Apparatus and method for padding and packet extension for downlink multiuser transmission
A transmission method comprises: generating a transmission signal including OFDM symbols, wherein the last OFDM symbol of the OFDM symbols can be partitioned into four segments, and wherein the generating includes: computing an initial padding factor value associated with one of the four segments and computing an initial number of OFDM symbols; determining a user with a longest packet duration among plural users; determining a common padding factor value being the initial padding factor value and a common number of OFDM symbols being the initial number of OFDM symbols of the determined user with the longest packet duration; adding pre-FEC padding bits toward one of four possible boundaries of the last OFDM symbol, the one of four possible boundaries being represented by the determined common padding factor value; and adding post-FEC padding bits in remaining segment(s) of the last OFDM symbol; and transmitting the generated transmission signal.
1. An integrated circuit comprising:
control circuitry, which, in operation, controls
generating a signal including a plurality of OFDM (Orthogonal Frequency Division Multiplexing) symbols for a data field, wherein a last OFDM symbol of the plurality of OFDM symbols is partitioned into four segments, the four segments ending with four boundaries, respectively, and the signal is generated based on pre-FEC (Forward Error Correction) padding bits added toward one of the four boundaries of the last OFDM symbol and post-FEC padding bits added in remaining segment(s) of the last OFDM symbol, the one of four possible boundaries being represented by a common padding factor value; and
transmitting the signal; and
at least one output coupled to the control circuitry, which, in operation outputs an electric signal,
wherein the common padding factor value is a padding factor value of a user with the longest packet duration among a plurality of users, and is determined based on defined padding factor values of the plurality of users and based on corresponding numbers of OFDM symbols for the data field of the plurality of users, and
the longest packet duration is determined by comparing tentative packet durations of the plurality of users, the tentative packet durations being calculated based on the defined padding factor values and the corresponding numbers of OFDM symbols.
2. The integrated circuit according to claim 1 , wherein a number of the pre-FEC padding bits is determined for each of the plurality of users based on the common padding factor value.
3. The integrated circuit according to claim 1 , wherein information bits and the pre-FEC padding bits in the data field are encoded using either a Binary Convolutional Code (BCC) or a Low Density Parity Check (LDPC).
4. The integrated circuit according to claim 1 , wherein the data field includes information bits, and a padding factor value for each of the plurality of users is determined based on the information bits.
5. The integrated circuit according to claim 1 , wherein a number of the post-FEC padding bits is determined based on the common padding factor value.
6. The integrated circuit according to claim 1 , wherein
when the plurality of users are grouped into a first group and a second group, and the second group has a shorter packet duration than the first group,
the pre-FEC padding bits are added toward one of the four boundaries of the last OFDM symbol in the signal for the first group; and
the pre-FEC padding bits are added toward one of the four boundaries of an OFDM symbol other than the last OFDM symbol and the pre-FEC padding bits are not included in the last OFDM symbol in the signal for the second group.