CN100563210C - The method of header compression, compressor reducer and transmission system - Google Patents
The method of header compression, compressor reducer and transmission system Download PDFInfo
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Abstract
The invention discloses a kind of method of header compression, comprising: generate initial frame according to datagram; Compare the frame head information of the first datagram header and initial frame, find out and remove the redundant information in the described datagram header, generate first condensed frame; Compare the frame head information of the previous frame of the second datagram header and the described second datagram header, find out and remove the redundant information in the described datagram header, generate second condensed frame.The invention also discloses a kind of compressor plant, comprise comparing unit and generation unit: generation unit is used for generating initial frame and condensed frame according to datagram; Comparing unit is used to find out redundant information.The invention also discloses a kind of transmission system, comprise compressor reducer and decompression machine: compressor reducer is used to generate and send initial frame and condensed frame; Decompression machine is used to receive initial frame and condensed frame, according to condensed frame restoring data newspaper, and the header information of storage datagram.By using the present invention's header compression effectively, improve efficiency of transmission.
Description
Technical field
The present invention relates to field of data transmission, relate in particular to a kind of method, compressor reducer and transmission system of header compression.
Background technology
Digital television broadcasting handheld terminal standard (Digital Video Broadcasting Handled, DVB-H) be the transmission standard that European digital television standard is organized as provides multimedia service to formulate by the received terrestrial digital broadcasting network to portable, handheld terminal, be European digital TV ground transmission standard (Digital VideoBroadcasting-Terrestrial, DVB-T) expanded application on portable terminal.Adopt the terminal of DVB-H to have lower power consumption, it is more superior to move reception and interference free performance, therefore this standard is applicable to that miniature portable equipment such as mobile phone, handheld computer by ground digital television broadcast network received signal, have boundless application prospect.
When carrying out the real time business of DVB-H, need to transmit in real time flow-type business such as video, audio frequency, captions, the transmission of these business datums need be adopted RTP (Realtime Transfer Protocol, RTP), User Datagram Protoco (UDP) (User Datagram Protocol, UDP) and Internet protocol (Internet Protocol, IP) agreement encapsulates.Carry out multi-protocols encapsulation (Multi-Protocol Encapsulation, MPE) the IP datagram structure after is as shown in table 1, its header comprises four parts: the MPE data segment header, the IP header, UDP header, the RTP header, wherein the MPE data segment header takies 12 bytes, the IP header is at the 4th edition (Internet Protocol Version 4 of internet usage agreement, IPV4) take 20 bytes the time, at internet usage agreement sixth version (Internet Protocol Version 6, IPV6) take 40 bytes the time, UDP header takies 8 bytes, the RTP header is minimum to take 12 bytes.
| MPE data segment header 12 bytes | IP header 20 or 40 bytes | UDP header 8 bytes | RTP header 〉=12 bytes | Payload |
Table 1, IP datagram structure
For the IP datagram after the multi-protocols encapsulation, header will take 6% resource when using IPV4, header will take general 8% resource when using IPV6, as seen when carrying out the DVB-H real time business, transmission header (TH) will take very many resources, and between continuous datagram, the unanimity of a lot of contents before and after being arranged, or regular change, add and some otherly can extrapolate content, cause having bulk redundancy information in the continuous datagram header, so protocol header compressed very is of practical significance, can effectively reduce the resource that transmission header (TH) takies, Limited resources is used on the payload (Payload) of bearer traffic content as far as possible.
Existing IP header compression scheme is commonly used Fan Jiakebusen header-compressed (Van JacobsonHeader Compression, VJHC) scheme, IP header-compressed (IP Header Compression, IPHC) scheme, RTP header-compressed (Compression RTP, CRTP) scheme and robust header compression (RobustHeader Compression, ROHC) scheme.
Wherein the IP header compression scheme that early proposes is the VJHC scheme, the IPHC scheme is that some of VJHC scheme are replenished, VJHC scheme and IPHC scheme are only supported the udp protocol of similar multicast, do not support Real-time Transport Protocol, for this reason, making that VJHC scheme and IPHC scheme are improper is applied in most multimedia transmission, the real time business of DVB-H particularly, and its header comprises the Real-time Transport Protocol header.
The CRTP scheme is the IP header compression scheme that proposes at Real-time Transport Protocol specially, can be used as replenishing to VJHC scheme and IPHC scheme, but these header compression scheme all design for wire link, adopt fragile differential coding mostly, error rate on the wire link is lower, these agreements can be worked well, yet, error rate on the Radio Link is higher, and present the burst feature, at this moment, VJHC scheme, IPHC scheme and CRTP scheme can not adapt to the high bit-error situation of this class wireless transmission of real time business of DVB-H, can't guarantee the accuracy rate of transmitting.
The ROHC scheme generally is applicable to have the long response time back and forth, carry out effectively header-compressed of stalwartness on the higher Radio Link of error rate, as cellular network etc., but ROHC scheme compression mechanism is complicated, ever-increasing complexity requires higher computing capability in the Coding Compression Algorithm, also mean simultaneously long time delay, this transmission for the real-time program is disadvantageous, and its real-time of the real time business of DVB-H is very important, obvious improper employing ROHC scheme, and DVB-H is mainly used in battery-powered hand-held mobile terminal, too complicated algorithm must cause the increase of amount of calculation, the power consumption of hand-held mobile terminal also can increase thereupon, is to seriously influence very much for energy-conservation very important battery-powered hand-held mobile terminal.
As from the foregoing, existing IP header compression scheme VJHC scheme, IPHC scheme, CRTP scheme, ROHC scheme are not the compression schemes that is fit to the DVB-H agreement, all the characteristics of IP datagram header are not effectively compressed, and adopt VJHC scheme, IPHC scheme and CRTP scheme can bring higher error rate, can't guarantee the accuracy transmitted, adopt ROHC scheme time delay oversize, can't guarantee the real-time of DVB-H real time business, also can bring the rising of hand-held mobile terminal power consumption, influence the service time of battery-powered hand-held mobile terminal.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of method, compressor plant and transmission system of header compression of effectively compressed IP datagram header.
For solving the problems of the technologies described above, the invention provides a kind of method of header compression, described method comprises:
Generate initial frame according to datagram;
Compare the frame head information of the first datagram header and initial frame, find out and remove in the described first datagram header can compressed redundant field, generate first condensed frame;
Compare the frame head information of the previous frame of the second datagram header and the described second datagram header, find out and remove in the described second datagram header can compressed redundant field, generate second condensed frame.
The present invention also provides a kind of compressor plant, and described compressor plant comprises comparing unit and generation unit:
Generation unit is used for generating initial frame according to datagram, and remove that comparing unit finds out from first datagram and second datagram can compressed redundant field, generate condensed frame;
Comparing unit is used to compare the frame head information of the first datagram header and initial frame, find out in the described first datagram header can compressed redundant field, the frame head information of comparing the previous frame of the second datagram header and the described second datagram header find out in the described second datagram header can compressed redundant field.
The present invention also provides a kind of transmission system, and described system comprises compressor reducer and decompression machine:
Compressor reducer is used for generating initial frame to decompression machine according to datagram; Compare the frame head information of the first datagram header and initial frame, find out and remove in the described first datagram header can compressed redundant field, generate first condensed frame; Compare the frame head information of the previous frame of the second datagram header and the described second datagram header, find out and remove in the described second datagram header can compressed redundant field, generate second condensed frame, and send the described initial frame and first condensed frame and second condensed frame to decompression machine;
Decompression machine is used to receive initial frame and condensed frame, after receiving described first condensed frame and second condensed frame, according to the frame head information reverting datagram of described first condensed frame and the previous frame of second condensed frame.
As from the foregoing, the present invention is by removing the bulk redundancy field that exists in the continuous IP datagram header, compressed the header of IP datagram effectively, improved the efficient of transmission, and the algorithm that adopts is very simple, be easy to realize can not increasing the weight of the burden of system, also can not have influence on professional real-time.
Description of drawings
The method embodiment flow chart of Fig. 1, header compression provided by the invention;
Fig. 2, compressor plant example structure figure provided by the invention;
Fig. 3, transmission system provided by the invention are implemented illustration;
Fig. 4, transmission system embodiment working method schematic diagram provided by the invention.
Embodiment
The invention provides a kind of method, compressor reducer and transmission system of header compression, can the protocol header of DVB-H effectively be compressed.
Following this paper will describe the embodiment of the method for header compression provided by the invention in detail.
IP datagram after the multi-protocols encapsulation, its header portion comprises: MPE data segment header, IP header, UDP header, RTP header, there is a large amount of redundant field in header inside, particularly between the continuous data segment header in front and back, the method embodiment of header compression provided by the invention realizes by compressing these redundant field.
Now with Multi-Protocol Encapsulation-Forward Error Correction in the DVB-H standard (Multi-ProtocolEncapsulation-Forward Error Correction, MPE-FEC) frame be example describe in detail exist in the IP datagram header can compressed redundant field.Regulation according to the DVB-H standard, each MPE-FEC frame is divided into MPE district and FEC district, wherein all be positioned at the MPE district through the IP datagram after the multi-protocols encapsulation, they are also referred to as the MPE data segment, a MPE-FEC frame comprises a lot of data segments, it is IP datagram that its MPE district also comprises a lot of MPE data segments, and each IP datagram all includes one group of IP datagram header, and the MPE data segment header that comprises in these IP datagram headers, IP header, UDP header, RTP header can be divided into five classes substantially:
The first kind, the type that can calculate by other field of header: the newspaper long word section in the datagram fragmentation length in the IP header, datagram total length field and the UDP header.
Owing to there is fixing relational expression between the newspaper long word section in datagram fragmentation length, datagram total length field and the UDP header in the IP header, with IPV4 is example, and the relational expression between datagram fragmentation length (Lmpe), IPV4 datagram total length (Lipv4), the UDP newspaper long (Ludp) is:
Lmpe＝Lipv4+9＝Ludp+29
So as long as send one of them data, just can extrapolate other value, other value is exactly can compressed redundant field.
The type that second class, front and back header respective field value remain unchanged substantially: the field of the 4th to 8 byte correspondence in the MPE data segment header; Fields such as the version in the IP header, header length, COS, segmentation marker district, life span, upper-layer protocol, source address and destination address; Source port, destination interface field in the UDP header; The field of the 1st, 2 byte correspondences and synchronisation source, contribution source indicator in the RTP header.
Because these fields are in continuous data segment, rare variation when transmitting continuous data segment, also is can compressed redundant field.
The 3rd class, front and back header respective field value change but rule is determined: the sequence number in identifier in the IP header and the RTP header, these fields belong to equally can compressed redundant field.
The 4th class, front and back header respective field value change irregular or difficult prediction: the data segment, length in the MPE paragraph header, real-time parameter district; Header check in the IP header and, the verification in the UDP header and and the RTP header in the timestamp field, these fields just belong to and are difficult to compressed field.
The 5th class, other: the remainder in each protocol header except that above-mentioned field.
The method embodiment of header compression provided by the invention can be called as simple header-compressed (SimpleHeader Compression, SHC) scheme, the redundancy section of the first kind, second class and the 3rd class field that main compression is above-mentioned, though the 4th class fields such as timestamp wherein can be compressed, need to adopt complicated encryption algorithm, for reducing the complexity of algorithm, do not increase the power consumption of hardware, the class field is not compressed, owing to be difficult to sort out, do not compressed yet as for the 5th class.
The method embodiment flow process of header compression provided by the invention is as shown in Figure 1:
Transmitting terminal is when beginning to transmit IP datagram, at first to set up an initial frame, an initial frame comprises all the elements of a common IP datagram, the frame head of initial frame and common IP datagram header are basic identical, other parts are then identical with common IP datagram, for to common IP datagram, promptly do not carry out the MPE data segment of overcompression or initialization process, the IPV4 initial frame, IPV6 initial frame and these 4 kinds of data of different types sections of condensed frame of compressing are distinguished, the 3rd of MPE data segment header 2nd byte of present embodiment by redefining reservation, 4, realize the differentiation of these 4 kinds of different pieces of information sections, now illustrate concrete differentiation mode, be shown in Table 2:
| The 3rd | The 4th | Segment type |
| ?1 | ?1 | Common IP datagram |
| ?0 | ?0 | The IPV4 initial frame |
| ?0 | ?1 | The IPV6 initial frame |
| ?1 | ?0 | Condensed frame |
Table 2,3,4 definition of MPE paragraph header the 2nd byte
Initial frame is mainly used in initialization transmitting terminal and receiving terminal, sets up context at two ends, and transmitting terminal does not carry out any compression to the content of initial frame, directly sends to receiving terminal, and the frame head information of initial frame is stored according to certain format simultaneously, forms context.
Still be example with the MPE-FEC frame, when beginning to transmit the IP datagram in MPE district, datagram is generated into an initial frame, send, in order to improve the reliability of transmission by transmitting terminal, avoid owing in transmission course, lose the fortuitous event of initial frame and so on, also can send a plurality of initial frames, just former datagrams all be generated initial frame, and send one by one, if generated a plurality of initial frames, all to refresh context according to initial frame head so at every turn.
The following step will be that example is described in detail with the MPE-FEC frame all.
Receiving terminal receives the data segment that transmitting terminal sends, it is an initial frame that by data segment header the 2nd byte the 3rd, 4 judges this, then the initial frame frame head that receives is stored according to certain format, set up the context of receiving terminal, this moment, receiving terminal and transmitting terminal entered synchronous regime.
Receiving terminal receives that at every turn initial frame all will refresh context according to the initial frame that newly receives.
Transmitting terminal begins to generate condensed frame after sending the initial frame of predetermined number, the numer of initial frames that sends before supposing is N, then transmitting terminal can generate into condensed frame to N+1 IP datagram content based on context, this datagram is first datagram that generates condensed frame, can be called as first datagram, thereafter datagram can be called as second datagram, this condensed frame also is the condensed frame of first generation, can be called as first condensed frame, the condensed frame of Sheng Chenging also can be called as second condensed frame thereafter.
Condensed frame comprises the payload of frame head and bearer traffic content, and its payload portions and compressed IP datagram are identical, and present embodiment is as shown in table 3 for the condensed frame frame head form that IPV4 provides:
Table 3, IPV4 condensed frame frame head form
This IPV4 condensed frame frame head comprises basic frame head and expansion frame head two parts, basic frame head is 20 bytes, mainly comprise the field that belongs to the 4th class in synchronous prefix (0X3E), each protocol header: MPE data segment, length, real-time parameter district, IP header check and, the UDP header verification and, the timestamp field, with expansion frame head logo area, the definition of this basic frame head part field is as shown in table 4.It is corresponding with the logo area indicating bit that the expansion frame head is used for transmission, the field value that changes.
| Bit | Title | Definition |
| ?a1 | The grammer indication | Identical with former MPE data segment definition |
| ?a2 | The payload indication | Identical with former MPE data segment definition |
| ?a3、4 | The indication of frame class | Reference table 2 |
| MPE logo area the 1st bit | The indication of MAC Address field | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 2nd bit | The indication of MPE scrambling byte | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 3rd bit | Current number-of-fragments indication | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 4th bit | Last number-of-fragments indication | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The the 5th to 8 bit | Expansion frame head length | The length of expression expansion frame head is unit with 4 bytes; Being to represent to compress frame head at 0 o'clock basic frame head part is only arranged, is to represent to expand frame head length at 1111 o'clock to be at least 60 bytes. |
| B1 | The end of list (EOL) sign | Identical with former MPE data segment definition |
| B2 | Frame end mark | Identical with former MPE data segment definition |
| IP logo area the 1st bit | IP version and head length sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 2nd bit | The COS sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 3rd bit | IP identifier sign | 0: this frame field value acquiescence increases by 1, and the expansion frame head does not have corresponding field 1: this field value changes in addition, transmits in the expansion frame head |
| The 4th bit | IP section of calling the score and drift marker | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 5th bit | Indicate life cycle | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 6th bit | The upper-layer protocol sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 7th bit | Source station IP address mark | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 8th bit | Purpose IP address mark | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| C1 | The source port sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| C2 | The destination interface sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| RTP logo area the 1st bit | RTP version, extension flag | Point to preceding 4 bits of RTP header first byte.0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 2nd bit | The CC sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 3rd bit | M | Identical with the definition of RTP header |
| The 4th bit | The PT sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 5th bit | The SN sign | 0: this frame field value acquiescence increases by 1, and the expansion frame head does not have corresponding field 1: this field value changes in addition, transmits in the expansion frame head |
| The 6th bit | The SSRC sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 7th bit | The CSRC sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head and points to field length and determined by the CC value |
| The 8th bit | RTP expansion area sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head and points to field length according to expansion area definition decision |
Table 4, the basic frame head part of IPV4 condensed frame Field Definition
All field signs and order of the field and MPE data segment header, IP header, UDP header, RTP header are consistent in this IPV4 condensed frame frame head.
Transmitting terminal can carry out different processing for aforesaid five class different pieces of information sections when generating the IPV4 condensed frame:
The field that belongs to above-mentioned the 4th class and the 5th class in the data segment is directly inserted the corresponding region of condensed frame frame head;
The field that belongs to second class and the 3rd class in the data segment, transmitting terminal can be successively compares the frame head of the previous frame that writes down in itself and the context, if remain unchanged, or meet predetermined Changing Pattern, then will the corresponding flag bit reset of the section of transformation of the way, otherwise set, and expanding the field that the frame head district opens up respective length, the value that changes is filled into, and this value will directly be delivered to receiving terminal with condensed frame like this, indicates that specifically bit position and definition are referring to table 3 and table 4;
The field that belongs to the first kind in the data segment, owing to there being following relational expression between datagram fragmentation length (Lmpe), IPV4 datagram total length (Lipv4), the UDP newspaper long (Ludp):
Lmpe＝Lipv4+9＝Ludp+29
So as long as send wherein any one data, just can extrapolate other value, what present embodiment adopted is the section length that sends datagram, and is about to datagram fragmentation length and is filled in the basic frame head MPE of condensed frame data segment, length part, is delivered to receiving terminal with condensed frame afterwards.
For guaranteeing that each field all is the integral words joint in the expansion frame head, when RTP version, extension flag and CC indicate that any one changes, whole RTP first byte should be transmitted in the past; When PT sign changes, whole RTP the 2nd byte should be transmitted in the past, handle above-mentioned five class fields after, will expand frame head length and insert MPE logo area the 5th to 8 bit.
Because in the DVB-H system, in the same MPE-FEC frame, list field value in the expansion frame head and generally remain unchanged, therefore, in most cases, condensed frame has only basic frame head part.For under the situation that the expansion frame head occurs, keeping whole expansion frame head partial-length is the integral multiple of 4 bytes, this frame head partly provides the Padding field at the expansion frame head, the filling of when the integral multiple that whole expansion frame head partial-length is not 4 bytes, carrying out, byte of padding is also can be " 1 " for " 0 ", it is the integral multiple of 4 bytes that whole expansion frame head partial-length is filled into, so that send.
Just finished the generation of an IPV4 condensed frame this moment, and in the generation of finishing condensed frame, transmitting terminal also will carry out the content of current frame head is noted in contextual renewal.
If the condensed frame frame head form that IPV6 condensed frame, present embodiment provide is as shown in table 5:
Table 5, IPV6 condensed frame frame head form
The same basic frame head and the expansion frame head two parts of comprising of this IPV6 condensed frame frame head with IPV4 condensed frame frame head, wherein basic frame head is 16 bytes, basic comprising is referring to table 5, the definition of this basic frame head most of field except the IP logo area is all consistent with IPV4 condensed frame frame head, and the definition of each bit of this IPV6 condensed frame frame head IP logo area is as shown in table 6:
| Bit | Title | Definition |
| The 1st bit | IP version and Priority flag | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 2nd bit | The number of failing to be sold at auction sign | 0: the former frame that writes down in this frame respective field value and the context is identical |
| 1: this field value changes, and is transmitted by corresponding field in the expansion frame head | ||
| The 3rd bit | Next header flag | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 4th bit | The website restriction sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 5th bit | The source IP address sign | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
| The 6th bit | Purpose IP address mark | 0: the former frame identical 1 that writes down in this frame respective field value and the context: this field value changes, and is transmitted by corresponding field in the expansion frame head |
The definition of table 6, each bit of IPV6 condensed frame frame head IP logo area
Transmitting terminal is when generating the IPV6 condensed frame, and processing method of taking and IPV4 condensed frame basically identical are not described further at this.
Wherein, the relational expression between datagram fragmentation length (Lmpe), IPV6 datagram total length (Lipv4), the UDP newspaper long (Ludp) is as follows in the first kind field of IPV6:
Lmpe＝Lipv6+49＝Ludp+49
Because the content of a condensed frame is very little, each what a condensed frame of generation promptly sends to receiving terminal and can cause waste of network resources, also can increase the weight of the burden of system handles, in order to make full use of network transmission resource, the method that present embodiment provides a plurality of condensed frames to send together.
At first will get a fixing press cycles K, consider that network data transmission all is the radix-2 algorithm that adopts, the number of the IP datagram in MPE district also all is 2
x(x round numbers) is individual, and the value of K is generally 2
xBut this value is unsuitable excessive, otherwise can have influence on the real-time of transmission, so the value of K is generally 8,16,32.
The number of supposing the initial frame that sends is N, just should generate K-N condensed frame in the press cycles that begins from initial frame, after transmitting terminal has generated K-N condensed frame, this K-N condensed frame as a superframe, is sent to receiving terminal together.
If do not comprise the press cycles of initial frame afterwards, the condensed frame number of generation just should be K.
Receiving terminal receives that transmitting terminal sends when comprising the superframe of K-N condensed frame, can handle the condensed frame of receiving successively in order, at first will judge this frame by the 3rd, 4 of MPE data segment header the 2nd byte is condensed frame, carries out following reduction then and handles:
Read the field that wherein belongs to the 4th class and the 5th class, directly be filled in the new IP datagram header corresponding field and go;
The reading of data segment length of calling the score, relational expression between growing according to datagram fragmentation length, datagram total length and UDP newspaper is then extrapolated the value between datagram total length and the UDP newspaper length, and these three numerical value are filled in the new IP datagram header corresponding field go, it should be noted that if in other embodiments the condensed frame transmission be the value of datagram total length or UDP newspaper between long, can extrapolate two other numerical value equally by relational expression;
Recovery for other field, receiving terminal will be handled according to the flag bit of each logo area correspondence, if flag bit is 0, respective field value during based on context receiving terminal incites somebody to action, rule by appointment, directly fill, or recharge after adding agreement numerical value in new IP datagram header corresponding field; If flag bit is 1, receiving terminal can draw the position of expanding flag bit corresponding field in the frame head according to flag bit order and field length, from the expansion frame head, read the field value corresponding successively then, be filled in the new IP datagram header corresponding field and go with flag bit.
Receiving terminal has reduced behind the IP datagram header, to upgrade according to the context of the IP datagram header after the reduction receiving terminal, so that next condensed frame is carried out decompress(ion), what the IP datagram header after the reduction comprised here also is the frame head information of this condensed frame, and the IP datagram header after the reduction will be formed new IP datagram with the Payload of bearer service content and be transferred into next processing links.
Transmission cycle of this moment finishes, transmitting terminal is after having generated and sent the condensed frame of one-period, continue to generate the condensed frame of next cycle, this moment, the number of condensed frame should be K, send to receiving terminal as a superframe after having generated K condensed frame, receiving terminal is repeating step 106 then, until transmitted the IP datagram in MPE district.
In order to improve the reliability of transmission, prevent the accidental transmission error that occurs, present embodiment gives the method for a kind of regular initialization transmitting terminal and receiving terminal, a default earlier value M, transmitting terminal regenerated initial frame at every turn once more after transmitting M frame, upgrade context according to new initial frame, repeat above-mentioned flow process up to the IP datagram that has transmitted the MPE district.
Compressor plant provided by the invention is the redundant field by the IP datagram header portion after the encapsulation of compression multi-protocols equally, realize compression to the IP datagram header, compressor plant example structure figure comprises comparing unit 201, generation unit 202 and memory cell 203 as shown in Figure 2:
Comparing unit 201 is used for comparing the frame head information of datagram header and context, finds out the redundant information in the described datagram header.
The generation initial frame among the process of its generation initial frame and condensed frame and the method embodiment of header compression mentioned above and the process of condensed frame are in full accord, no longer sew at this and tell.
The concrete application of compressor plant provided by the invention in transmission system provided by the invention vide infra to the description of transmission system.
Transmission system provided by the invention also is that the redundant field of the IP datagram header portion after encapsulating by the compression multi-protocols realizes that embodiment comprises compressor reducer 301 and decompression machine 302 as shown in Figure 3:
Following this paper will be described in detail transmission system embodiment provided by the invention:
Still be example with the MPE-FEC frame, the working method of transmission system embodiment provided by the invention as shown in Figure 4, when beginning to transmit the IP datagram in MPE district, the IP datagram that the compressor reducer of transmitting terminal will comprise datagram header and payload generates into an initial frame that comprises frame head and payload, send by Radio Link, frame head with initial frame stores according to certain format simultaneously, set up the context of transmitting terminal, this moment, compressor reducer was in initial state, initial frame among the initial frame form herein and the method embodiment of header compression mentioned above is in full accord, no longer sews at this and tells.
The decompression machine that is positioned at receiving terminal receives the data segment that compressor reducer sends, it is an initial frame that by data segment header the 2nd byte the 3rd, 4 judges this, the initial frame frame head that receives is stored according to certain format, set up the context of receiving terminal, this moment, receiving terminal also entered initial state and transmitting terminal enters synchronous regime.
In order to improve the reliability of transmission, avoid owing in transmission course, lose the fortuitous event of initial frame and so on, also can send a plurality of initial frames, just former datagrams are all generated into initial frame, and send one by one, if generated a plurality of initial frames, compressor reducer all will refresh the transmitting terminal context according to newly-generated initial frame head at every turn so, and decompression machine receives that at every turn initial frame all will refresh the receiving terminal context according to the initial frame that newly receives.
The compressor reducer that is positioned at transmitting terminal begins to generate the condensed frame that comprises frame head and payload after sending the initial frame of predetermined number, the numer of initial frames that sends before supposing is N, then the compressor reducer of transmitting terminal can generate into condensed frame to N+1 IP datagram content based on context, the condensed frame frame head form that present embodiment provides for IPV4 and IPV6 is respectively shown in table 3, table 5, that describes among the method embodiment of its particular content and generation method and header compression mentioned above is in full accord, no longer sews at this and tells.
The compressor reducer of transmitting terminal sends as a superframe generating good condensed frame after the condensed frame number that generates adds that the number of initial frame reaches a press cycles.
Because the content of a condensed frame is very little, each what a condensed frame of generation promptly sends to receiving terminal and can cause waste of network resources, also can increase the weight of the burden of system handles, in order to make full use of network transmission resource, the method that present embodiment provides a plurality of condensed frames to send together.
At first will get a fixing press cycles K, consider that network data transmission all is the radix-2 algorithm that adopts, the number of the IP datagram in MPE district also all is 2
x(x round numbers) is individual, and the value of K is generally 2
xBut this value is unsuitable excessive, otherwise can have influence on the real-time of transmission, so the value of K is generally 8,16,32.
The number of supposing the initial frame that sends is N, just should generate K-N condensed frame in the press cycles that begins from initial frame, after the compressor reducer of transmitting terminal has generated K-N condensed frame, this K-N condensed frame as a superframe, is sent together.
If do not comprise the press cycles of initial frame afterwards, the condensed frame number of generation just should be K.
The decompression machine that is positioned at receiving terminal receives that compressor reducer sends when comprising the superframe of K-N condensed frame, can handle the condensed frame of receiving successively in order, at first will judge this frame by the 3rd, 4 of MPE data segment header the 2nd byte is condensed frame, reduce processing then, it is reduced to the common IP datagram that comprises datagram header and payload, that describes among the method embodiment of its reduction process and header compression mentioned above is in full accord, no longer sews at this and tells.
The compressor reducer of transmitting terminal is after having generated and sent the condensed frame of one-period, continue to generate the condensed frame of next cycle, this moment, the number of condensed frame should be K, generated the decompression machine that sends to receiving terminal behind K the condensed frame as a superframe, decompression machine then continues the condensed frame of receiving is reduced, until transmitted the IP datagram in MPE district.
In order to improve the reliability of transmission, prevent the accidental transmission error that occurs, present embodiment gives the method for a kind of regular initialization compressor reducer and decompression machine, a default earlier value M, compressor reducer regenerated initial frame at every turn once more after transmitting M frame, upgrade context according to new initial frame, and then generate the condensed frame of new one-period, up to the IP datagram that has transmitted the MPE district.
More than method, compressor reducer and the transmission system of a kind of header compression provided by the present invention is described in detail, used specific case herein principle of the present invention and execution mode are set forth, the explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present invention, the part that all can change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.
Claims (16)
1, a kind of method of header compression is characterized in that, described method comprises:
Generate initial frame according to datagram;
Compare the frame head information of the first datagram header and initial frame, find out and remove in the described first datagram header can compressed redundant field, generate first condensed frame;
Compare the frame head information of the previous frame of the second datagram header and the described second datagram header, find out and remove in the described second datagram header can compressed redundant field, generate second condensed frame.
2, the method for header compression as claimed in claim 1, it is characterized in that, describedly can compressed redundant field be: field that the field that can be calculated by other fields or front and back datagram header respective field value remain unchanged substantially or front and back datagram header respective field value change but field clocklike.
3, the method for header compression as claimed in claim 1 is characterized in that, described method also comprises:
Send the described initial frame and first condensed frame and second condensed frame to receiving terminal, and at transmitting terminal storage frame header;
After receiving terminal receives initial frame, the frame head information of storing initial frame;
After receiving first condensed frame and second condensed frame, according to the frame head information reverting datagram of previous frame, and the frame head information of preserving described first condensed frame and second condensed frame.
4, the method for header compression as claimed in claim 3 is characterized in that, described transmission first condensed frame and second condensed frame to receiving terminal are:
When the number of datagrams of handling reaches default press cycles numerical value, send described first condensed frame and second condensed frame to receiving terminal, then begin next press cycles, next datagram is handled.
As the method for claim 1,2,3 or 4 described header compressions, it is characterized in that 5, described method also comprises:
When the number of datagrams of handling reaches default numerical value, generate initial frame according to datagram again, continue to generate new condensed frame then.
6, as the method for claim 1,2,3 or 4 described header compressions, it is characterized in that, describedly generate initial frame according to datagram and be:
According to above initial frame of a corresponding generation of above datagram.
As the method for claim 1,2,3 or 4 described header compressions, it is characterized in that 7, described method also comprises:
Transmitting terminal with the frame head information stores in the transmitting terminal context, generate new frame at every turn after, upgrade the transmitting terminal context;
Receiving terminal with the frame head information stores in the receiving terminal context, receive initial frame or restoring data newspaper at every turn after, upgrade the receiving terminal context.
8, a kind of compressor plant is characterized in that, described compressor plant comprises comparing unit and generation unit:
Generation unit is used for generating initial frame according to datagram, and remove that comparing unit finds out from first datagram and second datagram can compressed redundant field, generate condensed frame;
Comparing unit is used to compare the frame head information of the first datagram header and initial frame, find out in the described first datagram header can compressed redundant field, the frame head information of comparing the previous frame of the second datagram header and the described second datagram header find out in the described second datagram header can compressed redundant field.
9, compressor plant as claimed in claim 8, it is characterized in that the redundant field that described comparing unit obtains is: field that the field that can be calculated by other fields or front and back datagram header respective field value remain unchanged substantially or front and back header respective field value change but field clocklike.
10, compressor plant as claimed in claim 8 or 9 is characterized in that described compressor plant also comprises memory cell: be used for frame head information stores with described initial frame and condensed frame in context.
11, a kind of transmission system is characterized in that, described system comprises compressor reducer and decompression machine:
Compressor reducer is used for generating initial frame to decompression machine according to datagram; Compare the frame head information of the first datagram header and initial frame, find out and remove in the described first datagram header can compressed redundant field, generate first condensed frame; Compare the frame head information of the previous frame of the second datagram header and the described second datagram header, find out and remove in the described second datagram header can compressed redundant field, generate second condensed frame, and send the described initial frame and first condensed frame and second condensed frame to decompression machine;
Decompression machine is used to receive initial frame and condensed frame, after receiving described first condensed frame and second condensed frame, according to the frame head information reverting datagram of described first condensed frame and the previous frame of second condensed frame.
12, transmission system as claimed in claim 11, it is characterized in that described redundant field is: field that the field that can be calculated by other fields or front and back datagram header respective field value remain unchanged substantially or front and back datagram header respective field value change but field clocklike.
13, transmission system as claimed in claim 11 is characterized in that, described compressor reducer is used to send condensed frame to decompression machine and is:
Described compressor reducer is used for sending whole described condensed frames to decompression machine when the number of datagrams of handling reaches default press cycles numerical value, then begins next press cycles, and next datagram is handled.
As claim 11,12 or 13 described transmission systems, it is characterized in that 14, described compressor reducer also is used for generating initial frame according to datagram again when the number of datagrams of handling reaches default numerical value, continues to generate new condensed frame then.
As claim 11,12 or 13 described transmission systems, it is characterized in that 15, described compressor reducer is used for generating initial frame according to datagram and is: described compressor reducer is used for generating an above initial frame according to above datagram is corresponding.
As claim 11,12 or 13 described transmission systems, it is characterized in that 16, described compressor reducer also is used for the frame head information stores in the transmitting terminal context, generate new frame at every turn after, upgrade the transmitting terminal context;
Described decompression machine also is used for the frame head information stores in the receiving terminal context, receive initial frame or restoring data newspaper at every turn after, upgrade the receiving terminal context.
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| CN101969362B (en) * | 2010-09-30 | 2014-09-10 | 中兴通讯股份有限公司 | Mask generation method, method and corresponding device for selecting list compression encoding mode |
| WO2012103722A1 (en) * | 2011-06-29 | 2012-08-09 | 华为技术有限公司 | Reception method and apparatus, transmission method and apparatus, and processing system for rtp media data |
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| EP3050303B1 (en) * | 2013-09-27 | 2019-04-17 | LG Electronics Inc. | Apparatus for transmitting broadcast signals and method thereof |
| CN108307204B (en) * | 2017-01-13 | 2020-07-28 | 上海交通大学 | A L P packaging method based on multi-service TS flow |
| CN112468887A (en) * | 2019-09-06 | 2021-03-09 | 杭州海康微影传感科技有限公司 | Thermal imaging data transmission method and device and thermal imaging equipment |
| CN113868182A (en) * | 2021-09-28 | 2021-12-31 | 歌尔科技有限公司 | Data compression method, device, equipment and medium |
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