Optical spatial division multiplexing in 5G front-hauling

The fifth generation (5G) of mobile communications is the enabling platform for new applications (IoT to e-health services) thanks to its huge capacity and low latency. Reaching such properties requires a proper design of the radio access network (RAN), including the front-haul segment connecting the radio base station (BS) to the central office by an optical link.

The feasibility of using few mode fibers (FMFS) instead of single mode fibers, in front-hauling of 5G networks will be assessed by a system design and its test by simulations. The advantages of FMFs will be of reducing the number of fibers in ducts so sparing space in proportion to achieved data rate and the chance of implementing low cost microwave-photonic shifters for 5G high frequency carriers.

The project will develop specific software accounting for the digital radio signal generation and analysis, the optical propagation and the electrical-to-optical conversion. Low cost modulators (based on reflective semiconductor optical amplifiers) will be tested for application in the BSs, where the devices must be cheap and colorless to enable network flexibility. At the BS, a simple analog reconfigurable processing (beamforming) will be performed before transmissions on a large number of antennas; similarly, received signals are combined by an analog reconfigurable device before transmission (in digital) over the fiber. This beamformer/combining operation supports the exploitation of multiple antennas for steering the signal in specific direction, while reducing the required fiber data rate. Resource allocation algorithms will be considered for specific 5G applications having rate and latency requirements, in particular highly demanding services such as e-health and mobile health services.