Conference Paper

Performance analysis of A-MPDU and A-MSDU aggregation in IEEE 802.11n

Intel Corp., Haifa
DOI: 10.1109/SARNOF.2007.4567389 Conference: Sarnoff Symposium, 2007 IEEE
Source: IEEE Xplore


With recent improvements in physical layer (PHY) techniques, the achievable capacity for wireless LANs (WLANs) has grown significantly. However, the overhead of IEEE 802.11 MAC layer has limited the actual throughput of a WLAN. A-MPDU aggregation suggested in IEEE 802.11n draft is a key enhancement reducing the protocol timing overheads that enables aggregation of several MAC-level protocol data units (MPDUs) into a single PHY protocol data unit (PPDU). Another aggregation scheme proposed in IEEE 802.11n is A-MSDU aggregation, which allows several MAC-level service data units (MSDUs) to be aggregated into a single MPDU. In this work we present a novel analytic model for estimating the performance of a 802.11n high throughput wireless link between a station and an Access Point (AP). We consider a 2 times 2 MIMO system and investigate how the MAC goodput under TCP and UDP traffic is affected by the aggregation size, packet error rate and PHY settings. Our results demonstrate that for UDP traffic, A-MPDU aggregation allows to achieve a high channel utilization of 95% in the ideal case while without aggregation the channel utilization is limited by just 33%. We also show that A-MPDU aggregation outperforms A-MSDU aggregation, whose performance considerably degrades for high packet error rates and high PHY rates.

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    • "(ii) Unlike the frame aggregation schemes to increase throughput in1112131415, this work proposes a generalized solution; it (a) aims to improve both efficiency and fairness and (b) employs two-level aggregation to take advantage of both A-MSDU and A-MPDU. "
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    ABSTRACT: This paper deals with the problem of performance degradation in wireless local area networks (WLANs) based on IEEE 802.11n. When a wireless channel is shared by heterogeneous stations that have different data rates and packet sizes, each station occupies a different amount of airtime because the basic channel access mechanism of WLAN was originally designed to provide fair chance of channel access, regardless of packet size and data rate. This leads to the degradation of overall network throughput and airtime fairness among stations, which is known as performance anomaly. To resolve this problem, we firstly formulate an optimization problem for a generalized two-level frame aggregation whose objective is to maximize the achievable throughput under the constraint of airtime fairness. Then, we propose a frame size adaptation scheme that controls the number of packets in an aggregated frame. The proposed scheme is fully compatible with the IEEE 802.11 standard and works in a distributed manner, which neither modifies the channel access mechanism nor resorts to a centralized scheduling algorithm. The extensive simulation results confirm that the proposed scheme tightly regulates the airtime usage of each station to be almost the same and significantly improves the overall network throughput compared to other existing schemes.
    Full-text · Article · Jan 2015 · Mobile Information Systems
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    • "Several studies have investigated the effect of A-MPDU and/or A-MSDU frame sizes on the achievable throughput and their optimal sizes to improve throughput [6] [7] [8] [9]. In addition, a hybrid frame aggregation scheme known as 1389-1286/Ó 2014 Elsevier B.V. All rights reserved. "
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    ABSTRACT: The increase in physical (PHY) layer transmission rates in IEEE WLAN does not necessarily give the corresponding increase of MAC layer throughput because of MAC overhead such as PHY headers and contention time. To improve MAC layer efficiency, we propose the Transmission Order Deducing MAC (TOD-MAC) protocol, which controls packet length in such a way that the transmission duration is adjusted to implicitly provide necessary information for a node to determine its transmission order among all the nodes in a network. Each node transmits frames of different duration, and thus the other nodes can determine the time when they can transmit, which has the same effect as announcing the transmission order, without using a control message. Each node transmits a frame in a round robin manner, which minimizes the idle time between two consecutive transmissions without collisions, and significantly improves the MAC efficiency in very high speed CSMA/CA wireless networks. Extensive simulation results indicate that TOD-MAC achieves high throughput performance, short/long-term air-time fairness in multi-rate networks and excellent transient behavior in dynamic environments.
    Preview · Article · Nov 2014 · Computer Networks
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    • "[10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] the Throughput and Delay performance Figure 4: The generation and transmission of A-MSDU and A-MPDU frames in Two-level aggregation of the A-MSDU, A-MPDU and Two-level aggregation schemes is investigated. Several papers assume an error-free channel with-no collisions, several papers assume an error-prone channel and some papers also assume collisions. "
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    ABSTRACT: We compare between the Throughput performance of IEEE 802.11n and IEEE 802.11ac under the same PHY conditions and in the three aggregation schemes that are possible in the MAC layer of the two protocols. We find that for an error-free channel 802.11ac outperforms 802.11n due to its larger frame sizes, except for the case where there is a limit on the number of aggregated packets. In an error-prone channel the bit error rate sometimes determines the optimal frame sizes. Together with the limit on the number of aggregated packets, these two factors limit the advantage of 802.11ac.
    Full-text · Article · Sep 2014 · Physical Communication
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