Overcoming Interference Challenges when migrating from WiMAX to LTE
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Overcoming Interference Challenges when migrating from WiMAX to LTE

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Presented by Mike Stacey, CTO, Imagine Communications Group, Ireland in the LTE World Summit 2014 on 24th June 2014

Presented by Mike Stacey, CTO, Imagine Communications Group, Ireland in the LTE World Summit 2014 on 24th June 2014

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    Overcoming Interference Challenges when migrating from WiMAX to LTE Overcoming Interference Challenges when migrating from WiMAX to LTE Presentation 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 MOBILEFIXED CORPORATE SOHO&SME RESIDENTIAL 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 TDD (Unsynchronised) TDD (Synchronised) BS transmits BS transmits NetworkB Time NetworkANetworkB Time NetworkA 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 UpPTS 0 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 3:1 WiMAX UL symbol which used by common channel will be impacted, WiMAX subscriber can not access the network 29:18 2:2 The 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 WiFi Indoor Gemtek (Cat 4) 95.5 84.7 96.2 101.5 Indoor Gemtek (Cat 4) 92 85 Indoor BM593 (Cat3) 75.0 42.2 75.2 69.1 Mifi E5776 (Cat 4) 104.3 66.5 108.9 70.2 Outdoor B222s (Cat 3) 77.5* Cable WiFi Cable WiFi Cable WiFi Cable WiFi Indoor Gemtek (Cat 4) 9.6 9.5 9.6 10.3 Indoor Gemtek (Cat 4) 10 Indoor BM593 (Cat3) 9.3 9.5 10.3 10.3 Mifi E5776 (Cat 4) 9.3 9.2 10.3 10.3 Outdoor 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 Notes 1) Frame structure 10:2:2 in theory provides higher DL throughputs than frame structure 9:3:2 2) Frame structure 9:3:2 is required for synchronisation with WiMAX base stations to avoid co-channel interference Frame 10:2:2 Frame 9:3:2 PEAK 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 B PEAK 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 9:3:2 72** 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 ScenarioScenarioScenarioScenario SensitivitySensitivitySensitivitySensitivity worse than 1dBworse than 1dBworse than 1dBworse than 1dB SensitivitySensitivitySensitivitySensitivity worse than 3dBworse than 3dBworse than 3dBworse than 3dB Isolation for co-site 76.87dB 71.02dB Isolation for different site 85.27dB 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: Isolation Horizontal distance 1dB 85.27dB 176m 3dB 79.42dB 90m Isolation Horizontal distance only Vertical distance only Simultaneous Horizontal Vertical 1dB 76.87dB 37m 6.2m 27m 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