Method and apparatus for performing channel estimation for uplink data in NB-IoT physical layer

1 . A method comprising:

receiving, a plurality of uplink data signals from at least one User Equipment (UE);

dividing each of the uplink data signals into a plurality of processing blocks, each processing block of the plurality of processing blocks comprises a plurality of slots, wherein each slot of the plurality of slots comprising a plurality of data symbols, a reference signal symbol and a plurality of reference signal tones;

for each processing block:

estimating a time offset by determining a first correlation value between the plurality of reference signal tones within one reference signal symbol; and

estimating a frequency offset by determining a second correlation value between a plurality of reference signal symbols across the plurality of slots; and

performing channel estimation upon estimating the time offset and the frequency offset of all of the plurality of the processing blocks.

2 . The method as claimed in claim 1 , wherein the method is performed for a narrowband Physical Uplink Shared Channel (NPUSCH) format 1 .

3 . The method as claimed in claim 1 , further comprising:

obtaining a plurality of descrambled reference signal symbols by removing a predetermined pseudorandom binary sequence (PRBS) from the reference signal symbols;

obtaining a plurality of descrambled reference signal tones by removing the predetermined PRBS from the reference signal tones;

providing the plurality of descrambled reference signal symbols and the plurality of descrambled reference signal tones for estimating the time offset and frequency offset, respectively.

4 . The method as claimed in claim 1 , wherein estimating the time offset, further comprising:

determining if the processing block is a first processing block;

in response to the determination that the processing block is the first processing block:

obtaining the time offset estimate of current block based on data stored in a previous data transfer session with the same at least one UE, wherein the time offset estimate is indicative of a time offset value of a last processing block of the data stored in the previous data transfer session with the same at least one UE;

determining a noise power feedback from a plurality of reserved tones of the uplink data signals;

applying a time offset compensation over the plurality of the reference signal tones, based on the noise power feedback and the time offset estimate; and

in response to the determination that the processing block is not the first processing block:

obtaining an instantaneous time offset estimate of current processing block based on the first correlation value between the plurality of the reference signal tones within the one reference signal symbol;

estimating the time offset of the current processing block by:

determining a weighted moving average between the instantaneous time offset estimate of the current processing block and the time offset estimate of a previous processing block;

determining the noise power feedback from reserved tones of the uplink data signals; and

applying a time offset compensation over the plurality of the reference signal tones, based on the time offset and the noise power feedback.

5 . The method as claimed in claim 1 , wherein estimating the frequency offset, further comprising:

determining if the processing block is a first processing block;

obtain a frequency offset estimate of current block based on data stored in a previous data transfer session with the same at least one UE, wherein the frequency offset estimate is indicative of a frequency offset value of a last processing block of the data stored in the previous data transfer session with the same at least one UE;

determining a noise power feedback from the reserved tones of the uplink data signals;

applying a time offset compensation over the plurality of the reference signal tones, based on the time offset estimate and the noise power feedback;

in response to the determination that the current processing block is not a first processing block:

obtaining an instantaneous frequency offset estimate of the current processing block based on the second correlation value between the plurality of the reference symbols in each slot of the plurality of slots;

estimating the frequency offset of the current processing block by:

determining a weighted moving average of the instantaneous frequency offset estimate of the current processing block and the frequency offset estimate of a previous processing block;

determining the noise power feedback from reserved tones of the uplink data signals;

applying a frequency offset compensation over the plurality of the reference signal tones, based on the frequency offset estimate and the noise power feedback.

6 . The method as claimed in claim 1 , further comprising:

determining a plurality of Signal-to-interference-plus-noise ratio (SINR) estimates based on a signal power computed from the reference signal symbols and a plurality of noise estimates obtained from a plurality of reserved tones of the uplink data signals;

comparing each SINR estimate of the plurality of SINR estimates with a predetermined threshold indicative of a discontinuous transmission;

if each SINR estimate is less than the predetermined threshold:

detecting a discontinuous transmission from the at least one UE; and

sending a request to the at least one UE to retransmit the plurality of uplink data signals; and

if each SINR estimate is greater than a predetermined threshold:

determining based on the comparison that a transmission from the at least one UE is not a discontinuous transmission; and

performing decoding of the plurality of uplink data signals.

7 . An apparatus comprising:

a processor; and

a memory communicatively coupled to the processor, wherein the memory stores processor-executable instructions, which on execution, cause the processor to:

receive a plurality of uplink data signals from at least one User Equipment (UE);

divide the uplink data signal into a plurality of processing blocks, each processing block of the plurality of processing blocks comprises a plurality of slots, wherein each slot of the plurality of slots comprising a plurality of data symbols, a reference signal symbol and a plurality of reference signal tones;

for each processing block:

estimate a time offset by determining a first correlation value between the plurality of the reference signal tones within one reference signal symbol; and

estimate a frequency offset by determining a second correlation value between a plurality of the reference symbols across the plurality of slots; and

perform channel estimation upon estimating the time offset and the frequency offset of all of the plurality of the processing blocks.

8 . The apparatus as claimed in claim 7 , wherein the apparatus is implemented for a narrowband Physical Uplink Shared Channel (NPUSCH) format 1 .

9 . The apparatus as claimed in claim 7 , wherein the processor is further configured to:

obtain a plurality of descrambled reference signal symbols by removing a predetermined pseudorandom binary sequence (PRBS) from the reference signal symbols;

obtain a plurality of descrambled reference signal tones by removing the predetermined PRBS from the reference signal tones; and

provide the plurality of descrambled reference signal symbol and the plurality of descrambled reference signal tones for estimating the time offset and frequency offset, respectively.

10 . The apparatus as claimed in claim 7 , wherein to estimate the time offset, the processor is further configured to:

determine if the processing block is a first processing block;

in response to the determination that the processing block is a first processing block:

obtain the time offset estimate of current block based on data stored in a previous data transfer session with the same least one UE, wherein the time offset estimate is indicative of a time offset value of a last processing block of the data stored in the previous data transfer session of the same least one UE;

determine a noise power feedback from a plurality of reserved tones of the uplink data signals;

apply a time offset compensation over the plurality of the reference signal tones, based on the noise power feedback and the time offset estimate; and

in response to the determination that the processing block is not the first processing block:

obtain an instantaneous time offset estimate of current processing block based on the first correlation value between the plurality of the reference signal tones within the one reference signal symbol;

estimate the time offset of the current processing block by:

determining a weighted moving average between the instantaneous time offset estimate of the current processing block and the time offset estimate of a previous processing block;

determining the noise power feedback from the plurality of reserved tones of the uplink data signals;

applying a time offset compensation over the plurality of the reference signal tones, based on the time offset and the noise power feedback.

11 . The apparatus as claimed in claim 7 , wherein to estimate the frequency offset, the processor is further configured to:

determine if the processing block is a first processing block;

in response to the determination that the current processing block is the first processing block:

obtain a frequency offset estimate of current block based on data stored in a previous data transfer session with the same at least one UE, wherein the frequency offset estimate is indicative of a frequency offset value of a last processing block of the data stored in the previous data transfer session with the same least one UE;

determine a noise power feedback from a plurality of reserved tones of the uplink data signals; and

applying a time offset compensation over the plurality of the reference signal tones, based on the time offset estimate and the noise power feedback; and

in response to the determination that the current processing block is not a first processing block:

obtain an instantaneous frequency offset estimate of the current processing block based on the second correlation value between the plurality of the reference symbols in each slot of the plurality of slots;

estimate the frequency offset of the current processing block by:

determining a weighted moving average of the instantaneous frequency offset estimate of the current processing block and the frequency offset estimate of a previous processing block;

determining the noise power feedback from the plurality of reserved tones of the uplink data signals;

applying a frequency offset compensation over the plurality of the reference signal tones, based on the frequency offset estimate and the noise power feedback.

12 . The apparatus as claimed in claim 7 , wherein the processor is further configured to:

determine a plurality of Signal-to-interference-plus-noise ratio (SINR) estimates based on a signal power computed from the reference signal symbols and a plurality of noise estimates obtained from a plurality of reserved tones of the uplink data signals.

13 . The apparatus as claimed in claim 12 , wherein the processor is further configured to:

compare each SINR estimate of the plurality of SINR estimates with a predetermined threshold indicative of a discontinuous transmission;

if each SINR estimate is less than the predetermined threshold:

detect a discontinuous transmission from the at least one UE; and

send a request to the at least one UE to retransmit the plurality of uplink data signals; and

if each SINR estimate is greater than a predetermined threshold:

determine based on the comparison that a transmission from the at least one UE is not a discontinuous transmission; and

perform decoding of the plurality of uplink data signals.

14 . A non-transitory computer readable medium including instructions stored thereon that when processed by at least one processor, cause the at least one processor to perform operations comprising:

receiving, a plurality of uplink data signals from at least one User Equipment (UE);

dividing the uplink data signal into a plurality of processing blocks, each processing block of the plurality of processing blocks comprises a plurality of slots, wherein each slot of the plurality of slots comprising a plurality of data symbols, a reference signal symbol and a plurality of reference signal tones;

for each processing block:

estimating a time offset by determining a first correlation value between a plurality of the reference signal tones within one reference signal symbol; and

estimating a frequency offset by determining a second correlation value between a plurality of the reference symbols across the plurality of slots; and

performing channel estimation upon estimating the time offset and the frequency offset of all of the plurality of the processing blocks.

15 . The medium as claimed in claim 14 , wherein the non-transitory computer readable medium is implemented for a narrowband Physical Uplink Shared Channel (NPUSCH) format 1 .

16 . The medium as claimed in claim 14 , further comprising the instructions that when processed by the at least one processor, cause the at least one processor to perform operations comprising:

obtaining a plurality of descrambled reference signal symbols by removing a predetermined pseudorandom binary sequence (PRBS) from the reference signal symbols;

obtaining a plurality of descrambled reference signal tones by removing the predetermined PRBS from the reference signal tones; and

providing the plurality of descrambled reference signal and the plurality of descrambled reference signal tones for estimating the time offset and frequency offset.

17 . The medium as claimed in claim 14 , further comprising the instructions that when processed by the at least one processor, cause the at least one processor to estimate the time offset, by:

determining if the processing block is a first processing block;

in response to the determination that the current processing block is a first processing block:

obtaining the time offset estimate of current block based on data stored in a previous data transfer session with the same least one UE, wherein the time offset estimate is indicative of a time offset value of a last processing block of the data stored in the previous data transfer session with the same least one UE;

determining a noise power feedback from a plurality of reserved tones of the uplink data signals;

applying a time offset compensation over the plurality of the reference signal tones, based on the noise power feedback and the time offset estimate; and

in response to the determination that the processing block is not the first processing block:

obtaining an instantaneous time offset estimate of current processing block based on the first correlation value between the plurality of the reference signal tones within the one reference signal symbol;

estimating the time offset of the current processing block by:

determining a weighted moving average between the instantaneous time offset estimate of the current processing block and the time offset estimate of a previous processing block;

determining the noise power feedback from the plurality of reserved tones of the uplink data signals;

applying a time offset compensation over the plurality of the reference signal tones, based on the time offset and the noise power feedback.

18 . The medium as claimed in claim 14 , further comprising the instructions that when processed by the at least one processor, cause the at least one processor to estimate the frequency offset by:

determining if the processing block is a first processing block;

obtaining a frequency offset estimate of current block based on data stored in the previous data transfer session with the same at least one UE, wherein the frequency offset estimate is indicative of a frequency offset value of a last processing block of the data stored in the previous data transfer session with the same at least one UE;

determining a noise power feedback from a plurality of reserved tones of the uplink data signals;

applying a time offset compensation over the plurality of the reference signal tones, based on the time offset estimate and the noise power feedback;

in response to the determination that the current processing block is not a first processing block:

obtaining an instantaneous frequency offset estimate of the current processing block based on the second correlation value between the plurality of the reference symbols in each slot of the plurality of slots;

estimating the frequency offset of the current processing block by:

determining a weighted moving average of the instantaneous frequency offset estimate of the current processing block and the frequency offset estimate of a previous processing block;

determining the noise power feedback from reserved tones of the uplink data signals;

applying a frequency offset compensation over the plurality of the reference signal tones, based on the frequency offset estimate and the noise power feedback.

19 . The medium as claimed in claim 14 , further comprising the instructions that when processed by the at least one processor, cause the at least one processor to perform operations comprising:

determining a plurality of Signal-to-interference-plus-noise ratio (SINR) estimates based on a signal power computed from the reference signal symbols and a plurality of noise estimates obtained from the plurality of reserved tones of the uplink data signals.

20 . The medium as claimed in claim 14 , further comprising the instructions that when processed by the at least one processor, cause the at least one processor to perform operations comprising:

comparing each SINR estimate of the plurality of SINR estimates with a predetermined threshold indicative of a discontinuous transmission;

if each SINR estimate is less than the predetermined threshold:

detecting a discontinuous transmission from the at least one UE; and

sending a request to the at least one UE to retransmit the plurality of uplink data signals; and

if each SINR estimate is greater than a predetermined threshold:

determining based on the comparison that a transmission from the at least one UE is not a discontinuous transmission; and

performing decoding of the plurality of uplink data signals.