Millimeter wave technologies can provide the solution to the bandwidth crunch created by a growing number of Internet connected devices attempting to move ever-larger volumes of multimedia content across existing wired and wireless media. Operating at the unlicensed 60GHz frequency spectrum, a new breed of devices with integrated multi-gigabit transceivers are already delivering more bandwidth than those currently using the overcrowded 2.4GHz and 5GHz unlicensed bands. With multi-gigabit throughput, these devices are already delivering better services than the few hundreds of Mb/s available from today’s most advanced wireless products.
Many applications are expected to benefit from 60GHz millimeter-wave solutions. These include adding new capacity to the traditional Wi-Fi networks in your home and between office buildings for wireless data access and video streaming. And the same technologies are also demonstrating great promise as a wireless replacement for mechanical connectors in consumer electronics and mobile devices. These short-range wireless connectors enable sleeker, more robust products by eliminating bulky conventional connectors while purging the susceptibility to damages caused by exposure to water, humidity, dust, and other contaminants.
Manufacturers are already beginning to migrate to millimeter-wave-based technologies. But risk factors must be considered for adoption, both in terms of selecting the right emerging standards, and choosing the right technology partner to assist in their implementation. This article provides a concise overview of the technologies, applications, and implementation challenges facing manufacturers as they attempt to design products which will satisfy the needs of a bandwidth-hungry world.
Wi-Fi and Bluetooth wireless technologies, which made the mobile data revolution possible, have become victims of their own success. Originally intended to operate in the unlicensed 2.4GHz band, Wi-Fi’s widespread acceptance quickly forced the Wi-Fi Alliance to define its operation for a series of channels located in the next globally available unlicensed band located at 5 GHz. Thanks to steady improvements in efficient 5GHz wireless protocols and radio architectures, Wi-Fi has been able to keep pace with the growing demand for bandwidth from laptops, tablets and other mobile devices.
Excitement is growing as smart devices from DTVs to coffee makers, to refrigerators will now be connecting to the Internet. As the number of wirelessly connected devices continues to skyrocket, the growing demand they create for both access and capacity will quickly outstrip what’s available on the existing wireless spectrum. The problem is being compounded as wireless carriers offload increasing amounts of their multimedia traffic—their slices of the licensed cellular spectrum—to the ‘free’ spectrum available in the Wi-Fi bands.
As a result, both of today’s commonly-used ISM bands are rapidly approaching overload. Technical improvements under development can mitigate the problem, but cannot ultimately solve congestion issues, especially in apartments, offices, public spaces and other areas with high user density.
The logical solution to the growing congestion is the adoption of technologies and products capable of operating in the 60GHz (millimeter wave) region where the regulators such as FCC have designated a wide band of spectrum for unlicensed use by industries. With more than 7GHz of spectrum, broken down into four 1.8GHz channels, this new airspace provides 20X more bandwidth than its 5GHz counterpart.
60GHz millimeter wave also gives device designers an innovative solution to the annoying problems caused by mechanical connectors. When used with low power RF with the appropriate antenna, a millimeter-wave data interface can serve as a so-called ‘wireless connector’ which, at close proximity, provides more robust connectivity and can replace today’s mechanical connector solutions. In fact, SiBEAM has introduced a wireless connector solution that has demonstrated transfer rates of up to 12Gbp/s (full duplex). Known as Snap technology, it is intended as a replacement for most conventional data and video connectors, including all variations of USB 2.0, USB 3.0, HDMI, and DisplayPort.
Wireless connectors are especially valuable in mobile devices such as smartphones, tablets and cameras because they eliminate mechanical connectors, one of most failure-prone components in those products. Besides creating an entry point for the pocket lint, sweat and other common contaminants, most mechanical connectors have a tendency to wear out or shear off from their PCB mounts well before a product’s batteries or electronic components have a chance to fail. Eliminating mechanical connectors allows designers to “life-proof” their products against water, dust, dirt, moisture and the occasional spilled coffee.
More, using wireless connectors allows designers to create sleek, stylish products which would not be possible if they had to compromise their industrial designs by sacrificing precious space to mechanical connectors. In fact, mechanical connectors have already become a stumbling block in the design process as manufacturers struggle to meet the demand for ever-thinner tablets, mobile phones and other electronic devices. Even today, connectors can take up as much as half the height of a CE device.
Close proximity wireless connectors also help to eliminate EMI problems. Often, mechanical connectors are the largest source of unwanted radio ‘noise’, and at Gigabit speeds, suppressing connector-induced EMI becomes a major system level challenge. This adds to both the overall system design effort and the unit cost of each device.
So, wireless connector solutions such as SiBEAM’s Snap technology help designers to develop sleeker, more functional mobile electronic products which are better able to survive the real-world conditions.
Millimeter-wave radio’s unique propagation characteristics include:
- RF signals behave much more like light than conventional radio waves at millimeter-wave frequencies. Because of this, early implementations in the band were limited to line-of-sight applications. However, recent innovative techniques such as adaptive beam-forming and beam-steering have been implemented to provide a robust non line-of-sight communication.
- 60GHz signals are attenuated by oxygen, a phenomenon that can severely limit range. This problem must be overcome in order to deliver the wireless experience consumers expect, a task which requires system-level knowledge as well as radio and antenna design know-how.
- Unlike 2.4 & 5GHz signals, 60GHz RF cannot penetrate most walls. This makes 60GHz technologies suitable for consumer experience that is contained in the same room.
At first glance, these issues might seem to limit the utility of the millimeter-wave band, but properly defined applications deliver unique advantages to both users and manufacturers. These applications fall into three general categories, defined primarily by the distances they must span.
Wireless connectors, aka Close Proximity Data Links, provide high-bandwidth I/O in consumer electronics and computers at distances up to 10mm. One promising implementation of millimeter-wave interfaces is already available with SiBEAM’s wireless Snap technology. Its high data throughput makes it ideal for creating wireless docking solutions or device-to-device synch connections. Boasting a 12 Gb/s aggregate throughput, Snap can completely replace the USB, HDMI, or DisplayPort connectors for data and video transfers. Snap is complementary to wireless power charging technologies, and when combined, Snapallows designers to create device form factors which are truly connector-free (Figure 2).
Millimeter-wave technology can also be used to enhance today’s Wi-Fi networks by adding much-needed wireless capacity. In fact, one of the most active standards efforts for these applications is IEEE 802.11ad, formerly Wireless Gigabit – or “WiGig” for short. The standard defines a new physical layer for 802.11 networks in the 60GHz spectrum and is poised to become the next-generation Wi-Fi to alleviate the anticipated congestion in current 2.4GHz and 5.0GHz spectra.
The current 802.11ad specification includes an enhanced version of the standard 802.11 Media Access Control (MAC) layer to support data rates of up to 7Gbits/s. With a complete standard in place and early-market products already available, 802.11ad certification programs are now being implemented by the Wi-Fi Alliance.
While the up and coming 802.11ad standard can carry video streams over IP-based packet protocol, products based on the 60GHz WirelessHD standard have been shipping for almost a decade. Created to stream video content between HD audio/video devices such as HDTVs, DVRs, PCs, mobile and other consumer electronics, products supporting the WirelessHD standard provides the same 1080p60 Full HD video and multi-channel audio experience at near zero latency expected from cables. WirelessHD technology’s high capacity and low latency is well suited for uncompromised wireless video entertainment and highly interactive experiences such as wireless gaming and virtual reality applications. WirelessHD enables a “cable like” HDMI experience without the wires and utilizes the 7GHz channel to support data rates of up to 28 Gb/s while carrying both 2D and 3D formats as well as 4K video streams.
The first wave of WiHD-enabled laptops, smartphones, DTVs, video projectors and VR headsets have been well-received, thanks to the ease-of-use and performance they offer. For example, the LeTV’s MAX1 smartphone has garnered accolades and popularity in China, largely due to its integrated WiHD interface which lets users wirelessly beam games, movies or other video content playing on the MAX1 over to a video projector, LCD screen or other HD display. Users with non-WiHD-capable equipment can also enjoy the easy set-up and convenient operation afforded by a wireless connection with a WiHD-to-HDMI adapter, currently available from several manufacturers.
Both 802.11ad and WiHD compensate for the 60GHz band’s line-of-sight propagation characteristics through the use of beam forming and beam steering between the transmitter and receiver ICs. Network processors along with RF IC integrated with phased array antennas increase the signal’s effective radiated power and allows the wireless system to select the best available Tx/Rx path. In the case of WiHD, this technique has enabled products to support point-to-point, non-line-of-sight (NLOS) connections at distances of up to 10 meters.
While created to support different protocols and applications, WiHD and 802.11ad products are expected to peacefully co-exist in the same home, and even the same room (Figure 4).
Millimeter-wave technologies will also play an important role in future backhaul infrastructure applications that include next-generation 5G mobile broadband infrastructure, fixed access backhaul extension, and point-to point on-campus links where the 60GHz channel’s wireless capacity and highly optimized RF link make it an ideal ‘wireless fibre’ to replace today’s fibre-based backhaul applications.
At present, there are several approaches vying for market acceptance but most systems are currently based on some implementation of the IEEE 802.11ad standard currently being developed. In addition to the in-room applications mentioned earlier, this amendment to the existing 802.11 standard includes the support of long-reach links (up to 500 meters) in the 60GHz millimeter wave spectrum.
Implementing 60GHz millimeter wave technology does have its challenges but there are practical strategies which help. Perhaps the best advice is to choose CMOS RF ICs on which to base your system. Previously, most RFIC makers have relied on exotic, high cost processes such as Gallium-Arsenide (GaAs) or silicon-germanium (SiGe) which allow only limited integration and cost-reductions. Now, however, millimeter-wave devices using commodity-grade deep submicron CMOS processes are available. Such CMOS RFICs are helping to bring the cost of millimeter-wave products to cost points suitable for the consumer electronics market.
If a suitable commercially available solution is available, it is frequently the best choice, especially for early-entry products. Existing RFICs can reduce both time-to-market and development costs, allowing you to devote your resources to adding features which will help differentiate your product.
But there are considerations before you commit to a particular off-the-shelf chip/chipset:
- The application affects the type of 60GHz technology you should choose. Is it wireless video within the room? Or gigabits of data across a campus? Or is it the need to transfer a lot of data across short distances extremely quickly?
- Are you providing an end-to-end (closed) system or does the product have to comply to an industry standard?
l Is your product battery operated or will AC power be available? Trade-offs between link throughput, distance travelled, antenna design, and component selection will depend on the power available and operating time.
l What industrial design constraints will your product have? Any wireless design requires careful placement of the RF circuit within the system. 60GHz adds additional challenges due to the properties of short millimeter waves. In small form factors such as smartphones, heat dissipation and thermal management will add complexity as well.
l Budget. Depending on throughput, distance, form factor, and placement, different wireless components and system level implementation will impact the final cost.
With the 2.4GHz and 5GHz ISM bands approaching capacity saturation, the unlicensed portion of the millimeter-wave band offers a much-needed piece of open spectrum where wireless devices can enjoy new dimensions in capacity and access. Standards are already in place to define both indoor Wi-Fi service and outdoor long-haul links for point-to-point links as well as “last block” mobile access. Millimeter-wave technologies also show promise for use as ultra-short-range “wireless connectors” which eliminate the durability, EMI and industrial design issues associated with traditional mechanical connectors.
Advanced CMOS technologies are making it possible to unlock the potential of all these applications of the unlicensed 60GHz frequency spectrum in an economical manner. SiBEAM is one of the few companies in the world that has mass-produced millimeter-wave ICs in high-volume CMOS fabs on multiple process nodes for over a decade. Part of the company’s success can be attributed to its proven closed-loop design for production process where the device’s production test vectors are created using inputs from collected data from the CMOS processes used. During production tests, the results produced by these highly-accurate test vectors are then used as feedback by designers to fine-tune the design for optimal yield and performance. The methodology can be migrated between process nodes at different manufacturing foundries. SiBEAM provides support through every phase of design, manufacturing, test and deployment including: RF design, thermal management planning; ackaging and implementation; compliance testing, FCC Part 15B and Part 15C.