Simulation Models for NS-2

A simulation platform based on NS-2 as been developed in order to leverage publicly available modules for several wireless and wired technologies.

Models for IEEE 802.3 (Ethernet), IEEE 802.11b (WLAN), IEEE 802.15.1 (Bluetooth), and UMTS have been developed for various previous releases of NS-2, but have not been integrated to run jointly in a single simulation environment. By integrating various modules into a single platform, we make it possible to simulate heterogeneous environments that incorporate a variety of access networking technologies.

Frequently Asked Questions 

IEEE 802.16 model

1. Q: What does "bash: ns: command not found" mean?
   A: The NS-2 simulator is not properly installed/compiled. Execute "./configure; make clean; make" from the ns-2.29 directory.
2. Q: What does invalid command name "Phy/WirelessPhy/OFDM" while executing "Phy/WirelessPhy/OFDM set g_0" mean?
   A: The OFDM class is unknown to NS. This means the code has not been recompiled. Execute "./configure; make clean; make" from the ns-2.29 directory.
   
3. Q: What does invalid command name "Mac/802_16" while executing "Mac/802_16 set debug_ 0" mean?
   A: The Mac/802_16 class is unknown to NS. This means the code has not been recompiled. Execute "./configure; make clean; make" from the ns-2.29 directory.
   
4. Q: Compilation error "NeighborEntry already defined".
   A: A class with the same name is defined in the diffusion3 subdirectory. Rename the class NeighborEntry to WimaxNeighborEntry where used.
   Note: The updated pre-release contains the modification.
5. Q: Does the current model support class of service (UGS, RTPS, NRTPS and BE)?
   A: No. Though the architecture defines the structures to use it, the current scheduler does not make use of it.
   
6. Q: What scheduler is implemented?
   A: The scheduler allocates downlink bandwidth first according to pending traffic. Next, the contention periods are allocated in the uplink bandwidth. The rest of the uplink bandwidth is then allocated to one MS (The MS is picked in a Round Robin fashion). Currently the BS does not consider bandwidth requests from the MSs.
   
7. Q: How to set the -DDEBUG_WIMAX switch?
   A: Look for the line starting with "DEFINE = -DTCP_DELAY_BIND_ALL" and add the -DDEBUG_WIMAX.
   
8. Q: How to set the datarate?
   A: Unlike the 802.11 implementation, the datarate is not something set in TCL. Since each burst can use a different modulation and therefore have different datarates, we opted for a dynamic calculation of the datarate. By setting the frequency bandwidth, cyclic prefix and the modulation, the datarate will change. The scripts located in tcl/wimax/datarate/ show the maximum throughput achieved with frequency bandwidth of 7MHz.
   

Mobility package

1. Q: The scripts are not running in the pre-release dated 01/27/07. What is the problem?
   A: The model is under development. Therefore some older scripts may not have been updated. Download the new release with updated examples.
2. Q: How do I install the mobility package?
   A: The mobility package contains a complete ns-2.29 directory. Delete the default ns-2.29 directory and replace it with the one provided in the compressed file.
3. Q: Segmentation fault when using older scripts with the new model.
   A: The structures have changed for the MAC and classifier classes. The scripts have to be updated.