KR100752360B1 - Method for monitoring available resource in wireless network, and data transferring method, wireless communication terminal, network using the method - Google Patents

Abstract

A method for monitoring available wireless sources in a wireless network and a method for transmitting data, a wireless transmission terminal and a network using the method are provided to monitor the quantity of available wireless source in a data link layer of a transmission terminal in real time, thereby monitoring the quantity of available wireless source without additional wireless resources. A method for monitoring available wireless sources in a wireless network and a wireless transmission terminal using the method comprise the followings: a transmitting unit for transmitting data while changing a mode between at least two modes; and a resource monitor for computing available wireless resource quantity considering a change of the mode in the transmitting unit through monitoring periods in real time in a data link layer. The information is transmitted through a protocol having a link layer and a physical layer.

Description

Method for Monitoring Available Resource in Wireless Network, and Data Transferring Method, Wireless Communication Terminal, Network Using the Method}

1 is a diagram illustrating a wireless network according to an embodiment of the present invention.

2 is a schematic block diagram of a wireless communication unit of an access point and a terminal according to an embodiment of the present invention.

Figure 3 is a timing chart showing the relationship between the T_ EP, T_ RO [N] , T_ used [N] and T_ idle [N].

4 is a diagram illustrating the order and timing of packets when data transmission is successful.

FIG. 5 is a diagram illustrating transmission and timing that failed according to retransmission when data transmission is not successful.

<Description of the symbols for the main parts of the drawings>

101: access point 102: terminal

200: wireless communication unit 201: network interface

203: microprocessor 205: data memory

207: program memory 209: baseband processor

211: RF transceiver 213: antenna

The present invention relates to a method for measuring the amount of available radio resources, to a wireless terminal and a wireless network using such a method, and to a wireless terminal and a wireless network which change based on the measured amount of available radio resources. Specifically, the present invention relates to a method for monitoring the amount of available radio resources in a data link layer of a wireless communication protocol having a plurality of transmission rate modes, such as 802.11a, and a wireless terminal and a wireless network using the same.

Wireless network systems are increasing in use and interest due to the advantages of being less constrained in physical location than wired networks. In particular, 802.11-based wireless LAN has been increasingly used due to the relatively low installation cost and widespread use of compatible equipment.

However, wireless network systems, including those operating based on 802.11, have more fluctuating channel conditions over time and location than wired networks. Despite these different radio channel conditions, wireless protocols often provide several transmission modes in order to achieve an efficient transmission rate. For example, 802.11a provides eight transmission modes with different transmission speeds. In order to obtain an optimal transmission speed in a protocol provided with multiple transmission modes, the transmission rate must be adaptively changed according to the channel state.

In a wireless network in which the transmission mode is changed, a sufficient amount of radio resources is provided to receive a service that requires a certain quality of service (QoS), for example, a multimedia-based service. It should be determined whether or not there is. For example, Proc. "Dynamic admission control in IEEE 802.11e EDCA-based Wireless Home Network", published by IEEE CCNC, January 2006 edition of H. Yoon and J. Kim, or Proc. In a paper published by ACM WMASH'05, S. Park et al. In the September 2005 edition of the journal "Network-adaptive high definition MPEG2 streaming over IEEE 802.11a WLAN using frame-based prioritized packetization", The method of adaptively changing according to the state is described. However, this method disclosed in the paper is based on the quantitative or qualitative determination of the amount of available radio resources of the wireless network.

Such methods for determining the amount of available radio resources can be largely classified into two types, a theoretical analysis method based on a mathematical model of a wireless network system and a method of monitoring resources of a wireless network in real time.

First, the analysis method based on the mathematical model of the wireless network is described by G. Bianchi in IEEE J. Select. Areas Commun., Vol. 18, “Performance and analysis of the IEEE 802.11 DCF,” pages 535-547. Such an analysis method is effective for calculating accurate channel capacity, but has a problem in that it is limited in identifying available resources by reflecting the channel state of an actual WLAN system.

Next, M. Demircin and P. Beek have reviewed Proc. There is a method described in "Bandwidth estimation and robust video streaming over 802.11e" published in IEEE ICME, July 2005. In this paper, the end-to-end delay calculation method is applied to the wireless network to measure the limit of available resource in the existing wired network. However, this method has a problem in that incorrect network limit information can be calculated because the situation in which the transmission rate changes in time at the physical layer of the wireless network and the wireless terminal has a different physical layer transmission rate is not considered.

As a method of monitoring the amount of available resources of the wireless network in real time, a method of using the signal strength of the wireless channel in the physical layer may be assumed. This method has the advantage of being able to measure the amount of available resources of the wireless network most directly. However, in order to measure the signal strength at the physical layer, a new device must be added to the current wireless terminal, and the state information of the wireless network, such as packet loss rate, cannot be obtained in addition to the channel resource amount.

Accordingly, an object of the present invention is to provide a method capable of calculating or monitoring the amount of available radio resources in real time at the data link layer without the addition of additional equipment, and a wireless terminal and a wireless network using the method.

The present invention also provides a method for monitoring the amount of available radio resources, which eliminates the need to transmit data on the amount of available radio resources to the transmitting terminal by calculating the monitoring result of the amount of available radio resources at the transmitting terminal, not at the receiving terminal. The purpose is to provide.

In order to achieve this object, a wireless transmitting terminal according to the present invention transmits data in two or more modes having different radio transmission characteristics, and transmits information through a protocol including a data link layer and a physical layer. Specifically, the wireless transmitting terminal according to the present invention is a transmission unit for transmitting data while changing the mode between the two or more modes, and the amount of available radio resources in consideration of the change of the mode in the transmission unit over the monitoring period data It includes a resource monitor that calculates in real time at the link layer.

Preferably, the protocol is an 802.1X based wireless protocol, the wireless transmission characteristic is a transmission rate, and the transmission unit changes the mode in consideration of the amount of available radio resources calculated by the resource monitor.

In addition, the resource monitor is available in consideration of (1) the time required for the successful transmission of the data when the data transmission is successful and (2) the additional time required to retransmit the data when the transmission of the data fails. The amount of radio resources can be calculated.

In the wireless transmitting terminal according to the present invention, the time required for successful transmission of data is obtained by multiplying the number of packets transmitted in each mode by the average time spent transmitting successfully transmitted packets. The additional time required for the calculation may be calculated as the sum of the time spent according to the loss of the Request-To-Send (RTS) packet and the time spent according to the loss of the data packet or the ACK packet.

Preferably, the wireless transmitting terminal according to the present invention calculates the time taken for the successful data transmission and the additional time for retransmission in consideration of the average time waiting for the wireless transmitting terminal to start transmitting. The average time to wait for the radio transmitting terminal to start transmission is calculated from the packet loss rate during the monitoring period.

In addition, according to the present invention, a method for monitoring the amount of available radio resources in a wireless network using two or more modes having different radio transmission characteristics and transmitting information through a protocol including a data link layer and a physical layer,

Transmitting a request-to-end signal from a wireless transmitting terminal;

Transmitting a clear-to-send (CTS) signal from a wireless receiving terminal in response to the RTS signal;

Transmitting data from a wireless transmitting terminal in response to the CTS signal;

Transmitting an acknowledgment (ACK) signal in a wireless receiving terminal after completing the reception of the data;

(I) the time required for successful data transmission in the data link layer during a certain monitoring period, and (ii) the failure of data transmission due to an error in one or more of the transmission steps. Calculating additional time for retransmitting the data;

Estimating the amount of radio resources available through the successful transmission time and the time required for retransmission obtained in the calculation step.

Preferably, the time required for the successful data transmission is obtained by multiplying the number of packets transmitted in each mode by the average time required to transmit successfully transmitted packets, and the additional time required for the retransmission. It is calculated as the sum of time spent due to loss of Request-To-Send (RTS) packet and time spent due to loss of data packet or ACK packet.

Preferably, the time required for the successful transmission of the data and the additional time for retransmission are calculated in consideration of the average time waiting for the radio transmission terminal to begin transmission, and the radio transmission terminal performs the transmission. The average time to wait to start is calculated from the packet loss rate during the monitoring cycle.

In addition, according to the present invention, a method for transmitting data through a wireless protocol supporting two or more modes having different transmission characteristics is provided.

Establishing communication between the wireless transmitting terminal and the wireless receiving terminal;

Establishing data and then transmitting data from the wireless transmitting terminal to the wireless receiving terminal;

When the data transmission is successful in the data link layer for a certain monitoring period, the amount of available radio resources is calculated in real time in consideration of the time required for the successful transmission of such data and the time required for retransmission when the error occurs. Steps,

And selecting the mode based on the amount of available radio resources obtained by the calculating.

Preferably, the calculating step is calculated in consideration of the packet transmission failure rate in the previous monitoring period.

More preferably, establishing the communication,

Transmitting a request-to-send (RTS) signal of a wireless transmitting terminal according to a DCF protocol;

Transmitting a clear-to-send (CTS) signal from a wireless receiving terminal in response to the RTS signal according to the DCF protocol;

And transmitting data from a wireless transmitting terminal in response to the CTS signal according to the DCF protocol.

Further, preferably, calculating the amount of available radio resources in real time may include calculating a moving average value for the packet transmission failure rate in the current monitoring period and the packet transmission failure rate in the previous monitoring period.

In addition, the network according to the present invention may transmit data in two or more modes having different radio transmission characteristics, and may partially transmit information using a wireless protocol including a data link layer and a physical layer. Specifically, the network according to the present invention

A first wireless terminal including a resource monitor that estimates the amount of available radio resources in real time at the data link layer for transmissions transmitted through the radio protocol;

And a second wireless terminal communicating with the first wireless terminal via the wireless protocol.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The scope of the present invention is not limited to the present embodiment, and various modifications and changes can be made to the present embodiment within the scope of the present invention.

1 is a diagram illustrating a configuration of a wireless network used in an embodiment according to the present invention. The wireless network of this embodiment is composed of one access point (AP) 101 and a plurality of terminals (STAs) 102 as shown in FIG. This embodiment has been set up to operate in infrastructure mode 104. Thus, the access point 101 becomes the center of the wireless network and the terminal 102 in the basic service set (BSS) allows the access point 101 through the wireless channel 105 to exchange data with the network within or outside the BSS. Must be communicated with).

2 is a diagram illustrating a schematic configuration of a wireless communication unit 200 in an access point 101 or a terminal 102 used in an embodiment of the present invention. 2, the wireless communication unit of the access point 101 and the terminal 102 according to an embodiment of the present invention is an RF transceiver 211, an antenna 213, a baseband processor 209, and a microcomputer. A processor 203, a data memory 205, a program memory 207, and a network interface 201. The data memory 205 is a memory for storing data and the program memory 207 is a memory for storing a program, and the microprocessor 203 controls the operation of wireless communication using a program stored in the program memory 207. do. The baseband processor 209 according to the present exemplary embodiment performs processing necessary for transmitting a signal such as modulation and demodulation of a transmission / reception signal through the RF transceiver 211. The wireless communication unit 200 communicates with a host computer (not shown) through a network interface.

Referring to the layer of the network, the baseband processor 209, the RF transceiver 211 and the antenna 213 corresponds to the physical layer in the configuration shown in Figure 2, the microprocessor 203 and the memory (205, 207) Corresponds to the MAC layer (ie, data link layer) of the 802.11a standard.

In the embodiment according to FIG. 2, the wireless communication unit 200 is composed of separate circuit elements such as the microprocessor 203 and the memories 205 and 207, but may be implemented as one chip using a dedicated ASIC chip.

In this embodiment, a wireless network according to the 802.11a standard is formed between the access point 101 and the terminal 102 shown in FIG. As shown in Table 78 of § 17.3.2.2 of the 802.11a specification, eight transmission modes are provided for 802.11a.

TABLE 1

mode Modulation method Code rate Data rate BpS One BPSK 1/2 6 Mbps 3 2 BPSK 3/4 9 Mbps 4.5 3 QPSK 1/2 12 Mbps 6 4 QPSK 3/4 18 Mbps 9 5 16-QAM 1/2 24 Mbps 12 6 16-QAM 3/4 36 Mbps 18 7 64-QAM 2/3 48 Mbps 24 8 64-QAM 3/4 54 Mbps 27

In this embodiment, one of the above eight modes is taken according to the state of the wireless channel. In addition, in the present embodiment, since it operates in the infrastructure mode, it is preferable to perform the calculation or monitoring of the amount of available radio resources at the access point 101. In addition, collisions with multiple terminals and access points use the Distributed Coordination Function (DCF) as defined in § 9.2 of 801.11. Operation related to the DCF will be described later.

Under these conditions, the time that a channel of a wireless network uses to transmit a packet during a certain monitoring period, that is, a time when the channel of the wireless network is occupied is given as follows.

[Equation 1]

T_ busy [N] = T_ used [N] + T_ RO [N]

(Here, T_ used [N] is the time taken to transmit the actual data and T_ RO [N ] is the additional time required in case of retransmission due to data transmission failure, that is, additional transmission time required due to retransmission overhead.)

In this case, the available radio resource may be defined as a time when no packet is transmitted through the wireless network, that is, T_ idle [N] as follows.

[Equation 2]

T_ idle [N] = T_ EP  -T_ busy [N]

Where T_EP is the duration of the monitoring cycle.

The relationship between T_ idle [N] , T_ EP , T_ busy [N] and T_ RO [N] is summarized in FIG. On the other hand, T_ used [N] can be obtained by the following equation (3).

[Equation 3]

(Where m refers to the transmission mode in 802.11a, N_ tx [m] refers to the number of packets transmitted in m mode during the monitoring period, and T_ success [m] indicates successful transmission in the m mode during the monitoring period. Refers to the average channel occupancy time of a packet.)

In this embodiment, RTS and CTS signals are activated in 802.11a. Therefore, in order for data transmission to be successful, as shown in FIG. 4, the transmitting terminal transmits an RTS packet after the elapse of the cDIFS time and the backoff time, and after the elapse of the SIFS, the CTS signal is transmitted from the receiving terminal. After the elapse of time, the data packet is transmitted from the transmitting terminal, and finally, after the SIFS time elapses, the ACK packet is transmitted. In this case, the total time required for successful transmission is T_ success [m] and can be obtained by Equation 4 below.

[Equation 4]

In the above equation, B_ rts , B_ cts , B_ ack and B_ data are the packet sizes in bytes for RTS packet, CTS packet, ACK packet and data packet, respectively, and tSymbol is symbol interval (801.11a standard §17.3. T _SYM in Table 79 of 2.3 BpS (m) is in bytes per symbol, and is shown in Table 1 above. T_wait means an average backoff time that the terminal waits before accessing the channel, which will be described later. cSIFS refers to the cumulative transmission time of SIFS required for one physical protocoal data unit (PPDU), and tPLCPSignal is the length of the SIGNAL field of the PLCP (T _SIGNAL in Table 79 of § 17.3.2.3 of 802.11a). TPLCPPreamble is the duration of the PLCP preamble (T _PREAMBLE in Table 79 of § 17.3.2.3 of 802.11a). Corresponds to a value of 16 μs).

On the other hand, the time added by retransmission to the transmission of the data fails T_ RO [N] is given by:

[Equation 5]

Where N_ ret _ data [m] is the number of times the RTS and CTS packets failed in transmission after the successful exchange of RTS and CTS packets in the m mode during the monitoring period, and T_ data _ fail [m] is the time added That is, it refers to overhead due to transmission failure of a data packet or an ACK packet. N_ ret _ rts refers to the number of times the RTS signal is not properly transmitted from the transmitting terminal to the receiving terminal, and T_ rts _ fail Refers to the additional time, that is, overhead due to transmission failure of the RTS signal.

As described above in detail with reference to FIG. 5, a case in which data transmission fails and retransmission is as follows. First, when data transmission fails, the RTS signal is not properly transmitted from the transmitting terminal to the receiving terminal. The additional time required for retransmission is represented by T_ rts _ fail . This T rts _ fail is given by

[Equation 6]

(Here, tRTStimeout means the time to wait for retransmission of the RTS packet and follows the provision of 802.11a.)

Secondly, the data transmission fails when the RTS and CTS packets are successfully exchanged, and then the data packet or the ACK packet is failed to be transmitted. In this case, the additional time due to retransmission, that is, the overhead is expressed by the following equation. It can be represented by the given T_data_fail [m] .

[Equation 7]

T_ data _ fail [m] means the time to wait for the ACK packet after transmission of the data packet, and its value varies depending on the length and transmission mode of the data packet.

As described above, in this embodiment, the DCF specified in § 9.2 of 801.11 uses carrier sense and multiple access / collision avoidance (CSMA / CA). DCF detects whether a channel occupies a certain time before transmitting a packet and, if not occupied, uses a contention window (CW) to randomly set a backoff time to prevent a collision. In this case, CW is selected from a value between 2 ^K x CW _min and 1, which is the minimum contention window, and k may increase by 1 for each packet transmission failure and increase to CW _max . Therefore, if the packet loss rate during the monitoring period is p, the average waiting time until the UE accesses the channel is given as follows.

[Equation 8]

Here, W is the value of the minimum window CWmin, cDIFS refers to the cumulative transmission time of the CIFS required for one physical protocol data unit (PPDU). Retry_limit is a retry attempt limit value.

In addition, in the present embodiment, p value in the monitoring interval N is calculated as follows in the access point 101 using an exponential moving average (EWMA) function.

[Equation 9]

(Here, α is a value used for the calculation of EWMA and 0.9 was used in this example.)

In the present embodiment, the amount of available radio resources of the wireless network is determined based on the calculated T_ idle [N] value. T_ idle [N] has a value between 0 and 1. The closer to T_idle [N] , the higher the amount of available radio resources. On the contrary, the closer to 0, the smaller the amount of available radio resources. For example, a value of T_ idle [N] of 0.3 indicates that 70% of the current radio resource amount is used and 30% of the available radio resource amount remains.

In the present embodiment, the desired transmission mode can be manipulated in real time based on the information on the amount of available radio resources. In this embodiment, the MAC layer (i.e., data link layer) is "Goodput analysis and link adaptation for IEEE 802.11a wireless LANs" of IEEE Trans: Mobile Computing, Vol. 1, no. As described in the following, variables about the network state including T_ idle [N] were selectively transmitted to the application layer with reference to the packet error ratio (PER) value based on the reception strength and the transmission mode of the physical layer.

In addition, A. Kamerman et al., BellLabsTechnicalJ. ARF (auto-rate fallback (ARF)) was used as a physical layer transmission mode adaptation algorithm as described in "WaveLAN-II: A High-performance Wireless LAN for the unlicensed band," pages 1253-1265.

In addition, the present embodiment is configured to select a preferred transmission mode based on the amount of available radio resources obtained as described above.

Although the present embodiment is merely exemplary and various modifications may be made to the present embodiment. For example, although the present embodiment uses the standard of 802.11a, it can be applied to a similar wireless network protocol such as HIPERLAN / 2 (HIgh PErformance Radio Local Network type 2). It could also be applied in ad hoc mode rather than in 802.11's infrastructure mode. In addition, unlike the present embodiment, instead of selecting a transmission mode based on the amount of available radio resources, based on the amount of available radio resources, such as a case in which a service requiring a specific QoS is provided only when there is a certain amount of available radio resources. Wireless terminals or networks can be configured to limit work at the application layer.

According to the present invention, the amount of available radio resources can be monitored in real time at the data link layer of the transmitting terminal, thereby eliminating the need to add a separate device to the wireless terminal or to transmit data on the amount of available radio resources to the transmitting terminal. There is an advantage of not using a separate radio resource amount for monitoring.

Claims (16)

A radio transmitting terminal for transmitting data in two or more modes having different radio transmission characteristics and transmitting information through a protocol including a data link layer and a physical layer, A transmission unit for transmitting data while changing a mode between the two or more modes; A resource monitor that estimates, in real time, at the data link layer the amount of available radio resources in consideration of the change of the mode at the transmitter over a monitoring period; A wireless transmitting terminal for transmitting information through a protocol including a link layer and a physical layer. The method of claim 1, wherein the protocol is an 802.1X-based wireless protocol, the wireless transmission characteristic is a transmission rate, and the transmission unit changes the mode in consideration of the amount of available radio resources calculated by the resource monitor. Wireless transmitting terminal. 3. The resource monitor according to claim 2, wherein during the monitoring period, the resource monitor additionally (1) time spent for successful data transmission if data transmission is successful and (2) time spent for retransmitting data if data transmission fails. In consideration of this, the amount of available radio resources is calculated. 4. The method of claim 3, wherein the time required for successful data transmission is obtained by multiplying the number of packets transmitted in each mode by the average time required to transmit successfully transmitted packets, and additionally required for the retransmission. The calculated time is calculated as the sum of the time spent according to the loss of the Request-To-Send (RTS) packet and the time spent according to the loss of the data packet or the ACK packet. 5. The method of claim 4, wherein the time required for the successful data transmission and the additional time required for the retransmission are calculated in consideration of the average time waiting for the radio transmission terminal to start transmission. And a mean time to wait until the start of the packet is calculated from the packet loss rate during the monitoring period. A method for monitoring the amount of available radio resources in a wireless network using two or more modes having different radio transmission characteristics and transmitting information through a protocol including a data link layer and a physical layer, Transmitting a request-to-end signal from a wireless transmitting terminal; Transmitting a clear-to-send (CTS) signal from a wireless receiving terminal in response to the RTS signal; Transmitting data from a wireless transmitting terminal in response to the CTS signal; Transmitting an acknowledgment (ACK) signal in a wireless receiving terminal after completing the reception of the data; (I) the time required for successful transmission of this data in the data link layer during a certain monitoring period, and (ii) an error occurs in one or more of the transmission stages, causing the transmission of data to fail. Estimating additional time for retransmitting data; Estimating the amount of available radio resources based on the successful transmission time and the time required for retransmission obtained in the estimating step. 7. The method of claim 6, wherein the protocol is an 802.1X based wireless protocol and the wireless transmission characteristic is a transmission rate. 8. The method of claim 7, wherein the time required for successful data transmission is obtained by multiplying the number of packets transmitted in each mode by the average time required to transmit successfully transmitted packets, and additionally required for the retransmission. The amount of time is calculated as the sum of the time spent according to the loss of the Request-To-Send (RTS) packet and the time spent according to the loss of the data packet or the ACK packet. 9. The method of claim 8, wherein the time required for the successful data transmission and the additional time required for the retransmission are calculated in consideration of the average time waiting for the radio transmission terminal to start transmission. The average time to wait until the start is calculated from the packet loss rate during the monitoring period. A method of transmitting data through a wireless protocol supporting two or more modes having different transmission characteristics, Establishing communication between the wireless transmitting terminal and the wireless receiving terminal; Establishing data and then transmitting data from the wireless transmitting terminal to the wireless receiving terminal; When the data transmission is successful in the data link layer for a certain monitoring period, the amount of available radio resources is estimated in real time in consideration of the time required for successful transmission of such data and the time required for retransmission when data is retransmitted due to an error. To do that, Selecting the mode based on the amount of available radio resources obtained by the calculating. 12. The method of claim 10, wherein the calculating is performed in consideration of a packet transmission failure rate in a previous monitoring period. The method of claim 11, wherein establishing the communication comprises: Transmitting a request-to-send (RTS) signal of a wireless transmitting terminal according to a DCF protocol; Transmitting a clear-to-send (CTS) signal from a wireless receiving terminal in response to the RTS signal according to the DCF protocol; Transmitting data in a wireless transmitting terminal in response to the CTS signal according to the DCF protocol; Estimating the amount of available radio resources in real time, Calculating a moving average value for a packet transmission failure rate in the current monitoring period and a packet transmission failure rate in a previous monitoring period; In a network that transmits data in two or more modes having different radio transmission characteristics, and partially transmits information using a wireless protocol including a data link layer and a physical layer, A first wireless terminal including a resource monitor that estimates the amount of available radio resources in real time at the data link layer for transmissions transmitted through the radio protocol; A second wireless terminal communicating with the first wireless terminal via the wireless protocol. 14. The resource monitor of claim 13, wherein the resource monitor additionally takes (1) the time required for successful transmission of this data if the data transmission is successful and (2) retransmits the data if the data transmission fails during the predetermined monitoring period. And calculating the amount of available radio resources in consideration of the time. 15. The method of claim 14, wherein the time required for successful data transmission is obtained by multiplying the number of packets transmitted in each mode by the average time required to transmit successfully transmitted packets, and additionally required for the retransmission. The calculated time is calculated as the sum of the time spent according to the loss of the Request-To-Send (RTS) packet and the time spent according to the loss of the data packet or the ACK packet. 16. The method of claim 15, wherein the time required for the successful data transmission and the additional time required for the retransmission are calculated in consideration of the average time waiting for the radio transmission terminal to start transmission, and the radio transmission terminal transmits the data. The average time to wait to start the network is calculated from the packet loss rate during the monitoring period.

Images