On Achievable Rates in the Two User AWGN Broadcast Channel with Finite Input Alphabets

Achievable rate regions in broadcast channels are usually determined for infinite Gaussian input alphabets. Since these alphabets are not used for practical systems, we investigate the influence of finite signal constellations in the two user AWGN broadcast channel. We show that results derived with Gaussian inputs are not transferable to the finite case. For scenarios where the rate of one user should be maximized whilst a required rate for the other user is delivered we establish design rules.