Spectrally efficient universal time slots using time-frequency-code slicing

We propose a time-frequency-code-slicing technique that allows multiple users with different speed requirements access to a communications resource in a manner that is cost effective over a wide range of access speeds. Conventional systems require low-speed users to either pay a cost premium (e.g., high-speed burst modems for TDMA) or end up wasting some of the spectrum (e.g., universal time slots). The advantages of our proposed scheme can be demonstrated with any two combinations (or all three) of time slicing, frequency slicing, and code slicing. For instance, with a time-frequency-slicing approach, users can be assigned different portions of the spectrum (e.g., on a slot-by-slot basis), allowing them access to only the needed fraction of the shared resource. With time-code slicing, users are dynamically granted portions of the code space, during specified time periods. Finally, in frequency-code slicing, a user may be assigned a number of codes in different frequency bands. These codes can be of constant or variable chip rates