RF Drive Test Software & LTE 4G Tester tools along with Fysiskt lager NR
The 5G New Radio (NR) technology, while sharing some similarities with LTE, introduces significant advancements that enhance its flexibility and modernity. One of the major improvements in 5G NR is its ability to operate across a broader range of frequencies, including both sub-6GHz and millimeter-wave bands. This expansion allows for wider channel bandwidths, leading to higher data rates. Additionally, the use of shorter Transmission Time Intervals (TTIs) and symbol durations facilitates low-latency communication, which is crucial for many modern applications. The design of 5G NR is also future-proof, featuring a clean sub-frame structure that minimizes unnecessary transmissions. Unlike previous systems where reference signals were constantly transmitted, 5G NR adopts a more efficient approach, transmitting only when necessary. Moreover, it incorporates beam management, enabling better interworking across different spectrum bands, including those used by LTE. So, now let see 5G New Radio (NR) Physical Layer a Simplified Overview along with Smart LTE RF drive test tools in telecom & RF drive test software in telecom and Smart 4G Tester, 4G LTE Tester, 4G Network Tester and VOLTE Testing tools & Equipment in detail.
Key Features of 5G NR 5G NR is designed to support various numerologies, which are tailored to different frequency layers and specific use cases. The standard numerology is based on a subcarrier spacing (SCS) of 15 kHz, with the ability to scale up by factors of 2. This scalability extends to symbol length and Cyclic Prefix (CP) duration, with 60 kHz SCS being a common setting that supports a normal CP of 4.67 microseconds. Depending on the SCS, NR can accommodate either 7 or 14 symbols per slot, and unlike LTE, it does not include a Direct Current (DC) carrier within its frequency bands.
The modulation techniques used in 5G NR include BPSK, QPSK, 16QAM, 64QAM, and 256QAM, with an additional option for π/2-BPSK, which helps reduce the Peak-to-Average Power Ratio (PAPR) in uplink transmissions. The basic frame structure in NR consists of 12 subcarriers per Physical Resource Block (PRB), with a fixed sub-frame duration of 1 millisecond. Slot lengths vary between 7 and 14 symbols for SCS up to 60 kHz and remain at 14 symbols for higher SCS values. NR also ensures alignment across different SCSs by maintaining the same CP overhead and offers the flexibility of extended CP, particularly for 60 kHz SCS.
In NR, the concept of a slot is similar to a sub-frame in LTE’s Time Division Duplex (TDD) mode. Each slot comprises downlink symbols, uplink symbols, and flexible symbols, with no specific symbols designated for switching between downlink and uplink. NR supports up to 256 slot formats, as outlined in the 3GPP Release 15 specification. While LTE uses all symbols in a sub-frame for either downlink or uplink transmission, NR introduces a more adaptable slot structure, where segments within a slot can be allocated for specific uses. The network configures uplink and downlink allocations for each transmission period, with the flexibility to adjust these allocations for individual devices (UEs). This configuration can mirror the special subframe arrangement seen in Time Division LTE (TD-LTE).
Advanced Physical Layer Techniques in NR 5G NR introduces the concept of mini-slots, which are the smallest scheduling units and are particularly suited for low-latency transmissions and Ultra-Reliable Low-Latency Communications (URLLC). These mini-slots can start at any Orthogonal Frequency-Division Multiplexing (OFDM) symbol and include Demodulation Reference Signals (DMRS) positioned relative to the start of the mini-slot. They may interrupt ongoing enhanced Mobile Broadband (eMBB) transmissions, with a typical length of one slot, though two slots are used for URLLC. The design of mini-slots follows the same principles as regular slots, allowing them to be inserted into other transmissions and efficiently multiplex URLLC services with eMBB traffic.
To achieve low-latency transmissions, NR employs high numerologies for shorter slot lengths and uses asynchronous Hybrid Automatic Repeat Request (HARQ) for quick scheduling. Additionally, NR supports “self-contained” sub-frames, where data is both received and transmitted within a single sub-frame, incorporating HARQ to significantly reduce latency.
NR also allows for flexible bandwidth usage, supporting carrier channels up to 400 MHz wide, compared to LTE’s maximum of 20 MHz. The number of component carriers in NR can reach up to 16, with the overall bandwidth depending on the frequency band. Millimeter-wave frequencies, in particular, offer larger bandwidths and higher speeds. However, not all devices need to support the full network carrier bandwidth. The network can configure specific parts of the channel bandwidth as “Bandwidth Parts” for each device. Each device can use up to four bandwidth parts for uplink and downlink carriers, with each part potentially having different SCS, location, and bandwidth. The device transmits and receives signals on a single bandwidth part, as indicated by the control channel.
Initial Access in 5G NR The initial access procedure in 5G NR for each device to connect to the gNB (Next-Generation Node B) is handled by the NR Synchronization and Common Control Channel. The Synchronization Signal/Physical Broadcast Channel (SS-PBCH) block is used for initial cell search and Radio Resource Control (RRC) measurements. It carries crucial information such as symbol and frame timing, CP length, duplex mode, and the Reference Signal (RS) sequence for the physical cell identity (PCI).
The Narrow Band Physical Broadcast Channel (NPBCH) contains the Master Information Block (MIB) and provides the location of the SS/PBCH block and Control Resource Sets (CORESETs). The SS/PBCH block always spans the same number of tones, with its bandwidth scaling according to the SCS. This block can be located anywhere within the channel bandwidth and sub-frame, with its position relative to the lowest tone being part of the Physical Broadcast Channel (PBCH) information. The PBCH also provides the location and size of the CORESET for Residual Minimum System Information (RMSI) and Other System Information (OSI).
For system information, the device reads the PBCH, which provides basic cell configuration and identifies the downlink control channel that schedules the shared channel. The device retrieves other necessary system information and can request on-demand system information relevant to its specific needs.
Channel Coding in 5G NR Channel coding in 5G NR relies on HARQ and scheduling technologies. The data channel uses Low-Density Parity-Check (LDPC) coding, which offers implementation and latency benefits compared to other coding schemes. In incremental redundancy, each retransmission contains different information, while in chase combining, retransmissions contain the same data and parity bits as previous transmissions, with the receiver combining these bits from multiple transmissions.
Polar coding is used for control channels in 5G NR, where channels are polarized through successive combinations of binary channels. Some channels approach a capacity of 1 and are used for data transmissions, while others approach zero and are considered frozen bits. The maximum code block sizes for control channels are 512 for both downlink and uplink.
In summary, 5G NR’s physical layer brings significant advancements in flexibility, efficiency, and performance compared to previous technologies. Its support for various numerologies, flexible bandwidth usage, and low-latency features make it well-suited for a wide range of applications, from enhanced mobile broadband to ultra-reliable low-latency communications.
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