Spectral Efficiency Clause Samples
The Spectral Efficiency clause defines the minimum required efficiency with which a system or device utilizes the available frequency spectrum to transmit data. In practice, this clause sets specific benchmarks or ratios, such as bits per second per hertz (bps/Hz), that equipment or services must meet to ensure optimal use of bandwidth. By establishing these standards, the clause helps maximize data throughput while minimizing wasted spectrum, thereby addressing the need for efficient and fair allocation of limited frequency resources.
Spectral Efficiency. The physical path design of the Ethernet twisted-pair copper media standard 10GBASE-T (802.3an) represents one of the most advanced constellations in common use at very high symbol rates. As shown below in Figure 22, each of the four channels uses an 800 Mbaud symbol rate with 3.125 bits per DSQ-128 dimension, giving 2.5 Gb/s/copper pair. This is derived using 16-▇▇▇ at 4 bit/dim, which is reduced to 3.125 bit/dim by 2-D alphabet partitioning and coding. The cable transmission matrix is high cross-linked, suggesting that MIMO-OFDM could be used. However, latency issues make this a poor choice; a factor often overlooked in the use of OFDM signaling. The use of intrinsic echo and cross-talk cancellation offers a strong (and essential) advantage in signal-to-noise ratio (SNR). Overall a BER of 10-12 is achieved with a SNR of 23.32 dB. A low-density, parity check code (LDPC [2048,1723]) offers 8 dB coding gain. Figure 22: DSQ-128 Modulation. For microwave mobile backhaul, over the last ten years, state of the art spectral efficiency has increased from a modest 1.2 b/s/Hz to a record value of 35 b/s/Hz demonstrated by Ericsson at the Mobile World Congress 2011 in Barcelona. Enabling technologies for such an increase in spectral efficiency are MIMO technologies such as polarization multiplexing and spatial multiplexing, and high order modulation where 512QAM is commercially available and 1024QAM and higher are to be introduced to the market [31]. Recent records in spectral efficiencies achieved in optical communications e.g. over multi-mode fibres, rely all on off-line processing after sampling the signals in a high-speed oscilloscope.