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Public Safety

Current State of Application
Governmental private broadband networks are initially spurred by, and deployed for, specific applications.  This is generally because the funding for the network is allocated for specific mission critical needs. However, once deployed, governmental agencies quickly find their broadband networks lend themselves to a wide range of uses.  For instance, the police might want to deploy wireless broadband infrastructure for video surveillance systems, or alternatively the transportation department may need a wireless data infrastructure for traffic control functions implemented as part of intelligent transportation system (ITS).  After the network is deployed for these initial applications, though, the network managers quickly find the broadband system can support additional usage.  For example, the public safety network deployed for a video surveillance can also be used to provide data capability to mobile data terminals (MDTs, or hardened laptops) mounted in vehicles in coverage areas.

In addition to the network usage growth within a department, a coherent strategy within a region can allow usage growth across departments. In many cases, the deployment of the wireless broadband network is led by an Information Technology department because of the interagency usage.  In the previous example of the public safety and transportation departments, the usage requirements are complimentary on the same network.  As a result, the transportation network deployed to support traffic control applications will easily have sufficient bandwidth to support public safety applications.  Just as an enterprise wide area network (WAN) infrastructure can easily serve multiple agencies simultaneously, an enterprise wireless broadband network with advanced features like grade of service capability, authentication and encryption can allow the police applications to have secure, guaranteed throughput while the transportation ITS infrastructure operates in the background.

Public Sector Broadband Applications
With public safety, the typical application requiring broadband falls into a number of distinct classes.  The single biggest driver for broadband is video surveillance.  Video, and especially high resolution video, requires broadband because the quantity of information exceeds the bandwidth capabilities of other transmission media.  Although resolution and frame rate (the number of images per second) can be reduced, Public Safety strongly desires the real-time delivery of high resolution and high frame rate for both surveillance and evidentiary purposes.   In many cases, video surveillance networks can consist of hybrid networks that use both wire line and wireless transmissions.  Wire line networks can provide network connectivity for the  bulk of the cameras, but digging up city streets for installation of fiber optic cables can be expensive and disruptive.  In these cases, the ease and low cost with which wireless cameras can be deployed makes the hybrid network an attractive alternative.

Other secondary uses – such as vehicular access for delivery of time-critical graphical information like police suspect mug shots or fire incident building plans, can be accomplished, albeit slowly, with less than broadband connections.   Today’s wireless narrowband systems can deliver highly compressed jpeg images or other graphical information at slow but workable speeds. However, a broadband network improves the quality of the information, the delivery speed, and the number of concurrent users that can access the system.  A final class of public safety usage of broadband networks includes remote network connectivity for facilities and radio system backhaul (connecting remote radio transmission sites to the rest of the network).  In these cases, the capital expenditure for the broadband equipment can have a significantly better return on investment than the recurring cost of purchasing landline broadband from telecommunications provider.

In the fire services, broadband connectivity can be also be used to integrate dispatch operations like fire hall alerting.  Newer alerting systems use IP-based connectivity to allow dispatchers to control fire hall alarms, public address and access relays.  These systems can be combined with E911 Computer-Aided Dispatch (CAD) system using a common network infrastructure.  The data capability of the CAD systems provides the fire fighters with improved incident and situational awareness, and the wireless broadband network can be used to deliver this information directly to an MDT in the assigned vehicle prior to leaving the fire hall.  With these combined systems, fire fighters can provide improved response times and capabilities for incoming calls.

Within the transportation realm, the wireless broadband network can be used to provide connectivity to a wide variety of traffic monitoring and control equipment.   Roadway videos, traffic monitoring equipment, electronic signage and highway sensors can all utilize the same wireless network infrastructure for connectivity to traffic management centers.  The information provided to the traffic operation centers can be used to actively monitor and alleviate traffic congestion.

Minimum Technology Requirements
500 kbps per second is a break point for video (5 – 10 frames per second) and this capability is very limited.  Full motion video with a decent encoder can be done at 1 Mbps.

Recently, camera vendors have been going to “megapixel” cameras that send jpeg images at rates from 3 to 10 images per second.  Public safety personnel like these because of the “zoom” capabilities for investigative purposes.  These can be large bandwidth consumers, with upwards to 10 Mbps required for each camera.  The average megapixel camera is 2 to 3 Mpixels, but new cameras are 12 Mpixels and this is expected to increase considerably.

Typical deployments put multiple cameras on a wireless access point (for example, 4 cameras at a single intersection).  Large Mpixel cameras need 50 Mbps to support this type of implementation. Video streams from a camera can be IP multicast with many streams going to multiple viewing stations or DVRs and this can multiply the bandwidth requirements.

Business Aspects
Broadband deployment can help reduce costs by reducing the manpower needed to monitor situations. It can also provide savings by reducing losses due to crime, fires, and disasters.

There is another direct, but less obvious, economic benefit from deploying broadband infrastructure for public safety.  Virginia is home to Tyco Electronics, one of the largest and most respected suppliers of public safety communications and networking equipment. Within the Commonwealth of Virginia, and especially within the Lynchburg area, Tyco Electronics has over 500 employees that focus on production of MA-COMM brand critical communications systems and equipment for public safety, utility, federal and select commercial markets. Its products range from advanced IP-based voice and data networks to traditional wireless systems that offer high levels of reliability, interoperability, scalability and security.   Lynchburg has become a center of excellence for public safety communications, attracting other smaller companies to the area to service this market.

Obstacles or Barriers to Further Deployment
Within the Commonwealth of Virginia, public safety and other governmental agencies can benefit from the increased deployment of wireless broadband networks.  The requirements for both public safety and governmental wireless broadband networks are emerging and evolving, but the public sector needs are typically driven by, and funded for, a handful of mission critical applications.  Broadband networks can be either commercial or private. Commercial networks have the benefit of low capital outlay, but may not have coverage where required or capacity when required for critical communications.  Commercial networks are deployed to maximize revenue from subscribers, and as a result have coverage in areas of high population density.  Commercial broadband networks support limited hierarchy and prioritization, providing capacity on a relatively flat basis.  The result is that, frequently, public safety users have the same level of priority and same grade of service as teen-age “text messagers”.  Conversely, private networks require more up-front capital costs, but are engineered exclusively for the governmental requirements of coverage, capacity, security and robustness.  Another important consideration is the scope of deployment.  A common misconception is that a broadband network must have ubiquitous coverage throughout a large geographic region to be of value.  Actually, public sector networks may have very specific coverage requirements (e.g. a highway, a school campus or a downtown area).

Other Pertinent Information
Wireless broadband networks for governmental use can vary significantly in scale and architecture, but are generally made up of simple components.  The two most common types of components are Point-to-point (PtP) and Point-to-Multipoint (PtMP) networks.  A PtP network provides a simple connection, or link, for a span of approximately ten miles.  This link can be used connect a remote building to a network, or a Land Mobile Radio (LMR) antenna site to the rest of the radio system.  Multiple PtP links can be constructed, back to back, in a linear fashion to span long distances.

A PtMP network generally consists of a single base station (or access point) that services multiple subscriber (or clients).   For example, a PtMP network might have a single base station on top of a building that provides broadband connectivity to 10 traffic controllers located within a three-mile radius.  Other subscribers, such as a drive up vehicle within the base station coverage, can also access the same base station and be provisioned for broadband services.

A complex network can consist of both PtP and PtMP components.  From the previous example, the PtMP network might need a PtP link for connectivity back to wire line network if a fiber optic or Ethernet cable were not available at the top of the building.  An important consideration of these compound networks is the effect of multiple PtP links on overall bandwidth.  Mesh networks, that typically rely on a single frequency or RF channel for the PtP links can suffer from bandwidth degradation across multiple PtP links because each successive link can interfere with the other.  Conversely, a WiMAX network that combines time-division multiplexing techniques with a managed frequency plan can avoid the bandwidth degradation because the self-interference is eliminated.

Acknowledgement:  Paul May, Tyco Electronics (maypaul@tycoelectronics.com) for providing input to this section.