CN107172692A - Low time delay ensures slot allocation method - Google Patents

Abstract

The invention discloses a method for allocating time slots with low delay guarantee. The scheme is: 1. Adjust the superframe structure to the order of non-competition period, inactive period and contention access period; 2. The PAN coordinator broadcasts the beacon frame at the beginning of the adjusted superframe; 3. The beacon frame After the frame transmission ends, each node enters the non-competition period, and ordinary nodes that have applied for guaranteed time slots transmit GTS services during this period; 4. After the non-competition period ends, each node enters an inactive period, and all nodes remain dormant during this period; 5. After the inactive period ends, each node enters the contention access period, and ordinary nodes with GTS services to be sent send GTS requests to the PAN coordinator within this period to apply for guaranteed time slots; 6. After the contention access period ends, the current superframe ends, Each node enters the next superframe. The invention reduces the transmission time delay of the GTS service, improves the accuracy of guarantee time slot allocation, and can be used in the wireless personal area network.

Description

Low latency guaranteed time slot allocation method

technical field

The invention belongs to the technical field of communication, in particular to a method for allocating a guaranteed time slot GTS, which can be used to improve the IEEE802.15.4 communication standard.

Background technique

The IEEE 802.15.4 communication standard is designed for low-speed wireless personal area network WPAN. It focuses on low cost, low power consumption and easy installation, and aims to provide an Flexible and reliable low-speed wireless network standard.

IEEE 802.15.4 divides wireless devices in the network into two types according to their functions: PAN coordinator and common nodes. Among them, the PAN coordinator is the central control node of the entire network, and each IEEE 802.15.4 network can only have one PAN coordinator. Some ordinary nodes can associate other nodes as general coordinators.

IEEE 802.15.4 supports two basic types of topologies: star and peer-to-peer, and each topology supports two working modes: beacon-enabled mode and non-beacon-enabled mode. In non-beacon-enabled mode, all nodes in the network compete for channels through non-slotted carrier sense multi-point access/collision avoidance algorithm. Non-beacon-enabled mode can flexibly build a network, but cannot provide real-time guarantee And good service quality assurance.

In the beacon-enabled mode, the PAN coordinator divides the channel into continuous and non-overlapping time segments on the time axis, and each time segment is called a superframe, as shown in FIG. 4 . A superframe consists of an active period and an inactive period. The active period includes the beacon sending period, the contention access period CAP and the non-competition period CFP; during the inactive period, all nodes enter a sleep state and do not send data to reduce energy consumption.

The PAN coordinator broadcasts a beacon frame to the common nodes associated with it at the beginning of each superframe, and publishes the start and end moments of the current superframe and the channel allocation scheme in the superframe. The PAN coordinator realizes synchronization with surrounding nodes by periodically sending beacon frames, so the real-time communication and quality of service can be better guaranteed.

The IEEE 802.15.4 standard provides a guaranteed time slot GTS mechanism to meet service requirements that are sensitive to delay or require bandwidth. The GTS mechanism is a conflict-free access scheme. Common nodes can apply to the PAN coordinator for a certain guaranteed time slot as their own dedicated transmission time slot. The guaranteed time slot is located in the non-competition period. In the guaranteed time slot, nodes do not need to access channels through competition to obtain service transmission opportunities, but can directly interact with the PAN coordinator for services.

When an ordinary node needs a guaranteed time slot, it can send a GTS request to the PAN coordinator during the contention access period, and the PAN coordinator decides whether to allocate a guaranteed time slot to the node that sent the GTS request according to the current resource allocation situation. For the allocated guaranteed time slots, ordinary nodes can request to cancel them, and the PAN coordinator can also actively cancel them. GTS has the following usage rules:

(1) GTS can only be allocated by the PAN coordinator for communication between the PAN coordinator and its associated common nodes;

(2) The PAN coordinator allocates guaranteed time slots to at most 7 common nodes in each superframe;

(3) Guaranteed time slots can only be used for the transmission of data frames.

When IEEE 802.15.4 is applied to the wireless personal area network, although the non-competition period in the superframe structure can guarantee the low-delay characteristics of delay-sensitive services, and the sleep strategy in the inactive period is also conducive to reducing the energy of nodes in the network. consumption, but the standard still has the following two deficiencies:

1) GTS business has inherent delay

As shown in Figure 4, a common node sends a GTS request in the contention access period of the nth superframe, and needs to wait until the end of the current superframe and the beacon frame time of the n+1th superframe to obtain the allocation result of the GTS time slot , and the GTS service cannot be transmitted until the non-contention period of the n+1 superframe, which causes a certain inherent delay in the GTS service and affects the service quality of delay-sensitive services;

2) The accuracy of GTS distribution cannot be guaranteed

Because the PAN coordinator cannot respond to the node's GTS request in time, the business status of the node may have changed after a long wait. At this time, the original allocation scheme cannot reflect the actual business needs of the node, which affects the accuracy of GTS allocation.

Contents of the invention

The purpose of the present invention is to address the deficiencies of the above-mentioned prior art, and propose a method for allocating low-time-delay guaranteed time slots, so as to shorten the inherent waiting time delay of GTS services, improve the accuracy of guaranteed time-slot allocation, and better meet the needs of those with low-time delays. Services with delay or fixed bandwidth requirements.

The present invention adjusts the superframe structure so that common nodes can obtain the allocation result of the guaranteed time slot in time after sending the GTS request, and then start the transmission of the GTS service. The implementation scheme is as follows:

Technical solution 1:

A method for allocating low-latency guaranteed time slots in a wireless personal area network, characterized in that: proceed in the following order:

(1) Adjust the superframe structure, that is, adjust the order of the original agreement from the contention access period, the non-competition period and the inactive period to the non-competition period, the inactive period and the contention access period;

(2) The PAN coordinator broadcasts the beacon frame at the beginning of the adjusted nth superframe, and each common node receives the beacon frame, and records the protocol parameters in the local cache;

(3) After the beacon transmission ends, each node enters the non-competition period, and the PAN coordinator judges whether each ordinary node has GTS service to be sent: if the ordinary node has GTS service to send, and has successfully obtained the guaranteed time slot before the current superframe , then conduct business interaction with the PAN coordinator during the non-competition period; if the common node has no GTS service to send, the current superframe does not include the non-competition period;

(4) After the non-competition period ends, each node enters the inactive period, and all nodes are in a dormant state during the inactive period;

(5) After the inactive period is over, all nodes enter the contention access period. At this stage, if ordinary nodes need to guarantee time slots to send services with delay requirements, they will access the channel through the time slot CSMA/CA mechanism and coordinate with the PAN The device sends a GTS request to apply for a guaranteed time slot;

(6) The PAN coordinator allocates the received GTS request according to the resource status in the superframe, and broadcasts the allocation result to each common node in the beacon frame of the n+1th superframe;

(7) After the contention access period ends, the nth superframe ends, and the PAN coordinator and each common node enters the n+1th superframe, and turns to step (1).

Technical solution 2:

A method for allocating low-latency guaranteed time slots in a wireless personal area network, characterized in that: proceed in the following order:

1) Adjust the superframe structure, that is, adjust the order of the original protocol from the contention access period, non-competition period and inactive period to the order of non-competition period, contention access period and inactive period;

2) The PAN coordinator broadcasts the beacon frame at the beginning of the adjusted nth superframe, each common node receives the beacon frame, and records the protocol parameters in the local cache;

3) After the beacon transmission ends, each node enters the non-competition period, and the PAN coordinator judges whether each ordinary node has GTS service to be sent: if the ordinary node has GTS service to send, and has successfully obtained the guaranteed time slot before the current superframe, Then conduct business interaction with the PAN coordinator during the non-competition period; if the common node has no GTS service to send, the current superframe does not include the non-competition period;

4) After the non-competition period ends, all nodes enter the contention access period. At this stage, if ordinary nodes need to guarantee time slots to send services with delay requirements, they will access the channel through the time slot CSMA/CA mechanism during the contention access period. And send a GTS request to the PAN coordinator to apply for a guaranteed time slot;

5) The PAN coordinator allocates the received GTS request according to the resource status in the superframe, and broadcasts the allocation result to each common node in the beacon frame of the n+1th superframe;

6) After the competition access period ends, each node enters an inactive period, during which all nodes are in a dormant state;

7) After the inactive period ends, the nth superframe ends. The PAN coordinator and each common node enter the n+1th superframe, and turn to step 1).

The present invention has the following advantages:

First, it reduces the time delay of the GTS service.

In the original protocol, ordinary nodes send GTS requests in the contention access period of the current superframe, and need to wait until the non-contention period of the next superframe to start transmitting GTS services, which makes the inherent delay of GTS services larger. The adjusted superframe structure adopted by the present invention can obviously reduce the time delay of GTS service;

Second, the accuracy of guarantee slot allocation is improved.

In the original protocol, there is a certain inherent delay between the GTS request sending and the GTS service transmission, but the IEEE802.15.4 protocol stipulates that for the GTS service to be transmitted in the guaranteed time slot, if the applied for guaranteed time slot Nodes can still transmit this traffic during contention access periods. Since the node may have transmitted part of the GTS service during the waiting time, or a new GTS service has been generated, when the guaranteed time slot arrives, the service buffer status of the node changes, resulting in the length of the previously applied guaranteed time slot being different from that at this moment. The amount of traffic to be sent does not match.

However, the adjusted superframe structure used in the present invention can enable ordinary nodes to start the transmission of GTS services immediately after sending a GTS request, thus improving the accuracy of GTS time slot allocation and ensuring the utilization rate of time slot resources.

Description of drawings

FIG. 1 is a usage scenario diagram of an embodiment of the present invention;

Fig. 2 is the realization flowchart of technical scheme 1 of the present invention;

Fig. 3 is the realization flowchart of technical scheme 2 of the present invention;

Fig. 4 is a schematic diagram of a superframe structure in the IEEE 802.15.4 protocol;

Fig. 5 is a schematic diagram of the adjusted superframe structure of technical solution 1 of the present invention;

Fig. 6 is a schematic diagram of the adjusted superframe structure of technical solution 2 of the present invention;

Fig. 7 is a schematic diagram of the structure of the superframe configuration field of the beacon frame used in the present invention.

detailed description

The content of the present invention will be further elaborated below in conjunction with the accompanying drawings.

Referring to Figure 1, the topology used in this example is a star topology, all common nodes only interact with the PAN coordinator, and there is no data transmission between common nodes; the network adopts the beacon-enabled mode.

Embodiment one:

Referring to Figure 2, the specific implementation steps of this example are described as follows:

Step 1, adjusting the superframe structure.

Adjust the superframe structure, that is, adjust the original agreement from the order of contention access period, non-competition period and inactive period to the order of non-competition period, inactive period and contention access period. The original superframe structure is shown in Figure 4, and the adjusted superframe structure is shown in Figure 5;

The adjusted superframe structure makes it possible for ordinary nodes to obtain guaranteed time slot allocation results through the beacon frame of the current superframe immediately after sending a GTS request in the contention access period of the previous superframe, and then in the non-competition access period of the current superframe. Start GTS service transmission within the time period.

Step 2, sending a beacon frame.

The PAN coordinator constructs and broadcasts a beacon frame at the start time t0 of the adjusted nth superframe, and each common node receives the beacon frame, reads the protocol parameters in it and records it in the local cache.

The beacon frame is an improvement on the original protocol beacon frame, that is, the end time slot of the contention access period in the superframe configuration field is changed to the start time slot of the contention access period, as shown in FIG. 7 .

Step 3: Common nodes transmit GTS services during the non-contention period.

After the beacon frame is sent, each node enters the non-competition period, that is, the time period from t1 to t2;

Nodes that have applied for guaranteed time slots can transmit GTS services without competition within this period, and the PAN coordinator first determines whether each common node has GTS services to be sent:

If the normal node has GTS service to send and has successfully obtained the guaranteed time slot before the current superframe, it can transmit the GTS service in the guaranteed time slot specified by the beacon frame;

If the common node does not have GTS service or has GTS service but has not obtained guaranteed time slot allocation, the common node enters the dormant state;

If no common node sends a GTS request in the n-1th superframe, or the previously allocated guaranteed time slots have been revoked, the current superframe does not contain a non-contention period.

Step 4, each node enters a dormant state during the inactive period.

After the non-competition period ends, each node enters the inactive period, that is, the time period from t2 to t3. During this period, all nodes are in a dormant state. The introduction of the inactive period is a low power consumption strategy. The transmission occupation can be adjusted by adjusting the length of the inactive period. empty ratio.

It should be noted that: if the current superframe does not include a non-contention period, all nodes directly enter the non-active period after sending the beacon frame.

Step 5: Common nodes send GTS requests during the contention access period.

After the inactive period ends, all nodes enter the contention access period, that is, the time period from t3 to t4. During this period, if ordinary nodes have GTS services to send, they will access the channel through the time slot CSMA/CA mechanism and send to the PAN coordinator GTS request, apply for guaranteed time slot;

After receiving the GTS request sent by the common node, the PAN coordinator replies ACK to the common node for confirmation.

Step 6, GTS time slot allocation process.

The PAN coordinator allocates the received GTS request according to the resource status in the superframe:

First, check whether the number of nodes currently assigned guaranteed time slots reaches 7: if the number of nodes has reached 7, the PAN coordinator rejects the GTS request; if not, continue to judge downward;

Then, check whether there is enough space in the active period of the superframe to allocate this GTS request: the IEEE 802.15.4 protocol stipulates that the minimum length of the contention access period is 440symbols, so the PAN coordinator needs to determine that after the guaranteed time slot is allocated for the GTS request , whether the length of the contention access period will be reduced to less than 440symbols: if yes, the PAN coordinator rejects the GTS request; if not, the GTS request meets the allocation conditions;

Finally, for the GTS request that meets the above allocation conditions, the PAN coordinator puts the allocation result of the request into the beacon frame of the n+1th superframe, to be broadcast to each common node.

Step seven, after the contention access period ends at time t4, the current superframe ends, the PAN coordinator and each common node enter the n+1th superframe, and return to step one.

Embodiment two:

Referring to Figure 3, the specific implementation steps of this example are described as follows:

Step 1, adjusting the superframe structure.

Adjust the superframe structure, that is, adjust the order of the original protocol from the contention access period, the non-competition period and the inactive period to the non-competition period, the contention access period and the inactive period. The original superframe structure is as shown in Figure 4, and the adjusted superframe structure is as shown in Figure 6;

Ordinary nodes send GTS requests during the contention access period of the previous superframe, and after the inactive period ends, they can obtain the guaranteed time slot allocation results through the beacon frame of the current superframe, and then in the non-contention period of the current superframe Start GTS service transmission within the time period.

Step 2, sending a beacon frame.

The PAN coordinator constructs and broadcasts a beacon frame at the start time t0 of the adjusted nth superframe, and each common node receives the beacon frame, reads the protocol parameters in it and records it in the local cache.

The beacon frame is an improvement on the original protocol beacon frame, that is, the end time slot of the contention access period in the superframe configuration field is changed to the start time slot of the contention access period, as shown in FIG. 7 .

Step 3: Common nodes transmit GTS services during the non-contention period.

After the beacon frame is sent, each node enters the non-competition period, that is, the time period from t1 to t2;

Nodes that have applied for guaranteed time slots can transmit GTS services without competition within this period, and the PAN coordinator first determines whether each common node has GTS services to be sent:

If the normal node has GTS service to send and has successfully obtained the guaranteed time slot before the current superframe, it can transmit the GTS service in the guaranteed time slot specified by the beacon frame;

If the common node does not have GTS service or has GTS service but has not obtained guaranteed time slot allocation, the common node enters the dormant state;

If no common node sends a GTS request in the n-1th superframe, or the previously allocated guaranteed time slots have been revoked, the current superframe does not contain a non-contention period.

Step 4: Common nodes send GTS requests during the contention access period.

After the non-competition period ends, each node enters the competition access period, that is, the time period from t2 to t3. During this period, if a common node needs to send GTS services, it will access the channel through the time slot CSMA/CA mechanism and send GTS to the PAN coordinator Request, apply for guaranteed time slot;

After receiving the GTS request sent by the common node, the PAN coordinator replies ACK to the common node for confirmation.

It should be noted that: if the current superframe does not include the non-competition period, all nodes directly enter the contention access period after the beacon frame is sent.

Step five, the GTS time slot allocation process.

The PAN coordinator allocates the received GTS request according to the resource status in the superframe:

First, check whether the number of nodes currently assigned guaranteed time slots reaches 7: if the number of nodes has reached 7, the PAN coordinator rejects the GTS request; if not, continue to judge downward;

Then, check whether there is enough space in the active period of the superframe to allocate this GTS request: the IEEE 802.15.4 protocol stipulates that the minimum length of the contention access period is 440symbols, so the PAN coordinator needs to determine that after the guaranteed time slot is allocated for the GTS request , whether the length of the contention access period will be reduced to less than 440symbols: if yes, the PAN coordinator rejects the GTS request; if not, the GTS request meets the allocation conditions;

Finally, for the GTS request that meets the above allocation conditions, the PAN coordinator puts the allocation result of the request into the beacon frame of the n+1th superframe, to be broadcast to each common node.

Step 6, each node enters a dormant state during the inactive period.

After the competitive access period ends, each node enters the inactive period, that is, the time period from t3 to t4, during which all nodes are in a dormant state. The introduction of the inactive period is a low-power strategy, and the transmission can be adjusted by adjusting the length of the inactive period duty cycle.

Step seven, the inactive period ends at time t4, the current superframe ends, the PAN coordinator and each common node enter the next superframe, and return to step one.

The above descriptions are only two specific examples of the present invention, and do not constitute any limitation to the present invention. Obviously, for professionals in the field, after understanding the content and principles of the present invention, it is possible without departing from the principles and structures of the present invention. Various modifications and changes in form and details are made, but these modifications and changes based on the idea of the present invention are still within the protection scope of the claims of the present invention.

Claims (4)

1. a method for allocating time slots guaranteed by low delay in a wireless personal area network, characterized in that: proceed in the following order: (1) Adjust the superframe structure, that is, adjust the order of the original agreement from the contention access period, the non-competition period and the inactive period to the non-competition period, the inactive period and the contention access period; (2) The PAN coordinator broadcasts the beacon frame at the beginning of the adjusted nth superframe, and each common node receives the beacon frame, and records the protocol parameters in the local cache; (3) After the beacon transmission ends, each node enters the non-competition period, and the PAN coordinator judges whether each ordinary node has GTS service to be sent: if the ordinary node has GTS service to send, and has successfully obtained the guaranteed time slot before the current superframe , then conduct business interaction with the PAN coordinator during the non-competition period; if the common node has no GTS service to send, the current superframe does not include the non-competition period; (4) After the non-competition period ends, each node enters the inactive period, and all nodes are in a dormant state during the inactive period; (5) After the inactive period is over, all nodes enter the contention access period. At this stage, if ordinary nodes need to guarantee time slots to send services with delay requirements, they will access the channel through the time slot CSMA/CA mechanism and coordinate with the PAN The device sends a GTS request to apply for a guaranteed time slot; (6) The PAN coordinator allocates the received GTS request according to the resource status in the superframe, and broadcasts the allocation result to each common node in the beacon frame of the n+1th superframe; (7) After the contention access period ends, the nth superframe ends, and the PAN coordinator and each common node enters the n+1th superframe, and turns to step (1). 2. The method according to claim 1, wherein the beacon frame described in step (2) is an improvement to the original protocol beacon frame, that is, the competition access period end time slot in the superframe configuration field is changed to a competition Access period start time slot. 3. A method for allocating time slots with low delay guarantee in a wireless personal area network, characterized in that: proceed in the following order: 1) Adjust the superframe structure, that is, adjust the order of the original protocol from the contention access period, non-competition period and inactive period to the order of non-competition period, contention access period and inactive period; 2) The PAN coordinator broadcasts the beacon frame at the beginning of the adjusted nth superframe, each common node receives the beacon frame, and records the protocol parameters in the local cache; 3) After the beacon transmission ends, each node enters the non-competition period, and the PAN coordinator judges whether each ordinary node has GTS service to be sent: if the ordinary node has GTS service to send, and has successfully obtained the guaranteed time slot before the current superframe, Then conduct business interaction with the PAN coordinator during the non-competition period; if the common node has no GTS service to send, the current superframe does not include the non-competition period; 4) After the non-competition period ends, all nodes enter the contention access period. At this stage, if ordinary nodes need to guarantee time slots to send services with delay requirements, they will access the channel through the time slot CSMA/CA mechanism during the contention access period. And send a GTS request to the PAN coordinator to apply for a guaranteed time slot; 5) The PAN coordinator allocates the received GTS request according to the resource status in the superframe, and broadcasts the allocation result to each common node in the beacon frame of the n+1th superframe; 6) After the competition access period ends, each node enters an inactive period, during which all nodes are in a dormant state; 7) After the inactive period ends, the nth superframe ends. The PAN coordinator and each common node enter the n+1th superframe, and turn to step 1). 4. The method according to claim 3, wherein the beacon frame described in step 2) is an improvement to the original protocol beacon frame, that is, the time slot at the end of the contention access period in the superframe configuration field is changed into a contention access Period start slot.