LTE-Advanced
The next turning point in LTE’s exciting journey came on October 21, 2010 when
the ITU issued a press release which qualified LTE Advanced (LTE-A) and WiMAX 2
as meeting the requirements for 4G standard. Consequently, 3GPP, the
international body that developed the wideband CDMA-based UMTS 3G standard,
defined LTE as a 3.9G technology and designated LTE-A as the real 4G
technology. LTE-A is going to be built on the prior OFDM/ MIMO-based LTE
architecture to further increase data rate and subsequently defined in 3GPP
Releases 10 and 11.
The LTE-A standard ( expected to offer peak
rates up to 1 Gbit/s fixed speeds and 100 Mb/s to mobile
users) will be forward and backward compatible with basic
LTE, meaning that LTE handsets will work on LTE-A networks, and LTE-A handsets
will work on standard LTE networks. That makes LTE a stepping stone to the
much-higher-capacity LTE-A systems. The deployment of LTE-A is expected in 2014
and beyond. The LTE-A standard promises three times greater data speeds than
LTE. It boasts five major features: carrier aggregation, increased MIMO,
coordinated multipoint transmission, heterogeneous network (HetNet) support,
and relays. Carrier aggregation combines up to five 20-MHz channels into one
stream to increase data speed, making possible a peak downlink data rate of 1
Gbit/ s and uplink data rate of 500 Mbit/ s. Next, while the standard LTE
defines MIMO configurations of up to 4x4 arrangement, LTE-A extends that to 8x8
stream with support for two transmit antennas in the handset. Third,cooperative
MIMO— is a set of techniques using different forms of MIMO and beamforming to
improve the performance at cell edges. Finally, LTE-A defines a virtual base
station type called relay station. Relays use repeater stations to help
coverage in selected areas, especially indoors where most calls are initiated.
The five key technology features of LTE-A system are carrier aggregation,
increased MIMO, coordinated multipoint transmission, heterogeneous network
support, and relays. Image credit: EE Catalog
SMALL CELL NETWORKS
The first critical juncture in mobile industry’s quest for multifold increase in capacity and flexibility of cellular networks came with the realization that the big tower-based macro-umbrella networks that fueled two decades of voice services weren’t going to cut it in a data-centric world. So mobile carriers and their infrastructure vendors began designing new types of small cells and base stations intended to deliver intense levels of bandwidth over limited areas.
The first critical juncture in mobile industry’s quest for multifold increase in capacity and flexibility of cellular networks came with the realization that the big tower-based macro-umbrella networks that fueled two decades of voice services weren’t going to cut it in a data-centric world. So mobile carriers and their infrastructure vendors began designing new types of small cells and base stations intended to deliver intense levels of bandwidth over limited areas.
These small cell deployments— pico, micro, metro, femto, etc.—
are to evolve into the new heterogeneous network, or HetNet, which will
transform cellular systems from coverage- to capacity-focused systems. This
implies that the upcoming broadband mobile networks will have hundreds of
thousands if not millions of cells. LTE became a driving force behind the
small-cell movement. In retrospect, mobile operators could have created far
more capacity if they deployed smaller cells, reusing the spectrum they had to
the nth degree. But they couldn’t build the density of cells necessary to
support the demands for mobile data. It was a hard feat to pull off because at
any time, when two signals used the same frequency in the same space, there
would be interference. So, for several years, the mobile industry had been
trying to figure how to mitigate that interference. That’s why it had taken so
long to convert an ordinary picocell into a true small cell. Now, instead
station, typically designed for use in a home or small business.
Typically, the range of a standard macrocell is up to 35
kilometres or 22 miles; a microcell is less than two kilometers wide; a
picocell is 200 meters or less; and a femtocell is on the order of 10 meters.
At first, small cell network will function much like an extension of the large
cell counterparts. The network will pass mobile users from big cell to small
cell and vice versa. However, the key difference is
that when mobile users occupy the small cell, they will have a lot more
bandwidth at their disposal. Mobile devices will be able to link to multiple
cells simultaneously, and the same signals that once interfered with one
another will reinforce one another creating an even more powerful connection.
The high-capacity Wi-Fi networks will also get layered in,
creating a heterogeneous network in which mobile devices can establish multiple
simultaneous connections using multiple radio technologies. Apparently, that
boils down to an awful lot of bandwidth. The two main deployment scenarios for
small cells are in rural areas with poor or no indoor coverage, probably using
co-channel deployment, and in dense areas to provide
high data rates and capacity.
Femtocells and other microcell schemes are an integral part of
the LTE deployment strategy. With revenue per bit falling, costs for deployment
must be kept to a minimum while ensuring that the network is operating to its
greatest efficiency. In 2013, the U.S. mobile carriers were getting ready for
their first small cell deployments with an aim of implementing multi-technology
heterogeneous networks. Networking equipment maker Cisco estimates that Wi-Fi
and femtocells will handle nearly half of all mobile traffic by 2017.
MILLIMETER WAVE COMMUNICATIONS 70-80GHz
Cellular networks have always occupied frequencies lower on the spectrum, where carrier waves tens of centimeters long— hundreds of megahertz— pass easily around obstacles and through the air. But this coveted spectrum is now heavily used, making it difficult for mobile phone operators to acquire more of it.
Cellular networks have always occupied frequencies lower on the spectrum, where carrier waves tens of centimeters long— hundreds of megahertz— pass easily around obstacles and through the air. But this coveted spectrum is now heavily used, making it difficult for mobile phone operators to acquire more of it.
At the same time, many 4G networks have just about reached the
theoretical limit on how much data they could squeeze into a given amount of
spectrum. So, wireless engineers are now looking toward higher frequencies,
where radio use is lighter. Here, regulators can free as much as 100 GHz of
millimeter-wave spectrum for mobile communications— about 200 times what mobile
networks use in 2013. Wireless systems that use millimeter waves already exist
for fixed, line-of-sight transmissions.
Moreover, because a single millimeter-wave antenna has a small
aperture, it needs more power to send and receive data than is practical for
cellular systems. Beamforming is a signal processing technique that is used to
direct the reception or transmission of a signal in an array in a chosen
angular direction. Each user's signal is transmitted and received by the base
station only in the direction of that particular user; that drastically reduces
the overall interference in the system and improves the system capacity.
Therefore, not only could millimeter-wave technology merit for
those small cells,it could also provide a simple, inexpensive
alternative to backhaul links, which connect cellular base stations to mobile
operators’ core network. Today millimeter-wave deployments in Nigeria can
provide up to 10GBps with a single ODU. Deploying a 2+0 configuration
provides 20Gbps as well as a failover if one link goes down.
The small cells would be mounted on street
poles, building walls and every form of urban fixture where access to cable or
fiber isn’t readily available and the cost of laying fiber is prohibitive. LTE
requires fat backhaul pipes and millimeter wave technologies can provide both
the reach and capacity at the right prices for the HetNet backhaul.
Millimeter wave transmission systems suit to
small cell backhaul for two reasons. First, it is relatively easy to get
licenses for big blocks of millimeter wave spectrum, which will allow mobile
operators to deploy large backhaul pipes of over 1 Gbit/ s. While a single
small cell might not need that much capacity, the complexity of HetNets will
require daisy-chaining many small cells together, each cell passing its load
down the line. The final backhaul link in such a mesh or chain could end up
handling dozens of cells worth of traffic before it dumps the data onto a core
fiber network.
Second, by definition, the HetNet will be composed of densely
packed cells in urban environments, meaning millimeter wave won’t have to
travel far between hops. Millimeter wave communications technology is winning
merits in the evolving 5G domain because small cells architecture and HetNets
are inherently suitable for millimeter wave-based network configuration.
In Lagos, a densely congested city of more than 20mil, MMW can
cost effectively provide backhaul for LTE to achieve high QoS. It
will also be a cost effective means for bringing access to non/underserved
population estimated to be around 40mil. In addition, apart from MMW for
LTE, overall increase of QoS can be realized if more carriers and
operators would offload some of their MW transmissions to MMW.
NCC anticipated the benefits that millimeter-wave technology
would provide by releasing a "light licensing" model with low-cost
license fees as well as a simple application process soon to be online.
The regulator also envisioned that the millimeter-wave spectrum would
provide relief to the overuse of MW often causing interference. As more
operators and ISPs understand the many benefits of this spectrum, QoS will
quickly rise for Nigerian subscribers.
*Ken Spann contributed this from Lagos with credits for content
given to Ahmad, Majeed (2013-12-17). Essential 4G Guide: Learn 4G Wireless In
One Day (Smartphone Chronicle) Majeed Ahmad Kamran. Kindle Edition.
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PIX: Ken Spann
