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The standardization of IEEE802.11n aims to achieve 100Mbps at MAC-SAP (Medium Access Control -Service Access Point). The Frame Aggregation scheme in which MAC (Medium Access Control) frames are aggregated into one PHY (Physical) frame is proposed as the main MAC technique of IEEE802.11n, because it decreases MAC overhead. The Block Ack mechanism of IEEE802.11e is applied as a selective repeat method of the Frame Aggregation. In this paper, we propose the Extended Block Ack mechanism as a selective repeat mechanism to be adapted to the Frame Aggregation scheme. We present the performance evaluation to compare the throughput of the Extended Block Ack mechanism and the Legacy Block Ack of IEEE802.11e and show that the average improvement is expected to be around 10% and the maximum improvement is about 39% compared with the conventional method.

SUMMARY IEEE802.11-1999 Standard is widely known as a standard of WLAN and it has a number of amendments and supplements such as 802.11a, 802.11g, and 802.11i and also those under work in the current activities by the task groups (TGs). The one now attracting a great deal of attention is TGn, which is aimed at achieving high throughput. We are involved in this TGn standardization process. To achieve high throughput, MIMO technique is the main discussion point in the PHY layer in TGn. But another important point is the channel bundling method which extends the channel bandwidth from 20 MHz to 40-MHz. By doubling the channel bandwidth, the data rate can be increased. But when this channel bundling method is introduced, the question of how to cope with the legacy 20-MHz stations will arise. For this problem, we are proposing to control the 20-MHz and 40-MHz STAs by setting NAV to them in the MAC layer. This paper explains our coexistence proposal for the system where transmission in both 20-MHz and 40-MHz channel bandwidths is enabled. The performance is also examined to confirm the influence of applying our coexistence proposal.