Abstract: This article introduced in the TD-SCDMA signaling reflectoscope reflector data acquisition card realizes the plan based on PowerPC the network processor’s ATM, mainly has analyzed ATM data acquisition software’s each module, explained the data acquisition card data processing flow in detail. The actual use indicated that this article proposed the data acquisition card already succeeded carries on the correct receive to the ATM different adaptive level cell to reorganize and to assemble the transmission, has the very great use value.
Key word: TD-SCDMA; Network reflectoscope reflector; ATM data acquisition card; Data processing flow
Introduction
Our country proposed independently the TD-SCDMA standard is mature gradually along with the standard consummation and the system equipment, in addition government’s force support, will certainly to occupy the important small space in our country’s 3G construction. But can TD-SCDMA network each connection (Iub, Iur, Iu and so on) carry on the monitoring and the simulation signaling reflectoscope reflector is in the TD-SCDMA industry chain’s important link. At present between the TD-SCDMA transmission network various connections’ data transfer mainly uses the IMA agreement and STM-1 (even a higher speed) the connection ATM transmission. But realizes to various connections data acquisition is the important basis which the TD-SCDMA signaling reflectoscope reflector realizes. This article main introduction based on PowerPC TD-SCDMA network reflectoscope reflector ATM data acquisition card software module realization.
AAL2 and AAL5 partition and reorganization
The ATM cell is the ATM pass-along message basic carrier, uses the fixed length the cell form, has 53 bytes, 5 bytes are the headers, other 48 bytes for cell only Holland. Believes the round head to have 2 kind of forms: User network interface UNI and network-node interface NNI, concrete form as shown in Figure 1. In Figure 1, GFC is the general flow control, 4bit. Only uses in the UNI connection, the item pretage is “0000″, will use in the future possibly in the flow control; VPI is empty channel marking, NNI is 12bit, UNI is 8bit; VCI is empty circuit marking, 16bit, marks in the empty channel’s empty circuit, VCI and VPI combines marks an empty connection; PTI is the Dutch type instructed only, 3bit, uses for to instruct the cell type; CLP is the cell loss priority, 1bit. Uses in the cell loss rank the difference, CLP is 1, indicated that this cell is the low priority; HEC is the header error control, 8bit, monitors has mistake’s header, may correct in the header 1 bit mistake. HEC also uses in cell delimitation [1].
Figure 1 ATM letter round head form
ATM adaptive level AAL primary cognizance ATM level and high-level between cell repeater process. Receives the repeater information after the upper formation, AAL divides the data the cell; Receives the repeater information after the ATM level, AAL must gather the load to form the form which an upper formation can recognize. The above operation called it partitions and reorganizes SAR, it is the AAL primary mission. Different AAL supports the different current capacity or the service type. The following introduction AAL2 which and the AAL5 cell form and their partition and the reorganization uses in TD-SCDMA. [2]
AAL2 partition and reorganization
AAL2 is suitable for the transmission low gear rate pronunciation current capacity. AAL2 is divided into the common segment sublayer (CPS, Common Part Sublayer) and the service specific convergance sublayer (SSCS, Service Specific Convergence Sublayer). Figure 2 has given a CPS package of form. And CID: Channel marking, in CPS-PH CID may facilitate the CPS-PP distinction in the VCC condition, it has 8 elements, altogether 255 values, but only then 248 CID retentions give the user; LI: Length display. The data packet payload’s length is connected with each independent user, the value is smaller than the payload, and has 45 bytes (possible establishment is 64 bytes) default value, what it refers to is the wrapped gift carries while length (CPS-PP), when it is the zero hour, then the expression length is 1byte, therefore CPS-PP is 1byte at least; UUI: The user instructed to the user that provides CPS and during a suitable SSCS link, satisfies the high-level application procedure request; HEC: Header error control. Many CPS packages have composed CPS-PDU, many CPS-PDU have composed SSSAR-PDU, many SSSAR-PDU have composed SSSAR-SDU. Figure 3 has given the AAL2 data unit partition and the reorganization situation.
Figure 2 AAL2 CPS package of form
Figure 3 AAL2 partition and reorganization
AAL5 partition and reorganization
AAL5 is simple and effective AAL(SEAL), basically uses in the data current capacity question. It does not contain the Per-Cell length or Per-Cell the CRC field. Figure 4 has given the AAL5 data unit structure. CPCS-PDU Payload: May lengthen the user information field; PAD: Gap, length between 0 to 47 bytes; UU:CPCS user to user instruction; CPI- common segment instruction; Length: Length display.
Figure 4 AAL5 construction of data unit
The AAL5 reorganization and AAL2 are very similar, is carries on SAR-PDU the merge, becomes CPCS-SDU the Holland only. What is only different does not include the CID number in AAL5, therefore its reorganization must be simpler than AAL2. Figure 5 shows AAL5 the data unit partition and the reorganization situation.
Figure 5 the AAL5 partition and reorganizes [4]
ATM data acquisition card data processing flow
The network processor is one kind of programmable component, usually cooperates the processor by certain micro code processor and the hardware to be composed, may realize the service flexibility and the high performance organic synthesis. Motorola Corporation (editor note: Presently is Freescale) PowerPC is together the function formidable network processor, by G2_LE Core, correspondence processing module (CPM) constitutes a binuclear processor. In this design, we mainly realize the ATM agreement with it, completes the ATM cell the grouping and the reorganization function. Concrete data flow as shown in Figure 6.
Figure 6 STM-1 data flow diagram
ATM data acquisition card software design
Data when transmission, the news body is divided each one standard the ATM cell, seals the STM-1 frame transmission; When receive must take out the standard from the STM-1 frame the ATM cell, carries on the reorganization to the data, returns to original state the concrete news. In order to realize data gathering, the prime task solidifies by the PowerPC processor movement in the data acquisition card the software module realizes. The software module is composed of four parts: Initialization module, address mapping module, receive control module, activation module composition.
Initialization module
The initialization module completes PowerPC the parameter RAM disposition, the FCC corresponding register’s disposition and Interruption queue’s initialization, causes the overall system to maintain at one kind of readiness for action, its disposition flow as shown in Figure 7.
Figure 7 initialization module
Address mapping module
The address mapping module is responsible to come from different VPI/VCI the combination the ATM cell to lay aside to the SDRAM different position. Figure 8 gave the address mapping processing mechanism, the address mapping flow has been as follows:
A. using VPI, VP_MASK obtains VPpointer, this value uses in this VPI in the VPT form index;
The B. basis VPT_BASE VPpointer×4 obtains this VPI in the VPT table position, reads in “VC_MASK” in the corresponding territory and “VCOFFSET”. And VC_MASK by own definition, the VCOFFSET value “VCOFFSET(n 1) = VCOFFSETn 2 (number of ones in VC_MASKn)” calculates based on the formula;
C. with VCI which receives may obtain VCpointer using in VPT form VC_MASK, is similar with B, uses this VCT_BASE VCpointer×4 to locate this VCI in this VCT form the position;
D. address which obtains according to C, fills in “MS, Ch Code” in the related territory. And the MS expression match condition, MS=0 expresses the match. Docking received said that corresponding VPT and the VCT form must complete first, if received the letter round head just was this to VPI/VCI, then might obtain the MS=0 symbol, thus found out for this reason to the VPI/VCI assignment channel number “Ch Code”, then construction of data carried on the data according to Figure 4 receive processing; Otherwise this cell discarding.
Figure 8 address mapping mechanism
Receive control module
In the receive module, the system first a ATM cell which receives divides into two parts: Believes the round head and only Holland; Then the address mapping mechanism which according to shown in Figure 8, in use letter round head’s VPI searches the VPT table, afterward searches the VCT table again using VCI, takes out channel number Ch Code; According to this channel number achievement index, found corresponding RCT (receive connection form) to carry on the parameter the disposition, needed to define AAL in the RCT form the type, AAL2 must be more than CID AAL5 to reflect the firing table and the RxQD form search, with the difference was CPS or SSSAR; Then inside the basis address field found corresponding RxBD (receive cushion descrptor) and the initialization corresponding territory; Finally completes the data receive memory block according to the RxBD in data receive address field the initialization, receives cell Holland lays aside only to this region, when after activation module execution, CPM on the basis receive control module’s disposition, completes the different adaptive level the data reorganization, thus realizes the data receive. Concrete flow as shown in Figure 9.
Figure 9 data receive module
Activation module
The activation module is the system to the CPM transmission “CPCR” the order, causes all initialization module disposition the parameter to become effective, start receive. The system the data which receives puts according to the address mapping and the receive disposition module’s establishment to the corresponding position, (interrupt processing mechanism like chart 10) carries on the data through the interrupt way from the definition reorganization, adds on for each news body from defines the head, becomes one (its form as shown in Figure 11) from the definition frame, through the PCI interrupt, by the DMA way data transfer upper formation.
Figure 10 interrupt processing mechanism
Figure 11 from definition frame form
Conclusion
TD-SCDMA is the 3G standard which our country proposed independently, is also our country 3G network construction key consideration standard. At present the TD-SCDMA network construction aspect also has many work to need to do. Develops has the proprietary intellectual property rights TD-SCDMA network reflectoscope reflector, consummates the TD-SCDMA industry chain, will certainly to have the huge social efficiency and the economic efficiency. This article proposed the TD-SCDMA network reflectoscope reflector data acquisition card realized the plan already to succeed carries on the correct receive to the ATM different adaptive level cell to reorganize and to assemble the transmission. Has processed electric circuit’s revision based on this plan’s data acquisition cartoon to the physical level to be possible to facilitate realizes ATM IMA data gathering, has the very great use value.
Reference:
1. ITU-T Rec. I.361 B-ISDN ATM LAYER SPECIFICATION, Feb. 1999: 7-14
2. Wu Lingxi, yellow iris equality, “The data–gathering design and realization based on UTOPIA”. Journal of Xiangtan Normal University (Natural Science Edition). VoI.26 No.3 Sep.2004
3. The Liao hawk, with realizes based on AAL5 ATM and the IP high speed intercommunication connection’s design, computer project, the 31st volume, the 4th issue, in February, 2005
4. Veitch PA., Johnson D, Hawker I. Design of resilient core ATM networks[J].GLOBECOM ‘97. , IEEE, Volume 3, 3-8 Nov. 1997:1450 - 1454
