The document discusses the challenges and progress of achieving interoperability in small cell networks, particularly in multi-vendor environments. It highlights the historical context, key issues with current interfaces, and the ongoing efforts by industry groups to create standards and facilitate plugfests for testing. The author expresses optimism for future improvements through operator commitment and innovative technologies that can enhance interoperability.

1. Small Cell Interoperability in the RAN Impossible Physics, Hard Design, or just Red-Tape?
V2.4, 1st October 2014
CTO
N.D. Johnson

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Small Cell Interoperability
Why do we care?
•
Some anecdotes from history
•
Abis, Iu-b, Iu-r
Beyond standards
•
NGMN, SCF and other interoperability initiatives
Buridan Telecom
•
In the end, you have to choose
The schizophrenic vendor
•
Can you be the incumbent and the upstart at the same time?
Interoperability and cloud-RAN
•
Don’t be beguiled into another layer of private interfaces
A message of hope
•
It might just work!

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A traditional multi-vendor RAN deployment 3
A traditional multi-vendor RAN deployment divides the network into regions.
A “traditional” residential femto deployment has no such regionality.
Already we have a multi- vendor RAN, and it’s no niche.

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A new generation of problems – inter-layer multi-vendor IOT for handover 4
Where multi- vendor IOT used to be a line across a country, now It’s possible at every handover

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Laws-of-physics : Where are the issues?
Load balancing:
•
Reselection and Handover
•
both directions
•
3G and LTE
Interference Management
•
Pilot/FACH power tuning
•
Avoidance and coordination
•Open and Closed mode
Synchronisation
•Frequency synch
•Time/frame synch
Solved?
Relies On
Standard signalling
R9 CSG + delta-SFN, MLB
CCO, ICIC, eICIC, CSG
PTP/NTP transport
Off-channel NWL
…the physics is not impossible

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Small Cell Forum Plugfests summary
Topics
Taking Part
Test
cases
Venue
3G (1)
March 2010
IPSec,
Iuh interface
22
26
Sophia Antipolis,
France
3G (2)
Jan 2011
HMS (TR-069) interface
14
35
Sophia Antipolis,
France
3G (3)
June 2011
Mobility scenarios
12
42
Lannion, France
LTE (1)
June 2013
S1, X2, Mobility scenarios,
VoLTE
20
28
Kranj, Slovenia
LTE (2)
June/July 2014
Regression:
•
S1, X2, Mobility, VoLTE,
New
•
HEMS, CMAS, CSFB, SON (ANR, PCI, MRO)
25
94
Paris, France
3G participation diminishes as the problems disappear
LTE participation still growing as the problems are addressed

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But even here, the interoperability problems lurk
TR196 v2.0.1 is not backwards compatible with TR196 v.2.0.0
•
WTF?
SCF and NGMN studies have shown key procedures in X2 are non-interoperable
X
X
?
?
X

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How has it come to be like this?
GSM A-bis interoperability:
•
Late 90s, attempts to interoperate vendor E BSC with vendor P BTS fail
•
Largely due to management model incompatibility
Early noughties, Radioframe succeeds in interoperating E// and NSN A-bis
•
2009, Radioframe stops trading
ip.access tries to interoperate with 3rd party IP-BSCs
•
Just in time for the telecom winter
•
Pivots in 2001/2 to create a full RAN solution
2001, Kevab creates innovative node-B, with Iu-b to NSN and other RNCs
•
2003, Andrew Corp acquire Kevab, then 3GNS acquire the tech in 2009, now?
The lesson is:
•
working to non-interoperable interfaces through incumbent proprietary gateways is business suicide

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The scale of the problem – how big are these interfaces?
0
200
400
600
800
1000
1200
1400
1600
Abis+Gb
Iu-b
Iu-h
LTE
Basestation to Controller pages of spec.
0
200
400
600
800
1000
1200
1400
GSM
Iu-r
Iu-rh
X2
Cell to Cell pages of spec.
0
500
1000
1500
2000
2500
2G
3G
3G femto
4G
Radio Resource Control (RRC)
Pages of spec.
0
50
100
150
200
250
300
350
400
450
500
2G
3G
3G femto
4G
RAN to Core pages of spec.
…the design is hard
, but it is becoming more tractable

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Buridan Universal Text and Telephony Company
awarded an operator’s license, but couldn’t decide whether to build a single vendor RAN or multi-vendor HetNet
?
The message?
Commitment Matters
Multi-vendor:
Multiple procurement, OAM and training overheads
Take advantage of best-in- industry roadmaps
Flexible to vendor corporate strategy and pricing
Who’s the SI?
Optimal network performance
Single vendor:
Simple procurement, operations/maintenance and training
Tied to single roadmap
High cost to change
Vulnerable to vendor corporate strategy and pricing
Best effort network performance

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Schizophrenic vendors, they’re black and white
Vendors are ambivalent towards interoperability
“If we’re trying to displace an incumbent,
we’re all for it.”
Vendors are ambivalent towards interoperability
“ If we’re defending an incumbency,
we move heaven and earth to question the value of it.”

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Operator Process, and who’s the SI?
Operator processes are still largely tuned to macro deployment:
•
Operator A: “it takes us six weeks to deploy a cell”
•
Operator B: “each cell we deploy touches 17 departments in my organisation”
•
AT&T (SCA 2013): “we can’t order equipment to be installed at a location that doesn’t have a street address – our tools won’t let us.”
Who fixes it when it’s broken
If it takes time to fix, then the customer will
lose patience and revert to the
tried-and-tested
?

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A message of hope…
Operator processes are still largely tuned to macro deployment, but are moving:
•Operator A: “it used to take us six weeks to deploy a cell. Now it takes us two hours”
•Operator B: “each cell we deploy used to touch 17 departments in my organisation. Now it’s two.”
•AT&T (SCA 2013): “we couldn’t order equipment to be installed at a location that doesn’t have a street address – our tools wouldn’t let us. But now we can.”
…the red tape was there, but with the right commitment, it’s now being cut

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A message of hope… 14
Small Cell Management System
Small Cell
Gateway
Public/Private Internet
EPC
(LTE)
Backhaul
Basestations
Core
Gateway
Small Cell layer
MSC/GSN
(GSM+3G)
SecGW
Macro layer
Handset
RRC
X2,
Iu-r,
SON
IPSec
Iu-h, TR69/196v2
Iu, S1
The interoperable interfaces are at least countable, and based on standards

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… but with a cloud-RAN on the horizon 15
Small Cell Management System
Small Cell
Gateway
Public/Private
Internet
EPC
(LTE)
Backhaul
Radio heads
Core
Gateway
MSC/GSN
(GSM+3G)
SecGW
Macro and small cell layer
handset
RRC
X2,
Iu-r,
SON
IPSec
Iu-h, TR69/196v2
Iu, S1
Fronthaul
baseband
Security?
Transport , OAM incl. SON?
Control and Data?
Cloud-RAN offers another opportunity to privatise the interfaces, and force operators towards a single-vendor RAN

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A message of hope…
•Operators are vocally insistent on multi-vendor interoperability on key interfaces
•Incumbents will reluctantly agree to integrate in a multi-vendor context
•The “who’s the SI?” question remains an issue
•the answer is rarely “the incumbent”, though it’s expensive for the incomer
•Initiatives such as the SCF Interoperability Plugfests are removing the sting and the risk from multi-vendor integration
•Technology such as Self-Organisation (centralised, distributed and hybrid) with standardised interfaces and procedures will also reduce the SI burden.
•With these issues in place…
•Properly interoperable interfaces
•Technology to reduce the SI burden
•Exhaustive cross-industry laboratory pre-test
•Operator commitment, with business processes to match
…we can do it!
It can be done..

17. (C) 2014 ip.access Ltd All rights reserved
Nick Johnson
CTO, ip.access
Thanks for your attention…
ndj@ipaccess.com