Munawwar M. Sohul Dr. Taeyoung Yang Dr. Jeffrey H. Reed a LTE Communications Over 3.5 GHz Band for Broadband Public Safety Applications Munawwar M. Sohul Dr. Taeyoung Yang Dr. Jeffrey H. Reed a

Public Safety Network: Future Direction PS network is moving towards a broadband system LTE for public safety Priority access to network resources Desired services data, voice, and video communication, access to Internet Push-To-Talk (PTT) or Device-to-Device (D2D) comm. Group calling Greater interoperability and enhanced interagency cooperation Unprecedented broadband capabilities High reliability and security Cost effective Better performance, low latency Source: Homeland Security, “Public Safety Communications Evolution”, Brochure, Nov 2011

Public Safety Network: Future Direction Challenges: Broad range of stakeholders and context Efficient coordination and interoperability Rich content based information Existing spectrum allocation Enabling concept: Spectrum sharing Calls for a paradigm shift in sharing and managing the spectrum designing the radio architecture. Enabling technologies: Dynamic Spectrum Access (DSA) Carrier aggregation (CA) Self-organizing networks (SON) law enforcement, response to fire, natural and man-made disasters, medical emergencies, threats to public order and a host of other situations. 14,000 police departments, 3,000 sheriff’s offices, more than 6,000 911 centers, 1.2 million employees in city, county, state, and Federal law enforcement and 800,000 in private-sector security in the United States To design and develop an efficient and coordinated system to facilitate this gigantic workforce is a challenging task and the effectiveness of such a system is heavily dependent on the accuracy and detailed nature of the information shared within this complex topology. The use of 700 MHz spectrum for public safety applications is attractive because of its propagation and penetration characteristics. However, there is practically no room available in 700 MHz band to extend the spectrum further for future broadband PS applications.

Phase 1: Frequency Translating LTE Repeater Low-cost way to demonstrate the feasibility of spectrum sharing for broadband PS applications. Enables f1/f2 band (700 MHz/3.5 GHZ band) communication DSA enabled repeaters Designed and developed by Wireless@VT

Phase 2: Mobile Platform with Repeater Setting up the phase-1 repeater in a mobile platform: Easy to access emergency scenario Useful for non-emergency scenario Mobile platform equipped with LTE repeater Wireless services in the disaster affected area over licensed and unlicensed bands Self-sustainable in terms of power

Phase 2: Application Scenario

Impact and Significance Mobile infrastructure for broadband PS applications in rural areas Data, voice, and video communication, Access to internet Communication to the central PS command center Scalable and rapidly deployable small cell infrastructure Improve situational awareness Rapid dissemination of information to the deployed forces Option to provide some wireless service to non-PS users Backhaul connection even if the original link is faltered Attractive business opportunity for non-disaster scenarios Cellular communications, broadband internet connectivity, wireless services (WiFi, bluetooth) Operational data collection for future reference and analysis

Proof of Concept Demonstration Demonstrate The feasibility of broadband PS applications over the 3.5 GHz band The frequency agility provided by the repeater to use any of the NTIA identified shared bands Generate interest among the stakeholders Shared bands to achieve broadband PS services Scalable and rapidly deployable PS radio coverage Off-the-shelf equipments, Frequency translating LTE repeater Description Tentative timeline: October, 2014 LTE PS-UE and eNB (works in the PS band) DAS capability to identify spectrum opportunity Proof of communication between UE and eNB over 3.5 GHz band

Demo in the Indoor Environment Use available PS devices (Band 14) Ensure successful operation of the FD-LTE repeaters (Band 14 to 3.5 GHz) Communicate over the 3.5 GHz band DAS capability to identify spectrum opportunity Observe The successful SU hopping to avoid PU The impact of PU interference on the SU LTE link performance System Setup

FDD LTE Repeaters UE side repeater Two separate RF path Attaches to UE through Band-14 LTE duplexer Designed and developed by Wireless@VT eNB side repeater Two separate RF path Two ports to attach to the UL and DL port of CMW500 Designed and developed by Wireless@VT

Result: Impact of interference on the LTE Link Downlink at 3.5 GHz band Max Throughput: 5.74 Mbps Downlink at 3.5 GHz band Max Throughput: 5.74 Mbps Downlink at 3.5 GHz band Max Throughput: 5.74 Mbps Scenario UE-eNB Attachment throughput BLER Interference not hitting the LTE link Attached 4.61 Mbps 19.72% Interference hitting the LTE link 3.85 Mbps 32.93% LTE link moved to avoid Interference 3.75 Mbps 34.70%

Impact of Interference (without DSA) SINR calculated for Band14 Throughput and BLER shows flat regions LTE link tries to compensate through CQI adjustment The UE remains attached to the eNB for small SINR values Link performance is severely degraded

Impact of DSA Employing the DSA algorithm improves the LTE link performance The LTE link avoids interference: The external spectrum monitor detects the PU The LTE eNB switches to another channel that is reported empty Recovery time is smaller when DSA is employed LTE link is interfered by the PU for only a fraction of the time Similar performance is expected for multiple PU

Observations and Recommendations UE and eNB communicated over the 3.5GHz band using the repeaters Resilient: Even for low SINR values UE remained attached Once interfered The link recovers through CQI adjustment Long period of un-interfered state is required for recovery Recommendations Modifying LTE protocols to address strong and pulsating signal To ensure faster recovery through faster SINR to CQI mapping Observe the impact of interfering with different control channels Demonstrate successful communication using the repeaters in the outdoor environment Compare the performance of TD-LTE with the FD-LTE results.

Conclusion Public Safety Network Mobile infrastructure for broadband PS service Scalable and rapidly deployable wireless network Operational data collection for future reference and analysis Over the air hardware and software reconfig capability Useful in non-emergency scenario Enable spectrum sharing: use NTIA identified shared bands

Thank You Acknowledgements: This work is supported by the office of the Vice President for Information Technology, VT; Center for Innovative Technologies (CIT).