SUMMARYThis paper assesses the performance of dual header pulse interval modulation (DH-PIM) over indoor optical wireless systems. DH-PIM being anisochronous scheme offers a built-in symbol synchronization capability. Theoretical and simulation results demonstrate that DH-PIM offers shorter symbol length, improved transmission rate and bandwidth requirement and a comparable power spectral density profile compared with digital pulse interval modulation (DPIM) and pulse position modulation (PPM) schemes.It is shown that DH-PIM 2 ; with wider pulse duration is the preferred option when the available channel bandwidth is limited and higher optical power is tolerable. Whereas DH-PIM 1 ; with narrower pulse width, exhibits comparable power requirements but a marginally higher bandwidth compared with DPIM, and is also more bandwidth efficient than PPM at the cost of increased power requirement. However, at higher bit resolutions, i.e. M57; DH-PIM 1 is both bandwidth and power efficient compared with PPM. Error rate analysis show that DH-PIM offers improved packet error rate compared with on-off-keying (OOK) and DPIM, but marginally inferior as compared with PPM. The power requirement and penalty due to intersymbol interference for non-dispersive and dispersive channels is analysed and the results show that for given parameters, DH-PIM requires marginally higher optical power compared with PPM and DPIM, but it supports the same bit rate at much less bandwidth requirement.

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In this paper, we present a study of dual header-pulse interval modulation (DH-PIM) scheme for optical wireless communications. System theory and code properties of DH-PIM are discussed and expressions for the power spectral density, slot and packet error rates and optical power requirements are presented. The problem of baseline wander is also studied. The performance of DH-PIM is compared with other modulation schemes such as on-off keying (OOK), pulse position modulation (PPM), differential pulse position modulation (DPPM) and digital pulse interval modulation (PIM). We show that, DH-PIM offers higher bit rate and has a built-in frame synchronisation capability. For a simple threshold detector receiver, it offers improved error performance compared with OOK, but marginally inferior performance compared with PPM. The optimum system performance in terms of optical power and bandwidth requirements is achieved at bit resolution of 5.