Structural Analysis of Circular Convolution Breakdown in CP-OFDM for Half-Duplex Monostatic ISAC
2026 IEEE International Black Seas Conference on Communications and Networking (BlackSeaCom), Bucuresti, Romanya, 8 - 11 Haziran 2026, ss.1-6, (Tam Metin Bildiri)
- Yayın Türü: Bildiri / Tam Metin Bildiri
- Doi Numarası: 10.1109/blackseacom69760.2026.11598149
- Basıldığı Şehir: Bucuresti
- Basıldığı Ülke: Romanya
- Sayfa Sayıları: ss.1-6
- Ankara Yıldırım Beyazıt Üniversitesi Adresli: Evet
Özet
This paper presents a structural analysis of the circular convolution breakdown in cyclic-prefix orthogonal frequency division multiplexing (CP-OFDM) systems operating in half-duplex monostatic integrated sensing and communication (ISAC) mode. In conventional full-duplex CP-OFDM with sufficient CP, the channel matrix is circulant and can be diagonalized in the DFT domain, preserving the subcarrier orthogonality. However, in half-duplex operation, receiver inactivity and echo truncation lead to a masked linear convolution model, yielding a non-circulant and rectangular effective channel matrix. Through Gram matrix analysis, it is shown that full-duplex operation maintains a diagonal frequency-domain structure, whereas half-duplex echo reception introduces inherent inter-carrier coupling and loss of orthogonality. The results demonstrate that this breakdown is structural rather than parameter-dependent and persists even when the CP length satisfies the conventional design condition.