Microwave backhaul networks have historically relied on daisy chain and tree network topologies, ring network topologies were rarely deployed due to bandwidth inefficiencies associated with the SDH/SONET protocols available at the time. Specifically, dedicated protection capacity had to be reserved up-front, and this network capacity was only optimally used in the rare event of network failure, resulting in the waste of scarce microwave spectrum in environments characterized by fast-growing capacity demand. However, this has all changed with the introduction of standards based ITU-T G.8032v2 packet mirowave rings. In this blog, I’ll use a case study to demonstrate the financial advantages of moving to packet microwave ring topologies, and demonstrate how packet microwave rings optimize network capacity and minimize network TCO. New Carrier Ethernet technology based on the ITU-T G.8032v2 standard has emerged to take the place of legacy SDH/SONET networking capabilities. This standard was designed to address IP and LTE packet network requirements while also efficiently exploiting the inherent advantages of ring based network topologies:
- Traffic is sent in two directions around a ring, so network capacity is doubled.
- Reduced capital expenditures (CAPEX) by eliminating the need for fully protected sites.
Given these advantages, together with the explosive capacity demands to support new LTE based services it didn’t take long for ITU-T G.8032v2 implementations to get deployed.
Packet Microwave Ring Advantages
The following analysis is based on a live Middle East and Africa region mobile backhaul deployment that has enabled a mobile evolution to more 3G capacity and support a future move to LTE. In this network most of the existing links were deployed in a 1+1 protected, or Hot-Standby, arrangement in a daisy chain based network topology. The capacity demands on the network forced an evaluation of the best alternatives available to provide the highest network capacity at the lowest network total cost of ownership (TCO). Two approaches were considered:
- Maintain a 1+1 link, daisy chain network based design philosophy. This approach required a move to 2 sets of 1+1 links to support higher capacities, resulting in 8 microwave radios - two working and two protection at each end of the microwave connection. Although this approach doubled the microwave connection capacity, it could not leverage the ring topology advantage of doubling network capacity.
- Utilize an ITU-T G.8032v2 based network design together with 2+0 multichannel links to network high capacity hub/nodal sites together in a ring topology; 2+0 multichannel links leverage 2 underlying active microwave channels to create higher capacity virtual microwave links. This approach efficiently doubles microwave link capacities, and it also increases network capacity at key points in the network by leveraging the ring topology’s ability to double network capacity.
Packet Microwave Rings: 36% Fewer ODUs
In addition to network capacity advantages, the ring based approach resulted in the need for 36% fewer microwave radio outdoor units (ODU) as depicted in the following graphs. This despite the fact that the ring based approach required a few more interconnected microwave network sites/links (23 versus 18) to create ring topologies. The significant reduction of ODUs is due to the fact that higher capacity sites in the daisy chain model need 8 ODUs per high capacity microwave connection, whereas the ring approach only requires 4 ODUs per microwave connection.
Using fewer ODUs also means coupler utilization can also be reduced or eliminated (a coupler is a device that is used to get channels connected to the same microwave antenna). In the case of 2+0 multichannel ring links the network could be designed so that no couplers were required, whereas the daisy chain approach required couplers to bring channels on to the same antenna, adding to the daisy chain deployment cost. Even though the ring approach required a few more interconnected microwave network sites/links together with supporting antennas, the overall expense of the increased number of antennas was counter-balanced by a reduction of antenna size. Nearly 80% of the antennas had a diameter of either 30 cm or 60 cm (1 or 2 feet respectively). This size reduction is extremely important since smaller size antennas require less space on microwave towers and reduced installation effort, further minimizing network TCO. In the end the packet microwave ring technology from Alcatel-Lucent helps operators to optimize network capacity and minimize network TCO. Specifically, the packet microwave ring approach offered the lowest network TCO by reducing the number of radios and couplers required, reducing antenna sizes, and doubling network capacity.
Microwave Transmission website Microwave Backhaul for Long-Term Evolution application note Evolving to microwave ring protection with Alcatel-Lucent 9500 MPR and ITU-T G.8032v2 application note
To contact the author or request additional information, please send an email to firstname.lastname@example.org.