Enhanced ranging in WiMAX

1. In a WiMAX communication system configured to provide service at a plurality of quality of service (QoS) levels, a method for ranging comprising:

broadcasting a QoS level message in a downlink sub-frame, wherein the QoS level message comprises one or more spreading factor codes, and wherein each spreading factor code indicates a spreading factor for a particular QoS level;

receiving a ranging request from a device, wherein the ranging request comprises an orthogonal variable spreading factor (OVSF) code, wherein the OVSF code was selected according to the one or more spreading factor codes;

determining a spreading factor of the OVSF code in the received ranging request; and

using the spreading factor as a basis for selecting a QoS level at which to provide service to the device.

2. The method of claim 1 , wherein the QoS level message is an uplink MAP (UL-MAP) message.

3. The method of claim 1 , wherein the QoS level message is a downlink MAP (DL-MAP) message.

4. The method of claim 1 , wherein the QoS level message further comprises one or more QoS level codes for one or more of the QoS levels.

5. The method of claim 4 , wherein the QoS level message comprises one or more code pairs, wherein each code pair comprises a QoS level code and a spreading factor code that indicates the spreading factor for the QoS level code.

6. The method of claim 1 wherein the one or more spreading factor codes are included in the QoS level message in a predefined order, wherein the predefined order indicates which of the one or more spreading factor codes indicates the spreading factor for which of the one or more QoS levels.

7. The method of claim 1 , wherein the WiMAX communication system is configured to engage in one or more ranging processes.

8. The method of claim 7 , wherein the ranging processes comprise initial ranging, periodic ranging, bandwidth requests, and hand-off requests.

9. The method of claim 7 , wherein the QoS level message further comprises a message type code, wherein the message type code indicates which of the ranging processes the spreading factor codes indicate spreading factors for.

10. A method for WiMAX ranging, wherein a WiMAX base station is configured to provide service at a plurality of QoS levels, the method comprising:

receiving a QoS level message, wherein the QoS level message comprises one or more spreading factor codes, wherein each spreading factor code indicates a spreading factor for a particular QoS level;

determining a desired QoS level at which to request service from the WiMAX base station;

using the spreading factor codes as a basis for selecting an OVSF ranging code having the spreading factor for the desired QoS level; and

sending a ranging request to the WiMAX base station, wherein the ranging request comprises the selected OVSF code.

11. The method of claim 10 , further comprising, before receiving the QoS level message, detecting a preamble in a downlink sub-frame, wherein the preamble is broadcast by a WiMAX base station.

12. The method of claim 10 , wherein the ranging request comprises an initial ranging request, a periodic ranging request, a bandwidth request, or a hand-off ranging request.

13. The method of claim 10 , wherein receiving the QoS level message comprises receiving a UL-MAP message or a DL-MAP message, wherein the UL-MAP message or the DL-MAP message comprises the QoS level message.

14. A WiMAX communication system configured to perform ranging and configured to provide service at a plurality of QoS levels, the system comprising:

a transmitter configured to broadcast a QoS level message, wherein the QoS level message comprises one or more spreading factor codes, and wherein each spreading factor code indicates a spreading factor for a particular QoS level; and

a receiver configured to receive a ranging request from a device, wherein the ranging request comprises an orthogonal variable spreading factor (OVSF) code having a spreading factor selected by the device based at least in part on the spreading factor codes;

wherein the WiMAX communication system is further configured to:

determine the spreading factor of the OVSF code in the received ranging request; and

use the spreading factor as a basis for selecting a QoS level at which to provide service to the device.

15. The WiMAX communication system of claim 14 , wherein the WiMAX communication system is implemented in a WiMAX base station.

16. The WiMAX communication system of claim 14 , wherein the QoS level message is broadcast in a downlink sub-frame.

17. The WiMAX communication system of claim 16 , wherein the downlink sub-frame comprises an uplink MAP (UL-MAP) and a downlink MAP (DL-MAP), and wherein the QoS level message is broadcast in the UL-MAP or the DL-MAP of the downlink sub-frame.

18. The WiMAX communication system of claim 14 , wherein the QoS levels comprise a first QoS level having the highest QoS, a second QoS level having an intermediate QoS, and a third QoS level having the lowest QoS.

19. The WiMAX communication system of claim 18 , wherein the first QoS level is referred to as gold level service, wherein the second QoS level is referred to as silver level service, and wherein the third QoS level is referred to as bronze level service.