1. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 1 November20 01 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.

2. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 2 November20 01 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

3. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 3 November20 01 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

4. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 4 November20 01 Additional Implementation needed for Delayed Acknowledgement Additional implementation for sender: –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

5. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 5 November20 01 Additional Implementation needed for Delayed Acknowledgement (con’t) Additional implementation for receiver: –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.

6. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 6 November20 01 A example of Delayed Acknowledgement Transmission Sequence QoS Data S QoS CF-Poll P QoS Data S QoS Data S QoS Data TXOP Delayed ACK PP QoS CF-Poll AP/HC Sender

7. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 7 November20 01 TX & RX Buffering Mechanism Upper Layer Sender TC-Seq = 63 TC-Seq = 62 TC-Seq = 61 TC-Seq = 60 TC-Seq = 59 TC-Seq = 58 TC-Seq = 57 TC-Seq = 56 Empty UnACK ACK Fill in N-8 Data Frames Buffer Size = N Buffer Frames Delay ACK Message Payload Received after receiving 10 Data Frames Receiver TX to upper Layer TC-Seq = 63 TC-Seq = 62 TC-Seq = 61 TC-Seq = 60 TC-Seq = 58 TC-Seq = 55 TC-Seq = 54 Upper Layer Fetch Data Frames with TC-Seq 54 and 55 To upper layers & De-allocate Memory for Seq 54 & 55 Data Not Received Buffer Cleared

8. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 8 November20 01 One example of Delayed ACK Transmission Sequence 1 AP/HC Sender 2 Poll Receiver 3456789 1010 7 1111 1212 Poll 1 st D ACK Poll TXOP 3 1313 1414 1515 1616 1717 1818 Poll 2 nd D ACK TXOP Legend SIFS PIFS Poll QoS CF-Poll 1 QoS Data 3 QoS Data (Retransmission) Error in transmission Sender Buffer Receiver Buffer 123 Before Received 1 st Delayed ACK 45678 1010 9 4568 1010 9 37 After Received 1 st Delayed ACK 1111 37 Before Received 2 nd Delayed ACK 1212 1313 1414 1515 1616 1717 1818 1313 1414 1515 1717 1818 Data Seq 1 and 2 are being delivered to upper layer Data Seq 3 to 11 are being delivered to upper layer After Received 2 nd Delayed ACK 1212 1616 D ACK Delayed ACK 1 st Delayed ACK2 nd Delayed ACK

9. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 9 November20 01 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

10. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 10 November20 01 Normal Acknowledgement PER = 0%PER = 10% ACK Data

11. doc.: IEEE 802.11-01/601r0 Submission Harada Yasuo, Matsushita Electric Ind. Slide 11 November20 01 Delay Acknowledgement 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% Delayed ACK Data

12. doc.: IEEE 802.11-01/601r0 Submission Yasuo Harada et.al., Matsushita Electric Ind. Slide 12 November20 01 Summary Delay-Ack Policy perform effective high data transmission for AV data transmission