Suspendeable CSMA / ca for IEEE 802.15. 4 systems to reduce packet drop failure

Abstract

A computer-implemented method for providing an IEEE 802.15. 4 device for an IEEE 802.15. 4 network consisting of the IEEE 802.15. 4 device based on a carrier sense multiple access (CSMA / CA) control program with collision avoidance that can be suspended and a standard CSMA / CA control program. The computer-implemented method is provided on an IEEE 802.15. 4 device and causes a processor of the IEEE 802.15. 4 device to perform steps including determining a permission of a backoff suspend and an intention of the IEEE 802.15. 4 device to perform the backoff suspend, and selecting a CSMA / CA control program that can be suspended if the backoff suspend is permitted and the IEEE 802.15. 4 device intends to perform the backoff suspend. The suspend CSMA / CA control program is configured to perform active CCA in each unit backoff period, and suspend backoff if a channel is detected to be busy, perform CCA when backoff is completed, transmit a frame when the detected channel state is an idle state, or increments a backoff number (NB) when the detected channel state is a busy state, determine whether the NB exceeds macMaxCSMABackoff, and transmit the frame when the detected channel state is an idle state. The number of retransmissions (NR) is incremented when the NB exceeds the macMaxCSMABacks, and the frame is discarded when the NR exceeds the macMaxFrameRetries.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to co-pending U.S. non-provisional patent application No. 18 / 474291, filed September 26, 2023, pursuant to 35 USC §120, which claims the benefit of U.S. provisional patent application No. 63 / 465936, filed May 12, 2023. The contents of each of the above applications are incorporated herein by reference in their entirety and the benefits thereof are fully claimed. Technical Field

[0003] This invention relates generally to channel access in wireless communication networks, and more specifically to channel access in the IEEE 802.15.4 system. Background Technology

[0004] With the advent of 5G and more advanced communication technologies, consumer Internet of Things (IoT) devices are becoming increasingly capable of supporting IoT applications. The scale of IoT networks has rapidly grown from hundreds to thousands. As more and more devices compete for channel access, the efficiency of channel access mechanisms has become a critical issue that needs to be addressed.

[0005] Furthermore, to meet the diverse needs of IoT applications, a wide range of wireless communication technologies have been developed to cater to various IoT applications, such as smart meters and smart cities. However, spectrum allocation is limited. Therefore, multiple heterogeneous wireless networks may be forced to coexist and compete for spectrum resources. Consequently, interference among networks using different communication technologies leads to more competitive channel access, further increasing the demands on the efficiency of channel access mechanisms.

[0006] IEEE 802.15.4 is a common wireless standard family developed for indoor and outdoor applications. The IEEE 802.15.4 standard has been widely implemented in commercial products such as Bluetooth and smart meters. IEEE 802.15.4 is designed to operate in Sub-1 GHz (S1G) and 2.4 GHz bands, for example, IEEE 802.15.4g can operate in both Sub-1 GHz and 2.4 GHz bands. IEEE 802.15.4 networks can consist of hundreds to thousands of devices that contend for channel access and cause data loss due to backoff failure. IEEE 802.15.4 uses a carrier sense multiple access with collision avoidance (CSMA / CA) mechanism for channel access. For each channel access attempt, IEEE 802.15.4 does not perform clear channel assessment (CCA) during the backoff period and performs CCA only after the backoff procedure is completed. This approach works well in light traffic networks but does not work well in heavy traffic networks, especially when coexisting with more aggressive interference networks such as IEEE 802.11 networks. Therefore, there is a need to provide new channel access mechanisms for IEEE 802.15.4 systems.

[0007] In the IEEE 802.15.4 CSMA / CA mechanism, the term “backoff” means delay. Therefore, the term “multiple backoff” means multiple delays. Therefore, backoff time means delay time. Furthermore, backoff failure means that the CSMA / CA algorithm fails, which returns a success state or a failure state. Furthermore, a data structure for containing data has different names at different layers, for example, the data structure is named packet at the network layer and the data structure is called frame at the MAC layer.

[0008] The IEEE 802.15.4 CSMA / CA algorithm is divided into two branches, as shown in Figure 3 Time Synchronized Channel Hopping (TSCH) branch and non-TSCH branch. The TSCH mechanism uses time division multiple access (TDMA) to ensure no transmission collision among devices within an IEEE 802.15.4 network. In the TSCH mechanism, CCA can be used to detect transmissions of interference networks such as another IEEE 802.15.4 network or IEEE 802.11 network. In the non-TSCH branch, CSMA / CA is used, where there is a need to improve the efficiency of the CSMA / CA mechanism.

[0009] Therefore, it is desirable to provide new channel access methods for IEEE 802.15.4 to achieve better performance. SUMMARY

[0010] Some embodiments are based on the recognition that the IEEE 802.15.4 CSMA / CA mechanism is designed for low data rate and low power devices, for which energy saving is critical. Therefore, the IEEE 802.5.4 CSMA / CA mechanism does not support backoff suspension, and thus, does not work well for emerging devices without energy constraints, such as power smart meters.

[0011] To this end, it is an object of some embodiments to provide a suspendable CSMA / CA mechanism for IEEE 802.15.4 to support backoff suspension, which can reduce the probability of packet dropping due to backoff failure, as Figure 4 illustrated.

[0012] Therefore, some embodiments of the present invention provide a suspendable CSMA / CA mechanism for non-TSCH channel access for the IEEE 802.15.4 standard, in which CCA is actively performed within each of the unit backoff periods, and the backoff procedure is suspended once the channel is detected to be busy.

[0013] Some embodiments are based on the recognition that in non-slotted CSMA / CA, the first backoff period and CCA period can start at any time. However, in slotted CSMA / CA, the first backoff period and CCA period must start at the backoff period boundary.

[0014] Therefore, in slotted CSMA / CA, backoff suspension must not violate the backoff boundary rule.

[0015] Some embodiments are based on the recognition that energy saving is critical for battery-powered devices. However, for devices such as power smart meters connected to power lines, energy is not constrained. These devices can actively perform CCA to increase their channel access opportunities and reduce the probability of backoff failure.

[0016] Some embodiments are based on the recognition that macMaxCSMABackoffs (i.e., the maximum number of times the CSMA / CA algorithm can be delayed) specified in the IEEE 802.15.4 CSMA / CA mechanism is designed to limit the number of backoffs (NB). Once the NB exceeds the threshold macMaxCSMABackoffs, the packet is dropped. As more and more devices compete for channel access, the NB can quickly reach the threshold macMaxCSMABackoffs. Therefore, IEEE 802.15.4 packets can be dropped.

[0017] To this end, the suspendable CSMA / CA allows for suspension of backoff, which in turn slows down the increase of the NB to avoid dropping packets when the NB exceeds macMaxCSMABackoffs. With suspendable CSMA / CA, the CCA after backoff is performed only when the channel is idle in the last unit backoff period, instead of blindly performing the CCA after the backoff is completed. As Figure 4 As exemplified, the blind CCA increases the probability of backoff failure.

[0018] Some embodiments are based on the recognition that suspendable CSMA / CA can lead to indefinite holding of the backoff process, which is undesirable.

[0019] To this end, the suspendable CSMA / CA mechanism defines a maximum backoff time (BT) threshold macSuspendedCSMAMaxTime, which is the maximum time that the suspendable CSMA / CA algorithm can be delayed in one backoff. Once the BT exceeds the threshold macSuspendedCSMAMaxTime, the suspendable CSMA / CA algorithm is terminated with a failure status.

[0020] According to some embodiments of the application, a computer-implemented method for performing a suspendable carrier sense multiple access with collision avoidance (CSMA / CA) control procedure in an IEEE 802.15.4 network composed of IEEE 802.15.4 devices is provided. In this case, the computer-implemented method causes a processor of an IEEE 802.15.4 device to perform steps comprising: determining a permission to suspend backoff by receiving an association response command from a network manager of the IEEE 802.15.4 network; obtaining an intention of the IEEE 802.15.4 device to perform the suspend backoff contained in a suspendable CSMA / CA field of an association request command; if the suspend backoff is permitted and the IEEE 802.15.4 device intends to perform the suspend backoff, selecting a suspendable CSMA / CA control procedure from a memory, wherein the suspendable CSMA / CA control procedure performs the following steps: performing a passive CCA in each of unit backoff periods; suspending a backoff procedure when detecting that a channel status of the IEEE 802.15.4 network is busy; and resuming the backoff procedure once detecting that the channel status is idle; and determining whether a backoff time exceeds a predefined threshold macSuspendedCSMAMaxTime; and transmitting a data frame when the detected channel status is idle or incrementing a number of backoffs (NB) when the detected channel status is a busy state; determining whether the NB exceeds macMaxCSMABackoffs; incrementing a number of retransmissions (NR) when the NB exceeds macMaxCSMABackoffs, and discarding the data frame when the NR exceeds macMaxFrameRetries.

[0021] Further, some embodiments of the present application provide a network device for performing suspendable carrier sense multiple access with collision avoidance (CSMA / CA) in an IEEE 802.15.4 network. The network device can include a processor; and a memory configured to store a CSMA / CA mode control program, the CSMA / CA mode control program causing the processor to perform the steps of: determining a permission of backoff suspension by receiving an association response command from a network manager of the IEEE 802.15.4 network; obtaining an intention of the IEEE 802.15.4 device to perform the backoff suspension contained in a suspendable CSMA / CA field of an association request command; selecting a suspendable CSMA / CA control program from the memory if the backoff suspension is permitted and the IEEE 802.15.4 device intends to perform the backoff suspension, wherein the suspendable CSMA / CA control program is configured to perform: performing a passive CCA in each of unit backoff periods; suspending a backoff procedure when detecting that a channel of the IEEE 802.15.4 network is busy; and resuming the backoff procedure once detecting that the state of the channel is idle; and determining whether a backoff time exceeds a predefined threshold macSuspendedCSMAMaxTime; and transmitting a data frame when the detected state is idle or incrementing a number of backoffs (NB) when the detected state of the channel is a busy state; determining whether the NB exceeds macMaxCSMABackoffs; incrementing a number of retransmissions (NR) when the NB exceeds macMaxCSMABackoffs, and discarding the data frame when the NR exceeds macMaxFrameRetries. BRIEF DESCRIPTION OF DRAWINGS

[0022] The presently disclosed embodiments will be further described with reference to the drawings. The drawings shown are not necessarily to scale, with emphasis generally being placed upon illustrating the principles of the presently disclosed embodiments.

[0023] [ Figure 1 ]

[0024] Figure 1 is a schematic diagram of an IEEE 802.15.4 network according to some embodiments of the present application;

[0025] [ Figure 2A ]

[0026] Figure 2A depicts an IEEE 802.15.4 data transmission flow diagram and transmission status reporting to upper layers according to embodiments of the present application;

[0027] [ Figure 2B ]

[0028] Figure 2Bis a structure diagram of an IEEE 802.15.4 CSMA / CA device participating in forming a network according to an embodiment of the present application; Figure 1

[0029] [ Figure 3 ]

[0030] Figure 3 shows a standard Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) algorithm specified in IEEE 802.15.4-2020 with collision avoidance according to an embodiment of the present application;

[0031] [ Figure 4 ]

[0032] Figure 4 illustrates that a standard IEEE 802.15.4 CSMA / CA algorithm can cause more backoff failures compared to a suspendable IEEE 802.15.4 CSMA / CA algorithm according to an embodiment of the present application;

[0033] [ Figure 5A ]

[0034] Figure 5A shows a flowchart of a suspendable Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) mechanism for IEEE 802.15.4 to support suspendable backoff according to an embodiment of the present application;

[0035] [ Figure 5B ]

[0036] Figure 5B shows a flowchart of a suspendable Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) method for non-slotted IEEE 802.15.4 networks according to an embodiment of the present application;

[0037] [ Figure 5C ]

[0038] Figure 5C shows a flowchart of a suspendable Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) method for slotted IEEE 802.15.4 networks according to an embodiment of the present application;

[0039] [ Figure 6 ]

[0040] Figure 6 shows a structure of a unit backoff period specified in IEEE 802.15.4 according to an embodiment of the present application;

[0041] [ Figure 7A ]

[0042] ​Figure 7A An example of performing a passive CCA during the entire unit backoff period according to an embodiment of the present application is shown;

[0043] [ Figure 7B ]

[0044] Figure 7B An example of performing a passive CCA during the entire unit backoff period according to an embodiment of the present application is shown;

[0045] [ Figure 7C ]

[0046] Figure 7C An example of performing a passive CCA during the entire unit backoff period according to an embodiment of the present application is shown;

[0047] [ Figure 8 ]

[0048] Figure 8 An example of performing a passive CCA during the entire unit backoff period according to an embodiment of the present application is shown;

[0049] [ Figure 9A ]

[0050] Figure 9A An example of performing a passive CCA during the entire unit backoff period according to an embodiment of the present application is shown;

[0051] [ Figure 9B ]

[0052] Figure 9B An example of performing a passive CCA during the entire unit backoff period according to an embodiment of the present application is shown;

[0053] [ Figure 9C ]

[0054] Figure 9C An example of performing a passive CCA during the entire unit backoff period according to an embodiment of the present application is shown; DETAILED DESCRIPTION

[0055] Various embodiments of the present application will be described herein below with reference to the accompanying drawings. It is noted that the drawings are not drawn to scale and that like elements in the drawings are denoted by like reference numerals throughout the drawings. It is also noted that the drawings are merely intended to facilitate description of the particular embodiments of the present application. They are not intended as an exhaustive description of the present application or as a limitation on the scope thereof. In addition, aspects described in connection with a particular embodiment of the present application are not necessarily limited to that embodiment and can be practiced in any other embodiment of the present application.

[0056] The IEEE 802.15.4 family of standards is a widely used wireless technology for various indoor and outdoor applications, for example, IEEE 802.15.4g is a standard in the IEEE 802.15.4 family of standards designed for outdoor wireless smart utility networks (Wi-SUN) where the power smart meters have no energy constraints.

[0057] Figure 1 A schematic diagram showing an IEEE 802.15.4 network 100 comprising a personal area network coordinator (PANC) 101 and associated nodes. The PANC and nodes communicate using IEEE 802.15.4 wireless links 103.

[0058] The topology of an IEEE 802.15.4 network can be star, mesh or tree, for example, Figure 1 The IEEE 802.15.4 network 100 shown in FIG. 1 is a tree topology. In some cases, the IEEE 802.15.4 network 100 can be an IEEE 802.15.4 based smart meter network configured in a tree topology. It should be noted that the connections of the tree type configuration can change depending on the communication status. Furthermore, not all nodes need to have a direct connection with the PANC 101. In other words, IEEE 802.15.4 nodes can communicate with the PANC 101 in a multi-hop fashion, for example, the IEEE 802.15.4 node 104 can communicate with the PANC 101 via the intermediate IEEE 802.15.4 node 102.

[0059] Figure 2A An IEEE 802.15.4 data frame transmission procedure 200 is shown. The IEEE 802.15.4 MAC sets 201 the number of retransmissions (NR) to 0 and then invokes 202 the CSMA / CA algorithm, where the standard IEEE 802.15.4-2020 CSMA / CA algorithm is as depicted in Figure 3

[0060] ​If the CSMA / CA algorithm returns a success status 203, the channel is detected to be free, and therefore, the frame transmission 204 is started. If the frame does not require an ACK (AckTX = 0) 205, the IEEE 802.15.4 MAC concludes that the transmission was successful 207 and responds to the upper layer using the data confirmation interface with a transmission success status. If the frame requires an ACK (AckTX = 1) 205 and an ACK is received within the ACK wait time period 206, the IEEE 802.15.4 also concludes that the transmission was successful 207 and responds to the upper layer using the data confirmation interface with a transmission success status. If an ACK is required and no ACK is received within the ACK wait time period 206, the IEEE 802.15.4 MAC increments NR by 1 209 and checks whether NR exceeds the threshold macMaxFrameRetries 210. If the threshold is exceeded, the IEEE 802.15.4 MAC concludes that the frame transmission failed and discards the frame 211. The IEEE 802.15.4 MAC then responds to the upper layer using the data confirmation interface with a NO_ACK status. If NR is less than or equal to the threshold macMaxFrameRetries 210, the IEEE 802.15.4 MAC makes another transmission attempt.

[0061] If the CSMA / CA algorithm returns a failure status 203, the IEEE 802.15.4 MAC checks whether the frame is a unicast frame 208. If not, the IEEE 802.15.4 MAC concludes that the transmission failed and discards the frame 211. The IEEE 802.15.4 MAC then responds to the upper layer using the data confirmation interface with a CHANNEL ACCESS FAILURE status. If the frame is a unicast frame 208, the IEEE 802.15.4 MAC increments NR by 1 209 and then checks whether NR exceeds the threshold macMaxFrameRetries 210. If the threshold is exceeded, the IEEE 802.15.4 MAC concludes that the transmission failed and discards the frame 211. The IEEE 802.15.4 MAC then responds to the upper layer using the data confirmation interface with a CHANNEL ACCESS FAILURE status. If NR is less than or equal to the threshold macMaxFrameRetries, the IEEE 802.15.4 MAC makes another transmission attempt.

[0062] Figure 2B Participating in the formation of Figure 1IEEE 802.15.4 device, where the IEEE 802.15.4 device 230 can include a memory 236, a processor 237, a power supply 240, a transceiver 238 including a transmitter, a receiver, and an energy detector, and an RF antenna 239. In addition, a control program is included in a storage device 231 connected with the memory 236, the processor 237, and the transceiver 238. The control program 231 includes a CSMA / CA mode control program 233, a standard CSMA / CA program 234, a suspendable CSMA / CA program 235, and a timer 232 used by the transceiver 238 to execute the CSMA / CA mode control program 233. Depending on the permission to suspend backoff and the intention of the IEEE 802.15.4 device 230 regarding suspension of backoff, the CSMA / CA mode control program 233 can invoke either the standard IEEE 802.15.4 CSMA / CA program 234 or the suspendable CSMA / CA program 235.

[0063] Figure 3 The standard CSMA / CA algorithm specified in IEEE 802.15.4-2020 is shown. Embodiments of the present invention provide suspendable CSMA / CA for non-TSCH IEEE 802.15.4 networks. Therefore, only the non-TSCH branch in Figure 3

[0064] Each device maintains three variables for each transmission attempt: the number of backoffs (NB), the contention window length (CW), and the backoff exponent (BE). The NB is the number of backoffs the CSMA / CA algorithm needs to defer while attempting the current transmission. The CW is the number of backoff periods that need to be free of channel activity before the transmission can start. In addition, CW0 is defined with a default value of 2. The BE relates to the number of backoff periods the device needs to wait before attempting to assess the channel.

[0065] For non-slotted IEEE 802.15.4 networks, i.e., networks that are not beacon-enabled, the standard IEEE 802.15.4 CSMA / CA algorithm initializes the NB to 0 and the BE to macMinBE. Then, the CSMA / CA algorithm defers for a random number of unit backoff periods, which is in the interval [0, 2 BE ​-1], where BE is increased from macMinBE until macMaxBE. When the random backoff / delay is completed, the CSMA / CA algorithm performs a CCA operation. If the channel is detected idle, the CSMA / CA algorithm reports success and starts the frame transmission. If the channel is detected busy, the CSMA / CA algorithm updates NB and BE to NB = NB + 1 and BE = min{BE + 1, macMaxBE}. If NB exceeds the threshold macMaxCSMABackoffs, the CSMA / CA algorithm terminates with a failure status. Otherwise, the CSMA / CA algorithm continues, i.e., another random backoff / delay is performed.

[0066] For a slotted IEEE 802.15.4 network, i.e., a beacon-enabled network, the standard IEEE 802.15.4 CSMA / CA algorithm initializes NB to 0 and CW to CW0. If battery life extension is enabled, BE is set to min{2, macMinBE}. Otherwise, BE is set to macMinBE. Then, the CSMA / CA algorithm locates the backoff period boundary, where the start of the first backoff period of each device is aligned with the start of the beacon transmission. At this boundary, the CSMA / CA algorithm delays a random number of unit backoff periods, the random number being uniformly drawn in the interval [0, 2 BE -1], where BE is increased from macMinBE until macMaxBE. When the random backoff / delay is completed, the CSMA / CA algorithm performs a CCA operation. If the channel is detected idle, the CSMA / CA algorithm reports success and starts the frame transmission. If the channel is detected busy, the CSMA / CA algorithm updates NB and BE to NB = NB + 1 and BE = min{BE + 1, macMaxBE}. If NB exceeds the threshold macMaxCSMABackoffs, the CSMA / CA algorithm terminates with a failure status. Otherwise, the CSMA / CA algorithm continues, i.e., another random backoff / delay is performed.

[0067] For a non-TSCH network, the standard IEEE 802.15.4 CSMA / CA algorithm first performs a random backoff / delay, regardless of how long the channel has been idle. With this “backoff + CCA”-based CSMA / CA mechanism, the CCA is performed blindly and, thus, as Figure 4 illustrated, this mechanism reduces the channel access probability.

[0068] IEEE 802.15.4 CSMA / CA failure packet discard

[0069] In IEEE 802.15.4, data frame transmission failures are caused by a) CSMA / CA failure or b) transmission failure. As shown in Figure 2A CSMA / CA failure occurs when the CSMA / CA algorithm terminates in a failure state due to the NB exceeding the threshold macMaxCSMABackoffs. Transmission failure occurs due to unsuccessful frame transmission, unsuccessful acknowledgement transmission, or unsuccessful subsequent acknowledgement reception. For each CSMA / CA failure or transmission failure, the number of retransmissions (NR) is incremented by 1. When NR exceeds the threshold macMaxFrameRetries due to CSMA / CA failure, the IEEE 802.15.4 frame is discarded with the CHANNEL_ACCESS_FAILURE status. When NR exceeds the threshold macMaxFrameRetries due to transmission failure, the IEEE 802.15.4 frame is discarded with the NO_ACK status. As shown in Figure 4 other transmissions can cause CSMA / CA backoff failure, which in turn can cause packet discard by the IEEE 802.15.4 device.

[0070] Figure 4 An example is shown of standard IEEE 802.15.4 CSMA / CA backoff failure caused by other transmissions. However, the suspendable CSMA / CA procedure 235 avoids backoff failure by suspending the backoff process. In Figure 4At time T2, both the suspendable IEEE 802.15.4 backoff 401 and the standard IEEE 802.15.4 backoff 402 receive a data transmission request and thus start backoff at time T2. They also draw the same number of unit backoff periods and thus need to backoff the same amount of time. However, at an earlier time Tl, the other device 403 receives a data transmission request and starts backoff. At time T3, the other device 403 completes backoff and starts CCA operation. At time T4, the other device 403 completes CCA and detects an idle channel and thus starts data transmission. The suspendable IEEE 802.15.4 backoff 401 performs active CCA in each unit backoff period and detects the transmission by the other device 403 and thus suspends its backoff process. On the other hand, the standard IEEE 802.15.4 backoff 402 does not suspend its backoff and completes backoff at time T5 and thus performs CCA at time T5. However, at time T5, the other device 403 is still transmitting. As a result, the standard IEEE 802.15.4 backoff 402 detects a busy channel and returns a backoff failure at time T7. In addition, the suspendable IEEE 802.15.4 backoff 401 detects the end of the other device's transmission at time T6 and resumes the remaining backoff. At time T8, the suspendable IEEE 802.15.4 backoff 401 completes backoff and starts CCA, which ends at time T9 and reports an idle channel. Thus, the suspendable IEEE 802.15.4 backoff 401 successfully transmits its data at time T9 without a backoff failure.

[0071] Figure 4 It is clear that the standard IEEE 802.15.4 CSMA / CA mechanism can result in more packet drops compared to the suspendable IEEE 802.15.4 CSMA / CA mechanism.

[0072] Suspendable CSMA / CA for IEEE 802.15.4

[0073] Some embodiments of the present invention provide suspendable CSMA / CA for IEEE 802.15.4 to resolve CSMA / CA failure packet drops caused by other transmissions.

[0074] To allow IEEE 802.15.4 devices to perform suspended CSMA / CA, a suspended CSMA / CA field is defined. A suspended CSMA / CA field of 1 indicates that backoff suspension is allowed. In this case, the IEEE 802.15.4 device can suspend backoff in the CSMA / CA algorithm. If the IEEE 802.15.4 device intends to perform a backoff suspension, depending on whether the IEEE 802.15.4 network is a time-slotted network, either a non-time-slotted suspended CSMA-CA algorithm 504 or a time-slotted suspended CSMA-CA algorithm 521 is invoked. A suspended CSMA / CA field of 0 indicates that backoff suspension is not allowed. In this case, the IEEE 802.15.4 device cannot perform backoff suspension in the CSMA / CA algorithm. The default value of the suspended CSMA / CA field is 0, meaning that the suspended CSMA / CA field is initialized to 0, and backoff suspension is not allowed.

[0075] Backoff suspension permission can be determined by regional regulatory agencies, network managers, application developers, or a combination thereof. For example, in the United States, more spectrum is allocated to IEEE 802.15.4 communications, and therefore backoff suspension may not be required, while in Japan, less spectrum is allocated to IEEE 802.15.4 communications, and therefore backoff suspension may be required.

[0076] In IEEE 802.15.4 networks, the Personal Area Network Coordinator (PANC) (i.e., network manager) and devices can be accessed via the invented... Figure 9A and Figure 9B The associated request command capability information fields shown are as follows: Figure 9C The associated status field of the associated response command shown implements a suspendable CSMA-CA algorithm, where... Figure 9A Describes the capability information fields of the associated request command, and Figure 9BThe capability information field of the DSME Association Request command is shown, where DSME stands for Deterministic and Synchronous Multi-Channel Extension. More specifically, when IEEE 802.15.4 devices associate with a PANC via the Association Request command, these devices set the suspendable CSMA / CA bit (bit 5) to 1 in the capability information field of the Association Request command or the DSME Association Request command to indicate their intention to perform the backoff suspension. In response, when the PANC sends back the Association Response command to the devices, the PANC sets the association status of the Association Response command to 0x04 to indicate the suspendable CSMA / CA association success, i.e., the association is successful and the backoff suspension is permitted. If the devices receive the Association Response command with the association status of 0x04, these devices set their suspendable CSMA / CA field to 1. Otherwise, if the association status is not 0x04, the suspendable CSMA / CA field remains 0, i.e., the backoff suspension is not allowed. The PANC can determine the backoff suspension permission based on the regional regulatory body, the application requirement, the network performance, the number of devices intending to perform the backoff suspension, or a combination thereof.

[0077] Even if the association status of the Association Response command is 0x04, the IEEE 802.15.4 devices can choose not to perform the backoff suspension, e.g., in the case of no traffic congestion or the devices energy supply is limited.

[0078] Figure 5A A flowchart of the invented suspendable CSMA / CA mechanism 500 for IEEE 802.15.4 to support the backoff suspension is shown. The invented CSMA / CA allows the IEEE 802.15.4 devices to perform the backoff suspension to avoid the channel access failure packet drops.

[0079] The invented suspendable CSMA / CA mechanism 500 checks whether the IEEE 802.15.4 network is a TSCH network 501. If it is a TSCH network, the standard CSMA-CA algorithm is invoked. Otherwise, the suspendable CSMA / CA mechanism checks whether the IEEE 802.15.4 network is a time-slotted network 502. For non-time-slotted networks, the invented suspendable CSMA / CA mechanism checks 503 whether backoff suspension is allowed, i.e., is the suspendable CSMA / CA field = 1 or 0. If the suspendable CSMA / CA field = 1 and the device intends to perform backoff suspension, the invented suspendable CSMA / CA mechanism enters the non-time-slotted suspendable CSMA-CA algorithm 504. Otherwise, the suspendable CSMA / CA mechanism invokes the standard CSMA-CA algorithm. For time-slotted IEEE 802.15.4 networks, the invented suspendable CSMA / CA mechanism checks 520 whether backoff suspension is allowed, i.e., is the suspendable CSMA / CA field = 1 or 0. If the suspendable CSMA / CA field = 1 and the device intends to perform backoff suspension, the invented suspendable CSMA / CA mechanism enters the time-slotted suspendable CSMA-CA algorithm 521. Otherwise, the suspendable CSMA / CA mechanism invokes the standard CSMA-CA algorithm.

[0080] Figure 5B The non-time-slotted suspendable CSMA-CA algorithm is shown. The non-time-slotted suspendable CSMA-CA algorithm sets 505 NB = 0, BT = 0 and BE = macMinBE, and uniformly draws 506 a random number of unit backoff periods in [0, 2 BE -1] and sets the number of unit backoff periods (NUBP) to the drawn random number. Then, the non-time-slotted suspendable CSMA-CA algorithm performs 507 an active CCA for a unit backoff period, as shown in Figure 7A 、 Figure 7B or Figure 7C If the channel is busy 508, the non-time-slotted suspendable CSMA-CA algorithm waits 514 until the next unit backoff period. Then, the non-time-slotted suspendable CSMA-CA algorithm updates 518 the backoff time (BT) to BT = BT + aUnitBackoffPeriod, where aUnitBackoffPeriod is the sum of aTurnaroundTime and aCcaTime, as shown in Figure 6The non-slot-suspending CSMA-CA algorithm checks 519 whether BT exceeds the threshold macSuspendedCSMAMaxTime. If it does not, the non-slot-suspending CSMA-CA algorithm performs 507 the active CCA again. In this case, the NUPB is not decreased, in other words, the backoff is suspended, because none of the backoff variables NB, CW and BE are updated. If BT exceeds the threshold macSuspendedCSMAMaxTime, the non-slot-suspending CSMA-CA algorithm terminates 517 with a failure. If the channel is idle 508, the non-slot-suspending CSMA-CA algorithm decreases the NUPB by 1 509. If the NUPB is not 0 510, the backoff is not completed. Therefore, the non-slot-suspending CSMA-CA algorithm waits 514 until the next unit backoff period. The non-slot-suspending CSMA-CA algorithm updates 518 the backoff time BT to BT = BT + aUnitBackoffPeriod. The non-slot-suspending CSMA-CA algorithm checks 519 whether BT exceeds the threshold macSuspendedCSMAMaxTime. If it does not, the non-slot-suspending CSMA-CA algorithm performs 507 the active CCA again. If BT exceeds the threshold macSuspendedCSMAMaxTime, the non-slot-suspending CSMA-CA algorithm terminates 517 with a failure. Otherwise, if the NUPB is 0 510, the backoff is completed. Then, the non-slot-suspending CSMA-CA algorithm performs 511 the standard CCA. If the channel is idle 512, the backoff is successful 513. Otherwise, if the channel is busy 512, the non-slot-suspending CSMA-CA algorithm increases NB by 1 515 and updates BE to BE = min{BE + 1, macMaxBE}. If NB exceeds 516 the predefined threshold macMaxCSMABackoffs, the non-slot-suspending CSMA-CA algorithm fails 517. Otherwise, the non-slot-suspending CSMA-CA algorithm performs another round of backoff.

[0081] Figure 5C The slot-suspending CSMA-CA algorithm is shown 521. The slot-suspending CSMA-CA algorithm sets 522 NB = 0, BT = 0 and CW = CW0. If battery life extension is enabled 523, BE is set to BE = min{2, macMinBE} 524. Otherwise, BE is set to macMinBE 525. Then, the slot-suspending CSMA-CA algorithm locates the backoff period boundary 526. At the backoff period boundary, the slot-suspending CSMA-CA algorithm performs 527 the active CCA. If the channel is idle 528, the slot-suspending CSMA-CA algorithm decreases the NUPB by 1 529. If the NUPB is not 0 530, the backoff is not completed. Therefore, the slot-suspending CSMA-CA algorithm waits 531 until the next unit backoff period. The slot-suspending CSMA-CA algorithm updates 532 the backoff time BT to BT = BT + aUnitBackoffPeriod. The slot-suspending CSMA-CA algorithm checks 533 whether BT exceeds the threshold macSuspendedCSMAMaxTime. If it does not, the slot-suspending CSMA-CA algorithm performs 527 the active CCA again. If BT exceeds the threshold macSuspendedCSMAMaxTime, the slot-suspending CSMA-CA algorithm terminates 534 with a failure. Otherwise, if the NUPB is 0 530, the backoff is completed. Then, the slot-suspending CSMA-CA algorithm performs 535 the standard CCA. If the channel is idle 536, the backoff is successful 537. Otherwise, if the channel is busy 536, the slot-suspending CSMA-CA algorithm increases NB by 1 538 and updates BE to BE = min{BE + 1, macMaxBE}. If NB exceeds 539 the predefined threshold macMaxCSMABackoffs, the slot-suspending CSMA-CA algorithm fails 534. Otherwise, the slot-suspending CSMA-CA algorithm performs another round of backoff. BE-1] a random number of unit backoff periods 527 and sets the number of unit backoff periods (NUBP) to the drawn random number. Then, the suspendable CSMA-CA algorithm performs an active CCA 528 at the backoff period boundary, as shown in Figure 7A or Figure 7C If the channel is busy 529, the time-slot suspendable CSMA-CA algorithm locates 532 the backoff period boundary and updates BT to BT = BT + aUnitBackoffPeriod 533. The time-slot suspendable CSMA-CA algorithm checks 534 whether BT exceeds a threshold macSuspendedCSMAMaxTime. If the threshold is exceeded, the time-slot suspendable CSMA-CA algorithm terminates 539 with a failure status. Otherwise, the time-slot suspendable CSMA-CA algorithm performs an active CCA 528 at the backoff period boundary again. In this case, NUPB is not decreased, in other words, the backoff is suspended, since all backoff variables NB, CW and BE are not updated. If the channel is idle 529, the time-slot suspendable CSMA-CA algorithm decreases NUPB by one 530. If NUPB is not zero 531, the backoff has not finished. Therefore, the time-slot suspendable CSMA-CA algorithm locates the backoff period boundary 432 and updates BT to BT = BT + aUnitBackoffPeriod 533. The time-slot suspendable CSMA-CA algorithm checks 534 whether BT exceeds a threshold macSuspendedCSMAMaxTime. If the threshold is exceeded, the time-slot suspendable CSMA-CA algorithm terminates 539 with a failure status. Otherwise, the time-slot suspendable CSMA-CA algorithm performs an active CCA 528 at the backoff period boundary again. Otherwise, if NUPB is zero 531, the backoff has finished. Then, the time-slot suspendable CSMA-CA algorithm performs a standard CCA 535 at the backoff period boundary. If the channel is idle 536, the time-slot suspendable CSMA-CA algorithm updates 540 CW to CW = CW - 1. If CW is equal to zero 541, the time-slot suspendable CSMA-CA algorithm is successful 542. Otherwise, the time-slot suspendable CSMA-CA algorithm performs a CCA 535 at the backoff boundary again. If the channel is busy 536, the time-slot suspendable CSMA-CA algorithm updates 537 NB, CW and BE to NB = NB + 1, CW = CW0 and BE = min{BE + 1, macMaxBE}. If NB exceeds 538 a predefined threshold macMaxCSMABackoffs, the time-slot suspendable CSMA-CA algorithm fails 539. Otherwise, the time-slot suspendable CSMA-CA algorithm performs another round of backoff.

[0082] The main difference between the standard CSMA / CA algorithm and the suspendable CSMA / CA algorithm is:

[0083] The suspendable CSMA / CA algorithm performs CCA in each unit backoff period, while the standard CSMA / CA algorithm does not perform CCA during the entire backoff process.

[0084] The suspendable CSMA / CA algorithm performs CCA 511 or CCA 535 only when it detects that the channel is idle in the last unit backoff period. On the other hand, the standard CSMA / CA algorithm performs CCA 511 or CCA 535 regardless of whether the channel is busy or idle in the last unit backoff period.

[0085] The suspendable CSMA / CA algorithm increases NB only when the other transmission starts in the CCA period in which CCA 511 or CCA 535 is being performed. On the other hand, the standard CSMA / CA algorithm increases NB regardless of whether the other transmission starts before the CCA period or in the CCA period in which CCA 511 or CCA 535 is being performed. Thus, the standard CSMA / CA algorithm has a greater probability of increasing NB, which in turn leads to more backoff failure opportunities.

[0086] By performing proactive CCA, the suspendable CSMA / CA algorithm can avoid packet drops caused by interference from non-IEEE 802.15.4 devices, such as IEEE 802.11 devices.

[0087] In summary, the suspendable CSMA / CA algorithm can reduce the opportunities for backoff failure.

[0088] In the IEEE 802.15.4 standard, the unit backoff period is longer than the CCA period. Figure 6 The structure of the unit backoff period is shown, which includes aTurnaroundTime plus a CCA period. For all PHYs except the SUN PHY operating in the 920 MHz band, the CCA period is equal to aCcaTime, and for the SUN PHY operating in the 920 MHz band, the CCA period is equal to phyCcaDuration. This indicates that, in order to perform proactive CCA 507 in the unit backoff period or proactive CCA 528 on the backoff period boundary, the CSMA / CA algorithm has multiple choices. It can perform CCA during the entire unit backoff period, or perform CCA during a portion of the unit backoff period. Figure 7A An example is shown in which the CSMA / CA algorithm performs proactive CCA during the entire unit backoff period. Figure 7BAn example is shown in which the CSMA / CA algorithm performs the active CCA in a CCA period that is located within a unit backoff period. This scenario only applies to non-slot suspendable CSMA / CA. Figure 7C An example is shown in which the CSMA / CA algorithm performs the active CCA in a CCA period that starts at the boundary of a unit backoff period.

[0089] Figure 8 An example is shown in which the non-slot suspendable CSMA-CA algorithm is performed, where there is an IEEE 802.15.4 device 801 and other devices 802, which can be IEEE 802.15.4 devices or non-IEEE 802.15.4 devices such as IEEE 802.11 devices. At time Tl, the other devices receive a data request, and therefore, the devices 802 start a first backoff. At time T2, the IEEE 802.15.4 device 801 receives a data request, and therefore, it also starts a first backoff. At time T3, the other devices 802 complete the first backoff and start a CCA operation. At time T4, the other devices 802 complete the CCA and detect that the channel is idle. Therefore, the other devices 802 start a transmission. Meanwhile at time T4, the IEEE 802.15.4 device 801 detects the transmission of the other devices 802, and therefore, the IEEE 802.15.4 device 801 suspends its first backoff, and if the other devices 802 are IEEE 802.15.4 devices, the IEEE 802.15.4 device 801 performs data reception. At time T5, the other devices 802 complete the transmission, and the channel becomes idle. Therefore, the IEEE 802.15.4 device 801 resumes its first backoff. At time T6, the IEEE 802.15.4 device completes its first backoff and starts a CCA operation. At time T7, the IEEE 802.15.4 device 801 completes the CCA, and the channel is idle. Therefore, the IEEE 802.15.4 device 801 starts a data transmission. Meanwhile, if the other devices 802 are IEEE 802.15.4 devices, the other devices 802 start data reception. Finally, at time T8, the IEEE 802.15.4 device 801 completes the data transmission.

[0090] It is noted that if the other devices 802 are non-IEEE 802.15.4 devices, the device 801 and the devices 802 cannot receive data from each other. However, they will interfere with each other. By performing a suspendable CSMA / CA algorithm, the IEEE 802.15.4 device 801 can avoid packet drops due to interference.

[0091] The above-described embodiments of the application can be implemented in any of various ways. For example, the embodiments can be implemented using hardware, software or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether provided in a single computer or distributed among multiple computers. Such processors can be implemented as integrated circuits, with one or more processors in an integrated circuit component. Though, a processor can be implemented using circuitry in any suitable format.

[0092] Also, embodiments of the application can be embodied as a method, of which an example has been provided. The acts performed as part of the method can be ordered in any suitable way. Accordingly, some embodiments can be constituted as reciting acts in an order other than the order described, which can include simultaneous performance of acts described in an exemplary embodiment as sequential acts.

[0093] The use of ordinal terms such as "first", "second", etc., in the claims to modify a claim element does not imply any priority or order of one claim element over another, or the temporal order in which acts of a method are performed, but are used merely as labels to identify elements of the claims with like

[0094] While the application has been described by example with respect to preferred embodiments thereof, it is understood that various other adaptations and modifications can be made within the spirit and scope of the application.

[0095] Accordingly, it is the intent of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the application.

Claims

1. A computer-implemented method for performing a suspendable carrier sense multiple access with collision avoidance, CSMA / CA, control procedure in an IEEE 802.15.4 network consisting of IEEE 802.15.4 devices, wherein, The computer-implemented method causes a processor of the IEEE 802.15.4 device to perform steps comprising: determining a permission of backoff suspension by receiving an association response command from a network manager of the IEEE 802.15.4 network; obtaining an intention of the IEEE 802.15.4 device to perform backoff suspension contained in a suspendable CSMA / CA field of an association request command; if the backoff suspension is permitted and the IEEE 802.15.4 device intends to perform the backoff suspension, selecting a suspendable CSMA / CA control procedure from a memory, wherein the suspendable CSMA / CA control procedure performs the following steps: performing a passive CCA in each of unit backoff periods; suspending a backoff procedure when detecting a channel status of the IEEE 802.15.4 network as busy; and resuming the backoff procedure once detecting the channel status as idle; and determining whether a backoff time exceeds a predefined threshold macSuspendedCSMAMaxTime; and sending a data frame when the detected channel status is idle or incrementing a backoff number NB when the detected channel status is a busy status; determining whether the NB exceeds macMaxCSMABackoffs; incrementing a retransmission number NR when the NB exceeds the macMaxCSMABackoffs, and discarding the data frame when the NR exceeds macMaxFrameRetries.

2. The method of claim 1, wherein, if the backoff suspension is not permitted, the IEEE 802.15.4 device applies a standard CSMA / CA channel access mechanism, wherein if the backoff suspension is permitted, the IEEE 802.15.4 device applies a suspendable CSMA / CA channel access mechanism, wherein the suspendable CSMA / CA channel access mechanism can be a non-slotted suspendable CSMA-CA algorithm or a slotted suspendable CSMA-CA algorithm.

3. The method of claim 1, wherein, The backoff suspension is permitted by a network manager of a personal area network coordinator (PANC) based on a regional regulatory body, application requirements, network performance, a number of IEEE 802.15.4 devices intending to perform backoff suspension, or a combination thereof.

4. The method of claim 3, wherein, The network manager provides a backoff suspension permission to an IEEE 802.15.4 device during a network build-up procedure, or an IEEE 802.15.4 device dynamically requests a backoff permission from the network manager.

5. The method of claim 4, wherein, The IEEE 802.15.4 device elects not to perform the backoff suspension even though the backoff suspension is permitted. The IEEE 802.15.4 device elects not to perform the backoff suspension even though the backoff suspension is permitted.

6. The method of claim 1, wherein, The IEEE 802.15.4 device performing the backoff suspension performs the active CCA within each of the unit backoff periods and suspends backoff if the channel is detected as busy, wherein the suspendable CSMA / CA channel access mechanism fails if the number of backoffs exceeds a threshold macMaxCSMABackoffs or the backoff time exceeds a threshold macSuspendedCSMAMaxTime.

7. The method of claim 6, wherein, The IEEE 802.15.4 device performing CSMA / CA with suspension first draws a random number of unit back-off periods NUBP in [0, 2 BE -1] and then performs the passive CCA in each of the unit back-off periods, wherein if the channel is busy, the back-off is suspended (i.e., NUBP is not decreased), wherein if the channel is idle, the back-off procedure is continued, wherein the back-off procedure is completed once NUBP reaches zero.

8. The method of claim 6, wherein, Once the number of unit backoff periods NUBP reaches zero, the IEEE 802.15.4 device performs a standard CCA within a CCA period.

9. The method of claim 8, wherein, If the CCA reports the channel as idle, the IEEE 802.15.4 device transmits data, wherein the CSMA / CA algorithm reports a backoff failure if the CCA reports the channel as busy and the number of backoffs NB is increased by 1.

10. The method of claim 9, wherein, If the number of backoffs NB exceeds a predefined macMaxCSMABackoffs, the CSMA / CA algorithm reports a channel access failure, wherein the number of retransmissions NR is incremented by 1 if the CSMA / CA algorithm reports a channel access failure.

11. The method of claim 10, wherein, If the number of retransmissions NR exceeds macMaxFrameRetries, the IEEE 802.15.4 MAC discards the data.

12. The method of claim 6, wherein, The IEEE 802.15.4 device is able to perform the active CCA during the whole unit backoff period or during a part of the unit backoff period.

13. A network device for performing a suspendable collision-avoidance carrier sense multiple access CSMA / CA in an IEEE 802.15.4 network, the network device comprising: a processor; and a memory configured to store a CSMA / CA mode control program, the CSMA / CA mode control program causing the processor to perform the following steps: determining a permission of backoff suspension by receiving an association response command from a network manager of the IEEE 802.15.4 network; obtaining an intention of the IEEE 802.15.4 device to perform backoff suspension contained in a suspendable CSMA / CA field of an association request command; if the backoff suspension is permitted and the IEEE 802.15.4 device intends to perform the backoff suspension, selecting a suspendable CSMA / CA control program from the memory, wherein the suspendable CSMA / CA control program is configured to perform: performing an active CCA within each of the unit backoff periods; suspending a backoff procedure when detecting that a channel of the IEEE 802.15.4 network is busy; and resuming the backoff procedure once detecting that the state of the channel is idle; and determining whether a backoff time exceeds a predefined threshold macSuspendedCSMAMaxTime; and transmitting a data frame when the detected state is idle or incrementing a number of backoffs NB when the detected channel state is a busy state; determining whether the NB exceeds a macMaxCSMABackoffs; when the NB exceeds the macMaxCSMABackoffs, incrementing a number of retransmissions NR, and when the NR exceeds a macMaxFrameRetries, discarding the data frame.

14. The network device of claim 13, wherein, If the backoff suspension is not permitted, the network device applies a standard CSMA / CA channel access mechanism, wherein if the backoff suspension is permitted, the network device applies a suspendable CSMA / CA channel access mechanism, wherein the suspendable CSMA / CA channel access mechanism can be a non-slot suspendable CSMA-CA algorithm or a slot suspendable CSMA-CA algorithm.

15. The network device of claim 13, wherein, The backoff suspension permission is determined by the network manager, a regional regulatory authority, an application developer, or a combination thereof.

16. The network device of claim 15, wherein, The network manager provides the backoff suspension permission to network devices during a network build process, or a network device in the IEEE 802.15.4 network dynamically requests a backoff permission from the network manager.

17. The network device of claim 16, wherein, Other network devices choose not to perform the backoff suspension even if the backoff suspension is permitted.

18. The network device of claim 13, wherein, The network device performs the backoff suspension to perform the active CCA in each of the unit backoff periods, and suspends the backoff process if a channel is detected to be busy, wherein the suspendable CSMA / CA channel access mechanism fails if the number of backoffs exceeds a threshold macMaxCSMABackoffs or the backoff time exceeds a threshold macSuspendedCSMAMaxTime.

19. The network device of claim 18, wherein, The network device first performs a suspendable CSMA / CA and draws a random number of unit back-off periods NUBP within [0, 2 BE -1] and then performs the active CCA within each of the unit back-off periods, wherein if the channel is busy, the back-off is suspended (i.e., NUBP is not decreased), wherein if the channel is idle, the back-off procedure continues, wherein the back-off procedure is completed once the NUBP reaches zero.

20. The network device of claim 18, wherein, Once a number of unit backoff periods NUBP reaches zero, the IEEE 802.15.4 device performs a standard CCA in a CCA period.

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