Legacy IEEE Research Articles

Modeling and performance study of the packet fragmentation in an IEEE 802.11e-EDCA network over fading channel

Mathematical modeling and performance analysis of the IEEE 802.11e Enhanced Distributed Channel Access (EDCA) has been the subject of several research papers published in the literature. However, the Packet Fragmentation (PF) which has been proposed by the IEEE work group in the legacy IEEE 802.11 standard, has never been taken into account in the mathematical models available in the literature, in order to analyze the performance of the IEEE 802.11e-EDCA network under the influence of the Packet Error Rate (PER). Yet, the Packet Fragmentation is the only existing solution since 1999, which allows reducing the influence of the PER on the performance of IEEE 802.11 networks. In this paper, we aim at showing for the first time, how the Packet Fragmentation developed in the legacy IEEE 802.11 standard can be used to enhance the current IEEE 802.11e Quality of Service (QoS). Therefore, we propose an extension of the existing Markov chain models of the IEEE 802.11e EDCA function, in order to take into account the Packet Error Rate and Packet Fragmentation. Furthermore, we develop a mathematical model to derive the saturation throughput of a given Access Category (AC), namely: Voice (VO), Video (VI), Best Effort (BE) and Background (BK). The obtained analytical results show that, applying the Packet Fragmentation on the IEEE 802.11e-EDCA network, allows improving the utilization of the scarce wireless bandwidth under the impact of PER parameters, namely: Bit Error Rate (BER) and packet length.

Performance Analysis of Industrial WLAN Based on EDCA Scheme Defined in IEEE802.11e

In the last few years wireless local area network (WLAN) technology and products have grownunusually. This growth has encouraged many researchers to employ WLAN technology in differentapplication Areas. Recently, using IEEE 802.11 WLAN in industrial automation applications is attractiveand more interesting. However, the currently used medium access mechanism makes WLANs nondeterministicand hence not suitable for industrial real-time traffic. Legacy IEEE 802.11 WLANs wereinitially designed for best effort traffic only and did not provide any QoS support for this kind of traffic.The new amendment IEEE 802.11e standard was introduced and ratified in 2005. It defines the concept ofa Hybrid Co-ordination Function (HCF) at the MAC layer for medium access control. HCF is acombination of HCF Controlled Channel Access (HCCA) with parameterized quality of service (QoS)and Enhanced Distribution Channel Access (EDCA) with prioritized QoS. Enhanced DistributionChannel Access (EDCA) is an enhanced version of Distributed Coordination Function )DCF( mechanismused in the original IEEE 802.11 WLAN. This paper analyze the performance of the EDCA in anindustrial automation network with real-time requirements by means of a simulation with the networksimulator OPNET 11.5 and compares the results with the DCF in terms of latency and throughput invarious scenarios.

Design considerations of IEEE 802.15.4m low-rate WPAN in TV white space

This article provides an overview of technical design considerations for IEEE 802.15.4m LRWPAN operating in TVWS. We summarize and discuss TVWS regulatory requirements and LRWPAN applications, the two major driving forces motivating the formation of the new IEEE 802.15.4m standard. These forces define the criteria necessary for consideration during IEEE 802.15.4m system design to meet regulatory requirements and optimize performance. First, system design is presented from the perspective of LR-WPAN channelization with reference to the TV channel plan. Next, design considerations for network architecture and topology are discussed by relating the architecture requirement in TVWS regulations to that in the legacy IEEE 802.15.4 standard. Third, the PHY and MAC layer designs, which are crucial for meeting the criterion of optimizing LR-WPAN performance to support potential applications, are studied. In the PHY layer, the existing design in IEEE 802.15.4 is listed and discussed with regard to its applicability and reusability in TVWS. In the MAC layer, two functional entities, the TVWS operation-enabling feature and the dynamic frequency-band switching mechanism, are discussed with respect to their necessity and practicality for performance enhancement.

Congestion control with dynamic threshold adaptation and cross‐layer response for TCP Vegas over IEEE 802.11 wireless networks

SUMMARYWireless technologies provide mobile access and enable rapid andcost‐effective network deployment. But a wireless link is generally accompanied by high interference, transmission errors and a varying latency. The erratic packet losses usually lead to a curbing of the flow of segments on the TCP connection, and thus limit TCP performance. This paper presents a threshold control mechanism with cross‐layer response approach for improving TCP Vegas performance in IEEE 802.11 wireless networks. By making slight modifications to the legacy IEEE 802.11 MAC and TCP, the numerical results reveal that the proposed scheme provides a significant improvement in TCP performance under IEEE 802.11 wireless environments. Copyright © 2013 John Wiley & Sons, Ltd.

CAC-MAC: A Cross-Layer Adaptive Cooperative MAC for Wireless Ad Hoc Networks

Cooperative communication has been recently proposed as a way to mitigate fading in wireless networks. A cross-layer adaptive cooperative MAC (CAC-MAC) protocol for IEEE 802.11 DCF-based wireless ad hoc networks is proposed. The novel aspect and core idea of our proposal is a cross-layer adaptive data transmission algorithm considering both the length of data frame at the MAC layer and instantaneous wireless channel conditions. Under this algorithm, direct transmission mode or proper cooperative transmission mode will be adaptively selected for data packets according to both MAC layer and physical layer information. Analytical results demonstrate the effectiveness of the adaptive data transmission algorithm. Simulation studies based on NS2 show that the CAC-MAC protocol can significantly improve network throughput and reduce packet delay compared with legacy IEEE 802.11 protocol, which illustrate a new paradigm for realistic cross-layer cooperative MAC protocol design for next-generation wireless ad hoc networks.

RAM: Rate Adaptation in Mobile Environments

Channel asymmetry and high fluctuation of channel conditions are two salient characteristics of wireless channels in mobile environments. Therefore, when using IEEE 802.11 devices in mobile environments, it is critical to have an effective rate adaptation scheme that can deal with these issues. In this paper, we propose a practical rate adaptation scheme called Rate Adaptation in Mobile environments (RAM) and implement it in the MadWifi device driver. RAM uses a receiver-based approach to handle channel asymmetry and a conservative SNR prediction algorithm to deal with high channel fluctuation. More importantly, RAM allows the receiver to convey the feedback information to the transmitter in a creative manner via ACK transmission rate variation, which does not require changes to the device firmware and hence is implementable at the device driver level. In addition, RAM adopts an effective scheme to guarantee that RAM-based and legacy IEEE 802.11 devices can interoperate with each other. The effectiveness of RAM is demonstrated via in-depth experimental evaluation in indoor static and mobile environments as well as outdoor vehicular environments.

Outband Sensing-Based Dynamic Frequency Selection (DFS) Algorithm without Full DFS Test in IEEE 802.11h Protocol

We propose an outband sensing-based IEEE 802.11h protocol without a full dynamic frequency selection (DFS) test. This scheme has two features. Firstly, every station performs a cooperative outband sensing, instead of inband sensing during a quiet period. And secondly, as soon as a current channel becomes bad, every station immediately hops to a good channel using the result of outband sensing. Simulation shows the proposed scheme increases network throughput against the legacy IEEE 802.11h.

Analysis of Throughput and Energy Efficiency in the IEEE 802.11 Wireless Local Area Networks using Constant backoff Window Algorithm

The IEEE has standardized the 802.11 protocol for Wireless Local Area Networks. The primary medium access control (MAC) technique of 802.11 is called distributed coordination function (DCF). DCF is a carrier sense multiple access with collision avoidance (CSM A/CA) scheme with binary exponential backoff algorithm (BEB). DCF describes two techniques to employ for packet transmission: the two-way handshaking technique called basic access mechanism and an optional four way handshaking technique, known as request-tosend/clear-to-send (RTS/CTS) mechanism. In wireless networks, the energy consumed to transmit bits across a wireless link, is a critical design parameter. The Constant backoff Window Algorithm (CWA) is the modification of the IEEE 802.11 BEB algorithm, which is used to control the contention window in the case of collisions, in order to provide a better Throughput and Energy efficiency. The new algorithm has been tested against the legacy IEEE 802.11 through matlab simulation. The tests have shown significant improvements in performance in throughput and energy efficiency using CWA compared to the original BEB algorithm.

Joint paging area and location update optimization for IEEE 802.16m idle mode

As mobile devices are becoming smaller and users are desiring a longer battery life, the advanced power conservation mechanism, the idle mode, which is an enhanced version of the legacy IEEE 802.16 system’s idle mode, was proposed and adopted in IEEE 802.16m. Idle mode operation in IEEE 802.16m provides a lower location update overhead as well as a more efficient multiple paging-group operation compared to the legacy idle mode operation. However, there is a tradeoff between paging and location update overhead in the multiple paging-group operation. To address this issue, the paging-group location update timer (PG_LU_TIMER) was adopted in IEEE 802.16m. However, the manner in which this parameter balances the paging overhead and the location update overhead and the optimal value of the parameter are outside the scope of the IEEE 802.16m standard description. The main contribution of this paper is validation and further optimization of the joint paging area and location update proposed in the IEEE 802.16m air interface through analytical modeling and simulation of multiple paging-group operation with the PG_LU_TIMER. Our simulation results show that the PG_LU_TIMER can jointly reduce the location update overhead and paging overhead by up to 80.3% and 82.3% respectively. Furthermore our analysis shows that the proposed location update mechanism can save up to 640 μJ of energy compared to the legacy idle mode location update model.

무선랜에서 망 상태에 따른 DCF와 PCF 프로토콜의 선택적인 사용을 통한 MAC 성능 향상

The distributed coordination function (DCF) and point coordination function (PCF) protocols are the basic MAC protocols for legacy IEEE 802.11, IEEE 802.11a, IEEE 802.11b, IEEE 802.11e, IEEE 802.11g and IEEE 802.11n wireless LANs. When the DCF protocol is used for the various versions of IEEE 802.11 wireless LANs, the MAC performance seriously degrades due to the collisions among the stations (STAs) as more and more STAs attempt to transmit their data frames. On the other hand, the PCF MAC performance becomes poor when many STAs exist in IEEE 802.11 wireless LANs, however, only small number of STAs actually attempt to transmit their data frames. In this paper, we propose the algorithm for improving the MAC performance by selectively using the DCF and PCF protocols according to the state of IEEE 802.11 wireless LANs. Numerical examples are presented to show the MAC performance improvement by the selective use of the DCF and PCF protocols according to the network state.

A novel IEEE 802.11‐based MAC protocol supporting cooperative communications

AbstractCooperative diversity is a transmission technique, where multiple terminals form a virtual antenna array that realizes spatial diversity gain in a distributed fashion. The concept of cooperation has already been introduced to MAC layer to design MAC protocol. But it does not take advantage of physical layer's cooperation. In this paper, we present a novel MAC protocol based on IEEE 802.11, called C‐MAC, which is able to support the basic building block of cooperative system. In other words, in C‐MAC, a source would invite a relay node into data transmission if there exits an available one. During data transmission, the source sends the signal to destination in the first time slot. The relay node will retransmit the overheard information to the destination in the second time slot. The destination combines two signals from the source and the helper to create the spatial diversity and robustness against channel fading. The C‐MAC is backward compatible to the legacy IEEE 802.11 system. The performance of C‐MAC mainly depends on physical layer's performance as it just provides the support for cooperation at the MAC layer. If the physical layer works well, C‐MAC would outperform IEEE 802.11 when considering packet error rate (PER). We also perform extensive simulation using ns‐2 with assumptive physical parameters. The results show that C‐MAC would outperform 802.11 if PER is over some threshold, e.g. when PER is 0.4, C‐MAC can achieve up to 11.5% higher throughput than IEEE 802.11. Copyright © 2011 John Wiley & Sons, Ltd.

CMAC-ORS

In recent years, several studies have attempted to find and explore MAC protocols for supporting cooperative communication to improve reliability and throughput in wireless networks. The performance of these MAC protocols depends on how to select relay nodes. We propose a novel cooperative MAC protocol with reactive relay selection for wireless LANs that reduces collisions and overheads in relay selection. Since our MAC protocol is a modification of IEEE 802.11 distributed coordination function, it can be applied in the existing network interfaces with software MAC. Simulation results demonstrate that the proposed MAC protocol increases network throughput substantially compared to the legacy IEEE 802.11b system.

Short-range cognitive radio network: system architecture and MAC protocol for coexistence with legacy WLAN

To increase possible data transmission rate and to provide non-primary user's desired throughput in short-range communications, in this paper we propose new cognitive radio (CR) network architecture with the coexistence with the legacy IEEE 802.11 WLAN. The legacy WLAN ISM band channel is mostly used for common control channel for cognitive operation on the licensed bands to manage CR devices when they join the network and to announce the utilization of the licensed band or primary system appearance on the current used channels. The proposed CR-WLAN MAC protocol is designed to accommodate new CR related features in the proposed network architecture and it has backward compatibility to the legacy WLAN system: (1) Network entry procedure is modified to inform CR users the current licensed band status and to manage CR user group separately by AP; (2) During the operation, two types of CR beacon multicasting mechanisms are proposed, CR beacons help CR users to decide its service change or spectrum handover and to immediately evacuate from the current used channel when primary signal is detected, (3) When the CR user need to change the serving CR AP, not only the beacon frame body of neighbor APs but also the licensed and unlicensed band status is delivered to CR node to search the target CR-WLAN AP fast and (4) A new type of hidden node problem is introduced that focuses on possible signal collisions between incumbent devices and cognitive radio CR-WLAN devices, and a simple and efficient sensing information exchange mechanism between neighbor APs is proposed. The simulation results show that the proposed CR system can provide reliable protection to primary systems, as well as efficient utilization of given licensed spectrum resources, in which the network throughput can be greatly enhanced.

A Low-Complexity Transmission and Scheduling Scheme for WiMAX Systems with Base Station Cooperation

This paper considers base station cooperation as an interference management technique for the downlink of a WiMAX network (IEEE 802.16 standard) with frequency reuse factor of 1. A low-complexity cooperative transmission and scheduling scheme is proposed that requires limited feedback from the users and limited information exchange between the base stations. The proposed scheme requires minor modifications to the legacy IEEE 802.16e systems. The performance of the proposed scheme is compared with noncooperative schemes with similar complexity through computer simulations. Results demonstrate that base station cooperation provides an attractive solution for mitigating the cochannel interference and increases the system spectral efficiency compared to traditional cellular architectures based on frequency reuse.

Maximum-Throughput Access Control in Wireless LANs Through Max-Weight-Inspired Policies

The design of efficient medium access control (MAC) protocols that are backward compatible to legacy IEEE 802.11-based protocols is a central issue in the literature. This paper draws inspiration from utility-driven max-weight policies that lead to the maximum throughput region in synchronized slotted systems. It introduces two important enhancements to the IEEE 802.11 MAC protocols, which are not considered in current IEEE 802.11 protocol versions and 802.11x enhanced versions: consideration of the transmitter-receiver link state and the transmitter backlog size. Our objective is to characterize the impact of these parameters on access control and ultimately rely on them to enhance the capacity region and, thus, the total throughput, compared with legacy 802.11x MAC protocols. We consider a scenario of multiple nodes attempting to access an access point (AP). Each node is characterized by a link quality to the AP, which is essentially mapped to the physical (PHY)-layer rate that can be supported and a queue length that evolves based on the packetarrival process at the node and the transmissions. Motivated by the max-weight access control policy, we aim to increase the total uplink throughput while ensuring bounded queue lengths by making slight modifications to the legacy IEEE 802.11 protocol. Specifically, we make the contention window (CW) dependent on queue size and PHY-layer rate. The key idea is that a node with a large PHY transmission rate and large queue size should tend to use a smaller CW so that it gets higher chances of channel access. We take a first step toward this approach and suggest heuristic queue size and link-state-aware rules for defining the CW. Experimental performance evaluation shows significant enlargement of the capacity region and substantial performance improvement in the total throughput under our policy, compared with current protocols.

Advanced power management techniques in next-generation wireless networks [Topics in Wireless Communications

Because mobile devices are equipped with a limited amount of battery power, it is essential to have efficient power management mechanisms in mobile broadband networks such as mobile WiMAX and 3GPP Long Term Evolution that enable always on connectivity. This article presents the state-of-the-art power management methods in next-generation wireless networks with a focus on IEEE 802.16m based next-generation WiMAX networks and 3GPP LTE. To minimize and optimize user equipment power consumption, and further to support various services and large amounts of data transmissions, advanced power conservation mechanisms are being developed in IEEE 802.16m and 3GPP. Two advanced power conservation mechanisms, sleep and idle modes, which are enhanced versions of the legacy IEEE 802.16 system's sleep and idle modes, were proposed and adopted in IEEE 802.16m. Similarly, 3GPP LTE adopts a discontinuous reception mechanism for power conservation in RRC_CONNECTED and RRC_IDLE states. Power management techniques in WiMAX and 3GPP LTE provide less control signaling and operational overhead while providing more efficient power saving, and use simpler operation procedures than the existing power management techniques.

An adaptive cooperative MAC protocol compatible with legacy 802.11 DCF

A novel adaptive cooperative medium access control (MAC) protocol, which is completely backward compatible with the legacy IEEE 802.11 distributed coordination function (DCF), is proposed in this paper. To adapt to dynamic channel variation and network topology, the sender adaptively selects transmission scheme based on the instantaneous channel measurements. Analytical and simulation results show that the proposed protocol outperforms the existing one in terms of throughput, delay, energy and mobility.

A cognitive MAC protocol for QoS provisioning in ad hoc networks

In this paper, we consider an ad hoc network overlaying a legacy time-division multiple access (TDMA) system. This kind of ad hoc and infrastructure-based coexisting architecture can have an important application for the future cognitive radio (CR) network. To establish an overlaying ad hoc network in the presence of primary users, the medium access control (MAC) protocol shall achieve high spectrum utilization, avoid interfering the primary user and establish the link quickly. To this end, we propose four enhanced mechanisms for the carrier sense multiple access with collision avoidance (CSMA/CA) MAC protocol: (1) a neighbor list establishment mechanism for recognizing spectrum usage opportunities, (2) a set of contention resolution methods to reduce the collision and delay variance, (3) an invited reservation procedure for meeting the delay requirements of real-time traffic, and (4) a distributed frame synchronization mechanism for coordinating transmission without a centralized controller. Compared to the legacy IEEE 802.11 MAC protocol, the proposed CSMA/CA MAC protocol enhancement can improve the system throughput by 50% through analysis and NS-2 simulations, while keeping the dropping rate lower than 2% for delay-sensitive traffic. Furthermore, the standard deviation of the access delay is reduced by five times. With these QoS enhanced mechanisms, the proposed cognitive CSMA/CA MAC protocol can allow an ad hoc network to coexist with the legacy TDMA system.

Research of the QoS-Supporting IEEE 802.11 EDCA Performance

With the rapid development of wireless applications, the IEEE 802.11 task group proposed the QoS- supporting enhanced distributed channel access (EDCA) MAC mechanism, which is based on the legacy IEEE 802.11 DCF, to provide service differentiation for different types of traffic flows in the networks. This paper proposes a novel Markov chain-based analytical model for the IEEE 802.11 EDCA. Unlike the existing analytical models for the EDCA, the proposed model incorporates all the three major features of the EDCA, i.e., Wmin/Wmax, AIFS (arbitration inter-frame space), and TXOP (transmission opportunity). With this model, the paper presents the performance evaluations of the EDCA analytically, including each priority’s transmission throughput, media access delay, packet loss rate, etc. It dose not only analyze the saturated EDCA operation case, but also analyze the non-saturated EDCA operation case. Simulation results confirm the accuracy of the model analysis. Based on the model analysis, this paper proposes an admission control scheme D-TXOP (dynamic TXOP). While making admission decision, the scheme adjusts different priorities’ TXOP parameter settings adaptively according to their QoS requirements, which greatly enhances the network capacity.

CCMAC: Coordinated cooperative MAC for wireless LANs

In wireless LANs, throughput is one of, if not the most, important performance metric. This metric becomes more critical at the bottleneck area of the network, which is normally the area around the Access Point (AP). In this paper, we propose CCMAC, a coordinated cooperative MAC for wireless LANs. It is designed to improve the throughput performance in the region near the AP through cooperative communication, where data is forwarded through a two-hop high data rate link instead of a low data rate direct link. The most unique feature is that, it can coordinate nodes to perform concurrent transmissions which can further increase the throughput. To optimize the performance, the coordination problem is formulated as a Partially Observable Markov Decision Process and solved by a Reinforcement Learning algorithm. Through analysis and simulation, we show that CCMAC can significantly shorten the transmission time for stations with low data rate links to the AP and CCMAC has better throughput performance than other MAC protocols, such as CoopMAC and legacy IEEE 802.11.