There is a global trend towards migrating to millimeter wave frequencies in the fifth generation of mobile communications (5G) to further enhance the available capacity and data rates. Antenna arrays are usually applied to overcome the innate high path loss at the millimeter wave (mmW) frequency band. Moreover, the use of subarrays decreases design complexity and system cost. The goal of this paper is to present a design of a wideband subarray at the frequency range from 28 GHz to 32 GHz, i.e. the frequency range applied for Local Multipoint Distribution Service (LMDS), to be used in the antenna array design of next generation mobile networks. The proposed subarray consists of four radiating elements of proximity coupled stacked patch antennas. The unit-cell is first designed, fabricated and tested, which confirms the wideband coverage along the required band. The proposed subarray achieves a simulated gain that ranges between 11.1 dB and 12 dB along the frequency band from 28 GHz to 32 GHz. The impedance bandwidth and the 1-dB gain bandwidth are 30% and 21.2%, respectively.