Sign in Subscribe

VRB (virtual resource block)

Last updated on 

In the context of wireless communication systems, a Virtual Resource Block (VRB) is a fundamental unit of resource allocation used in Long-Term Evolution (LTE) and 5G New Radio (NR) networks. These networks employ Orthogonal Frequency Division Multiple Access (OFDMA) as the access scheme, where the available spectrum is divided into multiple subcarriers. VRBs represent a group of contiguous subcarriers in the time-frequency domain, used for transmitting user data, control information, or reference signals.

Resource Allocation in LTE and 5G NR:

LTE and 5G NR networks utilize a flexible resource allocation scheme to efficiently utilize the available spectrum and adapt to varying channel conditions and user demands. The key elements of resource allocation are:

  1. Frequency Domain: The frequency domain is divided into multiple subcarriers, each carrying a specific frequency. Subcarriers are usually organized in a grid-like structure.
  2. Time Domain: The time domain is divided into time slots, each of which has a fixed duration. These time slots are further grouped into frames.
  3. Resource Blocks: Resource Blocks (RBs) are the basic allocation units in LTE and 5G NR. Each RB comprises a group of contiguous subcarriers across a time slot. The number of subcarriers in an RB and the number of time slots in an RB depend on the specific system configuration.

Virtual Resource Blocks (VRBs) - The Concept:

The concept of Virtual Resource Blocks (VRBs) was introduced in 5G NR to improve the flexibility and efficiency of resource allocation. VRBs are logical entities that represent a subset of the physical Resource Blocks (RBs) and provide a mapping between the physical and logical resource grids.

In 5G NR, the subcarrier spacing (the frequency separation between adjacent subcarriers) can be configured to different values based on the specific use case and deployment scenario. The relationship between the physical RBs and the logical VRBs is determined by the subcarrier spacing and the numerology of the system.

Key Characteristics of VRBs:

  1. Variable Resource Allocation: VRBs allow for variable resource allocation, where the number of subcarriers and time slots assigned to a VRB can be configured independently.
  2. Flexibility and Adaptability: The concept of VRBs provides greater flexibility in resource allocation, making it easier to adapt the system to different channel conditions, traffic demands, and deployment scenarios.
  3. Efficient Utilization of Resources: By enabling more granular resource allocation, VRBs help to achieve efficient utilization of the available spectrum, improving overall system performance.
  4. Support for Different Subcarrier Spacings: VRBs support various subcarrier spacings, making them compatible with different numerologies and deployment scenarios in 5G NR.

Conclusion:

Virtual Resource Blocks (VRBs) are logical entities used in 5G NR to represent a subset of physical Resource Blocks (RBs) in wireless communication systems. VRBs provide a more flexible and adaptive approach to resource allocation, enabling efficient utilization of the available spectrum and improved system performance. By allowing independent configuration of subcarriers and time slots, VRBs contribute to the overall effectiveness and scalability of 5G NR networks, facilitating the delivery of high-speed data, low-latency communication, and support for diverse use cases in the evolving world of wireless communications.