Spectrum efficient multi-user access in visible light communications
A novel method to achieve spectrum efficient multi-user access in intensity modulated light communication systems. Orthogonal Frequency Division Multi-User Access (OFDMA) networking is used to split the entire modulation bandwidth into multiple parts, with different users on the network sharing separate portions of modulation bandwidth, so improving overall throughput.
- Internet of Things (IoT)
- Sensor networks
- Low energy communication systems
- Licensing and research collaboration
The multiplexing techniques used for multiuser Visible Light Communication (VLC) channels do not in general occupy all of the available spectrum. VLC effectively operates as a low-pass filter in the frequency domain. In multi-user optical systems, users at different locations are subject to different channels so that the usable bandwidth for each user is different. One way to address multiple users is by using time division multiple access (TDMA) to assign different users to different timeslots. Within each timeslot, Orthogonal Frequency Division Multiplexing (OFDM) is normally used by the physical layer to fill the available bandwidth for each user, and therefore to maximise the data rate. However for multiple users, the net effect overall is under-utilisation of the modulation bandwidth available within the timeslot.
This novel method of achieving spectrum efficient multi-user access in intensity modulated light communication systems is enabled through use of Orthogonal Frequency Division Multi-User Access (OFDMA) networking techniques. The entire modulation bandwidth is split into multiple parts, with different users on the network sharing separate portions of modulation bandwidth, so allowing otherwise unused modulation bandwidth in the TDMA slots to be exploited.
- Implementing multi-user access techniques in Visible Light Communication systems facilitates users to access different frequency sub-bands simultaneously
- By replacing Time Division Multiple Access (TDMA) with Orthogonal Frequency Division Multiple Access (OFDMA) over 30% data throughput improvement is achievable for a VLC system
D. A. Basnayaka DA, and H. Haas, “A new degree of freedom for energy efficiency of digital communication systems” IEEE Trans. Commun., Aug. 2016.