Cell-Site Router Redundancy

Used in conjunction with Cisco MWR 1941-DC-A Mobile Wireless Edge Router, the Cisco T1/E1 RAN VWIC supports router redundancy at a cell site while sharing a single T1/E1 Abis/Iub and backhaul links to yield highly available RAN transport. A pair of Cisco MWR 1941-DC-A routers is deployed at the cell site, providing an active and standby router for redundancy. A failure of one Cisco MWR 1941-DC-A router, or a component of the router, causes the standby router to take over as the active router for the cell site. Each pair of Cisco MWR 1941-DC-A routers at the cell site is identical in hardware configuration, and connected to each other through the integrated 100BASE-T interfaces. The individual T1/E1 links to a Cisco MWR 1941-DC-A are cabled from a single T1/E1 termination block in the cell site, connecting to both the active and standby routers utilizing a Y-cable. The redundancy design to control the active/standby transitions of the router pair uses Hot Standby Router Protocol Plus (HSRP+) to control the relays on the Cisco T1/E1 RAN VWIC in each router, which ensures that the relays on the active router are closed and the relays on the standby router are open to avoid double termination of the T1/E1 links.

Depending on the Cisco MWR 1941-DC-A router implementation, the Cisco T1/E1 RAN VWIC can be used in a standalone router or in redundant Cisco MWR 1941-DC-A router configurations. For redundant configurations, a special Y-cable is required to connect the active and standby routers. The Y-cable provides a dual E1 or T1 PRI connection.

The specifications of the Y-cable are: CISCO1841-ADSLI

• Cisco T1/E1 RAN VWIC Y-cables should be made with four twisted-pair, shielded, 28-gauge cables.

• The cable length of each stub (from the RJ-48C connector to the junction point) should not exceed 3 inches (76 mm).

• The cable length from junction point to the patch panel is determined by the customer.

• All signals that propagate in the same direction must share the same twisted pair. For example, RX TIP and RX RING must form a single twisted pair.

• All unused twisted pairs should be cut flush on both ends of the cable. Any unused wire in a twisted pair where one wire is in use should be cut flush at both ends.