Multi-Processor System-on-Chip 2. Liliana Andrade

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      1 For a color version of all figures in this book, see www.iste.co.uk/andrade/multi2.zip.

      2 ¹ According to data (GFK 2019), smartphone and related wearables were a $522 billion dollar market in 2018.

      3 ² Loosely translated as a single packet of data, for the broader audience.

      4 ³ Simplified: TTI consists of OFDM symbols, which, in turn, consist of transformed sets of quadrature amplitude modulation (QAM) symbols, which, in turn, consist of transformed sets of soft bits, which are a mix of guard and information bits.

      5 ⁴ TTI is inversely scaled with subcarrier frequency spacing (SCS). In 5G, SCS is base spacing (15 kHz, same as 4G) ×2μ and TTI is base TTI (1 ms, same as 4G) ×2−μ.

      6 ⁵ We do not have a reference for this rule of thumb, since the actual timing budget distribution is vendor-specific and kept private. This is a first-order approximation.

      7 ⁶ 1 kRB = 1,000 RB, 1 RB = 12 subcarriers × 2 slots of 7 (6) symbols per slot = 168 (144) RE, (·) – extended Cyclic Prefix (CP) mode possible for μ = 2 or LTE. An RB is a unit in technical terminology representing a grid section onto which QAM symbols are mapped; one element of that grid is called an resource element (RE).

      8 ⁷ Simplified: for a radio link.

      9 ⁸ Note that this should not be confused with massive MIMO, which uses constructive and destructive interferences of radio waves from multiple antennas to create a single data stream layer.

      10 ⁹ 4G modulation code rate schemes (MCS) (3GPP 2019b).

      11 ¹⁰ 5G MCS (3GPP 2019f).

      12 ¹¹ This is the lowest rate per smallest channel. Even though a voice call may require between 8 kb/s and 80 kb/s (depending on the codec (ITU 2019a, b)), the block nature of discrete Fourier transform (DFT) and the required sample rate used in 4G forces the modem to work with higher average rates than those required by the application.

      13 ¹² Simplified: simultaneously active multiple channels on different frequencies.

      14 ¹³ An additional motivation for having an extent of SW solutions in communication modems is 1) their ability to be exchanged easily via updates, compared to exchanging HW, and 2) they are ideal for multiplexing a multitude of standards on the same HW.

      15 ¹⁴ A self-contained piece of SW or function that fully captures the functionality of an algorithm.

      16 ¹⁵ Note that the first inner loop will not be executed for l = 0.

      17 ¹⁶ At each stage, quantization occurs anew, for example .

      18 ¹⁷ Accumulator quantization: the result of multiplying Q0.n numbers is Q0.2n, which still represents a value in the range [−1, 1), just with 2n bits, where n = databits. This value is then again requantized with ACCbits = m bits.