Method and transceiver of a wireless communication network for handling reference signals
Disclosed is a method and a first transceiver of a wireless communication network, for handling reference signals. The method comprises receiving, from a second transceiver, at antenna elements of each of M antenna branches of the first transceiver and in time domain, an OFDM modulated wideband reference signal comprising an OFDM reference signal symbol mapped to every K subcarrier frequency of at least a subset of a carrier frequency bandwidth, and, at each of the M antenna branches, sampling the received wideband reference signal using N samples per OFDM symbol. The method further comprises, for each of the M antenna branches, accumulating the received, sampled wideband reference signal over at least two repetition blocks, each of length of N/K, to obtain a condensed signal with the length N/K samples and conveying the condensed signal over an interface to an aggregate unit.
1. A method performed by a first transceiver of a wireless communication network, for handling reference signals, the first transceiver comprising M antenna branches, M being at least two, each antenna branch comprising an antenna element, the method comprising:
receiving, from a second transceiver of the wireless communication network, at the antenna elements of each of the M antenna branches and in time domain, an Orthogonal Frequency Division Multiplexing (OFDM) modulated wideband reference signal comprising an OFDM reference signal symbol mapped to every K subcarrier frequency, wherein K is equal to or greater than 1, of at least a subset of a carrier frequency bandwidth, K being called comb factor;
at each of the M antenna branches, sampling the received OFDM modulated wideband reference signal using N samples per OFDM symbol, wherein N is equal to or greater than 1;
for each of the M antenna branches, accumulating the received, sampled OFDM modulated wideband reference signal over at least two repetition blocks, each block having a length of N/K samples, to obtain a condensed signal with the length N/K samples, based on information on start times of the at least two repetition blocks,
for each of the M antenna branches, conveying the condensed signal over an interface to an aggregate unit for use in estimating a wireless communication channel between the second transceiver and the first transceiver.
2. The method according to claim 1 , wherein the OFDM reference signal symbol is a part of a sounding reference signal, SRS, and the comb factor K=4.
3. The method according to claim 1 , wherein the OFDM reference signal symbol is a part of a sounding reference signal, SRS, and the comb factor K=6, 8, 12 or 16.
4. The method according to claim 1 , wherein the received OFDM modulated wideband reference signal is sampled with a sampling frequency f s , and wherein the comb factor K and the sampling frequency f s are selected so that the at least two repetition blocks each comprises an equal number of samples.
5. The method according to claim 1 , wherein when the at least two repetition blocks comprises: a first repetition block in a first OFDM symbol and a second repetition block in a second OFDM symbol, the accumulation is compensated for a cyclic prefix of the first or second OFDM symbol so that a shift in time between the first repetition block and the second repetition block is an integer number of samples.
6. The method according to claim 1 , wherein the at least two repetition blocks comprises: a first set of repetition blocks in a first OFDM symbol and a second set of repetition blocks in a second OFDM symbol, the accumulation being performed so that firstly the first set of repetition blocks are accumulated, and if a time between the first OFDM symbol and the second OFDM symbol is not an integer number of samples, a fractional delay filter is applied to the second set of repetition blocks to align them with the first set of repetition blocks and thereafter the second set of repetition blocks are accumulated with the first set of repetition blocks.
7. The method according to claim 1 , further comprising:
obtaining the information on start times of the at least two repetition blocks, the information on start times comprising the N number of samples per OFDM symbol, the comb factor K and OFDM symbol start time.
8. The method according to claim 1 , further comprising:
obtaining information on a comb factor frequency offset K shift , when the OFDM reference signal symbol is not mapped on a lowest subcarrier of the at least subset of the carrier frequency bandwidth, and
when performing the accumulation, compensating for the comb factor frequency offset K shift .
9. A first transceiver operable in a wireless communication system configured for handling reference signals, the first transceiver comprising M antenna branches, M being at least two, each antenna branch comprising an antenna element, the first transceiver comprising a processing circuitry and a memory, said memory containing instructions executable by said processing circuitry, whereby first transceiver is operative for:
receiving, from a second transceiver of the wireless communication system, at the antenna elements of each of the M antenna branches and in time domain, an Orthogonal Frequency Division Multiplexing (OFDM) modulated wideband reference signal comprising an OFDM reference signal symbol mapped to every K subcarrier frequency, wherein K is equal to or greater than 1, of at least a subset of a carrier frequency bandwidth, K being called comb factor;
at each of the M antenna branches, sampling the received OFDM modulated wideband reference signal using N samples per OFDM symbol, wherein N is equal to or greater than 1;
for each of the M antenna branches, accumulating the received, sampled OFDM modulated wideband reference signal over at least two repetition blocks, each block having a length of N/K samples, to obtain a condensed signal with the length N/K samples, based on information on start times of the at least two repetition blocks,
for each of the M antenna branches, conveying the condensed signal over an interface to an aggregate unit for use in estimating a wireless communication channel between the second transceiver and the first transceiver.
10. The first transceiver according to claim 9 , wherein the OFDM reference signal symbol is a part of a sounding reference signal, SRS, and the comb factor K=4.
11. The first transceiver according to claim 9 , wherein the OFDM reference signal symbol is a part of a sounding reference signal, SRS, and the comb factor K=6, 8, 12 or 16.
12. The first transceiver according to claim 9 , operative for the sampling of the received OFDM modulated wideband reference signal with a sampling frequency f s , and wherein the comb factor K and the sampling frequency f s are selected so that the at least two repetition blocks each comprises an equal number of samples.
13. The first transceiver according to claim 9 , wherein the at least two repetition blocks comprises: a first repetition block in a first OFDM symbol and a second repetition block in a second OFDM symbol, and the first transceiver is operative for, in the accumulation, compensating for a cyclic prefix of the first or second OFDM symbol so that a shift in time between the first repetition block and the second repetition block is an integer number of samples.
14. The first transceiver according to claim 9 , wherein the at least two repetition blocks comprises: a first set of repetition blocks in a first OFDM symbol and a second set of repetition blocks in a second OFDM symbol, and the first transceiver is operative for performing the accumulation so that firstly the first set of repetition blocks are accumulated, and if a time between the first OFDM symbol and the second OFDM symbol is not an integer number of samples, a fractional delay filter is applied to the second set of repetition blocks to align them with the first set of repetition blocks and thereafter the second set of repetition blocks are accumulated with the first set of repetition blocks.
15. The first transceiver according to claim 9 , further being operative for:
obtaining the information on start times of the at least two repetition blocks, the information on start times comprising the N number of samples per OFDM symbol, the comb factor K and OFDM symbol start time.
16. The first transceiver according to claim 9 , further being operative for:
obtaining information on a comb factor frequency offset K shift , when the OFDM reference signal symbol is not mapped on a lowest subcarrier of the at least subset of the carrier frequency bandwidth, and
when performing the accumulation, compensating for the comb factor frequency offset K shift .
17. A non-transitory computer readable medium comprising instructions, which, when executed by at least one processing circuitry of a first transceiver of a wireless communication network, configured for handling reference signals, the first transceiver comprising M antenna branches, M being at least two, each antenna branch comprising an antenna element, causes the first transceiver to:
receive, from a second transceiver of the wireless communication network, at the antenna elements of each of the M antenna branches and in time domain, an Orthogonal Frequency Division Multiplexing (OFDM) modulated wideband reference signal comprising an OFDM reference signal symbol mapped to every K subcarrier frequency, wherein K is equal to or greater than 1, of at least a subset of a carrier frequency bandwidth, K being called comb factor;
at each of the M antenna branches, sample the received OFDM modulated wideband reference signal using N samples per OFDM symbol, wherein N is equal to or greater than 1;
for each of the M antenna branches, accumulate the received, sampled OFDM modulated wideband reference signal over at least two repetition blocks, each block having a length of N/K samples, to obtain a condensed signal with the length N/K samples, based on information on start times of the at least two repetition blocks,
for each of the M antenna branches, convey the condensed signal over an interface to an aggregate unit for use in estimating a wireless communication channel between the second transceiver and the first transceiver.