Data Communications - Assignment 1
- Assignment one is due at 5pm on the 23rd of September 2009.
- There are two parts to this assignment - you are required to complete both part A and part B.
- Part A is worth 12% of your final mark for this subject and part B is worth 8% of your final mark for this subject.
Part A
A small business wants to establish a "high speed" microwave radio data link to a remote site. The particular details of the connection are:
- Speed = 20 x 106 bps.
- Protocol = "Stop and Wait" with "one bit" sequence number.
- Error rate - see following table.
- Distance - see following table.
The distance and Bit Error Rate (BER) is given by the last and second last digits of your student number, as follows:
| Second Last Digit | Error Rate | Last Digit | Distance |
|---|---|---|---|
| 9 | 3 in 107 bits | 0 | 10 Km |
| 8 | 1 in 106 bits | 1 | 15 Km |
| 7 | 2 in 106 bits | 2 | 20 Km |
| 6 | 3 in 106 bits | 3 | 25 Km |
| 5 | 1 in 105 bits | 4 | 30 Km |
| 4 | 2 in 105 bits | 5 | 35 Km |
| 3 | 3 in 105 bits | 6 | 40 Km |
| 2 | 1 in 104 bits | 7 | 45 Km |
| 1 | 2 in 104 bits | 8 | 50 Km |
| 0 | 3 in 104 bits | 9 | 55 Km |
Hence if your student number was 11223309 you would use a BER of 3 in 104 bits and a distance of 55 kilometers.
You need to answer the following two questions, ignoring "on the fly" data compression and any processing overhead:
- What packet size will result in maximum throughput?
- What throughput is the achieved in Bits Per Second (bps)?
You should use one of the following two methods to find your solution:
- Differentiation - this is the most accurate approach. Express the utilisation as a function of n, the number of bits in a frame. Then take the derivative of this function and solve for zero in order to identify the turning point(s) for the function.
- Computation - write a program to find the optimal value of n for you. You may use any programming language you choose (yes, this includes assembly, Forth, Fortran and COBOL!). There are several approaches that can be used to find the optimal value, including Newton-Raphson Iteration and brute force via iteration.
Part B
-
Continuing from Part A, investigate the use of a multi-bit sequence
number in an attempt to increase the utilisation to 100%.
Answer the following questions:
- How many bits (N) must the sequence number have?
- What utilisation is actually achieved?
- How high do each of the terrestrial microwave dishes need to be in order to successfully communicate over the distance specified in Part A?
Submission
Submit basically no more than your "working out" and the answers. If you have used differentiation then your workings will consist of the mathematical equations. If you have taken the computational approach then your workings will consist of your source code.
Your submission must follow the guidelines detailed in the subject outline and adhere to the requirements of the La Trobe University, Assignment Guide.
A reminder regarding La Trobe University's policy on Academic Misconduct and Plagarism - please take care to acknowledge any sources of information used in your assignment.
Copyright © 2006 Phil Rice
Copyright © 2007-2009 Joel Sing