Scalable OFDM and OFDMA bandwidth allocation in communication systems

1. A method for allocating spectral bandwidth for an Orthogonal Frequency Division Multiplexing (OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), or Single Carrier Frequency-Division Multiple Access(SC-FDMA) system, comprising

dividing available spectral bandwidth into a channel raster and a plurality of nominal channels, each channel for carrying an independent OFDM or OFDMA or SC-FDM signal and each channel having a corresponding nominal channel bandwidth;

choosing a common subcarrier spacing of orthogonal subcarriers that divides the multiple nominal channel bandwidths and the channel raster evenly; and

allocating multiple carriers to be one next to another as a group in the same frequency band with reduced guard bands or without guard bands in between,

wherein a common subcarrier spacing of orthogonal subcarriers is aligned in frequency between boundaries of adjacent carriers to reduce or eliminate inter-carrier interference;

wherein the common subcarrier spacing can evenly divide each of multiple of different channel raster frequencies of one or more frequency bands.

2. The method of claim 1 , wherein:

the multiple carriers have the same or different nominal bandwidths.

3. The method of claim 1 , wherein:

the multiple carriers have different nominal bandwidths.

4. The method of claim 1 , wherein:

the multiple carriers have different multi-carrier channel bandwidths which are supported dynamically in time, from slot to slot or symbol to symbol.

5. The method of claim 1 , wherein

allocating multiple different nominal carriers to be side-by-side one next to another in frequency to allow a full carrier bandwidth to be utilized without guard bands in between.

6. The method of claim 3 , wherein

the common subcarrier spacing is selected to evenly divide the channel raster frequency of a frequency band.

7. The method of claim 6 , wherein

the common subcarrier spacing is 12.5 KHz which can divide the RF channel rasters of 250 KHz and 200 Khz to provide multi-carrier mixed bandwidth deployment.

8. The method of claim 6 , wherein:

the common subcarrier spacing is 10 KHz which can divide the RF channel rasters of 250 KHz and 200 Khz to provide multi-carrier mixed bandwidth deployment.

9. A method for allocating spectral bandwidth for an Orthogonal Frequency Division Multiplexing (OFDM), Orthogonal Frequency Division Multiple Access (OFDMA) system, or Single Carrier Frequency-Division Multiple Access(SC-FDMA), comprising:

dividing a frequency band into a plurality of channels with nominal channel bandwidths;

dividing each channel into a plurality of subchannels each comprising a plurality of subcarriers separated by a common subcarrier spacing, wherein the common subcarrier spacing is aligned in frequency between boundaries of adjacent carriers to reduce or eliminate inter-carrier interference, and wherein the common subcarrier spacing can evenly divide each of multiple of different channel raster frequencies of one or more frequency bands; and

selecting the nominal channel bandwidths so that each nominal channel bandwidth is evenly divided into a plurality of subchannels; and

using one or more edge subchannels at a spectral end of a channel as guard subchannels without transmitting signals.

10. The method of claim 9 , wherein:

each subchannel is configured to include 20 subcarriers for system deployment.

11. The method of claim 9 , wherein:

each subchannel is configured to include 16 subcarriers for system deployment.

12. The method of claims 9 , comprising:

providing a DC subcarrier at the center of the carrier bandwidth in a subchannel for system deployment.

13. The method of claim 9 , wherein:

allocating subchannels to be side-by-side one next to another across multiple carriers without any unassigned group of subcarriers.

14. The method of claim 9 , comprising:

using a common transmitter to transmit the channels.

15. The method of claim 9 , comprising:

using a plurality of different transmitters to transmit the plurality of channels, respectively, wherein the transmitters are synchronized in frequency.

16. A method for spectral bandwidth allocation for an Orthogonal Frequency Division Multiplexing (OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), or Single Carrier Frequency-Division Multiple Access(SC-FDMA) system, comprising:

dividing available spectral bandwidth into a channel raster and a plurality of nominal channels by allocating multiple different nominal channels to be sequentially next to one another in frequency without guard bands in between, wherein each channel carries an independent OFDM or OFDMA or SC-FDM signal;

assigning all subcarriers in the multiple different nominal channels to have a common subcarrier spacing, which evenly divides the channel raster, between two adjacent subcarriers and to be aligned across the multiple different nominal channels;

selecting a sampling frequency that is equal to or greater than a given nominal channel bandwidth or multiple nominal channel bandwidths;

using subcarriers within a given nominal channel bandwidth or multiple channel bandwidths for signal transmission without assigning subcarriers as guard subcarriers at both ends of the nominal channel bandwidth for each of the multiple different nominal channels;

wherein the common subcarrier spacing of orthogonal subcarriers is aligned in frequency between boundaries of adjacent carriers to reduce or eliminate inter-carrier interference; and

wherein the common subcarrier spacing can evenly divide each of multiple of different channel raster frequencies of one or more frequency bands.