KR20110046378A - Power Saving Method in Wireless Communication System - Google Patents

Abstract

PURPOSE: A power saving method in a wireless communication system is provided to control the sampling ratio of a modem processor and to increase power consumption efficiency in a wireless communication system. CONSTITUTION: A network node sets up a network management data on a network(602). The network node or a network control device subscribes one theme(604). The network control device or the network node notices data(606). The network control device or the managed object network node receives network management data based on a data distribution service(608).

Description

METHOD FOR SAVING POWER IN A WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a method and control apparatus for increasing resource utilization and reducing power consumption of a high speed wireless communication system.

As wireless communication systems evolve and the demand for high-capacity multimedia content available on the move increases, wireless communication systems have made efforts to improve transmission speeds. Wibro for using the Internet during high-speed movement and Wireless LAN that enables real-time viewing of high-definition video during low-speed movement is a typical example. Using the WLAN as an example, the IEEE 802.11a / g standard enables a 54Mbps physical layer transmission rate using a 20 MHz bandwidth in the 2.4 GHz or 5 GHz band with a single antenna, and up to four antennas and a 40 MHz bandwidth in the IEEE 802.11n standard. It can support up to 600Mbps Physical Layer Data Rate.

Currently, standardization of the next version of the 802.11n standard is being discussed as Next Generation Wireless LAN to ensure higher transmission rates. The IEEE 802.11n standard is commonly referred to as HT (High Throughput) mode and the IEEE 802.11a / b / g mode is called Legacy mode. On the other hand, a new standard under discussion in IEEE 802.11ac / ad is called Very High Throughput (VHT) mode.

Modern wireless communication systems are becoming more complex than in the past to handle high-speed data reliably. As a transmission speed improvement technology, channel bonding technology that bundles and transmits multiple channels is applied, a higher high-order modulation method and a channel coding method are introduced, and a technology that increases transmission speed by using multiple antennas is transmitted simultaneously to multiple users. Technology is being researched and developed. Such complicated transmission and reception techniques are increasing the size of the wireless communication system and the complexity of the circuit. In addition, the transmission of data using a wider bandwidth than in the past for high speed data transmission requires the demand of digital-to-analog converters, analog-to-digital converters and modem processors. The Required Operating Frequency has been increased. With this technical background, as a receiver optimization technology to efficiently use limited frequency resources and reduce noise, low power design is important for designing a wireless communication system capable of using dynamic channel bandwidth and high-speed data transmission. It became.

In addition, the WLAN is operated in a limited frequency band, the 160MHz bandwidth (8 bonds of 20MHz band) is a relatively wide band, which will cause interference and coexistence (Coexistence) problem between the terminals supporting various standards. In order to reliably detect such a multi-transmission mode frame, a technique for optimizing a receiver by informing a terminal through a control frame of preceding information before a data frame is required.

Accordingly, the present invention provides a transmission method and a control device for improving the efficiency of the low-power technology and low-power design at the same time in the physical layer and MAC layer.

The present invention also provides a method and a control device for improving the power consumption efficiency by controlling the sampling rate of the analog-to-digital converter or the digital-to-analog converter and the modem processor and the sampling rate of the modem processor according to the channel bandwidth used in the next generation WLAN. .

In addition, the present invention provides a method and apparatus for transmitting the information including the preceding information in the control frame to reduce noise and optimize the configuration of the receiver according to the type of the frame to receive.

According to an embodiment of the present invention, a method of transmitting a frame in a wireless communication system having two or more different bandwidth transmission modes includes a process of transmitting channel state information or data frame mode information to be transmitted when a request frame is transmitted. And the data based on the channel state information included in the response frame or the receivable data frame mode information when receiving the response frame for the request frame including the channel state information or the receivable data frame mode information from the receiving node. Generating and transmitting a frame.

The method according to another embodiment of the present invention is a power saving method in a wireless communication system having two or more bandwidth transmission modes, and when the control frame is received, the control frame is set to receive the mode having the lowest sampling rate among the bandwidth modes. Receiving the control frame and transmitting and receiving the data packet by setting the data packet to be transmitted / received in a mode having the highest sampling rate for transmitting / receiving the data packet after the control frame is received. It includes.

The method according to another embodiment of the present invention is a power saving method in a wireless communication system that transmits / receives data through carrier sensing, and the doze mode in a doze mode in which the carrier sensing is not required. Powering only a timer for the release, powering off the entire physical layer and the MAC layer, and if the carrier sensing is necessary, only the physical (PHY) layer and the MAC layer required for the carrier sensing. And powering on only a path required for data transmission / reception when data transmission / reception is required after the carrier sensing.

The method according to another embodiment of the present invention is a power saving method in a wireless communication system having two or more different transmission modes and performing data transmission / reception through carrier sensing, wherein the carrier sensing is not required. Powering only a timer for releasing the doze mode in a doze mode, powering off the entire physical layer and the MAC layer, and the lowest sampling rate among the different modes when the carrier sensing is required Performing the carrier sensing by setting to sense a carrier in a mode having a mode, and setting the data packet to transmit / receive the data packet in a mode having a highest transmission rate for transmitting / receiving a data packet after the carrier sensing. It includes the process of sending / receiving.

According to the configuration of the present invention, the power consumption efficiency can be improved by selectively converting the sampling rate and the power supply block of the terminal according to the operation mode and the frame format of the high speed wireless communication system. In addition, by using the present invention it is possible to compensate for the shortcomings of the low power mode made of the control of the conventional MAC layer, it is possible to improve the power consumption efficiency of the next-generation WLAN to be complicated at the same time using a wider bandwidth.

1A and 1B are block diagrams of a wireless communication terminal having three receive paths;
2 is a flowchart of a low power mode conversion transition according to the present invention;
3 is a timing diagram to help understand the operating principle of the four reception modes according to the present invention;
4 is a state transition diagram of cross-layer low power mode 2;
5 is a timing diagram for aiding in understanding the step of adjusting power in accordance with the present invention;
6 is a flowchart illustrating a transition process in a multi-channel low power mode according to an embodiment of the present invention;
7 and 8 are timing diagrams for noise reduction and coexistence of a multi-mode frame according to another embodiment of the present invention;
9 is a diagram for explaining the operation of the present invention in the condition of an overlapped basic service set (OBSS).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description of preferred embodiments of the present invention will be given with reference to the accompanying drawings. Specific details are set forth in the following description, which is provided to provide a more thorough understanding of the present invention. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The present invention relates to a method and a control technique for improving power consumption efficiency for a high speed wireless communication system. The present invention is largely divided into three components, each of which can be operated independently or in conjunction with each other. The first is three cross-layer low power modes, the second is a transmission method for improving the efficiency of the low power mode, and the third is a multi-channel low power mode (MC PS Mode) and a spatial multiplexing power save mode. Low power technology using SM PS Mode.

First, power consumption (P) of a general CMOS circuit will be described. The power consumption P of the CMOS circuit is modeled as in Equation 1 below.

In Equation 1, P _dynamic stands for Dynamic Power Consumption, P _static stands for Static Power Consumption, and C stands for Switched Total Capacitance. , V _Sig means Voltage Swing, V _DD means Supply Power, f _o means Operating Frequency, and n _t is one flip per clock. The number of times the flip-flop transitions.

According to Equation 1 above, P _dynamic is proportional to the total capacitance switched, the voltage swing width, the power supply, the operating frequency, and the number of times one flip-flop transitions per clock. P _static is also determined by the residual current of the ground or supply power, thermal noise, and current from the process. In other words, P _static is an important factor in determining power consumption, but P _static is a value determined by semiconductor process and industry-based technology, while P _dynamic is a value that depends on system design. From the designer's point of view, reducing dynamic power consumption is the goal of low-power system design.

The VHT mode, currently under discussion, is available with 8 or 16 antennas and is likely to support 80 MHz bandwidth. For example, the access relay point uses 16 antennas, and the UEs can apply multi-user multiple antenna technology using 4 antennas. Multi-Channel Transmission technology will be available.

Therefore, the VHT standard terminal has two to eight times the number and bandwidth of the conventional standard terminal. An increase in transmission path with increasing antennas means an increase in circuit and chip size, which leads to an increase in power consumption. In addition, the increased bandwidth used means an increase in the required operating frequency, which in turn increases power consumption.

The low power technologies used in the existing 802.11a / b / g / n WLAN standards include 802.11 legacy PSM, 802.11e Automatic Power Save Delivery (APSD), 802.11n Power Save Multi Poll (PSMP), and Spatial Multiplexing (SM) Low Power Mode. Etc. have been used. The prior art has the following problems.

First, the Awake Mode terminal should always be in a waiting state for reception. Second, PSM, APSD, and PSMP methods require separate control signals and large buffer sizes. Third, MAC-level low power technology requires a response delay time. Fourth, the IEEE 802.11n SM low power mode scheme is effective for multi-antenna systems, but still has poor power consumption efficiency of single path circuits. Fifth, the VHT mode is likely to use 80 MHz bandwidth, in which case the sampling rate of the analog-to-digital converter and the digital-to-analog converter requires 160 MHz or more, which is four times that of the conventional 11a / g. Sixth, the power consumption is proportional to the operating frequency and the circuit size, so the operating frequency and the number of toggling and the number of circuits to be operated must be minimized.

Although the conventional low power technology has been performed in the MAC layer, as described above, in order to improve the power consumption efficiency of a more complicated system and extend the battery charging cycle of the mobile terminal, the low power technology of the MAC layer is used. There is a need for a cross layer power save technique that compensates for this problem.

Therefore, in the present invention, a low power technology, which is the first component of the present invention, will be described first. In order to improve the power consumption efficiency by using the low power mode technology of the physical layer and the MAC layer at the same time, in the configuration of the present invention, a cross layer power save mode (CL PS Mode) is described as a low power mode. do.

One. Cross Tier Low Power Mode 1

In a standby state in which the terminal wakes up, the terminal minimizes operating frequencies of the analog-to-digital converter, the digital-to-analog converter, and the modem processor, thereby improving the efficiency of dynamic power consumption. Legacy mode uses 20MHz bandwidth, HT mode supports up to 40MHz bandwidth, and VHT mode supports up to 80MHz bandwidth. In general, RTS (Request to Send) and CTS (Clear to Send) frames are transmitted in the legacy mode so that legacy terminals can also receive them. If the data frame is in VHT mode, 160MHz sampling rate is used to support up to 80MHz bandwidth.In HT mode, 80MHz sampling rate is used to support up to 40MHz bandwidth.In legacy mode, 40MHz sampling rate is transmitted as it is. The power consumption efficiency can be improved by switching according to the data format.

At this time, even if the operating frequency of the analog-to-digital converter and the digital-to-analog converter changes, the baseband signal is controlled by the digital modem to control the RF bandwidth limiting filter width and the interpolator and the interpolator. And controlling the operating frequency of the decimator. The method according to the present invention includes a method and a control device in which a mode is controlled by a control packet such as a request frame and a response frame, for example, an RTS and a CTS or an ACK frame. In other words, by using the first cross-layer low power mode according to the present invention, the dynamic power consumption efficiency is optimized by optimizing the operating frequency of the analog-to-digital converter and the digital-to-analog converter and the operating frequency of the modem processor in the reception standby state before the request / response packet transmission and reception. Can improve.

This will be described in detail.

In the legacy / HT / VHT mixed mode basic service set, when a control signal such as a request / response frame is transmitted or received, the legacy / HT / VHT mixed mode basic service set is transmitted in a legacy mode format for compatibility. Therefore, in this case, the terminal in the standby state in the terminal awake mode sets the sampling rate of the analog-to-digital converter to 40MHz to improve the consumption efficiency.

In this case, the center frequency of the RF and the analog band limiting filter may be reconfigured. Also, the band limiting filter of the digital filter can be reconstructed. At the same time, the operating frequency of the decimator of the receiver is reconfigured.

When transmitting RTS / CTS, the transmitter lowers the sampling rate of the digital-to-analog converter to 40MHz bandwidth. In addition, as in the receiver, the RF center frequency, the analog band limiting filter, and the digital band limiting filter may be reconfigured at the transmitter. At the same time, the operating frequency of the interpolator of the transmitter is reconfigured.

Thereafter, the terminal that transmits and receives the request / response frame is switched to the maximum operating frequency that can be supported to transmit and receive the data packet. At this time, upon successfully receiving the ACK, the terminal switches to the low power mode again after the transmission opportunity period ends. In addition, the terminal that transmits the ACK and confirms that there is no retransmission is switched back to the low power mode. The cross-layer low power mode 1 of the present invention described above may be used together with a conventional technique.

2. Cross Tier Low Power Mode 2

In a standby state in which the UE wakes up, power is applied only to a carrier sensing-related block before carrier sensing, and all other blocks are cut off power before carrier sensing. In the conventional SM power save technology, only a few receive paths are turned on and the other paths are turned off before transmitting and receiving RTS and CTS packets for low power mode operation of a wireless communication system using a multi-antenna technology. This method requires that only a small number of receive paths are used and in a waiting state. On the other hand, in the case of using the cross-layer low power mode 2 according to the present invention, only the carrier sensing related block at the first stage of the modem unit is turned on before the carrier sensing, and the rest is cut off, and then power is supplied to the rest after the carrier sensing. It is a way to inject. This can further improve power consumption efficiency. In addition, although the conventional SM power save technology can be applied by using RTS and CTS, cross-layer low power mode 2 according to the present invention has an advantage that can be applied without using RTS and CTS.

Next, a cross layer low power mode 2 according to the present invention will be described in more detail.

Cross-layer low power mode 2 is the invention of the use of Korean application 10-2008-0127376 (US application No. 12/561076). The cross-layer low power mode 2 of the mentioned patent focused on the physical layer low power technology, but the present invention has been improved to the cross layer low power mode technology, and in conjunction with the cross layer low power mode 1, the effect of improving the performance is excellent. Will be explained in mode 3.

Basically, the receiving end of the wireless communication system is unpredictable when a signal is input, so that the receiving end is always in a waiting state in a waking state, which reduces the dynamic consumption efficiency of the receiving end circuit. According to the present invention, the carrier sensing block is used in the case of Doze mode, which is a MAC-level low power mode, while using the prior art of turning on only the carrier sensing block before the carrier sensing and powering the remaining blocks after the carrier sensing. Also included is a method of further improving power consumption efficiency using a method of shutting off (off) power.

1A and 1B are block diagrams of a wireless communication terminal having three receive paths.

First, FIG. 1A and FIG. 1B illustrate a multiple antenna system, and reference numerals are omitted for the same parts for processing signals received from each antenna. In addition, since parts to which reference numerals are not given perform the same operations as operations of the same other parts, the same description will be omitted. 1A and 1B also have a relationship connected to each other in one drawing. That is, the signal output from FIG. 1A is input to FIG. 1B, and this input / output relationship is also shown.

In the RF block 100 for processing radio signals received from the antennas, only a low noise amplifier (LNA) 101 and a voltage controlled gain amplifier (AGC) 102 are shown. The signal received from the antenna is amplified by suppressing noise in the low noise amplifier 101, and then an amplifying operation is performed in the voltage control amplifier 102. The RF block 100 converts a signal of an RF frequency band into a signal of a desired band and then converts an analog signal into a digital signal through an analog-to-digital converter (ADC) 111. The digital signals thus converted are DC cancel 112, energy detect 121, automatic gain controller AGC 131, and saturation based carrier sense 132. ) Is entered. First, the DC controller 112 removes and outputs a DC component included in a digital signal. The signal from which the DC component has been removed is input to the I / Q channel signal comparator (I / Q comp.) 113. The signal output from the I / Q channel signal comparator 113 is input to the buffer 115 and the channel mixer 141. The signal input to the buffer 115 is read in units of specific periods, and is input to a carrier frequency offset (CFO) controller 116. The CFO regulator 116 detects and adjusts the carrier frequency offset.

The signal output from the CFO regulator 116 is fast Fourier transformed by the fast Fourier transformer 117. That is, the signal in the time domain is converted into the signal in the frequency domain. Then, the phase comparator 118 performs phase comparison, and the MIMO detector 119 detects each antenna, each band, or each stream. As described above, the signal detected by the MIMO detector 119 demaps the signal of each antenna, each band, or each stream in the demapper 120.

The energy detector 121 which receives the digital signal output from the analog-to-digital converter 111 detects the energy of the digital signal and outputs it to the clear channel assessment (CCA) 122. The CCA 112 detects the presence or absence of a signal on the channel and informs the MAC layer. In addition, the carrier sensing based saturation detector 132 that receives the digital signal output from the analog-to-digital converter 111 determines the saturation by detecting the carrier signal, and also provides signal level information for providing to the automatic gain controller 131. To provide. The automatic gain controller 131 then controls the gain values of the low noise amplifier 101 and the voltage controlled gain amplifier 102 based on the received digital signal based on the signal level information received from the carrier sensing based saturation detector 132.

Meanwhile, the channel mixer 141 that receives the signal output from the I / Q channel comparator 113 mixes and outputs the received signal. The low pass filter and averager (LPF + deci / 2) 142 then low pass filters the received signal and divides the decimal value by one half to calculate the average. The output of the low pass filter and averager 142 is W-RSSI 123, RSSI based carrier sense 143 and auto correlation 144. ) And a cross correlation 145. The received field strength measuring instrument 123 measures the received field strength of the received signal and provides it to the CCA 122. When the carrier is detected, the carrier sensing-based received field strength measuring instrument 143 measures and outputs the received field strength of the detected carrier signal. The autocorrelator 144 and the cross correlator 145 calculate and output correlation values, respectively. The CFO estimator 146 estimates the CFO and provides the result to the frame synchronizer 147. Then, the frame synchronizer detects frame synchronization by receiving signals from the carrier sensing based receiving field strength meter 143, the cross correlator 145, the carrier sensing based saturation detector 132, and the CFO estimator 146. In addition, the CFO estimator 146 provides the estimated value to the CRO correct 117 provided for each antenna. The carrier sensing based XCR calculator 148 calculates an XCR.

The fast Fourier transformer 117 also provides fast Fourier transformed information to the CFO & phase estimator with pilot 151 to estimate the CFO and phase with the pilot. The estimated phase information is provided to the phase comparator 118. In addition, the fast Fourier transformer 117 provides information to the channel estimator (CH Est.) 152 for channel estimation. As described above, the MIMO detector 119 outputs a signal for each stream by using the channel estimation information made by the channel estimator 152.

The soft demappers perform demapping for each stream, and the deinterleaver deinterleaves the output of the corresponding demapper. The deinterleaved information is inserted into the information required by the deparser, and decoded by the decoder. It is then descrambled by the descrambler and transmitted to the MAC layer.

In the configuration of FIGS. 1A and 1B described above, a power supply unit and a configuration for controlling them are not illustrated. The part regarding these controls operates based on description mentioned later. In addition, the portion 150 indicated by a dotted line of FIG. 1A is a portion related to carrier sensing, and only this portion is turned on (turned on) in awake mode, and when the carrier is sensed, power is also supplied to subsequent blocks. In addition, except for the last MAC layer in FIGS. 1A and 1B, the remaining parts correspond to the physical layer unit.

 At this time, the difference from the prior art is as follows.

1) The four-level cross-layer low power mode wireless communication system is divided into four states: dust mode, state before RTS / CTS reception in waking mode, data reception after RTS / CTS reception in waking mode, and data receiving state. The present invention is a method of optimizing a low power mode according to these four reception states. That is, in the duds mode, all blocks except the timer of the MAC are turned off, and in the awake mode, only the minority path (one or more) carrier sensing blocks are turned on and after receiving the RTS / CTS, the minority path Turn on the rest of the block, and turn on all blocks of all paths when receiving data.

2) The present invention is a cross-layer low power technology using a low power technology of the physical layer and a low power technology of the MAC layer can improve the power consumption efficiency compared to the conventional single layer low power technology.

2 is a flowchart illustrating a low power mode conversion transition according to the present invention.

In the first 200 steps, the WLAN device checks whether it is in an awake state. If it is awake, go to step 206; otherwise, go to step 202. In step 202, the wireless LAN device checks whether the timer has expired. If the timer has expired, the process proceeds to step 206. Otherwise, in step 204, the power is turned off for all blocks, and then step 200 is performed.

If proceeding from step 200 or step 202 to step 206, power is supplied only to one or two receiving part carrier sensing blocks. Since the wake-up or wake-up mode by the expiration of the timer is all before the carrier sensing, the second reception state mentioned above becomes a state before the RTS / CTS reception.

After the power is supplied only to the carrier sensing block, the wireless LAN device proceeds to step 208 to check whether the carrier sensing is performed within a predetermined time. If the carrier sensing is performed, the wireless LAN device proceeds to step 210, otherwise proceeds to step 206.

Next, if carrier sensing is performed, the wireless LAN device proceeds to step 210 and supplies power to the remaining blocks of the reception path. In step 212, the WLAN device checks whether a packet category is available. It is to check if the packet type information is available. If the category of the packet, that is, the category of the packet such as RTS / CTS is available, the process proceeds to step 214; otherwise, the process proceeds to step 216.

First, in step 214, the WLAN device checks whether a received packet category is an RTS / CTS packet. In case of a packet of the RTS / CTS category, the WLAN device proceeds to step 218 and supplies power to the corresponding blocks of the reception path according to the number of streams.

On the other hand, if it is not a packet of the RTS / CTS category in step 214 or if the category of the packet is not available in step 212, the process proceeds to step 216 and powers up the blocks of all receiving paths.

In summary, when the timer is used up, all blocks are powered off (turned off) until the timer runs out, and when the timer runs out, only the path required for carrier sensing and the corresponding carrier sensing block are turned on (turned on). Carrier sensing in the waking state turns on the remaining blocks of the corresponding path for carrier sensing.If packet type information is available, more paths are used to improve the carrier sensing results of data packets when the received packet is RTS / CTS. If packet type information is not available or is a data packet, all paths are turned on.

3 is a timing diagram to help understand the operating principle of the four reception modes according to the present invention.

First, in the dust mode 300, the receiver is in a state in which power of all blocks is turned off 301. The waking mode 310 is divided into three types. First, there is a state 311 in which only a carrier sensing block corresponding to one or two reception paths is turned on for carrier sensing. In this case, it is a state 312 in which power is supplied to blocks corresponding to one or two reception paths by detecting a category of a received packet or whether a packet is received. That is, when the RTS 321 frame is received, power is supplied only to blocks for receiving the RTS 321 frame. When the data frame 323 is received, power is again supplied to all the blocks corresponding to the reception path 313. After all data frames are received, only the blocks for carrier sensing transition to a state where power is turned on (314). At this time, it is a state capable of receiving frames such as an acknowledgment (ACK) frame 324. After receiving the response frame, if the reception of the signal is not detected for a predetermined time, i.e., until the preset timer expires, it enters the dust mode 300 again and turns off all the blocks.

That is, as described in FIG. 3, the UE may operate in a doze mode or in a waking mode in a situation of sequentially transmitting and receiving RTS, CTS, data, and ACK frames, and may be received according to carrier sensing or frame type while waking up. It is possible to determine whether to supply power or a clock to the internal blocks.

FIG. 4 is a finite state machine of the cross layer low power mode 2. FIG.

In FIG. 4, the idle state 210 is one of the initial state and / or the standby state and / or the power off state, or the like. When the power is supplied in the idle state 210, it goes through a start state START 411 that is performed. Then, when the carrier is detected in the CS sensing (Carrier Sensing) (412) for sensing the carrier, enters the state (Enable Additional Radios) 413 to detect possible additional radios. Thereafter, a transition is made to the automatic gain control state (AGC) 414 which controls the gain of the received signal by the counter value. In AGC state 414, the gain of the received signal is adjusted. When the gain of the received signal is adjusted in this way, the state transitions to the CFO Est. Using Short Preamble 415 using the short preamble. When the estimation of the approximate CFO is completed, the system transitions to a synchronization signal 416 for synchronizing a signal provided by the system, that is, a frame. When synchronization is achieved in this manner, a transition to the CFO Est. Using Long Preamble 417 is performed using the long preamble. That is, the carrier frequency offset is compensated for in the state 415 and the synchronization state 416 of estimating the CFO and time synchronization is performed.

When the estimation of the CFO is successfully completed using the long preamble, it transitions to the signal field decoded state 418. This decodes the signal. When the decoding of the signal is validly completed, the state transitions to a data decoding state 419 for decoding data. When the decoding of the data is completed, the state transitions to the end state (END) 420, and then transitions back to the idle state 210.

If the carrier is not detected in the CS state 412 of sensing the carrier, the carrier continues to be detected. If the automatic gain control fails in the AGC state 414 which performs the automatic gain control, the state transitions to the idle state 210. Other cases of transition to the idle state include the following cases. First, in the estimation state 415 of the CFO using the short preamble, it is impossible to estimate the approximate CFO. Second, there is a case where synchronization is not possible in the synchronization state 416. Third, in the state 417 of estimating the CFO using the long preamble, it is impossible to accurately estimate the CFO. Fourth, the decoding of the signal field fails in the decoding state 418 of the signal field.

In the state transition diagram of FIG. 2, the power consumption and the clock supply to the sub blocks corresponding to all subsequent states are cut off while staying in the CS state. In addition, by using the above state transition, it is possible to apply both the carrier sensing method and the non-carrier sensing method according to the present invention.

On the other hand, the idle state 410 is maintained even in the Doze mode or the sleep mode (Sleep mode). In this case, when the carrier sensing block is turned off and in the idle state, and the timer value of the MAC layer is exhausted and converted to the awake mode, the carrier sensing is carried out through the START state 411 described above. In the sensing state 412, the terminal waits for carrier sensing. In this case, only the carrier sensing block of the receiving end of the terminal is turned on, thereby improving power consumption efficiency. After carrier sensing, all blocks in the path are turned on to process signals.

5 is a timing diagram to assist in understanding the step of adjusting power in accordance with the present invention.

As shown in FIG. 5, in the receiver according to the present invention, the waking mode 500 and the dust mode 510 coexist. In the waking mode 500, the physical layer power saving timing (PHY PS timing) is divided into a carrier sensing period (CP) and a carrier non-sensing period (Non-CP). The carrier sensing period CP ends at a time point 501 at which carrier sensing is performed, and becomes a carrier non-sensing period Non-CP while receiving the packet 1 521 after the carrier is sensed. In the doze mode, power is cut off in all blocks, which is called a doze period DP.

As such, the physical layer does not provide a clock to physical layer blocks that are not powered in order to reduce power consumption in the carry sensing period CP. This can be confirmed with the PHY PS clock and PHY CS valid information of the PHY PS clock shown in FIG. 5.

In the meantime, in the MAC layer, a power saving clock (MAC PS clock) is input only from a carrier sensing period CP necessary for carrier sensing. In order to detect carrier sensing, it may be checked from MAC carrier valid information. These intervals are made until the start of the doze mode.

As described above, the low power mode of the MAC layer and the physical layer are interlocked to ensure more efficient power consumption efficiency when the MAC layer or the physical layer is used alone.

3. Cross Tier Low Power Mode 3

Cross layer low power mode 3 according to the present invention is a mixed mode of cross layer low power mode 1 and cross layer low power mode 2. In the cross layer mode 1, the cross layer mode 1 is controlled as a result of carrier sensing of the cross layer mode 2 without the help of control packets such as a request / response frame and an ACK frame. Accordingly, the power consumption efficiency can be improved by reducing the dynamic power consumption during the interframe space (IFS) time (16 us) and the carrier sensing time (about 2 us) by the cross layer mode 2 compared to the cross layer mode 1. Cross-layer low power mode 3 is capable of switching to low power mode as a result of carrier sensing without RTS / CTS, unlike using RTS / CTS in cross layer low power mode 1.

According to the cross-layer low power mode 1 method described above, the signal passing through the 20 MHz band limiting filter in the radio part is digitally converted to a 40 MHz sampling rate and carrier sensed.

In addition, after carrier sensing is performed by the cross-layer low power mode 2 scheme, blocks other than carrier sensing are operated.

When a packet is received in the above manner, the packet is operated using the maximum sampling rate supported by the receiver of the WLAN system.

In this case, when the type of data packet to be received by the request / response packet is known in advance, the sampling rate may be determined according to the mode of the received packet rather than the maximum sampling rate.

In addition, the process includes converting the operating frequency of the interpolator and the decimator and reconstructing the analog band limiting filter and the digital band limiting filter of RF.

In the method according to the third exemplary embodiment of the present invention, the sampling rate of the modem unit for the baseband signal processing may be optimized for the corresponding mode.

So far, the configuration and operation of the cross-layer low power mode of the present invention have been described. The transmission method for improving the efficiency of the cross-layer low power mode described so far will be described as a component of the second invention.

By receiving the information of the frame to be received at the receiving end in the request frame or the response frame, the receiving end can wait in the optimal state for the corresponding bandwidth. In other words, by receiving the information of the next transmission mode of the data frame to be sent after the request / response frame, for example, RTS / CTS, etc., receiving the analog / digital filter setting or the RF center frequency setting or the operating frequency sampling rate, etc. Modes may be optimized according to the type of frames to be received to improve throughput and power consumption efficiency.

1) In this case, the required performance index values and the number of transmission streams are as follows.

-If the number of streams of the transmitted signal is smaller than the number of receiving antennas, it is not necessary to use all the multiple antennas, so the number of antennas to be used can be selected according to the required performance index value. The required performance indicator may be a content category or a link performance value, such as a signal-to-noise ratio and a channel change.

2) Transmission packet mode, channel bandwidth to be used and frame transmission method are as follows.

The receiver can use the optimal operating frequency for the packet mode without receiving the request / response packet and converting it to the maximum operating frequency supported by the receiver.

-In addition, it is possible to apply the optimal filter for the received signal, thereby improving the receiver detection reliability.

It is also possible to operate the green field mode of the data frame during the transmission opportunity period.

As a result, throughput and power consumption efficiency can be improved.

Here, let's look at how to inform the information in advance. Assume that communication occurs between a first node and a second node. Then, whether the first node or the second node includes the channel state information or the data frame mode information based on a dynamic channel bandwidth allocation supportable bit, for example, a 1-bit value, of the request frame or the response frame. Can be determined.

The transmission mode information of the request / response frame may be included in the request / response frame in the following embodiments and transmitted. However, it should be noted that the present invention can be realized while maintaining compatibility with the conventional standard by utilizing the reserved bits remaining in the request / response frame without being limited to the embodiments described below.

1) Service field of physical layer

2) Duration field of MAC header

3) Frame control field of MAC header

For example, four bandwidth support modes may be set using two bits in the service field or the duration field. Looking at this example, it can be classified as follows.

00: 20 MHz,

01: 40 MHz,

10: 80 MHz,

11: 160 MHz

The information of the next frame following the request / response frame included in the request / response frame is not for low power mode but for coexistence of noise reduction and multi-mode frames (20/40/80/160 MHz bandwidth or legacy / HT / VHT mode). Can be used for

7 and 8 illustrate timing diagrams for noise reduction and coexistence of a multi-mode frame according to another embodiment of the present invention.

First, it will be described with reference to FIG. 7. FIG. 7 transmits a 20 MHz bandwidth data frame from node 1 to node 2, and transmits a frame 711 in which four 20 MHz bandwidth RTSs are bonded to the entire 80 MHz band before data frame transmission. Through this, Node1 sets NAV (Network Allocation Vector) values of nodes in various modes that support the 20/40/80 MHz bandwidth of its own frame, rather than its own frame, to be in a standby state. On the other hand, the node 2 recognized as its own frame changes the center frequency and filter of the receiver based on the bandwidth value set in the frame 711 in which the four RTSs are bonded, and transmits the CTS frame 712 in the 20 MHz band. Node 1 receiving the CTS frame 712 transmits a 20 MHz bandwidth data frame 713. Then, the node 2 reconfigured to receive the data frame 713 receives the data frame 713 and transmits an ACK frame 714 when it is correctly restored.

FIG. 8 is a diagram illustrating the aforementioned embodiment of FIG. 7 divided for each channel bandwidth. That is, the RTS frames 811, 812, 813, 814 are transmitted with an 80 MHz bandwidth. Noise is reduced when transmitting or receiving the CTS frame 821 and the data frame 831 and the ACK frame 841 in the 20 MHz bandwidth mode by using the bandwidth information values set in the RTS frames 811, 812, 813, and 814. Can reduce power consumption.

FIG. 9 is a diagram for describing an operation of the present invention in an overlapped basic service set (OBSS) situation. In BSS1, when RS 1 transmits an RTS frame to transmit data to a STA, BSS1 is known to include a terminal capable of supporting up to 80 MHz band, and thus, four 20 MHz band RTSs. Send simultaneously. At this time, when the BSS2 is transmitting a signal in the 40MHz band, AP1 does not know whether the interference signal exists.

At this time, the STA STA sends the CTS through the remaining 40MHz band except for the band to which the interference signal affects, so that the AP1 transmits a data frame through the 40MHz band receiving the CTS. Here, in the case of the STA, the interference signal and the signal to be received must be distinguished, and since the unique BSSID (BSSID) is different for each AP, the received packet is transmitted to the BSS including the STA. It can be determined whether the node is from an external BSS or a node. Based on the determination, the interference signal is classified and the CTS is sent to the remaining bands excluding the interference signal region in the band identified by the RTS. AP1 can transmit data through the band receiving the CTS. In addition, the bandwidth occupied by the above process can be minimized, and the power consumption efficiency can be improved while utilizing frequency resources efficiently.

Finally, the present invention includes a low power mode of a multi-channel transmission method to be used as a next generation WLAN technology. Next-generation wireless LAN technology can increase the throughput by 2 to 4 times by using 80 MHz bandwidth which is 4 times or 2 times wider than the conventional 20 MHz or 40 MHz bandwidth. However, this also increases the sampling rates of analog-to-digital converters and digital-to-analog converters, resulting in higher power consumption. In addition, the modem processor uses a high operating frequency, causing a problem of degrading dynamic consumption efficiency. However, the terminal device does not always need to use a high sampling frequency, and according to the mode and packet type used, an appropriate sampling rate may be used to improve power consumption efficiency.

In the conventional low power mode for spatial multiplexing, the power consumption efficiency can be improved by turning on only a few reception paths and turning off the rest before receiving the RTS / CTS, but the low power mode for the multi-channel method of the present invention is RTS / Before receiving a CTS, a sampling rate that is capable of receiving legacy mode packets is used, and after receiving an RTS / CTS, the sampling rate is controlled according to a corresponding mode packet or a used mode. If the RTS / CTS packet can be transmitted with the type of data packet to be received next or the mode information to be used, it can be switched to the corresponding mode.If the packet type or mode information to be used cannot be delivered, the corresponding terminal supports it. And a control unit to convert to the maximum sampling rate for the mode.

The present invention can be supported when the multi-channel transmission scheme is continuous or discontinuous. In other words, when the multiple channels are continuous, the operation is performed with a simple sampling rate. However, when the multiple channels are not continuous, power consumption efficiency can be improved by determining whether to use a non-continuous path.

6 is a flowchart illustrating a transition process in a multi-channel low power mode according to an embodiment of the present invention.

In the first 600 steps, the WLAN receiver checks whether it is in an awake state. If it is awake, go to step 606; otherwise, go to step 602. In step 602, the WLAN device checks whether the timer has expired. If the timer has expired, the process proceeds to step 606. Otherwise, in step 604, the power is turned off for all blocks, and then step 600 is performed.

If the process proceeds from step 600 or step 602 to step 606, power is supplied only to one or two receiving part carrier sensing blocks. In this case, the injected WLAN receiver operates in a legacy mode sampling rate. Since the wake-up or wake-up mode by the expiration of the timer is all before the carrier sensing, the second reception state mentioned above becomes a state before the RTS / CTS reception.

After the power is supplied only to the carrier sensing block, the wireless LAN device proceeds to step 608 to check whether carrier sensing is performed within a predetermined time. If carrier sensing is performed, the wireless LAN device proceeds to step 610, and if not, proceeds to step 606.

Next, when the carrier sensing is performed, the wireless LAN device proceeds to step 610 to supply power to the remaining blocks of the reception path. In this case, the sampling rate may use the sampling rate of the legacy mode. This reduces power consumption by reducing the sampling rate. In operation 612, the WLAN receiver checks whether a packet category is available. It is to check if the packet type information is available. If the category of the packet, that is, the category of the packet such as RTS / CTS is available, the process proceeds to step 614; otherwise, the process proceeds to step 216.

In step 614, the WLAN receiver checks whether a received packet category is an RTS / CTS packet. In case of a packet of the RTS / CTS category, the WLAN receiver proceeds to step 618 and supplies power to the corresponding blocks of the reception path according to the number of streams.

On the other hand, if it is not a packet of the RTS / CTS category in step 614 or if the category of the packet is not available in step 612, the process proceeds to step 416 and powers up the blocks of all receiving paths.

In step 620, the WLAN receiver determines whether mode information is available. Such mode information is mode information transmitted in the manner described above. If the mode information is not available, the WLAN receiver proceeds to step 622 to operate at the maximum data rate supported by the receiver.

On the other hand, if mode information is available, the WLAN receiver first proceeds to step 624 to check whether the current mode is the legacy mode. If the test result of step 624 is the legacy mode, the wireless LAN receiver proceeds to step 626 to operate at the sampling rate of the legacy mode. However, if the test result of step 624 is not the legacy mode, the wireless LAN receiver proceeds to step 628 to check whether the HT mode. If the HT mode, the wireless LAN receiver proceeds to step 630 to operate at a sampling rate corresponding to the HT mode.

However, if the test result of the step 624 and step 628 is not the legacy mode and the HT mode, the VHT mode is. Therefore, the WLAN receiver proceeds to step 632 to check whether the data stream is continuously received (contiguous). If the data frame is continuously transmitted as a result of the check, the WLAN receiver proceeds to step 634 to operate at the sampling rate of the VHT mode. However, if not received continuously, the WLAN receiver proceeds to step 636 to perform a multi-channel power saving operation.

6 described above is a low power mode conversion procedure of the present invention according to the four reception states described above. That is, in the dust mode, all blocks are turned off until the timer runs out, and when the timer runs out, only the path required for carrier sensing and the corresponding carrier sensing block are turned on. At this time, since the RTS / CTS is transmitted in the legacy mode, the RTS / CTS is set to an operating frequency for the legacy mode. In addition, when the carrier sensing in the awake state, the remaining blocks of the corresponding path for the carrier sensing is turned on. After the packet type information is available, more paths can be turned on to improve the carrier sensing result of the data packet when the received packet is RTS / CTS. However, if packet type information is not available or is a data packet, all paths are turned on. At this time, the corresponding terminal converts to the maximum operating frequency that can be supported so that any kind of packet can be processed. When it is confirmed that the packet type information is available and is an RTS / CTS packet, if the mode information is available, it is switched to the sampling rate for the corresponding mode. At this time, if the mode information is not available, the corresponding terminal is converted to the maximum sampling rate that can be supported so that any mode packet can be processed. When the mode is a packet of the VHT mode, power and a clock may not be supplied to a path for a discontinuous channel that is not used as the low power mode for the multi-channel transmission described above.

100: RF block 101: low noise amplifier (LNA)
102: voltage controlled gain amplifier (AGC)
111: analog-to-digital converter (ADC)
112: DC controller 113: I / Q channel signal comparator
115: buffer
116: Carrier Frequency Offset (CFO)
117: Fast Fourier Converter 118: Phase Comparator
119: MIMO detector 120: Demapper (Soft Demap)
121: energy detect
122: clear channel assessment (CCA)
123: field strength measuring instrument (W-RSSI)
131: automatic gain controller (AGC)
132: Saturation based carrier sense
141: channel mixer
142 low pass filter and averager (LPF + deci / 2)
143: carrier detection based receiving field strength measurement unit (RSSI based carrier sense)
144: auto correlation
145 cross correlation
146: CFO estimator 147: frame synchronizer
148: XCR calculation unit based on carrier sensing

Claims (20)

A method of transmitting a frame in a wireless communication system having two or more different bandwidth transmission modes,
Transmitting the request information including channel state information or data frame mode information to be transmitted;
When receiving a response frame for the request frame including the channel state information or the receivable data frame mode information from the receiving node, the data frame is determined based on the channel state information included in the response frame or the receivable data frame mode information. A frame transmission method in a wireless communication system comprising the step of generating and transmitting.
The method of claim 1,
The channel state information includes available channel bandwidth information.
The method of claim 1,
The data frame mode information includes bandwidth information of a frame to be transmitted next.
The method of claim 1,
Wherein the data frame mode information comprises one of a required performance indicator of the data frame or the number of transmission streams.
The method of claim 1,
The receiving node determines whether the received frame is a request frame received from a basic service set (BSS) to which the receiving node belongs or based on an adjacent coexistence basic service set (OBSS) based on the BSSID of the MAC header included in the received frame. Determining whether the received interference frame;
And transmitting the response frame using the size information of the remaining bands except the bandwidth occupied by the interference signal in the bandwidth included in the request frame as the channel state information based on the determination result. Transmission method.

The method of claim 1,
The request frame or the response frame is transmitted using an idle channel,
Wherein each of the frames includes idle channel bandwidth information.
The method of claim 1,
And reconfiguring a filter and an RF center frequency for transmitting the data frame to be transmitted, based on the channel state information or the data frame information included in the received response frame.
The method of claim 1,
The receiving node reconfigures a filter and an RF center frequency for receiving the data frame based on the channel state information or the data frame information included in the transmitted response frame or the received request frame. Way.
The method of claim 1,
The receiving node receives a frame in a wireless communication system that receives the data frame at a minimum sampling operation frequency that satisfies a required bandwidth, based on the channel information or data frame information included in the response frame or the request frame. Way.
The method of claim 1,
And determining whether a counterpart node includes the channel state information or the data frame mode information based on the dynamic channel bandwidth allocation supportable information of the request frame or the response frame. Way.
The method of claim 1,
The channel state information or data frame information provided in advance,
A method of transmitting a frame in a wireless communication system, using at least one of an unused field value among a service field of a physical layer, a duration field of a MAC header, or a frame control field of a MAC header. In the power saving method in a wireless communication system having two or more bandwidth transmission mode with each other,
Receiving the control frame by setting to receive the control frame in a mode having the lowest sampling rate among the bandwidth modes when the control frame is received;
And transmitting / receiving the data packet by setting the data packet to be transmitted / received in a mode having the highest sampling rate for transmitting / receiving the data packet after receiving the control frame. Way.
The method of claim 12,
And setting the data packet to be transmitted / received in a mode corresponding to the information provided in advance for transmitting / receiving the data packet when the corresponding mode information among the bandwidth modes is previously provided for the data packet. Power saving method in wireless communication system.
The method of claim 12,
Switching to a mode having the lowest sampling rate when retransmission is not required after the data packet transmission / reception.
The method of claim 12, wherein the control frame,
At least one of a Request to Send (RTS) or a Request to Send (CTS) or Response (ACK) frame.
In the power saving method in a wireless communication system for transmitting and receiving data through carrier sensing,
Turning on power only to a timer for releasing the doze mode in a doze mode that does not require the carrier sensing, and cutting off power to the entire physical layer and the MAC layer;
Supplying power only to the physical (PHY) layer and the MAC (MAC) layer required for the carrier sensing when the carrier sensing is necessary;
And powering only a path necessary for data transmission / reception if data transmission / reception is required after the carrier sensing.
17. The method of claim 16,
Retransmission is not required after the data packet is transmitted / received, and upon returning to the doze mode, turning on only the timer for the release of the doze mode, and further comprising shutting off power to the physical layer and the entire MAC layer. , Power saving method in wireless communication system.
A power saving method in a wireless communication system having two or more different transmission modes and performing data transmission / reception through carrier sensing,
Turning on power only to a timer for releasing the doze mode in a doze mode that does not require the carrier sensing, and cutting off power to the entire physical layer and the MAC layer;
Performing the carrier sensing by setting the carrier sensing to a mode having the lowest sampling rate among the different modes when the carrier sensing is required;
And transmitting / receiving the data packet by setting the data packet to be transmitted / received in a mode having the highest transmission rate for transmission / reception of the data packet after the carrier sensing.
The method of claim 18,
And setting the data packet to be transmitted / received in a mode corresponding to information provided in advance for transmitting / receiving the data packet when the corresponding mode information among the bandwidth modes is provided in advance. , Power saving method in wireless communication system.
The method of claim 18,
Retransmission is not required after the data packet is transmitted / received, and upon returning to the doze mode, turning on only the timer for the release of the doze mode, and further comprising shutting off power to the physical layer and the entire MAC layer. , Power saving method in wireless communication system.

Images