Ephemeris, clock, ionosphere, troposphere, etc. data

Hi,

This is my second thread, I hope someone to answer and help me.
I am writing code for a GPS Simulator.
I have most of the code, but I do not know exactly how or where obtain real values for the variables presented in the list bellow.

I found in IGS -- International GNSS Service, formerly the International GPS Service thousand of files, but I do not know which ones to look up. The ephemeris send by the satellites contains the first variables that I need (but I do not know which files are).

Anyway, hope someone can help me.

List of variables

Identifier [Units] Description
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a [m^(1/2)] square root of the semi-major axis
e [-] orbit eccentricity
omega [rad] argument of perigee
i0 [rad] inclination angle
alpha0 [rad] right of ascension
Delta_n [rad/s] correcetion for mean motion
M0 [rad/s] mean anomaly at reference time
C_us [rad] amplitude of the cosine harmonic correction to the arg. of latitude
C_uc [rad] amplitude of the sine harmonic correction to the arg. of latitude
C_rs [m] amplitude of the cosine harmonic correction to the orbit radius
C_rc [m] amplitude of the sine harmonic correction to the orbit radius
C_is [rad] amplitude of the cosine harmonic corr. to the angle of inclination
C_ic [rad] amplitude of the sine harmonic correction to the angle of inclination
iDOT [rad/s] rate of inclination angle
alphaDOT [rad/s] rate of right ascension
toe reference time ephemeris
af0 [-] 0th order clock correction
af1 [1/s] 1th order clock correction
af2 [1/s^2] 2th order clock correction
toc clock reference time
tgd group delay
pr measured pseudo-range
VINA GPS time of week

alpha [-] coefficients of a cubix equation representing the amplitude of the vertical delay (4 coefficients - 8 bits each)
beta [-] coefficients of a cubic equation representing the period of the model (4 coefficients - 8 bits each)

T_amb [C] ambient temperature at receiver antenna location
P_amb [hPa] ambient pressure at receiver antenna location
P_vap [hPa] water vapor pressure at receiver antenna location