1. A Schnorr-Euchner (“SE”) expansion method for a multiple-input multiple-output (“MIMO”) communication system that includes a plurality of antennas at a transmitter side and a plurality of antennas at a receiver side, comprising: receiving, by the plurality of antennas at the receiver side of the MIMO communication system, a plurality of input signals, each input signal containing a symbol; and identifying a list of first 9 possible symbols that may be contained in each input signal received by each antenna at the receiver side; checking conditions when identifying 2 nd to 9 th possible symbols of the list of the first 9 possible symbols, the checking conditions being implemented by shifting and addition operations; determining a cost value for each of the first 9 possible symbols based on a cost function, the cost function being implemented without requiring a multiplier; and identifying the possible symbol with a lowest cost value as the symbol contained in the input signal, wherein the cost function has a mathematical representation of c=|y−rz| p , wherein y is the output, r is a system implementing the SE method, z is an input, c is the cost, and an integer p denotes a l p -norm, wherein p=2.