1. An ultraviolet absorbing, protective device comprising a matrix member having an azo dye therein, wherein said azo dye is formed by the reaction of an aromatic coupling agent with a diazonium salt selected from the group consisting of:
4
wherein R is hydrogen or an alkyl, Y is a halogen and X is an anion.
2. The ultraviolet absorbing, protective device of claim 1, wherein said aromatic compound is selected from the group consisting of:
5
wherein R is hydrogen or an alkyl and n is 0 or a positive integer.
3. The ultraviolet absorbing, protective device of claim 1, wherein said matrix member comprises a layer of polymeric material, and wherein said azo dye is dissolved therein.
4. The ultraviolet absorbing, protective device of claim 3, wherein said layer of polymeric material comprises a cellulose acetate polymer.
5. The ultraviolet absorbing, protective device of claim 1, wherein the amount of azo dye in said matrix is in the range of 10-100 mg of dye per cm2 of said device.
6. An ultraviolet absorbing, protective device comprising a matrix member having an ultraviolet absorbing dye therein, said device characterized in that it will absorb at least 90% of radiation incident thereupon having a wavelength in the range of 250 to 380 nm, and that it will transmit at least 80% of radiation incident thereupon having a wavelength in the range of 500 to 700 nm.
7. The device of claim 6, further characterized in that it will transmit at least 90% of radiation incident thereupon having said wavelength in the range of 500 to 700 nm.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprising:
a plurality of remote units;
a host unit that includes a demodulator;
wherein each of the remote units transmits an upstream OFDM signal using a multiple access scheme to the host unit demodulator using at least one of a plurality of orthogonal tones within an OFDM waveform;
wherein the host unit receives the upstream OFDM signals from a plurality of the remote units, the tones of the upstream signals being substantially orthogonal when received at the host unit;
wherein portions of upstream OFDM signals from at least two of the remote units arrive at the host unit at the same time;
wherein the host unit demodulator demodulates said portions of upstream OFDM signals;
wherein the upstream signals from the remote units each include a plurality of symbols; and
wherein each remote unit times its upstream signal transmission so that when multiple upstream signals arrive at the host unit the symbols of the multiple upstream signals are aligned.
2. The OFDM communication system of claim 1 wherein the system is used in a hybrid fiber coax network.
3. The OFDM communication system of claim 1 wherein the system is used in a wireless network.
4. The OFDM communication system of claim 1 wherein the remote units receive timing adjustment commands from the host unit to assist in aligning the symbols of the upstream signals at the host unit.
5. The OFDM communication system of claim 4 wherein the timing adjustment command is transmitted from the host unit to the remote unit via a control channel.
6. The OFDM communication system of claim 4 wherein the timing adjustment command is transmitted from the host unit to the remote unit using a lesser order modulation scheme than a modulation scheme used for transmitting payload data between the host unit and remote units.
7. The OFDM communication system of claim 4 wherein the host unit repeatedly sends timing adjustment commands to the remote units to maintain symbol alignment of the upstream signals at the host unit.
8. The OFDM communication system of claim 4 wherein the timing adjustment command to at least one of the remote units instructs the remote unit to delay its transmission by a fraction of a symbol period.
9. A system comprising:
a host unit including a multicarrier demodulator;
a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit multicarrier demodulator using orthogonal frequency division multiplexing (OFDM);
wherein the host unit determines a timing error for at least one of the remote units; and
wherein the host unit sends a timing adjustment signal to the at least one remote unit so that symbols received at the host unit from the plurality of remote units are aligned.
10. The OFDM communication system of claim 9 wherein the system is used in a hybrid fiber coax network.
11. The OFDM communication system of claim 9 wherein the system is used in a wireless network.
12. The OFDM communication system of claim 9 wherein the at least one remote unit makes an adjustment to the timing of its upstream signal transmission based on the timing adjustment signal from the host unit.
13. A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprising:
a plurality of remote units;
a host unit that includes a demodulator;
wherein each of the remote units transmits an upstream OFDM signal using a multiple access scheme to the host unit demodulator using at least one of a plurality of orthogonal tones within an OFDM waveform;
wherein the host unit receives the upstream OFDM signals from a plurality of the remote units, the tones of the upstream signals being substantially orthogonal when received at the host unit;
wherein portions of upstream OFDM signals from at least two of the remote units arrive at the host unit at the same time;
wherein the host unit demodulator demodulates said portions; and
wherein the host unit participates in controlling the transmission timing of the upstream signals from the remote units to assist in demodulating said portions at the host unit.
14. The OFDM communication system of claim 13 wherein the host unit controls the transmission timing of the upstream signals from the remote units to improve symbol alignment.
15. The OFDM communication system of claim 13 wherein the system is used in a hybrid fiber coax network.
16. The OFDM communication system of claim 13 wherein the system is used in a wireless network.
17. The OFDM communication system of claim 13 wherein the host unit participates in controlling the transmission timing of the upstream signals by sending a downstream timing adjustment signal to at least one of the plurality of remote units.
18. The OFDM communication system of claim 17 wherein the timing adjustment signal is transmitted from the host unit to the at least one remote unit using a lesser order modulation scheme than a modulation scheme used for transmitting payload data between the host unit and the at least one remote unit.
19. A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprising:
a plurality of remote units;
a host unit that includes a demodulator;
wherein each of the remote units transmits an upstream OFDM signal using a multiple access scheme to the host unit demodulator using at least one of a plurality of orthogonal tones within an OFDM waveform;
wherein the host unit receives the upstream OFDM signals from a plurality of the remote units, the tones of the upstream signals being substantially orthogonal when received at the host unit;
wherein portions of upstream OFDM signals from at least two of the remote units arrive at the host unit at the same time;
wherein the host unit demodulator demodulates said portions;
wherein the upstream signal transmissions from the plurality of remote units are synchronized in time to improve orthogonality of the upstream signals at the host unit; and
wherein the host unit and at least one remote unit participate in synchronizing the timing of the upstream OFDM signal transmissions.
20. The OFDM communication system of claim 19 wherein the at least one remote unit participates in synchronizing the timing of upstream OFDM signal transmissions by delaying transmission of its upstream OFDM signal in response to receiving a timing adjustment signal from the host unit.
21. The OFDM communication system of claim 19 wherein the system is used in a hybrid fiber coax network.
22. The OFDM communication system of claim 19 wherein the system is used in a wireless network.