  A combined technique of interference alignment (IA) and interference
cancellation (IC), known as interference alignment and cancellation (IAC)
scheme, has been proposed to improve the total achievable degrees of freedom
(DoFs) over IA. Since it is NP-hard to solve the transceiver under a given
tuple of DoFs or to maximize the total achievable DoFs in the general system
configuration by IA (or IAC), the optimal transceiver cannot be obtained in
polynomial time. Meanwhile, it has been known that a closed-form yet suboptimal
transceiver can be designed for IAC by employing a symbol-to-symbol (STS)
alignment structure. As its performance has not been known yet, we aim to
derive the total DoFs that can be achieved by such suboptimal but closed-form
IAC transceivers for Gaussian interference multiple access channels with K
receivers and J users (transmitters), each with M antennas. Our analysis shows
that the closed-form IAC transceivers under consideration can achieve a maximum
total achievable DoFs of 2M, which turns out to be larger than those achieved
in classical IA, e.g., 2MK/(K+1) DoFs by a specific configuration where each
link has the same target DoFs. Moreover, considering the NP-hardness of
deriving the maximum total achievable DoFs with the optimal IAC transceiver,
its upper bound has been derived for comparison with the results of our
closed-form IAC transceiver. Numerical results illustrate that its performance
can be guaranteed within 20% of the upper bound when the number of multiple
access channels are relatively small, e.g., K <=4.
