Huaiyu Zeng

Efficient Mobile Fronthaul via DSP-Based Channel Aggregation

Mobile fronthaul is an important network segment that bridges wireless baseband units and remote radio units to support cloud radio access network. We review recent progresses on the use of frequency-division multiplexing to achieve highly bandwidth-efficient mobile fronthaul with low latency. We present digital signal processing (DSP) techniques for channel aggregation and deaggregation, frequency-domain windowing, adjacent channel leak age ratio reduction, and synchronous transmission of both the I/Q waveforms of wireless signals and the control words (CWs) used for control and management purposes. In a proof-of-concept experiment, we demonstrate the transmission of 48 20-MHz LTE signals with a common public radio interface (CPRI) equivalent data rate of 59 Gb/s, achieving a low round-trip DSP latency of <;2 μs and a low mean error-vector magnitude (EVM) of ~2.5% after fiber transmission. In a follow-up experiment, we further demonstrate the transmission of 32 20-MHz LTE signals together with CPRI-compliant CWs, corresponding to a CPRI-equivalent data rate of 39.32 Gb/s, in single optical wavelength channel that requires an RF bandwidth of only ~1.6 GHz. After transmission over 5-km standard single-mode fiber, the CWs are recovered without error, while the LTE signals are recovered with an EVM of lower than 3%. Applying this technique to future 5G wireless networks with massive multiple-input multiple-output is also discussed. This efficient mobile fronthaul technique may find promising applications in future integrated fiber/wireless access networks to provide ultrabroadband access services.

CPRI-compatible efficient mobile fronthaul transmission via equalized TDMA achieving 256 Gb/s CPRI-equivalent data rate in a single 10-GHz-bandwidth IM-DD channel

We propose and experimentally demonstrate a CPRI-compatible efficient mobile fronthaul scheme for synchronous transmission of control words and IQ data via equalized TDMA, achieving 256 Gb/s CPRI-equivalent data rate in a 10-GHz-bandwidth IM-DD channel.

Experimental demonstration of high-throughput low-latency mobile fronthaul supporting 48 20-MHz LTE signals with 59-Gb/s CPRI-equivalent rate and 2-μs processing latency

We experimentally demonstrate the transmission of 48 20-MHz LTE signals with a CPRI-equivalent data rate of 59 Gb/s, achieving a low round-trip digital-signal-processing latency of <;2 μs and a low mean error-vector magnitude of ~2.5 % after fiber transmission.

Real-Time Demonstration of CPRI-Compatible Efficient Mobile Fronthaul Using FPGA

Mobile fronthaul is regarded as an important network segment for supporting cloud radio access network and massive multiple-input multiple-output in next-generation wireless networks. To achieve bandwidth-efficient mobile fronthaul (EMF), transmission of multiple wireless signals in a single wavelength channel has been demonstrated by digital signal processing (DSP)-assisted channel aggregation. The DSP-assisted channel aggregation has been realized via frequency-division multiple access. In addition, the control word (CW) information, as specified in the common public radio interface (CPRI) specification, has been transmitted with the wireless I/Q data synchronously. In this paper, we present CPRI-compatible efficient mobile fronthaul scheme for synchronous transmission of CWs and IQ data via equalized time-division multiple access (TDMA) We further experimentally demonstrate the real-time implementation of a TDMA-EMF transceiver based on field-programmable gate array. Long-term stable operation has been achieved showing the feasibility of using this EMF technology to meet the fronthaul demands of future 4.5 G and 5 G wireless systems in terms of bandwidth efficiency, power efficiency, and cost efficiency.

Bandwidth-Efficient Synchronous Transmission of I/Q Waveforms and Control Words via Frequency-Division Multiplexing for Mobile Fronthaul

We propose a novel mobile fronthaul transmission scheme to achieve bandwidth-efficient transmission of both the I/Q waveforms of wireless signals and the control words (CWs) between baseband units (BBUs) and remote radio units (RRUs). Unlike the common public radio interface (CPRI) where the I/Q waveforms and the control words are transmitted as a binary sequence in the time domain, the proposed transmission scheme aggregates multiple wireless signals in the frequency domain and transmits them synchronously with a single-carrier quadrature-amplitude-modulation (QAM) signal that contains the CWs on a single wavelength channel via frequency-division multiplexing. This approach substantially increases the bandwidth efficiency of the mobile fronthaul. Furthermore, we experimentally demonstrate this scheme by transmitting 32 20-MHz LTE signals together with CPRI-compliant CWs, corresponding to a CPRI-equivalent data rate of 39.32 Gb/s, in single optical channel that requires a RF bandwidth of only ~1.6 GHz. After transmission over 5-km standard single-mode fiber (SSMF), the CWs are recovered without error, while the LTE signals are recovered with an error-vector magnitude (EVM) of as low as 3%. This bandwidth-efficient mobile fronthaul technique may find applications in future integrated fiber/wireless access networks to provide ultra-broadband access services.