Abstract:
A wireless transport protocol for data packets transmitted over a wireless communication network includes a user data field having data to be transmitted by a sending party to a receiving party. At least one sequencing field is appended to the data field. The at least one sequencing field includes information identifying the last data packet received by the sending party that was transmitted by the receiving party. This allows a sending party to determine whether the receiving party has received data packets by examining data packets received from the receiving party.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of provisional patent application Ser. No. 60/111,556, filed Dec. 9, 1998, under the provisions of 35 U.S.C. §119(e). 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to communication systems and packet data networks and in particular to a wireless transport layer protocol for wireless packet data networks and a communications system employing the same. 
     BACKGROUND OF THE INVENTION 
     During recent years, tremendous growth within the telecommunications industry has been witnessed. Internet and global networks are now a consequential part of everyday life. The data communications segment of the telecommunications industry is developing and increasing at such a rate that it is becoming the dominant type of private and business commerce exchange on most networks. However, basically all data communications has been designated to conventional “wired” land-line networks. 
     On the other hand, the wireless industry has indeed become established, although wireless networks have only marginally been used for data communications. The success of wireless voice telephone (cellular) services as reflected by the significant traffic volume, makes it clear that wireless data communications are categorically destined to become a dominant, if not the dominant, type of data communications within the telecommunications industry. However, for this to happen, wireless networks must achieve at least a comparable throughput to their “wired” land-line counterparts in terms of capacity and reliability. The physical media for wireless communications is entirely different in all aspects and characteristics than its “wired” land-line counterpart. These differences must be dealt with to allow wireless and “wired” land-line communication domains to effectively, effortlessly and realistically interact. 
     It is therefore an object of the present invention to provide a novel wireless transport layer protocol for wireless packet data networks and a communications system employing the same. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention there is provided a wireless transport protocol for data packets transmitted over a communication network wherein at least one wireless party communicates with a wired party at least partially over a wireless packet data network, said wireless transport protocol comprising; 
     a user data field including data to be transmitted by a sending party to a receiving party; and 
     at least one sequencing field appended to said data field, said at least one sequencing field including information identifying the last data packet received by the sending party that was transmitted by the receiving party. 
     Preferably, the information identifies the identification (ID) number of the last data packet received by the sending party transmitting the current packet. In the preferred embodiment, the at least one sequencing field includes transmit and receive sequencing fields. The transmit sequencing field specifies a current packet ID and the receive sequencing field specifies the ID of the last received data packet. 
     According to another aspect of the present invention there is provided a communication system comprising: 
     at least one wireless client; 
     a wireless network; 
     at least one land-line client; and 
     a network backbone interfacing said at least one land-line client and said wireless network to allow data packets to be exchanged between a wireless client and a land-line client, said communication systems using a wireless transport protocol during exchange of data packets, said data packets including a user data field including data to be transmitted from one client to another client; and at least one sequencing field identifying the last packet received by the client that is transmitting the current packet. 
     In yet another aspect of the present invention there is provided in a wireless communication network, a method of confirming delivery of data packets during data exchange between parties comprising the steps of: 
     providing each data packet sent by one party to another party with information identifying the last data packet received by said one party that was transmitted by the other party; and 
     upon receipt of a data packet by one party from another party, examining said information to determine if the information confirms receipt of the last data packet transmitted by the one party to the other party. 
     Preferably, the method further includes the step of re-transmitting the last data packet sent by one party to another party when a data packet received by the one party from the other party does not include confirmation of receipt of the last packet sent by the one party. 
     The wireless transport layer protocol in accordance with the present invention operates the OSI transport layer and is suitable for basically any kind of wireless communications. The wireless transport layer protocol helps to reduce wireless traffic and therefore, significantly increases the actual wireless network throughput, regardless of the backbone connections, the backbone protocol, and/or overall network characteristics. The wireless transport layer protocol also allows basically any kind of remote backbone transport protocol layer, albeit connectionless or connectable oriented, to be controlled. 
     The present invention also provides advantages in that communication transport and bandwidth in wireless packet data networks is increased thereby enhancing communication characteristics. The wireless transport layer protocol also provides a guaranteed packet delivery mechanism and recovery algorithm without increasing communications overhead or introducing control packets. 
    
    
     BRIEF DESCRIPTION OF THE DIAGRAMS 
     An embodiment of the present invention will now be described more fully with reference to the accompanying drawings in which: 
     FIG. 1 illustrates data now and packet structure using a connection oriented communication protocol in a conventional prior art “wired” land-line network; 
     FIG. 2 illustrates data flow and packet structure using a wireless extension of a standard “wired” land-line connection oriented protocol in a wireless network; 
     FIG. 3 illustrates data flow and packet structure using a wireless transport layer protocol in accordance with the present invention in a wireless network; and 
     FIG. 4 illustrates the basic elements, structure of information and packet layout of the wireless transport layer protocol in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Presently defined and currently used data network and transport layer protocols that operate OSI layers 3 and 4, can be categorized into two significant classifications, namely connection oriented protocols and connectionless protocols. 
     Connection oriented protocols are characterized by additional packets dedicated to establish and/or end logical connection channels and virtual circuits between communicating parties. These additional packets are acknowledged by the communicating parties to confirm end-to-end packet delivery. 
     Connectionless protocols do not contain these additional packets, and as a result, they cannot guarantee delivery of packets to their final destinations. These connectionless protocols are commonly referred to as “best effort” protocols. 
     For ease of understanding, communications over a prior art “wired” land-line network will firstly be described. Turning now to FIG. 1, a standard client-server communication channel over a “wired” land-line network is shown implementing a standard connection oriented protocol such as X.25, TCP/IP, etc. During communications between the client  10  and the server  20 , if the client wishes to initiate communications, the client  10  sends a connection establishment request packet  31  to request a logical communication channel/virtual communication circuit to the server  20 . If the server  20  is capable of communicating and has available communication resources, the server  20  responds with a connection establishment confirmation packet  32 . From this moment, a logical communication channel/virtual communication circuit  22  is established between the client and the server  20  and transfer of data packets  33  between the client  10  and the server  20  commences. 
     If an application using this logical communication channel/virtual communication circuit  22  requires enhanced reliability and has strict data packet delivery time constraints, delivery of each data packet  33  to either the client  10  or the server  20  must be confirmed by the recipient via a frame acknowledgment packet  34 . In cases where delivery requirements are not so strict, delivery of every second, third, etc. data packet can be confirmed via a frame acknowledgment packet  34 . When either of the communicating parties needs to terminate the communications session, a connection end request packet  35  is sent which must be confirmed by the recipient with a proper connection end confirmation packet  36  in order to terminate the communications session. 
     As will be appreciated, packet delivery over the “wired” land-line network is guaranteed through use of the connection establishment confirmation and connection end confirmation packets  32  and  36  as well as the frame acknowledgment packets  34 . 
     Conventional connectionless protocols do not use additional packets such as the connection establishment confirmation and connection end confirmation packets or the frame acknowledgment packets nor do they include any means to notify communicating parties that packets have actually reached their destinations. As a result, no recovery mechanisms are provided in these connectionless protocols to verify successful data packet delivery. Based on these characteristics, connectionless protocols can only be used with a limited number of applications, and specifically those applications that do not resolutely rely on reliable communications. 
     Turning now to FIG. 2, an extension of a “wired” land-line connection oriented protocol used in a wireless network is shown. In this case, wireless client  15  behaves in a manner similar to wired client  10 . When wireless client  15  wishes to communicate with server  20 , wireless client  15  generates a wireless connection establishment request packet  41 , which is similar to the connection establishment request packet  31  except that it also includes wireless network overhead. The connection establishment request packet  41  is then transmitted over the wireless network  50  to a network backbone  52 . The network backbone  52  acts as a gateway or similar type of network bridge and strips the wireless network overhead from the connection establishment request packet  41  before conveying it to the server  20  as a connection establishment request packet  31 . 
     When the server  20  receives the connection establishment request packet  31 , the server  20  responds with a connection establishment confirmation packet  32 . The connection establishment confirmation packet  32  is then sent to the network backbone  52 . The wireless network overhead is then added to the connection establishment confirmation packet  32  to form a wireless connection confirmation packet  42 . The wireless connection confirmation packet  42  is then transmitted wirelessly over the wireless packet data network  50  to the client  15 . Frame acknowledgment, connection end and connection end confirmation packets are transmitted between the wireless client  15  and the server  20  in the same manner described above. As should be apparent, the packets received and transmitted by the server  20  are the same as the packets received and transmitted by the wireless client  15  with the exception that the packets received and transmitted by the wireless client  15  carry a wireless extension. As will be appreciated, using the connection oriented protocol over a wireless network requires the need for wireless extensions, which add more overhead to and increase communications over the logical communication channel. 
     Wireless networks have completely different characteristics than “wired” land-line networks and as such connection oriented protocols are generally unsuitable for wireless networks. In particular, connection oriented protocols congest the already limited throughput and channel bandwidth of wireless networks. The principal differences between “wired” land-line networks and wireless networks are reflected in media access algorithms and mechanisms derived from different physical transport media. Both communications media utilize a type of collision avoidance media access algorithm. However, wireless infrastructures have a more difficult task, and require more time to detect and resolve collisions, even in full duplex environments. Additional packets, control packets, frame acknowledgment packets or any packets that do not carry actual user data, dramatically reduce the throughput of wireless networks because of slower media access procedures. Most wireless packet data networks operate in strictly regulated narrowband channels. As a result, data transfer rates over wireless networks are significantly lower than over land-line networks. The same applies to wireless networks that operate on wideband channels, such as spread-spectrum CDMA networks. These wireless networks have the same throughput limitation problems but on a much higher level. Thus, protocols designed for land-line networks with considerable overhead, especially TCP/IP, are unsuitable for wireless networks. 
     To overcome the disadvantages associated with using connection oriented protocols in wireless networks, a wireless transport layer protocol in accordance with the present invention is provided. The wireless transport layer protocol reduces the gap between “wired” land-line networks and wireless networks while maintaining overhead and data packet transmission at acceptable levels. The wireless transport layer protocol also improves wireless-link throughputs within the limited bandwidths regardless of network backbone connections, protocols and characteristics. 
     Turning now to FIG. 3, end-to-end data packet flow in a wireless network utilizing the wireless transport layer protocol in accordance with the present invention is shown. Through its architecture, the wireless transport layer protocol is a connectionless protocol, but utilizes specific opening and closing data frames  61  and  63  that are capable of driving connection oriented protocols on the network backbone  152 . Protocol overhead is reduced by abandoning the idea of protocol embedding as discussed with reference to FIG.  2 . In other words, data frames transmitted over wireless packet data network  150  only carry the wireless overhead and user data and do not carry any land-line protocol overhead. 
     As can be seen, during communications between wireless client  115  and server  120 , data frames  61  to  63  are transmitted and received by wireless client  115  via wireless network  150 . Frame acknowledgment, connection establishment request and confirmation packets are not transmitted over the wireless network  150 . The network backbone  152  interfacing the wireless network  150  and the server  120  acts as the access gateway and is responsible for combining and assembling data packets dictated by the wireless transport protocol according to the protocol of the network backbone. As a result, acknowledgment, connection establishment request and connection establishment confirmation packets are transmitted between the network backbone  152  and the server  120  but these packets do not carry through to the wireless network  150 . 
     The wireless transport protocol utilizes additional on-line data compression for extra actual throughput and bandwidth gain. Specifically by eliminating transmission of acknowledgment and confirmation packets over the wireless network  150 , separate delivery confirmation procedures are introduced into the wireless transport protocol in order to overcome the reliability problems associated with conventional wireless networks implementing a “best effort” protocol. In particular, a specific sequencing algorithm is implemented, which relies on both incoming and outgoing sequence number tracking and processing to confirm packet delivery over the wireless network  150 . 
     FIG. 4 illustrates the basic topology of a wireless transport layer protocol frame. As can be seen, the wireless transport layer protocol frame includes a protocol ID  70 , a transmit sequence number  71 , a receive sequence number  72 , an action description field  73 , a variable action field  74  and a user data field  75 . The protocol ID  70  is a one byte field identifying the actual protocol implementation and provides space for future protocol enhancements and/or adaptations for any standard protocol. Transmit sequence number  71  is a word long field specifying the current message ID. Receive sequence number  72  is a word long field specifying the message ID of the last received message. 
     Action description field  73  provides information about the length of variable action field  74 , as well as additional packet descriptions such as session and connection handling information, connection establishment and request confirmation, session start/close, etc. Variable action field  74  contains the actual information necessary to execute the action described in action description field  73  such as connection addressing, source and destination physical and port addresses, session related information, call request user data, network management information, X.25 Q and D bit status, encryption handling data, etc. User data field  75  contains the actual end-to-end communications data. 
     During communications, the transmit and receive sequence number fields  71  and  72  respectively play a predominant role in assuring packet delivery. The wireless client  115  and the server  120  are both responsible for keeping track of transmit and receive sequence numbers  71  and  72 . Each data message received by the wireless client  115  is treated as a confirmation packet, since the received data message includes the packet ID of the last packet received by the server  120 . If the packet ID number does not correspond to the packet ID of the last packet transmitted by the wireless client  115  to the server  120 , the wireless client  115  establishes that the previously sent packet was not received by the server  120 . The previously sent packet can then be re-transmitted by the wireless client  115 . If communicating parties perform this sequence number check, packet delivery over the wireless network  150  can be guaranteed. If this sequence number check is utilized by the protocol of the network backbone  152 , packet delivery on the network backbone can also be guaranteed thereby achieving a reliable end-to-end communication channel between the wireless client  115  and the server  120 . 
     As will be appreciated by using transmit and receive sequence numbers in the wireless transport layer protocol, packet delivery over the wireless network can be guaranteed without the overhead of additional confirmation and acknowledgment packets. Thus, by using the wireless transport layer protocol in accordance with the present invention, reliable end-to-end communications channels between wireless clients and land-line servers can be established. 
     Although a preferred embodiment of the present invention has been described, those of skill in the art will appreciate that variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.