Aggregation with Fragment Retransmission for Very High-speed WLANs

 

In upcoming very high-speed WLANs the physical layer rate may reach 600 Mbps. To achieve high efficiency at the medium access control layer, we identify fundamental properties that must be satisfied by any CSMA/CA based MAC layer and develop a novel
scheme called Aggregation with Fragment Retransmission (AFR). In the AFR scheme, multiple packets are aggregated into and transmitted in a single large frame. If errors happen during the transmission, only the corrupted fragments of the large frame are retransmitted. We investigate by simulations the impact of AFR on the performance of realistic application traffic with diverse requirements. We have implemented the AFR scheme in the NS-2 simulator. The source code for NS 2.27 can be downloaded from here (for NS 2.30) the corresponding TCL scripts are here. The AFR scheme was developed as part of the 802.11n working group work. Trends indicated by our simulation results should extend to any well-designed aggregation scheme.

This implementation is based on NS 2.27 which you may need to download and install. Since I made the following modifications except the MAC itself:

• Disable ARP and assign destination MAC address in TCL scripts
  
• Disable CMU tracing and use C++ to compute what I want
• Some other details I can not remember.

the easiest way to start using this code is to:

• Download the source code named ns_afr.tar.gz and the TCL scripts named tcl_afr.zip
  
• tar xvfz ns_afr.tar.gz, it will generate a ns-2.27 directory
• Replace the 'ns-2.27' directory of your NS 2.27 installation by the generated ns-2.27 directory
• unzip tcl_afr.zip, then go to the generated directory called 'tcl' to try your luck
  

Tianji Li (tianji.li@nuim.ie)
Aug. 30 2006
Hamilton Institute, National University of Ireland at Maynooth. Ireland