Towers are the lifeblood of the wireless industry, and the tower industry remains healthy and dynamic despite a slowdown in spending on new tower sites. Tower owners report carrier spending on new sites is down, but for many of the construction and engineering companies, carrier spending remains strong as carriers are currently more focused on improving their existing networks than on building or acquiring new sites.
Modifications to cell towers are known as tower amendments and there are a number of reasons spending has shifted toward amendment activity. First and foremost, carriers are looking to squeeze as much performance as possible out of the existing assets for financial reasons. They are spending heavily on spectrum.
Despite numerous calls on their capital, carriers cannot stay competitive without continuing to invest in their macro networks. Right now much of that investment is focused on building network capacity by adding new radios and antennas to wireless sites and on building fiber networks.
In the meantime, much of the tower work is focused on network modifications. Carriers continue to add LTE bands and move radio heads to the tower tops, and to swap 3G equipment for LTE equipment. They are also starting to add more multiport antennas and adding software designed to aggregate frequencies. As demand for mobile data continues to accelerate, mobile operators are leveraging new technologies to maximize their spectrum assets and this is driving tower amendment activity.
LTE Upgrades Drive Amendment Activity
LTE upgrades remain the primary driver of tower amendment activity. Carriers are deploying LTE across their network footprints and adding capacity. This often means adding new radios and antennas to support additional spectrum bands.
There is demand for wideband antennas that support more spectrum bands, for then carriers do not need to add a new antenna to each tower for each spectrum band. This is a key consideration.
Once operators have a wide range of spectrum bands, it requires them to go up, and not just put up an antenna that covers one range of frequencies; they have to cover multiple ports, referred to as multiport. Today there are examples of 6, 8, 10 or 12 ports – six bands, if you will, going up on these towers. Also, many towers now support more than one operator, leaving even less room at the top for new antennas. Wideband antennas enable carriers to maximize their use of the available space on the towers.
Some operators are also evaluating leveraging their spectrum with small cell deployments. This network densification may result in tower activity with the operator backhauling a significant amount of small cell traffic to base stations located at cell towers and other macro sites. With small cells, towers become even more valuable because they support the small cells. Small cells have to hone back to something for backhaul, so what do they hone back to? They hone back to the macro, and so the small cell is really just an extension of a macro sector.
While towers and small cells do work together, some tower spending could shift to small cells in the years ahead. Network densification will account for some of the network spending.
The big question on the tower front is really the tradeoff between investing in non-macro site densification versus macro sites. Those economics are really going to drive go-forward spending in this space over the next three or four years.
Fiber Adds Flexibility
Fiber connections create new choices for operators because base station equipment no longer needs to be so tightly coupled with radio equipment. Connecting base station equipment to a remote radio head with fiber enables operators to locate their radios atop the towers next to the antennas, and to move the base station unit to a less expensive location. This is because fiber does not have the same signal loss as cable; so the radio head and the base station can be physically separated if they are connected by fiber.
Fiber-to-the-antenna is one of the most efficient ways to implement LTE. In this architecture, remote radio units are mounted at the top of the tower, or in the case of rooftop deployments, as close to the antenna as possible. In both scenarios, electrical and fiber connections are required to power the radio and give it a signal path.
Fiber is used to connect remote radio heads to the base station, and cable is used to connect the RRHs to power. Hybrid cable is a combination of fiber and power cable in a single run, and can reduce tower loading by up to 33 percent. These runs typically include multiple fiber strands so that one hybrid cable run can support the remote radio heads of multiple carriers. Fiber at the tower can generate significant cost savings for mobile operators. Placing the radio head next to the antenna means operators can eliminate the power amplifiers often used to compensate for signal loss when these elements are separated. They can also eliminate the climate control equipment used to cool those amplifiers, with energy bills typically going down because there is no longer a need to power large amplifiers and the associated cooling equipment. Battery backup for these elements can be eliminated as well. In summary, fiber can mean less equipment at the tower site. The next step may be moving the base station away from the tower altogether.
In some areas of the world, they are starting to deploy centralized BBU. Centralized BBU simply means that multiple BBUs can be pooled in a data center or central office to power these RRHs that are located in different areas of a city or town. So centralized BBU really brings additional cost savings to the whole mobile infrastructure. Fiber can clearly reduce costs for mobile operators, but only if it is efficiently deployed. A fiber connection that is not tested properly can result in a second tower climb.
Conversely, state-of-the-art test equipment means fewer climbs as one tower technician can stay on the ground while the other climbs up, instead of both technicians scaling the tower. This can reduce both costs and risk of injuries. Testing fiber connections is a new skill set for many tower technicians, who are more accustomed to working with cable.
Getting into the fiber connector, and then plugging them in together in the coupler, is tricky. If a connector is not fully plugged in, the connection between the radio head and the base station will be faulty. Test equipment designed to validate this link is valuable to service providers like network installation specialists as it can help them detect a problem while the technician is still on the tower. Construction crews cannot access the proprietary base station software, but they can test the link using the common public radio interface. CPRI validation will also be required with time.
MIMO and Carrier Aggregation
Multiple-input multiple-output (MIMO)means antennas at both the tower and the end-user device send and receive multiple data streams within one channel. Right now most high-end smartphones support 22 MIMO, but some operators are installing new tower-top antennas that can transmit four data streams. Since there are still just two receivers on the smartphone end, this is referred to as 42 MIMO. The next step is 44 MIMO, or four data streams to and from the tower and the device. Vendors have developed four-port side-by-side antennas, which will enable operators to deploy 44 MIMO using just one antenna. This efficiency is key to carriers and tower companies, both of whom want to get as much use as possible from the valuable real estate atop cell towers.
Of course 44 MIMO cannot deliver on its promise until there is end-user device support. Essential components of massive MIMO will include many physically small, low-power antennas; aggressive spatial multiplexing; and utilization of measured channels. Spatial multiplexing refers to the separate encoding of data streams so the same space can be used by two separate streams. Whether enabled by many small antennas or a smaller number of large ones, massive MIMO will almost certainly mean more trips to the tower tops. But for now, the hype around the technology is more massive than the reality.
While MIMO streams data over several paths within a channel, carrier aggregation is the use of more than one channel to deliver a single data stream. By aggregating more than one frequency band or carrier, this technology can deliver more bandwidth per cell site. It does not typically require a new piece of hardware at the tower, but it does require the installation of new network software.
Sectorization is often called cell splitting as it uses multiple antennas to enable one site to support multiple frequency bands. Operators often deploy three antennas, each with a 120-degree opening. Recently, antenna vendors have been helping operators compress the bandwidth to 60 degrees or even 30 degrees.
Horizontal beamwidth, which is the width of the antenna's primary beam, impacts sector overlap, which is something operators want to avoid. Horizontal beamwidth is impacted by the length of the antenna, which also impacts power requirements and weight on the tower top. The use of directional sector antennas may substantially reduce the interference among co-channel cells, allowing for denser frequency reuse. Interference caused by sector overlap can also be managed by multibeam antennas.
Multibeam antennas broadcast multiple beams from one antenna with unique beamforming and beam-shaping capabilities, enabling engineers to finely craft their sectors. These capabilities improve noise suppression between sectors, limiting the risk of interference. Multibeam antennas add instantaneous, cost-efficient capacity to macro sites in a minimized overlap pattern design
Point-to-Multipoint Mobile Backhaul
Point-to-multipoint solutions usually require new equipment at the macro sites. A single access point can backhaul a number of remote terminals at other macro sites. Fiber is not everywhere, and some of the locations that need more cellular capacity are places where running fiber is prohibitively expensive for mobile operators. And it is here that point-to-point and point-to-multipoint mobile backhaul may be used.
Will Drones Revolutionize the Tower Industry?
Unmanned aerial vehicles, or drones, are useful for three purposes in the tower industry – pre-installation inspections, post-installation/close-out inspections, and safety support.
Data is generated from aerial photographs, and the software enables operators to search and access tower images more quickly than they have in the past.
The entire tower can be modeled and hundreds of photos collected and then fed into a CAD-type software program that creates a 3-D model, which can be fed into every part of the tower. The photos may then be analyzed and ensured that everything is up to spec. Whether the antennas are installed in the right location and at the right downtilt, whether all the wires have been connected correctly, whether all the weatherproofing is in place correctly – all these issues are easily addressed.
Drone service providers are sharply divided over what drones may mean for the industry going forward, but they agree the information drones provide is invaluable.
In addition to the 3-D CAD packages drone cameras can create for tower companies, drones can make an important contribution to climber safety too.
UAS use can assist with scope of work including tower-site bid walks, tower-site hazard inspections, tower structural inspections, tower photo close out packages, etc. Additionally, utilizing UAS in this manner will reduce the numbers of times an elevated worker must ascend and descend a tower each day and, therefore, reduce the amount of repetitive climbing stress that is placed on the tower technician. Less time spent climbing towers and searching for photos could eventually mean the industry will need fewer climbers. Jobs will shift to new goals and tower technicians will want to become drone pilots.
The next step for drones will be actually touching the towers, and with robotic arm technology, drones could perhaps replace tower technicians. Of course at this stage, this is totally debatable.
Based on an article by RCR Wireless