What the Expansion of OpenRAN Means for Telecom Hardware

This month, multinational telecom giant Vodafone teamed up with Intel and a few other silicon vendors to design its own chipset for OpenRAN. Vodafone also released an executive summary on OpenRAN's technical requirements. 

OpenRAN is an industry-wide standard for the Radio Access Network (or RAN) that supports the disintegration of traditional RAN software and hardware. This enables telecom operators to choose from various vendors instead of relying on just one proprietary interface. This standard was part of a key discussion about extending 5G and 6G that took place at the Mobile World Congress last week. 

 

Side-by-side comparison of RAN (left) and OpenRAN. Image (modified) used courtesy of Mavenir

 

Mavenir and Qualcomm have also recently come together to manufacture OpenRAN-based radio units (RUs) ranging from 8T8R (8 transmit and 8 receive antenna elements—16 total) to 64T64R (64 transmit and 64 receive antenna elements—128 total). Mavenir says its existing R&D on OpenRAN will be combined with Qualcomm’s high-performance ASIC 5G solutions to create new technology for the OpenRAN infrastructure.  

Joining giants like Qualcomm and Intel on the OpenRAN front are players like Ericsson, Nokia, and Huawei—companies that used to sell their proprietary baseband units (BBUs) to telecom providers. This made the telecom market restricted to only a few equipment vendors. But with the ban of Chinese networks in certain countries, many of the world’s telecom leaders are now aiming to make their own OpenRAN technology. 

 

OpenRAN Spreads at an Infrastructural Level

The Telecom Infra Project (TIP) is a diverse community of various service providers and technology partners working together to deploy OpenRAN. Airtel, Vodafone, Intel, and T-Mobile are a few of the many participants under this initiative. TIP intends to release a framework every few months based on vendors' readiness and mobile network operators' priorities. 

 

Releases of OpenRAN. Image used courtesy of Telecom Infra Project

 

In contrast to the traditional RAN, the OpenRAN environment comprises three main building blocks: radio units (RUs), distribution units (DUs), and centralized units (CUs). 

 

RUs, CUs, and DUs in an OpenRAN environment. Image used courtesy of Nokia

 

The RUs digitize and amplify transmitted signals they receive. The DU and the CU are a part of the base station. A CU is located near the core while the DU is placed near the RU. This separation of a traditional BBU into an RU, DU, and CU provides higher flexibility for carriers. 

 

The Hardware Specifics of OpenRAN

The implementation of OpenRAN will require certain technological advancements in the form of chipsets, radio units, active antennas, distributed server units, and centralized server units. Traditional RANs had functions that were embedded in the hardware. But with the separation of these units, virtualized network functions (VNFs) and containerized network functions (CNFs) could run independently on the cloud hardware. 

According to the TIP’s OpenRAN documentation, an RU is expected to operate anywhere in the 2,496–2,690 MHz spectrum of the n41 band. The total bandwidth of this RU is 194 MHz. The functional module of an RU includes an RF front-end followed by a digital front-end, ethernet fronthaul transport, and a lower PHY layer for baseband processing.  

 

OpenRAN end-to-end architecture. Image used courtesy of the Telecom Infra Project

 

The processing functions include:

• Fast Fourier Transform/inverse Fast Fourier Transform (FFT/iFFT)
• Physical random access channel (PRACH)
• CP addition
• Digital beamforming

These functions are accomplished with FPGAs and ASICs. Bandpass filters, power amplifiers, DACs, and ADCs are all part of the RF front-end while the digital front-end consists of digital up and down converters.

The DU supports MIMO functionality with up to eight layers in the downlink and four layers in the uplink. The DU must be designed to work in both outdoor and indoor scenarios with multiple mounting options while the CU must be optimized to performed three-layer functions. The CU includes an NG-U/C and S1-U/C interface that is used to make a connection with a 5G core network and 5G-enabled evolved packet core (EPC), respectively.

 

Why Does OpenRAN Matter for Telecom Hardware?

The shift to the OpenRAN protocol may bring in a lot of new opportunities for hardware designers because it allows mix-matching of different technologies like network automation, analytics, and network slicing.

Traditional RAN vs. OpenRAN. Image used courtesy of NEC

 

Compared to traditional RAN, OpenRAN allows the telecom operator to use vendor-neutral hardware and software technology. This move will make the telecom vendor market more transparent and competitive. Many vendors will be able to interoperate with components from other vendors. Some of the business justifications for OpenRAN, according to a survey from Heavy Reading, include increased vendor diversity, reduced vendor lock-in time, improved coverage, and faster and greater control of feature development.

 

Business justifications for OpenRAN. Image used courtesy of the IEEE Communications Society

 

 

Next Steps for OpenRAN

When compared to the traditional network architecture approach, the OpenRAN does introduce certain levels of complexity, but this architecture will continuously expand and upgrade to provide flexibility to service operators and expand their service coverage.

The OpenRAN movement may also lead to a low-cost and innovative 5G-driven ecosystem. It remains to be seen how far telecom giants will go with OpenRAN and how will they overcome the challenge of security when a multi-vendor approach is implemented.