The rapid consumption of wireless data continues to outpace the industry’s ability to meet demand. Although today’s 4G networks incorporate the latest technologies and continue to offer faster data access, the road beyond LTE and LTE-A is far from clear.
The challenge is to develop 5G networks that can accommodate many more users and devices while delivering more data to each user at any instant in time. Since the dawn of digital communications in the 1990s, the cellular technology roadmap has followed a rigid path focused on increasing capacity and data rates to ultimately arrive where we are today.
5G targets peak data rates per user in the range of 10 Gb/s (over 1,000X 4G). To provide a frame of reference, a user can download an HD video in 40 minutes using the highest speed networks in good conditions. With 5G, a user can download this same video in a matter of seconds.
Faster data access is certainly exciting, but there are challenges to achieving this. The spectrum that service operators paid governments billions of dollars to acquire has simply run out. Today’s networks use spectrum anywhere from 700 MHz to almost 3 GHz, and a variety of public and private entities already claim this spectrum. This challenge, can be met in a number of ways, and the introduction of faster prototyping tools, such as the LabVIEW Communications System Design Suite from National Instruments, is bringing 5G closer to reality.
Making better use of the existing spectrum
With fixed spectrum allocations below 3 GHz, researchers are investigating waveforms that make better use of the existing spectrum to essentially increase the number of bits through a given amount of spectrum. Current standards based on orthogonal frequency-division multiplexing require more frequency to separate transmit and receive data with sufficient efficiency. New 5G waveforms attempt to address spectrum efficiency using the existing network infrastructure to accommodate more users and devices and to squeeze out more bits per hertz.
The Technical University in Dresden (TU Dresden) has prototyped one of these new waveforms called generalized frequency-division multiplexing and prototyped a complete link. TU-Dresden realized 30 percent improvement in data rates compared to 4G.
Another option is densification, which means increasing the number of access points, including macro cells, small cells, and pico cells, deployed in a geographic region. Densification relies on the theory that adding more access points to a served area divides the spectrum by geography rather than the spectrum itself. In addition to densification, new network topologies such as Cloud RAN or C-RAN enable service operators to locate their equipment in the cloud, which significantly reduces the heating and cooling costs of locally deployed equipment as well as the power consumption of a network. A critical challenge of distributed network control is latency. Researchers in the Connectivity management for eneRgy Optimised Wireless Dense (CROWD) networks project, which is funded by the European Union, have shown successful prototypes with these new architectures. This indicates that distributed control within a dense network is possible.
New base station technologies such as massive multiple input, multiple output (MIMO) promise more bandwidth and energy efficiency. Massive MIMO base stations incorporate hundreds of antenna elements to focus the energy per user, which increases data rates and improves the quality of the communications link particularly at the cell edges. Recent experiments by Lund University in Sweden indicate that massive MIMO can increase data rates by 100X or more.
Exploring new spectrum frontiers
New spectrum frontiers in the millimeter wave (mmWave) frequency range are being explored around 28 GHz, 38 GHz, and the 71 GHz to 76 GHz range. These frequency bands are “lightly” licensed and offer plentiful high-bandwidth spectrum. In the past, communication at these frequencies was thought impossible due to the propagation characteristics of electromagnetic waves and the cost of developing and implementing networks in these bands. But NYU WIRELESS has conducted channel-sounding measurements, and the channel profiles indicate that mmWave communications may in fact be feasible. Nokia Networks has prototyped a mmWave communication link and are achieving data rates 100X above current 4G rates with deterministic latency.
What does it mean?
5G will happen and its impact will be transformational, but researchers need the tools and technologies to design and rapidly prototype their concepts faster to expedite the time to market and, ultimately, the time to deployment. New 5G waveforms, network densification, massive MIMO, and mmWave communications may be incrementally deployed along a time curve and as such are not mutually exclusive and may be complementary.
Rahman Jamal, is global technology & marketing director, National Instruments
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