Glossary of terms

A - B

Algorithm is a set of mathematical operations for specific functionalities. These operations can be either implemented in a software language and operated on a generic hardware platform (such as CPU and GPU), or in a hardware language that will be translated into FPGA fabric or ASIC.
APIs - Application Programming Interface is the interface between typically two software components, or a software component and a hardware component. Acceleration Abstraction Layer (AAL) in DPDK, which is endorsed by ORAN, is now the default API to enable RAN software to work with different hardware accelerator implementations for vRAN applications.
ASIC - Application Specific Integrated Circuits (ASICs), which are custom manufactured for specific design tasks. AccelerComm IP blocks have been proven on 7nm ASIC and FPGA technology, allowing customer to select the most appropriate technology for the application.
Band n255 is designated for L-band Non-Terrestrial Networks (NTNs) transmission using Frequency Division Duplex (FDD).
Band n256 is designated for S-band Non-Terrestrial Networks (NTNs) transmission using Frequency Division Duplex (FDD).
Bent-Pipe – in NTN architectures, Bent-Pipe is a phrase used to describe a transparent architectures. The connection from the ground station to the device is thought of as a pipe, which is “bent” by the satellite repeating the signal coming up from the ground station back down to the device without processing it.
Beam Former – In a satellite, the beamformer is a the part of the payload that performs the signal processing that means that the antenna array forms beams. This can use a combination of digital and analogue processing techniques.
BLER - Block Error Rate is defined as the number of erroneous received code blocks divided by total number of received code blocks. The code block is considered to be error-free if its attached CRC code matches the one calculated by the receiver.

C - E

Channel Coding - Channel coding (also known as Forward Error Correction) is the process of correcting transmission errors inflicted by channel noise, interference and fading. This is done by adding extra (redundant) bits to the information bits before transmission. At the receiver, a channel decoder uses complex algorithms to extract the original information bits from the received data, correcting for errors introduced. 5G NR introduces the use of a Low-Density Parity Check (LDPC) channel coder for the Physical Uplink and Downlink Shared Channels (PUSCH and PDSCH) over which user data is passed, and a Polar coder for the 5G uplink and downlink control channels (PUCCH and PDCCH). For more information on Channel Coding, view our full post: What Is Channel Coding.
Channel estimation - This is a technique used in the High-PHY of a receiver to estimate the noise, fading, delay and frequency offset that has been imposed by a wireless channel upon reception of a transmitted signal. It leverages the known values of demodulation reference signals (DMRS) that are included into the transmitted signal to infer the effects of the channel.
Code block – In channel coding, code block refers to the original “raw” block of digital information prior to adding CRC and prior to channel coding. In the 5G LDPC code, the maximum Code Block size is 8424 bits.
Code rate – In channel coding, code rate (or information rate) is defined as the ratio between information bits and total transmitted bits (Information + Redundant Bits). Redundant bits are added by the physical layer for Forward Error Correction (FEC). Simply put, code rate is a measure of redundancy. A low coding rate corresponds to increased redundancy.
Core Network - is part of the 5G System which provides connectivity to the Internet and to application servers.
CRC - (Cyclic Redundancy Check) - CRC is a sequence of bits attached to a Code Block (CB) in the transmitter prior to encoding and is used for error detection. The CRC is checked in the receiver after the decoder to confirm whether or not the transmitted CB has been successfully received - If the CRC attached to the CB block matches the one calculated by the receiver the CB is considered to be error-free.
CU - The Centralised Unit (CU) of a base station includes the L3 of the L1. In a disaggregated architecture, many DUs (containing the L2 and the High-PHY of the L1) can be connected to the same CU and many RUs (containing the Low-PHY) can be connected to the same DU.
D2D Direct to Device – In NTN networks this refers to use cases where the user device, often but not always a smartphone, connects directly to the satellite. This is in contrast to uses cases where a separate satellite terminal connects to the satellite and then the end user device connects to this, typically through WiFi
Digital Front End (DFE) – In a 5G Physical layer the Digital Front End is the name given to the component that does the digital processing closest to the digital to analogue converters.
Downlink – in 3GPP systems Downlink is the name given to communications that flow in the direction from the base station to User Equipment.
DPDK – Data Plane Development Kit is an open source standard used to interface accelerator cards to the host processor. Often used for PCIe accelerator cards such as an LDPC accelerator card in a DU
DSP Digital Signal Processor – usually shortened to DSP this is a type of processor specifically designed for signal processing tasks
DU - The Distributed Unit (DU) of a base station includes the L2 and the High-PHY of the L1. In a disaggregated architecture, many DUs can be connected to the same CU (containing L3) and many RUs (containing the Low-PHY) can be connected to the same DU.
eMBB - Enhanced Mobile Broadband defines requirements for high throughput data-driven use cases requiring high data rates across a wide coverage area.
Equalisation - This is a technique used in the High-PHY of a receiver, following channel estimation. The equaliser has the role of using the estimated channel information to undo the effects of the channel and equalise the received signal so that it resembles the transmitted signal as closely as possible

F - G

FAPI - FAPI is an API interface for communication over the split-6 interface between the PHY and MAC layers of a 5G gNodeB or a 4G eNodeB. nFAPI is a wrapper for FAPI messages, which enable them to be transported over a network interface, such as Ethernet. Both FAPI and nFAPI are standards developed by the Small Cell Forum.
FEC - Forward Error Correction is sometimes known as Channel Coding, and refers to the process of correcting transmission errors inflicted by channel noise, interference and fading For more information on Channel Coding, view our full post: What Is Channel Coding.
Feeder link - In an NTN, the feeder link carries 5G NR or NB-IoT signals between ground stations connected to the Internet and satellites or airborne vehicles. The feeder link is the complement to the service link, which connects these satellites or airborne vehicles to user devices on the ground.
FDD Frequency Division Duplex – Is a configuration where simultaneous uplink and downlink transmission occur on separate frequencies. In contrast in a Time Division Duplex (TDD) configuration a single frequency is used but uplink and downlink transmissions occur at different times.
FFT/IFFT – Fast Fourier Transform / Inverse Fast Fourier Transform. A digital signal processing step that converts signals between a frequency domain representation and a time domain representation.
FPGA - Field Programmable Gate Arrays (FPGAs) are semiconductor devices that are based around a matrix of configurable logic blocks (CLBs) connected via programmable interconnects. FPGAs can be reprogrammed to desired application or functionality requirements after manufacturing. This feature distinguishes FPGAs from ASICs, which have fixed configurations.
FMC FPGA Mezzanine Card a small mezzanine module optimized to provide the physical interface for FPGAs on a carrier card
FR1/FR2 - 5G supports licensed spectrum from below 1 GHz up to 52.6 GHz. 3GPP divides this into two different frequency ranges (FRs) as follows:
FR1 - this includes existing bands in use, and bands below 7 GHz
FR2 - all new bands in the range of 24.25 GHz to 71.0 GHz FR2 offers the possibility for large amounts of spectrum and very wide transmission bandwidth. This enables support of extremely high data rates for end-users compared to the latest LTE networks. However, it should be noted that FR2 bands are prone to higher path loss and smaller cell coverage.
gNodeB – Often shortened to gNB, it refers to the current generation of 5G base station, as opposed to NodeB for 3G and eNodeB for 4G.

H - K

High Altitude Platforms (HAPs) – HAPs’ like satellites are considered to be elements of Non Terrestrial Network, however unlike a satellite they are at lower altitudes. Examples include drones and ballons.
HARQ - HARQ stands for Hybrid Automatic Repeat Request. In 5G NR, a block of data, referred to as a Transport Block (TB), is composed of many Code Blocks (CBs). After decoding, each CB is checked for correctness with a Cyclic Redundancy Check (CRC). If any CBs fail, the receiver system requests the retransmission of either the complete TB or of just the affected groups of CBs in the TB. When retransmission is received, the decoder combines it with the original and retries the decode. If this is successful it inserts the decoded bits into the transport block. Functionality to support this process and interface to a HARQ buffer provided by external DRAM is included in AccelerComm decoders.
High-PHY - is the ‘higher’ portion of the physical layer of a communication system, which typically encompasses digital signal processing performed on a per-user basis such as channel estimation, equalisation, QAM modulation/demodulation, channel coding and CRC check. This is in contrast to the low-PHY ‘lower’ portion of the physical layer, which typically performs OFDM modulation and demodulation on a per-carrier basis.
In-line Accelerator - An inline accelerator is an architecture where a signal processing device is located between the main CPU and the next network element so the signal only passes between the CPU and the accelerator once. In contrast in a lookaside architecture the signal passes from the CPU to the accelerator and then back to the CPU.
IEEE standards - define many industry standards for connectivity between two devices. Notably in the gNodeB, PCIe is a key piece of interconnect technology that allows data transfers between the CPU and the hardware accelerator(s).
Interleaving - is a set of operations that changes the order of the bits in messages to improve the performance of decoding at the receiver by randomizing bursts of contiguous bit errors generated by fades in the propagation channel.

L - N

L1 – In a 5G system L1 is the physical layer of the radio access network. It typically comprises Low-PHY which performs signal processing on a per-carrier basis, and High-PHY which performs signal processing on a per-user basis.
L2 – In a 5G system layer 2 contains the Media Access Control (MAC) and Radio Link Control (RLC) sublayers.
L3 - In a 5G system layer 3 contains the Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP) sublayers.
Latency - Network latency is the amount of time packets take to travel between points. This is normally quoted “end-to-end” from source to destination. In telecommunications, 5G offers latencies of 1 millisecond or lower.
Look-aside Accelerator – see inline accelerator.
LDPC Code - The LDPC code is a linear block channel code which is used for the Physical Uplink and Downlink Shared Channels (PUSCH and PDSCH) for 5G New Radio. AccelerComm has developed optimized FPGA and ASIC solutions for LDPC encoding and decoding, which have been designed to meet the most challenging throughput and latency requirements for 5G New Radio, whilst minimising resource requirements.
LLS - The O-RAN Alliance defines the 7-2 Low-Level Split (LLS) interface between the DU (containing a base station's L2 and the High-PHY of its L1) and the RU (containing the Low-PHY). LLS signals are typically carried by eCPRI traffic on an Ethernet interface.
Millimetre wave - The 5G Millimetre Wave (also known as the mm-wave, MMW or Extremely High Frequency -EHF) refers to a band of radio spectrum above 24.25 GHz. The name derives from the wavelength of these waves; which is measured in millimetres, rather than the higher wavelengths used in older technology. See also “FR1/FR2”
MIMO - Multiple Input, Multiple Output refers to a transmission technology that uses multiple smart antennas on the transmit and receive side in the wireless network. Using a technique called spatial multiplexing, it’s possible to send a different data stream on each antenna, thereby increasing the throughput to the cell tower and to the user device. 5G NR extends MIMO up to very high numbers of antenna elements and enables “massive MIMO”. This is a key enabler for achieving throughput in the higher spectrum bands.
mMTC - Massive Machine Type Communications refers to the requirements that enable support of a very large number of devices, which may only send data sporadically, such as Internet of Things (IoT) use cases.
NB-IoT (Narrow Band Internet of things) - IoT describes the network of physical objects—“things”—that are embedded within sensors, software, and other technologies for the purpose of connecting and exchanging data with other devices and systems over the Internet. NB-IoT is a 3GPP-defined waveform for serving these use cases.
Network slicing - Network slicing is a technology that separates virtual networks into independent logical partitions, or slices, that support different services and applications, all residing on the same hardware. Each slice has its own architecture, service characteristics, management and security, which are configured by the network operator in different use cases. Network slicing is a key feature of 5G.
nFAPI – See FAPI
NTN - Non-Terrestrial Networks comprise satellites and airborne vehicles to provide coverage of 3GPP waveforms for user devices on the ground.

O - Q

Onboad Processor (OBP) – Is the name given to the main processor in a satellite payload. Unlike processors found in terrestrial serves an OBP will have to meet strict Size, Weight and Power (SWaP) constraints as well as many other space specific requirements such as vibration, temperature and radiation tolerance.
OFDM - Orthogonal Frequency-Division Multiplexing is a method of encoding data on multiple carrier frequencies: One data stream divides over separate channels with different frequencies. These separate channels help reduce and avoid interference.
O-RAN - Open Radio Access Network architecture is the foundation for building the virtualized RAN on open hardware and cloud, with embedded AI-powered radio control. The architecture is based on standards defined by O-RAN ALLIANCE www.o-ran.org which are fully supporting and complimentary to standards promoted by 3GPP and other industry standards organizations. AccelerComm is a member of the O-RAN Alliance, and is contributing to the technical development of O-RAN standards, bringing its channel coding experience to reduce latency and increase spectrum efficiency for Open 5G Networks.
OSI model - The Open Systems Interconnection Model is a seven-layered conceptual framework designed to ensure the diverse range of telecommunication systems available can interconnect with one another seamlessly. The seven layers of these standardization guidelines are; the physical layer, the data link layer, the network layer, the transport layer, the session layer, the presentation layer and the application layer.
Payload – in a satellite architecture the payload is the part of the satellite that carries out the functions for which the satellite was launched, such as communications. In contrast the Bus refers to the parts of the satellite that support the payload and are often common to many missions, such as power supply, telemetry and spacecraft navigation.
Physical Layer - In the seven-layer OSI model of computer networking, the physical layer (or layer 1) is the first and lowest layer. The physical layer defines the means of transmitting bits over a physical data link. The bitstream (or channel) is grouped into symbols, coded, and converted to a physical signal that is transmitted over a transmission medium.
Polar Codes - The Polar code is a linear block channel code which is used for the 5G uplink and downlink control channels (PUCCH and PDCCH), and is designed to perform well with the shorter block lengths used for control information. AccelerComm has developed FPGA and ASIC solutions for Polar encoding and decoding which have been designed and optimized for 5G new radio.
QAM - Quadrature Amplitude Modulation is a technique widely used to modulate data signals on a carrier used for radio communication. When used for digital transmission of radio communication applications, QAM can carry higher data rates than ordinary amplitude-modulated and phase-modulated schemes. In QAM, the constellation points are normally arranged in a square grid with equal vertical and horizontal spacing. QAM constellations are normally expressed in powers of 2, where each point is referred to as a “symbol”. Thus, 256-QAM uses a 256-point constellation where each symbol contains 8 bits. By using higher order modulation formats (that is, more points on the constellation), it is possible to transmit more bits per symbol. However, the points for a higher QAM are closer together and are therefore more susceptible to noise and data errors. Channel coding is therefore essential, to avoid losing the information transmitted, maximizing the spectral efficiency of the channel.

R - T

RAN - Radio Access Network, also known as RAN, is technology that connects devices to various parts of networks through radio connections. The most recent RAN evolution divides the user plane and control plane into separate elements, which enables various 5G features, such as network slicing and MIMO, to function properly.
Regenerative NTN - In regenerative NTNs, 5G NR gNodeBs or NB-IoT eNodeBs are hosted on satellites or airborne vehicles, to provide coverage for user devices on the ground.
RU - The Radio Unit (RU) of a base station includes the Low-PHY of the L1. In a disaggregated architecture, many DUs (containing the L2 and the High-PHY of the L1) can be connected to the same CU (containing L3) and many RUs can be connected to the same DU.
SA 5G NR - Standalone (SA) 5G NR - Standalone 5G NR uses the 5G Core Network (5GCN) architecture, including the full control and user plane offered by 5G. SA supports a far wider range of use cases than non-standalone and offers ultra-low latency, better efficiency and a lower cost, but requires an end-to-end 5G network so cannot be deployed on pre-existing assets.
Service link - In an NTN, the service link carries 5G NR or NB-IoT signals between user devices on the ground and satellites or airborne vehicles. The service link is the complement to the feeder link, which connects these satellites or airborne vehicles to ground stations that provide connectivity to the Internet.
Spectral Efficiency - Spectral efficiency refers to the information rate that can be transmitted over a given bandwidth in a communication system. It is a measure of how efficiently a limited frequency spectrum is utilized by the physical layer.
SWaP Size Weight and Power – A term used to describe the requirements a payload or a part of a payload makes on a satellite bus. On board a satellite all of the attributes are extremely limited and so minimising them is critical to the success of the design.
TDD -Time Division Duplex – see FDD Frequency division duplex.
Transparent NTN - In transparent NTNs, 5G NR gNodeBs or NB-IoT eNodeBs are hosted in ground stations and satellites or airborne vehicles act as 'bent-pipe' relays, to provide coverage for user devices on the ground.
Transport block - The transport block is the fundamental payload which is passed between the MAC and PHY Layers, specifically for the shared data channel such as PDSCH and PUSCH . A Transport Block undergoes PHY layer processing at the transmitter before being mapped onto the shared data channels for transmission over the air interface.
Turbo Code – a channel coding technique used in 3G and 4G mobile communications and some other communication systems. For 5G they were replaced by LDPC codes

U - Z

Uplink – in 3GPP systems Downlink is the name given to communications that flow in the direction from User Equipment to the base station.
URLLC - Ultra-Reliable Low-Latency Communication defines a set of features that provide low latency and ultra-high reliability for mission critical applications such as industrial internet, smart grids, remote surgery and intelligent transportation systems.
User Equipment UE – In 3GPP standards UE is the term used to describe the part of the network that the user interacts with. Usually this refers to a smartphone.
Vector Processor – is a type of processor optimised for vector calculations. They are found in Graphics and AI processors and are also extremely efficient for carrying out some complex signal processing tasks.

3-5

3GPP - The 3rd Generation Partnership Project (3GPP) is a partnership of several telecommunications organizations developed to create standards for 3G technology. 3GPP has continued to develop standards for succeeding wireless generations, including 5G. This project uses standards based on the Global System for Mobile Communications specifications and radio access technology.
5G - Fifth-generation wireless, or 5G, is the next generation of cellular network technology. 5G will enable significantly greater mobile speeds than its predecessors; 1G, 2G, 3G and 4G — as much as 20 gigabits per second (Gbps) with less than one millisecond (ms) latency. This allows 5G to support real-time interactive communications services, such as VR (Virtual Reality), as well as to control autonomous cars and high precision mission-critical industrial devices in real-time. High reliability and availability at all times is a necessity for these use cases.
5G NR - 5G New Radio is the set of standards that replaces the Long Term Evolution (LTE) standard, with goals to support wireless communication growth. In December 2017, 3GPP released 5G NR specifications and updated several performance and connectivity requirements for connections to qualify as 5G NR.