ENHANCING EMERGENCY CALL PROCEDURE IN GSM/W-CDMA NETWORKS TO INCORPORATE PERSONAL SECURITY

ABSTRACT

This  project was  undertaken with the  objective of providing a  rather  more flexible Emergency Call Handling Procedure (ECHP) for the GSM/WCDMA network which will facilitate call termination to other sourcesof help (Commercial Emergency Service Operators, Vigilante groups etc.) in addition to the Public Safety Answering Point (PSAP) as a possible replacement for the existing procedure that routes all ECs to a PSAP. An alternate Enhanced Emergency Call  Handling Procedure (EECHP) was  suggested and  modeled using call flowchart and mathematical modeling techniques.The Models were then simulated andthe results obtained analyzed. The results analysisshowed significant improvement in call completion success (a measure of QoS) and decreasing Call blocking probability (increased accommodated EC traffic) for those GSM/W-CDMA originated emergency calls processed using the EECHP over those making use of the de-facto call handling procedure for same PSAP condition; thereby suggesting that the  EECHP can be effectively used as a replacement for existing ECHP forreducedemergency call drops associated with congested or out of service PSAP(s) and itsattendant adverse effecton people’s lives and property.

CHAPTER 1

INTRODUCTION

1.1. Background

Emergenciesarehigh stress situations,often with threat to life, health, property or environment [1]. They are stressful enoughtooverwhelm victims intoforgettingphone numbers of family members, associates or authorities from whom they could seek help.

In an attempt to easecommunication difficulty during emergencies, aglobally accepted Public Safety Emergency Response System (PSERS) was modelled for the Plain Old Telephone System (POTS) and the Cellular networks (GSM, CDMA,W-CDMA) on the basisof the following [2]:

(i)        Use of single, easy to remember,emergency number for all emergency needs.

(ii)       Publically funded Public Safety Answering Points (PSAP), meant to receive ECs anddispatch help to affected people.

(iii)      Priority treatment given to ECs over normal calls by Telecom operators. (iv)      EC calls are made free of chargeon both POTS and Wireless networks

This form of emergency communicationisbeing operated in many countries, includingtheUnited States, Canada United Kingdom, South Africa and Nigeria. However, in Nigeria, it is a common occurrence for PSERS being unable to meet theemergency needs of the peopledue toEC termination failure to a possible source of help. This leads to lower Quality of Experience (QoE) for callers that  attempt  ECS in Nigeria.Several militating factorsincluding (but not limited to) the Emergency Call Handling Procedure (ECHP) being usedby the GSM and W-CDMA networks are responsible for the callerslow QoE.

1.2. Objective of the study

This project is aimed at mitigatingidentified inadequacies, namely: – call drop and lack of flexibility -with the GSM/WCDMAECHP especiallyduring PSAP congestion.The project analyzed EC handling during PSAP congestions andoffered anEnhanced ECHP (EECHP) that will improve call termination success. This EECHP for the GSM/W- CDMAnetworksremoved the restriction ofEC from being terminated to other sources of help, while maintaining the benefits of emergency call.

1.3. Problem Statement

The GSM/WCDMA ECHP(for networks in Nigeria), implement a procedure that routes all ECs to a tandem switch at a Public Safety Answering Point (PSAP)[3].ECs receive no further processingas soon as they are received at the MSC.They are simply delivered to aconfigured

PSAP as fast as possible for all PSAP conditions – including congestionperiods.Thus, by default, ECs in GSM/W-CDMA networks are not subjected to any screening (including CAMEL Procedures) [3].

The absence of call processing for ECduring congestion at the PSAPprevents many people fromaccessing alternativesourcesof helpwhile enjoying the benefits ofemergency calls.Such sources of help include:Private Emergency Service Operators (PESOP) and Personal Emergency Contacts(PEC).

During congestion at the PSAP, the call blocking probability (i.e.the chance that an EC arriving at a PSAP would meet no available server)is very high, thereby limitingthe ability of the GSM/W-CDMA network tomatch an originating EC witha source of help within the PSAP.,

Sometimes ECs are routed to alternate distant PSAP,typically,an EC that originated from Lagos could end up at a PSAP in Abuja (a distance of over 600Km apart) and the vice-versa. Personnel at the called PSAP will then began the human process of locating a source of help closer to victims. This process results in a long waiting and eventually help may never get to the victimson time.

Since emergencies are time bound, the ability to reach a source of help closest to victims and as fast as possible is a critical requirement for improving victims QoE. For example,in the event of fire incidence,a dispatch of 10 water tankers arriving at the venue of the incident after the fire had completely razed a building may not be of any help to the victim(s). However, with effective ECS, a single water tanker from the neighborhood could make a lot of difference at the early stage of the fire.The same could be said of a case of kidnapping,where an early response from a local vigilante can foil the exercise and save the victim before the arrival of the police.

It is safe to say that, the ability of an EC to reach alternative destination(s)during PSAP

congestion is a critical requirement for improved efficacy of the GSM/ W-CDMA ECS.

In human response to the PSERS inadequacies above, vis-à-vis the urgent need for

emergency victims to get help,peopleoften resort to using other ways to seek help – by calling local vigilante group (for Criminal emergencies),personal physician (in case of health issues) andneighbors/ private fire service operators (in case of fire) incidences.

These options often attract fees, but arestill preferred tohaving a callto aPSAP that may be congested or not ready to offer the much desired help. A clear indication of this, can be seen fromthe patronage enjoyed by such private/commercial ventures from the general publici.e:- emergence of private security outfits, private ambulance services and community vigilante groups etc.

The calls to vigilante’ group, Private ambulance, etc; are not recognized as emergency calls by the GSM/W-CDMA network, despite their critical role, rather they are treated as normal calls, hence no preference of any sort is accorded them. Theymay even be denied by the networkfor lack of call credit balance.

It is noteworthy that, a GSM/W-CDMA ECHP as depicted above whereby EC targeted at congested PSAP fail to terminateand alternative sources were not supported, has left much to be desired of an effective ECS.

There is thus the need, to accommodate all these calls into a common and efficient ECS for the utmost satisfaction of emergency victimsin Nigeria and similar countries.

The aim of this project was simplyan adaptation of these new EC realities into the GSM/W- CDMA originating ECHP,through the introduction of an Enhanced ECHP that makes use of GSM operator’s Customized Application for Mobile networks Enhanced Logic (CAMEL) to offer some flexibility to EC termination.

This alternative originating EECHP will subject ECs to screening and processing at the gsmSSP andthat ECs were not dropped at the MSC or denied Radio Resource by the GSM RR management layer due to congestion, and to ensure that originating ECs are seamlessly terminated to PSAP, PESOP and/or to PEC by caller’s choice (even when PSAP entries are available).

1.4. Scope of work

The  scope  of work  coveredherein  was  foremergency  call  situation  during  congestionat PSAP.Performance was analyzed usingcall flow-chartsfor originated emergency call terminating at a congested PSAPvia a GSM/W-CDMA network for two scenarios: (i) using currentECHP and (ii)using Enhanced ECHP.

The twocall models were examined, mathematicallymodeled, simulated andanalyzed. Simulationresults were then compared to demonstrate benefits offered by EECHP over the existing ECHP.

1.5. Thesis Outline

The  thesis  is  divided  into  5  chapters.Chapter 1 covers the‘Introduction’, chapter 2  and Chapters 3coverthe Literature Review andNetwork Modeling respectively; whileChapter 4 coversSimulation and Results Analysis. Finally chapter 5has the Conclusion and Recommendation forfurtherwork.

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