System and apparatus for cascading and redistributing HDTV signals
View Patent ↗Redistribution of multimedia signals or the like within a service area is performed by identifying one or more pieces of white space in the VHF/UHF spectrum, selecting a carrier frequency for each piece of white space spectrum, parsing the signal into a like number of components and modulating each component over a carrier frequency. The receiving device performs the reverse operation for reconstructing the signal.
1. A gateway for redistributing an information signal of a specified bandwidth to a user device within a service area, comprising:
a spectrum detector for identifying k frequency-time cells of white space sufficient to accommodate the specified bandwidth of the information signal, where k is an integer, k≧1, the spectrum detector comprising
a tunable RF module for scanning specified spectrum sections and capturing any wireless signal present in the spectrum sections,
an analog to digital converter for converting the captured wireless signal to a digital signal,
a wavelet coefficient calculator for measuring an energy of the digital signal in each of a plurality of frequency-time cells formed within the specified spectrum sections, and
a sorting unit for selecting the k-frequency-time cells of white space where the energy of the digital signal is under a threshold; and
a transmitter for transmitting the information signal over the identified k frequency-time cells of white space to the user device;
wherein the wavelet coefficient calculator uses a wavelet function ψ ατ (t) providing a concentration of an energy of the frequency-time cells, in both time and frequency within a finite interval, according to this equation: ∫ψ ατ (t)dt=0, where α represents the scaling parameter of the wavelet waveform and τ represents the shifting parameter of the wavelet waveform.
2. A gateway as claimed in claim 1 , further comprising:
a control device for transmitting control messages on a dedicated control channel; and
a control signal detector for detecting the messages transmitted by the control device on the dedicated control channel.
3. A gateway as claimed in claim 2 , wherein the dedicated control channel is a bidirectional control channel, and wherein the gateway controls a operation of at least one of the spectrum detector and the transmitter based on the detected messages.
4. A gateway as claimed in claim 1 , wherein the gateway controls operation of at least one of the spectrum detector and the transmitter by transmitting in-band control messages.
5. A gateway as claimed in claim 1 , wherein the spectrum detector scans a spectrum based on a given current allocation of channels for the service area.
6. A gateway as claimed in claim 1 , wherein the spectrum detector selects a size of the frequency-time cells based on the bandwidth of the information signal and the detected current wireless activity at the service area.
7. A method for redistributing an information signal of a specified bandwidth, within a service area, comprising:
identifying k frequency-time cells of white space sufficient to accommodate the bandwidth of the information signal, where k is an integer, k≧1, the identifying comprising
scanning specified spectrum sections and capturing any wireless signal (Rx) present in the specified spectrum sections
converting the captured wireless signal to a digital signal,
measuring an energy of the digital signal in each of a plurality of frequency-time cells formed within the specified spectrum sections, and
selecting the k frequency-time cells of white space where the energy of the digital signal is under a threshold; and
broadcasting the information signal over the identified k frequency-time cells of white space to a user device;
wherein scanning specified spectrum sections uses a wavelet function ψ ατ (t) selected to concentrate an energy of the frequency-time cell, in both time and frequency within a finite interval, according to this equation: ∫ψ ατ (t)dt=0, where α represents the scaling parameter of the wavelet waveform and τ represents the shifting parameter of the wavelet waveform.
8. A method as claimed in claim 7 , further comprising detecting messages transmitted on a dedicated control channel.
9. A method as claimed in claim 8 , wherein the control channel is a bidirectional control channel.
10. A method as claimed in claim 8 , wherein the control channel is an uplink control channel, and downlink control messages are transmitted in-band with the data signal.
11. A method as claimed in claim 7 , wherein said identifying k frequency-time cells comprises scanning a spectrum based on a given current allocation of channels for a TV broadcast at the service area.
12. A method as claimed in claim 7 , wherein identifying k frequency-time cells of white space includes detecting a current wireless activity at the service area, and wherein the size of the frequency-time cells is selectable based on the bandwidth of the information signal and the current wireless activity detected at the service area.
13. A method as claimed in claim 7 , wherein said measuring an energy comprises measuring the energy of the digital signal in each frequency-time cell by calculating a wavelet coefficient for the digital signal detected in the respective frequency-time cell.
14. A method as claimed in claim 7 , wherein said calculating a wavelet coefficient uses shifted variants of the wavelet function (ψ(t−τ), and includes obtaining the shifted variants by performing integer shifts of an energy concentration center of the wavelet function, such that adjacent shifted waveforms {ψ(t−τ)} form an orthogonal basis.
15. A gateway for redistributing an information signal of a specified bandwidth to a user device within a service area, comprising:
a spectrum detector for identifying k frequency-time cells of white space sufficient to accommodate the specified bandwidth of the information signal, where k is an integer, k≧1, the spectrum detector comprising
a tunable RF module for scanning specified spectrum sections and capturing any wireless signal present in the spectrum sections,
an analog to digital converter for converting the captured wireless signal to a digital signal,
a wavelet coefficient calculator for measuring an energy of the digital signal in each of a plurality of frequency-time cells formed within the specified spectrum sections, and
a sorting unit for selecting the k frequency-time cells of white space where the energy of the digital signal is under a threshold; and
a transmitter for transmitting the information signal over the identified k frequency-time cells of white space to the user device;
wherein the wavelet coefficient calculator is capable of measuring an energy of the digital signal in each frequency-time cell by calculating a wavelet coefficient for the digital signal detected in the respective frequency-time cell and wherein the wavelet coefficient calculator is capable of calculating the wavelet coefficient using shifted variants of a wavelet function ψ ατ (t), wherein the wavelet coefficient calculator obtains the shifted variants by performing integer shifts of an energy concentration center of the wavelet function, such that adjacent shifted waveforms {ψ(t−τ)} form an orthogonal basis, where α represents the scaling parameter of the wavelet waveform and τ represents the shifting parameter of the wavelet waveform.
16. A gateway for redistributing an information signal of a specified bandwidth to a user device within a service area, comprising:
a spectrum detector for identifying k frequency-time cells of white space sufficient to accommodate the specified bandwidth of the information signal, where k is an integer, k≧1; and
a transmitter for transmitting the information signal over the identified k frequency-time cells of white space to the user device;
wherein the transmitter comprises
a baseband processor for converting the information signal into a baseband signal and parsing the baseband signal into n signal components where n is an integer, nε[1;k], and
a distributor unit with k branches for modulating each carrier frequency corresponding to a respective frequency-time cell of white space with a signal component, and broadcasting k RF signal components over the respective frequency-time cells of white space,
wherein each branch of the distributor unit modulates the baseband signal whenever a 6 MHz frequency-time cell of spectrum has been identified by the spectrum detector.
17. A gateway for redistributing an information signal of a specified bandwidth to a user device within a service area, comprising:
a spectrum detector for identifying k frequency-time cells of white space sufficient to accommodate the specified bandwidth of the information signal, where k is an integer, k≧1; and
a transmitter for transmitting the information signal over the identified k frequency-time cells of white space to the user device;
wherein the transmitter comprises
a baseband processor for converting the information signal into a baseband signal and parsing the baseband signal into n signal components where n is an integer, nε[1;k]and wherein for n=1, all carrier frequencies are modulated with the same baseband signal for obtaining spatial diversity, and
a distributor unit with k branches for modulating each carrier frequency corresponding to a respective frequency-time cell of white space with a signal component, and broadcasting k RF signal components over the respective frequency-time cells of white space.
18. A gateway as claimed in claim 17 , wherein the transmitter further comprises an interface for converting source signals received from a variety of signal sources over a variety of media into the information signal.
19. A method for redistributing an information signal of a specified bandwidth, within a service area, comprising:
identifying k frequency-time cells of white space sufficient to accommodate the bandwidth of the information signal, where k is an integer, k≧1;
broadcasting the information signal over the identified k frequency-time cells of white space to a user device;
wherein broadcasting the information comprises
converting the information signal into a baseband signal,
parsing the baseband signal into n signal components, where n is an integer nε[1;k],
selecting a carrier frequency for each of the k frequency-time cells of white space,
modulating each of the k carrier frequencies with a signal component, and
broadcasting the n signal components over the respective frequency-time cells of white space; and
wherein for n=1, all carrier frequencies are modulated with the same baseband signal for obtaining spatial diversity.
20. A method as claimed in claim 19 , wherein for n=k, each component signal modulates a carrier frequency.
21. A method as claimed in claim 19 , further comprising converting source signals received from a variety of signal sources over a variety of media into the information signal.