ARQ transmission and reception methods and apparatus
View Patent ↗The invention provides an ARQ scheme where data packets are transmitted from the transmitter to the receiver in first predetermined time intervals, and positive (ACK) and negative (NAK) acknowledgement messages are transmitted from the receiver to the transmitter in second predetermined time intervals. For each data packet that has been transmitted from the transmitter to the receiver, at least two second time intervals can be used for transmitting the acknowledgement message. The invention therefore improves over synchronous feedback transmission schemes by adding flexibility without incorporating the drawback of asynchronous transmission schemes that are known to have a high signalling overhead. The invention is preferably applicable to UMTS and HSDPA systems but can also be applied in any other communications system. The feedback channel may be uplink or downlink.
1. An Automatic Repeat Request (ARQ) transmitter for transmitting data on a radio channel in a communications system to a receiver, the transmitter comprising:
a transmission unit for encoding the data and transmitting an encoded data packet;
a receiving unit for receiving a positive or negative acknowledgment message from the receiver indicating that the receiver was or was not able to decode the data packet; and
a retransmission section for operating the transmission unit to perform a retransmission if a negative acknowledgment message was received;
wherein the transmitter transmits data packets in first predetermined time intervals and receives acknowledgment messages in second predetermined time intervals after the first time intervals; and
a control section for monitoring at least two second time intervals for possible reception of one acknowledgment message in response to each transmitted data packet, wherein:
said at least two second time intervals are shifted in time by more than the length of a first time interval.
2. The transmitter of claim 1 , wherein said transmission unit operates according to a hybrid ARQ scheme to retransmit the same or different code blocks from a data packet to be combined at the receiver.
3. The transmitter of claim 1 , wherein said transmission unit transmits the encoded data packet downlink to the receiver, and said receiving unit receives the acknowledgment message uplink from the receiver.
4. The transmitter of claim 1 , wherein said transmission unit transmits the encoded data packet uplink to the receiver, and said receiving unit receives the acknowledgment message downlink from the receiver.
5. The transmitter of claim 1 , wherein the receiving unit receives the acknowledgment message on a Dedicated Physical Control Channel of a Universal Mobile Telecommunications System (UMTS).
6. The transmitter of claim 5 , wherein said transmission unit operates according to the High Speed Downlink Packet Access (HSDPA) scheme.
7. The transmitter of claim 1 , wherein said transmission unit transmits the encoded data packet to the receiver on a shared packet channel where different users of the communication system are time-multiplexed.
8. The transmitter of claim 1 , wherein the length of the first time intervals is larger than the length of the second time intervals.
9. The transmitter of claim 8 , wherein the length of the first time interval is an integer multiple of the length of the second time interval.
10. The transmitter of claim 9 , wherein the transmission unit transmits data packets in first intervals of three time slots and receives acknowledgment messages in second time intervals of one time slot.
11. The transmitter of claim 1 , wherein the control section changes the length of the first and/or second time intervals during operation of the transmitter.
12. The transmitter of claim 1 , wherein the receiving unit receives simultaneously in one of the second time intervals, acknowledgment messages that relate to different data packets and that can be distinguished by the transmitter.
13. The transmitter of claim 12 , wherein the control unit distinguishes the acknowledgment messages relating to different data packets, based on channelization codes or signatures.
14. An Automatic Repeat Request (ARQ) method of operating a transmitter for transmitting data on a radio channel in a communications system to a receiver, the method comprising the steps of:
encoding the data and transmitting an encoded data packet;
receiving a positive or negative acknowledgment message from the receiver indicating that the receiver was or was not able to decode the data packet; and
if a negative acknowledgment message was received, performing a retransmission;
wherein data packets are transmitted in first predetermined time intervals and acknowledgment messages are received in second predetermined time intervals after the first time intervals;
monitoring at least two second time intervals for possible reception of one acknowledgment message in response to each transmitted data packet, wherein:
said at least two second time intervals are shifted in time by more than the length of a first time interval.
15. An Automatic Repeat Request (ARQ) receiver for receiving encoded data packets on a radio channel in a communications system from a transmitter, the receiver comprising:
a receiving unit for receiving an encoded data packet and decoding said data packet; and
a transmission unit for transmitting a positive or negative acknowledgment message to the transmitter indicating that the data packet could or could not be decoded;
wherein the receiving unit receives the encoded data packet in first predetermined time intervals and transmits acknowledgment messages in second predetermined time intervals after the first time intervals; and
the receiver further comprising a selection section for selecting, for each received encoded data packet, one of at least two second time intervals for transmission of the acknowledgment message, wherein:
said selection section selects, from said at least two second time intervals, a later time interval when a high modulation coding scheme level has been transmitted.
16. An Automatic Repeat Request (ARQ) receiver for receiving encoded data packets on a radio channel in a communications system from a transmitter, the receiver comprising:
a receiving unit for receiving an encoded data packet and decoding said data packet; and
a transmission unit for transmitting a positive or negative acknowledgment message to the transmitter indicating that the data packet could or could not be decoded;
wherein the receiving unit receives the encoded data packet in first predetermined time intervals and transmits acknowledgment messages in second predetermined time intervals after the first time intervals; and
the receiver further comprising a selection section for selecting, for each received encoded data packet, one of at least two second time intervals for transmission of the acknowledgment message, wherein:
said selection section selects, from said at least two second time intervals, a time interval dependent on the physical resources that have been allocated, such as frequencies, codes and time slots.
17. The receiver of claim 15 , wherein said selection section selects, from said at least two second time intervals, a time interval and one of at least two acknowledgment messages.
18. The receiver of claim 17 , wherein said selection section performs the selection of different acknowledgment messages based on channelization codes or signatures.
19. The receiver of claim 16 , wherein said selection section selects, from said at least two second time intervals, a time interval and one of at least two acknowledgment messages.
20. The receiver of claim 19 , wherein said selection section performs the selection of different acknowledgment messages based on channelization codes or signatures.