The problem of jointly estimating the number, the identities, and the data of active users in a time-varying multiuser environment was examined in a companion paper (IEEE Trans. Information Theory, vol. 53, no. 9, September 2007), at whose core was the use of the theory of finite random sets on countable spaces. Here we extend that theory to encompass the more general problem of estimating unknown continuous parameters of the active-user signals. This problem is solved here by applying the theory of random finite sets constructed on hybrid spaces. We do/nso deriving Bayesian recursions that describe the evolution with/ntime of a posteriori densities of the unknown parameters and data./nUnlike in the above cited paper, wherein one could evaluate the/nexact multiuser set posterior density, here the continuous-parameter Bayesian recursions do not admit closed-form expressions. To circumvent this difficulty, we develop numerical approximations/nfor the receivers that are based on Sequential Monte Carlo (SMC)/nmethods (“particle filtering”). Simulation results, referring to a/ncode-divisin multiple-access (CDMA) system, are presented to/nillustrate the theory.

The work of E. Biglieri was supported by the STREP Project No. IST-026905 (MASCOT) within the 6th framework program of the European Commission, and by the Spanish Ministry of Education and Science under Project TEC2006-01428/TCM.