Reduced complexity FDM-CPM detector with multiple access interference cancellation
AssigneeNewtec Cy
InventorsGiulio Colavolpe, Amina Piemontese
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Abstract
An FDM-CPM multi-user detector (30) jointly detects the received symbols for all users by determining from the received multi-user signal an a-posteriori probability mass function (pmf) of a time-sequence of states and transmitted symbols of all users, by iterative message passing corresponding to a specific factorisation of the pmf. The factorisation involves a combined variable representing possible transmitted symbols and CPM states of each user for each symbol time interval, so as to make the iterative process convergent. Non exponential complexity is enabled by disregarding multiple access interference (MAI) from at least some of the other users. Applications can include hubs for satellite communication ground stations.
Claims21
A frequency division multiplexed, continuous phase modulation (FDM-CPM) multi-user detector comprising:
- a processor for executing instructions stored in a memory, and the processor for operating a computational complexity that is related non exponentially to a number of users, the processor of the FDM-CPM multi-user detector being further configured to:
- jointly detect symbols of multiple users in a received multi-user FDM-CPM signal;
- and
- determine, from said received multi-user signal, marginal a-posteriori probability mass functions (pmf's) of a time-sequence of CPM states and transmitted symbols of all users,
- wherein the a-posteriori pmf's of the transmitted symbols are determined by carrying out an iterative message passing process corresponding to a specific factorization of a joint a-posteriori pmf of the transmitted symbols and CPM states,
- wherein the factorization involves a combined variable representing possible transmitted symbols and CPM states of each user for each symbol time interval, so as to make the iterative message passing process convergent, and
- wherein the iterative message passing process attains non exponential complexity with respect to the number of users by making an approximation by disregarding multiple access interference (MAI) from at least some of the other users.
A hub for a groundstation of a downlink of a satellite communication system, the hub comprising:
- a receiver for receiving frequency division multiplexed, continuous phase modulation (FDM-CPM) signals originating from many users, the receiver having a FDM-CPM multi-user detector comprising:
- a processor for executing instructions stored in a memory, and the processor for operating a computational complexity that is related non exponentially to a number of users, the processor of the FDM-CPM multi-user detector being configured to:
- jointly detect symbols of multiple users in a received multi-user FDM-CPM signal;
- and
- determine, from said received multi-user signal, marginal a-posteriori probability mass functions (pmf's) of a time-sequence of CPM states and transmitted symbols of all users,
- wherein the marginal a-posteriori pmf's of the transmitted symbols are determined by carrying out an iterative message passing process corresponding to a specific factorization of a joint a-posteriori pmf of the transmitted symbols and CPM states,
- wherein the factorization involves a combined variable representing possible transmitted symbols and CPM states of each user for each symbol time interval, so as to make the iterative message passing process convergent, and
- wherein the iterative message passing process attains non exponential complexity with respect to the number of users by making an approximation by disregarding multiple access interference (MAI) from at least some of the other users.
A method of jointly detecting symbols of multiple users in a received frequency division multiplexed, continuous phase modulation (FDM-CPM) multi-user signal with a computational complexity that is related non exponentially to a number of users, comprising the steps of:
- determining by a processor, from the received FDM-CPM multi-user signal, marginal a-posteriori probability mass functions (pmf's) of a time-sequence of CPM states and transmitted symbols of all users, and
- carrying out an iterative message passing process corresponding to a specific factorization of a joint a-posteriori pmf of the transmitted symbols and CPM states,
- wherein the factorization involves a combined variable representing possible transmitted symbols and CPM states of each user for each symbol time interval, so as to make the iterative message passing process convergent,
- wherein the iterative message passing process attains non-exponential complexity with respect to the number of users by making an approximation by disregarding multiple access interference (MAI) from at least some of the other users, and
- wherein the iterative message is transmitted for each user after making the approximation.
A program stored on a non-transitory computer readable medium which when executed by a processor, causes the processor to carry out a method for jointly detecting symbols of multiple users in a received multi-user frequency division multiplexed, continuous phase modulation (FDM-CPM) signal with a computational complexity that is related non exponentially to a number of users, the method comprising the steps of:
- Determining, from the received FDM-CPM multi-user signal, marginal a-posteriori probability mass functions (pmf's) of a time-sequence of CPM states and transmitted symbols of all users, and
- carrying out an iterative message passing process corresponding to a specific factorization of a joint a-posteriori pmf of the transmitted symbols and CPM states,
- wherein the factorisation involves a combined variable representing possible transmitted symbols and CPM states of each user for each symbol time interval, so as to make the iterative message passing process convergent, and
- wherein the iterative message passing process attains non-exponential complexity with respect to the number of users by making an approximation by disregarding multiple access interference (MAI) from at least some of the other users.
A method of producing a configuration for processors of an a frequency division multiplexed, continuous phase modulation (FDM-CPM) multi-user detector, the method comprising the steps of:
- determining by a processor a message flow for iteratively from a received multi-user signal:
- marginal a-posteriori probability mass functions (pmf's) of a time-sequence of CPM states and transmitted symbols of all users, corresponding to a specific factorization of a joint a-posteriori pmf of the transmitted symbols and CPM states, and
- producing the configuration from the determined message flow,
- wherein the factorization involves a combined variable representing possible transmitted symbols and CPM states of each user for each symbol time interval, so as to make the iterative process convergent,
- wherein the message flow has non-exponential complexity with respect to the number of users by making an approximation by disregarding multiple access interference (MAI) from at least some of the other users, and
- wherein the iterative message is transmitted for each user after making the approximation.
The method of 17, the received FDM-CPM signal having frequency overlaps between adjacent users.
A non-transitory storage medium storing a computer program product which when executed by a processor, causes the processor to carry out a method of producing a configuration for processors of a frequency division multiplexed, continuous phase modulation (FDM-CPM) multi-user detector, the method comprising the steps of:
- determining a message flow for iteratively determining, from a received multi-user signal, marginal a-posteriori probability mass functions (pmf's) of a time-sequence of CPM states and transmitted symbols of all users, corresponding to a specific factorization of the joint a posteriori pmf of the transmitted symbols and CPM states, and
- wherein the factorisation involves a combined variable representing possible transmitted symbols and CPM states of each user for each symbol time interval, so as to make the iterative process convergent, and
- wherein the message flow has non-exponential complexity with respect to the number of users by making an approximation by disregarding multiple access interference (MAI) from at least some of the other users.
Dependencies are inferred from the claim text.