Patent Publication Number: US-2019182773-A1

Title: Data transmission mechanism of time-division duplex communication system supporting different radio communication standards

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of U.S. provisional application Ser. No. 62/596,896 filed on Dec. 10, 2017, which is entirely incorporated herein by reference. 
    
    
     BACKGROUND 
     Generally speaking, a communication device may have co-located multi-radios (for example, WLAN, Bluetooth, LTE) to support different communication standards. Conventional WLAN transceiver in such multi-radios device may need to operate in a time-division duplex (TDD) mode with co-located radios to avoid mutual radio signal interference. Conventional WLAN transceiver typically adopts the scheme of switching between normal and radio inactive operation mode to support such TDD operation mode. In radio inactive mode, a WLAN transceiver is not be able to do frame exchange with peer WLAN radio circuit. Typically, a WLAN transceiver adopts power save protocol to switch between normal and radio inactive mode. A WLAN transceiver set the power management (PM) bit in a frame header to indicate its current power save mode to a peer access point. The PM bit is set to ‘1’ to indicate that the WLAN transceiver in the power save mode, and is set to ‘0’ to indicate that the WLAN transceiver in the normal mode. The access point shall check the PM bit from the associated WLAN transceiver to keep synchronization the power save mode with the associated WLAN transceiver. The peer access point should not initiate a frame exchange with WLAN transceiver in the power save mode. Before the WLAN transceiver switches to the power save mode, the WLAN transceiver needs to contend for the channel resources so as to transmit frame(s) to notify the conventional peer access point of this power save mode change information. 
     However, WLAN standard adopts the CSMA/CA back-off scheme, and it cannot be guaranteed that the channel resources can be successfully allocated to the conventional WLAN transceiver in this situation and the conventional WLAN transceiver may not be able to timely transmit a power save mode change notification to the conventional peer access point when needs to switch the power-save mode. This causes the loss of power save mode synchronization between the WALN transceiver and peer access point and bad frame exchange performance of multi-radios operated in TDD mode. 
     In addition, more seriously, new WLAN standards (such as IEEE802.11n/ac) support packet aggregation (A-MPDU) to transmit a bigger frame size in a single transmission to improve efficiency. The bigger frame takes a longer transmission time. Radio interferences are inevitably introduced when the transmission time of data packet/frames transmitted from the conventional peer access point to the conventional WLAN transceiver is too long to partially overlap with the BT/LTE TDD phase of the time-division duplex communication system. Alternatively, an access point may transmit short frames (for example, a small size A-MPDU aggregated frame or non-aggregation frame) to reduce the possibility of overlap with remote peer co-located BT/LTE radios operation phase. These short frames cause the data exchange performance of WLAN communication is significantly degraded. It is impossible to merely adopt the conventional WLAN transceiver and conventional peer access point to avoid interferences and improve performance simultaneously. 
     SUMMARY 
     Therefore one of the objectives of the invention is to provide a communication device with co-located multi-radios operating in time-division duplex mode, a corresponding method, and a peer communication device such as a peer access point, to provide a novel data transmission/exchange mechanism for the time-division duplex communication, so as to solve the above-mentioned problems. 
     According to embodiments of the invention, a communication device which is capable of respectively supporting different radio communication standards operating in time-division mode during different time periods is disclosed. The communication device comprises a first communication circuit and a second communication circuit. The first communication circuit is configured for supporting a first radio communication standard. The second communication circuit is configured for supporting a second radio communication standard different from the first radio communication standard. The first communication circuit is arranged to send time information to a peer communication circuit for notifying the peer communication circuit of when the first communication circuit will switch to a radio inactive mode. 
     According to the embodiments, a method of communication device which is capable of respectively supporting different radio communication standards during different time periods is disclosed. The communication device comprises a first communication circuit configured for supporting a first radio communication standard and a second communication circuit configured for supporting a second radio communication standard different from the first radio communication standard. The method comprises: using the first communication circuit to send time information to a peer communication circuit for notifying the peer communication circuit of when the first communication circuit will switch to a radio inactive mode. 
     According to the embodiments, an access point device in a communication system which is capable of supporting first radio communication standard peer operating between normal and radio inactive mode during different time periods is disclosed. The access point device comprises a transceiver. The transceiver is configured for receiving target time information from a peer communication circuit, and for dynamically determining a data length of an aggregation packet which is transmitted during a normal mode of the peer communication circuit according to the target time information. The target time information is used for indicating when the peer communication circuit will switch from the normal mode to a radio inactive mode. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a communication device according to embodiments of the invention. 
         FIG. 2  is a diagram of an example of the communication device operating under different TDD phases of the communication system according to the embodiments of the invention. 
         FIG. 3  is a flowchart diagram of the operation of communication device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The invention aims at providing a solution of a data transmission mechanism for a communication system in which a communication device has at least a first communication circuit and a second communication circuit wherein the first and second communication circuits respectively support different radio communication standards during different time periods/slots. For example, the first communication circuit may be a communication circuit supporting wireless local area network (WLAN) communication standard, e.g. IEEE 802.11a/b/g/n/ac. The second communication circuit may be a communication circuit supporting Bluetooth (BT) or Long Term Evolution (LTE) communication standard. That is, in one embodiment, the first communication circuit for example may be a contention-based communication circuit which needs to contend for channel resources with other communication circuits so as to transmit frames/packets, and the second communication may be a non-contention-based communication circuit which is arranged to transmit packets/frames during a corresponding allocated time period/slot and does not need to contend for channel resources; however, this is not intended to be a limitation. 
       FIG. 1  is a block diagram of a communication device  100  according to embodiments of the invention. The communication device  100  comprises a first communication circuit  105  and a second communication circuit  110  which respectively supporting WLAN communication standard and BT/LTE communication standard. For example, the first communication circuit  105  may be a WLAN communication circuit/transceiver which is arranged to contend for wireless channel(s) resource with other wireless station devices. The first communication circuit  105  may be arranged to communicate with the peer communication device  101  such as an access point which comprises a transceiver  101 A. 
     The second communication circuit  110  for example may be a circuit/transceiver employing BT/LTE communication standard (but not limited) which is arranged to transmit/receive data in allocated time slots. The second communication circuit  110  does not need to contend for channel resources, and for example may be arranged to communicate with the BT/LTE device  102 . 
     That is, such TDD communication system is a WLAN and BT/LTE co-existence communication system in which the communication device  100  supports both WLAN communication and BT/LTE communication standards. 
     Since the transmission power may cause severe interference to co-located radio&#39;s reception signal, a TDD (time division duplex) operation mode would be adopted to avoid such interference. The control circuit  115  may be arranged to alternately activate/deactivate the first communication circuit  105  during a first time period/slot such as 2.5 milliseconds (but not limited) and the second communication circuit  110  during a second time period/slot such as 1.25 milliseconds different and distinct from the first time period/slot. 
     For example, the control circuit  115  may deactivate the first communication circuit  105  such as a WLAN transceiver by controlling the first communication circuit  105  to enter a radio inactive mode (i.e. power save mode) when the second communication circuit  110  such as a BT/LTE transceiver is activated by the control circuit  115  to receive and/or transmit BT/LTE data frames/packets. Instead, the second communication circuit  110  is deactivated by the control circuit  115  when the control circuit  115  activates the first communication circuit  105  by controlling the first communication circuit  105  to switch from the radio inactive mode to a normal mode. 
     It should be noted that a conventional WLAN communication circuit such as a transceiver may need to contend for channel resources with other WLAN transceivers. If the conventional WLAN transceiver decides to enter the power-save mode, such WLAN transceiver may need to contend for the channel resource so as to notify a conventional peer access point of this power save mode change information. However, it cannot be guaranteed that the channel resource can be timely allocated by the conventional WLAN transceiver, and in this situation the conventional WLAN transceiver cannot successfully complete power-save mode change notification to the conventional peer access point. Thus, the data exchange performance/efficiency of the communication device will be degraded. 
     In the embodiments of the invention, to significantly improve the data exchange performance/efficiency of the communication device  100  as well as avoid severe interferences, the communication device  100  is arranged to control the first communication circuit  105  to send the frame embodied with target time information to notify the peer access point  101  that the first communication circuit  105  now is in normal mode to be able to do frame exchange with access point  101  till the target time, and will switch to radio inactive (power save) mode at the target time. Thus, the peer access point  101  can schedule an optimized frame exchange sequence based on the target time information. 
       FIG. 2  is a diagram of an example of the communication device  100  operating under different TDD phases of the communication system according to the embodiments of the invention. As shown in  FIG. 2 , during the first time period/slot (i.e. TDD WLAN phase), the control circuit  115  is arranged to activate the first communication circuit  105  and to deactivate the second communication circuit  110 . Instead, during the second time period/slot (i.e. TDD BT/LTE phase), the control circuit  115  is arranged to activate the second communication circuit  110  and to deactivate the first communication circuit  105 . 
     During the TDD WLAN phase, the first communication circuit  105  is arranged to operate under the normal mode and to send the target time information to the peer access point  101  to notify the peer access point  101  of when will the first communication circuit  105  enter the radio inactive (power-save) mode. For example, the transmission of such target time information can be transmitted immediately when the first communication circuit  105  switches from the radio inactive mode to the normal mode. Alternatively, such transmission may be triggered under the normal mode to update the target time information; this is not intended to be a limitation. 
     The first communication circuit  105  for example is arranged to send a specific control/data/management frame such as a QoS (quality of service) Null or an action frame (but not limited) to the peer access point  101  wherein the target time information is embodied within a QoS Control field of the QoS Null frame or information elements in action frame body. For instance, the first communication circuit  105  may employ and set bit  7  of QoS control field in the QoS Null frame to notify the peer access point  101  of this is a notification of the target time information. The first communication circuit  105  may employ and send bits  8 - 15  of QoS control field in the QoS Null frame to carry the value of target time information; this is not meant to be a limitation. 
     In addition, the target time information may carry absolute time information or offset time information. For example, timing synchronization between the peer access point  101  and the first communication circuit  105  can be achieved by periodically exchanging timing information through beacon frames. In the same BSS, a timing synchronization function (TSF) can be used to keep timers for all devices synchronized. The target time information may be a relative offset value to the TSF of the same BSS or may be an absolute value of such TSF. 
     Thus, when receiving the relative offset value or absolute value indicated by the target time information, the peer access point  101  can know the target time that the first communication circuit  105  will switch from the normal mode to the radio inactive mode. That is, the peer access point  101  can know when the first communication circuit  105  will go to power save mode. After receiving the relative offset value or absolute value, the peer access point  101  is arranged to use the transceiver  101 A to send an acknowledgement ACK back to the first communication circuit  105  and then to transmit MPDU frame (s) or an aggregated A-MPDU frame to the first communication circuit  105 . In the embodiment, the transceiver  101 A is arranged to send the aggregated A-MPDU frame to the first communication circuit  105  wherein the aggregated A-MPDU frame is generated by aggregating multiple MPDU frames having the whole frame exchange sequences not exceeding the TDD WLAN phase as illustrated in  FIG. 2 . For example, the transceiver  101 A of the peer access point  101  can be arranged to aggregate 64 MPDU frames as the aggregated A-MPDU frame. By referring to the target time information transmitted from communication circuit  105 , the peer access point  101  could know the end time of TDD WLAN phase of communication circuit  105 , and to determine the optimal A-MPDU frame size to successfully complete the A-MPDU frame exchange sequence before end of TDD WLAN phase of communication circuit  105 . 
     Thus, by sending the target time information embodied within the control/data/management frame to the peer access point  101 , this can make the peer access point  101 , after receiving such target time information, appropriately determine the size of the A-MPDU, i.e. the number of MPDU packets to be aggregated, so that the A-MPDU frame can be successfully received and acknowledged by the first communication circuit  105  before the first communication circuit  105  enters the power-save mode, to significantly improve the frame exchange efficiency of WLAN communication as well as avoid interferences between WLAN and BT/LTE communications. 
     The first communication circuit  105  is arranged to send an acknowledgement signal BA back to the peer access point  101  after receiving the aggregation frame A-MPDU. Such acknowledgement signal BA is transmitted before the first communication circuit  105  enters the power-save mode and the second communication circuit  110  is activated. Based on the target time information, the transceiver  101 A of the peer access point  101  can appropriately handle/determined/adjust the transmission frame size of A-MPDU frame so as to make the acknowledgement signal BA can be successfully transmitted at the later or last timing during the normal mode before the first communication circuit  105  enters the power-save mode. 
     Then, after the first communication circuit  105  enters the power-save mode and the second communication circuit  110  is activated, the second communication circuit  110  can be arranged to communicate with the BT/LTE device  102  via BT/LTE communication standard without interference between WLAN and BT/LTE communication circuits. 
     Compared to the conventional data transmission scheme, by sending the target time information to the peer access point  101  from the first communication circuit  105  to notify the peer access point  101  of when will the first communication circuit  105  be deactivated, i.e. enter the power-save mode, this can make the peer access point  101  appropriately transmit an aggregation packet having appropriate frame size to the first communication circuit  105 . Accordingly, the interferences can be avoided and the WLAN throughput performance can be significantly improved. That is, the peer access point  101  based on the target time information can schedule optimized frame exchange sequence and/or schedule optimized frame size. 
     Further, the communication device  100  can be arranged to decide when to send the target time information to the peer access point  101 . For example, in an embodiment, the control circuit  115  is arranged to control the first communication circuit  105  to send the target time information to the peer access point  101  immediately when the communication device  100  enters the normal mode of WLAN communication. In other embodiments, the communication device  100  may be arranged to send the target time information at different timings during the normal mode. 
     Further, in other embodiments, the target time information may be embodied by the communication device into an action frame which is a type of management frame used to trigger an action. This modification also falls within the scope of the invention. 
     Additionally, to make readers more clearly understand the spirits of the invention,  FIG. 3  shows a flowchart of the operation of communication device  100  of  FIG. 1 . Provided that substantially the same result is achieved, the steps of the flowchart shown in  FIG. 3  need not be in the exact order shown and need not be contiguous, that is, other steps can be intermediate. Steps are detailed in the following: 
     Step  305 : Start; 
     Step  310 : The control circuit  115  is arranged to activate the first communication circuit  105  enter the normal mode and deactivate the second communication circuit  110 ; 
     Step  315 : The first communication circuit  105  sends the target time information which is embodied within a frame such as IEEE 802.11 QoS Null or action frame to the transceiver  101 A of peer access point  101 ; 
     Step  320 : The transceiver  101 A of peer access point  101  sends an acknowledgement ACK corresponding to the IEEE 802.11 QoS Null or action frame to the first communication circuit  105 ; 
     Step  325 : The transceiver  101 A of peer access point  101  determine the frame size of aggregated A-MPDU frame such whole frame exchange sequence end before target time of the first communication circuit  105 , sending the A-MPDU frame to the first communication circuit  105 ; 
     Step  330 : The first communication circuit  105  sends the acknowledgement signal BA, corresponding to the aggregated A-MPDU frame, to the transceiver  101 A of peer access point  101  after receiving the aggregated A-MPDU frame; 
     Step  335 : The control circuit  115  deactivates the first communication circuit  105  to enter the radio inactive mode and activates the second communication circuit  110 ; and 
     Step  340 : End. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.