Having been with Qualcomm for more than 15 years and working in wireless for most of my life, I've seen many changes and amazing innovations in wireless technology, but nothing quite compares to the fundamental shift on the horizon with the 5th Generation (5G) of mobile networks.
Over the last several years, I've been leading a Qualcomm Research project to design a new wireless air interface that, along with a new 5G network architecture, will make our 5G vision a reality. And now that 3rd Generation Partnership Project (3GPP) 5G standardization efforts to develop a global specification called 5G New Radio (5G NR) are well underway, we are actively contributing our 5G designs to drive and accelerate it.
Making 5G NR a reality is incredibly complex. 5G NR must meet an expanding and radically diverse set of connectivity requirements that will not only interconnect people, but also interconnect and control machines, objects and devices across a wide range of industries and services. This unified air interface needs to be flexible and nimble at applying the right techniques, spectrum and bandwidth to match the needs of each application, and to support efficient multiplexing for future services and device types.
5G NR also needs to get the most out of every bit of spectrum across a wide array of available spectrum regulatory paradigms and bands -- from low bands below 1 GHz, to mid bands from 1 GHz to 6 GHz, to high bands known as millimeter-wave (mmWave).
There is no one single technology component that defines 5G. Instead, 5G will be built out of many disparate technology inventions. At Qualcomm, we have been developing these 5G building blocks for years -- inventing new 5G technologies that are pushing, and often redefining, the boundaries of wireless. And now, as we stand on the cusp of 5G mobile networks, our wireless inventions are driving the development of the global 5G NR standards in 3GPP to enable wide-scale 5G deployments based on standard-compliant infrastructure and devices starting in 2019.
One of the most rewarding aspects of my work in Qualcomm Research is seeing our advanced system designs and wireless techniques progress from theory through design, standardization, implementation and ultimately commercialization. Here’s a quick glimpse of five key wireless inventions that are making 5G NR -- and our 5G vision -- a reality.
Invention #1: Scalable OFDM numerology with 2n scaling of subcarrier spacing One of the foremost decisions for 5G NR design is the choice of radio waveforms and multiple access techniques. While many approaches have been evaluated and will continue to be, we have found through extensive studies (published in a Qualcomm Research paper more than a year ago) that the OFDM (Orthogonal Frequency Division Multiplexing) family -- specifically CP-OFDM and DFT-Spread (DFT-S) OFDM, are the right choices for 5G enhanced mobile broadband (eMBB) and beyond.
Whereas LTE uses OFDM in the downlink and DFT-S OFDM in the uplink, our research has shown an advantage to the uplink supporting both DFT-S-OFDM and CP OFDM, adaptively switching to get the link budget benefit of DFT-S OFDM and the MIMO spatial multiplexing benefit of CP-OFDM based on the scenario. The 3GPP NR Release 14 study item has recently agreed to the support of CP-OFDM on the eMBB downlink, and DFT-S-OFDM complementary to CP-OFDM for the eMBB uplink.
Since OFDM is used today, you might ask where’s the further innovation? The answer is scalable OFDM multi-tone numerology (See below). Today, LTE supports carrier bandwidths up to 20 MHz with a mostly fixed OFDM numerology of 15 kHz spacing between OFDM tones (often called subcarriers). With 5G NR, we have introduced scalable OFDM numerology to support diverse spectrum bands/types and deployment models. For example, 5G NR must be able to operate in mmWave bands that have wider channel widths (e.g., 100s of MHz). Our design introduces OFDM subcarrier spacing that is able to scale with the channel width, so the FFT size scales such that processing complexity does not increase unnecessarily for wider bandwidths. 3GPP has recently decided on scalable OFDM numerology with 2N scaling of subcarrier spacing in the 5G NR Release 14 study item.
Invention #2: Flexible, dynamic, self-contained TDD subframe design Another key component of the 5G NR design is a flexible framework that will allow network operators to efficiently multiplex the envisioned (and unforeseen) 5G services on the same frequency. A key component of our design for this 5G NR framework is the self-contained integrated subframe. Lower latency is achieved by enabling the data transmission and its acknowledgement post-decoding to be contained within the same subframe (e.g., a TDD downlink-centric subframe) shown in Figure 2. With the 5G NR self-contained integrated subframe, each transmission is a modular transaction (e.g., DL grant > DL data > Guard Period > UL Acknowledgement) that is completed within a time period. Beyond lower latency, this modular subframe design enables forward compatibility, adaptive UL/DL configuration, advanced reciprocity-based antenna techniques (e.g., downlink Massive MIMO [multiple input, multiple output antenna aarrays] steering based on fast uplink sounding) as well as additional use cases enabled by adding subframe headers (e.g., contention resolution headers for unlicensed spectrum) -- making this invention a key enabler to meeting many of the 5G NR requirements.
Invention #3: Advanced, flexible LDPC channel coding Along with the scalable numerology and flexible framework for 5G NR services, the physical layer design should include an efficient channel coding scheme that can provide robust performance and flexibility. Although Turbo codes have been well suited for 3G and 4G, Qualcomm Research has demonstrated that low-density parity check (LDPC) codes have advantages from both complexity and implementation standpoints when scaling to very high throughputs and larger block lengths as demonstrated in Figure 3. In addition, LDPC coding has been shown to be an ideal solution for wireless fading channels, which need an efficient hybrid ARQ scheme. As a result, 3GPP has recently decided on advanced LDPC as the coding scheme for the eMBB data channel.
Invention #4: Advanced massive MIMO antenna technologies Our 5G design is also advancing MIMO antenna technologies. By using more antennas intelligently, one can improve both network capacity and coverage. That is, more spatial data streams can significantly increase spectral efficiency (e.g., with multi-user massive MIMO), allowing more bits to be transmitted per Hertz, and smart beamforming and beam-tracking techniques can extend the reach of base stations by focusing RF energy in specific directions.
We have shown how 5G NR massive MIMO technology will make use of 2D antenna arrays at the base station capable of 3D beamforming, to open up the higher frequency bands of sub-6 GHz spectrum. With fast reciprocity-based TDD Massive MIMO, our test results have shown that it is possible to reuse existing macro cell sites (e.g., at 2 GHz) for new 5G NR deployments that operate in bands between 3 GHz to 5GHz. These test results with new multiuser user massive MIMO designs have shown significant gains in both capacity and cell-edge user throughput, which is key to delivering a more uniform 5G mobile broadband user experience.
Our 5G design does not only enable the use of higher frequencies in the 3 to 6 GHz band for macro/small cell deployments, but it will also open up new mmWave opportunities at spectrum bands above 24 GHz for mobile broadband. The abundant spectrum available at these high frequencies is capable of delivering extreme data speeds and capacity that will reshape the mobile experience. However, mobilizing the mmWave comes with its own set of challenges. Transmissions in these higher bands suffer from significantly higher path loss as well as susceptibility to blockage. But as we have proven, through extensive testing with the Qualcomm Research 5G mmWave prototype system seen in Figure 4, the idea of mobilizing mmWave bands is no longer out of reach. We are utilizing a large number of antenna elements in both the base station and the device, along with intelligent beamforming and beam-tracking algorithms, to showcase sustained broadband communications even for non-line-of-sight communications and device mobility. Our early research and development in this area has led to our first 5G modem -- the Qualcomm X50 Snapdragon modem that will enable early 5G mmWave trials and deployments.
Invention #5: Advanced spectrum sharing techniques Spectrum is the most essential resource for mobile communications, and having access to more of it means the network can deliver higher user throughput and capacity. However, spectrum is scarce, and we must find creative ways to make the best use of what’s available. Today, we are pioneering spectrum sharing technologies such as LTE-U/LAA, LWA, LSA, CBRS and MulteFire.
5G NR is designed to natively support all spectrum types with the flexibility to take advantage of potentially new spectrum-sharing paradigms, thanks to the design of frame structure with forward compatibility. This creates opportunities for innovation to take spectrum sharing to the next level in 5G. These inventions will make more spectrum available, but also increase overall utilization by enabling a coordinated, tier-based sharing mechanism that can dynamically adapt to loading conditions. To make this a reality, we have just announced our 5G NR spectrum sharing prototype system (Figure 5) that will drive 3GPP standardization and enable impactful trials.
And that's only the beginning...
These five key inventions are just a few of the amazing innovations that are part of our 5G design. They would only be concepts on a piece of paper without the proper hardware, software and firmware to advance them. Our 5G NR prototype systems are not only being utilized as a testbed for our 5G designs, they are also trial platforms that will track 3GPP standardization progress closely to enable 5G NR trials with leading mobile network operators and infrastructure vendors, such as our recent announcement with AT&T and Ericsson. These activities are critical to accelerating wide-scale 5G commercial network launches.
Want to learn more about these inventions and other 5G work? Check out our new 5G NR Whitepaper, which provides a comprehensive overview into our 5G vision and further details of our new 5G NR design. Also, stay tuned to future OnQ blogs where our Qualcomm inventors will provide more details on each of these five key 5G NR inventions.
— Dr. John E. Smee, Vice President, Engineering, Qualcomm Technologies, Inc.