Small Cell LTE Deployments Tightly Integrating Access and Backhaul Paul Trubridge VP Product Management, Airspan November 2012
A definition of Small Cells… • There are many different definitions for small cells - this is ours!
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• In this classification there are three types of small cells 1.
2.
R e s i d en t i a l a n d B u s i n e s s F e m t o
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Indoor, Low Power (typically 100mW), Closed User Groups
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These are traditional 3G Femto Cells
2
Open “Enterprise- Class” F em t o s a n d P i c o s
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Outdoor and Indoor Cells, Open Access, Higher power (1W)
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These are cells I focused on in this presentation (and perhaps the future of Mobile Cellular Networks)
3 3.
Micro and Com pact Macro Cells
• All-in-One Outdoor Base Stations •
Much higher power (2-10W), Open Access
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Optimized for non-traditional deployment locations (Rooftops, Sides of Buildings etc…)
A i r s p a n i s f o c u s e d o n Ty p e 2 a n d T y p e 3 S m a l l C el l s
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.
Dynamic Resource Block Allocation
All Resource Blocks
Frequency All Resource Blocks
• Closely Coupled (Macros) Time
• Typically a Tri-Sectored Base Station – sectors share the same frequency. X2 communication over Closely Coupled: Ethernet or internal messages Sectors at same cell location between sector RRMs
• Loo sely Coup led (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
Dynamic Resource Block Allocation
All Resource Blocks
Loosely Coupled: Omni Cells at different location s
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
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capacity enhancement by optimal UE to eNodeB mapping
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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.
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. •
X2
X2
The X2AP interface was enhanced in Release 10 explicitly for eICIC and ABS X2
• 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.
X 2 c o m m u n i c a t io n s a re cr itic al to LTE-A eICIC and Small cell deploym ent.
Release 10/11/12: eICIC and SON
Small Cell Networks: Capacity Enhancement 20x 18x 16x 14x 12x 10x 8x 6x 4x 2x 0x
Macro Cell Edge Median
Assumptions*: N=1 reuse 10 MHz FDD 4 Pico cells per Macro cell eICIC, SON, High Power Macro, Hotspot Deployment
Downlink
Uplink
• 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. 4 x G a in s u s i n g 4 P i c o C e ll p e r M a c r o C e l l in S a m e S p e c t r u m A l l o c a t i o n
Small Cell Backhaul Requirements 200 180
Busy Hour
160
Non Busy Hour
140 s / 120 t i b 100 M
Average per Pico Peak per Pico (90%)
80 60 40 20 0 Macro Only
1 Pico
2 Pico
3 Pico
4 Pico
• 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
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Backhaul needed per Pico decreases as number of Pico increases
Small Cells and Frequency Re-use: eICIC at Work Macro Cell
Macro Cell Pico Cells
• Small cell capacity gains come from better frequency re-use. •
LTE-Advanced protocols m a p U E s t o t h e o p t i m a l c e l l (Macro or Pico), i.e. with the best signal conditions (better MCS and MIMO). Mapping is independent of RSSI (with Cell Range Extension).
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Small cells are typically “Buried in the clutter” , so that p r o p a g a t i o n i s c o n t a i n ed and extensive reuse of frequencies can happen.
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LTE-Advanced eICIC and Almost Blank Sub-frames (ABS) features ensures potential areas of Pico, and Pico to Pico are “mapped out ”. interference between Macro -
Small Cells are deployed in lo cation s that are generally Non-Line-of-Sight f r o m M a c r o C e l ls , o r o t h e r P i c o C e l l s t o m a x i m i z e c ap a c i t y g a i n s
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
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Introduction of tablets and Post-PC devices
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Broadband interfaces in non-PC devices (Gaming, Appliances, Cars…)
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Cloud Computing
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New Social Networking Applications and Networks
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Streaming Video and the death of the traditional broadcast TV
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Standard definition content becoming HD content
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Email and Messaging Multiplication
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Speech recognition (Siri and Google Voice)
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etc… etc…
• Most of today’s content must be delivered in real-time. • This forces carriers care about “ Q u a l i t y o f S e r v i ce ” . If they don’t, a lot of applications stop working or become unusable.
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…
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 AirInterface
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Not something that can easily be done using code-point markings, or other simple packet marking (ToS bits)
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Any contention based scheduling must take LTE Air-Interface QoS needs into account. • Ensuring Signaling gets and Real-Time / GBR service gets served first
S S y 1 n c a n , d M g X m 2 t ,
R e a l S T m e i r v e i a c e n s d G B R
N N o o n n - R G B e R a l S T m e i r v e i a c e n s d
eNodeB Traffic B a c k h a u l
Instantaneous Offered Load
Instantaneous Backhaul Capacity
LT E Q o S m u s t b e s u p p o r t e d b y an y c o n t e n t e d back haul so lution for LTE Sm all Cells
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 RealTime and GBR traffic is properly managed and prioritized, ensuring QoS is honored the solution is flawed.
NLOS P-MP
NLOS P-MP
• 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)
Uncontended Metro Ethernet
• We call this technology C o o p e r at i v e Q o S
S o l u t i o n t o S m a ll C el l B a c k h a u l i s T ig h t l y c o u p l ed N L O S B ac k h au l t ec h n o l o g y
Fiber
P-MP NLOS Backhaul: Cooperative QoS Real-Time
LTE QCI Service Flow Data LTE Pico Access Coverage
LTE Pico Access Coverage
LTE QCI Scheduler Information
Fiber
NLOS Wireless Backhaul Coverage
P-MP NLOS Backhaul Base Station Node
LTE Pico Access Coverage
• 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
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
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LTE and backhaul QoS must work cooperatively to deliver the ever increasing levels of real time services.
The Core of any Small Cell deplo ym ent is NLOS P-MP Back haul Te c h n o l o g y w i t h Q o S s u p p o r t a u g m e n t ed w i t h F ib e r an d P-P LOS Wireless B ackh aul.
Th a n k y o u f o r y o u r t im e!
