Packet Error Rate (PER) is used to test the performance of an access terminal's receiver. PER is the ratio, in percent, of the number of FTAP or FETAP Test Packets not successfully received by the access terminal (AT) to the number of FTAP or FETAP Test Packets sent to the AT by the test set. See Forward Test Application Protocol (FTAP) , Multi-carrier Test Application Protocol and Forward Enhanced Test Application Protocol (FETAP) .
To perform a packet error rate measurement, the test set sends an FTAP (when current physical layer subtype is subtype 0) or FETAP Test Packet (when current physical layer subtype is subtype 2) or FMCTAP Test Packet (when current physical layer subtype is subtype 3) to the access terminal. See Release A Physical Layer Subtype or Release B Physical Layer Subtype to configure the physical layer subtype. Each packet contains 16 FCS (Frame Check Sequence) bit, which provide information about the packet. If the AT is able to decode the packet and the FCS checks (the information relayed by the FCS matches the packet characteristics), then the packet is successfully received.
The AT sends one or more FTAP/FETAP/FMCTAP Loop Back Packets to the test set to indicate how many FTAP/FETAP/FMCTAP Test Packets were successfully received for each 16-slot "observation interval" (frame). The AT sends one Loop Back Packet (or more, if needed to convey all of the records) containing a record for each FTAP/FETAP/FMCTAP Test Packet in the observation interval. The Loop Back Packets are queued for transmission on the Reverse Traffic Channel, and the AT must provide buffering for at least 8 FTAP/FETAP/FMCTAP Loop Back Packets. An FTAP/FETAP/FMCTAP Loop Back Packet is generated even if no FTAP/FETAP/FMCTAP Test Packets were received during the 16-slot observation interval.
You must establish an FTAP (for Subtype 0 Physical Layer) or FETAP (for Subtype 2 Physical Layer) or FMCTAP (for Subtype 3 Physical Layer) connection to perform packet error rate measurements (see Measuring Packet Error Rate (PER) for detailed procedure).
When confidence level is on, the PER measurement keeps track of the number of packets measured, the number of packet errors and performs a statistical analysis of the probability that the value entered in the PER requirement field will (or will not) be exceeded.
The confidence level parameter is typically set at 95%. With that setting, the PER measurement returns a pass result before the maximum packet count is reached if statistically there is a 95% probability that the percentage of packet errors will not exceed the PER requirement value if the measurement is allowed to reach the maximum packet count. The PER measurement returns a fail result before the maximum packet count is reached if statistically there is a 95% probability that the percentage of packet errors counted will exceed the PER requirement if the measurement is allowed to reach the maximum packet count. If the number of packet errors counted does not allow a reliable prediction of "pass" or "fail," the measurement continues until the number of packets tested equals max packets. "Max packets" and the PER percentage result are then returned.
During a fading test, the PER measurement must run for a sufficient length of time (the minimum number of packets) to allow fading statistics to average out (mean power standard deviation must be less than 0.2 dB). After the minimum number of packets have been measured, the statistical analysis is applied. This can prevent the PER measurement from failure too early due to power uncertainty. The early failure termination is not compatible with some tests (such as requiring faded signals) to achieve reliable results.
3.2.2 Demodulation of Forward Traffic Channel in Multipath Fading Channel ( Lab Application Only )
Manual Operation: Measuring Packet Error Rate (PER)