Abstract
Internet of everything is being build up rapidly, which causes much higher requirements towards the flexibility of communication resources, especially the adaptivity of the fronthaul to various transmission distances and capacities. In this paper, we proposed a low-cost and spectrum efficient 5G fronthaul broadband connection solution that combines hierarchical modulation technology and delta-sigma modulation. The proposed scheme can double the number of accesses without occupying extra wavelengths. Moreover, such architecture can flexibly allocate the SNR of a group of remote radio units for different user requirement of transmission rate and reaches. Simulation results show that the proposed scheme can increase the access distance of the fronthaul network by 23% and the capacity by 16.7%. The feasibility of the solution is verified through a proof-of-concept experiment. After 20 km transmission, the OFDM-64QAM and -256QAM signal with a center frequency of 3.5 GHz and a bandwidth of 500 MHz can meet the EVM requirements of 8% and 3.5%, respectively. And when the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${R_{LM}}$</tex-math></inline-formula> of the hierarchical PAM4 signal is 0.6, the ROP required by the most-significant bit branch can be reduced by ∼1.5 dB.
Highlights
E MERGING broadband services such as 8K video, virtual reality and augmented reality are driving the explosive growth of mobile data traffic
The transmission rate is varied from 576 Gb/s to 1.15 Tb/s, while the transmission distances change from 5540 km to 470 km. Another time-domain hybrid (TDH) pulse amplitude modulation (PAM) – orthogonal frequency division multiplexing (OFDM) system is reported that the data rate of multiple sub-carriers with a fixed baud rate can be flexibly changed from 40 Gb/s to 80 Gb/s using mixed on-off keying (OOK) and PAM4 signals [6]
If the hierarchical modulation (HM) PAM4 scheme shown in Fig. 8(b) is used, the redundant power of the less-significant bit (LSB) sequence can be transfered to the most-significant bit (MSB) branch, so that enough signalto-noise ratio (SNR) for both branches are guaranteed
Summary
E MERGING broadband services such as 8K video, virtual reality and augmented reality are driving the explosive growth of mobile data traffic. The IP traffic distribution may vary due to many factors, such as location and tidal effect To meet these requirements, some flexible modulation schemes have been investigated to adaptively distribute signal quality. Some flexible modulation schemes have been investigated to adaptively distribute signal quality They can mainly be divided into two categories, the time-domain hybrid (TDH) modulation and hierarchical modulation (HM). The transmission rate is varied from 576 Gb/s to 1.15 Tb/s, while the transmission distances change from 5540 km to 470 km Another TDH pulse amplitude modulation (PAM) – orthogonal frequency division multiplexing (OFDM) system is reported that the data rate of multiple sub-carriers with a fixed baud rate can be flexibly changed from 40 Gb/s to 80 Gb/s using mixed on-off keying (OOK) and PAM4 signals [6]. What’s more, HM has been proved with PAM4 format in PON downstream systems to increase network power budget by 3.5 dB [10]
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