Method and apparatus for simultaneous multi-user and direct link transmission with reduced interferences
The present invention concerns a transmission system where DiL and MU UL scheme are triggered by the AP simultaneously. According to a first aspect of the invention, the data frame sent in DiL mode by a station in response to an AP triggering frame are emitted according to the synchronization scheme adopted in MU scheme. This means that pre-correction parameters are computed based on the triggering frame from the AP for the transmission of the data frame. According to a second aspect of the invention, the return frame from the destination station of a DiL transmission to the source station, typically an acknowledge frame, when present, is transmitted using pre-correction parameters computed by the destination of the DiL transmission. These pre-correction parameters may be computed based on the received data frame from the source station of the DiL transmission or, when available, based on a previous frame received from the AP.
1 . A communication method in a wireless network, at a peer-to-peer source station comprising:
receiving from an access point a triggering frame reserving a transmission opportunity, the triggering frame allocating a first resource unit to the peer-to-peer source station for a direct link communication with a peer-to-peer destination station, the triggering frame further allocating at least one second resource unit for uplink communication to at least one station in multi user mode;
transmitting to the peer-to-peer destination station a frame on the first resource unit;
computing pre-correction parameters based on the received triggering frame from the access point; and
applying the pre-correction parameters when transmitting to the peer-to-peer destination station the frame on the first resource unit.
2 . The method of claim 1 , wherein the pre-correction parameters are related to a transmit center frequency and symbol clock frequency error compensation.
3 . The method of claim 1 , wherein applying the pre-correction parameters comprising pre-correcting a center frequency of the transmitted frame from a nominal transmit center frequency used by the access point to transmit the triggering frame, preferably the transmit center frequency is pre-corrected within a ±350 Hz window from the nominal transmit center frequency and the frame is transmitted within a SIFS ±0.4 μs period from an end of the triggering frame.
4 . A communication method in a wireless network, at a peer-to-peer destination station comprising:
transmitting to a peer-to-peer source station a second frame on a first resource unit allocated for a direct link communication with the peer-to-peer source station by a triggering frame transmitted by an access point, the triggering frame further allocating to at least one station at least one second resource unit for uplink transmission in multi user mode;
computing pre-correction parameters based on a previously received frame for guaranteeing that simultaneous transmission of the second frame by the peer-to-peer destination on the first resource unit for direct link communication and a transmission on the second resource unit for uplink transmission are synchronized; and
applying the pre-correction parameters when transmitting the second frame to the peer-to-peer source station on the first resource unit.
5 . The method of claim 4 , further comprising receiving from the peer-to-peer source station a first frame and wherein the previously received frame is the first frame received from the peer-to-peer source station.
6 . The method of claim 4 , wherein:
the peer-to-peer destination station is within a radio range of the access point to which the peer-to-peer source station is connected; and
the previously received frame is the triggering frame transmitted by the access point.
7 . The method of claim 6 , wherein the previously received frame is the last received frame from the access point.
8 . The method of claim 4 , wherein the pre-correction parameters applied when transmitting to the peer-to-peer source station the second frame are:
the pre-correction parameters computed based on the previously received frame from the access point when available; and
the pre-correction parameters computed based on a first frame received from the peer-to-peer source station otherwise.
9 . The method of claim 4 , wherein the pre-correction parameters are related to a transmit center frequency and symbol clock frequency error compensation.
10 . The method of claim 4 , wherein applying the pre-correction parameters comprising pre-correcting a center frequency of the transmitted second frame from a nominal transmit center frequency, the nominal transmit center frequency being used either by the peer-to-peer source station to transmit a frame or by an access point to transmit a frame.
11 . The method of claim 10 , wherein the center frequency of the transmitted second frame is pre-corrected within a ±350 Hz window from the nominal transmit center frequency.
12 . A non-transitory computer-readable storage medium storing instructions of a computer program that when executed by a processor implement the following operations:
receive from an access point a triggering frame reserving a transmission opportunity, the triggering frame allocating a first resource unit to the peer-to-peer source station for a direct link communication with a peer-to-peer destination station, the triggering frame further allocating at least one second resource unit for uplink communication to at least one station in multi user mode;
transmit to the peer-to-peer destination station a frame on the first resource unit;
compute pre-correction parameters based on the received triggering frame from the access point; and
apply the pre-correction parameters when transmitting to the peer-to-peer destination station the frame on the first resource unit.
13 . A communication device in a wireless network, capable of operating as a peer-to-peer source station, the communication device comprising a processor configured for:
receiving from an access point a triggering frame reserving a transmission opportunity, the triggering frame allocating a first resource unit to the peer-to-peer source station for a direct link communication with a peer-to-peer destination station, the triggering frame further allocating at least one second resource unit for uplink communication to at least one station in multi user mode;
transmitting to the peer-to-peer destination station a frame on the first resource unit;
wherein the method further comprises:
computing pre-correction parameters based on the received triggering frame from the access point; and
applying the pre-correction parameters when transmitting to the peer-to-peer destination station the frame on the first resource unit.
14 . A communication device in a wireless network, capable of operating as a peer-to-peer destination station, the communication device comprising a processor configured for:
transmitting to a peer-to-peer source station a frame on a first resource unit allocated for a direct link communication with the peer-to-peer source station by a triggering frame transmitted by an access point, the triggering frame further allocating to at least one station at least one second resource unit for uplink transmission in multi user mode;
computing pre-correction parameters based on a previously received frame for guaranteeing that simultaneous transmission of the frame by the peer-to-peer destination on the first resource unit for direct link communication and a transmission on the second resource unit for uplink transmission are synchronized; and
applying the pre-correction parameters when transmitting to the frame to the peer-to-peer source station.