Design

The 1 MORE system has, from the user point of view, two different pOints of entry: the telephony entry-point and the Internet entry-point. As mentioned before, the Venuslab provides the Internet side, consisting of firewall, web server and database. However, The Garage is responsible for the design of the 1 MORE homepages and the structure of the database. More on the layout of the WebPages is found in [2}. These pages use Active Server Pages (ASP) to provide database access and secure data handling [7}. ASP is a Microsoft technology based on a script version of Visual Basic that enables designers to build intelligent web-servers and is comparable in functionality to CGI-scripting or PHP.

The next sUbsections describe the design of the database, the Group Call architecture and the Group SMS architecture in corresponding order.

3.3.1 1 MORE database

The SQl (Structured Query language) database contains exactly the information needed by the prototype (see also section 3.1) as can be seen from the tables below. In table 'Abonnees' the subscriber's telephone-number AbNummer is the primary key. Table 'Vrienden' is linked to the subscriber table trough VrAbNummer, which is equal to AbNummer in table 3-1. In table 'Vrienden', VrAbNummer and VrNummer are combined to form the primary key. AbUser!eve! is used to identity new users that have never placed a call to 1 MORE yet (0) and users that have called at least once (1). In later versions this might be extended to identify advanced users or it might be changed to contain the total number of calls to 1 MORE.

Table 3-1 Subscriber table ('Abonnees')

Fieldname Field type Size

AbNummer VarChar 10

AbVoornaam VarChar 20

Ab T ussenvoegsels VarChar 10

AbAchternaam VarChar 20

Table 3·2 Friend table ('Vrienden') Fieldname Field type Size VrAbNummer VarChar 10

Note: Nummer is Dutch for number, Voomaam for first name, Tussenvoegse/s for middle names, Achternaam for last name, Map for folder

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All telephone-numbers are stored as 10 byte long VarChars, the length of all Dutch telephone-numbers. Please note that VarChar is a SOL type of string-array. The Int type variables, which are all used as a Boolean, are 4 bytes long as this is the smallest possible length for an Int. VrMap1 to 5 are used to identify whether a Friend is in the corresponding Folder. VrMapX is 1 if the Friend is a member of the Folder or 0 if the friend is not included. This way each user has 5 Folders (with names AbMapX) and an unlimited amount of Friends that can be included in 0 to 5 of these Folders.

3.3.2 Group Call

The telephony-side of the Group Call consists of a PC (telephony Server) and a PBX. The PC is connected to the database on the Internet through a SSL link (Secure Socket Layer) as can be seen in Figure 3-3. SSL and its successor TLS, Transport Layer Security, are described in Appendix A. In addition to the 1 MORE hardware, this picture also shows two customer's devices. Through the User PC, the user administrates his Personal Profile and Favo Friends information on the web. With the User telephone he connects to the actual service.

telephony Server

~Ul----User PC

... _ _ _ _ _ _ _ _ ((f\~ ,

~~-User telephone

Figure 3-3 1 MORE prototype hardware for Group Call

The PBX is connected to the mobile network via an ISDN-30 connection, also called E1, thus allowing for a total of 30 simultaneous calls. Actually the ISDN-30 is not connected to the KPN Mobile network but to the fixed KPN network. This enables subscribers of providers other than KPN Mobile to join in the pilot study as well. The PBX is equipped with two conference cards, each of which can handle one conference call of up to eight conferees. If both are used at the same time with the maximum number of conferees, only 16 of the 30 available channels to the network are occupied. Unfortunately, the PBX is not equipped with a CSTAlCTllink (Computer Supported Telecommunications

Applications / Computer Telephony Interface). This means that all signalling to and from the PC has to be sent with standard ISDN commands.

The PC has very high processing power since it both controls the PBX and runs the complete IVR program. It is equipped with an Intel Pentium III 800 MHz processor and it has 256 Mbytes of internal memory. It runs Microsoft Windows NT 4.0 with service pack 6 to support the used software. The built-in AVM C4 active ISDN card is capable of

connecting up to four ISDN-2 lines (i.e. eight voice channels) and is controlled with CAPI 2.0 (Common ISDN Application Programming Interface). CAPI includes functions for call set-up, Explicit Call Transfer (ECT) and Three-Party-Conference (3PTY), all of which are of used by the 1 MORE service. For more information on CAPI, see Appendix B.

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Although the ISDN card is capable of connecting 4 ISDN-2 lines, the PBX has only two lines available, thus limiting the number of simultaneous calls to four. Moreover, since the PBX is configured for normal telephones that can only handle one voice call at a time, each ISDN line can only use the second channel if the first call is put on hold. In other words, not more than two voice calls can be handled simultaneously! One of these channels should always be available to inform calling subscribers that all lines are occupied, so only one subscriber can be processed at a time. Figure 3-4 displays all system nodes and the communication between them.

User telephone

1111111

I-ISDr~.30--l1l111l1 1111111 HSDN.2-r;:

1111111 1111111 ' - = - - - - . 0

AVMCard lMORE PBX

Sal

A l::J

lMORE telephony Server

lMORE database

1 MORE database web server

Figure 3-4 Communication between nodes for Group Call

3.3.3 Group SMS

Figure 3-5 shows the hardware for the Group SMS function. As can be seen, the Internet side is the same as for the Group Call implementation. All SMS functionality is combined in one server, the SMS server, which has connections to the database and the SMSC, or Short Message Service Center, of KPN Mobile. The SMSC is the node in the mobile network that receives and delivers SMS messages. The 1 MORE service is connected to the SMSC with a X.25 link, using a normal ISDN modem that is capable of employ the X.25 protocol on the ISDN D-channel. For more information on X.25 see [8,9].

User PC

User telephone

Figure 3-5 1 MORE prototype hardware for Group SMS

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The X.25 link is only used for transmitting SMS messages. It could be used for receiving messages as well, but this would only work for messages sent to a short number, e.g.

333, 121 or 247. These short numbers are only available to subscribers of the operator of the SMSC because they are internal numbers. This of course would mean that only KPN Mobile subscribers could use the SMS function. Therefore, the SMS server also has a direct connection to the mobile network via a GSM card. This card is used for receiving SMS messages and has a normal, 10-digit, GSM telephone-number.

Since the SMSC of KPN Mobile is produced by CMG Communications, the SMS transmitting software uses the CMG SMS programming API called SM API. The GSM card behaves as a normal modem and can be addressed with the Hayes AT command set, which includes the SMS subset. Both the transmitting and receiving blocks were already made by the KPN Research lSI lab.

Unfortunately, the GSM card was not available in time for the pilot study. A demonstration version of the multicasting functionality is created based on X.25 receiving (Le. using a short number). However, since this is only available to KPN Mobile subscribers, the SMS functionality could not be included in the pilot prototype and will therefore not be

discussed in the remainder of this chapter. Figure 3-6 shows communication between the nodes. The Internet part is not included, as this is equal to that of Figure 3-4.

c(f :('»

®S\- _~g.- -~~~

User telephone

KPN SMSC

1f--I-1aV,eS AT

---...LJIf--- ~~~ ---L::J

lMORE SMSServer

1MORE database

Figure 3-6 Communication between nodes for Group SMS