Data Packet Format

The communication is transferred asynchronously in bytes.

        The total length of packets is (10+N) Bytes.

1.          

2.          

3.          

4.          

4.1.         Start Bit

Fixed value in HEX 0x78 0x78.

4.2.         Packet Length

Length = Protocol Number + Information Content + Information Serial Number + Error Check, totally (5+N)Bytes, because the Information Content is a variable length field.

4.3.         Protocol Number

4.4.         Information Contents

The specific contents are determined by the protocol numbers corresponding to different applications.

4.5.         Information Serial Number

The serial number of the first GPRS data (including status packet and data packet such as GPS, LBS) sent after booting is ‘1’, and the serial number of data sent later at each time will be automatically added ‘1’.

4.6.         Error Check

A check code may be used by the terminal or the server to distinguish whether the received information is error or not. To prevent errors occur during data transmission, error check is added to against data misoperation, so as to increase the security and efficiency of the system. The check code is generated by the CRC-ITU checking method.

CRC error occur when the received information is calculated, the receiver will ignore and discard the data packet.

4.7.         Stop Bit

Fixed value in HEX 0x0D 0x0A.

The commonly used information packages sent by the terminal and those sent by the server will be interpreted separately.

4.          

5.          

5.1.         Login Message Packet

5.1.1.          Terminal Sending Data Packet to Server

The login message packet is used to be sent to the server with the terminal ID so as to confirm the established connection is normal or not.

5.1.1.1.         Start Bit

For details see Data Packet Format section 4.1.

5.1.1.2.         Packet Length

For details see Data Packet Format section 4.2.

5.1.1.3.         Protocol Number

For details see Data Packet Format section 4.3.

5.1.1.4.         Terminal ID

The terminal ID applies IMEI number of 15 bits.

Example: if the IMEI is 123456789012345,

the terminal ID is 0x01 0x23 0x45 0x67 0x89 0x01 0x23 0x45.

5.1.1.5.         Information Serial Number

For details see Data Packet Format section 4.5.

5.1.1.6.         Error Check

For details see Data Packet Format section 4.6.

5.1.1.7.         Stop Bit

For details see Data Packet Format section 4.7.

5.1.2.          Server Responds the Data Packet

The response packet from the server to the terminal: the protocol number in the response packet is identical to the protocol number in the data packet sent by the terminal.

5.1.2.1.         Start Bit

For details see Data Packet Format section 4.1.

5.1.2.2.         Packet Length

For details see Data Packet Format section 4.2.

5.1.2.3.         Protocol Number

 For details see Data Packet Format section 4.3.

5.1.2.4.         Information Serial Number

For details see Data Packet Format section 4.5.

5.1.2.5.         Error Check

5.1.2.6.         Stop Bit

For details see Data Packet Format section 4.7.

5.1.3.      Examples

Examples of the login message packet sent by the terminal to the server and the response packet sent by the server to the terminal are as follows: (in the examples the terminal ID is 123456789012345.

5.2.1.       Terminal Sending Location Data Packet to Server

5.2.1.1.         Start Bit

For details see Data Packet Format section 4.1.

5.2.1.2.         Packet Length

For details see Data Packet Format section 4.2.

5.2.1.3.         Protocol Number

For details see Data Packet Format section 4.3.

5.2.1.4.         Date Time

         Example: 2010-03-23 15:30:23

        Calculated as follows:       10(Decimal)=0A(Hexadecimal)

                                              3 (Decimal)=03(Hexadecimal)

                                              23(Decimal)=17(Hexadecimal)

                                              50(Decimal)=32(Hexadecimal)

            23(Decimal)=17(Hexadecimal)

        Then the value is: 0x0A 0x03 0x17 0x0F 0x32 0x17

5.2.1.5.         Length of GPS information, quantity of positioning satellites

The field is 1 Byte displayed by two hex digits, wherein the first one is for the length of GPS information and the second one for the number of the satellites join in positioning.

Example: if the value is 0xCB, it means the length of GPS information is 12 and the number of the positioning satellites is 11.

               (C = 12Bit Lenght ，B = 11 satellites)

5.2.1.6.         Latitude

Four bytes are consumed, defining the latitude value of location data. The range of the value is 0-162000000, indicating a range of 0°-90°. The conversion method thereof is as follow:

converting the value of latitude and longitude output by GPS module into a decimal based on minute; multiplying the converted decimal by 30000; and converting the multiplied result into hexadecimal.

Example: 22º32.7658’=(22X60+32.7658)X3000=40582974, then converted into a hexadecimal number

40582974(Decimal)= 26B3F3E(Hexadecimal)

at last the value is 0x02 0x6B 0x3F 0x3E.

5.2.1.7.         Longitude

Four bytes are consumed, defining the longitude value of location data. The range of the value is 0-324000000, indicating a range of 0°-180°.

       The conversion method herein is same to the method mentioned in Latitude (see section 5.2.1.6).

5.2.1.8.         Speed

One byte is consumed, defining the running Speed of GPS. The value ranges from 0x00 to 0xFF indicating a range from 0 to 225km/h.

e.g.       0x00 represents 0 km/h.

              0x10 represents 16km/h.

                   0xFF represents 255 km/h.

5.2.1.9.         Course Status

Two bytes are consumed, defining the running direction of GPS. The value ranges from 0° to 360° measured clockwise from north of 0°.

Note: The status information in the data packet is the status corresponding to the time bit recorded in the data packet.

For example: the value is 0x15 0x4C, the corresponding binary is 00010101 01001100,

BYTE_1 Bit7          0

BYTE_1 Bit6          0

BYTE_1 Bit5          0 (real time GPS)

BYTE_1 Bit4          1 (GPS has been positioned)

BYTE_1 Bit3          0 (East Longitude)

BYTE_1 Bit2          1 (North Latitude)

BYTE_1 Bit1          0

BYTE_1 Bit0          1

BYTE_2 Bit7          0

BYTE_2 Bit7          1

BYTE_2 Bit7          0                               Course 332° (0101001100 in Binary, or 332 in decimal)

BYTE_2 Bit7          0

BYTE_2 Bit7          1

BYTE_2 Bit7          1

BYTE_2 Bit7          0

BYTE_2 Bit7          0

which means GPS tracking is on, real time GPS, location at north latitude, east longitude and the course is 332°.

5.2.1.10.       MCC

The country code to which a mobile user belongs, i.e., Mobile Country Code(MCC).

Example: Chinese MCC is 460 in decimal, or 0x01 0xCC in Hex (that is, a decimal value of 460 converting into a hexadecimal value, and 0 is added at the left side because the converted hexadecimal value is less than four digits).

Herein the range is 0x0000 ~ 0x03E7.

5.2.1.11.       MNC

Mobile Network Code(MNC)

Example: Chinese MNC is 0x00.

5.2.1.12.       LAC

Location Area Code (LAC) included in LAI consists of two bytes and is encoded in hexadecimal. The available range is 0x0001-0xFFFE, and the code group 0x0000 and 0xFFFF cannot be used. (see GSM specification 03.03, 04.08 and 11.11).

5.2.1.13.       Cell ID

Cell Tower ID (Cell ID), which value ranges from 0x000000 to 0xFFFFFF.

5.2.1.14.       Information Serial Number

For details see Data Packet Format section 4.5.

5.2.1.15.       Error Check

For details see Data Packet Format section 4.6.

5.2.1.16.       Stop Bit

For details see Data Packet Format section 4.7.

5.2.2.          Examples of Packet Sent from Terminal to Server

5.3.1.          Server Sending Alarm Data Packet to Server

Alarm packet is consisted by adding status information to location packet, so does the encoding format of the protocol.

5.3.1.1.         Start Bit

For details see Data Packet Format section 4.1.

5.3.1.2.         Packet Length

For details see Data Packet Format section 4.2.

5.3.1.3.         Protocol Number

For details see Data Packet Format section 4.3.

5.3.1.4.         Date Time

For details see Location Data Packet Format section 5.2.1.4.

5.3.1.5.         Length of GPS information, quantity of positioning satellites

For details see Location Data Packet Format section 5.2.1.5.

5.3.1.6.         Latitude

For details see Location Data Packet Format section 5.2.1.6.

5.3.1.7.         Longitude

For details see Location Data Packet Format section 5.2.1.7.

5.3.1.8.         Speed

5.3.1.9.         Status and Course

For details see Location Data Packet Format section 5.2.1.9.

5.3.1.10.       MCC

For details see Location Data Packet Format section 5.2.1.10.

5.3.1.11.       MNC

For details see Location Data Packet Format section 5.2.1.11.

5.3.1.12.       LAC

For details see Location Data Packet Format section 5.2.1.12.

5.3.1.13.       Cell ID

For details see Location Data Packet Format section 5.2.1.13.

5.3.1.14.    Terminal Information

One byte is consumed, defining various status information of the mobile phone.

Example: 0x44, corresponding binary value is 01000100,

indicates that the status of the terminal is: oil and electricity connected, GPS tracking is on, normal without any alarm, charge on, ACC is low, and deactivated.

5.3.1.15.    Voltage Level

The arrange is 0~6 defining the voltage is from low to high.

0: No Power (shutdown)

1: Extremely Low Battery (not enough for calling or sending text messages, etc.)

2: Very Low Battery (Low Battery Alarm)

3: Low Battery (can be used normally)

4: Medium

5: High

6: Very High

Example: 0x02 indicates very low battery and a Low Battery Alarm is sending.

5.3.1.16.    GSM Signal Strength Levels

0x00: no signal;

0x01: extremely weak signal;

0x02: very weak signal;

0x03: good signal;

0x04: strong signal.

Example: 0x03 indicates the GSM signal is good.

5.3.1.17.       Alarm/Language

0x00 (former bit) 0x01 (latter bit)

former bit: terminal alarm status (suitable for alarm packet and electronic fence project)

latter bit: the current language used in the terminal

Examples:

No Alarm and Language is Chinese: 0x00 0x01

No Alarm and Language is English: 0x00 0x02

To increase the reliability of alarm information, labeling the alarm information repeatedly; in most cases, the alarm information keeps consistent with information of former terminal, while the inconsistencies are as follows:

A． Low Battery Alarm occurred in the information of the terminal

B． Fence in and out Alarm in the Alarm/Language information

5.3.1.18.       Information Serial Number

For details see Data Packet Format section 4.5.

5.3.1.19.       Error Check

For details see Data Packet Format section 4.6.

5.3.1.20.       Stop Bit

For details see Data Packet Format section 4.7.

5.3.2.          Examples

Note: The status information in the data packet is the status corresponding to the time bit recorded in the data packet.