Like the Interstate Highway system in the 1950s, building out a national LTE infrastructure in the U.S. is a major undertaking. The largest challenges in building out an LTE network consider of planning, staging, and deploying the technology at maximum speed and with minimal costs. Mobile operators are in a tight race to build out LTE networks in the U.S. as quickly and cost-effectively as possible, and backhaul is a key component of the job.
There are more than 300,000 2G/3G cell sites in the United States; LTE penetration is at approximately 50,000 sites today. Mobile operators want to have 95% of their footprints covered with LTE within the next year or two, so a massive construction project lies ahead with a tight timeframe for completing it.
To give this some perspective, we can use the Interstate Highways analogy: Building networks to support 4G LTE is similar to the concerted, 35-year effort spearheaded by President Eisenhower in building the Interstate Highway System (IHS), a national network of high speed highways which began in 1956. With the IHS, it wasn’t the size of the highways that meant 35 years of work, it was the sheer number of highways that needed to be built in a specific timeframe. Similarly, network build-out to support 4G LTE is not about the capacity needs of backhaul (as both microwave and fiber both exceed the capacity requirement), but rather the massive construction that is both urgent (speed of deployment) and expensive (cost of build).
Backhaul is the significant factor in accomplishing LTE rollouts. After all, mobile operators can simply overlay LTE base stations on their existing cell site infrastructure to handle the Radio Access Network (RAN) portion of the deployment, but backhaul in most cases will require switching from copper to either fiber or microwave because of the capacity required.
Both fiber and microwave have ample capacity to handle 4G backhaul. It is estimated that it will require 200 Mbps to backhaul 3G and 4G services over the same link, and microwave and fiber both provide this level of capacity. The backhaul must also provide QoS capabilities to discriminate between applications and to deliver the right level of service to each application.
The issues are deploying LTE backhaul quickly and with minimal cost. Today, 50% of the total cell site operations cost for 2G and 3G is associated with backhaul build. These operational costs are proportional to capacity. Since 4G LTE has two to five times more capacity than 3G, we can expect these operational costs to at least double, in line with the increased capacity offering of 4G LTE. 2G and 3G networks are not going away either. It is therefore essential to hold down backhaul costs as much as possible.
What are the choices? Fiber is usually an excellent choice in fiber-rich environments because it is easy to deploy. However, in suburban and rural areas, microwave is a better fit because it is much easier and more cost-effective to deploy in the long run. With fiber, carriers must pay monthly leasing costs and often an up-front fee to have the fiber deployed. In addition, it can take months to run fiber to a distant cell site. Microwave can be deployed in days or weeks and carries no monthly leasing charges because carriers own it.
Another requirement is the ability to carry 2G, 3G, and 4G traffic on the same backhaul link. 2G networks run TDM traffic rather than IP, so the microwave solutions must therefore use hybrid radios that can carry both TDM and IP.
From a deployment standpoint, microwave radios require site surveys and engineering, path planning, and installation. It is therefore essential for mobile operators to work with a technology provider who has strong experience in deploying microwave for cellular backhaul.
Rolling out 4G LTE will require deploying new backhaul to tens of thousands of cell sites, all within a tight timeframe and budget. When fiber is not readily available, microwave technology is the best choice for backhaul technology. But in seeking a solution to the backhaul problem, mobile operators should look for microwave technology vendors who have extensive experience in successfully deploying their products in telecommunications networks. If microwave technology helps to address the cost issues of LTE backhaul, an experienced microwave vendor will solve the logistical issues in getting it deployed.