GB2537904A

GB2537904A - Method of controlling a wireless link in a multi-radio communication system

Info

Publication number: GB2537904A
Application number: GB1507406.5A
Authority: GB
Inventors: Le Houerou Brice; Visa Pierre
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2015-04-30
Filing date: 2015-04-30
Publication date: 2016-11-02
Anticipated expiration: 2035-04-30
Also published as: GB2537904B; GB201507406D0

Abstract

One wireless controller inside a source device is selected in order to perform link communication while other wireless controller(s), not selected, is/are configured in a specific mode, called mirror mode in which physical transmission of data frame(s) over the medium is disabled. The selected controller is configured into a transmission mode also called normal mode in which physical transmission of data frame(s) over the medium is enabled. Data frame(s) to be transmitted are stored in buffers for both the normal and mirror mode before transmission. During the wireless communication, the wireless controllers are controlled and switched over the time from normal mode to mirror mode by a link controller. The link controller advantageously selects the most effective wireless controller(s) for the transmission of data frame(s). The mirror buffer is updated based on a virtual reception acknowledgement determined from a reception acknowledgment to ensure all buffers content is identical. Accordingly, a swap between the wireless controllers may be carried out without disturbing a real time transmission.

Description

TITLE OF THE INVENTION

Method of controlling a wireless link in a multi-radio communication system

FIELD OF THE INVENTION

The invention belongs to the field of wireless network for which communication devices operate through multiple wireless communication links.

The invention relates more particularly to a method for controlling a wireless communication between a source device and a sink device by dynamically switching wireless communication links usage without service interruption.

BACKGROUND OF THE INVENTION

Figure la illustrates the state of the art of a basic MAC protocol used for wireless communication between a source device and a sink device. This figure represents a peer protocol chart between a MAC entity in a source device and a MAC entity in a sink device adapted to transmit data frames with an automatic retransmission mechanism in case of errors.

MAC 1 122 transmits a first radio frame 141 containing data packets D1 and D2 to MAC_2 126. The MAC_2 126 replies with a frame control message 131 indicating the reception status of the first radio frame 141.

For example, the MAC_2 126 may indicate that only data packet D1 has been correctly received. According to the reception status, the MAC_1 122 proceeds for a retransmission 142 of the corrupted or lost data (D2) in the previous transmission 141. Finally, the MAC_2 126 acknowledges the completion of the data frame transmission 141 by a second frame control message 132. Following this first flow control, the MAC_1 122 transmits a second radio frame 143 containing data packets D3 and D4 to the MAC_2 126. The MAC_2 acknowledges the completion of the transmission with another frame control message 133 indicating that data packets D3 and D4 have been correctly received.

Figure lb represents the source device and the sink device of figure la exchanging different data frames with a retransmission mechanism in case of errors according to the state of art.

A source device 101 is composed of a Protocol Adaptation Layer PALI 120, a MAC 1 122 and a PHY_1 124 in order to transmit data frames over the link 140 and receive data frames over the link 130. The MAC 1 122 embeds a data frame buffer 123 used to temporary store any data previously transmitted which are not yet acknowledged by the MAC_2 126 of the sink device.

A sink device 102 is composed of a PAL_2 121, a MAC_2 126 and a PHY_2 127 in order to receive data frames over the link 140 and to transmit data frames over the link 130. The MAC_2 126 embeds a data frame buffer 125 used to temporary store any (partial) data previously received in order to be reordered if necessary (e.g. for a retransmission mechanism). The source device 101 transmits successively the radio frames 141, 142 and 143, each including one or more data packets. The sink device 102 proceeds for the acknowledgement of the data packets included in the radio frames by generating the corresponding frame control messages 131, 132 and 133 in the MAC_2 126 and transmitting successively radio frames including these frame control messages.

In order to increase the robustness of the communication in a wireless communication network, communication devices may be equipped with multiple wireless controllers either to aggregate bandwidth, to extend network coverage, or to improve robustness. Bandwidth aggregation can be achieved by using several radio communication modules working simultaneously on different frequency bands or channels. Network coverage extension can be achieved through the implementation of a relay device receiving data from a first wireless controller covering a first spatial sector, and forwarding these data through a second wireless controller covering a second spatial sector. Robustness improvement can be achieved creating transmit diversity by using several wireless controllers for the data transmission providing multiple alternative radio link to the destination device. Here, data can be simultaneously transmitted when wireless controllers operate on different radio channels, or when wireless controllers operate on the same radio channel without interference (typically by using directional antenna). Otherwise data can be successively transmitted during different time intervals using alternatively different wireless controllers.

One implementation of multiple radio system is the case of devices equipped with two identical wireless controllers operating in different frequency bands, as for example the 2.4GHz, 5GHz or 60GHz bands. Such system combines two wireless controllers equipped with chipset operating in a same or different frequency band. For the transmission of a data stream between a source device and a sink device, the data stream may be transmitted by selecting one wireless chipset at a time. This selection permits to increase the robustness of the communication by offering alternative communication link between the source device and the sink device. Also Fast Session Transfer (FST) protocol is specified in IEEE 802.11 standard to smoothly transfer communications from one frequency band to another or from one channel to another within the same frequency band. The minimum achievable switching time would be in the order of 5 ms.

However, when considering applications having low latency requirements as for example video streaming applications or real time transmissions, the switching mechanisms can become disruptive for the communication. This is particularly the case when the latency requirement is lower than the time required to perform the switching.

An example of switching is given by US2013/0083678. This publication describes a multi-radio medium-agnostic access architecture. A multi-radio management function performs activation of one of the plurality of radios, switching between two of the plurality of radios, and/or aggregation of two or more radios, based on metrics collected by a radio resource measurement function. A test of availability and quality is required prior to switching between radios. The execution of the required test before switching may cause a disruption of a low latency application.

A goal of the present invention is to provide a method to control a plurality of wireless controllers of a source device in order to dynamically select one wireless controller to transmit data frames to a sink device while preventing the disruption of the ongoing communication. The invention is particularly adapted for low latency applications as video streaming or real time transmissions. Another goal of the present invention is to provide a control method for swapping from a wireless controller to another without impacting the transmission of the data frames to the sink device.

SUMMARY OF THE INVENTION

The present invention has been devised to address one or more of the foregoing concerns.

The present invention provides a method for controlling a wireless link in the context of network devices having multiple wireless controllers. A wireless controller 10 comprises a medium access controller (MAC) and a physical layer transceiver (P HY).

The main principle is to select one wireless controller inside a network device in order to perform the link communication while the other wireless controller(s), not selected, is/are configured in a specific mode, called mirror mode in which physical transmission of data frame(s) over the medium is disabled. The selected controller is configured into a transmission mode also called normal mode in which physical transmission of data frame(s) over the medium is enabled. During the wireless communication, the wireless controllers are controlled and switched over the time from normal mode to mirror mode. The invention provides a method permitting to perform efficiently the wireless controllers switching between normal and mirror mode. The wireless controllers switching or mode swapping is preferably controlled by a link controller. The link controller advantageously selects the most effective wireless controller(s) for the transmission of data frame.

In mirror mode, the link controller sets up the parameters of the non-selected wireless controllers with same parameters used to configure the selected wireless controller. These parameters may include the frequency band and the channel, the modulation and coding scheme (MCS) as well as the policy used for the transmission in case of errors (ARQ, automatic repeat request). The link controller may set up specific MAC parameters used to establish a MAC protocol between the source device and the sink device. Advantageously, the source address of the source device and the destination address are configured in the MAC entity in order to operate a peer protocol. Other parameters as key encryption, network name or operating modes (e.g. adhoc or infrastructure) can also be part of the parameters setting.

In mirror mode, a wireless controller: - Is configured and requested to transmit the same payload at the same time as the wireless controller in normal mode. The link controller configures any parameters required to process a similar radio frame as the one processed by the wireless controller in normal mode. These parameters can also include specific data parts of the radio frame like device source address, encryption keys.

- Performs the transmission operation accordingly to the MAC protocol including the transmission errors policy (ARQ status feedback) and/or flow control management established between the source device and the sink device.

- Does not perform the effective physical transmission on the medium. The physical layer transmission is therefore not performed. For a wireless controller, this can be done by switching off the power amplifier transmitter.

Is able to receive the flow control messages directly from the medium or relayed by the link controller from the selected wireless controller.

- Preferably, the configuration in normal mode or mirror mode of the different wireless controllers is scheduled over time.

A synchronization of the same payload consumption inside all the wireless controllers is therefore performed. The synchronization allows continuously supporting the flow control management protocol including errors transmission policy used during the established link between the source device and the sink device. The synchronization also allows to transparently switch from one wireless controller to another during the communication without impacting the data frame transmission.

According to a first aspect of the invention there is provided a method for 30 controlling a wireless communication between a source device and a sink device, the source device comprising a plurality of wireless controllers each comprising a medium access controller (MAC) for accessing the medium, a physical transceiver (PHY) for physical emission and a buffer for storing data before emission, the method comprising: selecting a first wireless controller among the plurality of wireless controllers, configuring the selected wireless controller into a transmission mode for transmitting data frame(s) and configuring the non-selected wireless controller(s) into a mirror mode in which physical transmission of data frame(s) over the medium is disabled, loading the buffers of the selected first wireless controller and the non-selected wireless controller(s) with data frame(s), transmitting said data frame(s) from the physical transceiver of the first wireless controller, receiving by at least one of the wireless controllers from the sink device of a reception acknowledgement of the transmitted data frame(s), providing to the other wireless controller(s) not having received a reception 15 acknowledgment a virtual reception acknowledgement based on said received acknowledgement, updating the buffers of the selected first wireless controller and the non-selected wireless controller(s) based on said reception acknowledgement and said virtual reception acknowledgement.

According to this method, the data frame(s) is/are processed simultaneously in all the wireless controllers. Therefore, the behavior of the wireless controllers in transmission mode and in mirror mode is maintained close to each other so that a swap between the two modes can be carried out without disturbing a real time transmission. Advantageously, a mode swap will be transparent from the sink side and will not require any additional means inside the sink device.

In an embodiment, the step of updating the buffers is carried out so as to maintain all the buffers content identical. The buffers are thus kept synchronized in term of data content so that a new transmission can take place without service interruption.

In another embodiment, the configuring in the mirror mode comprises setting MAC and/or PHY parameters with parameters used for configuring the wireless controller in the transmission mode. This feature allows the processing of the wireless controllers in transmission mode and in mirror mode to be identical or very close to each other allowing to carry out a mode swap instantly.

In another embodiment, the method further comprises: receiving through at least one of the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted data frame(s), and, based on a corrupted reception status of at least one data frame 10 among the data frame(s), swapping the wireless controllers mode by setting the selected wireless controller into a mirror mode and a second wireless controller among the plurality of wireless controllers into a transmission mode, retransmitting the at least one corrupted data frame with the second wireless controller.

Thereby, the retransmission can immediately be executed from the second wireless controller without waiting since the at least one data frame is already present in the buffer of the second wireless controller. This brings robustness and diversity to the transmission.

In still another embodiment, the reception status includes a status of correctly received data frame(s) and the method further comprises before the re-transmitting step, erasing from all the buffers the correctly received data frame(s).

These features allow to keep all the buffer synchronized in term of data content by erasing the correctly transmitted data frame(s) from the buffers. It also further allows to load new data frame(s) while the non-successfully transmitted data frame(s) is/are kept in all buffers.

In a particular embodiment, the method further comprises loading all the buffers with same new data frame(s) to be transmitted and transmitting said new data frame(s) during the retransmitting step. The buffers are thereby kept synchronized in term of data content so that a real time transmission is not affected.

In an embodiment, the method further comprises simultaneously sending to the wireless controllers a frame control message triggering the transmitting of new data frame(s) from the physical transceiver of the selected wireless controller and the consumption of the same data frame(s) within the wireless controller(s) set in mirror mode. This feature allows to synchronize the wireless controllers in transmission mode and in mirror mode by synchronously consuming the payload inside all the wireless controllers. The synchronization allows continuously supporting the flow control management protocol.

In a particular embodiment, the physical transmission of data frame(s) over the medium is disabled by reducing a radio transmission power or disabling a baseband processing or disabling one element in the physical transceiver.

In an embodiment, the source device comprises a link controller for controlling the operating mode of the wireless controllers and the method further comprises at the link controller: obtaining from at least one of the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted data frame(s), determining, based on the reception status, if a mode swap of the wireless controllers is required, sending a mode swap command to the wireless controllers, the swap command comprising setting the selected wireless controller into a mirror mode and a second wireless controller among the plurality of wireless controllers into a transmission mode.

These features allow to control the wireless controllers so that a mode swap is carried out without disturbing a real time transmission.

According to a specific feature, all the medium access controllers (MAC) of the source device are configured with a same source address. Advantageously, a mode swap will be transparent from the sink side and will not require any additional means inside the sink device.

According to a second aspect of the invention there is provided a source device for wirelessly communicating with a sink device, the source device comprising a plurality of wireless controllers each comprising a medium access controller (MAC) for accessing the medium, a physical transceiver (PHY) for physical emission and a buffer for storing data before emission, the source device further comprising: a configuration module for selecting a first wireless controller among the plurality of wireless controllers, for configuring the first wireless controller into a transmission mode for transmitting data frame(s) and for configuring the non-selected wireless controller(s) into a mirror mode in which physical transmission of data frame(s) over the medium is disabled, means for receiving by at least one of the wireless controllers from the sink 10 device of a reception acknowledgement of transmitted data frame(s), means for providing to the other wireless controller(s) a virtual reception acknowledgement based on said received acknowledgement, and means for updating the buffers of the selected first wireless controller and the non-selected wireless controller(s) based on said reception acknowledgement and said virtual reception acknowledgement.

In an embodiment, the means for updating the buffers maintains all the buffers content identical.

In another embodiment, the means for the configuring in the mirror mode comprises means for setting MAC and/or PHY parameters with parameters used for configuring the wireless controller in the transmission mode.

In a further embodiment the source device comprises: means for receiving through at least one of the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted data frame(s), and, based on a corrupted reception status of at least one 25 data frame among the data frame(s), means for swapping the wireless controllers mode by setting the selected wireless controller into a mirror mode and a second wireless controller among the plurality of wireless controllers into a transmission mode, means for retransmitting the at least one corrupted data frame with the second wireless controller.

In still another embodiment the reception status includes a status of correctly received data frame(s) and the device further comprises means for erasing from all the buffers the correctly received data frame(s) before the re-transmission.

In a particular embodiment, the source device comprises means for loading all 5 the emission buffers with same new data frame(s) to be transmitted and means for transmitting said new data frame(s) during the retransmission.

In an embodiment, the source device further comprises means for simultaneously sending to the wireless controllers a frame control message triggering the transmitting of data frame(s) from the physical transceiver of the selected wireless controller and the processing of the same data frame(s) within the non-selected wireless controller(s).

In an embodiment, the source device further comprises a link controller for controlling the operating mode of the wireless controllers, the link controller comprising: means for obtaining from at least one of the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted data frame(s), means for determining, based on the reception status, if a mode swap of the wireless controllers is required, means for sending a mode swap command to the wireless controllers.

In a specific embodiment, the source device further comprises means for receiving through all the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted data frame(s).

According to a specific feature, all the medium access controllers (MAC) of the source device are configured with a same source address.

According to a third aspect, the invention provides a wireless controller for wirelessly communicating with a sink device, the wireless controller comprising a medium access controller (MAC), a physical layer transceiver (PHY) for physical emission and a buffer for storing data before emission, the wireless controller further comprising: means for configuring the wireless controller either into a transmission mode for transmitting data frame(s) or into a mirror mode in which physical transmission of data frame(s) over the medium is disabled, and means for receiving a virtual reception acknowledgement based on a reception acknowledgement received by another wireless controller, means for updating the buffer based on said virtual reception 10 acknowledgement.

In an embodiment, the wireless controller comprises means for swapping the wireless controller mode between the transmission mode and the mirror mode.

Another aspect of the invention relates to a computer program product for a programmable apparatus, the computer program product comprising a sequence of instructions for implementing any method as defined above.

Another aspect of the invention relates to a method for controlling a wireless communication between a source device and a sink device substantially as described with reference to, and as shown in Figures 3, 5 and 6.

Another aspect of the invention relates to a source device for wirelessly communicating with a sink device substantially as described with reference to, and as shown in Figures 2 and 4.

At least parts of the methods according to the invention may be computer implemented. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit", "module" or "system". Furthermore, the present invention may take the form of a computer program product embodied in any tangible medium of expression having computer usable program code embodied in the medium.

Since the present invention can be implemented in software, the present invention can be embodied as computer readable code for provision to a programmable apparatus on any suitable carrier medium. A tangible carrier medium may comprise a storage medium such as a floppy disk, a CD-ROM, a hard disk drive, a magnetic tape device or a solid state memory device and the like. A transient carrier medium may include a signal such as an electrical signal, an electronic signal, an optical signal, an acoustic signal, a magnetic signal or an electromagnetic signal, e.g. a microwave or RF signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the present invention will become apparent to those skilled in the art upon examination of the drawings and detailed description.

Embodiments of the invention will now be described, by way of example only, and with reference to the following drawings in which: Figure la represents a peer protocol chart between a MAC entity in a source device and a MAC entity in a sink device in order to transmit data frames with an automatic retransmission mechanism in case of errors according to the state of art.

Figure lb represents the source device and the sink device exchanging different data frames with a retransmission mechanism in case of errors according to the state of art.

Figure 2 is a functional block diagram of a device according to an embodiment of the invention Figure 3 represents a link control mechanism chart used to manage two wireless controllers in a source device communicating with a wireless controller in a sink device according to an embodiment of the invention.

Figure 4 represents the source device and the sink device using multiple 25 wireless controllers exchanging different data frames using the link control mechanism of figure 3.

Figure 5 is a flow chart of an algorithm executed by a link controller according to an embodiment of the invention.

Figure 6 is a flow chart of an algorithm executed by a wireless controller 30 according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 2 is a functional block diagram of a device according to an embodiment of the invention. A device 200 provides a multi radio connectivity through multiple wireless controllers operating for instance in respective frequency bands: 2.4GHz, 5GHz and 60GHz. The device 200 comprises: *a Random Access Memory 203 (denoted RAM), *a Read-Only Memory 202 (denoted ROM), *a micro-controller or Central Processing Unit 201 (denoted CPU), *a Link Controller 204 (denoted LLC), *three wireless controllers 231, 232, 233, each respectively composed of a Medium Access Controller 211, 212, 213 (denoted MAC_A, MAC_B, MAC_C, and sometimes denoted MAC when a description concerns the three controllers) and a Physical Layer module 221, 222, 223 (denoted PHY_A, PHY_B, PHY_C, and sometimes denoted PHY when a description concerns the three physical layer modules).

An application adapter 205 (denoted PAL), CPU 201, LLC 204, PAL 205 exchange control information through a communication bus 210, on which is also connected RAM 203, and ROM 202. The CPU 201 controls the overall operation of the device as it is capable of executing, from the memory RAM 203, instructions pertaining to a computer program, once these instructions have been loaded from the memory ROM 202.

The PAL 205 performs all necessary transformations of application data (packetization, fragmentation). The PAL 205 achieves the interface between applications through the external interface 220 and the LLC 204 to transmit and to receive application data on the network. There may be several interfaces between LLC 204 and PAL 205.

LLC 204 is in charge of routing data fragments from PAL 205 to the multiple network interfaces (MAC 211, 212, 213) for data transmission, and from the network interfaces to the PAL for data reception. LLC 204 controls scheduling of transmissions via the network interfaces by defining the transmission schemes. LLC 204 implements an embodiment of the invention by controlling the various MAC and PHY modules during wireless link communication.

MAC _A 211, MAC _B 212 and MAC _C 213 are in charge of controlling the emission and reception of MAC frames conveying control data and application data according to a transmission protocol. MAC_A 211, MAC_B 212 and MAC_C 213 may operate a same standard like IEEE 802.11 on a same frequency band.

Each MAC relies on a PHY module: PHY_A 221 for MAC_A 211, PHY_B 222 5 for MAC _B 212 and PHY _C 223 for MAC _C 213. Each PHY embeds a modem, a radio communication module and antennas. The radio module is responsible for processing a signal output by the modem before it is sent out by means of the antenna. For example, the processing can be done by frequency transposition and power amplification processes. Conversely, the radio module is also responsible for 10 processing a signal received by the antenna before being provided to the modem. The modem is responsible for modulating and demodulating the digital data exchanged with the radio module.

Among the devices in the network, one is identified as a master in charge of defining the data transmission schemes and synchronizing the system. For instance when a TDMA (Time Division Multiple Access) scheme is applied (like with IEEE 802.1 lad standard), the master device transmits a beacon frame marking the beginning of each TDMA sequence. The set of MAC frames transmitted during one TDMA sequence is then called a super-frame. The beacon frame is used by other devices in the network to be synchronized with the master device.

On the reception side, the modem of PHY module collects the radio frames received from the radio module through antenna, and transmits radio frames to the associated MAC. The MAC is therefore able to detect if a radio frame is missing. This detection is made when the MAC is expecting a radio frame during a scheduled receiving time slot but no data comes from the communication module. This situation occurs when the modem has failed to recognize the radio frame preamble: the synchronization was unsuccessful because the signal-to-noise ratio (SNR) or received signal strength indication (RSSI) was to low (the signal has been indiscernible from noise). Also, MAC is able to detect transmission errors within a radio frame. As radio frame payload can be divided into several packets, CRC (Cyclic Redundancy Check) data computed by MAC can be appended at the end of each packet. For a given packet received in a destination device, if CRC computation result is different from the one received with the packet, then MAC can decide to drop this packet as it is very likely to contain one or several erroneous bits.

Additionally, the MAC can request a retransmission of the corrupted data packets to the MAC transmitter in the source device.

Figure 3 represents a link control mechanism according to an embodiment of 5 the present invention used to manage two wireless controllers in a source device communicating with a wireless controller inside a sink device. The same reference numbers used in figures 3 and 4 refers to the same elements.

This figure illustrates the MAC protocol execution over the time between a source device including a first and a second wireless controllers and a sink device including a single wireless controller. In the source device, a first MAC_1A 414 is configured by the link controller 411 in a normal mode 371 while a second MAC_1B 416 is configured in a mirror mode 370. At the same time, the MAC_1B 416 and the MAC _lA 414 proceeds for a first data frames transmission request 351 from the link controller 411, generating the transmission of a first radio frame 441 encapsulating data frames D1 and D2. The data frames D1 and D2 are effectively transmitted to the MAC_2 226 in the sink device 202 (see figure 4) by the wireless controller which is configured in normal mode. The mirror mode configuration of the wireless controller involving the MAC_1B 416 has the effect to disable a physical transmission 445 from MAC 1B. Following the reception of the data frames D1, the MAC_2 226 of the sink device 202 transmits to the source device 401 (see figure 4) a frame control message 431 including the reception status ACK D1 indicating that only the data frame D1 has correctly been received by the MAC_2 226. The MAC 1A 414 transmits 335 the reception status issued by the MAC_2 226 to the link controller 411 by a message Si. The link controller 411 decides then to select another wireless controller to effectively and immediately proceed for a new communication. This decision is triggered by the reception status Si indicating that errors occurred during the previous transmission 441.

In order to select another wireless controller, the link controller 411 sets the previously used first wireless controller in mirror mode by sending a message 373 to 30 the MAC 1A 414 and sets the second wireless controller in normal mode by sending a message 372 to the MAC_1B 416.

Following this selection, the link controller 411 sends a frame control message 361. The message 361 provides the MAC_1B 416 with a virtual acknowledgement of the correct reception of the data frame D1 by the MAC2 226, which permits to continue the MAC protocol and in particular to execute a retransmission of the corrupted data frame D2. The link controller 411 sends a second transmission request 352 to both MAC_1A 414 and MAC_1B 416 in order to transmit the data frame D2 with a new data frame D3, the data frames D2,D3 being encapsulated in a second radio frame 442. The second transmission request 352 generates the transmission of the radio frame 442 containing data frames D2 and D3 from the MAC 1B 416. In parallel, at the same time, the MAC 1 A 414 proceeds in mirror mode of a non-effective transmission 446 of the same data frames D2, D3 as the ones effectively transmitted by the MAC_1B 416 to the MAC_2 226 in the second radio frame 442. The mirror mode configuration of the wireless controller involving the MAC 1A 414 has the effect to disable the physical transmission 446 from MAC_1A. Following this transmission, the MAC2 226 acknowledges the reception of the data frames D2, D3 over a frame control message 432. The MAC_1B 416 delivers to the link controller 411 a message 336 indicating the reception status S2a of the second radio frame 442. The link controller 411 transmits a frame control message 362 to the MAC_1A 414 in mirror mode in order to flush its internal storage/buffer of the data frames D2 and D3. The control message 362 is equivalent for the MAC 1A 414 to the reception of a virtual acknowledgement of a successful transmission of data frame D2, D3, which has for effect to free the memory allocated to data frames D2, D3 in a transmission buffer of MAC_1A. This message permits to keep the internal buffers of the different MACs, i.e. MAC_1A 414 and MAC_1B 416 filled with the same data frames. The link controller 411 proceeds for a third data frame transmission request 353, causing the transmission of a third radio frame 443 for data frame D4. Still configured in mirror mode, the MAC_1A 414 proceeds for non-effective data frame transmission 448 while the MAC 1B proceeds for an effective data frame transmission of data frame D4. The MAC _2 226 transmits a frame control message 433 ACK D4 which is received by the MAC_1B 416. The frame control message 433 may also be received by the MAC_1A 414 as illustrated with dotted line in figure 3. Both MAC transmit a reception status S3a 337 and S3b 338 to the link controller 411. The link controller 411 transmits a frame control message 363 indicating the reception status ACKLLC of the data frame transmission of the third radio frame 443 to both MAC lA 414 and MAC 1B 416. In mirror mode, the MAC 1A 414 is thus able to receive the reception status from the link controller 411 and also from the MAC_2 226. Such a dual reception may advantageously prevent error(s) on the frame control message used to transmit the reception status of the data frame transmission.

Figure 4 represents the source device and a sink device using multiple wireless controllers exchanging different data frames and frame control messages using the link controller mechanism described in relation to figure 3.

A source device 401 comprises a PAL_1 410, a link controller 411 and two wireless controllers respectively comprising a MAC_1A 414, a PHY_1A 418 and a MAC 1B 416, a PHY 1B 419. The source device 4ffi is able to transmit data frames to the sink device 202 using the MAC_1A and the PHY_1A over a link 450 or using MAC 1B and the PHY 1B over a link 451. Indifferently of the wireless controller used by the source device 401, the sink device receives the data frames and transmits frame control messages over a link 452 whatever the link 450 or the link 451 used to transmit the data frames to the two wireless controllers.

The MAC 1A 414 and the MAC 1B 416 embed respectively data frame buffers 415 and 417, which are used to temporary store data frames previously 20 transmitted which reception has not yet been acknowledged by the MAC_2 226 of the sink device.

The sink device 202 is composed of a PAL_2 221, a MAC_2 226 and a PHY_2 227 in order to transmit frame control messages over the link 452 and receive data frames over the links 450 or 451. The MAC_2 226 embeds a data frame buffer 225, which is used to temporary store data previously received in view to proceed any reordering of data after retransmission of data frame. The source device 401 transmits successively the radio frames 441, 442 and 443 which include data frames. The sink device 202 proceeds for the acknowledge of the data frames included in the radio frame by transmitting successively over the link 452 the frame control messages 431, 432 and 433 including the reception status corresponding respectively to radio frames 441, 442 and 443.

For each transmission, the link controller 411 selects one set of MAC and PHY to be effective for the transmission and configures the other, non-selected, set(s) of MAC and PHY in mirror mode. In accordance with the figure 3, the link controller 411 selects the set MAC lA 414 and PHY_1 A 418 to perform the transmission of the first radio frame 441 by setting the MAC_1A in normal mode and the link controller 411 configures the second wireless controller composed of the MAC_1B 416 and the PHY 1B 419 in mirror mode.

With this configuration, the radio frame 441 is transmitted by the first wireless controller composed of the MAC_1A 414 and the PHY_1A 418. The link controller 411 requests the MAC_1A and the MAC_1B to process the same data frames. The request is preferably sent simultaneously to both MAC_1A and the MAC_1B.

When receiving the request, the MAC_1A 414 and the MAC_1B 417 operate a synchronization of the data content of their respective buffers 415 and 417. The synchronization consists in a duplication of the data content of the respective buffers whereby the data contents of the different buffers are made identical at the moment the transmission starts, as will be explained here below.

Using the PHY_2 227, the MAC2 226 of the sink device 202 transmits a frame control message 431 comprising the reception status corresponding to the radio frame 441 transmission of data frames D1, 02. The link controller 411 receives from the MAC_1A 414 and optionally from the MAC_1B 416 the reception status message of the data frames D1, 02 indicating that only the data frame D1 has correctly been received.

According to the reception status, the link controller 411 decides to use the other wireless controller, i.e. MAC_1B 416 and PHY_1B 419, to process the second radio frame 442 which will include the corrupted data frame D2. This decision may be motivated by an estimation of a bad link quality based on the reception status using the first wireless controller or in order to increase transmission diversity. The reception status can be used to estimate a data frame error rate of the wireless controller in normal mode. The link controller can decide to use another wireless controller using the data frame error rate as a link assessment mean.

The link controller 411 sets the MAC 1 A 414 in mirror mode 373 and the MAC 1B 416 in normal mode 372 as explained with reference to figure 3.

The link controller 411 delivers a frame control message ACKLLC (361, figure 3) to the MAC_1B 416 based on the reception status message (335, figure 3) delivered by the MAC_1A 414 while in normal mode. This frame control message permits to update the MAC data buffers 415 and 417 with the same content regarding the data frames to be transmitted. Based on this frame control message 361, the MAC_1B 416 updates the buffer 417 and in a similar manner the MAC_1A updates the buffer 415. The update consists in deleting the correctly transmitted data frame D1 from buffers 415 and 417 while duplicating the data frames D2, D3 and D4 in buffers 415 and 417. A synchronization of the data frame content of the different buffers is therefore achieved. The buffers content of the wireless controller in normal mode and in mirror mode are thus maintained identical.

The radio frames 442,443 respectively comprising the data frames D2, D3 and D4 are transmitted by the second wireless controller composed of the MAC_1B 416 and the PHY_1B 419. At the same time, the link controller 411 controls in mirror mode the first wireless controller composed of the MAC_1B 414 and the PHY_1B 418. Following the successive transmission 442 of data frames D2, D3 and 443 of data frame D4, the link controller receives the corresponding reception status message 432 and 433 and delivers to the MAC_1A 414 the frame control messages ACKLLC (see 362 and 363 in figure 3) to update the buffers 415 and 417 of the different MAC. The update consists in deleting the correctly transmitted data frames D2, D3 and D4 from the buffers 415 and 417 while feeding both buffers with new data frame(s) to be sent during the next transmission. A synchronization of the data frame content of the different buffers is therefore achieved.

Figure 5 is a flow chart of an algorithm executed by a link controller according to an embodiment of the present invention.

In step 501, the link controller selects and configures one wireless controller in normal mode to transmit the next data frame(s) and configures the others wireless controllers in mirror mode.

In step 502, the link controller requests all wireless controllers to proceed for a 30 same data frame transmission.

In step 503, the link controller waits the reception status from at least one of the wireless controllers.

In step 504, the link controller checks if a reception status is received. If no reception status is received, step 507 is executed, otherwise, if a reception status is received, step 505 is executed.

In step 505, the link controller estimates if the current usage of the wireless controller selected to transmit is efficient. This estimation can be based on data frame error rates corresponding to the ratio between data frames correctly received and corrupted data frames. This ratio is compared to a threshold in order to determine if the errors transmission are correctly recovered by the retransmission mechanism. Typically, a wireless link can support few percent of corrupted data frames.

In case the wireless controller in normal mode is considered efficient (test 506 positive), in step 510, the link controller send to the wireless controller in mirror mode a frame control message based on the reception status delivered by at least one of the wireless controllers. This frame control message permits to keep synchronized all the MAC entities of the different wireless controller(s) in mirror mode with the MAC entity of the wireless controller in normal mode. The synchronization comprises the erasing of the data successfully transmitted from the different buffers and the duplication of the data to be transmitted in the different buffers. It may additionally comprise a re-configuration of the MAC and/or PHY parameters of the wireless controller(s) with those used by the wireless controller in normal mode. The re-configuration operation permits to keep compatibility with the MAC protocol as defined between the source device and the sink device having a single wireless controller.

It follows that once the MAC entities of a wireless controller are synchronized they will have identical behavior for the next transmission and will produce the same radio frame(s) at a same rate. From the point of sight of the wireless controller in the sink device, the source device behaves as if having a single wireless controller. A mode swap (step 508) will therefore appear transparent from the side of the wireless controller in the sink device. In this view the MAC of the wireless controllers in the source device may advantageously be configured with the same -single-source address.

The above features allow swapping the operating mode between different wireless controllers in the source device to be executed instantly while continuously transmitting the successive radio frames.

In step 507 (test 506 negative), the link controller estimates that the wireless controller in normal mode is not efficient and decides to use another wireless controller. This decision can result from a bad frame error rate or loss of radio frames detected by the non-delivery of reception status message from the sink device. The link controller choses another wireless controller previously set in mirror mode to be used for the next data frame transmission. In step 508, the wireless controller previously used to transmit is configured in mirror mode and the newly selected wireless controller is set in normal mode, swapping thereby the operating mode of the wireless controllers. In step 509, the link controller sends a frame control message to the newly selected wireless controller in normal mode in order to proceed for data transmission. The data transmission includes a retransmission of the corrupted data frames indicated by the reception status. The frame control message is also sent to the wireless controller(s) in mirror mode via step 510 so that a transmission can be triggered at the same time from all the wireless controller(s) in step 502. The transmission from the wireless controller in normal mode is effective while the transmission from the wireless controller(s) in mirror mode is non-effective due to the disabled physical emission.

Figure 6 is a flow chart of an algorithm executed by a wireless controller according to an embodiment of the present invention.

In test 601, the wireless controller detects to implement a behavior corresponding to a normal mode (negative test) or to a mirror mode (positive test) as instructed by the link controller. In step 602a or 602b, the wireless controller waits a request from the link controller to transmit a data frame. After receiving a request from the link controller the wireless controller implements, either the step 605 according to the normal mode, or the step 603 according to the mirror mode.

In step 603, corresponding to the mirror mode, the wireless controller is configured with the configuration of the wireless controller in normal mode in order to proceed in a similar manner and to generate a similar radio frame as the wireless controller set in normal mode. In step 604, the wireless controller proceeds for the data frame transmission while disabling the physical transmission. The disabling of the physical transmission can be performed by reducing the radio transmission power, disabling the baseband processing or disabling one element in the radio transceiver (modulator, frequency shifter, transmitter antenna switch).

This transmission is performed accordingly to a frame control message received from the other wireless controller. This frame control message can indicate the reception status of the previous data frame transmission and is used to build the next data frame transmission.

In step 605, corresponding to a normal mode, the wireless controller is configured with a configuration adapted to proceed for a new radio frame transmission taking into account the previous reception status received. In step 606, the wireless controller proceeds for the data frame transmission with an effective physical transmission.

In step 607, the wireless controller sends to the other wireless controller a frame control message based on the reception status delivered by the sink device.

Claims

CLAIMS1. A method for controlling a wireless communication between a source device and a sink device, the source device comprising a plurality of wireless controllers each comprising a medium access controller (MAC) for accessing the medium, a physical transceiver (PHY) for physical emission and a buffer for storing data before emission, the method comprising: selecting a first wireless controller among the plurality of wireless controllers, configuring the selected wireless controller into a transmission mode for transmitting data frame(s) and configuring the non-selected wireless controller(s) into 10 a mirror mode in which physical transmission of data frame(s) over the medium is disabled, loading the buffers of the selected first wireless controller and the non-selected wireless controller(s) with data frame(s), transmitting said data frame(s) from the physical transceiver of the first wireless controller, receiving by at least one of the wireless controllers from the sink device of a reception acknowledgement of the transmitted data frame(s), providing to the other wireless controller(s) not having received a reception acknowledgment a virtual reception acknowledgement based on said received 20 acknowledgement, and updating the buffers of the selected first wireless controller and the non-selected wireless controller(s) based on said reception acknowledgement and said virtual reception acknowledgement.
2. The method according to claim 1 wherein the step of updating the buffers is carried out so as to maintain all the buffers content identical.
3. The method according to claims 1 or 2 wherein the configuring in the mirror mode comprises setting MAC and/or PHY parameters with parameters used for configuring the wireless controller in the transmission mode.
The method according to any of claims 1 to 3 further comprising: receiving through at least one of the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted data frame(s), and, based on a corrupted reception status of at least one data frame among the data frame(s), swapping the wireless controllers mode by setting the selected wireless controller into a mirror mode and a second wireless controller among the plurality of wireless controllers into a transmission mode, and retransmitting the at least one corrupted data frame with the second wireless controller.
5. The method according to 4 wherein the reception status includes a status of correctly received data frame(s), the method further comprising before the retransmitting step, erasing from all the buffers the correctly received data frame(s).
6. The method according to claim 5 further comprising loading all the buffers with same new data frame(s) to be transmitted and transmitting said new data frame(s) during the retransmitting step.
7. The method according to any of claims 1 to 6 further comprising simultaneously sending to the wireless controllers a frame control message triggering the transmitting of new data frame(s) from the physical transceiver of the selected wireless controller and the consumption of the same data frame(s) within the wireless controller(s) set in mirror mode.
8. The method according to any of claims 1 to 7 wherein the physical transmission of data frame(s) over the medium is disabled by reducing a radio transmission power or disabling a baseband processing or disabling one element in the physical transceiver.
9. The method according to any of claims 1 to 8 wherein the source device comprises a link controller for controlling the operating mode of the wireless controllers, the method further comprising at the link controller: obtaining from at least one of the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted data frame(s), determining, based on the reception status, if a mode swap of the wireless controllers is required, and sending a mode swap command to the wireless controllers, the swap command comprising setting the selected wireless controller into a mirror mode and a second wireless controller among the plurality of wireless controllers into a transmission mode.
10. The method according to any of claims 1 to 9 wherein all the medium access controllers (MAC) of the source device are configured with a same source address.
11. A source device for wirelessly communicating with a sink device, the source device comprising a plurality of wireless controllers each comprising a medium access controller (MAC) for accessing the medium, a physical transceiver (PHY) for physical emission and a buffer for storing data before emission, the source device further comprising: a configuration module for selecting a first wireless controller among the plurality of wireless controllers, for configuring the first wireless controller into a transmission mode for transmitting data frame(s) and for configuring the non-selected wireless controller(s) into a mirror mode in which physical transmission of data frame(s) over the medium is disabled, means for receiving by at least one of the wireless controllers from the sink 25 device of a reception acknowledgement of transmitted data frame(s), means for providing to the other wireless controller(s) a virtual reception acknowledgement based on said received acknowledgement, and means for updating the buffers of the selected first wireless controller and the non-selected wireless controller(s) based on said reception acknowledgement and said virtual reception acknowledgement.
12. The source device according to claim 11 wherein the means for updating the buffers maintains all the buffers content identical.
13. The source device according to claims 11 or 12 wherein the means for configuring in the mirror mode comprises means for setting MAC and/or PHY parameters with parameters used for configuring the wireless controller in the transmission mode.
14 The source device according to any of claims 11 to 13 further comprising: means for receiving through at least one of the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted 10 data frame(s), and, based on a corrupted reception status of at least one data frame among the data frame(s), means for swapping the wireless controllers mode by setting the selected wireless controller into a mirror mode and a second wireless controller among the plurality of wireless controllers into a transmission mode, and means for retransmitting the at least one corrupted data frame with the second wireless controller.
15. The source device according to claim 14 wherein the reception status includes a status of correctly received data frame(s), the device further comprising means for erasing from all the buffers the correctly received data frame(s) before the re-transmission.
16. The source device according to claim 15 comprising means for loading all the emission buffers with same new data frame(s) to be transmitted and means for transmitting said new data frame(s) during the retransmission.
17. The source device according to any of claims 11 to 16 further comprising means for simultaneously sending to the wireless controllers a frame control message triggering the transmitting of data frame(s) from the physical transceiver of the selected wireless controller and the processing of the same data frame(s) within the non-selected wireless controller(s).
18. The source device according to any of claims 11 to 17 wherein the physical transmission of data frame(s) over the medium is disabled by reducing a radio transmission power or disabling a baseband processing or disabling one element in the physical transceiver.
19. The source device according to any of claims 11 to 18 comprising a link controller for controlling the operating mode of the wireless controllers, the link controller comprising: means for obtaining from at least one of the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted data frame(s), means for determining, based on the reception status, if a mode swap of the wireless controllers is required, and means for sending a mode swap command to the wireless controllers.
20. The source device according to any of claims 11 to 19 further comprising means for receiving through all the wireless controllers a reception status representative of the reception in the in the sink device of the transmitted data frame(s).
21. The source device according to any of claims 11 to 20 wherein all the medium access controllers (MAC) of the source device are configured with a same source address.
22. A wireless controller for wirelessly communicating with a sink device, the wireless controller comprising a medium access controller (MAC), a physical layer transceiver (PHY) for physical emission and a buffer for storing data before emission, the wireless controller further comprising: means for configuring the wireless controller either into a transmission mode for transmitting data frame(s) or into a mirror mode in which physical transmission of data frame(s) over the medium is disabled, means for receiving a virtual reception acknowledgement based on a reception acknowledgement received by another wireless controller, and means for updating the buffer based on said virtual reception acknowledgement.
23. The wireless controller of claim 22 further comprising means for swapping the 5 wireless controller mode between the transmission mode and the mirror mode.
24. A computer program product for a programmable apparatus, the computer program product comprising a sequence of instructions for implementing a method according to any one of claims 1 to 10, when loaded into and executed by the 10 programmable apparatus.
25. A computer-readable storage medium storing instructions of a computer program for implementing a method according to any one of claims 1 to 10.
26. A method for controlling a wireless communication between a source device and a sink device substantially as hereinbefore described with reference to, and as shown in Figures 3, 5 and 6.
27. A source device for wirelessly communicating with a sink device substantially as hereinbefore described with reference to, and as shown in Figures 2 and 4.