Abstract:
The present invention is a power saving method for wireless network communication which is applicable to wireless network equipment comprising of the following steps: receiving the frame in wireless network; getting the frame header in frame; according the frame header, judge whether the frames in channel is useful or not; if the received frame is useless, stopping receiving the left parts of the frame or the left frames; according to the frame header, calculating the duration time of left parts in the frame or the left frames; entering power saving status automatically; finally, returning to active status, after the channel is idle again.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a power saving method for a wireless network communication device and, more particularly, to power saving method applicable to wireless network equipment.  
         [0003]     2. Description of Related Art  
         [0004]     In a distributed wireless network, such as an ANSI/IEEE 802.11, power management protocol can manage power consumption for wireless network equipment effectively. Wireless network equipment will be set to active mode when a station needs to receive or transmit data under the control of upper layer. On the contrary, the wireless network equipment is set to power save mode under the control of upper layer and wake up from power save mode periodically to receive a beacon.  
         [0005]     However, this power management method depends on the control of upper layer and shall be available only when station doesn&#39;t want to transmit. In the distributed wireless network, such as wireless local area network (WLAN) base service set (BSS) of ANSI/IEEE 802.11, using carrier sense multiple access with a collision avoidance (CSMA/CA) medium sharing mechanism, once the station has contended for the channel, that station shall continue to transmit fragments until either all fragments of a single MSDU or MMPDU have been transmitted. At the same time, the stations that have failed to contend for the channel are also in active mode and shall receive every package transmitted in the channel till the channel is free. Then all the stations in this BSS shall start to contend for the channel again.  
         [0006]     Further more, if the destination address (DA) in the frame header does not match with the medium access control address of the station, the duration field in this frame header will be used to update the network allocate vector (NAV) of the station. The other frames of the channel have nothing to do with the station during the frame end (equal to network allocate vector) time. The station knows these frames are useless in advance, but the station is in active mode. So it still receives these frames during this time.  
         [0007]      FIG. 1  is a chart describing the method for wireless network communication of the prior art. A source station  16  transmits a require to send (RTS)  20  to a destination station  18  in order to inform other stations in the base service set (BSS) or independent base service set (IBSS), such as the station  10 , that it has reserved a time section equaled to the network allocation vector (NAV)  12  provided by RTS  20  to transmit data. The destination station  18  that is addressed by RTS  20  shall send a clear to send (CTS)  26  after a short interframe space in order to allow the source station  16  transmitting. At the same time, the source station  16  has reserved a time section equaled to NAV  14  provided by CTS  26  to transmit the first data fragment  24 .  
         [0008]     The source station  16  receives the CTS  26  and sends the first data fragment  24  to the destination station  18  after a SIFS  22 . At the same time, the source station  16  has reserved a time section equaled to NAV  86  provide by the first data fragment  24  to transmit the second data fragment  32 . The destination station  18  receives the first data fragment  24  successfully and sends an acknowledgment (ACK)  28  to the source station  16  after a SIFS  22 . At the same time, the source station  16  has reserved a time section equaled to NAV  88  provided by ACK  28  to transmit the second data fragment  32 . The source station  16  receives the ACK  28  and transmits the second data fragment  32  to the destination station  18  after a SIFS  22 .  
         [0009]     The destination station  18  receives the second data fragment  32  successfully and sends an ACK  34  to the source station  16  after a SIFS  22 . This transmission is now completed. All the stations in the BSS (or IBSS) now wait for a distributed interframe space (DIFS)  30  and start to contend for the channel.  
         [0010]     For the stations in BSS or IBSS, such as the station  10 , the received packages, including RTS  20 , the first data fragment  24 , CTS  26 , ACK  28 , the second data fragment  32  and ACK  34 , are useless. So the power is wasted by receiving these useless frames.  
       SUMMARY OF THE INVENTION  
       [0011]     Because of several stations contending for a channel and only one station transmitting every time, most of stations shall be idle in active mode till channel is free. For the portable electronic equipment depending on battery, the power consumption of idle status will affect its available work time. So an improvement method that makes idle wireless network device into power save mode to reduce the power consumption of idle status is most desirable. The primary objective of the present invention is to provide an effective method to make idle wireless network device into power save mode to reduce the power consumption of idle status and to extend the available work time of portable electronic equipment.  
         [0012]     To achieve the above objective, the present invention provides a power saving method for wireless network communication comprising of the steps of receiving the frame in wireless network; getting the frame header in frame; according the frame header, judge whether the frames in channel is useful or not; if the received frame is useless, stopping receiving the left parts of the frame or the left frames; according to the frame header, calculating the duration time of left parts in the frame or the left frames; entering power saving status automatically; returning to active status, after the channel is idle again. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The various objectives and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings, in which:  
         [0014]      FIG. 1  is a chart of the method wireless network communication of prior art;  
         [0015]      FIG. 2  is a format chart of the ANSI/IEEE 802.11 physical layer convergence protocol data unit (PPDU);  
         [0016]      FIG. 3   a  is a format chart of the ANSI/IEEE 802.11 Management frame;  
         [0017]      FIG. 3   b  is a format chart of the ANSI/IEEE 802.11 Data frame;  
         [0018]      FIG. 4  is a station power saving chart for wireless network equipment of the present invention;  
         [0019]      FIG. 5  is a another station power saving chart for wireless net work equipment of the present invention fitting for a simpler transmitting (No RTS/CTS); and  
         [0020]      FIG. 6  is a power saving method flowchart for wireless network communication of the present invention.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]     Normally, the network protocol adopts a section parts transmit method for continuous pulsing to improve the throughput of the distributed wireless network. The source station will distribute the necessary data to several continuous frames and transmit them to the destination station continuously after it obtains the usufruct of channel. At the same time, via setting a time section in the frame header, the source station informs the other stations that it has reserved the time section to transmit. The other stations, which failed to obtain the usufruct of channel, receives these frames and be in backoff status till the source station finishes transmitting these continuous frames. Because of being in backoff status, these stations can not contend for the channel with the source station. So this transmittal isn&#39;t interrupted or interfered by the other stations. And the throughput is improved. However, a station still receives the useless frames in the channel till the backoff status ends. The next part uses ANSI/IEEE 802.11 as an example to describe how a station uses a new method to save power in this case in detail.  
         [0022]      FIG. 2  shows the format for the ANSI/IEEE 802.11 physical layer protocol data unit (PPDU)  40  including the DSSS physical convergence procedure (PLCP) Preamble  42 , the DSSS physical convergence procedure (PLCP) Header  44 , and the physical convergence procedure service data unit (PSDU)  46 . The PLCP Preamble  42  contains the following fields: Synchronization (Sync)  48  and Start Frame Delimiter (SFD)  50 . The PLCP Header  44  contains the following fields: IEEE 802.11 Signaling (Signal)  52 , IEEE 802.11 Service (Service)  54 , LENGTH (Length)  56 , and CCITT CRC-16  58 .  
         [0023]      FIG. 3   a  is a format chart of the ANSI/IEEE 802.11 Management frame. The management frame contains the following fields: Frame Control  60 , Duration  62 , Destination Address (DA)  64 , Source Address (SA)  66 , a basic service set identifier (BSSID)  68 , Sequence Control  70 , Frame Body  72  and Frame Check Sequence (FCS)  74 .  
         [0024]      FIG. 3   b  is a format chart of the ANSI/IEEE 802.11 Data frame. The data frame contains the following fields: Frame Control  60 , Duration  62 , Address 1  76 , Address 2  78 , Address 3  80 , Sequence Control  70 , Address 4  82 , Frame Body  72  and Frame Check Sequence (FCS)  74 .  
         [0025]     As shown in  FIG. 3   a  and  FIG. 3   b , based on destination address  64 , the station can decide whether the frame is useful. If the frame is useful, then the station continuously receives the remaining parts till the end; otherwise the station stops receiving, enters power save mode, closes the medium access control layer (MAC), the physical layer (PHY), the analog circuit and the RF circuit. Based on Signal  52 , Service  54  and Length  56  of PLCP Header  44 , the station can calculate the frame of continuous time. This time determines when the station will return from power save mode and enter active mode again.  
         [0026]      FIG. 4  is a station power saving chart for wireless network equipment of the present invention. For the station  10 , all the frames in the first time section  36  and the second time section  38  are useless. The station  10  uses the Duration field of RTS  20  to update its NAV and enters a power save period  90  until the first data fragment  24  ends. The station  10  starts a normal receive period  92  and receive the ACK  28  after the power save period  90  ends.  
         [0027]     The station  10  uses the Duration field of RTS  20  to update its NAV and enters a power save period  90  again until the second data fragment  32  ends. All of the data has been transmitted and the process is completed after the second data fragment  32  ends. So duration filed of the ACK  34  is zero. Then NAV of the station  10  updates to zero. This means the station  10  can contend for the channel again after the ACK  34  ends.  
         [0028]     Comparing to the current power management, such as shown in  FIG. 1 , the new power save method decreases the power consumption of the station  10  obviously. During most of time in the second time section  38 , the station  10 , which adopts the new power save method, is in power save mode. However, if not a adopting it, the station  10  will be in active mode after failing to contend for the channel and spend lots of power in receiving the useless frames in the channel.  
         [0029]     Sometimes, source station  16  does not transmit RTS  20  to destination station  18  before the first data fragment  24 . And destination station  18  does not reply RTS  20  to source station  16 , either. So station  10  can not update its NAV via receive duration field of RTS  20  or CTS  26  and then enter power save period  90 . However, if station  10  wants to update its NAV via receive duration field of the first data fragment  24 , the other problem will emerge. For checking the received frame, frame check sequence (FCS) appends at the end of frame. For example, in ANSI/IEEE 802.11, a double word CCITT CRC 32 FCS appends at the end of frame. The medium access control layer protocol uses the frame duration field to update its network allocation vector only after passing CRC-32 check. Station  10  has no time to enter power save period  90  after checking the first data fragment  24  via CRC-32 FCS. A simple solution is shown in  FIG. 5 . Station  10  only receives MAC Header of the first data fragment  24  and then enters power save period  90  directly. It uses duration field of the first data fragment  24  without CRC-32 check to update its NAV. This solution is a little risky because of no CRC-32 check. However, when saving power is prior, this solution is available.  
         [0030]      FIG. 6  is a flowchart of a power saving method for wireless network communication of the present invention. The method comprises of receiving a complex number frame in a wireless network (S 100 ), getting the complex number frame header in the frames (S 102 ), and the frame headers comprises of a frame rate field, a frame length field, a destination address, a duration time and a CRC  16  field. According to the frame headers, the station judges whether the received frame is useful or not (S 104 ). If the received frame is useful, it will continue to receive the left parts of the frame (S 106 ) until end and accomplish the corresponding operation, such as transmitting ACK frame to the source station. Then it will return to the active status and wait the frame signal in the wireless network (S 100 ) and wait the next frame.  
         [0031]     Otherwise, if the received frame is useless, the station will stop receiving the left parts of the frames (S 108 ). As mentioned above, according to the frame headers, the station is able to calculate the duration time of left parts in the frame or the left frames (S 112 ). The wireless network equipment will enter power saving status (S 110 ) automatically. After a channel of the wireless network equipment is idle again, the station can return to active status (S 114 ) and waiting the next frame (S 100 ). The wireless network equipment is a medium access control layer, a physical layer, an analog circuit and a RF circuit.  
         [0032]     The power saving method for wireless network communication lowers power consumption in wireless network equipment and allows users to work continuously for a longer period of time on the limited battery power provided.  
         [0033]     Although the present invention has been described with reference to the preferred embodiments thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.