KR101705977B1 - Energy efficient spatial stream allocation method and apparatus in 802.11ac network - Google Patents

Abstract

An energy efficient spatial stream allocation method and apparatus in an 802.11ac network are disclosed. A method for allocating a spatial stream for each terminal in a repeater, the method comprising: (a) determining a number of spatial streams of each terminal according to a length of a data packet (PSDU) to be transmitted to each terminal; And (b) transmitting a null data packet including the number of spatial streams of each terminal to each of the terminals.

Description

[0001] The present invention relates to an energy efficient spatial stream allocation method and apparatus for an 802.11ac network,

The present invention relates to an energy efficient spatial stream allocation method and apparatus in an 802.11ac network.

802.11ac downlink (DL) In an MU-MIMO, an access point (AP) transmits data to a plurality of receiver terminals. That is, the AP can simultaneously transmit data to a plurality of terminals having the same group identification information (Group ID).

However, since each receiving terminal can not share channel coefficients received for each antenna, the inter-terminal interference can not be eliminated. Accordingly, the AP multiplexes the data streams of the receiving terminals into one PPDU (PLC Protocol Data Unit (PLCP)) through precoding.

Then, each receiving terminal can eliminate inter-terminal interference. However, if the length of the physical service data unit (PSDU) between receiving terminals differs, the multiple PSDUs are determined by the largest PSDU transmission time. Padding is performed on short PSDUs to match the largest PSDU transmission time.

As a result, resources and energy are wasted. In the prior art, energy efficiency is improved by specifying the frame length per terminal in order to solve this problem.

The conventional technique uses an algorithm that specifies the frame length per terminal in order to reduce the energy loss on the receiving side which is wasted due to padding. However, this method has a problem of changing the standard and the wireless LAN structure.

The present invention relates to an energy efficient spatial stream allocation method and apparatus in an 802.11ac network capable of reducing energy waste of a receiving terminal caused by a spatial stream transmission difference due to a difference in source rate in an 802.11 ac network .

In addition, the present invention increases the energy efficiency at the receiving terminal without decreasing the throughput by reducing the MCS (Modulation Coding Scheme) and the number of antennas in transmitting a spatial stream having a short transmission length, Efficient spatial stream allocation method and apparatus in an 802.11ac network.

The present invention provides an energy efficient spatial stream allocation method in an 802.11ac network.

According to an embodiment of the present invention, there is provided a method of allocating a spatial stream for each terminal in a repeater, the method comprising the steps of: (a) determining a number of spatial streams of each terminal according to a length of a data packet (PSDU) ; And (b) transmitting a null data packet including the number of spatial streams of each terminal to each of the terminals.

In the step (a), the number of spatial streams of each terminal can be determined in proportion to the length of a data packet (PSDU) to be transmitted to each terminal.

And transmit the data packet to each terminal using the determined number of spatial streams of each terminal.

If the data packet (PSDU) is shorter than the other data packets, a smaller number of spatial streams are allocated, or a lower version of a modulation coding technique (MCS) is applied to adjust the length of time.

According to another embodiment of the present invention, there is provided a method of receiving data according to spatial stream allocation in a terminal, comprising the steps of: (a) receiving a null data packet including a spatial stream number from a relay; (b) extracting the number of spatial streams in the null data packet, determining and activating the number of antennas to be activated by the terminal according to the extracted number of spatial streams; And (c) receiving a data packet from the repeater using the number of active antennas.

In the step (b), the number of antennas corresponding to the number of spatial streams may be activated among all the antennas provided.

In accordance with another aspect of the present invention, an apparatus is disclosed for allocating energy efficient spatial streams in an 802.11ac network.

According to an embodiment of the present invention, there is provided a repeater for allocating a spatial stream for each terminal, the repeater comprising: a determining unit for determining the number of spatial streams of each terminal according to a length of a data packet (PSDU) to be transmitted to each terminal; And a communication unit for transmitting a null data packet including the number of spatial streams of each terminal to each of the terminals.

The determination unit may determine the number of spatial streams for each terminal in proportion to a length of a data packet to be transmitted to each terminal.

According to another embodiment of the present invention, there is provided a terminal for receiving data according to a spatial stream allocation, comprising: a communication unit for receiving a null data packet including a number of spatial streams from a repeater; And an antenna setting unit for extracting the number of spatial streams from the null data packet and determining and activating the number of antennas to be activated according to the extracted number of spatial streams, And a data packet is received from the repeater by using the data packet.

By providing an energy efficient spatial stream allocation method and apparatus in an 802.11ac network in accordance with an embodiment of the present invention, There is an advantage that energy waste of the terminal can be reduced.

In addition, the present invention increases the energy efficiency at the receiving terminal without decreasing the throughput by reducing the MCS (Modulation Coding Scheme) and the number of antennas in transmitting a spatial stream having a short transmission length, There is also an advantage.

In addition, the present invention not only reduces energy loss through removal of pad bits in MU-MIMO, but also has the advantage of providing higher energy efficiency to a receiving terminal while maintaining performance in an 802.11ac network.

FIG. 1 is a table for explaining a power consumption model of a receiving terminal according to an embodiment of the present invention; FIG.
2 is a block diagram illustrating an 802.11ac network architecture in accordance with an embodiment of the present invention.
3 is a flow diagram illustrating an energy efficient spatial stream allocation method in an 802.11ac network in accordance with an embodiment of the present invention.
FIG. 4 illustrates a conventional spatial stream allocation operation according to an embodiment of the present invention.
5 is a diagram showing simulation results according to an embodiment of the present invention.
6 is a block diagram schematically illustrating an internal configuration of a repeater according to an embodiment of the present invention;
FIG. 7 is a block diagram schematically illustrating an internal configuration of a terminal according to an embodiment of the present invention; FIG.

The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated and described in the drawings. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

An energy efficient spatial stream allocation method and apparatus for reducing energy loss through removal of pad bits in an MU-MIMO according to an embodiment of the present invention will be described with reference to FIG. 1, The model will be described.

1 is a table for explaining a power consumption model of a receiving terminal according to an embodiment of the present invention.

C. Li, C. Peng, S. Li and X. Wang, "Energy-based rate adaptation for 802.11n," models idle power and received power of a receiving terminal in an 802.11n network, have. The received power consumption of the receiving terminal and the consumed power during the idle time are expressed by Equations (1) and (2), respectively.

는 수신 소모 파워를 나타내고, 수학식 2의

는 유휴 시간 동안 소모 파워(즉, 유휴 소모 파워)를 나타내며,

는 수신 안테나 개수를 나타내고,

는 공간 스트림 개수를 나타내며,

는 채널 대역폭을 나타내고,

은 전송률을 나타낸다.In Equation (1)

Represents the reception consumed power, and Equation 2

Represents the consumed power (i.e., idle consumed power) during the idle time,

Represents the number of receiving antennas,

Represents the number of spatial streams,

Represents the channel bandwidth,

Indicates a transmission rate.

Referring to C. Li, C. Peng, S. Li and X. Wang, "Modeling of Energy-based rate adaptation for 802.11n", the equation obtained by measuring data using a receiving terminal providing 802.11ac, (1) and (2), and the changed variables are summarized as shown in Table 1.

As shown in Equations (1) and (2), it can be seen that the number of antennas of the receiving terminal greatly affects the power consumption.

Accordingly, in an embodiment of the present invention, a technique for reducing the power consumed by selecting only the number of spatial streams and turning on only the antennas corresponding to the number of spatial streams at the receiving terminal will be proposed.

2 is a block diagram illustrating an 802.11ac network architecture according to an embodiment of the present invention.

Referring to FIG. 2, an 802.11ac network according to an embodiment of the present invention includes a relay 210 and a plurality of terminals 220.

The repeater 210 functions to relay data in the network.

For example, the repeater 210 functions to transmit data to a terminal having the same group identification information (group ID). In addition, the repeater 210 may perform a function of receiving a data transmission request of each terminal and processing it.

In addition, the repeater 210 can notify each receiving terminal of the number of selected spatial streams through Null Data Packet (NDP).

Each terminal 220 functions to transmit and receive data through a repeater 210.

Each terminal 220 according to an exemplary embodiment of the present invention includes a plurality of antennas and is configured to transmit data according to the number of selected spatial streams corresponding to each terminal 220 included in the null data packet received from the repeater 210, Can be turned on or off to receive data.

More specifically, for example, suppose that the number of spatial streams corresponding to the first terminal is four, and the number of spatial streams corresponding to the second terminal is two. The repeater 210 may transmit the number of selected spatial streams corresponding to each terminal 220 to each terminal 220 in a null data packet. Accordingly, the first terminal extracts the number of spatial streams included in the null data packet (i.e., 4), and since the number of spatial streams is four, the first terminal can receive data by turning on four antennas. On the other hand, the second terminal can receive data by turning on two antennas because the number of spatial streams included in the null data packet received from the repeater is 2.

This will be described in more detail below with reference to the related drawings.

FIG. 3 is a flowchart illustrating an energy efficient spatial stream allocation method in an 802.11ac network according to an exemplary embodiment of the present invention. FIG. 4 is a diagram illustrating a method of allocating spatial streams according to an exemplary embodiment of the present invention. And FIG. 5 is a diagram showing simulation results according to an embodiment of the present invention.

In step 310, the repeater 210 determines the number of spatial streams for each terminal according to the length of a physical service data unit (PSDU) to be transmitted to each terminal.

For example, assume that the length of the second PSDU to be transmitted to the second terminal is half as long as the length of the first PSDU to be transmitted to the first terminal. Here, it is assumed that the numbers of antennas of the first terminal and the second terminal are the same.

Since the length of the first PSDU for the first terminal is greater than the length of the second PSDU for the second terminal, the repeater 210 can determine the number of spatial streams of the first terminal to be n. Here, n is a natural number and may be equal to or less than the total number of antennas provided in each terminal.

Then, the repeater 210 can determine the number of spatial streams for the second terminal to be n / 2 since the length of the second PSDU for the second terminal is half the length of the first PSDU.

In this way, the repeater 210 can determine the number of spatial streams for each terminal using the length of the PSDU to be transmitted to each terminal.

Then, in step 315, the repeater 210 transmits the number of spatial streams determined for each terminal to each terminal by including it in a null data packet.

In step 320, each terminal extracts the number of spatial streams for each terminal in the null data packet received from the repeater.

In step 325, each terminal activates at least a part of the plurality of antennas according to the extracted number of spatial streams.

In step 330, the repeater 210 transmits a data packet according to the determined number of spatial streams for each terminal.

Accordingly, each mobile station can receive a data packet for each mobile station using the number of active antennas according to the number of spatial streams.

In this way, the repeater 210 according to the embodiment of the present invention can not add pad bits to the short PSDU or specify the length of the data frame for each terminal, It is advantageous in that the energy efficiency can be improved without decreasing the throughput by informing each terminal by transmitting it.

3, it is assumed that the repeater 210 determines only the number of spatial streams according to the length of the PSDU for each terminal. However, the repeater 210 may further include a modulation coding technique (MCS) according to the length of the PSDU for each terminal, Modulation Coding Scheme may be determined differently.

For example, the repeater 210 may select a lower order modulation coding technique compared to a PSDU having a relatively long length for a relatively short PSDU.

Accordingly, the repeater 210 can increase the energy efficiency by adjusting the PSDU transmission time regardless of the length of the PSDU to be transmitted to each terminal.

FIG. 4 is a diagram illustrating a conventional spatial stream allocation operation according to an embodiment of the present invention.

As shown in FIG. 4A, conventionally, unnecessary pad bits are added to a PSDU for a short PSDU, and the length of the entire PSDU is adjusted to be transmitted. This is problematic in that a terminal receiving a PSDU having a relatively short length is followed by an unnecessary task of removing a pad bit.

4 (b) illustrates a spatial stream allocation operation according to an embodiment of the present invention. In an embodiment of the present invention, the number of spatial streams is differently allocated according to the length of each PSDU of each terminal, In a terminal having a short length, data can be received relatively slowly, so that the total transmission time of the PSDU can be adjusted.

That is, the horizontal axis in Fig. 4 represents time. When the length of the data packet transmitted to each user in the MU-MIMO is different in time, the number of the spatial streams and the MCS can be adjusted to reduce the addition of pad bits. Even if the same amount of data is sent, the sending time depends on the number of spatial streams or the MCS. Thus, the present invention can match a relatively long data packet and a sending time by sending a short data packet using a small number of spatial streams or a low MCS. This has the advantage that the portion of the pad bits added to the short data packet is reduced. In addition, using a small number of spatial streams and a lower version of MCS can reduce energy consumption at the UE, thereby improving energy efficiency. This is an advantage that the throughput is not affected because the gain is obtained by reducing the pad bits.

5 is a diagram showing simulation results according to an embodiment of the present invention. In an embodiment of the present invention, it is assumed that each terminal has four antennas, and a network has four terminals. At this time, it is assumed that each terminal is set to be randomly located in the radius of 1 m from the relay, and the repeater services two terminals at a time and returns to the round robin scheduling.

In the round robin scheduling scheme, the greater the difference in the source rate between the terminals being simultaneously served, the greater the effect. Therefore, the energy efficiency and the throughput were checked while changing the source rate ratio between the two terminals served simultaneously. Pattern.

The basic source rate of each terminal is 100Mbps, and one of two terminals simultaneously maintained 100Mbps and the other terminal performs simulation by decreasing from 100Mbps to 10Mbps and has a value of 100 ~ 10Mbps. When it is assumed that sending a single aggregated packet is a period, the simulation is run for 20 periods and the results of each period are averaged.

Highest Goodput (HG) is an algorithm that selects the number of antennas and MCS that can achieve the highest throughput to achieve the highest throughput in a given channel environment. We compared the performance of the HG algorithm with the performance of EESA.

Figure 5 (a) shows the total throughput of the network. FIG. 5 (b) is a graph showing the energy efficiency (J / bit), which is the energy J consumed to transmit one bit. The horizontal axis represents the ratio of the source rate between the two terminals. As shown in FIG. 5, the spatial stream allocation method according to an embodiment of the present invention shows that the larger the difference in source rate between the two terminals, the greater the effect is.

This is because as the difference in the source rate between the terminals increases, the length difference between the PSDUs transmitted to the two terminals increases, and the number of pad bits increases. Therefore, the spatial stream allocation method according to an embodiment of the present invention reduces energy waste due to pad bits, and thus energy efficiency is high.

6 is a block diagram schematically illustrating the internal structure of a repeater according to an embodiment of the present invention.

6, a repeater 210 according to an exemplary embodiment of the present invention includes a communication unit 610, a determination unit 615, a memory 620, and a processor 625.

The communication unit 610 is a means for transmitting and receiving data to and from another device (e.g., a terminal) through a communication network.

For example, the communication unit 610 may transmit a null data packet including the number of spatial streams to each terminal under the control of the processor 625. [

The determination unit 615 determines the number of spatial streams of each terminal according to the length of a data packet (PSDU) to be transmitted to each terminal.

For example, the determination unit 615 can determine the number of spatial streams for each terminal in proportion to the length of a data packet to be transmitted to each terminal. This is the same as that described above with reference to FIG. 3, so that redundant description will be omitted.

The memory 620 stores various algorithms necessary for performing an energy efficient spatial stream allocation method in an 802.11ac network according to an embodiment of the present invention, various data derived from the algorithm, and the like.

The processor 625 functions to control the internal components (e.g., the communication unit 610, the determination unit 615, the memory 620, etc.) of the repeater 210 according to an embodiment of the present invention do.

7 is a block diagram schematically illustrating an internal configuration of a terminal according to an embodiment of the present invention.

Referring to FIG. 7, a terminal 220 according to an embodiment of the present invention includes a communication unit 710, an antenna setting unit 715, a memory 720, and a processor 725.

The communication unit 710 transmits and receives data to and from other devices (e.g., the repeater 210) via a communication network.

The communication unit 710 may receive the null data packet including the number of spatial streams from the repeater 210 under the control of the processor 725 and output it to the antenna setting unit 715. [

The antenna setting unit 715 functions to activate the number of antennas according to the number of spatial streams.

For example, the antenna setting unit 715 extracts the number of spatial streams included in the null data packet received from the repeater 210, and then activates the number of antennas to match the extracted number of spatial streams.

For example, assume that the terminal 220 has four antennas in total, and that the number of spatial streams included in the null data packet received from the repeater 210 is two. The antenna setting unit 715 can activate two of the four antennas according to the extracted number of spatial streams (2).

Accordingly, the terminal 220 can receive data received from the repeater 210 using the two antennas.

The memory 720 stores various algorithms necessary for performing a method of receiving data according to a spatial stream allocation according to an embodiment of the present invention, various data derived from the algorithm, and the like.

The processor 725 has a function of controlling internal components (e.g., the communication unit 710, the antenna setting unit 715, the memory 720, and the like) of the terminal according to an embodiment of the present invention do.

Meanwhile, an energy efficient spatial stream allocation method in an 802.11ac network according to an embodiment of the present invention can be implemented in a form of a program command that can be performed through a variety of electronic information processing means and recorded in a storage medium. The storage medium may include program instructions, data files, data structures, and the like, alone or in combination.

Examples of program instructions include machine language code such as those produced by a compiler, as well as devices for processing information electronically using an interpreter or the like, for example, a high-level language code that can be executed by a computer.

The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

210: repeater
220: first terminal, second terminal

Claims (11)

A method for allocating a spatial stream for each terminal in a repeater,
(a) determining a number of spatial streams of each terminal according to a length of a data packet (PSDU) to be transmitted to each terminal; And
(b) transmitting a null data packet including the number of spatial streams of each terminal to each of the terminals.
The method according to claim 1,
The step (a)
Wherein the number of spatial streams of each terminal is determined in proportion to a length of a data packet (PSDU) to be transmitted to each terminal.
The method according to claim 1,
And transmitting the data packet to each terminal using the determined number of spatial streams of each terminal.
The method according to claim 1,
The step (a)
Wherein a modulation coding technique is further determined according to a length of a data packet (PSDU) to be transmitted to each of the terminals.
The method according to claim 1,
Characterized in that when the data packet (PSDU) is shorter than the other data packets, a small number of spatial streams are allocated or a length of time is adjusted by applying a lower version of a modulation coding technique (MCS). Spatial stream allocation method.
A method for receiving data according to spatial stream allocation in a terminal,
(a) receiving a null data packet comprising a spatial stream number from a repeater;
(b) extracting the number of spatial streams in the null data packet, determining and activating the number of antennas to be activated by the terminal according to the extracted number of spatial streams; And
(c) receiving a data packet from the repeater using the number of active antennas.
The method according to claim 6,
The step (b)
And activating the number of antennas corresponding to the number of spatial streams in the entire antenna.
A computer-readable recording medium having recorded thereon a program code for performing the method of any one of claims 1 to 7.
A repeater for allocating a spatial stream for each terminal,
A determination unit for determining the number of spatial streams of each terminal according to a length of a data packet (PSDU) to be transmitted to each terminal; And
And a null data packet including a number of spatial streams of each terminal is transmitted to each of the terminals.
10. The method of claim 9,
Wherein,
Wherein the number of spatial streams for each terminal is determined in proportion to a length of a data packet to be transmitted to each terminal.
A terminal for receiving data according to a spatial stream allocation,
A communication unit for receiving a null data packet including a number of spatial streams from a repeater; And
And an antenna setting unit for extracting the number of spatial streams from the null data packet and determining and activating the number of antennas to be activated by the terminal according to the extracted number of spatial streams,
Wherein,
And receives a data packet from the repeater using the number of active antennas.

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