CN110856262A - Authorization-free uplink transmission method based on joint time-frequency diversity - Google Patents

Authorization-free uplink transmission method based on joint time-frequency diversity Download PDF

Info

Publication number
CN110856262A
CN110856262A CN201910913021.5A CN201910913021A CN110856262A CN 110856262 A CN110856262 A CN 110856262A CN 201910913021 A CN201910913021 A CN 201910913021A CN 110856262 A CN110856262 A CN 110856262A
Authority
CN
China
Prior art keywords
time
data packet
probability
diversity
user equipment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN201910913021.5A
Other languages
Chinese (zh)
Other versions
CN110856262B (en
Inventor
王熠晨
赵书玉
谢云聪
徐东阳
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xian Jiaotong University
Original Assignee
Xian Jiaotong University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Xian Jiaotong University filed Critical Xian Jiaotong University
Priority to CN201910913021.5A priority Critical patent/CN110856262B/en
Publication of CN110856262A publication Critical patent/CN110856262A/en
Priority to PCT/CN2020/117165 priority patent/WO2021057799A1/en
Application granted granted Critical
Publication of CN110856262B publication Critical patent/CN110856262B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
    • H04W72/543—Allocation or scheduling criteria for wireless resources based on quality criteria based on requested quality, e.g. QoS
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0446—Resources in time domain, e.g. slots or frames
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/04—Wireless resource allocation
    • H04W72/044—Wireless resource allocation based on the type of the allocated resource
    • H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
    • H04W72/542—Allocation or scheduling criteria for wireless resources based on quality criteria using measured or perceived quality
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0404—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas the mobile station comprising multiple antennas, e.g. to provide uplink diversity

Landscapes

  • Engineering & Computer Science (AREA)
  • Quality & Reliability (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The invention discloses an authorization-free uplink transmission method based on joint time-frequency diversity, which jointly applies time diversity and frequency diversity technology based on a Slotted-Aloha model, equally divides uplink transmission time into a plurality of mini time slots with equal length, and in each time slot, user equipment randomly selects a plurality of copies for transmitting the same data packet in all sub-channels provided by a system; in the transmission mode, the situation that two or even a plurality of user equipment try to send data packets on the same shared channel at the same time can occur, so that collision can occur between the data packets; based on the transmission scheme of the invention, under the condition of simultaneously meeting the requirements of ultra-reliability and low time delay of URLLC, the number of copies of the data packets in the time domain and the frequency domain is simultaneously optimized, so that the number of user equipment which can be supported by a system is maximized.

Description

Authorization-free uplink transmission method based on joint time-frequency diversity
Technical Field
The invention belongs to the technical field of uplink transmission of machine equipment communication services, and particularly relates to an authorization-free uplink transmission method based on joint time-frequency diversity.
Background
The 5G mobile communication technology is a new generation mobile communication technology that is being developed to meet the rapid popularization of smart terminals and the rapid development of mobile internet following 4G. Ultra-Reliable and Low-latency Communications (URLLC) is one of three major application scenarios of 5G, and the service quality requirements thereof include the following two aspects: one is ultra-short end-to-end (E2E) delay, requiring no more than 1 ms; the other is transmission reliability, which is required to be not less than 99.999%. According to the existing research results, in order to reduce the system delay, the uplink transmission process may adopt a contention-based authorization-free mode, in which the ue does not need to wait for resource allocation information or transmission authorization before sending a data packet, but can send the data packet immediately. In the contention-based unlicensed transmission mode, two or even more ues may attempt to transmit data packets simultaneously on the same shared channel, and thus collisions between data packets may occur.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an authorization-free uplink transmission method based on joint time-frequency diversity, which improves the reliability of a system, improves the probability of successful transmission of data packets by repeatedly sending the same data packet, meets the requirements of ultra-reliable and low-delay service quality of URLLC service, and maximizes the number of user equipment which can be supported by the system.
In order to achieve the above object, the present invention adopts a technical solution that an authorization-free uplink transmission method based on joint time-frequency diversity includes the following steps:
s1, establishing a data packet transmission system, wherein the data packet transmission system comprises M user equipment with single antenna and a base station, and the base station is provided with NtN shared sub-channels are arranged in the system;
s2, based on the system established by S1, the total time delay of the uplink transmission process is equally divided into gamma time slots, and in each time slot, the user equipment randomly selects a plurality of copies for transmitting the same data packet from all sub-channels provided by the system; and the data packet adopts a Slotted-Aloha-based protocol and an authorization-free transmission mode;
s3, calculating the probability of data packet transmission failure of the target device in the time slot S2;
and S4, under the condition that the URLLC time delay requirement and the reliability requirement are met, maximizing the number of the devices which can be supported by the system in the S1, obtaining a series of optimal solutions of the time diversity and the frequency diversity times corresponding to the optimal solutions, and obtaining the maximum value of the supportable devices through the optimal solutions.
S1 instantaneous channel gains of the N sub-channels are independent of each other, i.e. the frequency spacing of the N sub-channels exceeds the channel coherence bandwidth Wc(ii) a Total system bandwidth of WmaxThe bandwidth allocated to each shared sub-channel is
Figure BDA0002215260440000021
Each shared subchannel is flat fading.
The data packet can be successfully transmitted on the sub-channel with the instantaneous channel gain greater than or equal to the set threshold value, and on the channel with the instantaneous channel gain smaller than the threshold value, the data packet is considered to be lost, namely, the data packet is successfully transmitted under the condition that the data packet does not collide with other packets, and the instantaneous channel gain of the selected sub-channel is not smaller than the required channel gain threshold value.
In S3, the probability that any other user equipment does not collide with the target packet is:
P0＝(1-Pran)+PranPacc
wherein, PaccProbability that the data packet sent by any other user equipment does not select the same subchannel with the target data packet; pranIs the packet sending probability of each device in the total time delay of the uplink transmission process;
Pran＝1-e-λ
Figure BDA0002215260440000022
wherein λ represents DuThe number of data packets arriving internally, the average inter-arrival time of the data packets is mu, then
Figure BDA0002215260440000031
The probability that any other user equipment does not collide with the target data packet is as follows:
P0＝(1-Pran)+PranPacc
when all other user equipment send data packets without collision with the target data packet, the target data packet does not collide; the probability of no collision is:
Psucc＝P0 M-1＝[(1-Pran)+PranPacc]M-1。
then, the probability that the target data packet collides in one time slot is obtained, which is:
in repeating Γ slots, the probability of a target UE transmission failure is:
Figure BDA0002215260440000033
wherein, PFDThe probability of transmission failure of a data packet sent by a target device UE in one time slot,
Figure BDA0002215260440000034
probability of collision of target data packets in a time slot, PtThe packet loss probability of a data packet on a certain channel is shown.
In S4, the optimal solution of the corresponding times of time diversity and frequency diversity is obtained as follows:
giving the value of the frequency diversity times, optimizing the length of a time slot by applying a particle swarm algorithm, solving according to the relation between the time slot length and the time diversity times to obtain the optimal solution of the time diversity times, and solving the maximum value of the corresponding supportable equipment;
converting the time diversity times and the frequency diversity times of the joint optimization into a calculation model, which comprises the following specific steps:
Figure BDA0002215260440000035
t is the length of each time slot, DuIs the total delay of the uplink transmission process, β denotes the frequency diversity times,
let St.T ∈ [ T ∈ [ ]min,Du]As a constraint condition, the time slot length is ensured not to exceed the value interval in the solving process,
Figure BDA0002215260440000036
Figure BDA0002215260440000037
shows the relation between the time diversity times and the time slot length, restrains the time diversity times by optimizing the length of TTI,
P≤1-Prel
finally, the optimal solution T is obtained*The obtained optimal solution of the corresponding time diversity order is expressed as Γ*The maximum value of the user equipment corresponding to the optimal solution of the time diversity times is expressed as M*；
Optimizing frequency diversity times, wherein β belongs to {1,2,3, …, N }, carrying out one-dimensional search on all possible values of a β value interval to obtain N groups of optimal solutions of time slot length and equipment number, namely { T }* 1，M* 1}，{T* 2，M* 2}，{T* 3，M* 3}，…，{T* N，M* NFinding out the maximum user equipment number M from the optimal solutionsopt。
Compared with the prior art, the invention has at least the following beneficial effects:
the invention adopts a competition-based authorization-free transmission mode, and under the mode, the user equipment does not need to wait for resource allocation information or transmission authorization before sending the data packet, but can send the data packet immediately, thereby effectively reducing the system time delay; the invention jointly applies time diversity and frequency diversity technology based on a Slotted-Aloha model, namely, the uplink transmission time is equally divided into a plurality of mini time slots with equal length, the length of each time slot is equal to the length of a system TTI (transmission time interval), and in each TTI, user equipment randomly selects a plurality of copies for transmitting the same data packet in all sub-channels provided by the system; in this transmission mode, two or even a plurality of user equipments may try to send data packets on the same shared channel at the same time, so that collision may occur between the data packets, and by randomly selecting a channel and repeatedly transmitting the data packets for a plurality of times, the successful transmission probability of the data packets is greatly improved, thereby being beneficial to improving the reliability of the system; based on the transmission scheme, under the condition of simultaneously meeting the requirements of ultra-reliability and low time delay of URLLC, the invention simultaneously optimizes the transmission times of the data packet copies on the time domain and the frequency domain so as to maximize the number of user equipment which can be supported by the system.
Drawings
FIG. 1 is a diagram of a system model contemplated by the present invention.
Fig. 2 is a view showing a structure of a time frame considered by the present invention.
Fig. 3 is a diagram of a data packet transmission model according to the present invention.
FIG. 4 shows the value of the optimal solution of the time domain multiple-etching times and the optimal solution of the frequency domain multiple-etching times of the data packet along with the lower bound T of the TTI lengthminThe change curve of (2).
FIG. 5 shows a lower bound T on the TTI lengthminWhen the time domain multiple engraving times and the frequency domain multiple engraving times of the data packet respectively take the optimal solutions under different values, the maximum number of the user equipment supported by the systemA change in value curve.
FIG. 6 shows the time TminAnd when the time is 0.1ms, the system can support a three-dimensional relationship image between the number of the devices and the time domain multiple engraving times and the frequency domain multiple engraving times.
FIG. 7 shows the time TminAt 0.1ms, the relationship between the number of supportable devices and the packet arrival rate is represented by three schemes of joint time-frequency diversity (Γ 10, β 2), time-domain only complex imprinting (Γ 10, β 1), and frequency-domain only complex imprinting (Γ 1, β 16).
FIG. 8 shows the time TminAt 0.1ms, under three schemes of joint time-frequency diversity (Γ 10, β ═ 2), time-domain-only complex imprinting (Γ 10, β ═ 1), and frequency-domain-only complex imprinting (Γ 1, β ═ 16), a relationship curve between the number of devices and the total number of shared subchannels can be supported.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
Referring to fig. 1 to fig. 3, an authorization-free uplink transmission method based on joint time-frequency diversity includes the following steps:
s1, establishing a data packet transmission system, wherein the data packet transmission system comprises M user equipment with single antenna and a base station, and the base station is provided with NtN shared sub-channels are arranged in the system;
s2, based on the system established by S1, the total time delay of the uplink transmission process is equally divided into gamma time slots, and in each time slot, the user equipment randomly selects a plurality of copies for transmitting the same data packet from all sub-channels provided by the system; and the data packet adopts a Slotted-Aloha-based protocol and an authorization-free transmission mode;
s3, calculating the probability of data packet transmission failure of the target device in the time slot S2;
and S4, under the condition of simultaneously meeting the URLLC delay requirement and the reliability requirement, maximizing the number of the devices which can be supported by the system in the S1, and obtaining the optimal solution of the time diversity and the frequency diversity times corresponding to the optimal solution.
The ultra-reliable low-delay communication is one of three application scenes of a fifth generation mobile communication system, and is required to have millisecond-level time delay and ultra-high reliability; in order to meet the requirements of ultra-reliability and low time delay of URLLC at the same time, the invention provides an authorization-free uplink transmission method based on joint time-frequency diversity.
First, contention-based unlicensed transmission: aiming at the low delay requirement of URLLC, the invention adopts a competition-based authorization-free transmission mode, and under the mode, the user equipment does not need to wait for resource allocation information or transmission authorization before sending the data packet, but can send the data packet immediately, thereby effectively reducing the system delay.
Secondly, joint time-frequency diversity: aiming at the ultra-high reliability requirement of URLLC, the invention jointly applies the time diversity and frequency diversity technology based on the Slotted-Aloha model, namely, the uplink transmission time is equally divided into a plurality of mini-slots (mini-slots) with equal length, and in each slot, the user equipment randomly selects a plurality of copies for transmitting the same data packet in all sub-channels provided by the system. In this transmission mode, it may happen that two or even more ues try to send data packets simultaneously on the same shared channel, and therefore collisions between data packets may occur. The scheme greatly improves the success probability of data packet transmission by randomly selecting channels and repeatedly transmitting the data packet copies for a plurality of times, thereby being beneficial to improving the reliability of the system.
Based on the transmission scheme, under the condition of simultaneously meeting the requirements of ultra-reliability and low time delay of URLLC, the invention simultaneously optimizes the number of copies of the data packet transmitted in time domain and frequency domain so as to maximize the number of user equipment which can be supported by the system.
And (3) system model: considering the contention-based unlicensed uplink transmission scenario, as shown in fig. 1, the data packet transmission system of the present invention includes M single-antenna User Equipments (UEs) and a base station, where the base station is equipped with NtAn antenna. The user equipment transmits data by randomly using resources; for each user equipment, the data packet arrival process is modeled as a poisson process, and M poisson processes are independent of each other becauseSince the uplink transmission process for the ue is unlicensed, and therefore the device that needs to send the data packet does not need to send a scheduling request, and therefore does not need to wait for transmission of the grant or resource allocation information, the Slotted-Aloha protocol is a typical contention-based transmission model, and the contention model is used herein.
In order to apply frequency diversity, the system provides N shared sub-channels for M user equipments, and in each time slot, the equipment randomly selects β pieces in the shared sub-channels to transmit data packet copies, and in order to maximize the gain of frequency diversity, the instantaneous channel gains on the N sub-channels are independent, i.e. the frequency interval of the N sub-channels should exceed the coherence bandwidth W of the channelc(ii) a Let total bandwidth of system be WmaxThe bandwidth allocated to each shared sub-channel is
Figure BDA0002215260440000071
It is assumed that each shared sub-channel is allocated a bandwidth B less than the effective bandwidth W of the channelcThus, each shared subchannel is flat fading.
Let the large scale fading coefficient be α for the m, m-1, 2 …, N devicesmInstantaneous channel gain of giThe maximum transmission power of each user equipment is divided into β sub-channels because the channel state information is unknown at the equipment due to the unlicensed transmission, and the maximum transmission power of each equipment is set as PmaxThen the transmission power allocated to each sub-channel is
Figure BDA0002215260440000072
Data packet transmission scheme based on joint time-frequency diversity
The invention discloses a transmission mechanism of a Sooka book data packet: in the contention-based authorization-free uplink transmission scenario, the user equipment can transmit the data packet in an 'instant-to-instant' manner without sending a scheduling request and receiving transmission authorization and resource allocation information; in order to improve the reliability of the system, time diversity and frequency diversity techniques are applied simultaneously in the data packet transmission process.
Total time delay D of uplink transmission processuThe total delay of the uplink transmission process is equally divided into Γ slots, and the time frame structure is shown in fig. 2. The length of each time slot is
Figure BDA0002215260440000073
The system provides N shared sub-channels for M user equipments, and in each time slot, the user equipment needing to send packets randomly selects β (β ≦ N) channels from the N shared sub-channels provided by the system for transmitting β copies of data packets, wherein β represents the frequency diversity times, i.e. the number of copies of data packets transmitted in the frequency domain.
Even if a packet is fortunately enough to select a sub-channel that will not collide, the packet may fail to be sent due to poor channel performance. Applying a two-state channel transmission model; the meaning of the two states is: the data packet can be successfully transmitted only on the sub-channel with the instantaneous channel gain greater than or equal to the set threshold value, and the data packet is considered to be lost on the channel with the instantaneous channel gain less than the threshold value. Thus, a data packet can only be successfully transmitted without colliding with other packets and without the instantaneous channel gain of the selected sub-channel being less than the desired channel gain threshold.
Transmission failure probability analysis and calculation:
at DuAnd the packet sending probability of each device is as follows:
Pran＝1-e-λ(4)
wherein λ represents DuThe number of data packets arriving in. Let the average inter-arrival time of a packet be mu, then
For any user equipment except the target equipment, the target data packet does not collide with the data packet sent by any user equipment, and the following two conditions exist: firstly, the arbitrary user equipment does not send a packet, only the equipment to which the target data packet belongs can send the data packet, and the data packets from the same equipment cannot collide with each other, so that the target data packet cannot collide under the condition that the equipment to which the target data packet belongs can send the data packet; the second situation is that although any user equipment also sends a data packet, the data packet sent by the user equipment does not select the same subchannel as the target data packet, so that the target data packet is ensured not to collide; therefore, the probability that any other ue will not collide with the target packet is:
P0＝(1-Pran)+PranPacc(5)
wherein, PaccProbability that the data packet sent by any other user equipment does not select the same subchannel with the target data packet; then, when all other user equipments send data packets without collision with the target data packet, the target data packet will not collide; the probability of no collision is:
Psucc＝P0 M-1＝[(1-Pran)+PranPacc]M-1(6)
the probability P is as followsaccThe solving process of (1).
Firstly, a target data packet is set to select a certain sub-channel, and all data packets sent by other user equipment are not allowed to select the sub-channel selected by the target data packet in order to ensure that the data packet does not collide with other data packets; therefore, in a timeslot, the probability that a data packet sent by any other ue and a target data packet do not select the same subchannel is:
Figure BDA0002215260440000091
in a timeslot, the probability of collision of the target packet is:
Figure BDA0002215260440000092
in the data packet transmission scheme of joint time-frequency diversity, each user equipment transmits the Γ multiplied by β data packet copies altogether, and for any user equipment, as long as at least one data packet in the data packet copies is ensured to be successfully transmitted, the user equipment transmitting the data packet can be considered to be successfully transmitted.
The successful transmission of a data packet needs to satisfy two conditions: the first condition is that when randomly selecting a sub-channel, the selected sub-channel is selected by only one data packet of a target data packet, namely the data packets cannot collide; the second condition is that the channel performance of the selected sub-channel of the data packet needs to meet the transmission condition on the premise of no collision, i.e. the instantaneous channel gain of the selected channel should not be less than the required channel gain threshold; if the instantaneous channel gain is greater than or equal to the channel gain threshold (g)i≥gth) Then the data packet can be transmitted toIs successful, wherein
Figure BDA0002215260440000094
Representing the bit error rate; if the instantaneous channel gain is less than the channel gainThreshold value (g)i<gth) The packet is considered lost.
For a single-input multiple-output system, in each time slot, the maximum number of bits transmitted on the ith subchannel by the mth device is,
Figure BDA0002215260440000101
where, i is 1,2 …, β, T is the length of the slot, B is the bandwidth allocated to each subchannel, αmIs the large-scale fading coefficient, P, of the device mmaxFor maximum transmission power per device, giFor instantaneous channel gain, N0Is a single-sided power spectral density, em,iIn order to be an error rate,
Figure BDA0002215260440000102
representing the inverse of the Q function. From the calculation formula (1), the maximum number of bits to be transmitted increases with the increase of the instantaneous channel gain, and the size of the data packet to be transmitted is set to b bits when R ism,iWhen b is equal, the channel gain threshold can be obtained by the calculation formula (1)
Figure BDA0002215260440000103
Comprises the following steps:
Figure BDA0002215260440000104
if the instantaneous channel gain is greater than or equal to the channel gain threshold (g)i≥gth) Then the data packet can be transmitted to
Figure BDA0002215260440000105
The probability of being successful; if the instantaneous channel gain is less than the channel gain threshold (g)i<gth) The packet is considered lost. Then the packet loss probability on the ith channel is:
Figure BDA0002215260440000106
wherein the content of the first and second substances,
Figure BDA0002215260440000107
Ntthe number of antennas.
Therefore, the packet loss probability of the data packet on the ith channel is PtThen, the transmission failure probability of the target data packet on the channel is:
Figure BDA0002215260440000108
then the probability of transmission failure of the data packet sent by the target device UE in one timeslot (i.e. the probability of transmission failure of all the selected β channels) is:
Figure BDA0002215260440000109
each UE also repeats the transmission of packets in Γ slots, and then the probability of the target UE failing to transmit (i.e., Γ × β packets failing to transmit in all) in the repeated Γ slots is:
Figure BDA0002215260440000111
2.3 optimization problem modeling
And constructing an optimization problem based on the derivation, jointly optimizing the time diversity times and the frequency diversity times, maximizing the number of devices supported by the system under the condition of simultaneously meeting the URLLC time delay requirement and the reliability requirement, and solving the optimal solution of the corresponding time diversity times and the frequency diversity times. The optimization problem is modeled as follows:
Figure BDA0002215260440000112
St.T∈[Tmin,Du](13)
Figure BDA0002215260440000113
Figure BDA0002215260440000114
P≤1-Prel(16)
the constraint condition of the expression (13) ensures that the time slot length cannot exceed the value interval in the optimization process; the constraint of expression (14) embodies the relation of the time diversity times and the time slot length, where [ ·]Indicates rounding down the number in parentheses, pass; the constraint condition of expression (15) is to limit the frequency diversity order; the constraint of expression (16) ensures the URLLC reliability requirement, P, of the systemrelIs a constant; the constraint of expression (17) constrains the number of user equipments to a positive integer.
3 solving an optimization problem using a two-step method based on the PSO algorithm
A two-step approach is proposed to solve the above optimization problem;
step 1: optimizing time diversity order
Giving the value of the frequency diversity times, optimizing the length of a time slot by applying a particle swarm algorithm, solving according to a relational expression (14) of the time slot length and the time diversity times to obtain an optimal solution of the time diversity times, and solving the maximum value of corresponding supportable equipment; since the probability of packet transmission errors increases with the number of ues, we solve the maximum probability of packet transmission errors by directly substituting the maximum probability of packet transmission errors into the optimization problem (12) in order to obtain the maximum number of ues that can be supported. In addition, in order to further simplify the solving process of the optimization problem, the positive integer limiting condition of the equipment number M is not considered, and only the downward rounding operation is carried out on the obtained maximum value of M; thus, the original optimization problem can then be simplified as follows:
Figure BDA0002215260440000121
St.T∈[Tmin,Du](19)
Figure BDA0002215260440000122
P＝1-Prel(21)
wherein, the constraint condition of the expression (19) is the whole search space of the time slot length solved by the particle swarm algorithm; the constraint condition of expression (20) represents the time slot length versus the time diversity order; the constraint condition of the expression (21) ensures the system reliability requirement; the optimal solution obtained by the optimization problem is represented as T*The obtained optimal solution of the corresponding time diversity order is represented as Г*The maximum value of the user equipment corresponding to the optimal solution of the time diversity times is expressed as M*。
Step 2, optimizing frequency diversity times
Because the number of shared subchannels provided by the system is limited, all possible values of the frequency diversity times are also limited, namely β E {1,2,3, …, N }, and one-dimensional search is carried out on all possible values of the β value interval, so that N groups of optimal solutions about the time slot length and the equipment number, namely { T }, can be obtained* 1，M* 1}，{T* 2，M* 2}，{T* 3，M* 3}，…，{T* N，M* NThe subscripts of the optimal solutions correspond to the values of the corresponding frequency diversity times; then, the maximum user equipment number M is found out from the optimal solutionsoptAnd the corresponding optimal solution of the time slot length and the optimal solution of the frequency diversity times are the optimal solutions of the original optimization problem.
The method of the invention is adopted to carry out numerical simulation and result analysis
The system parameters set by the simulation are shown in table 1:
TABLE 1 simulation parameters
Figure BDA0002215260440000131
Lower bound T of value range of time slot length in optimization problemminThe value of the optimal solution is also affected.
FIG. 4 shows the lower bound T on the slot lengthminUnder different value conditions, optimizing the value condition of the optimal solution of the problem. As can be seen from the figure, as the lower bound of the time slot length increases, the optimal solution of the time domain multiple engraving times decreases progressively, and the optimal solution of the frequency domain multiple engraving times increases progressively.
FIG. 5 shows the lower bound T on the slot lengthminAnd under the condition of different values, when the time domain multiple engraving times and the frequency domain multiple engraving times respectively take the optimal solutions, the number of the supportable user equipment is taken as a value. As can be seen from the figure, as the lower bound of the slot length increases, the maximum supportable number of ues decreases; in the following experimental simulation, T is takenmin＝0.1ms。
Fig. 6 shows the variation of the number of user equipments supportable by the system under different frequency domain multiple engraving times and time domain multiple engraving times. It can be seen from the figure that no matter what value the time domain multiple engraving times are, the number of the user equipments supportable by the system always increases and then decreases with the increase of the frequency domain multiple engraving times. On the one hand, the increase of the frequency domain duplication times means that the number of subchannels which can be selected by the user equipment for transmitting the data packet duplicates is increased in each time slot, which reduces the probability of collision between data packets; on the other hand, since the maximum transmission power allocated to each device is limited, when the number of frequency domain repetitions increases, the transmission power allocated to each subchannel decreases, resulting in an increase in the packet loss rate occurring on the channel. When the frequency domain repeated engraving times are smaller, the influence of the reduction of the collision probability is larger than the influence of the increase of the packet loss rate, so that the system can support the equipment number to be in an ascending trend; when the frequency domain repetition times increase to exceed a certain threshold, the influence of the increase of the packet loss rate becomes a dominant factor influencing the number of supportable devices, so that the number of user devices meeting the QoS requirement tends to decrease. Fig. 6 also shows the relationship between the number of supportable devices and the number of time domain multiple engraving. As can be seen from the figure, the more the time domain repetition times are, the more the number of user equipments can be supported by the system. This is because by increasing the number of time domain repetitions, the probability of collisions between packets is greatly reduced, thereby allowing a significant increase in supportable user equipment.
Fig. 7 shows a relationship between the number of supportable devices and an arrival rate of a data packet in a case where an optimal solution is respectively obtained for a joint diversity scheme, a time-domain-only complex etching scheme, and a frequency-domain-only complex etching scheme, where the time-domain complex etching frequency of the joint scheme is 10 and the frequency-domain complex etching frequency is 2; in the time domain only multiple engraving scheme, the frequency domain multiple engraving frequency is 1, and the time domain multiple engraving frequency is 10; in the frequency domain only repeated engraving scheme, the frequency domain repeated engraving frequency is 16, and the time domain repeated engraving frequency is 1; as can be seen, as the packet arrival rate increases, the number of supportable ues decreases. This is because the higher the arrival rate of the data packets, the higher the probability that the user equipment is activated, the greater the number of devices that need to transmit the data packets, the greater the probability that collisions occur between the data packets, and thus the fewer the number of devices that can be supported by the system.
Fig. 8 shows the relationship between the number of supportable devices and the total number of shared sub-channels in the case that the joint diversity scheme, the time-domain-only complex etching scheme, and the frequency-domain-only complex etching scheme respectively take optimal solutions. The more number of shared subchannels the system provides, the more number of devices that can be supported, while ensuring that the allocated bandwidth per subchannel remains the same. Since the more the number of shared channels, the greater the probability that a packet will select a different sub-channel, the lower the probability of collision between packets, and thus the number of supportable devices will increase.
As can be seen from the figure, the performance gain of the joint diversity scheme is the best, which is only a time domain multiple etching scheme, and the performance gain of the frequency domain multiple etching scheme is the smallest. It can be seen that the performance advantages of the joint diversity scheme proposed by the present invention mainly result from the optimization of the slot length and the random selection of different sub-channels for data packet transmission in each slot for the data packet copy.
In summary, the authorization-free URLLC uplink transmission scheme based on joint time-frequency diversity provided by the present invention not only can meet the delay and reliability requirements of URLLC service, but also can maximize the number of devices supportable by the system by selecting the optimal time domain multiple engraving times and frequency domain multiple engraving times of the data packet.
Simulation results show that: compared with the existing scheme, the scheme provided by the invention not only effectively guarantees the service quality requirement of the URLLC service, but also obviously improves the number of user equipment which can be supported by the system, and has very important practical significance and application prospect.
The foregoing is a detailed description of the invention and is not to be taken as limiting, since numerous simple deductions and substitutions may be made by those skilled in the art without departing from the spirit of the invention, which is to be construed as falling within the scope of the invention as defined by the appended claims.

Claims (6)

1. An authorization-free uplink transmission method based on joint time-frequency diversity is characterized by comprising the following steps:
s1, establishing a data packet transmission system, wherein the data packet transmission system comprises M user equipment with single antenna and a base station, and the base station is provided with NtN shared sub-channels are arranged in the system;
s2, based on the system established by S1, the total time delay of the uplink transmission process is equally divided into gamma time slots, and in each time slot, the user equipment randomly selects a plurality of copies for transmitting the same data packet from all sub-channels provided by the system; and the data packet adopts a Slotted-Aloha-based protocol and an authorization-free transmission mode;
s3, calculating the probability of data packet transmission failure of the target device in the time slot S2;
and S4, under the condition that the URLLC time delay requirement and the reliability requirement are met, maximizing the number of the devices which can be supported by the system in the S1, obtaining a series of optimal solutions of the time diversity and the frequency diversity times corresponding to the optimal solutions, and obtaining the maximum value of the supportable devices through the optimal solutions.
2. According to claimThe grant-free uplink transmission method based on joint time-frequency diversity as claimed in claim 1, wherein the instantaneous channel gains of the N sub-channels at S1 are independent from each other, that is, the frequency interval of the N sub-channels exceeds the channel coherence bandwidth Wc(ii) a The total system bandwidth is Wmax, and the bandwidth allocated to each shared sub-channel is
Figure FDA0002215260430000011
Each shared subchannel is flat fading.
3. The method of claim 1, wherein in S2, the data packet can be successfully transmitted on the sub-channel with the instantaneous channel gain greater than or equal to the predetermined threshold, and on the channel with the instantaneous channel gain less than the threshold, the data packet is considered to be lost, that is, the data packet is successfully transmitted without colliding with other packets and the instantaneous channel gain of the selected sub-channel is not less than the required channel gain threshold.
4. The grant-free uplink transmission method based on joint time-frequency diversity according to claim 1, wherein in S3, the probability that any other ue will not collide with the target packet is:
P0＝(1-Pran)+PranPacc
wherein, PaccProbability that the data packet sent by any other user equipment does not select the same subchannel with the target data packet; pranIs the packet sending probability of each device in the total time delay of the uplink transmission process;
Pran＝1-e-λ
wherein λ represents DuThe number of data packets arriving internally, the average inter-arrival time of the data packets is mu, then
The probability that any other user equipment does not collide with the target data packet is as follows:
P0＝(1-Pran)+PranPacc
when all other user equipment send data packets without collision with the target data packet, the target data packet does not collide; the probability of no collision is:
Psucc＝P0 M-1＝[(1-Pran)+PranPacc]M-1；
then, the probability that the target data packet collides in one time slot is obtained, which is:
Figure FDA0002215260430000023
5. the grant-free uplink transmission method based on joint time-frequency diversity according to claim 4, wherein in repeating Γ slots, the probability of transmission failure of the target UE is:
wherein, PFDThe probability of transmission failure of a data packet sent by a target device UE in one time slot,
Figure FDA0002215260430000025
probability of collision of target data packets in a time slot, PtThe packet loss probability of a data packet on a certain channel is shown.
6. The method of claim 5, wherein in step S4, the optimal solution of the time diversity and frequency diversity times corresponding to the optimal solution is obtained as follows:
giving the value of the frequency diversity times, optimizing the length of a time slot by applying a particle swarm algorithm, solving according to the relation between the time slot length and the time diversity times to obtain the optimal solution of the time diversity times, and solving the maximum value of the corresponding supportable equipment;
converting the time diversity times and the frequency diversity times of the joint optimization into a calculation model, which comprises the following specific steps:
Figure FDA0002215260430000031
t is the length of each time slot, DuIs the total delay of the uplink transmission process, β denotes the frequency diversity times,
let St.T ∈ [ T ∈ [ ]min，Du]As a constraint condition, the time slot length is ensured not to exceed the value interval in the solving process,
Figure FDA0002215260430000032
Figure FDA0002215260430000033
shows the relation between the time diversity times and the time slot length, restrains the time diversity times by optimizing the length of TTI,
P≤1-Prel
finally, the optimal solution T is obtained*The obtained optimal solution of the corresponding time diversity order is expressed as Γ*The maximum value of the user equipment corresponding to the optimal solution of the time diversity times is expressed as M*；
Optimizing frequency diversity times, wherein β belongs to {1,2, 3.., N }, carrying out one-dimensional search on all possible values of a β value interval to obtain N groups of optimal solutions of time slot length and equipment number, namely { T }* 1，M* 1}，{T* 2，M* 2}，{T* 3，M* 3}，...，{T* N，M* NFinding out the maximum user equipment number M from the optimal solutionsopt。
CN201910913021.5A 2019-09-25 2019-09-25 Authorization-free uplink transmission method based on joint time-frequency diversity Active CN110856262B (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CN201910913021.5A CN110856262B (en) 2019-09-25 2019-09-25 Authorization-free uplink transmission method based on joint time-frequency diversity
PCT/CN2020/117165 WO2021057799A1 (en) 2019-09-25 2020-09-23 Joint time-frequency diversity-based unlicensed uplink transmission method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201910913021.5A CN110856262B (en) 2019-09-25 2019-09-25 Authorization-free uplink transmission method based on joint time-frequency diversity

Publications (2)

Publication Number Publication Date
CN110856262A true CN110856262A (en) 2020-02-28
CN110856262B CN110856262B (en) 2022-03-01

Family

ID=69595934

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201910913021.5A Active CN110856262B (en) 2019-09-25 2019-09-25 Authorization-free uplink transmission method based on joint time-frequency diversity

Country Status (2)

Country Link
CN (1) CN110856262B (en)
WO (1) WO2021057799A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021057799A1 (en) * 2019-09-25 2021-04-01 西安交通大学 Joint time-frequency diversity-based unlicensed uplink transmission method
CN115278593A (en) * 2022-06-20 2022-11-01 重庆邮电大学 Transmission method of unmanned aerial vehicle-non-orthogonal multiple access communication system based on semi-authorization-free protocol
CN115278593B (en) * 2022-06-20 2024-07-12 南京中科上元科技有限公司 Transmission method of unmanned aerial vehicle-non-orthogonal multiple access communication system based on semi-unlicensed protocol

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100124222A1 (en) * 2008-11-14 2010-05-20 Deutsches Zentrum Fur Luft- Und Raumfahrt E.V. Method of transmitting data
CN109392163A (en) * 2018-11-01 2019-02-26 西安交通大学 A kind of random fdma system multi-subcarrier allocation method based on collision probability
CN109392099A (en) * 2017-08-03 2019-02-26 维沃移动通信有限公司 Uplink exempts from method, user side equipment and the network side equipment of authorized transmissions in URLLC
CN109937603A (en) * 2017-05-03 2019-06-25 华为技术有限公司 Transmission method competition-based and equipment
CN110121212A (en) * 2018-10-18 2019-08-13 西安交通大学 A kind of ascending transmission method towards periodic group URLLC business

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107889231B (en) * 2016-09-30 2021-03-23 华为技术有限公司 Method, network equipment and terminal equipment for transmitting uplink information without authorization
KR102033353B1 (en) * 2017-09-08 2019-10-17 한국전자통신연구원 Method for transmitting and receiving uplink data channel, and apparatus therefor
CN110856262B (en) * 2019-09-25 2022-03-01 西安交通大学 Authorization-free uplink transmission method based on joint time-frequency diversity

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100124222A1 (en) * 2008-11-14 2010-05-20 Deutsches Zentrum Fur Luft- Und Raumfahrt E.V. Method of transmitting data
CN109937603A (en) * 2017-05-03 2019-06-25 华为技术有限公司 Transmission method competition-based and equipment
CN109392099A (en) * 2017-08-03 2019-02-26 维沃移动通信有限公司 Uplink exempts from method, user side equipment and the network side equipment of authorized transmissions in URLLC
CN110121212A (en) * 2018-10-18 2019-08-13 西安交通大学 A kind of ascending transmission method towards periodic group URLLC business
CN109392163A (en) * 2018-11-01 2019-02-26 西安交通大学 A kind of random fdma system multi-subcarrier allocation method based on collision probability

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021057799A1 (en) * 2019-09-25 2021-04-01 西安交通大学 Joint time-frequency diversity-based unlicensed uplink transmission method
CN115278593A (en) * 2022-06-20 2022-11-01 重庆邮电大学 Transmission method of unmanned aerial vehicle-non-orthogonal multiple access communication system based on semi-authorization-free protocol
CN115278593B (en) * 2022-06-20 2024-07-12 南京中科上元科技有限公司 Transmission method of unmanned aerial vehicle-non-orthogonal multiple access communication system based on semi-unlicensed protocol

Also Published As

Publication number Publication date
CN110856262B (en) 2022-03-01
WO2021057799A1 (en) 2021-04-01

Similar Documents

Publication Publication Date Title
US11943747B2 (en) Method and user equipment for multi-carrier data transmission
US10623219B2 (en) Multi-user communication in wireless networks
KR102573498B1 (en) Pre-conversation listening parameter processing method, and contention window adjustment method and device
US8792577B2 (en) Method and apparatus for medium access control in a wireless broadband system with multiple-input multiple-output or multiple-input single-output technology with multiuser capabilities
CN105393589B (en) A kind of method and apparatus of data transmission
US9445432B2 (en) Fine-grained channel access in wireless networks
CN107113826A (en) Transmission system and method for exempting from authorized uplink transmission plan
Pei et al. Performance analysis of licensed-assisted access to unlicensed spectrum in LTE release 13
CN110062477A (en) A kind of cut-in method and device
CN107211323A (en) System and method for transmitting data in WLAN multi-user transmission chance
CN108141325B (en) ACK/NACK signal processing method and device for uplink multi-user transmission
CN110062359B (en) High-reliability low-delay wireless resource allocation optimization method based on NOMA short coding block transmission in MTC
CN107251629A (en) System and method for setting circulating prefix-length
CN106559900B (en) A kind of multi-channel multi-address access method based on asymmetric bandwidth
US10701686B1 (en) Protection mechanism for multi-user transmission
CN104378828A (en) Channel access method, device and system
CN101527969A (en) Information interaction method
EP3247165B1 (en) Station (sta)
Islam et al. Efficient resource allocation in the IEEE 802.11 ax network leveraging OFDMA technology
CN110856262B (en) Authorization-free uplink transmission method based on joint time-frequency diversity
CN100429899C (en) Random access method for frequency division multiple address of time division orthogonal frequency
Islam et al. A Proportional Scheduling Protocol for the OFDMA-Based Future Wi-Fi Network.
CN105165098A (en) User data transmission method, device and network equipment
CN110831239B (en) Data transmission method, data transmission device and communication equipment
Liu et al. DRL-based channel access in NR unlicensed spectrum for downlink URLLC

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant