This paper concerns the cross-layer design between physical layer and MAC (Multiple Access Control) layer in asynchronous wireless random access network. The proposed cross-layer design consists of two parts: a MPR (Multiple Packet Reception) physical layer and a collisionaware MAC layer. In the physical layer design, different spreading codes are assigned to packets according to their frame types at the transmitter, and at the receiver, an enhanced synchronization method and MUD (Multi-user Detection) are utilized to synchronize the collided packets and recover packets. In order to reduce the computational complexity of the receiver, interference cancellation is performed at the receiver by utilizing the known preamble and the partially known frame header information. In the MAC layer design, collisions are divided into different types according to frame types and packet arrival time, and different operations are developed for different collision types to tactically access the channel...