Is Random Network Coding Helpful in WiMAX?

The IEEE 802.16 standard, or WiMAX, has emerged to facilitate high-bandwidth wireless access in real- world metropolitan areas, commonly referred to as 4G. In WiMAX, hybrid automatic repeat request (HARQ) is adopted to transmit data packets reliably. However, it sacrifices resilience in time varying channels, and it may under-utilize the wireless medium in the cases of multi-path and multi-hop transmissions. On the other hand, random network coding has been shown to be effective towards improving throughput in multi-hop wireless networks, when deployed above the physical and MAC layers. It would be encouraging to observe that network coding is also helpful at the MAC layer in practice, especially within the emerging WiMAX standard. Is random network coding beneficial in WiMAX at the MAC layer? In this paper, we seek to answer this question by evaluating network coding in three cases: single-hop transmissions, handovers, and multi-hop transmissions. We show that random network coding has indeed offered important advantages as compared to traditional HARQ. Our observations may lead to the use of random network coding at the MAC layer in practical WiMAX systems.