Communication toolbox objects/function for diversity combining

I am trying to use communication toolbox QPSKModulator and QPSKDemodulator objects to simulate the diversity receiver.

Assume that I have two branch receiver

y1 = h1*x + n1

y2 = h2*x + n2

where h1,h2 are independent Rayleigh fading coefficient (complex Gaussian random variables) and x is the QPSK symbol with power normalized 1. n1, n2 are receiver noise (complex Gaussian random variables with variance adjusted according to signal-to-noise ratio).

In order to use the step function with QPSKDemodulator object, we can only specify the received vector and the noise variance with QPSKDemodulation object. How can we use the step function for maximal ratio combining of y1 and y2?

Can we pass the modified combined signal

(h1*y1+h2*y2)/(|h1|^2+|h2|^2)

to the step function (here * means conjugate)? This is because, with this processing to the received signal, we have the transmitted signal x in the form of a constellation point embedded in modified noise. That is

(h1*y1+h2*y2)/(|h1|^2+|h2|^2) = x + (h1*n1+h2*n2)/(|h1|^2+|h2|^2)

In this case what is the noise variance parameter value to step function should be? Is it original noise variance according to satisfy SNR or different?

Thank you very much

San