KR20030033124A - Upstream channel controlling device of cable modem - Google Patents

Abstract

PURPOSE: An upstream channel control device of a cable modem is provided to perform data transmission without delay by checking data time interval accurately. CONSTITUTION: A MAC(Media Access Control) chip(200) transmits data to a cable modem termination system using a MAC frame in upstream. A MAC chip driver(100) outputs a control signal to control operation of the MAC chip. And a physical layer(300) converts data applied from the MAC chip and then transmits it to a network. According to the MAC chip, a MAP processor(202) outputs information as to each section of a mini slot by analyzing MAP, and a ranging control part(201) corrects delay time of a REQ signal by the control signal applied from the MAC chip driver. A ranging processing part(204) controls ranging data of the REQ signal applied from the ranging control part when MAP information is applied from the MAP processor. A service queue(203) transmits user information and MAC management message by the control signal applied from the MAC chip driver. A data control unit(206) controls data of a corresponding mini slot section in correspondence to each section of the mini slot applied from the MAP processor. A REQ generation part(208) generates the REQ signal by a signal applied from the data control unit. A FIFO(First In First Out) buffer(210) stores information applied from the ranging processing part and the data control unit and the REQ generation part in sequence. And a data conversion unit converts information applied from the FIFO buffer in order to transmit it to the physical layer.

Description

Upstream channel controlling device of cable modem

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an up channel control apparatus for a cable modem, and more particularly, to a media access control defined in Radio Frequency Interface Specification 1.0 of DOCSIS protocol. A structure of an uplink channel of a MAC (hereinafter, referred to as a MAC) to locate a MAC frame accurately by placing a FIFO (First In First Out) buffer between a time division multiple access (TDMA) controller and a service queue. The present invention relates to an up channel control apparatus of a cable modem for fast transmission.

In general, cable modem network is a network system that is attracting attention along with general information communication network and multi-digital subscriber line in the field of remote access.It is connected to the Internet and intranet to provide subscribers with high speed data transmission speed of Mbps. Provides various services such as web search.

1 is a schematic diagram of a typical cable modem network, in which a plurality of cable modems (30 to 50) are located at a head end and provide a cable modem terminal system (20). A personal computer PC, which is a subscriber facility, is connected to each cable modem 30-50. In addition, a digital back-bone network (10) for receiving Internet multimedia services using cable modems (30 to 50) is connected to the CMTS (20).

Here, the cable modems 30 to 50 store packets of an upstream channel input from a PC and packets of a Dom stream input from the CMTS 20 in a buffer and a memory, respectively. To control this.

2 is a schematic diagram of an uplink channel of such a cable modem.

Referring to FIG. 2, the cable modem 30 includes a MAC chip 32 that processes a MAC frame to exchange data with the CMTS 20 using a MAC frame which is a basic transmission unit in an upstream stream. In addition, the MAC chip driver 31 for applying various programs and control signals for controlling the operation of the MAC chip 32 and the physical layer 33 for modulating the control signal applied from the MAC chip 32. It is composed.

However, the MAC chip of such a cable modem must accurately check the transmission time of data generated when the MAC frame is transmitted to the CMTS through an uplink channel. However, in the conventional MAC chip structure, the transmission time of the data cannot be accurately checked. There is a problem that a delay occurs.

The present invention was created to solve the above problems, and in particular, suggests the structure of the uplink channel of the MAC chip prescribed in Radio Frequency Interface Protocol 1.0 of the DOCSIS protocol to accurately check the data time interval without delaying data transmission. Its purpose is to.

1 is a schematic diagram of a typical cable modem network.

2 is a schematic diagram of an uplink channel of a typical cable modem;

Figure 3 is a detailed configuration of the MAC chip for the uplink channel control apparatus of the cable modem according to the present invention.

4 illustrates a data structure of a FIFO buffer in a MAC chip according to the present invention.

<Description of Symbols for Main Parts of Drawings>

100: MAC chip driver 200: MAC chip

300: physical layer

An apparatus for controlling an uplink channel of a cable modem of the present invention for achieving the above object includes a MAC chip for transmitting data to a cable modem terminal system using a MAC frame in an upstream stream, and a control signal for controlling the operation of the MAC chip. A MAC chip driver for outputting the data and a physical layer for converting data applied from the MAC chip and transmitting the data to the network; The MAC chip includes: a MAP processor for interpreting the MAP and outputting information on each section of the mini slot; A ranging controller for correcting a delay time of the REQ signal by a control signal applied from a MAC chip driver; A ranging processor configured to control ranging data of a REQ signal applied from the ranging controller when MAP information is applied from the MAP processor; A service queue for transmitting information on a user and a MAC management message by a control signal applied from a MAC chip driver; Data control means for controlling data of a corresponding minislot section corresponding to each section of the minislot applied from the MAP processor; A REQ generator for generating a REQ signal by a signal applied from the data control means; It consists of a FIFO buffer that sequentially stores the information applied from the ranging processor, the data control means and the REQ generator in the form of a MAC frame, and data conversion means for performing a transformation for transmitting the information applied from the FIFO buffer to the physical layer. It is characterized by.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.

The present invention relates to the implementation of the MAC chip of the upstream channel of a cable modem, and the basic functions such as SYNC (Synchronous), MAP, UCD (Upstream Channel Descripter), and related MAC management messages, and SID (Service) for defining services. IDentifier) is briefly described as follows.

First, the CMTS sends a counter value that operates on a global reference clock of 10.24 MHz to all cable modems through a SYNC message. The cable modem transmits a request signal to the CMTS and receives a response signal from the CMTS to actually transmit data. Accordingly, the cable modem uses the SYNC message sent from the CMTS to control the 10.24 MHz local clock to synchronize with the global reference clock of the CMTS. Here, a minislot divided by a predetermined time interval using a counter operated by a local clock of a cable modem is defined, and a field value of a minislot size of a UCD message defines its size.

In the present invention, it is assumed that a minislot counter and a minislot tick are provided as a result of processing the above-described messages. These minislot counters and minislot teak values are used to determine the transmission start time of the MAC frame in the MAC chip.

Next, the MAP message defines an uplink channel as a minislot interval. Each interval defines a cable modem that can use the interval and a MAC frame that can be transmitted according to the Interval Usage Code (IUC) and the SID. The modulation format is also determined in relation to the UCD.

In the present invention, a MAP processor is assumed. The MAP processor analyzes the MAP to determine the use time, size, and the like of each section, as well as to perform an interaction with a module using the section.

Figure 3 shows the detailed configuration of the MAC chip module to interact with the MAP processor.

Referring to FIG. 3, the cable modem according to the present invention includes a MAC chip 200 which processes a MAC frame to exchange data with a CMTS using a MAC frame which is a basic transmission unit in an upstream stream. In addition, the MAC chip driver 100 for applying various programs and control signals for controlling the operation of the MAC chip 200 and the physical layer 300 for modulating the control signal applied from the MAC chip 200. It is composed.

In this case, the MAC chip 200 is controlled by the ranging controller 201 and the service queue 203 receiving the control signal from the MAC chip driver 100 and the MAP control signal applied from the MAP processor 202. And a ranging processing unit 204, an REQ Grant processing unit 207, a REQ control unit 205, and a REQ / Data control unit 206 for controlling the (Information Elements). Then, from the FIFO buffer 210 that stores all the information applied from the ranging processor 204, the REQ Grant processor 207 and the REQ generator 208, from the ranging processor 204 and the DPLL (211) And a section checker 209 for checking each minislot section based on the applied information. In addition, the TDMA control unit 212 controls time-division multiple access by data applied from the DPLL 211 and the FIFO buffer 210, and the data applied from the TDMA control unit 212 to the physical layer 300. A UTOPIA 213 and a physical layer 300 for modulating data applied from the UTOPIA 213 are provided.

Here, six types of IEs defined in the above-described MAP processor are as follows.

First, REQ (Request) is a signal that provides a minislot interval of upstream when a bandwidth allocation for upstream data transmission is requested to the CMTS, and REQ / Data is an upstream stream when a short data packet is requested. This signal provides the minislot spacing. In addition, Initial Maintenance is provided as a mini slot when a new cable modem is connected to a network, and Station Maintenance is provided as a mini slot for continuous ranging by a cable modem. In addition, data grants provide an opportunity for a cable modem to transmit one or more upstream protocol data units (PDUs). Short data grants are used when the data to be transmitted is less than or equal to the maximum burst size specified in UCD. Long data grant is used when there is more transmission data than the maximum transmission data amount defined in UCD.

As above, the role of the service queue can be limited to data transmission by classifying the processing module according to the IUC and the SID.

In the configuration of FIG. 3, the ranging controller 201 corrects the delay time by measuring the real-time distance of the REQ signal by the control signal applied from the MAC chip driver 100. In this case, the ranging processing unit 204 needs to transmit the ranging REQ data to the station maintenance periodically transmitted, so that the ranging processing unit 204 separates it from other MAC frames. The service queue 203 transmits information about a user and a MAC management message to the REQ Grant processor 207 by a control signal applied from the MAC chip driver 100.

When the ranging processing unit 204 receives information on the Station Maintenance and Initial Maintenance intervals from the MAP processor 202, the ranging processing unit 204 processes the ranging REQ data applied from the ranging control unit 201. Transfer to the FIFO buffer 210.

If the SID value of the signal applied from the MAP processor 202 is a unicast short data grant or long data grant section, the REQ Grant processing unit 207 may provide information about the section. Transfer to the FIFO buffer 210. Here, the REQ Grant processing unit 207 checks whether the Grant has arrived late from the section checker 209 in the case of the unicast section, and if not, transfers the MAC frame to the FIFO buffer 210 according to the state. .

In addition, when the MAP information applied from the MAP processor 202 is a REQ that is a broadcast / multicast period, the REQ control unit 205 divides the REQ into smaller sections in which the REQ can be transmitted and transmits it to the REQ Grant processing unit 207. .

When the signal applied from the MAP processor 202 is REQ / Data, which is a multicast section, the REQ / Data controller 206 divides the REQ / Data section into smaller sections according to the SID and transmits the divided sections to the REQ Grant processing unit 207. do.

Meanwhile, the FIFO buffer 210 stores information transmitted from the ranging processor 204, the REQ Grant processor 207, and the REQ generator 208 in a MAC frame in order to sequentially transmit the information to the TDMA controller 212. .

Then, the section checker 209 compares the minislot counter applied from the ranging processor 204 and the DPLL 211 with the start time of each section, and compares the FIFO buffer 210 with the minislot start time of each section. Check the deadline of the MAC frame to be saved. The REQ Grant processing unit 207 receives each section signal from the MAP processor 202, the REQ control section 205, and the REQ / Data control section 206, which use the required section according to the state of the section check section 209. Unnecessary sections can be ignored. In detail, when the ranging processor 204 receives the Initial Maintenance data from the MAP processor 202, the interval may be ignored if the status is a periodic ranging state. However, in case of Station Maintenance, the MAC frame applied from the ranging controller 201 is transmitted to the FIFO buffer 210 in the structure of FIG. 4. However, if the information about the section arrives too late, the section checker 209 passes it to the ranging processor 204 to ignore the section.

The TDMA controller 212 compares the mini slot counter signal applied from the DPLL 211 and the start time of the MAC frame applied from the FIFO buffer 210 to physically modulate the modulation format of the MAC frame applied from the FIFO buffer 210. Control to transfer to the modulator of the layer (300). Here, the TDMA control unit 212 starts the operation according to the state of the FIFO buffer 210 transmits all MAC frames and stops the operation when there are no more MAC frames to be transmitted in advance or arrives too late. Discard the MAC frame.

In addition, the UTOPIA 213 is an Asynchronous Transfer Mode (ATM) forum data protocol controller, and transmits data applied from the TDMA controller 212 to the physical layer 300 using the ATM forum data protocol.

4 shows the data structure of such a FIFO buffer.

Referring to FIG. 4, the 3-bit burst profile field is used to transmit the modulation format of each MAC frame to the TDMA controller 212 via UCD when the MAC frame is transmitted to the cable network through the modulator. . Here, the ranging processing unit 204 should specify a burst profile that defines the format of station maintenance, initial maintenance, REQ generation unit 208 may specify the format of REQ, REQ / DATA, Grant, REQ Grant processing unit 207 may specify the format of REQ / DATA and Grant.

In addition, the value of the Tx Time In Minislot field defines the start time of a subsequent MAC frame. In addition, the 12-bit Tx byte Length field relates to size information of the MAC frame to be transmitted, and the TDMA controller 212 uses the Tx byte Length field value applied from the FIFO buffer 210 to transmit the MAC frame. Recognize size. Therefore, the FIFO buffer 210 of the present invention can transmit data to the physical layer using the data structure as shown in FIG.

As described above, in the present invention, a FIFO buffer may be provided between the TDMA controller and the service queue to design two functions independently. In addition, in order to separate the ranging process from the data transmission function, a ranging processing module for separately managing the ranging control unit may facilitate processing of a station maintenance interval that occurs periodically.

Claims (6)

A MAC chip for transmitting data to a cable modem terminal system using a MAC frame in an upstream stream; A MAC chip driver for outputting a control signal for controlling the operation of the MAC chip; And a physical layer for converting data applied from the MAC chip and transmitting it to a network. The MAC chip is A MAP processor for interpreting the MAP and outputting information on each section of the mini slot; A ranging controller configured to correct a delay time of the REQ signal by a control signal applied from the MAC chip driver; A ranging processor for controlling ranging data of an REQ signal applied from the ranging controller when MAP information is applied from the MAP processor; A service queue for transmitting information on a user and a MAC management message by a control signal applied from the MAC chip driver; Data control means for controlling data of a corresponding minislot section corresponding to each section of the minislot applied from the MAP processor; A REQ generator for generating a REQ signal by a signal applied from the data control means; A FIFO buffer which sequentially stores information applied from the ranging processor, the data control means, and the REQ generator in the form of the MAC frame; And And a data conversion means for converting the information applied from the FIFO buffer to the physical layer. The method of claim 1, A phase locked loop for generating an arbitrary frequency by an external control signal; And And a section checker for checking a start time of each section of the minislot by comparing the signal applied from the ranging processor with the phase-locked loop. The method of claim 2, wherein the data conversion means A TDMA controller for performing data conversion for transmitting the format of the MAC frame to the physical layer by comparing the counter signal of the mini slot applied from the FIFO buffer and the start time of the MAC frame applied from the DPLL; And And a data protocol control unit for transmitting data applied to the TDMA control unit to the physical layer using a specific data protocol. The method of claim 1, wherein the data control means A REQ grant processor for controlling data of a section in which minislot information applied from the MAP processor is a unicast according to a control signal applied from the service queue; A REQ controller for dividing REQ data into smaller sections when the minislot information applied from the MAP processor is a broadcast / multicast section and transmitting the divided REQ data to a smaller section; If the signal applied from the MAP processor is a multicast section, the REQ / data section is divided into a smaller section is composed of a REQ / data control unit for transmitting to the REQ grant processing unit, characterized in that the cable modem up channel control apparatus. The method of claim 1, wherein the data conversion means And a data conversion means for converting the information applied from the FIFO buffer to the physical layer. The method of claim 1, wherein the FIFO buffer A burst profile field for transmitting the modulation format of the MAC frame to the data conversion means; A minislot time field controlling a start time of the minislot; Transmission byte control field for managing the size information of the MAC frame to be transmitted; And And an MAC frame for sequentially storing data information applied from the data control means.