Apparatus and method for processing a corrupted frame
View Patent ↗An apparatus and method for processing a corrupted frame. The corrupted frame is analyzed to ascertain whether the rate can be determined. If the rate can be determined, steps for identifying the rate are executed. After the rate is identified, the method scans the corrupted frame by checking the MM/TT/TM or MM/FM bits (depending on the radio configuration) to determine whether signaling is present in the frame. If the scan finds potential signaling information, the BTS informs the transcoder of the frame rate, that signaling is present in the frame and that the outer CRC failed. The transcoder attempts to recover the signaling information based upon the inner CRC and discards the bearer information. If the signaling message is spread over multiple frames, the entire frame is discarded to avoid confusion when the signaling message has to be reassembled. The entire frame is also discarded if the inner CRC fails.
1. A method of processing a corrupted frame comprising the steps of:
detecting that a corrupted frame has been received;
determining a rate of the corrupted frame;
determining a radio configuration of the corrupted frame;
using the radio configuration of the frame, rate of the frame and predetermined bits in the frame, determining whether signaling information is present in the corrupted frame;
when signaling information is present in the corrupted frame, reporting the rate, that there is signaling present in the frame and that a frame cyclic redundancy check failed.
2. The method of claim 1 wherein the step of determining a rate of the corrupted frame comprises the steps of:
determining whether the frame is so corrupted that a rate cannot be determined; and
when the rate is not so corrupted that the rate cannot be determined,
normalizing subrate system error rates of the frame to full rate;
determining that the rate of the corrupted frame is equal to a lowest normalized subrate system error rate.
3. The method of claim 2 wherein the step of determining whether signaling information is present in the corrupted frame comprises determining whether the radio configuration is one of radio configuration one and radio configuration 3 .
4. The method of claim 3 wherein the step of determining whether signaling information is present in the corrupted frame further comprises:
determining whether the rate of the corrupted frame is full;
when the rate of the corrupted frame is full, determining whether the predetermined bits equal one of 1000, 1001, 1010 and 1011; and
when the predetermined bits equal one of 1000, 1001, 1010 and 1011, determining that there is signaling information in the frame.
5. The method of claim 4 wherein when the rate of the corrupted frame is not full, the method comprises:
determining that signaling is not present in the corrupted frame; and
reporting that the rate is erasure.
6. The method of claim 4 wherein the predetermined bits do not equal one of 1000, 1001, 1010 and 1011, the method comprises:
determining that signaling is not present in the corrupted frame; and
reporting that the rate is erasure.
7. The method of claim 2 wherein the step of determining whether signaling information is present in the corrupted frame comprises determining whether the radio configuration is either radio configuration two or radio configuration four.
8. The method of claim 7 wherein the step of determining whether signaling information is present in the corrupted frame further comprises:
determining whether the rate of the corrupted frame is full;
when the rate of the corrupted frame is full, determining whether the predetermined bits equal one of 10000, 10001, 10010, 10011 and 11000; and
when the predetermined bits equal one of 10000, 10001, 10010, 10011 and 11000, determining that there is signaling information in the frame.
9. The method of claim 7 wherein the step of determining whether signaling information is present in the corrupted frame further comprises:
determining whether the rate of the corrupted frame is half;
when the rate of the corrupted frame is half, determining whether the predetermined bits equal one of 1000, 1001, 1010 and 1110; and
when the predetermined bits equal one of 1000, 1001, 1010 and 1110, determining that there is signaling information in the frame.
10. The method of claim 7 wherein the step of determining whether signaling information is present in the corrupted frame further comprises:
determining whether the rate of the corrupted frame is a quarter;
when the rate of the corrupted frame is a quarter, determining whether the predetermined bits equal one of 100 and 101; and
when the predetermined bits equal one of 100 and 101, determining that there is signaling information in the frame.
11. A method of processing a corrupted frame comprising the steps of:
detecting that a corrupted frame has been received;
determining a rate of the corrupted frame;
determining a radio configuration of the corrupted frame;
using the radio configuration of the frame, rate of the frame and predetermined bits in the frame, determining whether signaling information is present in the corrupted frame;
when signaling information is present in the corrupted frame, determining whether the signaling information is contained within a single frame; and
when the signaling information is contained within a single frame, reporting the rate, that there is signaling present in the frame and that a frame cyclic redundancy check failed.
12. The method of claim 11 wherein when the signaling information is not contained within a single frame, reporting the rate as erasure.
13. The method of claim 11 wherein the step of determining a rate of the corrupted frame comprises the steps of:
determining whether the frame is so corrupted that a rate cannot be determined; and
when the rate is not so corrupted that the rate cannot be determined,
normalizing subrate system error rates of the frame to full rate;
determining that the rate of the corrupted frame is equal to a lowest normalized subrate system error rate.
14. The method of claim 11 wherein the step of determining whether signaling information is present in the corrupted frame comprises
determining whether the radio configuration is one of radio configuration one and radio configuration three;
when the radio configuration is one of radio configuration one and radio configuration three 3, determining whether the rate of the corrupted frame is full;
when the rate of the corrupted frame is full, determining whether the predetermined bits equal one of 1000, 1001, 1010 and 1011; and when the predetermined bits equal one of 1000, 1001, 1010 and 1011, determining that there is signaling information in the frame.
15. The method of claim 11 wherein the step of determining whether signaling information is present in the corrupted frame comprises:
determining whether the radio configuration is one of radio configuration two and radio configuration four;
when the radio configuration is one of radio configuration two and radio configuration four, determining whether the rate of the corrupted frame is full;
when the rate of the corrupted frame is full, determining whether the predetermined bits equal one of 10000, 10001, 10010, 10011 and 11000; and
when the predetermined bits equal one of 10000, 10001, 10010, 10011 and 11000, determining that there is signaling information in the frame.
16. The method of claim 11 wherein the step of determining whether signaling information is present in the corrupted frame further comprises:
determining whether the radio configuration is one of radio configuration two and radio configuration four;
when the radio configuration is one of radio configuration two and radio configuration four, determining whether the rate of the corrupted frame is half;
when the rate of the corrupted frame is half, determining whether the predetermined bits equal one of 1000, 1001, 1010 and 1110; and
when the predetermined bits equal one of 1000, 1001, 1010 and 1110, determining that there is signaling information in the frame.
17. The method of claim 11 wherein the step of determining whether signaling information is present in the corrupted frame further comprises:
determining whether the radio configuration is one of radio configuration two and radio configuration four;
when the radio configuration is one of radio configuration two and radio configuration four, determining whether the rate of the corrupted frame is a quarter;
when the rate of the corrupted frame is a quarter, determining whether the predetermined bits equal one of 100 and 101; and
when the predetermined bits equal one of 100 and 101, determining that there is signaling information in the frame.
18. A method of processing a corrupted frame comprising the steps of:
receiving a rate of a corrupted frame;
receiving notification that there is signaling in the corrupted frame;
receiving notification that a traffic cyclic redundancy check failed;
performing an inner cyclic redundancy check;
when the inner cyclic redundancy check passes, recovering the frame's signaling content; and
discarding the frame's bearer traffic content.
19. A storage medium having stored thereon a set of instructions which, when loaded into a microprocessor, causes the microprocessor to perform the following steps:
detecting that a corrupted frame has been received;
determining a rate of the corrupted frame;
determining a radio configuration of the corrupted frame;
using the radio configuration of the frame, rate of the frame and predetermined bits in the frame, determining whether signaling information is present in the corrupted frame;
when signaling information is present in the corrupted frame, reporting the rate, that there is signaling present in the frame and that a frame cyclic redundancy check failed.