RF5G NR Numerology and Terminology Explained
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This page describes 5G NR Numerology or 5G NR Terminology as per 3GPP NR (New Radio) release 15 standards.
Introduction
As shown in Figure-1, a frame in 5G NR has a duration of 10 ms. A frame consists of 10 subframes, each having a 1ms duration, similar to LTE. Each subframe consists of slots. Each slot can have either 14 (normal CP) or 12 (extended CP) OFDM symbols. All the subcarrier spacing options have 14 OFDM symbols. 60 KHz spacing supports both normal and extended CP types.
Figure-1: 5G NR Frame showing frame, subframes, and slots
For , there is 1 slot per subframe. For , there are 2 slots per subframe. For , there are 4 slots per subframe, and so on. The number of slots per frame is ten times the number of slots per subframe. Hence, for , there are 40 slots/frame.
5G NR uses 4096 FFT points, which consists of 3300 data subcarriers for a maximum bandwidth of 400 MHz.
Table-1 : μ, symbols per slot and slots per frame
Figure-2: RG, RB and REs as per μ
Table-2: Number of RBs as per μ and SCS (i.e. Δf)
| Subcarrier spacing (KHz) | 15 | 30 | 60 | 120 | 240 |
|---|---|---|---|---|---|
| Symbol duration (µs) | 66.7 | 33.3 | 16.7 | 8.33 | 4.17 |
| CP duration (µS) | 4.7 | 2.3 | 1.2 (Normal CP), 4.13 (Extended CP) | 0.59 | 0.29 |
| Max. nominal system BW (MHz) | 50 | 100 | 100 (sub-6 GHz), 200 (mmwave) | 400 | 400 |
| FFT size (max.) | 4096 | 4096 | 4096 | 4096 | 4096 |
| Symbols per slot | 14 | 14 | 14 (normal CP), 12 (extended CP) | 14 | 14 |
| Slots per subframe | 1 | 2 | 4 | 8 | 16 |
| Slots per frame | 10 | 20 | 40 | 80 | 160 |
Table-3: Subcarrier spacing, Number of OFDM symbols, and slots
5G NR Numerology | 5G NR Terminology
The following table describes terms used in 5G NR numerology as defined in the 3GPP standard.
| 5G NR Numerology | Description |
|---|---|
| Frequency Range | • There are two frequency ranges supported in 5G NR viz. FR1 and FR2. • FR1 supports frequencies below 6 GHz whereas FR2 supports frequencies above 6 GHz (i.e. mmwave range). • FR1: Frequency range is from 450 to 6000 MHz • FR2: Frequency range is from 24250 to 52600 MHz >> . |
| eMBB, mMTC, URLLC | eMBB stands for Enhanced Mobile Broadband, mMTC stands for massive Machine Type Communication and URLLC stands for Ultra Reliability and Low Latency Communication. >> . |
| Frame | A frame in 5G NR consists of 10 ms duration. |
| Subframe | A frame consists of 10 subframes with each having 1ms duration similar to LTE. Each subframe consists of slots. μ can be any value from 0 to 5. |
| Slot | A normal slot occupies either 14 (normal CP) or 12 (Extended CP) OFDM symbols. It enables slot-based scheduling. One slot is the possible scheduling unit, and slot aggregation is also allowed. Slot length scales with subcarrier spacing. Slot length = , Where μ can be any value from 0 to 5. |
| Mini-slot | A Mini-slot occupies 2, 4, or 7 OFDM symbols. It enables non-slot based scheduling. It is the minimum scheduling unit used in 5G NR. As mentioned, mini-slots can occupy as little as 2 OFDM symbols and are variable in length. They can be positioned asynchronously with respect to the beginning of a standard slot. |
| Subcarrier spacing (SCS) | It can be any value from 15/30/60/120/240/480 KHz based on the 5G NR numerology parameter, μ which has a value from 0 to 5. For μ = 0, an SCS of 15 KHz is used; for μ = 1, an SCS of 30 KHz is used, and so on. |
| Slots per frame and subframe | • Slots per subframe depends on μ. For μ = 0 to 5, slots/subframe vary from 1/2/4/8/16/32. • There are 10 subframes per frame, and hence slots per frame are ten times the slots per subframe as mentioned in the table. |
| OFDM symbol duration () | , For SCS = 15 KHz, , , and so on. |
| Numerology, μ | It is the 5G NR parameter which changes SCS and other system parameters. It is denoted as μ and ranges from 0 to 5. |
| Resource Grid | • The resource grid, which consists of the number of subcarriers in the frequency axis and the number of OFDM symbols in the time axis, is known as the resource grid. • 5G NR supports () X () subcarriers and () OFDM symbols. |
| Resource Block | • RB (Resource Block) consists of a total of 12 consecutive subcarriers in the frequency domain. • () = 12 • There are more than one RB in a resource grid. • Resource elements are grouped into PRB (Physical Resource Blocks). Each PRB consists of 12 subcarriers as mentioned. |
| Resource Element | • Each element in the resource grid for antenna port (“p”) and subcarrier spacing configuration (“μ”) is known as a Resource Element. • It is uniquely identified by (), where k = index in the frequency domain and l = symbol position in the time domain. |
| Cyclic Prefix type and duration | There are two types viz. normal and extended. For normal each slot occupies 14 symbols and for extended each slot occupies 12 symbols. Extended CP type is used for SCS of 60 KHz only. |
