Study Of Multi-cell Multi-carrier Wireless Access Network Based On Radio-over-Fiber System

In the current wireless access system, the limited bandwidth has been the bottleneck to fulfill the drastically growing wireless data demand. Small cell, which splits traditional macro-cell into multiple low power wireless access notes, helps increase bandwidth to each user. However, to insure coverage, the amount of wireless access notes increases accordingly. On the other hand, the amount of wireless services on different RF carriers keeps increasing as well. Multiplexing techniques are desired to re-use system infrastructure to reduce CAPEX and OPEX. Thanks to the high bandwidth and low loss transmission capability, extremely simple and low cost Radio Antenna Unit (RAU) configuration, as well as the inherent central control mechanism, Radio Over Fiber System (ROF) is the perfect solution to address the above issues. Based on ROF technology, this thesis explored the solutions for a high speed, high performance and high efficiency multi-cell multi-carrier wireless access system. The detailed contents and contributions are as follows:In order to maximize the utilization of the network infrastructure, three multiplexing technologies of the multi-cell, multi-carrier ROF system are discussed:Wavelength Division Multiplexing (WDM)/ Subcarrier Multiplexing (SCM)/Coherence Multiplexing (CM). The transmission models of these ROF architectures are derived, simulated and experimentally demonstrated. Using the derived models, a WDM-SCM ROF system is experimentally demonstrated to simultaneously transmit 4 different wireless carriers to 4 different cells. On the other hand, CM is a new multiplexing technique for multi-cell signal transmission. When the fiber transmission length is<1km, multiplexing cells<5, CM is a competitive candidate due to its low cost and high flexibility.In order to achieve high performance transmission, linearization technologies are desired to overcome the Electro-Optic nonlinearity of the ROF system. For downlink, a Multi-carrier digital pre-distortion (DPD) technique is proposed, which performs on the baseband signal of each individual RF carriers. By disregarding the blank spectra between the RF carriers, the processing bandwidth of the proposed DPD technique is greatly reduced. In the experimental demonstration on a two-carrier ROF systems occupying several GHz spectrum,>14dB Adjacent Channel Power (ACP) has been suppressed by using 100MHz DSP devices. For uplink, an advanced DSP technique is proposed to correct the non-ideal characteristics and the phase ambiguity effect in a coherent receiver of a Phase Modulation/Coherent Detection ROF link to further increase its dynamic range. Experimental results show Spur Free Dynamic Range (SFDR) of 10.2 dB-Hz2/3 is achieved, which leads to a shot noise limited SFDR of 128.8 dB-Hz2/3.In order to achieve high speed, low power consumption wireless access system, dynamic resource allocation technologies for ROF system are explored to maximize the unitization of the wireless resources. For multi-carrier transmission, a Desire to Undesired signal Ratio (DUR) balancing power control technique is proposed to control the downlink power to only satisfy the error free transmission performance. This technique can save 4.3dB downlink power in average. For multi-cell transmission, a Cognition, Collaboration, power Conservation Radio over Fiber System (3C-ROF)is proposed and demonstrated. By dynamic optical broadcasting and routing, the bandwidth resources can be allocated to each cell according to demands.