questions","basePath":"/gcse/computer-science/aqa/data-compression/questions","formulaUrl":null,"initialIndex":20,"initialQuestionWindow":[{"id":"48750713-1bc9-4d23-b8a4-4cf5830d2fbd","revisionId":"a7bed58f-6183-4442-93a4-11c0136b0b1f","questionNumber":null,"questionType":"LA","specification":"An autonomous underwater vehicle (AUV) is deployed to collect high-resolution oceanographic telemetry data. This data is compressed on-board before being transmitted back to a marine research station via a low-bandwidth satellite uplink.","difficulty":4,"difficultyBand":"medium","totalMarks":4,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"4a261d85-92b8-467b-9082-442a794a101e","label":null,"content":"Explain **two** distinct benefits of compressing this telemetry data prior to transmission.","markscheme":"- Reduces the transmission time, meaning the data is uploaded faster over the slow satellite link. C1\n- Conserves the AUV's battery/power, as the transmitter needs to be active for a shorter duration. C1\n- Reduces bandwidth consumption, lowering data transmission costs or preventing satellite channel congestion. C1\n- Reduces the local storage capacity required on the AUV's onboard storage drive before transmission occurs. C1","marks":4,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"4de3f075-4dc4-441e-990a-de0af5cfeb07","revisionId":"6ceebed4-72ff-4ae9-a3d5-aad56dc9718e","questionNumber":null,"questionType":"LA","specification":"An automated environmental monitoring station transmits the status log message `SYSTEM ONLINE AND SECURE` to a central server. Using Huffman coding, this message can be compressed and stored in 91 bits.","difficulty":3,"difficultyBand":"medium","totalMarks":3,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"a00e5c25-407d-4309-b7a0-42043fa161da","label":null,"content":"Calculate the number of additional bits required to store the exact same status message using standard 8-bit ASCII characters. Show your working.","markscheme":"- Identifies that there are 24 characters (including spaces) in the status message B1\n- Calculates the storage required using 8-bit ASCII as $24 \\times 8 = 192$ bits (or $24 \\times 7 = 168$ bits if 7-bit ASCII is assumed) M1\n- Obtains a final difference of $101$ bits (or $77$ bits if 7-bit ASCII is used) A1","marks":3,"order":0,"markingRubric":null,"explanation":null,"options":[]}],"options":[],"explanation":null,"firstAttemptFullMarks":null},{"id":"50b76925-b246-4448-b02c-6171db9fb754","revisionId":"88ce95b9-c0b9-44ac-be03-cf3026ea4edb","questionNumber":null,"questionType":"LA","specification":"A student was asked to describe how a Huffman tree could be created for the string in **Figure 1**.\n\nFigure 1\n```text\nBANANA SPLIT\n```\n\nHer response was:\n\n\"I would count the frequency of each character in the string and write them in a table sorted by their order of appearance. For example, the character 'N' has the highest frequency in this string. Then, I would take the two characters with the largest frequencies and combine them into a new parent node. The frequency of this new parent node is calculated by subtracting the smaller frequency from the larger frequency. I would then repeat this process with the remaining largest nodes until the entire tree is built.\"","difficulty":4,"difficultyBand":"medium","totalMarks":4,"sourceTitle":null,"calculatorUse":null,"parts":[{"id":"ec901338-cc7e-4c7a-8f93-a6e6d071715d","label":null,"content":"State **four** mistakes the student has made in her response.","markscheme":"- Identifies that the table should be sorted by frequency (usually ascending), not by the order of character appearance B1\n- Identifies that 'A' has the highest frequency in the string (appearing 3 times), not 'N' (which appears 2 times) B1\n- Identifies that the two nodes with the smallest/lowest frequencies should be combined, not

Data compression

Question 12

Data compression Questions

Data compression

Question 12

Data compression Questions