An Almost Overhead-Free Error Control Scheme for IEEE 802.16-Based Multi-hop Networks

Based on IEEE 802.16 specifications, the convergence sublayer (CS) of 802.16-based networks provides the function for heterogeneous upper layer protocols. The CS can encapsulate such as IP packets with variable lengths or ATM cells with fixed length in its MAC PDU and usually adds a CRC-32 field to the rear of the MAC PDU. Based on the CRC-32, each 802.16 relay node or BS can detect error occurrence on a MAC PDU and use ARQ mechanism to retransmit the corrupt MAC PDU. However, for real-time streaming (e.g., UDP streaming), the ARQ mechanism is not required and the CRC-32 is also removed. Once CRC-32 is removed from the MAC PDUs, PDU error will not be detected by the intermediate nodes in time and these corrupt IP packets or ATM cells will be still forwarded in the networks to waste radio bandwidth. Hence, the error detection mechanism could be maintained, but the large overhead of CRC-32 should be reduced for real-time streaming. In this paper, we propose an efficient discrete-error-checking scheme (DECS) to reduce the overhead of error detection for real-time streaming. The proposed DECS only needs a few checking bits inserted in the MAC PDU, and it can efficiently provide the error detection function. Moreover, a chase mechanism concurrently works on each relay node and BS to early discard these corrupt and useless IP packets or ATM cells. The concept of the DECS including the chase mechanism can be extensively implemented in many wire and wireless multi-hop networks to further improve bandwidth utilization.