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Telemetry Data Transmission
Transcript of Telemetry Data Transmission
Ahmed Mohamed Mahmoud
Ahmed Alaa El-Deen INTRO :
It is normal for the payload transmission system to give some structure to the data transmission so that the receiver can synchronize itself to the transmitter. A telemetry frame is the standard method for packaging data for transmission from the payload to the user’s receiver.
-AND WE HAVE 5 Objects To Achive the Transmission of telemetry Data . Objects :
1-Describe the standard IRIG frame structure.
2-synchronization within the frame structure.
3-Present a data set in the IRIG frame format .
4-strengths and weaknesses of packet versus frame telemetry systems.
5-purposes, and results of data formatters used prior to transmission of digital data. Block Diagram that involves Telemetry data Transmission Object 1 :
Describe the standard IRIG frame structure The structure of the frame contain some elements: minor frame.
supercommutated data. Minor frame the number of bits between the start of successive frame synchronization markers. Each marker is located as the first word in a minor frame. Major frame an integer number of minor frames such that each telemetry parameter is sampled at least once. Commutated data commutated signals are sent once per minor frame and appear at the same location relative to the synchronization marker in each minor frame. Supercommutated data signals are telemetry parameters that appear at a sampling rate that is an integer factor greater than the minor frame rate with each appearance at a fixed location relative to the synchronization marker within the minor frame. Ex : SprCom 1 is the first appearance of the supercommutated sensor reading. The column holding SprCom 2 is the second appearance of the supercommutated data. Subframes columns within the major frame. Subframes are for signals coming from a common subsystem sampler such that all subsystem values are sampled at least once per major frame. Object 2 meaning of synchronization within the frame structure. Steps in Sync process elements 1. Carrier synchronization
2. Bit synchronization
3. Frame synchronization
4. Network synchronization it to say that this stage requires that a data signal come from the radio. Carrier synchronization Bit synchronization The goal of bit synchronization is to produce stable data and a stable data clock. Frame synchronization The purpose of frame synchronization is to lock onto the data structure embedded in the received data. network synchronization the coordination between the entities based on common timing and using protocols such as the Network Time Protocol. Object3 Present a data set in the IRIG frame format . Factors that enter into the frame design include: 1.Transmission rate of the data because it influences how rapidly the signals from a sensor can be retransmitted.
2.Allowable bandwidth for the system which will be influenced by the transmission rate plus any error-correcting coding applied.
3.Quantization resolution needed because this will determine the total number of bits per second that need to be transmitted as a minimum.
4.Required sampling rate for each parameter.
5.Number of parameters of each type: bilevel (single bit), sampled analog value, digital value, etc., that must be included.
6.Error checking and correcting code parameters (if used).
7.Length of the individual subframes from the subsystems; not all will have the same length so some scheme will be needed to even them out.
8.Required overhead for frame and subframe identification and synchronization, timing or counting parameters, command-link status and repetition, etc.
9.Buffer sizes of the input computer or similar electronics for efficiently moving a frame or portion thereof through the synchronization and analysis hardware. Object 4 strengths and weaknesses of packet versus frame telemetry systems. Packet Telemetry Packet telemetry is a relatively new area in the telemetering field, as compared to traditional frame formatting. Advantages & Disadvantages for packet data The advantagesare as follows:
1.The system can be flexible and tailored to the needs of the individual subsystems. It can allow for upgrades of subsystems without reorganizing the rest of the system because data can be transmitted as generated and packaged when there is a significant quantity or conditions warrant.
2.The system can use standard communications protocols such as TCP/IP for which standard computer hardware and software drivers exist.
3.It is possible to interface the telemetry system with standard commercial carrier systems such as the Internet.
4.The data stream has a structure that allows for error correction and retransmission.
5.Data packets can be given relative priorities to allow more important data to be transmitted first. disadvantages are :
1.They may not be practical for small systems or systems with little internal processing capability.
2.They may increase system complexity.
3.They may contribute more overhead to the transmitted data than is acceptable. Protocol Data Unit Format (PDU) : The general transmission format for packet communications, regardless ofthe protocol standard used, is similar to the format shown A packet insertion is shown in Figure The overall telemetry data can be envisioned as a file in the payload. The file is broken into manageable packets that identify the data set and contains other information necessary for processing. As these data packets become available, they are inserted in the channel packet. Object 5 data formatters used prior to transmission of digital data. Formatting for Transmission After data are gathered, they must be made ready for transmission. This process involves the specifications of the transmission hardware used at both ends of the transmission link. It may also include regulatory concerns dealing with the occupied bandwidth. In this section, we will look at these issues. General Structure the data transmission that defines the correspondence between the logic level and the actual voltage level used in the hardware and the waveform encoding used to transmit a logical zero and a logical one. Data Randomizers The function of a data randomizer is to provide an approximately equal number of zeroes and ones in the data stream without arranging long consecutive strings of zeroes and ones. Data Format Specification Digital data can be formatted for transmission by several methods.