DSS Part-3

Home                 LTE                NB-IoT               5G(NR-NSA) DSS: Other NR UE features that are considered important for an efficient operation of spectrum sharing are: PDCCH in symbol 2 Rate matching pattern to map around LTE PSS/SSS and PBCH TRS in symbol 6 and 10 Flexible CSI-RS placement Alternative PDSCH DM-RS pattern when LTE CRS rate matching is configured 7.5 kHz UL shift DSS will help a mobile operator to flexibly allocate existing spectrum across low-, mid- and high- frequency bands, by dynamically switching between 4G LTE and 5G NR coverage based on traffic demand.Mobile operators can hold DSS to deliver the best possible performance and coverage for a mix of 4G and 5G devices. How LTE overhead can be avoided? 5G capacity is impacted by LTE Cell Reference Signals (CRSs),PDCCH, PSS, SSS, PBCH and MBSFN subframes overheads as well as NR PDSCH DMRS and NR corset.There is less impact from the 5G control channels on LTE as 5G does not use an

DSS Part-2

Home                 LTE                NB-IoT               5G(NR-NSA) DSS: When it comes to deploying 5G, spectrum is a key differentiator for operators. And while 24 GHz millimeter wave (mmWave) spectrum is being auctioned specifically for 5G, mid-band spectrum will be critical for operators to get widespread 5G coverage across their markets.  That’s why a technology called DSS (dynamic spectrum sharing) is so compelling. This technology, which is part of the 3GPP Release 15, allows operators to dynamically allocate some of their existing 4G LTE spectrum to 5G and use existing radios to deliver 5G services by deploying a software upgrade. DSS allows 4G and 5G to exist simultaneously on the same band while adjusting the bandwidth allocated to each generation dependent on demand. This is clearly ideal for low-band rollout, as it will allow operators to continue to use valuable spectrum for LTE, while adding 5G (NR) capacity as demand grows. But whether it will be enough

DSS Part-1

Home                 LTE                NB-IoT               5G(NR-NSA) In this article, we will discuss about Dynamic spectrum sharing abbreviated as DSS What is spectrum refarming? It is the process of redeploying spectrum from available users and re-allocating it to others. Legacy technology must be eliminated from a part of the spectrum, which must then be allocated for the new technology. It was not possible for operators to share the spectrum between different technologies but, spectrum refarming from LTE to 5G will be simpler with Dynamic Spectrum Sharing (DSS) which is introduced in 3GPP r15.  5G and LTE can occupy the same spectrum band from the control channel point of view, and the resources are allocated dynamically between the two technologies depending on the instantaneous device distribution and capacity needs. As many LTE bands have been refarmed as NR bands how to share the same spectrum between LTE and NR is an important issue, which can potentially aff

cell selection part-2

Home                 LTE                NB-IoT               5G(NR-NSA) In this section, we will learn about cell selection criteria for SA and LTE. How is cell selection criteria defined? The cell selection criterion which is abbreviated as S in normal coverage is fulfilled when: Srxlev > 0 AND Squal > 0 Where: Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) – Pcompensation - Qoffsettemp Squal = Qqualmeas – (Qqualmin + Qqualminoffset) - Qoffsettemp Where: Srxlev Cell selection RX level value (dB) Squal Cell selection quality value (dB) Qoffsettemp Offset temporarily applied to a cell (dB) Qrxlevmeas Measured cell RX level value (RSRP) Qqualmeas Measured cell quality value (RSRQ) Qrxlevmin Minimum required RX level in the cell (dBm). If the UE supports SUL frequency for this cell, Qrxlevmin is obtained from q-Qrxlevmin-sul, if present, in SIB1, else Qrxlevmin is obtained from

HARQ Basic Part-1

Home                 LTE                NB-IoT               5G(NR-NSA) In this section, we will learn about HARQ basic.  What is ARQ? ARQ stands for automatic repeat request. It refers to the re-transmission protocol in which the receiver checks for errors within the received data and if an error is detected then the receiver discards the data and request a re-transmission forms the sender. For acknowledged mode the RLC layer uses an ARQ protocol.   What is HARQ? HARQ stands for hybrid ARQ. It refers to a re-transmission protocol in which the receiver checks for errors in the received data and if an error is detected then the receiver buffers (soft buffers) the data and requests a retransmission from sender. HARQ receiver then is able to combine the buffered data with the re-transmitted data to channel decoding and error detection. This improves the performance of re-transmissions. HARQ re-transmissions can benefit from either chase combining or incremental redundancy

cell selection part-1

Home                 LTE                NB-IoT               5G(NR-NSA) In this section, we will learn about cell selection basics for SA and LTE. What is cell selection? If a device is under circumstances where UE needs to be switched on or after UE has left RRC connected mode or UE returns to a coverage area, it sees many base stations around it. Many a times UE might be surrounded by multiple base stations from different operators. So from this many base stations, UE can register to only one cell. So to register to a specific cell UE goes through a dedicated process. This specific decision making process where UE decides to which cell to camp on is known as cell selection. Is the initial cell selection procedure reacquired in the case of NSA ? When UE is connected to MCG that time only cell selection procedure is reacquired. Note: ENDC cells (SCG) are not used for initial cell selection. What is the cell selection procedure for LTE and SA? Cell selectio

Reference signals Part-3

Home                 LTE                NB-IoT               5G(NR-NSA) In the previous section, we learn about the DMRS, TRS, SRS reference signals. in this section, we will learn the remaining reference signals:- PTRS: What is PTRS? Now next is PTRS, this reference signal is introduced in NR to enable compensation of oscillator phase noise. Usually, phase noise increases as a function of the oscillator carrier frequency. Thus PTRS can be utilized at high carrier frequencies such as mm wave to reduce phase noise. In an OFDM signal, one of the main degradations caused by phase noise is an identical phase rotation of all the subcarriers, called as common phase error or CPE. it is designed so as to have high density in the time domain   and   low density in the frequency domain, as the phase rotation produced by common phase error is identical for all subcarriers within an OFDM symbols, but there is low correlation of phase noise across OFDM symbols. This RS is UE