BACKGROUND

1. Technical Field

The present disclosure generally pertains to wireless communications and, more particularly, to a method for formatting and transmitting data in a wireless communications system.

2. Description of the Related Art

The IEEE (Institute of Electrical and Electronics Engineers) 802.11 Working Group is developing 802.11ax HE (High Efficiency) WLAN (Wireless Local Area Network) air interface in order to achieve a very substantial increase in the real-world throughput achieved by users in high density scenarios. OFDMA (Orthogonal Frequency Division Multiple Access) multiuser transmission has been envisioned as one of the most important features in 802.11ax. OFDMA is a multiple access scheme that performs multiple operations of data streams to and from the plurality of users over the time and frequency resources of the OFDM (Orthogonal Frequency Division Multiplexing) system.

Frequency scheduling is generally performed for OFDMA multiuser transmission in 802.11ax. According to frequency scheduling, a radio communication access point apparatus (hereinafter simply “access point” or “AP”) adaptively assigns subcarriers to a plurality of radio communication station apparatuses (hereinafter simply “terminal stations” or “STAs”) based on reception qualities of frequency bands of the STAs. This makes it possible to obtain a maximum multiuser diversity effect and to perform communication quite efficiently.

Frequency scheduling is generally performed based on a Resource Unit (RU). A RU comprises a plurality of consecutive subcarriers. A RU may have different types depending on the number of constituent subcarriers per RU. The RUs are assigned by an AP to each of a plurality of STAs with which the AP communicates. The RU assignment result of frequency scheduling performed by the AP shall be reported to the STAs as RU assignment information. In addition, the AP shall also report other control signaling such as common control information and per-user allocation information to STAs. IEEE Std 802.11ac-2013 is an example of related art.

SUMMARY

The transmission for all the STAs in downlink OFDMA shall end at the same time. Padding is a straightforward method for achieving this goal. In addition, packet extension may be applied to an HE packet in order for the receiver to have enough time to process the last OFDM symbol of the received HE packet since 802.11ax has an OFDM symbol duration which is four time larger than 802.11n/ac. Packet extension increases system overhead and but reduces implementation complexity of the receiver. Studies are underway to perform efficient padding and packet extension for downlink OFDMA multiuser transmission in 802.11ax to compromise implementation complexity and system overhead.

In one general aspect, the techniques disclosed here feature: a transmission method comprising: generating a transmission signal for each of a plurality of users, the transmission signal including a plurality of OFDM symbols for a data field, wherein the last OFDM symbol of the plurality of OFDM symbols can be partitioned into four segments, and wherein the generating of the transmission signal includes: computing, for each of the plurality of users, an initial padding factor value that is associated with one of the four segments and computing, for each of the plurality of users, an initial number of OFDM symbols for the data field; determining a user with a longest packet duration among the plurality of users; determining a common padding factor value that is the initial padding factor value of the determined user with the longest packet duration; determining a common number of OFDM symbols that is the initial number of OFDM symbols for the data field of the determined user with the longest packet duration; adding, for each of the plurality of users, 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.

With padding and packet extension for downlink OFDMA multiuser transmission of the present disclosure, it is possible to minimize implementation complexity of the receiver while suppressing an increase of the system overhead due to packet extension.

It should be noted that general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the specification and drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages.

