Abstract:
A power-saving wireless network, a packet transmitting method for use in the wireless network, and computer readable medium therefor are provided. The wireless network comprises a PAN coordinator, a receiving node and a transferring node. When the transmitting node has a packet planed to be transmitted to the receiving node which is in a sleep mode, the packet is alternatively transmitted to the PAN coordinator. As soon as the receiving node wakes from the sleep mode, all packets are transmitted to the receiving node from the PAN coordinator. After the packets are all successfully transmitted, the receiving node turns back to the sleep mode subsequently. Thereby, the performance of the wireless network would not be restricted to the sleep period and memory capacity. Thus, the nodes in the wireless network would greatly facilitate saving power.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application benefits from the priority of Taiwan Patent Application No. 095112717 filed on Apr. 10, 2006.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a wireless network, a packet transmitting method for use in the wireless network, and a computer readable medium therefor. In particular, the invention relates to a power-saving wireless network with packets buffering performance, a packet transmitting method for use in the wireless network, and a computer readable medium therefor.  
         [0004]     2. Descriptions of the Related Art  
         [0005]     Low speed wireless communication devices are highly noticed recently in the fields of household appliances, toys, industries, security services, and medical care. For the characteristics of low cost, low power consumption, and easily disposed of those low speed wireless communication devices, they are especially proper to be applied in a broad service area with little maintenance. Among various low speed wireless communication protocols, the most representative standard among them is IEEE 802.15.4/ZigBee.  
         [0006]     In a ZigBee wireless network, the coverage is limited due to the restricted radio wave strength. When a large service area is desired, access points are usually needed to be disposed to form a union to provide better radio wave coverage.  
         [0007]     As shown in  FIG. 1 , a conventional wireless network  1  is illustrated. The wireless network  1  comprises a personal area network coordinator (PAN coordinator)  10 , a sending node  11 , a receiving node  13 , a first access node  12 , a second access node  14 , a third access node  16 , and a fourth access node  18 . When the sending node  11  requires sending a packet to the receiving node  13 , the packet has to be transmitted by the access nodes  12 ,  14 ,  16  and  18  to the receiving node  13 , due to the limited radio wave coverage. A transmitting path  1   a  for illustrating the transmitted packet is approximately indicated in  FIG. 1 .  
         [0008]     However, for the purpose of power-saving, nodes in the ZigBee wireless network frequently enter into a sleeping mode. For example, the node may shut down the wireless antenna which may be the most power consuming element thereof. Meanwhile, as shown in the transmitting path  1   a,  the packet would not be received by the receiving node  13  correctly, and thus, the packet would be lost. To solve the problem, generally, there are two conventional solutions. One is to temporarily store the packet in the neighbor nodes (e.g. the fourth access node  18 ), and the other is to shorten the sleep period of the receiving node  13 .  
         [0009]     In point of the first solution, the memory size of the access nodes would be a key factor. The memory size of the access node needs to be increased for providing sufficient space to store packets temporarily. Furthermore, when an access node corresponds to a plurality of receiving nodes, the memory size thereof would be inestimable and then the costs of constructing the wireless network would be raised. Moreover, the conventional technology uses the MAC (medium access control) layer of the packet. In accordance with the conventional ZigBee standards, it only stipulates that “at least reserving a packet” in the MAC layer. Just a few companies develop technologies which support seven-packet storage. Nevertheless, the problem of memory requirements will definitely occur in some situations and result in loss of packets and restrict the applications of the ZigBee wireless network as well.  
         [0010]     In point of the second solution, shortening the sleep periods of the receiving node would simultaneously shorten the power-saving period of the receiving nodes. It would be a disadvantage to construct a power-saving wireless network. Furthermore, the temporary period of the packets is three seconds by present ZigBee standards. It could simply infer that the receiving nodes have to return to working mode in three seconds (e.g. waking up every two seconds). Thus, power-saving efficiency of the nodes would be greatly reduced.  
         [0011]     Given the above, a novel power-saving wireless network, a packet transmitting method for use in the wireless network, and a computer readable medium therefor need to be developed in this field.  
       SUMMARY OF THE INVENTION  
       [0012]     The primary objective of this invention is to provide a wireless network, a packet transmitting method for use in the wireless network, and a computer readable medium therefor. By temporarily storing the packets in a coordinator, waiting for a receiving node actively requesting after waking from a sleep mode, the packets are subsequently transmitted to the receiving node. It could eliminate the restrictions on the sleep mode of the receiving node.  
         [0013]     Another objective of this invention is to provide a wireless network, a packet transmitting method for use in the wireless network, and a computer readable medium therefor. Since the packets are temporarily stored in the coordinator, the memory requirements of the nodes or routers could be greatly diminished. It would benefit for constructing a large service area. Furthermore, the coordinator generally possesses superior hardware than other devices in the network so that the whole wireless network can be constructed and operated merely depending on the performance of the coordinator but not other devices such as nodes or routers in the present invention.  
         [0014]     A further objective of this invention is to provide a wireless network, a packet transmitting method for use in the wireless network, and a computer readable medium therefor. By the routing rules in the present invention, a power-saving wireless network would be obtained. It can extend the sleep period of the devices so as to prolong the battery life of the devices.  
         [0015]     Yet a further objective of this invention is to provide a wireless network, a packet transmitting method for use in the wireless network, and a computer readable medium therefor. By temporarily storing the packets in the coordinator, it is no longer restricted by the present ZigBee standards including the periods of temporarily storing packets not longer than three seconds, maximum of temporarily storing packets on the nodes, etc.  
         [0016]     To achieve the above-mentioned objectives, the power-saving wireless network of the present invention comprises a coordinator, a receiving node and a transferring node. The transferring node has a packet required to be transmitted to the receiving node. The transferring node transmits the packet to the coordinator and stores a pending flag recording the packet waiting to be received by the receiving node when the transferring node determines the receiving node being in a sleep mode. Then, the coordinator receives and stores the packet.  
         [0017]     The present invention further comprises a packet transmitting method for use in the above-mentioned wireless network. The method comprises the steps as follows: determines by the transferring node that the receiving node is in a sleep mode; transmitting the packet to the coordinator by the transferring node; storing a pending flag in the transferring node wherein the pending flag records the packet waiting to be received by the receiving node; and receiving and storing the packet by the coordinator.  
         [0018]     The present invention further comprises a computer-readable medium, storing a computer program to perform the above-mentioned method.  
         [0019]     The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a schematic view illustrating packet transmission in a conventional wireless network;  
         [0021]      FIG. 2  is a schematic view illustrating the receiving node in a sleep mode in the wireless network of the present invention;  
         [0022]      FIG. 3  is a schematic view illustrating the packet stored in the coordinator in the wireless network of the present invention;  
         [0023]      FIG. 4  is a schematic view illustrating the receiving node waking from the sleep mode in the wireless network of the present invention;  
         [0024]      FIG. 5  is a schematic view illustrating that the receiving node has no packet waiting to be received in the wireless network of the present invention; and  
         [0025]      FIG. 6  is a schematic view illustrating that the receiving node has the packet waiting to be received in the wireless network of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]      FIG. 2  shows a power-saving wireless network  2  as the first embodiment of the present invention. The power-saving wireless network  2  comprises a coordinator  20 , a receiving node  23 , and a transferring node  28 . In this embodiment, the wireless network  2  further comprises a sending node  21  attempting to transmit a packet to the receiving node  23 . As shown in the figure, when the radio wave of the sending node  21  cannot cover the receiving node  23 , the packet would be transferred along a transmitting path  2   a  to the transferring node  28 . Then, the transferring node  28  prepares for transmitting the packet to the receiving node  23 .  
         [0027]     Subsequently, the transferring node  28  determines whether the receiving node  23  is in a sleep mode by sending a sleep request packet. A transmitting path  2 b illustrating the path of the sleep request packet is shown in  FIG. 2 . Please referring to  FIG. 3 , when the receiving node  23  is in the sleep mode, the transferring node  28  transmits and stores the packet to the coordinator  20  (e.g. a transmitting path  2   c ). Besides, it stores a pending flag in the transferring node  28  which records the packet waiting to be received by the receiving node  23 .  
         [0028]     When the receiving node  23  wakes from the sleep mode to enter to a working status, it transmits a request signal to the transferring node  28 . A transmitting path  2 d is shown in  FIG. 4 . The transferring node  28  determines whether the packet exists or not by checking the pending flag corresponding to the request signal.  
         [0029]     When the transferring node  28  determines that the packet does not exist, it will transmit an ending packet to the receiving node  23 . A transmitting path  2   e  for transmitting the ending packet is shown in  FIG. 5 . Then, the receiving node  23  returns to the sleep mode when it receives the ending packet. Preferably, the ending packet is a packet with zero-length.  
         [0030]     When the transferring node  28  determines that the packet exists, the transferring node  28  transmits a retrieving command packet to the coordinator  20 . After the coordinator  20  receives the retrieving command packet, the coordinator  20  would check all packets which are corresponding to the retrieving command packet and transmit them to the receiving node  23 . Subsequently, the coordinator  20  transmits an ending packet to the receiving node  23 . Similarly, the receiving node  23  returns to the sleep mode corresponding to the ending packet and the ending packet is a packet with zero-length in a preferred embodiment.  
         [0031]     The second embodiment of the present invention is a packet transmitting method for use in a wireless network. Preferably, the wireless network is the same with the above-mentioned of the first embodiment. The wireless network comprises the coordinator  20 , the receiving node  23  and the transferring node  28  as well. The transferring node  28  has a packet required to be transmitted from the sending node  21  to the receiving node  23 . The steps of this embodiment are described as follows. It is noted that the processes of transferring and transmitting in this embodiment will follow IEEE 802.15.4/ZigBee which stipulates the transmitting technology by using the network layer. Advantageously, it would not suffer from the restrictions on using the MAC layer in the prior art.  
         [0032]     Firstly, the sending node  21  sends the packet, which is originally desired to be transmitted to the receiving node  23 , to the transferring node  28 . When the transferring node  28  has a packet to be transmitted, it will determine whether the receiving node  23  is in a sleep mode first. If the receiving node  23  is in a sleep mode and is unable to receive the packet, the transferring node  28  will transmit the packet to the coordinator  20  and store a pending flag in itself The pending flag records that the packet is stored and waiting to be received by the receiving node  23 . Subsequently, the coordinator  20  receives and stores the packet.  
         [0033]     As shown in  FIG. 2 , the transmitting path  2   a  illustrates that the packet is transmitted through a first access node  22 , a second access node  24 , and a third access node  26 , to the transferring node  28 . At least a source address, an objective address and information contents are recorded in the packet. The source address could be the network address of the sending node  21  (e.g. 0×0021) and the objective address could be the network address of the receiving node  23  (e.g. 0×0023) which are utilized to recognize the packet during transmission.  
         [0034]     As shown in  FIG. 3 , when the transferring node  28  transmits the packet to the coordinator  20 , the method further comprises a step of setting a pending bit as “1” in the packet. The pending bit could also be named as a pending-packet flag or a reserved bit. Furthermore, the pending bit is one of a plurality of bits in the packet. When the coordinator  20  receives the packet having the pending bit as “1,” it would temporarily store the packet.  
         [0035]     The transmitting path  2   d,  shown in  FIG. 4 , illustrates that the receiving node  23  would send a request signal to the transferring node, when the receiving node  23  wakes from the sleep mode, to ask whether any packet exists and waits to be received or not. More specifically, the request signal includes the address of the receiving node  23  (e.g. 0×0023). The transferring node  28  will compare the request signal with the aforesaid pending flag. By checking the pending flag, the transferring node  28  may determine whether the packet exists or not.  
         [0036]     When the transferring node  28  determines that the packet exists, it sends a retrieving command packet to the coordinator  20 . The coordinator  20  subsequently checks all packets corresponding to the retrieving command packet, and then, transmits such packets to the receiving node  23  along a transmitting path  2   f  as shown in  FIG. 6 . Preferably, the coordinator  20  transmits all packets in a manner of FIFO (first-in-first-out) transmission. More specifically, the retrieving command packet includes the address of the receiving node  23  (e.g. 0×0023) and the address of the coordinator  20  (e.g. 0×0020). Thus, the coordinator  20  may easily recognize and arrange all packets so that all packets can be subsequently transmitted.  
         [0037]     Eventually, the coordinator  20  transmits an ending packet to the receiving node  23  while the ending packet is a packet with zero-length preferably. More specifically, the ending packet merely records the address of the receiving node  23  (0×0023) and the address of the coordinator  20  (0×0020) in the head of the packet in which the data length is zero. Furthermore, the receiving node  23  determines whether all packets have been received corresponding to the ending packet, and then, it will return to the sleep mode for reducing power consumptions. Soon after, since the packet has been transmitted from the coordinator  20  to the receiving node  23 , the transferring node  28  would update the pending flag as “none.” 
         [0038]     In other words, if there is no packet waiting to be received by the receiving node  23  during the sleep period, the pending flag should be “none.” As shown in  FIG. 5 , when the transferring node  28  determines that the packet does not exist, it would transmit an ending packet to the receiving node  23  along a transmitting path  2   e.  Preferably, the ending packet is a packet with zero-length. Then, the receiving node  23  returns to the sleep mode corresponding to the ending packet.  
         [0039]     The present invention also comprises a computer-readable medium, storing a computer program to perform said method. The computer-readable medium could be floppy disks, hard disks, CD-ROMs, portable storing devices, magnetic tapes, accessible database via network or any other storage media possessing the same functions that people skilled in the art could easily conceive.  
         [0040]     According to the disclosure of the present invention, the sleep period of the receiving node  23  could be prolonged effectively under the ZigBee standards. In convention, the nodes need to wake from the sleep mode every two seconds, while in the present invention, the sleep period of the nodes could be prolonged to two minutes in a practical application. Moreover, the battery life of the conventional nodes is 70.73 days approximately, while in the present invention, the battery life of the nodes is 250.7 days (183.4 days in the most serious consumptions) under the same conditions. Regarding to packet transmission, there is a limitation in the prior art, that is approximately 3.5 packets per second. In the present invention, 116 packets per second can be achieved in the non-sleep period. Obviously, the present invention provides a wireless network and a packet transmitting method with lower costs and higher efficiencies.  
         [0041]     The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.