OSA/OFC/NFOEC 2011
OThJ3.pdf OThJ3.pdf
Field Demonstration of Bi-directional Millimeter Wave RoF Systems Inter-operable with 60 GHz Multi-gigabit CMOS Transceivers for In-building HD Video and Data Delivery Arshad Chowdhury, Kevin Chuang, Hung-Chang Chien, David Yeh, Jianjun Yu, Gee-Kung Chang School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
[email protected]
Abstract: We demonstrate, for the first time, a bi-directional in-building radio-over-fiber access network to deliver multi-gigabit, high-definition video and data services using all-optical conversion at the head-end and single-chip, 60GHz CMOS radio transceiver at the end-terminals. OCIS codes: (060.4510) Optical communications; (060.5625) Radio frequency photonics 1. Introduction Over the last few years, optical-wireless access using radio-over-fiber (RoF) technology has been received tremendous attention as the most practical and cost-effective solution to provide protocol independent, transparent connectivity with increased capacity, coverage, bandwidth, and mobility [1]-[3] to the end users’ terminals, specially for the in-building environments such as conference centers, airports, hotels, shopping malls, small offices, and ultimately homes. On the other hand, the development of the low-cost, single-chip CMOS IC solution with integrated 60-GHz mm-wave radio frequency (RF) front-end functions, baseband processing capabilities, and lowpower mixed-signal modulation/demodulation techniques makes mobile multi-gigabit (≥ 1 Gbps) wireless access a reality in the near future [4]. In this context, it is important to verify the interoperability between the 60-GHz mmwave RoF signals received by the end user’s terminals equipped with 60-GHz mm-wave CMOS Radio transceiver. Recently, we demonstrated a super-broadband 60 GHz optical wireless downstream transmission received by the millimeter-wave (mm-wave) multi-gigabit 60 GHz CMOS Radio receiver [5]. In this paper, for the first time to our knowledge, we demonstrated a field-trial testbed of in-building radio-over-fiber system that supports bi-directional 60 GHz mm-wave optical wireless access by providing 1.485 Gbps uncompressed high-definition (HD) video connectivity between the optical head-end gateway and end user’s mobile terminals located at two separate Research buildings at Georgia Institute of Technology (GT) campus. At the head-end gateway, we used all-optical upconversion and reception of the downstream and upstream signals, respectively. At the mobile end user terminal, we used the integrated single-chip multi-gigabit 60 GHz CMOS radio developed by Georgia Electronic Design Center (GEDC) at Georgia Tech. 2. Integrated Multi-Gigabit 60 GHz CMOS Radio Fig. 1 shows the block diagram of the integrated 60-GHz radio transceiver using a standard 90 nm digital 1P7M CMOS process. The mm-wave front-end is controlled digitally through a serial peripheral interface and integrated with the baseband signal processor using high-speed digital-to-analog (D/A) and analog-to-digital (A/D) converters. In the transmitter chain, the baseband signal is first up-converted to an intermediate frequency (IF) using a doublebalanced quadrature Gilbert-cell mixer and a quadrature voltage-controlled oscillator (QVCO) fixed by a phase-lock loop (PLL). In order to perform frequency translation from IF to RF, the differential RF output of the mm-wave Gilbert-cell mixer is matched to 50 Ω using microstrip transmission lines, followed by a four-stage common source power amplifier (PA). In the single-chip receiver, the 60 GHz RF signal is first amplified by the mm-wave lownoise amplifier (LNA) that employs common-source topology, and then down-converted to the IF, followed by a two-stage variable-gain amplifier (VGA). The resulting IF signal is mixed with the QVCO outputs. Since the QVCO is not synchronized with the modulating local oscillator (LO) of the transmitter, the baseband I-Q signals contain the transmitted digital signal with an envelope that corresponds to the frequency difference between the QVCO and LO. Based on quadrature receiver architecture, the I-channel and Q-channel signals have their envelope offset by 90 °. Finally, the down-converted non-coherent amplitude shift keying (ASK) or coherent BPSK modulated signals can be recovered by means of innovative mixed-signal signal processing.
OSA/OFC/NFOEC 2011
OThJ3.pdf OThJ3.pdf
Fig. 1: Schematic of integrated multi-gigabit 60 GHz CMOS transceiver
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Fig. 2: Testbed setup of in-building bi-directional mm-wave RoF network interoperates with multi-gigabit 60 GHz CMOS wireless transceiver.
3. Testbed Setup and Results Fig. 2 shows the experimental testbed setup of the in-building bi-directional super-broadband 60 GHz radio-overover fiber network system deployed in Technology Square Research Building (TSRB) at the Georgia Institute of Technology campus. The head-end gateway (HE) of the in-building RoF network is located at the RoF Access Network Lab while, the remote antenna unit (RAU) and mobile end user terminals (MT) are located in the Gigabit Wireless Lab TSRB. At the HE, the 1.485 Gbps uncompressed HD video signal from a Blue-ray player is upconverted to 60 GHz mm-wave using all-optical up-conversion method realized by an optical phase modulator (PM) and a 33/66 GHz optical interleaver (IL). Inset (i) and (ii) of Fig. 2 shows the optical spectrum before and after the IL. The spacing between the two first-order sidebands is 60 GHz and the carrier suppression ratio is over 30 dB. The generated optical mm-wave signal is then amplified by an erbium-doped fiber amplifier (EDFA) and transmitted over 12.5 km standard single mode fiber (SMF-28) link to the RAU. At the RAU, direct detection of optical mmwave signal is performed by a PIN photodiode with 60-GHz bandwidth. The converted electrical mm-wave signal is amplified by an electrical amplifier (EA) with BW of 5 GHz centered at 60 GHz and 3.55 Vpp before it is broadcasted through a double-ridge guide rectangular horn antenna with a gain of 25 dBi, frequency range of 50 to 75 GHz and 3 dB beam width of 7 °. After the wireless transmission, the 60 GHz mm-wave RF signal is received by the mobile terminal (MT), using multi-gigabit 60 GHz 90 nm CMOS Radio receiver module. Fig. 3 shows the
OSA/OFC/NFOEC 2011
OThJ3.pdf OThJ3.pdf
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Fig. 3: BER measurements and electrical and optical eye diagrams Downstream video at source Received upstream video Blu-ray Player
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Fig. 4: Testbed modules (a) Head-end gateway at RoF Access Lab (b) RAU and mobile terminal at Gigabit Wireless lab
achievable BER for various transmission distances and corresponding electrical eye diagrams. Again, at the MT, the upstream 1.485 Gbps HD video signal is up-converted using a 60 GHz single-chip 90 nm CMOS Radio transmitter (Tx) before wirelessly broadcasted to the RAU. At the RAU, the upstream wireless signal is electrically downconverted to 1.485 Gbps upstream data stream using another set of GEDC 60-GHz CMOS radio Rx module before optically transmitted to the head-end gateway. At the head-end, the upstream HD signal is received by the 2.5 Gbps APD photodiode and fed into the HD display unit. Fig. 4 (a) and (b) show the transmitter and receiver modules, the received downstream and upstream signals at the head-end gateway and the MT. 4. Conclusion A field-trial testbed is demonstrated for in-building radio-over-fiber access system that supports bi-directional multigigabit 60 GHz mm-wave optical wireless transport between the two in-building research laboratories at Georgia Tech. The testbed uses optical up-conversion and reception at the head-end gateway, and multi-gigabit 60 GHz CMOS radio transceiver developed by GEDC of Georgia Tech, at the mobile terminals in order to provide bidirectional 1.485 Gbps uncompressed HD video connectivity. The testbed successfully confirms the inter-operability between 60-GHz transceiver based on low-cost 90nm CMOS technology and the 60-GHz mm-wave RoF technology for future-proof very high throughput, in-building wireless over fiber access networks. References [1] G.-K. Chang, Z. Jia, J. Yu, A. Chowdhury, ―Super broadband optical wireless access technologies," OFC/NFOEC 2008, paper OThD1M. [2] A. Seeds, T. Ismail, ―Broadband Access Using Wireless Over Multimode Fiber Systems,‖ J. of Lightwave Technology, Vol 28, No. 16, pp.2430-2435, August, 2010 [3] M. J. Koonen and M. García Larrodé, ―Radio-Over-MMF Techniques—Part II: Microwave to Millimeter-Wave Systems ,‖ J. of Lightwave technologies, vol. 26, no. 15, pp. 2396- 2408, Aug. 2007 [4] M. Bakaul, A. Nirmalathas, C. Lim, D. Novak and R. Waterhouse, ―Simultaneous multiplexing and demultiplexing of wavelength-interleaved channels in DWDM millimeter-wave fiber-radio networks,‖ J. Lightwave Technology, vol. 24, no. 9, pp. 3341–3352, Sep. 2006 [5] S. Pinel, S. Sarkar, P. Sen, B. Perumana, D. Yeh, D. Dawn and J. Laskar, ―A 90nm CMOS 60GHz Radio,‖ in IEEE International Solid-State Circuits Conference, Dig. Tech. Papers, pp.130-131, Feb. 2008. [6] David A. Yeh et al., ―Millimeter-wave Multi-Gigabit IC Technologies for Super Broadband Wireless Over Fiber Systems,‖ OFC/NFOEC 2009, paper OTuB3
