Spectrum efficiency

Beam Forming

To better cover changing, dynamic network demand, beam forming allows a MIMO configuration to adapt to changing conditions and focus in areas of increased demand while reducing interference elsewhere.

Multiband combiners

Antennas can be shared by combining multiple radios into a single RF path at the antenna feeder, multiplying equipment utilization.

Multiport antennas

Multiple input/outputs allow a single antenna to integrate multiple antennas simultaneously within the same package, allowing one antenna to perform the work of two or more.

Splitting sectors

Sector splitting is the practice of increasing capacity by splitting a sector into multiple cells. Using multibeam antennas to split a single beam into multiple beams, the same number of antennas can carry more traffic while ensuring the beams don’t interfere with each other. CommScope’s six-sector solution is a highly efficient turnkey example of multibeam technology. CommScope even offers a solution that provides up to 18 beams from a single antenna, an industry first.

Small cell and DAS deployments

One of the best ways to improve utilization of a given amount of spectrum is to increase the number of cells. Small cells and distributed antenna systems (DAS) can be deployed in densely-populated urban areas where demand is high, but macro site availability is not.

Simplify installation

Installation errors are a frequent cause of PIM, as a mistorqued connection can go unnoticed until long after the work is done. Pre-assembled, factory-configured and PIM-tested tower tops, such as CommScope’s SiteRise™ solution, can speed up installations and reduce opportunities to introduce PIM.

Monitoring and detection

Onsite PIM testing can isolate problems. Modern PIM testing equipment can check all frequencies and sectors with a single unit that injects signals into the downlink to spot PIM in the uplink, where PIM is most harmful.

RF planning

4G/LTE performance drops dramatically where cell boundaries overlap—a significant challenge when increasing cell density. Advanced site features like remote electrical tilt (RET), sector sculpting and low-side lobe antenna patterns can greatly reduce interference (received and given) from adjacent or co-sited sectors. Narrow-beam antennas can be more precisely sculpted to cover a specific area and minimize cell overlap.

Equipment selection

Purchase 100 percent PIM-tested equipment and, if possible, avoid combining components from low-quality manufacturers. Carefully review existing components, jumpers, etc., to ensure they remain in good condition and are compatible with present requirements. Replace and upgrade as needed to reduce the chance that PIM will arise from mismatched equipment. Interference mitigation filters (IMFs) can be employed to stop some interfering signals at the antenna.

Interference analysis.

Examine the transmit and receive frequencies in use at the site and identify those that may interfere or generate PIM. Ensure that any transmitters or receivers that cause a third-order PIM issue do not share a common RF path. CommScope’s Band and Block calculator can help facilitate the analysis.

And it is part migration, as the advantages of MIMO evolve into ever more efficient standards that can further multiply the carrying capacity of a given amount of spectrum.

It is part adoption, as the emergence of network densification practices and small cell technologies attest.

It is part prevention, as interference can greatly reduce network efficiency and drain utility—as well as revenue—from your spectrum.

Prevention, adoption and migration

Multiple antenna techniques

Network densification

Interference mitigation

The only static factor a wireless operator can depend on is limited access to additional spectrum, whether governed by regulation or cost. But, by using these practices to develop and follow an integrated strategy, that operator has a wide variety of options to increase the efficiency and profitability of the spectrum at hand, and make more efficient use of new spectrum as it becomes available.

Optimizing spectrum efficiency is a big idea. Successful execution follows multiple related yet distinct paths, each with its own best practices and preferred solutions.

In the here and now, however, making the move to 4x4 MIMO represents a valuable opportunity to optimize existing spectrum use. These best practices can maximize your MIMO investment:

However, the industry is now migrating to 4x4 MIMO, which stands to potentially double again the amount of traffic an operator can move within given spectrum. The future promise of massive MIMO elevates the practice to virtually unlimited scale via a dynamic network of hundreds or even thousands of antennas over a wide area.

Multiple-input, multiple-output (MIMO) antenna technology, in its traditional 2x2 deployment, can ideally double cell capacity by doubling antennas and using parallel signals to add a second “lane” to the user link on the same spectrum. 2x2 MIMO means there can be two transmission paths simultaneously using the same frequency.

Operators also have an opportunity to magnify the effectiveness of the spectrum they have through network densification. In general, these practices improve density of capacity in a given spectrum bandwidth and geographic area when applied with these best practices:

With so many places for interference to occur, it’s hard to isolate and address. These best practices and solutions can help solve the interference challenge:

One of the costliest and most elusive kinds of interference is passive intermodulation (PIM), which is interference arising within the RF path itself due to interaction between two or more carrier frequencies. Internally-generated PIM is generally caused by nonlinearities—that is, improperly installed or torqued connectors, poor material selection, damaged cables, water infiltration or other defects in the RF path. PIM can also be caused by external objects.

Perhaps the most diverse and difficult challenge is that of interference. It can come from a number of sources, internal and external to the cell site—including nearby electrical equipment, poor equipment connections, or interfering signals from nearby radio installations. Within a cellular network, interference between co-sited or adjacent cells is a constant concern. Interference reduces available throughput; one can increase the power to regain lost throughput by brute force, but that approach is expensive even where it’s possible. Even worse, if power increases are applied to every site, there is no net gain to the network. LTE/4G networks are particularly vulnerable to interference—much more so than 3G networks are.

Best practices for a higher-capacity network

Spectrum efficiency:

One of the most restrictive limiting factors mobile operators face is that of available spectrum. While it is possible to purchase more—though those opportunities are fewer and fewer—it comes at prohibitive cost. Faced with rising demand, operators therefore are forced to find other ways to optimize the use of bandwidth within their current spectrum. It’s as much a business challenge as it is an engineering one. To maximize spectrum use, the first step is to identify and remedy inefficiencies wherever they arise. This takes a holistic approach, ranging from the technical to the strategic. There is no single weak point but a host of challenges that can reduce efficiency and negatively impact spectrum ROI. Let’s examine some of the most common sources of spectrum inefficiency and the best practices available to optimize the spectrum you have.