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Home > News > Industry News > 5G and IoT create a market for.....

5G and IoT create a market for mmWave

  • Author:Ella Cai
  • Release on:2017-06-14
The adoption of mmWave technologies will speed the integration of IoT devices into the 5G network, writes Adam Smith.

Millimeter wave (mmWave) represents the next frontier of wireless technology, bringing 10 times higher frequencies and 10 times wider channel bandwidths than the most advanced Wi-Fi and cellular technologies.

Today’s cellular networks operate in bands from 700MHz to 2.6GHz, while mmWave will run in nearly 20GHz of underutilised spectrum in the 28GHz, 39GHz, and 60GHz bands. MmWave wireless is a tantalising opportunity for companies to develop new wireless products with mobile data rates into the multi-Gbps range.

Wi-Gig (IEEE 802.11ad), operating in the 57GHz to 66GHz frequency range, is an initial foray into mmWave wireless that offers a maximum data rate of 7Gbps. Future mmWave products will operate in other underutilised bands and will share much of Wi-Gig technology.

5G progress

5G, the next wireless initiative expected in the 2020-time frame, will include mmWave bands in ‘New Radio’ (NR) technology that seamlessly combines licensed, shared licensed, and unlicensed spectrum across radio technologies. 5G basestations will support and transparently interface with older technologies.

TX Antenna array gain and DC power consumption versus number of antenna elements

MmWave applications include replacement for wired/fibre connections such as in enterprise campuses or for point-to-point and cellular backhaul/fronthaul uplinks. The availability of multi-Gbps connections will make possible new video and high data rate applications such as medical imaging. Within the home, mmWave will serve to link several high data rate components, including HDTVs, DVDs, set-top boxes, and computers. 
There is even some suggestion that mmWaves will be used in wireless versions of PCI Express and USB 3.0.

MmWave small cells may eventually be found in very dense urban areas.

The short wavelength (1mm to 10mm) associated with mmWave makes possible the use of large numbers of antennas in a multiple-in multiple-out (MIMO) configuration. Arrays of antennas , connected to inexpensive, low-power amplifiers in the milli-Watt range can simultaneously connect to tens of terminals. LTE-Advanced, for comparison, allows a maximum of 8 MIMO antennas. With massive MIMO and adaptive beamforming, mmWave bas stations will be able focus energy into very small spaces.

The result of these technology advances is high spectrum efficiency through spatial reuse. Overall capacity should increase by a factor of 10 over the use of a single antenna and radiated energy-efficiency should increase 100-fold. At the same time, latency and jitter are reduced, opening new latency-dependent, real-time applications such as autonomous vehicle control and industrial automation.

Testing challenges
Example of a mmmWave stack-up IC with antenna array
Example of a mmmWave stack-up IC with antenna array

Developing mmWave basestations and receivers represents a technological challenge for wireless component and system suppliers. Services that replace wired alternatives must match their reliability and performance to earn customer trust.

For current mainstream wireless technologies below 6GHz, component and subassembly system testing is typically performed in a controlled, conducted (cabled) environment. This allows for repeatable test setups where individual variables can be manipulated and measured.

In particular, this excludes the performance impact of the radiating antenna (which is an entire topic on its own).  However, with these emerging mmWave technologies, the physics of this spectrum makes cabled testing less practical. Now, test engineers must enter a new reality where device characterisation requires over-the-air (OTA) testing – and that’s where the complexity begins.

As mentioned, an advantage of these mmWave frequencies is that they make the development of relatively small antenna arrays possible, which enables a large amount of gain and spatial reuse through beamforming technology.  As seen in Figure xxx, in a typical mmWave antenna array, each antenna element has a phase shifter .  Beamforming requires that each antenna’s phase can be controlled, which requires new measurement techniques. With a daunting number of per-antenna phase configurations, test equipment must be able to efficiently validate that each phase shifter is working properly, ensuring that these arrays can effectively “steer” energy to the end-user.

Testing the entire antenna array versus a single element requires high dynamic range
Testing the entire antenna array versus a single element requires high dynamic range
Another challenge with antenna array OTA testing is largely due to increased path loss at these high frequencies. Because the technology relies on the aggregated gain of many antennas acting in unison, the entire array needs to be measured as a whole. At the same time, if a single antenna element in the array is “bad,” it would be almost impossible to detect if you only test the entire array at a single, fixed angle. This requires that tests are performed on a per-element basis as well.

One obvious drawback to this is the additional test time of measuring each element, but there is also a hefty technical demand on the test equipment to have a high “dynamic range,” measuring both the high power levels of the entire array as well as the relatively low power levels of each individual element. As shown in Figure xxx , both the entire array and the single antenna element should be measured with the same high dynamic range setup. This not only ensures a consistent OTA path loss between the measurements, but it also the fastest methodology, since the measurement antenna is stationary the measurements.

Related to per-element testing, a clever selection of test methodology is required to keep test times as fast as possible while still guaranteeing the product quality. The test methodology needs to validate that all the components of the device function properly. This includes the device’s power control on the transmitter(s), accuracy of the antenna beamforming, and the quality of the device’s ability to modulate and receive data.

Developing a test plan that covers these parameters in an efficient way is crucial to transitioning this technology from exotic to mainstream.

mmWave technologies will be an integral component of 5G and NR technologies, interfacing seamlessly with 2G, 3G, and 4G technologies and other mmWave devices. Control-plane handoffs between technologies and adjacent base stations will be complex, yet must be handled quickly and seamlessly for successful deployments. Test equipment will be required to simulate a variety of the coexistence and interference scenarios.  With so many combinations, testing must be automated and highly repeatable if it is to be useful.

mmWave technology promises much higher data rates and spectrum efficiency that enhances existing basestations and offers new applications. Successful deployment and acceptance will depend on proven performance and reliability, which can only be accomplished through sophisticated test equipment. In spite of the large number of use scenarios, such equipment must be able to provide extensive tests quickly and efficiently.