1. Cambridge Wireless
Small Cell SIG
31st January 2013
Let’s Get Real!
Non-Line-of-Sight Wireless Backhaul
for LTE Picocell Deployments
Peter Claydon
Managing Director, Airspan UK
v1

2. 2
A definition of Small Cells…
• There are many different definitions
• This is ours (for the purpose of this presentation)
• Uses “official” Small Cell Forum use case names
• Three types of small cells
1. Home and Enterprise
• Indoor, Low Power (typically 100mW)
• “Traditional” femtocells
2. Metro
• Outdoor, open access
• Higher power (1W)
• Focus of this presentation
3. Rural - Micro and Compact Macro Cells
• All-in-One outdoor base stations
• Much higher power (2-10W), open access
• Optimized for non-traditional locations
(Rooftops, Sides of Buildings etc…)
Comprehensive Suite of Flexible Back
Flexible Assembly
ADSL/VDS
FE/POE
Optical
MW/TDD
Small Cell
Radio Transport
＋
In case of no wire
line backhaul
Copper
MicroWave
ADSL/VDSL
FE / POE
Cable
1
2
3

3. 3
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Small Cell HetNets = Network Capacity Enhancement
• Small Cells will deliver huge network capacity increases…
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Macro-only
LTE Network
HetNet LTE
Network
Capacity Enhancement comes from
Aggressive Frequency Re-use

4. 4
Dynamic
Resource Block
Allocation
The Power of LTE-Advanced: eICIC and SON
• Enables aggressive deployment
of LTE small cells
• Allowing Time and Frequency
resource block re-use.
• Closely Coupled (Macros)
• Typically a Tri-Sectored Base
Station – sectors share the same
frequency. X2 communication over
Ethernet or internal messages
between sector RRMs
• Loosely Coupled (Small Cells)
• Auto-Optimizing and Configuring
cells that share the same spectrum
(i.e. N=1 re-use). X2
communications over wide-area
backhaul to other cells
All
Resource
Blocks
All
Resource
Blocks
All
Resource
Blocks
Loosely Coupled: Omni
Cells at different locations
Closely Coupled:
Sectors at same cell location
Dynamic
Resource Block
Allocation
Frequency
Time

5. 5
Small Cells and Frequency Re-use: eICIC at Work
• Small cell capacity gains come from better frequency re-use.
• LTE-Advanced protocols map UEs to the optimal cell (Macro or Pico), i.e. with the best signal
conditions (better MCS and MIMO). Mapping is independent of RSSI (with Cell Range Extension).
• Small cells are typically “Buried in the clutter”, so that propagation is contained and extensive re-
use of frequencies can happen.
• LTE-Advanced eICIC and Almost Blank Sub-frames (ABS) features ensures potential areas of
interference between Macro-Pico, and Pico to Pico are “mapped out”.
Macro Cell Macro Cell
Pico Cells
Small Cells are deployed in locations that are generally Non-Line-of-Sight
from Macro Cells, or other Pico Cells to maximize capacity gains

6. 6
Small Cell Networks: Capacity Enhancement
• LTE-Advanced eICIC and SON technology can deliver large capacity gains with even limited
numbers of Pico cells
• Macro cell footprint DL traffic boosted from 33Mbit/s to >130Mbit/s (with 4 Picos) – in Busy Hour
• Actual gains vary significantly depending on number of Pico cells deployed per Macro cell,
location of Pico cells, Busy Hour, versus Non-Busy Hour traffic patterns.
0x
2x
4x
6x
8x
10x
12x
14x
16x
18x
20x
Downlink Uplink
Macro
Cell Edge
Median
Assumptions*:
N=1 reuse 10 MHz FDD
4 Pico cells per Macro cell
eICIC, SON, High Power
Macro, Hotspot Deployment
SON
* 3GPP TS 36.814, Macro ISD 1500m, Full Buffer Model, Even UE Distribution, Cell Range Extension (12dB), 10 MHz (FDD) at 2.6 GHz
4x Gains using 4 Pico Cell per Macro Cell in Same Spectrum Allocation

7. 7
Small Cell Backhaul Requirements
• Assumptions: LTE-A eICIC, Hot Spots Deployment, Urban Model
• Busy Hour vs. Non Busy Hour with statistical sharing of backhaul
• Typical Backhaul for LTE Small Cells is around 40 Mbit/s (for 10 MHz FDD)
• Non Busy Hour Pico backhaul traffic typically ~1.3 times Busy Hour
• Backhaul needed per Pico decreases as number of Pico increases
* 3GPP TS 36.814, Macro ISD 1500m, Full Buffer Model, Even UE Distribution, Cell Range Extension (12dB), 10 MHz (FDD) at 2.6 GHz
0
20
40
60
80
100
120
140
160
180
200
Macro Only 1 Pico 2 Pico 3 Pico 4 Pico
Busy Hour
Non Busy Hour
Average per Pico
Peak per Pico (90%)
Mbit/s

8. 8
Summary
• eICIC, and SON are key features for building LTE Small Cell networks
• These allow aggressive frequency re-use when cells are optimally located
• Small cells will generally be located in NLOS locations
• They can’t see Macro Cells, and mostly can’t see other Pico cells (by design)
• Small cells typically require ~40 Mbit/s backhaul per node
• If backhaul is less than 40 Mbit/s overall network capacity gains reduce
These technical characteristics drive the
backhaul requirements for Small Cells

9. 9
Let’s Get Real! Outdoor Picocell Deployments
A variety of deployment locations
Side of Building Metal Scaffold
Poles
Rooftops Wooden
Telephone Pole
Street Lamps Low-rise cell
Towers

10. 10
Let’s Get Real! LTE Small Cell Deployment

11. 11
Let’s Get Real! LTE Small Cell Deployment
Containing LTE Small Cell Propagation
maximizes capacity gains

12. 12
Small Cell Backhaul Traffic
• Three types of traffic from a small cell
• Signaling and Management Traffic, S1 and X2 interfaces – Highest Priority,
Latency Sensitive, Mission Critical
• Synchronization Messages, 1588v2, Sync-E (assisting GPS), often critical
• Real-Time Services Traffic, Voice and Video, Cloud UI, Real-time Gaming etc…
• Non Real-Time Services Traffic, variety of types
• All LTE Traffic is classified using QCIs
• Each UE contains multiple traffic flows with different requirements
• VoLTE requires Real-Time, Low Latency support

13. 13
Backhaul
Impact on QoS of contended backhaul…
• If backhaul is contented (in any way), the QoS
and service reliability delivered over the LTE Uu
interface becomes impaired.
• If the backhaul randomly introduces latency and/or
reduces the capacity allocated to service flows
(especially GBR), the service is negatively impacted.
• Therefore, any backhaul solution must ensure
that the LTE radio-interface QoS is respected
and maintained across the contented backhaul.
• Typically this requires a detailed understanding of the
LTE Air-Interface
• Not something that can easily be done using code-point
markings, or other simple packet marking (ToS bits)
• Any contention based scheduling must take LTE Air-
Interface QoS needs into account.
• Ensuring Signaling gets and Real-Time / GBR
service gets served first
LTE QoS must be supported by any contented
backhaul solution for LTE Small Cells
eNodeB
Traffic
Instantaneous
Backhaul
Capacity
Instantaneous
Offered Load
S1andX2,
Sync,Mgmt
Real-TimeandGBR
Services
NonReal-Timeand
Non-GBRServices

14. 14
Wireless Backhaul Characteristics
• The capacity of “Ethernet based” wireless backhaul varies;
• Wireless has variable capacity by design
• Applies to both LOS and NLOS wireless solutions
• LOS capacity varies due to rain-fade
• P-MP backhaul shares it’s capacity over multiple nodes
• Takes advantage of statistical multiplexing
• Best when dimensioned using average, or mean traffic, not peak traffic
• Two Choices
• “Over provision” wireless backhaul to every small cell
• Ensure backhaul capacity always exceeds offered load. Economics are unattractive!
• LOS P-P links $,$$$’s per small cell (typically twice the cost of the small cell)
• Dimensioning using “average demand” using P-MP
• Makes economics attractive
• Implies support for QoS mechanisms in backhaul radio interface
LTE small cell deployments must solve
the QoS problem to be successful.

15. 15
Solution: Outdoor Picocell deployment with Fibre
• Typical deployment of 5 LTE Pico cells sharing a single Fibre connection
• Metro Ethernet service economically serves 5 LTE Pico Cells. Business case works…
Fibre
Uncontende
d 200 Mbit/s
Metro
Ethernet
NLOS NLOS NLOS NLOS
60Mbit/s 
 20Mbit/s
60Mbit/s 
 20Mbit/s
30Mbit/s 
 10Mbit/s
30Mbit/s 
 10Mbit/s 150Mbit/s
50Mbit/s
eICIC
Dynamic
Resource
Block
Allocation

16. 16
Solution: Picocells with P-P LOS and P-MP NLOS
• Deployment model mirrors the use of Fibre
• Backhaul comes from Macro cells sites
• Uses LOS P-P to a small cell with LOS to Macro cell
NLOS NLOS NLOS
60Mbit/s 
 20Mbit/s
60Mbit/s 
 20Mbit/s
30Mbit/s 
 10Mbit/s
eICIC
Dynamic
Resource
Block
Allocation
NLOS
30Mbit/s 
 10Mbit/s
Macro
Cell

17. 17
Fiber
NLOS Wireless
Backhaul
Coverage
P-MP NLOS Backhaul: Cooperative QoS
LTE Pico
Access
Coverage
LTE Pico
Access
Coverage
LTE Pico
Access
Coverage
P-MP NLOS
Backhaul Base
Station Node
LTE QCI
Scheduler
Information
 Real-Time LTE
QCI Service Flow
Data
• In Cooperative QoS mode the Backhaul Scheduler maintains visibility of Pico scheduling
requirements for UEs (MSs), tracking QoS commitments on bandwidth, latency and priority
• In addition the Backhaul Scheduler also has visibility of the backhaul radio interface and it’s
interference environment.
• The scheduling by the Pico cells takes accounts of both requirements to deliver high performance over
the backhaul and end-to-end QoS over the 4G LTE or 4G WiMAX Pico access interface

18. 18
Let’s Get Real! AirSynergy: Airspan’s Small Cell
A compact, low power, multi-standard, carrier-class LTE eNodeB with
integrated backhaul
“Single Box, Optimised”
Form-Factor
Integrated High Capacity Backhaul
with Relay Capabilities
Self Optimizing
Access and Backhaul
Airspan | AirSynergy Gen2 | Environment visuals – initial image selection | 22 Feb 2012 | P.6
Environment Visuals – Example renderings
Initial renderings indicating the potential level of visualisation
urban setting, visible, eye-level rural
Airspan | AirSynergy Gen2 | Environment visuals – low res previews | 23 Feb 2012 | P.4
Environment Visuals – Rural 2
Low-res preview

19. 19
Let’s Get Real! Carrier Trial - Feeder Base

20. 20
Let’s Get Real! Carrier Trial - Feeder Terminal A

21. 21
Summary and Conclusions
• LTE small cells can dramatically increase the capacity of LTE networks
• The enabling technology for LTE small cell is cost effective backhaul
• Unless the backhaul costs are right, small cell deployment won’t happen.
• Outdoor LTE small cells will mainly be deployed in NLOS locations
• Requires NLOS Backhaul technology, as Fiber based solution uneconomic
• Supporting QoS across any backhaul technology necessary
There is a Small Cell Backhaul Solution!
Core of the solution is NLOS P-MP Technology
with QoS support augmented with Fibre and
P-P LOS Wireless Backhaul

22. 22
Demonstration of eICIC
Cell Range Extension & Almost Blank Subframes
The power of Cooperative QoS
Let’s Get Real!
See it for real

23. 23
MWC - Picocells

24. 24
MWC - Picocells with LTE-Advanced

25. 25
Come and see us
Hall 6 Booth #D90