Patent Application
20160344535
The present invention relates generally to wireless networking, and more particularly to methods for efficiently using communication channels of a WLAN network with both duplex and half duplex wireless stations.
A Wireless Local Area Network (WLAN) generally consists of either independent basic service sets (BSSs) or infrastructure BSSs. The independent BSSs are also referred to as Ad Hoc BSSs. An Infrastructure BSS usually includes one or more access points (AP), a distribution system, etc. and generally employs the AP in all communications including communication between wireless stations (STA). In most current wireless communication systems, APs and the non-AP wireless stations operate in half-duplex mode.
In application Ser. No. 14/213,987 entitled “Method and Apparatus for in-band full duplex wireless communications” for a wireless system that includes basic channel access in the presence of full duplex communications, co-existence with legacy non-full duplex IEEE 802.11 systems, a mechanism is disclosed to schedule full duplex transmissions, support for full duplex communications with half duplex STAs and the transmission of acknowledgements from the full duplex receiving devices. As a background, the specification of application Ser. No. 14/213,987 is incorporated here as a by reference as if fully set forth herein.
In
Additionally, when the duration of a PPDU_1 is very short, dT is comparable to the duration of PPDU_1. For example, AP to STAy transmission time is calculated as follows:
T
APtoSTA TX
=T
Preamble
+T
MAC Header+MPDU of length 1500 bytes (1)
For transmission data rate at 6 Mbps, it becomes:
T
APtoSTA TX
=T
Preamble+50 μs+2000 μs*Num_of_MPDUS (2)
Or, for transmission data rate at 54 Mbps,
T
APtoSTA TX
=T
Preamble+5 μs+223 μs*Num_of_MPDUS (3)
If dT is equal to the time of Preamble and MAC Header, and Num_MPDUS equals 1, this leaves little time available for STAx to transmit data using the channel in the uplink direction. The only way STAx can send an MPDU of 1500 bytes is if STAx were to use data rate higher than the transmission rate AP uses for the transmission to STAy. Otherwise, it is not possible for STAx to use the channel in the uplink direction to finish the transmission of its data in the allowed time. Accordingly, the current IEEE 802.11 or the invention disclosed in the application Ser. No. 14/213,987 does not support this uplink transmission from STA to AP when a PPDU transmitted from AP to STA is short.
This problem could potentially be mitigated by the aggregation feature that the current IEEE 802.11 specification supports, which allows for an AP to aggregate data intended to be transmitted to different STAs as long as the data transmitted is of the same Access Category. As there is larger amount of data to be transmitted by the AP to one or more STAs, this gives the STA sufficient time to transmit all of its MPDU data. Therefore, aggregation can reduce the inefficiency in using the channel in the uplink direction when the PPDU transmitted from AP to one STA is short.
However, even with this approach, additional latency results for transmitting data with access categories that are AC_VO and AC_VI (for audio and video). Also, for AC_VO and AC_VI traffic, typical IEEE 802.11 systems allow for a period of time called Transmission Opportunity (TXOP) to be used to complete the transmission of data related to that access category, and the data can be destined to different STAs in the network. However, given that the actual size of the data related to these access categories transmitted to each STA is small, the conventional mechanism that requires dT time to process the header will not allow for the medium to be used by an STA to transmit its data to the AP. The same is true even for longer period of time TXOP. Hence the STAs using the medium have to operate in a half-duplex mode for the entire TXOP period.
Accordingly there remains a need in the art for a solution that addresses the problems above among others.
The present invention relates generally to wireless networking, and more particularly to methods for improving communication channel use efficiency of a WLAN network that contains both full duplex and half duplex wireless stations. Embodiments of the invention include changes in the PHY layer protocol in IEEE 802.11. According to certain aspects, embodiments of the invention include methods that allow an AP to signal in a PPDU as to which STA can transmit data to the AP during the following PPDU time thus improve the efficiency of communication channels for uplink transmission. According to certain other aspects, embodiments of the invention include methods that allow further improvement of the use of the communication channels by sending data from STA to AP when there is no need for acknowledgement for data from STA to AP.
These and other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures, wherein:
The present invention will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and examples below are not meant to limit the scope of the present invention to a single embodiment, but other embodiments are possible by way of interchange of some or all of the described or illustrated elements. Moreover, where certain elements of the present invention can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention. Embodiments described as being implemented in software should not be limited thereto, but can include embodiments implemented in hardware, or combinations of software and hardware, and vice-versa, as will be apparent to those skilled in the art, unless otherwise specified herein. In the present specification, an embodiment showing a singular component should not be considered limiting; rather, the invention is intended to encompass other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present invention encompasses present and future known equivalents to the known components referred to herein by way of illustration.
According to certain aspects, embodiments of the invention include methods that allow an AP to signal in an earlier PPDU about which STA can transmit data during the next PPDU time thus lower the inefficiency of using the uplink medium. According to certain other aspects, embodiments of the invention include methods that allow the efficiency of medium use to be further improved by sending data from STA to AP when there is no need for acknowledgement for data from STA to AP.
The present invention will be described below in conjunction with embodiments compatible with standards such as the IEEE 802.11. However, the invention is not limited to these embodiments, and the principles of the invention can be extended using other standards or proprietary or other wireless environments such as Bluetooth, Zigbee, etc that typically operate in half duplex mode.
In some embodiments of the invention, the STAs are typically any portable devices (e.g. iPhone or similar smartphone, iPad or similar tablet computer, smart watch, laptop or notebook computer, etc.) that have built-in WiFi and/or Bluetooth transceiver capabilities such as those provided in chipsets and associated firmware from manufacturers. Those skilled in the art will be able to implement the STA functionality of the invention by adapting such chipsets and/or firmware after being taught by the present examples.
In some embodiments of the invention, the AP device is a device that is wireless or wired and has full duplex capability. In some embodiments of the invention, a station that has full duplex capacity is used in place of an AP device.
To address the issues discussed above and other issues, some of the embodiments of the invention implement new behavior and functionality at an AP and the STAs of a WLAN network are discussed in more details below.
In
The bottom row depicts the corresponding timing and duration of the PPDUs and ACK/BA frames that a transmitting wireless station STAx sends to the AP. For example, “STAx1 to AP” is the first PPDU STAx sends to AP, ACK/BA is the acknowledge frame STAy sends to AP for the first PPDU (“AP to STAy1”) it receives from AP, and “STA2 to AP” is the second PPDU STAx sends to AP, and so on.
In some embodiments of the invention, STAx and STAy are the same wireless station as long as it has a full-duplex capability. In some other embodiments of the invention, STAx and STAy are two different wireless stations each with only a hall-duplex capacity. For brevity and without the loss of generality, the following description with respect to
During the transmission as depicted in
As shown in
In some embodiments of the invention, the transmission of the first PPDU from AP to a wireless station STAy (“APtoSTAy1”) and the transmission of the first PPDU from STAx to AP (STAx1toAP) completes at the same time, as depicted in
In some embodiments of the invention, if AP expects an ACK/BA from STAy for the current PPDU1 that is being transmitted to STAy, AP also includes a bit in the header of the PPDU (“AP to STAy1”) to signal to STAx that STAx needs to hold off sending the next PPDU during the next data frame time.
In some embodiments of the invention, if AP uses a Block Acknowledgement (BA) instead of an ACK frame to acknowledge the received data, the wireless station STAx will need to use the same data rate for its BA frame as the data rate of the BA frame sent by AP to a wireless station STAy. It should be noted that if the AP does use/send a BA frame, the acknowledge frame sent by STAx can be either an ACK for a single MPDU or a BA for multiple MPDUs.
In some other embodiments of the invention, if AP does not require an ACK/BA from STAy for the current PPDU that is being transmitted to STAy, AP includes data in the header of the PPDU to signal to STAx that the next PPDU STAx sends to AP should not require an ACK/BA right immediately after that next PPDU transmission is completed. This is discussed further below with respect to
Returning to
According to some embodiments of the invention, in the TXOP case as discussed above, STAx needs to send multiple PPDUs to AP. However, having decoded the header of the PPDU(“AP to STAy1”), STAx knows that AP expects an BA frame from STAy, STAx waits after the ACK/BA frame is finished and then immediately sends the next PPDU to AP.
After transmission of the ACK/BA frames is completed, STAx starts transmission of the second PPDU (STAx2toAP) to AP at the same time when AP starts its transmission of the second PPDU to STAy (APtoSTAy2). Note that there is no processing time delay for the transmission of the second PPDU (STAx2toAP) as STAx2 already knows that it has the permission to use the channel in the uplink direction based on the decoding and processing of the preamble and additional signaling in the data transmitted from APtoSTAy1, as discussed above. The efficiency in using the channel in the uplink direction is therefore improved.
In the above discussion, AP sends multiple PPDUs consecutively to the same STAy, i.e., “AP to STAy1,” “AP to STAy2,”. . . and “AP to STAyn” represent the multiple PPDUs AP sends to STAy. It should be apparent to a person of ordinary skill in the art that AP may also send PPDUs to different STAs. For example, “AP to STAy1” may be the last of the data unit that AP transmits to a wireless station STAy1. After the ACK/BA, AP sends a PPDU to a different STA (STAy2), and to another different STA after that. As long as AP does not change its permission for STAx to use the uplink of the channel, the above discussion of the invention with respect to the improvement of channel use in the uplink direction still applies.
In some embodiments of the invention, the AP identifies in the PHY header the STA ID of an STA allowed to use the channel in the uplink direction during the current PPDU time, and then identifies the STA ID and duration in terms of the number of PPDUs or the actual PPDU duration allowed in either the PHY header or MAC Header or MAC frame of PPDU1 to STAy. This flexibility in the signaling is due to the fact that the timing for a receiving STA that is going to use the channel in the uplink direction during the next PPDU (that is not ACK/BA frame) is not timing critical.
In some embodiments of the invention, if the same STA (i.e., the STAx identified in the PHY header of the current PPDU duration) is allowed to use the channel in the uplink direction after its transmission of its PPDU, AP uses just a single bit to signal to the permission to STAx.
In
Turning to
It should be noted that the wireless station STAx that is transmitting data to the AP needs to complete its transmission before or exactly at the end of PPDU transmission by AP to an STAy.
It should also be noted that because the time duration of a PPDU data frame maybe different from the time duration of an standard ACK/BA frame, as depicted in
In the above discussion, AP sends multiple PPDUs consecutively to the same STAy, i.e., “AP to STAy1,” “AP to STAy2,” . . . and “AP to STAyn” represent the multiple PPDUs AP sends to STAy. It should be apparent to a person of skill in the art that AP may also send PPDUs to different STAs. For example, “AP to STAy1” may be the last of the data unit that AP transmits to a wireless station STAy1. After the ACK/BA, AP sends a PPDU to a different STA (STAy2), and to another different STA after that. As long as AP does not change its permission for STAx to use the uplink of the channel, the above discussion of the invention with respect to the improvement of channel use in the uplink direction remains true.
In
Turning to
At step 501, a first wireless station in the WLAN starts transmitting a first data unit over a communication channel to a second wireless station in the WLAN network. The first wireless station includes in the data unit header information identifying a wireless station in the WLAN network to signal that identified wireless station can transmit data to the first wireless station using the communication channel in the uplink direction.
At S502, the identified wireless station waits to see if the transmission of the first data unit has completed. According to some embodiments, the identified wireless station uses a counter to determine whether the transmission of the data unit from the first wireless station to the second wireless station is completed based on the information contained in the identifying information it decodes. In some embodiments, the second wireless station and the identified wireless station are the same full duplex device.
In some embodiments, the identifying information contained in the header of the first data unit further contains information to signal to the identified wireless station to wait for an acknowledgement data frame before transmitting a data unit to the first wireless station. If this is the case, the identified wireless station determines (S503) based on the identifying information it received whether the first wireless station expects an ACK/BA frame after finish sending the data unit. If yes, the identified wireless station waits for an acknowledgement data frame to finish (S504) before starts to transmit a data unit to the first wireless station (S505).
If the further information signals that no ACK/BA frame is expected after the current data frame, the first wireless station starts transmitting another data unit during the next transmission time period. The identified wireless station starts transmitting a data unit to the first wireless station (S505) at the same time as the first wireless station starts its transmission.
As discussed above, when the first station has acquired the channel for communication for the TXOP period and signals to the identified wireless station to use the entire TXOP time window, the identified wireless station checks to see if it has finished sending all the data units for the TXOP time window at S506. If not, the identified wireless station returns to step S502 to repeat the process for sending another data unit to the first wireless station. If yes, the process may return to step S501 and the first station may include in a new data unit identifying information signaling to the same or a different wireless station to use the communication channel in the uplink direction.
It should be apparent that many variations can be made to the above protocol and signaling to achieve the same or similar result, and the invention is not limited to the examples discussed in
Additionally, Table 1 compares the various current behaviors and expected behaviors according to different embodiments of the Invention.
Although the present invention has been particularly described with reference to the preferred embodiments thereof, it should be readily apparent to those of ordinary skill in the art that changes and modifications in the form and details may be made without departing from the spirit and scope of the invention. It is intended that the appended claims encompass such changes and modifications.
