SYSTEM OPERATION (BRIEF EXAMPLE)
When a call request arrives at a SmarTrunk Xpress/SmarTrunk II controller, a short data packet will be sent from the controller's RS-232 data port to the ST-422 board which serves as the switch gate for that controller. Immediately, this packet is processed by the main ST-510 CPU and software, which decodes all information such as subscriber number, required service, etc. Once the subscriber name is decoded, the program will access the main database, looking for the subscriber profile and checking if the service request is valid for that particular subscriber.
If the requested service was a mobile-to-mobile call, the system software will search for the profile and status of the called party, checking if the party is busy or free and if this type of call is valid for the called party. If so, the ST-510 will send a new data packet (via a 4800 baud Roaming Bus) to each site in the network where the called party is authorized to roam. The ST-510 at the remote site(s) will then direct a free SmarTrunk II controller to page the called party.
At this moment, the SmarTrunk II controller will look for the acknowledgment signal from the called party. If the called party is out of range or his/her radio is turned off, the main ST-510 computer will immediately transfer the caller to Voice Mail.
If the called party is within range, the main ST-510 CPU opens an audio path from the original controller (calling party) to the second controller (called party) in a process which requires no more than one-half second beyond the normal SmarTrunk Xpress or SmarTrunk II signaling time. If the called party answers, the conversation takes place as normal. If the called party does not answer within a programmed time, the calling party is directed to Voice Mail. When either party ends the call, all resources are set free and the call information is reported to the call record account file.
Note: ST-853 SmarTrunk II controllers and ST-858 SmarTrunk Xpress controllers cannot co-exist within the same system
SYSTEM REQUIREMENTS
Operators considering a ST-510 Network Switch should first be thoroughly familiar with the Smartrunk Xpress/SmarTrunk II signaling protocols and basic operation, as described in the SmarTrunk Xpress Features Overview, SmarTrunk II System Overview and the operating manual for the ST-853/858 Digital Trunking Controller. The ST-510 system operates with both SmarTrunk II and SmarTrunk Xpress protocol, using the same ST-853 or ST-858 controllers as a conventional SmarTrunk System; however, a new firmware EPROM is required for each ST-858 controller.
Each SmarTrunk controller is connected to the ST-510 switch by two links: an RS-232 data cable and an audio link from the controller's TELCO port to the audio port of the ST-422 board assigned to that controller.
If the system has more than one site, a RS-232 low speed data link(4800 baud) must be installed, plus an audio link for each simultaneous call between sites. The number of audio paths required depends on the anticipated volume of traffic between the various sites at peak times. For PSTN or PBX interconnection, the ST-510 has a conventional line termination for an analog TELCO line (2 wire, loop start).
The system power supply is available in 110 or 220 VAC (50/60 Hz) versions.
WIDE AREA ROAMING
The ST-510 supports two basic configurations for roaming (see Figure 1 below).
Single ST-510 Switch ( Solution 1)
In smaller networks, it is often possible to have a single ST-510 Network Switch support multiple repeater sites. In this example of a ten channel system, the ST-510 and the SmarTrunk controllers are all located at Site B, with the remote repeaters at Sites A and C connected only by audio links (i.e., no data link is required). Different roaming areas may be defined which correspond to the different repeater sites.
For many applications, this may be the most economical scenario because only one ST-510 switch is required to support the entire network. However, there must be a separate audio link for each repeater at the remote site(s), which increases the cost of the linking equipment.
Larger networks may use multiple ST-510 switches, requiring a low speed data bus (4800 baud) to link the switches. In the above example (Solution 2), a ten channel system consists of three sites: Sites A and C each have three channels (with repeaters and ST-853/ST-858 controllers) and a ST-510 switch, while Site B has four channels and a ST-510 switch. Note that the ST-853 controllers are co-located with the repeaters at each site, requiring a real time data channel connecting the three sites. However, this configuration does not require a separate audio path for each remote channel, which may reduce the cost of linking equipment.
In
this scenario, the number of audio links required depends on the anticipated
traffic among the various sites. If most of the traffic is local (intrasite),
then perhaps only one or two audio links may be required between sites.
If so, it is possible that the lower cost of linking equipment would offset
the additional cost of ST-510 switches at the remote sites.
Another factor requiring multiple ST-510 switches is whether telephone interconnect (PSTN or PABX) is required at the remote sites. If so, a remote switch may be required to manage the telco interface functions.
As with the single switch scenario, this service allows customers to locate any subscriber in the entire network simply by dialing the subscriber's number. For this searching process, the system will use only one free channel in each roaming area, and only the two channels supporting the call (one at each site) will remain in use until the call ends. The entire searching process requires only a half second more than the standard SmarTrunk II signaling time.
The definition of the roaming areas and the associated subscriber profiles will be automatically edited using the comprehensive management software included with the system. For more details on the multi-switch scenario, refer to Network Topology.
NETWORKING OVER E1/T1 LINK
Figure #1 shows a standard way to link a ST-510 using a shared or fractional E1/T1 link. On the ST-510 side, there is only a data connection for the Roaming Bus and, in this example, four simultaneous audio ports that may be multiplexed by a digital MUX and inserted into the E1/T1 scheme.
In a real case, it is necessary to install as many audio ports as the traffic will require, but only one data port for each ST-510 to be connected with any node in the network.
ANALOG RADIO LINK
In case of linking using analog radios, the ST-510 will be connected through auxiliary audio ports for audio paths and may use the ST-100 Data Modem for the Roaming Bus connection. The ST-100 may also be used as a phone patch to provide local dial tone at a remote site without a ST-510 switch.
NETWORK TOPOLOGY
In the following examples, the audio channels are shown as single lines but in a real application, they may be multiplexed signals from E1/T1 links.
In the following examples, the orange arrows represent the 4800-baud data channel while the green arrows represent analog audio paths.
Bus
Topology
In this case, note that the ST-510 nodes #2 and #3 will have two data ports, one for each ST-510 connected through.
The greater number of audio lines between nodes #2 and #3 reflect the higher traffic flow, because they must support the traffic between nodes #1 to #3, #1 to #4, #2 to #4, and #2 to #3.
Star
Topology
LINKING REMOTE AREAS
In some applications it may be necessary to place one or more channels in a shadow area to obtain wider RF coverage. In order for all controllers to be connected to the network, it is necessary to place a link between each channel and any ST-510 in the network.
Remote
Repeater Channel
One of the ways to cover a remote area is to leave the SmarTrunk controller
at the primary site and place a remote repeater at the remote high-site.
In this case, all the signaling between the repeater and the controller will be carried by a link. The SmarTrunk controller remains close to the switch, so the audio and data connection will be only wires.
In this application, the Rx-Tx delay in the radio link must be less than100 mSec.
Remote
Controller Channel
In another case, the repeater and the controller are located at the remote
high-site, but audio and data is carried by a link to the main ST-510
switch. In this case, a data and audio link must be used for each channel,
which may increase the cost of the linking equipment.
