LTE-Advanced Pro: The bridge to 5G

-May 03, 2017

Recently, I received a press release from Ixia about the company's IxLoad-Wireless XAir2 LTE emulation tester. The press release describes IxLoad LTE XAir2 as a "radio access network (RAN) test product specifically designed for service providers, equipment and chip-set makers, as well as enterprises developing LTE Advanced Pro (4.5G) and 5G-related products and services." See Figure 1.

Cellular data technology through the years

Figure 1. Cellular technology has advanced from analog to 4G LTE-Advanced Pro, with 5G in development. Image courtesy of SK Telecom.

To find out more about LTE-Advanced Pro, I spoke with Ixia's Gabriel Chiriacescu. "We see cellular IoT devices and the growing demand for greater bandwidth from mobile users as driving 5G. LTE-Advanced Pro is a bridge from LTE-Advanced to 5G." he said. "The IoT market can't wait for 5G."

Ixia's LTE XAir2 emulates thousands of calls and is designed to test ICs, network equipment, and entire networks. A look at what it does gives you a good idea of LTE_Advanced Pro's capabilities. Here are few of them.

LTE-Advanced Carrier Aggregation (2CA through 4CA): Carrier aggregation finally gets its place in the sun. The idea behind it is to use two-to-five carriers, each 20-MHz wide, to form either bandwidth block of up to 100 MHz (Figure 2). The carriers can also be sent across different blocks. Testing carrier aggregation in LTE-Advanced network infrastructure describes carrier aggregation in detail. Chiriacescu noted that LTE-A Pro can accommodate up to 32 carriers, each at 20 MHz for a theoretical 640 MHz bandwidth.

Figure 2. Carrier aggregation uses multiple carriers, each with up to 20 MHz bandwidth.

SISO, 2x2 and 4x4 MIMO antenna configurations: Multiple antennas let wireless systems such as LTE and Wi-Fi increase throughput over single antennas; each antenna operates in the same RF band. The receiver combines the signals into a single data stream. Figure 3 shows a typical MIMO configuration.

Figure 3. Typical MIMO configurations consist of 2x2, 4x4, and 8x2 antennas.

256QAM: Another way to increase data throughout is by cramming more bits into a symbol. Adopted in 3GPP release 12, 256QAM (Figure 4) encodes eight bits per symbol. That's up from 64QAM in previous releases. With 256QAM, each carrier is capable of 100 Mbits/s data throughput.

256 QAM modulation

Figure 4. In a 256QAM constellation diagram, each IO point represents eight bits.

Unlicensed spectrum: LTE-Advanced Pro takes advantage of the 5 GHz unlicensed spectrum. The primary carrier operates at frequencies from 400 MHz to 3.8 GHz. Carriers can use the unlicensed spectrum either standalone or aggregated with licensed spectrum, which can more effectively use expensive cellular resources and provide subscribers with a speed increase.

According to Chiriacescu, these and other features of LTE-Advanced Pro can result in theoretical download speeds of up to 3 Gbits/s. That should be enough to keep the public satisfied, for a while. Personally, I don’t have an LTE-capable phone and usually leave 4G disabled for longer battery life (Figure 5).


iPhone 4S 4G disabled
Figure 5. Who needs 4G, anyway?

Martin Rowe covers test and measurement for EDN and EE Times. Contact him at martin.rowe@aspencore.com Follow me on TwitterVisit my LinkedIn page

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