This paper proposes a scalable heuristic spatial time division multiple access (STDMA) time-slot scheduling algorithm for millimeter-wave wireless personal area network (WPAN) with spatial division multiple access (SDMA) through directional antenna system. A detailed cross layer design is proposed including the medium access control (MAC) layer and the physical (PHY) layer designs. The proposed hybrid STDMA/SDMA scheduling engine possesses the capability of flexible throughput-enhancement employing different levels (i.e. heuristic order) of algorithm complexity. Firstly, it is found that the scheduling engine with exhaustive searching algorithm is able to improve up to 9-fold of the achievable system throughput. Secondly, it is determined that heuristic order of 5 is sufficient to provide optimum throughput enhancement with minimized system complexity. Thirdly, the analysis of required overhead to perform the STDMA scheduling engine is also discussed.