Mobile networks have experienced rapid growth over the past decade to meet the ever-increasing demand for mobile communications. As society becomes more dependent on these services, users expect networks to be available anytime, anywhere.
To meet customer expectations, reduce operational expenses (OPEX), minimize revenue loss from service interruptions, and comply with regulatory KPIs and Service Level Agreements (SLAs), telecommunication operators must ensure network availability.
From a Reliability Engineering perspective, the performance of a system is evaluated through Reliability, Availability, and Maintainability (RAM):
Reliability – The probability that a system performs its intended function over a specified time and operating conditions.
Availability – The proportion of time subscribers have access to mobile services (signal, voice, internet, etc.) within covered areas.
Maintainability – The probability that a failed system or network can be restored within a given time frame.
In simple terms:
- Reliability keeps the network running without failure.
- Maintainability ensures outages are fixed quickly.
- Availability measures how often the network is ready when users need it.
Network availability is therefore a function of reliability (frequency of outages) and maintainability (repair duration).
Why It Matters
Studies reveal that network outages and performance issues are the leading causes of customer churn. Globally, telecom operators spend around $20 billion annually addressing service interruptions and degradation.
For ethio telecom (ET), which operates a vast mobile infrastructure and serves a rapidly growing customer base, outages remain a significant challenge. Understanding and analyzing availability and maintainability is crucial for:
- Enhancing customer satisfaction
- Reducing downtime and revenue loss
- Achieving business and regulatory performance targets
Statement of the Problem
The mobile industry is massive, with 7.8 billion SIM connections worldwide, provided by nearly 800 operators. By 2017, the sector contributed 4.5% of global GDP and created 29 million jobs. Technology continues to evolve rapidly—4G subscriptions are forecasted to reach 53% globally by 2025, while 5G will account for about 14%.
However, despite these advancements, operators face persistent challenges in maintaining network efficiency. Outages are becoming more frequent and take longer to resolve.
In Ethiopia, ethio telecom (ET) is the sole telecom operator, managing GSM, UMTS, and LTE networks. As of November 2017, ET had 57.34 million mobile subscribers, making it the largest mobile operator in Africa. ET requires high RAM standards during vendor selection, expecting networks to perform at design targets.
Yet, real-world performance data tells a different story:
- Around 70% of total network outages originate from mobile sites.
- More than 30% of these sites in outage remain down for over 3 days.
Performance assessments often consider availability only, without fully analyzing reliability and maintainability using standard metrics like:
- Mean Time Between Failures (MTBF)
- Mean Time To Repair (MTTR)
Moreover, mobile sites in Addis Ababa handle higher traffic loads compared to regional or remote areas, making outages especially disruptive.
Therefore, a deeper empirical analysis is needed to:
- Accurately measure availability, reliability, and maintainability
- Ensure compliance with SLAs
- Plan maintenance resources (labor, spare parts, logistics, etc.)
- Minimize downtime, revenue loss, and customer dissatisfaction.
