Signal analyzer UMTS - voxo22/hackrf-spectrum-analyzer GitHub Wiki

3G UMTS (Universal Mobile Telecommunications System) is a third-generation mobile communication technology developed as part of the IMT-2000 family. It was designed to provide higher data rates, improved voice quality, and multimedia services compared to second-generation (2G GSM).

UMTS uses W-CDMA to allow multiple users to share the same frequency channel through different spreading codes. This enables efficient use of radio spectrum and supports simultaneous voice and data services.

Typical bandwidth of UMTS downlink channel is 5 MHz.

UMTS analyzer searches for downlink scrambling codes, decodes CPICH/BCH/System Information and estimates code-domain air load.

Cell table columns

  • PSC - Primary Scrambling Code.
  • PLMN - Public Land Mobile Network.
  • LAC - Location Area Code.
  • Cell ID - UTRAN Cell Identity.
  • UARFCN - UMTS Absolute Radio Frequency Channel Number.
  • CPICH - Common Pilot Channel frequency.
  • Air load - code-domain occupancy estimate.
  • Code group - one of 64 downlink primary scrambling-code groups.
  • Ec/N0 - pilot energy relative to received spectral density.
  • RSCP - Received Signal Code Power, shown here as uncalibrated dBFS.
  • CFO - carrier frequency offset.
  • IQ - detected complex-sample orientation, normal or conjugated.
  • BCH - Broadcast Channel transport status.
  • MIB / SIB1 / SIB3 - decoded system information status.

System details

  • Primary Scrambling Code - physical-layer cell identity, not globally unique.
  • PLMN - public mobile network identifier decoded from MIB.
  • Location Area Code - circuit-switched mobility area from SIB1.
  • UTRAN Cell Identity - 28-bit cell identity from SIB3.
  • RNC / local Cell ID - conventional split of the 28-bit identity into 12-bit RNC ID and 16-bit local cell ID.
  • UARFCN - UMTS channel number.
  • CPICH frequency - measured carrier center including estimated tuning offset.

Radio details

  • P-SCH - Primary Synchronization Channel.
  • CPICH - Common Pilot Channel.
  • CPICH correlation - pilot correlation used to confirm the PSC.
  • CPICH Ec/N0 - pilot energy relative to received spectral density.
  • CPICH RSCP - uncalibrated pilot level relative to I/Q full scale.
  • Frame slot phase - slot phase used by the current frame-timing hypothesis.
  • IQ orientation - complex-sample orientation that produced a valid CPICH lock.

MIB / SIB

  • BCH - Broadcast Channel.
  • P-CCPCH - Primary Common Control Physical Channel carrying BCH.
  • SFN - System Frame Number.
  • MIB - Master Information Block; includes PLMN and schedules remaining System Information.
  • SIB1 - core-network and location-area information.
  • SIB3 - UTRAN Cell Identity, access and reselection parameters.
  • SIB5 - common physical channels including paging configuration.
  • SIB7 - dynamic uplink interference information.
  • SIB11 / SIB12 - neighbouring-cell information.

Paging

  • PICH - Paging Indicator Channel.
  • S-CCPCH - Secondary Common Control Physical Channel.
  • PCH - Paging Channel.
  • TTI - Transmission Time Interval.
  • Paging Type 1 - UMTS paging message decoded from CRC-valid PCH blocks.
  • Anonymous UE - session-only anonymous label. Raw identities are never displayed.
  • Domain - circuit-switched or packet-switched paging domain.
  • Cause - paging cause decoded from the paging record.
  • Relation - LOCAL, ROAMING or UNKNOWN compared to the serving PLMN.

Air load

The UMTS air-load estimate is a smoothed occupied SF256-equivalent OVSF code estimate for the selected PSC. It is a radio code occupancy estimate, not BTS CPU load, backhaul load, user count, uplink load or guaranteed throughput.