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Main principles of SEAMCAT

The Monte-Carlo simulation method is based upon the principle of taking samples of random variables, by using their probability density functions (for simplicity called "distributions" in the SEAMCAT environment). Hence, first a user defines the distributions of possible values of the parameters of considered radiocommunications systems (e.g. antenna heights, powers, operating frequencies, positions of the transceivers, etc.) and then, SEAMCAT uses those distributions to generate random samples (also called trials or snapshots) of subject parameters. Afterwards for each trial SEAMCAT calculates the strength of the interfering and the desired signals and stores them in data arrays. As a final step, SEAMCAT derives the probability of interference by comparing relation of wanted and unwanted signals at victim receiver in each snapshot to its interference criterion, such as C/I.

For CDMA simulations, generation of snapshots includes additional complexity, as for CDMA systems several iterations of power control loop may be needed within each snapshot, as well as some initial pre-calculations are usually required, such as calculation of non-interfered (nominal) capacity. For victim CDMA systems the interference criteria is the excess outage, i.e. what percentage of previously served users was disconnected as a result of interference impact.

SEAMCAT can address virtually all radio interference scenarios on terrestrial paths in both co-channel (sharing) and adjacent frequency (compatibility) interference studies. This flexibility is achieved by the way the system parameters are defined as variable (or constant) through their distribution functions. It is therefore possible to model even very complex situations by relatively simple variation of some elementary functions.
In general,

SEAMCAT may be used to address the following spectrum engineering issues:

• Sharing and compatibility studies between different radiocommunications systems operating in the same or adjacent frequency bands;
• Evaluation of transmitter and receiver masks;
• Evaluation of limits for certain system parameters, such as unwanted emissions (spurious and out-of-band), blocking or intermodulation levels.

A number of various radiocommunications services can be modelled using SEAMCAT, such as:

• Mobile Services: Land Mobile Systems, Short Range Devices and Earth based components of satellite systems;
• Fixed Services: Point-to-Point and Point-to-Multipoint fixed systems;
• Broadcasting: terrestrial systems and Earth stations (e.g. DTH receivers) of satellite systems.

OBS: It should be noted that the current version of SEAMCAT assumes flat Earth model for calculating path geometries and propagation losses, this limits the range of considered standard interference scenarios to terrestrial configurations and non-path-specific propagation models.

Architecture of SEAMCAT-3

The architecture of SEAMCAT software has changed with the upgrade to SEAMCAT-3. Although the two most fundamental elements of original architecture: the Event Generation Engine and Interference Calculation Engine remain, the rest of the architecture was overhauled significantly in particular by extending user interface outputs and changing data storage from database-centred to XML-based files.

The architecture of SEAMCAT-3 is shown below.

The three main computational engines of SEAMCAT-3 are described in more detail in separate sub-sections of this user guide:

• Event Generation Engine (EGE)
• CDMA simulation Engine (CDMAE)
• Interference Calculation Engine (ICE)

Several other program modules are used for data storage, user interface and other system management functions.

Historical references:

• WGSE document SE(97)30;
• ERC Report 68 (available from  www.ero.dk)