Patent ID: 7035412
Filing Date: 2006-04-25
Classification: H04L,H04W

Abstract:
1. A method for limiting error propagation due to scrambler seed value transmission errors in a wireless communication network comprising at least one transmitting device ( 1 ) and at least one receiving device ( 2 ), wherein each transmitting device ( 1 ) has an associated transmitting address and each receiving device ( 2 ) has at least one associated receiving address, wherein each transmitting device ( 1 ) applies a forward error correction code to transmitted messages followed by scrambling of the message, and the scrambling is generated from a seed value, and each transmitted message is structured in such a manner that said seed value can be inferred at a receiving device ( 2 ) in the case of an error-free received message, the method comprising the steps of: providing state information at the transmitting device ( 1 ) for each message transmitted from said transmitting device ( 1 ) in such a manner that the transmitting device ( 1 ) can generate a sequence of seed values associated with each receiving address, providing state information at the receiving device ( 2 ) for each received message in such a manner that the receiving device ( 2 ) can generate sequences of seed values, each sequence associated with a unique combination of a transmitting address and a receiving address, the transmitting device ( 1 ) attempting to retrieve state information regarding a receiving address associated with the receiving device ( 2 ), if no state information is retrievable by said transmitting device ( 1 ) such state information is generated by an arbitrary method in order to generate a new seed value for a message to be transmitted, if state information is retrievable by said transmitting device ( 1 ), this information is utilized to initialize a first seed-generating algorithm in order to generate a new seed value for the message to be transmitted, and is updated by said algorithm, applying a scrambling algorithm initialized by the new seed value to said message to be transmitted, thereby creating a scrambled message, transmitting the scrambled message from said transmitting device ( 1 ), receiving and descrambling the scrambled message at said receiving device ( 2 ), based on the seed value deduced from the received message, checking the received descrambled message for errors that are not corrected by the forward error correction code, using received messages that are free from errors to synchronize a second seed-generating algorithm in said receiving device ( 2 ) with said first seed-generating algorithm in said transmitting device ( 1 ), using a current local seed value in said receiving device ( 2 ) to attempt to correct errors in the descrambled message caused by an incorrect received seed.