overcoming interference challenges when migrating from wimax to lte
TRANSCRIPT
… and anything is possible-1-Imagine Confidential
Overcoming Interference Challenges when
migrating from WiMAX to LTE
24th June, 2015
Mike Stacey, CTO, Imagine Wireless
… and anything is possible-2-Imagine Confidential
Overcoming Interference Challenges when migrating from WiMAX to LTE
! Imagine Background
! Mitigating interference between WiMAX and LTE
! Reducing customer churn whilst migrating
! Exploiting existing WiMAX infrastructure to migrate to LTE
… and anything is possible-3-Imagine Confidential
Imagine Background
! Irish Broadband formed in 2003 to take advantage of the slow development of DSL services
� Initial Fixed Wireless deployment using unlicensed technology 2.4GHz, 5.4/5.8GHz,
� Followed by fixed WiMAX and pre WiMAX nomadic networks in 2005
� > 50,000 Wireless customers, 6,500 corporate (12%) 46,500 residential (88%)
! Network
� 200 sites, >1000 Base Station sectors
� Extensive National Fibre & Wireless transmission network (Population covered: ~1.8m)
! In 2008 acquired by Imagine Communications Group:
� Full Service Telecoms Group
� > 100,000 customers, Fixed Voice, Broadband, Data and ISP services to Business and Residential
� International Call Termination, Call Origination & Premium Services across Europe
� Full capability ADSL / Wireless, VOIP, ISP, WiMAX, Mobile, Triple Play
! Imagine Group is a privately owned company with turnover in excess of €100m.
… and anything is possible-4-Imagine Confidential
Wireless Network Deployment
! Deployment of Fixed Wireless Access technology since 2003
! Over 200 High Sites Locations and >1000 Base Stations deployed
� WiMAX rollout completed in 2011 with 135 sites and over 500 base stations
! Wide range of products from entry level broadband and voice to Gbps corporate WAN
! All IP RAN, Backhaul and Core network
! Architecture NGN based and designed to easily scale, evolve and integrate with back end systems
… and anything is possible-5-Imagine Confidential
3.5GHz Spectrum & WiMAX Coverage
• >200 MHz of 3.5GHz Spectrum in key areas
• Minimum of 100MHz Spectrum available for LTE
Rollout
… and anything is possible-6-Imagine Confidential
Imagine Network Evolution & Spectrum
2003
2004
2005
2006
2007
2008
2009
2010
MOBILE
FIXED
CO
RP
OR
AT
E
SO
HO
& S
ME
RE
SID
EN
TIA
L
NOMADIC
2011
2012
2013
Migrated to
WiMAX
Migrate to
LTE
… and anything is possible-7-Imagine Confidential
Summary of Radio Network Deployment
Technology No of Sites No of Sectors Frequency Band
Motorola WiMAX 16e 134 507 3.5GHz
Alvarion Breezemax
WiMAX 16d
21 51 3.5GHz
Alvarion Breeze VL 110 315 5.4-5.8GHz
Alvarion Walkair 26 40 10.5GHz & 26GHz
Microwave Pt-Pt 275+ n/a Multiple licenced
Pt-Pt bands
Navini Pre WiMAX 100+ 250 3.5GHz
NextNet Expedience 140+ 400+ 3.5GHz
Migrated to
WiMAX
… and anything is possible-8-Imagine Confidential
Radio Network Evolution
Technology No of Sites No of Sectors Frequency Band
TD-LTE 900+ 2,700 3.5GHz-3.6GHz
(Band 42,43)
Motorola WiMAX 16e 134 507 3.5GHz
Alvarion Breezemax
WiMAX 16d
21 51 3.5GHz
Alvarion Breeze VL 110 315 5.4-5.8GHz
Alvarion Walkair 26 40 10.5GHz & 26GHz
Microwave Pt-Pt 275+ n/a Multiple licenced
Pt-Pt bands
Navini Pre WiMAX 100+ 250 3.5GHz
NextNet Expedience 140+ 400+ 3.5GHz
Migrate to
LTE
… and anything is possible-9-Imagine Confidential
Business Objective
! Get to commercial 20MHz, 2x20MHz LTE asap, - when available, with outdoor CPE
! Issue:-
�What is cost/benefit of
− upgrading existing WiMAX pre LTE �
− deploying LTE with only indoor CPE �
− deploying new “LTE ready” WiMAX to new sites prior to full LTE �
� How to minimise risks/costs associated with deployment of new LTE technology �
− Risk minimised by keeping WiMAX network stable, grow/maintain customer base until
LTE fully ready
− Rollout LTE in areas where WiMAX was not rolled out
− focus on areas where broadband demand not met by current infrastructure
− Migrate WiMAX areas to LTE eventually if there is sufficient demand to justify
… and anything is possible-10-Imagine Confidential
Mitigating interference between WiMAX and LTE
Physical
Isolation
Spectrum and
Geographic
Separation
Synchronisation
and Frame
Alignment
… and anything is possible-11-Imagine Confidential
Spectrum and Geographic Separation
! Spectrum:
�With sufficient spectrum it is possible to avoid re-use of frequencies on WiMAX and LTE
� Interference issues at co-located sites still requires attention
! Geographic:
� Prioritisation of LTE rollout into areas where WiMAX was not rolled out
� Commercially driven decision to focus on areas where broadband demand not met by
current infrastructure
�Where LTE and WIMAX areas are adjacent careful use of frequencies minimises
interference
… and anything is possible-12-Imagine Confidential
WiMAX -LTE Interference Scenarios
Majority of the interference
occurs between un-
synchronized
Base Stations
… and anything is possible-13-Imagine Confidential
WiMAX –LTE Interference Scenario
BS receives BS receives
TD
D(U
nsy
nch
ron
ised
)T
DD
(Syn
chro
nis
ed)
BS transmits BS transmits
Net
wor
k B
Time
Net
wor
k A
Net
wor
k B
Time
Net
wor
k A
BS transmits BS receives BS transmits BS receives
BS transmits BS receives BS transmits
BS transmits BS receives BS transmits BS receives
BS receiv
Downlink (DL) Uplink (UL) BS-to-BS Interference
Interference occurs when one system transmits at the same time as the other receives
… and anything is possible-14-Imagine Confidential
WiMAX & LTE Frame Structure
LTE Frame Structure
WiMAX Frame Structure
Downlink Uplink
LTE Subframes may be
Downlink, Uplink or Special Interference
… and anything is possible-15-Imagine Confidential
TDD-LTE Frame Structure
! TDD-LTE frame structure: 10ms.
! It consists of “2 half frame” X “5 sub-frames” (1ms)
! Each sub-frame can be used for DL (D), UL (U), S (Special)
Uplink-downlink
configuration
Downlink-to-Uplink
Switch-point
periodicity
Subframe number
0 1 2 3 4 5 6 7 8 9
0 5 ms D S U U U D S U U U
1 5 ms D S U U D D S U U D
2 5 ms D S U D D D S U D D
3 10 ms D S U U U D D D D D
4 10 ms D S U U D D D D D D
5 10 ms D S U D D D D D D D
6 5 ms D S U U U D S U U D
Configuration #2 allows 3:1
DL:UL ratio and alignment
with existing WiMAX Frame
… and anything is possible-16-Imagine Confidential
TDD LTE Special Frame Introduction
Index DwPTS GP UpPTS0 3 10
1 9 4
2 10 3
3 11 2
4 12 1
5 3 9
6 9 3
7 10 2
2
Number of symbols occupied by DwPTS, GP and UpPTS
1
Special Sub Frame 9:3:2 gives optimal alignment to WiMAX Frame
… and anything is possible-17-Imagine Confidential
WiMAX & LTE Frame Structure
LTE Frame Structure
WiMAX Frame Structure
D S U DDD S U DD
5 7
… and anything is possible-18-Imagine Confidential
Feasible Co-existence Configurations
WiMAX DL/UL configuration
TDD-LTE DL/UL configuration
WiMAX Performance TDD-LTE Performance
35:12 3:1 No impact to WiMAX network
No impact to WiMAX network;LTE DwPTS length is changed to 9os, about 2% capacity loss (compare with special frame configuration 7)
35:12 2:2
WiMAX will impact UpPTS which transmits RACH in LTE, subscribers of LTE can not access Network; WiMAX lose 8 Symbols for synchronization, system DL capacity lose 26%
No impact to LTE;
29:18 3:1WiMAX UL symbol which used by common channel will be impacted, WiMAX subscriber can not access the network
29:18 2:2The last two symbols of WIMAX downlink need to be punctured, about 6% capacity loss
No impact to LTE;
Special Sub Frame 9:3:2 gives optimal alignment to WiMAX Frame without altering DL:UL Ratio
… and anything is possible-19-Imagine Confidential
Test Results
Results vary – on one instance 9:3:2 resulted in 15% loss of performance, in another there was
negligible decrease in LTE throughput. There was no interference on the existing WiMAX
network.
Cable WiFi Cable WiFi Cable WiFi Cable WiFiIndoor Gemtek (Cat 4) 95.5 84.7 96.2 101.5 Indoor Gemtek (Cat 4) 92 85Indoor BM593 (Cat3) 75.0 42.2 75.2 69.1Mifi E5776 (Cat 4) 104.3 66.5 108.9 70.2Outdoor B222s (Cat 3) 77.5*
Cable WiFi Cable WiFi Cable WiFi Cable WiFiIndoor Gemtek (Cat 4) 9.6 9.5 9.6 10.3 Indoor Gemtek (Cat 4) 10Indoor BM593 (Cat3) 9.3 9.5 10.3 10.3Mifi E5776 (Cat 4) 9.3 9.2 10.3 10.3Outdoor B222s (Cat 3) 9.6*
Indoor BM593 (Cat 3) x3 Indoor Gemtek (Cat 4) x9
Indoor BM593 (Cat 3) x3 Indoor Gemtek (Cat 4) x9
Mifi E5776 (Cat 4) x2
* Not peak, tested outdoor UE installed on office and connecting to Belmont ** Not peak, highest coding rate could not be achieved on all UE
Notes1) Frame structure 10:2:2 in theory provides higher DL throughputs than frame structure 9:3:22) Frame structure 9:3:2 is required for synchronisation with WiMAX base stations to avoid co-channel interference
Frame 10:2:2 Frame 9:3:2PEAK MULTI USER DOWNLOAD (Mb/s) 20MHz
107.5 104.3
PEAK MULTI USER UPLOAD (Mb/s) 20MHz Frame 10:2:2 Frame 9:3:2
Frame 9:3:2
PEAK SINGLE USER DOWNLOAD (Mb/s) 20MHz
PEAK SINGLE USER UPLOAD (Mb/s) 20MHz Frame 10:2:2 Frame 9:3:2
Frame 10:2:2 Frame 9:3:2
Vendor A Vendor BPEAK SINGLE USER DOWNLOAD (Mb/s) 20MHz
Frame 10:2:2 Frame 9:3:2
203.4
9.8 10.18
PEAK MULTI USER DOWNLOAD (Mb/s) 2x20MHz
Frame 10:2:2 Frame 9:3:272** 57**
PEAK SINGLE USER UPLOAD (Mb/s) 20MHz Frame 10:2:2 Frame 9:3:2
PEAK MULTI USER DOWNLOAD (Mb/s) 20MHz
PEAK MULTI USER UPLOAD (Mb/s) 20MHz Frame 10:2:2 Frame 9:3:2
9
… and anything is possible-20-Imagine Confidential
Physical Isolation
ScenarioScenarioScenarioScenarioSensitivity Sensitivity Sensitivity Sensitivity
worse than 1dBworse than 1dBworse than 1dBworse than 1dB
Sensitivity Sensitivity Sensitivity Sensitivity
worse than 3dBworse than 3dBworse than 3dBworse than 3dB
Isolation for co-site 76.87dB 71.02dB
Isolation for different
site85.27dB 79.42dB
Assumption
1. Capacity/Coverage loss <5%,which equals to sensitivity worse than 1dB
2. Capacity loss <7%,coverage loss <17.7% ,which equals to sensitivity worse than 3dB
3. Consider the worst situation for different scenario
• Two antenna radiate each other
• Antenna down tilt is 6 deg
• Antenna height is same
… and anything is possible-21-Imagine Confidential
Space Distance Analysis
Different-site:
Co-site:
IsolationHorizontal
distance
1dB 85.27dB 176m
3dB 79.42dB 90m
IsolationHorizontal
distance only
Vertical
distance only
Simultaneous
Horizontal Vertical
1dB 76.87dB 37m 6.2m27m 1m
0.7m 2m
3dB 71.02dB 18.9m 3.2m
0.2m 1m
0m 2m
27m 1m
! Required isolation using combination of vertical and horizontal separation feasible on most sites
! In other cases isolation can be achieved by careful selection of antenna location
… and anything is possible-22-Imagine Confidential
Reducing customer churn whilst migrating
Technology Solutions
! Single RAN solutions:- Base station supports WiMAX and LTE Simultaneously
Source: WiMAX Forum/Heavy Reading “WiMAX Advanced to Harmonize with TD-LTE in the 2.3, 2.5 & 3.5GHz Bands: Opportunities & Challenges for WiMAX 2”
! Introduce LTE Carriers in
parallel with WiMAX
! Deploy dual mode CPE
during migration phase
! May impact coverage from
some sites requiring infill
! When customers migrated
change WiMAX carriers to
LTE
… and anything is possible-23-Imagine Confidential
Dual Mode WiMAX – TD LTE CPE
! 3.5GHz TD-LTE Indoor & Outdoor Units
! WiMAX Capability can be incorporated for relatively small cost
… and anything is possible-24-Imagine Confidential
Reducing customer churn whilst migrating
Technology Solutions
! Potential Drawbacks of Single RAN solution
! Capacity of WiMAX & LTE not optimised during migration
! Possible coverage gaps
! Dependant on Core network ability to support new base stations
! Works well if existing WiMAX base stations can be upgraded but…
! E.g. Current Imagine WiMAX base stations not able to support upgrade
! Case for new “LTE Ready” WiMAX deployment not as good as deploying LTE in
new areas
! If existing WiMAX base stations require swap out then why not migrate directly to
LTE
… and anything is possible-25-Imagine Confidential
Reducing customer churn whilst migrating
Managing Technology/Base Station swap
! Used successfully to migrate pre-WiMAX technologies to WiMAX
! Hard Cut-over on Network from non WiMAX to WiMAX:
! Customers informed and signed up well in advance
! CPE shipped to customer in advance
! LTE has option for dual mode device to be installed in advance of
cutover
! Significantly Improved service offering to customers – minimises churn
! New Base Stations built, commissioned and integrated quickly 24-48Hrs
maximum
… and anything is possible-26-Imagine Confidential
! The existing WiMAX Network has been deployed with the following capabilities:
� High Capacity Base Stations
� Beamforming and MIMO technology to give superior coverage and capacity
� 10MHz Channel bandwidth to give over 15Mbps throughput per sector
� Architecture designed to facilitate simple upgrades to increase capacity via additional
cards/ports
� High Capacity all IP Backhaul via microwave and managed bandwidth
� Minimum bandwidth 100Mbps from High Sites
� High sites designed and built with capability to readily upgrade to LTE
Exploiting existing WiMAX infrastructure to migrate to LTE
… and anything is possible-27-Imagine Confidential
! The existing WiMAX Network has been deployed with the following capabilities:
� High Capacity WiMAX Base Stations
� Beamforming and MIMO technology to give superior coverage and capacity
� 10MHz Channel bandwidth to give over 15Mbps throughput per sector
� Architecture designed to facilitate simple upgrades to increase capacity via additional
cards/ports
� High Capacity all IP Backhaul via microwave and managed bandwidth � capacity
expansion required
� Minimum bandwidth 100Mbps from High Sites � Requires upgrade to 300-400Mbps
per site
� High sites designed and built with capability to readily upgrade to LTE � basic site
infrastructure re-used
Exploiting existing WiMAX infrastructure to migrate to LTE
… and anything is possible-28-Imagine Confidential
Exploiting existing WiMAX infrastructure to migrate to LTE: Core Network
! WiMAX
� Proprietary platforms
� WiMAX Specific elements:
• ASN G/W
• NMS, EMS
! LTE
� Generic Computing Platforms with LTE
specific S/W e.g:
• MME, HSS, PCRF etc.
With the exception of some generic elements e.g AAA, and Switch/Router elements majority of WiMAX core cannot be reused, however
More recent LTE solutions are capable of supporting WiMAX with additional cards/software
… and anything is possible-29-Imagine Confidential
Conclusions
! In the short term migration may not be best business case
� Greater revenue opportunity from deploying LTE in non WiMAX areas
� in the short term avoids migration issues
! Solutions do however exist to support migration
� Single RAN, Core, CPE support for dual LTE/WiMAX in later generations of equipment
� Interference can be mitigated with synchronisation and physical isolation
! Churn can be minimised by timely and clear communication with customers and attraction of
greatly improved service
! Some elements of the WiMAX network can be re-used – mostly more generic elements, re-use
better on later generations of WiMAX equipment
! Biggest challenge in migration is getting LTE industry into a fixed broadband mindset when
planning the LTE network