This paper focused its main research on the antenna port (AP) placement optimization of distributed multiple-input multiple-output (DMIMO) system in a circular cell.For this purpose

a composite channel model integrating with Nakagami-m fading

shadow fading

and path loss was established firstly;next

an approximate closed-form expression of downlink average cell ergodic capacity was deduced under the condition that high signal-to-noise ratio (SNR) was assumed

and multiple antennas were equipped at both the transmitter and receiver sides

which applied selective transmission (ST) and maximum ratio combining (MRC) schemes respectively

and moreover

the distribution of mobile station (MS) in the cell was arbitrary;then

a fast searching method based on particle swarm optimization (PSO) instead of traditional genetic algorithm was proposed to find the optimum positions of APs in the circular cell through dividing the cell into several predefined sections;and finally

the optimum APs' layout was provided according to the overall cell searching results.Computer simulation results show that

the approximate closed-form expression can exactly represent the performance of the DMIMO system

and the finally searched results of optimum AP positions in the cell based on PSO are very close to the theoretical antenna locations.