Systems and methods for delta-sigma digitization
A baseband processing unit includes a baseband processor configured to receive a plurality of component carriers of a radio access technology wireless service, and a delta-sigma digitization interface configured to digitize at least one carrier signal of the plurality of component carriers into a digitized bit stream, for transport over a transport medium, by (i) oversampling the at least one carrier signal, (ii) quantizing the oversampled carrier signal into the digitized bit stream using two or fewer quantization bits.
1. A digital radio frequency transmitter, comprising:
a digital signal processor configured to (i) digitize an input analog carrier signal in a baseband at a predetermined sampling rate to produce a sampled analog signal, (ii) perform baseband processing within a digital domain of the transmitter, and (iii) produce the sampled analog signal as a sampled in-phase signal portion and a sampled quadrature signal portion separate from the sampled in-phase signal portion;
an up-sampling unit configured to up-sample baseband components of the sampled analog signal;
a digital up-converter configured to combine and up-convert the up-sampled baseband components; and
a bandpass delta-sigma modulator configured to encode the up-converted baseband components into a digitized bit stream for output to a transport medium.
2. The transmitter of claim 1 , wherein the up-sampling unit, the digital up-converter, and the bandpass delta-sigma modulator are further configured to operate within digital domain portion.
3. The transmitter of claim 1 , wherein the up-sampling unit comprises a first sub-unit configured to up-sample the sampled in-phase signal portion, and a second sub-unit configured to up-sample the sampled quadrature signal portion.
4. The transmitter of claim 3 , wherein the digital up-converter is further configured to combine the up-sampled in-phase signal portion and up-sampled quadrature signal portion.
5. The transmitter of claim 4 , wherein the digital up-converter is further configured to operate at a clock rate substantially equal to four times a carrier frequency of the input analog carrier signal.
6. The transmitter of claim 1 , wherein the bandpass delta-sigma modulator further comprises a noise-shaping unit configured to push quantization noise contained within the up-sampled baseband components out of a signal band of the input analog carrier signal.
7. A communication system, comprising:
a core network;
a central unit (CU) in operable communication with the core network;
a distributed unit (DU) in operable communication with the CU, the DU including a next generation fronthaul interface (NGFI) and a first digital transceiver, wherein the first digital transceiver comprises (i) a digital high radio frequency (high-RF) layer, (ii) a digital RF transmitter including an up-sampling unit, an up-conversion unit, and a delta-sigma modulator, and (iii) a digital RF receiver including a down-sampling unit, a down-conversion unit, and a delta-sigma analog-to-digital converter (ADC); and
a radio resource unit (RRU) including a second digital transceiver having a low radio frequency (low-RF) layer,
wherein the low-RF layer of the RRU is configured for operable communication, over a communication medium, with the high-RF layer of the first digital transceiver through the NGFI, and
wherein the NGFI is configured to implement a downstream function split between the digital RF transmitter and the low-RF layer of the RRU.
8. The system of claim 7 , wherein the communication medium is one of a wired and a wireless medium.
9. The system of claim 8 , wherein the communication medium is a wired medium comprising at least one of a single mode fiber and a pair of optical transport fibers.
10. The system of claim 8 , wherein the communication medium is a wireless medium, and wherein the RRU further includes an antenna.
11. The system of claim 7 , wherein the second digital transceiver further includes a bandpass filter configured to receive an input digitized bit stream from the first digital transceiver.
12. The system of claim 11 , wherein the second digital transceiver is configured to extract an analog signal from an output digitized bit stream from the bandpass filter.
13. The system of claim 11 , wherein the second digital transceiver includes a power amplifier disposed between the bandpass filter and the communication medium.
14. The system of claim 13 , wherein the low-RF layer includes the bandpass filter and the power amplifier.
15. The system of claim 14 , wherein functionality of the high-RF layer is consolidated within the DU.
16. A communication system, comprising:
a core network;
a central unit (CU) in operable communication with the core network;
a distributed unit (DU) in operable communication with the CU, the DU including a next generation fronthaul interface (NGFI) and a first digital transceiver, wherein the first digital transceiver comprises (i) a digital high radio frequency (high-RF) layer, (ii) a digital RF transmitter including an up-sampling unit, an up-conversion unit, and a delta-sigma modulator, and (iii) a digital RF receiver including a down-sampling unit, a down-conversion unit, and a delta-sigma analog-to-digital converter (ADC); and
a radio resource unit (RRU) including a second digital transceiver having a low radio frequency (low-RF) layer,
wherein the low-RF layer of the RRU is configured for operable communication, over a communication medium, with the high-RF layer of the first digital transceiver through the NGFI,
wherein the NGFI is configured to implement an upstream function split between down-conversion unit and the delta-sigma ADC of the digital RF receiver.