Slot Management Method and System for Improving QoS of MANET Multimedia Services

Abstract

The present invention provides a time slot management method and system for improving the QoS of MANET multimedia services, including: Step S1: Determine whether to apply for a time slot according to the time slot application policy; Step S2: Apply for and reserve a time slot for the multimedia service that needs to apply for time slot resources; Step S3: Send data packets on the time slots that have been applied for and reserved; Step S4: Release the time slot resources for the reserved time slots that have not had data packets to be sent within a fixed time period; When it is determined in Step S1 that there is no need to apply for time slot resources, directly jump to Step S3. The present invention can ensure the minimum delay, especially in multi-hop transmission, the delay accumulation effect is more obvious; The reservation of time slot resources can ensure that all nodes on the transmission path do not need to frequently apply for and release time slot resources during the transmission of multimedia service data, thereby effectively reducing the end-to-end transmission delay.

Description

Technical Field

[0001] The present invention relates to the fields of time division multiple access (TDMA) communication and multimedia in mobile wireless ad hoc networks (MANETs). Specifically, it relates to a time slot management method and system for improving the QoS of multimedia services in MANETs. Background Art

[0002] As Figure 1 shown, a mobile wireless ad hoc network (MANET) is a centerless, distributed, randomly dynamic multi-hop network. With its advantages of high efficiency, fast networking, strong anti-destruction ability, low cost, etc., it is widely used in military communications, natural disaster relief, scientific expeditions, emergency communications and other fields. With the rapid development of Internet services and wireless mobile communication services, the demand for real-time multimedia services such as voice and video is increasing day by day, and users' requirements for their quality of service (QoS) are also getting higher and higher.

[0003] A MANET network based on time division multiple access (TDMA) contains multiple mobile nodes, and information is exchanged between nodes through a wireless medium. Transmission resources are divided based on time slots. Only by using a certain strategy to exclusively occupy time slot resources within a range of 2 hops or more hops can each node send data to other nodes. When transmitting data between two nodes, one or more intermediate nodes may be required as transmission relays. Different from traditional cellular networks and public mobile communication networks with infrastructure, its transmission bandwidth is limited, the link quality is unstable, the multi-hop transmission link changes dynamically, and time slot resources are dynamically allocated based on competition. These factors all have an adverse impact on performance such as transmission bandwidth, bit error rate, and delay, thus posing a greater challenge to the transmission service quality of multimedia services.

[0004] As Figure 2 shown, the transmission resources of a TDMA system are evenly divided into time periods on the entire time axis, and each time period is called a TDMA time frame. Each time frame consists of N time slot resource blocks, where N is the number of time slots in a time frame period, and the length of each time slot is M milliseconds. Therefore, the length of a time frame period is N * M milliseconds.

[0005] The length of the time frame period is generally jointly determined by factors such as network scale, system bandwidth, time slot length, throughput, and delay requirements. Generally speaking, the time frame length is proportional to the network scale, inversely proportional to the physical carrying capacity, and inversely proportional to the system performance requirements. (The more nodes supported by the network, the longer the time frame period; the weaker the physical carrying capacity, the longer the time frame period; the higher the throughput and delay requirements of the system, the shorter the time frame period)

[0006] As Figure 3As shown, the transmission of multimedia service data is characterized by burstiness and periodicity.

[0007] 1) Burstiness: The transmission can start and end at any time.

[0008] 2) Periodicity: The generation of data packets is periodic, and the data packets are transmitted at equal intervals on the time axis.

[0009] The transmission cycle length of multimedia services depends on the data sampling cycle and is related to the software, hardware, and settings that generate the data. Generally speaking, once the software, hardware, and settings are determined, the transmission cycle of multimedia service data remains fixed.

[0010] The traditional IEEE802.11 WLAN standard can only provide best-effort services and has no guarantee for service quality. The IEEE802.11e standard can provide different service levels for different service types, which improves the transmission service quality of various services to a certain extent. However, for services that are sensitive to delay and delay jitter, the user experience is still not good. Some researchers have proposed a strategy of ordinary time slot reservation, which can improve the delay and jitter of service data to a certain extent. However, for bursty and periodic multimedia services, its effect is limited, resulting in a still poor user experience.

[0011] Based on the above analysis, in order to overcome the problem that there is generally a large delay and delay jitter in MANET networks based on TDMA, which leads to a poor multimedia service experience, the present invention provides an efficient time slot management method. Based on the bursty and periodic transmission characteristics of multimedia services, this method reduces the end-to-end transmission delay and jitter through an optimal time slot selection strategy and a management strategy based on the time slot resource set, thereby effectively improving the user experience of multimedia services. For multimedia services in MANET networks based on time division multiple access, such as real-time voice services and real-time video services, due to their sensitivity to transmission delay and transmission delay jitter, problems such as poor user experience are likely to occur. An innovative method of periodically reserving time slot resources is proposed. According to the periodic and bursty characteristics of multimedia services, this method performs periodic time slot resource reservation, which not only reduces the transmission delay but also reduces the transmission delay jitter, ultimately greatly improving the user experience.

[0012] The MANET network is a multi-hop transmission network, and the end-to-end transmission delay is the sum of the transmission delays of each hop on the transmission path. Based on the real-time transmission of multimedia service data packets, this method tries to select the nearest time slot for sending or forwarding and performs time slot resource reservation. Selecting the nearest time slot can ensure the minimum delay. Especially in multi-hop transmission, the delay accumulation effect is more obvious. Time slot resource reservation can ensure that all nodes on the transmission path do not need to frequently apply for and release time slot resources during the transmission of multimedia service data, thereby effectively reducing the end-to-end transmission delay.

[0013] As Figure 10 shown, the horizontal axis is the time frame length and the vertical axis is the end-to-end average delay. It can be seen that the delay generated by the efficient time slot reservation strategy is not only much smaller than that generated by the ordinary time slot reservation strategy, but also does not increase with the increase of the time frame length. Generally, as the supported network scale increases, the time frame length needs to be increased accordingly.

[0014] Multimedia services have the characteristic of bursty periodic transmission. Based on the transmission period of multimedia service data packets, when a node applies for time slot resources, a set of time slots is reserved for this service. The arrangement positions of all time slots in this set of time slots are as consistent as possible with the transmission period of multimedia service data packets, so as to minimize the delay jitter of service data transmission.

[0015] As Figure 11 shown, the horizontal axis is the time frame length and the vertical axis is the end-to-end average delay jitter. It can be seen that the delay jitter generated by the efficient time slot reservation strategy is much smaller than that generated by the ordinary time slot reservation strategy.

[0016] Patent document CN107707326B (application number: CN201711106854.8) discloses a TDMA two-level time slot management method for terminals, which manages time slots according to the types of customer terminals, including: refining and classifying the actual application requirements of customer terminals into high, medium, and low levels according to delay sensitivity, bandwidth requirements, and priorities respectively; dividing the time slot allocation of each customer terminal into high, medium, and low levels according to bandwidth requirements respectively; dividing the time slot scheduling of each customer terminal into high, medium, and low levels according to delay sensitivity and priority respectively; dividing all access customer terminals into first-level and second-level polling queues according to priority and delay sensitivity; adopting a two-layer polling system to poll the above two-level customer terminal polling queues respectively; when the polling ends, moving the customer terminals that meet the predetermined conditions into or out of the inactive queue. However, this invention cannot be consistent with the transmission period of multimedia service data packets, so as to minimize the delay jitter of service data transmission. Summary of the Invention

[0017] Aiming at the defects in the prior art, the purpose of the present invention is to provide a time slot management method and system for improving the Qos of MANET multimedia services.

[0018] A time slot management method for improving the Qos of MANET multimedia services provided by the present invention includes:

[0019] Step S1: Determine whether to apply for a time slot according to the time slot application strategy;

[0020] Step S2: Apply for and reserve time slots for the multimedia service that needs to apply for time slot resources;

[0021] Step S3: Transmit data packets on the already applied and reserved time slots;

[0022] Step S4: Release the time slot resources for the reserved time slots where no data packets need to be transmitted within a fixed time period;

[0023] When it is determined in Step S1 that no time slot resources need to be applied, directly jump to Step S3.

[0024] Preferably, in the process of transmitting a single service data packet in a mobile wireless ad hoc network, the sum of the transmission delays of each hop is called the end-to-end transmission delay of the data packet. The transmission delay of each hop is denoted as Td. The greater the end-to-end transmission delay, the worse the user experience. For continuously transmitted data packets, the variance of the transmission delays between them is called the delay jitter. The greater the delay jitter, the worse the user experience.

[0025] The transmission delay of each hop = data processing time + air interface transmission time + time slot application time

[0026] For a time division multiple access system that requires dynamic time slot application, the time taken for data processing time and air interface transmission time is less than the time slot application time. Therefore, without considering the data processing time and air interface transmission time of each hop, the transmission delay of each hop depends on the time slot application time. When a node has available time slot resources and skips the time slot application stage, the transmission delay of each hop depends on the waiting time, and the waiting time is denoted as Tw.

[0027] The end-to-end transmission delay of a service data packet is the sum of the single-hop delays from a node to the next node. Different data packets will have different end-to-end transmission delay values, and the difference in the end-to-end transmission delays of consecutive data packets will cause delay jitter.

[0028] When no time slot reservation is performed, for single-hop transmission, each data packet needs to apply for a time slot before transmission. The time for applying for a time slot is Ta. Without considering other delay factors, the delay generated by each data packet at the node is Td = Ta. Since the time for applying for a time slot may be different, or due to time slot application conflicts resulting in re-application for a time slot, the time Ta for each application for a time slot is different, and the transmission delay Td is also different.

[0029] The longer the time taken to apply for a time slot, the greater the single-hop transmission delay Td. The time slots for service data transmission are not arranged at equal intervals, which will cause single-hop delay jitter. For multi-hop transmission, the transmission delay and jitter of multimedia service data are the accumulation of the single-hop transmission delays and jitters on the entire path. Due to the large single-hop delay and jitter, the end-to-end transmission delay and jitter of multimedia service data are large.

[0030] When each node applies for time slot resources for a multimedia service data packet, it applies for a set of time slots each time. All the time slots in this set meet the following requirements:

[0031] a. The time interval between the applied and reserved time slots and the arrival time of the data packet is short;

[0032] b. The time interval between the reserved time slots is equal to or greater than the transmission period of the multimedia service;

[0033] After the data packet arrives, apply for a set of time slots to make the waiting time Tw for each data packet to be sent the shortest and the transmission intervals equal;

[0034] The positions of the applied and reserved time slots are independent of the time Ta spent in the time slot application process.

[0035] Preferably, in the step S1:

[0036] There are two ways to apply for time slots, static time slot allocation and dynamic time slot application; due to the bursty characteristics of multimedia services, the dynamic time slot application method is used. Dynamic time slot application means that when a node needs to use time slot resources, it competes and interacts with adjacent nodes through air interface signaling to exclusively occupy the time slot resources for a period of time and then releases the resources after use; if there are no time slot resources available for sending this data packet when the data packet arrives, it is determined that time slots need to be applied, otherwise no time slot resources are applied, but the data packet is sent on the already applied and reserved time slots.

[0037] Preferably, in the step S2:

[0038] The applied time slots need to meet two conditions:

[0039] a. The time interval between the applied and reserved time slots and the arrival time of the data packet is short;

[0040] b. The time interval between the reserved time slots is equal to or greater than the transmission period of the multimedia service;

[0041] The relevant nodes in the neighborhood make a judgment on the time slot application request, and the adjacent nodes determine whether this application is successful; the judgment method is centralized or distributed. The distributed judgment method means that multiple nodes in the neighborhood jointly participate in the judgment; the centralized judgment method means that a certain management node in the neighborhood makes an independent judgment; when multiple nodes in the area apply for time slots simultaneously or compete for the same time slot resource simultaneously, conflicts will occur, resulting in the failure of this time slot application; there will be a time interval of one or more time frame periods, called the time slot application time, denoted as Ta, between the arrival of the data packet at this node and the availability of the time slot resources applied for it; after the time slot application is successful, record the current time stamp, and this set of time slots is reserved for this node to use for a period of time, and the reserved time is denoted as Tr.

[0042] Preferably, in the step S3:

[0043] The data packet is a multimedia service data packet sent from the application layer or forwarded from other nodes;

[0044] The waiting time from when the data packet arrives until the data is actually transmitted in this time slot is denoted as Tw, and Tw is less than Ta; if the time slot used this time is reserved instead of applied for, then update the time stamp and record the time when the last data packet was sent;

[0045] Preferably, in the step S4:

[0046] For the reserved time slot of a certain node, if there are no relevant multimedia service data packets to be sent during the Tr time period, then release the time slot resource so that the released time slot resource can be competed for and applied for again by all other nodes.

[0047] A time slot management system for improving the QoS of MANET multimedia services provided by the present invention includes:

[0048] Module M1: Determine whether to apply for a time slot according to the time slot application strategy;

[0049] Module M2: Apply for and reserve a time slot for the multimedia service that needs to apply for time slot resources;

[0050] Module M3: Send data packets on the applied-for and reserved time slots;

[0051] Module M4: Release the time slot resource for the reserved time slot for which there are no data packets to be sent during a fixed time period;

[0052] Module M3 works when Module M1 determines that there is no need to apply for time slot resources.

[0053] Preferably, during the transmission process of a single service data packet in a mobile wireless ad hoc network, the sum of the transmission delays of each hop is called the end-to-end transmission delay of the data packet, and the transmission delay of each hop is denoted as Td. The greater the end-to-end transmission delay, the worse the user experience; for continuously transmitted data packets, the variance of the transmission delays between them is called the delay jitter; the greater the delay jitter, the worse the user experience;

[0054] The transmission delay of each hop = data processing time + air interface transmission time + time slot application time

[0055] For a time-division multiple access system that requires dynamic slot allocation, the time taken for data processing and air interface transmission is less than the slot allocation time. Therefore, without considering the data processing time and air interface transmission time for each hop, the transmission delay for each hop depends on the slot allocation time. When a node has available slot resources and skips the slot allocation phase, the transmission delay for each hop depends on the waiting time, denoted as Tw.

[0056] The end-to-end transmission delay of service data packets is the sum of the single-hop delays from a node to the next node. Different data packets will have different end-to-end transmission delay values, and the difference in the end-to-end transmission delays of consecutive data packets will result in delay jitter.

[0057] When no slot reservation is performed, for single-hop transmission, each data packet needs to allocate a slot before transmission. The time for slot allocation is Ta. Without considering other delay factors, the delay generated by each data packet at the node is Td = Ta. Since the slot allocation time may be different, or due to slot allocation conflicts resulting in re-allocation of slots, the time Ta for each slot allocation is different, and the transmission delay Td is also different.

[0058] The longer the time taken for slot allocation, the greater the single-hop transmission delay Td. The service data transmission slots are not arranged at equal intervals, resulting in single-hop delay jitter. For multi-hop transmission, the transmission delay and jitter of multimedia service data are the accumulation of the single-hop transmission delays and jitters along the entire path. Due to the large single-hop delays and jitters, the end-to-end transmission delay and jitter of multimedia service data are large.

[0059] When each node allocates slot resources for multimedia service data packets, it allocates a set of slots each time. All the slots in this set meet the following requirements:

[0060] a. The time interval between slot allocation and reservation and the arrival time of the data packet is short.

[0061] b. The time interval between reserved slots is equal to or greater than the transmission period of the multimedia service.

[0062] After the data packet arrives, allocate a set of slots to minimize the waiting time Tw for each data packet to be sent and ensure equal transmission intervals.

[0063] The position of the allocated and reserved slots is independent of the time Ta taken for the slot allocation process.

[0064] Preferably, in the module M1:

[0065] There are two ways of time slot application, static time slot allocation and dynamic time slot application. Due to the bursty characteristics of multimedia services, the dynamic time slot application method is used. Dynamic time slot application means that when a node needs to use time slot resources, it competes with adjacent nodes through air interface signaling to exclusively occupy the time slot resources for a period of time and then releases the resources after use. If when the data packet arrives, the node does not have time slot resources for transmitting the data packet, it is determined that a time slot needs to be applied; otherwise, it does not apply for time slot resources but transmits on the already applied and reserved time slots.

[0066] Preferably, in the module M2:

[0067] The applied time slot needs to meet two conditions:

[0068] a. The time interval between the application and reservation of the time slot and the arrival time of the data packet is short;

[0069] b. The time interval between reserved time slots is equal to or greater than the transmission period of multimedia services;

[0070] Related nodes in the neighborhood adjudicate the time slot application request, and adjacent nodes determine whether this application is successful. The adjudication method is either centralized or distributed. The distributed adjudication method means that multiple nodes in the neighborhood jointly participate in the adjudication. The centralized adjudication method means that a certain management node in the neighborhood conducts independent adjudication. When multiple nodes in the area apply for time slots simultaneously or compete for the same time slot resource simultaneously, conflicts will occur, resulting in the failure of this time slot application. From the time when the data packet arrives at the node to the time when an available time slot resource is applied for it, there will be a time interval of one or more time frame periods, which is called the time slot application time and is denoted as Ta. After the time slot application is successful, the current time stamp is recorded, and this time slot set is reserved for the node to use for a period of time, and the reserved time is denoted as Tr.

[0071] Preferably, in the module M3:

[0072] The data packet is a multimedia service data packet sent from the application layer or forwarded from other nodes;

[0073] The waiting time from the arrival of the data packet to the actual data transmission on this time slot is denoted as Tw, and Tw is less than Ta. If the time slot used this time is reserved instead of applied, the time stamp is updated to record the time of the last sent data packet;

[0074] Preferably, in the module M4:

[0075] For the reserved time slots of a certain node, if no relevant multimedia service data packets need to be sent during the Tr period, the time slot resources are released so that the released time slot resources can be competed for and applied by all other nodes again.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] 1. The present invention reduces the transmission delay. Based on the real-time transmission of multimedia service data packets, it tries to select the nearest time slot for sending or forwarding and reserves time slot resources. Selecting the nearest time slot can ensure the minimum delay. Especially in multi-hop transmission, the delay accumulation effect is more obvious. The reservation of time slot resources can ensure that all nodes on the transmission path do not need to frequently apply for and release time slot resources during the transmission of multimedia service data, thus effectively reducing the end-to-end transmission delay.

[0078] 2. The present invention reduces the transmission delay jitter. Based on the transmission period of multimedia service data packets, when a node applies for time slot resources, a time slot set is reserved for this service. The arrangement positions of all time slots in this time slot set are as consistent as possible with the transmission period of the multimedia service data packets, thereby minimizing the transmission delay jitter of the service data. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Other features, objects and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0080] Figure 1 is the MANET network system topology;

[0081] Figure 2 is the TDMA time frame structure;

[0082] Figure 3 is the transmission of multimedia service data packets;

[0083] Figure 4 is the MANET multi-hop transmission;

[0084] Figure 5 is the data transmission without time slot reservation;

[0085] Figure 6 is the data transmission with ordinary time slot reservation;

[0086] Figure 7 is the data transmission with efficient time slot reservation;

[0087] Figure 8 is the efficient time slot management process - time slot application and reservation;

[0088] Figure 9 is the efficient time slot management process - time slot release;

[0089] Figure 10 is the delay comparison;

[0090] Figure 11For delay jitter comparison. Detailed implementation manners

[0091] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0092] Example 1:

[0093] According to a time slot management method for improving the QoS of MANET multimedia services provided by the present invention, as Figures 1 - 11 shown, it includes:

[0094] Step S1: Determine whether to apply for a time slot according to the time slot application strategy;

[0095] Step S2: Apply for and reserve a time slot for the multimedia service that needs to apply for time slot resources;

[0096] Step S3: Send data packets on the time slots that have been applied for and reserved;

[0097] Step S4: Release the time slot resources for the reserved time slots that have no data packets to be sent within a fixed time period;

[0098] When it is determined in step S1 that there is no need to apply for time slot resources, directly jump to step S3.

[0099] Specifically, in the process of transmitting a single service data packet in a mobile wireless ad hoc network, the sum of the transmission delays of each hop is called the end-to-end transmission delay of the data packet, and the transmission delay of each hop is denoted as Td. The greater the end-to-end transmission delay, the worse the user experience; for continuously transmitted data packets, the variance of the transmission delays between them is called delay jitter; the greater the delay jitter, the worse the user experience;

[0100] The transmission delay of each hop = data processing time + air interface transmission time + time slot application time

[0101] For a time division multiple access system that requires dynamic time slot application, the time spent on data processing time and air interface transmission time is less than the time slot application time. Therefore, without considering the data processing time and air interface transmission time of each hop, the transmission delay of each hop depends on the time slot application time; when the node has available time slot resources and skips the time slot application stage, the transmission delay of each hop depends on the waiting time, and the waiting time is denoted as Tw;

[0102] The end-to-end transmission delay of service data packets is the sum of the single-hop delays from a node to the next node; different data packets may have different end-to-end transmission delay values, and the difference in the end-to-end transmission delays of consecutive data packets will result in delay jitter.

[0103] When no time slot reservation is performed, for single-hop transmission, each data packet needs to apply for a time slot before transmission, and the time for applying for a time slot is Ta. Without considering other delay factors, the delay generated by each data packet at the node is Td = Ta; since the time for applying for a time slot may be different, or due to time slot application conflicts resulting in re-application for time slots, the time Ta for each time slot application is different, and the transmission delay Td is also different.

[0104] The longer the time spent applying for a time slot, the greater the single-hop transmission delay Td; the service data transmission time slots are not arranged at equal intervals, resulting in single-hop delay jitter; for multi-hop transmission, the transmission delay and jitter of multimedia service data are the accumulation of the single-hop transmission delays and jitters on the entire path. Due to the large single-hop delays and jitters, the end-to-end transmission delay and jitter of multimedia service data are large.

[0105] When each node applies for time slot resources for multimedia service data packets, it applies for a set of time slots each time. All the time slots in this set meet the following requirements:

[0106] a. The time interval between applying for and reserving time slots and the arrival time of the data packet is short.

[0107] b. The time interval between reserved time slots is equal to or greater than the transmission period of the multimedia service.

[0108] After the data packet arrives, apply for a set of time slots to make the waiting time Tw for each data packet to be sent the shortest and the transmission intervals equal.

[0109] The position of the applied and reserved time slots has nothing to do with the time Ta spent in the process of applying for time slots.

[0110] Specifically, in the step S1:

[0111] There are two ways to apply for time slots, static time slot allocation and dynamic time slot application; due to the bursty characteristics of multimedia services, the dynamic time slot application method is used. Dynamic time slot application means that when a node needs to use time slot resources, it competes to interact with adjacent nodes through air interface signaling to exclusively occupy time slot resources for a period of time and then releases the resources after use; if when the data packet arrives, the node does not have time slot resources for sending this data packet, it is determined that a time slot needs to be applied, otherwise no time slot resources are applied, but it is sent on the already applied and reserved time slots.

[0112] Specifically, in the step S2:

[0113] The time slots applied for need to meet two conditions:

[0114] a. The time interval between the application and reservation of time slots and the arrival time of the data packet is short;

[0115] b. The time interval between reserved time slots is equal to or greater than the transmission period of the multimedia service;

[0116] The relevant nodes in the neighborhood adjudicate the time slot application requests, and the adjacent nodes determine whether this application is successful; the adjudication method is centralized or distributed. The distributed adjudication method means that multiple nodes in the neighborhood participate in the adjudication together; the centralized adjudication method means that a certain management node in the neighborhood conducts independent adjudication; when there are multiple nodes in the area applying for time slots simultaneously, or competing for the same time slot resource simultaneously, conflicts will occur, resulting in the failure of this time slot application; from the time when the data packet arrives at this node to the time when an available time slot resource is applied for it, there will be a time interval of one or more time frame periods, which is called the time slot application time and is denoted as Ta; after the time slot application is successful, the current time stamp is recorded, and this time slot set is reserved for this node to use for a period of time, and the reserved time is denoted as Tr.

[0117] Specifically, in the step S3:

[0118] The data packet is a multimedia service data packet sent from the application layer or forwarded from other nodes;

[0119] The waiting time from the arrival of the data packet to the actual data transmission on this time slot is denoted as Tw, and Tw is less than Ta; if the time slot used this time is reserved instead of applied for, the time stamp is updated to record the time of the last sent data packet;

[0120] Specifically, in the step S4:

[0121] For the reserved time slots of a certain node, if there are no relevant multimedia service data packets to be sent during the Tr period, the time slot resources are released so that the released time slot resources can be competed for and applied for by all other nodes again.

[0122] Example 2:

[0123] Embodiment 2 is a preferred example of Embodiment 1 to illustrate the present invention more specifically.

[0124] Those skilled in the art can understand a time slot management method for improving the QoS of MANET multimedia services provided by the present invention as the specific implementation manner of a time slot management system for improving the QoS of MANET multimedia services, that is, the time slot management system for improving the QoS of MANET multimedia services can be implemented by executing the step process of the time slot management method for improving the QoS of MANET multimedia services.

[0125] A time slot management system for improving the QoS of MANET multimedia services provided by the present invention includes:

[0126] Module M1: Determine whether to apply for a time slot according to the time slot application strategy;

[0127] Module M2: Apply for and reserve a time slot for the multimedia service that needs to apply for time slot resources;

[0128] Module M3: Send data packets on the already applied and reserved time slots;

[0129] Module M4: Release the time slot resources for the reserved time slots that have no data packets to be sent within a fixed time period;

[0130] Module M3 works when Module M1 determines that there is no need to apply for time slot resources.

[0131] Specifically, in the process of transmitting a single service data packet in a mobile wireless ad hoc network, the sum of the transmission delays of each hop is called the end-to-end transmission delay of the data packet. The transmission delay of each hop is denoted as Td. The greater the end-to-end transmission delay, the worse the user experience. For continuously transmitted data packets, the variance of the transmission delays between them is called the delay jitter. The greater the delay jitter, the worse the user experience.

[0132] The transmission delay of each hop = data processing time + air interface transmission time + time slot application time

[0133] For a time division multiple access system that requires dynamic time slot application, the time spent on data processing time and air interface transmission time is less than the time slot application time. Therefore, without considering the data processing time and air interface transmission time of each hop, the transmission delay of each hop depends on the time slot application time. When the node has available time slot resources and skips the time slot application stage, the transmission delay of each hop depends on the waiting time, and the waiting time is denoted as Tw.

[0134] The end-to-end transmission delay of the service data packet is the sum of the single-hop delays from the node to the next node. Different data packets will have different end-to-end transmission delay values. The difference in the end-to-end transmission delays of consecutive data packets will cause delay jitter.

[0135] When no time slot reservation is performed, for single-hop transmission, each data packet needs to apply for a time slot before transmission. The time for applying for a time slot is Ta. Without considering other delay factors, the delay generated by each data packet of the node is Td = Ta. Since the time for applying for a time slot may be different, or due to time slot application conflicts resulting in re-application for a time slot, the time Ta for each application for a time slot is different, and the transmission delay Td is also different.

[0136] The time taken to apply for time slots is long, and the single-hop transmission delay Td is large; the time slots for service data transmission are not arranged at equal intervals, resulting in single-hop delay jitter; for multi-hop transmission, the transmission delay and jitter of multimedia service data are the accumulation of single-hop transmission delay and jitter along the entire path. Due to the large single-hop delay and jitter, the end-to-end transmission delay and jitter of multimedia service data are large;

[0137] When each node applies for time slot resources for multimedia service data packets, it applies for a set of time slots each time. All the time slots in this set meet the following requirements:

[0138] a. The time interval between the application and reservation of time slots and the arrival time of the data packet is short;

[0139] b. The time interval between reserved time slots is equal to or greater than the transmission period of the multimedia service;

[0140] After the data packet arrives, apply for a set of time slots to minimize the waiting time Tw for each data packet to be sent and make the transmission intervals equal;

[0141] The position of the applied and reserved time slots is independent of the time Ta spent in the time slot application process.

[0142] Specifically, in the module M1:

[0143] There are two ways to apply for time slots: static time slot allocation and dynamic time slot application; due to the bursty characteristics of multimedia services, the dynamic time slot application method is used. Dynamic time slot application means that when a node needs to use time slot resources, it competes with adjacent nodes through air interface signaling to interact, so as to exclusively occupy time slot resources for a period of time and release the resources after use; if there are no time slot resources for sending this data packet when the data packet arrives, it is determined that time slots need to be applied, otherwise no time slot resources are applied, but the data packet is sent on the already applied and reserved time slots.

[0144] Specifically, in the module M2:

[0145] The applied time slots need to meet two conditions:

[0146] a. The time interval between the application and reservation of time slots and the arrival time of the data packet is short;

[0147] b. The time interval between reserved time slots is equal to or greater than the transmission period of the multimedia service;

[0148] Relevant nodes within the neighborhood adjudicate the time slot application requests, and adjacent nodes determine whether this application is successful; the adjudication method is either centralized or distributed. The distributed adjudication method means that multiple nodes within the neighborhood jointly participate in the adjudication; the centralized adjudication method means that a certain management node within the neighborhood conducts independent adjudication; when multiple nodes within the area apply for time slots simultaneously, or compete for the same time slot resource simultaneously, conflicts will occur, resulting in the failure of this time slot application; from the time when the data packet arrives at this node to the time when an available time slot resource is applied for it, there will be a time interval of one or more time frame periods, which is called the time slot application time and is denoted as Ta; after the time slot application is successful, record the current time stamp, and this time slot set is reserved for this node to use for a period of time, and the reserved time is denoted as Tr.

[0149] Specifically, in the module M3:

[0150] The data packet is a multimedia service data packet sent from the application layer or forwarded from other nodes;

[0151] The waiting time from when the data packet arrives to when data is actually transmitted on this time slot is denoted as Tw, and Tw is less than Ta; if the time slot used this time is reserved instead of applied for, then update the time stamp and record the time when the last data packet was sent;

[0152] Specifically, in the module M4:

[0153] For the reserved time slot of a certain node, if there are no relevant multimedia service data packets to be sent during the Tr time period, then release the time slot resource so that the released time slot resource can be competed for and applied for by all other nodes again.

[0154] Example 3:

[0155] Embodiment 3 is a preferred example of Embodiment 1 to more specifically illustrate the present invention.

[0156] During the MANET network service transmission process, the general time slot application and sending process is as follows:

[0157] Step 1: Determine whether to apply for a time slot according to the time slot application strategy. There are two ways of time slot application, static time slot allocation and dynamic time slot application. Static time slot allocation means that according to a certain strategy, fixed time slots or time slot sets are pre-allocated to each node. Dynamic time slot application means that when a node needs to use time slot resources, it competes to interact with adjacent nodes through air interface signaling, so as to exclusively occupy the time slot resources for a period of time and release the resources after use. Due to the bursty characteristics of multimedia services, the static time slot allocation strategy is obviously not applicable, so only the dynamic time slot application method can be used. That is, if there are no available time slot resources currently, then it is judged that a time slot needs to be applied for, otherwise directly go to Step 3;

[0158] Step 2: If the decision requires applying for time slot resources, apply for a time slot for this multimedia service. The relevant nodes in the neighborhood adjudicate the time slot application request to determine whether the application is successful. The adjudication method can be centralized or distributed. The distributed adjudication method means that multiple nodes in the neighborhood jointly participate in the adjudication; the centralized adjudication method means that a certain management node in the neighborhood makes an independent adjudication. When multiple nodes in the area apply for time slots simultaneously or compete for the same time slot resource, conflicts may occur, resulting in the failure of this time slot application. Regardless of which method, there will be a time interval of one or more time frame periods, called the time slot application time ApplyTime (Ta), between the arrival of the data packet at this node and the acquisition of available time slot resources for it;

[0159] Step 3: Transmit the data packet on the available time slot. If Step 2 is skipped because time slot resources are available, there is a waiting time, denoted as WaitTime (Tw), between the arrival of the data packet and the actual data transmission on this time slot. Usually, Tw < Ta.

[0160] In the MANET network, during the transmission process of a single service data packet, the sum of the transmission delays of each hop is called the end-to-end transmission delay of this data packet. The larger the end-to-end transmission delay, the worse the user experience; for continuously transmitted data packets, the variance of the transmission delays between them is called the delay jitter. The larger the delay jitter, the worse the user experience.

[0161] The transmission delay (Td) of each hop = data processing time + air interface transmission time + time slot application time (Ta). For a TDMA system that requires dynamic time slot application, the time spent on the former two is much less than the latter. Therefore, without considering the data processing time and air interface transmission time of each hop, the transmission delay Td of each hop depends on the time Ta for applying for a time slot. When the node has available time slot resources and skips the time slot application stage, then Td depends on the waiting time Tw.

[0162] As Figure 4 shown, the source node is A, the destination node is H, and the nodes on the service transmission path are node A, B, D, E, G, H in sequence. The single-hop delay from node A to node B is Td1, the single-hop delay from node B to node D is Td2, and so on. Then the end-to-end transmission delay Td of the service data packet = Td1 + Td2 + Td3 + Td4 + Td5; different data packets may have different Td values, and the difference in the transmission delays Td of consecutive data packets will generate the delay jitter Jitter.

[0163] As Figure 5As shown in the figure, when no time slot reservation is performed, for single-hop transmission, each data packet needs to apply for a time slot before it can be transmitted. The time for applying for a time slot is Ta. For example, the time difference between the arrival of data packet D1 and the successful application for time slot Si is Ta1, the time difference between the arrival of data packet D2 and the successful application for time slot Sj is Ta2, and the time difference between the arrival of data packet D3 and the successful application for time slot Sk is Ta3. Without considering other delay factors, the delay generated by each data packet at this node is Td = Ta. For example, the delay generated by data packet D1 is Td1 = Ta1, the delay generated by data packet D2 is Td2 = Ta2, and so on. Since the time for applying for a time slot may be different, or due to time slot application conflicts resulting in re-application for time slots, the time Ta for each application for a time slot is likely to be different, and the transmission delay Td is also different, that is, Td1 ≠ Td2 ≠ Td3.

[0164] It is not difficult to see that when the time spent applying for a time slot is relatively long, the single-hop transmission delay Td will be relatively large; in addition, the service data transmission time slots Si, Sj, and Sk are not arranged at equal intervals, so single-hop delay jitter will occur.

[0165] For multi-hop transmission, the transmission delay and jitter of multimedia service data are the accumulation of the single-hop transmission delay and jitter on the entire path. Therefore, due to the relatively large single-hop delay and jitter, the end-to-end transmission delay and jitter of multimedia service data are relatively large, and the quality of service cannot be guaranteed.

[0166] As Figure 6 shown in the figure, when performing an ordinary time slot reservation strategy, for single-hop transmission, each time a time slot is applied for a data packet, a period of time will be reserved. During this period, the reserved time slot does not need to be re-applied and can be directly used to transmit data. The node applies for time slot Si for data packet D1, and the delay generated by applying for the time slot is Ta1; it applies for time slot Sj for data packet D2, and the delay generated by applying for the time slot is Ta2. Generally speaking, the TDMA time frame period and the data packet transmission period are not equal, and there is no correlation between them. In the figure, the TDMA time frame period is twice the data packet transmission period. Each TDMA time frame contains N time slots. Then time slots such as Si + N and Sj + N, Si + 2N and Sj + 2N are reserved for this node. When data packets D3 and D4 need to be sent, there is no need for a time slot application process and they can be directly transmitted on Si + N and Sj + N respectively. The time interval between the arrival time of data packet D3 and time slot Si + N is Tw1, which is called the waiting time for sending data packet D3. Similarly, Tw2 is the waiting time for sending data packet D4. Their relationship is: Ta1 = Tw1, Ta2 = Tw2, Ta1 ≠ Ta2, Tw1 ≠ Tw2.

[0167] It is not difficult to see that: 1) Even if there are reserved time slots available, the ordinary time slot reservation strategy cannot effectively reduce the transmission delay. 2) During the TDMA time frame period when time slots need to be applied for, the time for each time slot application may be different. For example, Ta1 and Ta2 are not equal, resulting in unequal waiting times Tw1 and Tw2 for transmitting data packets on the reserved time slots subsequently, thus causing the delay jitter to still exist. However, since the applied time slot and its corresponding reserved time slot are equidistant, to a certain extent, the delay jitter of service data transmission is reduced, which has a certain improvement on the user experience.

[0168] As Figure 7 shown, it reflects the efficient time slot management strategy provided by the present invention. When each node applies for time slot resources for multimedia service data packets, it applies for a set of time slots each time. All the time slots in this set meet the following requirements:

[0169] 1) The time interval between the applied and reserved time slots and the arrival time of the data packet is as short as possible;

[0170] 2) The time interval between the reserved time slots is preferably equal to or slightly greater than the transmission period of the multimedia service;

[0171] As shown in the figure, in an ideal situation, after the data packet D1 arrives, a set of time slots {i, i + T, i + 2T, i + 3T,...} is applied for, making the waiting time Tw for each data packet to be sent the shortest and the transmission intervals equal.

[0172] Due to strategy 1), the single-hop delay can be minimized, thereby minimizing the transmission delay Td on the entire transmission path;

[0173] Due to strategy 2), it can be ensured as much as possible that on the entire transmission path, the data packets are transmitted at equal intervals, thereby minimizing the delay jitter Jitter.

[0174] It should be noted that the positions of the applied and reserved time slots are independent of the time Ta spent in the time slot application process. If Ta is less than or equal to Tw, the data packet D1 is transmitted on the time slot Si; otherwise, one possible method is that D1 is transmitted together with other data packets on the subsequent reserved time slots, and another possible method is to discard some data packets that are too late to be sent. No matter what method is used, for multimedia services, there will only be a relatively large delay and frame loss for a very short time when the service session is established, which does not affect the service data transmission.

[0175] It can be seen that when the efficient time slot management strategy provided by the present invention is executed, the delay and jitter of multimedia service data packets are both minimized, thus greatly improving the user experience.

[0176] Example 4:

[0177] Embodiment 4 is a preferred example of Embodiment 1 to illustrate the present invention more specifically.

[0178] As Figure 8 and Figure 9 shown, the process for each node in the present invention to perform efficient time slot management and data transmission for multimedia services is as follows:

[0179] Step 1: Determine whether to apply for a time slot according to the time slot application policy. The possible policies are as follows. If there is no time slot resource available for sending this data packet when this data packet arrives, it is determined that a time slot needs to be applied for; otherwise, no time slot resource is applied for, but the data packet is sent on the already applied and reserved time slots, that is, directly go to Step 3.

[0180] Step 2: If it is determined that a time slot resource needs to be applied for, apply for a set of time slots for this multimedia service at one time. This set of time slots satisfies two conditions: 1) The time interval between the applied and reserved time slots and the arrival time of the data packet is as short as possible; 2) The time interval between the reserved time slots is preferably equal to or slightly greater than the transmission period of the multimedia service. The relevant nodes in the neighborhood make a decision on the time slot application request, and the adjacent nodes determine whether this application is successful. The decision-making method can be either centralized or distributed. After the time slot application is successful, record the current timestamp, and this set of time slots is reserved for this node to use within a period of time ReverseTime(Tr).

[0181] Step 3: Send the data packet on the already applied and reserved time slots. If the time slot used this time is reserved instead of applied for, update the timestamp to record the time of the last sent data packet.

[0182] Step 4: For the reserved time slots of a certain node, if there are no relevant multimedia service data packets to be sent within its Tr period, release the time slot resources so that the released time slot resources can be competed for and applied for by all other nodes again.

[0183] Those skilled in the art know that in addition to implementing the system, device, and their respective modules provided by the present invention in the form of pure computer-readable program codes, the method steps can be logically programmed to enable the system, device, and their respective modules provided by the present invention to be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers, etc., to implement the same program. Therefore, the system, device, and their respective modules provided by the present invention can be regarded as a kind of hardware component, and the modules included therein for implementing various programs can also be regarded as the structures within the hardware component; the modules for implementing various functions can also be regarded as either software programs for implementing the methods or the structures within the hardware component.

[0184] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other.

Claims

1. A time slot management method for improving the QoS of MANET multimedia services, characterized in that, including: Step S1: Determine whether to apply for a time slot according to the time slot application policy; Step S2: Apply for and reserve a time slot for the multimedia service that needs to apply for time slot resources; Step S3: Send data packets on the already applied and reserved time slots; Step S4: Release the time slot resources for the reserved time slots that have not had data packets to send within a fixed time period; When it is determined in Step S1 that there is no need to apply for time slot resources, directly jump to Step S3; During the transmission process of a single service data packet in a mobile wireless ad hoc network, the sum of the transmission delays of each hop is called the end-to-end transmission delay of the data packet. The transmission delay of each hop is denoted as Td. The larger the end-to-end transmission delay, the worse the user experience; For continuously transmitted data packets, the variance of the transmission delays between them is called delay jitter; the larger the delay jitter, the worse the user experience; The transmission delay of each hop = data processing time + air interface transmission time + time slot application time For a time division multiple access system that requires dynamic time slot application, the time spent on data processing time and air interface transmission time is less than the time slot application time. Therefore, without considering the data processing time and air interface transmission time of each hop, the transmission delay of each hop depends on the time slot application time; When a node skips the time slot application stage when there are available time slot resources, the transmission delay of each hop depends on the waiting time, and the waiting time is denoted as Tw; The end-to-end transmission delay of the service data packet is the sum of the single-hop delays from the node to the next node; different data packets will have different end-to-end transmission delay values, and the difference in the end-to-end transmission delays of consecutive data packets will generate delay jitter; When no time slot reservation is performed, for single-hop transmission, each data packet needs to apply for a time slot before transmission. The time for applying for a time slot is Ta. Without considering other delay factors, the delay generated by each data packet of the node is Td = Ta; since the time for applying for a time slot may be different, or due to time slot application conflicts resulting in re-application for a time slot, the time Ta for each application for a time slot is different, and the transmission delay Td is also different; The longer the time spent on applying for a time slot, the larger the single-hop transmission delay Td; the transmission time slots of the service data are not arranged at equal intervals, which will generate single-hop delay jitter; for multi-hop transmission, the transmission delay and jitter of the multimedia service data are the accumulation of the single-hop transmission delay and jitter on the entire path. Due to the large single-hop delay and jitter, the end-to-end transmission delay and jitter of the multimedia service data are large; When each node applies for time slot resources for the multimedia service data packet, each time a set of time slots is applied for, and all the time slots in this set meet the following requirements: a. The time interval between applying for and reserving the time slot and the arrival time of the data packet is short; b. The time interval between the reserved time slots is equal to or greater than the transmission period of the multimedia service; After the data packet arrives, apply for a set of time slots to make the waiting time Tw for each data packet to be sent the shortest and the transmission intervals equal; The position of the applied and reserved time slots has nothing to do with the time Ta spent in the time slot application process; In the said Step S1: There are two ways to apply for time slots, static time slot allocation and dynamic time slot application. Due to the bursty characteristics of multimedia services, the dynamic time slot application method is used. Dynamic time slot application means that when a node needs to use time slot resources, it competes with adjacent nodes through air interface signaling to exclusively occupy the time slot resources for a period of time and then releases the resources after use. If there is no time slot resource available for sending the data packet when the data packet arrives at the node, it is determined that a time slot needs to be applied for; otherwise, no time slot resource is applied for, and the data packet is sent on the already applied and reserved time slots. In step S2: The applied time slots need to meet two conditions: a. The time interval between the application and reservation of the time slot and the arrival time of the data packet is short. b. The time interval between reserved time slots is equal to or greater than the transmission period of the multimedia service. Related nodes in the neighborhood adjudicate the time slot application request, and adjacent nodes determine whether the application is successful. The adjudication method can be centralized or distributed. The distributed adjudication method means that multiple nodes in the neighborhood jointly participate in the adjudication. The centralized adjudication method means that a certain management node in the neighborhood makes an independent adjudication. When multiple nodes in the area apply for time slots simultaneously or compete for the same time slot resource, conflicts will occur, resulting in the failure of this time slot application. There will be a time interval of one or more time frame periods, called the time slot application time and denoted as Ta, between the arrival of the data packet at the node and the acquisition of available time slot resources for it. After the time slot application is successful, the current timestamp is recorded, and the time slot set is reserved for the node to use for a period of time, and the reserved time is denoted as Tr. In step S3: The data packet is a multimedia service data packet sent from the application layer or forwarded from other nodes. The waiting time from the arrival of the data packet to the actual data transmission on this time slot is denoted as Tw, and Tw is less than Ta. If the time slot used this time is reserved instead of applied for, the timestamp is updated to record the time of the last sent data packet. In step S4: For the reserved time slots of a certain node, if there are no relevant multimedia service data packets to be sent during the Tr period, the time slot resources are released so that the released time slot resources can be competed for and applied for by all other nodes again.

2. A slot management system for improving the QoS of MANET multimedia services, characterized in that, It includes: Module M1: Determine whether to apply for a time slot according to the time slot application strategy. Module M2: Apply for and reserve time slots for multimedia services that need to apply for time slot resources. Module M3: Send data packets on the already applied and reserved time slots. Module M4: Release the time slot resources for reserved time slots where there are no data packets to be sent within a fixed period. Module M3 works when Module M1 determines that no time slot resource needs to be applied for. During the transmission process of a single service data packet in a mobile wireless ad hoc network, the sum of the transmission delays of each hop is called the end-to-end transmission delay of the data packet. The transmission delay of each hop is denoted as Td. The larger the end-to-end transmission delay, the worse the user experience. For continuously transmitted data packets, the variance of the transmission delays between them is called the delay jitter. The larger the delay jitter, the worse the user experience. Transmission delay per hop = data processing time + air interface transmission time + time slot application time For a time division multiple access system that requires dynamic time slot application, the time taken for data processing time and air interface transmission time is less than the time slot application time. Therefore, without considering the data processing time and air interface transmission time per hop, the transmission delay per hop depends on the time for applying for a time slot; When a node skips the time slot application phase because it has available time slot resources, the transmission delay per hop depends on the waiting time, denoted as Tw; The end-to-end transmission delay of service data packets is the sum of the single-hop delays from one node to the next node; different data packets will have different end-to-end transmission delay values, and the difference in the end-to-end transmission delays of consecutive data packets will result in delay jitter; When no time slot reservation is performed, for single-hop transmission, each data packet needs to apply for a time slot before transmission. The time for applying for a time slot is Ta. Without considering other delay factors, the delay generated by each data packet at the node is Td = Ta; since the time for applying for a time slot may be different, or due to time slot application conflicts resulting in re-application for a time slot, the time Ta for each application for a time slot is different, and the transmission delay Td is also different; The longer the time taken for applying for a time slot, the greater the single-hop transmission delay Td; the service data transmission time slots are not arranged at equal intervals, resulting in single-hop delay jitter; for multi-hop transmission, the transmission delay and jitter of multimedia service data are the accumulation of the single-hop transmission delay and jitter on the entire path. Due to the large single-hop delay and jitter, the end-to-end transmission delay and jitter of multimedia service data are large; When each node applies for time slot resources for multimedia service data packets, it applies for a set of time slots each time. All the time slots in this set meet the following requirements: a. The time interval between applying for and reserving a time slot and the arrival time of the data packet is short; b. The time interval between reserved time slots is equal to or greater than the transmission period of the multimedia service; After the data packet arrives, apply for a set of time slots to make the waiting time Tw for each data packet to be sent the shortest and the transmission intervals equal; The positions of the applied and reserved time slots are independent of the time Ta spent in the time slot application process; In the module M1: There are two ways of time slot application, static time slot allocation and dynamic time slot application; due to the bursty characteristics of multimedia services, the dynamic time slot application method is used. Dynamic time slot application means that when a node needs to use time slot resources, it competes and interacts with adjacent nodes through air interface signaling to exclusively occupy time slot resources for a period of time and then releases the resources after use; if when the data packet arrives, the node does not have time slot resources for sending this data packet, it is determined that a time slot needs to be applied, otherwise no time slot resources are applied, but it is sent on the already applied and reserved time slots; In the module M2: The applied time slots need to meet two conditions: a. The time interval between applying for and reserving a time slot and the arrival time of the data packet is short; b. The time interval between reserved time slots is equal to or greater than the transmission period of the multimedia service; Relevant node pairs within the neighborhood adjudicate the time slot application requests, and adjacent nodes determine whether this application is successful; the adjudication method is either centralized or distributed. The distributed adjudication method means that multiple nodes within the neighborhood jointly participate in the adjudication; the centralized adjudication method means that a certain management node within the neighborhood makes an independent adjudication; when multiple nodes within the area make time slot applications simultaneously or compete for the same time slot resource simultaneously, conflicts will occur, resulting in the failure of this time slot application; there will be a time interval of one or more time frame periods, called the time slot application time, denoted as Ta, between the arrival of the data packet at this node and the acquisition of an available time slot resource for it; after the time slot application is successful, record the current time stamp, and this time slot set is reserved for this node for use within a certain period of time, and the reserved time is denoted as Tr; In the module M3: The data packet is a multimedia service data packet sent from the application layer or forwarded from other nodes; The waiting time between the arrival of the data packet and the actual data transmission on this time slot is denoted as Tw, and Tw is less than Ta; if the time slot used this time is reserved instead of applied for, then update the time stamp and record the time of the last sent data packet; In the module M4: For the reserved time slot of a certain node, if there are no relevant multimedia service data packets to be sent within the Tr time period, then release the time slot resource so that the released time slot resource can be competed for and applied for by all other nodes again.

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