Circuit Switched Fallback can cause underused LTE

Telecom Lead India: With LTE becoming pervasive
across the globe, more operators have started rolling-out their VoLTE services.


In order to successfully operate LTE network and provide VoLTE
services, operators need to understand the possible unintended consequences.


For the initial adopters of the LTE technology, it is
necessary to learn that the initial deployments of LTE, which consider all
sessions as data, do not support voice calls as data.


Until an operator deploys VoLTE, LTE voice calls are
supported in the 3G network through an implementation known as Circuit Switched
(CS) Fallback in 3GPP networks.


CS Fallback is a temporary measure via core network
upgrades. Until a more robust VoLTE implementation is deployed, operators are
often unaware of the unintended consequences on their LTE and 3G network.


In India, LTE is yet to pick up and VoLTE service will
soon be launched by BWA license holders such as Reliance-Infotel, Airtel and Aircel.
These operators could also face these issues, unless a proper solution is


Telecom Lead interacted with Marc Bensadoun, CEO
of Newfield Wireless, to learn more on CS Fallback and underused LTE


What is the role of Circuit Switched (CS) Fallback while
making a voice call on LTE network?


Until VoLTE is deployed in LTE networks, voice calls are
supported in the 3G network through a standards-based implementation known as
Circuit Switched (CS) Fallback. When an LTE subscriber makes or receives a
voice call, the network redirects the device to the 3G network where the
circuit-switched voice call is attempted.


What are the shortcomings of Circuit Switched (CS)
Fallback? How is it affecting the end-user experience?


While CS Fallback is operating as expected in routing
voice calls to the 3G network – there are some short comings to the approach.
When a subscriber on the LTE network makes or receives a voice call, the
network redirects the device to the 3G network, where the voice call is attempted. Upon
completion of the voice call and any active data session, the device must
re-select the LTE network.  An unintended consequence is that if an LTE
subscriber is using an application (e.g. Facebook) on the 4G network at the
time of the call, both the voice and data session are moved back to the 3G
network. Until the data session is completed or the device is reset, the
subscriber will camp on the 3G network. Subscribers may be ‘disappointed by
their supposed -4G’ service which is actually being delivered through the
operator’s legacy 3G infrastructure.


What are the consequences of Circuit Switched (CS)
Fallback in operators’ LTE and 3G networks?


The 4G network assets may be underutilised as more
subscribers than expected will fallback and stay on the 3G network. While the
migration to 4G is meant to alleviate capacity constraints on 3G networks, 4G
subscribers camping on the network might cause blocks and access failures for
subscribers with only 3G user equipment.


How operators can identify the critical hand-off points
between their LTE and 3G networks?


Using a big data analytics application, such as Newfield
Wireless’ TrueCall,an operator’s engineering department is able tovisualise all
geo-located data sessions on its 3G and 4G networks. This allows engineers to
identify the critical hand-off points between their LTE and 3G networks.


How operators can evaluate how much data capacity is
really being provided by its LTE network for any given area?


Using TrueCall, an operator can determine the carried
traffic in MB or Mbps for any defined polygon. This could be a sector, a
cluster of sites, or even the entire network.


How operators can initiate site planning for small cells
using LTE visualization and optimization tools?


TrueCall can provide operators with a traffic map of
their existing 3G network, which can be used to prioritise site acquisition
candidates for an LTE network. Similarly, traffic maps of the on-air 4G network
can be used to diagnose capacity issues. Small-cell solutions can be deployed
and their impact can be viewed in real time.


How voice-over LTE (VoLTE) can help operators in ensuring
a ROI?


The promise of LTE depends on its increased spectral
efficiency and its use of an all internet protocol (IP) based infrastructure
that reduces network latency. This allows for voice calls – the traditional use
case for mobile networks – based on VoLTE. These calls can be handled using
less spectrum, enabling more bandwidth for data applications driven by
smartphones, tablets and Machine to Machine (M2M).


With VoLTE, operators can free up spectrum from less
efficient legacy technologies (e.g. where the frequency is LTE compatible) and
redeploy it for greater utilization in the new LTE network.


Danish Khan
[email protected]