How Can I Compute Channel Capacity for My Communications Link?

Channel capacity is the tight upper bound on the (data) rate at which a transmitter can reliably send information over a communications channel. You can calculate it using the following equation:

C (MBPS) = B (MHz) x log2(1 + S/N), where you can interchange S/N and C/N, which is a power ratio (not in dB)

Here are the steps to create the elements in the formula, using the Calculation Tool (the Calculation tab) in STK's Analysis Workbench capability:
A. Create a Data Element for C/N from the Link Information Data Provider for an access between a transmitter and a receiver.

1. On the left, highlight the access object you want to analyze.
2. Click the Create new Scalar Calculation icon in the middle section. The Add Calculation Component dialog box will appear.
3. For Type, click the Select button, choose Data Element, and click OK.
4. For Name, use CoverN.
5. For Select Data Element, click the + button next to Link Information and select C/N.
6. Click OK to create the CoverN scalar component.

B. Use the binary logarithmic single variable function to calculate L = log2(1+CoverN).

1. Click the Create new Scalar Calculation icon in the middle section. The Add Calculation Component dialog box will appear.
2. For Type, click the Select button, choose Function(x), and click OK.
3. For Name, use L.
4. For Function, click the drop-down arrow and choose a*Log2(bx+c)+d.
5. For Argument, select "x is a scalar." Click the ellipsis (...) next to it and select CoverN under My Components.
6. For Coefficients, set the following: a=1, b=1, c=0, and d=0.
7. Click OK to create L.

C. Create a Data Element for Bandwidth (B) from the Link Information Data Provider for an access between a transmitter and a receiver. Use the same steps as in A, except use Name=B and select the data element Bandwidth (not C/N).

D. Use a multiplication two variable function to form the result: Capacity = B x L.

1. Click the Create new Scalar Calculation icon in the middle section. The Add Calculation Component dialog box will appear.
2. For Type, click the Select button, choose Function(x,y), and click OK.
3. For Name, use C.
4. For Function, click the drop-down arrow and choose a*x*y.
5. For Arguments: Click the ellipsis (...) next to x and select B under My Components. Click the ellipsis (...) next to y and select L under My Components.
6. For Coefficients, set a=1.
7. Click OK to create C.

Now that you have created C, you can use this Capacity scalar calculation to create a Figure of Merit for a Coverage between a transmitter Asset and receiver Grid Object or a receiver Asset and transmitter Grid Object. You can use this Analysis Workbench component to optimize a chain and constrain routing.

A Capacity Scalar Coverage example scenario is attached.

You can also replace the C/N calculation with C/(N+I) and create an interference capacity metric.