October 2016 15
THE LATEST IN NETWORKING AND WIRELESS TECHNOLOGIES
cells since the majority of cell phone calls are made from
inside somewhere. Additional smaller cells will be needed
to cover the same area because of the limited range of
millimeter wave signals. The smaller cells will also be
controlled by a network that is primarily software rather
The high speed capabilities of 5G arise not only from
wider bandwidth but also from the use of MIMO (multiple
input multiple output). MIMO is the technique of using
multiple transmitters, receivers, and antennas to divide up
a high speed data stream into multiple signal streams. This
provides not only higher speed, but also minimizes the
effect of fading and multipath transmission common in the
millimeter wave bands.
Antennas will also use adaptive beamforming. This
technique automatically focuses the transmitted and
received radiation into narrower streams to eliminate
interference between cells and to improve transmission
5G technology will not be with us for several more
years. However, considerable development is underway
to make this happen. The availability of millimeter wave
integrated circuits will certainly help this movement. One
such device which is available now is shown in Figure 1. It
is a complete 28 GHz transceiver that supports up to four
transmit/receive antennas. Until 5G is available in 2020
and beyond, we will just have to be comfortable with the
current 4G LTE systems, and that’s not a bad thing at all.
LTE is Here Now
The 4G LTE systems that we now use have only
been around since about 2008. It is a fully developed
system that has been amazingly successful worldwide.
Currently, there are 428 LTE networks in 155 countries,
and that number continues to increase. Furthermore,
upgrades and improvements are continually being made.
LTE uses conventional cellular spectrum below 2. 5 GHz.
Using 20 MHz channels and 4 x 2 MIMO, it is possible
to achieve download data rates of 150 Mb per second.
The average download speed is considerably less than
that by approximately a factor of 10, but this is more than
adequate for most users. The actual download speed is
a function of the capabilities of the cellular system, the
number of users, as well as the range and environment of
One of the most important improvements to LTE is
the current rollout of LTE-Advanced. LTE-A provides for
a feature called carrier aggregation. Carrier aggregation
allows the cellular operators to combine up to five 20 MHz
channels for up to 100 MHz of bandwidth. Combining
that with 8 x 8 MIMO higher level QAM modulation can
produce a maximum download speed of 1 Gbps. While
not all systems will get this capability, most will adequately
boost their download speeds to keep users happy with
Another LTE upgrade going on right now is the
addition of voice over LTE or VoLTE. This means that
voice phone calls will be made digitally over LTE systems.
Currently, most cellular carriers still widely use 2G and
3G cellular technology to carry voice traffic. VoLTE will
improve voice quality and should lower overall costs.
Eventually, most carriers will phase out older 2G and 3G
One interesting development with LTE is LTE
Unlicensed and an equivalent technology called Licensed
Assisted Access (LAA). Both of these are techniques
that cellular operators can use to increase data rates.
This is done by tapping into the unlicensed 5 GHz band
spectrum. Where possible, LTE carriers can offload some
high speed data to nearby Wi-Fi networks operating in the
5 GHz spectrum. While this can produce significant data
rate increases to handle the video load, it can also cause
interference to Wi-Fi signals in this unlicensed spectrum.
The latest Wi-Fi version 802.11ac uses 5 GHz
spectrum exclusively. LTE-U and LAA technologies are not
widely implemented yet, and the Wi-Fi Alliance is working
with standards organizations and the carriers to ensure that
data rate increases can occur but without interference to
The Internet of Things Movement
The Internet of Things and an earlier technology
known as machine-to-machine (M2M) communications are
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n FIGURE 1. The Anokiwave IC is a complete 28 GHz Ka
band millimeter wave band transceiver. It supports up to
4 x 4 MIMO and comes in a 6 x 6 mm package.