Suspendable CSMA / CA for IEEE 802.15. 4 systems to reduce packet discard caused by backoff failure

Abstract

Provided is a computer-implemented method for an IEEE 802.15. 4 device, the computer-implemented method being used for an IEEE 802.15. 4 network composed of the IEEE 802.15. 4 device based on a suspensible carrier sense multiple access / collision avoidance (CSMA / CA) control program 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 the steps including determining permission of a backoff suspend and an intention of the IEEE 802.15. 4 device to perform the backoff suspend, and selecting a suspend CSMA / CA control program 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 a detected channel state is an idle state, or increments a number of backoff (NB) when the detected channel state is a busy state, determine whether the NB exceeds macMaxCSMABackoff, and transmit a 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 Reference to Related Applications

[0002] This patent application claims the priority benefit of commonly-uncleated U.S. Provisional Patent Application No. 63 / 465,936, filed May 12, 2023, the disclosure of which is incorporated by reference herein in its entirety pursuant to 35 U.S.C. § 119(e). This application also claims the priority benefit of commonly-uncleated U.S. Nonprovisional Patent Application No. 17 / 466,420, filed September 3, 2021, which claims the benefit of U.S. Provisional Patent Application No. 63 / 236,305, filed August 24, 2021, the contents of each of which are incorporated by reference in their entirety, and the benefit of each of which is fully incorporated. TECHNICAL FIELD

[0003] The present invention relates generally to channel access in wireless communication networks, and in particular to channel access for IEEE 802.15.4 systems. BACKGROUND

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

[0005] IEEE 802.15.4 is a common wireless standard family developed for indoor and outdoor applications. IEEE 802.15.4 standards have 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) band and 2.4 GHz band, for example, IEEE 802.15.4g can operate in both Sub-1 GHz band and 2.4 GHz band. 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 / collision avoidance (CSMA / CA) mechanism for channel access. For each channel access attempt, IEEE 802.15.4 does not perform a clear channel assessment (CCA) during the backoff period and only performs a CCA after the backoff procedure is completed. This approach works well for light traffic networks, but it does not work well for heavy traffic networks, especially when coexisting with more aggressive interfering networks such as IEEE 802.11 networks. Therefore, there is a need to provide new channel access mechanisms for IEEE 802.15.4 systems.

[0006] Therefore, it is desirable to provide new channel access methods for IEEE 802.15.4 to achieve better performance. SUMMARY

[0007] 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 electric smart meters.

[0008] 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 caused by backoff failure, as shown in Figure 4

[0009] Therefore, some embodiments of the present application provide a suspendable CSMA / CA mechanism for IEEE 802.15.4 standards, in which a CCA is performed within each unit backoff period and the backoff procedure is suspended once a busy channel is detected.

[0010] ​Some embodiments are based on the recognition that energy saving is critical for battery-powered devices. However, for devices such as power line connected electric smart meters, energy is not a concern. These devices can actively perform CCA to increase their channel access opportunity and reduce the probability of backoff failure.

[0011] Some embodiments are based on the recognition that the maximum number of backoffs (macMaxCSMABackoffs) 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 discarded. As more and more devices compete for channel access, the NB can quickly reach the threshold macMaxCSMABackoffs. As a result, IEEE 802.15.4 packets can be discarded.

[0012] To this end, suspendable CSMA / CA allows backoff suspension, which in turn slows down the increase of NB by suspending the backoff process to avoid discarding packets when the NB exceeds macMaxCSMABackoffs. With suspendable CSMA / CA, CCA is performed after a backoff only when the channel is idle in the last backoff period, instead of blindly performing CCA after a backoff. Blind CCA increases the probability of backoff failure, as shown in Figure 4 BRIEF DESCRIPTION OF DRAWINGS

[0013] The presently disclosed embodiments will be further explained with reference to the drawings. The depicted drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the presently disclosed embodiments.

[0014] [ Figure 1 ]

[0015] Figure 1 is a schematic diagram of an IEEE 82.15.4 network according to some embodiments of the present invention;

[0016] [ Figure 2A ]

[0017] Figure 2A draws a data transmission flow diagram and a transmission status report to upper layers according to embodiments of the present invention;

[0018] [ Figure 2B ]

[0019] Figure 2B is a schematic diagram of the structure of an IEEE 802.15.4 CSMA / CA device participating in forming a network according to embodiments of the present invention; Figure 1

[0020] [ Figure 3 ]​​

[0021] Figure 3 A standard Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) algorithm specified in IEEE 802.15.4-2020 is shown according to embodiments of the present application;

[0022] [ Figure 4 ]

[0023] Figure 4 A standard IEEE 802.15.4 CSMA / CA algorithm according to embodiments of the present application can result in more backoff failures compared to a suspendable IEEE 802.15.4 CSMA / CA algorithm is shown;

[0024] [ Figure 5A ]

[0025] Figure 5A A flowchart of an enhanced Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) mechanism for IEEE 802.15.4 according to embodiments of the present application is shown;

[0026] [ Figure 5B ]

[0027] Figure 5B A flowchart of a suspendable Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) method for IEEE 802.15.4 according to embodiments of the present application is shown;

[0028] [ Figure 6 ]

[0029] Figure 6 A structure of a unit backoff period specified in IEEE 802.15.4 according to embodiments of the present application is shown;

[0030] [ Figure 7A ]

[0031] Figure 7A An example of performing an active CCA during the entire unit backoff period according to embodiments of the present application is shown;

[0032] [ Figure 7B ]

[0033] Figure 7B An example of performing an active CCA during a portion of the unit backoff period according to embodiments of the present application is shown;

[0034] [ Figure 8 ]

[0035] Figure 8An example of backoff suspension execution provided in a suspendable CSMA / CA mechanism is shown according to an embodiment of the present application;

[0036] [ Figure 9A ]

[0037] Figure 9A The format of the invented frame control field is shown to indicate whether backoff suspension is allowed.

[0038] [ Figure 9B ]

[0039] Figure 9B The capability information field of the invented association request command according to an embodiment of the present application is shown; and

[0040] [ Figure 9C ]

[0041] Figure 9C The capability information field of the invented DSME association request command according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0042] Various embodiments of the application are described hereinafter with reference to the drawings. It should be noted that the drawings are not to scale and that elements of similar structure or function are denoted by common reference numerals throughout the Figures. It should also be noted that the Figures are merely intended to facilitate the description of the specific embodiments of the application. They are not intended to limit the application in any way. Furthermore, aspects described in connection with a particular embodiment of the application are not necessarily limited to that embodiment and can be practiced in any of the other embodiments of the application.

[0043] 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 electrically smart meters do not have energy constraints.

[0044] Figure 1 A schematic diagram of an IEEE 802.15.4 network 100 containing a Personal Area Network Coordinator (PANC) 101 and associated nodes is shown. The PANC and nodes communicate using IEEE 802.15.4 wireless links 103.

[0045] The topology of the IEEE 802.15.4 network can be star, mesh or tree, for example, Figure 1The illustrated IEEE 802.15.4 network 100 is a tree topology. In some cases, the IEEE 802.15.4 network 100 can be an IEEE 802.15.4 based smart metering network configured in a tree topology. It should be noted that the connections of the tree type configuration can be changed according to the communication status. Moreover, not all nodes must be connected directly to 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.

[0046] Figure 2A An IEEE 802.15.4 data frame transmission procedure 200 is illustrated. The IEEE 802.15.4 MAC sets 201 the number of retransmission (NR) to 0 and then invokes 202 the CSMA / CA algorithm, where the standard IEEE 802.15.4-2020 CSMA / CA algorithm is illustrated in Figure 3

[0047] If the CSMA / CA algorithm returns a success status 203, then the channel is detected to be idle, so the frame transmission starts 204. If no ACK is required for the frame (AckTX = 0) 205, then the IEEE 802.15.4 MAC ends the transmission successfully 207 and responds to the upper layer using the data confirmation interface with the transmission success status. If an ACK is required (AckTX = 1) 205 and an ACK is received within the ACK waiting period 206, then the IEEE 802.15.4 also ends the transmission successfully 207 and responds to the upper layer using the data confirmation interface with the transmission success status. If an ACK is required and no ACK is received within the ACK waiting period 206, then the IEEE 802.15.4 increments 209 the NR by 1 and checks if the NR exceeds the threshold macMaxFrameRetries 210. If yes, then the IEEE 802.15.4 MAC ends the frame transmission unsuccessfully and discards the frame 211. The IEEE 802.15.4 MAC then responds to the upper layer using the data confirmation interface with the NO_ACK status. If the NR is less than or equal to the threshold macMaxFrameRetries 210, then the IEEE 802.15.4 MAC makes another transmission attempt.

[0048] ​If the CSMA / CA algorithm returns a failure status 203, the IEEE 802.15.4 MAC checks if the frame is a unicast frame 208. If not, the IEEE 802.15.4 MAC ends the transmission failure and discards the frame 211. Then, the IEEE 802.15.4 MAC responds to the upper layer using the data confirm interface with a CHANNEK_ACCESS_FAILURE status. If the frame is a unicast frame 208, the IEEE 802.15.4 MAC increments NR 209 by 1 and then checks if NR exceeds the threshold macMaxFrameRetries 210. If yes, the IEEE 802.15.4 MAC ends the transmission failure and discards the frame 211. Then, the IEEE 802.15.4 MAC responds to the upper layer using the data confirm interface with a CHANNEK_ACCESS_FAILURE status. If NR is less than or equal to the threshold macMaxFrameRetries, the IEEE 802.15.4 MAC makes another transmission attempt.

[0049] Figure 2B An example of the structure of an IEEE 802.15.4 device participating in forming a network of Figure 1 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 of backoff suspension and the intention of the IEEE 802.15.4 device 230 to suspend the backoff, the CSMA / CA mode control program 233 can call either the standard IEEE 802.15.4 CSMA / CA program 234 or the suspendable CSMA / CA program 235.

[0050] Figure 3 The standard CSMA / CA algorithm in IEEE 802.15.4-2020 is shown. Embodiments of the present invention provide suspendable CSMA / CA for non-slotted IEEE 802.15.4 networks. Therefore, only the Figure 3non-slot branch in the IEEE 802.15.4 standard. For non-slot IEEE 802.15.4 networks, i.e. beaconless networks, the standard IEEE 802.15.4 CSMA / CA algorithm initializes the number of backoffs (NB) to 0 and the backoff exponent (BE) to macMinBE. Then, the CSMA / CA algorithm delays a random number of unit backoff periods with a random number uniformly drawn in the interval [0, 2 BE -1], which is called the backoff window or delay window, where BE starts at macMinBE and increases up to macMaxBE. When the random backoff / delay is completed, the CSMA / CA algorithm performs a CCA operation. If the channel is detected as idle, the CSMA / CA algorithm reports success and the frame transmission starts. If the channel is detected as 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 (goes to random backoff / delay).

[0051] For non-slot networks, the standard IEEE 802.15.4 CSMA / CA algorithm first performs a random delay, regardless of how long the channel has been idle. With this "backoff + CCA" based CSMA / CA mechanism, the CCA is performed blindly, thus reducing the channel access probability, as shown in Figure 4 .

[0052] IEEE 802.15.4 CSMA / CA failure packet discarding

[0053] In IEEE 802.15.4, data frame transmission failures are caused by a) CSMA / CA failure or b) transmission failure. A CSMA / CA failure occurs when the CSMA / CA algorithm terminates with a failure status because NB exceeds the threshold macMaxCSMABackoffs, as shown in Figure 2A . A transmission failure occurs due to unsuccessful frame transmission or unsuccessful acknowledgement transmission or later 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 a CSMA / CA failure, the IEEE 802.15.4 frame with the CHANNEL_ACCESS_FAILURE status is discarded. When NR exceeds the threshold macMaxFrameRetries due to a transmission failure, the IEEE 802.15.4 frame with the NO_ACK status is discarded. Other transmissions can cause a CSMA / CA backoff failure, as shown in Figure 4As shown, this in turn can cause packet drops for the IEEE 802.15.4 device.

[0054] Figure 4 An example of a standard IEEE 802.15.4 CSMA / CA backoff failure caused by other transmissions is shown. However, the suspendable CSMA / CA procedure 235 avoids backoff failure by suspending the backoff process. In Figure 4 In the example, the suspendable IEEE 802.15.4 backoff device 401 and the standard IEEE 802.15.4 backoff device 402 receive a data transmission request at time T2 and thus start backoff at time T2. They also extract the same number of unit backoff periods and thus need to backoff the same amount of time. However, at an earlier time Tl, 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 device 401 performs active CCA in each unit backoff period and detects the transmission of the other device 403 and thus suspends its backoff process. On the other hand, the standard IEEE 802.15.4 backoff device 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 device 402 detects a busy channel and returns a backoff failure at time T7. Meanwhile, the suspendable IEEE 802.15.4 backoff device 401 detects the end of the other device transmission at time T6 and resumes the remaining backoff. At time T8, the suspendable IEEE 802.15.4 backoff device 401 completes backoff and starts CCA, which ends at time T9 and reports an idle channel. Thus, the suspendable IEEE 802.15.4 backoff device 401 successfully transmits its data at time T9 without backoff failure.

[0055] Figure 4 It is clear that the standard IEEE 802.15.4 CSMA / CA mechanism can cause more packet drops compared to the suspendable IEEE 802.15.4 CSMA / CA mechanism.

[0056] Suspendable CSMA / CA for IEEE 802.15.4

[0057] 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.

[0058] To allow suspendable CSMA / CA, a suspendable CSMA / CA field is defined. Suspendable CSMA / CA field = 1 indicates that backoff suspension is allowed. In this case, IEEE 802.15.4 devices can suspend backoff in the CSMA / CA algorithm. If IEEE 802.15.4 devices intend to perform backoff suspension, they invoke suspendable CSMA CA algorithm 504. Suspendable CSMA / CA field = 0 indicates that backoff suspension is not permitted. In this case, IEEE 802.15.4 devices cannot perform backoff suspension in the CSMA / CA algorithm.

[0059] The backoff suspension permission can be determined by the regional regulator or network manager or application developer or a combination of them, for example, in the United States, more spectrum is allocated to IEEE 802.15.4 communication, so there is no need for backoff suspension, and in Japan, less spectrum is allocated to IEEE 802.15.4 communication, so backoff suspension is needed.

[0060] Even if suspendable CSMA / CA field = 1, IEEE 802.15.4 devices can choose not to perform backoff suspension, for example, if there is no traffic congestion or device energy supply is limited.

[0061] Figure 5A A flowchart of the invented CSMA / CA 500 with backoff suspension support for IEEE 802.15.4 is shown. The invented CSMA / CA allows IEEE 802.15.4 devices to perform backoff suspension to avoid channel access failure packet drops.

[0062] The invented CSMA / CA 500 checks whether the IEEE 802.15.4 network is a TSCH network 501 and a time-slotted network 502. For non-time-slotted networks, the invented CSMA / CA checks 503 whether backoff suspension is allowed, i.e., suspendable CSMA / CA field = 1 or 0. If suspendable CSMA / CA field = 1 and the device intends to perform backoff suspension, the invented CSMA / CA goes to suspendable CSMA / CA algorithm 504.

[0063] Figure 5B The suspendable CSMA / CA 504 is shown. The suspendable CSMA / CA algorithm sets 505 NB = 0 and BE = macMinBE. Then, it checks 506 whether the backoff suspension is allowed. If the backoff suspension is not allowed, the suspendable CSMA / CA algorithm 504 goes to the normal CSMA / CA algorithm 507. If the backoff suspension is allowed, the suspendable CSMA / CA algorithm 504 goes to the backoff suspension algorithm 508. BEThe suspended CSMA / CA algorithm uniformly extracts 506 a random number of unit backoff periods and sets the number of unit backoff periods (NUBP) to the extracted random number. Then, the suspended CSMA / CA algorithm performs 507 the active CCA for each unit backoff period, as shown in Figure 5B If the channel is busy 508, the suspended CSMA / CA algorithm waits 514 until the next unit backoff period and performs 507 the active CCA again. In this case, the NUPB is not decreased, in other words, the suspension backoff is not decreased because all backoff parameters including the NB are not updated. If the channel is idle 508, the suspended CSMA / CA algorithm decreases 509 the NUPB by 1. If the NUPB 510 is not 0, the backoff is not yet completed. Therefore, the suspended CSMA / CA algorithm waits 514 until the next unit backoff period and performs 507 the active CCA again. Otherwise, if the NUPB 510 is 0, the backoff has been completed. Then, the suspended 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 suspended CSMA / CA algorithm increases 515 the NB by 1. If the NB exceeds 516 a predefined threshold macMaxCSMABackoffs, the backoff fails 517. Otherwise, the suspended CSMA / CA algorithm performs another round of backoff.

[0064] Key differences between the standard CSMA / CA algorithm and the suspended CSMA / CA algorithm:

[0065] The suspended CSMA / CA algorithm performs CCA in each unit backoff period, while the standard CSMA / CA algorithm does not perform CCA during the whole backoff procedure.

[0066] The suspended CSMA / CA algorithm performs CCA 511 only when the channel in the last unit backoff period is detected to be idle. On the other hand, the standard CSMA / CA algorithm performs CCA 511 regardless of whether the channel in the last unit backoff period is busy or idle.

[0067] The suspended CSMA / CA algorithm increases the NB only when other transmissions start in the CCA period in which CCA 511 is being performed. On the other hand, the standard CSMA / CA algorithm increases the NB regardless of whether other transmissions start before the CCA period or in the CCA period in which CCA 511 is being performed. Therefore, the standard CSMA / CA algorithm has a greater probability of increasing the NB, which in turn leads to more opportunities for backoff failure.

[0068] By performing the active CCA, the puschable CSMA / CA algorithm has the ability to avoid packet drops caused by interference from non-IEEE 802.15.4 devices such as IEEE 802.11 devices.

[0069] In summary, the puschable CSMA / CA algorithm can reduce the chance of backoff failure.

[0070] 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. The CCA period is equal to aCcaTime for all PHYs except SUN PHYs operating in the 920 MHz band, and is equal to phyCcaDuration for SUN PHYs operating in the 920 MHz band. This indicates that in order to perform 507 the active CCA within the unit backoff period, the CSMA / CA algorithm has multiple choices. It can perform the CCA during the entire unit backoff period or during a portion of the unit backoff period. Figure 7A An example is shown in which the CSMA / CA algorithm performs the active CCA during the entire unit backoff period. Figure 7B An example is shown in which the CSMA / CA algorithm performs the active CCA within the CCA period, i.e., a portion of the unit backoff period.

[0071] Figure 8An example of the suspendable CSMA / CA algorithm execution is shown, where there is an IEEE 802.15.4 device 801 and other device 802, which can be an IEEE 802.15.4 device or a non-IEEE 802.15.4 device, such as an IEEE 802.11 device. At time Tl, the other device receives a data request and thus device 802 starts a first backoff. At time T2, IEEE 802.15.4 device 801 receives a data request and thus also starts a first backoff. At time T3, the other device 802 completes the first backoff and starts a CCA operation. At time T4, the other device 802 completes the CCA and detects that the channel is idle. Thus, the other device 802 starts transmission. At the same time T4, IEEE 802.15.4 device 801 detects the transmission of the other device 802 and thus, if the other device 802 is an IEEE 802.15.4 device, suspends its first backoff and performs data reception. At time T5, the other device 802 completes the transmission and the channel becomes idle. Thus, 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, IEEE 802.15.4 device 801 completes the CCA and the channel is idle. Thus, it starts data transmission. At the same time, if the other device 802 is an IEEE 802.15.4 device, the other device 802 starts data reception. Finally, at time T8, IEEE 802.15.4 device 801 completes the data transmission.

[0072] It should be noted that if the other device 802 is a non-IEEE 802.15.4 device, devices 801 and 802 cannot receive data from each other. However, they can interfere with each other. By performing the suspendable CSMA / CA algorithm, IEEE 802.15.4 device 801 can avoid packet drops due to interference.

[0073] In an IEEE 802.15.4 network, a Personal Area Network Coordinator (PANC), i.e. a network manager, and devices can communicate via Figure 9A the frame control field of the invented association response command shown and Figure 9B and Figure 9C the capability information field of the association request command shown, wherein Figure 9B the capability information field of the association request command is drawn, and Figure 9CThe capability information field of the DSME association request command is shown, where DSME stands for Deterministic and Synchronous Multi-Channel Extension. More specifically, 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 backoff suspension. In response, the PANC sets the suspendable CSMA / CA bit (bit 7) to 1 in the frame control field of the association response command to indicate that backoff suspension is not permitted, or sets the suspendable CSMA / CA bit (bit 7) to 0 in the frame control field of the association response command to indicate that backoff suspension is not permitted. The PANC can determine the backoff suspension permission based on the zone regulator or application requirements or network performance or the number of devices that intend to perform backoff suspension or a combination thereof.

[0074] The above-described embodiments of the present application can be implemented in any of numerous 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. However, a processor can be implemented using circuitry in any suitable format.

[0075] Additionally, embodiments of the present 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, embodiments can be constructed in which acts are performed in an order different than illustrated, which can include performing some acts simultaneously, even though shown as serial act in illustrative embodiments.

[0076] The use of ordinal terms such as "first", "second", "third" etc. to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another, or of an action performed in one claim element over an action performed in another, but are used merely as labels to identify elements of the claims with particular names. The use of "a" or "an" to refer to an element does not exclude the presence of more than one of the element.

[0077] While the present application has been described by example with respect to preferred embodiments, it is understood that various other adaptations and modifications can be made within the spirit and scope of the present application.

[0078] 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 present application.

Claims

1. A computer-implemented method for performing a suspendable carrier sense multiple access / collision avoidance (CSMA / CA) control procedure in an IEEE 802.15.4 network composed of IEEE 802.15.4 devices, wherein, The computer-implemented method causes a processor of the IEEE 802.15.4 device 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 the 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 a memory, wherein the suspendable CSMA / CA control program performs the following steps: performing a passive CCA in each unit backoff period of the unit backoff period; 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 status of the channel is idle; and sending a data frame when the detected status is idle or incrementing a number of backoffs (NB) when the detected status of the channel is a busy status; determining whether the NB exceeds a macMaxCSMABackoffs; incrementing a number of retransmissions (NR) when the NB exceeds the macMaxCSMABackoffs, and discarding the data frame when the NR exceeds a macMaxFrameRetries.

2. The computer-implemented 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.

3. The computer-implemented method of claim 1, wherein, The backoff suspension permission is determined by the network manager PANC based on a zone regulator or application requirements or network performance or a number of IEEE 802.15.4 devices intending to perform backoff suspension or a combination thereof.

4. The computer-implemented method of claim 3, wherein, The network manager provides the backoff suspension permission to IEEE 802.15.4 devices during a network construction process or IEEE 802.15.4 devices dynamically request a backoff permission from the network manager.

5. The computer-implemented method of claim 4, wherein, The IEEE 802.15.4 device chooses not to perform the backoff suspension even if the backoff suspension is permitted.

6. The computer-implemented method of claim 1, wherein, The IEEE 802.15.4 device performs the backoff suspension to perform the passive CCA in each unit backoff period of the unit backoff period and suspends backoff if a channel is detected to be busy.

7. The computer-implemented method of claim 6, wherein, The IEEE 802.15.4 device that performs suspendable CSMA / CA first in The system extracts a unit backoff period of random number of bytes (NUBP) and then performs the active CCA within each unit backoff period, wherein if the channel is busy, the backoff is suspended (i.e., NUBP is not reduced), wherein if the channel is idle, the backoff process continues, and wherein the backoff process is completed once NUBP reaches zero.

8. The computer-implemented method of claim 6, 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.

9. The computer-implemented method of claim 8, wherein, The IEEE 802.15.4 device sends a data frame if the CCA reports an idle channel, wherein the CSMA / CA algorithm reports a backoff failure if the CCA reports a busy channel and a number of backoffs (NB) is incremented by 1.

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

11. The computer-implemented method of claim 10, wherein, The IEEE 802.15.4 MAC discards the data if the number of retransmissions (NR) exceeds macMaxFrameRetries.

12. The computer-implemented method of claim 6, wherein, The IEEE 802.15.4 device is capable of performing an active CCA during the entire unit backoff period or during a portion of the unit backoff period.

13. A network device for performing suspendable carrier sense multiple access / collision avoidance (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 that causes 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 a backoff suspension contained in a suspendable CSMA / CA field of the 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 unit backoff period; 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 status of the channel is idle; and sending a data frame when the detected status is idle or incrementing a number of backoffs (NB) when the detected status of the channel is a busy status; determining whether the NB exceeds a macMaxCSMABackoffs; incrementing a number of retransmissions (NR) when the NB exceeds the macMaxCSMABackoffs, and discarding the data frame when the NR exceeds a macMaxFrameRetries.

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.

15. The network device of claim 13, wherein, The backoff suspension permission is determined by the network manager or a regional regulator or 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 formation procedure or network devices in the IEEE 802.15.4 network dynamically request 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 procedure if a channel is detected to be busy.

19. The network device of claim 18, wherein, The network device first performs a suspendable CSMA / CA and, in extracts a random number (NUBP) of unit backoff periods and then performs the active CCA in each of the unit backoff periods, wherein if the channel is busy, the backoff is suspended (i.e., NUPB is not decremented), wherein if the channel is idle, the backoff process continues, wherein the backoff process is completed once NUPB reaches zero.

20. The network device of claim 18, wherein, Once the 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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