The only way is UP!

Author : Mihnea Trifan, National Instruments

27 June 2016

Figure 1 - mmWave Frequencies provide greater Spectrum opportunity

This article is the second instalment of the trends in test series delivered by National Instruments focusing on challenges facing the test industry. This article looks at the next generation of wireless communications.

(Click here to view article in digi-issue)

Prototypes that enable 5G are already in use and engineers are iterating designs and theories to realise what can be achieved in the future. In order to deliver these advancements within the planned timeframe for 5G and at a realistic cost, the correct choice of testing platform is essential. Here, National Instruments will discuss the challenges for exploring the mmWave spectrum and the benefits this could ultimately deliver to consumers. 

The next generation of wireless communications – 5G – is expected to provide network connections 40 times faster than 4G LTE, whilst simultaneously handling a huge increase in the number of connected devices. It is expected that by 2020 the number of connected devices will exceed 50 billion, compared to 23 billion in 2016.

As well as the consumer applications for 5G, there is already a high expectation for it to be a key enabler for the Industrial Internet of Things (IIoT). With its ability to provide connection density 4 times that of the previous generation of wireless communication, it offers huge potential for interconnected industrial systems. The IIoT will facilitate the massive deployments of sensors and actuators as well as real-time automation and advanced machine-to-machine (M2M) communications. 5G will be essential in delivering a stable communications network, allowing the inter-connectivity of these systems. The vision for 5G delivers enhanced capabilities, for development of mission critical services through low latency connections. One example of this includes autonomous cars and intelligent transportation where the use of interconnected proximity sensors is essential. 

Higher bandwidth is another important capability being developed for 5G. Higher bandwidth allocation will allow the delivery of faster and higher quality data for applications such as video streaming. High frequency signals in the millimetre wave (mmWave) band or extremely high frequency (EHF) band, offer significant opportunity to help meet these capability needs. Currently, digital rates over cellular networks are limited to 1 Gbit/s with LTE Advanced. By going into the mmWave spectrum there is the potential of achieving data rates 10 times higher.

Historically, this part of the spectrum was unused due to challenges with operating at higher frequencies. One of the key challenges at these frequencies is ensuring transmission through the atmosphere. Signals at these higher frequencies are very susceptible to absorption in the atmosphere, significantly limiting the range of the signal. Rain and fog increase the signal attenuation further presenting real challenges in the practical application of this band for over the air signals. 

Figure 2 - Modular systems provide the flexibility to scale for mmWave, whilst maintaining existing capabilities for sub 6 GHz testing.

Technological advancements are allowing new techniques to be identified that can overcome these challenges. This has focused attention and development on expanding wireless communications beyond 6GHz. The only way (from here) is UP!

The benefits of extending communications networks into the mmWave band are derived from the physical characteristics of operating at such high frequencies. These include greater spectrum efficiency from wider bandwidth signals and shorter wavelengths that require smaller component dimensions. This allows more antennas to be packed into the same space, enabling larger network capacity, and better isolation of simultaneous users.

These benefits bring huge advantages to the consumer, however they present RFIC manufacturers with real challenges that need to be overcome in order to realise the true potential of the mmWave spectrum. To overcome the financial and technical challenges presented by mmWave exploration, leading RFIC manufacturers are adopting modular hardware and scalable software to test mmWave frequencies. 

Maintaining profitability when prototyping in the mmWave band is vital, but the cost of supporting new frequencies and bandwidths which are currently unused is a challenge. Investing in a future proof test system means investing in modularity. An economically efficient test system provides a core platform; isolating functional components for modulation, demodulation, data movement and processing. A modular system design allows investment in components that scale across frequencies, ensuring that engineers can prototype 5G systems today whilst maintaining the flexibility to meet future development needs. 

The shorter wavelengths found at these higher frequencies lead to the antenna dimensions being very small. Patch array antennas, bonded to the IC itself, are likely to be used which makes transmission technologies like beamforming more economical. However, it is increasingly challenging to characterise. Previously, the devices were placed in anechoic chambers and tested in order to validate the emission patterns over the air. Although these tests are essential for validating device performance, there are drawbacks encountered in this process such as difficulty in ensuring radiation isolation, the physical size of the test environment, and most importantly the test cost.  

Figure 3 - NI mmWave Transceiver System 2x2 MIMO Unidirectional Link

Another challenge in terms of testing is the integration of mmWave technologies with other standards to form a “multiband” wireless test system. As new wireless standards are released, devices are continuing to support legacy standards and this trend is expected to continue in the era of 5G. An example is wireless routers touting “triband” Wi-Fi, although today 2 channels are actually used (2.4GHz and 5GHz unlicensed bands). With the addition of WiGig (802.11ad) at 60GHz, this system will be truly “triband”.  

A typical 802.11ad signal requires up to 50x the data movement capacity compared to an 802.11ac signal. Unlike traditional instrumentation, the PXI form factor can offer a balanced combination of size, cost and I/O to support the increasing demands from these applications. PXI can handle almost 24 GB/s of throughput today and with the future advancements in this technology, PXI will be an imperative test platform for future test systems.

The combined needs for higher bandwidth and lower latency, along with the exponentially increasing number of connected devices, is continuing to drive researchers to investigate networks that operate in the mmWave band. 

NI recently launched the NI mmWave Transceiver System; a full transceiver that can transmit and/or receive wide-bandwidth signals at an unprecedented 2 GHz real-time bandwidth, covering the spectrum in the E-band, 71-76 GHz. Built on the PXI platform, it can be configured for single-input single-output (SISO) and multiple-input multiple-output (MIMO) delivering the flexibility needed to prototype future designs. The system also integrates FPGA technology allowing real time signal processing for prototyping applications such as Digital Pre-distortion (DPD).

Nokia Networks is paving the way for next-generation wireless communications by working with NI to investigate mobile access in the spectrum mentioned above. Tod Sizer, head of mobile radio research for Nokia Bell Labs, said NI’s mmWave transceiver system has been a key research platform for mmWave research. The platform delivers the right combination of hardware and software necessary to expedite research and has given Nokia confidence that mmWave will indeed be a critical technology for 5G. Developing one of the first mmWave communication links capable of streaming data at speeds exceeding 10 Gb/s—the fastest mobile access wireless system ever publicly demonstrated, NI and Nokia Networks are on the road to making 5G a commercial reality. Using LabVIEW and PXI, Nokia are aiming to develop the world’s first field-deployed 5G proof of concept system. 

Going up in the frequency spectrum will open new challenges that engineers need to embrace and overcome. Modular platforms will continue to lead the way in exploring potential 5G technologies. Its ability to deliver cost-effective, long lasting and flexible solutions is proving essential for the development of future complex applications. Savvy organisations will come up with test plans and set up partnerships with vendors that can offer flexible test platforms. Higher frequency research will continue to be supported with long-term product strategies. Engineers cannot ignore the fact that going into a higher frequency spectrum will bring huge benefits for applications around the world. From here, the only way is up!

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