3.1 GSM Circuit and Packet Data Services
GSM data service can be classified into two types, circuit data services and packet data services, which are respectively decribed in the following sections.
Circuit data services incude bearer services such as asynchronous circuit service (BS2X), synchronous circuit service (BS3X), asynchronous PAD circuit service (BS4X), synchronous packet service (BS5X), alternate voice/data service (BS61), voice followed by data service (BS81) and tele-services such as group-3 facsimile service, alternate voice/fax. The circuit data services are different from speech services in the processing of modules such as MS, BTS, MSC and TC in the GSM system. The following describes the data transmission flow of data services in the GSM system.
Figure 3-1 The data flow of data services in the GSM system
The circuit data service can be applied within PLMS and between PLMN and PSTN/ISDN/PSPDN. The interworking between PLMN and PSPDN is via PSTN/ISDN. Different bearer services have different transmission paths. Accordingly, the networking modes are also different. Here the transmission path of the asynchronous circuit data service (BS2X) is taken as an example for illustration. As shown in the following Figure, the BS2X service has three connection modes: 3.1K Hz audio connection, 64Kbit/s unrestricted digital connection, and basic PAD access. Among them, the basic PAD access is via PSTN (3.1K Audio) or ISDN (3.1k Audio or 64k UDI). In the basic PAD access, the connection between the mobile subscriber and the X.25 card of PSPDN is based on dual numbers. The dialup program of the dailing subscriber is the same as that of the PSTN asynchronous terminal user to dialup and access the PSPDN, i.e. the second-dialing mode is adopted. In addition, the networking modes of BS3X, BS4X and BS5X are different. This will not be reiterated due to the size limitation of this document.
Figure 3-2 Transmission path of BS2x service
3.1.2 Packet Data Service
The relevant specifications for General Packet Radio Service (GPRS) are formulated in the latest Phase II+ standard. Such concepts as packet switching and packet transmission are introducted in the GPRS architecture, hence enhancing the GSM network to support data services in the aspect of network architecture. On the basis of the original GSM networks, some functional functional entities such as Serving GPRS Support Node (SGSN), Gateway GPRS Support Node (GGSN) and Point-to-Multi-point Service Center (PTMSC) are added into the GPRS networks. In addition, some modifications and additions are made to the orginal MS, base station and the relevant signaling.
3.1.3 Related Terms
GSM circuit data services include bearer service and fax service. Bearer service refers to the capability of transmitting information between the network and the user node. Tele-service refers to the capability of transmitting all information between the terminals. GSM entity, as the bearer network, is independent from the end-to-end service. It is only reflected in the bearer capability of transmission data streams. Fax service include group 3 facsimile service (TS62) and voice fax alternate service (TS61).
Bearer services include BS2X, BS3X, BS4X and BS5X. BS2X supports the circtuit switching, and full-duplex and asynchronous data transmission. This service can be either transparent or non-transparent. It can be use for communications between the data terminal equipment and provides 3.1kHz audio or 64kbits/s unrestricted digital connection. BS3X supports circuit switching, and full-duplex and synchronous (bit-orienated) data transmission. It is used for the basic packet access. BS4X supports circuit switching, and full-duplex and asynchronous data transmission. The simple terminal can be allowed to communicate with X25 terminal via X28 protocol. It directly adopts PAD instead of ISDN and PSTN to access PSPDN. BS5X supports the full-duplex synchronous data transmission and the synchronous terminal to access PSPDN in the pakcet mode.
Some concepts will be often used in the GSM circuit data services. They will be briefly introduced here.
Transparent service and non-transparent service. Transparent service does not provide the error correction mechanism in the link layer between MT (TA) and IWF, while non-transparent service does. The link layer of the latter is composed of Radio Link Protocol (RLP) and Layer 2 Protocol (L2R). The L2R provides the interface from IWF to the link layer protocol of the fixed network (such as LAPB and ISO6429). Non-transparent transmission can achieve the errorless transmission of the information between MT (TA) and IWF .
Second, the concepts of synchonization and asynchronization should be made clear. Synchronization and asyncronization here refer to the compostion mode of the information flow between TE/TA and MT, and between IWF and the fixed network. Of which, the asynchronous transfer mode is orienated to characters, that is, the information is transmitted as different characters. Each character has its start bit and stop bit. The synchronous transfer mode corresponds to the Packet Access service.
Furthermore, 3.1K Audio/UDI should be made clear. It refers to the coding format of the informationfrom from IWF to the fixed network. The so-called 3.1K Audio is derived from the change of the data stream via MODEM, while UDI is the form of data without change via MODEM. PLMN can only interwork with PSTN via 3.1k Audio. Generally, PLMN interworks with PSPDN via UDI, while PLMN interworks with ISDN via 3.1k Audio and UDI.
Currently, BS2X series of transparent and non-transparent bearer services, group 3 auto facsimile service and voice fax alternate service are the major services in the
market. Our IWF equipment supports BS2X and BS4X series of transparent and non-transparent bearer services, and TS61 and TS62 fax services.
Besides the mobile-to-mobile fax services, TS61 and TS62 services are mainly compatible with the telecommunication fax services in the public fixed network, and they enable the mobile subscribers to realize their dreams that the fax file can be sent or received at any time and any place. For specific operations, please refer to the User?s Operation Guide. BS2X bearer service refers to the capability of transmitting information between the network and the user node. The actual application of the user is based on this capability, such as dialup access to Internet, , E-mail and file transfer of mobile subscribers. For the detailed operations of the bearer services, please refer to the User?s Operation Guide.
3.2 Implementation of GSM Circuit Data Services
3.2.1 Introduction to IWF
IWF, i.e. InterWorking Function, means the interwoking function between networks. As for PLMN, the protocol specifies two types of data services: circuit data services and packet data services. Circuit data services include all bearer services and partial tele-services (Facsmile service). As PLMN GSM is different from PSTN in the internal transmission and processing, we cannot connect the PSTN subscribers directly by processing the link layer as in the mobile speech service. Instead, we need to process by adding the end-to-end protocol in the network layer. Here IWF refers to the means of enabling PLMN to interconnect and interwork with the circuiit data services of other networks (e.g. PSTN, ISDN and X.25) so as to make the transmission feature of the service in GSM adapt to that of the services in the fixed network, thus to ultimately achieve the objective: IWF is equal to a mobile terminal from the view of the mobile subscriber, and a fixed terminal from the view of the fixed subscriber. The adaptation is the interworking function (IWF). Logically, it is basically composed of a transmission equipment and a protocol adaptation unit. Specifically, the IWF unit processes functions such as Rate Adaption (RA), Radio Link Protocol (RLP/L2R) and Fax Adaptation (FA).
3.2.2 Implementation of IWF
I. Signaling flow of the host
The normal flow of the speech call will not be described in detail here. The differences of the call flow and the signaling between bearer/facsimile servce and the speech service are addrssed only.
- Calling flow
Figure 3-3 IWF basic calling flow
a) The CM receives the Setup message from the calling MS. If the BCdata ?3.1k Auto? or ?FASCIMILE GROUP 3? (for the BC format, see the appendix) are included in the Setup message, the CM will save this message after checking the basic format of the BC. Then the message will be sent to MAP for negotiation via "CM_MP_ObtainSubscriberParaOutgoingCall?. MAP will negotiate the BC reported by the calling Setup message according to the BC corrsponding to the calling subscriber in the VLR and the capability of MSC. If the BC has been modified, the negotiation result will be reported to CM via ?MP_CM_SubscriberPara?. If there is transparent preferred parameter (Both, transparent prefered) in the BC parameters sent from the calling subscriber, the MSC at the calling side will decide whether to use transparent or non-transparent in the end according to the protocol. This modification is accomplisshed in MAP. Meanwhile, other associated parameters need to be modified according to the rules as given in the Appendix of GSM protocol 0701. If the negotiation fails, the MAP will initiate the disconnection with the following possible causes: #57 ?bearer capability not authorized?, #58 ?bearer capability not presently available?, #70 ?only restricted digital information bearer capability is available?.
b) The CM receives the MP_CM_SubscriberPara message. If BC is included, it should be compared with the previously-saved BC. If there is any difference, the result will be sent to the MS via the Call Proceeding message. If there is data BC (No matter whether the data BC is prior or not) in the BC, the IWF channel will be pre-empted. In the radio channel assignment command ?Asssignement Request? to follow, the channel type in ?Channel Type? should be consistent with that required by the start BC, and the corresponding attributes (transparent/non-transparent, rate parameter) should consistent with that of the start data BC. If it fails to pre-empt the
IWF channel, the disconnect procedure will be initiated, with the cause being #65 ?bearer service not implemented?.
c) If the CM judges that the current BC is the data BC after having received the CONNECT message from the called subscriber, the IWF management module will send the activation command to the IWF board to acitvate the pre-empted IWF channel and to connect the HANDLE at the radio side of the IWF channel and the HANDLE at the A-Interface side. Till now, the channel setup has been accomplished.
- Called flow
Figure 3-4 IWF basic called flow
a) The called CM receives the Setup message from the calling side. If the BC is included, it will negotiated with the BC in the called subscriber data of the called CM sent by the previous MAP. The BC obtained by negotiation will be carried in the Setup message and sent to the called mobile station. The negotiation process is based on GSM protocol 0701. If there is no BC in the Setup message sent by the calling CCB, the message will be sent to the mobile station only according to the BC in the called subscriber data. In some special situations, the called subscriber data do not include the BC, either. Then the voice BC can be constructed and sent to the mobile station via the Setup message. The BC may not be provided for the mobile station and the Call Confirmed message in the mobile station determins which type of BC to use. This is controlled by the software parameter "ISUP_PARA_2_BIT1?. According to GSM protocol 0907, if the single-MSISDN scheme is used, the BC may not be provided for the mobile station. Instead, the mobile station will decide to use which kind of BC.
b) If the CM receives the Call Confirmed message from the MS which includes BC, it means that the BC in the Setup message has been modified in the called MS. In this case, it is necessary to initiate the check flow ?CM_MP_SubscriptionCheck_Req and
MP_CM_SubscriptionCheck_Rsp? to the MAP to just check the validity of the last used BC, and no modification will be conducted. If the BC is not included in the Call Confirmed message, then the called mobile can receive the BC in the Setup message, and the CM will no longer initiate the check flow to the MAP. After the necessary check, if the BC contains the data BC (No matter whether the data BC is prior or not), the CM will pre-empt the IWF channel. In the radio channel assignment command ?Asssignement Request? to follow, the channel type in ?Channel Type? should be consistent with that required by the start BC, and the corresponding attributes (transparent/non-transparent, rate parameter) should consistent with that of the start BC. If it fails to pre-empt the IWF channel, then it will initiate the disconnect procedure, with the cause being #65 ?bearer service not implemented?.
c) If the CM judges that the current BC is the data BC after having received the CONNECT message from the called MS. the IWF management module will send the activation command to the IWF board to acitvate the pre-empted IWF channels and connect the HANDLE at the radio side of the IWF channel with the HANDLE at the A-Interface side. Till now, the channel setup has been accomplished.
- Modify flow
Figure 3-5 Modify flow
As for TS61 (voice/fax alternate), BS61 (voice/data alternate) and BS81 (data followed by voice), after a call is set up, if the service attribute has been modified, the requirements for the channel all need to be modified. In this case, it only needs to re-assign the channel meeting the requirements at the network side instead of setting up a call again. This process is called the Modify process. According to GSM protocol 0408, the Modify process can be initiated by either the MS or the MSC. Currently, Huawei MSC only supports the Modify process initiated by a MS.
a) After the CM has received the Modify message sent by a MS, it will first check the mandatory BC information element. If it is consistent with the currently-used BC, the CM will directly return the Modify Complete message to the MS (if the 0xA3 redirection infromation element is carried in the Modify message, it also must be carried in the Modify Complete message). If different from the current BC, the BC information element should be compared with another BC in the CM. In case it is still different, the CM will reutrn the Modify Reject message to the MS, with the cause value being #57 ?bearer capability not authorized?. If the BC information is the same as another BC, the CM will send the Modify message to CCB.
b) After the CCB has received the voice-data Modify message, it will perform different processing operations according to the direction of the Modify message and it needs to conduct the iPath request process again. If at the other subscriber side is TUP/ISUP, the CCB is required to send the Modify message to TUP/ISUP. If the direction of the Modify message is from voice to data, then the TUP/ISUP module will send a command to the ECI board to disable the echo control function. If the direction of the Modify message is from data to voice, the echo control function will be enabled.
c) After the CM has received the Modify Complete message, it will proceed with the following process: if the current Modify process is from voice to data, the CM will activate the pre-empted IWF channel and then assign the data channel, with the correspongding parameters being consistent with the data BC; if the current Modify process is from data to voice, the CM will deactivate the pre-empted IWF channel (still pre-empted) and then de-assign the voice channel, with the corresponding parameters being consistent with the voice BC.
d) After the assignment is complete, the CM will send the Modify Complete message to the MS, with BC being the mandatory information element. If the 0xA3 redirection information element is included in the Modify message, it must also be carried in the Modify Complete message.
From the aforesaid IWF basic calling and called flows, we know that if the BC saved by the CM carries the data BC, the IWF channel will be pre-empted and the IWF resource will not be released in a call. Therefore, it is unnecessary to request the IWF resoucce again during the Modify process, and only activate/de-activate operations need to be performed.
As for 0xA3 redirection information element: in the facsimle service, there are two directions, i.e. sending and receiving directions. This parameter is required when the IWF channel is activated. As for TS61 service, if the Modify message is from voice to fax, the called subscriber can send the fax file. In this case, the direction of activating the IWF channel is just reverse to that in the normal situation. The protocol specifies that the 0xA3 redirection information element (This information element only carries Tag byte rather than L and V.) should be carried in the Modify and Modify Complete messages in this case.
II. CMM (Channel Mode Modify) process
Figure 3-6 CMM process
After the channel is established, it enters the data service processing stage. If the initial bit error rate is too high, the rate will be reduced. In this case, the low rate should be used to re-assign the radio channel and this is called Channel Mode Modify(CMM) proccess, which is initiated by the IWF board.
a) After the CM has received the CMM command, it will re-assign the data channel according to the rate, parameter, with other relevant parameters being identical with those of the currently-used data BC.
b) After the assignment, the CM will modify the rate parameter of the currently-used BC and give response to the IWF management moddule.
III. Table query process
IWF channel adopts the polling algorithm with the module preferred. First, the configurations in [IWF channel] table should be available; then, the state reported by the board should be available.
IV. Service processing
- Bearer service flow
The host sends the command with BC_IE to activate the IWF board, through which this command is forwarded to the IWF. After having received this command, the IWF will analyze the BC_IE and decide the drection, mid-rate and service type of this call and other parameters. Then the processing flow will be divided into three parts according to different service types.
- Processing flow of the transparent bearer service:
After the activation command is received, the host will instruct the MODEM chip in the IWF board to make a call or give an answer according to the call direction.
It sets the mid-rate, the initialization variable and the buffer.
Then it enters the synchronization frame search state, sends the synchronization frame to the radio side, and meanwhile searches the synchronization frame received from the radio side.
After more than 3 synchronization frames have been received from the radio side, the IWF enters the synchronization frame check state. Then, it will start the 600ms timer according to the protocol and waits for expiry.
After the timer expires, the IWF enters the data transmission state to judge whether the terminal has the V42 (transparent error correction) function.
If the V42 frame has not been received from the radio side, the IWF will wait to connect the MODEM of this board. After the MODEM is connected, the IWF will enter the normal non-error correction transparent data transmission state. If the V42 frame has been received from the radio side, the IWF will enter the stage of setting up the V42 protocol. For the specific flow, please refer to the V42 Protocol.
In the case of non-error correction transparent transmission, the IWF will only perform the conversion of RA2, RA1 and RA0 rates as well as the synchronization and asynchronization conversion instead of correcting the error data. Therefore, the transmission effect in this case is greatly related to the network quality. However, if the network quality is not satisfactory, there will be many error codes displayed in the terminal.
V. Processing flow of the bearer service in the non-transparent layer
After the activation command has been received, the host will instruct the MODEM chip in the IWF board to make a call or give an answer according to the call direction.
It sets the mid-rate, the initialization variable and the buffer.
It also sets the IWF to the data transmission state. The IWF communicates with the radio side via the exchange of RLP frame. The RLP is divided into the following states: AdmDetached, AdmAttached, PendingConnReq, PendingConnInd, AbmConnEstablish, DiscInitiated, PendingResetReq, PendingResetInd, PermanentError. It performs the corresponding processing according to different frames received in each stage.
After the AdmDetached enters the AbmConnEstablish state, the IWF board will wait to connect the MODEM of this board. After the MODEM is connected, the IWF enters the normal non-transparent data transmission state.
If the subscriber data are transmitted by the data encapsulated in the RLP information frame, the basic functions of error correction, re-transmission and flow control with the radio side can be implemented. After receiving the information frame, the IWF will
extract the valid data and send them to the MODEM of this board so as to achieve the data transmission.
As the non-transparent bearer service has such mechanisms as re-transmission and flow control, the network quality will not greatly affect the display effect of the user?s terminal. However, if the network quality is too poor and the number of re-transmissions is increased, the data transmission speed will slow down. Sometimes, the call will be disconnected.
- Processing flow of the facsimile service
MODEM makes a call or gives an answer. After the activation command has been received, the host will instruct the MODEM chip in the IWF board to make a call or give an answer according to the call direction. In addition, the host will start the IWF as the process of sending or receiving the fax file.
Variable initialization. It resolves the BC_IE parameter, and sets the mid-rate, the initialization variable and the buffer.
Synchronous search. The IWF intends to transmit the synchronization frame to the radio side. At the same time, it searches the synchronization frame received from the radio side.
Frame synchronization. After more than 3 synchronization frames have been received from the radio side, the IWF will be regarded to have set up synchronization with the radio side and have the adaptation and inverse-adaptation conditions of exchanging the fax data with the radio side.
Dialed Identification Signal (DIS) frame processing. The DIS frame of the IWF fax receiver is forwarded to the peer end (MODEM and radio terminal). This frame contains the capability information of the fax receiver.
Digital Command Signal (DCS) frame processing. The fax sender checks the facsimile capability of the other party. After the successful negotiation, the fax sender sends the DCS frame to instruct the fax receiver to be ready for reception.
Training processing. The line is checked to find whether the fax quality can be guaranteed with the current facsimile rate. If the condition is not satisfied, the facsimile rate will be reduced. This process is from end to end. The IWF only transfers the training frame rather than processing the data.
Message confirmation processing. If the IWF has received the message confirmation from the receiver, it will transfer this message to the fax terminal and enter the stage of transferring the fax data (message data). If receiving the message denial message, the IWF will start the rate decreasing process, at the same time, it will check whether the CMM process has been initiated and then enter the stage of transferring the DCS frame.
Message transfer stage. This is to transfer the fax data scanned and encoded in the fax terminal.
Processing upon the end of a page. This includes End of Process (DOP), End of Message (followed by different types of EOM) and Multiple-page Signal (MPS) frame and transfer of them to the receiving terminal.
Process of receiving the message response frame from the receiver. If the fax quality of the receiver is acceptable, it will respond with a Message Confirmation Frame (MCF) and perform the response processing in conjunction with EOP, EOM and MPS frames. If the fax quality is unacceptable, it will respond with a message denial message and conduct the re-transmission process with a lowered rate, and change to the DCS process.
Disconnect processing. The fax terminal receives the Disconnect (DCN) frame from the sender and transfers it to the receiver. Then the call is disconnected.
3.3 Single-MSISDN and Multi-MSISDN Principles
3.3.1 Introduction of the Single-MSISDN and the Multi-MSISDN Concepts
If the calling subscriber initiates a data call, the called subscriber must be informed via some method to complete the call. As for the mobile calling subscriber, the carried bearer capability indicates the service requirements of the calling subscriber during the Setup initiation. The GMSC will transfer this bearer capability to the HLR while obtaining the routing information request. The HLR will make a negotiation according to the bearer capability of the calling subscriber in the SRI and the subscribed bearer capability of the called MSISDN so as to obtain the bearer capability that can be used by the called MSISDN. The bearer capability should be carried in PRN to be sent to VMSC/VLR and inserted in the VLR. However, as for the bearer capability unable to be carried by the intra-office signaling such as TUP and TK signaling, it is necessary to provide other methods to implement the transmission of the calling service requirement to the called subscriber. Therefore, in view of different services represented by different MSISDNs, such a scheme of one IMSI corresponding to multiple MSISDNs can satisfactorily meet the requirements of the bearer transmission.
I. Multi-MSISDN scheme
The multi-MSISDN scheme is to provide one number for each service. To make a call of a certain service, the number corresponding to the service can be directly dialed. In the multi-MSISDN scheme, after the HLR receives the Send Routing Information (SRI) request sent by GMSC, if it detects that the bearer capability is not included in the request information, it will take out the bearer capability from the database corresponding to this number and transfer it to the VMSC/VLR in the PRN message so as to implement the transmission of calling subscriber service requirement. Figure 3-7 depicts the normal routing procedure in the multi-MSISDN scheme.
Refer to the Figure below.
1) HLR finds the corresponding bearer capability (BCk) according to the received MSISDNk in the SRI.
2) MSC negotiates the BCk in the received PRN according to its own capability, and sends the negotiation result BC?k to the called MS.
3) The mobile negotiates according to the BC sent from the MSC and its own capability, and sends the negotiation result, i.e. ?Call Confirmed? message, to the MSC.
Figure 3-7 Bearer capability of the called subscriber in the multi-MSISDN scheme
II. Single-MSISDN scheme
In the single-MSISDN scheme, the home PLMN allocates one MSISDN for the subscriber to use all the services. In this case, if the SRI command received by the HLR contains the GSM BC whose negotiation information is not enough for the GSM BC to be converted into that of the calling subscriber, the PRN from HLR to VLR will not carry GSM BC.
In the MSC/VLR, as no GSM BC is correlated with MSRN, there is not any GSM BC information element in the Setup message of the called MS during the call setup process. In this case, the MS will return one or two complete GCM BCs in the Call Confirmed message to indicate the service required by the MS. The VMSC checks the GSM BC. If the VMSC can satisfy the requirement, the call will be established, otherwise, the call will be released.
Figure 3-8 Single-MSISDN scheme
BC comes from the bearer information saved in the MS and can be used to set the type of the next call according to the settings of MS (e.g. Ericsson MS).
3.4 Operation Guide to GSM Circuit Data Services
3.4.1 Requirements for the Network Hardware Platform
I. General
The data service is a kind of application service of the VMSC. Its subscribers are greatly converged compared with those of the speech service subscribers. Therefore, the optimal scenario is to design the IWF as a function frame of the internal resources. The schematic diagram of the logical relationship of the subscriber channel is shown in the following:
Figure 3-9 Position of the IWF in the system
Specifically speaking, it is a standard device in the VMSC and is placed in a frame alone (IWF function frame for short). The physical interface (service interface) of the subscriber?s code stream is directly connected with the active/standby network board via the HW cable, which is commonly called as 2MHW cable and is divided into two cables, i.e. the active and the standby HW. Each HW cable includes: 2M signal +/_, 8K signal +/_, 4M signal +/_, DHW0 signal +/_, UHW0 signal +/_, DHW1 signal +/_, UHW1 signal +/_, valid indication signal ACT+/_. Communication control cable is connected with the NOD board via the NOD cable an includes DNOD+/- and UNOD+/-, with the rate of 187.5K. The schematic diagram is as follows:
Figure 3-10 IWF hardware design
II. Composition of the data service hardware platform
The IWF device uses one 2M HW as the basic processing unit. Each basic processing unit includes 10 boards: 2 GM11IWC boards (active/standby) and 8 GM11IWF boards, which are accommodated in the standard frame of the MSC. The structure of the IWF frame is shown in the following Figure. Each frame consists of 2 IWF basic processing units.
Note: each IWF board supports 2 subscribers (CH0/CH1), but each of the IWF boards in slots 2, 8, 14 and 20 can only support CH1.
III. Function overview of the IWC
The IWC board mainly implements three functions:
1) Dividing/combining the incoming/outgoing HW signals (32 time slots). Dividing is to divide one channel of signal (32 time slots) evenly into 8 IWF boards. As for each IWF board, the allocated 4 time slots are located in the first 4 time slots of the 32 time slots. Combining is to combine the first 4 time slots in the 8 IWF boards into one channel of HW signal.
2) Communicating between the IWF and the MSC via the master node.
3) Reporting the maintenance information and receiving the control information from the GMPU.
IV. Functional overview of the IWF
1) Providing the basic inter-network connection function based on 3.2KKz audio transparent/non-transparent (T/NT) so as to meet the requirements as specified in the relevant specifications and standards regarding PSTN.
2) Rate adaptation of the service information
3) Processing of the Radio Link Protocol (RLP). As the error code rate of the radio link is high, some protocols regarding the link layer are specified in some standards so as to ensure the correct data transmission.
4) Processing of the fax protocol It is to control and process T.30 fax protocol regarding G3 fax machine and fax adaptation (FA) protocols.
5) Processing of the data bearer services, e.g.BS2X, TS61 and TS62.
3.4.2 Network Configuration of Data Services
I. Software configuration and management of MSC/IWF
- Configuring the data management console
1) The half-frame IWF boards are conFigured with two HWs (the HW numbers should be consecutive) and one NOD cable. So the entire frame are conFigured with 4 HWs and 2 NOD cables. All the IWF boards within the frame should be numbered uniformly. So are all the IWC boards.
Configuring the IWF frame in [Frame description table]
Configuring the IWF and IWC slot in [Slot description table]
[Master Node Description Table] , the write-read length of the mailbox is 40 and that of the report/issue command is 32.
[IWF Channel]: each IWF board is originally designed to support 4 channels, but actually it only supports 2 channels. Therefore, the channels numbered as 4n, 4n+1 (n= 0..15) are available and those numbered as 4n+2, 4n+3 (n= 0..15) are unavailable. Furthermore, there is only one channel for the IWF boards in slots 2, 8, 14 and 20. The channels numbered as 0, 16, 32 and 48 should be conFigured as unavailable. If they are not fully conFigured, for example, only 6 boards are conFigured, these boards should be inserted in slots 3, 4, 5, 9, 10 and 11. Then each board can support two channels so as to avoid the situation where only one channel is available when the boards are inserted in slots 2, 8, 14 and 20.
[A interface circuit pool] table, the configuration should support full rate data. Currently, both TC2.0 and TC3.0 support data services. However, the current Huawei MSC does not support the half-rate data services.
5) The implicit table [GSM Service Table] should support TS61, TS62, BS24, BS25 and BS26 services. Of which, the corresponding relationship between the service type and the service code is shown in the following:
Table 3-1 Table of the service code correspondence
6) Special data configurations in the case of crossing modules: if the IWF resource is not in the local module, besides the data in the IWF, the search module from the local module to the BSC sub-route should be conFigured in the sub-route table, including the module No. of the IWF resource. For example, if there are a total of 4 modules in an MSC, the IWF is located in modules 1 and 3, and the BSC is connected with module 2, then:
Figure 3-13 Special data configurations in the case of crossing modules
7) As for the relevant software parameters, taking the MSCV330R002iA1B02D009 as an example, please refer to Software Parameter Specifications of the used version.
CCB_PARA_1_BIT3:
Set the bearer capability of the call initiated by the ST subscriber to voice or 3.1k audio. Setting to 1 indicates voice, while setting to 0 indicates 3.1k audio. This is only applicable to PSTN rather than MSC at present.
Default value: 1.
CCB_PARA_13_BIT7:
If the software parameter is set to 0, the MSC will compulsorily use the non-transparent service when the mobile subscriber of this office uses the BS26 service. As the IWF board, it does not support the preventive measures of the V42 function.
Default value: 1. This method is not adopted for the preventive measures, It should be processed according to the normal BC negotiation.
CCB_PARA_13_BIT8:
If the software parameter is set to 0, for the calling subscriber, when the facsimile service is used in the inter-office and if the facsimile service is first (currently including the TS62 service and the TS61 service with the facsimile service being first), the ATP information element in the outgoing signaling IAM message should carry HLC. While for the called subscriber, if the ATP information element in the incoming signaling IAM message contains HLC, the TS61 service with the facsimile service being first will be sent to the called subscriber (two BCs with the fax BC first).
If the software parameter is set to 1, for the incoming facsimile service (TS62 or TS61), the MSC will send TS61 service with the speech service being first to the called mobile subscriber of the local office. While for the outgoing facsimile service, the MSC will always carry the HLC in the ATP information element so as to enable the called office to send the TS61 service with facsimile service being first to the called subscriber.
Default value: 1.
CCB_PARA_13_BIT9:
If the software parameter is set to 0 and the intra-office facsimile service is used, the calling subscriber will send the facsimile service with fax being first to the called subscriber when he uses TS62 service, or send the TS61 service whose BC sequence is the same as that of the calling subscriber to the called subscriber when he uses the TS61 service.
If the software parameter is set to 1 and the calling subscriber initiates TS62 or TS61, and he will always send the TS61 service with the speech service being first to the called subscriber.
Default value: 1.
ISUP_PARA_2_BIT1:
In case the VLR does save the BCs corresponding to the called MSISDN, if this software parameter is set to 1, the Setup message sent to the called subscriber will carry the constructed voice BC; if it is set to 0, the Setup message will not carry BC. The BC to be used will be decided by the Call Confirmed message of the called MS.
Default value: 1. If it is necessary to test the incoming data call, this bit should be set to 0 (it is used in the PSTN inter-office signaling in which BC is not carried).
ISUP_PARA_10_BIT13:
As for the data service requiring N*64K or multi-rate connection type, this software parameter decides whether to carry the BC in the ?User service information? information element. If the software parameter is set to 0, BC will be carried in ?User service information? for transmission (also carried in ?Transmission media request? parameter). If it is set to 1, BC will not be carried in the ?User service information? (only carried in ?Transmission media request?;).
Default value: 1. (Currently, Huawei MSC does not support the data service based on N*64K or multi-rate connection type)
ISUP_PARA_10_BIT14:
It decides whether to carry HLC in the ?User service information? or in the ATP. If the software parameter is set to 1, the HLC will be carried in ?Access transport parameter?; if the software parameter is set to 0, the HLC provided by our office will be carried in ?User service information?.
Default value: 1.
Calculation of the IWF traffic
In its full configuration, the IWF frame contains 16 IWF boards and 4 IWC boards. According to the IWF channel configuration table, as each board supports 2 data channels, 16 boards will support 2 ×16 =32 channels, but channels 0, 16, 32 and 48 are unavailable. Therefore, the full frame can actually support 28 channels.
- Set-up of the IWF traffic model
Supposed that:
One call attempt processing is a complete call proceeding, i.e. a successful call from the time when the subscriber imitates the call to the time when the traffic channel is released. All other unsuccessful calls will not be taken into consideration.
Only the max. originating traffic is taken into account. The current max. GSM traffic is 0.03 Erl/subscriber and 0.7Erl/trunk in China.
The average duration of a radio speech call is 60s. The average duration of a data call is specified as 3 minutes per subscriber and 4 minutes per trunk.
- Calculation of the IWF traffic
BHCA of the GSM radio voice service = Traffic ÷ Average duration of each call = 0.03 ÷ 60 × 3600 = 1.8 calls.
As the calls of the radio data service are not many (take one-tenth of that in the speech service), but the duration of each call is long.
BHCA of the radio data service = 1 ÷ 10 × 1.8 = 0.18 calls.
- IWF management through the maintenance console
[IWF Channel] menu of the maintenance console provides such functions as state query, channel reset and channel query for the IWF board. In the debugging state of the maintenance console, there are also blocking and unblocking functions; Each IWF board corresponds to 4 channels. Only channels 1 and 2 respectively correspond to CH0 and CH1. Channels 3 and 4 are not useful.
3.4.3 HLR Subscription Data Service Setting
Note: operations performed on the HLR Subscriber data management console.
I. Bearer Capability Table
[Bearer Capability]:
Figure 3-14 Bearer Capability Table
Service Code: Selectively set according to the service supported by the system.
ITC: 3.1KHz audio (only this mode is supported at present).
CE: it can be any value for the BS service, but it can only be Transparent for TS service.
S: if the CE is Transparent, select ?unstructured?; otherwise, select ?Service data unit integrity?.
UI2P: if the CE is not ?Transparent?, select ?COPnoFlCtl?. The others are meaningless.
DC: When the CE is ?Transparent?, select any value. The others are meaningless.
NDB: 8 bits;
NPB: none;
NSB: 1bit;
IR: if the UR is 9.6kbps X.1 and V.110, select 16kbps; for others, select 8kbps.
MT: for different rates, select accordingly: 2400 V.22, 4800 V.32, 9600 V.32
The above options follow the correlation regarding the BC as specified in Appendix of GSM Protocol 07.01. For example, as for the correlation of the BC parameter in the 3.1 kHz audio ex-PLMN service, please refer to Part B.1.2.2.
II. Supported Telecom Service Table
[Supported Telecom Service] according to the system support. As for Huawei GSM, select first voice, then fax and auto fax, as shown in the Figure.
Figure 3-15 Supported Telecom Service Table
III. Supported Bearer Service Table
[Supported Bearer Service]:
Figure 3-16 Supported Bearer Service Table
According to the system support, the first five items are mandatory for Huawei GSM.
IV. Settings of the multi-MSISDN
[Define Multi-MSISDN Subscriber]:
Multi-MSISDN means one IMSI corresponds to multi-MSISDNs. First, add the MSISDN resource. Then set the multi-MSISDN of subscriber data management. Note that one MSISDN can only correspond to one service and the [Set BC] can be executed. Finally set the BC corresponding to this MSISDN stored in the HLR. The corresponding parameters must be consistent with the line matching map in the appendix of the GSM 07.01 protocol.
Figure 3-18 Setting BC when a multi-MSISDN subscriber is defined
3.5 Introduction of Common Data Terminals
3.5.1 GSM Data Terminals
The mobile terminals include data terminal (computer), MS (portable MS) and terminal adapter. The data terminal is connected with the MS via the terminal adapter or is directly connected with the MS. As for the current equipment of different manufacturers, the following products are available:
1. Adopting RS232 interface to connect the data terminal and the MS, such as NOKIA5110, 3810 and SIMENS1088.
2. Adopting PCMCCIA data interface card to connect the terminal equipment and the MS, such as ERICCSION mobile office DC23.
3. Adopting the infrared ray connection to perform such service as WAP access to Internet, e.g. Nokia7110.
4. Fully integrated data terminal. It can support both data function and MT function. This terminal is functionally a part of PLMN, e.g. the POSSIO-developed PM80 mobile fax machine.
Several common data suites are as follows:
Nokia Data Suit 1.0 (1.0c):
Supporting non-transparent bearer 9600bits/s;
Supporting TS62 transparent facsimile service (Based on various rates), and Class 1 but not Class 2 and TS61.
Nokia Data Suit 2.0:
Supporting non-transparent and transparent bearer 9600, 4800 and 2400bits/s;
Supporting TS62 transparent facsimile service (based on various rates) and Class 1 but not Class 2 and TS61.
Ericsson DC23v4:
Supporting non-transparent and transparent bearer 9600, 4800 and 2400bits/s;
Supporting the transparent facsimile service (based on various rates) and Class 1, Class 2, TS61 and TS62.
Ericsson SH888 MS and the corresponding infrared Modem:
Supporting non-transparent and transparent bearer 9600, 4800 and 2400bits/s, the transparent facsimile service (based on various rates), Class 1, TS61 and TS62 but not Class 2.
The customer can buy and install the appropriate data suites on the basis of the used MS. For example, NOKIA3810 and 8110 MSs can use NOKIA DATA SUIT1.0;
NOKIA5110, while 6110 and 6150 MSs can use NOKIA DATA SUIT 2.0; and ERICCSION 788 MS can use ERICCSION mobile office DC23. NOKIA DATA SUIT 1.0 is taken as an example in the following to describe the installation and the use of the data suit. NOKIA DATA SUIT 2.0 has the same installation and use method as NOKIA DATA SUIT 1.0, but it supports more services, such as transparent bearer service.
The MSs adopting NOKIA DATA SUIT 1.0 include NOKIA8810 and 3810, which use RS232 to connect with the computer. NOKIA DATA SUIT 1.0 include one cable and three floppy disks. One end of the cable is connected to the rear socket of the MS, while the other end is connected with the serial interface of the computer.
Some common terminals are introduced in the above. The installation of the common mobile terminals will be described in the following. As for the system, the data suit is a MODEM. First, connect the computer with the MS according to the instructions of the MS suit. After the computer and the MS are connected, you can start to install the driver software. During the installation, just proceed according to the prompt. As the installation of the data suit and the software provided by different vendors are different, NOKIA product is taken as an example in the following description. Note specially that the appropriate data suit must be inserted when the software is being installed. After the installation, open the ?MODEM? under ?Control Panel?. The pop-up dialogue box will display the newly-installed modem ?Nokia Gsm Data 3.0?, as shown in the following Figure.
Figure 3-19 Setting the properties of the MODEM
The subscriber can use an MS to dial the data or fax phone number after he has subscribed to the data service. The subscriber can select any kind of communication software or facsimile software, such as BITWARE, WINFAX PRO, HyperTerminal and Dial-up networking. By the means of dial-up access to Internet, the subscriber can send or receive the E-mail so as to enjoy more value-added services.
Figure 3-20 Settings of the dialup networking
3.5.2 PSTN Data Terminals
I. Computer MODEM
1) MODEM selection
Generally, the MODEM falls into two kinds: one is the external MODEM, the other is MODEM plug-in card. As it is unnecessary to use a cable to connect with the computer for the MODEM plug-in card, the interference is reduced. However, the MODEM plug-in card will occupy one more expansion slot, and the IRQ and I/O address conflicts of COM1 and COM2 should be avoided, so the installation is comparatively more complex. MODEM plug-in card is further divided into ISA card
and PIC card. The ISA card is not recommended as it comparatively occupies more system resources. The external MODEM is equipped with an indicator to show the state and its installation is thus much simpler. One more cable will be needed and one serial interface will be occupied.
According to the supported max. rate, the major MODEMs in the current market include those based on 14.4Kbps, 28.8Kbps, 33.6Kbps and 57.6Kbps. All MODEMs are compatible with the MODEM with a lower rate.
The MODEMs of different manufacturers have different functions. Some do not have the data compression function, some do not have the facsimile function and some provide the speech function. How do we select from various MODEMs? In the long run, it is recommended that the subscriber select an external MODEM or PCI plug-in MODEM, which supports ITU-T V series protocols, with the rate being 57.6kbps and providing data compression and facsimile functions, and supporting the Plug-and-Play function.
2) Installing the MODEM
Shut off the computer. Connect the MODEM in the idle COM port or the expansion slot, and connect the phone line.
Power on the computer. The WINDOWS system prompts to have found the new hardware and requires to insert the driver disc. Insert the driver floppy disc or CD. The WINDOWS system will automatically copy the driver and prompt that the installation is complete.
Install the dial-up network adapter, and restart the computer.
Setting the MODEM. Sportster 56000 is taken as an example in the following to describe how to set the MODEM.
Enter [Start], [Settings], [Control Panel], [System], [Device Manager], [MODEM], double click the installed MODEM, and set the port, max. rate and speaker volume, as shown in the following Figure:
Figure 3-21 Setting the MODEM properties
Set the connection properties, with the data bit ?8?, stop bit ?1?, and parity check ?none?.
Set the compression and flow control options of the advanced properties.
Figure 3-22 Setting the MODEM connection parameters
Figure 3-23 Advanced setting of the MODEM
II. Ordinary fax machine
1) Principle of the fax machine
The basic process of the fax communication is to de-compose, process, modulate, de-modulate and synthesize the image. At the transmitting end, the image is horizontally and vertically decomposed on the basis of a certain density. The viewpoint switching technique is adopted to convert the decomposed pixels into electrical signals in sequence. Then the electrical signals of the image are processed through analog-digit conversion, encoding and modulation, etc., and transmitted to the receiving end via the radio or wired channels. The receiving end will first de-modulate and decode the signals, and restores them to the image which is the same as that in the transmitting end via the digital-anal conversion. The following shows the principle of the G3 facsimile machine.
Figure 3-24 Principle of the facsimile machine
2) Types of fax machine
So far, the fax communication technique has become very mature and stable. The fax machine has been developed from G1 to G4 with difference in coding format, modulation mode and transmission rate. Today?s most popular fax machines are G3. G1, G2 and G3 fax machines are applicable to PSTN. G1 and G2 fax machines are seldom found because the adopted technologies are out of date. G4 fax machines of high rates are applicable to PDN and ISDN and it is seldom used in small networks.
3) Basic functions of G3 fax machine
Generally, G3 fax machine provides such functions as voice and fax communication, dialing, auto management and special file processing.
One-to-one communication functions include manual sending and receiving, polling transmission, scheduled transmission, auto receiving, timing & polling receiving, and scheduled sending.
One-to-one dialing functions include complete-digit dialing, abbreviated dialing, single-trigger dialing and group dialing.
One-to-one auto management functions include transmission report, reception report, parameter table check and remaining paper check.
One-to-one special file processing functions include copy, zoom in or out, and print of the sent records as well as the brightness and color adjustment.
III. Terminal software
The common terminal software includes the dialup networking, Bitware and Winfax attached with the Windows system software. The dial-up networking function embedded in Windows system software is simple and easy to use. But its user interface is not so satisfactory, and it does not have the facsimile function. Bitwares is a successful data terminal software and it is widely used for a long time thanks to its advantages of powerful functions and easy usage. Winfax is a specialized fax software, with perfect fax functions, powerful compatibility and friendly user interface. It is mainly used in the institutions and organizations which require a high fax quality. However, it needs to conFigure a high-level computer (Pentium 32MB or above memory, 50MB hard disc). The following table gives a comparison of these three kinds of terminal software for the customer?s reference.
Table 3-2 Signaling comparison of the three kinds of terminal software
The installation and usage of the two kinds of terminal software, i.e. Bitware and Winfax will be respectively described in the following so as to enable the reader to have a preliminary understanding.
IV. Bitware
- The functions of Bitware
The terminal software Bitware has such key functions as fax emulation, dial-up access to Internet, telephone book and voice mailbox. Bitware is widely used in circuit data services thanks to its complete functions, compactness and ease of use. As it is developed in the early time, the compatibility with the latest data terminals is not satisfactory.
- Installing the Bitware
Run ?Setup.exe? under the Windows environment. Accept the license agreement.
Enter the installation source directory and the destination directory, and click "OK". Then enter the user information (optional), and click "OK" to start copying the program.
After the copy, the installation program prompts to enter the group name of the application program. Enter the default group name and click "OK".
When the system prompts whether to create a detached program interface, click "CANCEL"
The system prompts to enter the directory of the application programs such as WORD and EXCEL so as to install the program and copy the relevant macro programs. Directly click "COPY" .
Wait for the installation program to browse all COMs and find the MODEM. If the MODEM is found, the MODEM configuration of the Bitware will be automatically completed (if the MODEM needs to be installed after the Bitware is installed, the Bitware must be manually conFigured.), then click " CLOSE" .
The system prompts whether to set the Bitware fax driver to the default virtual printer. Click "NO" .
The system prompts that the installation is complete and whether to restart the computer. Click "YES" to restart the computer.
- Using Bitware to dial up and access the Internet
Run the Bitware to enter the main window as shown in the following Figure.
Figure 3-25 Bitware main window
Click "Setup/MODEM" to set the MODEM parameters of the Bitware, as shown in the following Figure.
Figure 3-26 Setting the MODEM of the Bitware
Click "OK" to return. Click "BitCom" in the main window, enter ?ATDTxxx? and press "Enter" , as shown in the Figure.
Note:
?xxx? is the number to be dialed. The area code should be added if necessary.
You can also click "PhoneBook" or "Dial" to dial the number.
To redial, use the ATDL command.
To set the auto data call answer, user the ?ATS0=1? command.
Figure 3-27 BitCom user interface
When the connection is shown to be based on a certain rate, you can click "Send/Receive" of the BitCom to send or receive the file, or use the Internet browser to access the Internet.
- Using Bitware to send or receive fax files
Click "RECEIVE" in the main window to enter the status of automatically sending/receiving fax files, as shown in the following Figure.
Figure 3-28 Sending/receiving the fax files via Bitware automatically
Click "Transmit" and "New" to enter the sending dialog box. Fill in the receiver?s name, company name and fax No. Click "Attachments" to add one or several files. Select such options as cover page and Fine mode. Finally, click "Start/Fax" to start sending the fax files.
Figure 3-29 Sending fax files via Bitware
Figure 3-30 Fax log
You can also click "Txlog" in the main window to enter the transmission record window. Select several sent fax files. Press "F2" to change the receiver?s name, company name or fax number so as to conduct quick sending.
Note: before sending or receiving the fax file, you can click "Setup" in the main window to set the parameters of fax sending and receiving. For detailed operations, please refer to the User Manual or
