European Transactions on Telecommunications · 1998 · 150 citations · 5 references
EngineeringCommunicationElectrical EngineeringComputer NetworksDigital CommunicationWireless CommunicationsCommunication NetworksCommunication SystemsInterference ManagementModulationMultiple Access TechniquesWireless NetworksDiscrete Fourier TransformFrequency Division Multiple AccessImpulse NoiseOrthogonal Frequency Division Multiple AccessOrthogonal Frequency-division MultiplexingPilot ChannelsTime Division Multiple Access
The authors propose using orthogonal frequency‑division multiple access (OFDMA) for upstream data in cable TV networks and evaluate its performance against time‑division multiple access (TDMA). OFDMA achieves subscriber orthogonality through head‑end pilot‑signal synchronization and replaces multiple demodulators with a single demodulator followed by an N‑point DFT, enabling efficient multi‑user reception. Results show OFDMA provides greater resilience to narrowband interference, impulse noise, and other CATV impairments compared to TDMA.
Abstract We introduce the concept of orthogonal frequency‐division multiple access (OFDMA) and investigate its application to send upstream information from subscriber premises to the cable head‐end in cable TV (CATV) networks. The carrier and timing synchronizations needed to ensure orthogonality between different subscriber signals are achieved by sending common pilot signals from the head‐end. Whereas N demodulators are required to accommodate N simultaneous users in conventional FDMA systems, OFDMA only requires a single demodulator followed by an N ‐point discrete Fourier transform (DFT). We analyze the performance of this technique and compare it to time‐division multiple access (TDMA) which appears in several international standards. Our results indicate that OFDMA is an attractive multiple access technique which offers increased robustness to narrowband interference, impulse noise, and other signal impairments which characterize typical CATV networks.
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