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

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…)

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eNB(TDD)

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Mobile Network Operators Demand a Portfolio of Backhaul Options Designed for Scenario

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F1

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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

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

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

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

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

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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

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

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Let’s Get Real! LTE Small Cell Deployment

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Let’s Get Real! LTE Small Cell Deployment

Containing LTE Small Cell Propagation

maximizes capacity gains

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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

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Ba

ck

ha

ul

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

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

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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.

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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 1

50

Mb

it/s

5

0M

bit/s

eICIC

Dynamic

Resource

Block

Allocation

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

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

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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 setting, invisible, 1k spacing

Airspan | AirSynergy Gen2 | Environment visuals – low res previews | 23 Feb 2012 | P.4

Environment Visuals – Rural 2 Low-res preview

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Let’s Get Real! Carrier Trial - Feeder Base

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

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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

Demonstration of eICIC

Cell Range Extension & Almost Blank Subframes

The power of Cooperative QoS

Let’s Get Real!

See it for real

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MWC - Picocells

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MWC - Picocells with LTE-Advanced

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Come and see us

Hall 6 Booth #D90