Radio unit, method of communicating between radio units over a communications channel and method of preparing a sequence of data cells for transmission over a radio channel

摘要

A radio unit (12) for communication over a communication channel (300) having repeating frames. The radio unit has a memory (131) with a table (280) of time locations in a frame and indications of the availability of time locations for transmission. A time is selected from the table and a cell of data is transmitted on the channel at the selected time. If an acknowledgement to the cell is received at a receiver (102) the transmitter sends a series of further cells at corresponding times in later frames. Otherwise a different time is selected for a new access attempt. A sequence of ATM cells is prepared for transmission by forming data into cells each having synchronization information (230), a physical layer field (251), a sequence number (253) and an error check number (254). Error coding cells (245) are added, with error coding which is spread across the cells such that a lost cell is recoverable from adjacent cells.