ALLPCB
Single-sideband (SSB) overview
Single-sideband (SSB) refers to a modulation format in which one sideband of a double-sideband signal (commonly the lower sideband) and the carrier are removed, leaving only a single sideband (commonly the upper sideband). This reduces the occupied bandwidth and improves spectral efficiency. SSB is typically generated using a balanced modulator.
Note: SSB can also denote the synchronization signal/PBCH block in 5G NR, a different concept described below.
Basic generation method
The most direct method to produce an SSB waveform is to pass a double-sideband signal through a sideband filter that rejects the unwanted sideband and retains the desired one.
Lower and upper sideband extraction
For lower-sideband SSB (LSSB), design the filter H(ω) as a low-pass filter to extract the lower sideband spectrum. For upper-sideband SSB (USSB), design H(ω) as a high-pass filter to extract the upper sideband spectrum.
Bandwidth and power
The bandwidth of an SSB signal is half that of a DSB-SC or AM signal and equals the message bandwidth, commonly denoted Bssb = fH. The power of an SSB signal can be expressed as Pssb = Ps/4, where Ps is the message signal power.
SSB in 5G NR: channels and signals
In 5G NR, SSB refers to the synchronization signal/PBCH block. The SSB contains several key physical channels and signals:
- Primary Synchronization Signal (PSS): used for cell search and physical-layer synchronization; it has a fixed time-frequency position and appears once per SSB.
- Secondary Synchronization Signal (SSS): used together with PSS for cell search and physical-layer synchronization; it also conveys information about the physical cell ID group.
- Physical Broadcast Channel (PBCH): carries system broadcast information required by the user equipment (UE); PBCH payload and its associated demodulation reference signals (DMRS) are included in the SSB.
In the SSB time-frequency structure, PSS occupies the first OFDM symbol (sym0), SSS occupies the third OFDM symbol (sym2), and PBCH data plus DMRS are distributed across multiple OFDM symbols and resource blocks.
