Patent Application
20110200130
The present application claims priority of Korean Patent Application No. 10-2010-0012791 filed on Feb. 11, 2010, which is incorporated herein by reference in its entirety.
1. Field of the Invention
Exemplary embodiments of the present invention relate to a method and apparatus for transmitting/receiving data; and, more particularly, to a method and apparatus for transmitting/receiving data in a Multi User-Multi Input Multi Output (MU-MIMO) system.
2. Description of Related Art
An 802.11 wireless LAN basically supports an access point (AP) serving as an association point of a distributed system (DS), and a basic service set (BSS) including a plurality of stations (STAs).
As the number of wireless LAN users has recently increased, there is an increasing demand for increasing data throughput provided by a single BSS. An existing wireless LAN does not allow a single terminal to communicate with two or more terminals at the same time. To provide the throughput of gigabytes or more, extensive research has been conducted to make it possible for a single terminal to communicate with a plurality of terminals at the same time. Representative examples are a MU-MIMO technique and a multi frequency channel technique. If using these techniques, a single terminal operates as if it exchanges data with a plurality of terminals through independent communication paths at the same time. Accordingly, a single terminal can transmit data to a plurality of terminals at the same time, leading to a significant increase in the throughput of a BSS.
Meanwhile, it is general that data is transmitted using a plurality of independent communication paths at the same time, and a control signal (a reception acknowledgement (Ack) signal), such as Ack or block Ack, is transmitted not through independent communication paths but through a communication path shared by all terminals. This is done for preventing collision due to the simultaneous transmission of data by receiving a control signal transmitted from other terminal. Hereinafter, the plurality of independent communication paths will be referred to as multi channels, and the communication path shared by all terminals will be referred to as a primary channel.
As described above, if a single terminal (e.g., an AP) transmits data to a plurality of terminals (e.g., STAs) through multi channels at the same time, the STAs having received the data transmit an Ack or block Ack signal through a primary channel. At this time, the above-mentioned data collision may occur if the plurality of STAs having received the data transmit the Ack or block Ack signal through the same primary channel, without taking into consideration the data reception of other STAs.
An embodiment of the present invention is directed to prevent data collision by setting an order in which receiving stations having received data transmit reception Ack signals to a transmitting station, when one transmitting station transmits data to the plurality of receiving stations.
Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it is obvious to those skilled in the art to which the present invention pertains that the objects and advantages of the present invention can be realized by the means as claimed and combinations thereof.
In accordance with an embodiment of the present invention, a method for transmitting, by a single transmitting station, data to a plurality of receiving stations includes: generating a plurality of data frames including the data and Ack order information; transmitting the plurality of data frames to the plurality of receiving stations; and sequentially receiving block Ack signals from the plurality of receiving stations according to the Ack order information.
In accordance with another embodiment of the present invention, a method for receiving, by a plurality of receiving stations, data transmitted from a single transmitting station includes: receiving data frames including the data and Ack order information; acquiring the Ack order information from the data frames; and sequentially transmitting block Ack signals to the transmitting station according to the Ack order information.
In accordance with another embodiment of the present invention, a method for transmitting, by a single transmitting station, data to a plurality of receiving stations includes: generating, by the transmitting station, a plurality of data frames including the data and Ack order information; transmitting, by the transmitting station, the plurality of data frames to the plurality of receiving stations; receiving, by the plurality of receiving stations, the data frames; acquiring, by the plurality of receiving stations, the Ack order information from the data frames; and sequentially transmitting, by the plurality of receiving stations, block Ack signals to the transmitting station according to the Ack order information.
Exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present invention.
In a wired/wireless communication network, data is processed in predetermined units. Such data unit is different in each communication protocol. For example, in IEEE 802.11, the international standard for wireless LAN, data unit in a Media Access Control (MAC) is called a MAC Protocol Data Unit (MPDU). To increase the efficiency of a MAC layer with respect to a data rate of a physical layer, IEEE 802.11 proposes a method that aggregates a plurality of MPDUs and processes them by a single data unit in the physical layer. The aggregated MPDUs are referred to as Aggregated-MPDU (A-MPDU).
As illustrated in
Referring again to
According to the conventional art, when a receiving station receives the A-MPDU of
The data transmission and reception process and the data reception Ack process illustrated in
To solve such problems, the present invention provides a method for transmitting/receiving data, which is capable of preventing the collision of reception Ack signals by setting an order in which a plurality of receiving stations having received data frames transmit reception Ack signals.
Hereinafter, a method for transmitting/receiving data in accordance with exemplary embodiments of the present invention will be described in detail.
To set the reception Ack signal transmitting order of the receiving stations, a subframe structure illustrated in
Referring to
Therefore, the transmitting station generates a plurality of data frames including data to be transmitted to the respective receiving stations and Ack order information, or receives them from the outside. In this embodiment, the Ack order information included in the data frame contains information representing a relative order in which a plurality of receiving stations are to transmit the block Ack signals. For example, the Ack order information of the second A-MPDU may contain information of “Ack Order=2”. The second receiving station having received the data frame containing this Ack order information can know that it should transmit the block Ack signal for the second time after another station.
As described above, the data frame from the transmitting station is transmitted through a plurality of independent paths, i.e., multi channels, whereas the block Ack signals from the receiving stations are transmitted through a communication path shared by all stations, i.e., a primary channel. Therefore, in this embodiment, the respective receiving stations check its own Ack order, checks whether another receiving station transmits a block Ack signal, and transmits a block Ack signal in its own turn. For example, in the case of
In addition, in another embodiment of the present invention, the receiving stations may calculate (SIFS time+block Ack transmission time) according to their Ack order and transmit their block Ack signals, without confirming the block Ack transmission of other receiving stations. For example, in the case of
In the embodiment of
Therefore, in the embodiment of
As illustrated in
Like in the embodiment of
For example, the Ack order information may contain information (Ack order=1, 2, 3) representing a relative order in which the receiving stations are to transmit their block Ack signals, which has been described above in the embodiments 1 and 2, and information on relative transmission time (e.g., 2 seconds). The second receiving station having received the data frame containing the Ack order information checks its own Ack order and relative transmission time information, and transmits a block Ack signal two seconds after the first receiving station transmits a block Ack signal. Therefore, the relative transmission time information represents the relative order to transmit the block Ack signals, which has been described above in the embodiment 1.
Meanwhile, in another embodiment, the Ack order information may contain absolute time information for the respective receiving stations to transmit their block Ack signals. In this case, the receiving stations transmit their block Ack signals at time specified in the Ack order information, regardless of whether other receiving stations transmit their block Ack signals or not.
In another embodiment, instead of the above-described relative or absolute time information, information on the longest data frame may be contained in the Ack order information. For example, in a case in which the third A-MPDU is the longest data frame as illustrated in
The information on the longest data frame may be contained in the data frame transmitted by the transmitting station, or may be transmitted to the receiving stations as separate data. In a case in which the information on the longest data frame is transmitted as separate data, it may be transmitted through multi channels or a primary channel.
The information contained in the Ack order information described above with reference to
In step S804, the plurality of data frames are transmitted to the plurality of receiving stations. In step S806, if the respective receiving stations complete the reception of the data frames, block Ack signals are sequentially received from the plurality of receiving stations according to the Ack order information contained in the respective data frames. The Ack order information may contain information representing a relative order for the plurality of receiving stations to transmit the block Ack signal, information on the longest data frames among the plurality of data frames, or information representing time for the plurality of receiving stations to transmit their block Ack signals.
In step S902, data frames containing data and Ack order information, transmitted by a transmitting station, are received. In step S904, the Ack order information is acquired from the received data frames. Each of the data frames may include a padding bit to make it have the same length as the longest data frame. In addition, the Ack order information may contain information representing a relative order for the plurality of receiving stations to transmit the block Ack signal, information on the longest data frames among the plurality of data frames, or information representing time for the plurality of receiving stations to transmit their block Ack signals.
In step S906, block Ack signals are sequentially transmitted to the transmitting station according to the acquired Ack order information. The process of sequentially transmitting the block Ack signals is substantially identical to that described above with reference to
In step S1002, a transmitting station generates a plurality of data frames to be transmitted to a plurality of receiving stations. Each of the data frames contains data to be transmitted and Ack order information. In addition, each of the data frames may include a padding bit to make it have the same length as the longest data frame. In another embodiment, the plurality of data frames may be inputted from other devices. In step S1004, the transmitting station transmits the plurality of data frames to the plurality of receiving stations. In step S1006, the plurality of receiving stations receive the data frames transmitted from the transmitting station.
In step S1008, the plurality of receiving stations acquire the Ack order information from the received data frames. Each of the data frames may include a padding bit to make it have the same length as the longest data frame. In addition, the Ack order information may contain information representing a relative order for the plurality of receiving stations to transmit the block Ack signal, information on the longest data frames among the plurality of data frames, or information representing time for the plurality of receiving stations to transmit their block Ack signals.
In step S1010, the plurality of receiving stations sequentially transmit block Ack signals to the transmitting station according to the acquired Ack order information. The process of sequentially transmitting the block Ack signals is substantially identical to that described above with reference to
In accordance with the exemplary embodiments of the present invention, when a single transmitting station transmits data to a plurality of receiving stations, data collision can be substantially prevented by setting an order in which the receiving stations having received data are to transmit their block Ack signals to the transmitting station.
While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2010-0012791 | Feb 2010 | KR | national |
