Semi-persistent scheduling method for transmission resources in wireless ad hoc networks based on multi-hop cooperation

Abstract

The present invention discloses a semi-permanent scheduling method for transmission resources of a wireless self-organizing network based on multi-hop collaboration, which adopts semi-permanent scheduling to apply for transmission resources for certain types of services. In order to ensure that the transmission resources are exclusively occupied by a certain service, the transmission resources are bound to the service ID. In the semi-permanent scheduling process, when the "current decision node" selects and determines the transmission resources from the available transmission resources, it selects the transmission resources that are closer in time to the transmission resources of the "adjacent upstream sending node". Whether the current decision node is the current sending node or the current receiving node is related to the semi-permanent scheduling method adopted, and the decision node is the node that sends the grant message. The present invention forms a low-latency pipeline mechanism for end-to-end multi-hop link communication by adding a collaboration mechanism to the semi-permanent scheduling process of the front and rear nodes of the wireless self-organizing network, thereby achieving the purpose of reducing the total delay of end-to-end communication.

Description

Technical Field

[0001] The present invention relates to a semi-permanent scheduling method for wireless ad hoc network transmission resources based on multi-hop collaboration, which is a medium network control technology for wireless ad hoc networks based on multi-hop collaboration and belongs to communication network technology. Background Art

[0002] Currently, wireless mesh networks (WLANs) are being extensively researched as a technology for building flexible wide-area wireless local area networks (WLANs). They have broad application prospects, such as intelligent transportation, multimedia access, and environmental monitoring. These applications often require high QoS (Quality of Service) while ensuring throughput, requiring the network to have the necessary capabilities to guarantee these QoS requirements.

[0003] Semi-Persistent Scheduling (SPS), also known as semi-static scheduling, differs from dynamic scheduling, where each node applies for radio resources once with its desired neighbor. SPS allows for semi-static configuration of radio resources and periodic allocation of these resources to a specific link at a specific node. In other words, the sending node completes semi-persistent scheduling through a three-way handshake with the receiving node, securing conflict-free transmission resources within two hops.

[0004] Because SPS offers "one-time allocation, multiple uses," dynamic scheduling doesn't need to be enabled for every transmission cycle. While SPS offers slightly less flexibility, it also reduces control signaling overhead. It's suitable for services with less pronounced burst characteristics and guaranteed rate requirements, primarily for periodic small packet services such as VoIP (Voice over Internet Protocol). The cycle and required radio resources for these services are predictable. Uncoordinated semi-persistent scheduling uses a three-way handshake to acquire transmission resources, enabling continuous multi-frame transmission.

[0005] However, when using uncoordinated semi-persistent scheduling to reserve multi-hop transmission resources, since the previous hop transmission resources are not considered, the calculated optimal time slot may be in the next frame or a frame far away from the previous hop transmission resource, such as Figure 1 shown. Summary of the Invention

[0006] Purpose of the invention: To overcome the deficiencies in the prior art, the present invention provides a semi-persistent scheduling method based on multi-hop collaboration, which is improved by combining semi-persistent scheduling to optimize the delay problem caused by non-cooperative semi-persistent scheduling and ensure end-to-end delay.

[0007] Technical solution: To achieve the above-mentioned purpose, the technical solution adopted by the present invention includes the following processes: SPS resource allocation process and SPS resource recovery process.

[0008] (1) During the SPS resource allocation process, the initiating node initiates a semi-persistent scheduling request based on its local SPS record. When the "current decision node" selects a transmission resource from the available transmission resources, it chooses an SPS resource that is closer in time to the SPS resource of the "adjacent upstream sending node." This SPS resource is called the optimal transmission time slot. The SPS resource allocation process is completed through multiple signaling interactions.

[0009] (1.1) Initiate semi-permanent scheduling

[0010] The initiating node searches for the local SPS record by the service ID and initiates a semi-persistent scheduling application based on the matching SPS record; if no corresponding record is found, an application is initiated based on the service type.

[0011] (1.2) Bind business ID

[0012] The authorization node (decision node) searches for the corresponding previous-hop transmission resource in its local semi-permanent record based on the matching service ID. The service ID also needs to be bound when sending an application. Multi-hop transmission data packets also need to be bound to services.

[0013] (1.3) Calculate the available time slot set

[0014] During the search process, an available time slot set is generated. First, all time slots occupied by semi-persistent scheduling are deleted from the set of all available time slot ranges SLOT_ALL to obtain a remaining available time slot range SLOT.

[0015] SLOT_ALL=[slot0,slot m ]

[0016] SLOT={slot1,slot2,…,slot n}

[0017] SLOT∈SLOT_ALL

[0018] Among them, slot0, slot m Not consecutive time slots.

[0019] Since the transmission time slot range must also be considered, any slot in SLOT i The following formula must be satisfied.

[0020]

[0021] slot i ∈[slot x,slot x +Minislot range-1]

[0022] Wherein, Minislot range is the transmission resource length m required for this service. In some cases, there may not be a set of continuous available time slots. In this case, the Minislot range can be adjusted to calculate multiple separate transmission time slot ranges and integrate them into a transmission resource that meets the requested time slot range.

[0023] If the available time slot set is empty or the number of elements in the available time slot set is less than m+1-M, a rejection message is sent or semi-persistent data scheduling is not initiated.

[0024] Wherein, M is the total number of time slots supporting semi-persistent data scheduling in one frame.

[0025] (1.4) Available time slot table

[0026] Based on the available time slot set, a time slot table for N consecutive frames starting from the current frame is generated. Then, an available time slot table is generated based on the data scheduling information. Regardless of whether a two-way handshake, a three-way handshake, or a four-way handshake is used, both the sending node and the receiving node need to generate the corresponding available time slot table.

[0027] (1.5) Calculate the optimal transmission start time slot

[0028] Generate authorization information based on the available time slot table and calculate the optimal transmission time slot. The optimal transmission time slot needs to satisfy the following formula:

[0029] FS i +CF≥Fs i-1

[0030]

[0031]

[0032] Ms i =Ms i mod slot_num

[0033] FS i +CF≥Fs i-1 +F_a i

[0034] Mr i =Mr i-1

[0035] Still need to meet

[0036] [Ms i , Ms. i +Mr i -1]∈SLOTi

[0037] Among them, FS i For node N i The distance between the semi-persistently scheduled frame number and the current frame, Fs i-1 For node N i-1 The starting frame number of semi-persistent scheduling. Node N i The node currently applying for SPS resources, node N i-1 and N i+1 Node N i Previous hop and next hop nodes. CF is the current frame number, Ms i For node N i The minimum starting time slot number for semi-persistent scheduling, Ms i-1 Node N in the local SPS record i-1 The semi-permanent scheduling starting time slot number, Mr i-1 Node N in the local SPS record i-1 The semi-permanent scheduling time slot range. i The minimum number of frames between the current node and the previous hop node. slot_num is the number of transmission resources in one frame, slot_time is the time length of the transmission resource, delay i For node N i-1 and node N i processing delay.

[0038] When the above conditions are met, try to find the closest [Ms i-1 , Ms. i-1 +Mr i-1 -1] transmission start time slot, does not require the minimum transmission delay of the current packet. And find the corresponding FS i .

[0039] Because SPS resources are long-term, semi-persistent scheduling information must be broadcast periodically. Therefore, after either node completes semi-persistent scheduling, it initiates periodic broadcasts. Through a semi-persistent scheduling handshake or periodic broadcasts of semi-persistent scheduling information, both nodes currently participating in the scheduling can obtain the previous hop's semi-persistent scheduling information.

[0040] (2) SPS resource recovery process: When the transmission route changes or no data packet is received for a long time, the node initiates semi-persistent scheduling cancellation, which includes explicit recovery and implicit recovery.

[0041] (2.1) Implicit recycling

[0042] If no semi-persistent resource broadcast message is received for a long time or no corresponding application message is received when the occupied SPS resources are about to be exhausted, the corresponding SPS resources will be implicitly reclaimed.

[0043] (2.2) Explicit Recycling

[0044] If the route changes or a service fails to receive data packets for a specific service for an extended period, the corresponding SPS resources are explicitly reclaimed, triggering a cancellation mechanism. The node that triggers the cancellation mechanism initiates a semi-persistent scheduling cancellation and sends a semi-persistent scheduling cancellation message. Upon receiving the semi-persistent scheduling cancellation message, the destination node responds by sending a cancellation confirmation message.

[0045] In the present invention, the authorization node calculates the best transmission resource, mainly relying on the local SPS resource record and unique service identifier formed by multiple signaling interactions, and can find the corresponding previous hop transmission resource.

[0046] Beneficial effects: The semi-permanent scheduling method for wireless ad hoc network transmission resources based on multi-hop collaboration provided by the present invention has the following advantages: Low delay: The introduction of multi-hop collaboration can ensure that the transmission time slot obtained by the current node must be the transmission resource closest to the transmission resource of the previous hop, which can greatly reduce the end-to-end delay and the single-hop delay. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A graph of possible occupied transmission resources for non-cooperative semi-persistent scheduling multi-hop transmission in the present invention;

[0048] Figure 2 This is the frame format used in the case of the present invention;

[0049] Figure 3 This is the semi-persistent scheduling three-way handshake diagram used in the present invention;

[0050] Figure 4 This is a diagram of a three-way handshake retry after a semi-permanent scheduling handshake failure used in the present invention;

[0051] Figure 5 This is a diagram of a set of continuous time slots available when the number of continuous time slot resources required is 2 in the present invention;

[0052] Figure 6 This is a possible transmission resource diagram of cooperative semi-persistent scheduling multi-hop when the processing time slot Δ=3 in the present invention. DETAILED DESCRIPTION

[0053] The present invention will be further described below with reference to the accompanying drawings.

[0054] In a synchronous system, the frame format is as follows Figure 2As shown, the current frame data transmission time slot is 20. Taking the "semi-permanent scheduling + timely renewal" mechanism for semi-permanent scheduling handshake as an example, each scheduling of transmission resources for N consecutive frames is divided into application messages, authorization messages or rejection messages and broadcast messages. The application message is generated according to the service type, the authorization message or rejection message is generated according to the application message and some restrictions, and the broadcast message is generated according to the authorization message. The three-way handshake success process is shown in Figure 3 , the three-way handshake failure retransmission process see Figure 4 .

[0055] Under the conditions of the same transmission rate and the same load, this method optimizes the reserved time slot resources, forms a pipeline mechanism, and reduces the end-to-end delay.

[0056] The specific embodiments of this method are as follows:

[0057] 1. Determine whether the current service supports semi-permanent scheduling through the service ID.

[0058] 2. Match the local semi-permanent scheduling record according to the service ID and destination address (MAC layer unique identifier). If the service ID matches but the destination address does not match, it means that the current transmission path has changed and the semi-permanent scheduling release mechanism is started; if the service ID does not match, it means that the semi-permanent scheduling mechanism has not been initiated yet. This is the first packet of the service and the semi-permanent scheduling mechanism is started; if both the service ID and the destination address match, it means that transmission resources have been allocated for the current service and data is sent according to the allocated transmission resources.

[0059] 3. In multi-hop transmission, nodes are divided into starting nodes, intermediate nodes, and end nodes. The starting node is the source node that initiates the service; the intermediate nodes are the nodes that forward service data packets; and the end node is the destination node. The starting node initiates a semi-persistent scheduling request, the intermediate nodes grant and request semi-persistent scheduling, and the end node grants semi-persistent scheduling authorization. If a semi-persistent scheduling record exists and the destination address is the current node ID, it is an intermediate node.

[0060] 4. Semi-permanent scheduling of three-way handshake

[0061] 4.1 The applying node obtains the semi-persistent scheduling application resource size based on the service type. If it is an intermediate node, the semi-persistent scheduling application transmission resource size is determined based on the semi-persistent scheduling record; if it is a starting node, the semi-persistent scheduling application transmission resource size is determined based on the service type.

[0062] 4.2 Upon receiving a semi-permanent scheduling request, the granting node searches its local availability table for relevant reservation records, as shown in Table 1. If the renewal mechanism is in place or available time slots are fragmented, there may be multiple local records. Alternatively, a single request may receive multiple grant messages.

[0063] The process of the authorized node generating the optimal transmission time slot is shown in 5.

[0064] Table 1 Local semi-permanent scheduling record format

[0065] Field meaning Service ID Business ID TX Node Sending Node RX Node Receiving Node GRANT_NUM Number of grants for(i=0;i<GRANT_NUM;i++) { Frame_Range Frame Range Frame_Start Starting frame number Slot_Range Time slot range Slot_Start Starting timeslot number }

[0066] If the local grant expires, delete the corresponding expired grant.

[0067] If the number of semi-permanent scheduling resources granted to the node exceeds the limit, a rejection message will be sent with the rejection type number. Otherwise, a grant is generated and the local semi-permanent scheduling record is updated.

[0068] 4.3 If the applicant node receives the grant message, it generates a grant confirmation message based on the grant message and periodically broadcasts the grant message, updates the local semi-permanent scheduling record and updates the scheduling status of the data packet; otherwise, it re-initiates the semi-permanent scheduling handshake based on the rejection message.

[0069] 4.4 After receiving the authorization message, the one-hop neighbor node of the granting node updates the local semi-permanent scheduling record.

[0070] 4.5 After receiving the broadcast message, the one-hop neighbor node of the applicant node updates the local semi-permanent scheduling record and updates the status of the data packet.

[0071] 5. Calculate the optimal transmission time slot

[0072] 5.1 Obtaining Available Time Slot Sets

[0073] like Figure 5 As shown, the set SLOT_ALL = [0, 19], where slots 0, 2, 3, 7, and 8 are occupied SPS resources. The resulting idle slots are {1, 4, 5, 6, 9-19}. When the number of required slot resources is 2, SLOT = {[4, 6], [9, 19]}. If the available slot set is empty, semi-persistent scheduling is not supported. However, an available slot set must still be generated for other scheduling purposes. This available slot set is SLOT_ALL.

[0074] 5.2 Obtaining Available Time Slots

[0075] Generate the Available table starting from the current frame number CURRENT_FRAME and continuing until it reaches a point 128 frames away. The table is further narrowed based on normal scheduling. Calculate the Available table to find the closest slot range [Minislot start, Minislot start + Minislotrange - 1] that satisfies the requirement for transmission from CURRENT_FRAME + Frame_Start to CURRENT_FRAME + 128 frames without any node occupying this slot range. Alternatively, find a slot range that satisfies the application requirements, or find multiple grants or grants that satisfy the application requirements.

[0076] 5.3 Optimal Transmission Resources

[0077] The time interval between adjacent upstream and downstream nodes must be as small as possible and also greater than the delay required for the current node to process a data packet. Δ represents the minimum time slot difference. The node's available table is calculated based on information from semi-persistent scheduling and normal data scheduling. The optimal transmission delay is determined based on the available table and the minimum delay difference.

[0078] Assume that the node currently requesting scheduling is node N i ,i∈[1,n-1]; It should be noted that time slot 19 and time slot 0 are not continuous, there is a time difference and the time difference is greater than Δ.

[0079] Table 2 Symbols and their meanings

[0080]

[0081]

[0082] N i The previous hop node is N i-1 , the next hop node is N i+1 , the previous hop node N i-1 The scheduling information initiated includes the frame number Fs i-1 , occupied time slot range [Ms i-1 , Ms. i-1 +Mr i-1 -1]; N i The frame number and time slot range of the semi-persistent scheduling application must first meet the following conditions:

[0083] Fs i =(FS i +CF)≥Fs i-1

[0084]

[0085]

[0086] Ms i =Ms i mod slot_num

[0087] Fs i =(FS i +CF)≥Fs i-1 +F_a i

[0088] Mr i =Mr i-1

[0089] Still need to meet

[0090] [Ms i , Ms. i +Mr i -1]∈SLOT i

[0091] Formula 1 ensures that the start frame sent by the current node is greater than or equal to the start frame sent by the previous hop node.

[0092] Formula 2 calculates that the starting time slot of the current node must be greater than or equal to the ending time slot sent by the previous hop node plus the number of processing time slots.

[0093] Formula 3 calculates the minimum frame difference between the current node and the previous hop node caused by the start time slot of the current node crossing the boundary.

[0094] Formula 4 ensures that the starting time slot of the current node falls within the range [0, slot_num).

[0095] Formula 5 ensures that the current node transmits after the previous hop node.

[0096] Formula 6 ensures that the time slot range is consistent.

[0097] Formula 7 ensures that the occupied time slots of the current node are continuous.

[0098] When the above conditions are met, try to find the closest [Ms i-1 , Ms. i-1 +Mr i-1 -1] transmission start time slot, does not require the minimum transmission delay of the current packet. And find the corresponding FS i The possible transmission resources of cooperative semi-persistent scheduling multi-hop can be seen Figure 6 .

[0099] The above embodiments are merely examples to clarify the present invention and are not intended to limit its implementation. For example, the single-hop semi-persistent scheduling handshake employed in the present invention can be replaced with any other handshake mechanism, including a two-way handshake, a four-way handshake, or a "persistent scheduling + timeout exit" mechanism. Furthermore, it is assumed that there is an upper limit on the total number of semi-persistently scheduled resources. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications derived from these variations remain within the scope of protection of the present invention.

Claims

1. A semi-persistent scheduling method for transmission resources in a wireless ad hoc network based on multi-hop cooperation, characterized by: During the SPS resource allocation process, the initiating node initiates a semi-persistent scheduling request based on the local SPS record. When the authorizing node selects a transmission resource from the available transmission resources, it chooses an SPS resource that is closer in time to the SPS resource of the "adjacent upstream sending node". Through multiple signaling interactions, the SPS resource allocation process within two hops is completed without conflict. The steps of the authorization node selecting and determining a transmission resource from available transmission resources include: Calculate the available time slot set: first delete all semi-persistently scheduled occupied time slots from the set of all available time slot ranges SLOT_ALL to obtain a remaining available time slot range SLOT; Any slot in SLOT i The following formula must be satisfied: slot i ∈[slot x ,slot x +Minislot range-1] Among them, Minislot range is the transmission resource length m required for this service; slot i 、slot x Respectively represent the i-th and x-th available time slots in SLOT; If the available time slot set is empty or the number of elements in the available time slot set is less than m+1-M, a rejection message is sent or semi-persistent data scheduling is not initiated, where M is the total number of time slots supporting semi-persistent data scheduling in one frame; Generate available time slot table: Generate a time slot table of N consecutive frames starting from the current frame based on the available time slot set, and then generate an available time slot table based on the data scheduling information; Calculate the optimal transmission start time slot: Generate authorization information based on the available time slot table and calculate the optimal transmission time slot; The optimal transmission time slot needs to satisfy the following formula: FS i +CF≥Fs i-1 (1) Ms i =Ms i mod slot_num (4) FS i +CF≥Fs i-1 +F_a i (5) mr i =Mr i-1 (6) [Ms i ,Ms i +Mr i -1]∈SLOT i (7) Among them, FS i For node N i The distance between the semi-persistently scheduled frame number and the current frame, Fs i-1 For node N i-1 The starting frame number of semi-persistent scheduling; node N i The node currently applying for SPS resources, node N i-1 and N i+1 Node N i Previous hop and next hop nodes; CF is the current frame number, Ms i For node N i The minimum starting time slot number for semi-persistent scheduling, Ms i-1 Node N in the local SPS record i-1 The semi-permanent scheduling starting time slot number, Mr i-1 Node N in the local SPS record i-1 The range of semi-permanent scheduling time slots; F_a i The minimum number of frames between the current node and the previous hop node; slot_num is the number of transmission resources in one frame, slot_time is the time length of the transmission resource, delay i For node N i-1 and node N i processing delay; In the case of satisfying formulas (1)-(7), find the closest [Ms i-1 ,Ms i-1 +Mr i-1 -1] transmission start time slot, does not require the minimum transmission delay of the current packet, and finds the corresponding MS i .

2. The method for semi-persistent scheduling of transmission resources in a wireless ad hoc network based on multi-hop cooperation according to claim 1, characterized in that: The initiating node searches for the local SPS record by the service ID and initiates a semi-persistent scheduling application based on the matching SPS record; if no corresponding record is found, an application is initiated based on the service type.

3. The method for semi-persistent scheduling of transmission resources in a wireless ad hoc network based on multi-hop cooperation according to claim 1, characterized in that: The authorization node searches for the corresponding previous-hop transmission resource in the local semi-permanent record based on the matching service ID. The service ID needs to be bound when sending an application, and multi-hop transmission data packets also need to be bound to the service.

4. The method for semi-persistent scheduling of transmission resources in a wireless ad hoc network based on multi-hop cooperation according to claim 1, characterized in that: The applicant node receives the grant message, generates a grant confirmation message based on the grant message and periodically broadcasts the grant message, updates the local semi-permanent scheduling record and updates the scheduling status of the data packet; Otherwise, the semi-persistent scheduling handshake is reinitiated according to the rejection message.

5. The method for semi-persistent scheduling of transmission resources in a wireless ad hoc network based on multi-hop cooperation according to claim 1, characterized in that: Match the local semi-permanent scheduling record according to the service ID and destination address. If the service ID matches but the destination address does not match, it means that the current transmission path has changed and the semi-permanent scheduling release mechanism is started; if the service ID does not match, it means that the semi-permanent scheduling mechanism has not been initiated yet and it is the first packet of the service, so the semi-permanent scheduling mechanism is started; if both the service ID and the destination address match, it means that transmission resources have been allocated for the current service and data is sent according to the allocated transmission resources.

6. The method for semi-persistent scheduling of transmission resources in a wireless ad hoc network based on multi-hop cooperation according to claim 1, characterized in that: When the transmission route changes or no data packet is received for a long time, the authorized node initiates semi-persistent scheduling cancellation, including explicit recovery and implicit recovery.

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