Systems and methods for OFDM channelization
Systems and methods for OFDM channelization are provided that allow for the coexistence of sub-band channels and diversity channels. Methods of defining diversity sub-channels and sub-band sub-channels are provided and systematic channel definition and labeling schemes are provided.
1. A method for operating a base station to communicate with one or more mobile stations, the method comprising:
transmitting OFDM symbols using a plurality of sub-carriers within an OFDM band;
the OFDM symbols collectively containing diversity channels and sub-band channels, each diversity channel utilizing a plurality of sub-carriers distributed across the OFDM band, and each sub-band channel utilizing a contiguous set of sub-carriers within the OFDM band; and
at least one of the OFDM symbols simultaneously including sub-carriers utilized by a sub-band channel and sub-carriers utilized by a diversity channel.
2. The method of claim 1 , further comprising performing partial tree activation by:
using a respective sub-channelization tree to organize sub-channels into allowable channels for at least one of diversity channel definition and sub-band channel definition;
for at least one sub-channelization tree, activating a portion of the sub-channelization tree and sending information identifying the portion; and
assigning channels from the portion of the sub-channelization tree.
3. The method of claim 2 wherein activating a portion of the sub-channelization tree comprises activating a certain set of consecutive levels within the tree.
4. The method of claim 2 wherein activating a portion of the sub-channelization tree comprises activating a respective set of consecutive levels within the tree for each of a respective set of at least one defined top node.
5. The method of claim 2 wherein activating a portion of the sub-channelization tree comprises:
employing a first bitmap to identify a subset of nodes of the sub-channelization tree that are active.
6. The method of claim 5 further comprising:
using a second bitmap to identify which nodes of the subset of nodes are being assigned, and for each node being assigned, assigning a user identifier.
7. The method of claim 2 , further comprising:
updating the partial tree activation from time to time.
8. The method of claim 7 wherein updating the partial tree activation from time to time comprises:
sending update information only for segments of the tree that have changed.
9. The method of claim 1 , further comprising:
persistently allocating a sub-band or diversity channel transmission resource for VoIP traffic; and
using one of two MCS (modulation and coding scheme) levels VoIP traffic by assigning one of the two MCS levels at a beginning of a call and only changing the MCS level if a significant change in a receiver's average reported CQI is detected.
10. The method of claim 9 , further comprising:
if a mobile station reports a CQI that maps to a higher MCS than an operating MCS, decreasing a transmit power by an amount specified for the difference between the two MCS levels; and
if the mobile station reports a CQI that maps to a lower MCS than the operating MCS, performing no power adjustment.
11. A base station for communicating with one or more mobile stations, the base station comprising:
a processor coupled to a memory, the memory storing processor executable program instructions, which when executed by the processor, cause the processor to:
transmit OFDM symbols using a plurality of sub-carriers within an OFDM band;
the OFDM symbols collectively containing diversity channels and sub-band channels, each diversity channel utilizing a plurality of sub-carriers distributed across the OFDM band, and each sub-band channel utilizing a contiguous set of sub-carriers within the OFDM band; and
at least one of the OFDM symbols simultaneously including sub-carriers utilized by a sub-band channel and sub-carriers utilized by a diversity channel.
12. The base station of claim 11 , the processor executable program instructions further causing the processor to perform partial tree activation by:
using a respective sub-channelization tree to organize sub-channels into allowable channels for at least one of diversity channel definition and sub-band channel definition;
for at least one sub-channelization tree, activating a portion of the sub-channelization tree and sending information identifying the portion; and
assigning channels from the portion of the sub-channelization tree.
13. The base station of claim 12 wherein activating a portion of the sub-channelization tree comprises activating a certain set of consecutive levels within the tree.
14. The base station of claim 12 wherein activating a portion of the sub-channelization tree comprises activating a respective set of consecutive levels within the tree for each of a respective set of at least one defined top node.
15. The base station of claim 12 wherein activating a portion of the sub-channelization tree comprises:
employing a first bitmap to identify a subset of nodes of the sub-channelization tree that are active.
16. The base station of claim 12 , the processor executable program instructions further causing the processor to:
update the partial tree activation from time to time.
17. The base station of claim 16 wherein updating the partial tree activation from time to time comprises:
sending update information only for segments of the tree that have changed.
18. The base station of claim 11 , the processor executable program instructions further causing the processor to:
persistently allocate a sub-band or diversity channel transmission resource for VoIP traffic; and
use one of two MCS (modulation and coding scheme) levels VoIP traffic by assigning one of the two MCS levels at a beginning of a call and only changing the MCS level if a significant change in a receiver's average reported CQI is detected.
19. The base station of claim 18 , the processor executable program instructions further causing the processor to:
if a mobile station reports a CQI that maps to a higher MCS than an operating MCS, decrease a transmit power by an amount specified for the difference between the two MCS levels; and
if the mobile station reports a CQI that maps to a lower MCS than the operating MCS, perform no power adjustment.
20. An integrated circuit for communicating with one or more mobile stations, the integrated circuit comprising:
circuitry configured to:
transmit OFDM symbols using a plurality of sub-carriers within an OFDM band;
the OFDM symbols collectively containing diversity channels and sub-band channels, each diversity channel utilizing a plurality of sub-carriers distributed across the OFDM band, and each sub-band channel utilizing a contiguous set of sub-carriers within the OFDM band; and
at least one of the OFDM symbols simultaneously including sub-carriers utilized by a sub-band channel and sub-carriers utilized by a diversity channel.