Packet Error Rate (PER) Test Explained
The Packet Error Rate test is an application which was written to support the MC9S08GB60 microcontroller. In order for the test to work, the 13213-SRB ZigBee units included in Freescale's Networking Starter Kit (NSK) were set up to communicate to one another across a peer-to-peer wireless IEEE connection. For this test, one 13213-SRB was configued with the transmitting version of the test application and the receiving end of the test was downloaded into the memory of a PC-connected 13213-SRB.
Once the test has been started, the quality of the wireless transmission between the two devices is monitored by the test application and packet-based information is recorded at a PC-connected 13213-SRB. This data is recorded through a virtual COM port connection and utilization by the PER Test application of HyperTerminal.
Once HyperTerminal is active, it listens for the 1000-packet burst to be sent by the transmitter and received locally. Meanwhile, the Link Quality Index (LQI), which is a measure of the Packet Error Rate, is recorded for further analysis. The frame of each packet (see diagram) allows for a maximum of 104 information bytes to be stored per packet and the test uses only 8 bytes of these. The transmission of the 1000-packet burst takes roughly 30 seconds to complete. The devices used in the test were immobilized during each burst to maximize the stability of the wireless connection.
The tests run during evaluation and characterization of the 13213-SRB were as follows:
- RF CAD LAB Area
View - [ 1st test area ] [ 2nd test area ] [ 3rd test area ] [ 4th test area ]
A number of fixed locations were chosen radially outwards from the position of the receiver, with increasing obstruction density. The 15 locations which were chosen for the test are listed below. See the graphical results.
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1. On top of each other |
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2. Behind 2nd chair 3. Behind 3rd chair 4. Behind 4th chair 5. Next to telephone 6. Next to RF CAD Lab door (inside) |
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7. Next to RF CAD Lab door (outside) 8. Outside door of CAD Lab 2 9. Outside door of Postgrad Room 10. Teltec hallway door (inside) |
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11. Teltec hallway door (outside) 12. Interior hallway window (nearby) 13. Laser lab door (outside) 14. Laser lab corridor archway |
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15. Second floor elevator door (outside) |
- Main Hall, LOS [ view test area ]
Line of sight test in the electromagnetically-noisy Electrical Engineering building. This test allowed for analysis of signal fall-off and increasing error rate with linear displacement from the receiver. See the graphical results.
- Alongside Kane Building, LOS [ view test area ]
Line of sight test in an outdoor, "noise-free" enviroment. This test eliminated the noise element coupled into the results from the Electrical Engineering building tests. In the outdoor environment, signal quality per distance was expected to improve. See the graphical results.