Implementation of a GSM Based Nationwide Medical Call Center

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JOURNAL OF TELECOMMUNICATIONS, VOLUME 8, ISSUE 2, MAY 2011 51

Implementation of a GSM Based Nationwide Medical Call Center Ishtiak Al Mamoon and Shahriar Khan Independent University, Bangladesh Abstract - An inbound time switching based nationwide call center for medical consultation is a relatively new concept in real-time telemedicine. In this work, a telemedicine project based on the GSM network, is implemented, and analyzed. The GSM Medical call center is accessible through dialing 789 on the GP mobile phone, allowing patients to consult directly with doctors. A brief discussion of the technology and the setup of a GSM/PSTN call center is given. The commissioning of different equipments, system integration, results, technical follow up, and error handing are described. It is intended that these tools and guidelines will aid those involved in the development of telemedicine projects in creating successful and sustainable systems. The implementation of these telemedicine systems is a first for Bangladesh. Challenges are identified, with real-life data from a running commercial system. The findings will provide academic and research issues for those building and running a telemedicine system in a developed or a developing country. Key Words - GSM, Telemedicine, Conferencing, Public Switch, Call center, Bangladesh

1 INTRODUCTION Consultations through a medical call center can alleviate medical emergencies, and reduce prohibitive travel costs, making health care more accessible to a rural population. A medical call center is a natural consequence of the progress in telemedicine and telecommunications. Implementation of such a call center requires interfacing between different telecommunication standards. Implementation and maintenance raises many issues, which must be addressed. A. The Project An interactive teleconference between a patient and a licensed physician was implemented, described and analyzed. Patients call a health information center, which provides health information and advice by registered physicians live through mobile phones. This links the individual to healthcare information, products and services through the mobile phone [1]. This study gives a brief discussion on technology commissioning, and a detailed description on the setup of a GSM/PSTN call centre. This project was made possible through collaboration between two companies [2].

signaling protocols such as SS7, ISDN-PRI, ISUP, conversion of C7 to DSS1, SMPP, call routing procedure, different definitions about switching and call types, channels E1 PCM ,Fiber optic, Radio, and various telecommunication equipments such as class IV public switch (TELES.iSWITCH ), SMPP API and Siemens Hipath 3750 PBX system. A. SS7 Enabled E1 and SS7 to ISDN – Purpose of Conversion. This project focuses on the conversion of non ISDN (SS7) to ISDN-PRI (EDSS1), as the medical call center uses ISDN based PBX and GP network carries SS7. It is needed to convert the signals using ITU-T Q699 and ISUP. The TELES.iSWITCH converts the signaling using those protocols by MST (Matrix switching Card) [3]. DSS1-SS7 internetworking is activated for call completion on no reply, if ITU-T Q703 and Q 699 are applied.

B Background Work Telemedicine and call centers have been in existence for several decades, but the medical call center is a relatively new concept. Besides the legal issues, the medical call center presents a number of technical challenges, such as interfacing various technical standards with a GSM system. 2 MATERIAL & METHODS The inbound medical call center, the focus of this study, is equipped with public switches, high end PBX, software and an SS7 transmission system. The descriptions include different methods, such as GSM core network based transmission, SMSC connectivity,

Figure 1: Protocol Conversion HealthLine B. Infrastructure & Technical Details Signal Protocol : CCS7 and ISDN-PRI(DSS1) E1 PIN Configuration: (TX: 1,2 RX: 4,5)

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Law protocol: mulax, Alaw User Part: ISDN user part Framing: no framing(SS7) & extended(DSS1) Line Code : B8ZS, HDB3 National Point Code: Available Signaling Link Code (SLC): 0 & 1 Voice Circuit: Clear TDM (multiplex)

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C. Major Equipment and Telecom Tools: 1. TELES.iSWITCH XC-S48 This is a class four public switch, of the type non blocking TST (time-space-time). The purpose of this switch is to convert the SS7 (common channel signaling) to EDSS1 (European Digital Signaling System 1) for call routing to PBX. TELES.iSWITCH (NT) was deployed in TRCL premise and considered as Signal End Point (SEP) switch. 2. Siemens Hipath 3750(IP enable PBX) with ACD PBX server In TRCL calls are routed to Siemens Hipath 3750 PBX(ISDN).Then PBX route the call to appropriate extension with the help of ACD(automatic call distribution) server . The PBX was commissioned in TRCL that acts as Terminal Equipment (TE) [5].

Fig. 2 Core Network Planning for Telemedicine Call Center [6]

D. Connectivity Infrastructure & Technical Details Communication Channel 1. Call Traffic Carrier E1 PCM (Not TDM only convertible IP) 2. Alap Provided Clear voice TDM channel Location: 1. TRCL TELES.iSWITCH 2. MSC (TSC04), Grameen Bank Mirpur-1[5] To implement the specification that is described in the previous chapter, the following network connectivity was set up. E. Commission and configuration of TELES.iSWITCH TELES.iSWITCH is considered as SEP (Signaling end point) and GP MSC (AXE703) acts as STP (signaling transfer point). TELES.iSWITCH was commissioned at TRCL premise using the following parameter to connect with GP MSC.

Figure 3: SP and STP concept Signaling Point Code (SPC) In 789 project destination point code (DPC) was configured to 3850 and TELES.iSWITCH was considered as originating point code (OPC) which was 3277. Circuit Switch Matrix setup MTS component of TELES.iSWITCH was configured by TRCL engineer over the modules backplane. In a distributed system, it is transmitted from its source to the line units and then from the line unit to the MTS component of the switching unit. Two common channel signaling (SS7) enabled E1 line carried 60 channels (each E1 contains 30 voice). These are dropped into the inter-exchange carrier (TELES.iSWITCH) to convert SS7 to EDSS1 (ISDNpri) for the PBX (Siemens HiPath 3750) [6].

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Figure 6: Switching Matrix [5] Fig. 4: System Technical Overview Alap communication provides TDM clear channel, and hence carries the voice trunk (64 Kbps because each E1 consists of 30 channel, 30 X 64 Kbps = 2.048 Mbps) in optical form. This data is converted to Electrical or IEEE 803.2 using an O/E converter [7]. The electrical data is converted to E1 PCM circuit using Ethernet/E1 converter. The leased 64 Kbps data channel for SMS server and TCP/IP is used for SMS system. F. Traffic Redundancy Ports 5 and 6 were configured for SS7, which are considered as inlet of TELES.iSWITCH. Calls are routed to both ports. Port 5 was configured as the main inlet and Port 6 was redundant with Port 5. This was done by setting the priority level of those ports. The above figure show that the priority level of Port 5 is 50 and Port 6 is 40. This means that call traffic drops to port 5. If the main inlet is down, the calls are routed to 2nd SS7 enabled redundant port [8].

Figure 5: Priority level of Port 5 G. Implementing Routing in the TELES The routing configuration determines the manner in which incoming calls are distributed among the outgoing ports on the TELES.iSWITCH. When the route has been chosen, the connection is set up by the switching matrix.

A connection was defined as the switching of two user channels in the switching matrix. Several trunks can be bundled to form a trunk group. A continuity check can be carried with a TELES.iSWITCH. 3 TECHNICAL DATA ANALYSIS In this section, different technical outputs, service level data, findings and different test trial for call routing are discussed. Primary data regarding problems is taken from connectivity, process barrier, symmetric barrier, analysis of switch and PBX. To analyze all these parameters, the following findings are presented. Setting up the call routing system in both switch and PBX system, raised some issues, which are described below: A. Connectivity related issues: • A problem was faced connecting TELES.iSWITCH and the Mobile Switching centre (MSC). The MSC uses ITU T Q703 for ISUP (ISDN user part) and TELES.iSWITCH uses ITU T Q767 protocol, recognized internationally. The problem was solved by tuning and synchronizing the two public switches. • The concept of country code that is used in Bangladesh GSM system is the same as TELES.iSWITCH. But GP MSC (TSC04) using ‘1’ as country mode and as per international protocol, where as the mode should be ‘0’. There was a technical misunderstanding between MSC and TELES IXC. The problem was solved by invoking ‘0’ instead of country mode ‘1’ in TELES.iSWITCH. • A system clock synchronization related problem occurred, as TELES.iSWITCH took the clock cycle from Ericsson MSC (AXE 703). Moreover as the TELES.iSWITCH was considered as Network Terminal (NT) and the PBX was as Terminal Equipment (TE), the PBX took the clock cycle form TELES.iSWITCH. A well-defined synchronization for system clock was applied over the whole system.

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• Sometimes license related issue occurred, during the operational period. • Some problems were found in the call detail record (CDR).

Fig. 7 Call setup and channel allocation and its functionality • Two SS7 enabled E1 PCM (30 X 2 channel) were commissioned from the MSC to TELES.iSWITCH and one EDSS1 enabled E1 PCM (30 B-Channel) was connected from TELES.iSWITCH (NT) to Siemens HiPath 3750(TE). Initially there were only 4 B-channels among 30 channels which were opened for call centre purposes. It was found that four calls come through these channel simultaneously and if a 5th caller tries to get the service from ‘Dial 789’ the call was dropped. And this call was not able to hit the PBX or even TELES.iSWITCH. This specific call hit the first phrase (nearby) BSC and was dropped .The connection between the MSC (DPC 3850) and TELES.iSWITCH (OPC 3277) is peer to peer or cumbered connection. According to link set in Teles switch, no routing policy was used over the two switches. Only STP and SEP concept were used here [5], [9]. B. TELES.iSWITCH Related issues: TELES.iSWITCH works as an SS7 to EDSS1 signal converter but this class IV public switch also does some switching in this system. This switch’s MST (matrix switching card) has 24 E1 ports. The matrix of the switch is Space-Time-Space (STS). So the number of inlet and outlet ports is same. Here Port number (Destination No) 1 was enabled for EDSS1 loop back. DNO 5 and 6 were configured for SS7 signal. This iSWITCH has that sort of flexibility to configure any ITU recommended signaling protocol to any port. The switching policy was configured such a way that call traffic from port 5 and 6 was routed to port 1. • For test purposes four channels were open from Port 1(ISDN enable). This meant from Port 5 and 6, four channels are also synchronized with Port 1. SS7 enabled ports were configured in such a way that 2 E1 PCM were redundant with each other. If any link is down, the other is activated with four enabled channels. • Though there were some machine and service level problems, the functionality level of TELES.iSWITCH was quite satisfactory. Calls are properly landed and routed to the correct destination [10].

C. Siemens HighPath 3750 PBX related issues: When any call (B-Channel) entered the PBX SLM024 card, the call is routed to destination according to automatic call distribution (ACD), universal call distribution (UCD) and Hunts group policy. • Initially 104,108,111,114 and 116 were enabled for 5 exclusive services and 103 extension was configured for time out purpose (time out state is occurred, if all channels are busy and the queue time to stay (TTS) was ended). • It was observed that if call director server in HPPC / PBX server was down, there was no announcement when dialling, and every call goes to time out extension (Ext:103). • Calls were routed to proper destination as per ACD [11]. ACD is able to intelligently distribute the call in such a way that if any agent attends any call, no call will go to his extension within 2 minutes. The routing system finds out the agent who has been idle for long time and routes the call to the appropriate agent following UCD and hunt group manner. If any group is totally occupied, the ACD route group overflows the call to another group according to the rules of ACD overflow. 6 subscribers can access Med Advice - Press 4 by dialing 789. The switching functionality 1st hit call takes place in the 1st available group ID extension. The next call follows the same procedure. Automatic call distribution system is connected with hunt group by a group ID (UCD)[10,11]. 4 CONCLUSION The GSM medical call center was a service point where cell phone subscribers, as patients, received medication, emergency and medical facility information by doctors over the mobile phone. This paper addresses the challenges in setting up a GSM based call centre using TELES.iSWITCH and Siemens PBX system. The GSM call centre is technically equipped with a class IV public switch as Inter exchange carrier, and a PBX. Subscribers can dial 789 from their phone in Bangladesh. In spite of some technical shortcomings, subscribers were wellbenefited from consulting over cellular phone. Although the period of observation and study was short, the figure and call patterns indicate that this project may be sustainable. It was found that PSTN and GSM network are very useful for long distance telemedicine, but for short distance telemedicine system E1 PCM fiber optic or any dedicated fixed transmission is an efficient solution.

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