# US 10,320,678 B2 · Mapping control protocol time onto a physical layer

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- Number: US 10,320,678 B2
- Document ID: US10320678B2
- Status: Granted
- Kind: B2
- Application number: 14/657,458
- Filed: 2015-03-13
- Published: 2015-09-24
- Granted: 2019-06-11
- Earliest claimed: 2014-03-21
- Assignees: Avago Technologies International Sales Pte. Limited
- Applicants: Broadcom Corporation
- Inventors: Ryan Edgar Hirth
- Web page: https://patentgrep.com/patent/US10320678B2

## CPC

- H04L 47/12: Avoiding congestion; Recovering from congestion
- H04L 47/25: with rate being modified by the source upon detecting a change of network conditions
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

An IDLE insertion technique maps MPCP time onto an EPoC PHY. The techniques address the variability of bandwidth due to bit loading over time. The techniques allow MPCP time to follow wall time at the MAC layer while tracking bytes at the PMD layer. The techniques also facilitate use of the EPON MAC with few changes in an EPoC environment. The bandwidth allocation messages may follow the same format as in EPON, and the techniques may implement IDLE insertion that accounts for EPoC PHY FEC overhead and datarate differences compared to the MAC.

## Claims

### Claim 1

A method comprising:
in a communication device comprising a Media Access Control (MAC) layer and a Physical (PHY) layer:
determining a MAC layer data rate of the MAC layer;
determining a PHY layer data rate at which communication will occur over a physical communication medium; and
at the MAC layer:
determining a rate difference between the MAC layer data rate and the PHY layer data rate;
communicating a data flow from the MAC layer to the PHY layer, the data flow comprising data for communication over the physical communication medium, including inserting IDLE characters into the data flow responsive to the rate difference; and
in the PHY layer, replacing, prior to forward error correction encoding, selected IDLE characters among those inserted into the data flow at the MAC layer with data bytes of the data flow received from the MAC layer to adapt to the rate difference between the MAC layer and the PHY layer.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
determining an error correcting overhead incurred in the PHY layer; and
accounting for the error correcting overhead in the rate difference used for inserting the IDLE characters.

### Claim 3 (depends on 1)

The method of claim 1, further comprising:
in the PHY layer, replacing selected IDLE characters among those inserted at the MAC layer with data bytes to adapt to the rate difference between the MAC layer and the PHY layer.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
in the PHY layer, replacing other selected IDLE characters among those inserted at the MAC layer with parity bits generated from the forward error correction coding.

### Claim 5 (depends on 1)

The method of claim 1, where inserting comprises:
inserting the IDLE characters for the PHY layer to perform rate conversion to account for the rate difference and run the physical communication medium at the PHY layer data rate.

### Claim 6 (depends on 1)

The method of claim 1, where:
the MAC layer data rate is a constant rate;
the PHY layer data rate is a subrated rate with respect to the MAC layer data rate; and
where inserting comprises:
inserting the IDLE characters to facilitate adaptation of the constant rate of the MAC layer to the subrated rate of PHY layer.

### Claim 7 (depends on 1)

The method of claim 1, where the data flow comprises a packet comprising:
a packet starting point followed by an interpacket gap.

### Claim 8 (depends on 7)

The method of claim 7, further comprising:
referencing packet timing to the packet starting point.

### Claim 9 (depends on 8)

The method of claim 8, where inserting comprises:
inserting the IDLE characters in the data flow after the packet starting point and prior to the interpacket gap so that packet timing is maintained after:
mapping the data flow to carriers on the physical communication medium and recovery of the data flow by applying an inverse of the mapping at a receiver.

### Claim 10 (depends on 9)

The method of claim 9, further comprising:
in the PHY layer, transferring specific bytes of the packet into locations held by specific IDLE characters among those inserted at the MAC layer with data.

### Claim 11 (depends on 9)

The method of claim 9, further comprising:
in the PHY layer, replacing selected IDLE characters among those inserted at the MAC layer with data accumulated from the data flow that is temporarily held to accommodate for the rate difference.

### Claim 12

A system comprising:
control circuitry characterized by a control layer data rate; and
communication medium circuitry comprising:
a communication interface to a communication medium; where:
the communication medium characterized by a transmit data rate at which
the communication interface places data onto the communication medium; at the control circuitry:
determining a rate difference between the control layer data rate and the transmit data rate;
preparing a data flow for the communication medium circuitry; and
responsive to the rate difference, inserting spacing characters in the data flow to the communication medium circuitry, wherein the spacing characters are inserted into the data flow after a start of a packet and before an interpacket gap; and
the communication medium circuitry configured to:
replace selected spacing characters among those inserted into the data flow at the control circuitry with data bytes of the data flow received from the control circuitry to adapt to the rate difference between the control layer data rate and the transmit data rate.

### Claim 13 (depends on 12)

The system of claim 12, where the control circuitry is further configured to:
determine an error coding overhead incurred by the communication medium circuitry; and
where the rate difference accounts for the error coding overhead, the control layer data rate, and the transmit data rate.

### Claim 14 (depends on 12)

The system of claim 12, where:
the control circuitry comprises a Media Access Control (MAC) layer configured to receive data from an optical communication interface.

### Claim 15 (depends on 12)

The system of claim 12, where:
the communication medium circuitry comprises a Physical (PHY) layer and the communication interface comprises a coaxial cable interface.

### Claim 16 (depends on 12)

The system of claim 12, where the communication medium circuitry is configured to:
replace other selected spacing characters among those inserted by the control circuitry with parity bits generated from forward error correction coding.

### Claim 17 (depends on 12)

The system of claim 12, where the data flow includes a packet comprising:
a packet starting point and where the control circuitry is configured to reference packet timing to the packet starting point.

### Claim 18 (depends on 17)

The system of claim 17, where:
an interpacket gap follows the packet; and where:
the control circuitry is configured to insert spacing characters in the data flow after the packet starting point and prior to the interpacket gap so that packet timing is maintained after:
mapping the data flow to frequency sub-carriers on the communication medium and recovery of the data flow by applying an inverse of the mapping at a receiver.

### Claim 19

A system comprising:
an optical communication interface;
a coaxial communication interface;
control circuitry in communication with the optical communication interface and the coaxial communication interface, the control circuitry comprising:
a Media Access Control (MAC) layer configured to operate at a fixed MAC layer data rate; and
a Physical (PHY) layer configured to transmit data through the coaxial communication interface at a PHY layer data rate subrated with respect to the fixed MAC layer data rate; where:
the MAC layer is configured to:
determine a rate difference between the fixed MAC layer data rate and the PHY layer data rate;
communicate a datastream from the MAC layer to the PHY layer, the datastream comprising data bits for communication through the coaxial communication interface; and
insert, into the datastream, IDLE characters for adapting the PHY layer to the rate difference; and
the PHY layer is configured to:
hold data from the datastream received from the MAC layer; and
replace selected IDLE characters among those inserted at the MAC layer with the data from the datastream that was held in the PHY layer due to the rate difference.

### Claim 20 (depends on 19)

The system of claim 19, where:
the MAC layer is further configured to:
determine an error coding overhead added by the PHY layer;
where the rate difference accounts for the error coding overhead, the MAC layer data rate, and the PHY layer data rate;
insert a packet into the datastream followed by an interpacket gap, the packet comprising a packet starting point to which the MAC layer references packet timing; and
insert the IDLE characters in the datastream after the packet starting point and prior to the interpacket gap so that packet timing is maintained after:
mapping the datastream to frequency sub-carriers in the PHY layer and recovering the datastream by applying an inverse of the mapping.