CN114826986B - Performance analysis method for ALOHA protocol with priority frameless structure - Google Patents
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Abstract
The invention discloses a performance analysis method for an ALOHA protocol with a priority frameless structure, which divides users into different priorities according to the demand degree of the users for time delay, and the users with higher time delay demands preferentially transmit packets so as to meet the access time delay demands of different users and reduce the average time delay of a performance analysis system; further, the optimal time slot allocation scheme of the priority ALOHA protocol without the frame structure is solved by using a particle swarm algorithm; the protocol classifies users into different priorities according to the demands of the users for time delay, and the users with higher time delay demands can transmit packets preferentially. Further, the optimal time slot allocation scheme of the priority ALOHA protocol without the frame structure is solved by using a particle swarm algorithm. The simulation verifies the proposed theoretical analysis, and simultaneously proves that compared with the ALOHA protocol without the frame structure, the average time delay of the ALOHA protocol with the priority without the frame structure can be reduced by about 50 percent, and meanwhile, different requirements of users on time delay are met.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a performance analysis method for an ALOHA protocol with a priority frameless structure.
Background
Random multiple access protocols are techniques to address how efficiently access users share a common channel. ALOHA protocol is a network protocol developed by university of hawaii in the united states. ALOHA adopts a random access channel access mode, and is in the data link layer in OSI model. It belongs to one of the random access protocols (Random Access Protocol). The time slot ALOHA (Slotted ALOHA) protocol is an improvement over the pure ALOHA protocol in that the idea is to use a clock to unify the data transmissions of the users. The improvement is that it segments the channel in time, each transmission point being able to transmit only at the beginning of one segment. The user must wait until the next time slice to begin transmitting data each time the data transmitted must be less than or equal to one time segment of one channel each time. This greatly reduces collisions of transmission channels. Therefore, the randomness of data transmission of the user is avoided, the possibility of collision of the data is reduced, and the utilization rate of the channel is improved. Slotted ALOHA is one of the typical random multiple access protocols, widely used in satellite networks and cellular mobile communication networks. However, since the users randomly transmit the packets, when the number of access users is high, the probability of collision of the packets in the time slot is high, the packets that have generated collision cannot be decoded and are discarded, and the packets that have collided are retransmitted in the following time slot, which may cause performance degradation such as throughput delay of the system. In 1983, choudhury et al proposed a DSA (Diversity Slotted ALOHA) protocol, which can reduce the number of packet retransmissions by transmitting the same packet twice in different time slots, reduce the user delay, and improve the system throughput. However, although the number of packet retransmissions can be reduced by transmitting the same packet 2 times, the packet collision probability in the slot is increased, and the serial interference cancellation technique (SIC) queues the received signal from large to small in intensity, and then the users are sequentially despread. Once a signal is detected, the receiver will reconstruct the signal and then cancel it from the received signal, thereby reducing the interference to the remaining signal, effectively solving the problem that multiple packet collisions in the slot ALOHA can not be decoded, and improving the system capacity. In 2007, casini et al proposed a CRDSA protocol, and applied the SIC technology to S-ALOHA for the first time, and the manner that the receiving end applies the SIC technology to decode the received packet by repeating the transmission of 2 times in the transmission period by the transmitting end effectively solves the problem that the packet collision in the time slot cannot be decoded, reduces the delay caused by packet retransmission, and greatly improves the system performance. The application of the SIC technology in the S-ALOHA protocol greatly changes the performance of the random multiple access protocol, promotes the development and research of the S-ALOHA protocol based on SIC, and is collectively called as the frame structure ALOHA protocol. Compared with the DSA protocol, the frame structure ALOHA protocol can greatly improve the system throughput, but the decoding complexity of the receiving end is increased due to the introduction of the serial interference technology. In 2013, stefanovic et al first applied the concept of rateless codes to the study of the S-ALOHA protocol, and proposed a frame-free ALOHA protocol on the basis of a frame-free ALOHA. In the ALOHA protocol without frame structure, the transmission period changes according to the decoding condition fed back by the base station, compared with the ALOHA protocol with frame structure, the ALOHA protocol without frame structure can reduce the waste of time slot resources and improve the channel utilization rate. Based on the flexibility of the ALOHA transmission period of the frameless structure, a great amount of system performance analysis based on the ALOHA protocol of the frameless structure is sequentially proposed, and most of the research is focused on improving the throughput of the system, and the research and analysis on the time delay performance of the ALOHA protocol of the frameless structure are fresh.
Disclosure of Invention
Aiming at the defects of the prior art, the embodiment of the invention provides a performance analysis method for an ALOHA protocol with a priority and a frameless structure, and provides the ALOHA protocol with the priority on the basis of the ALOHA protocol with the frameless structure. The invention provides theoretical analysis of the priority frame-free structure ALOHA protocol performance and carries out simulation verification. Meanwhile, in order to obtain a time slot allocation scheme which meets the time delay requirement of a high-priority user and ensures the better system performance, the invention provides a time slot allocation method based on a Particle Swarm (PSO).
In order to achieve the above purpose, the present invention provides the following technical solutions: a performance analysis method for an ALOHA protocol with a priority frameless structure divides users into different priorities according to the demand degree of the users for time delay, and the users with higher time delay demands transmit packets preferentially, so as to meet the access time delay demands of different users and reduce the average time delay of a performance analysis system; further, the optimal time slot allocation scheme of the priority ALOHA protocol without the frame structure is solved by using a particle swarm algorithm; the method specifically comprises the following steps:
step 1: u users randomly compete with the access base station to send a group according to the probability p, and the access users have different requirements on time delay; according to different demands of users on time delay, the users are divided into c priorities, corresponding time slots divided into c levels are allocated to users with different priorities, the number of the time slots in the frame structure ALOHA is different from the fixed frame length, and the number s of the time slots in the frame structure ALOHA is changed in real time according to the decoding condition of the users until the block transmitted by most of the users is successfully decoded;
step 2: to simplify the theoretical analysis of the subsequent system, assume the system: 1) Time synchronization of the base station and the user; 2) The time of the user transmitting the packet is not more than the time of the time slot; the base station decodes the received packet by using a serial interference elimination technology and feeds back the decoded packet to a user;
to analyze system performance, a degree distribution is introduced to describe the user's transmit packets and slot accept packets; the degree distribution of the ith priority user and slot is expressed by formula (1), where Λ i (x) For the degree distribution of the user,representing the probability that the user transmits the same packet one time in the assigned time slot; wherein Ω i (x) For the degree distribution of time slots, +.>Representing the probability that the number of packets received in one slot is l; with U= { U 1 ,u 2 ,...,u c ' represent a set of users, where u i Representing the number of i-th priority users; correspondingly, use s= { S 1 ,s 2 ,...,s c ' represent a set of time slots, where s i Representing the number of time slots of the ith level, and changing in real time according to the decoding condition of the user; the slot degree distribution of the ith class may obey the binomial distribution +.>Approximately poisson's distribution is formula (2), wherein +.>Competing the number of users accessing the base station for the ith priority;
x l is that a slot node receives l packets or a user sends a packet l times, k represents the value of a variable, k and e -λ Is the quantity in poisson distribution formula, pe i-1 A packet error probability Pe indicating an i-1-level slot; k-! Is the factorization of k;
step 3: when a feedback process user is used as a receiving end, modeling is carried out on a block decoding process based on serial interference elimination, and all time slots of an ith level are divided into different sets according to definition 1, definition 2 and definition 3:
definition 1 is set Z i : the set element is the time slot of which all received packets are successfully decoded, namely the time slot with the degree of 0, and the set Z i The number of elements in (a) is z i A representation;
definition 2 is set R i The aggregate element is a time slot in which one packet is still not successfully decoded in all received packets, and the aggregate R i The number of elements in (1) is r i A representation;
definition 3 as set C i : the aggregate element is a time slot in which two or more packets are not successfully decoded in all received packets, aggregate C i The number of elements in c i A representation;
after the ith grade time slot is finished, the base station starts to decode the received packets time slot by time slot, and defines a time slot decoding completion as an iteration; after each iteration, according to the number of packets which are not successfully decoded in the time slots before and after the time slot iteration, the transfer conditions of the set to which all the time slot states of the ith level belong are four: from set C i Transfer to set C i The method comprises the steps of carrying out a first treatment on the surface of the From set C i Transfer ofTo set R i The method comprises the steps of carrying out a first treatment on the surface of the From the set R i Transfer to set R i The method comprises the steps of carrying out a first treatment on the surface of the From the set R i Transfer to set Z i The method comprises the steps of carrying out a first treatment on the surface of the The necessary condition for each iteration to be able to decode successfully is set R i The element in (a) is not 0, namely, only one time slot with the packet not successfully decoded exists, and decoding based on serial interference elimination can be continued;
for subsequent numerical analysis of the performance of the ith priority user, the following notation is introduced and described:
from set C after each iteration is completed i Transfer to set R i Is a number of slots;
from set R after each iteration is completed i Transfer to set Z i Is a number of slots;
time slot is formed by set C i Transfer to set R i Probability of (2);
Pe i : packet drop rate for the ith priority user;
T i : system throughput for the ith priority user;
D i : average delay of the ith priority user;
introducing a subscript n to represent the number of the packets which are not successfully decoded in the packet decoding process; focusing on the state transition from n to n-1, representing a time slot from the set R i Transfer to set Z i The method comprises the steps of carrying out a first treatment on the surface of the The introduction state such as formula (3) and lemma 1 analyzes the i-th priority user packet decoding process:
lemma 1: the decoder current state of the known decoding process isWhen->The decoder is in state->The probability of (2) is calculated by the formula (4);
wherein
In formula (4): pr is the probability of being set as the probability,for the former state, ++>For the number of time slots in which two or more packets are not successfully decoded in all packets received after each iteration is completed +.>For the number of slots in which one packet is still not decoded successfully in all packets received after each iteration is completed, <>S is the number of slots successfully decoded in all packets received after each iteration is completed i The number of all slots;
in formula (5): omega shape d For a distribution of the number d of undecoded packets in a slot,the method comprises the steps that a set of all time slots with the number of the undecoded packets being 1 is adopted, and y is the current time slot;
when the R is set i When the element number is 0, namelyAt this time, two or more packets in all time slots of the ith level are not successfully decoded, the packet dropping rate of the ith priority user is deduced according to a decoder state machine to be expressed as a formula (6), the throughput is expressed as a formula (7), and the average time delay is expressed as a formula (8), wherein>Representing the time slot position accessed by the j-th user with the priority of i;
since the base station will send the packet information of decoding failure to the user after the i-th hierarchical time slot ends, the packet of decoding failure can be retransmitted with probability p in the following i+1th hierarchical time slot, so the system packet dropping rate is only related to the lowest priority packet dropping rate, and is deduced as formula (9); deriving the system throughput as a formula (10), and expressing the system average time delay as a weighted average of the time delays of the priorities as a formula (11);
wherein ,
in the above formula: pe is the system packet drop rate, pe c Packet drop rate for the c-th priority user,competing the number of users accessing to the base station for the c priority, wherein T is the throughput of the system;
step 4: the priority ALOHA with the frameless structure effectively reduces the access time delay of the user by distributing time slots with different levels to users with different time delay requirements, and meets the different requirements of different users on the time delay; however, if the slot allocation scheme is not reasonable, if a large amount of slot resources are allocated to the high-priority users, a problem that the low-priority users have a higher packet drop rate and thus the system performance is greatly affected is caused; therefore, a reasonable time slot allocation scheme needs to be searched to ensure that the stability of the system performance is ensured while the time delay requirement of the high-priority user is met;
assume that among c priority users, there is c r The priority users have demands for time delay; the user with priority of i needs d for time delay r Representing, i.e. average delay of, i-th priority userWhile meeting priority versus time requirements, system performance can be optimized, i.e., system throughputThe amount can be maximized, and meanwhile, the packet dropping rate of the system meets the condition that Pe is less than or equal to Pe r The problem of the system is modeled as equation (12):
since the packet drop rate of the ith priority of formulas (4) - (6) is a function of the number of competing intervening users, the number of allocated slots and the probability of packet transmissionRepresenting;
solving the formula (12) as an optimal solution by a traversing method to obtain a time slot allocation scheme for optimizing the system performance; due to the functionThe traversal method greatly increases the cost of calculation time; to reduce the computation time costs, a computation function +.>A particle PSO algorithm is used for solving a formula (12) to obtain a time slot allocation scheme, and the time delay requirement of a priority user is ensured while the system performance is maximized; in the time slot allocation scheme based on the particle PSO, the number of time slots allocated to different priorities represents particles, and the system throughput is an evaluation function.
Preferably, in the step 1, the user with the ith priority may transmit its packet multiple times in the allocated time slot with the ith level, and the packet that the user fails to transmit successfully is retransmitted with probability p in the next time slot with the (i+1) th level.
Preferably, in the step 2, for the user with priority i, the base station sends the packet information of decoding failure to the user after the end of the i-th class slot, and the packet of decoding failure is retransmitted with probability p in the following i+1th class slot.
The beneficial effects are that:
the invention provides a performance analysis method for an ALOHA protocol with a priority frameless structure, which has the following beneficial effects:
(1) Different time delay requirements of users in the random multiple access system are met;
(2) The particle swarm algorithm can obtain a time slot allocation scheme which enables the system to be better with lower calculation cost.
Drawings
FIG. 1 is a schematic diagram of a system model of the present invention;
FIG. 2 is a graph of theoretical analysis and simulation versus fit of packet drop rate in accordance with the present invention;
FIG. 3 is a graph of throughput theory analysis and simulation versus fit of the present invention;
fig. 4 is a schematic diagram of an iterative result of a timeslot allocation scheme based on a particle swarm algorithm according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Embodiment of the invention a performance analysis method for an ALOHA protocol with priority frameless structure according to the invention as shown in fig. 1-4, the specific steps are shown in table 1.
Table 1 PSO-based slot allocation scheme
Performance analysis:
a. simulation verification
To evaluate 3.1 usersAnd effectiveness of theoretical deduction of system performance, first give the priority users and fitting graphs of theoretical analysis and simulation result of system performance as figure 2 and figure 3. Analysis user u=8, user access probability p=0.5, slot number s=32, user and slot set u= {4,4} s= { s,31-s, respectively 1 }＝{9～28,31-s 1 Performance of the system at time. As can be seen from fig. 2, in a given time slot resource allocation range, when the time slot resources allocated to the high priority users gradually increase, the packet drop rate of the high priority users gradually decreases, but the packet drop rate of the entire system gradually increases due to the gradually decrease in the time slot resources obtained by the low priority users. At the same time, as can be seen from fig. 3, s is the time slot allocation is within a certain range 1 The throughput of the high-priority user and the low-priority user are in complementary states, i.e. the number of packets that can be decoded by the decoder is in a relatively steady state at this time, so the throughput of the whole system is in a relatively steady state, when s 1 At > 20, due to unreasonable allocation of time slot resources, time slot resource waste is caused for high priority users, and due to less time slot resources, successful decoding packet reduction is caused for low priority users, and thus the overall throughput of the system is gradually reduced.
b. Performance comparison
First, according to the parameter settings of table 2, the slot allocation scheme that optimizes the system throughput under the conditions of satisfying the delay and packet drop rate is found out by using the exhaustion method as shown in table 2. The performance of the frameless ALOHA and priority frameless ALOHA systems is then analyzed for example given the same user and the same time slot resources as table 3. From table 3, it can be seen that, although the priority ALOHA with the frameless structure is reduced in system throughput and packet dropping rate compared to the ALOHA with the frameless structure, the priority ALOHA with the frameless structure can satisfy the requirement of the high priority user for the delay while the average delay of the system is relatively low.
Table 2 ALOHA performance comparison with priority ALOHA with no frame structure
Table 3 comparison of time slot allocation schemes based on particle swarm and exhaustive method
According to the parameter setting of table 2, the optimal time slot allocation scheme is determined by using a particle swarm algorithm and compared with the time slot allocation scheme determined by an exhaustion method. Fig. 4 shows the results of the iteration of the particle swarm algorithm, the particle swarm size n=10, the maximum iteration number is 10, and table 3 shows the results of a comparison of two schemes, wherein the calculation costs (calculation functionThe number of times of (2) can be given an exhaustive calculation cost C according to the formulas (6) (10) (12) Exhaustive list = (s-1) C, the calculation cost of the time slot allocation method based on particle swarm is C PSO ＝c*N*I max . It can be seen from table 3 that compared to the exhaustive method of slot allocation, the PSO-based slot allocation mechanism can result in a better slot allocation scheme at a lower computational cost.
In order to meet different delay requirements of users in a random multiple access system, a priority ALOHA protocol without a frame structure is proposed. The protocol classifies users into different priorities according to the demands of the users for time delay, and the users with higher time delay demands can transmit packets preferentially. Further, the optimal time slot allocation scheme of the priority ALOHA protocol without the frame structure is solved by using a particle swarm algorithm. The simulation verifies the proposed theoretical analysis, and simultaneously proves that compared with the ALOHA protocol without the frame structure, the average time delay of the ALOHA protocol with the priority without the frame structure can be reduced by about 50 percent, and meanwhile, different requirements of users on time delay are met. Further, the simulation data demonstrate that the particle swarm algorithm can obtain a time slot allocation scheme which makes the system better at a lower calculation cost.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (2)
1. A performance analysis method for an ALOHA protocol with a priority frameless structure is characterized by comprising the following steps:
step 1:uprobability of individual userspThe random competition access base station sends a group, and the access user has different demands on time delay; according to different demands of users for time delay, the users are divided intocPriority, respectively divided intocThe time slots of each level are allocated to users of different priorities, different from the fixed frame length of the number of time slots in the frame structure ALOHA, the number of time slots in the frame structure ALOHAsAccording to the decoding condition of the user, the method changes in time until the block transmitted by most users is successfully decoded;
step 2: the system comprises: 1) Time synchronization of the base station and the user; 2) The time of the user transmitting the packet is not more than the time of the time slot; the base station decodes the received packet by using a serial interference elimination technology and feeds back the decoded packet to a user;
first, theiThe degree distribution of the individual priority users and time slots is expressed by formula (1) in whichFor the user's degree distribution +.>Transmitting the same packet in an allocated time slot on behalf of a userlProbability of the secondary; wherein->For the degree distribution of time slots, +.>Representing the number of packets received in a slot aslProbability of (2); use->Representing a user set, wherein->Represents the firstiThe number of individual priority users; correspondingly, use->Representing a set of time slots, wherein->Represents the firstiThe number of time slots of each level is changed in real time according to the decoding condition of the user; first, theiThe slot degree distribution of the individual levels can obey the binomial distributionApproximately poisson's distribution is formula (2), wherein +.>Is the firstiThe number of users competing for access to the base station with each priority;
is that the slot node receives l packets or one user sends one packet l times,krepresentative of the value of the variable is the value of,kandis the quantity in poisson distribution formula, +.>A packet error probability Pe indicating an i-1-level slot; />Is the factorization of k;
（1）
（2）
step 3: modeling a block decoding process based on serial interference cancellation when a feedback process user is used as a receiving end, and modeling the first stepiAll slots of the individual classes are divided into different sets according to definition 1, definition 2, definition 3:
definition 1 is set: the aggregate element is the time slot of which all received packets are successfully decoded, namely the time slot with the degree of 0, and is an aggregateThe number of elements in ∈>A representation;
definition 2 is the setThe aggregate element is a time slot in which one packet is still not successfully decoded in all received packets, and the aggregateThe number of elements in ∈>A representation;
definition 3 as a set: the aggregate element is the time slot in which two or more packets are not successfully decoded in all the received packets, aggregate +.>The number of elements in ∈>A representation;
the base station is at the firstiAfter the end of each grade time slot, starting to decode the received grouping time slot by time slot, and defining a time slot decoding completion into an iteration; each iteration is completed according to the number of the groups which are not successfully decoded in the time slots before and after the time slot iterationiThe transition conditions of the set to which all the slot states of the respective classes belong are four: from a collectionTransfer to Collection->The method comprises the steps of carrying out a first treatment on the surface of the From the collection->Transfer to Collection->The method comprises the steps of carrying out a first treatment on the surface of the From the collection->Transfer to Collection->The method comprises the steps of carrying out a first treatment on the surface of the From the collection->Transfer to Collection->The method comprises the steps of carrying out a first treatment on the surface of the The necessary condition for each iteration to be able to decode successfully is the set +.>The element in (a) is not 0, namely, only one time slot with the packet not successfully decoded exists, and decoding based on serial interference elimination can be continued;
for the subsequent pair ofiThe performance of each priority user is numerically analyzed, and the following symbols are introduced and described:
: from the set after each iteration is completed>Transfer to Collection->Is a number of slots;
: from the set after each iteration is completed>Transfer to Collection->Is a number of slots;
: time slot is defined by the set->Transfer to Collection->Probability of (2);
: first, theiPacket drop rates for individual priority users;
: first, theiSystem throughput for individual priority users;
: first, theiAverage time delay of individual priority users;
introduction of subscriptsnRepresenting the number of packets that were not successfully decoded in the packet decoding process; attention to the slavenTo the point ofn-1Representing a state transition of a time slot from a setTransfer to Collection->The method comprises the steps of carrying out a first treatment on the surface of the The states of introduction are as shown in formula (3) and the pair 1 of quotation marksiThe individual priority user packet decoding process performs the analysis:
（3）；
lemma 1: the decoder current state of the known decoding process isWhen->The decoder is in stateThe probability of (2) is calculated by the formula (4);
（4）；
wherein
In formula (4): pr is the probability of being set as the probability,for the former state, ++>For the number of time slots in which two or more packets are not successfully decoded in all packets received after each iteration is completed +.>For the number of slots in which one packet is still not decoded successfully in all packets received after each iteration is completed, <>For the number of slots successfully decoded in all packets received after each iteration is completed, +.>The number of all slots;
（5）；
in formula (5):for a distribution of d number of undecoded packets in a slot, ">The method comprises the steps that a set of all time slots with the number of the undecoded packets being 1 is adopted, and y is the current time slot;
when collectingThe element number is 0 +.>At this time the firstiTwo or more groups in all time slots of each level are not decoded successfully, the process based on the serial interference elimination is ended, and the first is deduced according to a decoder state machineiPacket drop rate of individual priority users is expressed as formula (6), throughput is expressed as formula (7), average delay is expressed as formula (8), wherein +.>Indicating priority asiIs the first of (2)jThe time slot position accessed by the individual user;
（6）；
（7）；
（8）；
because the base station will be at the firstiTransmitting decoding failure to user after finishing each grade time slotThe packet information of (a) and the packet failed in decoding is in the following firsti+1Probability of each class of time slotpIs retransmitted so that the systematic packet dropping rate is related only to the lowest priority packet dropping rate, derived as equation (9); deriving the system throughput as a formula (10), and expressing the system average time delay as a weighted average of the time delays of the priorities as a formula (11);
（9）；
wherein ,
（10）；
（11）；
in the above formula:for system packet drop rate, +.>Is the firstcPacket drop rate for individual priority users, +.>Is the firstcNumber of users competing for access to the base station with a priority, +.>Is the system throughput;
step 4: is assumed to be incAmong the priority users areThe priority users have demands for time delay; priority is ofiIs to be added to the time delay requirement of the user>Representation, i.e. the firstiAverage delay of individual priority users +.>The method comprises the steps of carrying out a first treatment on the surface of the While meeting the priority versus time requirement, the system performance can be optimized, i.e. the system throughput can be maximized, while the packet drop rate of the system satisfiesThe problem of the system is modeled as equation (12):
（12）
the following formulas (4) - (6)iThe packet dropping rate of each priority is a function of the number of competing intervening users, the number of assigned slots and the probability of packet transmissionRepresenting;
solving a formula (12) by using a particle PSO algorithm to obtain a time slot allocation scheme, and maximizing system performance while guaranteeing the time delay requirement of priority users; in the time slot allocation scheme based on the particle PSO, the number of time slots allocated to different priorities represents particles, and the system throughput is an evaluation function.
2. The method for analyzing the performance of ALOHA protocol with priority frame-less architecture according to claim 1, wherein the step 1 isiThe user of each priority is allocated with the firstiMultiple transmissions of its packets in each level of time slot, packets for which the user failed to transmit are nexti+1Probability within each class of time slotspIs retransmitted.
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