Highly Efficient Multi-Hop Packet Transmission Using Intra-Flow Interference Cancellation and Maximal-Ratio Combining

Conventional Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) multi-hop transmission suffers severely from intra-flow interference (IFI) in dense traffic, due to the hidden terminal (HT) problem. We propose a non-CSMA/CA multi-hop transmission scheme with IFI-canceler (IFIC) that can efficiently relay packets under high traffic loads in fading environments. This interference cancellation technique employs adaptive equalization with a normalized least mean square (NLMS) algorithm for channel estimation and has good BER/PER performance under a wide range of SNR and SIR conditions. It is also capable of canceling multiple interference sources. A multi-hop packet transmission frame format dedicated to the IFIC proposal is designed. An analysis model is created that considers possible outage events in multi-hop traffic flows. Simulations of multi-hop transmission indicate that IFIC throughput under slow Rayleigh fading linearly increases with traffic load and is 3.5 times higher than that of current CSMA/CA systems at the highest normalized traffic load. When 2-branch maximal-ratio combining (MRC) reception is added after IC, the throughput is further improved to a level very close to the theoretical maximum for additive white Gaussian noise (AWGN) channels. We also assess the impact of maximum Doppler frequency, and show that the best performance is maintained if the frequency is less than 10 Hz and the performance under higher Doppler frequencies can be effectively improved by retransmission.