MATLAB  5G Waveform Generator Terms

MATLAB 5G Waveform Generator Terms

Steps :

Open the MATLAB

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On the APPS section, under Signal Processing and Communications, click on the 5G waveform generator app.

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Now, it opens the wireless waveform generator window.

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Select the waveform type in the generator tab. Learn more about 5G toolbox here.

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There are different waveforms present in 5G(NR), choose 1 of them.
For now I am selecting Downlink FRC(Frequency Reference Channel).

Note : NR(New Radio) is used in place of 5G at many places.

FRC(Frequency Reference Channel) - This channel is a special channel that carry reference signals. This signal is not used for delivering any specific information(alike channels, e.g. PBCH, DPCCH, etc), instead it delivers the reference point for the downlink power(the power of the signal from eNodeB) to the UEs.

Visualize : Visualization is a technique in which images, diagrams, animation or any pictorial form is created to represent any data or message.

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Some visualization techniques provided by MATLAB in 5G simulation :

(a) Time Scope : Display time domain signals(it means at what particular time interval, the signal are at the peak point).

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(b) Spectrum Analyzer : Use to measure/represent the power/RF(Radio Frequency) of the input signals.

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(c) Constellation Diagram : Display the constellation of a digitally modulated signal(means digital information signal is encoded into amplitude, frequency, etc, of the transmitted signal).

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(d) Resource Grid : Represents Bandwidth Part(BWP) carrier with different SCS(Sub Carrier Spacing).

BWP(Bandwidth Part) - a 5G feature for dynamically adapting the carrier bandwidth(a contiguous set of Physical Resource Blocks(PRB)) and numerology(or Sub Carrier Spacing having formula = 15kHz * 2^n) in which UE operates.
A UE can be configured with up to 4 BWP in which only 1 BWP is active at a time(UE doesn't receive data outside of active BWP).

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Resource Element(RE) - It is the smallest unit(physical resource) in NR, made up of 1 subcarrier in frequency domain(frequency domain graph shows how much of the signal exists within a given frequency band over a range of frequencies) and 1 OFDM symbol in time domain(time domain graph shows how signals change over time) .
It is uniquely identified by (k, l) where 'k' is the index in the frequency domain and 'l' refers to the symbol position in the time domain relative to some reference point.

Resource Block(RB) - It is defined as 12 no. of consecutive subcarriers in frequency domain.

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(e) Channel View : Shows how main frequency is divided into linear frequencies(Subcarrier) to transmit data.

(f) 2D Spectrogram : Represents the signal strength of a signal over time at different frequencies present in a waveform.

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Terms related to Downlink FRC(Frequency Reference Channel) -

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(1) Frequency Range - In 5G technology, 2 different frequency ranges are designed for a bandwidth :
FR1(Frequency Range 1)[410MHz - 7.125GHz] - It was designed to carry much of the traditional cellular mobile communications traffic.
FR2(Frequency Range 2)[24.25GHz-52.6GHz] - Higher frequency bands, aimed at providing short range very high data rate capability.

(2) MCS(Modulation and Coding Scheme) - MCS defines the numbers of useful bits which can carried by one symbol(a symbol is transmitted within RE).

Better Radio Signal Quality >> Higher MCS >> More useful bits can be transmitted with a symbol.
Bad Signal Quality >> Lower MCS >> Less useful data transmitted.

It has 2 aspects :
(a) Modulation(Qm) - Defines how many bits can be carried by a single RE(resource element) irrespective of whether it is useful bit or parity bit(parity bit is extra bit send with the main bits to detect error). Modulation Order = 2^n
2 bits can be transmitted per RE.
With 16QAM, it can be 4 bits,
with 64QAM, it can be 6 bits,
with 256QAM, it can be 8 bits.

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QAM(Quadrature Amplitude Modulation) : It is a modulation technique(process in which information is converted into electrical signals for transmission over a medium) in which information is transmitted by changing the amplitude and phase of a carrier wave, which doubles the effective bandwidth(by combining 2 amplitude modulated signals into a single channel).
QAM is also known as “Quadrature Carrier Multiplexing”.

Quadrature : It indicates that the phase difference between two carriers is 90 degrees but each having the same frequency.

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Note : 16-QAM is considered as the lowest order QAM because 2-QAM is considered the same as for BPSK(Binary Phase Shift Keying) and 4-QAM is the same as QPSK(Quadrature Phase Shift Keying). In addition to the error-rate performance of 8-QAM is almost the same as that of 16-QAM hence it is not widely used.

PSK(Phase Shift Key) : The digital modulation technique in which the phase of the carrier signal is changed by varying the sine and cosine inputs at a particular time.
BPSK(Binary Phase Shift Keying) : It is also known as 2-phase PSK in which sine wave carrier takes 2 phase reversals such as 0 degree(for no phase change) and 180 degree(for phase change of 180).
QPSK(Quadrature Phase Shift Keying) : It is any modulation technique in which 2 bits of digital information is send at a time.

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Signal Components -
(i) "I" Signal(In-phase Signal) : Carrier signal represented by a sine wave(i.e. sinwt).
(ii) "Q" Signal(Quadrature Signal) : Carrier signal represented by a cosine wave(i.e. coswt).

The two modulated carrier signals are transmitted together at the source and at the destination, these two carrier signals are demodulated(i.e. separated/decoded) independently.

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Learn more about QAM here.

(b) Code Rate(R) - It is the ratio between the number of information bits at the top of the Physical layer and the number of bits which are mapped to PDSCH(Physical Downlink Channel) at the bottom of the Physical layer. In other words we can say that it is the ratio between useful bits and total transmitted bits(Useful + Redundant Bits).

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5G Terminologies :

Note : 1 Frame = 2 Half Frames || 1 Half Frame = 5 Subframes || 1 Subframe = no. of Slots depends upon SCS || 1 Slot = 24-275 Physical Resource Blocks || 1 Resource Block = 12 Subcarriers || 1 Subcarrier ~ 1 Resource Element

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(3) Subcarrier Spacing(SCS) - SCS is the gap between 2 consecutive subcarriers/frequencies . 5G SCS is not limited to 15KHz unlike LTE, instead it scales by 2^n * 15KHz to cover different services such as QoS(Quality of Service), frequency ranges and latency requirements.
15, 30, and 60 kHz SCS are used for the lower frequency bands.
60, 120, and 240 kHz SCS are used for the higher frequency bands.

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(4) Channel Bandwidth - The information-carrying capacity of a channel is called its channel bandwidth.
LTE carriers are narrower in bandwidth, up to 20 MHz maximum whereas 5G NR maximum carrier bandwidth is up to 100 MHz in FR1 or up to 400 MHz in FR2.

(5) Subframes - Downlink and Uplink are organized into frames with 10ms(milli second) duration.
Each frame is further divided into 2 equally sized half frames of 5 subframes each.

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In LTE, there are fixed 2 slots per subframe, but in NR, no. of slot may vary, depending on different Subcarrier Spacing. Link direction(Uplink, downlink or flexible) can be dynamically assigned in NR slots.

Note : No. of symbols within a slot does not change with the SCS. OFDM symbols in a slot can be classified as ‘downlink’ (denoted ‘D’), ‘flexible’ (denoted ‘X’), or ‘uplink’ (denoted ‘U’).

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There can be 1, 2, 4, 8, or 16 slots per subframe. Subcarrier Spacing increase >> Slot length decrease.

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(6) Cell Identity(CI or Cell ID) - In 5G, NR Cell Global Identifier(NCGI) is used to identify NR cells globally and similar to ECGI(EUTRA Cell Global Identifier) in 4G LTE.
The NCI(NR Cell Identity) has a total size of 36bits constituting of gNB Identity and Cell Identity.

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5G NR has also downlink synchronization(it is the process in which UE calculate the exact timing when it should send/receive Uplink(UL)/Downlink(DL) data) signal like LTE. These are PSS(Primary Synchronization Signal) and SSS(Secondary Synchronization Signal). Learn MORE.

Formula to calculate Cell ID = 3*N(SSS) + N(PSS)

(7) RNTI(Radio Network Temporary Identifier) - It is used to differentiate/identify a connected UE in the cell, a specific radio channel, system information(SIB) transmitted for all the UEs by 5G gNB. Learn MORE.

Different types of RNTI are :

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(8) Bit Source - This part provides you an option to generate a sequence of Pseudorandom(or Pseudo-Noise) binary numbers using LFSR(Linear Feedback Shift Register) which are used for pseudorandom scrambling(ability of gNodeB and UE to distinguish signals coming simultaneously from many different UEs and gNodeBs respectively) and in direct sequence spread spectrum system(modulation technique used to reduce overall signal interference).
The sequence of bits are generated to create a high correlation between the transmitted and received signals.
e.g. in a range finding application, the local station generates a pseudorandom bit sequence and transmit it to the target point(remote location). At the remote location, some objects echoes this PN signal back to the local station and by correlating a delayed version of the transmitted signal with the original signal, a time is estimated and thus the distance.

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(9) Filtering Configuration - Filters are used to remove the unwanted content(e.g. noise) from the signal spectrum to perform mathematical operations such as differentiation and integration. But filtering also introduce delay(constant over all frequencies or vary with frequency) in the signal.

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FRC_info :

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(1) Duplex mode - Any communication between UE and network(downlink/uplink) is determined by duplex method being used.

There are 2 types of duplexing scheme used in mobile communications.

(a) FDD(Frequency Division Duplex) : In this system, UE use 2 different frequency bands from the available frequency spectrum as dedicated uplink and downlink bands.
(b) TDD(Time Division Duplex) : Whereas in TDD, only 1 frequency band is used for both UL and DL but at different time slots.

There are 2 systems to ensure 2 way communication between users :
(a) Full duplex system, that accommodate 2 way communication simultaneously. e.g. mobile phone.
(b) Half duplex system, which facilitates communication in only 1 direction at a time. e.g. walkie-talkie.

Alike 4G, 5G can be operated in both FDD and TDD schemes. On adding, 5G radio frame structure is designed to support both half-duplex and full-duplex communication.

FDD is full-duplex, whereas TDD and the half-duplex version of FDD are half-duplex systems. Since, 5G NR networks are operated in higher frequency bands, TDD can be very effective for some of the futuristic use cases of 5G.
TDD provides flexibility to dynamically allocate downlink/uplink network resources depending on the data needs.

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(2) Payload(bits/slot) - Carrying capacity of a packet or other transmission data unit.

(3) PDSCH(Physical Downlink Shared Channel) mapping type - PDSCH carry user data and transmit it through each transmission antenna.

CORESET(Control Resource SET) sets the time/frequency resources where PDCCH(Physical Downlink Control Channel) can be transmitted. There can be many CORESETs in a carrier and can be occur anywhere in the slot.

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Note : DCI(Downlink Control Information) carries control information like which resource block carries your data?, what kind of demodulation scheme we have to use to decode data? and some other additional information. This means user need to decode DCI before they can decode or transmit data.

Scheduling PDSCH : decode PDCCH which carry DCI >> decode PDSCH in order to transmit the received data.
To understand the main difference between PDCCH and PDSCH, we need to understand the concept of UE decoding. The UE needs to read the PDCCH first to find the location of the PDSCH. If the UE finds the PDSCH, then based on the decoding result of the PDSCH, it sends feedback to the gNB (ACK/NACK).
In simple words, if UE decode the PDCCH successfully, then only UE gets the PDSCH location and based on received information/data, it sends ACK/NACK feedback to gNB. If it fails to decode PDCCH then, it send no feedback to gNB.

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Scheduling PUSCH(Physical Uplink Shared Channel) : schedule request from the network(uplink) >> uplink granted >> transmit data through PUSCH using DCI information.

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RACH(Random Access Channel) : used to access the network or send scheduling requests.

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(4) Allocated Symbols - The symbol allocation of PDSCH indicates the OFDM symbol(a complex no. representing the amplitude and phase of the modulation scheme) locations used by the PDSCH transmission in a slot.

DM-RS(Demodulation Reference Signal) and PT-RS(Phase Tracking Reference Signal) are the reference signals associated with PDSCH.

DM-RS(Demodulation Reference Signal) : DM-RS is used to estimate the radio channel for demodulation of associated physical channel.
PT-RS(Phase Tracking Reference Signal) : track the phase of the local oscillator at transmitter and receiver and enables suppression of phase noise and CPE(Common Phase Error) specially at higher mmWave frequencies.

The mapping type of PDSCH is either :
Slot-wise (type A) : For mapping type A, the DM-RS OFDM symbol locations are defined relative to the first OFDM symbol of the slot.
Non-slot-wise (type B) : For mapping type B, the DM-RS OFDM symbol locations are defined relative to the first OFDM symbol of allocated PDSCH resources.

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DM-RS(Demodulation Reference Signal) configuration type - It indicates the frequency density of DM-RS and is signaled by RRC message DM-RS-Type.

Configuration type 1 : defines six subcarriers per physical resource block (PRB) per antenna port, comprising alternate subcarriers.
Configuration type 2 : defines four subcarriers per PRB per antenna port, consisting of two groups of two consecutive subcarriers.

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For more details, just go through this.

Add yours thoughts in the comment section and let me know if it's clear to you.