Digital microwave radio link with a variety of ports
View Patent ↗A microwave radio terminal capable of multiple gigabits/sec bit rate is provided. The radio terminal may use QAM modulation, including the two lowest modulation formats of BPSK and QPSK. The serial bit stream, including forward error correction (FEC) and all other overhead, is prepared in a digital circuit, such as a filed programmable gate array (FPGA) and is output serially, using SERDES devices inside the FPGA, as two separate channels known as “I-channel” and “Q-channel”.
1. A rate-adaptive digital microwave radio terminal at frequencies above 30 GHz and at least one operating mode with aggregate bit rate exceeding 1 gigabits per second, the radio terminal comprising:
a quadrature modulator having an I-port to receive an I-channel and a Q-port to receive a Q-channel wherein the quadrature modulator generates a modulated signal;
a digital processing unit with at least two SERDES ports including a first SERDES port transmitting a serial bit stream directed to the I-port of the quadrature modulator and a second SERDES port transmitting a serial bit stream directed to the Q port of said quadrature modulator;
and the digital processing unit switches bit rates based on a link condition.
2. The terminal of claim 1 , wherein the first SERDES port serial bit stream passes through a filter before it is input to the I-port of the quadrature modulator and wherein the second SERDES port serial bit stream passes through a filter before it is input to the Q-port of the quadrature modulator.
3. The terminal of claim 2 , wherein each filter further comprises a switched bank of one or more filters with each filter of the switched bank of filters corresponding to a different symbol rate.
4. The terminal of claim 1 further comprising a data segregating unit and a data mapping unit having at least two priorities and wherein one of the I-port and Q-port contains lower priority data segregated and mapped onto a low-priority port.
5. The terminal of claim 4 , wherein said low priority port is disabled during a link fade event.
6. The terminal of claim 5 , wherein each port outputs binary phase shift keying (BPSK) symbols and the combined traffic of the ports are output as quaternary phase shift keying (QPSK) symbols.
7. The terminal of claim 5 , wherein the disabled low priority port degrades the modulator from QPSK modulation to BPSK modulation.
8. The terminal of claim 4 , wherein the data segregating unit further comprises an Ethernet Switch.
9. The terminal of claim 4 , wherein the data mapping unit further comprises a digital multiplexer.
10. The terminal of claim 9 , wherein the digital multiplexer further comprises a payload framer.
11. The terminal of claim 10 , wherein the payload framer maps at least some of the data of lower priority to distinct positions within said payload frame.
12. The terminal of claim 11 , wherein the distinct positions of said payload frame are mapped to one specific subset of the SERDES ports.
13. The terminal of claim 1 , wherein the digital processing unit is a field programmable gate array.