  In this paper, diversity analysis of bit-interleaved coded multiple
beamforming (BICMB) is extended to the case of general spatial interleavers,
removing a condition on their previously known design criteria and quantifying
the resulting diversity order. The diversity order is determined by a parameter
Qmax which is inherited from the convolutional code and the spatial
de-multiplexer used in BICMB. We introduce a method to find this parameter by
employing a transfer function approach as in finding the weight spectrum of a
convolutional code. By using this method, several Qmax values are shown and
verified to be identical with the results from a computer search. The diversity
analysis and the method to find the parameter are supported by simulation
results. By using the Singleton bound, we also show that Qmax is lower bounded
by the product of the number of streams and the code rate of an encoder. The
design rule of the spatial de-multiplexer for a given convolutional code is
proposed to meet the condition on the maximum achievable diversity order.
