Bidirectional point to multipoint network using multicarrier modulation
First Claim
1. A two-way point to multipoint data transmission system comprising an upstream unit, a plurality of downstream units, and a transmission line connecting said downstream units to said upstream unit, wherein at least one headend modem is located at said upstream unit and at least one downstream modem is located at said downstream units, said modems employs multitone orthogonal frequency division multiplexing (OFDM) to establish two-way communication channels between said upstream and downstream units, said OFDM has a tone spacing selected to minimize the ingress of electromagnetic interference at least in the upstream direction, and said headend modem includes a local oscillator and each downstream modems is synchronized with said local oscillator at the headend modem by means of a remote tracking loop.
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Accused Products
Abstract
A two-way point to multipoint data transmission system comprises an upstream unit, a plurality of downstream units, and a transmission line connecting the downstream units to the upstream unit. At least one headend modem is located at the upstream unit and at least one downstream modem is located at the downstream units. The modems employ multitone orthogonal frequency division multiplexing (OFDM) to establish two-way communication between the upstream and downstream units. The OFDM has a tone spacing selected to minimize the ingress of electromagnetic interference at least in the upstream direction.
321 Citations
21 Claims
- 1. A two-way point to multipoint data transmission system comprising an upstream unit, a plurality of downstream units, and a transmission line connecting said downstream units to said upstream unit, wherein at least one headend modem is located at said upstream unit and at least one downstream modem is located at said downstream units, said modems employs multitone orthogonal frequency division multiplexing (OFDM) to establish two-way communication channels between said upstream and downstream units, said OFDM has a tone spacing selected to minimize the ingress of electromagnetic interference at least in the upstream direction, and said headend modem includes a local oscillator and each downstream modems is synchronized with said local oscillator at the headend modem by means of a remote tracking loop.
- 18. A method of establishing two-way point to multipoint communication between a headend modem and a plurality of downstream modems over a transmission line wherein multitone orthogonal frequency division multiplexing (OFDM) is employed to establish two-way communication channels between said headend and downstream modems, said OFDM having a tone spacing selected to minimize the ingress of electromagnetic interference at least in the upstream direction, and said downstream modems are synchronized with a local oscillator at the headend modem by means of a remote tracking loop.
Specification