Indoor MIMO Visible Light Communications: Novel Angle Diversity Receivers for Mobile Users

Abstract

Abstract-This paper proposes two novel and practical designs of angle diversity receivers to achieve multiple-input-multipleoutput (MIMO) capacity for indoor visible light communications (VLC). Both designs are easy to be constructed and suitable for small mobile devices. By using light emitting diodes for both illumination and data transmission, our receiver designs consist of multiple photodetectors (PDs) which are oriented with different inclination angles to achieve high-rank MIMO channels and can be closely packed without the requirement of spatial separation. Due to the orientations of the PDs, the proposed receiver designs are named pyramid receiver (PR) and hemispheric receiver (HR). In a PR, the normal vectors of PDs are chosen the same as the normal vectors of the triangle faces of a pyramid with equilateral N -gon base. On the other hand, the idea of HR is to evenly distribute the PDs on a hemisphere. Through analytical investigation, simulations and experiments, the channel capacity and bit-error-rate (BER) performance under various settings are presented to show that our receiver designs are practical and promising for enabling VLC-MIMO. In comparison to induced link-blocked receiver, our designs do not require any hardware adjustment at the receiver from location to location so that they can support user mobility. Besides, their channel capacities and BER performance are quite close to that of link-blocked receiver. Meanwhile, they substantially outperform spatiallyseparated receiver. This study reveals that using angle diversity to build VLC-MIMO system is very promising.Index Terms-Visible light communications, multiple-inputmultiple-output (MIMO), angle diversity, pyramid receiver, hemispheric receiver.

A Novel Mirror-Aided Non-Imaging Receiver for Indoor $2\times 2$ MIMO-Visible Light Communication Systems

“…We note that we utilize a mirror with fixed height, which is not optimal at each receiver position but is practical to implement adaptively with user mobility and location. In addition, except for the mirror's parameters, we use similar system parameters as used in the simulations in [18], [19].…”

“…(7.43)]. We note that the above capacity formula is enough to verify the performance of various receivers because 1) it is used in the previous literature (See [19], [25] and references therein performance comparison and evaluation of the optical wireless intensity channel); and 2) it is in the same form as the achievable rate formula of constant power and continuous rate adaptation optical MIMO systems in [12, Eq. (24)- (25)] with the bit error rate (BER) requirement introduced.…”

“…This method is practical to implement; however, it leads to larger receiver sizes with limited performance enhancement. Receivers that reduce channel gains from specific directions have also been proposed to reduce channel correlation [9], [19]- [21]. An angle diversity receiver (ADR) was proposed to vary the orientation angles of PDs so that the incident light from a specific direction does not reach the receiver or is directed out of the receivers FoV [19].…”

“…Receivers that reduce channel gains from specific directions have also been proposed to reduce channel correlation [9], [19]- [21]. An angle diversity receiver (ADR) was proposed to vary the orientation angles of PDs so that the incident light from a specific direction does not reach the receiver or is directed out of the receivers FoV [19]. The prism array receiver (PAR) described in [20] deploys a prism on the top of each PD to orient the direction of the received light.…”

A Tight Upper Bound on Channel Capacity for Visible Light Communications

“…However, the capacity of the optical wireless channel is still an open issue. Although most literatures relevant to the channel capacity for VLC systems use the classic Shannon channel capacity formula [4], [5], it is not suitable for actual optical wireless channel due to the following reasons:…”