Despite LTE being a competent technology, there are specific 5G requirements such as mMTC, and URLLC that are not possible to be met, even with LTE Advanced releases. To meet these new requirements, 3GPP initiated the development of a new radio access technology known as New Radio (NR). A first workshop setting scope was held in 2015, and technical work began in the spring of 2016. The first version of the NR specification was available at the end of 2017, also known as Non-Standalone, built on a top of the existing LTE network. Early Drop specification addressed the most urgent deployment needs for eMBB, used LTE anchor with 5G NR in Dual Connectivity configuration, and accelerated specification to ensure a single 5G global ecosystem. The standalone specification was finished in June 2018 with Release 15 (Main Drop), which contains full independent 5G support with 5G Core. Release 16 (Late Drop), among other NR topics, includes specifications for all potential migration options to accelerate migration to 5G standalone.
3GPP has defined two frequency ranges for 5G NR, Frequency Range 1 (FR1) for sub-6 GHz bands, and Frequency Range 2 (FR1) for millimeter-wave bands. The corresponding frequency ranges are 450 MHz – 6000 MHz for FR1 and 24250 MHz – 52600 MHz for FR2. Specific NR bands within each frequency range, are indicated with a prefix of “n”. FR1 holds bands from n1 up to n90 with different spacings, and duplex modes (FDD or TDD), while FR2 holds bands in four different ranges, n257 at 28GHz (LMDS), n258 at 26GHz (K-band), n260 at 39GHz and n261 at 28GHz (Ka-Band), initially supported in Rel-15 for TDD duplex mode. When an NR band is overlapping with a 4G LTE band, the same band number is used. While 5G NR requirements are often generic and frequency agnostic, there may, in many cases, be separate requirements for different bands. In some cases, these are identified directly using the band number.
NR Sub-Carrier Spacing (SCS)
NR supports the operation of different numerologies involving different sub-carrier spacings, as well as operation in different parts of the frequency domain. Range 1 below 1GHz supports 15 and 30 kHz SCS, while Range 1 above 1GHz supports 15, 30, and 60 kHz. Range 2 supports 60 and 120 kHz.
The characteristics of range 1 and range 2 in terms of achievable phase noise, channel delay profiles, and expected bandwidths differ considerably. Hence, the supported SCS options were decided separately for range 1 and range 2. Several options for SCS are supported for each range. The SCS supported for each band will be selected on a band-specific basis from the options defined for the corresponding spectrum. For example, Band n38 (2.6 GHz TDD) was standardized to SCS 15, 30, 60, and maximum BW of 20MHz. In the case of a 30-40 MHz license, Carrier Aggregation has to be used to utilize the spectrum fully.
A potential feature of NR is that the 5G Base Station may transmit data using multiple numerologies in the same sub-frame using frequency division multiplexing. It has been agreed that in release 15, UEs will not be required to be able to receive data on multiple numerologies. If different parts of the same carrier are used for transmitting different numerologies, then the numerologies will not be fully orthogonal. Potentially, filtering or windowing could be used to achieve isolation between numerologies. In-band emissions or error vector magnitude (EVM), and receiver selectivity requirements could be considered to improve the inter-numerology isolation.
NR channel bandwidth
For NR, the term BS channel bandwidth has been defined. A contiguous block of transmitting/receiving spectrum may consist of one or more BS channel bandwidths. Different UE channel bandwidths may be supported within the same range.
The BS channel bandwidth is understood to be a range of spectrum which can be used to transmit to UEs with different bandwidths. The essential characteristic of the BS channel bandwidth is that placing UEs within the BS channel bandwidth is flexible. It is possible to assign a single carrier to a UE covering most or all of the BS channel bandwidth. Also, it is possible to transmit a carrier to a UE with less than the BS channel bandwidth, but placed anywhere within the BS channel bandwidth or to transmit multiple carriers to a UE. On the other hand, it is not possible to transmit a carrier to a UE that crosses the boundary between two BS channel bandwidths.
According to 3GPP 38.101, the maximum bandwidth for some selected bands was boosted to 100 MHz for FR1 or 400 MHz for FR2, respectively. The maximum number of Resource Blocks in 20 MHz BW was increased to 106 (LTE has 100) due to narrower guard-band specification (452.5 kHz on each side, LTE has 1000 kHz). The maximum channel bandwidth shall not exceed 3300 subcarriers and 4096 FFT size. UE can operate in asymmetric UL and DL bandwidths.
Output power aspects
The NR UE Power Classes define the maximum output power for any transmission bandwidth within the channel bandwidth for non-CA configuration, unless otherwise stated. Class 3 is designated for NR operating bands n1, n3, n7, n8, n20, n38, n50 at 23 dBm with ± 2 dB tolerance. N28 and n78 are defined at 23 dBm with +2/-2.5 dB, and +2/-3 dB tolerance, respectively. The period of measurement shall be at least one subframe (1ms). The values for handheld UEs, defined as minimum peak EIRP without tolerance, are 21.2-25.2 dBm for NR band n257, 21.2-25.2 dBm for n258, and 19.4-23.7 dBm for n260.
There are two types of NSA UEs supported by the specification. UE Type 1 is capable of dynamic LTE-NR power sharing. This means that there exists a converged NR and LTE modem with high speed interface capability. These UEs can operate with PLTE + PNR > Ppowerclass configuration or with no PLTE or PNR configuration. UE Type 2 is not capable of dynamic LTE-NR power sharing. Separate NR and LTE modem is used with limited interface capability. These UEs can only operate in EN-DC when a configuration is received with PLTE + PNR <= Ppowerclass. Neither type of UEs is allowed to transmit with power above Ppowerclass in FR1.
Receiver Sensitivity aspects
REFSENS is known as the reference sensitivity power level. This is the minimum mean over-the-air (OTA) power applied to each one of the UE antenna ports. This is true for all UE categories, at which the throughput shall meet or exceed the requirements for the specified reference measurement channel. For NR Bands n7, n38, n41, n77, n78, and n79, the UE shall be equipped with 4Rx ports as a baseline.
For a channel bandwidth of 50MHz, operating bands n257 and n258 are defined at -92.1 to -85.4 dBm, while n260 at -91.8 to -82.6 dBm. For a channel bandwidth of 100MHz, operating bands n257 and n258 are defined at -89.1 to -82.4, while n260 at -88.8 to -79.6 dBm. Finally, for a channel bandwidth of 400MHz, operating bands n257 and n258 are defined at -83.1 to -76.4, and n260 at -82.8 to -73.6 dBm.
