Resource Allocation in Co-Existing Optical Wireless HetNets

In multi-user optical wireless communication (OWC) systems interference between users and cells can significantly affect the quality of OWC links. Thus, in this paper, a mixed-integer linear programming (MILP) model is developed to establish the optimum resource allocation in wavelength division multiple access (WDMA) optical wireless systems. Consideration is given to the optimum allocation of wavelengths and access points (APs) to each user to support multiple users in an environment where Micro, Pico and Atto Cells co-exist for downlink communication. The high directionality of light rays in small cells, such as Pico and Atto cells, can offer a very high signal to noise and interference ratio (SINR) at high data rates. Consideration is given in this work to visible light communication links which utilise four wavelengths per access point (red, green, yellow and blue) for Pico and Atto cells systems, while the Micro cell system uses an infrared (IR) transmitter. Two 10-user scenarios are considered in this work. All users in both scenarios achieve a high optical channel bandwidth beyond 7.8 GHz. In addition, all users in the two scenarios achieve high SINR beyond the threshold (15.6 dB) needed for 10 -9 on off keying (OOK) bit error rate at a data rate of 7.1 Gbps

Impact of User Distribution on Optical Wireless Systems

In this paper, we investigate the impact of user distribution on resource allocation in visible light communication (VLC) systems, using a wavelength division multiple access (WDMA) scheme. Two different room layouts are examined in this study. Three 10-user scenarios are considered, while an optical angle diversity receiver (ADR) with four faces is used. A mixed-integer linear programming (MILP) model is utilized to identify the optimum wavelengths and access point (AP) allocation in each scenario. The results show that a change in user distribution can affect the level of channel bandwidth and SINR. However, a uniform distribution of users in the room can provide a higher channel bandwidth as well as high SINR above the threshold (15.6 dB) for all users compared to clustered users, which is a scenario that has the lowest SINR with supported data rate above 3.2 Gbps