Patent Description:
IEEE <NUM>-based wireless local area network (WLAN) becomes popular at an unprecedented rate. The IEEE <NUM> standard defines two access methods, namely Distributed Coordination Function (DCF) and Point Coordination Function (PCF). Most access points (APs) use only the DCF, and the PCF is excluded in IEEE <NUM>-<NUM>.

The DCF uses a carrier-sense multiple access with collision avoidance (CSMA/CA) algorithm, which is a simple access algorithm that was one of the main contributions to the huge success of Wireless Fidelity (Wi-Fi). 11e introduces enhanced distributed channel access (EDCA) that adds a statistical prioritization between devices to a distributed channel access (DCA).

The CSMA/CA implements time-sharing of the medium (in time and space) i.e., as one device is active and all other are in idle mode. As shown in <FIG>, by sharing the medium a total channel performance in a high density (HD) / very high density (VHD) deployment stays about the same, although the number of APs increases. Because the number of APs increases, the performance of each device is reduced accordingly, i.e., to the channel capacity divided by the number of devices connected.

11ax introduces a spatial reuse feature that allows multiple devices to use the same medium (in the same time and frequency). Furthermore, coloring enables devices to differentiate transmissions in their own network from transmissions in neighboring networks.

Adaptive power and sensitivity thresholds allow dynamically adjusting transmit power and signal detection threshold to increase spatial reuse by reducing the interference between medium sharing devices. However, each AP still needs to perform the EDCA procedure (BO count) with new clear channel assessment (CCA). In the spatial reuse method, all transmissions need to end at the same time. Consequently, all devices that want to participate in a session, must align their transmit (Tx) time to the Tx time of a first device.

In case that a Tx duration of the first device is small, a potential gain is reduced as the overhead of the other devices will be relatively high. Notably, in short data scenarios, there may even be negative gain, as no other device will reuse the medium.

Other solutions are proposed. In one solution, only devices with long Tx durations are allowed to initiate / enable a spatial reuse. This solution reduces the potential gain, as only a few devices access the medium, and the access probability decreases, which decreases the medium usage and the potential gain. Another solution proposes to use the maximum or a very long Tx duration (up to <NUM>) for all transmissions (regardless of an actual Tx duration). However, this will dramatically increase the Tx overhead and reduce the potential gain of the spatial reuse as well, due to an idle Tx time.

Document <CIT> discloses scheduling time division multiple access communications where: resource requests are received from a plurality of wireless stations, which may form a personal basic service set (PBSS) according to <NUM>. Had, for a scheduler to allocate time intervals between repeated scheduling intervals, an adapter for adjusting the duration of scheduling intervals in response to resource requests, and a transmitter sends scheduling messages to stations indicating the scheduling arrangements. The adapted duration depends on the total amount of data pending, increasing due to a higher combined amount needed. The scheduler determines priorities for each link between pairs of stations, calculated based on a current and average value for link data rate.

The duration may be changed to remain between maximum and minimum lengths.

In view of the above-mentioned disadvantages, embodiments of the present invention aim to improve the conventional approaches, in particular, to increase a spatial reuse efficiency. An objective is thus to optimize a network performance. One aim is to provide an optimal transmission duration for the entire network for reusing a medium of a wireless network.

The objective is achieved by the embodiments provided in the enclosed independent claims. Advantageous implementations of the embodiments of the present invention are further defined in the dependent claims.

A first aspect of the invention provides a device for a wireless network, wherein the device is configured to: share an own potential transmission duration with a plurality of other devices, obtain a potential transmission duration from each of the other devices, and perform an access method to gain direct access to a medium of the wireless network, wherein the device is configured to, if gaining direct access to the medium: determine an shared transmission duration based on all the potential transmission durations, and publish the shared transmission duration.

Thus, potential transmission durations of multiple devices (e.g. APs) in the wireless network can be shared among the devices. In this way, it is possible to find the shared transmission duration, which may be an optimal transmission duration for the entire system. This improves the spatial reuse efficiency in the wireless network, and thus the network performance.

In an implementation form of the first aspect, the access method includes a Carrier-Sense Multiple Access with Collusion Avoidance, CSMA/CA, method.

Particularly, all devices in the same wireless network may use CSMA/CA procedures to access the medium.

In an implementation form of the first aspect, the device is further configured to determine the shared transmission duration based on an average duration of all the potential transmission durations.

The shared transmission duration, for example, the optimal transmission duration, may be determined by the device that gains direct access to the medium. The determination may be performed based on the own potential transmission duration of the device and the potential durations of the other (neighbor) devices. In this implementation form, the average duration of all potential transmission durations is calculated as a simple solution.

In an implementation form of the first aspect, the device is configured to determine the shared transmission duration according to the shorter one of the average duration and a determined maximum duration.

Particularly, if the calculated average duration is shorter than the determined maximum duration, the calculated average duration may be set as the shared transmission duration. If it is not shorter, the determined maximum duration may be set as the shared transmission duration.

In an implementation form of the first aspect, the device is configured to provide medium reuse information to the other devices.

Once the shared transmission duration has been published by the device that gains access to the medium, all other devices in the network may obtain the information to efficiently reuse the medium of the wireless network.

In an implementation form of the first aspect, if the own potential transmission duration is zero, the device is configured to allow the other devices to reuse the medium during the entire shared transmission duration.

In case that the device has no traffic to be transmitted for the time being, the other devices are allowed to reuse the medium during the entire shared transmission duration. This increases the chances of the devices, which share their potential transmission durations with each other, to gain access to the medium.

In an implementation form of the first aspect, if not gaining direct access to the medium, the device is configured to obtain medium reuse information and the shared transmission duration determined by one of the other devices, which has gained direct access to the medium, and reuse the medium based on the reuse information and the shared transmission duration. This is claimed.

Accordingly, if the device is not a device gaining direct access to the medium, i.e. if one of the other devices gains access to the medium, the device obtains medium reuse information and the shared transmission duration from the other device that gains access to the medium.

In an implementation form of the first aspect, the device is configured to select an own transmission duration based on the own potential transmission duration and the shared transmission duration.

In an implementation form of the first aspect, the device is configured to select the own transmission duration according to the longer one of the own potential transmission duration and the shared transmission duration.

In particular, if the own potential transmission duration of the device is longer than the shared transmission duration, the own potential transmission duration may be set as the own transmission duration. If it is the other way around, the shared transmission duration may be set as the own transmission duration.

In an implementation form of the first aspect, the device is configured to reduce a transmission power and/or a throughput rate for transmitting data, if the shared transmission duration is longer than the own transmission duration.

In order to reduce an interference to transmissions of other devices, and to better utilize the (air) medium, all devices with shorter traffic duration may reduce their transmission power, and a physical level data rate of the transmission.

In an implementation form of the first aspect, the device is configured to transmit data during the own transmission duration, and transmit NULL data during the remaining time of the shared transmission duration, if the shared transmission duration is longer than the own transmission duration.

For the devices with shorter traffic duration, a data transmission may occupy only a part of the shared transmission duration. The remaining time of the shared transmission duration may be used to transmit NULL data until the end of the transmission.

A second aspect of the present invention provides a system comprising a plurality of devices for a wireless network, wherein each of the plurality of devices is configured to: share an own potential transmission duration with the other devices, and perform an access method to gain direct access to a medium of the wireless network, in particular perform a CSMA/CA method, wherein the device gaining direct access to the medium is configured to: determine an shared transmission duration based on all the potential transmission durations, and publish the shared transmission duration to the other devices. This is claimed.

All devices in the system are aware of their neighboring devices. Potential transmission durations of all the devices are shared with each other, in order to more efficiently reuse the medium. Thus, the system performance is improved.

In an implementation form of the second aspect, wherein the devices not gaining direct access to the medium are each configured to: obtain medium reuse information from the device gaining direct access to the medium, and reuse the medium based on the reuse information and the shared transmission duration. This is claimed.

The device, which gains direct access to the medium, shares medium reuse information and the determined shared transmission duration to the other devices. In particular, the other devices are the devices not gaining direct access to the medium.

A third aspect of the present invention provides a method performed by a device for a wireless network, wherein the method comprises: sharing an own potential transmission duration with a plurality of other devices, obtaining a potential transmission duration from each of the other devices, performing an access method to gain direct access to a medium of the wireless network, determining, if gaining direct access to the medium, an shared transmission duration based on all the potential transmission durations, and publishing the shared transmission duration.

The method of the third aspect and its implementation forms provide the same advantages and effects as described above for the wireless transmitting device of the first aspect and its respective implementation forms.

A fourth aspect of the present invention provides a method performed by a system of a plurality of devices for a wireless network, wherein the method comprises: sharing, by each of the devices, an own potential transmission duration with the other devices, performing, by each of the device, an access method to gain direct access to a medium of the wireless network, and determining, by the device gaining direct access to the medium, an shared transmission duration based on all the potential transmission durations, and publishing the shared transmission duration to the other devices.

The method of the fourth aspect and its implementation forms provide the same advantages and effects as described above for the wireless receiving device of the second aspect and its respective implementation forms.

<FIG> shows a device <NUM> according to an embodiment of the invention. The device <NUM> may comprise processing circuitry (not shown) configured to perform, conduct or initiate the various operations of the device <NUM> described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the device <NUM> to perform, conduct or initiate the operations or methods described herein.

The device <NUM> is configured to share an own potential transmission duration <NUM> with a plurality of other devices <NUM> (one of which is illustrated). The device <NUM> is configured to obtain a potential transmission duration <NUM> from each of the other devices <NUM>. The device <NUM> is further configured to perform an access method to gain direct access to a medium of the wireless network. If gaining direct access to the medium, the device <NUM> is configured to determine a shared transmission duration <NUM> based on all the potential transmission durations <NUM> and <NUM>, and publish the shared transmission duration <NUM>. This is claimed.

The device <NUM> according to an embodiment of the invention may be an AP or access node (AN) in the wireless network. A device <NUM> may be an AP or AN in the same wireless network. Particularly, the device <NUM> is aware of its neighbor devices, i.e. of the other devices <NUM>, and shares its own potential transmission duration <NUM> with all other devices <NUM>. Notably, the other devices <NUM> are also aware of the device <NUM>, and share their own potential transmission duration <NUM> with the device <NUM>.

The device <NUM> and the other devices <NUM>, according to an embodiment of the invention, are allowed to access the medium of the wireless network. In wireless transmission, the medium used may be the air, through electromagnetic, radio and microwave signals. Optionally, the device <NUM> may access the medium by using a CSMA/CA procedure. The other devices <NUM> may use CSMA/CA procedures to access the medium as well. The CSMA/CA procedures may all be identical.

Optionally, the device <NUM> according to an embodiment of the invention is configured to determine the shared transmission duration <NUM> based on an average duration of all the potential transmission durations <NUM>.

It should be understood that, the potential transmission duration <NUM> of each AP (including the device <NUM> and the other devices <NUM>, i.e. exemplarily each being an AP) is a potential transmission duration of the next traffic of each AP. Each AP may publish the potential transmission duration <NUM> by using an access controller (AC) of the system as shown in <FIG>. Alternatively, each AP may also share the potential transmission duration <NUM> by a direct communication between neighboring APs. In particular, each AP may publish its own transmission duration <NUM> together with any overheads needed to be added to the spatial reuse process.

The device <NUM>, particularly, the device <NUM> when gaining direct access to the medium, may calculate the average duration of all the potential transmission durations <NUM> obtained from each of the other devices <NUM>. The shared transmission duration <NUM> may be determined based on that average duration accordingly.

Optionally, the device <NUM> according to an embodiment of the invention is configured to determine the shared transmission duration <NUM> according to the shorter one of the average duration and a determined maximum duration. For example, the determined maximum duration is <NUM>. The shared transmission duration <NUM> may be calculated by equation (<NUM>) as: <MAT>.

Further, the device <NUM> according to an embodiment of the invention may be configured to provide medium reuse information to the other devices <NUM>. The device <NUM> may be an initiator AP of the system. Upon initiating a transmission duration, the device <NUM> may publish the shared transmission duration <NUM> and medium reuse information to the entire network system. Each participator AP in the spatial reuse system may align its own transmission duration to the shared transmission duration <NUM> published by the initiator AP, as shown in <FIG>.

Optionally, if the own potential transmission duration <NUM> of the device <NUM> is zero, the device <NUM> may allow the other devices <NUM> to reuse the medium during the entire shared transmission duration <NUM>.

According to the claimed invention, in case the device <NUM> does not gain direct access to the medium, the device <NUM> is configured to obtain medium reuse information and the shared transmission duration <NUM> determined by one of the other devices <NUM>, which has gained direct access to the medium. Then the device <NUM> is further configured to reuse the medium based on the reuse information and the shared transmission duration <NUM>.

If the device <NUM> has no direct access to the medium, that means, one of the other devices <NUM> has gained direct access to the medium, the other device <NUM> may determine the shared transmission duration <NUM>, and publish the medium reuse information and the shared transmission duration <NUM> accordingly.

Optionally, the device <NUM>, according to an embodiment of the present invention, may be configured to select the own transmission duration based on the own potential transmission duration <NUM> and the shared transmission duration <NUM>. In particular, in an implementation of the present invention, the device <NUM> is configured to select the own transmission duration according to the longer one of the own potential transmission duration <NUM> and the shared transmission duration <NUM>. For instance, the own transmission duration of each participator AP is selected by using equation (<NUM>) as: <MAT>.

A system according to an embodiment of the present invention comprises a plurality of devices for a wireless network. Particularly, the devices included in the system are the device <NUM> and the other devices <NUM> shown in <FIG>. Each of the plurality of devices <NUM> and <NUM> is configured to share an own potential transmission duration <NUM> with the other devices <NUM> and <NUM>. Each of the plurality of devices <NUM> and <NUM> is further configured to perform an access method to gain direct access to a medium of the wireless network, in particular perform a CSMA/CA method. In addition, if a device <NUM> or <NUM> gains direct access to the medium, the device <NUM> or <NUM> is configured to determine an shared transmission duration <NUM> based on all the potential transmission durations <NUM>, and publish the shared transmission duration <NUM> to the other devices <NUM> and/or <NUM>.

Optionally, if a device <NUM> or <NUM> does not gain direct access to the medium, the device <NUM> or <NUM> may be configured to obtain medium reuse information from another device <NUM> or <NUM> that gains direct access to the medium. And the device <NUM> or <NUM> may also configured to reuse the medium based on the reuse information and the shared transmission duration <NUM>.

<FIG> shows a transmission duration usage according to an embodiment of the present invention.

Device A shown in <FIG> is the device <NUM> that gains direct access to the medium of the wireless network. Accordingly, Device B, C and D are other devices <NUM> in the same wireless network. "Non Participates" are devices that not participate in the medium reuse process (i.e. are not included in the system <NUM>).

In particular, all Device A - D use CSMA/CA procedures to access the medium as shown in <FIG>. Device A, that gains direct access to the medium, determines a shared transmission duration <NUM>. Further, medium reuse information and the determined shared transmission duration <NUM> are published by Device A. A length of each "traffic data" block refers to an own potential transmission duration <NUM> of each device. All devices with shorter potential transmission duration <NUM>, namely, Device A, B, C and D that participate in the reuse of the medium, may reduce a transmission power and/or a throughput rate for transmitting data. The traffic data may be transmitted through a physic layer. The throughput rate may include a modulation coding scheme (MCS) rate, a CC rate, a dual carrier modulation (DCM) rate, or a guard interval (GI) rate. The transmission power and the throughput rate may be reduced in order to reduce interference, and to better utilize the air medium.

Possibly, one of the participator devices may have no traffic data, in other words, the own potential transmission duration <NUM> for next traffic of this device may be zero. Then the device without any traffic may capture the medium (using CSMA/CA) and enable the other devices to send data. This increases a network utilization, specifically by prioritizing the device (e.g. AP) traffic.

Upon getting access to the medium, a Tx device may check if reuse of the medium is possible and needed. If no reuse is needed/possible, the Tx device may use its own transmission duration. If reuse is needed/possible, the Tx device may publish an optimal transmission duration, i.e. the shared transmission duration <NUM>, needed for all potential participators in the reuse. According to the reuse method, the published transmission duration should include all overheads.

Notably, all devices, which participate in the medium reuse process, may follow a reuse method guideline (e.g. such as reduce CCA and Tx Power). In addition, all devices may transmit their own data traffics in parallel. As defined by the spatial reuse process, the participator Tx devices will never extend traffic over the protected shared transmission duration published <NUM> by the first Tx device (in case a new traffic arrived that is not calculated yet). Possibly, the participator Tx devices may adjust their transmit time using an aggregation and fragmentation method, in order to reduce a throughput rate and transmit power, or add NULL data to be transmitted.

Optionally, each Tx device may update a new transmission duration upon each change in Tx buffers. In addition, to avoid "flooding" the network with updates, a timer may be applied that prevents new update before this timer expires.

In this way, a medium reuse efficiency is increased by using a specific designed optimal transmission duration for the entire network, instead of a respective transmission duration for respective device according to needs of the device. Notably, an optimal transmission duration may optimize a network performance.

When working in HD/VHD enterprise environment, a cell size is relatively small. Most stations (STAs) are close to the APs and thus keep a high MCS. In a HD/VHD environment, the DCF CSMA/CA process itself is a bottleneck. Specifically, by allowing one device giving access to the medium to several devices, a reuse increases and shortens the overall access time of the entire network.

Even when a STA is in an active traffic, buffers are not always full, and some transmissions will be very short transmissions (High MCS with low traffic). In one example, it is estimated that an amount of short transmission durations to be ~<NUM>% of all traffic in the network. By increasing the transmission duration to the optimal duration of the entire network, a method according to an embodiment of the present invention will reduce a need for multiple CSMA/CA and a huge overhead. Thus, the method according to an embodiment of the present invention is able to allow using the reuse process even for very short traffic duration.

In a specific implementation according to an embodiment of the invention, <NUM> APs (devices <NUM>/<NUM>) are included in a wireless system. Particularly, <NUM> APs in all <NUM> APs are participated in a reuse network, wherein <NUM> APs have 2mSec Tx durations and other <NUM> APs have <NUM>. 5mSec Tx durations. Assuming all APs have constant traffic and durations, and there is no additional reuse overhead, according to the embodiment of the invention, an average time of transmission is calculated as: Average time of transmission = (DCF Overhead + <NUM>)). However, in a conventional method, the average time of transmission is calculated as:
Average time of transmission = (<NUM>% * (DCF Overhead + <NUM> + DCF Overhead + <NUM>)) + (<NUM>% * (DCF Overhead + <NUM>)).

Considering <NUM> networks (each including <NUM> APs in the network and <NUM> AP in reuse network) with similar behavior, and a DCF overhead > <NUM>, the average time of transmission according to a conventional method is equals to <NUM>% *(<NUM> + <NUM> + <NUM> + <NUM>) + <NUM>% * (<NUM> + <NUM>) = <NUM>. By contrast, the average time of transmission according to an embodiment of the invention will be (<NUM> + <NUM>) = <NUM>. A Gain of <NUM>%, i.e. (<NUM>/<NUM>) - <NUM>%, can be achieved.

<FIG> shows a method <NUM> performed by a device <NUM> for a wireless network, according to an embodiment of the present invention. In particular, the device <NUM> is the device <NUM> of <FIG>. The method <NUM> comprises: a step <NUM> of sharing an own potential transmission duration <NUM> with a plurality of other devices <NUM>; a step <NUM> of obtaining a potential transmission duration <NUM> from each of the other devices <NUM>; a step <NUM> of performing an access method to gain direct access to a medium of the wireless network; a step <NUM> of determining, if gaining direct access to the medium, an shared transmission duration <NUM> based on all the potential transmission durations <NUM>; and a step <NUM> of publishing the shared transmission duration <NUM>. Particularly, the other devices <NUM> are the other devices <NUM> of <FIG>.

<FIG> shows a method <NUM> performed by a system of a plurality of devices <NUM> and <NUM> for a wireless network, according to an embodiment of the present invention. In particular, the device <NUM> is the device <NUM> of <FIG>, and the other devices <NUM> are the other devices <NUM> of <FIG>. The method <NUM> comprises: a step <NUM> of sharing, by each of the devices <NUM> and <NUM>, an own potential transmission duration <NUM> with the other devices <NUM> and <NUM>; a step <NUM> of performing, by each of the devices <NUM> and <NUM>, an access method to gain direct access to a medium of the wireless network; and a step <NUM> of determining, by the device <NUM> or <NUM> gaining direct access to the medium, an shared transmission duration <NUM> based on all the potential transmission durations <NUM>, and publishing the shared transmission duration <NUM> to the other devices <NUM> and <NUM>.

The present invention has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed invention, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word "comprising" does not exclude other elements or steps and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.

Claim 1:
Device (<NUM>) for a wireless network, wherein the device (<NUM>) is configured to:
share an own potential transmission duration (<NUM>) with a plurality of other devices (<NUM>),
obtain a potential transmission duration (<NUM>) from each of the other devices (<NUM>), and
perform an access method to gain direct access to a medium of the wireless network,
wherein the device (<NUM>) is configured to, if gaining direct access to the medium:
determine a shared transmission duration (<NUM>) based on all the potential transmission durations (<NUM>, <NUM>), and
publish the shared transmission duration (<NUM>), and
wherein the device (<NUM>) is configured to, if not gaining direct access to the medium:
obtain medium reuse information and the shared transmission duration (<NUM>) determined by one of the other devices (<NUM>), which has gained direct access to the medium, and
reuse the medium based on the reuse information and the shared transmission duration (<NUM>).