Apparatus for OFDMA transmission and reception for coherent detection in uplink of wireless communication system and method thereof

An apparatus for OFDMA reception, which is for coherent detection in an uplink of a wireless communication system supporting multiple subscribers, the apparatus comprising:

• an OFDM demodulator for converting OFDM received symbols at respective antennas into frequency-domain received symbols, the OFDM received symbol including a pilot symbol that has the same transmission power as a data symbol;
• a resource-block-based time-frequency demapper for separating the frequency-domain received symbols of the OFDM demodulator by subscribers according to a resource mapping method for each subscriber, and rearranging the separated frequency-domain received symbols based on a resource block, the resource mapping method mapping multiple resource blocks that are well-distributed in time and frequency domains to each subscriber, each resource block comprising consecutive subcarriers of consecutive OFDM symbols;
• a channel estimator for estimating a channel in units of resource blocks based on the output of the resource-block-based time-frequency demapper, wherein the channel estimator estimates, at a first iteration, the channel of a corresponding resource block based on a pilot channel estimate obtained by dividing the received pilot symbol output from the OFDM demodulator by a given pilot symbol and refines the estimated channel based on the pilot channel estimate and a data channel estimate in subsequent iterations;
• a demodulator for coherently calculating a channel decoding input metric by using the channel estimate of the channel estimator;
• and
• a channel decoder for performing channel decoding by using the calculated metric of the demodulator according to a channel encoding methods
• wherein when using a single-pilot-based resource block having the pilot inserted in the center of the resource block, the channel estimator comprises:
• an instantaneous pilot channel estimator for calculating an instantaneous pilot channel estimate;
• a symbol mapper for estimating a transmit symbol from the output bit of the channel decoder;
• an instantaneous data channel estimator for calculating an instantaneous data channel estimate by using the output of the symbol mapper;
• a weighted sum calculator for transmitting the instantaneous pilot channel estimate as a channel value of the resource block in a first iteration, and calculating a weighted sum in the resource block according to a channel estimation method from the outputs of the instantaneous pilot channel estimator and the instantaneous data channel estimator in the subsequent iterations;
• and
• a noise variance estimator for calculating the noise variance of the received symbols in the resource block.

A method for OFDMA transmission, which is for coherent detection in an uplink of a wireless communication system supporting multiple subscribers, the method comprising:

• (a) channel-encoding a subscriber data block;
• (b) mapping the encoded data into a data symbol;
• (c) generating a pilot symbol, the pilot symbol having the same transmission power as the data symbol;
• (d) mapping the symbol-mapped data symbol and the generated pilot symbol into a time-frequency index of an OFDM symbol according to a resource-block-based mapping method, the resource-block-based mapping method mapping multiple resource blocks that are well-distributed in time and frequency domains to a channel allocated to a subscriber, each resource block comprising consecutive subcarriers of consecutive OFDM symbols and including at least one pilot symbol and multiple data symbols;
• and
• (e) generating an OFDM signal from the output of the time-frequency mapping step and transmitting the generated OFDM signal,
• wherein each resource block includes a single pilot symbol at the center of the resource block, the size of the resource block determined by Rfx Rt, where Rf and Rt satisfy the following expressions:
• fDTRt << 1/2 , and τmaxΔf/Rf<<½, where fD is a maximum Doppler frequency of the channel. Ts is a symbol interval, and τmax is the maximum delay time of the channel, and Δf is the subcarrier spacing,
• or each resource block includes multiple pilot symbols located at the same frequency and spaced in the time domain by a time spacing P determined by the following expression:
• fDTsP<½.

A method for OFDMA reception, which is for coherent detection in an uplink of a wireless communication system supporting multiple subscribers, the method comprising:

• (a) converting OFDM received symbols at respective antennas into frequency-domain received symbols by OFDM demodulation, the OFDM received symbol including a pilot symbol that has the same transmission power as a data symbol;
• (b) separating the frequency-domain received symbols by subscribers according to a resource mapping method of each subscriber, and rearranging the separated frequency-domain received symbols based on a resource block by resource-block-based demapping, the resource mapping method mapping multiple resource blocks that are well-distributed in time and frequency domains to each subscriber, each resource block comprising consecutive subcarriers of consecutive OFDM symbols;
• (c) estimating a channel in units of resource blocks by using the output of the time-frequency demapping, wherein the channel of a corresponding resource block is estimated, at a first iteration, based on a pilot channel obtained by dividing the received pilot symbol output from the OFDM demodulation by a given pilot symbol and is refined based on the pilot channel and a data channel estimate in subsequent iterations;
• (d) coherently generating a channel decoding input metric from the received symbol, the estimated channel, and the estimated noise variance by demodulation;
• (e) channel-decoding based on the generated metric according to a channel encoding method;
• and
• (f) determining whether to repeat a reception process when a decoding stop condition provided in the channel decoding step is not satisfied, or when a iteration count is less than a maximum iteration counts
• wherein when using a single-pilot-based resource block having the pilot inserted in the center of the resource block, estimating the channel in (c) comprises:
• estimating an instantaneous pilot channel for calculating an instantaneous pilot channel estimate;
• mapping a symbol for estimating a transmit symbol from the output bit of the channel decoder;
• estimating an instantaneous data channel for calculating an instantaneous data channel estimate by using output of symbol mapping;
• calculating a weighted sum for transmitting the instantaneous pilot channel estimate as a channel value of the resource block in a first iteration, and calculating a weighted sum in the resource block according to a channel estimation method from the instantaneous pilot channel estimate and the instantaneous data channel estimate in the subsequent iterations;
• and
• estimating a noise variance for calculating the noise variance of the received symbols in the resource block.

A method for OFDMA transmission and reception, which is for coherent detection in an uplink of a wireless communication system supporting multiple subscribers, the method comprising:

• a transmission process comprising (a) dividing time-frequency resources of a time slot comprising a plurality of orthogonal frequency division multiplexing symbols into a plurality of traffic channels, each traffic channel comprising a plurality of resource blocks that are well-distributed in time and frequency domains of the time slot, (b) generating pilot symbols according to a resource-block-based resource mapping method with a minimum resource unit being one of the resource blocks, each resource block comprising consecutive subcarriers of consecutive OFDM symbols having at least one inserted pilot symbol for each traffic channel, and (c) processing the pilot symbols and channel-encoded and modulated data symbols by time-frequency mapping according to the resource-block-based mapping method to generate and transmit an OFDM signal, wherein each resource block includes a single pilot symbol at the center of the resource block, the size of the resource block determined by Rfx Rt, where Rf and Rt satisfy the following expressions:
• fDTsRt <<½, and τmaxΔf / Rf ½, where fD is a maximum Doppler frequency of the channel, Ts is a symbol interval, and τmax is the maximum delay time of the channel, and Δf is the subcarrier spacing,
• or each resource block includes multiple pilot symbols located at the same frequency and spaced in the time domain by a time spacing P determined by the following expression:
• fDTsP<½;
• and
• a reception process comprising (d) processing the received OFDM signal according to the resource-block-based mapping method in the frequency domain, separating the received symbols by subscribers, and rearranging the separated symbols based on the resource block, and (e) performing iterative channel estimation, demodulation, and decoding by using the pilot symbols and data symbols estimated with the channel decoded bits after decoding for each traffic channel, wherein the traffic channel of a corresponding resource block is estimated, at a first iteration, based on a pilot channel estimate obtained by dividing the received pilot symbol output from the demodulation by a given pilot symbol and is refined based on the pilot channel and a data channel estimate in subsequent iterations.