(lte) in public-safety networks

The Importance of Testing Long Term Evolution (LTE) in Public-Safety Networks

White Paper

In emergencies, it is imperative that government agencies can communicate internally, that emergency professionals have secure and uninterrupted communications, and that the population is kept informed—needs that demand a reliable and robust network.

The U.S. has a sophisticated, if aging, emergency-communications network that reliably delivers public safety information, and it has served us well. However, it is outdated and is designed only for voice communications. Today, the ever-growing sophistication of network components, devices (smartphones and tablets), and ways in which we communicate (video, e-mail, social sites) have in turn created more sophisticated communications methods for emergency services. To take advantage of these methods, the network must be upgraded.

The National Institute of Standards and Technology (NIST) is the first federal agency to research guidelines for telecommunications and information technology standards for interoperability and information sharing among public safety agencies. NIST, through its Public Safety Communications Research (PSCR) program, is building a 700 MHz public-safety broadband trial network to give manufacturers and first responders a location to deploy and test their systems in a multivendor, neutral host environment. The goal is to demonstrate and evaluate the behaviors of 3GPP/LTE technology deployed in the 700 MHz bands, specifically to meet the needs of public-safety agencies.

LTE is a new, all-IP, high-bandwidth, wireless technology that enables the delivery of new, advanced services in a guaranteed, secure and reliable way. The U.S. government has already licensed the 700 MHz frequency range for the access network for LTE and the new Public-Emergency System will use band 14 within this range.

This paper is organized in four sections:

y Benefits of an LTE-based network

y What needs to be done?

y What happens after deployment?

y Lessons learned

2 The Importance of Testing Long Term Evolution (LTE) in Public-Safety Networks

Benefits of an LTE-based networkHigh bandwidth LTE enables new, advanced services that will significantly improve emergency communications with improved capabilities for:

y Real-time video

– Face scanning and recognition for quick verification against centralized facial recognition databases from any location

– Video surveillance of areas not served with a fixed connection (for example, coastal areas and deserts) resulting in better security

– Instant visual emergency assessments

y E-mail

– Fast and reliable delivery

y Recorded communications

– Database interrogation

– Fast access to suspect information from anywhere

– Fast retrieval of information needed during an emergency

y Voice

– Higher-quality transmissions and transcriptions

These new services will be delivered via a single, integrated, all-IP network that will better inform emergency service providers, letting them make better decisions faster.

What needs to be done?Work on this new network has already begun and Viavi Solutions® has been closely involved with NIST in testing its capabilities to prove that LTE can deliver these services, particularly in emergency situations, when networks will be stressed to their limit. Part of this work is validating and testing LTE-enabled equipment with a view to creating standards needed for a national, next-generation public-safety network.

Viavi products support both the Altair chipset and the IPWireless Band 14 UE (http://www.ipwireless.com/government/products/devices) earmarked for public safety and being used by NIST in several of the first waiverholders’ network rollouts. Viavi is a key contributor to the Multi-Service Forum (www.msforum.org) and has contributed heavily to the VoLTE Interoperability Event 2011 and whitepaper (http://www.msforum.org/interoperability/MSF_VoLTE%20_2011_WhitePaper.pdf).

There are three key areas where testing will help establish a reliable and conformant network:

y Basic functionality testing—does it work?

y Comprehensive system and node-level testing—does it work efficiently?

y Inter-operability testing—does it work everywhere?


Basic functionality testing—does it work?

To determine if LTE equipment submitted for use in the trial project has been configured correctly to achieve desired functionality, it is necessary to validate the RF environment to ensure cells are deployed in the optimal locations and that they are optimized for most efficient operation. Figure 1 shows a typical scenario using Viavi Drive Test, which in conjunction with Altair chipsets and an IP Wireless Band 14 device, validates the RF performance of the proposed network. Emergency services will need guaranteed communications, both outdoor and indoor. The Viavi Drive Test solution can be used in a vehicle or backpack, enabling validation of RF coverage and service capability within complex buildings (malls, airports, skyscrapers, stadiums). Typical tests will include:

y RF layer tests to ensure that the deployed equipment will not interfere with other existing 700 MHz LMR, PSCR systems

y Service coverage validation

y Outdoor and indoor scenarios

y Handover verification

y Messaging/protocol tests

y Public-safety application tests (video, data)

y Performance tests (throughput, latency etc)

Figure 1. RF performance validation

(b) Indoor Use Model (In Building)Laptop PC and Phone/Receiver equipment

in backpack or Viavi FTA Phone

(a) Outdoor Use ModelAttended Drive Test with laptop PC and Phone/

Receiver equipment in moving vehicle

CorrectiveActions Optimization

Process

Drive Testing(Outdoor/Indoor)

Post ProcessingData Analysis

Customer/NetworkTrouble ticket,Initial Planning,

Optimisation

1

3

24


Comprehensive system and node-level testing—does it work efficiently?

Typically, this area of testing requires complex protocol scenarios to validate that the performance of the core network is able to meet the demand placed on it during emergency situations. Ideally, a testing solution allows many engineers to share the same hardware without impacting other tests, making the process efficient, consistent, and reliable.

Figure 2 below shows the typical configuration of a Viavi Signaling Analyzer Real Time (SART) deployed in a lab which can be used to test all the areas described below. Its multi-user architecture lets large numbers of engineers perform testing simultaneously. Capabilities include:

y In-depth and advanced performance testing

y Multiuser, loaded-network stress testing

y Network architecture type testing

y Interoperability testing that includes testing the evolved packet core (EPC) and inter-connecting, multiple EPCs

y eNodeB - eNodeB handovers

y Mobility management entity (MME) - MME handovers

y LTE-to-LTE handover testing and evaluation

Figure 2. Service verification and services quality testing

KPI’s & Analytics with DMTReal-Time Protocol Analysis Historic Analysis with Call Manager

Multi-User ArchitectureCentralized configuration and s/w management

Serving Network SS7, Services, IMS, IN

Internet

2G/3G/LTE RAN

UE’s

Uu


Control and user plane traffic will be significantly higher in emergency situations due to the volume of calls. In addition, LTE introduces a significant increase in the number of messages required to set up, maintain, and tear down a session compared to previous technologies. It is, therefore, imperative that all sessions can be captured and analyzed in a simple way that expedites network deployment and troubleshooting. Viavi is unique in correlating the LTE signaling generated by UEs connected to its Drive Test solution and correlating it with the protocol captured in the network by SART. This enables a much greater insight into problems. Figure 3 shows a typical scenario where the Viavi SART solution enables higher-quality testing.

Figure 3. Load and stress testing


Inter-operability testing—does it work everywhere?

New networks are expensive and deploying LTE will be no different; however, unlike previous technologies where all the network elements or components of the network (RAN, CORE) would typically be supplied by a single vendor, the LTE standards body has insisted on interoperability. This requires all LTE network elements to work with each other irrespective of vendor. This is a crucial step in providing a more competitive environment for network operators as they will no longer be tied to a single vendor’s pricing model. Figure 4 shows a typical scenario for this interoperation where a confirmation needs to be made that eNodeBs from different vendors interoperate and work with an EPC from another vendor.

Figure 4. Multi-vendor interoperability

In addition to ensuring that network elements are interoperable, it is also crucial to confirm that Altair chipsets and the IPWireless UEs which will be used by the emergency services also work on any combination of vendor network elements. This flexibility of interoperation available in LTE networks presents significant challenges particularly in the areas of testing, where it is now even more important to be able to test and confirm that equipment from different vendors can coexist. The Viavi SART solution lets engineers independently check that the operation of one vendor’s equipment is exactly the same as another vendor’s—rather than simply assuming it is so.

EPC

eNodeBVendor A

S1-MME

X2

EPCVendor B

X2

Uu

EPCVendor A

eNodeBVendor A

S1-u

S1-MME

S1-u

S1-MME

S1-u

S1-MME

S1-u

Uu

IOT S1Validate single vendor eNodeB with EPC from different vendor

IOT X2Validate eNodeB from

different vendors

eNodeBVendor A

eNodeBVendor B

EPC


In addition to the interoperability of multiple vendors’ equipment, it is essential that handovers between the eNodeBs and handovers between multiple MMEs can be tested. Figure 5 shows a high-level network schematic for LTE where the S10 interface is the link that interconnects multiple MMEs which will be located in multiple locations. Handovers, whether between eNodeBs on the same MME, or between eNodeBs on different MMEs, present specific test challenges, which are addressed by both Viavi Drive Test and SART solutions.

Losing service is not acceptable in an emergency system during a crisis. The system needs to work 24/7/365 without exception, and therefore must be tested thoroughly.

Figure 5. High-level LTE network view

What happens after deployment?We have discussed how to test the network during development prior to deployment. Once the network is deployed it must be operated, managed, and maintained. RF performance and service accessibility must be continually validated using Drive Test, both outdoors and indoors, to ensure that emergency services can always access the network.

Problems will always occur and the challenge is to minimize their impact by testing early in the lab as described above, as well as continually monitoring during operation to identify problems before they impact users. However, as perfect as plans may be, problems will still occur in the deployed network and the Viavi Drive Test and SART solutions can be used to identify these problems. Viavi also has an assurance solution that can be deployed on the entire network, enabling alarming and troubleshooting of network and service problems before users become aware.

Gn/GpSG SN

MMES1-MME

UE SGW PGW

Gr

Gn

Gn

Gx

Rx

= User Plane

= Control Plane

S5

SGi

S6a

S10 S11

U TRAN

GERAN 2G/3G/Common

LTE/EPC

Operator’s IP Services

(IMS, PSS, etc.)

E-UTRAN

S1u

HSS

PCRF

© 2016 Viavi Solutions Inc. Product specifications and descriptions in this document are subject to change without notice. lte-wp-nsd-tm-ae 30173085 901 0316

Contact Us +1 844 GO VIAVI (+1 844 468 4284)

To reach the Viavi office nearest you, visit viavisolutions.com/contacts.

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ConclusionWithout rigorous testing of the whole network—RF, access, and core—you cannot have confidence that it will work when it is most needed during emergencies when loading will be at its highest. In addition to experience with NIST, Viavi has considerable LTE expertise, helping deliver LTE network testing solutions to TDC, the leading provider of communications solutions in Denmark , and CSL, Hong Kong’s first and leading mobile network operator. Viavi also provides practical advice on what is required to get an LTE network up and running. This combination of experience, solutions, and consulting are key components required when delivering any new network, not just LTE. Viavi is uniquely positioned to ensure efficient deployments with solutions covering:

y Drive test

– Optimizing and troubleshooting FDD-LTE and TD-LTE networks

– Supporting UE device measurements and multi-band, multi-technology receivers

– Maximizing efficiency in the detection and isolation of problems

– Reducing the cost of ownership through a single test platform

y Protocol analysis

– End-to-end analysis and troubleshooting for LTE lab networks

– Comprehensive monitoring and network diagnostics by interpreting, correlating and analyzing protocol signaling messages produced by multiple network technologies at mobile network interfaces

– Real-time performance analysis and measurements against key performance indicators (KPIs)

– Intelligent hardware probes

– Multiuser access

– A robust API to enable workflow automation, speeding deployments and reducing time-to-revenue and operating costs

y Customer experience management

– End-to-end analysis and troubleshooting for live LTE networks

– Analytics to validate performance

– QoS analysis including KPIs

– LTE QoS class identifiers

As one of the world’s largest communications test equipment companies, Viavi is the only vendor who has won an independent award for our LTE solutions and that has a portfolio of solutions addressing all of the components that are required to be tested in a network. Our heritage, people, knowledge, experience, and ethics make us the ideal partner to ensure successful deployment of emergency systems for public safety.

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