Industrial wireless system has been considered as a potential application in the upcoming wireless system (e.g. 5G and IoT era). The main requirements of this application are ultra-reliable low-latency and low-power massive machine type communication. Satisfying all these requirements at the same time is still big technical challenge, since many aspects from different layers of network system are inter-dependent in affecting overall system performance. Therefore, system design and optimization are difficult and could not be carried out solely in one part. To overcome these issues, this paper presents cross-layer optimization in order to achieve energy-efficient wireless system, while maintaining low-latency and high-reliability requirements. The cross-layer optimization is performed within Medium Access Layer (MAC) and Physical Layer (PHY), which are devoted as the backbone for radio access. The optimizations include system level design, low-power aware protocol and resource management design, signal processing algorithm design and circuit design techniques of transceiver system. Furthermore, the implementation of overall PHY-MAC hardware design for industrial wireless LAN system is presented. The proposed design offers an advantage, in terms of energy-efficient wireless system, as compared to the other classes of low-power wireless systems (e.g. Bluetooth, Zigbee) and the conventional WLAN systems.