A vertical cavity surface-emitting laser (VCSEL) relies on a three-dimensional (3D) structure for light emission. A photonic crystal surface-emitting laser (PCSEL) incorporates a 2D photonic crystal (PhC) layer to manipulate light emission. Those structural differences lead to different performance and application possibilities. An obvious difference between the various types of semiconductor lasers is the beam…
What is precoding? What does it do?
Precoding is a signal processing technique that modifies the phases and amplitudes of wireless signals to combat channel distortion and optimize the quality and reliability of data transmissions. It can support beamforming in multiple-input, multiple-output (MIMO) and massive MIMO antenna arrays. This article reviews some of the benefits of precoding, looks at how it’s implemented,…
How does mobile edge computing work?
Mobile edge computing (MEC), also called multi-access edge computing or simply multi-access computing, is part of the confluence of the Internet of Things (IoT) and mobile devices. MEC doesn’t mean processing data on mobile devices. MEC simply processes data closer to its origin. Instead of sending data to the cloud, MEC utilizes edge computing resources…
How does a 5G core work?
A 5G core (5GC) provides the central control and management for a 5G network. It roughly corresponds with the Evolved Packet Core (EPC) that supports converged voice and data services on a 4G Long-Term Evolution (LTE) network. The 4G EPC is a flat architecture using point-to-point connectivity and is limited in scalability. The 5GC is…
What is the 5G protocol stack?
The 5G protocol stack is the architecture of protocols within a 5G network that perform specific functions like managing data transmission, error correction, and resource allocation. It exists as two separate elements: the control plane (CP) and the user plane (UP). It’s more complex than the 4G protocol stack due to the numerous advanced features…
What is beamforming?
Beamforming uses phased array antennae systems to focus the wireless signal toward a specific receiver or target instead of an omnidirectional broadcast. Combined with massive multiple input / multiple output (MIMO) antenna technology, beamforming is a key enabler of faster data rates and higher device densities supported by 5G networks compared with 4G technology. The…
What are the integration and test issues with O-RAN?
Integration and test issues with Open Radio Access Networks (O-RAN) arise from their multi-vendor architecture. O-RAN consists of separate elements, such as radios, baseband units, and software, that can be sourced from different vendors. O-RAN was developed to promote greater flexibility, competition, and cost-efficiency compared to proprietary RAN alternatives. The elements are complex sub-systems that…
What are the fiber options for 5G fronthaul?
Fiber is required to deliver low latency, which is crucial for a 5G fronthaul between the base station and the core network. Several fiber options can increase installation density and/or flexibility in this fronthaul. Common choices include bend-insensitive fiber (BIF), OM5 fiber, ultra-low-loss (ULL) fiber, and reduced-diameter fiber. Each offers different performance tradeoffs for specific…
What is a scheduler and what does it do in a 5G network?
A scheduler dynamically allocates resources, including time, frequency, and power, to serve user equipment (UEs) connected to a base station (gNB) on a 5G network. Delivering high-quality service (QoS) to diverse 5G use cases, such as ultra-reliable Low-Latency Communication (uRLLC), Massive Machine-Type Communication (mMTC), and Enhanced Mobile Broadband (eMBB), is critical. Scheduling is not explicitly…
Why do high frequency signals reflect?
High-frequency signals, like those used in 5G communications, are reflected by impedance discontinuities. Their shorter wavelengths can change their impedance. When a signal arrives at an impedance transition, part of it is absorbed and transmitted, and part is reflected. The strength of the reflection depends on the magnitude of the impedance mismatch. The phenomenon of…