Competition in the mobile industry is continuing to increase as markets saturate, subscribers become more demanding and mobile broadband traffic grows at an astonishing rate. In the face of heightened competition, mobile operators are seeking cost-effective network solutions to improve coverage, capacity and overall service reliability. Increasingly, mobile operators are looking to overlay small-cells to address local coverage and capacity challenges in their networks.
Although small-cells have been available virtually as long as mobile communications, small-cell radio base stations have only recently become sufficiently cost-effective for large-scale implementations. These implementations not only depend on low-cost radio equipment, but also require that the small-cells are sufficiently integrated and automated for cost-effective implementations, operations and backhaul capabilities.
While a great deal of attention has been paid to optimizing the costs for implementing small-cell radio infrastructure, recent efforts have focused on small-cell backhaul solutions that are capable of addressing the needs of high-capacity demands. Key to these backhaul solutions are low equipment costs and “zero-footprint” form-factors, flexible architectures and automated operational capabilities.
Small-cell backhaul providers including Alcatel-Lucent, BLinQ, E-Band, Ericsson, Ceragon, Cambridge Broadband, Radwin and Silku have introduced a variety of innovations to lower the small-cell backhaul equipment costs with integrated solutions that aim to deliver zero-footprint form-factors.
The small-cell industry has established a $5,000 average target cost for each small-cell implementation and is aiming for backhaul to constitute 20-30% of this cost, namely between $1,000 and $1,500. This price target challenges conventional backhaul solutions and has resulted in a variety of innovations, such as highly integrated and purpose-built architectures, seamless carrier grade Ethernet, and the use of both licensed and unlicensed radio spectrum for wireless links.
For most implementations, further innovations are still needed to reach the price targets that are being pursued by the industry. Given their impact on backhaul costs, we expect that many of the innovations being pioneered for small-cells will ultimately be applied to macro-cellular solutions in the future.
Flexible and reliable architectures
Unlike traditional macro-cellular backhaul, which consists of carefully architected point-to-point solutions, backhaul solutions for small-cells must have sufficient flexibility to enable radio base station sites to be implemented rapidly and cost effectively. This calls for point-to-point and point-to-multipoint solutions that are optimized among a tapestry of transmission solutions available, whether fixed fiber or copper or microwave radio. In most cases operators lack fiber or copper resources at the small-cell sites, and must use radio technologies for lateral connections to these sites.
Since these lateral connections are over a relatively short range, high-frequency microwave solutions, such as those operating in the E-Band (70- to 80-GHz range) and more recently the unlicensed V-Band (6-GHz range), have been adopted. While some industry pundits suggest that these solutions can be deployed with non-line-of-sight (NLOS) links, we believe that these solutions will only operate reliably with LOS links.
Lower frequency implementations are necessary in cases where NLOS links are required and, therefore, typical small-cell implementations will include radio links operating among sub-10-GHz, 10-30-GHz and E-Band and V-Band frequency ranges.
Backhaul solutions must be capable of adapting as small-cell implementations are modified and expanded and must also be capable of self-healing in cases where link failures occur. When small-cell solutions are implemented at scale, conventional backhaul optimization solutions cannot achieve the operational efficiencies needed. In response, small-cell backhaul solutions are increasingly embracing the principles of self-organizing network (SON) technologies, which include automated infrastructure provisioning, configuration management and optimization, and self-healing capabilities. This represents a natural extension of the SON capabilities that are being applied to the small-cell radio access network implementations. It is underpinned by a broader industry trend toward operational automation.
Fueled by the strong market momentum, small-cell backhaul solutions will benefit from significant innovation over the next two to three years. While we expect these innovations will address many of the technical and economic challenges for small-cell backhaul, they will require mobile operators to transition from the status quo and embrace technologies such as point-to-multipoint, SON automation, ultra-high frequency operations and in some cases the use of unlicensed radio spectrum bands. It is this transition from status quo that will ultimately determine the rate of small-cell adoption.
Phil Marshall is chief research officer at Tolaga Research