Novel multireceiver communication systems configurations based on optimal estimation theory

This publication presentsa novel multireceiver configuration for the purpose of carrier arraying and/or signal arraying. Such a problem arises for example, in the NASA Deep SpaceNetwork where the samedata-modulated signal from a spacecraft is receivedby a number of geographically separatedantennasand the data detection must be ef/iciently performed on the basisof the various receivedsignals. The proposed configuration is arrived at by formulating the carrier and/or signal arraying problem as an optimal estimation problem. Two specific solutions are proposed. The first solution is to simultaneously and optimally estimate the various phase processesreceivedat different receivers with coupled phase-locked loops (PLLs) wherein the individual PLLs acquire and track their respective receivers' phase processes, but are aided by each other in an optimal manner. The coupled PLL estimator is followed by simple addition of the quadrature-phase components of the mixers from various receivers for the purpose of data detection. Such signal combining, of course, requires the transmission of high information rate (the rate related to the data transmission rate) baseband signals from all the receivers to one of the selected receivers, as expected. For relatively strong correlation among various phase processes, the detection performance as measured in terms of radio loss is near optimal; in this case the phase error processes themselves are also highly correlated. However, when the phase processes are relatively weakly correlated, coupling among loops is of only marginal significance (in the limit the improvement due to coupling is zero for zero cross-correlation). In this case, most of the gain is expected to result from the post-loop combining. However, simple combining of b_seband signals