A DATA PACKET TRANSACTION TIMING SOLUTION FOR A WIRELESS COMMUNICATION SYSTEM

The invention relates to a wireless communication system (100) comprising a plurality of radio devices (102, 202, 204). Each of the plurality of radio devices (102, 202, 204) is capable of transmit and receive data packets (220). At least one radio device (102, 202, 204) is configured to: ACK packets (240) received from one or more neighbouring radio devices (102, 202, 204) in response to transmitted data packets (220); determine lengths of ACK gap (230) periods of the one or more neighbouring radio devices (102, 202, 204) based on the observed ACK packets (240); and adjust its ACK listening duration (250) based on the determined lengths of the ACK gap periods (230). The invention relates also to a method for a wireless communication system (100), a radio device (102, 202, 204) for a wireless communication system (100), a method for the radio device (102, 202, 204), a computer program (505), and a tangible non-volatile computer-readable medium.

TECHNICAL FIELD

The invention concerns in general the technical field of wireless communication. Especially the invention concerns wireless communication systems.

BACKGROUND

A wireless communication system, i.e. a wireless communication network, comprises a plurality of radio devices which may communicate with each other. The plurality of radio devices of the wireless communication system may transmit data packets to one or more other radio devices of the wireless communication system to communicate with each other. The transmission of the data packet may be e.g. a unicast transmission, a multicast transmission or a broadcast transmission. In response to receiving a data packet from another radio device (i.e. a transmitting device), a receiving radio device may transmit an acknowledgement (ACK) packet to the transmitting device. The ACK packets are typically used in the unicast communication and usually also in the multicast communication.

Typically, a performance of the wireless communication system may be significantly affected by a length of a packet transaction. The unicast packet transaction (i.e. point-to-point packet transaction or packet transaction between two radio devices) may typically comprise at least the following parts: a Clear Channel Assessment (CCA) duration, an actual data packet transmission from a source device (i.e. the transmitting device) to a target device (i.e. the receiving device), an ACK gap period, and an ACK packet transmission from the target device to the source device. During the CCA duration, the source device evaluates whether a channel to be used for the transmission is free of congestion, i.e. the transmission of the data packet does not interfere other already ongoing transmissions. During the actual data packet transmission, the source device transmits the data packet. During the ACK gap period, the target device handles a reception of the data packet transmitted by the source device and creates the ACK packet. During the ACK packet transmission, the target device transmits the ACK packet to the source device.

Typically, in a single modulation scheme the duration of the maximum length data packet transmission and the duration of the ACK packet transmission are fixed. A CCA duration should cover the ACK gap period so that if another radio device pair within the neighbourhood has already initiated a packet transaction, i.e. already transmitted a data packet, no-one would interrupt their packet transaction by start transmitting during their ACK gap period. The CCA may often be included with some additional random delay to decrease possible collisions between devices that start CCA at the same time.

The length of the ACK gap period (and therefore also the CCA duration) varies within wireless communication systems as different implementations need different amount of time to handle the received data packet and to create the ACK packet. At least one drawback with the varying length of the ACK gap period is that all radio devices within the wireless communication system should use the worst case length of the ACK gap period, i.e. the longest possible length of the ACK gap period occurring in the wireless communication system, to avoid interfering the slowest implementations. This in turn causes suboptimal performance of the wireless communication system.

Thus, there is a need to develop solutions to improve a performance of a wireless communication system.

SUMMARY

The following presents a simplified summary in order to provide basic under-standing of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention.

The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

An objective of the invention is to present a wireless communication system, methods, a radio device, a computer program, and a tangible non-volatile computer-readable medium. Another objective of the invention is that the wireless communication system, the methods, the radio device, the computer program, the tangible non-volatile computer-readable medium improve a performance of a wireless communication system.

The objectives of the invention are reached by a wireless communication system, methods, a radio device, a computer program, and a tangible non-volatile computer-readable medium as defined by the respective independent claims.

According to a first aspect, a wireless communication system comprising a plurality of radio devices is provided, wherein each of the plurality of radio devices is capable of transmit and receive data packets, wherein at least one radio device of the plurality of radio devices is configured to: observe acknowledgement (ACK) packets received from one or more neighbouring radio devices belonging to the plurality of radio devices in response to transmitted data packets; determine lengths of ACK gap periods of the one or more neighbouring radio devices based on the observed ACK packets; and adjust its ACK listening duration based on the determined lengths of the ACK gap periods of the one or more neighbouring radio devices.

The at least one radio device may further be configured to adjust its Clear Channel Assessment (CCA) duration based on the determined lengths of the ACK gap periods of the one or more neighbouring radio devices.

Furthermore, the at least one radio device may be configured to: categorize the determined lengths of the ACK gap periods of the one or more neighbouring radio devices into two or more categories, and include, exclude, and/or weight at least one of the two or more categories when adjusting its CCA duration.

Alternatively or in addition, the at least one radio device may be configured to adjust its CCA duration based on ACK gap period information received from a neighbouring radio device, wherein the received ACK gap period information may comprise the length of the ACK gap period of said neighbouring radio device itself, the CCA duration of said neighbouring radio device itself, and/or lengths of the ACK gap periods of one or more neighbouring radio devices of said neighbouring radio device determined based on observed received ACK packets by said neighbouring radio device.

Alternatively or in addition, the at least one radio device may be configured to include its prevailing CCA duration and/or its prevailing length of the ACK gap period as a data field within a beacon packet.

Alternatively or in addition, the at least one radio device may be configured to provide its prevailing CCA duration and/or its prevailing length of the ACK gap period to at least one new radio device associating with the wireless communication system as a part of an association packet exchange.

Each transmitted data packet may comprise a sequence number, which is incremented only when a new data packet is prepared for transmission.

Moreover, at least one radio device of the plurality of radio devices may be configured to adjust the length of its ACK gap period and/or its ACK packet transmission period in response to receiving data packets with the same sequence number.

The at least one radio device may be configured to observe the ACK packets received from the one or more neighbouring radio devices during an observation time window.

Furthermore, the at least one radio device may be configured to adjust a length of the observation time window based on a rate of changes within the wireless communication system.

According to a second aspect, a method for a wireless communication system comprising a plurality of radio devices is provided, wherein each of the plurality of radio devices is capable of transmit and receive data packets, wherein the method comprises: observing, by at least one radio device of the plurality of radio devices, acknowledgement (ACK) packets received from one or more neighbouring radio devices belonging to the plurality of radio devices in response to transmitted data packets; determining, by the at least one radio device of the plurality of radio devices, lengths of ACK gap periods of the one or more neighbouring radio devices based on the observed ACK packets; and adjusting, by the at least one radio device of the plurality of radio devices, its ACK listening duration based on the determined lengths of the ACK gap periods of the one or more neighbouring radio devices.

According to a third aspect, a radio device for a wireless communication system is provided, wherein the radio device is configured to: observe acknowledgement (ACK) packets received from one or more neighbouring radio devices in response to transmitted data packets; determine lengths of ACK gap periods of the one or more neighbouring radio devices based on the observed ACK packets; and adjust its ACK listening duration based on the determined lengths of the ACK gap periods of the one or more neighbouring radio devices.

According to a fourth aspect, a method for the radio device described above within a wireless communication system is provided, wherein the method comprises: observing, by the radio device, acknowledgement (ACK) packets received from one or more neighbouring radio devices in response to transmitted data packets; determining, by the radio device, lengths of ACK gap periods of the one or more neighbouring radio devices based on the observed ACK packets; and adjusting, by the radio device, its ACK listening duration based on the determined lengths of the ACK gap periods of the one or more neighbouring radio devices.

According to a fifth aspect, a computer program is provided, wherein the computer program comprises instructions which, when the program is executed by the radio device described above, cause the radio device to carry out at least the steps of the method described above.

According to a sixth aspect, a tangible non-volatile computer-readable medium comprising the computer program described above is provided.

The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of unrecited features.

The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

DESCRIPTION OF THE EXEMPLIFYING EMBODIMENTS

FIG.1illustrates schematically an example of a wireless communication system, i.e. a wireless communication network,100according to the invention. The example wireless communication system100ofFIG.1is implemented in a mesh topology. However, the invention is not limited to the mesh topology and the wireless communication system100may also be implemented in any other network topologies, e.g. a star topology, a ring topology, a hybrid topology, or any other network topologies. Some non-limiting examples of wireless communication technologies to which the wireless communication system100may be applied may comprise, but is not limited to, Bluetooth Low Energy (BLE) mesh network, Public Land Mobile Network (PLMN), Wireless Local Area network (WLAN), cellular network, or wireless mesh network, e.g. wireless sensor network, and/or any other wireless networks.

The wireless communication system100comprises a plurality of radio devices102, e.g. radio nodes. Each of the plurality of radio devices102of the wireless communication system100is capable of transmit and receive one or more data packets220. The term “data packet” means throughout this application any radio transmission carrying information needed by the wireless communication system100itself and/or higher layer applications using the wireless communication system100. The data packets220may be transmitted to and/or received from one or more other radio devices102of the wireless communication system100to communicate with the one or more other radio devices102. The transmission of the data packets220may comprise unicast transmission of the data packets220and/or multicast transmission of the data packets220. The unicast transmissions may be used in point-to-point communication, i.e. communication between two radio devices. The multicast transmissions may be used in multicast communication, i.e. communication between one transmitting radio device and a limited number of receiving radio devices. The wireless communication system100may comprise at least one sink device that may be part of gateways to other networks, e.g. Internet, and deliver data to and from the wireless communication system100. In the example ofFIG.1the two radio devices102illustrated with solid black circles are operating as the sink devices.

In response to receiving a data packet220from another radio device, i.e. a transmitting device202, a receiving radio device204may transmit an acknowledgement (ACK) packet240to the transmitting radio device202to indicate whether the reception of the data packet220was correct or not. The term “ACK packet” means throughout this application any radio transmission that carries information as a feedback for receiving or not receiving the data packet220. The receiving radio device202performs an error detection calculation process to ensure, i.e. check, whether the reception of the data packet220was correct or not, and transmits the ACK packet240that indicates the result of the error detection calculation process. The error detection calculation process may be e.g. a Cyclic Redundancy Check (CRC) process or any other suitable error detection process. The ACK packet240may be a positive ACK packet, i.e. indicate a correct reception of the data packet220, or a negative ACK packet, i.e. indicate an incorrect reception of the data packet220, depending on the result of the error detection calculation. The terms “acknowledgement packet” and “ACK packet” used throughout this application mean any kind acknowledgement packet, either positive or negative. In some cases, the negative ACK packets240are not transmitted. Thus, if the transmitting radio device202does not receive the ACK packet240from the receiving device204in response to the transmitted data packet220, it may be an indication of an incorrect reception of the data packet220or an indication that the receiving radio device204did not receive the data packet220at all. Alternatively or in addition, in some cases, instead of transmitting the ACK packet240separately in response to receiving each data packet220, the receiving radio device202may transmit one common ACK packet240to the transmitting radio device202in response to receiving two or more data packets220from the same transmitting device202. Alternatively or in addition, in some cases, if the transmitting radio device202does not receive the ACK packet240from the receiving radio device204and/or the received ACK packet240is negative, the transmitting radio device202may retransmit the data packet220to the receiving radio device204until a positive ACK packet240is received or until a predefined limit amount of retransmissions of the same data packet220is met. The transmission of the data packet220and the ACK packet240are discussed more next referring toFIGS.2A and2Bthat illustrate timing examples of a data packet transaction with an ACK packet240.

FIG.2Aillustrates a simple timing example of the data packet transaction with the ACK packet240between two radio devices102. The two radio devices102may comprise a first radio device, i.e. a transmitting radio device or a source device,202and a second radio device, i.e. a receiving radio device or a target radio device,204.FIG.2Aillustrates main phases of the data packet transaction with the ACK packet. The main phases of the data packet transaction with the ACK packet may comprise at least the following phases: a Clear Channel Assessment (CCA) duration210, a data packet220transmission period, an ACK gap period230, and an ACK packet240transmission period. The example ofFIG.2Aintroduces the main phases of the data packet transaction between two radio devices102without specifying operations of the two devices during the data packet transaction.

During the CCA duration210, the first radio device202performs a CCA process, in which the first radio device202evaluates whether a channel to be used for the transmission of the data packet220is free of congestion, i.e. the transmission of the data packet220does not interfere other already ongoing transmissions. During the data packet220transmission period, the data packet220is transmitted from the first radio device202to the second radio device204. During the ACK gap period230, the second radio device204processes a reception of the data packet220transmitted by the first radio device202and creates the ACK packet240, e.g. according to the result of the error detection calculation as discussed above. During the ACK packet240transmission period, the ACK packet240is transmitted from the second radio device204to the first radio device202. In the example ofFIG.2AT1represents a time period that the first radio device202needs for preparing before it is ready to receive the ACK packet240, i.e. the first radio device202switches from a transmitting mode Tx to a receiving mode Rx. In the example of FIG.2A T2represents a time period that the first radio device202maintains its receiving mode Rx on while waiting for the ACK packet240transmission from the second radio device204to start. In the example ofFIG.2AT3represents an additional time period for receiving the whole ACK packet240, if the transmission of the ACK packet240is started during the T2but is not completed during the T2.

FIG.2Billustrates another non-limiting timing example of the data packet transaction with the ACK packet between two radio devices102. The two radio devices102may comprise a first radio device, i.e. a transmitting radio device or a source radio device,202and a second radio device, i.e. a receiving radio device or a target radio device,204, similarly as in the example ofFIG.2A. The example ofFIG.2Billustrates a more detailed timing example of the data packet220transaction with the ACK packet240between two radio devices102, wherein activities, i.e. operations, of the first radio device202and the second radio device204are separated, i.e. the data packet transaction is illustrated separately from the perspective of the first radio device202and from the perspective of the second radio device204. The upper diagram, i.e. the upper graph, ofFIG.2Billustrates the activities of the second radio device204during the data packet transaction and the lower diagram, i.e. the lower graph, ofFIG.2Billustrates the activities of the first radio device204during the data packet transaction. Rx means a receiving mode of a device and Tx means a transmitting mode of a device in the example ofFIG.2B.

At a time instant t1the CCA duration210starts, during which the first radio device202performs the CCA process. At a time instant t2the first radio device202ends the CCA process. A time period between the time instant t1and the time instant t2represents the CCA duration210of the first radio device202, i.e. a duration of the CCA process of the first radio device202. During a time period between the time instant t2and a time instant t3the first radio device202switches from the receiving mode Rx to the transmitting mode Tx. At the time instant t3the first radio device202starts the transmission of the data packet220and the transmission of the data packet220ends at a time instant t4. A time period between the time instant t3and the time instant t4represents the data packet220transmission period of the first radio device202. A time period between the time instant t4and a time instant t5corresponds to the time period T1discussed above referring to the example ofFIG.2A. In other words, during the time period between the time instant t4and the time instant t5the first radio device202prepares to be ready to receive the ACK packet, i.e. the first radio device202switches from the transmitting mode Tx to the receiving mode Rx. At the time instant t5the first radio device202starts an ACK listening phase. During the ACK listening phase, the first radio device202waits to receive the ACK packet240transmission from the second radio device204. An ACK listening duration250represents the duration of the ACK listening phase, i.e. a time period during which the first radio device202waits to receive the ACK packet240transmission from the second radio device204. At a time instant to the first radio device202starts a reception of the ACK packet240from the second device204and the reception of the ACK packet240ends at a time instant t7. The first radio device202waits for the whole ACK listening duration250before making the decision that there is no response, i.e. the ACK packet240, coming. The ACK listening duration250corresponds to the time period T2discussed above referring to the example ofFIG.2A. The first radio device202may extend the ACK listening duration250until the end of the ACK packet240transmission to reduce retransmissions of the data packet, if the ACK packet240transmission by the second radio device204starts close to the end of the ACK listening duration250of the first radio device202. The possible extended duration of the ACK listening duration250corresponds to the represents the additional time period T3discussed above referring to the example ofFIG.2A. In the Example ofFIG.2Bthe reception of the ACK packet240ends during the ACK listening duration250, thus in the example ofFIG.2B, the additional time period T3is not needed.

At a starting point of the data packet transaction, the second radio device204is in the receiving mode Rx waiting to receive one or more data packets220from the first radio device202. At the time instant t3the second radio device204starts a reception of the data packet220from the first device202and the reception of the data packet220ends at the time instant t4. At the time instant t4the second radio device204starts the ACK gap period230phase. During the ACK gap period230phase the second radio device204processes the reception of the data packet220transmitted by the first radio device202and creates the ACK packet240, e.g. according to the result of the error detection calculation as discussed above. A length of the ACK gap period230represents the duration of the ACK gap period230phase. The second radio device202switches from the receiving mode Rx to the transmitting mode Tx during ACK gap period230. At the time instant to the second radio device204starts the transmission of the ACK packet240and the transmission of the ACK packet240ends at a time instant t7. The time period between the time instant t6and the time instant t7represents the ACK packet240transmission period of the second radio device204.

A timing method according to the invention may be used in the previously discussed wireless communication system100. An example of the timing method according to the invention is described next referring toFIG.3, which schematically illustrates an example of the invention as a flow chart. The method is explained mainly by referring to one radio device102, i.e. the first radio device202, which belongs to the wireless communication system100. However, each radio device102,202,204of the wireless communication system100is able to perform the method steps. Each radio device102,202,204of the wireless communication system100is able to transmit at least one data packet220to one or more other radio devices, i.e. one or more neighbouring radio devices,102,202,204and to receive at least one data packet220from the one or more other devices102,202,204as previously has been discussed. In other words, each radio device102,202,204of the wireless communication system100is able to provide, by means of its data transfer part506, a bi-directional radio communication with one or more other radio devices, i.e. one or more neighbouring radio devices,102,202,204in the wireless communication system100. In other words, each radio device102,202,204of the wireless communication system100may act as the first radio device202and/or as the second radio device204.

The term “neighbouring radio device” means throughout this application a radio device whose radio transmissions may be detected by a receiving radio device. An extended meaning of the term “neighbouring radio device” takes into account the neighbour(s) of the neighbour(s) of the radio device, i.e. multi-hop neighbour(s), such as two-hop neighbour(s), three-hop neighbour(s), four-hop neighbour(s), and/or so on. The term “neighbourhood of a radio device” mean throughout this application one or more radio devices whose radio transmissions may be detected by a receiving radio device. An extended meaning of the term “neighbourhood of a radio device” takes into account the neighbour(s) of the neighbour(s) of the radio device, i.e. multi-hop neighbourhood, such as two-hop neighbourhood, three-hop neighbourhood, four-hop neighbourhood, and/or so on.

At a step310the first radio device202observes ACK packets240received from one or more neighbouring radio devices102,204belonging to the plurality of radio devices of the wireless communication system100. The ACK packets240are received by the first radio device202in response to transmitted data packets220. In other words, the first radio device202transmits one or more data packets220to the one or more neighbouring radio devices102,204and observes the respective one or more received ACK packets240from the one or more neighbouring radio devices102,204.

The first radio device202may observe the ACK packets240received from the one or more neighbouring radio devices102,204during an observation time window. The first radio device202may adjust a length of the observation time window based on a rate of changes within the wireless communication system100. In other words, the first radio device202may adjust the length of the observation time window based on how fast changes may happen within the wireless communication system100. For example, if one or more of the plurality of radio devices102starts to move more or faster than previously, the first radio device202may shorten the length of the observation time window in order to take into account only the latest observed ACK packets240.

At a step320, the first radio device202determines lengths of the ACK gap periods230of the one or more neighbouring radio devices102,204based on the observed ACK packets240. The determination of the length of the ACK gap period230of each of the one or more neighbouring radio device102,204may comprise e.g. measuring a time elapsed from the end of the data packet220transmission to the start of the respective ACK packet240reception.

At a step330, the first radio device202adjusts its ACK listening duration250based on the determined lengths of the ACK gap periods230of the one or more neighbouring radio devices. This improves the performance of the wireless communication system100and reduces power consumption. The adjusting of the ACK listening duration250of the first radio device202may comprise determining e.g. a maximum length of the ACK gap period230based on the determined lengths of the ACK gap periods230of the one or more neighbouring radio devices and adjusting the ACK listening duration250of the first radio device202according to the determined maximum length of the ACK gap period230. The adjusting may comprise increasing or decreasing the ACK listening duration250of the first radio device202. For example, if the determined maximum length of the ACK gap period230is substantially short, the ACK listening duration250of the first radio device202may be decreased, which improves the performance of the wireless communication system100and reduces the power consumption of the first radio device202. Alternatively, if the determined maximum length of the ACK gap period230is substantially long, the ACK listening duration250of the first radio device202may be increased.

At an optional step340, the first radio device202may further adjust its CCA duration210. This improves the performance of the wireless communication system100. The CCA duration210of the first radio device202needs to cover the lengths of the ACK gap periods230of the one or more neighbouring radio devices102,202so that if at least one other radio device pair within the neighbourhood has already initiated a data packet transaction, i.e. already transmitted a data packet, the first device202does not interrupt the packet transaction of the at least one other radio device pair by starting transmitting the data packet220during the ACK gap period230of the at least one other radio device pair. The at least one other radio device pair may be e.g. at least one second transmitting radio device and at least one second receiving radio device belonging to the one or more neighbouring radio devices of the first radio device204. The adjusting may comprise increasing or decreasing the CCA duration210of the first radio device202.

According to an example of the invention, at the step340the first radio device202may adjust its CCA duration210based on the determined lengths of the ACK gap periods230of the one or more neighbouring radio devices. The adjusting of the CCA duration210of the first radio device202may comprise determining e.g. a maximum length of the ACK gap period230based on the determined lengths of the ACK gap periods230of the one or more neighbouring radio devices and adjusting the CCA duration210of the first radio device202according to the determined maximum length of the ACK gap period230. For example, if the maximum length of the ACK gap period230is substantially short, the CCA duration210of the first radio device202may be decreased, which improves the performance of the wireless communication system100. Alternatively, if the determined maximum length of the ACK gap period230is substantially long, the CCA duration210of the first radio device202may be increased. In addition, the CCA duration may be added with a random delay e.g. in wireless communication systems where simultaneous start times of CCA are likely.

Alternatively or in addition, at the step340the first radio device202may adjust its CCA210duration based on ACK gap period230information received from a neighbouring radio device, i.e. a reporting radio device. The received ACK gap period230information may comprise e.g. the length of the ACK gap period230of the reporting radio device itself, the CCA duration210of the reporting radio device itself, and/or lengths of the ACK gap periods230of one or more neighbouring radio devices of the reporting radio device determined based on observed received ACK packets240by the reporting radio device.

According to an example of the invention, the first radio device202may further categorize410the determined lengths of the ACK gap periods230of the one or more neighbouring radio devices102,204into two or more categories. The determined lengths of the ACK gap periods230of the one or more neighbouring radio devices102,204may be categorized e.g. based on delays in the ACK packet240transmissions and/or a nature of the determined lengths of the ACK gap periods230of the one or more neighbouring radio devices102,204, e.g. the nature may be deterministic etc. For example, there may be occasionally longer delays transmitting the ACK packet240, e.g. if the second radio device204prioritizes a transmission or a reception of one or more beacon messages over the ACK packet240transmission. The first radio device202may further include, exclude, and/or weight at least one of the two or more categories when adjusting its CCA duration210at the step340. This enables taking into account in the adjusting of the CCA duration210only the most relevant determined lengths of the ACK gap periods230of the one or more neighbouring radio devices102,204.FIG.4illustrates schematically an example of the method according to the invention comprising the optional categorizing step410of the determined lengths of the ACK gap periods230of the one or more neighbouring radio devices102,204into the two or more categories. Moreover, in the example ofFIG.4, the first radio device202includes, excludes, and/or weights at least one of the two or more categories when adjusting its CCA duration210at the step340.

According to an example of the invention, the first radio device202may include its prevailing CCA duration210, i.e. the CCA duration210which the first radio device202is currently using, and/or its prevailing length of the ACK gap period230, i.e. the length of the ACK gap period230which the first radio device202is currently using, as a data field within a beacon packet. The first radio device202may broadcast the beacon packet to one or more neighbouring radio devices102,202,204belonging to the wireless communication system100. This may allow the one or more neighbouring radio devices102,202to adjust their CCA duration210and/or ACK listening duration250with less own observation and/or more quickly. The one or more neighbouring radio devices102,202,204may adjust their CCA duration210and/or their ACK listening duration250in response to receiving the beacon message from the first radio device202. In other words, the one or more neighbouring radio devices102,202,204may adjust their CCA duration210and/or their ACK listening duration250based on the CCA duration210and/or the length of the ACK gap period230included in the beacon packet broadcasted by the first radio device202.

Alternatively or in addition, the first radio device202may provide its prevailing CCA duration210and/or its prevailing length of the ACK gap period230to at least one new radio device associating with the wireless communication system100as a part of an association packet exchange, when the at least one new radio device is associating with, i.e. joining to, the wireless communication system100. This may allow the at least one new radio device to adjust their CCA duration210and/or ACK listening duration250with less own observation and/or more quickly. For example, the first radio device202may include its prevailing CCA duration210and/or its prevailing length of the ACK gap period230in an association packet, e.g. an association message. The first radio device202may provide, e.g. transmit, the association packet to the at least one new radio device associating with the wireless communication system100as a part of the association packet exchange, when the at least one new radio device is associating with the wireless communication system100. The at least one new radio device associating with the wireless communication system100may adjust their CCA duration210and/or their ACK listening duration250in response to the association packet exchange with the first radio device202, e.g. in response to receiving the association packet from the first radio device202. In other words, the at least one new radio device associating with the wireless communication system100may adjust their CCA duration210and/or their ACK listening duration250based on the CCA duration210and/or the length of the ACK gap period230provided by the first radio device202.

According to an example of the invention, each transmitted data packet220may comprise a sequence number, which is incremented only when a new data packet220is prepared for transmission. In other words, the sequence number is maintained the same for retransmissions of the data packets220and incremented for the transmission the new data packet220. Each radio device102,202,204of the wireless communication system100may further adjust the length of its ACK gap period230and/or its ACK packet240transmission period in response to receiving data220packets with the same sequence number. According to a non-limiting example, each radio device102,202,204may adjust the length of its ACK gap period230and/or its ACK packet240transmission period in response to receiving a predefined number of data packets220with the same sequence number. The use of the sequence number may enable detecting possible timing mismatches with the plurality of radio devices102. It may allow identifying too fast or too slow ACK packets240e.g. by detecting persistent retransmission of the data packet220with the same sequence number. For example, if the first radio device202switches its receiving mode Rx on after the second radio device204has already started to transmit the respective ACK packet240, the first device202misses the reception of the ACK packet240.

FIG.5illustrates an example of a radio device (apparatus)102,202,204according to the invention. The radio device102,202,204comprises a processing part502that is configured to perform user and/or computer program (software) initiated instructions, and to process data in order to run an application and communication protocol. The processing part502may comprise at least one processor, e.g. one, two, or three processors. The radio device102,202,204further comprises a memory part504in order to store and to maintain data. The data may be instructions, computer programs, and data files. The memory part504may comprise at least one memory, e.g. one, two, or three memories.

The radio device102,202,204further comprises a data transfer part506and an antenna part508for providing a bi-directional radio communication with at least one other radio device102,202,204. The radio device102,202,204may use the data transfer part506in order to transmit data packets220, ACK packets240, commands, requests, messages, and data to at least one of other radio devices102,202,204of the wireless communication system100via the antenna part508. The data transfer part506also receives data packets220, ACK packets240, commands, requests, messages, and data from at least one of the other radio devices102,202,204via the antenna part508in the wireless communication system100. The radio device102,202,204may further comprise a power supply part510. The power supply part510comprises components for powering the radio102,202,204, e.g. a battery and a regulator.

The memory part502comprises a data transfer application for operating, i.e. controlling, the data transfer part506, an antenna application for operating the antenna part508, and a power supply application for operating the power supply part510.

The memory part504comprises also a timing application, i.e. a computer program,505comprising instructions which, is configured to use at least one of parts506,508,510in order to perform, i.e. carry out, at least the operations, i.e. the method steps, of the radio device102,202,204described above in this description part and figures, when it is run, i.e. executed, by a computer, e.g. by the radio device102,202,204by means of the processing part502.

The computer program505may be stored in a non-statutory tangible computer readable medium, e.g. an USB stick or a CD-ROM disc.