An HARQ method for guaranteeing a QoS in a wireless communication system is provided. The racket frame also comprises a self-powered piezoelectric damping system for damping vibrations of the racket during play. Additionally, the protocols enable two or more identical encryptable objects to be processed with different encryption keys, yet be stored in a manner so that the total required storage space is proportional to the space that is required to store a single encryptable object, plus a constant amount for each distinct encryption key. An indicator detects the machine’s current work function and updates the data in the database based on the current work function.