## SCS (sub-carrier space)-sub-carrier space

SCS is the space between 2 OFDM symbols.

In LTE it is fixed at 15KHz.

In 5G NR, there are 5 possible values based on numerology.

## Slot

In the time domain, 5G and LTE are the same: 1 frame=10ms, 1 frame contains 10 subframes, and each subframe=1ms.

## Point A

PointA is a reference point in frequency domain to allocate other resources.

Below parameters define PointA

> offsetToPointA : This parameter defines the frequency deviation between Point A and the lowest point in the frequency domain.

> absoluteFrequencyPointA : This parameter directly defines the frequency of Point A, the unit is ARFCN.

## CRB

CRB stands for Common Resource Block and it is the center of Subcarrier 0 of CRB0 is PointA.

## RE: Resource Element

RE is the smallest resource unit in NR phy resource.

It will occupy 1 OFDM symbol in time domain and 1 Sub Carrier in frequency domain.

## RB: Resource Block

It will occupy 12 sub carriers in frequency domain.

## RBG: Resource Block Group

## REG: Resource Element Group

It is a control channel resource, it consist of 1 ofdm symbol × 12 subcarrier, i.e, one REG contains 12 REs

## CCE: Channel Control Element

It is a unit of PDCCH resource allocation.

A CCE occupies 6 REGs.

## CORESET:

It is used to decode PDCCH in this region.

There are 2 different types of CORESET.

1. Common Control Region: This is referred as common CORESET and is shared by multiple UE in a cell. It can be used for RAR/paging/system information,

2. UE Specific Region:This is defined for one particular UE.

Network can define 3 CORESET per BWP.

## Search Space

A search space is a set of control channel elements at a different aggregation levels.

A CORESET may have multiple search space, where UE attempts for blind decoding.

## Aggregation Level

It is used to inform UE the number of bits used for PDCCH transmission.

Possible aggregation level in NR is — 1,2,4,8,16

**Example:**

Aggregation Level = 6 REG and REG = 12 RE, so one aggregation level means (72 RE)

## Bandwidth Part (BWP):

BWP is a subset of CRB.

There are 4 different types of BWP:

1. Initial BWP

2. Dedicated BWP

3. Activate BWP

4. Default BWP