I prefer using OPNET and MATLAB software packages to carry out my simulations and numerical solutions. However, there are a number of good alternatives. It certainly pays off to be familiar with these other tools. Specially, two very good "free" and similar alternatives are OMNeT++ and Scilab.
* Simulation packages:
OPNET: widely used by major
research labs and universities, state-of-the-art hierarchical and
modular
programming environment based on C and state machines with easy-to-use
GUI, extensive model libraries for many
technologies/protocols/vendors/standards, comprehensive library of
useful functions (called kernel procedures), powerful debugger, university
program;
"OPNET ModelerŽ accelerates network R&D, reduces
time-to-market, and improves product quality. Using simulation, network
designers reduce research costs and ensure optimal product quality.
OPNET Modeler’s cutting-edge technology provides an environment
for designing protocols and technologies as well as testing and
demonstrating designs in realistic scenarios prior to production. OPNET
ModelerŽ is used by the world's largest network equipment
manufacturers to enhance the design of network devices, technologies
such as VoIP, TCP, OSPFv3, MPLS, IPv6, and much more."
NS2: free, heavily supported
by the academic community, full access to the source
code, comprehensive
models especially for TCP;
"Ns is a discrete event simulator targeted at networking research. Ns
provides substantial support for simulation of TCP, routing, and
multicast protocols over wired and wireless (local and satellite)
networks."
OMNet++: free, graphical user
interface similar to OPNET;
"OMNeT++ is a public-source, component-based, modular and
open-architecture simulation environment with strong GUI support and an
embeddable simulation kernel."
QualNet: see here for QualNet
product family or here for a list of model
libraries,
multi-core support, university
program;
"QualNet is network modeling software that predicts performance of
networks through simulation and emulation."
Signal Processing Designer (CoWareŽ SPD, formerly CadenceŽ SPW): "accelerates the design of complex, digital signal processing (DSP) systems. It is a C-based modeling and simulation environment that facilitates structured modeling and model reuse across design teams. Its efficient creation of complex DSP system models and extremely fast simulation makes Signal Processing Designer the premier choice for today’s complex, multi-standard designs in the wireless and multimedia markets."
* Computational packages:
MATLAB: (A good tutorial on MATLAB graphics: Getting a handle on MATLAB graphics)
Scilab: an open-source platform similar to MATLAB, pronounced 'sailab' as in scientific laboratory, see a concise tutorial,
Note: for installing OPNET under Windows OS, the environment variables have to be set correctly to make the installed C compiler available to OPNET. For a list of such variables see here or here.
For a list of my publications, please refer to My CV (pdf).