Showing posts from September, 2019

Why PHICH and PCFICH channel is not present in NR

Home                 LTE                NB-IoT            5G(NR-NSA) Why PHICH and PCFICH channel is not present in NR(5G) ? The two channels PHICH and PCFICH which are present in LTE but are not required in NR. PHICH channel i s  used in LTE to handle uplink re-transmissions and are tightly coupled to use of synchronous hybrid-ARQ protocol, but as the HARQ protocol is asynchronous in NR in both downlink as well as uplink. Hence the PHICH is not required in NR. Also as the size of the CORESERTs does not vary dynamically and reuse of control resources for data is handled in a different way than it is done in LTE, thus the PCFICH is not necessary in NR. CORESET is nothing but the concept of central to downlink controlling signaling in NR. CORESET is a time frequency resource in which the device tries to decode candidate control   channels using one or more search spaces.   The PDCCH in NR does not necessarily span the full carrier bandwidth but it does in LTE PDCCH. --PI


Home                 LTE                NB-IoT            5G(NR-NSA) CORESET Part-1 What is CORESET? The set of physical resources that is time frequency resource in which device tries to decode candidate control channels using one or more search spaces is called as the control resource set (CORESET). Coreset is the concept of central to downlink control signaling in 5G NR. Need to introduce CORESET: The downlink control signaling in LTE uses the full carrier bandwidth in the first 1-3 OFDM symbols (four for the most narrowband case). This is known as the control region in LTE. The desire for frequency diversity and the fact that all LTE devices support the full 20 MHz carrier bandwidth motivated the need of having control channels covering the full carrier bandwidth. However this was one of the cons as this lead to complications when introducing support for device not supporting the full carrier bandwidth in later LTE release. (EG. eMTC devices i

5G Flexible Numerology

Home                 LTE                NB-IoT            5G(NR-NSA) 5G Flexible Numerology The concept of flexible sub-carrier spacing is called Numerology. It was defined in Release 15, spec 38.211. It is denoted by μ. µ’s value can vary from 0 to 4. The sub-carrier spacing can be found based on the formula:                                                                 ∆f=(2^μ)*15 kHz  A table specifying different subcarrier spacing based on the value of µ is shown below: 480 kHz subcarrier spacing for µ=5 is also specified in 3GPP specifications but it would be available in phase 2 (Release 16). The frequency band in which 5G will operate can be divided into two groups:            1)     FR1 (sub 6GHz) lower frequency bands  They will support 15, 30, and 60 kHz SCS.            2)     FR2 (above 6GHz, also called mmWave) higher frequency bands  They will support 60, 120 and 240 kHz SCS. Another reason that higher frequenci


Home                 LTE                NB-IoT            5G(NR-NSA) Hi Guys today we are learning about Power Control in LTE. If you are interested in learning more about LTE please  click here. POWER CONTROL IN LTE When dealing with wireless communication of any kind, one of the most important things to keep in mind is the kind of effect/change that the air interface is going to make on the signal. Unlike wires, air is not a static, immutable path whose effect on the signal can be predicted with a fairly high accuracy. The signal, when travelling through the air interface goes through distortion, attenuation, reflection through multiple surfaces, and many other things. So, it’s important for both the UE and the eNodeB, to have some kind of arrangement to take care of this. Power Control is the mechanism through which the UE and the eNodeB handle the attenuation of the signal. There are two types of Power Control mechanisms as per Control Theory and LTE uses both of th