1. Linked Capacity Plus. General Information. Requirements


When operating in Linked Capacity Plus Mode, MOTOTRBO trunks the logical channels of multiple MOTOTRBO repeaters at multiple locations and combines the logical channels into one logical channel. This allows radios to share the logical channels and increase the RF coverage area of a MOTOTRBO system.

Linked Capacity Plus (LCP) is a trunked multisite multi-channel configuration of MOTOTRBO, which combines both the Capacity Plus and IP Site Connect configurations. This combined configuration requires only software updates for radios and repeaters, but does not require any new hardware.

Linked Capacity Plus allows up to 15 sites in a system. Each LCP site can have up to 6 trunked repeaters (12 logical channels) and 3 Data Revert repeaters (6 logical channels) per site. It is not a requirement to have the same number of repeaters at each site.

NOTE: Only repeaters with 32 MB of internal memory (e.g. DR 3000 or MTR3000) can support the LCP configuration.

The call start-up of LCP is a combination of IP Site Connect and Capacity Plus configurations with the following enhancements:

- LCP supports both local and wide area talkgroups. A wide area talkgroup call lights up only the sites which are statically associated with the talkgroup. Please note that if even one of sites does not have idle channel for Wide Group Call, then this call won’t be established. So to transmit Wide Group Call, all associated sites should have idle channel for this call. In Master codeplug you can set amount of Reserved Wide Area Channels if needed.

- The talkgroups not defined as wide-area are local talkgroups. A local call ‘lights-up’ only one site where the initiating radio is located.

- The LCP Private Call initially “lights-up” all the sites but after approximately 400 milliseconds, the call continues only at the sites (at most two) where the source radio or destination radio are present.

- LCP allows a customer to reserve a number of logical channels for wide area talkgroup calls only.

- Just like a Capacity Plus system, an LCP system has no controller. Repeaters of a site trunk the logical channels available at the site. The trunking process in LCP is similar to that of Capacity Plus. Repeaters of a site do not participate in trunking the RF resources of another site. Each site trunks their channels independently.

All repeaters at a site must be on the same LAN, in other words, they must be behind the same router and plugged into the same network switch. It is strongly recommended that no other device be present on the LAN. The broadcast messages may produce some adverse effects on the other devices present on the LAN.

The router must support NAT. In NAT, internal UDP/IP addresses are translated to external UDP/IP addresses. In the simplest and most common configuration, an Ethernet switch with a router is used to connect all the repeaters at a site. Although Linked Capacity Plus works with most off-the-shelf network devices, the following Ethernet switch and router are suggested for use (recommended by Motorola).

• Switch – HP Procurve 2510-24 (J9019B)

• Router – HP MSR 20-20


The backend network cannot be based on dial-up connection (due to small bandwidth) or Satellite Internet access (due to large delay).

Note! For LCP software versions R02.10.00 and prior, the router at the Master repeater’s site should be capable of hair-pinning, to ensure that the firewall is open to limited UDP and IP addresses. In software versions R02.20.00 and later, LCP can work with, or without hairpinning capabilities in the router at the Master repeater’s site. When a non-hair-pinning router is utilized, each LCP repeater at the Master repeater’s site must be configured with a unique static IP address and a unique UDP port. The Rest Channel/Site IP address must also be configured as a unique static IP address and a unique UDP port for the site. If a non-hair-pinning router is utilized, the router must be configured to “no port address translation/port preservation for UDP”.

Every LCP system needs one repeater to act as the Master. The Master repeater has a static IP address, while other repeaters can have static or dynamic IP addresses. All the repeaters in the LCP configuration register with the Master using its static IP address.

The Master then notifies all the devices whenever the IPv4 address of a device changes. The devices may be behind firewalls. For successful communication between two devices (D1 and D2), the firewall of D1 must be open for messages from D2 and vice versa. Since the IPv4/UDP address of an IP Site Connect device is dynamic, it is not possible to manually configure the firewalls. The Link Management procedure overcomes this problem by periodically sending a message from D1 to D2 and vice versa. On a receipt of an outbound message (for example, from D1 to D2), the D1’s firewall keeps itself open for a short duration of approximately 20 seconds for an inbound message from R2. A device sends the dummy message to another device only if they are parties to the same call.

In LCP, a channel is configured either for trunking or for data revert. But both channels of a repeater should be used for the same purpose. In LCP, a Data Revert Channel can be configured either as a local Data Revert Channel, or as a wide area Data Revert Channel.

A Data Revert Channel could be either an Enhanced GPS Revert Channel or a normal Data Revert Channel. Each logical channel of a Data Revert Repeater can be independently configured either as an Enhanced GPS Revert Channel or as a normal Data Revert Channel. A radio has a list of all Trunked Channels and a list of Data Revert Channels for each site.

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