System and method for improved decoding using identified recurring side information
Methods and systems for decoding monitored communication signals using previously identified side information. Information, which is used for decoding a given frame and is provided to the decoder not via the main communication channel between a base station and a mobile station, is referred to herein as “side information.” The side information can also be viewed as extrinsic information that was derived during previous decoding operations. The monitoring system holds, for certain frames, a-priori information of one or more data values that are expected in these frames. Decoding using this a-priori information enables an Error Correcting Code decoder to successfully decode such frames, which would otherwise fail to decode.
1. A method, comprising:
monitoring a plurality of communication sessions that convey communication frames in a communication network;
deriving from the monitored communication sessions, for a given type of the communication frames that are encoded with an Error Correction Code (ECC), recurrence information that indicates one or more data values that recur among the communication frames of the given type; receiving a communication frame; and
in response to verifying that the communication frame belongs to the given type, decoding the ECC in the communication frame based on the recurrence information.
2. The method according to claim 1 , wherein deriving the recurrence information comprises analyzing the communication frames exchanged with multiple communication terminals.
3. The method according to claim 1 , wherein deriving the recurrence information comprises analyzing the communication frames exchanged with two or more base stations.
4. The method according to claim 1 , wherein decoding the ECC comprises applying a Viterbi algorithm with the recurrence information serving as side information.
5. The method according to claim 1 , wherein the given type comprises a channel Assignment command frame or a Handover command frame.
6. The method according to claim 1 , wherein deriving the recurrence information comprises extracting the one or more data values from one or more communication frames received prior to the communication frame.
7. The method according to claim 6 , wherein extracting the one or more data values comprises extracting the one or more data values at least from a first communication frame communicated with a first device, and wherein receiving the communication frame comprises receiving a second communication frame communicated with a second device, which is different from the first device.
8. The method according to claim 1 , wherein deriving the recurrence information comprises receiving multiple communication frames that belong to one or more types, and classifying the multiple communication frames into the types based on the recurring data values among the communication frames of each type.
9. The method according to claim 1 , wherein deriving the recurrence information comprises deriving the recurrence information for first and second different frame types, wherein decoding the ECC comprises performing first and second ECC decoding attempts using the respective recurrence information associated with the first and second frame types to produce first and second decoded frames, and selecting either the first or second decoded frames.
10. The method according to claim 1 , wherein receiving the communication frame comprises assigning reliability measures to encoded symbols of the ECC, and modifying the assigned reliability measures based on the recurrence information.
11. The method according to claim 10 , wherein deriving the recurrence information comprises assigning respective modification factors to the one or more data values, and adding the modification factors to the respective reliability measures.
12. The method according to claim 11 , wherein assigning the modification factors comprises evaluating a number of occurrences of each of the data values at respective position in the communication frames among multiple communication frames that belong to different types.
13. The method according to claim 11 , wherein the modification factors are derived from predefined maximal and minimal reliability measure values.