Mitigating interference in channel access involving multiple systems

Abstract

In connection with an RF communication system, example aspects relate to a method for use in a communication system in which a first system (e.g., 802.11) is asynchronous based and susceptible to interference from a second system (e.g., synchronous based LTE-CV2X). Such interference is due to overlapping spectrum used by the first and second systems. To mitigate the interference problem, an example method extends time for a message in the first system based on information about occupancy of the channel, and transmits the message relative to an end of a recurring transmission allocated for use by the second system.

Description

TECHNICAL FIELD

[0001] Aspects of various embodiments are directed to RF frequency co- channel coexistence involving an asynchronous-based system and a second potentially interfering system, which can be synchronous-based in that its transmissions rely on a synchronous network communication protocol. BACKGROUND

[0002] Different wireless communication systems are implemented in various environments in different regions around the world for use of the same frequency spectrum. Without careful deployment, such systems can interfere with each other. Non-limiting examples of such spectrum sharing (or spectrum contention) systems include technologies using Intelligent Transport Systems (ITS), where the spectrum for implementing communications to a vehicle-to-anything transceiver or “V2X” has been discussed for some time.

[0003] These and other problems have presented challenges to the efficiency of spectrum sharing for asynchronous and synchronous communication system implementations for various applications. SUMMARY

[0004] Various example embodiments relate to spectrum sharing between two or more technology groups, specifically co-channel coexistence, for example, those problems set forth above, and / or other example embodiments that can become apparent from the disclosure below relate to any mix of two or more technologies, specifically, C-V2X-based (e.g., LTE-V2X or 5G NR V2X) technologies and IEEE 802.11-based technologies.

[0005] In certain example embodiments, aspects of the present disclosure relate to a first asynchronous communication system that is susceptible to interference from a second (synchronous communication) system. This second system, which can refer to one or more (e.g., independently operating) systems, can produce interference (e.g., message collisions and / or contention for channel access) to the first system, and the first system modifies transmission of its messages to overcome or mitigate such interference.

[0006] In one example, the present disclosure relates to a method for communicating on a channel in a first system, the first system being asynchronous-based and susceptible to interference from a second system that at least partially overlaps the channel of the first system, the method comprising: extending a time for a message of the first system to be transmitted relative to an end of a recurring transmission time allocated for use by the second system based on information about an occupancy duration of the channel.

[0007] In one or more embodiments, the method can additionally include evaluating or measuring whether the channel is too busy relative to a threshold, wherein the information about the duration of occupancy of the channel comprises data based on the step of evaluating or measuring whether the channel is too busy, and wherein the second system transmits messages in synchronization time slots according to the recurring transmission time, and wherein the end of the recurring transmission time is aligned at the next start time of one of the synchronization time slots or just after the end of one of the synchronization time slots.

[0008] In one or more embodiments, the method can additionally include evaluating or measuring whether the channel is too busy relative to a threshold corresponding to a synchronization frame allocated to messages to be transmitted via the second system.

[0009] In one or more embodiments, the method can additionally include evaluating the channel as persistently busy relative to a threshold corresponding to a synchronization subframe of the second system, and in response, increasing a contention parameter to indicate that an increased random or pseudo-random backoff period will be applied before a station of the first system is to access the channel.

[0010] In one or more embodiments, the channel can be common or fully overlapping via the first system and the second system for transmitting messages, and the first system can conform to a CSMA communication protocol and the second system can conform to a synchronization-based communication protocol.

[0011] In one or more embodiments, the first system can be based on or use a CSMA or 802.11 communication protocol, and the second system can be based on or use a C-V2X communication protocol, and the first system can include an RF transceiver integrated with a microcontroller or computer circuitry for controlling the propagation of the messages of the first system.

[0012] In one or more embodiments, the channel can be common or fully overlapping via the first system and the second system for transmitting messages, and the first system can conform to a CSMA communication protocol and the second system can conform to a synchronization-based communication protocol, and the method can additionally include evaluating the channel as persistently busy relative to a threshold corresponding to a synchronization subframe of the second system, and in response, increasing a contention parameter to indicate that an increased contention window will be used to apply a new pseudo-random backoff period before a station of the first system is to access the channel.

[0013] In one or more embodiments, the method can additionally include dispersing the messages of the first system over individual transmission times to avoid queuing or congestion of the messages of the first system, and / or to moderate temporary contention for the channel when the channel becomes available for use by the first system.

[0014] In one or more embodiments, the information about the duration of occupancy of the channel can be based on detection of the recurring transmission times by monitoring and aggregating statistics as background processing while a station is operating in at least one of a receive mode and a transmit mode.

[0015] In one or more embodiments, the method can additionally include a station of the first system detecting the recurring transmission times of the second system by detecting energy other than CSMA / CA traffic.

[0016] In one or more embodiments, the method can additionally include a station of the first system detecting the recurring transmission times of the second system by detecting whether there are no more than a threshold number of CSMA / CA packets received within a time period corresponding to N recurring transmission time allocations, where N is a positive integer equal to the threshold number.

[0017] In one or more embodiments, the method can additionally include a station of the first system detecting the recurring transmission times of the second system by determining exact start and stop times of a superframe using a synchronized time source.

[0018] In one or more embodiments, the method can additionally include a station of the first system detecting the recurring transmission times of the second system by inferring from one or more previous detections of recurring transmission times to predict an upcoming start of a C-V2X slot structure based on known repetitive properties of the C-V2X slot structure.

[0019] In one or more embodiments, the method can additionally include a station of the first system detecting the recurring transmission times of the second system by using information associated with detected CSMA / CA traffic and in conjunction with a predicted presence of a C-V2X slot to provide at least a portion of the information about the duration of occupancy of the channel.

[0020] In one or more embodiments, the information about the duration of occupancy of the channel can be based at least in part on a detection of one of the recurring transmission times of the second system being at least one of: longer than a duration of a desired medium containing transmission; and longer than one millisecond.

[0021] In one or more embodiments, the step of extending the time for messages to be transmitted by the first system can include allocating the messages to be transmitted by the first system to cause a delay of messages to circuitry ready for transmission, or associated with controlling transmission of each message by the first system, and the step of extending the time for messages to be transmitted by the first system can include allocating the messages to be transmitted by the first system at one of a plurality of OSI data processing layers higher than a physical layer to cause a delay of each message to be transmitted by the first system.

[0022] In one or more embodiments, the step of extending the time for messages to be transmitted by the first system can include allocating the messages to be transmitted by the first system to cause a delay of messages to circuitry ready for transmission, or associated with controlling transmission of each message by the first system, and the step of extending the time for messages to be transmitted by the first system can include allocating the messages to be transmitted by the first system at one of a plurality of OSI data processing layers higher than a physical layer to cause a delay of each message to be transmitted by the first system.

[0023] In one or more embodiments, the step of extending the time for messages to be transmitted by the first system can include allocating the messages to be transmitted by the first system to cause a delay of messages to circuitry ready for transmission, or associated with controlling transmission of each message by the first system, and the step of extending the time for messages to be transmitted by the first system can include allocating the messages to be transmitted by the first system at one of a plurality of OSI data processing layers higher than a physical layer to cause a delay of each message to be transmitted by the first system.

[0024] In another example, the disclosure relates to a device (e.g., a system, radio, transceiver circuitry, or other such related circuitry) for communicating on a channel via a first system that is asynchronous and susceptible to interference from a second system that communicates on a spectrum that at least partially overlaps the channel of the first system. The device includes processing circuitry to use information about an occupancy duration of the channel and to extend a time for messages of the first system to be transmitted relative to an end of a recurring transmission time allocated for use by the second system.

[0025] In a more particular example, the device can have processing circuitry configured to cause the time for a message to be transmitted by the first system to be extended to include holding or delaying the start of a CSMA / CA procedure for the first message to be transmitted by the first system, and then passing an allocated time to circuitry associated with controlling the transmission of each message by the first system. Alternatively and / or in combination, the device can have processing circuitry configured to cause the time for a message to be transmitted by the first system to be extended to include evenly distributing the messages to be transmitted by the first system over the time granted or allocated for transmission by the first system, so that the messages are proportionally moved or delayed relative to the end of the current one of the cyclic transmission times of the second system, while preserving the previous order in which the messages are to be transmitted, and to prevent the messages for transmission from otherwise backing up at the end of the current one of the cyclic transmission times of the second system.

[0026] In yet another particular example, time slot timing discovery and message queuing and transmission for measurement can be used to implement cooperative channel sharing.

[0027] Another example involves a method for use in a communication system in which a first system is asynchronous-based and subject to interference from a second system. Such interference is due to the spectrum used by the first and second systems at least partially or completely overlapping, such as when interference occurs due to a transceiver of a second (synchronous-based, e.g., C-V2X) system operating on the same channel as an asynchronous-based (e.g., CSMA or 802.11) system. To mitigate such interference problems, in one example, the time for a message to be transmitted via the first system is processed to be extended based on information regarding the occupancy of the channel, and then the message is transmitted relative to the end of a cyclic transmission allocated for use by the second system. This example method can avoid queuing or jamming of messages by the first system, and / or otherwise mitigate temporary contention for access to the channel when the channel becomes available for use by the first system.

[0028] In one or more embodiments, the information about the duration of occupancy of the channel can be based at least in part on a detection of one of the recurring transmission times of the second system that is at least one of: longer than a duration of a desired medium containing transmissions; and longer than one millisecond, and wherein the processing circuitry is to hold or delay allocation of messages to be transmitted by the first system for a time, then allocate the held or delayed messages of the first system to be transmitted evenly over the time granted or allocated to the first system for transmission, so that the messages are proportionally moved or delayed relative to an end of the one of the recurring transmission times of the second system currently, while preserving a previous order in which the messages are to be transmitted.

[0029] The above discussion / summary is not intended to describe every embodiment or implementation of the present disclosure. The figures and detailed description that follow also illustrate various embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0030] Various example embodiments can be more fully understood with the following detailed description in connection with the accompanying drawings, in which:

[0031] Figure 1A is a system level diagram showing an example of a first system that can be interfered with due to a second system, in accordance with the present disclosure;

[0032] Figure 1B is a block diagram showing an example of a C-V2X transceiver station, in accordance with the present disclosure;

[0033] Figure 2 is a time diagram showing an example of a C-V2X system sharing a frequency channel with an ITS-G5 system, in accordance with the present disclosure;

[0034] Figure 3 is a time diagram showing an example of a time sharing method for two technologies, in accordance with the present disclosure;

[0035] Figure 4 is a time versus position diagram showing an example of vehicle movement and subsequent packet success, in accordance with the present disclosure;

[0036] Figure 5 is a time diagram showing an example of an ITS-G5 station transmitting messages in unused C-V2X subframes, in accordance with the present disclosure;

[0037] Figure 6 is a flow diagram showing a set of example activities and / or dataflows for a system for adjusting backoff time in CSMA / CA in broadcast mode, in accordance with the present disclosure;

[0038] Figure 7a time diagram illustrating an example of sharing time using an inserted latency for LTE systems and ITS-G5 systems according to the present disclosure;

[0039] Figure 8 a time diagram illustrating an example of performing a pre-busy check for ITS-G5 according to the present disclosure; and

[0040] Figure 9 a flow diagram illustrating a set of example activities and / or data flows for a system type for implementing a CSMA / CA transmission procedure using a pre-busy check according to the present disclosure.

[0041] While various embodiments discussed herein can be capable of various modifications and alternative forms, aspects of the various embodiments are shown and described in detail in the figures and will be described in detail in the following detailed description. It should be understood, however, that there is no intent to limit the disclosure to the particular embodiments described. DETAILED DESCRIPTION

[0042] Aspects of the present disclosure are believed to be applicable to a variety of different types of devices, systems, and methods involving multiple data transmission systems sharing a frequency channel by a time sharing approach, in an effort to mitigate collisions due to interference of transmissions, such as when two transceiver stations of respective first and second systems are geographically close enough to each other. While the following discussion relates to various protocols for certain communication systems (e.g., IEEE 802.11, IEEE 802.11p, IEEE 802.11bd, LTE-V2X sidelink, 5G NR V2X, C-V2X, etc.), such discussion is merely used to provide an exemplary context that helps explain such aspects, and the present disclosure is not necessarily limited as such.

[0043] Accordingly, in the following description, specific details are set forth to describe various examples presented herein. It should be apparent, however, to one skilled in the art that one or more other examples and / or variations of the examples presented herein can be practiced without such specific details. In other instances, well-known features have not been described in detail so as not to obscure the description of the examples herein. For ease of illustration, the same reference numerals can be used in different drawings to refer to the same or like elements or additional instances of the same element. Also, while aspects and features can be described in the context of some examples, it should be understood that features from one example can be combined with features of another example, even if explicitly described in combination in another example, unless explicitly stated otherwise.

[0044] In particular examples according to the present disclosure, certain embodiments relate to a method for use in a communication system in which a first system (e.g., 802.11 using a CSMA channel access mechanism) is thus asynchronous based (i.e., uses asynchronous network transmissions) and is susceptible to interference from a second system (e.g., a synchronous based C-V2X). Such interference is due to the overlapping spectrum used by the first and second systems. To mitigate the interference problem, the example method extends the time for a message in the first system based on information about the occupancy of the channel and transmits the message relative to the end of a recurring transmission time allocated for use by the second system (e.g., the next start time or just after the end of a LTE-V2X slot). In certain more particular examples, the first system can include a radio frequency (RF) transceiver integrated with a microcontroller or computer circuitry (e.g., in a vehicle communication system) for controlling the propagation of messages of the first system. The example method can avoid queuing or congestion of messages of the first system and / or otherwise mitigate the first system from being subject to temporary contention for access to the channel when the channel becomes available for use by the first system. The acronym LTE-V2X is an example of a more general class of technology that can be referred to as C-V2X, which can be, for example, 4G LTE-V2X sidelink Mode 3 or Mode 4, 4G LTE-V2X Uu, 5G NR-V2X, etc.

[0045] In another particular example according to the present disclosure, certain embodiments relate to a method in which a first system evaluates a channel as persistently busy relative to a threshold corresponding to a synchronous subframe of a second system. In response to finding the channel persistently busy, the first system can increase a contention parameter to indicate that an increased contention window (CW) range can be used for applying a new (pseudo) random backoff period. The backoff period is used by the first system to delay before it accesses the channel. The evaluation of the channel can be done based on detection of a recurring transmission time (C-V2X). The detection can be done by a first system station that acts as a receiver, monitors the channel and aggregates statistics related to transmission times.

[0046] Reference will now be made to the drawings and to the aspects and embodiments disclosed above, Figure 1AAn example of two transceiver systems operating at least some of the time on the same spectral channel is shown. In this example, the second system 150 is a synchronous based system (e.g., LTE-CV2X) that transmits in defined time slots. The first system 110 is an asynchronous based system (e.g., 802.11) and can be susceptible to interference when operating in the same channel as the second system, for example, when two stations associated with the first and second systems respectively are simultaneously using or attempting to use the same channel (or partially overlapping spectrum used by one of the channels). To mitigate the effects of such interference, the first system can use the method of slot timing detection depicted as block 125 of the second system transmissions to timely propagate messages to detect the end of its timing slots. From this information, an assessment can be made by block 130 to determine when transmission block 140 can send the next message from the transmission queue 135. Figure 1B An example of a hardware block is shown that can include at least a portion of a typical LTE-V2X as a second system as described in Figure 1A

[0047] Figure 2 An example of an LTE-V2X system sharing a frequency channel with an ITS-G5 system using time domain multiplexing (TDM). In a TDM scheme as contemplated in ETSI TR103766, time can be divided into slots, where one technology can occupy the entire bandwidth for a certain period of time. Figure 2 An example of a scenario is shown where ITS-G5 occupies the entire channel for a period of time and LTE-V2X can decide to use a portion of the total channel depending on the modulation scheme, coding scheme and packet length chosen. Each technology (LTE-V2X or ITS-G5) has multiple consecutive slots (which can each be 1 ms, matching the duration of an LTE subframe). Figure 3 An example of this is shown, which shows two examples of a 10 ms superframe. Row 310 has a 50%-50% configuration, while row 320 has a 70%-30% configuration.

[0048] Figure 4 A time versus position graph showing an example of vehicle movement and subsequent packet success is shown and created by simulation. Figure 4 The graph of depicts the congestion of ITS-G5 (802.11p based protocol) packets that are waiting to be sent, when ITS-G5 time resumes, creating substantially more collisions and hidden node situations immediately after the end of a (long) LTE-V2X transmission slot. This is because multiple ITS-G5 equipped vehicles with new messages generated by the ITS overlay during LTE time can simultaneously sense the medium idle while performing backoff, then transmit simultaneously. In Figure 4 ​In the figure, the x-axis is time and the y-axis is the position relative to the highway. The circle marks the position where the vehicle starts transmitting, the blue dots and red x's correspond to the position where there can be a node that correctly received the packet or failed to decode the packet, respectively. The boundaries of the time slots are marked with dashed lines. It can be noted that there can be more transmissions at the beginning of the time slots and most of the reception errors occur at the beginning of the time slots. The probability of packet loss is roughly proportional to the square of the ITS-G5 medium load multiplied by the square of the duration of the LTE-V2X time slots. This means that, due to the longer LTE-V2X times, the ITS-G5 messages can not be evenly distributed over the time granted by ITS-G5 and this becomes a key factor for the performance degradation.

[0049] Figure 5 Time diagram for an example of an ITS-G5 station transmitting a message in an unused LTE-V2X subframe. In case the LTE-V2X system decides not to use one or more 1 ms subframes, the ITS-G5 message accesses the channel. If the LTE-V2X system "resumes" the transmission (in the sense that the same or another LTE-V2X user can start the next transmission), a collision can occur, as shown in the example of 1 ms of ITS-G5 time. Figure 5 "release" time from LTE transmission (71 microseconds + 1 ms) can be obtained. Thus, any traffic type of ITS-G5 messages can use the channel while it is idle for this long time.

[0050] Figure 6 The example flowchart shown illustrates an example method of adjusting the backoff time in CSMA / CA in broadcast mode. The standard MAC procedure in ITS-G5 BROADCAST works as follows: First, an integer (backoff value) is drawn from a uniform distribution [0, CW], where CW refers to the current maximum value of the contention window (the total number of integers to draw is CW + 1). Second, the backoff value is decremented by one when the channel is idle for the entire time slot time of 13 μβ. If the channel becomes busy during the time slot time, the node has to pause the countdown until the channel becomes idle again. After each busy channel period, the node can first wait for the channel to be idle for the arbitration interframe space (AIFS) and then the backoff value is further decremented. Third, after reaching a backoff value of 0, the message is transmitted. In broadcast operation, the node can only invoke the first step once during the initial listening period. In broadcast mode, due to the lack of ACK in broadcast transmissions, the first step of the backoff procedure is only invoked once during the initial listening to the channel (arbitration interframe space (AIFS)). Thus, CW is always set to its minimum value CWmin and can never double.

[0051] Figure 6The flowchart also shows a method of the ITS-G5 station measuring the time the channel is continuously busy. This method is done with the help of a local counter called busytime. When the channel becomes available again, the busytime value is checked in the following way: if busytime is greater than a threshold of e.g. 1 ms (this threshold is the duration of 1 LTE subframe), the estimated number of LTE subframes is calculated, the CW is increased, a new random backoff is extracted. Every time the channel becomes available again (channel idle = Y), the local counter busytime and CW can be reinitialized to default values. This mechanism can ensure that every time the transmission of the ITS-G5 station can be put on hold due to a series of subframes, this ITS-G5 message can propagate over time. It should also be noted that the intention is to not modify the CW and busytime counters when the channel is busy due to an ITS-G5 message. This is possible because the duration of the vast majority of ITS-G5 messages does not exceed 1 ms. The rules for increasing the size of the contention window CW can depend on the ITS application and the TDM scheme configuration.

[0052] Figure 7 A time diagram showing an example of the LTE system and the ITSG5 system sharing time using an inserted latency. The latency period can be added after the packet is generated to hold the latency period before passing down to the MAC layer. This helps or ensures that no new packet arrives during the LTE time slot in conjunction with the CSM A MAC function, but all new packets can be proportionally moved and / or delayed to the next time slot when the CSM A MAC function has access to the medium.

[0053] In one specific example of using this delay according to the present disclosure, the latency is applied proportionally to all packets (e.g., regardless of whether the packet has been generated by the upper layer of the ITS stack during the LTE or ITS-G5 time). In this way, the order of the start of the CSMA / CA procedure of the ITS-G5 message can be preserved (after which there can be a little randomness in the CSMA / CA procedure). In particularly high contention environments, preserving the order of the start of the CSMA procedure can be advantageous in one or more respects, including, for example: less randomness in the message delay and / or increased fairness in the message delay; the system behaves practically the same as the original CSMA system at a relative load equal to the load of the channel without interference from the second system; and there is no need to adjust or set specific (e.g., empirically obtained test) parameters in the modified MAC algorithm to create the desired system behavior.

[0054] In another specific example involving this waiting period, the ITS-G5 packet generation time can not directly translate into the start time of the CSMA / CA procedure, as a waiting time can be added in between, which varies with the LTE time slot duration and with the superframe duration, as shown in the following mathematical expression for one of the various ways to implement this delay or waiting time:

[0055]

[0056] where t wait is the waiting time (when the message is saved at the upper layer of the ITS stack before being passed down to the MAC layer), t superframe is the time of the total cycle (the sum of t LTE + t ITS-G5 ), t packet_gen is the time of the upper layer to generate the packet, and t LTE is the time granted to the LTE-V2X technology within the superframe. For example, for a superframe of 10 ms, ITS-G5 and LTE time slots of 5 ms, when t packet_gen equals one millisecond (ms), the following waiting time is obtained:

[0057]

[0058] While this method can not immediately mitigate the impact of a higher collision probability due to an overall higher medium load, it does maintain (almost) the same behavior as if the CSMA medium was always loaded with the same load during its CSMA time slot. One exception is the period just before the start of the LTE time slot is too short to transmit many CSMA packets (as this can lead to collisions). Assuming this represents only a small fraction of the total medium time, this is acceptable, but alternatively, it can be compensated by subtracting the typical CSMA packet transmission time from the end time of the CSMA time slot.

[0059] Figure 8 A time diagram showing an example of ITS-G5 performing a pre-busy check, which can prevent CSMA / CA channel access just before the LTE-V2X time slot. In this example, the ITS-G5 knows when the LTE time slot starts, and thus can check if the selected message can overlap with the end of the LTE-V2X time slot. In this case, the channel is considered “pre-busy” and the ITS-G5 station can not transmit the packet. Figure 8 A flowchart showing this example of implementing a pre-busy check. Figure 9

[0060] ​In certain specific examples regarding collisions of transmissions, the collisions can be mitigated by methods for evaluating or measuring whether a channel is too busy relative to a threshold. In this example, the information regarding the duration of occupancy of the channel includes data based on the evaluation or measurement of whether the channel is too busy relative to the threshold.

[0061] In similar examples regarding collisions of transmissions, the collisions can be mitigated by methods for evaluating or measuring whether a channel is too busy relative to a threshold. In this example, for a message to be transmitted via the second system, the information regarding the duration of occupancy of the channel includes data based on the evaluation or measurement of whether the channel is too busy relative to the threshold corresponding to the allocated synchronization frame.

[0062] In another embodiment, the channel can be persistently busy relative to a threshold corresponding to a synchronization subframe of the second system. Accordingly, before a station of the first system can access the channel, the contention parameter (previously identified as CW in the DCF) can be increased to indicate that an increased (pseudo) random backoff period will be applied. Figure 6

[0063] In yet another example, the channel is common to both the first system and the second system for transmitting messages. Again, the first system conforms to the 802.11 communication protocol, and the second system conforms to a synchronization-based communication protocol (e.g., LTE-CV2X).

[0064] In certain specific examples, the first system can detect the recurring transmission time (LTE-V2X slot) of the second system by detecting energy other than CSMA / CA traffic.

[0065] In another specific example, the station of the first system additionally includes detecting the recurring transmission time (LTE-V2X slot) of the second system by detecting whether there are no more than a threshold number of CSMA / CA packets received within a time period corresponding to N recurring transmission time allocations, where N is a positive integer equal to the threshold number. In this example, N is a positive integer equal to the threshold number.

[0066] In another example embodiment, since time can be an important aspect when interworking an asynchronous system with a recurring transmission time (LTE-V2X slot), methods of time synchronization can be required. In this example embodiment related to time synchronization, the station of the first system can be used to detect the recurring transmission time of the second system by having a synchronized time source (e.g., GNSS). This can be used to determine the exact start and stop times of the superframe, and / or make inferences from one or more previous detections of the recurring transmission time to predict the upcoming start of the LTE-V2X slot (assuming the known repetitive nature of the LTE-V2X slot structure).

[0067] ​In another example, aspects of the disclosure relate to a station of a first system detecting a recurring transmission time (LTE-V2X slot) of a second system by utilizing information associated with detected CSMA / CA traffic. Utilizing such information, along with a predicted presence of LTE-V2X slots, can provide at least a portion of information about the duration of occupancy of a channel.

[0068] In yet another example, aspects of the disclosure relate to information about the duration of occupancy of a channel. Such information can be based at least in part on a detection that one of the recurring transmission times (LTE-V2X slots) of a second system is longer than a target duration (e.g., > 1 ms). Within this target duration, the medium is expected to contain transmissions. Otherwise, information about the occupancy of a channel can be based at least in part on a detection of a transmission (non-CSMA) pattern associated with detected CSMA / CA traffic.

[0069] In a specific example related to propagating messages for transmission in a shared channel, the step of extending the time for a message to be transmitted by the first system can include uniformly distributing the message to be transmitted by the first system so that the message is proportionally moved or delayed relative to the end of one of the current recurring transmission times. This also prevents the message for transmission from otherwise appearing to be backed up at the end of one of the current recurring transmission times of the second system.

[0070] Another specific example can relate to the step of extending the time for a message to be transmitted by the first system. This step can include distributing the message to be transmitted by the first system at one of the OSI layers above the physical layer of the OSI layers.

[0071] In yet another example, the step of extending the time for a message to be transmitted by the first system can include holding or delaying the distribution time for a message to be transmitted by the first system, and then passing the distribution time to a circuit portion of the system that affects or controls the transmission time of messages (e.g., a CSMA algorithm with respect to messages that need to be transmitted) through the physical layer of the OSI layers. In the process of so delaying the presentation of the message to the transmission-ready circuitry, a time skew is achieved so that other queued messages appear to arrive with a propagation interval relative to the start time mentioned above. Although in certain example embodiments this time skew effort is achieved via a proportional distribution, in other examples consistent with the disclosure, a smaller proportional distribution is used.

[0072] In another specific example, the channel can not completely overlap in the frequency spectrum with a channel used by the second system.

[0073] In connection with an RF communication system, example aspects relate to a method for use in a communication system in which a first system (e.g., 802.11) is asynchronous based and susceptible to interference from a second system (e.g., synchronous based LTE-CV2X). Such interference is due to overlapping spectrum used by the first and second systems. To mitigate the interference problem, an example method extends time for a message in the first system based on information about occupancy of the channel and transmits the message relative to an end of a recurring transmission allocated for use by the second system.

[0074] Unless otherwise indicated, those skilled in the art will recognize that the various terminology used in the specification (including the claims) as used herein implies the ordinary meaning as is taken by one skilled in the art. For example, the specification describes and / or illustrates aspects of the claimed disclosure that can be implemented by way of various circuits or circuitry, which can be depicted as various blocks, modules, devices, systems, units, controllers, and / or other circuitry-type depictions (e.g., Figure 1A The reference numerals 12-140 of the accompanying drawings depict blocks / modules as described herein. Such circuits or circuitry are used in conjunction with other elements in illustrating how certain embodiments can be realized in form or structure, steps, functions, operations, activities, etc. For example, in certain of the embodiments discussed above, one or more modules are discrete logic circuitry or programmable logic circuitry configured and arranged to implement the operations / activities, as can be depicted in Figure 6 and 9 The methods shown are implemented. In certain embodiments, this programmable circuitry is one or more computer circuits, including memory circuitry for storing and accessing programs to be executed as instruction sets (and / or used as configuration data to define how the programmable circuitry is to execute), and the programmable circuitry uses algorithms or processes as described above to perform the relevant steps, functions, operations, activities, etc. Depending on the application, the instructions (and / or configuration data), whether characterized as being in the form of object code, firmware or software, are configured to be implemented in logic circuitry, where the instructions are stored in memory (circuitry) and accessible from memory. As another example, where the specification can refer to a “first [structure type],” a “second [structure type],” etc., where [structure type] can be replaced by terms such as [“circuit,” “circuitry,” etc.], the adjectives “first” and “second” are not used to imply any description or provide any substantive meaning to the structures.

[0075] Based on the above discussion and illustration, those skilled in the art will readily recognize that various modifications and changes can be made to the various embodiments without strictly following the exemplary embodiments and applications illustrated and described herein. For example, methods illustrated in the figures can involve steps that are performed in a different order than illustrated, where one or more aspects of the embodiments herein are maintained, or the methods can involve fewer or additional steps. For example, as Figure 6 Such modifications do not depart from the true spirit and scope of the various aspects of the present disclosure, including those aspects set forth in the claims.

Claims

1. A method for communicating on a channel in a first system, the first system being asynchronous and susceptible to interference from a second system whose channel at least partially overlaps with that of the first system, characterized in that, The method includes: Based on information about the duration of channel occupancy, extending the time for messages used by the first system to transmit the messages relative to the end of the cycle transmission time allocated for use by the second system includes: Assess whether the channel is busy; In response to determining that the channel is busy, a local counter is used to measure the duration for which the channel remains busy; Determine whether the duration of the channel being continuously busy exceeds a threshold; and In response to determining that the channel has been busy for more than a threshold time, the contention parameter is increased to indicate that an increased random or pseudo-random backoff period will be applied before a station of the first system attempts to access the channel.

2. The method according to claim 1, characterized in that, The second system transmits messages in synchronization time slots according to the cyclic transmission time, wherein the end of the cyclic transmission time is aligned with the next start time of one of the synchronization time slots or exactly after the end of one of the synchronization time slots.

3. The method according to claim 1, characterized in that, The threshold corresponds to the synchronization frame assigned to the message to be transmitted via the second system.

4. The method according to claim 1, characterized in that, The first system and the second system include multiple subframes for transmitting messages, and the threshold corresponds to the duration of one of the multiple subframes.

5. The method according to claim 1, characterized in that, The channel is common to the first system and the second system used for transmitting messages or is completely overlapping via the first system and the second system, wherein the first system conforms to the CSMA communication protocol and the second system conforms to the synchronization-based communication protocol.

6. The method according to claim 1, characterized in that, Additionally, the station of the first system detects the cyclic transmission time of the second system by detecting whether there are CSMA / CA packets received within a time period corresponding to N cyclic transmission time allocations, not exceeding a threshold number, where N is a positive integer equal to the threshold number.

7. The method according to claim 1, characterized in that, Additionally, the station of the first system detects the loop transmission time of the second system by using a synchronization time source to determine the exact start and stop times of the superframe.

8. The method according to claim 1, characterized in that, Additionally, the station of the first system detects the cycle time of the second system by inferring from one or more previous detections of the cycle time to predict the imminent start of the C-V2X time slot structure based on the known repeatability of the C-V2X time slot structure.

9. The method according to claim 1, characterized in that, Additionally, the station of the first system detects the cycle time of the second system by using at least a portion of the information associated with detected CSMA / CA traffic and combined with the predicted presence of C-V2X time slots to provide information about the duration of channel occupancy.

10. An apparatus for communicating over a channel via a first system, the first system being asynchronous and susceptible to interference from a second system communicating over a spectrum that at least partially overlaps with the channel of the first system, characterized in that, The device includes: A processing circuit system, the processing circuit system being configured to use information about the occupancy duration of the channel and to extend the time for messages used by the first system to transmit the messages relative to the end of the cycle transmission time allocated for use by the second system, wherein the processing circuit system is further configured to: Assess whether the channel is busy; In response to determining that the channel is busy, a local counter is used to measure the duration for which the channel remains busy; Determine whether the duration of the channel being continuously busy exceeds a threshold; and In response to determining that the channel has been busy for more than a threshold time, the contention parameter is increased to indicate that an increased random or pseudo-random backoff period will be applied before a station of the first system attempts to access the channel.

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