Estimating noise power on a frequency channel based on at least one unused orthogonal spreading code

1. A receiving device in a communication system, comprising:

at least one processor configured to estimate noise power on a frequency channel by despreading a reception on the frequency channel using at least one non-assigned despreading code, wherein the at least one non-assigned despreading code is a complex-conjugate of at least one spreading code that is unused by transmitting devices in the communication system on the frequency channel, wherein the least one spreading code are among N spreading codes for the frequency channel, wherein the N spreading codes are orthogonal to each other; and

wherein noise and interference power estimated using an individual non-assigned dispreading code represents 1/N of a total noise and interference power experienced by the receiving device on the frequency channel.

2. The receiving device of claim 1 , wherein the frequency channel is a physical uplink control channel (PUCCH).

3. The receiving device of claim 1 , wherein the communication system implements a Long Term Evolution (LTE) air interface.

4. The receiving device of claim 1 , wherein the communication system implements a Third Generation Partnership Project (3GPP) Fifth Generation (5G) air interface.

5. The receiving device of claim 1 , wherein the reception comprises:

desired signal components present on the frequency channel and orthogonal to the at least one non-assigned despreading code; and

noise and interference that is uniformly distributed in power across the N spreading codes forming a basis for the reception.

6. The receiving device of claim 1 , wherein the at least one processor is configured to despread the reception by:

during a first despreading stage:

despreading each combined symbol in a baseband signal, using at least one assigned despreading code in a first set of orthogonal sequences, to produce symbols from a subset of all users and a fraction of the noise; and

despreading each combined symbol using the at least one non-assigned despreading code in the first set of orthogonal sequences, to produce to produce a noise estimate represented by a set of additional zero-mean random variables.

7. The receiving device of claim 6 , wherein the at least one processor is further configured to despread the reception by:

during a second despreading stage:

despreading the symbols from the subset of all the users using one or more assigned despreading code in a second set of orthogonal sequences to obtain user symbols; and

despreading the symbols from the subset of all the users using the at least one non-assigned despreading code in the second set of orthogonal sequences to obtain an additional noise estimate represented by an additional set of zero-mean random variables.

8. The receiving device of claim 7 , wherein the at least one processor is configured to estimate the noise power by:

determining a variance, for each of a plurality of antennas, a variance of the zero-mean random variables for the non-assigned despreading codes; and

estimate the noise power by averaging the variances across the zero-mean random variables, and normalizing by a ratio of a total number of despreading codes to non-assigned despreading codes.

9. A method for estimating noise power on a frequency channel in a communication system, the method being performed by a receiving device, the method comprising:

estimating the noise power on the frequency channel by despreading a reception on the frequency channel using at least one non-assigned despreading code, wherein the at least one non-assigned despreading code is a complex-conjugate of at least one spreading code that is unused by transmitting devices in the communication system on the frequency channel, wherein the at least one spreading code are among N spreading codes for the frequency channel, wherein the N spreading codes are orthogonal to each other; and

wherein the noise and interference power estimated using an individual non-assigned dispreading code represents 1/N of a total noise and interference power experienced by the receiving device on the frequency channel.

10. The method of claim 9 , wherein the frequency channel is a physical uplink control channel (PUCCH).

11. The method of claim 9 , wherein the communication system implements a Long Term Evolution (LTE) air interface.

12. The method of claim 9 , wherein the communication system implements a Third Generation Partnership Project (3GPP) Fifth Generation (5G) air interface.

13. The method of claim 9 , wherein the reception comprises:

desired signal components present on the frequency channel and orthogonal to the at least one non-assigned despreading code; and

noise and interference that is uniformly distributed in power across the N spreading codes forming a basis for the reception.

14. The method of claim 9 , further comprising despreading the reception by:

during a first despreading stage:

despreading each combined symbol in a baseband signal, using at least one assigned despreading code in a first set of orthogonal sequences, to produce symbols from a subset of all users and a fraction of the noise; and

despreading each combined symbol using the at least one non-assigned despreading code in the first set of orthogonal sequences, to produce to produce a noise estimate represented by a set of additional zero-mean random variables.

15. The method of claim 14 , further comprising despreading he reception by:

during a second despreading stage:

despreading the symbols from the subset of all the users using one or more assigned despreading code in a second set of orthogonal sequences to obtain user symbols; and

despreading the symbols from the subset of all the users using the at least one non-assigned despreading code in the second set of orthogonal sequences to obtain an additional noise estimate represented by an additional set of zero-mean random variables.

16. The method of claim 15 , further comprising estimating the noise power by:

determining a variance, for each of a plurality of antennas, a variance of the zero-mean random variables for the non-assigned despreading codes; and

estimate the noise power by averaging the variances across the zero-mean random variables, and normalizing by a ratio of a total number of despreading codes to non-assigned despreading codes.