Pilot design for wireless system
View Patent ↗The description herein relates to pilot designs for an Orthogonal Frequency Division Multiplexing (OFDM) based communication system. In at least one embodiment, the communication system is one operating according to the IEEE 802.16m, or WiMax, standard. In general, an OFDM transmitter operates to insert pilot symbols into a resource of a transmit frame according to a predetermined staggered pilot symbol pattern defining pilot symbol locations within the resource of the transmit frame. The predetermined pilot symbol pattern is defined such that pilot symbols are located at or near time boundaries of the resource, at or near frequency boundaries of the resource, or both. By doing so, when generating a channel estimate for the communication channel between the OFDM transmitter and an OFDM receiver based on the pilot symbols, extrapolations needed to estimate the channel near the boundaries of the resource are optimized, thereby improving overall channel estimation accuracy.
1. One or more computer-readable hardware storage memory devices comprising processor-executable instructions which, responsive to execution by one or more processors, are configured to enable a device to:
receive data symbols for a resource of a transmit frame;
receive the one or more pilot symbols from the pilot symbol generation circuitry; and
insert the one or more pilot symbols into the resource of the transmit frame according to a predetermined staggered pilot symbol pattern including one or more of a group comprising:
pilot symbol locations located at or near each time boundary of the resource; and
pilot symbol locations located at or near each frequency boundary of the resource,
wherein the pilot symbol locations located at or near each time boundary of the resource comprises one of:
pilot symbol locations less than or equal to two Orthogonal Frequency Division Multiplexing (OFDM) symbols from a first time boundary of the resource and pilot symbol locations less than or equal to two OFDM symbols from a second time boundary of the resource; or
pilot symbol locations in an OFDM symbol at a first time boundary of the resource and pilot symbol locations in an OFDM symbol at a second time boundary of the resource; and
wherein the pilot symbols located at or near each frequency boundary of the resource comprises one of:
pilot symbol locations less than or equal to three sub-carriers from a first frequency boundary of the resource and pilot symbol locations less than or equal to three sub-carriers from a second frequency boundary of the resource; or
pilot symbol locations at a sub-carrier at a first frequency boundary of the resource and pilot symbol locations at a sub-carrier at a second frequency boundary of the resource.
2. The one or more computer-readable hardware storage memory devices of claim 1 wherein the resource of the transmit frame is one or more sub-frames of a downlink frame.
3. The one or more computer-readable hardware storage memory devices of claim 2 , wherein a density of the predetermined staggered pilot symbol pattern is inversely related to a number of sub-frames in the one or more sub-frames.
4. The one or more computer-readable hardware storage memory devices of claim 2 , wherein the one or more pilot symbols inserted into the one or more sub-frames of the downlink frame are common pilots.
5. The one or more computer-readable hardware storage memory devices of claim 2 , wherein the predetermined staggered pilot symbol pattern includes:
a basic pilot symbol pattern that is uniform and includes a plurality of basic pilot symbol locations; and
one or more additional time boundary pilot symbol locations.
6. The one or more computer-readable hardware storage memory devices of claim 2 , wherein the predetermined staggered pilot symbol pattern includes:
a basic pilot symbol pattern that is uniform and includes a plurality of basic pilot symbol locations; and
one or more additional frequency boundary pilot symbol locations.
7. The one or more computer-readable hardware storage memory devices of 1 , wherein the resource of the transmit frame is a block of symbol locations within a sub-frame of the transmit frame.
8. A computer-implemented method comprising:
receiving data symbols for a resource of a transmit frame;
receiving one or more pilot symbols; and
inserting, using a pilot inserter, the one or more pilot symbols into the resource of the transmit frame according to a predetermined staggered pilot symbol pattern including one or more of a group consisting of:
pilot symbol locations located at or near each time boundary of the resource; and
pilot symbol locations located at or near each frequency boundary of the resource,
wherein the pilot symbol locations located at or near each time boundary of the resource comprises one of:
pilot symbol locations less than or equal to two Orthogonal Frequency Division Multiplexing (OFDM) symbols from a first time boundary of the resource and pilot symbol locations less than or equal to two OFDM symbols from a second time boundary of the resource; or
pilot symbol locations in an OFDM symbol at a first time boundary of the resource and pilot symbol locations in an OFDM symbol at a second time boundary of the resource; and
wherein the pilot symbols located at or near each frequency boundary of the resource comprises one of:
pilot symbol locations less than or equal to three sub-carriers from a first frequency boundary of the resource and pilot symbol locations less than or equal to three sub-carriers from a second frequency boundary of the resource; or
pilot symbol locations at a sub-carrier at a first frequency boundary of the resource and pilot symbol locations at a sub-carrier at a second frequency boundary of the resource.
9. The computer-implemented of claim 8 , wherein the resource of the transmit frame is one or more sub-frames of a downlink frame.
10. The computer-implemented method of claim 9 , wherein a density of the predetermined staggered pilot symbol pattern is inversely related to a number of sub-frames in the one or more sub-frames.
11. The computer-implemented method of claim 9 , wherein the one or more pilot symbols inserted into the one or more sub-frames of the downlink frame are common pilots.
12. The computer-implemented method of claim 9 , wherein the predetermined staggered pilot symbol pattern includes:
a basic pilot symbol pattern that is uniform and includes a plurality of basic pilot symbol locations; and
one or more additional time boundary pilot symbol locations.
13. The computer-implemented method of claim 9 , wherein the predetermined staggered pilot symbol pattern includes:
a basic pilot symbol pattern that is uniform and includes a plurality of basic pilot symbol locations; and
one or more additional frequency boundary pilot symbol locations.
14. The computer-implemented method of claim 9 , wherein the predetermined staggered pilot symbol pattern includes:
a basic pilot symbol pattern that is uniform and includes a plurality of basic pilot symbol locations;
one or more additional time boundary pilot symbol locations; and
one or more additional frequency boundary pilot symbol locations.
15. The computer-implemented method of claim 8 , wherein the resource unit is a plurality of continuous blocks of symbol locations within two or more sub-frames of the transmit frame.
16. One or more computer-readable hardware storage memory devices comprising processor-executable instructions which, responsive to execution by one or more processors, are configured to enable a device to:
receive data symbols for a resource of a transmit frame, wherein the resource of the transmit frame is one or more sub-frames of a downlink frame;
receive the one or more pilot symbols; and
insert the one or more pilot symbols into the resource of the transmit frame according to a predetermined staggered pilot symbol pattern including one or more of a group comprising:
pilot symbol locations located at or near each time boundary of the resource; and
pilot symbol locations located at or near each frequency boundary of the resource,
wherein the predetermined staggered pilot symbol pattern includes pilot symbol locations in a last sub-frame of the one or more sub-frames that are adjusted with respect to pilot symbol locations for other sub-frames of the one or more sub-frames such that the predetermined staggered pilot symbol pattern includes pilot symbol locations at or near an ending time boundary of the last sub-frame of the one or more sub-frames.
17. The one or more computer-readable hardware storage memory devices of claim 16 , wherein the one or more sub-frames are a plurality of sub-frames, the predetermined staggered pilot symbol pattern is uniform from a first sub-frame of the plurality of sub-frames through a next-to-last sub-frame of the plurality of sub-frames, and the pilot symbol locations in the last sub-frame are substantially uniform with pilot symbol locations in the first through next-to-last sub-frames.
18. The one or more computer-readable hardware storage memory devices of claim 17 , wherein the predetermined staggered pilot symbol pattern starts at or near a starting time boundary of the first sub-frame.
19. The one or more computer-readable hardware storage memory devices of claim 16 , wherein a time spacing between the pilot symbol locations in the last sub-frame is greater than a time spacing between the pilot symbol locations in the other sub-frames.
20. The one or more computer-readable hardware storage memory devices of claim 16 , wherein the last sub-frame includes additional pilot symbol locations as compared to the other sub-frames.