A design of cooperative slotted ALOHA system with HARQ

We consider a simple fundamental MAC protocol - the slotted ALOHA random access protocol. The stability region can be enlarged by two methods, the cooperation between users and hybrid automatic repeat request (HARQ). The cooperative transmission allows users to exploit cooperative gains in random access networks. The HARQ technique increases the transmission efficiency in retransmission. This idea of introduce cooperation in the slotted ALOHA has been implemented in an earlier work. In this paper, we propose to further integrate HARQ into the slotted ALOHA with cooperation to enlarge the stability region. Mathematical analysis and simulation are provided to describe the two-user stability region. Our simulation is practical cross-layer simulation that uses LDPC code in the physical layer first and then simulates the stability region based on the resultant packet-level phenomenon.