Graphennas: The Wonder Compound Meets Nano-Scale Wireless Communications
Clearing the Air for 5G Wireless
Hype surrounding 5G wireless networks may be more pervasive than the networks themselves, but new research is suggesting practical ways to overcome issues brought on by the very methods of expanding these networks.
If the research—which addresses two of the most prominent wireless expansion methods, mass femtocells and millimeter-wavelength (mmW) antennas—hold true, wireless developers and carriers may have some valuable tools at their disposals to make 5G more of a widespread reality.
Currently, the two expansion methods aim to achieve similar goals but in different ways. Femtocells are already being implemented by commercial carriers to extend a networks’ breadth, whereas mmW antennas are being studied to extend a network’s depth. Femtocells, also known as microcells, exist at the edges of macrocells to allow coverage in spotty areas and boost a network’s overall capacity. mmW antennas, on the other hand, work to leverage underutilized spectrum.
As these methods go from hopeful concepts to deployment in varying stages, their merge with the existing wireless network threatens some problems. For femtocells, the problem is interference issues, and for mmW, it’s determining how the tiny new wavelengths will respond to outside environmental factors.
Studies from IEEE Xplore tackle these issues with proposed solutions for each method, proving that expanding 5G networks with femtocells and mmW may not be as problematic as some may think.
Femtocell solution: Using graph theory to overcome interference
Femtocells risk major interference problems because they operate at the same frequency as macrocells, and simply adding them onto a network will cause signals to cross and bottleneck (a detriment to any carrier).
To solve for this, a research team from the University of California, Los Angeles came up with their own interference management policy using signal scheduling, and taking into account the physical qualities of femtocells. Traditionally, wireless interference can be controlled by adjusting either the power or the scheduling of a signal. Adjusting the power allows signals to be transmitted at weaker levels to not interrupt neighboring messages, but it easily fails when there are too many users in one area. On the other hand, scheduling signals can avoid cross-over no matter how many users are present, but it inherently leads to delays—which is detrimental in today’s market as users consume more delay-sensitive media, such as video.
The team went with the scheduling approach, but used graph theory to maximize the amount of signals that can be scheduled at a given time to reduce delays. With the new policy, signals are scheduled not one-by-one in sequential order, but rather in sets determined by their unlikelihood to cross based on the physics of femtocells. Deciding which sets of signals can go at the same time is based on methods in graph and optimization theory, and is made to ensure a network can meet its minimal throughput and delay requirements.
Sequential scheduling in (a) schedules less than two devices (UEs) per time slot on an average, while the team’s proposed set scheduling in (b) is more efficient and schedules two UEs per time slot.