High-speed serial interface for orthogonal frequency division multiplexing (OFDM) cable modems
A high-speed serial interface (HSIF) for communicating between an analog front end (AFE) and a System on a Chip (SoC) digital radio via a bi-directional serial bit connection for an OFDM cable modem includes generating Status Frames and Data Frames to be communicated between the tuner and AFE and sending the generated Status Frames and Data Frames on a continual basis. Each Frame is a 10-bit K.28 Comma Sync word followed by a payload and when no data is queued to be communicated, Status Frames are sent asynchronously as filler frames.
1. A communication device in an orthogonal frequency division multiplexing (OFDM) enabled modem having an analog front end (AFE) and a digital radio, the communication device comprising:
the AFE configured to send and receive OFDM modem channels, down convert received OFDM channels into a plurality of I and Q digital samples, the AFE including a high-speed serial interface (HSIF) to communicate the plurality of OFDM I and Q digital samples to the digital radio by continually generating and transferring downstream frames to the digital radio, wherein the downstream frames include data frames and status frames comprising a control portion followed by a payload, the downstream data frames including at least one redundant byte for error detection, the data frames including baseband samples for OFDM channels received by the communication device in their payload.
2. The communication device of claim 1 wherein each frame comprises a plurality of 8/10b encoded words.
3. The communication device of claim 1 wherein said downstream data frames include a frame sync, a header, 238 data payload words each including 68 I and Q digital sample pairs and wherein said downstream data frames including an error detection portion at their end that includes the at least one redundant byte.
4. The communication device of claim 3 wherein the error detection portion comprises one of a cyclic redundancy check (CRC) or Reed Solomon (RS) forward error correction block code.
5. The communication device of claim 1 wherein the HSIF of the AFE comprises at least one of: a framer, a deframer, a serializer or a deserializer.
6. The communication device of claim 5 further comprising:
the digital radio including a second HSIF comprising a second framer/deframer and a second serializer/deserializer.
7. The communication device of claim 1 wherein the AFE and HSIF are configured to down convert two downstream OFDM channels at a 6 gigabit per second (Gbps) serial rate transfer to the digital radio in a full rate mode (FM).
8. The communication device of claim 1 wherein the AFE and HSIF are configured to down convert one downstream OFDM channel at a 3 Gbps serial rate transfer to the digital radio in a half rate mode (HM).
9. The communication device of claim 6 wherein the digital radio comprises a System on a Chip (SoC) coupled to the AFE via a bi-directional serial interface.
10. The communication device of claim 1 wherein the OFDM-enabled modem is compliant with a Data Over Cable Service Interface Specification (DOCSIS) 3.1.
11. A device configured to communicate orthogonal frequency division multiplexed (OFDM) signals upstream and downstream with a network, the device comprising:
a digital radio including a high speed serial interface (HSIF) to receive digital samples of two OFDM downstream radio frequency (RF) channels and digital samples of two downstream quadrature amplitude modulated (QAM) channels from a separately provided analog front end (AFE), the HSIF sending and receiving constant frames over a bi-directional serial connection to and from the AFE in the form of status and data frames, wherein when no data is needed to be transferred, status frames are inserted asynchronously as filler frames, said status and data frames comprising a control portion and a payload.
12. The device of claim 11 wherein each frame comprises a plurality of 8/10b encoded words and wherein a K28.5 identifies the data frames and K28.1 identifies status frames.
13. The device of claim 11 wherein said downstream data frames include a frame sync, a header, 238 data payload words each including 68 I and Q digital sample pairs and wherein said downstream data frames including an error detection portion at their end that includes the at least one redundant byte.
14. The device of claim 13 wherein the error detection portion comprises one of a cyclic redundancy check (CRC) or Reed Solomon (RS) forward error correction block code.
15. The device of claim 11 wherein the HSIF of the digital radio comprises a framer/deframer and a serializer/deserializer.
16. The device of claim 15 further comprising:
the AFE including a second HSIF comprising a second framer/deframer and a second serializer/deserializer.
17. The device of claim 11 wherein the digital radio and HSIF are configured to sample, frame and serialize upstream data to send to the AFE at a 600 Mega samples per second (Msps) rate for 15-bit real samples fed least significant bit (LSB) first to most significant bit (MSB).
18. The device of claim 16 wherein the digital radio comprises a System on a Chip (SoC) coupled to the AFE via a bi-directional serial interface.
19. The device of claim 18 wherein the device comprises a cable modem compliant with a Data Over Cable Service Interface Specification (DOCSIS) 3.1 standard.