Delayed Acknowledgement v.s. Normal Acknowledgement November 2001 Delayed Acknowledgement v.s. Normal Acknowledgement Yasuo HARADA, Tan Pek Yew Matsushita Electric Ind. John Kowalski and Yoshihiro Ohtani Sharp Corp. Toshihiro Fujita Sony Corp. Harada Yasuo, Matsushita Electric Ind.

November 2001 Introduction Sharp, Panasonic and Sony Requires High Bandwidth AV Transmission over IEEE802.11e AV data of up to 24 Mbps Reasonably reliable AV Data transmission at MAC Current Draft offers 4 types of Acknowledgement policies: Delay ACK offers low overheads with reasonable reliability We find option of Delay ACK meets our requirement for AV Data transmission Harada Yasuo, Matsushita Electric Ind.

Content This presentations demonstrates November 2001 Content This presentations demonstrates The simple buffering mechanism needed for Delay ACK It frees complex buffering mechanism at layer above MAC for High Data traffic (such as 24 Mbps AV Stream) Simulation results of Delay ACK vs. Normal ACK Two Scenarios are performed 0% PER & 10% PER Harada Yasuo, Matsushita Electric Ind.

Implementation needed for Delayed Acknowledgement November 2001 Implementation needed for Delayed Acknowledgement Needs to: Allocate fixed size of buffer to store transmitted packets that have not being acknowledged. Update acknowledged buffer entries on upon reception of delayed ACK Set retransmitted data packet to higher priority Remove buffered data packet if it is not being acknowledged after delay bound Stop pull for MSDU when buffer size is full Harada Yasuo, Matsushita Electric Ind.

Implementation needed for Delayed Acknowledgement (con’t) November 2001 Implementation needed for Delayed Acknowledgement (con’t) Receiver Needs to: Allocate fixed size of buffer to store out of sequence data frames Transmit delayed acknowledgement after received certain numbers of data packets Set delayed acknowledgement frame to higher priority Keep acknowledgement history up to certain size Deliver buffered packets that are in sequence at the head of the list to upper layer when buffer is full. For example as shown in the following figure, the receiver buffer will be filled up after received packet ID 10. So, Packet ID 2 to 4 will be delivered to upper layer, even through Packet ID 1 is still not yet being received. Error handling for this case is upper layer decision. Harada Yasuo, Matsushita Electric Ind.

A example of Delayed Acknowledgement Transmission Sequence November 2001 A example of Delayed Acknowledgement Transmission Sequence TXOP CF-Poll QoS P P Delayed ACK P CF-Poll QoS AP/HC Data QoS S Data QoS S Data QoS S Data QoS Sender Harada Yasuo, Matsushita Electric Ind.

TX & RX Buffering Mechanism November 2001 TX & RX Buffering Mechanism Upper Layer Fill in N-8 Data Frames Upper Layer Fetch Data Frames with TC-Seq 54 and 55 To upper layers & De-allocate Memory for Seq 54 & 55 Buffer Size = N Buffer Frames Receiver Buffer Cleared Sender TC-Seq = 54 TC-Seq = 56 TC-Seq = 55 TC-Seq = 57 TC-Seq = 58 TC-Seq = 59 TC-Seq = 58 TC-Seq = 60 TC-Seq = 61 TC-Seq = 60 TC-Seq = 62 TC-Seq = 61 TC-Seq = 63 TC-Seq = 62 TC-Seq = 63 Delay ACK Message Payload Received after receiving 10 Data Frames Empty Data Not Received UnACK ACK TX to upper Layer Harada Yasuo, Matsushita Electric Ind.

One example of Delayed ACK Transmission Sequence November 2001 One example of Delayed ACK Transmission Sequence TXOP TXOP TXOP TXOP Legend Poll Poll Poll Poll SIFS AP/HC PIFS Poll QoS CF-Poll 1 2 3 4 5 6 7 8 9 1 3 7 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 Sender 1 QoS Data QoS Data (Retransmission) 3 1st D ACK 2nd D ACK Receiver D ACK Delayed ACK 1st Delayed ACK 2nd Delayed ACK Error in transmission Before Received 1st Delayed ACK After Received 1st Delayed ACK Before Received 2nd Delayed ACK After Received 2nd Delayed ACK Sender Buffer 1 2 3 4 5 6 7 8 9 1 3 7 3 7 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 2 1 6 Data Seq 1 and 2 are being delivered to upper layer Receiver Buffer 4 5 6 8 9 1 Data Seq 3 to 11 are being delivered to upper layer 1 3 1 4 1 5 1 7 1 8 Harada Yasuo, Matsushita Electric Ind.

Simulation Aim Scenario November 2001 Simulation Aim Compare MSDU throughput of the following acknowledgement policy: Normal Acknowledgement Delayed Acknowledgement Scenario AP/HC poll a wireless station using QoS CF-Poll at the rate of 250 polls per sec Sender: Wireless station (send at full rate) Receiver: AP/HC (acknowledgement generator) MSDU size = 1402 bytes, PHY Rate = 36Mbps OFDM Harada Yasuo, Matsushita Electric Ind.

Normal Acknowledgement November 2001 Normal Acknowledgement ACK Data PER = 0% PER = 10% Harada Yasuo, Matsushita Electric Ind.

Delay Acknowledgement November 2001 Delay Acknowledgement Delayed ACK Data Configuration: Duplication History Length = 64 a Delayed ACK is being generated after received 10 data frames Retransmission Time: 0.001s, Receiver Buffer Size: 200 frames PER = 0% PER = 10% Harada Yasuo, Matsushita Electric Ind.

November 2001 Summary Delay-Ack Policy perform effective high data transmission for AV data transmission Yasuo Harada et.al., Matsushita Electric Ind.