Croatian Operators Overcame Challenges at a Historic Concert

The record-breaking concert, held last weekend in Zagreb by the national music icon Marko Perković–Thompson, which attracted over half a million fans, presented a real challenge for Croatian mobile operators. They overcame numerous challenges, including a large crowd in a relatively small area, and kept operating with no delays.

At the Zagreb Hippodrome, speeds reached up to 700 Mbps, fans made over 226,000 minutes of voice, while data traffic reached 15 TB

Telemach successfully provided an extremely high-quality and stable mobile network during the largest and most organizationally demanding event in Croatia, representatives of Telemach Hrvatska, the third-largest domestic telecom operator, told ICT Business. In addition to optimizing capacity in surrounding neighborhoods, on highways, and throughout the wider Zagreb area, temporary mobile infrastructure was also set up at seven locations within the concert venue itself. Telemach experts planned, installed, optimized, and monitored the most advanced 4G and 5G technology in the world, enabling flawless connectivity and a top-tier user experience despite the exceptionally large number of users and heavy data load.

During the day, 5G speeds of up to 700 Mbps were recorded, and during the concert, over 300 Mbps, which can support more than 100 simultaneous HD video calls or over 50 simultaneous HD streams. At the concert venue alone, 226,000 minutes of voice calls were recorded, while data traffic reached 15 TB. Compared to the previous Saturday, traffic in Zagreb increased by as much as 35 TB.

More than 60 Telemach experts worked on detailed preparation and planning, ensuring excellent network coverage and capacity at all stages of the event, the telecom explains, adding that their expertise was perfected through years of experience in providing infrastructure for one of the largest music festivals in this part of Europe, Ultra in Split, for which preparations are underway.

“This project represents a precedent in Croatian history and a confirmation of Telemach’s commitment to innovation and top-quality service. The quality of Telemach’s mobile network, even at an event of such unprecedented scale, was in line with Opensignal’s analysis—a global leader in independent measurements—according to which it was earlier this year declared the most reliable and best quality network in Croatia. Confirmation that Telemach made the biggest improvement in mobile service quality over the past year was recently provided by HAKOM as well,” Telemach Hrvatska emphasized.

At the concert, attendees made 272,000 calls, with over 204,000 minutes of conversation. As much as 16.2 TB of data was transferred

To cope with the expected traffic from over 500,000 visitors, A1 Hrvatska provided network coverage from as many as 7 locations (five at the Hippodrome, one at the Bundek lake, and one in the fan-zone), the second-largest domestic telecom operator emphasized in response to ICTbusiness.info.

They pointed out that their technical preparation included the activation of 20 temporary base stations, the installation of additional base stations, on-the-fly optimization, and the deactivation of surrounding sectors to avoid interference. They also ensured technical and customer support on the ground throughout the entire day, with continuous monitoring and real-time adjustment of parameters.

“Our users made 272,000 calls, with over 204,000 minutes of conversation. As much as 16.2 TB of data was transferred, and the A1 network successfully handled the intense traffic that changed in real time, following the rhythm of the concert, from live videos, calls, and messages to thousands of selfies from the stands. Also, 5G network speeds reached up to 500 Mbps, depending on the stage of the event and cell load,” A1 Hrvatska said.

New base stations and network management, fiber deployment, and in just a few hours, over 33.8 TB of data transferred on the HT network

While hundreds of thousands of visitors streamed into Zagreb’s Hippodrome and surrounding areas for the Marko Perković Thompson concert on July 5th, few could have imagined that all of them would be able to make calls, exchange messages, and use mobile internet at the same time without any difficulties. However, thanks to the exceptional commitment and expertise of Croatian Telecom (HT) employees, this became a reality—in circumstances not yet seen on a global level, according to Croatia’s leading telecom, HT, in response to an ICTbusiness.info inquiry.

Nearly 200 HT employees participated in this exceptionally demanding operation. On the day of the event itself, network operations were monitored from the Situation Room at the company’s headquarters on Radnička cesta, where 15 experts were engaged, while an additional 50 employees were deployed in the field or working online. The use of a special new tool enabled real-time monitoring of network performance, allowing immediate corrections based on current needs and load. In total, more than 33.8 TB of data was transferred from 6 p.m. until midnight.

The heart of the entire project was the RAN (Radio Access Network)—the system of base stations that provides users with access to mobile services. HT carried out significant capacity expansion, ensuring that all visitors could use basic mobile services simultaneously. The density of users per square meter was such that no similar example could be found, not even at the largest stadiums or festivals worldwide.

In addition to the demanding basic infrastructure, HT had to respond to a special request from the Ministry of the Interior—to provide priority communication for emergency services. In record time, a solution was developed and implemented, raising the security of the event to a higher level.

Not only did HT provide mobile connectivity for visitors, but it was also the key technological partner to the event organizer. It was responsible for establishing and managing the entire digital infrastructure, including an active IP network for more than a thousand cash registers and POS devices at the Hippodrome, Bundek, and the eastern parking lot of the Zagreb Fair. In addition, a private 5G campus network was implemented to connect 735 cash registers and a special local IP network for security video surveillance. This ensured flawless operation of cash registers and their communication with banks and tax authorities, as well as a parallel system for connecting cameras.

The team building the RAN network was led by Goran Toplek, while business services via the IP and 5G campus networks were overseen by Robert Manenica. Preparations included consultations with colleagues from Deutsche Telekom, who also emphasized that such a large number of people was unprecedented and expressed doubts about whether everything could function properly. The HT team proved that such a challenge could be successfully overcome.

Just two days before the concert, a ban was issued on running fiber optic cables above Bundek for safety reasons. Within a few hours, a crisis plan was activated: around twenty HT employees were urgently sent into the field, where they worked nonstop until late at night, while the rest of the team completed equipment installation at the Hippodrome.

During 15 working days, HT experts connected and activated more than 130 network switches and over 3,600 UTP cables to 100 IP switches—a highly demanding task in field conditions. At Bundek alone, 15 kilometers of UTP cable were used on July 4th.

A network was set up for 1,800 cash registers (fixed and mobile); 1,000 cash registers were connected to the HT professional data network via 85 IP switches, while 735 cash registers were connected to the campus mobile network. A network for 200 video surveillance cameras (in cooperation with the Ministry of the Interior) was set up and connected to 35 IP switches. All traffic was delivered to the Situation Room.

The concert organizer received a turnkey system, and the HT team adapted solutions in real time and resolved any issues that arose. The cash registers, in addition to the optical network, were also connected to the mobile campus network, providing additional stability and reliability.

The greatest tension was at the beginning, as visitors started to enter. During performances of popular songs, network traffic would spike sharply, especially uplink, due to the uploading of photos and videos to social networks. Despite this, there was no congestion—everything worked flawlessly, a testament to excellent planning and execution.

With this project, HT set new standards in the event industry, not only in Croatia but also beyond. According to Robert Manenica, no other team in the region could have delivered such a level of complexity and quality in such a short timeframe. User and organizer feedback confirms that HT has become a benchmark for communication technology at major events.

Heading the team responsible for building the RAN network, i.e., the base infrastructure, was Goran Toplek, Director of the Mobile Network Engineering and Access Network Performance Department at Croatian Telecom.

“Preparations for the project began with the announcement by the concert organizer back in February. Although the planned scale of the event and the number of visitors were unprecedented, we decided to proceed with capacity analysis and calculation without hesitation, defining the minimum uplink capacity, which is always more critical than downlink for mass events, from megabits per second, aiming to ensure priority for calls, SMS, and then WhatsApp and Viber messages,” Toplek explained, continuing, “The calculation showed extremely high capacity requirements, which meant very extensive preparations and budget were needed, but we persisted. The nature of mobile networks is such that the margin for error in calculations is very narrow—either it works or it doesn’t. There is no room in between. After the final decision, we started implementation. It was necessary to secure infrastructure, with masts prepared by the organizer and mobile operators finishing the top for antenna installation. Then, space under the mast for equipment. Transmission and power were provided by optical and power cables in underground ducts, done jointly with all operators and the organizer,” Toplek emphasized.

HT installed a total of 15 new base stations at 11 locations, but only the number of cells shows the installed capacity: 684 4G and 30 5G cells. For the successful operation of such a network, radio planning was crucial to avoid interference between newly installed antennas and between new and existing base stations. Enormous effort was invested in design, optimization of 132 sectors of the existing network, and field measurements. At the new locations, the full available spectrum was implemented, and an additional 30 MHz of free spectrum was used on 5G to increase capacity. At each new location, processing power was tripled compared to regular base stations. Permanent base stations in the vicinity of the concert venue were optimized for this event to the greatest possible extent, with over 130 optimization interventions carried out. Also, the network on highways up to 200 kilometers from Zagreb was tuned for heavy load, although this later proved unnecessary.

“We established a campus network at the Hippodrome, Bundek, and Eastern Parking Lot of Zagreb Fair for business-critical communications and all emergency services,” Toplek explains. HT experts provided the complete end-to-end solution for business-critical communications, directly communicating with end users of these networks, all types of cash registers (fixed, mobile, hybrid), and all CCTV cameras. All emergency services were coordinated by the Ministry of the Interior command center, and we provided a certain number of prioritized connections,” emphasized Robert Manenica, Principal in the Business Services Development and Portfolio Management Sector at Goran Toplek, Director of the Mobile Network Engineering and Access Network Performance Department at Croatian Telecom, added that business services over the IP and 5G campus network included data transfer from base stations to the core network and monitoring systems, and between base stations was exclusively provided by high-capacity optical links.

“In addition to the mobile network, HT also provided ICT solutions for the organization of the concert, requiring additional optical capacity. A total of 6 kilometers of optical cable was used. Given the significance of the event, we organized a Situation Center in our premises and online expert shifts. In addition to regular monitoring systems—several dozen—for ICT solutions and the mobile network, we also used special real-time monitoring of the mobile network provided by the radio equipment supplier,” Toplek explained.

System monitoring began early afternoon the day before the concert, due to the expected gathering of visitors, and intensified on the day of the concert from noon, lasting until the final departure of visitors in the early hours of Sunday, Toplek said, adding that overall service availability did not fall below 95%, with this being the lowest value recorded during the entry to the concert area, while during the concert itself, it was above 99%. “We did not record any service outages at any time, although we did observe some repeated attempts to establish voice calls after the concert due to users moving towards base stations outside the concert area. In the busiest hour, we recorded over 55,000 voice calls. Data traffic in the concert area was extremely high, reaching 6 terabytes per hour, with a very high share of 50% of traffic in the uplink direction. For comparison, the maximum average hourly traffic in Zagreb is seven times lower for a comparable number of locations. Users mostly used WhatsApp, Instagram, and Facebook, and we did not record any significant complaints about network operation. On the contrary, the feedback from the Hippodrome was praise, with very satisfactory feedback,” Toplek concluded.

This technological achievement remains an example of how top teamwork, innovation, and experience can enable flawless digital connectivity and security at an unprecedented event, setting new standards for the entire industry, HT concluded.