Showing posts from March, 2020

beamforming basic part-3

Home                 LTE                NB-IoT               5G(NR-NSA) (Qus: what are the types of beam forming?) In this section let us know what the types of beam forming are. In general beam forming can be implemented in the digital domain, in the analogue domain or in a combination of both digital and analogue domain that is a hybrid domain.  There are Advantages and disadvantages associated with each approach. Usually, we can say that digital beam forming is applicable to frequency range 1(450 MHz to 6 GHz) while analogue beam forming is applicable to frequency range 2(24.25 GHz to 52.60 GHz).  (Qus: What is digital beam-forming and its drawback and benefit?)   In case of digital beam forming the signal is pre coded in baseband processing before RF transmission. The pre coding is applied in the digital domain and there is a requirement to have multiple parallel RF chains.  This is major drawback for digital beam forming when the number of controllable ant

beamforming basic part-2

Home                 LTE                NB-IoT               5G(NR-NSA) In this section we will learn about how beamforming benefits are obtained in practice with massive MIMO antennas. With the deployment of NR, the target is to make 5G radio design fully optimized for massive MIMO beamforming. Unlike a traditional solution, beamforming sends the data with narrow beams to the users. The same resource can be reused for multiple users within a sector, thus minimizing the interference and increasing the cell capacity. Massive MIMO is the extinction of traditional MIMO technology to antenna arrays having a large number of controllable transmitters. 3GPP defines massive MIMO as more than 8 transmitters. To deliver either a fixed grid of beams or UE specific beamforming beams can be formed in a number of different ways. Suppose, if the antenna has 2 TRX (transceiver) branches it can send with two parallel streams to one UE.   Similarly, if the antenna has 4 TRXs it can send

DC Carrier in NR

Home                 LTE                NB-IoT               5G(NR-NSA) In this article, we will learn the basics of DC Carrier and why it is needed. Why in NR, DC subcarrier is not reserved like LTE? With legacy LTE (4G) it was decided that all devices (UE) should be capable of the maximum carrier bandwidth of 20MHz (UE can also support 10/15/5/3 MHz). This was a reasonable assumption at the time given the relatively modest bandwidth compared to NR, Whereas NR is designed to support very wide bandwidths up to 400MHz (for FR2) and 100Mhz (for FR1) for a single carrier. As well as NR supports multiple numerologies on the same transmitted carrier frequency. It is not necessary that all devices can support up to 400 MHz Bandwidth, hence in NR BWP concept is introduced. (To learn more about BWP Click here ). Note: in the above and below NR case figure, we assume that for each and every BWP have configured some  txDirectCurrentLocation  value.     As shown in the a

beamforming basic part-1

Home                 LTE                NB-IoT               5G(NR-NSA) In this article we will learn basics about beam forming and why it is needed. QUS- What is Beam-Forming and its benefits? As the name suggest beam forming is the forming of beam of RF energy. Fundamentally the electromagnetic wave radiation pattern from a system is focused like a beam from torch or beam. It is a traffic signaling system for cellular base stations that identifies the most efficient data delivery route to particular user. It also reduces interference for nearby users in the process. At the same time it is used to detect and estimate the signal of spatial filtering and interference rejection. It will also improve the overall radio environment of a cell by limiting interference to small fractions of the entire space around a transmitter and likewise limiting the impact of interference on a receiver to infrequent stochastic events and thus sometimes referred as beam shaping. Beam

PRACH Basic-3

Home                 LTE                NB-IoT               5G(NR-NSA) In this section we will learn about PRACH Preamble Format and its basics as well as interview questions. Random access with NR supports different PRACH formats and numerologies to cope up with different deployments. The random access sequences themselves are based on the preamble format. Preamble Format: (Qus: How many new preamble format are introduce by 3gpp in NSA or SA case?) In 5G NSA or SA cases, there are 13 types of preamble format for FR1/FR2 and they are known as Format 0/1/2/3, Format A1/A2/A3, Format B1/B2/B3/B4, Format C0/C2. These 13 types of preamble format can be categorized into two categories: • Sequence length of L = 139, with subcarrier spacing of 15, 30, 60, and 120 kHz. These can be solutions for different coverage situations. • Sequence length of L = 839, with subcarrier spacing of 1.25 kHz and 5 kHz. This sequence can be used for very large cells (up to 100 km). (Qu