Patent Document

BACKGROUND 
       [0001]    The disclosed invention relates to WLAN systems, and more particularly, to WLAN systems that have reduced power consumption during an active transceiving mode and related methods thereof. 
         [0002]    A conventional wireless local area network (WLAN) system is divided into a front-end section and a back-end section. The front-end section comprises an RF circuit, for converting RF signals to baseband signals in receiving (Rx) mode, and for converting baseband signals to RF signals in transmitting (Tx) mode. The front-end section further comprises an analog front-end (AFE) circuit for converting analog baseband signals to digital baseband data in Rx mode and converting digital baseband data to analog baseband signals in Tx mode. The back-end section comprises a baseband circuit, containing a Medium Access Controller (MAC) for processing the digital baseband signal and packet data. 
         [0003]    Data packets of WLAN systems comprise a preamble, a header having information such as the data packet modulation scheme, and the data. The data is typically modulated in one of the modulation schemes: BPSK, QPSK, 8QAM, 16QAM, 64QAM, where BPSK is the lowest modulation and 64QAM is the highest among these modulation schemes. Data transmitted by a more complicated modulation scheme has a higher bit rate, which requires a higher power for receiving the data. 
         [0004]    WLAN products are designed to consume as little power as possible, for example, RF and digital parts of an integrated circuit (IC) chip have various reduced power operation modes such as standby mode, sleeping mode, and deep sleeping mode. It normally takes a period of time to switch between a normal mode and a reduced power operation mode, so frequently or immediately switching from the normal mode to the reduced power operation mode is not practical. 
       SUMMARY 
       [0005]    WLAN systems that can further reduce power consumption are provided. Some embodiments of the WLAN systems have both front-end and baseband circuits integrated on a single chip, which can dynamically adjust some settings of the chip based on the signal format of packets. 
         [0006]    A WLAN system comprises a radio frequency (RF) circuit, an analog front-end (AFE) circuit, and a baseband circuit. In some embodiments, the baseband circuit sends a command to dynamically change a setting of the AFE circuit, RF circuit, or both AFE and RF circuits in accordance with a content of the digital baseband data. More specifically, the setting of the AFE or RF circuit can be determined by a transmission rate, modulation type, or a packet type defined in the digital baseband data. For example, when the content of a received packet indicates a low transmission rate, requiring a relatively low signal to noise ratio (SNR), the setting of an analog to digital converter (ADC) in the AFE module and RF Amplifier in the RF module can be dynamically set to make the ADC and RF circuits consume less power. Similarly, when transmitting a packet using a low bit rate modulation scheme (e.g. BPSK), a digital to analog converter (DAC) in the AFE module and RF Amplifier in RF module can be dynamically set to make the DAC and RF circuits consume less power. 
         [0007]    In some embodiments, a pre-amplifier or a mixer can be dynamically modified in a transmission mode depending on the transmission rate, and the setting of a low noise amplifier (LNA), mixer, or synthesizer can be dynamically modified in a receiving mode depending on the receiving rate. 
         [0008]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a diagram of a WLAN system according to an embodiment of the disclosed invention. 
           [0010]      FIG. 2  is a diagram of a data packet conforming to the 802.11a/g standard. 
           [0011]      FIG. 3  is a flowchart for transmitting packets in the WLAN system shown in  FIG. 1 . 
           [0012]      FIG. 4  is a flowchart for receiving packets in the WLAN system shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  is a diagram of a WLAN system  100  according to an embodiment of the disclosed invention. The WLAN system  100  is a wireless communication system capable of signal receiving and transmitting, and the WLAN system  100  comprises an RF circuit  30 , an AFE circuit  50 , and a Digital Design Block  90 , comprising a baseband circuit  70 , and a Media Access Controller (MAC)  80 . The RF circuit  30  is further coupled to an antenna  20 . 
         [0014]    Data modulated by a modulation scheme with a higher transmission rate requires a higher power setting for receiving or transmitting by the WLAN system  100 . This is because the Signal-to-Noise Ratio (SNR) requirement is higher when transmitting or receiving signals carrying more bits in one symbol. The MAC  80  and the baseband circuit  70  can dynamically change the setting of the front-end circuits  30 ,  50  when a different modulation scheme or a different packet type is transmitted in the transmitting mode or is detected in the receiving mode. This can be achieved by adjusting registers (parameters) of the front-end circuits  30 ,  50  that influence the amount of power consumed in the WLAN system  100 . It should be noted that, in addition to setting the registers, other means for changing the power relevant settings are possible. 
         [0015]    In a case where the WLAN system  100  operates under a transmitting (Tx) mode, register setting of a digital-to-analog converter (DAC) in the AFE circuit  50  can be controlled to consume less power when transmitting data using a lower rate modulation scheme. For example, by controlling the reference current fed into the DAC, the resulting SNR level is adjusted accordingly. Regarding the RF circuit  30 , register setting of a pre-amplifier, a mixer, or a combination thereof can be controlled to change the resulting SNR level. 
         [0016]    In a case where the WLAN system  100  operates under a receiving (Rx) mode, register setting of an analog-to-digital converter (ADC) in the AFE circuit  50  can be controlled to consume less power when receiving data modulated by a lower rate modulation scheme. For example, by controlling the reference current fed into the ADC, the resulting SNR level is adjusted accordingly. Regarding the RF circuit  30 , register setting of a low-noise amplifier (LNA), a mixer, a synthesizer, or any combinations thereof can be controlled to change the resulting SNR level. SNR levels required for Tx or Rx, various operation states, operation modes, or data rates are different depending on the design requirements. Additionally, the corresponding register settings of the aforementioned ADC, DAC, LNA, mixer, and synthesizer in response to different SNR levels can be configured according to different design requirements as well. The way of mapping the SNR levels and the register settings of hardware components within the WLAN system  100  is not meant to be a limitation of the present invention. Any alternative designs using the disclosed feature of dynamically setting the RF module or AFE module in response to different transmitting or receiving conditions all fall within the scope of the present invention. 
         [0017]      FIG. 2  is a diagram of a data packet conforming to the 802.11a/g standard. As can be seen from the diagram with data lengths shown thereon, the data packet comprises a preamble, a header, and a data section. The preamble and header section of the data packet are modulated with a BPSK modulation scheme. The data packet can be initially received or transmitted at a lower SNR setting, which means the power required by the WLAN system  100  can be reduced, and then the MAC  80  and baseband circuit  70  can dynamically increase the power level by changing the settings of the RF and AFE modules to raise the SNR when receiving or transmitting the preamble or signal. 
         [0018]    The detailed operation of the disclosed WLAN system  100  will now be described using examples, with reference to transmitting and receiving methods respectively. 
         [0019]    Transmitting (Tx) Mode 
         [0020]    Initially, the front-end circuits  30 ,  50  are at a setting corresponding to a low SNR setting. The WLAN system  100  determines a transmission rate based on the selected modulation scheme. The MAC  80  can dynamically set registers of the front end circuits  30 ,  50  to a setting corresponding to an appropriate SNR level for data transmission based on the determined transmission rate or modulation scheme. Taking the DAC for example, the DAC setting can be dynamically switched in synchronous with packets. When operating at 11 g OFDM 6 Mbps packet transmission mode, the DAC setting is set to C 1  before packet transmission, and when operating at 111 g OFDM 54 Mbps packet transmission mode, the DAC setting is set to D 1  before packet transmission, where C 1  setting consumes less power than D 1  setting. After the data packet is transmitted, if no more data packets are to be transmitted, the MAC  80  will again dynamically set front-end circuit register settings to correspond to the original lowest SNR setting or turn the DAC off for power saving. 
         [0021]    Receiving (Rx) Mode 
         [0022]    In this example, the WLAN system  100  complies with 802.11g, and can be operated in sleeping mode, packet detection mode, or packet decoding mode. When operating in the sleeping mode, the LNA, mixer, synthesizer in the RF circuit  30  are set to low SNR settings (e.g. A 2 , A 3 , A 4  respectively), and the ADC  50  is also set to a low SNR setting (e.g. A 1  setting) as the system only wakes up for beacon listening at a predetermined time interval. When the system  100  is in the packet detection mode, the packet detection mechanism continuously detects the arrival of a packet. If a packet is detected, the LNA, mixer and synthesizer settings change from A 2 , A 3 , A 4  to B 2 , B 3 , B 4  respectively, and the ADC setting changes from A 1  to B 1  since a higher SNR requirement is needed for later packet decoding. In some embodiments, the packet will be initially received at a low SNR setting corresponding to the BPSK modulation scheme, which is the modulation scheme of the preamble and signal parts of the data packet. At some point during the preamble (e.g. long preamble symbol in 802.11a/g), the MAC  80  will operate to update the register settings of the front-end circuits  30 ,  50 , thereby raising the SNR to a level appropriate for a higher modulation scheme (e.g. 64QAM). After the data packet has been demodulated, the MAC  80  can then operate to change the front-end circuit register settings to correspond to an SNR level appropriate for packet detection. In this way, the WLAN system  100  only operates at maximum power when data in a data packet is actively being received. 
         [0023]      FIG. 3  is a flowchart of an exemplary transmitting method of the WLAN system  100 . 
         [0000]    The steps are as follows: 
         [0024]    Step  300 : Start; 
         [0025]    Step  302 : Determine the transmission rate of the data packet; 
         [0026]    Step  304 : Set front-end circuit registers to appropriate setting; 
         [0027]    Step  306 : Transmit the packet; 
         [0028]    Step  308 : Is another packet to be transmitted? If yes go back to Step  302 , if no go to Step  310 ; 
         [0029]    Step  310 : Set front-end circuit registers to setting corresponding to low SNR; 
         [0030]    Step  312 : End. 
         [0031]    The WLAN system  100  is initially in a normal transmitting mode (Step  300 ). The transmission rate of a data packet is determined by the MAC  80  (Step  302 ) and the WLAN system  100  sets front end circuit registers to a corresponding SNR level setting, so that the higher the transmission rate, the higher the SNR level setting (Step  304 ). The packet is transmitted at the desired power setting (Step  306 ). If the WLAN system  100  determines another packet needs to be transmitted (Step  308 ) then steps  302 - 306  will be repeated. If not, then the front-end circuit registers  30  and  50  will be reset to the original low power setting (Step  310 ). The process ends (Step  312 ). 
         [0032]      FIG. 4  is a flowchart of an exemplary receiving method of the WLAN system  100 . The steps are as follows: 
         [0033]    Step  400 : Start; 
         [0034]    Step  402 : Set front-end circuit registers to a setting corresponding to a sleeping mode for beacon listening, or a setting corresponding to a packet detection mode; 
         [0035]    Step  404 : Is a signal containing valid packet preamble detected? If yes go to Step  406 , if no go back to Step  404 ; 
         [0036]    Step  406 : Set front-end circuit registers to a setting corresponding to packet decoding mode; 
         [0037]    Step  408 : Decode received packet; 
         [0038]    Step  410 : Terminate RX mode? If yes go to Step  412 , if no go to Step  402 ; 
         [0039]    Step  412 : End. 
         [0040]    If the system is initially in a sleeping mood, the front-end circuit registers are set by the MAC  80  to correspond to a lowest SNR level, and the system enters a packet detection mode (e.g. MAC  80  sets the front end circuit registers to low SNR level) if it detects a beacon indicating the arrival of packets. If the system is initially in a packet detection mode, it is set to a setting corresponding to a low SNR level (Step  402 ). If it is determined that a signal with valid packets is received (Step  404 ), the front-end circuit registers will be set to a packet decoding mode corresponding to a higher SNR (Step  406 ) and the received packet will be decoded (Step  408 ). After the packet is decoded (Step  408 ), the MAC  80  will set the front-end circuit registers to the packet detection mode (Step  402 ) if the RX mode has not been terminated (Step  410 ). Otherwise, if the RX mode has been terminated (Step  410 ), the RX mode will end (Step  412 ). 
         [0041]    Please note that, in the Rx mode, the front-end circuit register settings can be increased in stages (i.e. steps) during the received preamble, or can jump from a low setting to a high setting directly, and both modifications are covered by the present invention. Furthermore, after the signal part of a data packet is decoded and the modulation scheme therefore determined, the WLAN system  100  can further adjust the front-end circuit register settings to correspond to the exact modulation scheme of the received data packet. 
         [0042]    By integrating the front-end and baseband circuits on the same chip, the WLAN system  100  can dynamically alter front-end circuit register settings when the system is in an active Rx or Tx mode. Furthermore, by controlling the SNR the WLAN system  100  is operating at, the power consumption of the system  100  can also be controlled. It should be noted in a case where latency of data delivery between circuits of the WLAN system is negligible due to higher operating clock speed or other improvements, the RF circuit  30 , the AFE circuit  50 , the baseband circuit  70 , and MAC  80  are not limited to be integrated in a single chip. 
         [0043]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Technology Category: y