What are the True Costs for Mobile 5G mmWave Phased Array Antenna Systems?
When discussing future 5G systems and the need for more spectrum to accommodate the bandwidth needed for greater than 1 Gbps data rates, one of the most popular ideas is the use of the mmWave (milli-meter Wave) spectrum, with 28 GHz and 39 GHz being the prevalent frequencies in the United States. While the available bandwidth is desirable and will support the anticipated data rates, the propagation characteristics of mmWaves are equally undesirable. The propagation characteristics have high path losses and need line of sight (LOS) to overcome building penetration losses. Both problems require high gain, narrow beam width antennas. This can be accomplished for stationary point to multi-point applications, like last mile wireless connectivity to the home. But when mobility is added, then this also needs to be a steered high gain, narrow beam (a.k.a. phased array) antenna designed to follow the paths of several mobile users.
Does this technology exist?
Yes, there are existing mmWave phased array antennas that do everything required: for example, the Fire Control Radar for the F-15E Fighter Jet, an Active Electronic Scanning Array (AESA) with beam steering with a 16 x 16 array with Power Amps (Tx) and Low Noise Amps (Rx). How much does a high gain, narrow beam width mmWave phased array antenna system like this cost? The cost of the APG-63 and APG-82 modernization upgrades for 71 F-15 fighter aircraft is $558 million (assuming no over runs).1 That is almost $8 million per AESA.
How many antennas are required?
Again, due to the short range due to poor propagation characteristics of mmWaves, a very dense network is needed. Possibly one phased array antenna system per city block (200 m) to accommodate 16 mobile users could be required. Having one system per city block would be 64 per square mile and for my little town of Lafayette, Colorado (9.6 miles2) this is 614 antennas. That is almost 5 billion dollars if the current F-15 APG-82 AESA is used – a lot of money for one little town! Of course, the mmWave phased array antenna on the average city street corner will not be subjected to the environment of an F-15 fighter aircraft and only tracks cars, not enemy fighter aircraft. But even at a fraction of the cost, having some type of phased array antennas with the density needed to provide truly mobile performance is going to be very expensive. I personally think that the hype of mmWave for 5G is outrunning the true costs of implementing mmWave phased array antenna systems for mobile applications.
While mmWave 5G phased array antenna systems will provide the desired bandwidth, it would be wise to evaluate the true costs of such systems before jumping on the bandwagon of mmWave spectrum. Having worked on various “low cost” phased array antennas for almost 40 years, the “low cost” aspect has not yet emerged and it doesn’t appear that traditional approaches like the F-15 APG-82 are trending that direction. The most promising approaches on the horizon are software oriented. There are several companies with new software oriented methods under development for delivering cost effective phased array antennas. However, even these disruptive technical solutions are still five to ten years out until successful deployment.
In the near term, perhaps more can be done with existing sub-6 GHz spectrum to progress to 5G mobile data rates. Adding shared spectrum (such as 3.5 GHz) provides a more cost effective way of achieving greater than 1 Gbps data rates. Other cost effective methods would include massive MIMO (mMIMO) and advanced modulation techniques. Since the sub-6 GHz spectrum is not subject to the propagation problems of mmWaves, combining these innovative sub-6GHz solutions could be the answer for 5G mobile applications for the next five to ten years while cost effective mmWave phased array antennas are developed.
Director of Sales Engineering, Kathrein USA
Mr. Veghte leads the Sales Engineering team at Kathrein USA and has 35+ years experience designing Antennas and RF Circuits for both Commercial and Military/Defense applications. Rick holds several patents in antenna design and received his BSEE from University of Colorado and MSEE and MBA degrees from Arizona State.