CN101562898B - High-efficiency wireless access system RTP agent technology - Google Patents
High-efficiency wireless access system RTP agent technology Download PDFInfo
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Abstract
The invention provides a RTP agent technology which is suitable for improving the transmission efficiency of an air interface and IP backhaul when a wireless access system provides VOIP voice service. The method completes the RTP agent between a user and a soft switch core network by the cooperation of a terminal of the wireless access system, a base station, a gateway, and the like. The invention adopts the core processing that original user media packets are directly transmitted in air interface frames; multipath user data at the same base station is multiplexed into a UDP/IP packet to be transmitted by a private protocol on the wireless backhaul; and the media negotiation and the conversion of a private media data packet to a standard RTP packet are carried out on the interfaces of an access network and the core network. The RTP agent technology can improve the transmission efficiency of the air interface of the wireless access system and the IP backhaul, and can not change the interface between the access system and the soft switch core network simultaneously.
Description
Technical field
The eat dishes without rice or wine RTP agent skill group of interface efficient of efficiency of transmission and base station passback of the raising multimedia service that is applicable to wireless access system that the present invention proposes a kind of novelty.
Background technology
In the wireless access system that adopts the Soft core net, the professional RTP encapsulation of adopting mostly based on the UDP host-host protocol of real-time multimedias such as VoIP, Vedio is to provide real-time Transmission end to end.
But for voice and some chat class data services, the packet header of each RTP/UDP/IP bag is longer, and business datum is less relatively, directly eating dishes without rice or wine to transmit the RTP bag, will cause the effective rate of utilization of Radio Resource not high.
In addition, the IP backhaul data traffic between base station and the gateway is very big, and bandwidth resources are limited, become the bottleneck of transmission bandwidth in the Access Network.If with each user's RTP bag transmission separately, efficiency of transmission is low, certainly will further increase bandwidth and the expense of IP backhaul.
Summary of the invention
Basic thought of the present invention is to cooperate the RTP agency who finishes jointly between user and the SoftSwitch by equipment such as wireless access system terminal, base station and gateways.
For realizing purpose of the present invention, a kind of method of wireless access system RTP agent has efficiently been proposed, may further comprise the steps:
1, directly with the load transmission of user data package as the frame of eating dishes without rice or wine, the recipient receives processing for interface aloft, the transmit leg of user data package;
2, the IP backhaul between base station and gateway, base station and gateway all need the proprietary protocol of supporting that the present invention designs, the transmit leg of regulation uplink and downlink link is all with the data encapsulation of unique user, again with a plurality of user's data under the base station according to certain format multiplexing after transmission again;
3, the standard SIP/RTP interface between Access Network and core net, gateway is responsible for finishing media negotiation; Before each road media delivery began, gateway need be consulted the RTP context of this session with SoftSwitch, comprises CODEC, RTP packaging time length, sampling rate etc.;
4, after media negotiation was finished, gateway is responsible for realizing the media data packet of Access Network proprietary protocol and the conversion of standard RTP bag: up link, gateway at first decomposited multiplexing multichannel user data, carry out the conversion of SRTP and Real-time Transport Protocol again; Down link, gateway are converted to the SRTP bag with the RTP bag of each reception earlier, carry out multiplexed again.
Method of the present invention can improve the efficiency of transmission of wireless access system air interface and backhaul, does not change the interface between connecting system and the Soft core net simultaneously again.
Description of drawings
Below in conjunction with accompanying drawing the specific embodiment of the present invention is described in further detail.
Fig. 1 acts on behalf of the network structure of RTP technology for being suitable for wireless access system;
Fig. 2 is the schematic diagram of bag of the next round of SRTPSN1 for SRTPSN2;
Fig. 3 is that SRTPSN2 and SRTPSN1 are one of schematic diagrames of same bag of taking turns;
Fig. 4 for SRTPSN2 and SRTPSN1 be same bag of taking turns schematic diagram two;
Fig. 5 is the schematic diagram of the last round of bag of SRTPSN1 for SRTPSN2.
Embodiment
Be suitable for network configuration of the present invention as shown in Figure 1.The network element of present networks framework comprises: terminal (UT), base station (BS), gateway (SAG) and SoftSwitch (SS).
Air interface between terminal 1 and base station 2, terminal 1 and base station 2 are directly with the load transmission of user data as the frame of eating dishes without rice or wine.In theory, transmit leg only needs to carry out the processing of original media data, but because the circumstance complication of eating dishes without rice or wine, the situation that packet loss and irregular delay take place is more serious, and the mechanism that also needs guarantees the correct transmission that Media Stream is being eated dishes without rice or wine.The present invention adds sequence number to the original media bag of air interface transmission, carries out buffer memory and ordering the recipient simultaneously, to guarantee the correct reception of Media Stream as far as possible.That is to say that terminal 1 also needs to carry out the buffer memory and the ordering of downlink data packet, and the upstream data bag adds sign.Buffer memory and ordering also will be carried out to uplink data packet in base station 2 simultaneously, and downlink data packet is added sign.
IP backhaul between base station 2 and gateway 3, the present invention has designed proprietary protocol, and base station and gateway all need to support this proprietary protocol.This proprietary protocol comprises two parts operation.At first, with the data encapsulation of unique user, its header field comprises Session ID, bag sequence number and time stamp etc., is called the SRTP agreement among the present invention.Then, again transmission in the UDP/IP bag is used in a plurality of user's data claddings.When multiplexing, also need to increase the multiplexing control word of DMUX in the back of UDP header field, its content comprises the encapsulation format of packet, priority and multiplexing bag number etc.
As the interface of Access Network and core net, the interface between gateway 3 and the SoftSwitch 4 is the SIP/RTP agreement of standard.Gateway need be finished the media data packet of Access Network proprietary protocol and the conversion of standard RTP bag.Up link, gateway 3 at first decomposite multiplexing multichannel user data, carry out the conversion of SRTP and Real-time Transport Protocol again; Down link, gateway 3 are converted to the SRTP bag with the RTP bag of each reception earlier, carry out multiplexed again.Simultaneously, before each road media delivery began, gateway 3 need be consulted the RTP context of this session with SoftSwitch 4, comprises CODEC, packaging time length, sampling rate etc.
In order to save link circuit resource to greatest extent, the bag sequence number of SRTP agreement and time stamp all are bytes, and the bag sequence number of Real-time Transport Protocol and time stamp are respectively 2 and 4 bytes.When carrying out the conversion of SRTP and RTP bag, the present invention has also designed the algorithm of sequence number and time stamp bi-directional conversion.Concrete grammar is as follows:
(1) sequence number (SN) conversion
A.SRTP SN-＞RTP SN conversion
During the SN conversion, SN is 1byte among the SRTP, and promptly the SN counter-rotating appears in 256 voice packets; SN is 2byte among the standard RTP, and promptly counter-rotating appears in 65536 voice packets.So the SN of the 1byte among the SRTP need be transformed to the SN of 2byte, and calculate correct RTP and send sequence number.
Under the gateway transparent transmission mechanism, gateway only carries out the protocol conversion from SRTP to RTP, realize two kinds of agreements sequence number synchronously.Wherein the serial number range of SRTP bag is 0～255, and the serial number range of RTP bag is 0～65535, and the sequence number that how sequence number of SRTP bag is converted to the RTP bag is the key of whole transparent transmission mechanism.Suppose that gateway receives two SRTP bag, its sequence number is respectively SRTPSN1 and SRTPSN2, the sequence number of supposing its corresponding RTP bag is respectively RTPSN1 and RTPSN2, we look at the relation between these sequence numbers: SRTPSNDEF=SRTPSN2-SRTPSN1, consider the sequence number turning problem of SRTP bag, we must consider that whether upset has taken place two SRTP bags.
As shown in Figure 2, as can be seen from Figure 2 SRTPSNDEF=SRTPSN2-SRTPSN1=10-200=-190＜-128, and dis1＞dis2 clearly, nearby principle, SRTPSN2 is relative, and upset has taken place in SRTPSN1, that is to say that SRTPSN2 is the bag of next round, i.e. SRTPSN2=((256+SRTPSNDEF)+SRTPSN1) %256.
If as shown in Figure 3, from Fig. 3, calculate SRTPSNDEF=SRTPSN2-SRTPSN1=10-110=-100＞-128 and＜128, and dis1＜dis2 clearly, nearby principle, SRTPSN2 is relative, and SRTPSN1 does not overturn, and SRTPSN2 and SRTPSN1 are same bags of taking turns in other words.Perhaps as shown in Figure 4, from Fig. 4, calculate SRTPSNDEF=SRTPSN2-SRTPSN1=110-10=100＞-128 and＜128, and dis1＜dis2 clearly, nearby principle, SRTPSN2 is relative, and SRTPSN1 does not overturn, and SRTPSN2 and SRTPSN1 are same bags of taking turns in other words.
If but as shown in Figure 5, from Fig. 5, can calculate SRTPSNDEF=SRTPSN2-SRTPSN1=190-10=180＞128, and dis1＜dis2 clearly, nearby principle, SRTPSN1 is relative, and upset has taken place in SRTPSN2, that is to say that SRTPSN2 is last round of bag, i.e. SRTPSN1=(SRTPSN2+ (256-SRTPSNDEF)) %256.
Sum up above-mentioned several situation, we can provide a relational expression of several sequence numbers:
IF?SRTPSNDEF＜-128
RTPSN2＝(RTPSN1+(256+SRTPSNDEF))％65536
IF?SRTPSNDEF＞＝-128?AND?SRTPSNDEF＜128
RTPSN2＝(RTPSN1+SRTPSNDEF)％65536
IF?SRTPSNDEF＞128
RTPSN2＝RTPSN1+(SRTPSNDEF-256)
B.RTP SN-＞SRTP SN conversion
RTP SN becomes 1byte with sequence number from 2byte exactly to SRTP SN and gets final product, and directly the SN mould 256 of RTP is got remainder and gets final product.Computing formula is as follows:
SRTP?SN＝RTP?SN％256
(2) time stamp conversion
In standard RTP, the time stamp in the voice packet is each sampling period to increase by 1.For example, sample rate is the G.729 coded system of 8K, and every 10ms RTP time stamp increases by 80, and promptly the RTP time stamp cycle is 1/8ms.Because the time stamp length of SRTP is short, for fear of the frequent upset of time stamp, adopt every 10ms time stamp to increase by 1, promptly the SRTP time stamp cycle is 10ms, with the ratio in RTP time stamp cycle be 80.
The a.SRTP time stamp-＞the RTP time stamp
Need the SRTP time stamp of 1byte is become 4byte standard RTP time stamp herein.
Suppose that gateway receives two SRTP bag, its time stamp is respectively SRTPTIME1 and SRTPTIME2, and SRTPTIMEDEF=SRTPTIME2-SRTPTIME1; And the time stamp that the SRTP through 4byte upset processing after corresponding with it wraps is respectively RTPTIME1 and RTPTIME2.
During the time stamp conversion, need judge whether present time stamp upset has taken place according to the value of previous time stamp, concrete upset judgment mode can be referring to the determination methods of SN sequence number upset.
IF?SRTPTIMEDEF＜-128
RTPTIME2＝(RTPTIME1+(256+SRTPTIMEDEF))％2^32
IF?SRTPTIMEDEF＞＝-128AND?SRTPTIMEDEF＜128
RTPTIME2＝(RTPTIME1+SRTPTIMEDEF)％2^32
IF?SRTPTIMEDEF＞128
RTPTIME2＝RTPTIME1+(SRTPTIMEDEF-256)
Then the time stamp of RTP is: (the initial time stamp of RTPTIME2 * 80+RTP) %2^32.
The b.RTP time stamp-＞the SRTP time stamp
According to the description of up time stamp conversion, descending RTP time stamp is exactly the every increase 80 of RTP time stamp to the conversion of SRTP time stamp in fact, and the SRTP time stamp increases by 1 (based on the sampling rate of 8k), and the per 256 generation upsets of SRTP time stamp get final product.Account form is as follows:
SRTP time stamp=((the initial time stamp of RTP time stamp-RTP)/initial time stamp of 80+SRTP) %256
Claims (7)
1. a wireless access system RTP agent method is characterized in that, may further comprise the steps:
A. interface aloft, directly with the load transmission of user data package as the frame of eating dishes without rice or wine, the recipient receives processing to the transmit leg of user data package;
B. the IP backhaul between base station and gateway adopts proprietary protocol, this proprietary protocol comprises SRTP agreement and the multiplexing two-layer content of multichannel data that realizes single user data encapsulation, the transmit leg of regulation uplink and downlink link is all with the data encapsulation of unique user, again with a plurality of user's data under the base station according to certain format multiplexing after transmission again;
C. the standard SIP/RTP interface between Access Network and core net, gateway is responsible for finishing media negotiation; Before each road media delivery began, gateway need be consulted the RTP context of this session with SoftSwitch, comprises CODEC, RTP packaging time length, sampling rate;
D. after media negotiation was finished, gateway is responsible for realizing the media data packet of Access Network proprietary protocol and the conversion of standard RTP bag: up link, gateway at first decomposited multiplexing multichannel user data, carry out the conversion of SRTP agreement and Real-time Transport Protocol again; Down link, gateway are converted to the SRTP bag with the RTP bag of each reception earlier, carry out multiplexed again.
2. method according to claim 1 is characterized in that, the described frame of eating dishes without rice or wine of step a also can add sequence number for user data package, to guarantee its correct transmission.
3. method according to claim 2 is characterized in that, terminal or base station receive to be cushioned according to sequence number behind the user data and sort.
4. method according to claim 1 is characterized in that, the header field of the SRTP agreement of the single user data encapsulation of the described realization of step b comprises Session ID, bag sequence number and time stamp.
5. method according to claim 4 is characterized in that, the bag sequence number of described SRTP agreement and time stamp all are bytes, and the bag sequence number of Real-time Transport Protocol and time stamp are respectively 2 bytes and 4 bytes.
6. method according to claim 5 is characterized in that steps d, and the conversion method of SRTP bag sequence number and RTP bag sequence number is as follows:
(1) SRTP bag sequence number is converted to RTP bag sequence number:
At first calculate the difference that SRTP bag sequence number deducts previous SRTP bag sequence number; If this difference is less than-128, then to previous RTP bag sequence number, this difference and 256 3 numerical value summations, divided by 65536, the gained remainder is RTP bag sequence number with the gained summation; If this difference is greater than-128 and less than 128, then to previous RTP bag sequence number and the summation of this difference, divided by 65536, the gained remainder is RTP bag sequence number with the gained summation; If this difference is greater than 128, then previous RTP bag sequence number adds that this difference deducts 256 again, and the gained result is RTP bag sequence number;
(2) RTP bag sequence number is converted to SRTP bag sequence number:
Directly RTP is wrapped sequence number divided by 256, the gained remainder is SRTP bag sequence number.
7. method according to claim 5 is characterized in that steps d, and the conversion method of SRTP time stamp and RTP time stamp is as follows:
(1) the SRTP time stamp is converted to the RTP time stamp according to following steps:
A, the SRTP time stamp is converted to 4 bytes: at first calculate the difference that the SRTP time stamp deducts previous SRTP time stamp; If this difference is less than-128, then to previous SRTP time stamp conversion value, this difference and 256 3 numerical value summations, divided by 2 32 powers, the gained remainder is SRTP time stamp conversion value with the gained summation; If this difference is greater than-128 and less than 128, then to previous SRTP time stamp conversion value and the summation of this difference, divided by 2 32 powers, the gained remainder is SRTP time stamp conversion value with the gained summation; If this difference is greater than 128, then previous SRTP time stamp conversion value adds that this difference deducts 256 again, and the gained result is SRTP time stamp conversion value;
B, calculate the ratio of SRTP time stamp cycle divided by the RTP time stamp cycle;
C, calculate the RTP time stamp: SRTP time stamp conversion value be multiply by the time stamp periodic ratio, and the gained product adds the initial time stamp of RTP, again with the gained summation divided by 2 32 powers, the gained remainder is the RTP time stamp;
(2) the RTP time stamp is converted to the SRTP time stamp:
The result that the RTP time stamp is deducted the initial time stamp of RTP is divided by 80, and the gained quotient adds the initial time stamp of SRTP, again with the gained summation divided by 256, the gained remainder is the SRTP time stamp.
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| CN1633102A (en) * | 2003-12-24 | 2005-06-29 | 华为技术有限公司 | Method for implementing NAT traversing and system thereof |
| CN1556628A (en) * | 2003-12-30 | 2004-12-22 | Method of realizing signalling, speech sound cross network transmission |
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Assignee: SHENZHEN XINWEI TELECOMM TECHNOLOGY CO., LTD. Assignor: Xinwei Communications Technological Co., Ltd., Beijing Contract record no.: 2011110000200 Denomination of invention: High-efficiency wireless access system RTP agent technology Granted publication date: 20110406 License type: Exclusive License Open date: 20091021 Record date: 20111226 |
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