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Addis Ababa, the capital city of Ethiopia and the country’s economic and transportation hub, has a high population density and traffic congestion. To ease the latter, the Ethiopian government invested USD $475 million into the Addis Ababa Light Rail Transit project.
Ethiopia’s light rail project marks the first time that Huawei’s LTE technologies have been applied to light rail voice dispatch and ticketing data transmission. Huawei won the project with its innovative LTE technologies featuring powerful broadband voice and data concurrent transmission, and multi-product solutions, providing a comprehensive, integrated communications network and basic support for Ethiopia’s light rail transit project.
The project has two phases covering a total length of 75 kilometers. The first phase rolled out the 31 kilometer South-North and East-West railway lines which were required to be completed simultaneously and put into trial use by January 2015. These lines provide services for the African Union Conference and Ethiopian election early in that year.The first phase of the project consisted of construction of a control center, 39 stations (including 12 elevated stations and 2 underground stations), 14 substations (with equipment rooms), 4 section substations, 2 rolling stock depots, and 20 grade crossings. When the first phase was completed, 41 trains were put into service at a design speed of 70 km/h. The departure interval was initially 6 minutes, with the expectation that departures would be further reduced to 5.4 minutes in the medium-term future, and 4 minutes over the long run.
Based on actual conditions, the Ethiopian government required full-coverage wireless communications and a combination of orderwire and private phone services. A single backbone network operates along the entire railway lines, featuring unified multiple services and less trackside equipment.
The customer needed one wireless network to deliver trunking and ticketing services, and one wired backbone network to carry communications, signaling, ticketing, and Supervisory Control And Data Acquisition (SCADA) services. Unified multiple services are expected to reduce trackside equipment.
The orderwire system and private phone system needed to be combined to reduce the number of devices.
It was essential that equipment at each station be able to access substations through access networks free from any single point of failure. The access equipment was expected to perform well, even under adverse trackside environmental conditions.
A network management system was needed to ensure unified management of the communication systems. The network management system uniformly collects and manages alarms from communication systems.
The innovative Huawei Digital Urban Rail Solution allows both real-time and non-real-time services such as communications, signaling, ticketing, electric power monitoring, voice, and data to be carried on a single network. It also provides air-interface encryption functions and board redundancy protection for core network platforms, greatly improving network reliability and security. Switching time for the Multiple Spanning Tree Protocol (MSTP) ring network (STM-16) is less than 50 ms. Dedicated frequency bands (400 MHz TDD spectrum chunks) are free from interruption. A 9-level Quality of Service (QoS) mechanism is available. Cell coverage diameter is 1.2 kilometers. Only 4 Baseband Units (BBUs) and 9 Remote Radio Units (RRUs) were deployed along the 31 kilometer railway lines to reduce equipment and maintenance expenditures.
The system features low latency, a high performance dispatching platform, and a flattened network architecture. By integrating multiple networks such as the communication and ticketing networks, the system enables real-time wireless transmission of large amounts of data for the ticketing system and allows concurrent voice dispatching and data transmission.
Industrial Access Routers (ARs) were deployed at each station/grade crossing to form Smart Ethernet Protection (SEP) rings, improving the reliability of the access network.
Huawei’s Digital Urban Rail Solution ensures stable operations across the entire light rail transit system, dramatically alleviating traffic congestion throughout Addis Ababa.
The ultra-broadband technology enables wireless dispatching and allows one network to deliver multiple services such as voice trunking and ticketing data services, largely reducing trackside equipment and effectively cutting down on maintenance costs.
The 9-level QoS mechanism distinguishes service priorities, secures critical real-time services, provides dedicated frequency bands with unique anti-interruption technology, and ensures high efficiency of daily operations.
The urban rail transit system now includes multiple services carried over the MSTP backbone network, a combination of orderwire and private telephone systems, and secure access ensured by industrial ARs and SEP rings. This streamlines network equipment to the maximum degree, and eliminates construction of multiple networks, thereby greatly reducing the customer’s construction costs and Operating Expenditure (OPEX).
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