A method for multiple access in the Internet of Things based on information timeliness

Abstract

This invention proposes an IoT multiple access method based on information timeliness, allowing the age gain threshold and frame length to dynamically change with each frame under a multi-packet reception mechanism. The method provides an initial age gain distribution and performs the following steps in each frame: At the beginning of each frame, the access point sets the frame length and age gain threshold based on the estimated age gain distribution, aiming to maximize the expected reduction in the average AoI of the current frame slot; within each frame, users with a real-time age gain greater than or equal to the set threshold independently and equally select any slot within the frame for data transmission; if the number of users transmitting simultaneously in the same slot is less than or equal to the receiving end's packet reception capacity γ, the transmission is successful; otherwise, all transmissions fail; at the end of each frame, the access point records the observation information of the number of users transmitting simultaneously in each slot within that frame; and at the end of each frame, the access point estimates the age gain distribution at the beginning of the next frame based on the estimated age gain distribution at the beginning of the frame, the observation information within the frame, and the data arrival probability, using Bayesian update and combinatorial mathematics theory.

Description

Technical Field

[0001] This invention relates to the field of wireless network communication technology, specifically to an Internet of Things (IoT) multiple access method based on information timeliness. Background Technology

[0002] In IoT scenarios, end users need to send data updates to access points in real time so that they can make timely decisions based on the received information. Age of Information (AoI), as an important performance indicator characterizing the freshness of information received by the receiver, has become a research hotspot. On the other hand, the frame-slotted ALOHA method is increasingly widely used in the communications field; for example, the EPCGlobal organization has officially incorporated it into the RFID standard. Therefore, how to design IoT multiple access methods based on information timeliness to optimize AoI performance has received widespread attention. Due to mutual interference among users, prioritizing channel access for different users based on age information can achieve better system information age performance. However, previous research lacked exploration of how to design age-based adaptive random access methods under the physical layer multiple-packet reception (MPR) mechanism. Under the single-packet reception mechanism, the maximum likelihood estimation method used in the T-DFSA method proposed by Moradian et al. suffers from accuracy degradation when frame length is short and observation information is limited, and requires additional simulation search to design access parameters, resulting in significant overhead. Therefore, setting reasonable time-varying access parameters under the MPR mechanism to adapt to the dynamically changing interference environment within the system is of great significance. Summary of the Invention

[0003] This invention aims to provide an IoT multiple access method based on information timeliness, which can provide excellent system mean AoI performance under the MPR mechanism. The technical solution to achieve this objective is as follows: given an initial age gain distribution, perform the following steps in each frame:

[0004] Step 1: For each frame, the initial AP sets the frame length and age gain threshold based on the estimated age gain distribution, with the goal of maximizing the expected reduction in the average AoI of the current frame slot.

[0005] Step 2: Users whose real-time age gain is greater than or equal to the set threshold in each frame independently and equally select any time slot in the frame to send data. If the number of users transmitting at the same time slot is less than or equal to the packet receiving capacity γ of the AP, the transmission is successful; otherwise, all transmissions fail.

[0006] Step 3: At the end of each frame, the AP records the observation information of the number of users transmitting simultaneously in each time slot within that frame;

[0007] Step 4: At the end of each frame, the AP estimates the age gain distribution at the beginning of the next frame based on the age gain distribution estimated at the beginning of the frame, the observation information and data arrival probability within the frame, and Bayesian update and combinatorial mathematics theory.

[0008] Compared with the prior art, the significant advantages of this invention are: this invention considers the data non-saturation model and MPR mechanism, and can achieve excellent system mean AoI performance under different parameters with low complexity. Attached Figure Description

[0009] Figure 1 This is a schematic diagram illustrating an application scenario of the present invention;

[0010] Figure 2 This is a flowchart illustrating the IoT multiple access method based on information timeliness according to the present invention.

[0011] Figure 3-4 The figure shows the system mean AoI curve for the IoT multiple access method based on information timeliness implemented in this invention under different data arrival probabilities and MPR capabilities. Detailed Implementation

[0012] This invention focuses on an uplink scenario consisting of N (N≥2) users with the same priority and one access point. In this scenario, the time axis is divided into equal-length time slots, and each user and the access point (AP) can accurately locate the boundaries of the time slots. Assume any user... At the initial time of each time slot k, a data packet is generated independently with probability λ, and each user retains only the most recently generated data packet. The real-time AoI of user i locally and at the AP for any time slot k are respectively... and And set initial values If user i generates a new data packet at the initial time of time slot k, then update Otherwise update like Figure 1 As shown, assume that the N users transmit data to the AP through a shared channel, and the AP's data packet receiving capacity is 1 ≤ γ ≤ N, meaning that all data packets are successfully transmitted when the number of packets transmitted simultaneously in each time slot is less than or equal to γ; otherwise, all transmissions fail. Assume that at the end of any time slot, the AP sends transmission feedback for that time slot to each user through an error-free and delay-free control channel. Define the real-time age gain of user i in any time slot k as... Let f be the probability that the real-time AoI of any user terminal in the system estimated by the AP at the initial time slot k is x and the real-time AoI of the AP terminal is y. k (x,y),x≥0,y≥1,y≥x.

[0013] Figure 2This is a flowchart illustrating the IoT multiple access method based on information timeliness according to the present invention. Figure 2 As shown, an IoT multiple access method based on information timeliness is described. The method, after providing an initial age gain distribution, performs the following steps within each frame:

[0014] Step 1-1: Based on the estimated age gain distribution, calculate the probability that the real-time age gain of any user in the system estimated by AP at the initial time of frame t is g. g≥0.

[0015] Step 1-2: Calculate the probability π that any user in the system meets the threshold condition at the initial time of frame t, given a certain age gain threshold Γ. t :

[0016] π t =∑ g≥Γ h t,g (1)

[0017] Steps 1-3: Assuming that each user's state satisfying the threshold condition is independent of each other, then the number of users n that satisfy the threshold condition is... t The probability of taking the value n can be calculated based on the existing parameters as follows:

[0018]

[0019] Steps 1-4: Calculate the estimated value of the expected reduction in slot-average AoI within frame t. as follows:

[0020]

[0021] Steps 1-5: Set the age gain threshold Γ for frame t t as follows:

[0022]

[0023] Steps 1-6: Set the frame length w of frame t t as follows:

[0024]

[0025] in, The parameter z is solved using the following fixed-point iterative formula:

[0026]

[0027] The initial value z(0) of the iteration is any real number in [1, γ].

[0028] Step 2: Within frame t, users who meet the threshold condition independently and equally select any time slot within the frame for data transmission: in the initial time slot k of frame t... t Set of users that meet the threshold condition Any user in the time slot set Each user j independently and equally selects a time slot for data transmission. If data transmission is successful, the real-time AoI of the AP will become... The real-time AoI for the AP of the remaining unsuccessful users will be incremented by 1.

[0029] Step 3: At the end of frame t, the AP records the observation information of the number of users transmitting simultaneously in each time slot within the frame: mark the channel state of time slot k that the AP can observe as c. k And defined as follows:

[0030]

[0031] Where, r k This represents the number of users transmitting within time slot k. All channel observation information of the AP within frame t can be represented as:

[0032]

[0033] Step 4: At the end of frame t, the AP, based on the age gain distribution estimated at the beginning of the frame, the observation information within the frame, and the data arrival probability, updates the age gain distribution for the beginning of the next frame using Bayesian update and combinatorial mathematics theory.

[0034] Step 4-1: Based on observation information O t Calculate the number of successful time slots within frame t.

[0035] and number of collision time slots

[0036] Step 4-2: Based on observation information O t Calculate the number of users v that completed data updates in the j-th successful time slot within frame t. j and the vectors they form

[0037] Step 4-3: Based on observation information O t Calculate the total number of users successfully transmitted within frame t. and total number of users involved in collisions

[0038] Step 4-4: Based on observation information O t Calculate the lower bound of the number of active users within frame t.

[0039] Steps 4-5: Calculate the observation information when the number of active users satisfying the threshold condition is n, which is O. t conditional probability η o,n :

[0040]

[0041] Among them, C suc C col These respectively represent observation information of O t Under the given conditions, the total number of possible transmission options for successful users and colliding users within frame t can be calculated as follows:

[0042]

[0043]

[0044] Steps 4-6: Calculate the initial time slot k in frame t. t Given that the real-time AoI value of any user terminal is x′ and the real-time AoI value of the AP terminal is y′, in the initial time slot k of frame t+1 t+1 The conditional probability β of any user terminal's real-time AoI value being x, the AP terminal's real-time AoI value being y, and the observed information being 0. x,y,o,x′,y′ Based on whether the real-time age gain of any user i reaches the threshold, and whether user i successfully transmits data packets within frame t, β x,y,o,x′,y′ The calculation can be divided into the following four cases:

[0045] (1) When Furthermore, user i successfully transmitted the data packet within frame t, i.e., y′-x′<Γ. t x∈{0,1,...,w t -1,x′+w t}, y=x′+w t :

[0046] β x,y,o,x′,y′ =0. (12)

[0047] (2) When Furthermore, user i failed to successfully transmit data packets within frame t, i.e., y′-x′<Γ. t x∈{0,1,...,w t -1,x′+w t}, y=y′+w t :

[0048]

[0049] (3) When And user i successfully transmitted the data packet within frame t, i.e., y′-x′≥Γ. tx∈{0,1,...,w t -1,x′+w t}, y=x′+w t :

[0050]

[0051] (4) When Furthermore, user i failed to successfully transmit a data packet within frame t, i.e., y′-x′≥Γ. t x∈{0,1,...,w t -1,x′+w t}, y=y′+w t :

[0052]

[0053] Steps 4-7: Update f t+1 (x,y) are as follows:

[0054]

[0055] The present invention uses MATLAB software to implement the method, setting the number of devices in the network N=100 and the simulation time T=100000 frames.

[0056] Figure 3-4 With other parameters remaining constant, the data arrival probability λ and MPR capability γ were changed sequentially. The results showed that the method proposed in this invention has excellent system mean AoI performance under each parameter, thus verifying the effectiveness of this invention.

Claims

1. A method for multiple access in the Internet of Things (IoT) based on information timeliness, wherein the scenario includes N users with the same priority and 1 access point (AP), characterized in that, This invention divides the time axis into equal-length time slots, and each user can accurately locate the boundaries of the time slots; assuming any user Data packets are generated with probability λ at the initial time of each time slot k. Each user sends the newly generated data packet to the AP through a shared channel, and the AP's data packet receiving capacity is 1 ≤ γ ≤ N. That is, all data packets are successfully sent when the number of data packets sent simultaneously in each time slot is less than or equal to γ; otherwise, all data packets fail. The real-time AoI of user i locally and at the AP in any time slot k are labeled as follows: and And set initial values If user i generates a new data packet at the initial time of time slot k, then otherwise Define the real-time age gain of user i in any time slot k as: Let f be the probability that the real-time AoI of any user terminal in the system estimated by the AP at the initial time of any frame t is x, and the real-time AoI of the AP terminal is y. t (x,y), x≥0,y≥1,y≥x; Given an initial distribution of age gain, perform the following steps in each frame: Step 1: For each frame, the initial AP sets the frame length and age gain threshold based on the estimated age gain distribution, with the goal of maximizing the expected reduction in the average age of information (AoI) of the current frame slot; the frame length w of any frame t in Step 1 is... t and age gain threshold Γ t The setup method is as follows: Step 1-1: Based on the estimated age gain distribution, calculate the probability that the real-time age gain of any user in the system estimated by AP at the initial time of frame t is g. Step 1-2: Calculate the probability π that any user in the system meets the threshold condition at the initial time of frame t, given a certain age gain threshold Γ. t : π t ＝∑ g≥Γ h t,g ； (1) Steps 1-3: Assuming that each user's state satisfying the threshold condition is independent of each other, then the number of users n that satisfy the threshold condition is... t The probability of taking the value n can be calculated based on the existing parameters as follows: Steps 1-4: Given a frame length w and an age gain threshold Γ, calculate the estimated value of the expected reduction in slot-average AoI within frame t. as follows: Steps 1-5: Set the age gain threshold Γ for frame t t as follows: Steps 1-6: Set the frame length w of frame t t as follows: in, w∈{v L ,v U } represents the frame length w t The possible values ​​of z are given, and the parameter z is solved using the following fixed-point iterative formula: The initial value of the iteration z(0) is any real number in [1, γ]; where j∈{0,1,…,γ-1} represents the number of users whose real-time age gain is greater than or equal to the set threshold within frame t. Step 2: Users whose real-time age gain is greater than or equal to the set threshold within each frame independently and equally select any time slot within the frame for data transmission. If the number of users transmitting simultaneously in the same time slot is less than or equal to the packet receiving capacity γ of the AP, the transmission is successful; otherwise, all transmissions fail. The specific process for a user to access the channel within any frame t is as follows: In the initial time slot k of frame t... t Set of users that meet the threshold condition Any user in the time slot set Each user j independently and equally selects a time slot for data transmission; if a user j selects a time slot... If data transmission is successful, the real-time AoI of the AP in the next time slot will become [AoI value]. The real-time AoI of the AP for the remaining unsuccessful users will be incremented by 1. Step 3: At the end of each frame, the AP records the observation information of the number of users simultaneously transmitting in each time slot within that frame; the specific process of the AP recording the observation information of the number of users simultaneously transmitting in each time slot within any frame t is as follows: Mark the channel state of time slot k that the AP can observe as c. k And defined as follows: Where, r k This represents the number of users transmitting within time slot k; while all channel observation information of the AP within frame t can be represented as: Step 4: At the end of each frame, the AP estimates the age gain distribution at the beginning of the next frame based on the age gain distribution estimated at the beginning of that frame, the observation information within that frame, and the data arrival probability, using Bayesian update and combinatorial mathematics theory; at the end of any frame t, the AP estimates the age gain distribution {f} at the beginning of the next frame based on the age gain distribution estimated at the beginning of that frame, the observation information within that frame, and the data arrival probability, using Bayesian update and combinatorial mathematics theory. t+1 (x,y) x≥0,y≥1,y≥x The specific process of estimation is as follows: Step 4-1: Based on observation information O t Calculate the number of successful time slots within frame t. and number of collision time slots Step 4-2: Based on observation information O t Calculate the number of users v that completed data updates in the j-th successful time slot within frame t. j and the vectors they form Step 4-3: Based on observation information O t Calculate the total number of users successfully transmitted within frame t. and total number of users involved in collisions Step 4-4: Based on observation information O t Calculate the lower bound of the number of active users within frame t. Steps 4-5: Calculate the observation information when the number of active users satisfying the threshold condition is n, which is O. t conditional probability η o,n : Among them, C suc C col These respectively represent observation information of O t Under the given conditions, the total number of possible transmission options for successful users and colliding users within frame t can be calculated as follows: Steps 4-6: Calculate the initial time slot k in frame t. t Given that the real-time AoI value of any user terminal is x′ and the real-time AoI value of the AP terminal is y′, in the initial time slot k of frame t+1 t+1 The conditional probability β of any user terminal's real-time AoI value being x, the AP terminal's real-time AoI value being y, and the observed information being 0. x,y,o,x′,y′ ; β is determined based on whether the real-time age gain of any user i reaches the threshold, and whether user i successfully transmits data packets within frame t. x,y,o,x′,y′ The calculation can be divided into the following four cases: (1) When Furthermore, user i successfully transmitted the data packet within frame t, i.e., y′-x′<Γ. t x∈{0,1,...,w t -1,x′+w t }, y=x′+w t : β x,y,o,x′,y′ ＝0； (12) (2) When Furthermore, user i failed to successfully transmit data packets within frame t, i.e., y′-x′<Γ. t x∈{0,1,...,w t -1,x′+w t }, y=y′+w t : (3) When And user i successfully transmitted the data packet within frame t, i.e., y′-x′≥Γ. t x∈{0,1,...,w t -1,x′+w t }, y=x′+w t : (4) When Furthermore, user i failed to successfully transmit a data packet within frame t, i.e., y′-x′≥Γ. t x∈{0,1,...,w t -1,x′+w t }, y=y′+w t : Steps 4-7: Update f t+1 (x,y) are as follows:

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