A memory controller reads data from DRAM at a request from a plurality of masters. A transmitter generates a plurality of spatial streams of data and transmits the spatial streams via a plurality of transmit antennas. In addition, by allowing the compression code volume to exceed the target in correspondence to the excess of the remaining capacity, a planned reduction in the remaining area is achieved. A plurality of cooperating nuts 42, 44 are provided on each end of the threaded shafts 40 to secure the first clamp half 20, the second clamp half 22, the linear guide rail 14 and the key 12.