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Small Cell
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Small Cell LTE
Deployments Tightly Integrating Access and
Backhaul
Paul Trubridge
VP Product Management, Airspan
November 2012
2 Airspan Confidential information
A definition of Small Cells…
• There are many different definitions for small
cells - this is ours!
• In this classification there are three types of
small cells
1. Residential and Business Femto
• Indoor, Low Power (typically 100mW), Closed
User Groups
• These are traditional 3G Femto Cells
2. Open “Enterprise-Class” Femtos and Picos
• Outdoor and Indoor Cells, Open Access, Higher
power (1W)
• These are cells I focused on in this presentation
(and perhaps the future of Mobile Cellular
Networks)
3. Micro and Compact Macro Cells
• All-in-One Outdoor Base Stations
• Much higher power (2-10W), Open Access
• Optimized for non-traditional deployment
locations (Rooftops, Sides of Buildings etc…)
HISILICON SEMICONDUCTOR HUAWEI TECHNOLOGIES CO., LTD. Page 7 Huawei Confidential
Comprehensive Suite of Flexible Backhaul Products
Flexible Assembly
AD
SL / VD
SL
FE / PO
E
Op
tical
MW
/ TDD
BH
Small Cell
Radio Transport
+
UE(TDD)
NLOS, PMP
eNB(TDD)
FDD
FDD
FDD
TDD FDD
FDD
FDD
Spectrum
In case of no wire line backhaul
xPON OLT
SFP
Copper
MicroWave
Optical
TDD Backhaul
ADSL/VDSL
FE / POE
Cable
Mobile Network Operators Demand a Portfolio of Backhaul Options Designed for Scenario
1
2
3
Airspan is focused on Type 2 and Type 3 Small Cells
3 Airspan Confidential information
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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 Airspan Confidential information
Dynamic
Resource Block
Allocation
The Power of LTE-Advanced: eICIC and SON
• LTE-A 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 Airspan Confidential information
LTE-Advanced: Small Cell Deployment Life Cycle
• Small cell deployment requires
LTE-Advanced eICIC and SON.
• Elimination of co-channel
Interference by inter-cell
coordination
• capacity enhancement by optimal
UE to eNodeB mapping
• Remove the need for Frequency
Planning by Self Optimisation and
Self Configuration
• Cells automatically get
configured by SON server as
they become active.
• Without impacting / interfering with
existing network
• Removes the need for complex
network design ahead of deployment
Step 1: Typical Tri-Sector Macro-cell
deployment. Release 8/9 ICIC auto
configures sector radio interfaces using
X2 comms between sectors and
dynamically schedules traffic. SON not
required. Uses SFR
Step 2: Omni small cells added to the
deployment. Small cells impact
resource block mapping. Static SON
and eICIC re-configs to ensure optimal
mapping. Uses ABS Patterns in areas
of co-channel overlap.
Step 3: Mass deployment of Omni small cells.
Dynamic SON and eICIC also drive Tx
powers and Range Extension bias to
best optimize resources across the
network. Uses ABS Patterns in areas
of co-channel overlap.
6 Airspan Confidential information
LTE-Advanced X2 Communications for eICIC
• At the heart of this LTE-Advanced eICIC is
extensive use of the X2 interface which
allows communications between RRMs
within each eNodeB.
• The X2AP interface was enhanced in Release 10
explicitly for eICIC and ABS
• X2 requires communications occur between
Macro and Pico, and Pico to Pico.
• The eICIC process ensures that traffic
scheduling by Macro and Pico eliminates
co-channel interference
• By stop simultaneously use of time/frequency
resource blocks in locations where interference
would occur.
X2 X2
X2
Release 10/11/12:
eICIC and SON X2 communications are
critical to LTE-A eICIC and
Small cell deployment.
7 Airspan Confidential information
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.
0x2x4x6x8x
10x12x14x16x18x20x
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
* 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
8 Airspan Confidential information
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%)
Mb
it/s
9 Airspan Confidential information
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
10 Airspan Confidential information
4G Traffic: Everything is becoming real-time…
• Mobile Broadband data consumption is growing rapidly… It’s important
we understand why….
• What’s driving this growth?
• Smartphone adoption
• Introduction of tablets and Post-PC devices
• Broadband interfaces in non-PC devices (Gaming, Appliances, Cars…)
• Cloud Computing
• New Social Networking Applications and Networks
• Streaming Video and the death of the traditional broadcast TV
• Standard definition content becoming HD content
• Email and Messaging Multiplication
• Speech recognition (Siri and Google Voice)
• etc… etc…
• Most of today’s content must be delivered in real-time.
• This forces carriers care about “Quality of Service”. If they don’t, a
lot of applications stop working or become unusable.
11 Airspan Confidential information
QoS: Supporting Real Time Traffic
• Large percentage of traffic over a 4G network needs to have sub 300ms
response
• QoS classifications of traffic over the radio interface have become critical to
end user experience and service satisfaction.
• Small Pico cells, need to deliver traffic associated with LTE QoS Classes
(QCIs) just like Macro cells do…
• Guaranteed Bit Rate Services, Allocation and Retention Priority, Maximum Bit Rate
(MBR), Aggregate MBR, etc…
12 Airspan Confidential information
Ba
ck
ha
ul
Contended Backhaul and QoS
• 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.
• THIS IS UNACCEPTABLE TO CARRIERS
• Therefore, any backhaul solution must ensure that the
LTE radio-interface QoS is respected and maintained
across 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
S1 a
nd X
2,
Sync, M
gm
t
Real-T
ime a
nd G
BR
Serv
ices
Non R
eal-T
ime a
nd
Non-G
BR
Serv
ices
13 Airspan Confidential information
Small Cell Backhaul with End-to-End QoS
• The ideal arrangement for Small Cell
backhaul is a combination of LOS P-P links
and/or Fiber, feeding P-MP NLOS backhaul
links to the small cells
• Best economics with excellent ROI
• However, unless LTE Signaling and Real-
Time and GBR traffic is properly managed
and prioritized, ensuring QoS is honored the
solution is flawed.
• By tightly combining LTE Small Cell Access
technology of NLOS backhaul technology
the QoS can be solved
• The solution requires visibility of LTE QoS QCIs on a
service flow basis to be available to the P-MP NLOS
backhaul (and for LOS or Fiber to be uncontended)
Solution to Small Cell Backhaul is Tightly
coupled NLOS Backhaul technology
Fiber Uncontended
Metro Ethernet
NLOS P-MP NLOS P-MP
• We call this technology Cooperative QoS
14 Airspan Confidential information
Fiber
NLOS Wireless
Backhaul
Coverage
P-MP NLOS Backhaul: Cooperative QoS
• In Cooperative QoS mode the P-MP NLOS backhaul Scheduler maintains visibility of LTE Small Cell
scheduling requirements for UEs, tracking QoS commitments on bandwidth, latency and priority
• In addition the Backhaul Scheduler also has visibility of the iBridge 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 Pico access interface
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
15 Airspan Confidential information
Summary and Conclusions
• LTE-Advanced Small Cells can dramatically increase the capacity of Macro
LTE Networks
• X2 communications are increasingly important to achieve this.
• The enabling technology for LTE small cells is small-cell 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
• A small amount (10-20MHz) of 2.x,3.x or 4.9GHz licensed spectrum can backhaul a network with
10-20 small-cells per macro-cell.
• Contended small-cell backhaul demands end to end QoS
• The backhaul requires access class latency aware QoS
• LTE and backhaul QoS must work cooperatively to deliver the ever increasing levels of real time
services.
The Core of any Small Cell deployment is NLOS P-MP Backhaul
Technology with QoS support augmented with Fiber and
P-P LOS Wireless Backhaul.
16 Airspan Confidential information
Thank you for your time!