CP-OFDM

Cyclic Prefix Orthogonal Frequency Division Multiplexing

Physical Layer →
Introduced in Rel-15 Also in: User Equipment

CP-OFDM is the foundational waveform for 5G NR that uses orthogonal subcarriers and a cyclic prefix to enable efficient, high-speed data transmission by combating multipath delay and simplifying equalization.

Category
Physical Layer
Introduced
Rel-15
Where
Radio Access Network › NG-RAN (5G)
Also touches
1 segments
Specifications
22 specs
CP-OFDM Description Purpose Related Classification Detected Changes Specifications

Description

Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) is the primary waveform adopted for the 5G New Radio (NR) air interface in both downlink and uplink (with some supplementary options for uplink). It is a multi-carrier modulation scheme where a high-rate data stream is divided into numerous lower-rate streams, each modulating a separate orthogonal subcarrier. These subcarriers are closely spaced in frequency, with their orthogonality—ensured by precise frequency spacing equal to the inverse of the symbol duration—preventing inter-carrier interference (ICI). The key architectural component is the cyclic prefix (CP), which is a copy of the end portion of an OFDM symbol prepended to its beginning. This transforms the linear convolution of the transmitted signal with the multipath channel into a circular convolution, a critical property that simplifies channel equalization at the receiver to a simple per-subcarrier complex gain multiplication.

In operation, the transmitter performs an Inverse Fast Fourier Transform (IFFT) to convert frequency-domain data symbols (mapped to subcarriers) into a time-domain OFDM symbol. The cyclic prefix is then appended. After transmission through the radio channel, the receiver first removes the CP. The remaining samples, representing the circular convolution, are processed by a Fast Fourier Transform (FFT) to recover the frequency-domain symbols. Channel estimation, typically using reference signals like DM-RS, provides the complex channel coefficients for each subcarrier, enabling one-tap equalization to compensate for amplitude and phase distortions. This efficient equalization is a major advantage in wideband channels with significant delay spread.

CP-OFDM's role in the 5G network is foundational. Its design parameters, known as numerology, are defined by subcarrier spacing and symbol duration, which are scalable (e.g., 15, 30, 60, 120, 240 kHz). This scalability, tied to the frame structure, is essential for supporting diverse 5G use cases: wider subcarrier spacing for low-latency transmissions and robust high-speed mobility, and narrower effective spacing (via larger FFT sizes) for enhanced mobile broadband with wide channel bandwidths. The waveform's compatibility with advanced multi-antenna techniques like Massive MIMO and beamforming is also a key strength, as it allows for precise precoding and combining in the frequency domain. Furthermore, its spectral efficiency and ability to handle frequency-selective fading make it the workhorse for the 5G physical layer across all deployment scenarios.

Purpose & Motivation

CP-OFDM was adopted as the 5G NR waveform to address the limitations of previous cellular technologies and meet the stringent, diverse performance targets of IMT-2020. In 4G LTE, CP-OFDM was used only in the downlink, with the uplink employing Single-Carrier FDMA (SC-FDMA) to achieve better power amplifier efficiency at the user equipment (UE) at the cost of some scheduling flexibility and multi-user MIMO complexity. A key motivation for standardizing CP-OFDM for both links in 5G was to unify the waveform, thereby simplifying system design, enabling more efficient and flexible uplink multi-user MIMO and non-orthogonal multiple access schemes, and fully leveraging wider bandwidths available at higher frequencies.

The technology fundamentally solves the problem of inter-symbol interference (ISI) caused by multipath propagation in wireless channels. The cyclic prefix acts as a guard interval that absorbs the delay spread of the channel. As long as the length of the CP exceeds the maximum delay spread of the channel, ISI from a previous symbol is confined to the CP portion, which is discarded at the receiver. This elegantly mitigates one of the primary impairments in wideband wireless communication. Furthermore, by enabling simple frequency-domain equalization, it reduces receiver complexity for high-data-rate transmissions over frequency-selective channels, a scenario that becomes more pronounced with the wider bandwidths used in 5G.

Historically, OFDM has been successful in standards like IEEE 802.11 (Wi-Fi) and 4G LTE downlink. Its extension as the unified 5G waveform was driven by the need for forward compatibility, extreme flexibility in numerology to support services ranging from massive IoT to enhanced mobile broadband and ultra-reliable low-latency communications (URLLC), and inherent suitability for advanced antenna systems. CP-OFDM provides a robust, spectrally efficient, and computationally manageable foundation upon which all other 5G physical layer advancements are built.

Classification

Part ofSC-FDMA

Detected Changes Across Releases

from 3GPP Change Requests

Specific changes extracted from the „Change history“ tables of 3GPP specifications (15 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.

Rel-15 2 changes

In Release 15, CP-OFDM was introduced as a new uplink waveform for the Physical Uplink Shared Channel (PUSCH), alongside the existing DFT-s-OFDM. This is reflected in the establishment of specific performance requirements for CP-OFDM-based PUSCH transmissions in both FR1 and FR2, as detailed in new base station demodulation requirements. The release also defined corresponding EVM (Error Vector Magnitude) measurements and reference signals for this waveform to ensure proper operation.

  • CR to TS 38.104 on Combined updates from RAN4 #90 This document combines the proposed changes in the following Draft CRs from RAN4 #90: - R4-1900284, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1900763, "Draft CR to TS 38.104: Update of performance requirement numbers for DFT-s-OFDM based PUSCH" - R4-1900876, "Draft CR to TS 38.104: On RX spurious emissions requirement" - R4-1900968, "Draft CR for 38.104: Performance requirements for NR PUCCH format 1" - R4-1901329, "Draft CR to 38.104: Annex C.6 correction" - R4-1901330, "Draft CR to 38.104: Abbreviations addition" - R4-1901387, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1901474, "Draft CR to TS 38.104: Corrections on transmitter co-existence and co-location requirements" - R4-1901483, "Draft CR to TS 38.104: Corrections on general intermodulation requirement" - R4-1902239, "Draft CR to TS 38.104: Addition of missing EIRP/EIS definitions in terminology in clause 3.1" - R4-1902241, "Draft CR to 38.104; clarification of BS power limits" - R4-1902245, "Draft CR to 38.104: Correction to FR2 OTA Interfering signal mean power units" - R4-1902246, "Draft CR to 38.104; Correction to definition of OTA reference sensitivity" - R4-1902260, "draft CR to TS 38.104 - update emissions scaling" - R4-1902338, "Draft CR: Update on FR1 range extension for TS38.104" - R4-1902389, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1902394, "Draft CR to TS 38.104 – PUSCH requirements with CP-OFDM for FR2" - R4-1902396, "CR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1902444, "Draft CR to TS 38.104: Editorial CR for BS demodulation requirements" - R4-1902561, "Draft CR for updating PRACH performance requirements in TS38.104" - R4-1902571, "Corrections to 38.104 Delay profile calculation" - R4-1902642, "Draft CR to TS 38.104: Correction on multi-band operation related requirements" TS 38.104CR0019
  • CR to TS 38.104 Combined updates from RAN4 #90bis and RAN4#91 From RAN4 #90bis: - R4-1903105, "Draft CR to TS 38.104: Corrections on terminologies and editorial errors" - R4-1903319, "Draft CR to TS 38.104: removal of unused definition: "minimum EIRP level under extreme condition"" - R4-1903320, "Draft CR to TS 38.104: OSDD information correction" - R4-1903457, "Draft CR to TS 38.104: Removal of FFS for FR2 TDD OFF power level requirement in clause 9.5" - R4-1903499, "Draft CR to 38.104: Correction to unwanted emissions mask for bands n7 and n38" - R4-1903836, "Draft CR to TS 38.104: Correction on description on multi-band operation in section 4.8" - R4-1904024, "Draft CR to TS 38.104 Applicability rules for BS demodulation" - R4-1904234, "draftCR: Correlation matrix for 8Rx in TS 38.104" - R4-1904723, "Draft CR to TS 38.104: Update of performance requirements for DFT-s-OFDM based PUSCH" - R4-1904726, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1904729, "Draft CR on PRACH performance requirements in TS38.104" - R4-1904734, "Draft CR on TS 38.104 Performance requirement for PUCCH format 1" - R4-1904735, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1904739, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1904745, "draftCR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1904799, "Draft CR to TS 38.104: FRC update for PUSCH FR1 mapping type B and FR2 DMRS 1+1" - R4-1904816, "Draft CR : Clarification on step 5 and step 6 for delay profiles calculation (38.104)" - R4-1904842, "Draft CR to TS 38.104 BS demodulation CP-OFDM PUSCH FR2 requirements" - R4-1905126, "draft CR to 38.104 for TAE requirements" - R4-1905139, "draft CR to TS 38.104 on EVM measurement (Annex B and C)" - R4-1905140, "Draft CR: editorial correction on FR1 spurious emission requirement in TS38.104" - R4-1905143, "Draft CR for TS 38.104: Addition of NOTE for transmitter intermodulation requirements in certain regions" - R4-1905144, "Draft CR to TS 38.104: FRC reference corrections for the Rx requirements" - R4-1905145, "Draft CR to TS 38.104: Clarification on application of interfering signal offsets for ACS, blocking and intermodulation requirements" - R4-1905148, "Draft CR to TS 38.104: Corrections on out-of-band blocking requirement" From RAN4 #91: - R4-1906002, "Draft CR to 38.104: Subclause 6.7 and 9.8 transmitter intermodulation – correction of interfering signal type" - R4-1906096, "Draft CR to 38.104: Correction of frequency range for OTA spurious emissions" - R4-1906311, "Draft CR to 38.104: Correction on FRC (Annex A)" - R4-1906346, "Removal of n65 in Rel-15 38.104" - R4-1906915, "Draft CR to TS 38.104: Clarification on application of interfering signal offsets for OTA ACS, blocking and intermodulation requirements" - R4-1906918, "Draft CR to TS 38.104: Clarification on type of interfering signal for ACS, in-band blocking and ICS requirements" - R4-1907110, "Draft CR to TS 38.104: correction of the fundamental frequency limit of 2.55GHz for the spurious emissions" - R4-1907246, "Draft CR to TS 38.104: Update of performance requirements for DFT-s-OFDM based PUSCH" - R4-1907249, "Draft CR to TS 38.104: Correction on the terminology in PUSCH FRC tables" - R4-1907252, "Draft CR to TS38.104: Updates of PRACH performance requirements" - R4-1907255, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1907258, "Draft CR on NR UCI on PUSCH performance requirements for TS 38.104" - R4-1907261, "draftCR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1907266, "Draft CR on TS 38.104 Performance requirement for PUCCH format 1" - R4-1907267, "Draft CR on TS 38.104 Performance requirement for multi-slot PUCCH format 1" - R4-1907272, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1907275, "Draft CR to TS 38.104 BS demodulation CP-OFDM PUSCH FR2 requirements" - R4-1907277, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1907629, "Draft CR to 38.104: Term “reference signal” replacing by term “ideal signal” in EVM context" - R4-1907634, "Draft CR to 38.104: corrections to the EVM annex" - R4-1907659, "Draft CR to TS 38.104 on Spurious emission Category B in FR2" - R4-1907661, "Draft CR to 38.104 Definition of contiguous transmission bandwidth" - R4-1907662, "Draft CR to 38.104: BS TAE requirements" - R4-1907664, "Draft CR to 38.104: Clarification of interferer RB frequency for narrowband blocking" - R4-1907672, "Draft CR for TS 38.104: Correction on EVM" - R4-1907689, "Correction to CA carrier spacing" TS 38.104CR0029
Rel-16 7 changes

In Release 16, specific performance requirements for CP-OFDM were formalized, particularly for the Physical Uplink Shared Channel (PUSCH) in Frequency Range 1 (FR1) and Frequency Range 2 (FR2). This included detailed Base Station (BS) demodulation requirements and corrections to the Error Vector Magnitude (EVM) window length calculations for CP-OFDM signals. Additionally, the release introduced updates for CP-OFDM in conjunction with new features like intra-slot frequency hopping applicability.

  • Introduction of LTE/NR spectrum sharing in band 48/n48 frequency range TS 38.104CR0220
  • CR to TS 38.104 BS demodulation CP-OFDM PUSCH FR2 requirements TS 38.104CR0102
  • CR to T 38.104: Implementation of endorsed draft CRs from RAN4#92 (Rel-16) (Mirrors changes in R4-1908440 for Rel-15 TS 38.104) - R4-1907940, "Draft CR to TS 38.104: Correction on the terminology in FRC tables in A.1 and A.2" - R4-1908307, "Draft CR to TS 38.104: Clarification on application of OTA receiver requirements for BS supporting polarization" - R4-1908387, "Draft CR for TS38.104: editorial correction for reference meausrement channel" - R4-1908619, "Draft CR to TS38.104: Correction on interferer frequency offset values for ACS" - R4-1908629, "Draft CR to TS38.104: Corrections on EVM window length (Annex B.5.2, C.5.2)" - R4-1908774, "DraftCR to 38.104: Editorial Corrections to redudant units in clause 10.8.3" - R4-1908805, "Draft CR to 38.104: Limits in FCC title 47 for OTA operating band unwanted emissions (9.7)" - R4-1909270, "Draft CR to TS 38.104: Receiver spurious emissions frequency correction" - R4-1909309, "DraftCR to TS 38.104: text corrections, Rel-15" - R4-1909310, "DraftCR to 38.104: correction of TAB connectors mapping to TAB connector TX min cell group, Rel-15" - R4-1909416, "draft CR 38.104 - correct reference to annex F" - R4-1910066, "Draft CR to TS 38.104: Update of performance requirements for DFT-s-OFDM based PUSCH" - R4-1910069, "Draft CR on NR PUCCH format2 performance requirements for TS 38.104" - R4-1910072, "Draft CR on NR UCI on PUSCH performance requirements for TS 38.104" - R4-1910075, "draftCR for 38.104 on PUSCH requirements with CP-OFDM and FR1" - R4-1910078, "Draft CR to TS38.104: Updates to NR PRACH performance requirements" - R4-1910081, "Draft CR to TS 38.104 BS demodulation PUCCH format 0 requirements" - R4-1910084, "Draft CR to TS 38.104 BS demodulation CP-OFDM PUSCH FR2 requirements" - R4-1910088, "Draft CR for 38.104: Performance requirements for NR PUCCH format 1" - R4-1910089, "Draft CR for 38.104: Performance requirements for NR multi-slot PUCCH" - R4-1910094, "draftCR: Updates to PUCCH formats 3 and 4 performance requirements in TS 38.104" - R4-1910431, "Corrections to EVM calculations in 38.141-1 annex B" - R4-1910462, "Draft CR to 38.104: Correction on regional requirements (4.5)" - R4-1910493, "Draft CR to TS 38.104 correction to Annex C.7" - R4-1910606, "Draft CR for TS 38.104: Channel spacing for adjacent NR carriers" TS 38.104CR0034
  • CR for 38.104 on PUSCH requirements with CP-OFDM and FR1 TS 38.104CR0063
  • CR to TS 38.104: Finalization of interfering RB centre frequency offsets in receiver narrowband blocking requirement TS 38.104CR0083
  • CR to TS 38.104: Correction on interfering signal frequency offsets for receiver intermodulation requirements TS 38.104CR0087

+ 1 more changes

Rel-17 1 change

In Release 17, a specific correction was introduced for CP-OFDM-based transmissions concerning the Spectrum Emission Mask (SEM). The update provided clarified definitions and calculation methods for the frequency offset of symbols at the channel edge to ensure accurate mask measurements, particularly for non-transmitted channels. This refinement aimed to improve the precision of out-of-band emission requirements for base stations (SANs) operating with defined transmission bandwidth configurations.

  • CR to TS 38.104: Corrections on frequency offset symbols for spectrum emission mask for non-transmitted channels TS 38.104CR0307
Rel-18 3 changes

In Release 18, the CP-OFDM function was enhanced to support Non-Terrestrial Networks (NTN), specifically through updates to the defined frequency ranges for operation. This included technical corrections and expansions for FR2-NTN and the incorporation of provisions for the 1610-1626.5 MHz band, aligning with international WRC regulations. These changes refined the channel raster and carrier frequency definitions for NTN operation within the existing CP-OFDM framework.

  • (NR_NTN_enh-Core) CR for TS 38.108 Correction on FR2-NTN frequency range TS 38.108CR0104
  • (NR_NTN_LSband-Core) Additional information on the international regulations and WRC provisions for a UE operating in 1610-1626.5 MHz frequency range TS 38.741CR0007
  • (NR_NTN_solutions-Core) CR for TS 38.108 to update NTN frequency range (R18) TS 38.108CR0053
Rel-19 2 changes

In Release 19, the CP-OFDM function was extended for Non-Terrestrial Networks (NTN) with the definition of a new FR1-NTN frequency range for the Ku band. This involved specifying the operating band, channel raster, and carrier frequency parameters to enable NR operation in this satellite band, as detailed in updates to the frequency range definitions.

  • (NR_NTN_Ku_bands-Core)CR for 38.108, On FR1-NTN frequency range for NR NTN Ku band TS 38.108CR0132
  • CR on NTN frequency range defintion (38.108) TS 38.108CR0138

Explore further

Broader topics and technologies where CP-OFDM plays a role.

Topics
MIMO & BeamformingLTE / LTE-Advanced5G NR (New Radio)Lawful InterceptIoT & MTCServices & Applications
Technologies
LTE5G

Defining Specifications

3GPP specifications that define or reference CP-OFDM, with the latest known release. Sourced from the 3GPP document catalog — see methodology.

SpecificationTitleRelease
TS 36.108 vj10 Satellite Access Node RF Requirements Rel-19
TS 36.181 vj30 E-UTRA RF Test Methods for Satellite Access Node Rel-19
TS 38.101 vj31 NR User Equipment Radio Transmissions Rel-19
TS 38.104 vj20 NR Base Station RF Requirements Rel-19
TS 38.106 vj20 NR Repeater Radio Transmission and Reception Rel-19
TS 38.108 vj20 NTN NR Satellite Access Node RF Requirements Rel-19
TS 38.115 vj20 NR Repeater RF Conformance Testing Part 1 Rel-19
TS 38.141 vj20 NR Base Station RF Conformance Testing Part 1 Rel-19
TS 38.174 vj10 NR Integrated Access and Backhaul Radio Spec Rel-19
TS 38.176 vj20 IAB Conformance Testing Specification Rel-19
TS 38.181 vj10 NR Satellite Access Node RF Testing Rel-19
TS 38.521 vj20 NR Physical Layer UE Conformance Testing Rel-19
TS 38.741 vj00 NTN L-/S-band for NR Technical Specification Rel-19
TR 38.785 vh00 UE radio transmission for enhanced NR sidelink Rel-17
TR 38.786 vi20 Technical Report for NR Sidelink Evolution Rel-18
TS 38.787 vj00 UE Radio Transmission for Sidelink CA in ITS Band Rel-19
TS 38.819 vg00 Band n65 for New Radio Technical Report Rel-16
TS 38.863 vj10 NR NTN RF and Co-existence Spec Rel-19
TR 38.868 vh00 Optimizations of pi/2 BPSK uplink power in NR Rel-17
TS 38.870 vj20 Enhanced OTA Test Methods for NR FR1 TRP/TRS Rel-19
TR 38.886 vg30 NR V2X UE Radio Transmission & Reception Rel-16
TR 38.903 vj00 Test Tolerances & Measurement Uncertainties Rel-19