Our latest FLASH report from the RAN USA 2016 event

1. www.signalsresearch.com
Dispatches from the frontier of wireless research
February 9, 2016
CLOUD RAN WITH A CHANCE OF
VIRTUALIZATION
Key Takeaways from the RAN USA
Conference 2016

2. 2 | Signals Flash February 9, 2016
EXECUTIVE SUMMARY
In late January we attended the RAN USA event in downtown San Francisco. The event brought
together a great contingent of operators and vendors from Asia, Latin America, and the United
States for two days of in-depth discussions on everything RAN. In addition to attending the
event, we also had the opportunity to speak and chair the antenna workshop which took place
on the second day of the event.
As always, unlike our subscription-based Signals Ahead reports, you may forward this abbrevi-
ated Signals Flash! report, which quickly highlights a few key themes from the conference, to
whomever you want. Please also note that if your organization subscribes to Signals Ahead, you
will not be receiving a report this month due to preparatory work for a couple of upcoming
Signals Ahead reports as well as our participation at Mobile World Congress. We intend to make
up for the shortfall over the next two months.
KEY HIGHLIGHTS
➤➤ C-RAN – Lovers and skeptics. Like certain polarizing political figures, you either love “the
C-RAN” or you are strongly skeptical. For those that have dared to give it a try, they have cast
their votes in its favor while others are still caucusing amongst themselves and waiting to make
a decision.
➤➤ All choked up over the Fronthaul. The fly in the ointment for C-RAN is the fronthaul, or the
pipe between the baseband functionality and the remote radio head. Despite the promises
from more than a decade ago, CPRI isn’t living up to expectations and its days are probably
numbered.
➤➤ Looking ahead to what comes next. With more advanced antenna schemes and far fatter
pipes, the next-generation air interface will make things even more problematic. Fortunately,
potential solutions are in the works.
➤➤ Random thoughts. We throw in some tidbits from other presentations, plus provide a few
updates from our last Signals Ahead report on the 3GPP family of CIoT standards.

3. 3 | Signals Flash February 9, 2016
Unlike our more in-depth Signals Ahead research reports, there are not any restrictions associ-
ated with the redistribution of this document. Recipients of Signals Flash! may share this docu-
ment both internally within their organization and externally with reckless abandon. In fact,
we encourage it! In addition to providing near-real-time commentary and analysis of industry
noteworthy events, Signals Flash! provides readers with a summary of past and planned research
reports that we offer through our subscription-based Signals Ahead research product. We have
also taken the opportunity to promote a couple of our most recent and futuristic reports for
readers of this Signals Flash! who don’t subscribe to Signals Ahead.
We attended the Avren Events’ RAN USA, which was held in San Francisco in late January. In our
mind, the event definitely exceeded our expectations. Although there wasn’t necessarily a large
attendance, there was a great contingent of speakers representing operators from around the
world (CMCC, KDDI, NTT DoCoMo, Softbank, T-Mobile, AT&T and Telefonica) and the presenta-
tions were technology oriented versus being marketing hype. The smaller crowd also allowed for
lots of interaction, both during the sessions and during the breaks.
Given our schedule – we are currently “Down Under” doing something that Signals Ahead
subscribers will be able to read about in a few weeks – and with MWC 2016 taking place the last
full week of February, we are going to “miss” a Signals Ahead report this month. We hope to
more than make up for it in the next two months, including another report from our 5G series of
reports. This report will stem from RAN #71, where we expect the RAN Plenary will discuss and
approve the 5G Study Item for Release 14.
We should also note that we have an ambition to do a full-blown report on C-RAN and network
virtualization at some point in the future. As such, we are retaining a lot of additional insight for
future use.
C-RAN – Lovers and skeptics
The definition of C-RAN isn’t as broad and all-encompassing as IoT or 4G, but there are at least
two basic definitions to consider. The most basic approach to C-RAN is to centralize or pool
the baseband functionality of a cellular base station within the network and then connect the
baseband functionality via fiber with the distant radio elements, which are located at the cell
site. The more advanced approach to doing C-RAN is to virtualize the centralized baseband func-
tionality such that the baseband functionality can be pooled and then distributed throughout
the network as it is needed. With this approach it is also more than likely that the baseband
functionality runs on a common hardware platform with customized software running on top
which provides the specialized functionality.
Even the most basic approach to doing C-RAN is problematic for most operators, especially
if they want to do it across a large swath of the network. The primary problem, as operators
discussed at the event and which we highlight in the next section, is the fronthaul. However, if
the fronthaul problem can be solved, either by increasing the bandwidth/lowering the latency of
the connection or by redefining the specifications such that uber-high bandwidth and ultra-low
latency are not required then the prospects are compelling.

4. 4 | Signals Flash February 9, 2016
IN CASE YOU MISSED IT: SIGNALS AHEAD BACK ISSUES
➤ 1/29/2016 “The Murky Underworld of IoT - How
3GPP-based Solutions Pave the Way to a Connected
World” While there is a lot of industry interest in IoT air
interfaces and their individual merits, there is also more than a
fair amount of uncertainty and unknowns regarding these tech-
nologies and what they can and cannot do, both in the short term
and in the longer term. In this Signals Ahead report we look at
the collective group of 3GPP-based CIoT technologies, by lever-
aging operator and vendor interviews, our analysis of 3GPP filings,
and our recent participation in the last few 3GPP standardiza-
tion meetings. Key Highlights include the following: (1) History
101. We take a trip back through memory lane to show how and
why we ended with the existing family of 3GPP-based CIoT tech-
nologies and device categories, including Cat 0, Cat M1, EC-GSM
and Cat M2 (aka “NB-IoT”). (2) The Traffic Profiles. The best way
to understand what NB-IoT / EC-GSM can and cannot do is to
understand the traffic profiles and use cases used by 3GPP during
the standardization process. (3) Performance Analysis. Leveraging
the traffic profiles and published performance analysis results,
we show what the marketing claims of NB-IoT really mean, the
inherent tradeoffs that exist, and why we believe capacity is (or
at least should be) dead last in terms of operator requirements.
(4) Getting from Here to There. We discuss the likely impacts to
the RAN and CN, including the potential / likely role of network
virtualization and the use of an “EPC-lite” network. Included in
this discussion is an update on the status of the NB-IoT specifi-
cation, including some of the outstanding issues that remain. (5)
The Deployment Scenarios. We discuss the pros and cons of the
3 deployment scenarios, namely standalone / GSM refarming,
guard band, and in-band. (6) Adding another “G”. Based on what
NB-IoT can and cannot do, as well as the likely traffic profiles, we
discuss the practicality of NB-IoT fulfilling the 5G use cases being
discussed that pertain to uMTC and cMTC. (7) And in the other
Corner. CIoT technologies are not the only option that exists. In
addition to the non-3GPP wide area technologies there are also
the local and personal area technologies that play a role, either in
a complementary or competitive role. We discuss.
➤ 12/21/2015 “ALL QUIET ON THE 5G FRONT –an update
on the 5G standardization efforts and other
3GPP-related activities” Just recently we returned from
the 3GPP RAN#70 Plenary, which was held it Sitges, Spain.
Conventional wisdom suggests that the 5G standard is baked
and resting on a hot plate, given all of the operator claims about
forthcoming trials, not to mention commercial launches and
anticipated vendor demos at MWC 2016. The reality, we believe,
is entirely different with much work to remain – starting with
RAN Plenary Group Study Items on the next-generation wireless
network that have yet to begin. Topics Discussed in this Report
Include the Following: 1) We take a look at where the 3GPP RAN
and SA working groups are with respect to standardizing the next-
generation network (aka 5G).2) We examine the current and yet-
to-be approved Study Items to provide an extremely preliminary
view of what is in store. Unlike earlier technical requirements (TR)
documents, the 5G TR is shaping up to be entirely different. 3)
Speaking of TRs, we take a trip down memory lane and revisit the
initial TR documents for UMTS (3G) and LTE (Evolved UTRAN) to
see if the proposed requirements were achieved, and, if so, when
they were achieved. 4) Given the equal focus being given to LTE
and its evolution (LTE-Advanced Pro), we highlight and discuss
many of the Work Items being considered within the RAN Plenary.
If nothing else these Work Items provide great insight into near-
term and future operator strategies.
➤ 12/8/15 “Get SMART[er] - the ins and outs of the
5G Use Cases” Unlike what occurred during the previous
introductions of a new family of technologies, 3GPP has leveraged
the work of the NGMN Alliance and other entities to define the
Use Cases for 5G. Although the Use Cases are still in a state of flux,
there is at least some initial insight to be gained regarding what is
driving the 5G requirements and how the Use Cases will change
the very nature of the industry. Highlights of the Study include
the following: (1) We break out the 72 Use Cases into several
distinct categories, based on their requirements, and discuss the
scenarios they address as well as their subsequent requirements.
(2) Although eMBB (enhanced Mobile Broadband) gets all the buzz,
the overwhelming majority of the Use Cases have very little to
do with mobile broadband. Instead, their requirements include
capabilities that we believe are more challenging than delivering
a high bit rate, or the Use Case is extremely futuristic in terms
of what 5G may be asked to do in the future. (3) To us, Network
Slicing is by far the most interesting Use Case. In addition to giving
more power to third parties to specify and implement how the
network will support their needs, Network Slicing introduces an
entirely new paradigm, as well as creating the need for new busi-
ness models / billing strategies that operators will need to pursue
(if net neutrality doesn’t get in the way). (4) 5G could result in a
bit of a land grab for the cellular industry. If nothing else, they
will need to work more closely with other standards bodies and
vertical markets who seek to benefit from the capabilities that 5G
is supposed to deliver. Given the timing of the 5G core network
relative to the 5G radio access network, it will be well into 2020
before the full vision of 5G is realized.
➤ 10/29/15 “When Iconic Meets Anechoic, Part II - Over-
the-Air (OTA) MIMO Performance Results of Fifteen
Smartphones - From Apple to ZTE” In our 20th Chips and
Salsa, we collaborated closely with Spirent Communications,
PCTEST, and EMT Labs, to conduct arguably the industry’s most
extensive independent OTA MIMO performance testing of
leading smartphones - from the Apple iPhone to the ZTE Nubia.
All testing took place within an ETS-Lindgren anechoic chamber.
In total, we tested 15 different smartphones (3 bands per phone)
that we procured from around the world, including LTE chipsets
from 4 different baseband suppliers. Highlights of the study
include the following: (1) Two of the top performing smartphones,
the Nokia Lumia 930 and the Alcatel OneTouch Idol 3 are “value-
priced” smartphones, indicating a disparity between price and
performance. (2) In general there was a large variance in the
results with the top performing smartphone in a particular band
outperforming most of its peers by 50% or more with moderate
SNR values.

5. EXPLORE THE
WORLD OF
5GWIRELESS
January 31, 2012, Vol. 8 No. 2January 31, 2012, Vol. 8 No. 2Redefining Research
J F M A M J J A O N D J F M A M J J A S O NS
December 8, 2015 Vol. 11, No. 10
EXPLORING THE WORLD OF WIRELESS
GET SMART[ER]
January 31, 2012, Vol. 8 NoJanuary 31, 2012, Vol. 8 NoRedefining Research
J F M A M J J A O N D J F M A M JS
December 8, 2015 Vol. 11, No
EXPLORING THE WORLD OF WIRELE
MORE 5G
EXPLORING THE WORLD OF WIRELES
MORE 5G
EXPLORING THE WORLD OF WIRELE
MORE 5G
EXPLORING THE WORLD OF WIREL
MORE 5G
January 31, 2012, Vol. 8 No. 2January 31, 2012, Vol. 8 No. 2Redefining Research
J F M A M J J A O N D J F M A M J J A S O NS
September 30, 2015 Vol. 11, No. 8
EXPLORING THE WORLD OF WIRELESS
LOOKING FURTHER
AHEAD TO 5.5G1
1
Feel free to note the sarcasm
New subscribers to SIGNALS AHEAD will receive these
5G-related back issues FOR FREE with a paid subscription.
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to come!
FOLLOW THE 5G STANDARDIZATION EFFORT AS IT HAPPENS
January 31, 2012, Vol. 8 No. 2December 8, 2015 Vol. 11, No. 10 PREVIEWJanuary 31, 2012, Vol. 8 No. 2January 31, 2012, Vol. 8 No. 2Redefining Research
J F M A M J J A O N D J F M A M J J A S O NS
December 22, 2015 Vol. 11, No. 11 PREVIEW
EXPLORING THE WORLD OF WIRELESS
ALL QUIET ON THE 5G FRONT

6. 6 | Signals Flash February 9, 2016
Asian operators are perhaps the strongest advocates for C-RAN and it stands to reason given the
preponderance of dark fiber in the region, and, depending on the particular region, regulatory
requirements (i.e., China) and dense population centers (i.e., South Korea and Japan, etc.).
KDDI, for example, commented during a panel session that C-RAN is an important tool when it
comes to combining macro and micro/pico cells since the centralized controller can provide a
more efficient and effective means of coordinating the interference between the two network
layers. Softbank, who is right around the corner from KDDI, also noted that C-RAN is impor-
tant for interference cancellation, especially when dealing with a densely-deployed network.
Softbank commented that in one area of its network the site density is 44 sites/square kilometer
and with C-RAN it is witnessing a 10 dB improvement and 23% higher data speeds. The chal-
lenge for Softbank is that its FDD and TDD network (operated and branded under Wireless City
Planning) are essentially two separate networks and in many cases the FDD and TDD sites are
not co-located. We also know from past experiences that in many cases the operator has two
different vendors in the same market – one for the FDD network and one for the TDD network.
Given the quasi-proprietary nature of the fronthaul interface (CPRI), it would be next to impos-
sible for the operator to mix and match its RAN vendors in a C-RAN deployment scenario.
China Mobile (CMCC) is perhaps the strongest advocate for C-RAN and as far as we are consid-
ered it is leading the industry, in particular the operator community, when it comes to researching
C-RAN and its potential for LTE and for next-generation network topologies which follow. In the
case of CMCC, the operator noted that it wasn’t originally a proponent of the feature for LTE
networks due to concerns about the fronthaul (see next section). However, it is now a strong
advocate, noting that it is seeing energy savings of 60% and that its deployment time is reduced
to one-third the time. Artiza Networks cited slightly different metrics for CMCC, indicating a
CapEx reduction of 35% and a 53% reduction in OpEx with a 75% savings in power. We note the
power savings stems primarily from only having the remote radio head unit at the cell site.
C-RAN is also being used when it comes to 3G networks. Telefonica discussed its FARM-RAN
strategy which is deployed across 80% of its sites in one of its networks in Latin America. For
Telefonica, the benefits of C-RAN include much lower power requirements and the ability to
quickly migrate their network from 3G to LTE without having to go to the site. Our personal view
is that nothing is as simple as a simple software upgrade and that network optimization require-
ments could still result in a site visit.
A virtualized C-RAN takes things to an entirely new level since with virtualization the baseband
functionality is shared across the entire network covered by the centralized control node. Traffic
is never uniformly distributed throughout the network. People commute into the city when
going to work and they return home at the end of the day. There are also the occasional sporting
events and other occasions which cause people to congregate and various times throughout
the week. If an operator dedicates baseband functionality to the stadium then the resource is
essentially wasted the overwhelming majority of the time. This inefficiency not only increases
the CapEx and OpEx costs for covering the stadium but it also means that the other regions of
the network since baseband processing power that could have been reassigned from the stadium
to the suburbs cannot be used. Instead, the operator is forced to deploy new hardware at each
specific site in its network where it is needed, even if it is only needed for a brief period of time
each day.
Asian operators are perhaps
the strongest advocates for
C-RAN.
China Mobile (CMCC) is
perhaps the strongest
advocate for C-RAN, but this
preference wasn’t always the
case.
With virtualization the
baseband functionality is
shared across the entire
network covered by the
centralized control node.

7. 7 | Signals Flash February 9, 2016
T-Mobile is in the other corner when it comes to C-RAN. In its opinion, there isn’t a business case
for C-RAN with reasons cited including the fronthaul, a poor CPRI interface, and the tremen-
dous amount of processing power which means that it can’t run on a common silicon platform.
To varying degrees the other operators agreed with T-Mobile on the challenges of C-RAN but
for various reasons they still believe that it is the way forward. We also point out the obvious
that T-Mobile isn’t based in Asia so its access to dark fiber is far more limited, in particular given
that it doesn’t have a wireline business to leverage for fiber. Secondly, T-Mobile’s geographic
coverage is significantly greater than most Asian operators, although the Chinese operators are
a notable exception.
All choked up over the fronthaul
Regardless of how someone views the prospects of C-RAN, they must recognize that C-RAN has
its challenges with a truly virtualized C-RAN being even more problematic. The CPRI interface has
been around since at least 2004, or prior to most mobile operators first launching 3G, although
it has evolved since it was first introduced. The intent of CPRI is to provide a common interface
between the radio baseband processing functionality, or what CPRI calls the Radio Equipment
Control (REC), and the remote radio head (RRH), or Radio Element (RE) using the CPRI vernacular.
Since the CPRI specification was first published and available for download, the implication has
been that it can support a multi-vendor RAN solution. The most likely scenario described by
its founding members at the time was that a major OEM would provide the REC while it would
compete with much smaller suppliers for RE market share. The open interface would then drive
competition and innovation, which would benefit operators at the expense of the major OEMs
who would otherwise have had a lock on the full system.
Unfortunately, CPRI is a somewhat incomplete specification instead of a complete standard and
it doesn’t address all OSI layers. For example, CPRI does not fully specify the protocols used
to transport the O&M messages sent back and forth between the REC and the RE. As a result,
major vendors implement their own messaging system and unless they provide all of this detailed
information to a third party (competitor), it is unlikely that a multi-vendor RAN solution would
be feasible. Therefore, it becomes extremely difficult to achieve one of the basic tenets of the
CPRI initiative.
CPRI can still be useful with a single vendor implementation since it does make it possible to
implement a C-RAN strategy. However, the bandwidth requirements of the LTE air interface make
it far more challenging for the fronthaul, in terms of both bandwidth and latency. It becomes
even more problematic to meet the fronthaul bandwidth requirements when operators deploy
multiple LTE radio carriers at the cell site or if they introduce 256 QAM or 4x4 MIMO. Figure
1 shows information provided by KDDI regarding the fronthaul bandwidth requirements for
CPRI with various antenna configurations. It is important to note that while the more advanced
antenna schemes – beyond 4x4 MIMO – are still a bit futuristic, especially outside of Asia, they
are part of LTE Advanced Pro.
Further, in many developed markets the mobile operator’s LTE network is comprised of more than
a single 20 MHz channel. For example, we know from firsthand experience that Telstra already has
three 20 MHz LTE carriers at many of its cell sites. KDDI also indicated that it has approximately
80 MHz of LTE at its sites and that in the near future it will be going to 150 MHz of spectrum for
LTE. With 80 MHz of LTE and a 16x16 antenna configuration, which is something that it is actively
T-Mobile is in the other
corner when it comes to
C-RAN.
Since CPRI first became
available, the implication has
been that it can support a
multi-vendor RAN solution.
More advanced LTE features
and the use of multiple
LTE radio carriers at a cell
site make the fronthaul
requirements even more
challenging.

8. 8 | Signals Flash February 9, 2016
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9. 9 | Signals Flash February 9, 2016
pursuing, the operator would require nearly 240 Gbps of fronthaul capacity or approximately 450
Gbps with 150 MHz of actively used LTE spectrum. As far as we know the information presented
by KDDI excluded 256 QAM which would mean there would be another multiplying effect.
Figure 1. CPRI Fronthaul Requirements for LTE (Gbps)
The eventual migration to the next generation wireless technology means that even more
demands will be placed on the fronthaul. Although the ITU and the standards bodies are still
determining what the peak data rates should be and the peak data rate will be a function of the
frequency band/channel bandwidth, the expectation is that the fronthaul requirements will be
even more demanding. CMCC showed what it defined as the potential fronthaul requirements
for a couple of scenarios using the Release 15/16 air interface (reference Figure 2). Clearly, some-
thing has to give.
Another challenge associated with CPRI is the latency requirements for the fronthaul, which is
typically viewed to be sub 1 ms. This tight requirement is essential for many of the interference
cancellation/coordination methods, such as CoMP (Coordinated Multipoint). This requirement
A sub 1 ms latency
requirement for the
fronthaul is also problematic.
4.9
9.8
19.7
39.3
2.5
4.9
9.8
19.7
14.7
29.5
59
7.4
1 Sector
(2x20 MHz)
2 Sectors
(2x20 MHz)
3 Sectors
(2x20 MHz)
2x2
1 Sector
(2x20 MHz)
2 Sectors
(2x20 MHz)
3 Sectors
(2x20 MHz)
4x4
1 Sector
(2x20 MHz)
2 Sectors
(2x20 MHz)
3 Sectors
(2x20 MHz)
8x8
1 Sector
(2x20 MHz)
2 Sectors
(2x20 MHz)
3 Sectors
(2x20 MHz)
16x16
Source: KDDI (recreated by SRG)
1 GHz TDD Channel Bandwidth and 256
Antenna Configuration (> 6 GHz)
16,000 Gbps
1,600 Gbps
200 MHz TDD Channel Bandwidth and
128 Antenna Configuration (< 6 GHz)
Source: CMCC (recreated by SRG)
Figure 2. CPRI Fronthaul Requirements for the Release 16/16 Air Interface (Gbps)

10. 10 | Signals Flash February 9, 2016
all but rules out the use of eNB routers, or concentrators, in the network – a popular strategy
used by many operators.
The last challenge is specific to a virtualized C-RAN in which the baseband functionality is pooled.
The challenge is that the common hardware platform lacks the processing power to handle all
of the tasks without the use of dedicated hardware accelerators. In essence, this requirement
somewhat defeats the original purpose of virtualization. In addition to the basic requirements
of LTE, some of the new functionalities being introduced with LTE further increases the demand
on the BBU processing. The information provided in Figure 3 stems from a Softbank presenta-
tion. In hindsight, we are not certain if the increases in baseband processing shown in the figure
and provided in the presentation are incremental or not. However, the point remains that the
industry is quickly moving to adopt more advanced network features and that these features can
have a significant impact on the baseband, potentially even calling into question whether or not
RAN virtualization is worth pursuing.
Looking ahead to what comes next
As mentioned in the last section, the likely capabilities of the next-generation air interface will
place even greater demands on the fronthaul. Further, the importance of separating the radio
units from the baseband processing functionality will become even more important with the
use of higher frequency bands and the greater dependence on highly concentrated small cells.
Release 15 and Release 16 involve far more than basic mobile broadband but in the context of
delivering ultra-high broadband (enhanced MBB), one cannot discount the extreme importance
of the small cell architecture.
For the last few years there has been a lot of discussion about various CPRI compression algo-
rithms which can minimize the fronthaul requirements while retaining much of the CPRI inter-
face. Unfortunately, these compression algorithms don’t go nearly far enough when it comes to
closing the divide between the capabilities and the requirements of the fronthaul. For example,
operators generally recommend not going beyond 50% compression, yet as we presented in an
earlier figure, reducing the bandwidth requirements by 50% is barely a drop in the bucket.
Although outside the scope of this Signals Flash! edition (we plan to focus a lot of our forthcoming
report on this topic), there are two industry initiatives which are worth mentioning. First, there
More advanced network
features can have a significant
impact on the baseband
processor requirements.
CPRI compression algorithms
do not go far enough
to meeting the present,
let alone the long-term
fronthaul requirements.
Example @ BBUExample @ BBU Example @ BBU Example @ BBU
4T4R
30MHz
x 12
CA
CoMP
x 8
8T8R
4MIMO
x 6
256QAM
8MIMO
x 2
Source: Softbank (recreated by SRG)
Figure 3. Baseband Processing Requirements

11. 11 | Signals Flash February 9, 2016
is the IEEE 1904 working group, which is tasked with developing “a standard for encapsulating
fronthaul digitalized radio samples into Ethernet frames, as well as mapping CPRI into Ethernet
frames.” It isn’t clear to us how far this working group can push the existing protocols, but it is at
least a step in the right direction.
CMCC is also heading a more radical approach in which it wants to redefine the Layer 1 through
Layer 3 protocols through its MCD (Multi-level Centralized and Decentralized) initiative. It isn’t
entirely clear how broad in scope this initiative is, but it could have quite a profound impact on
the amount of information being sent between the remote radio and the centralized baseband
processor. In CMCC’s vision, with the new network architecture the concept of cells will go away
and we will have what it called a user centric network (UCN) with the user data link separated
from the “cell” at the S1 interface. Our big concern is that these changes could involve a lot of
work and a lot of politics within the standardization process, meaning that it wouldn’t be done in
time to be included in Release 15 and potentially not even in Release 16.
Random thoughts
In this section, and in no particular order, we provide some random thoughts based on other
things we heard at the RAN event or over the last few weeks.
Both T-Mobile and AT&T and going to three-carrier carrier aggregation (CA) later this year, if
they haven’t done so already. Our belief is that these deployments are relatively modest at
the moment and largely concentrated in areas of the network that generate the most data
traffic. In other words, small clusters of cells versus an entire urban area. AT&T also indicated it
is four different radio carriers/frequencies supporting LTE in San Francisco, which we believe
includes the WCS spectrum. Given the 3GPP standardization process, it will be a while before
AT&T will be able to support CA with these four frequencies, especially given that it includes
the WCS spectrum.
T-Mobile described its unlicensed spectrum strategy, to include the 3.5 GHz spectrum, as being
very important and we point out that the operator was an early mover when it came to Wi-Fi/
VoWi-Fi as well as a vocal advocate of LTE-U/LAA. That being said, T-Mobile also notes that Wi-Fi
offloading hasn’t been very successful to date, largely because it is not a seamless experience. As
someone who switches off Wi-Fi when leaving the house because our AT&T smartphone always
switches to, and then remains attached to, a Wi-Fi AP that requires pre-authentication (i.e., we
lose all data connectivity unless we manually click on a few links), we share their concerns. To
address this problem, T-Mobile believes there needs to be more intelligence in the network and
in the devices. Hotspot 2.0 Release 2 is one incremental solution, but venues still need to update
their infrastructure and the devices need to support the functionality.
Following on the heels of our last Signals Ahead report on the various cellular IoT (CIoT) stan-
dards being defined by 3GPP, KDDI provided some good context on the importance of Network
Slicing when it comes to implementing IoT in its network. First, the operator noted that IoT can
generate tremendous spikes in user (data) and control channel (signaling) traffic and that the
distribution of the IoT traffic isn’t necessarily evenly spread throughout the course of a day. For
example, a rogue IoT application being used to report electricity usage could be programmed
to report the daily usage at the exact same time. The net effect would severely tax the network
even though the individual contribution from each IoT device was trivial.
Both T-Mobile and AT&T and
going to three-carrier carrier
aggregation (CA) later this
year.
KDDI provided some good
context on the importance
of Network Slicing when it
comes to implementing IoT in
its network.

12. 12 | Signals Flash February 9, 2016
For this reason, KDDI advocated the need for operators to be able to control the applications to
prevent this scenario from taking place. Secondly, this type of network traffic suggests the need
for a separate network that is dedicated to handle IoT traffic. At this point, the operator felt that
the next logical step would be to use Network Slicing to control the allocation of radio access
and core network resources. IoT traffic hitting the network would automatically be routed to the
dedicated IoT core network, which was dimensioned and provisioned to handle very small data
bursts with a disproportionate amount of signaling traffic and without the need for basic cellular
features, such as handovers, etc. In our report, we indicated that operators would likely follow
this strategy since the unique IoT requirements relative to the “normal” LTE traffic patterns made
Network Slicing an ideal solution.
Although the main theme of the conference seemed to be more focused on C-RAN than anything
else, there was at least some discussion on small cells and their merits. AT&T indicated that its
biggest challenge is figuring out where to place them. Although the operator knows where it has
high concentrations of data traffic in the horizontal plane, they don’t necessarily know where the
traffic is in the vertical plane – for example, the 6th floor of an office building versus the lobby. All
that being said, AT&T does see the merits of small cells in dense urban markets while advanced
antenna technologies are more appropriate in urban/suburban areas where there may be lots of
data traffic but it isn’t as concentrated.
T-Mobile seemed to echo a somewhat similar concern. In its case, the operator indicated that
venue owners need to be partners when it comes to solving the capacity challenge. We would
infer this could mean that venue owners would be more willing to accept small cells with better
economic terms for the mobile operator (and for the venue owner) if the small cells were neutral
host, meaning that like DAS, they could support the coverage and capacity requirements of
multiple operators. Small cells are now coming to the market which can be configured to support
at least two mobile operators, but at least in the United States this type of an approach may
not work for mobile operators. We point out that AT&T seemed less than convinced that RAN
sharing makes sense. In an upcoming paragraph we discuss another potential means of addressing
the indoor capacity crunch with a neutral host solution that could make the venue owners happy.
Although we don’t recall KDDI indicating any major challenges associated with deploying small
cells, it did indicate an important justification for their use. In their market (Japan), they are seeing
that the density of data traffic is the big issue and not necessarily the total amount of data traffic.
For example, the operator is witnessing up to a 1,000x difference in the data traffic between its
hottest hot spots and areas with less data traffic. Therefore, the operator believes that indoor
small cells are the way to go, including both Wi-Fi and LTE.
Speaking of Wi-Fi and LTE, we will be hosting the MulteFire technology panel at this year’s
Mobile World Congress. According to our calendar, the two hour event starts at 1400 hours on
Tuesday with our technology panel starting at 1500 hours. MulteFire is an interesting concept
since it removes the requirement for the primary carrier using licensed spectrum. Instead, the LTE
transmissions run autonomously on the 5 GHz spectrum, leveraging many of the Wi-Fi coordina-
tion and cooperation mechanisms currently being pursued by 3GPP and/or the LTE-U Forum.
Separate from the technology aspects of how this will all work, MulteFire creates an interesting
opportunity for a neutral host solution in very dense networks, such as stadiums or potentially
airports and shopping malls. It isn’t clear to us that mobile operators will embrace it with open
arms, but then again it does create the opportunity for new operators to enter and competition
is generally a good thing.
AT&T views small cells as
being more valuable in dense
urban areas, assuming that
they are able to precisely
identify the origin of the
high concentrations of data
traffic.
We will be hosting the
MulteFire technology panel
at this year’s Mobile World
Congress on Tuesday.

13. 13 | Signals Flash February 9, 2016
ON THE HORIZON: POTENTIAL SIGNALS AHEAD/SIGNALS FLASH! TOPICS
We have identified a list of pending research topics that we are currently considering or presently working on completing.
The topics at the top of the list are definitive with many of them already in the works. The topics toward the bottom of
the page are a bit more speculative. Obviously, this list is subject to change based on various factors and market trends. As
always, we welcome suggestions from our readers.
➤➤ Ongoing Series on the 5G Standardization Process
➤➤ LTE and the Connected Car
➤➤ The Core Network evolution
➤➤ LTE Broadcast versus LTE unicast video benchmark study
➤➤ VoLTE Part Five – multi-vendor, multi-operator benchmark study to include feature sets, call quality, reliability,
performance and scheduling
➤➤ VoLTE Part Six – lab-based testing of VoLTE clients and VoWi-Fi
➤➤ Chips and Salsa OTA smartphone performance benchmark study – Transmission Mode 2
➤➤ Multi-vendor HetNet benchmark study
➤➤ Network impacts (to include signaling) of using various smartphone OS platforms and/or applications (video,
VoLTE, social networking, etc.)
➤➤ VoLTE Part Seven – IR.94 and RCS
➤➤ Mobile Computing platforms and the impact of data caching at the cell edge
➤➤ Cloud RAN
➤➤ Uplink CoMP network benchmark study
➤➤ 4x4 MIMO network benchmark study
➤➤ LTE FDD and LTE TDD Carrier Aggregation network benchmark study
➤➤ Chips and Salsa – LTE TDD chipset benchmark study
➤➤ MU-MIMO

14. 14 | Signals Flash February 9, 2016
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