Backhaul is generally defined as any point-to-point (P2P) communications link between remotely connected sites. It can be wired or wireless. In telecommunications, both fiber and microwave backhaul are common. Cellular basestation sites are connected to the main switching office by backhaul. While fiber probably dominates the backhaul space because of its high-speed capacity, microwave and millimeter-wave backhaul are becoming more widespread.
Millimeter-wave backhaul is particularly attractive for the new small-cell movement. Smaller basestations called picocells, microcells, and metro cells are projected to be widespread in rolling out LTE 4G cellular services in high-density areas. It appears that the best way to connect these cells to the main office is millimeter-wave links.
The typical microwave backhaul bands are 6, 11, 18, 23, and 38 GHz. Unlicensed 60-GHz backhaul equipment is inexpensive but offers limited range due to its high oxygen absorption levels. Some 80-GHz backhaul units are also available. The most popular new millimeter band is the E-band, which covers 71 to 76 GHz, 81 to 86 GHz, and 92 to 95 GHz.
These bands require a Federal Communications Commission (FCC) license. They aren’t afflicted with the high-water and other atmospheric loss effects of 60 GHz, though. The millimeter bands also offer very high data rates from 1 Gbit/s to over 10 Gbits/s in some cases. While the communications range is short, they offer excellent privacy, security, and frequency reuse. The protocol of choice is Ethernet.
The Siklu Etherehaul-1200T small-cell backhaul unit operates in the 71- to 76-GHz E-band (Fig. 5a). It offers a data rate to 1 Gbit/s using adaptive coding and modulation. Features include carrier Ethernet bandwidth-aware quality of service (QoS), service management, and operations administration and maintenance (OAM) as well as advanced timing over packet handling with SyncE or IEEE 1588.