CN1352844A - Packet based client/server protocol - Google Patents

Abstract

A method and system for client/server data exchange. Transmitting and receiving a protocol data unit (PDU) over a data communications network includes the steps of: receiving the PDU for transmission; encoding the PDU into a plurality of alphanumeric data packets such that each data packet is smaller than a predetermined size; making the or each data packet is associated with an address frame including the destination of the or each data packet; transmitting the or each data packet. The data packets are preferably delivered by SMS or cell broadcast.

Description

Packet-based client/server protocol

The present invention relates to a compact, packet-based data communication protocol, which is especially suitable for use on GSM-type mobile phones.

The Internet and indeed most data communication networks are based on packet-based data communication protocols. The most commonly used protocol is the Internet Protocol (IP), and this is the basic protocol on which the Internet is based. Packet-based protocols divide transmitted data into packets, each transmitted over the network as a separate protocol data unit (PDU). Packets are routed on the network by routing nodes, which maintain routing tables to indicate routes between themselves and other nodes, and adjust the routes of their forwarded traffic according to network traffic and other factors. Each packet is numbered as it is transmitted, allowing data to be reordered upon receipt and retransmission of lost packets requested.

Where fixed line connections are not available, remote access to the data network is normally performed by some form of mobile telephone system. The most common system is the GSM (Group Specific Mobile) system, in which access to the data network is via a mobile telephone system offering limited bandwidth and various connection reliability. Unfortunately, limited bandwidth typically limits the rate at which data can be transmitted and received to 9600bps. This limitation, combined with various connection reliability, conflicts with packet-based protocols, which assume high-bandwidth data links with little or no packet loss. Also, for the GSM system, the minimum size of some packets will in some cases be too large.

According to a first aspect of the present invention, a method for transmitting a Protocol Data Unit (PDU) over a data communication network comprises the steps of:

Receive PDUs for transmission;

encoding the PDU into a plurality of alphanumeric data packets such that each data packet is smaller than a predetermined size;

associating the or each data packet with an address frame including the destination of the or each data packet; and

This or each data packet is transmitted.

A particular advantage of the present invention is to provide Internet access to mobile phones without the need to adapt the GSM protocol or infrastructure on which the mobile phone is currently running.

By repackaging data into data packets smaller than a predetermined size, the probability of successful transmission of each packet over a limited data communication link is significantly increased. In addition, the loss of single or multiple packets does not incur large overhead since packets can be retransmitted quickly. By regrouping the PDUs without regard to their content, the protocol overhead of reassembling data from the composed PDUs prior to regrouping the PDUs is avoided. Encoding, compression, and error correction are available extensions that require no further overhead or protocol layers.

The step of encoding the PDU includes the step of applying an alphanumeric encoding scheme if the PDU is not all alphanumeric. The alphanumeric encoding scheme is preferably uuencoding (a tool used in electronic mail to textually encode binary data) encoding.

uuencoding enables data to be sent over existing text-based links with unmodified reserved features.

The step of encoding the PDU comprises: determining the length of the PDU; generating a data packet from the PDU, wherein if the PDU is larger than a predetermined size, it is divided into a sequence of data packets.

The step of generating data packets may further comprise the step of associating the generated data packets with a packet identifier, wherein if the PDU is divided into a sequence of data packets, the packet identifier of each data packet will identify it as a divided PDU and identifies the relative position of the data packet in the sequence.

Preferably, the address frame may contain a Short Message Service (SMS) address by which the or each data packet is conveyed.

Short Message Service (SMS) is a function available to all GSM service users. For short alphanumeric messages, SMS is a two-way service. Typically, SMS messages are limited to a strict 160 bytes of letters and numbers, which limits their use to personal messages and business such as traffic and news updates.

Often, SMS prohibits messages from using reserved characters (such as control characters) that conflict with such characters in the data being transmitted. By using uuencoding encoding, such conflicts are easily and simply resolved. Since SMS systems are generally underutilized, piggybacking WWW data on existing SMS traffic links generally does not affect the performance of the SMS system. However, the use of existing links and underlying protocols greatly reduces the complexity of data transfer, as there is no need to cater for signal interactions such as handshaking. This reduction in complexity in turn reduces the data overhead required in header frames, since handshaking etc. can be handled elsewhere. The present invention thus provides a powerful communication mechanism without the complexity of providing a fundamentally new mechanism.

In the SMS alternative, the address frame may contain a cell broadcast address, and the or each data packet is transmitted by the cell broadcast.

Cell broadcasting provides a simple and efficient way to make World Wide Web-type data available to many users who do not have a fixed Internet link.

The step of encoding the PDU into a plurality of alphanumeric data packets includes the step of compressing the PDU.

The method of receiving a protocol data unit (PDU) transmitted over a data communications network according to the above method comprises the steps of receiving a plurality of alphanumeric data packets, removing an address frame associated with each data packet, and deriving from the plurality of A PDU is regenerated from the received alphanumeric data packet. The step of regenerating a PDU includes uudecoding the plurality of received alphanumeric data packets.

The step of regenerating the PDU includes sorting the received alphanumeric data packets by a packet identifier associated with each data packet, removing the packet identifier associated with each data packet and recombining into data packets. The step of ordering the received alphanumeric data packets includes the step of detecting data packets not received and requesting their retransmission.

According to another aspect of the present invention, a system for transmitting protocol data units (PDUs) over a data communications network includes a receiver for receiving a PDU for transmission, a receiver for encoding the PDU into a plurality of numeric character data packets such that each data packet An encoder smaller than a predetermined size, an address system that associates the or each data packet with an address frame containing the or each data packet's destination, and a transmitter that sends the or each data packet.

If the PDU is not all alphanumeric, the encoder may apply an alphanumeric encoding scheme.

The sender preferably includes a Short Message Service (SMS) system to address and transmit the or each data packet.

The system further comprises a receiver for receiving protocol data units (PDUs) transmitted over the data communication network by the transmitting unit of the above system, the receiver comprising a receiving system for receiving a plurality of alphanumeric data packets, a processor for The address frame associated with each data packet is removed and a PDU is regenerated from the plurality of received alphanumeric data packets. The processor may be configured to uudecode decode the plurality of received packets of alphanumeric data. The processor may be configured to sort the received alphanumeric data packets by a packet identifier associated with each data packet, remove the packet identifier associated with each data packet and rejoin the data packets. Preferably, the processor is configured to detect data packets not received and request their retransmission.

Preferably, the receiver is an SMS receiver, such as a GSM mobile phone, and the alphanumeric data packets are received by SMS. Alternatively, the receiver may be a cell broadcast receiver, the alphanumeric data packets being received by cell broadcast.

The sender can also be a GSM mobile phone.

The PDU contains data generated by browsing and/or interacting with the World Wide Web, wherein the system further includes a Web Server as a gateway for the PDU to transmit the PDU to the World Wide Web and receive the PDU from the World Wide Web.

In a preferred aspect of the invention, the PDU contains data resulting from browsing and/or interacting with the World Wide Web, wherein the SMS system is housed in a Web Server that also acts as a PDU Gateway to transmit PDUs to and receive PDUs from the World Wide Web.

In the context of SMS, alphanumeric characters include the following settings:

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz<>

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic block diagram of a data communication network used in the present invention;

Figures 2a and 2b are representations of the format of data packets transmitted and received in a data communication session in accordance with the present invention; and

Figures 3a-3e and 4a-4e are examples of data packets transmitted and received in a data communication session according to the format defined with reference to Figure 2 .

Fig. 1 is a schematic block diagram of a data communication network used in or for the invention. The GSM service provider has a mobile telephone network comprising a plurality of transmission cells 10 . This network is linked to an SMS system 20 which in turn is linked to a World Wide Web (WWW) server 30 which is connected to WWW40. A mobile phone user 50 in the delivery area of one of the cells 10 uses a microbrowser installed on his mobile phone 50 to browse the WWW. Since the user interacts with the microbrowser, requests for data from the WWW are sent by the microbrowser. The request is encoded and transmitted by the mobile phone as an SMS message addressed to the WWW server 30 . This message is treated as a normal SMS message and forwarded by the cell 10 to the SMS system 20 . The SMS system 20 forwards this message to the WWW server 30 . Upon receipt of the SMS message, WWW server 30 decodes it into an appropriate HTTP (Hypertext Transfer Protocol) request which is then processed.

The data received by WWW server 30 via WWW 40 in response to the HTTP request is encoded as an SMS message addressed to the microbrowser of mobile phone 50 . The WWW server 30 forwards the message to the SMS system 20 which transmits it to the mobile phone 50 via the cell 10 . The mobile phone receives the message, decodes it and passes it to the microbrowser for appropriate action such as displaying a WWW page to the user.

Figures 2a and b are representations of the format of data packets produced in accordance with the present invention. The transport protocol used by the mobile phone 50 and the WWW server 30 to generate SMS messages upon request and to decode received messages is divided into two layers: the session layer is responsible for encoding and decoding data and requests into messages in SMS format, and the transport layer is responsible for Prepares and addresses SMS messages, and performs error checking on received messages. Since there is a limit on the size of SMS messages, requests or responses exceeding this limit must be broken into discrete packets. The transport layer divides such messages into multiple packets, and each packet is transmitted as an independent SMS message, and the received packet messages are reassembled by the transport layer.

SMS allows messages of 160 7-bit characters that must be uuencoded or 140 8-bit characters that do not need to be uuencoded. The remainder of the description refers to messages of 160 7-bit characters, but the experienced reader will understand that the invention is applicable to either type.

Figure 2a represents the messages prepared by the session layer. Each message contains a CommandID field 100 indicating the type of command the message refers to (open, close, request, send or request again), and a MsgSize field 110 indicating the character length of the particular message (this is encoded using a 7 bit value loendian i.e. size=byte 1+byte 2*2 ⁷ ), a header field 120 (discussed below), a data field 130 containing data (URI, data sent by the server or packet number of the re-request message), and A trailing field indicating the next CommandID or NULL when it is the last message.

The contents of the header field refer to optional data. Each header field contains a value followed by a NULL-terminated string. A header can consist of the following items:

describe value following string end of header field 0 N/A Content Type of Data Field 130 1 see below user agent profile 2 see below User agent profile update 3 see below URI of additional data field 130 4 URI string A URI called the current URI (required by the HDML microbrowser) 5 URI string Encoding/compression type used in data field 130 6 see below Type of alarm hold in data field 130 7 see below The name of the alarm hold in the data field 130 8 name string

The content-type field contains, for example, one of the following types of identifiers: content-type string describe 0 Unknown data type - to be ignored 1 Uncompiled HDML 2 Compiled HDML 3 original text 8 Images in PCC format (static or dynamic) 9 Image in vector format (VGX) 53 Huffman decoding table 64+ error value

The encoding field may specify a value corresponding to an encoding or compression scheme such as Huffman encoding or run-length encoding.

The type of alarm field specifies the data field that relates to one of the following types of alarms:

alarm type string describe 0 No alerts - the user was not notified and no data was added to the alert list 1 list - add alert to alert list, user is not notified 2 Notify - the alert is added to the alert list and the user is notified, e.g. via the message icon 3 show - show alert on arrival 4 Show if new - if not already in cache, show on arrival, otherwise overwrite old version in cache and don't show

Proxy profiles are used to tailor the type of data and/or content delivered by the service or server depending on the type of device accessing the data. Since different browsers (especially in mobile phones) support different features, it is not enough to identify a browser by name. A profile identifies the main functions of the browser, such as support for HTML/HDML/WML, the types of images it can display, screen size, etc. The business or server can use this information to adjust the data returned to the browser.

Figure 2b represents the messages prepared by the transport layer. Session layer messages are processed and, if necessary, divided into multiple packets with a maximum length of 157 bytes, as indicated by data field 200 . For each packet, there is a header attached, including a MessageID field 210, a packet number field 220, an error detection field 230 and a total number of packets field 240. MessageID field 210 identifies the message associated with the packet. If the message is divided into more than one packet, the header of each packet will contain the same MessageID so that upon receipt, the packets can be identified and merged together to reform the message. Since packets may be received in any order and packets may be lost, the Packet Number and Packet Total fields (220, 240) are also used in this regard. The packet number and total number fields allow receivers to reorder packets and request retransmission of lost packets. Error detection field 230 indicates the type of error detection used for the accompanying data.

Figures 3a-3e represent data packets sent and received in a data communication session using a protocol according to the present invention. Figure 3a represents the data packets prepared by the session layer in response to the request of the mobile phone's microbrowser for the URI (Universal Resource Indicator) "http://hdmlhost/home.hdml". The session layer determines that the message is for a request (commandID=3), MsgSize is 29 (header 4+URI string 25), and no header field is required. Therefore, the message of Figure 3a is passed to the transport layer.

After receiving it, the transport layer determines that only one SMS message is needed, so it allocates messageID1, packet number 0, error detection level 0 (no error detection) and total number of packets 0. This information is concatenated with the session message to generate the SMS packet of Figure 3b, which is then sent out.

Having received and decoded the SMS message, the server requests the URI over HTTP and receives 200 bytes of data in response.

The session layer of the server processes the data, fetches the data and assigns a commandID4 (send), a message length 207 encoded into 79+1*2 ⁷ (header 6+data 200+terminator 1). A header field of content type 1 (HDML) is added, followed by data (200 bytes) and next commandID 0 (no more messages). The assembled message as shown in Figure 3c is passed to the transport layer of the server.

The transport layer constructs the first SMS packet with MsgID 1, packet number 0, error detection 0 and total number of packets 1. The synthesized SMS message shown in Fig. 3d cannot retain all the session layer messages, so it can only contain the first 151 bytes with a 9-byte header. As shown in Figure 3e, a second SMS packet having the same transport layer data as the first SMS packet is generated to accommodate the last 49 bytes of data, except that the packet number is 1. Both SMS packets are sent to the mobile phone and decoded, reconstituting the data for display by the microbrowser.

Figures 4a-4d represent data packets sent and received in a data communication session using a protocol according to the present invention. Figure 4a represents the data packets prepared by the session layer in response to a request by the mobile phone's microbrowser for the URI (Universal Resource Indicator) http://hdmlhost/home.hdml. The session layer determines that the message is for a request (commandID=3), the MsgSize is 29 (header 4+URI string 25), and no header field is required. So, the message of Figure 4a is passed to the transport layer.

After receiving it, the transport layer determines that only one SMS message is needed, so it allocates messageID1, packet number 0, error detection level 0 (no error detection) and total number of packets 0. This information is concatenated with the session message to generate the SMS packet of Figure 4b, which is then sent out.

Having received and decoded the SMS message, the server requests the URI over HTTP and receives 200 bytes of data in response. Because both the server and the client support Huffman coded data compression, 200 bytes are compressed to 87 bytes by the server.

The session layer of the server processes the data, extracts the compressed data and assigns a commandID 4 (send), a message length 96 (header 8+ data 87+ terminator 1) encoded into 96+0*2 ⁷ . A header field with content type 1, 2 (HDMLC) and huffman encoding (6, 1, 0) is added, followed by data (87 bytes) and the next commandID0 (no more messages). The assembled message as shown in Figure 4c is passed to the transport layer of the server.

The transport layer constructs the first SMS packet with MsgID 1, packet number 0, error detection 0 and total number of packets 0. The SMS packets are transmitted to the mobile phone and decoded and decompressed, reconstituting the data for display by the microbrowser.

Preferably, a uuencoding encoding scheme is applied to received data packets in order to avoid attempts to transmit non-alphanumeric characters not supported by SMS.

Although the above description relates to data transfer by packetizing data and using SMS, it is clear that the invention is applicable to many transfer protocols and mechanisms such as cell broadcast. In cell broadcast and SMS alerts, there is no initial request for data from the phone. A URI is created in the WWW server and transmitted to the phone according to many criteria such as a prior request to receive certain data or a decision of the service provider to notify some/all users of an event. Since the maximum size of a cell broadcast packet is 88 bytes, the transport layer will modify the message length. As previously described, a Cell Broadcast message uses the Alert field to identify the type of data being transmitted and whether/how the user should be notified when the broadcast arrives. Although cell broadcast is only a one-way transfer mechanism from the server to any recipient in the corresponding cell, it can also use the protocol of the present invention, such as broadcasting a page with local information (such as where is the local branch of a well-known store, etc.) wait.

Claims (19)

1. the method for a transport protocol data unit on data communication network (PDU) comprises following steps:

The PDU that reception is used to transmit;

This PDU is encoded to a plurality of alphanumeric packets, makes each packet less than predetermined size;

Make this or the related address frame of each packet, this address frame comprise the destination of this or each packet; And

Transmit this or each packet.

2. according to the process of claim 1 wherein that the step of coding PDU comprises if PDU is not the step that alphanumeric is then used an alphanumeric coding scheme entirely.

3. according to the method for claim 2, the step that the step of the PDU that wherein encodes comprises has:

Determine the length of PDU;

Produce a data grouping from this PDU, if wherein this PDU is greater than predetermined size, it just is divided into the packet of a sequence.

4. according to the method for claim 3, wherein producing the step that the step of packet further comprises is the related packet identifier of packet that makes generation, if wherein PDU is divided into the packet of a sequence, then the packet identifier of each packet will identify it and be the part of separated PDU, and identify the relevant position of this packet in this sequence.

5. according to the method for arbitrary aforementioned claim, the step that wherein PDU is encoded to a plurality of alphanumeric data groupings comprises the step of compressing PDU.

6. any one method and be received in the method for the protocol Data Unit (PDU) that transmits on the data communication network in the aforementioned claim of foundation comprises following steps:

Receive a plurality of alphanumeric data groupings;

Remove the address frame that is associated with each packet; And,

From these a plurality of alphanumeric data groupings that receive, produce a PDU again.

7. according to the method for claim 6, wherein producing the step that the step of PDU comprises again has: rely on each packet associated packet identifier and come alphanumeric data packet sequencing to receiving, remove with each packet associated packet identifier and combine this packet again.

8. the system of a transport protocol data unit on data communication network (PDU) comprises:

The receiver of the PDU that reception is used to transmit;

One is encoded to the grouping of a plurality of numeric character datas with this PDU and makes the encoder of each packet less than preliminary dimension;

An address system that makes this or the related address frame of each packet, this address frame comprise the destination of this or each packet; And,

A transmitter that sends this or each packet.

9. according to the system of claim 8, if wherein PDU is not alphanumeric then alphanumeric coding scheme of encoder applies entirely.

10. according to the system of claim 9, wherein encoder is configured to determine the length of this PDU, and produces a data grouping from this PDU, if wherein this PDU is greater than predetermined size, then encoder is configured to this PDU is divided into a sequence of data packets.

11. system according to claim 10, wherein encoder is configured to make related packet identifier of packet of generation, if wherein PDU is divided into the packet of a sequence, then the packet identifier of each packet sign it be the part of separated PDU, and identify the relevant position of this packet in this sequence.

12. according to any one system in the claim 8 to 11, wherein encoder is configured to compress this PDU.

13. the system of the protocol Data Unit (PDU) that a reception is transmitted on data communication network by any one system in the claim 8 to 12, comprise a receiver and be used to receive the grouping of a plurality of alphanumeric datas, processor is used for removing the address frame that is associated with each packet and produces a PDU again from these a plurality of alphanumeric datas groupings that receive.

14. system according to claim 13, wherein this processor is configured to rely on each packet associated packet identifier and comes alphanumeric data packet sequencing to receiving, removes with each packet associated packet identifier and combines this packet again.

15. according to any one system in the claim 8 to 14, wherein this PDU comprise browse the World Wide Web (WWW) and/or with the mutual data that produce in World Wide Web (WWW), wherein this system further comprises a Web server, transmits PDU to the World Wide Web (WWW) as gateway, and receives PDU from the World Wide Web (WWW).

16. an energy is read by machine and encodes and is used for the program storage device that enforcement of rights requires the instruction repertorie of 1 to 7 any one method.

17. an energy is read by machine and the program storage device of the instruction repertorie that is used for implementing any one system of claim 8 to 15 of encoding.

18. computer data signal that is used for the instruction repertorie of enforcement of rights requirement 1 to 7 any one method with carrier format realization, coding.

19. computer data signal with the instruction repertorie that carrier format realizes, coding is used for implementing any one system of claim 8 to 15.

Images