Showing papers on "Frame aggregation published in 2007"

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

Abstract: 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.

Enhanced management frame aggregation in a wireless network system

Abstract: Systems and methodologies are described that facilitate enhanced aggregation of management frames in a wireless communication system. Various aspects described herein provide for the encapsulation of management frames into respective data frames, thereby allowing management frames to be aggregated with data frames. Upon aggregation of an encapsulated management frame with data frames, the aggregated frames can be transmitted to one or more stations using a block acknowledgement scheme. Further, information contained in a management frame can be encrypted prior to transmission. Upon transmission of an aggregated frame, indications can be provided to a receiving station to indicate the presence of an encapsulated management frame and/or encrypted management information within the aggregated frame. Based on these indications, the receiving station can extract and/or decrypt the management information from the aggregated frame.

Necessary Modifications on Conventional IEEE802.15.3b MAC to Achieve IEEE802.15.3c Millimeter Wave WPAN

Abstract: To achieve ultra high speed (several gigabits/s) transmission over 60 GHz system efficiently, this paper proposes Automatic Device Discover (ADD) and frame aggregation. The computer simulation results show good feasibility of handling directional antenna for ultra high speed transmission and highly efficient transmission up to 87 percent over 4.094 Gbps PHY-SAP with 8PSK modulation.

100+ VoIP Calls on 802.11b: The Power of Combining Voice Frame Aggregation and Uplink-Downlink Bandwidth Control in Wireless LANs

Abstract: The bandwidth efficiency of voice over IP (VoIP) traffic on the IEEE 802.11 WLAN is notoriously low. VoIP over 802.11 incurs high bandwidth cost for voice frame packetization and MAC/PHY framing, which is aggravated by channel access overhead. For instance, 10 calls with the G.729 codec can barely be supported on 802.11b with acceptable QoS - less than 2% efficiency. As WLANs and VoIP services become increasingly widespread, this inefficiency must be overcome. This paper proposes a solution that boosts the efficiency high enough to support a significantly larger number of calls than existing schemes, with fair call quality. The solution comes in two parts: adaptive frame aggregation and uplink/downlink bandwidth equalization. The former reduces the absolute number of MAC frames according to the link congestion level, and the latter balances the bandwidth usage between the access point (AP) and wireless stations. When used in combination, they yield superior performance, for instance, supporting more than 100 VoIP calls over an IEEE 802.11b link. The authors demonstrate the performance of the proposed approach through extensive simulation, and validate the simulation through analysis.

Automatic power save delivery (APSD) compatible with 802.11n frame aggregation and block acknowledgement

Abstract: A mechanism to create Automatic Power Save Delivery (APSD) compatible with 802.11 n frame aggregation and block acknowledgement (ack) mechanisms is provided. Various methods of using block acknowledgments are provided. Additionally, bit handling for defining an unscheduled APSD (U-APSD) service period and ending it is explained. A method of aggregating a plurality of data frames into an aggregated data frame, starting a service period based on the transmitting of the aggregated frame, receiving an acknowledgement for the transmitted frame, and upon receiving the acknowledgement frame containing an indicator indicating end of service period, entering low power mode of operation is enabled.

A Simple and Efficient Selective Repeat Scheme for High Throughput WLAN, IEEE802.11n

Abstract: The standardization of IEEE802.11n aims to achieve 100 Mbps 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.

A Novel Adaptive Scheme to Improve the Performance of the IEEE 802.11n WLANs

Abstract: With the advent of the IEEE 802.11n standard , that uses multiple input multiple output (MIMO) technology at the physical layer, there has been awareness about harnessing the physical layer techniques to improve the performance of a wireless local area network (WLAN) system. Our proposed scheme adoptively changes the number of antennas and the modulation scheme based on the channel conditions and type of traffic. Dynamic frame aggregation at the MAC layer is also proposed based on the channel conditions. The proposed scheme shows marked overall system improvement in terms of throughput and lesser number of automatic repeat requests (ARQ), with better overall channel utilization.

Method and arrangement for adapting transmission of encoded media

Abstract: The present invention is to select an adaptation scheme for the transmission of the encoded media that results in a satisfactory performance of the transmitted encoded media. A difference from the prior art is that each adaptation scheme defines a set of different transmission formats, wherein each transmission formats is a combination of at least two of the parameters the source codec bit rate, the packet rate, the number of frames of each packet (referred to as frame aggregation), and the level of redundancy. By using the different transmission formats, the transmission can be adapted to different operating scenarios and the performance is hence improved.

Frame aggregation control parameters

Abstract: A method and system for defining a transmission of data within a transmission opportunity (TXOP) is described. Aspects of the present system and method are related to wireless local area network (WLAN) systems. In one embodiment, aspects of the present system may be utilized within a WLAN system operating in accordance with frame aggregation mechanisms. Other aspects of the system specify the role of access point (AP) and non-AP stations operating in a bidirectional single receiver aggregation procedure. Aspects of the described system and method provide control to an AP or other station to limit the duration of the response burst, including acknowledgement message, aggregated with one or more data frames. Other aspects indicate how bi-directional single receiver aggregate data flow should be used in infrastructure, mesh and ad hoc operation scenarios.

Access Scheduling Based on Time Water-Filling for Next Generation Wireless LANs

Abstract: Opportunistic user access scheduling enhances the capacity of wireless networks by exploiting the multi user diversity. When frame aggregation is used, opportunistic schemes are no longer optimal, since users with high capacity links are frequently served, causing small queue sizes and low throughput. Recently, we have proposed schedulers that take queue and channel conditions into account jointly, to maximize the instantaneous throughput. In this paper, we extend this work to design a scheduler that performs block scheduling for maximizing network throughput over multiple transmission sequences. This scheduler makes use of the estimated evolution of the aggregation process by queueing theory and determines users' temporal access proportions using an approach based on the water-filling principle. Through detailed simulations, we show that our new algorithm with block scheduling offers further improvement in throughput over the previous schedulers, along with better fairness.

Rotating Priority Queue based Scheduling Algorithm for IEEE 802.11n WLAN

Abstract: The IEEE 802.11 working groups are currently working on the support of quality of service (QoS) and enhancements for higher throughput in a new standard called IEEE 802.11e and IEEE 802.11n, respectively. Although each standard focuses on only the specified issue as mentioned, the wireless LAN (WLAN) products based on IEEE 802.11n have to support both of them. IEEE 802.11n products provide QoS support as well as high throughput with frame aggregation. In this paper, we propose QoS scheduling and frame aggregation algorithm on the basis of rotating priority queue to manage the delay budget and control frame aggregation. Simulation results show the performance improvement of the proposed algorithm in the context of average delay and packet drop rate.

Adaptive contention access suspension in IEEE 802.15.3 MAC

Abstract: In IEEE 802.15.3 MAC, CSMA/CA is used in contention periods (CPs) to send commands. The brief occurrences of CPs cause bursty channel access, thus conventional models based on Poisson arrivals and saturation assumptions are no longer applicable. In this paper, we model CP access in each superframe as a contention resolution problem by applying a frame aggregation strategy for efficient frame transmissions in CPs. Insight gained from this problem formulation motivates us to propose a novel Adaptive CP Suspend (ACS) scheme that is easily implemented using a CP Counter (CPC) at the piconet controller (PNC). The CPC counts down in each idle slot and resets with the appropriate contention windows size after each collision. When the CPC reaches zero, which implies the completion of the contention resolution process, the PNC can safely suspend the remaining CP and devices (DEVs) can go into SLEEP mode to save power. Simulation results show that ACS effectively adapts to changes in channel traffic, substantially shortening the effective region in a CP in which all active DEVs continue to sense the channel, and significantly reducing the system energy cost by allowing DEVs to turn off their radios during the suspended parts of the CPs.

Opportunistic scheduling in IEEE 802.11n WLAN

Abstract: In wireless local area network (WLAN) environment with independent user fading, at least one user is likely to undergo very good channel state at any time, and this is called multiuser diversity. For high system performance, a transmission scheduler at the LLC layer is required to exploit this multi-user diversity by opportunistically selecting a feasible user with a good channel, and it is referred to as Opportunistic Scheduling (OS). In this paper, we proposed an OS scheme which is adaptive to the 802.11n WLAN. Different with existing OS schemes, it takes into account the two distinct characteristics of 802.11n, which are the frame aggregation and the quality of service (QoS) requirements according to the access categories (ACs). Through the simulation results, we prove that the proposed scheme not only improves the total system throughput, but it also preserves fairness and the QoS requirements corresponding to the ACs in the 802.11n WLAN.

Boosting VoIP Capacity of Wireless Mesh Networks through Lazy Frame Aggregation

Abstract: A novel method of voice frame aggregation for wireless mesh networks is presented. In the method, the degree of aggregation is automatically regulated by the congestion level on the wireless link. On the IEEE 802.11-based mesh network, it is shown to yield approximately twice the call capacity, while incurring no additional delay for frame aggregation.

Throughput analysis for wireless LAN with frame aggregation under mixed traffic

Abstract: Frame aggregation is a mandatory feature of the high throughput wireless LAN MAC to improve the performance. Frame aggregation can be implemented at MAC or PHY layer. However, implementing only one type of aggregation will be more cost-effective. This paper derives an upper bound of MSDU throughput (MT) for the two types of aggregation under mixed traffic.

Transmission of Multimedia Data over Next Generation Wireless Networks

Abstract: To overcome the low effective throughput of the popular IEEE 802.11 WLANs, a high performance WLAN standard is being developed. This new standard not only increases the raw PHY data rate but also increases the effective throughput with different MAC layer enhancements, such as frame aggregation. For small size multimedia data packet frame aggregation can improve the quality of service (QoS) of the applications. However, the wireless channel is often time varying and location dependent. Therefore aggregation of frames increases the probability of error, since the size of the frame is increased. With erroneous wireless channel an optimum value of aggregation size can greatly improve the performance of the multimedia applications. In this paper we propose a mechanism to dynamically select the aggregation size based on the channel condition prediction which reduces the number frames dropped due to wireless error. Also within a certain delay bound a link level retransmission mechanism can be used to improve the quality of the multimedia applications.

Communication device, control method of communication device, and computer program making computer implement the control method

Abstract: PROBLEM TO BE SOLVED: To solve the problem that communication of other equipment is possibly affected as a time for which a band is occupied by 802.11n becomes long depending upon whether a frame aggregation system is used and the kind of communication frames. SOLUTION: Priority level information on a plurality of communication devices is taken into consideration to determine the length of communication frames (the number of communication frames to be used and frames to be aggregated). COPYRIGHT: (C)2009,JPO&INPIT

Slotted Transmissions using Frame aggregation : A MAC protocol for Capacity Enhancement in Ad-hoc Wireless LANs

Abstract: IEEE 802.11 DCF 채널 접근 기능은 충돌을 피하고 hidden-terminal과 exposed-terminal 문제를 회피하기 위하여 두 홉 네트워크 내에서는 단일 전송을 허락한다. 이러한 단일 전송은 전송자의 이웃 노드가 전체 왕복시간 동안 데이터 프레임을 기다리게 하며, 프레임 지연의 증가와 네트워크 처리량을 낮게 하는 결과를 초래한다. 실시간 응용들은 낮은 매체 이용, 특히 높은 네트워크 트래픽에 대해 심하게 영향을 받는다. 본 논문은 IEEE 802.11의 프레임 집합화 기술을 이용하여 기본적인 DCF 기능을 유지한 단일 전송 장애를 극복하는 새로운 방안을 제시한다. 제안한 방안은 비 간섭 동기화 슬롯에서 병렬 전송을 허용한다. 병렬 전송은 몇몇 상황에서 물리적인 전송자 감지와 랜덤 백오프 타임을 회피하며, 프레임 지연을 줄이고 매체 이용과 네트워크 용량을 증가시킨다.

of IEEE 802.11 for Asynchronous Networks: Mixed Data Rate and Packet Size

Abstract: 8throughput of the high data-rate stations. We introduce a simple 9 and standard-compliant algorithm to fairly utilize the channel. 10 We first provide a formulation for the throughput with mixed 11 data-rate connections. To alleviate the low performance of the high 12 data-rate stations, we introduce a mechanism that implements 13 an adaptive scheme to adjust the packet size according to the 14 data rate. With this scheme, stations occupy the channel for 15 equal amounts of time. We then extend the scheme to a frame16 aggregation scheme to show how different packet sizes affect 17 performance. 18 Index Terms—Distributed coordination function, fairness, 19 frame aggregation, IEEE 802.11, Markov model, QoS, wireless 20 voice over Internet protocol (VoIP). AQ3 21

Demonstration of HDTV Transmission Using 324Mbps WLAN Equipment

Abstract: We developed a high speed wireless LAN prototype in the 5GHz band. Maximum transmission rate of the developed WLAN equipment was 324Mbit/sec using 6 multi-channels of 802.11a (1). We implemented a frame aggregation scheme to improve MAC efficiency (2-3). The evaluated system throughput was achieved more than 170Mbit/sec using the implemented frame aggregation. The HDTV transmission using 324Mbit/sec WLAN equipment was demonstrated. We compared the developed prototype and the conventional 802.11g (4).