WO2009082974A1

WO2009082974A1 - An indicating method and device of data packet header

Info

Publication number: WO2009082974A1
Application number: PCT/CN2008/073792
Authority: WO
Inventors: Rongdao Yu
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2007-12-27
Filing date: 2008-12-26
Publication date: 2009-07-09
Also published as: CN101471924A

Abstract

An indicating method and device of data packet header are provided, the method includes that: a transmission end device determines to generate a corresponding Cyclic Redundancy Check (CRC) indicating field according to the length of the Medium Access Control Protocol Data Unit (MAC PDU); the transmission end device sends a MAC frame carrying the CRC indicating field to a receiving end device so that the receiving end device performs a CRC check with the corresponding size. In an embodiment of the present invention, a flexible universal MAC header structure is provided, the size of CRC can be selected flexibly according to the size of the PDU, such as CRC8, CRC16, CRC24, CRC32 etc., thereby the overhead is reduced, and then the requirements of optimizing the MAC layer and reducing the overhead of the MAC layer in the 802.16e+ system are satisfied.

Description

The present invention claims the priority of the Chinese patent application filed on December 27, 2007, the Chinese Patent Application No. 200710301450.4, entitled "A Data Header Indicating Method and Apparatus", The entire contents are incorporated herein by reference. Technical field

The present invention relates to the field of communications technologies, and in particular, to a data packet header indicating method and device. Background technique

802.16e MAC (Medium Access Control) PDU (Protocol Data Unit) format is shown in Figure 1. Each PDU contains a fixed-length general-purpose MAC frame header, which is after the common MAC frame header. MAC PDU payload; the payload contains zero or more sub-packets, zero or more MAC SDUs (Service Data Units), and/or their segments. The length of the payload information is variable, so the MAC PDU can also represent a variable-length byte stream, so that the MAC layer does not need to know the format and bit arrangement of the message, and only provides transparent transmission channels of various high-level service types.

At the MAC layer, the generic MAC frame header includes a downlink MAC frame header that contains MAC management messages or CS (Cross Section) data after the frame header. The MAC layer defines two UL (uplink) MAC management message formats, the first one is a downlink MAC frame header with a common MAC frame header, and includes a MAC management message or CS data after the frame header, where HT (Header Type, The frame header type is set to 0; the second is the MAC frame header format that does not contain the payload, where HT is set to 1. The MAC layer frame header format is defined as Table 1.

Syntax size (bits) MAC Header() {

HT 1 0 = general MAC layer header

1 = bandwidth request frame header

EC 1 If HT = 1 then EC = 0 if (HT = 0) {

Type 6

Reserved 1 should be set to 0

CI 1

EKS 2

Reserved 1 should be set to 0

LEN 11

}

Else {

Type 3

BR 19

}

CID 16

HCS 8

}

When HT=0 indicates a general MAC frame header, the type field (type) has a total of 6 bits, and its meaning is as shown in Table 2: Table 2:

1=exist, 0= does not exist

#3 extension type

For connections that do not use ARQ, if extended, this bit indicates if there is a packed or fragmented sub-packet for the non-ARQ-activated connection.

1 = extended

0 = no extension.

For connections using ARQ, this bit will be set to 1.

#2 Segment sub-header

1=exist, 0= does not exist

#1 Packing subheader

1=exist, 0= does not exist

#0 Downlink: Fast feedback allocation sub-packet least significant bit (LSB) Uplink: Authorization management sub-header

1=exist, 0= does not exist

In addition, an extended subheader format is provided in the system. The extended sub-header group starts with an 8-bit length field and carries one or more extended sub-headers. The length field defines the byte length of this sub-packet header group and contains all extended sub-packet headers and length bytes. Each extended sub-packet header contains reserved bits, a 7-bit extended sub-packet header type field, and a variable-length extended sub-packet header body. The size of each extended sub-packet header is determined by the type of extended word frame header in Table 3. table 3:

Name Length Description

( bits )

The Extended 8 Extended Subheader Group Length field indicates the subheader group The total length of the subheader, including all extension sub-headers and the length word group length V.

Reserved 1 Reserved = 0

Extended 7 The sub-packet header type defined in Table 1.

Subheader type

Extended Variable The extension sub-packet header type defined in Table 1 determines the length of the extended subheader body. The size of this extended sub-header body is counted in bytes. Table 4: Extended Sub-Terminal Group Type Description (DL)

The general MAC frame header format is shown in Figure 2, including: HT, 1 byte, indicating the frame header type; EC (Encrypt Control), 1 byte, indicating encryption control, 0 is not encrypted for the payload, 1 is used to encrypt the payload; Type, 6 bytes, indicating the sub-packet header and the type of the specified payload present in the message payload; ESF (Extended Subheader Field) , 1 byte, indicates the extended sub-packet header field. If ESF = 0, the extended sub-packet header does not exist. If ESF = 1, the extended sub-packet header will appear, followed by GMH; CI, 1 byte, indicating CRC (Cyclic Redundancy Check) , Cyclic Redundancy Check) indicator, when 1 is the CRC is included in the PDU, attached to the PDU payload, if encryption is required, after it is appended to the PDU payload after encryption, 0 is not included CRC function; EKS, 2 bytes, indicating the encryption key sequence, the traffic encryption key and the index of the initial vector will be used for payload encryption. This field is valid only when the EC field is set to 1; Rsv, 1 byte, Represents reserved bits; LEN, 11 bytes, indicates length, refers to the length of the MAC PDU in bytes containing the MAC header and CRC check (if any); CID, 16 bytes, indicating the connection identifier; HCS, 8 words Section, indicating the frame header check sequence, An 8-bit field is used for error detection of the frame header, and the sender will calculate the HCS value of the first 5 bytes of the cell frame header, and insert the result into the HCS field (ie, the last byte of the MAC frame header), HCS The calculation method is as follows: Multiply the frame header other than the HCS field by D8, divide (modulo 2) to generate the polynomial g(D)=D8+D2+D+l to obtain the remainder as the HCS, for example: [HT EC Type] = 0x80, BR=0xAAAA, CID=0x0F0F; HCS should be set to 0xD5.

Each frame header is encoded starting with the frame header type HT field and the encryption control EC field. The encoding of these fields should follow: The first byte of the MAC header cannot be equal to OxFX (X stands for any value) to prevent false detection of padding bytes used by the transmit convergence sublayer. A service data stream can add a cyclic redundancy check CRC to each MAC PDU that carries data for the data stream. In this case, for each MAC PDU with frame header type = 0, the cyclic redundancy check CRC32 can be added to the payload of the MAC PDU, ie the request MAC PDU is unprotected. Cyclic Redundancy Check The CRC must cover the payload of the generic MAC header and MAC PDU. Cyclic Redundancy Check The CRC must be calculated after encryption, ie the Cyclic Redundancy Check CRC protects the generic header and the encrypted payload.

The above CRC uses a 32 CRC, and the CRC32 will be calculated using the following 32-order standard generator polynomial: 32, 26, 23, 22, 16 , 12 , 11 , 10 , 8 , 7 , 5 , 4 , 2 , , _Λ In the process of implementing the present invention, the following drawbacks have been found in the prior art:

In the MAC frame header, the field Len is 11 bits, indicating the length of the MAC PDU in bytes including the MAC header and the CRC check (if any), so the maximum is 2 ^Λ 11 = 2048 bytes. Therefore, the entire MAC PDU variation range is very large, and the existing protocol only uses a fixed CRC32, which causes unnecessary overhead for a smaller PDU. Summary of the invention

The embodiment of the invention provides a data packet header indication method and device, so as to save unnecessary overhead in the redundancy cycle check.

An embodiment of the present invention provides a data packet header indication method, including:

The sending end device determines to generate a corresponding cyclic redundancy check CRC indication field according to the media access control protocol data unit MAC PDU length;

The sending end device sends the MAC frame carrying the CRC indication field to the receiving end device, and the receiving end device performs a CRC check of the corresponding size.

The embodiment of the present invention further provides a data packet header indication method, including: the receiving end device receives a MAC frame carrying a CRC indication field from a sending end device, where the CRC indication field is determined according to a length of a media access control protocol data unit MAC PDU Generate

The receiving end device checks the MAC frame by using a CRC of a corresponding size according to the indication field.

The embodiment of the invention further provides a sending end device, including:

a CRC indication field setting unit, configured to generate a corresponding CRC indication field according to the medium access control protocol data unit MAC PDU length determination;

And a sending unit, configured to send the MAC frame carrying the CRC indication field to the receiving end device, where the receiving end device performs a CRC check of the corresponding size.

The embodiment of the invention further provides a receiving end device, including: a receiving unit, configured to receive a MAC frame, where the MAC frame header includes an indication field of a CRC size, where the CRC indication field is determined according to a medium access control protocol data unit MAC PDU length;

And a verification unit, configured to perform verification on the MAC frame by using a CRC of a corresponding size according to the indication field.

In the embodiment of the present invention, a flexible universal MAC header structure is provided, and the CRC size, such as CRC8, CRC16, CRC24, CRC32, etc., can be flexibly selected according to the size of the PDU, thereby reducing overhead and further satisfying the 802.16e+ system. The MAC layer optimizes the need to reduce the overhead of the MAC layer. DRAWINGS

1 is a schematic diagram of a format of a MAC layer PDU in the prior art;

2 is a schematic diagram of a format of a general MAC frame header in the prior art;

3 is a flowchart of a method for indicating a packet header according to an embodiment of the present invention;

4 is a structural diagram of a data packet header indication system in an embodiment of the present invention. detailed description

An embodiment of the present invention provides a data packet header indication method, as shown in FIG. 3, including the following steps:

Step s301: The source device determines, according to the length of the protocol data unit PDU in the media access control MAC frame, a corresponding CRC indication field.

In the embodiment of the present invention, the CRC indication field may be set by a field in the MAC header, for example, may be a 2-bit field in the MAC header. Specifically, in the existing general MAC header, the field CI is an indication of the CRC, CI = 1 indicates that the CRC is used, and CRC=0 indicates that the CRC function is not included; the field Rsv is a reserved field, which is not used in the 802.16e. In the embodiment of the present invention, a 1-bit field CI and a 1-bit field Rsv are combined to form a total of 2 bits, and the CRC size used by the PDU is indicated according to different PDU sizes. The basic principle is that the size of the CRC is proportional to the size of the PDU, that is, The larger the PDU, the larger the CRC. General The CRC size may be CRCO, CRC8, CRC12, CRC16, CRC24, CRC32 „ where CRCn indicates the CRC using n bits. The 2-bit CI and Rsv may be as shown in Table 5:

The CI field and the Rsv field jointly indicate the CRC size used. The CRC size can be selected according to the size of the PDU. Typically, the CRC size can be CRC0, CRC8, CRC12, CRC16, CRC24, CRC32, as shown in Tables 6, 7, and 8:

Table 6:

CI Rsv CRC

0 0 0

0 1 CRC 8

1 0 CRC 32

1 1 CRC 16 Table 7:

CI Rsv CRC

0 0 0

0 1 CRC 8

1 0 CRC 32

1 1 CRC 24 Table 8:

CI Rsv CRC 0 0 0

0 1 CRC 12

1 0 CRC 32

1 1 CRC 24 , where CRC 32 is calculated using the following formula:

/ \ 32 , 26 , 23 , 22 , 16 , 12 , 11 , 10 , 8 , 7 , 5 , 4 , 2 , , ι g _cse32 (x) = X + X + X + X + X + X + X + X + X + X + X + X + X + X + 1

The CRC24 is calculated using the following generator polynomial: g _CRC24 (x) = X ²⁴ + X ²³ + x ⁶ + x ⁵ + X + 1

CRC16 is calculated using the following generator polynomial; g _CRC16 (x) = X ¹⁶ + X ¹² + X ⁵ + 1 CRC 12 is calculated using the following generator polynomial; g _C Rci ₂ (x) = X ¹² + X ¹¹ + X + X ² + x + 1

CRC 8 is calculated using the following generator polynomial; gcR _C8 (x) = X ⁸ + X ⁷ + X ⁴ + X ³ + X + 1

Step s302: The sending end device sends the MAC frame carrying the CRC indication field to the receiving end device.

Step s303: The receiving end device receives the MAC frame, where the MAC frame header includes an indication field of a CRC size, and performs verification on the MAC frame according to the indication field by using a CRC of a corresponding size. Normally, the terminal needs to negotiate with the base station during initialization.

In addition, in the existing 802.16e protocol, the field Rsv is a reserved field whose value is set to zero. Therefore, in the existing 802.16e, the value of the 2-bit CI and Rsv and the CRC indicated are as shown in Table 9:

Table 9:

In order to ensure compatibility, the 802.16+ terminal can work normally in the 802.16e system. Therefore, in 802.16e+, the CI field and the Rsv field jointly indicate that 00 still indicates CRC 0, and 1 0 still indicates CRC32. 01, 11 can flexibly indicate other CRC sizes, such as CRC 8, CRC12, CRC16, CRC24.

In the embodiment of the present invention, the CI field in the universal MAC header may also be used to indicate whether to use a variable CRC subheader.

CI =1, using a variable CRC subheader, otherwise no variable CRC subheaders are used. The variable CRC subheader is shown in Table 10.

Table 10:

In the embodiment of the present invention, a sub-header of a variable CRC size may also be defined by an extended sub-header, as shown in Table 11,

Table 11:

3 SN request extended 1

Subheader

4 PDU SN(short) 1

Extended subheader

5 PDU SN(long) 2

Extended subheader

6 Variable CRC extended 1

Subheader

In the second embodiment of the present invention, the CRC 32 is taken as an example for description.

The transmitting device determines the CRC size as CRC 32 according to the CRC indication field in the MAC frame header, and generates a corresponding CRC 32 field. The specific process includes: The initial 32-bit complement code, which is equivalent to setting the initial value of the CRC register to OxFFFFFFFF; the first word bit of the first field (the MSB of the first byte of the MAC header) corresponds to Xn-1 , the last word bit of the last field corresponds to X0, where n is the number of bits of the input data stream; the polynomial obtained by multiplying X32 is divided by G(x); the remainder is complemented by word bits; CRC value The 32 word bits are placed in the CRC field, so that X31 becomes the leftmost word bit of the first byte, and X0 is the rightmost word bit of the last byte; the generated CRC field, which first sends the MSB.

The receiving end device receives the MAC frame carrying the CRC field, and verifies the MAC frame by using the CRC32 of the corresponding size according to the indication field of the CRC size in the MAC frame header. The specific process includes: The initial value of the remainder is all preset to 1, and the input byte is sent to the CRC engine with the MSB first; when divided by G(x), the polynomial has a unique non-zero remainder, then no transmission is generated. Error, the only residual value is a polynomial:

31 , 30 , 26 , 25 , 24 , 18 , 15 , 14 , 12 , 11 , 10 , 8 , 6 , 5 , 4 , 3 X + X + X + X + X + X + X + X + X + X + X + X + X + X + X + X

The embodiment of the invention further provides a data packet header indication system, as shown in FIG. 4, The sender device 100 and the receiver device 200 are included.

The sending end device 100 specifically includes: a CRC indication field setting unit 110, configured to generate a corresponding CRC indication field according to the protocol data unit PDU length determination in the medium access control MAC frame, and a sending unit 120, configured to carry the CRC The MAC frame of the indication field is sent to the receiving end device, and the receiving end device performs a CRC check of the corresponding size. The negotiating unit 130 is configured to negotiate with the receiver device whether the capability of using multiple CRC sizes is available. The CRC indication field may be set by a field in the MAC header, for example, may be a 2-bit field in the MAC header. Specifically, it can also be set by combining the CRC indicator field CI with the reserved field Rsv.

The receiving device 200 includes: a receiving unit 210, configured to receive a MAC frame, where the MAC frame header includes an indication field of a CRC size, where the CRC indication field is determined according to a PDU length, and a verification unit 220, configured to The indication field uses the CRC of the corresponding size to check the MAC frame; the negotiating unit 230 is configured to negotiate with the sender device whether the capability of using multiple CRC sizes is used.

The embodiment of the invention provides a flexible universal MAC header structure, which can flexibly select the size of the CRC according to the size of the PDU, such as CRC8, CRC16, CRC24, CRC32, etc., thereby reducing overhead. In turn, it satisfies the need for MAC layer optimization in the 802.16e+ system and reduces the overhead of the MAC layer.

Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be implemented by hardware, or can be implemented by means of software plus necessary general hardware platform, and the technical solution of the present invention. It can be embodied in the form of a software product that can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), including a number of instructions for making a computer device (may It is a personal computer, a server, or a network device, etc.) that performs the methods described in various embodiments of the present invention.

In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

Rights request

A data packet header indication method, comprising:

The data packet header indication method according to claim 1, wherein said CRC indication field is set by a field in a MAC frame header.

The data packet header indication method according to claim 1, wherein said CRC indication field is set by a CRC indicator field CI in combination with a reserved field Rsv; or

Indicate whether to use a variable CRC subheader by the CI field in the universal MAC header; or

A sub-header of variable CRC size is set by the extended subheader.

The data packet header indication method according to claim 3, wherein when the CI field is 0 and Rsv is 0, CRC0 is used; when the CI field is 1 and Rsv is 0, CRC32 is used.

The data packet header indication method according to claim 3, wherein the size of the CRC subheader is proportional to the length of the protocol data unit PDU in the MAC frame.

6. A data packet header indication method, comprising:

Receiving, by the receiving end device, a MAC frame carrying a CRC indication field from the sending end device, where the CRC indicating field is determined according to a length of the medium access control protocol data unit MAC PDU;

The data packet header indication method according to claim 6, wherein before the receiving the MAC frame, the method further includes:

It is negotiated with the sender device whether it has the ability to use multiple CRC sizes.

8. A transmitting device, comprising: a CRC indication field setting unit, configured to generate a corresponding CRC indication field according to the medium access control protocol data unit MAC PDU length determination;

9. The transmitting device according to claim 8, wherein the CRC indication field is set by a field in a MAC frame header.

A receiving end device, comprising:

a receiving unit, configured to receive a MAC frame, where the MAC frame header includes an indication field of a CRC size, where the CRC indication field is determined according to a medium access control protocol data unit MAC PDU length;

The receiving device according to claim 10, further comprising: a negotiating unit, configured to negotiate with the sender device whether the capability of using multiple CRC sizes is used.