Patent ID: 6477384
Filing Date: 2002-11-05
Classification: H04B,H04W

Abstract:
A method for checking the presence of mobile stations communicating on a direct mode channel, the method comprising:a) sending a presence inquiry message from a first mobile station to a second mobile station on the direct mode channel, the presence inquiry message being provided with an identity and containing negation data; b) receiving said presence inquiry message at the second mobile station; c) comparing at the second mobile station, the identity contained in said presence inquiry message with the identity found in memory of the second mobile station; d) if the comparison shows that the identities are different, taking into account the negation data of the inquiry message, sending an acknowledgement from the second mobile station on the direct mode channel in response to said negation data and the comparison made in step c), the acknowledgement indicating the presence of the second mobile station to the first mobile station which sent the presence inquiry message; and e) indicating by the first mobile station, the result of the presence inquiry to the user of the first mobile station.