Connecting eLTE and TETRA to Build Smarter Cities
From Old to New
Since its introduction in the 1990s, Terrestrial Trunked Radio (TETRA) has become the most widely-deployed emergency communications system in the world, providing basic communications services to organizations in the public safety sector for all command and dispatch requirements. TETRA provides many useful functions, and is a mature and stable system that supports flexible networking, wide coverage, powerful error correction, anti-interference capabilities, and the added advantage of a complete industry chain.
However, new Smart City platforms in the public safety sector are demanding data throughput capabilities that TETRA was never designed to support, with higher bandwidth and lower latencies to manage multimedia transmissions.
There is a surge in demand from urban planning engineers for multimedia visual dispatching services that require real-time video transmission and low-latency access to databases. The current wave of specifications expect that a full-range of new technologies be incorporated into Smart City solutions critical for public safety such as cloud computing, Big Data analytics, Bring Your Own Device (BYOD) connectivity, and Internet of Things (IoT) sensor networks. Support for high-resolution images, two-way video, and high-speed data transmission are above and beyond the scope of the legacy TETRA infrastructure and requires the deployment of a modern broadband wireless platform to cope with the new, higher-performance requirements.
A typical multi-dimensional Public Protection and Disaster Relief (PPDR) command and dispatch system must be built to satisfy:
- Basic emergency communication networks for wide radio coverage and voice trunking through multiple, integrated wireless digital networks.
- Dedicated wireless multimedia hotspots for multi-dimensional control and management, mobile office facilitation, BYOD, and Geographic Information System (GIS) coordination for public safety departments, including police, fire, and medical rescue.
Comprehensive Smart City solutions necessarily include the capacity to interface and coordinate with urban and regional rail transportation systems. By today’s standards, previous generations of train-to-ground communication solutions are vulnerable to crosstalk interference and service disruption due to multiple trackside radio networks, and unable to integrate at either the application or data layer. TETRA networks have typically been used for voice-based dispatch, for both operations and emergency services. Wi-Fi and/or analog wireless data systems have been applied to train-to-ground video and control data transmission. LTE entered the scene to operate Passenger Information Systems (PIS) and Closed Circuit Television (CCTV). In the future, it is expected that the LTE platform will be extended to become a unified communication system by also incorporating control data transmission, or Communication-Based Train Control (CBTC).
eLTE Supports TETRA
Based on 4G LTE standards, Huawei’s eLTE is a multimedia, application-oriented, wireless broadband system developed to meet enterprises’ demanding requirements for broadband data and a seamless interconnection between TETRA and LTE systems. An eLTE-TETRA interconnection is established either as a Gateway Interconnection or a System Interconnection. Both types enable hybrid user groups across eLTE and TETRA systems, Point-To-Point (P2P) voice calls, and priority traffic preemption.
For a Gateway Interconnection, the Trunk Gateway and TETRA Vehicle-Radio are connected to the eLTE and TETRA terminals, respectively. The Gateway Interconnect enables coordination between systems while ensuring the ability of each node to operate signaling and service processes independently.
The Gateway Interconnection option has resulted in widespread adoption owing to the capacity of the system to provision services with great flexibility.
The System Interconnection option, employs a Software Development Kit (SDK) to meet the needs for project-specific customization. The complete kit includes qualified software frameworks that are matched to compatible hardware platforms and operating systems with standard open interfaces. A pre-integration service suite enables systems integrators to connect the LTE transmission and session layers with upper-layer applications. The result is a system-level interconnection between eLTE and TETRA that provisions a wide range of reliable trunking services with high-levels of service capacity and the unified management of complex services.
eLTE Smart City Projects
The recently deployed municipal network in Nanjing, China, is the world’s first LTE-based, dedicated broadband trunking network for government. Nanjing had been operating a TETRA voice trunking system and chose to meet growing information processing demands within the public sector with an eLTE overlay.
The Nanjing investment focused on deploying a single, hybrid network that protected the sunk cost of the TETRA platform while adding LTE capacity to implement an advanced data plant capable of scaling well beyond the first generation of smart applications.
Interoperability between the TETRA and eLTE networks was achieved by employing a Gateway and System Interconnection hybrid that supports group and P2P voice calls, two-way multimedia command and dispatch, and priority preemption functions that are operated from either side of the combined eLTE and TETRA network.
Among the services employed by the Nanjing city government is a unified information platform for real-time monitoring and cross-departmental exchange of electricity and hydrological data, and video surveillance of the city’s transportation system and mobile offices. System capacity was tested early at the 2013 Asian Youth Games and 2014 Youth Olympic Games.
In the urban rail sector, “Line 1” of the Zhengzhou subway system installed a TETRA network for voice command and vehicle dispatching, and an eLTE platform for dedicated broadband data services, including PIS and real-time train-to-ground video streaming to the command and control center.
Huawei is actively working with partners in the rail transportation sector, including Alstom S.A., headquartered in Levallois-Perret, France, to conduct tests on LTE-based CBTC solutions. CBTC functions on an eLTE platform present operators the opportunity for significant cost savings and synergies in our new era of wireless broadband communications.