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Com-Net Ericsson EDACS Trunking Systems Information
Page Last Updated: 01/23/01
EDACS Whitepaper - (PDF Format) - This is an excellent whitepaper written by Com-Net Ericsson regarding how EDACS systems work, EDACS technologies overview, and other technical details of an EDACS infrastructure.
EDACS Talkgroups Conversions
The Uniden EDACS format (which will be called AFS, for (Agency-Fleet-Subfleet): Using this example (586 DECIMAL = 04-092 AFS = 24a HEX): (1) 586 decimal = 01001001010 binary (talkgroups are 11-bit binary) (2) Split the binary as follows 0100 | 1001 | 010 (3) Convert each group to decimal 04 09 2 (4) Format as 04-092 The HEX translation would be: (1) 586 decimal = 01001001010 binary (2) Split binary as 010 | 0100 | 1010 (3) Convert each group to HEX 2 4 a (4) Write as 24a The BC245 can do the DECIMAL/AFS conversion internally, and the user can choose either mode of entry and display. So it won't be necessary to do this by hand. |
See this link for an Conversion Table to help with these conversions between AFS, DEC and HEX.
See this link for an Excel Spreadsheet to convert talkgroups for you. (Thanks to tvsjr@sprynet.com)
GEAFS Utility for managing EDACS talkgroups in the Etrunker program. Note this is a DOS application, but is compiled to only run under Windows.
- Download the GEAFS Utility here
Also Available at:
http://www.egroups.com/files/BrevardRadio/Utilities/GEAFS/
- This application also has a feature which takes your Etrunker group file and formats the information in HTML for submission to the Trunked Radio Information Homepage - see this sample for and example.
EDACS Fleet mapping
Establishing a fleet map structure dictates the max number of agency and fleet calls which can be assigned. Within the fleet map structure, the more agencies that are setup, the more agency calls that can be assigned. The same is true for fleet calls. To enhance each agencies flexibility, you can have different fleet and subfleet structures for each agency to suit specific radio communications requirements
A group call is addresses using a Group ID (GID). The GID is composed of 11 bits to define a total of 2048 max groups. The fleet map is structures for each agency to suit their specific requirements.
Some examples of the possible fleetmaps are shown below (similar to Motorola Fleetmaps)
Agencies | Fleets | Subfleets |
2 | 32 | 32 |
2 | 16 | 64 |
2 | 8 | 128 |
2 | 4 | 256 |
4 | 32 | 16 |
8 | 8 | 32 |
8 | 16 | 16 |
16 | 16 | 8 |
The most common fleet map used by EDACS systems is 8 (3 bits) agencies, 16 (4 bits) fleets and 16 (4 bits) subfleets. If we take a couple of examples of group calls, you can easily see how simple the fleet structure really is.
Using a 3/4/4 structure, we can now partition the 11 bit Group ID (GID) as follows:
_ _ _ / _ _ _ / _ _ _ _
Agency Fleet Subfleet
Binary examples are shown below:
Agency 1, Fleet 1, Subfleet 1 (GID 273 Decimal)
0 0 1 / 0 0 0 1 / 0 0 0 1
Agency 1, Fleet 1, Subfleet 15 (GID 287 Decimal)
0 0 1 / 0 0 0 1 / 1 1 1 1
A group call for Agency 1, Fleet 1, Subfleet 0 (GID 272) is a Fleet group call. All subfleets in Agency 1, Fleet 1 will respond to the call. A binary representation is as follows:
0 0 1 / 0 0 0 1 / 0 0 0 0
When an EDACS radio sees the fleet call assignment (GID 272), it immediately associates Subfleet 0 as being a Fleet call for Agency 1, Fleet 1. If the radio's channel selector is on a subfleet within Agency 1, Fleet 1, the radio hears the call.
A group call for Agency 1, Fleet 0, Subfleet 0 (GID 256) represents an Agency Group call. All fleets and subfleets in Agency 1 will respond to the call. A binary representation is as follows:
0 0 1 / 0 0 0 0 / 0 0 0 0
When the radio sees the Fleet call assignment (GID 256), it will immediately associate Fleet 0, Subfleet 0 as being an Agency call for Agency 1. If the radio's channel know is on a subfleet within Agency 1, the radio will automatically hear the call on GID 256.
This type of fleet mapping ensures Agency Fleet calls under failure mode of operation (such if the Site Controller were to fail)
All EDACS systems have 25 real LCN channel frequencies, and then an additional six 'status' channels that show up under Etrunk. They are not actual frequencies, but they indicate a certain status message to the calling radio. Here is what I have added to all my EDACS system files. s DOWNLINK,1a,ffff,0 s RESERVED,1b,ffff,0 s CONVERTc,1c,ffff,0 s QUEUEDid,1d,ffff,0 s SYS-BUSY,1e,ffff,0 s DENIEDid,1f,ffff,0 I'm not too sure about the first two, but CONVERTc is used to tell a radio who PTTs while there talkgroup is active, and sends them to listen to the talkgroup, giving them an error beep as well. QUEUEDid is where a calling radio will be placed if they are waiting for a next available voice channel or phone patch, etc. SYS-BUSY, means the system is busy, no channels available, and somebody is in the Queue. DENIEDid is if that radio ID is not allowed on the system for some reason.
EDACS System Overview
Enhanced Digital Access Communications System (EDACS) is available in VHF, UHF, 800 and 900 frequency bands and wideband (25 kHz) and narrowband (12.5 kHz) configurations. This spectrum resource provided a springboard for the development of trunking systems. Public service radio manufactures working with Associated Public-Safety Communications Officers (APCO) developed a requirements document (APCO 16) for trunked radio systems.
EDACS provides coordinated communication between agencies and integrates all services; Dispatch, Secure Voice, Telephone and Data within a single common communication system. EDACS systems have a single control channel communicating between the system and the field radios. These configurations range from Basic EDACS to EDACS Level 4, consisting of Voted and Simulcast Systems. An EDACS Multisite Network links Systems together via a Multisite Controller (MSC) or Integrated Multisite and Console Controller (IMC).
There are two types of radio channel designations are used in EDACS: One of them is the Control Channel and the other is the Working Channel. The Control Channel is used to send digital data between sites to the radios. This data is continually transmitted to the field units.The Working Channels sends voice and data over the air.
Used for continuous data (full duplex) Inbound and Outbound 9600/4800 bits per second.
Working Channel
Up to 23 per Site
Voice and Data
Data message 9600/4800 bits per second.
Low Speed Data for updating units: Analog Calls 150 Bits per sec, Individual and
scan group calls
Units will send 75Hz and 150Hz Trunked Unit Transmitting.
Control Channel GETC must be reset to bring site out of Failsoft Manual or
Remote accomplished.
Failsoft sites can work in Multisite configuration less than .5 second Channel Access.
If NO Working Channel available the Call goes into Queuing an available channel.
Wide Band
(25/30) kHz: 9600 baud
Narrow Band (12.5) kHz 4800
baud
9600 Baud Rate at 0.1 bit
(0.01ms)
150 Baud Rate at 0.01 bit (0.06ms)
Amplitude of 0.25 dB
(300-3000Hz)
Phase of 25 degrees (600-2600 Hz)
Channel Access Time: Less than 500 ms
Max ISI Time: 52 uS (Allowing for 10 uS of Jitter)
Max Site Separation: 7.8 miles (Without Timing Adjustments)
Velocity of Propagation: 3.0 X 10E8 m/s
9600 Baud Period: 104 uS
Bell Standard T1 or DS1 Grade Circuits Via: Digital Microwave - Fiber Optic - Phase Stable Analog Multiplex / Microwave
Total Number of Logical Address Schemes: 16,384 (0 to 16,383)
Logical ID uses 14 bits
Used for System Validation
LID 0: Test Unit when making Test Calls
LID < 64 for Host Computers or Mainframe
LID > 100 for Consoles
Total Number of Group Address Scheme: 0 to 2048
Each Radio has a Physical ID
20 bits Physical ID
1,048,576 possibilities
ESN
Simultaneous Broadcast by two or more transmitters located at different sites operating on the same RF Frequency. A Simulcast trunked system requires the same number of channels with a common set of RF Frequencies at each site. For this reason, alignment of simulcast systems become very important.
The ability of an FM Discriminator to lock on the incoming signal: RF Level 1 > RF Level 2 by 12 dB