When it comes to delivering the best in wireless backhaul solutions, Aviat sets the bar high, and now we have been selected as one of the “best-positioned suppliers” for the OpenSoftHaul (OSH) global RFI sponsored by Telecom Infra Project’s Wireless Backhaul Project Group (WBH PG).
Cell tower, Ghana. Photo credit: aripeskoe2 / Foter.com / CC BY-NC-SA
A growing telecommunications trend in South Africa and other emerging markets across the African continent is the move to cell tower sharing. There are many reasons for this, but the need to reduce capital expenditure (capex) on towers and other infrastructure and retarget spending toward network development, customer acquisition and retention and need to accommodate growing mobile data traffic levels have forced the issue.
The trend toward independent ownership of telecommunications infrastructure such as tower sites, with leasing arrangements for multiple operators on each tower, closely mirrors moves in mature telecommunications markets around the globe, including the U.S. and Europe, as well as other big emerging markets such as India and the Middle East.
Tower sharing prevalent
While there is some reluctance by industry incumbents to offload tower infrastructure because they fear losing market share and network coverage, the tower-sharing model is still becoming more prevalent. This is particularly evident in markets where there are new players trying to penetrate the market, as well as in countries where coverage in rural, sparsely populated areas is needed to drive growth. Other important factors, such as the rising cost of power in South Africa, or unreliable power delivery in other parts of the continent have also helped to drive this trend.
Thus, the adoption of this model has gained significant momentum in Africa since 2008, with major mobile operators in Ghana, South Africa, Tanzania and Uganda striking deals to offload existing infrastructure to independent companies. These independent “tower operators” handle the operation and management of these towers, leasing space back on the towers to multiple network operators. This helps to reduce operating costs, improve efficiency and potentially boost an operator’s network coverage significantly and rapidly.
Smaller equipment requirements
To accommodate multiple network operators on a tower and cell site, smaller antennas are preferred, with additional requirements for smaller indoor equipment that draw less power. This configuration helps to decrease power consumption and cooling requirements resulting in more efficient use of diesel generators during times of power failure. However, having smaller antennas affects transmission power, capacity and efficiency. As such, mobile operators are turning to on-site solutions that offer all these benefits, but do not compromise on quality of service, capacity or data transmission speeds.
This also extends to the backhaul network, which often poses the most significant challenge for mobile network operators, especially as mobile networks continue to evolve from 2G and 3G to LTE. For example, as mobile networks continue to evolve, backhaul network architectures will need to change from simple point-to-point to more complex ring-based architectures. Operators that choose to share infrastructure will need on-site equipment that is capable of accommodating these changes, while still offering optimal transmit speeds and reduced operational costs.
Traditionally, most network operators also used optical fiber for their high-capacity fixed line core/trunking networks. However, as tower sharing becomes more prominent fewer operators are willing to spend the capital required to enable fixed-line backhaul from shared sites due to the associated costs. Therefore, more operators are turning to wireless backhaul as a suitable solution to transport data between the cell site and the core transport telephone network.
More capacity needed
As users demand more capacity on the access portion of the network, the core/trunking network also needs to sufficient capacity to be able to transport the aggregated traffic from all these sites. Many operators have turned to high-capacity trunking microwave systems to provide the required high capacity. These high-capacity trunking microwave systems have traditionally been installed indoors, usually in a standalone rack. They were also installed in a way that radio signal strength diminished significantly before reaching the antenna at the top of the tower, ,necessitating a bigger antenna to compensate. These all-indoor configurations also required big shelters and costly air conditioning.
Developing new technologies
In an effort to improve the efficiencies of mobile backhaul to meet modern demands, tower operators and their solution providers are reconfiguring these shared sites, and new technologies are being developed to solve these challenges.
For example, split-mount trunking solutions allow for up to four radio channels on a single microwave antenna, and lower costs associated with deploying and operating ultra-high capacity microwave links for increased capacity. Smaller and lighter antenna solutions can also be lifted and installed higher on towers more easily, which helps to decrease tower space and loading requirements, making these solutions less prone to wind damage. Moving radios from the shelter to the tower, next to the antenna, further reduces deployment and operational costs and simplifies antenna connections (e.g. eliminates inefficient, long waveguides; costly unreliable pressurization/dehydration systems). In these cases, smaller shelters or cabinets can be used, which decrease air-conditioning requirements even further.
However, regardless of how tower operators are able to reduce costs and improve efficiencies, the trend of this form of infrastructure sharing is set to continue, which will help to drive increased competitiveness in mobile markets across Africa. This will have a positive impact on the prices end-users pay for mobile data and voice services, and will help to accelerate the availability of connectivity across the continent.
Siphiwe Nelwamondo
Technical Marketing Manager, South Africa
Aviat Networks
Ultra-long microwave links between backhaul towers enable long-distance telecommunications in the Mojave Desert. Photo credit: °Florian / Foter.com / CC BY-SA
Designing and engineering microwave radio networks has always been challenging and a bit of an art—especially when they are ultra-long point-to-point wireless networks. In an article published February 25, 2013, Aviat’s solutions architect Charles Dionne outlines some of the key considerations that need to be made when designing and building these ultra-long microwave backhaul links for point-to-point wireless networks.
The article on RCR Wireless provides an overview and detailed checklist of the relevant items for designing ultra-long point-to-point wireless microwave links including:
Readers will take away more than just a laundry list of potential pitfalls; they will gain an enhanced appreciation of the very specialized skills and thorough understanding of microwave technology that is necessary for successfully implementing point-to-point wireless microwave backhaul.
To help relieve wireless network congestion, the Obama Administration made a commitment to release up to 500 MHz of spectrum for reuse in commercial wireless solutions. In April 2011, the NTIA updated the progress toward this commitment in its first interim report. This 500 MHz of spectrum—comprising 280 MHz of underused commercial spectrum and 220 MHz of federally owned radio spectrum now administered by the NTIA—would help ease the growing shortage of spectrum as demands on the wireless network rise. This demand is primarily fueled by the explosive adoption rate of smartphones and other mobile broadband devices and the corresponding infrastructure—both access and mobile backhaul—required to support their use.
The timescales and conditions for the availability of this spectrum is in the hands of the FCC and is expected to take about five years as the first part of its 10 year plan. However, the first four blocks of spectrum have recently been identified for release by the NTIA at 1675-1710 MHz, 1755-1780 MHz, 3500-3650 MHz, 4200-4220 MHz and 4380-4400 MHz.
It is estimated that an auction of 500 MHz of spectrum could raise more than $20 billion for the U.S Treasury.
Many wireless technology industry commentators expect the lower bands to be taken up for wireless access. But the higher three bands could be allocated for mobile backhaul use to begin the process of easing congestion in the current 6GHz bands.
The microwave backhaul industry welcomes this first step. We look forward to follow through on further spectrum releases—especially in the 4 to 8GHz range—which is suitable for high-capacity trunking backhaul.
Ian Marshall
Regulatory Manager, Aviat Networks
With immense mass-market demand for mobile broadband services, and emergence of new high-capacity mobile devices (e.g., smartphones, tablets) and applications, many of the world’s most advanced mobile networks are struggling to deliver a high-quality consumer experience. Explosion of per-user data consumption, combined with subscriber growth and mobility needs, is putting today’s networks are under tremendous pressure. In addition, as operators continuously evolve networks with the latest technology (e.g., 2G, 3G, 4G) to meet these capacity and coverage demands, network costs are exploding and operators are struggling to keep up profitable businesses.
LTE, representing a 4x capacity improvement over current 3G networks, on its own will be insufficient to address all future capacity demands, as mobile data traffic will double every year equating to a 32x growth by 2014 (Figure 1).
Figure 1: The forecast 32x jump in data demand cannot be met alone by LTE, which can only offer a 4x increase over current wireless technologies.
Increasing spectral efficiency with new versions of LTE will help manage the shortfall, but these solutions are not yet available and again will not provide the volume of capacity necessary. Acquiring more spectrum would help but additional spectrum is costly and in most cases not available. Traffic management approaches such as caching and mobile data offloading are emerging to help manage the load but because of limited cache hit rates, these solutions will be insufficient to address the capacity shortfall. Offload techniques, such as in-home femto cells and mobile offload gateways, are emerging to reduce load on mobile infrastructure, but again they will be insufficient. A new approach is required.
Emergence of Small Cells
To meet these capacity challenges, and address ever-prevalent coverage issues, new small cell network architectures are emerging based on a new generation of low power, small cell (i.e., micro, pico, femto) mobile base stations. ABI Research estimates 4 million pico base stations will be shipped per year by 2015. Being deployed into an existing network on lampposts, utility poles and building walls, these base stations offer a way for operators to meet challenges of urban, suburban and in-building locations. Combined with existing base station infrastructure, these small cells are transforming the flat macro mobile network into a multi-level, hierarchical radio access network (Figure 2).
Figure 2: Combined with existing macro base station infrastructure, small cells are transforming the flat mobile network into a multi-level, hierarchical radio access network.
Small Cell Backhaul: Wired or Wireless
When considering IP mobile backhaul options, operators must first ponder the choice between wireline or wireless solutions. There is generally no “one-size-fits-all” solution, and in reality we’re likely to see a mix of mobile backhaul technologies deployed to meet the small cell backhaul challenge. However, because of challenging utility pole and lamppost deployments, operators cannot count on fixed line options (e.g., fiber, cable, copper/DSL) being ubiquitously available. Moreover, more than 40 percent of the world’s macrocell base stations are backhauled wirelessly and because of these challenging locations, we’re likely to see a much higher percentage of wireless-based backhaul in small cell applications.
Wireless Backhaul for Small Cells: Challenges
Small cell deployments present a number of challenges—not the least of which is impact on mobile backhaul. Operators—and equipment vendors—must consider the key factors below when selecting (and designing) wireless backhaul solutions for small cells:
• Lower cost solutions needed—Smaller cells mean more cells and thus more mobile backhaul. To meet overall cost objectives, lower cost backhaul solutions will be required to make sure small cells can be deployed cost effectively. Typical macrocell backhaul CapEx is about 50 percent of the total base station CapEx, and similar ratios will be required to ensure a cost-effective solution.
• Space-optimized solutions required—To improve street-level coverage and capacity, small cells are being deployed on lampposts and utility poles. These challenging deployment locations place demands on the physical attributes of backhaul solutions. Unlike traditional cellsites, typical dish antennas will not be feasible for such deployments. In addition, because of space constraints and operations costs, backhaul and base station hardware integrated into common enclosures would be ideal.
• Line-of-Sight (LOS) not possible—Street level, metro area deployments mean line of sight to backhaul hub locations are not always—in fact—rarely possible. Requiring large antennas, combined with lack of LOS characteristics, makes traditional point-to-point wireless backhaul ineffective for most small cell backhaul applications.
• Interference must be carefully managed—When it comes to wireless backhaul solutions, close proximity of cellsites creates possible interference issues for the backhaul system. These interference issues are relatively new for backhaul systems and need to be considered.
• High-capacity solutions required—Driven by increasing demand for mobile data, backhaul requirements for small cells are expected to approach macro cell capacity requirements (50-100Mbps per cellsite) in the next three years.
Which challenges matter most will depend heavily on how small cells eventually are deployed. Stay tuned for a followup blog post where I discuss small cell backhaul deployment options and available solutions to address these needs. In the meantime, feel free to leave me your thoughts, or comments.
Gary Croke
Sr. Product Marketing Manager, Aviat Networks