Showing papers on "Frame aggregation published in 2016"

Comprehensive Spectrum Management for Heterogeneous Networks in LTE-U

Abstract: Recent interesting activities in spectrum analysis have introduced an additional band, the 5 GHz unlicensed spectrum, which has been primarily used for Wi-Fi. There are many challenges related to the coexistence of two different networks, a Wi-Fi network and an LTE network, sharing unlicensed bands but causing interference with each other. In this article, to solve the coexistence challenges, we propose a new protocol for carrier sensing and interference avoidance for heterogeneous networks: carrier sense LTE unlicensed access (CASLUA). The key idea of this protocol is that it listens to the channel by using a Wi-Fi air interface, but actually transmits data via an LTE air interface. This is achieved by using a proposed dual frame aggregation scheme where two frames (an L-frame and a U-frame) are allocated to licensed and unlicensed bands, respectively. Two implementations of CASLUA are carried out, one based on standalone operation (S-CASLUA)and the other operating with assistance from a software-defined network controller (SDN-CASLUA). SDN assistance lies in the monitoring of multiple network parameters, which are then used to make a decision on effective spectrum allocation with awareness of interference and capacity demands. Simulation results show that the CASLUA protocol helps to avoid interference and increases the average throughput by up to 40 percent for both Wi-Fi and LTE users in LTE-Unlicensed.

Alleviating Hidden and Exposed Nodes in High-Throughput Wireless Mesh Networks

Abstract: This paper proposes an opportunistic approach to mitigating the hidden and exposed node problem in a high-throughput mesh network, by exploiting the frame aggregation and block acknowledgment (BACK) capabilities of IEEE 802.11n/ac wireless networking standard. Hidden nodes significantly drop down the throughput of a wireless mesh network by increasing data loss due to collision, whereas exposed nodes cause under-utilization of the achievable network capacity. The problem becomes worse in IEEE 802.11n/ac supported high-throughput mesh networks, due to the large physical layer frame size and prolonged channel reservation from frame aggregation. The proposed approach uses the standard carrier sense multiple access (CSMA) technology along with an opportunistic collision avoidance (OCA) method that blocks the communication for hidden nodes and opportunistically allows exposed nodes to communicate with the peers. The performance of the proposed CSMA/OCA mechanism for high throughput mesh networks is studied using the results from an IEEE 802.11n+s wireless mesh networking testbed, and the scalability of the scheme has been analyzed using simulation results.

Dynamic Link Adaptation in IEEE 802.11ac: A Distributed Learning Based Approach

Abstract: High throughput wireless access networks based on IEEE 802.11ac show a significant challenge in dynamically selecting the link configuration parameters based on channel conditions due to large pool of design set, like number of spatial streams, channel bonding, guard intervals, frame aggregation and different modulation and coding schemes. In this paper, we develop a learning based approach for link adaptation motivated by the multi-armed bandit based distributed learning algorithm. The proposed link adaptation algorithm, BanditLink, explores different possible configuration options based on observing their impact over the network performance at various channel conditions. We analyze the performance of BanditLink from simulation results, and observe that it performs significantly better compared to other competing mechanisms proposed in the literature.

Throughput and range characterization of IEEE 802.11ah

Abstract: The most essential part of Internet of Things (IoT) infrastructure is the wireless communication system that acts as a bridge for the delivery of data and control messages. However, the existing wireless technologies lack the ability to support a huge amount of data exchange from many battery driven devices spread over a wide area. In order to support the IoT paradigm, the IEEE 802.11 standard committee is in process of introducing a new standard, called IEEE 802.11ah. This is one of the most promising and appealing standards, which aims to bridge the gap between traditional mobile networks and the demands of the IoT. In this paper, we first discuss the main PHY and MAC layer amendments proposed for IEEE 802.11ah. Furthermore, we investigate the operability of IEEE 802.11ah as a backhaul link to connect devices over a long range. Additionally, we compare the aforementioned standard with previous notable IEEE 802.11 amendments (i.e. IEEE 802.11n and IEEE 802.11ac) in terms of throughput (with and without frame aggregation) by utilizing the most robust modulation schemes. The results show an improved performance of IEEE 802.11ah (in terms of power received at long range while experiencing different packet error rates) as compared to previous IEEE 802.11 standards.

QoS based aggregation in high speed IEEE802.11 wireless networks

Abstract: We propose a novel frame aggregation algorithm with statistical delay guarantee for high speed IEEE802.11 networks considering link quality fluctuations. We use the concept of effective capacity to formulate frame aggregation with QoS guarantee as an optimization problem. The QoS guarantee is in the form of a target delay bound and violation probability. We apply proper approximations to derive a simple formulation, which is solved using a Proportional-Integral-Derivative (PID) controller. The proposed PID aggregation algorithm independently adapts the amount of time allowance for each link, while it needs to be implemented only at the Access Point (AP), without requiring any change to the 802.11 Medium Access Control (MAC). More importantly, the aggregator does not consider any physical layer or channel information, as it only makes use of queue level metrics, such as average queue length and link utilization, for tuning the amount of time allowance. NS-3 simulations show that our proposed scheme outperforms Earliest Deadline First (EDF) scheduling with maximum aggregation size and pure deadline-based aggregation, both in terms of maximum number of stations and channel efficiency.

Modeling, implementation and evaluation of IEEE 802.11ac in NS-3 for enterprise networks

Abstract: In this work we implement features for IEEE 802.11ac in the NS-3 simulator, in particular wider channels and bit-error calculations for higher modulation coding schemes. We also implement four wireless LAN deployment scenarios from the 802.11ax working group scenario document, and evaluate their performance under different operating conditions. Our simulation results demonstrate that many nodes in an enterprise network will yield lower average throughput to each AP and several APs on the same channel will create unreliable networks with some stations getting high throughput and some not able to send at all. Significant improvement in throughput was also observed with the use of frame aggregation.

Channel Access Fairness in IEEE 802.11ac: A Retrospective Analysis and Protocol Enhancement

Abstract: High throughput wireless access networks based on IEEE 802.11ac support a number of protocol enhancements at the physical and medium access control sublayer for supporting data rates in the order of Gigabits per second. These include multiple antenna technologies, wider bandwidth via channel bonding, reducing access overhead via short guard intervals, higher order modulation and coding rates, frame aggregation and block acknowledgements. As these features have their internal trade-offs based on channel conditions, the protocol generally employs a rate/link adaptation technique (sometime called dynamic bandwidth channel access) at the data link layer, that dynamically selects the channel access parameters based on the environment condition. However, this paper shows that such heterogeneity in selecting channel access parameters among neighboring wireless access points results in severe unfairness. In this paper, we address such unfairness in channel access, and develop an intelligent decentralized link parameter selection procedure that significantly improves the protocol performance in terms of fairness and overall network throughput. The proposed scheme, FairHT-MAC, has been implemented in a 26-node (6 access points and 20 client stations) indoor testbed, and the performance is analyzed and compared with other state-of-the-art link adaptation methods, like SampleLite and Minstrel-HT. We observe that FairHT-MAC significantly boosts up access fairness and overall network throughput, while keeps the access overhead (in terms of channel access delay) and average power consumption almost same that of Minstrel-HT and SampleLite.

Suitability of IEEE 802.11ac/n/p for Bandwidth Hungry and Infotainment Applications for Cities

Abstract: The Intelligent Transportation System (ITS) addresses issues regarding road safety and efficiency in the domain of Vehicular Ad hoc Networks (VANETs). In the last few years, research in ITS has been focused on delay sensitive and bandwidth hungry applications, which demand time bounded and high throughput services. In this paper, we analyzed 802.11ac, n and p with regard to their suitability in different VANET scenarios, specifically where applications require reliability and high data rate. We simulated these standards by considering different urban scenarios and varying different parameters such as speed, nodes, traffic loads, and bit error rate etc. We observed that 802.11n and 802.11ac performed comparatively well in most of the scenarios due to their enhanced MAC layer mechanisms. Frame aggregation with block acknowledgement significantly increases the bandwidth and reduces the delay. IEEE 802.11p, on other hand, allows transmission range of 1000 m, which is five times larger than for 802.11n or 802.11ac.

Joint rate adaptation, frame aggregation and MIMO mode selection for IEEE 802.11ac

Abstract: The recently approved IEEE 802.11ac WLAN standard has dramatically boosted Wi-Fi capabilities through supporting more data streams, larger bandwidth and more efficient frame-aggregation, leading to significantly higher data rates. The multitude of data rates and MIMO configurations to choose from has made it crucial to develop efficient algorithms for rate adaptation and MIMO mode selection (spatial multiplexing versus spatial diversity) in order to realize the promised gains in data rate. At the MAC layer, the optimal level of frame aggregation needs to be chosen in order to maximize the throughput. The adaptation approach uses very limited feedback provided within the Wi-Fi packet acknowledgement protocol. In this paper, we develop a framework for jointly selecting the data rate, the MIMO mode and the frame aggregation configuration at the access point (AP) using subcarrier-level channel state information (CSI). We use approximate expressions for the BER based on the union bound for the first-event error probability in order to obtain approximate throughput expressions for the different rates and MIMO modes. Assuming A-MPDU aggregation, we also show that for each data rate and MIMO-mode pair, there is a corresponding optimal aggregation level, which we find analytically. Our numerical results reveal that the proposed joint selection scheme yields significant improvements in throughput.

RAMCAST: Reliable and Adaptive Multicast Over IEEE 802.11n WLANs

Abstract: Wireless multicast over IEEE 802.11 WLANs suffers from two well-known problems: poor reliability and low spectral efficiency. To overcome these problems, we propose a novel PHY/MAC cross-layer wireless multicast scheme called reliable and adaptive multicast (RAMCAST). By considering the frame aggregation of IEEE 802.11n, RAMCAST enables an access point (AP) to selectively retransmit erroneous multicast frames and to dynamically adjust modulation and coding scheme under varying channel conditions. In particular, empowered by the orthogonality of subcarriers in the OFDM symbol, RAMCAST enables multiple multicast clients to transmit feedback to the AP simultaneously without collision, resulting in very low feedback overhead. We verified the feasibility of RAMCAST through USRP/GNU radio-based experiments and conducted an extensive simulation study using ns-2, and we found that RAMCAST outperforms the state-of-the-art wireless multicast scheme.

A delay-aware packet prioritisation mechanism for voice over IP in Wireless Mesh Networks

Abstract: This work proposes a novel Delay-aware Packet Prioritisation Mechanism (DPPM) to uniformly distribute the Quality of Service (QoS) level across all Voice Over IP (VoIP) calls in a Wireless Mesh Network (WMN). The method prioritises VoIP packets based on the amount of queueing delay that has been accumulated across multiple hops within the WMN. The accumulated queueing delay is piggybacked over every VoIP packet and is used at the enqueueing phase to place more delayed packets towards the head of the queue. This assures higher priority for more delayed VoIP packets over less delayed VoIP packets. The influence of the queueing delay on voice call quality is further reduced by utilising the proposed DPPM in conjunction with WiFi frame aggregation. This conjunction increases the network's VoIP call capacity, and this is validated through NS-3 simulations.

Passive Wi-Fi Link Capacity Estimation on Commodity Access Points

Abstract: Wi-Fi is the preferred way of accessing the internet for many devices at home, but it is vulnerable to performance problems. In this work, we propose a method to estimate the link capacity of a Wi-Fi link using physical layer metrics passively sampled on commodity access points. We build a model that predicts the maximum UDP throughput a device can sustain, which extends previous models to consider IEEE 802.11n optimizations such as frame aggregation. We validate our model through controlled experiments in an anechoic chamber. Over 95% of the link capacity predictions present errors below 5% when using our model with reference data. We show how link capacity estimation enables Wi-Fi diagnosis in two case studies where we predict the available bandwidth under microwave interference and in an office environment.

Performance modeling and analysis of high throughput wireless media access with QoS in noisy channel for different traffic conditions

Abstract: The high throughput wireless extensions based on IEEE 802.11 or wireless-fidelity (Wi-Fi) support varieties of physical and media access control (MAC) sublayer features to boost up the physical data rate in wireless media. These include multiple input multiple out (MIMO) spatial multiplexing and spatial diversity, channel bonding, short guard intervals, advanced modulation and coding schemes (MCS), frame aggregations and block acknowledgements; for different Wi-Fi extensions like IEEE 802.11n, IEEE 802.11ac and IEEE 802.11ad. The existing studies show that although such physical extensions improve data rates, they have internal trade-offs in channel error and sustainability that directly impact the MAC layer frame aggregation and block acknowledgement performance. In this paper, we model the impact of the channel errors over MAC layer channel access with frame aggregation and block acknowledgement, considering the standard IEEE 802.11 service class differentiation for quality of service (QoS). The evolution of aggregated frame transmission has been modeled using a three dimension Markov chain diagram, considering channel error from physical layer and different traffic conditions. The model is validated through simulation results. The mathematical model is further explored to observe and analyze the impact of channel error over the aggregated frame based MAC scheduling with different QoS performance parameters, like channel throughput, frame loss probability and channel access delay. We observe that frame aggregation sometimes shows negative impact on channel access performance that demands the need for designing an adaptive aggregation strategy.

Improving Energy Efficiency in Idle Listening of IEEE 802.11 WLANs

Abstract: This paper aims to improve energy efficiency of IEEE 802.11 wireless local area networks (WLANs) by effectively dealing with idle listening (IL), which is required for channel sensing and is unavoidable in a contention-based channel access mechanism. Firstly, we show that IL is a dominant source of energy drain in WLANs and it cannot be effectively alleviated by the power saving mechanism proposed in the IEEE 802.11 standard. To solve this problem, we propose an energy-efficient mechanism that combines three schemes in a systematic way: downclocking, frame aggregation, and contention window adjustment. The downclocking scheme lets a station remain in a semisleep state when overhearing frames destined to neighbor stations, whereby the station consumes the minimal energy without impairing channel access capability. As well as decreasing the channel access overhead, the frame aggregation scheme prolongs the period of semisleep time. Moreover, by controlling the size of contention window based on the number of stations, the proposed mechanism decreases unnecessary IL time due to collision and retransmission. By deriving an analysis model and performing extensive simulations, we confirm that the proposed mechanism significantly improves the energy efficiency and throughput, by up to 2.8 and 1.8 times, respectively, compared to the conventional power saving mechanisms.

Packet mass transit: Improving frame aggregation in 60 GHz networks

Abstract: The impact of frame aggregation on wireless network performance increases dramatically with higher data rates. The key problem is that the transmission time of packets decreases while the medium access, preamble and packet header overhead remain the same. Recent 802.11 standards address this issue using frame aggregation, i.e., grouping multiple data frames in a single transmission to reduce the overhead. This already provides substantial efficiency gains in networks operating in the 2.4 GHz and 5 GHz bands, and for future 60 GHz networks such as 802.11ad, gains are even more pronounced due to the order-of-magnitude higher data rates. In 802.11ad, frame aggregation becomes crucial to achieve the multi-gbps data rates that are possible in theory, since medium access overhead can be 20x larger than the time required to transmit a single packet. While frame aggregation is essential, it very much depends on the traffic patterns present in the wireless network, and a node may not always have enough packets in the transmit queue to achieve a sufficiently large aggregated frame size. In this paper, we investigate in which case nodes should wait to construct a larger aggregated packet before starting the channel access procedure. We present a simple waiting policy for the uplink case that either waits for a minimum number of packets or for a maximum amount of time, whichever comes first. For the downlink case, we utilize a maximum weight scheduling policy with a maximum waiting time. Our results show that both policies significantly improve medium utilization, thus increasing throughput and reducing end-to-end delay.

Performance Study of Frame Aggregation Mechanisms in the New Generation WiFi.

Abstract: The new generation WiFi (Widely Fidelity), which is called 802.11ac, has the goal of reaching at least 1 Gbps on bands below 6 GHz. This is why, the standard has been extended with new features at both PHYsical (PHY) and Medium Access Control (MAC) layers level. One of the key features of MAC layer is the ability of aggregating frames in order to reduce temporal overheads that significantly harm the performance of 802.11 networks. Three forms of aggregation exist, namely Aggregate MAC Service Data Unit (A-MSDU), Aggregate MAC Protocol Data Unit (A-MPDU) and hybrid A-MSDU/A-MPDU Aggregation (A-hybrid). In this paper, we study the impact of Frame Aggregation Mechanisms (FAMs) for improving the overall throughput of 802.11ac networks. Furthermore, we highlight the need of PHY/MAC cross-layer communications for optimizing the wireless bandwidth utilization. Simulation results demonstrate the gains offered by the FAMs.

T-SIMn: Towards a Framework for the Trace-Based Simulation of 802.11n Networks

Abstract: With billions of WiFi devices now in use, and growing, combined with the rising popularity of high-bandwidth applications, such as streaming video, demands on WiFi networks continue to rise. To increase performance for end users the 802.11n WiFi standard introduces several new features that increase Physical Layer Data Rates (PLDRs). However, the rates are less robust (i.e., more prone error). Optimizing throughput in an 802.11n network requires choosing the combination of features that results in the greatest balance between PLDRs and error rates, which is highly dependent on the environmental conditions. While the faster PLDRs are an important factor in the throughput gains afforded by 802.11n, it is only when they are used in combination with the new MAC layer features, namely Frame Aggregation (FA) and Block Acknowledgments (BAs), that 802.11n achieves significant gains when compared to the older 802.11g standard. FA allows multiple frames to be combined into a large frame so that they can be transmitted and acknowledged as one aggregated packet, which results in the channel being used more efficiently. Unfortunately, it is challenging to experimentally evaluate and compare the performance of WiFi networks using different combinations of 802.11n features. WiFi networks operate in 2.4 and 5 GHz bands, which are shared by WiFi devices, included in computers, cell phones and tablets; as well as Bluetooth devices, wireless keyboards/mice, cordless phones, microwave ovens and many others. Competition for the shared medium can negatively impact throughput by increasing transmission delays or error rates. This makes it difficult to perform repeatable experiments that are representative of the conditions in which WiFi devices are typically used. Therefore, we need new methodologies for understanding and evaluating how to best use these new 802.11n features. An existing trace-based simulation framework, called T-RATE, has been shown to be an accurate alternative to experimentally evaluating throughput in 802.11g networks. We propose T-SIMn, an extension of the T-RATE framework that includes support for the newer 802.11n WiFi standard. In particular, we implement a new 802.11n network simulator, which we call SIMn. Furthermore, we develop a new implementation of the trace collection phase that incorporates FA. We demonstrate that SIMn accurately simulates throughput for one, two and three-antenna PLDRs in 802.11n with FA. We also show that SIMn accurately simulates delay due to WiFi and non-WiFi interference, as well as error due to path loss in mobile scenarios. Finally, we evaluate the T-SIMn framework (including trace collection) by collecting traces using an iPhone. The iPhone is representative of a wide variety of one antenna devices. We find that our framework can be used to accurately simulate these scenarios and we demonstrate the fidelity of SIMn by uncovering problems with our initial evaluation methodology. We expect that the T-SIMn framework will be

ES2: Managing link level parameters for elevating data rate and stability in High Throughput WLAN

Abstract: High Throughput (HT) IEEE 802.11n/ac wireless networks support a large set of configuration parameters, like Multiple Input Multiple Output (MIMO) streaming, modulation and coding scheme, channel bonding, short guard interval, frame aggregation levels etc., that determine its physical data rate. However, all these parameters have an optimal performance region based on the link quality and external interference. Therefore, dynamically tuning the link parameters based on channel condition can significantly boost up the network performance. The major challenge in adapting all these parameters dynamically is that a large feature set need to be enumerated during run-time to find out the optimal configuration, which is a not feasible in real time. Therefore in this paper, we propose an estimation and sampling mechanism to filter out the non-preferable features on the fly, and then apply a learning mechanism to find out the best features dynamically. We apply a Kalman filtering mechanism to figure out the preferable feature sets from all possible feature combinations. A novel metric has been defined, called the diffESNR, which is used to select the best features from the sampled feature sets. The proposed scheme, Estimate-Sample-Select (ES2) is implemented and tested over a mixed wireless testbed using IEEE 802.11n and IEEE 802.11ac HT wireless routers, and the performance is analyzed and compared with other related mechanisms proposed in the literature. The analysis from the testbed shows that ES2 results in approx 60% performance improvement compared to the standard and other related mechanisms.

Analysis of the downlink saturation throughput of an asymmetric IEEE 802.11n-based WLAN

Abstract: Frame aggregation (FA) mechanisms improve the throughput of WLANs. In this paper, the effect of the FA mechanism on the throughput of wireless local area networks (WLANs) has been investigated. To this end, we propose an analytical model in order to analyze an IEEE 802.11n network comprised of an access point (AP) and several conventional nodes (CNs), all in the coverage area of each other. With respect to the heavier download traffic compared to the upload one, in our scenario, only the AP uses an FA mechanism and the other nodes use the basic IEEE 802.11 standard. In our proposed analytical model, the maximum downlink (DL) throughput is derived. Regarding the asymmetry among nodes, our analytical model consists of two different queueing networks: one for the AP and the other one for CNs. We verify the accuracy of our analytical results by simulations, i.e., less than 5% mismatch between the analytical and simulation results. We show that there is a tradeoff between the DL saturation throughput and performance of CNs. In other words, the FA improves the AP saturation throughput at the cost of a little degradation of the performance for CNs.

Control frame aggregation frame

Abstract: Systems and methods are disclosed that may communicate a control aggregate frame from a first wireless device to a second wireless device. A first wireless device may form a control aggregate frame by aggregating a plurality of first control frames into the control aggregate frame. The control aggregate frame may include a single media access control (MAC) header, a plurality of first aggregation fields, each storing a control frame subtype for a corresponding one of the plurality of first control frames, and a plurality of first payload fields, each storing a corresponding one of the plurality of first control frames. After generating the control aggregate frame, the first wireless device may transmit it to the second wireless device.

Cross talk MAC: A directional MAC scheme for enhancing frame aggregation in mm-Wave wireless personal area networks

Abstract: The abundance of unlicensed frequency resources in the mm-Wave frequency range, especially round 60 GHz bands, have a great potential to fulfill the increasing demands of high speed wireless applications. In mm-Wave wireless communication systems, directional transmission technologies become an inherent feature to compensate the high pathloss. The frame aggregation scheme is designed to maximize network throughput and efficiency for packet-based systems by grouping and transmitting multiple packets in a single channel access. In this paper, by jointly considering the benefits of directional transmission and frame aggregation, we propose a paradigm of parallel directional transmission, named cross talk MAC (CTMAC), for enhancing the spatial reuse of mm-Wave directional wireless networks. Enabled by its packet level channel access algorithm, CTMAC allows parallel transmissions even under the strongest interfered topologies to enhance the performance of the mm-Wave wireless personal area network. The numeric results show that the proposed CTMAC dominates the conventional scheme in nearly all scenarios. Especially, CTMAC outperforms the conventional scheme up to 2-fold with good antenna directivity.

Millimeter-wave blind spots: Mitigating deafness collisions using frame aggregation

Abstract: Multi-gigabit-per-second data rates in millimeter-wave networks can result in an excessive amount of channel accesses. Transmitting a single packet at such rates often only requires a few microseconds. In contrast, the medium access control (MAC) overhead is about 20× larger. This is particularly harmful if one or more nodes are deaf due to the use of directional antennas. Deaf nodes cannot overhear ongoing transmissions, and thus cause a high number of collisions, exacerbating MAC overhead even more. In addition, the contention window of deaf nodes becomes very large since their transmissions often fail, resulting in unfairness. To mitigate this issue, we suggest increasing traffic burstiness deliberately to allow for higher frame aggregation at the physical layer. This reduces the number of medium accesses, and thus decreases the probability of collision in case of deafness. We adapt existing theoretical models to our scenario to show the effectiveness of this strategy. Moreover, we validate our scheme in a practical testbed operating in the 60 GHz band. In particular, our evaluation shows that our strategy improves fairness by 20% and throughput by 66% compared to a system that does not exploit deliberate burstiness.

Block acknowledgement system and block acknowledgement method based on A-MPDU sub-frame position information control

Abstract: The invention discloses a block acknowledgement system and a block acknowledgement method based on A-MPDU sub-frame position information control, and mainly aims to solve the problem that the number of A-MPDU aggregated sub-frames is decreased mandatorily and fluctuates remarkably due to the influence of lost sub-frames in an IEEE802.11n/ac/ad wireless network. The method comprises the following steps: a sender puts the position information of an aggregated sub-frame in A-MPDU in an MAC layer frame header during A-MPDU frame aggregation; after receiving the aggregated frame, a receiver fills the bit in a corresponding position in a Bitmap acknowledgement table with '1' according to the position information of the received sub-frame; and the receiver assembles the filled Bitmap in BlockACK and feeds the Bitmap back to the sender to complete acknowledgement of the aggregated frame. According to the invention, the number of A-MPDU aggregated sub-frames is no longer subject to the influence of lost sub-frames, the length of aggregated frames is stabilized, and the transmission efficiency is improved. The block acknowledgement system and the block acknowledgement method can be used in a high-speed wireless network.

Performance Analysis of IEEE802.11ac DCF Enhancement for VHT with Frame Aggregation

Abstract: IEEE 80211ac standard has brought several significant improvements compared to its predecessor IEEE 80211n It managed to break the Gigabits barrier with a combination of both refining older techniques and presenting new ones The new enhancements such as channel bonding, beamforming, frames aggregation and finer modulation allow Wireless Local Area Networks (WLAN) the use of Very High Throughput (VHT) The physical layer (PHY) data rates are in the range of Gbps in the 5 GHz band But the variety of releases and options available for this standard has left many ambiguities regarding its real capabilities The Medium Access Control layer (MAC) throughput is influenced by several factors, causing the MAC efficiency to decrease In this paper we present a performance analysis in the VHT with frame aggregation for different access mechanisms, different channels and different modulation schemes

Signaling-Free Max-Min Airtime Fairness in IEEE 802.11 Ad Hoc Networks

Abstract: We propose a novel media access control (MAC) protocol, referred to as signaling-free max-min airtime fair (SMAF) MAC, to improve fairness and channel utilization in ad hoc networks based on IEEE 802.11 wireless local area networks (WLANs). We introduce busy time ratio (BTR) as a measure for max-min airtime fairness. Each node estimates its BTR and adjusts the transmission duration by means of frame aggregation and fragmentation, so that it can implicitly announce the BTR to neighbor nodes. Based on the announced BTR, each of the neighbor nodes controls its contention window. In this way, the SMAF MAC works in a distributed manner without the need to know the max-min fair share of airtime, and it does not require exchanging explicit control messages among nodes to attain fairness. Moreover, we successfully incorporate the hidden node detection and resolution mechanisms into the SMAF MAC to deal with the hidden node problem in ad hoc networks. The simulation results confirm that the SMAF MAC enhances airtime fairness without degrading channel utilization, and it effectively resolves several serious problems in ad hoc networks such as the starvation, performance anomaly, and hidden node problems.

100 Gb/s Data Link Layer - from a Simulation to FPGA Implementation

Abstract: In this paper, a simulation and hardware implementation of a data link layer for 100 Gb/s terahertz wireless communications is presented. In this solution the overhead of protocols and coding should be reduced to a minimum. This is especially important for high-speed networks, where a small degradation of efficiency will lower the user data throughput by several gigabytes per second. The following aspects are explained: an acknowledge frame compression, the optimal frame segmentation and aggregation, Reed-Solomon forward error correction, an algorithm to control the transmitted data redundancy (link adaptation), and FPGA implementation of a demonstrator. The most important conclusion is that changing the segment size influences the uncoded transmissions mostly, and the FPGA memory footprint can be significantly reduced when the hybrid automatic repeat request type II is replaced by the type I with a link adaptation. Additionally, an algorithm for controlling the Reed-Solomon redundancy is presented. Hardware implementation is demonstrated, and the device achieves net data rate of 97 Gb/s. Keywords—ARQ, FEC, frame aggregation, HARQ, link adaptation, Reed-Solomon FEC, segmentation.

T-SIMn: Towards the High Fidelity Trace-Based Simulation of 802.11n Networks

Abstract: In this paper, we describe the design, implementation and evaluation of a new framework for the trace-based evaluation of 802.11n networks, which we call T-SIMn. We first develop novel techniques for collecting and processing traces for 802.11n networks that incorporate Frame Aggregation (FA). We then demonstrate that the simulator portion of our framework (SIMn) accurately simulates throughput for one, two and three-antenna Physical Layer Data Rates in 802.11n with FA. Finally, we evaluate the T-SIMn framework (including trace collection) by collecting traces using an iPhone which is representative of a wide variety of one antenna devices. We show that our framework can be used to accurately simulate these scenarios and we demonstrate the fidelity of SIMn by uncovering problems with our initial evaluation methodology. We expect that the T-SIMn framework will be suitable for easily and fairly comparing algorithms that must be optimized for different and varying 802.11n channel conditions which are challenging to evaluate experimentally. These include rate adaptation, frame aggregation and channel bandwidth adaptation algorithms. git

Communication device, and communication method for frame aggregation and transmission

Abstract: A method for transmitting an aggregated frame is disclosed. The method includes: estimating channel condition; comparing the channel condition with first threshold for selecting an aggregation scheme; and comparing the channel condition with second threshold, which is different with the first threshold, for selecting an aggregation scheme; performing the aggregation using the selected aggregation scheme with position information, which indicates the positions of sub-frame in the aggregated frame.