800 MHz Information Sheet

Regional System Map

System Diagram

Information Sheet

King County Regional 800 Mhz Trunked Radio System

Background: The King County regional 800 MHz trunked radio system was approved by voters in September 1992 with the authorization of a three year special levy to finance the development of the system. Included in the funding package were mobile and portable radios, transmitter site equipment, an interconnecting microwave transmission network, network controllers and other related equipment. The levy was collected in 1993, 1994 and 1995 at a rate not to exceed $.16 per $1000 of assessed valuation, for a total amount of $57,016,764.

The primary purpose of the system is to provide emergency radio communications services for all the police, fire, emergency medical services, public school districts and public hospitals within King County. The secondary purpose of the system is to provide, to the extent possible within the constraints of available funding and limited spectrum availability, sufficient capacity within the system to service other public agencies with emergency response duties.

The regional system consists of several subsystems joined together by electronic switching equipment to provide highly reliable region-wide communications. Each subsystem has been implemented by what is called a Subregion. Subregions are either individual governments or interlocal agencies who have a shared responsibility to build and operate the system. Subregions include: The City of Seattle, King County, Valley Communications Center (an interlocal agency composed of the cities of Auburn, Kent, Renton, Tukwila and Federal Way), and the Eastside Public Safety Communications Agency (EPSCA, an interlocal agency composed of the cities of Bellevue, Kirkland, Redmond, Mercer Island and Issaquah).

Central coordination for the regional system is provided by the King County Regional Communications Board (KCRCB). This a joint board consisting of one representative from each Subregion and an at-large member who represents the interests of system users who do not have a voting representative on the governing body of any Subregion. Each member of the Board has equal voting authority. Decisions concerning network design require unanimous approval by the Board.

System Design: The Subregions have worked cooperatively through the Regional Communications Board to implement a design for the entire county-wide system that is able to meet performance needs within the limited number of frequencies and available funding. Some of the major design considerations related to coverage, performance standards, and the sheer number of diverse government users within King County.

A majority of King County’s population lies in a region that is within 140km of the Canadian border. Treaties between the US and Canada allow agencies in these border areas to only have clear use of about 1/2 of the available 800 MHz spectrum. All other spectrum utilization needs to be on a non-interference basis to the neighboring country. Given the unique terrain and topography of the Puget Sound region, the design of the system needed to carefully plan spectrum utilization so that capacity needs could be met without causing interference problems to our Canadian neighbors.

King County covers approximately 2,200 square miles. Approximately 80% of the 1.7 million population lives in the western 20% of the land area. The eastern portion of the county reaches to the crest of the Cascade Mountains, where radio coverage is more difficult to provide. This area is sparsely populated but has several major transportation corridors that have heavy commercial and recreational use.

The large number of separate governments within King County include 39 cities, 24 fire districts, the Port of Seattle, 4 hospital districts, 20 school districts, and 43 water and sewer districts. There are a total of 68 separate public safety agencies delivering police, fire and EMS services to our citizens. Over the years these agencies had developed a collection of over 100 separate VHF, UHF and 800 MHz radio systems.

The levy-funded 800 MHz trunked radio system has been designed with the capacity to meet the diverse needs of these users with one compatible radio network. This network has sufficient capacity to meet the growth needs of our region; it provides the coverage capabilities essential to public safety services that many of the older systems lack; it has a high likelihood of surviving a natural disaster for the delivery of reliable service; and it provides for direct communications between jurisdictions to better meet mutual response needs during single incidents or during a disaster.

The county-wide network is essentially configured as three subsystems that work through common network controller equipment. Subsystems include the City of Seattle subsystem, the EPSCA subsystem, and the subsystem that was jointly developed by King County and Valley Communications Center. By connecting all sites within the subsystems to common network controller equipment, it is possible to implement Talkgroups that have seamless coverage over the entire county. Please see attached diagrams of the overall system design and site distribution.

The system has been designed for portable grade coverage wherever possible and the system loading is patterned so that all areas of the county experience relatively similar system capacity access. The overall county-wide system has been designed with sufficient frequency capacity to include most, if not all, general government users within King County.

The regional system currently uses predominately analog audio technology rather than digital audio technology. Analog technology for 800 MHz trunking is proven and reliable, is lower cost than digital technology, and provides better audio quality with fewer sites when compared to a digital trunking system. The system is however “mixed-mode” and supports a few channels and subscriber units that are digital instead of analog. This allows those radios to operate in a digitally encrypted mode that provides secure communications for sensitive law enforcement activities.

The following table outlines some of the general statistics of the system: