Broadband network for coaxial cable using multi-carrier modulation
View Patent ↗A broadband local area data network uses coaxial cable wiring for interconnection of terminal devices. Orthogonal frequency division multiplexing (OFDM) with bit loading is used to overcome channel impairments and provide a path for terminal devices to transmit to and receive from other terminal devices. Probe messages are sent between devices to characterize the communication channel and determine optimum bit loading. The data network shares the cable spectrum with other services and uses frequency bands not used by other services. Adaptive power control can be used to maintain signal to noise ratio in a communication between terminal devices. Frequency coordination can be used to avoid interference between the LAN communications and other services transmitted on the cable.
1. A method of characterizing a communication channel used for communication between devices comprising the steps of:
a) forming a probe message comprising a preamble, a channel estimation training sequence, and a bit loading training sequence;
b) transmitting the probe message through the communication channel;
c) receiving the probe message;
d) from the received probe message, analyzing the preamble to estimate carrier and timing offset, analyzing the channel estimation training sequence to produce a set of equalizer coefficients, and analyzing the bit loading training sequence to determine a bit loading profile used for transmitting data.
2. The method of claim 1 wherein:
a) the preamble is a predetermined sequence of QPSK encoded data bits;
b) the channel estimation training sequence is a predetermined sequence of QPSK encoded OFDM symbols; and
c) the bit loading training sequence is a predetermined sequence of BPSK encoded OFDM symbols.