S2-5: calculating to obtain the time range of the head chip according to the arrival wave position time of the wave beam;
step S2-6: randomly selecting a sending time t within the time range of the head chip;
step S2-7: waiting for the arrival of the beam, and executing the step S2-8 after the arrival of the beam;
step S2-8: after the wave beam arrives, the chip sequence after the spread spectrum is modulated, frequency-converted and amplified;
step S2-9: sending information to the satellite at fixed time according to the sending time t;
step S2-10: the information transmitted in step S2-9 reaches the satellite receiving antenna through the user uplink;
step S2-11: the satellite receives information sent by a plurality of users, and performs low-noise amplification, filtering, frequency conversion and demodulation processing on all the information to obtain chip data of each information before despreading;
step S2-12: despreading by using a corresponding PN sequence, and acquiring a data frame of a specific user from information sent by all users;
step S2-13: de-framing and decoding the de-spread data to obtain the original data of each user;
step S2-14: under a beam hopping satellite communication system with uniformly distributed users, the process that the users access the satellite by adopting an SSA random access protocol is ended;
and step 3: in a beam hopping satellite communication system with non-uniform distribution of users, the users perform beam scheduling and access to the satellite in batches, and the method specifically comprises the following steps:
step S3-1: the user carries out system time synchronization according to the system time broadcast message and acquires hopping beam pattern information;
step S3-2: the user determines the time when the wave position b is lighted and the number N of times that the wave position b is lighted according to the information of the beam hopping patternb；
Step S3-3: the number N of times that the user is lighted according to the position of the wavebAccording to probability
Selecting a hopping wave beam interval for access;
step S3-4: in the beam hopping period, if a user has a service, the user encodes and frames service data;
step S3-5: for the user information after the coding framing is finished, a preset PN sequence is used for carrying out spread spectrum to obtain sending chip data;
step S3-6: the user calculates the time range of the head chip according to the selected wave beam hopping interval and the time of the wave beam reaching the wave position;
step S3-7: randomly selecting a sending time t1 in the time of the head chip;
step S3-8: waiting for the arrival of the beam, and executing the step S3-9 after the arrival of the beam;
step S3-9: when the wave beam arrives, the chip sequence after the spread spectrum is modulated, frequency-converted and amplified;
step S3-10: according to the sending time t1, information is sent to the satellite in a timed mode;
step S3-11: the information transmitted in step S3-10 reaches the satellite receiving antenna through the user uplink;
step S3-12: the satellite receives information sent by a plurality of users, and performs low-noise amplification, filtering, frequency conversion and demodulation processing on all the information to obtain chip data of each information before despreading;
step S3-13: despreading by using a corresponding PN sequence, and acquiring a data frame of a specific user from information sent by all users;
step S3-14: de-framing and decoding the de-spread data to obtain the original data of each user;
step S3-15: and under the beam hopping satellite communication system with the non-uniform distribution of the users, the process that the users carry out beam scheduling and access the satellite in batches is finished.
2. A spread spectrum based satellite communication random access method as claimed in claim 1, wherein: the time range of the head chip is the time range of the access information transmission which can be selected by the user after the wave beam reaches the wave position of the user set by the system.
3. A spread spectrum based satellite communication random access method as claimed in claim 1, wherein: in both steps S2-4 and S3-5, spreading is performed using a predetermined PN sequence, specifically, using a spread spectrum Aloha protocol.
4. A spread spectrum based satellite communication random access method as claimed in claim 1, wherein: in step S3-3, the users in the wave position access the satellites in batches according to the number of the wave positions lighted by the wave beam in each wave beam jumping period, i.e. the users in the wave position are divided into NbAnd (4) accessing each batch.
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