Showing papers on "Frame aggregation published in 2010"

A frame aggregation scheduler for IEEE 802.11n

Abstract: Wireless Local Area Networks (WLANs) based on the IEEE 802.11 standard are widely deployed in the home and enterprise segments across the globe. The IEEE 802.11n is the latest amendment that aims to achieve throughput higher than 100 Mbps at the medium access control (MAC) layer. It defines two frame aggregation schemes to improve the efficiency over the basic 802.11 MAC layer. However, the IEEE specifications do not specify the scheduler for these schemes and it is left as vendor's choice. This paper presents a detailed simulation study of these aggregation schemes and presents a simple frame aggregation scheduler. The proposed method dynamically chooses the aggregated frame size and aggregation technique based on various relevant parameters.

Video transmission over IEEE 802.11n WLAN with adaptive aggregation scheme

Abstract: IEEE 802.11n is a next-generation wireless WLAN standard which can support a MAC data throughput over 100Mbps. Frame aggregation mechanism is a key feature at the MAC layer which can improve the efficiency of channel utilization. In this paper, we investigate the performance of video transmission over IEEE 802.11n with frame aggregation mechanism. We derive the relationship between Subframe size and bit error rate and the relationship between retry limit and packet loss rate, which can be easily used to design adaptive scheme for video transmission. Simulation results shown that the optimal subframe size adaptively to channel conditions can improve the throughput but has little effect on the video quality, and proper retransmission policy can significantly improve the video quality without increasing the end-to-end delay.

Frame-aggregated link adaptation protocol for next generation wireless local area networks

Abstract: The performance of wireless networks is affected by channel conditions. Link Adaptation techniques have been proposed to improve the degraded network performance by adjusting the design parameters, for example, the modulation and coding schemes, in order to adapt to the dynamically changing channel conditions. Furthermore, due to the advancement of the IEEE 802.11n standard, the network goodput can be enhanced with the exploitation of its frame aggregation schemes. However, none of the existing link adaption algorithms are designed to consider the feasible number of aggregated frames that should be utilized for channel-changing environments. In this paper, a frame-aggregated link adaptation (FALA) protocol is proposed to dynamically adjust system parameters in order to improve the network goodput under varying channel conditions. For the purpose of maximizing network goodput, both the optimal frame payload size and the modulation and coding schemes are jointly obtained according to the signal-to-noise ratio under specific channel conditions. The performance evaluation is conducted and compared to the existing link adaption protocols via simulations. The simulation results show that the proposed FALA protocol can effectively increase the goodput performance compared to other baseline schemes, especially under dynamically-changing environments.

Impact of aggregation headers on aggregating small MSDUs in 802.11n WLANs

Abstract: The main goal of the IEEE 802.11n standard is to achieve more than 100Mbps of throughput at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. A key enhancement is frame aggregation which reduces the overheads and increases the channel utilization efficiency. The MAC layer defines A-MSDU and A-MPDU frame aggregations in which MAC overheads are squeezed by aggregating multiple frames into a single large frame before being transmitted. As a consequence of the aggregation, new aggregation headers are introduced and become parts of the transmitted frame. The existence of such headers will have a negative impact on the performance, especially when aggregating frames of small payloads. In this paper, we have analysed the aggregation headers of the 802.11n aggregation schemes and introduced an MSDU frame aggregation that reduces the header's overhead and supports the applications that have a small frame size such as VoIP.

Error-Sensitive adaptive frame aggregation in 802.11n WLAN

Abstract: IEEE 802.11n is an emerging standard for high data-rate wireless local area networks (WLAN). Frame aggregation is vital for enhancing its MAC layer efficiency. A large frame size can usually boost network throughput, yet it also causes a high frame-error rate (FER), which is undesirable for many real-time applications. This paper proposes a novel scheme, the Error-Sensitive Adaptive Frame Aggregation (ESAFA). The ESAFA utilizes the two-layer frame aggregation method specified in 802.11n. It dynamically adjusts the frame aggregation size according to the current channel conditions to satisfy the FER level required by the application. Performance evaluation shows that, when compared with an existing scheme, OFA (Optimal Frame Aggregation), ESAFA greatly improves network throughput and decreases delay, especially in error-prone channels. It also satisfies the FER required by applications in most conditions. We believe that the proposed method is significant for supporting ubiquitous, seamless multimedia services over high-speed WLAN.

QoS-Aware Radio-and-Fiber (R&F) Access-Metro Networks

Abstract: Future bimodal fiber-wireless (FiWi) access-metro networks may deploy both radio-over-fiber (RoF) and radio-and-fiber (R&F) technologies. RoF networks are rapidly becoming mature, but they fall short of interworking with distributed wireless MAC protocols such as DCF in widely deployed IEEE 802.11 WLANs. While R&F networks are able to avoid this limitation by means of protocol translation at the optical-wireless interface, recent testbed activities demonstrated that their multimedia QoS performance is far from acceptable, giving rise to various open R&F networking issues. In this paper, we report on our ongoing research activities on providing improved QoS support in R&F access-metro networks by means of (i) hierarchical scheduling and hybrid access control in integrated RPR/WiMAX metro networks, and (ii) hierarchical frame aggregation in integrated EPON/next-generation WLAN-based mesh access networks.

Throughput maximization of a Hybrid Dynamic Frame Aggregation and Block-ACK scheme for 60 GHz high speed communications

Abstract: Recently, a strong demand on high data rate wireless communication can be observed. The development of multi-gigabit wireless transmission systems has become very attractive. For achieving such data rates, the exploitation of 60 GHz mm wave is a very promising technical approach [1] and has been adopted in IEEE 802.15.3c. Except for physical layer (PHY) designs, the Medium Access Control (MAC) layer design is also crucial for the achievable system throughput (TP). Among the MAC functionalities, the acknowledgment (ACK) mechanism is a very important component affecting the transmission reliability and efficiency. Based on the ACK-mechanisms in 802.15.3c, this paper proposes a Hybrid Dynamic Frame Aggregation and Block-ACK (HD-FABA) scheme, which can further enhance the transmission efficiency and the system throughput. A theoretical model is developed to enable efficient parameter optimization and throughput maximization. In this way, the system can adaptively adjust its parameters according to the PHY conditions, so that the PHY data rate is exploited at best. The effectiveness of the proposed scheme was verified by numerical simulations.

Prioritized medium access in ad-hoc networks with a SystemClick model of the IEEE 802.11n MAC

Abstract: For ad-hoc home networks without central coordinator, IEEE 802.11 systems merely support service differentiation. In many usage scenarios of a typical home network with applications requiring a strict quality of service (QoS), this MAC functionality is not sufficient. In order to counteract this problem, we developed in previous works a modified MAC scheme based on the IEEE 802.11 enhanced distributed channel access (EDCA) function. This paper describes enhancements of the modified MAC scheme enforcing prioritized medium access for strict QoS applications. For the first time, the established concept is realized in a distributed way with in-band signaling. Our enhanced MAC is embedded into a comprehensive IEEE 802.11n reference application to demonstrate its effectiveness in combination with the latest amendments like frame aggregation. The reference application is modeled in SystemClick, a framework for describing and evaluating packet processing applications on resource constraint network nodes. This enables functional validation and provides a path to future, cost-efficient implementations on programmable devices. On this basis, the paper presents simulation results substantiating the significant improvement of QoS parameters like delay and throughput. Besides enforcing strict priorities, collisions can be reduced to zero and the average waiting time can be decreased by up to 33 % for typical usage scenarios.

Method for determining an aggregation scheme in a wireless network

Abstract: A method and arrangement for employing media layer adaptation in a wireless communication of media in data packets from a sending node to a receiving node, by determining a fitting frame aggregation scheme in an effective and accurate manner. An arrival time AT and generation time GT are monitored for packets when received at the packet receiving node. A difference ATdiff in the arrival time of consecutive packets and a difference GTdiff in the generation time of the packets, are calculated. Then, an inter-arrival measure IA is calculated as the deviation between the arrival time difference ATdiff and generation time difference GTdiff. When the inter-arrival jitter exceeds a preset threshold (Th), a frame aggregation scheme is determined based on the calculated inter-arrival jitter IA and applied in the packet communication.

Frame aggregation in fibre-wireless (FiWi) broadband access networks

Abstract: MAC enhancements of emerging high-throughput WLANs are considered and a novel FiWi network architecture is introduced that integrates next-generation WLAN-based WMN and EPON in a pay-as-you-grow manner while providing backward compatibility with a legacy infrastructure and protecting previous investments. To investigate the performance of FiWi networks, the capacity of WMNs is evaluated through probabilistic analysis and verifying simulations. Advanced aggregation techniques are proposed and examined to improve FiWi network throughput-delay performance for voice, video, and data traffic under realistic wireless channel conditions.

Efficiency of frame aggregation in wireless multimedia networks based on IEEE 802.11n

Abstract: This paper evaluates the major MAC enhancement of IEEE 802.11n to realize high throughput, i.e. frame aggregation. In contrast to existing studies of this enhancement, we analyze the efficiency instead of the mere performance. The results show significant efficiency improvement by frame aggregation. Furthermore, the efficiency analysis leads to important conclusions for system configuration and adaptation and reveals effects which are beyond the scope of existing work. It is shown that the most feasible configuration is to apply maximum aggregation and to adapt the modulation and coding scheme (MCS) instead of the frame size. Furthermore, the efficiency analysis points out that in case the network is not saturated the 20 MHz mode is more efficient than the 40 MHz option.

Analyzing the effective throughput in multi-hop IEEE 802.1 in networks

Abstract: In this paper we characterize the effective throughput for multi-hop paths in IEEE 802.1 In based wireless mesh networks. We derive an analytical model capturing the effects of frame aggregation and block acknowledgements, features found in the new IEEE 802.1 In standard. We describe the throughput at MAC layer as a function of bit error rate, aggregation level and path length. Using the results of our model as an upper bound, we show that current TCP implementations do not harness the bandwidth provided by the IEEE 802.1 In MAC layer. Subsequently we introduce collision induced rate control which uses cross layer feedback to effectively estimate the available bandwidth based on our analytical model. We conduct a comprehensive performance study, showing that results from our analytical model are closely matched by simulation results. Furthermore we show that the proposed protocol achieves up to 50% more goodput and up to 70% less frame collisions compared to TCP-SACK and TCP-NewReno.

Medium access control and network layer design for 60 GHz wireless personal area networks

Abstract: The unlicensed frequency band around 60 GHz is a very promising spectrum due to its potential to provide multiple gigabits per second based data rates for short range wireless communication. Hence, 60 GHz radio is an attractive candidate to enable ultra high rate Wireless Personal Area Networks (WPANs), which are expected to support wireless multimedia applications like high-definition video streaming, ultra high speed content download, etc. Till now, the main research effort related to 60 GHz radio is at the physical layer design and channel model investigation. However, the unique properties of 60 GHz radio also create new research challenges for 60 GHz networking. Hence the aim of this dissertation is to provide an in-depth view on the Medium Access Control (MAC) layer and Network layer design for 60 GHz WPANs. To obtain sufficient link budget for multiple gigabits per second based wireless communication, directional antennas are needed in 60 GHz systems. Although directional antennas exhibit many advantages compared to omni-directional antennas, their deployment is very challenging for the MAC and Network layer protocols. For instance, to set-up directional connections, devices are expected to know the direction of their neighbors. The performance of directional neighbor discovery protocols is investigated in this dissertation to review the impact of directional antennas on the network setup durations. With the knowledge of orientation information of the network components, a resource management scheme, especially for the IEEE 802.15.3 featured WPANs, is proposed to support concurrent transmissions using directional antennas in a Time Division Multiple Access (TDMA) fashion with Quality of Service (QoS) and fairness provisioning. To further improve the transmission efficiency of the MAC layer protocol, standard frame aggregation and low latency frame aggregation mechanisms are investigated to alleviate the impact of transmission overhead. Another issue addressed at the MAC layer in this dissertation is how to support highly-reliable transmissions using 60 GHz radio. Due to the weak penetration and reflection properties, the Line-of-Sight (LOS) link between two 60 GHz components is easily blocked by obstacles in indoor environments, which is a severe hurdle that influences the reliability of 60 GHz systems. To resolve the link blockage problem, instant decision based beam switching mechanisms and environment learning based beam switching mechanisms are proposed in this dissertation targeting for different usage scenarios. Furthermore, to support the coexistence of multiple 60 GHz WPANs, a systematic analysis of using synchronization frame to mitigate Co-Channel Interference (CCI) is performed. It has been shown that the link capacity and the guaranteed transmission distance within a WPAN are upper bounded by the CCI. To enable the multi-hop communication among these inter-connected 60 GHz WPANs, the Network layer design is involved in this dissertation. First, a fundamental investigation is provided in ad-hoc networks for using directional antennas in the aspects of topology control and message dissemination. The results provide valuable insights for using directional antennas for multi-hop communication. Second, focusing on the specific network topology of WPANs, the performance of inter-piconet route discovery is examined. Moreover, a joint QoS routing and channel resource allocation mechanism is proposed to resolve the inter-piconet channel resource reservation collision problem.

The performance of adaptive frame aggregation with delay limits in ultrahigh-speed WLAN

Abstract: In order to improve the throughput under delay limits for different applications in WLAN, A-MSDU and A-MPDU aggregation in IEEE 802.11n was analyzed, and a new physical layer super-frame technology was put forward to further improve the performance. In noisy channel, the distributed coordination function (DCF) saturation throughput was derived and the impact of frame length on the throughput was discussed. Based on all these analysis, an algorithm of adaptive frame aggregation was proposed. The results show that on the condition of delay limits, there exists an optimal aggregation method to achieve maximum system throughput under a certain bit error rate (BER). Compared to the fixed frame, the proposed algorithm can effectively improve the throughput.

Using a backlogged queue approach for adaptive MAC frame aggregation

Abstract: Frame aggregation is a wireless link optimization mechanism that aims to reduce transmission overheads by sending multiple frames as the payload of a single MAC frame. Static assignment of frame aggregation parameters can result in delay penalties due to variations in traffic type or load levels. Another possible side effect is an increase in packet error rate in noisy environments due to large aggregated frame size. Adaptive aggregation methods have previously been proposed to deal with the above problems independently, but there is still a need for a unified adaptation algorithm that addresses both aspects in an integrated manner. In this study, a backlogged queue (BQ) aggregation approach is proposed that considers both these aspects, and also ensures inter-operability with other WLAN devices that are not capable of frame aggregation. Performance evaluation of the proposed algorithm on the ORBIT testbed shows throughput improvements of up to 56% in the presence of channel noise and 25% in scenarios with high contention over using a simple txop. An experimental case study shows improvement in FTP file transfer times of up to 11% while preserving performance for real time traffic.

Frame Synchronization based on robust header recovery and Bayesian testing

Abstract: Video transmission on wireless links usually requires some frame aggregation, so that the overhead due to the headers is not a too large percentage of the bit-stream. In such a situation, header error detection is essential, because any error in the header may cause a loss of several consecutive frames. The contributions of this paper are (i) an improved reception of the length field of the header and (ii) an improved Frame Synchronization (FS) algorithm for aggregated frames. The FS algorithm has the following characteristics: (i) it makes use of the implicit redundancies which are present in the headers, thus resulting in an efficient synchronization of the variable-length frames; (ii) Bayesian hypothesis testing is used to estimate the correct synchronization; (iii) the proposed algorithm performs estimation on-the-fly and does not require reading the whole bit-stream. A comparative performance evaluation with respect to previously proposed algorithms is provided in the context of WiMAX MAC.

On Maximizing VoIP Capacity and Energy Conservation in Multi-Rate WLANs

Abstract: This letter highlights a key problem that arises when frame aggregation, a popular method for boosting VoIP capacity, is used in Wireless Local Area Networks (WLANs) that employ asynchronous power save mode (PSM). Specifically, it shows how the PSM proposed by the Wi-Fi Alliance renders frame aggregation ineffective. It then proposes a novel opportunistic scheduler that restores the benefits of frame aggregation whilst ensuring stations have minimal energy expenditure.

A Throughput Performance for a Point-to-Multipoint Gigabit WLAN System on 60 GHz Millimeter Wave

Abstract: Increasing demand on the broadband wireless communication over Gigabits has focused renewed attention on 60 GHz millimeter wave. We developed a novel Point-to-Multipoint (P2MP) Gigabit WLAN System on 60 GHz millimeter wave. The proposed system employed wide angle beams antenna overcomes the usability of the conventional system, covers larger areas. Maximum transmission rate was designed to be 1.2 Gigabit/sec. Orthogonal frequency division multiplex (OFDM) using 1024 points FFT and convolutional code were implemented with PHY layer of the WLAN equipments. Superframe for multiple beams and frame aggregation for high throughput were designed for MAC layer. All control channels for downlink such as broadcast, frame control and access feedback were aggregated to reduce overhead in addition to aggregation of data frame. Evaluated throughput using proposed frame aggregation was confirmed to be more than 800 Mbit/sec with developed prototype in the case of aggregation size of 10 t1500byte.

Advanced Aggregation Techniques for Integrated Next-Generation WLAN and EPON Networks

Abstract: In this paper, we focus on the MAC enhancements of emerging high-throughput WLANs and introduce a novel fiber-wireless (FiWi) network architecture that integrates next-generation WLAN and EPON in a pay-as-you-grow manner while providing backward compatibility with legacy infrastructure and protecting previous investments. Our work sheds light onto the benefits of extending advanced frame aggregation techniques from next-generation WLANs to EPONs as well. We examine different path selection schemes to improve FiWi network performance by means of wireless mesh networking, considering not only throughput and delay but also overhead and packet loss.

Research on Adaptive Frame Aggregation Mechanism for IEEE 802.11n

Abstract: In this paper we analysis the main causes for the throughput bottleneck in the conventional Wireless Local Area Networks standard, and then study the principle of frame aggregation mechanism for 802.11n, and finally propose an adaptive frame aggregation mechanism. Simulation results show that the frame aggregation mechanism can reduce overhead of frame header and network delay, and improve the channel utilization, and the presented frame aggregation mechanism can also optimize the performance of system by dynamically selecting the subframe size and retry times according to the channel condition.

Method for operating a wireless network and a wireless network

Abstract: In order to allow an efficient use of data or frame aggregation techniques with real-time communications a method for operating a wireless network, especially a Wi-Fi technology based network, is described, wherein the network includes at least one wireless device for transmission of data and wherein the device may use a data or frame aggregation technique to provide an adjustable amount of aggregation. The method is characterized in that the amount of aggregation provided by the aggregation technique will be adjusted depending on a level of congestion in the network. Further, an according wireless network is described, preferably for carrying out the above mentioned method.

Frame aggregation control method and device of WLAN (Wireless Local Area Network)

Abstract: The invention provides a frame aggregation control method of a WLAN (Wireless Local Area Network). The method comprises the following steps of: acquiring the quality of a current wireless transmission environment by a transmitting end; and judging whether to start the frame aggregation function or not according to the quality of the wireless transmission environment. The invention also provides a frame aggregation control device of the WLAN. The method and the device of the invention can flexibly adjust whether to start the frame aggregation function or not according to the conditions of the wireless environment where WLAN equipment is arranged, thereby improving the data transmission reliability.

Efficient implementation of a frame aggregation unit for optical frame-based switching

Abstract: Aggregating Ethernet frame or IP packet in large fixed-size frames allows for building scalable core network architectures. Classifying the arriving traffic based on destination core node information and quality of service parameters alleviates the need of performing table look-ups on packet basis. These advantages come at the cost of extra logic at the network egress, as regards implementation, and additional jitter due to the frame assembly process. This paper describes the efficient implementation of a frame aggregation unit that gathers Ethernet packets in G.709 containers, handles 10 Gb/s links, performs classification based on 24-byte headers, and includes a highly pipelined Queue Manager to cope with the considered rates while a specific scheduler controls the quality of service per core network flow. Based on the developed demonstrator, we provide results both as regards area and performance for an FPGA (field programmable gate array) Virtex-4 implementation as well as regarding the introduced jitter.

Overcoming MAC Overhead Using Packet-Size Dependent Channel Widths

Abstract: : In this paper, we propose to reduce the MAC overheads in random access protocols by partitioning the channel spectrum used into a narrow channel and a wide channel. The narrow channel is used for transmitting the short packets (approximately 100 bytes long) and the wide channel is used for transmitting the longer packets. We intend to use multiple radios, one each for the different channel partitions. Narrow width channels have a reduced capacity, which lowers the maximum transmission rate achievable on these channels. As a result the channel wastage due to the rate-independent MAC overhead can be reduced. We propose a protocol called WiSP (channel Width Selection based on Packet size) to estimate the appropriate channel widths depending on the relative traffic load involving short and long packets in the network. We evaluate our protocol using extensive simulations and demonstrate its effectiveness in achieving higher throughputs. We propose our algorithm to complement frame aggregation (which is an existing approach for minimizing MAC overheads). We show that there are scenarios during which the frame aggregation can perform poorly, and show that our proposed algorithm can provide a good performance even in those situations.

Throughput Upper Limit for IEEE 802.11 Networks with Block Acknowledge and Frame Aggregation

Abstract: The paper presents new transmission procedures present in IEEE 802.11 standard and compares them to the “traditional” frame exchange method. On the basis of their operating rules, analytical equations are derived that allow calculate network efficiency or effective throughput. The throughput upper limit is also calculated and compared for all considered frame exchange procedures.

Prioritized Aggregation for Compressed Video Streaming on mmWave WPAN Systems

Abstract: This paper proposes a prioritized aggregation method that supports compressed video transmission on millimeter wave wireless personal area network (mmWave WPAN) systems. Frame aggregation is an effective means to improve system efficiency and throughput for wide band systems such as mmWave WPAN. It is required by the applications that the mmWave WPAN systems should provide Gbps or multiGbps transmission capability. The proposed scheme targets not only transmission efficiency but also support of compressed video transmission which currently is very popular. The proposal combines MAC layer aggregation with PHY layer skew modulation to facilitate the video transmission in a way that more important data is better protected. Simulation results show that the average peak signal to noise ratio (PSNR) performance is improved by 5dB compared to conventional method, while the Gbps transmission requirement is fulfilled.

Control method and appratus for frame aggregation of wireless local area network

Abstract: A control method and apparatus for frame aggregation of Wireless Local Area Network (WLAN) are provided, and the method includes that: a transmitting end obtains the current wireless transmission environment quality, determines whether to enable the frame aggregation function according to the wireless transmission environment quality. The present invention can flexibly adjust whether to enable the frame aggregation function according to the status of the wireless environment where WLAN apparatus are located; thereby improve the reliability of data transmission.

Medium access control and network planning in wireless networks

Abstract: Wireless Local Area Networks (WLANs) and Wireless Metropolitan Area Networks (WMANs) are two of the main technologies in wireless data networks. WLANs have a short range and aim at providing connectivity to end users. On the other hand, WMANs have a long range and aim at serving as a backbone network and also at serving end users. In this dissertation, we consider the problem of Medium Access Control (MAC) in WLANs and the placement of Relay Stations (RSs) in WMANs. We propose a MAC scheme for WLANs in which stations contend by using jams on the channel. We present analytic and simulation results to find the optimal parameters of the scheme and measure its performance. Our scheme has a low collision rate and delay and a high throughput and fairness performance. Secondly, we present a MAC scheme for the latest generation of WLANs which have very high data rates. In this scheme, we divide the stations into groups and only one station from each group contends to the channel. We also use frame aggregation to reduce the overhead. We present analytic and simulation results which show that our scheme provides a small collision rate and, hence, achieves a high throughput. The results also show that our scheme provides a delay performance that is suitable for real-time applications and also has a high level of fairness. Finally, we consider the problem of placing Relay Stations (RSs) in WMANs. We consider the Worldwide Interoperability for Microwave Access (WIMAX) technology. The RSs are used to increase the capacity of the network and to extend its range. We present an optimization formulation that places RSs in the WiMAX network to serve a number of customers with a pre-defined bit rate. Our solution also provides fault-tolerance by allowing one RS to fail at a given time so that the performance to the users remains at a predictable level. The goal of our solution is to meet the demands of the users, provide fault-tolerance and minimize the number of RSs used.

Cooperative Frame Aggregation in IEEE 802.11n Wireless Networks

Abstract: IEEE 802.11n supports two frame aggregation schemes, aggregation for MAC service data unit (A-MSDU) and aggregation for MAC protocol data unit (A-MPDU), to improve throughput at the MAC layer. In this paper, we propose a cooperative frame aggregation (CoFA), which can recover erroneous frames in a cooperative manner based on A-MPDU. Specifically, CoFA receive multiple frames from direct and relay paths, and combined multiple frames jointly. Numerical results show that CoFA outperforms direct transmission and relay transmission over diverse channel conditions.