Where Can You See Subcarriers or Resource Blocks (RBs) in LTE?

QXDM (Qualcomm eXtensible Diagnostic Monitor)

• Logs related to RBs, subcarriers, and OFDM symbols can be checked in:
• LTE_PHY_PDSCH_Packet (Downlink RB allocation)
• LTE_PHY_PUSCH_Packet (Uplink RB allocation)
• LTE_PHY_Connected_Mode_Measurements (CQI and signal quality)
• LTE_MAC_UL_Buffer_Status (UE buffer for uplink scheduling)

Wireshark (LTE PCAP Analysis)

• RB and OFDM symbols can be analyzed in S1AP and MAC layer messages.

Network Simulation Tools (like Keysight, TEMS, Rohde & Schwarz)

• Provide graphical views of subcarrier allocation over time.

Relation between Subcarriers, Resource Blocks (RBs), and OFDM Symbols:-

1. Subcarriers vs. Resource Blocks

• A Resource Block (RB) consists of 12 subcarriers in the frequency domain.
• Each subcarrier has a bandwidth of 15 kHz, so an RB spans 180 kHz.
• Multiple RBs form the LTE channel bandwidth (1.4, 3, 5, 10, 15, 20 MHz).

2. Resource Blocks vs. OFDM Symbols

• An RB extends across time and frequency.
• In time, it consists of 7 OFDM symbols per slot (normal CP).
• In frequency, it consists of 12 subcarriers.
• A TTI (Transmission Time Interval) = 1 ms = 2 slots = 14 OFDM symbols.

·         Each square represents a single subcarrier carrying a modulated symbol.

·         An RB contains (12 subcarriers × 7 OFDM symbols) = 84 REs (Resource Elements).