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Examining 5G base station architecture (Part 1)

02 Jun 2015  | Steve Taranovich

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I thought that now would be a good time to review where we are at technically with the formation of 5G technology in light of the recent Brooklyn 5G Summit that took place on April 8-10, 2015 jointly organised by Nokia Networks and the NYU Wireless research Center at Polytechnic School of Engineering at New York University. (A few days after this Summit, Nokia agreed to buy Alcatel-Lucent which will strengthen their base station infrastructure as well as to get Nokia into the $13B router market where Alcatel-Lucent is strong . Reuters reported that: Carriers will judge suppliers for 5G technology by their ability to present a single product roadmap by late 2017. Surely the joining of these companies will help assure that Nokia become more cost-effective and their technology more advanced.)

The other recent big 5G meeting took place shortly thereafter on April 14-15 in Palo Alto, CA. This was called the 5G Forum USA launched by the LTE World Series and brought together senior executives and key decision makers from the 5G ecosystem to discuss the 5G future.

In this multi-part article, I will examine the view and challenges of the big players in this market from semiconductor suppliers, to Test & Measurement developers as well as university and telecom carriers. Part one will examine the 5G concept as it exists today as well as some early development ideas and hardware/software developments. We will also discuss the need for Test & Measurement to step up and get design tools ready quickly for developers to test their ideas and designs. Finally, we will discuss the first area in 5G that needs to be investigated: The channel.

In Part two we will reveal the challenges and development ideas of the semiconductor IC suppliers in our industry for 5G solutions.

What is 5G?
Next Generation Mobile Networks (NGMN) says:

5G is an end-to-end ecosystem to enable a fully mobile and connected society. It empowers value creation towards customers and partners, through existing and emerging use cases delivered with consistent experience and enabled by sustainable business models.

Tom Keathley, SVP, Wireless Network Architecture & Design for AT&T says that 5G is expected to appear as enhanced capabilities of LTE-Advanced (LTE-A). So 4.5G will emerge on the way to 5G as LTE-A evolves. Right now 4G is still being deployed, but early designs have started on its replacement: 5G.

Essentially Qualcomm states that LTE Advanced is evolving to include carrier aggregation, enable hyper-dense Heterogeneous Networks (HetNet) with enhanced receivers. HetNets or Heterogeneous cellular networks (HCN) introduce small cells within the transmission range of a macrocell. For proper operation the high power macrocell will need to shut down its transmissions for a period of time to enable the smaller cells to transmit. This can be achieved by Time-Domain Resource Partitioning (TDRP)2 (figure 1).

Figure 1: An example of an HCN made up of a single macro base station and several pico and femto base stations. Each base station can, for example, stream videos to a subset of users2. (Image courtesy of Reference 2)

Extension of LTE into the unlicensed spectrum and moves LTE towards such things as device-to-device functionality, broadcast TV and higher bands.

Carrier Aggregation
LTE-A will promote wider bandwidths towards 100MHz via carrier aggregation which means higher data rates (bps) to enhance the user experience. See figure 2.

Figure 2: In applications such as web browsing, with its bursty nature, aggregated carriers will be able to support more users at the same response (user experience) as compared to two individual carriers. 5G will have higher peak data rates, enable higher user data rates and lower latencies and will leverage all spectrum assets. (Image courtesy of Qualcomm)

It will use more antennas with MIMO for higher spectral efficiency (bps/Hz). And it will employ HetNets with advanced interference management via small cell range expansion which leads to higher spectral efficiency per coverage area (bps/Hz/km2)

More antennas with MIMO
More antennas will be deployed to achieve large gain from receive diversity and MIMO. See figure 3.

Figure 3: LTE-A R10 and beyond will require 8x8 Downlink MIMO, enhanced Multi-User MIMO (MU-MIMO) and uplink MIMO up to 4x4. (Image courtesy of Qualcomm)

The system will need to leverage fibre backhaul infrastructure and use Coordinated Multipoint1 (CoMP) to increase capacity and improve the user experience. The CoMP technique mitigates inter-cell interference (ICI) and enhances the performance of cell edge users. Groups of Remote Radio Equipment (RRE) are connected to the central Base Station (eNode B) via optical fibre (figure 4).

Figure 4: Radio network structure for fast inter-cell radio resource management using (RRE) deployment to achieve CoMP transmission and reception among different cell sites for LTE-A (Image courtesy of Reference 1)

First up: Test & Measurement
Test & Measurement (T&M) must be one of the first areas to align test tool solutions quickly so that 5G developers can accurately verify their prototype design performance both in hardware and in software.

National Instruments: "Tools are enzymes"
"Tools are enzymes" says Dr. James Truchard, President, CEO and co-Founder of National Instruments (NI) at the Brooklyn 5G Summit. We will need next generation tools for next-generation 5G research (See NI 5G wireless portfolio). Platforms drive innovation. Communications Systems Platform-Based Design is shown in figure 5.

Figure 5: A communications System Platform-based Design (Image courtesy of A. Sangiovanni-Vincentelli, UC Berkeley, Defining Platform Based Design, EEDesign, Feb 2002)

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