An image forming process and apparatus, the apparatus including a toner container, a transfer belt below the toner container, a process cartridge below the transfer belt, and an imaging device below the process cartridge. An example method in a mobile station disclosed herein comprises receiving a request for acknowledgment information expected to be transmitted with data, and transmitting a control message in response to the request if a previously transmitted data block is associated with a tentative acknowledgment state, the control message including acknowledgment information. A chamfered portion or a rounded corner portion is formed at the edge of the header portion of the stem or the edge of the header portion of the sub-mount provided on the stem. , using the format of explicit weighted prediction to allow for offsets to predictive data that is otherwise determined by implicit or default weighted prediction.