Background [0002] The present invention is generally related to identifying sources and intended recipients in a communications protocol, and more specifically to identifying ports in a cable modem protocol.

[0003] A typical cable modem specification, such as the data over cable service interface specification (DOCSIS), restricts communications between a base station and remote stations to using Ethernet addressees as the filtering scheme at the remote stations.

A further limitation is typically presented by the requirement that an Ethernet address must be assigned to each POTS (plain old telephone service) interface. An improved scheme is desired.

[0004] In one embodiment, a method for identifying an intended recipient of information conveyed by a signal in a point to multi-point system includes determining the intended recipient in accordance with a port identification portion of the signal. The signal comprises at least one frame. Each frame comprises a header portion configured to identify contents of a respective frame, a protocol data unit (PDU) portion configured to contain data, and the port identification portion having a port identifier configured to identify an intended recipient of information contained in the respective frame.

[0005] In another embodiment, a base station in a point to multi-point system includes a memory portion for storing at least one port identifier indicative of an intended recipient in the point to multi-point system. The system includes a transmitter portion configured to transmit at least one signal comprising at least one frame. Each frame includes a header portion configured to identify contents of a respective frame, a protocol data unit (PDU) portion configured to contain data, and a port identification portion having a respective port identifier in said respective frame. The system also includes a

formater portion configured to format the at least one signal to contain the port identification portion within a respective frame.

[0006] In yet another embodiment, a remote station in a point to multi-point system includes a receiver portion configured to receive at least one signal comprising at least one frame. Each frame includes a header portion configured to identify contents of a respective frame, a protocol data unit (PDU) portion configured to contain data, and a port identification portion having a respective port identifier in the respective frame. The port identifier being indicative of an intended recipient in the point to multi-point system.

The system also includes a decoder portion configured to decode the port identifier to determine an intended recipient.

Brief Description of the Drawings [0007] In the drawings: [0008] Figure 1 is a diagram illustrating the format of one embodiment of a signal having a header portion and a data portion, wherein the data portion includes a port identification portion appended to one, in accordance with an embodiment of the present invention; [0009] Figure 2 is a diagram illustrating the format of another embodiment of a signal having a header portion and a data portion, wherein the header portion includes a port identification portion appended to one end of an extended header portion, in accordance with an embodiment of the present invention; [0010] Figure 3 is a block diagram of a point to multi-point system utilizing a port identifier in accordance with an embodiment of the present invention; [0011] Figure 4 is a functional block diagram of a base station in accordance with an embodiment of the present invention; [0012] Figure 5 is a is a functional block diagram of remote station in accordance with an embodiment of the present invention; and

[0013] Figure 6 is a flow diagram of an exemplary process for identifying an intended recipient in a point to multi-point system utilizing a port identification portion in accordance with an embodiment of the present invention.

Detailed Description [0014] A system and method for identifying an intended recipient in a point to multi-point system utilizing a port identifier, as described herein include formatting signal frames in the communications protocol used to convey information in the system.

The system and method are particularly applicable to formatting signal frames of signals used to convey information between a cable modem (CM) and a cable modem termination system (CMTS) conforming to the data over cable service interface specification (DOCSIS). In one embodiment, a port identifier is appended to the data portion of the frame, e. g., the protocol data unit (PDU) portion of a frame. In another embodiment, the port identifier is appended to the header portion of the frame. The addition of this port identifier increases the number of potential intended recipients that may be addressed. For example, a two-byte, i. e., 16 bit, port identifier increases addressability by 216 = 65,536.

[0015] Figure 1 and Figure 2 illustrate two embodiments of a signal frame 12 having a port identification portion 28. Figure 1 is a diagram illustrating the format of a signal containing a port identification portion 28 for identifying intended recipients in a point to multi-point system. The frame 12 is a media access control (MAC) frame. A MAC frame refers to a portion of a signal formatted to have a header portion 14 and an optional variable length data protocol data unit (PDU) 30. The MAC frame 12 has a header portion 14 and a data portion 16, wherein the data portion 16 includes a port identification portion 28 appended to one end. The header portion 14 includes frame control (FC) field 18, MAC parameter (MAC_PARM) field 20, frame length (LEN) field 22, optional extended header (EHDR) field 24, and header check sequence (HCS) field 26. The FC field 18 identifies the contents of the frame 12. In one embodiment, the FC field 18 is located at the first byte position of frame 12, as shown in Figure 1. The MACPARM field 20 and the LEN field 22 indicate the length of the frame 12. The EHDR field 24 is optional. The length of the EHDR field 24 is variable between 0 and 240 bytes, inclusively. The HCS field 26 is used to ensure the integrity of the header

portion 14. In one embodiment, the data portion 16 includes a port identification (ID) portion 28 and data field 30 formatted in accordance with the packet protocol data unit (PDU) format. In another embodiment, as shown in Figure 2, the port ID portion 28 is positioned within the EHDR field 24. As shown in Figure 1, the port ID portion 28 may be appended to the data portion 16, or as shown in Figure 2, the port ID portion 28 may be appended to the EHDR field 24.

[0016] The port identification portion 28 contains a port identifier having a value, which is decodable and is associated with an intended recipient (destination) of information contained in the frame 12. The port ID portion 28 may be of any length. In one embodiment, the port ID portion 28 is 2 bytes. For example, if the port ID portion 28 is 2 bytes (16 bits) in length, the value of the port identifier for this port ID portion 28 may by be selected from 216 = 65,536 unique values. Each of these values may be associated with an intended recipient.

[0017] The format for frame 12, with the exception of the port ID portion 28, is in compliance with the data over cable service interface specification, referred to as DOCSIS. DOCSIS is a specification well known in the art. Further detail related to DOCSIS may be obtained from the following documents: Data-Over-Cable-Service Interface Specifications, Radio Frequency Interface Specification, SP-RFIv2. 0-I01- 011231; Data-Over-Cable-Service Interface Specifications, Cable Modem Termination System-Network Side Interface Specification, SP-CMTS-NSI-I01-010829 ; Data-Over- Cable-Service Interface Specifications, Cable Modem to Customer Premise Equipment Interface Specification, SP-CMCI-106-010829 ; Data-Over-Cable-Service Interface Specifications, Operations Support System Interface Specification, SP-OSSIv2. 0-I01- 012131; Data-Over-Cable-Service Interface Specifications, Cable Modem Telephony Return Interface Specification, SP-CMTRI-101-970804 ; Data-Over-Cable-Service Interface Specifications, Baseline Privacy Plus Interface Specification, SP-BPI-I07- 010829; Data-Over-Cable-Service Interface Specifications, Radio Frequency Interface Specification, SP-RFI-C01-011119 ; Data-Over-Cable-Service Interface Specifications, Baseline Privacy Interface Specification, SP-BPI-C01-011119 ; and Data-Over-Cable- Service Interface Specifications, Radio Frequency Interface Specification v 1.1, SP- RFIvl.l-I07-010829.

[0018] Figure 3 is a block diagram of a point to multi-point system 300 utilizing a port identifier as described herein. System 300 includes at least one base station 34 (also referred to as a base station), and at least one remote station 36 (also referred to as a remote station). Signals conveyed from the base station 34 to remote station 36 are referred to as downstream signals and signals conveyed from the remote stations 36 to the base station are referred to as upstream signals.

[0019] Downstream signals are broadcast to all remote stations 36 concurrently.

Downstream signals are formatted to include a security association identifier (SAID) for identifying a remote station as an intended remote station. The SAID is decoded, also referred to as filtered, to determine which remote station is the intended recipient. Thus, only the remote station with the proper SAID will receive the downstream signal.

Hardware limitations restrict the maximum number of concurrent SAIDs per remote station is limited to 16. Adding a port ID portion 28 to the DOCSIS signal format increases the number of potential intended recipients per remote station 36.

[0020] Upstream signals are time domain multiplexed. Thus the base station 34 "knows"which remote station 36 is transmitting by the time period in which the communication occurs. The port ID portion 28 of the upstream signal may be decoded to further determine the source of the signal associated with a remote station 36. For example, remote station 36 may have a several devices (lines) attached, such as Ethernet addressable lines, El lines, T1 lines, plain old telephone service (POTS) lines, constant bit rate clear channels, or a combination thereof. Each of these lines may be assigned an associated port identifier. Upon receiving a signal from a remote station, during its allotted time slot, the signal frame may be further decoded to determine the source, e. g., line/device, of the signal. Referring again to Figure 3, signal 38 represents a signal transmitted by base station 34 to a remote station 36, received by base station 34 from a remote station 36, or a combination thereof. The signals 40,42, and 44 are signals transmitted by remote stations 36, received by remote stations 36, or a combination thereof. Each of the signals 38,40,42, and 44 may comprise an upstream component and a downstream component.

[0021] Figure 4 is a functional block diagram of a base station 34. The base station 34 includes a formater portion 50, a transmitter/receiver portion 52, a memory

portion 54, and a decoder portion 56. In one embodiment, the transmitter portion of the transmitter/receiver portion 52 of base station 34 is configured to transmit signal 38, wherein signal 38 is formatted into at least one frame. Each frame includes a header portion 14, a protocol data unit (PDU) portion 30, and a port identification portion 28 having a port identifier. The port identifier represents the value of the contents of the port ID portion 28 indicating an intended recipient, or intended destination, associated with a remote station 36. The formater portion 50 is configured to format the signal 38 into frames containing the port identification portion 28. As previously described (See Figure 1), the port id portion 28 may be appended to the EHDR field 24 or the header portion 16 of each frame 12. The memory portion 54 is configured to store the port identifiers, which are indicative of respective intended recipients. The decoder portion 56 is configured to decode, e. g., demultiplex, the time multiplexed signal to determine the source remote station 36. The decoder portion 56 is also configured to decode the port identifiers of the port ID portions 28 of each frame 12 to determine the respective sources of the respective frames 12.

[0022] Figure 5 is a functional block diagram of remote station 36. The remote station 36 includes a transmitter/receiver portion 60 and a decoder portion 62. In one embodiment, the receiver portion of the transmitter/receiver portion 60 of remote station 34 is configured to receive at least one of signals 40,42, and 44, wherein each of signals 40,42, and 44 are formatted into at least one frame. Each frame includes a header portion 14, a protocol data unit (PDU) portion 30, and a port identification portion 28 having a port identifier. The port identifier represents the value of the contents of the port ID portion 28 indicating an intended source, associated with a remote station 36.

The decoder portion 62 is configured to decode the SAID contained in a signal to determine the intended remote station 36. The decoder portion 62 is also configured to decode the port identifiers of the port ID portions 28 of each frame 12 to determine the respective intended recipients of the respective frames 12.

[0023] Figure 6 is a flow diagram of an exemplary process for identifying an intended recipient and/or source in a point to multi-point system utilizing a port ID portion 28. Potential intended recipients/sources are assigned port identifiers at step 66.

This may be accomplished by the base station 34, by a remote station 36, by a separate

processor, or by a combination thereof. Further, this may be accomplished at the time the point to multi-point system is started, or at any appropriate time prior to communication between the base station 34 and the remote station 36. The port identifiers assigned to each potential intended recipient/source are stored at step 68. The port identifiers may be stored in any appropriate memory, such as memory portion 54 of base station 34. The stored port identifiers are accessible for decoding signals having port ID portions 28.

Signals are formatted to include the port ID portion 28, having a respective port identifier at step 70. This may be accomplished by any appropriate processor, such as formatter 50 of base station 34. The respective frames of the signals may be formatted to append the port ID portion 28 to an end of the data portion 16 or to end of the EHDR portion 24.

The port ID portion 28 may be encoded. This encoding may be accomplished by any appropriate encoding technique, which renders the port ID portion 28 capable of being decoded upon receipt of the respective signal. In one embodiment, the port ID portion is encoded in accordance with a predetermined extended header type field (EHTYPE).

The EHTYPE is a field contained in the EHDR field. A more detailed description of the EHTYPE field may be found in the DOCSIS Radio Frequency Interface Specification, SP-RFIv2. 0-I01-011231, December 31,2001.

[0024] The signals formatted to contain the port ID portion 28 (such as signals 38, 40,42,44, and/or 44) are conveyed at step 72. Conveying the signal may involve conveying signals from the base station 34 to remote station (s) 36, e. g., downstream, or from remote station (s) 36 to the base station 34, e. g., upstream. These signals may be conveyed by any appropriate means, such as transmitter/receiver portion 52 and/or transmitter/receiver portion 60 for example. If the signal is a downstream signal (step 74), the SAID of the conveyed downstream signal is decoded to determine the intended recipient remote station 36 at step 76. The port ID portion 28 of the signal frames 12 are decoded at step 78. This decoding determines the intended recipient of information contained in the respective frame of the respective signal. If the conveyed signal is an upstream signal (step 74), the time multiplexed signal is decoded, e. g. demultiplexed, at step 80 to determine the source remote station 36 of the respective portion of the signal.

The port ID portion 28 of the signal frames 12 are decoded at step 82, to determine the source of the respective portion of the signal.

[0001] The method and system for identifying a device in a point to multi-point system as described herein may be embodied in the form of computer-implemented processes and apparatus for practicing those processes. The method and system for identifying a device in a point to multi-point system may also be embodied in the form of computer program code embodied in tangible media, such as floppy diskettes, read only memories (ROMs), CD-ROMs, hard drives, high density disk, or any other computer- readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention.

The method and system for identifying a device in a point to multi-point system may also be embodied in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over the electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose processor, the computer program code segments configure the processor to create specific logic circuits.

[0002] Although illustrated and described with reference to certain specific embodiments, the method and system for identifying a device in a point to multi-point system as described herein is nevertheless not intended to be limited to the details shown.

Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention.