CN100502383C - A method and device for uplink decoding control - Google Patents

Abstract

The invention discloses a method for controlling RS decoding positioning of burst data packet on receiving end comprising the steps of, determining the time of arrival on the receiving end for each of the uplink business allocated in each uplink business bandwidth allocation device on the receiving end, establishing the corresponding relation between the business arrival time and business coding length for the cycle using MAP as periodic time on the receiving end, determining demodulator time sequence based on the determined business arrival time, thus producing the positioning signal needed by the decoder. The invention also discloses an apparatus for controlling RS decoding positioning of burst data packet on receiving end.

Description

A method and device for uplink decoding control

technical field

The present invention relates to a method and a device for determining the corresponding positions of effective data and Reed_Solomon (RS, Reed Solomon) codes in a burst data packet in the process of realizing uplink business transmission by using DOCSIS (Data Over Cable Service Transmission Specification), especially The invention relates to a method and a device for determining the corresponding positions of effective data and RS codes in the burst data packet for the data demodulated by a demodulator after the Reed_Solomon code is added to the sent burst packet.

Background technique

DOCSIS specifies the physical layer and media access control (MAC) layer protocol between the cable modem (CM) located in the customer premises and the cable modem termination system (CMTS) located in the carrier network. Between the CM and the CMTS is the cable network, which is at a minimum a traditional two-way tree and branch coax network.

DOCSIS is a high-speed bidirectional data transmission protocol on the HFC (Hybrid Fiber/Coaxial Cable) network, and the frequency range of its uplink channel is 5-42MHz. The uplink channel of DOCSIS uses a combination of FDMA and TDMA two access methods, and the frequency division multiple access (FDMA) method enables the system to have multiple uplink channels. The standard specifies the burst transmission format for time division multiple access (TDMA) access, supports flexible modulation methods, multiple transmission symbol rates and pre-bits, and supports fixed and variable length data frames and programmable Reed- Solomon block encoding, etc. DOCSIS flexible uplink FEC (forward error correction, Forward Error Correction) encoding enables system operators to specify the length of error correction data packets and the number of correctable bit errors in each packet.

Since it is easily interfered by other signals in the frequency range of 5-42MHz, in the point-to-multipoint broadband wireless communication system using the DOCSIS protocol as the air protocol, in order to improve the wireless transmission performance of the system and reduce the bit error in the wireless transmission process Reed_Solomon encoding is used in the baseband processing of the burst data stream sent uplink. In order to extract valid data from the Reed_Solomon encoded data stream at the receiving end, it is necessary to determine the position of the Reed_Solomon code in the uplink burst data. However, there is no such decoding function in the demodulation chip that adopts the DOCSIS protocol to realize the uplink burst packet at present. In addition, due to inaccurate ranging, there is a problem that the location of uplink burst data is misplaced.

Contents of the invention

The purpose of the present invention is to provide a method and device for controlling the Reed_Solomon decoder at the receiving end to locate the corresponding position of the Reed_Solomon decoding in the burst data packet after the uplink burst data is encoded using the DOCSIS protocol.

According to the first aspect of the present invention, there is provided a method for controlling the RS decoding and positioning in the burst data packet at the receiving end, wherein at the sending end, the uplink burst traffic is classified according to the DOCSIS protocol, and the MAC frame is divided into E1 traffic, IP traffic , management information business, request frame business, five kinds of ranging request frame business, according to the requirements of uplink bandwidth and system transmission reliability, select coded data with a set length for each kind of business, the method includes the steps: at the receiving end according to DOCSIS The sending time of the uplink service in the protocol is defined by the downlink MAP, and the downlink MAP determines the sending time of the sending end service, and determines the time when the service arrives at the receiving end according to the delay of the ranging; the receiving end takes the MAP as a period to establish the service arrival time The corresponding relationship with the service code length; determine the demodulator timing according to the determined service arrival time; locate the Reed-Solomon coded field in the uplink burst data in the data stream according to the DOSCSIS uplink burst data packet characteristics and demodulator timing The position in , so as to generate the positioning signal required by the decoder, and provide the K/T value switching signal required by the decoder, where K is the length of the data in the burst packet, and 2*T is the length of the RS code.

According to the second aspect of the present invention, an uplink decoding control device is provided, wherein the uplink burst business is classified according to the DOCSIS protocol at the sending end, and the coded data of an appropriate length is selected for each business according to the uplink bandwidth and system transmission reliability requirements , the device includes: a DOCSIS protocol processor, which is used to determine which uplink services are allocated by each MAP according to the MAP and system ranging information, and the coding parameter (K/T) value corresponding to each uplink service, and the service arrival The relationship table between time and K/T; the media access controller stores the relationship data formed by the DOCSIS protocol processor, generates the reference clock, and generates and outputs the control signal used to control the Reed Solomon (RS) decoder and parameters; the burst demodulator provides burst interface timing and RS encoded burst data stream to the decoder; RS decoder, according to the RS decoding control signal and parameters, burst data supplied by the burst demodulator The stream is decoded; and the decoded burst data stream and timing are output.

The invention solves the positioning problem at the receiving end of the service data RS decoding based on the DOCSIS uplink RS coding, and simultaneously solves the problem that the positioning of the uplink burst data is misplaced due to inaccurate distance measurement.

Description of drawings

The above-mentioned and other objects and advantages of the present invention will be made clearer by describing preferred embodiments of the present invention below in conjunction with the accompanying drawings, wherein

Fig. 1 is a receiving timing diagram for determining an uplink demodulator;

FIG. 2 is a block diagram showing uplink decoding control based on DOCSIS according to an embodiment of the present invention;

3 is a schematic diagram showing a mini-slot reference generator according to an embodiment of the present invention;

4 is a block diagram representing RS decoding control according to an embodiment of the present invention; and

FIG. 5 is a flowchart of RS decoding control processing according to an embodiment of the present invention.

Detailed ways

The principles and preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

In the DOCSIS standard, the MAC layer is above the uplink physical layer (or downlink transmission and convergence sublayer) and under the link security sublayer. One of the main features of the MAC protocol is that the CMTS assigns the upstream channel bandwidth to the CM. The upstream channel is composed of mini-slots, has the function of business classification, provides various data transmission rates, and supports virtual LAN at the data link layer.

The DOCSIS protocol has four major categories of MAC frames altogether, including the MAC frame based on the packet, the ATM cell MAC frame, the MAC frame of the PDU (protocol data unit), and the MAC frame of the specific header. In addition, in the present invention, the DOCSIS protocol Made an extension, adding a special MAC frame to transmit E1 services. Specific MAC frames include timing MAC frames (only for downlink), management MAC frames, request MAC frames, segmented MAC frames, and concatenated MAC frames. There are more than 20 types of MAC frames such as UCD, MAP, etc. for management MAC frames. In addition, the above MAC frames are classified into five types of MAC frames: E1 (European line standard) service, IP service, management information service, request frame service, and ranging request frame service. The uplink burst packets composed of five kinds of services are allocated to different characteristics, such as different encoding parameters.

According to the uplink bandwidth and system transmission reliability requirements, select the appropriate length of coded data for each service. The following table 1 lists the encoding parameters selected according to the frame characteristics of different uplink services, and select different Reed_Solomon encoding parameters for the uplink burst packets composed of different services to improve its correction under the condition of bandwidth utilization. wrong ability. The following is the selection parameter correspondence table.

Table 1

business name frame length (bytes) RS code K value RS coded T value IP business 88-1524 128 4 E1 business 2-514 64 3 management information 30-1534 128 4 request frame 6 6 2 ranging request 30 30 3

According to the DOCSIS protocol, the receiving end determines the moment when each uplink service allocated in each MAP (uplink service bandwidth allocation) arrives at the receiving end. The corresponding relationship between the service arrival time and the service code length is established at the receiving end with MAP as the cycle. The demodulator timing is determined according to the determined service arrival time. Position the Reed_Solomon coded field in the upstream burst data in the data stream according to the characteristics of the DOSCSIS upstream burst data packet and the timing of the demodulator, generate the positioning signal required by the decoder, and provide the K/T value switching signal required by the decoder. Among them, K is the length of the data in the burst packet, and 2*T is the length of the Reed_Solomon code. The requirement for selecting the encoding parameters is to increase the transmission bandwidth as much as possible within the allowable range of the air transmission bit error rate. For example, the length of the ranging request service data is 30, and the encoding parameter K is selected as 32, and T is 2, that is, the utilization ratio of valid information during transmission is 30/(2+2*2), where K is the effective data length, and 2 *T is the encoded byte length.

In the DOCSIS protocol, the sending time of the uplink service is defined by the downlink MAP. The sending timing of the service at the sending end is defined through the MAP, and the time when the service arrives at the receiving end is determined according to the delay of ranging. If it is specified that the sending time of an IP frame in a MAP is X time, and the uplink delay is Y, then the time when it arrives at the receiving end is X+Y time. Based on this, the moment when the uplink traffic arrives at the receiving end can be determined. The time when the service (IE) in each MAP arrives at the receiving end is in one-to-one correspondence with the coding parameter K/T allocated to this IE.

FIG. 1 shows a timing diagram for determining the reception of an uplink demodulator. That is, CLOCKOUT is the demodulation clock, DATA_VALID indicates that the demodulation data is valid, and DATA is data. The relationship is that the data is adopted on the falling edge of CLOCK during the effective period of DATA_VALID.

The following describes an apparatus for controlling a corresponding position of DOCSIS uplink RS decoding according to an embodiment of the present invention with reference to FIG. 2 . The device includes a processor 1 , a media access controller 2 , a burst demodulator 3 , and an RS decoder 4 . The processor 1 is connected to the media access controller 2 through a bus, and the burst demodulator 3 is connected to the RS decoder 4 through a demodulator interface signal line. As an example, the processor 1 can be a personal computer such as PowerPC (MC8240), but the present invention is not limited thereto. As an example, the burst demodulator 3 can use a 9257 demodulator. The media access controller 2 is connected to the RS decoder 4 through an interface line. Processor 1 is a DOCSIS protocol processor. It mainly processes the DOCSIS protocol. According to the MAP and system ranging information, it determines which uplink services are assigned to each MAP, and the K/T value corresponding to each uplink service, as well as the service arrival time and K/T relationship table. The media access controller 2 mainly stores the relationship data formed by the processor 1, generates a reference clock, and generates and outputs control signals and parameters for controlling the Reed-Solomon decoder.

The burst demodulator 3 provides the burst interface timing and the burst data stream encoded by Reed_Solomon. As an example, the burst demodulator 3 can use a 9257 demodulator. The RS decoder decodes the corresponding uplink service according to the decoding control signal and parameters. Provide decoded burst data flow and timing. The burst demodulator 3 provides the demodulation clock CLK to the RS decoder 4, the demodulation data DATA, the data valid indicator DATA_VALID, and the demodulation clock GUARD_CLK during the valid data period. In the RS decoder 4, the interface signal lines of the burst demodulator 3 are sent to the media access controller 2 all the way to generate the decoding control signals (RSCS0, RSCS1, CHECKNUM) required by the RS decoder, and all the way is used for decoding . The RS decoder 4 sends the last decoded data, clock, and burst data valid indication to the MAC controller 4 for extracting valid service data from various services. Other interfaces between the media access controller 2 and the RS decoder 4 are defined as follows: CLK_B is the demodulation clock from the burst demodulator 3, DATA_B is the demodulated data from the burst demodulator 3, and DATA_VALID_B is the demodulation clock from the burst demodulator 3. The data legal signal of the demodulator 3, GUARD_CLK_B is the clock from the data legal period of the burst demodulator 3, RSCS0 indicates the decoding parameter selection switch of the RS decoder 4, RSCS1 indicates the decoder decoding parameter selection switch, RS_EN indicates the decoding enable Enable signal, CHECKSUM represents the position positioning signal of the decoding code word, the high level period is the effective data period, and the low level period is the decoding period. CLK_N represents the output clock of the RS decoder 4, DATA_N represents the demodulated data output by the RS decoder 4, CHECKSUM_N represents the decoding code word position positioning signal output by the RS decoder 4, a high level indicates a valid data period, and a low level indicates during decoding.

Fig. 3 is a mini-slot reference generator according to the present invention for providing a reference clock. The time scale counter is a 32-bit counter with a count clock of 1024Mhz. The processor 1 provides the clear signal Start_Clear to the time scale counter 5. The micro-slot counter 6 is synchronized with the time scale counter 5. The time scale counter 5 increases by 256, The minislot counter is incremented by 1.

2 and 4 is the operation process of controlling the RS decoder 4 below. The clock counter 3 is supplied with a clear signal Start_Clear from the processor 1 . The counting clock of the time scale counter 3 is 1024Mhz. The upper 24 bits of the time scale counter 3 correspond to the lower 24 bits of the mini-slot counter 2, and the counting clock for one mini-slot count is 25us. When the processor 1 generates the arrival time of the first uplink service and the service K/T corresponding table according to the MAP, it writes 4-I and 6-I in the corresponding storage area in the media access controller 2, and then writes a start signal (MAPSTART). This signal is used as the address reset signal of the service arrival time memory and K/T memory, so that the initial address is zero address. Read the business arrival time and K/T value of the corresponding address. When the micro-slot count value reaches the time when the business arrives from the memory (through comparator 1), a start pulse is generated. Once this signal arrives, pass Decoder 15 generates coding switching signal (RSC0, RSC1), and the address generators 7 and 5 control the K/T memory read address, and add one to the memory address at the time of business arrival, and this signal starts to detect the data from demodulator 14 Whether the valid signal (DATA_VALID) is valid (high level active), when it is valid, start the K*8 counter 12, and set the RS coding control signal to low, when the counter counts to K*8, start 2*T*8 The counter 13 sets the RS encoding control signal to be high at the same time, and this signal period is generated until the DATA_VALID signal becomes low.

In order to realize the cycle control of MAP, when the upper 8 bits of the data read from the memory at the time of service arrival are 0xFF, the first address read from the memory at the time of service arrival and the K/T value memory is switched to the next storage unit in the ping-pong structure ( 4-II and 6-II). If the IE item in the MAP is 256, when the read address increases to 255 or 511, the address will automatically ping-pong switch.

The following describes a flowchart of the process of controlling RS decoding with reference to FIG. 5 . Among them, the uplink burst business is classified according to the DOCSIS protocol at the sending end, and the coded data of an appropriate length is selected for each business according to the uplink bandwidth and system transmission reliability requirements. First, in step S51, a system reference clock is generated. Since the reference clock realized by the system is based on the bit time slot (25us) and the DOCSIS system clock is 10.24Mhz, the mini-slot reference generation circuit is used to strictly synchronize the mini-slot clock and the system clock. In step S52, assign one in the media access controller 2FPGA to store the moment when each IE (information element) in the MAP arrives at the receiving end, and then allocate an RS encoding parameter for storing the uplink burst data of the corresponding IE in the corresponding MAP K/T value. In order to realize the periodical transmission control of MAP, the memory for storing the time when IE (information element) arrives at the receiving end and the K/T value is allocated to store two MAP information volumes. In the implementation, the ping-pong method is used for switching. Table 2 lists the characteristics of service area allocation in MAP:

Competitive Request Area Competitive ranging area Initialize the ranging unicast area Periodic ranging area Unicast Request Area data area

Among them, the contention request area, the contention ranging area, and the initial ranging unicast area only allocate one arrival time at the receiving end, but there will be multiple burst packets arriving in this area, and the burst packets arriving in this area are stipulated have the same coding characteristics and have the same coding parameters (K/T value). In the periodical ranging area, the unicast request area and the data area, only one arrival time is assigned at the receiving end. In this area, at most one burst packet arrives.

In step S53, according to the timing generated by the demodulator, a switching control signal for sending the K/T value to the decoder is generated within the time of the burst header field (32 Clocks). In step S54, according to the timing generated by the demodulator, locate the moment when the valid data in the uplink burst packet arrives, that is, the moment when the RS decoding and positioning control signal starts to be output. In step S55, according to the characteristics of the DOSCSIS uplink burst data packet and the timing of the demodulator, locate the position of the RS code field in the uplink burst data in the data stream, thereby generating the positioning signal required by the decoder, and providing the K/T required by the decoder Value switching signal, where K is the length of the data in the burst packet, and 2*T is the length of the RS code. According to K/T during the effective period of data, the RS decoding control signal is output to obtain the corresponding position of RS decoding in the burst data packet. (It would be nice to have a more detailed description of the decoding process).

The present invention has been described in detail in conjunction with the preferred embodiments of the present invention so far, and various improvements and changes can be made by those skilled in the art without departing from the scope and spirit of the appended claims.

Claims (3)

1. An uplink decoding control method, wherein at the sending end, according to the cable data service transmission standard DOCSIS protocol, the uplink burst service is classified, and the media access control MAC frame is divided into European line standard E1 service, IP service, and management information Business, request frame business, five kinds of ranging request frame business, according to the requirements of uplink bandwidth and system transmission reliability, select the coded data with a set length for each kind of business, and the method includes steps: At the receiving end, according to the regulation that the sending time of the uplink service in the DOCSIS protocol is defined by the downlink service bandwidth allocation MAP, the downlink MAP determines the sending time of the sending end service, and determines the time when the service arrives at the receiving end according to the delay of ranging; At the receiving end, the corresponding relationship between the service arrival time and the service code length is established with MAP as the cycle; Determining the demodulator timing according to the determined service arrival time; Locate the position of the Reed-Solomon RS coding field in the upstream burst data in the data stream according to the characteristics of the DOCSIS upstream burst data packet and the timing sequence of the demodulator, thereby generating the positioning signal required by the decoder and providing the encoding parameters required by the decoder K/T value switching signal, where K is the length of the data in the burst packet, and 2*T is the length of the RS code. 2. An uplink decoding control device, wherein at the sending end, the uplink burst business is classified according to the cable data service transmission standard DOCSIS protocol, and according to the uplink bandwidth and system transmission reliability requirements, the coded data of the set length is selected for each kind of business , the device includes: The DOCSIS protocol processor is used to determine which uplink services are allocated by each MAP according to the service bandwidth allocation MAP and system ranging information, and the coding parameter K/T value corresponding to each uplink service, and the relationship between the service arrival time and K/T Relational tables; The media access controller stores the relationship data formed by the DOCSIS protocol processor, generates a reference clock, and generates and outputs control signals and parameters for controlling the Reed Solomon RS decoder; A burst demodulator, which provides burst interface timing and RS-encoded burst data streams to the decoder; and The RS decoder decodes the burst data stream supplied by the burst demodulator according to the RS decoding control signal and parameters, and outputs the decoded burst data stream and timing. 3. The uplink decoding control device according to claim 2, wherein said medium access controller comprises a mini-slot reference generating circuit, which is used for strictly synchronizing the mini-slot clock and the system clock.

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