Method of transmitting downlink channel rank information through physical uplink shared channel

Abstract

Provided is a method of transmitting channel rank information (RI) when the number of bits for transmitting the channel RI to be transmitted through a physical uplink shared channel (PUSCH) is three or more. The method includes mapping channel RI to be transmitted to a channel RI bit string of 3 bits or more, Reed-Muller coding and rate-matching the channel RI bit string using a basis sequence having a 32-bit code length, and generating modulation symbols by applying the bit sequence that has been Reed-Muller coded and rate-matched to a modulation mapper. Accordingly, the method of transmitting downlink channel RI can be employed when five or more antennas are used for downlink transmission or several carrier bands are used by carrier aggregation as specified in Third Generation Partnership Project (3GPP) long term evolution (LTE)-advanced following 3GPP LTE release 10.

Description

CLAIM FOR PRIORITY

This application

In other words, in the case of a QPSK symbol, two pieces of bit information can be transmitted per modulation symbol, and the three channel RI bits may be repeatedly coded two times per three symbols as shown in Expression 1.

Second, when the 3-bit channel RI bit string is mapped to a 16-quadrature amplitude modulation (QAM) symbol, the channel RI bits may be mapped as shown in Expression 2 below.
[O₀^RIO₁^RIxxO₂^RIO₀^RIxxO₁^RIO₂^RIxx]  [Expression 2]

In other words, in the case of a 16-QAM symbol, four pieces of bit information can be transmitted per modulation symbol, and the three channel RI bits may be repeatedly coded two times per three symbols as shown in Expression 2. Here, “x” denotes a placeholder, which is a value selected to maximize a Euclidean distance between 16-QAM modulation symbols including channel RI.

Third, when the 3-bit channel RI bit string is mapped to a 64-QAM symbol, the channel RI bits may be mapped as shown in Expression 3 below.
[O₀^RIO₁^RIxxxxO₂^RIO₀^RIxxxxO₁^RIO₂^RIxxxx][Expression 3]

In other words, in the case of a 64-QAM symbol, six pieces of bit information can be transmitted per modulation symbol, and the three channel RI bits may be repeatedly coded two times per three symbols as shown in Expression 3. Here, “x” denotes a placeholder, which is a value selected to maximize a Euclidean distance between 64-QAM modulation symbols including channel RI.

Second Example Embodiment

The second example embodiment corresponds to a method of transmitting channel RI when the number of bits for transmitting the channel RI through a PUSCH is three or more. When the number of bits for transmitting the channel RI is three or more, the number of downlink transmitter antennas may be five or more, or the number of carrier bands in which the channel RI needs to be transmitted by carrier aggregation is two or more.

FIG. 3 is a flowchart illustrating a method of transmitting channel RI according to the second example embodiment of the present invention.

Referring to FIG. 3, a method of transmitting channel RI according to the second example embodiment of the present invention may include mapping channel RI to be transmitted to a channel RI bit string of 3 bits or more (S310), Reed-Muller coding the channel RI bit string using a basis sequence having a 32-bit code length (S320), and generating modulation symbols by applying the Reed-Muller coded bit sequence to a modulation mapper (S330).

First, in the mapping step (S310), channel RI to be transmitted is mapped to a channel RI bit string [O₀^RI, O₁^RI, . . . , O_NRI-1^RI] of 3 bits or more.

Here, N^RI denotes the number of bits required to transmit channel RI (N^RI≥3 in the second example embodiment), O₀^RI denotes the MSB of N^RI-bit input information, and O_NRI-1^RI denotes the LSB of the N^RI-bit input information.

For example, when the number of bits for transmitting channel RI is three (i.e., N^RI=3), a 3-bit channel RI bit string [O₀^RIO₁^RIO₂^RI] may be determined according to the mapping relation illustrated in FIG. 2 between values of {1, 2, 3, 4, 5, 6, 7, 8} that the RI of a downlink channel matrix can have and channel RI bit strings. In other words, this case is the same as the mapping relation exemplified in the first example embodiment. Also, when the number of bits for transmitting channel RI is four or more, a channel RI bit string may be mapped in a similar way as illustrated in FIG. 2.

Next, the Reed-Muller coding step (S320) may be performed as will be described below.

The above-mentioned Reed-Muller coding may be expressed by Expression 4 below and a basis sequence illustrated in FIG. 4 that will be described later.

$\begin{array}{cc}{q}_i^{\mathrm{RI}}=\underset{n=0}{\sum ^{N^{\mathrm{RI}}-1}}\left(O_n^{\mathrm{RI}}·M_{\left(\mathrm{imod}32\right),n}\right)\mathrm{mod}2& \left[\mathrm{Expression}4\right]\\ \left(i=0,1,\dots ,Q_{\mathrm{RI}}-1\right)& \end{array}$

Here, q_i^RI denotes a bit sequence obtained after encoding, Q_RI denotes the number of bits after encoding. M_i,n denotes a basis sequence having a value of 0 or 1.

FIG. 4 is a table showing an example of a basis sequence that can be applied to Reed-Muller coding of channel RI in the method of transmitting channel RI according to the second example embodiment of the present invention.

In the transmission method according to an example embodiment of the present invention, channel RI is Reed-Muller coded using a basis sequence having a 32-bit code length. Expression 4 above expresses Reed-Muller coding together with a process of generating a bit sequence to be transmitted by circular repetition.

In other words, Q_RI denotes the number of bits to be transmitted through a wireless link and is determined according to the number of modulation symbols and a modulation order to be used to transmit a channel RI bit string through a PUSCH. When N^RI channel rank bits are Reed-Muller coded into a bit sequence having a length of 32 bits, the coded bit sequences having a length of 32 bits are concatenated in a length of Q_RI and rate-matched. For example, when Q_RI is 100, a Reed-Muller coded 32-bit bit sequence is repeated three times, and last four (=100−32×3) bits may be the foremost four bits of the Reed-Muller coded bit sequence.

In other words, in a method of encoding channel RI according to an example embodiment of the present invention, linear combination is applied to three or more channel RI bits to perform encoding.

Finally, in the modulation symbol generating step (S330), the bit sequence that has been Reed-Muller coded and rate-matched is applied to a modulation mapper to generate modulation symbols, and the generated modulation symbols are mapped to resource locations designated in a PUSCH and transmitted.

Using a method of transmitting downlink channel RI through a PUSCH according to example embodiments of the present invention, the channel RI can be efficiently encoded and transmitted even if three or more channel RI bits are required to transmit the downlink channel RI.

In particular, a method of transmitting downlink channel RI according to example embodiments of the present invention can be employed when five or more antennas are required for downlink transmission or several carrier bands are used by carrier aggregation as specified in 3GPP LTE-advanced following 3GPP LTE release 10.

While the example embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the scope of the invention.

Claims

1. A communication method of transmitting channel rank information (RI) when a number of bits for transmitting the channel RI to be transmitted through a physical uplink shared channel (PUSCH) is three or more, the method comprising:

mapping the channel RI to be transmitted rank indication (RI) to a channel RI bit string of 3 bits or more set of bits, the set of bits comprising N^RI bits {O₀^RI O₁^RI . . . O^RI_NRI-1}, wherein N^RI is an integer equal to or larger than 3;

Reed-Muller coding encoding the channel RI bit string using a basis sequence having a 32-bit code length set of bits to generate a set of encoded bits; and

generating modulation symbols by applying the Reed-Muller coded bit sequence to a modulation mapper based on the set of encoded bits; and

transmitting the symbols,

wherein, when the channel RI to be transmitted is mapped to a 3-bit channel RI bit string, mapping the channel RI includes mapping the channel RI (one value of {1, 2, 3, 4, 5, 6, 7, 8}) to a bit 3-bit channel RI bit string [O₀^RIO₁^RIO₂^RI] according to the table of FIG. 2, and

wherein the Reed-Muller coding encoding is performed by the following expression: