Practical Training Course Exercises

SMS, CS calls and GPRS sessionsPage1SMSPage2SMS - OverviewReferred to as Point to Point Short Message ServiceBlock mode - This was the original mode implemented initially for GSM. This is not supported by anyone any more.PDU mode - Mode implemented in all of the previous generation of modules, gives more control of SMS than text mode but is more complex. This is the raw data that is sent over the air to the network.Text mode - A later mode designed to make it easier for people to write software, basically translation software from text to PDU.

The two types of SMS which are seen by the MS are.SMS submit - This is sent to the network when sending an SMS.SMS deliver - This is received from the network when receiving an SMS.SMS delivers and submits are different in the way they are coded, this is described in the document How to send SMS contained on the CDs.Point to Point-SMS is detailed in GSM 3.40 or 3GPP 23.040.

Page3SMS - PDU modeInformation is sent to the module in PDU format which is described in GSM 3.40This gives far more control over the parameters of the SMS which are being sent such as SMS class, validity period, service centre address to be sent to, reply paths, status reports, etc. It is not very readable as shown belowat+cmgs=21>0011000C9144777851042400118F08D4F29C0E9A36A7

PDUs are shown how to be constructed in the document How to handle SMS contained on the CD.Page4SMS Text ModeAs said before text mode is effectively translation software in the module allowing people to input text rather than numbers, the information that is actually sent is still a PDU.

Setting parametersat+cmgf=1Sets the module to use text modeat+csdh=1Allows user to edit/use the text mode parametersat+csmp=17,167,0,0Sets Validity periodSending an SMSat+cgms=+447787154042Phone number SMS is to be sent to> HelloText to send, ended with the ctrl-z charactercgms : 128Confirmation from the module that the SMS has been sent

Page5Cell broadcastMessages are Broadcast by each cell, these are in a similar format to SMS as a result they are known as SMS-CB.Detailed in GSM 3.41 or 3GPP 23.041Generally used in location based services.Example of a Vodafone CB message from Sony Ericsson Maplewood building.+CBM:8800B200320111B098AC66038140205043D168341A8D46A3D168341A8D46A3D168341A8D46A3D168341A8D46A3D168341A8D46A3D168341A8D46A3D168341A8D46A3D168341A8D46A3D168341A8D46A3D168341A8D46A3D100Controlled using the CNMI and CSCB commandsNew message indications need to be set to at+cnmi=3,0,2The CSCB command needs to be setup to receive the correct message type from the network I.e. Vodafone use message type 50.

Page6SMS storageThe module has two areas of storage SM (SIM) and ME which it can use, these are controlled by the followingAT+CPMS commandat+cpms?+CPMS: "SM",0,15,"SM",0,15,"ME",0,40Default settingat+cpms="sm","sm","smCommand all preferred memory to be set to SIM+CPMS: 0,15,0,15,0,15Return from the module showing the capacity and amount used SMS and where they are stored is controlled with a combination of the different classes of SMS and the preferred storage commandClass 0 - Displayed immediately on a screen, not really applicable to modulesClass 1 (default value) - ME specificClass 2 - SIM specificClass 3 - TE specificIf all storage is set to that above no SMSs will ever be stored on the module, they will all go to the SIM.Page7Reading and writing SMS from memoryThere are 2 different methods of reading messages from memoryAT+CMGR - Read an individual slotAT+CMGL - List all SMS of a particular type or all, slightly different between PDU and text mode.AT+CMGW - Write an SMS to a specific location in a specific memoryAT+CMGD - Delete a location of the currently specified memoryNote : All of these commands read from the currently preferred memory, (see previous slide).Page8New message indicationsWhen using SMS, how the messages are received and passed onto the module is of paramount importance. This is achieved using the CNMI command.AT+CNMI - parameters which it can use to route messages in different ways areClass of SMS routing, see parameterCell broadcast messages - These have been mentioned previously.Status reportsDelivery reports

Page9Other types of SMSCommand - Used for applications such as over the air updating of WAP and data accounts. Currently there is no way to handle this as previously it was handled by the MMI software.Status - This is a request sent to the network to find the status of previously sent SMSs.Delivery - This is a bit which is set in the PDU to tell the network to report to the terminal when the SMS has been delivered, this would consist of a class zero SMS sent to the terminal.Note : Both status and delivery SMSs may not be supported by all networks.Page10Circuit switched callsPage11Voice and data callsVoice calls are very simple with the only thing differentiating between the two being a ; at the end of the string for a voice call and no ; for a data call.

atd01256774626;Voice call

atd01256774626Data call

Data calls will be examined more in detail later.Page12Audio paths and parametersThere are 3 audio paths out of the unitAUX 1 Differential based audio pathAUX 2 Differential based audio pathPCM Digital audio providing raw audio output allowing external echo cancellation to be applied

Main commands to be used areAt+speaker Controls the audio output usedAt+vgt, at+vgr Basic volume control settingsAt+echo Controls the echo cancellation settings. Very detailed and allows individual adjustment of tap filters.

Page13Data calls - Circuit switchedA data call is an ordinary circuit switched call which engages the internal modem, this is signalled to the network and it routes the information as raw data rather than being encoded as voice.A number of important points to note about data calls areOnline command/data mode - In a data call the module can be in either online data mode where data sent to the module is directed across the network to the modem on the other side or online on line command mode where ordinary AT commands can be used to request various information such as signal strength, registration status, etc.Escape sequences - To get into on line command mode and to end the call an escape sequence needs to be used, we support +++AT, we also support a guard time after this sequence has been received, although this switched off as default.Hanging up a data call - There are two ways to hang a data call up.Enter on line command mode as described above and type the ATH command.Use the escape sequence +++ATH, this will cause the call to hangup instantly.

Page14Data calls - Circuit switched (cont)Example of a data call session

atd07787159314Dial string, note no ;CONNECT 9600Response from modem dfglkstmklsgbjsfhData sent from modem on other sideOKThis modem sent escape sequence +++at (not seen)at+csqEntered into on line command mode and requested signal strength+CSQ: 6,0OKatoReturn to on line data modeCONNECT 9600Response to confirm returndfglkstmklsgbjsfhData sent from modem on other sideOKThis modem sent escape sequence +++at (not seen)athHangup callOKPage15GPRS sessionsPage16Setting data accounts and parameters upWhen making a GPRS call a data account held by the phone must be used, the module can hold upto 10 different accounts. These contain the following informationAPN (Access Point Name)Connection type (SEM only support Internet Protocol (IP))Compression information at+cgdcont commandThe command below creates a data account in profile 1 of type IP with an APN of internet

at+cgdcont=1,IP,internet,0,0

Quality of Service parameters are specified by the commands at+cgqreq and at+cgqminat+cgqmin=?Requests the minimum acceptable QoS+CGQMIN: "IP",(0-3),(0-4),(0-5),(0-5),(0-18,31)OKat+cgqreq=?Request the required QoS+CGQREQ: "IP",(0-3),(0-4),(0-5),(0-5),(0-18,31)OK

Page17Data calls - GPRSWhen a call is made by the module on the GPRS network it connects to the APN, specified in the data account being used for the callThe dial string for making a GPRS call is ATD*99***X#, where X is the account number you want to use.There are a few ways to connect to the network.Go into hyperterminal and type ATD*99***1# after the module has registered on the network, this should return the CONNECT prompt and enter the module into V.250 on line data mode.Use dialup networking, which we will go through now.Another option is to use the Vodafone Connect me software which does the above in a more complete and transparent way and can be found on the Vodafone web site.Page18Starting a GPRS sessionBelow are examples of GPRS commands setting up accounts and calls

at+cgdcont=1,"IP","internet","",0,0Create a data accountOK

at+cgdcont?Request what data accounts exist+CGDCONT: 1,"IP","internet","",0,0Account 1 setup for Vodafone+CGDCONT: 2,"IP","adf.btcellnet.net","",0,0Account 2 setup for BTCellnet

OKatd*99***1#Place a GPRS call using profile 1CONNECTResponse from the network stating it has connected successfullyat+cgdcont=1Request the module to clear account 1OKat+cgdcont?Request existing accounts+CGDCONT: 2,"IP","adf.btcellnet.net","",0,0BTCellnet account remainsOKPage19FTP, PPP and TCP/IP PPP - Point to Point ProtocolPPP is the underlying protocol used by the internet to establish and secure a point to point link. The module has a PPP stack on board which we shall go through in a moment. Extra security can be added using PAP (PPP Authentication Protocol) and CHAP (Configure Handshake Authentication Protocol). TCP/IPThis is the protocol used to route and address information going across the internet. FTP - File transfer protocolThis is a protocol used specifically to transfer files between servers. WAP - Wireless Application ProtocolThis is a cut down version of TCP/IP optimised for wireless networks. The module does have a WAP stack on board but there is currently no way to make a WAP call as this was previously done through the MMI software.

Page20Network management and controlPage21RegistrationRegistrationAT+CREG shows information regarding registration on the GSM networkAT+CGREG shows information regarding registration on the GPRS network (or packet based bearers)

at+creg?Requests the GSM registration status+CREG: 0,1OKat+cgreg?Queries the status of GPRS registration+CGREG: 0,1Module is registered on the GPRS networkOKat+cgreg=2Changes the mode of the at+cgreg commandOKat+cgreg?+CGREG: 2,1,"1600","0D91Returns the status in the new modeOKPage22NetworksThe module provides a number of commands which allow the user to monitor and control the networks around it

Available networksAT+COPS shows more user facing information I.e. network nameat+cops=?+COPS: (2,"UK VODAFONE","UK VODA","23415")+COPS: (3,"UK Orange PCS Ltd","Orange","23433")+COPS: (3,"UK BTCELLNET","BTCELLNET","23410")+COPS: (3,"UK one2one","one2one","23430")

OKCell and network information AT*E2CDAT*E2EMM

Page23Cell and environment informationAT*CCED Cell environment descriptionat+cced=0+CSQ: 21,99+CCED: 234,33,0014,4bd4,41,815,39,,,0,,,0,234,33,0014,0ceb,43,837,35,234,33,0014,,42,760,25,234,33,0078,,43,820,21,234,33,0014,0cec,46,798,21,234,33,0014,,45,759,21,234,33,0014,,44,801,26,1OK

Timing advanceThis is a parameter that is generated in CS calls (data or voice) which give you a time (at the speed of light) to the base station the MS has the call up with

Page24GlossaryBCCH - Broadcast Control ChannelCB - Cell BroadcastCGSN - Combined GPRS Support NodeEDGE - Enhanced GSM Data for GSMFDMA - Frequency Division Multiple AccessFTP - File Transfer ProtocolGGSN - Gateway GPRS Support NodeGM - GSM ModuleGPRS - General Packet Radio SystemGSM - Global System for Mobile communicationsHDLC - High Data Link ControlIETF - Internet Engineering Task ForceIMEI - Individual Mobile Equipment IdentityIMSI - Individual Mobile Subscriber IdentityIP - Internet ProtocolISP - Internet Service ProviderITU - International Telecoms UnionLA - Location AreaLAC - Location Area CodeMCC - Mobile Country CodeMNC - Mobile Network CodeMS - Mobile StationMSC - Mobile Switching CentrePACCH - Packet Associated Control ChannelPAGCH - Packet Access Grant ChannelPBCCH - Packet Broadcast Control ChannelPCCCH - Packet Common Control ChannelP-Channels - Collective name for PBCCH, PACCH, PAGCH, PCCCH, PDTCH, PNCH, PRACH and PTCCH - Packet Traffic Control ChannelPDP - Packet Data ProtocolPDTCH - Packet Data Traffic ChannelPDU - Protocol Data UnitPNCH - Packet Notification ChannelPPP - Point to Point ProtocolPRACH - Packet Radio Access ChannelPTACH - Packet Timing Advance Control ChannelQoS - Quality of ServiceRA - Routing AreaRF - Radio FrequencySAR - Specific Absorption RateSGSN - Serving GPRS Support NodeSIM - Subscriber Identity ModuleSMS - Short Message ServiceSS7 - Signalling System number 7TCP - Transfer Control ProtocolTDMA - Time Division Multiple AccessTE - Terminal EquipmentUMTS - Universal Mobile Telephone SystemWAN - Wide Area NetworkWAP - Wireless Application ProtocolWML - Wireless Markup LanguageWWW - World Wide Web

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