The present invention relates to a network node and a method in a network node for admission control of broadcast transmission sessions. The method comprises receiving a broadcast transmission session start request for a first broadcast transmission session, obtaining at least a first traffic statistics parameter related to said first broadcast transmission session, obtaining the available bit rate for the broadcast transmission area, and obtaining a re-synchronization parameter indicating the time between re-synchronization of transmissions for said broadcast transmission session. The method also calculates a first expected bit error rate based on said at least first traffic statistics parameter, said available bit rate and said re-synchronization parameter, and admits said first broadcast transmission session if said first expected bit error rate is less than a first bit error rate threshold.