MAC Service Data Unit Research Articles

PERFORMANCE EVALUATION OF DATA TRANSPORT OVER DIFFERENT-NODE DENSITY OF ZIGBEE SENSOR NETWORK – AN OPNET SIMULATION STUDY

In this paper, we analyze the performance of different node density of Wireless Sensor Network (WSN) operating under the IEEE Standard 802.15.4 in the beacon-enabled mode. The motivation for evaluating the beacon-enabled mode is due to its flexibility for WSN applications as compared to the non-beacon enabled mode. The analysis is based on an accurate OPNET simulation model which supports slotted Carrier Sense Multiple Access Mechanism with Collision Avoidance (CSMA/CA) mechanism and Guaranteed Time Slot (GTS). The performance of the slotted CSMA/CA sensor network is evaluated and analyzed for different network settings to understand the impact of the protocol attributes, including super-frame order (SO), beacon order (BO), data packet size and maximum back-off number. Through the simulation results, high SO provides better network throughput, otherwise results in lower average latency. We also found that the MAC overheads on small MAC Service Data Unit (MSDU) are more significant than the overheads on large MSDU. And the back-off mechanism results in longer delays when the network traffic is heavy.

Exploiting frame aggregation and weighted round robin with beamforming smart antennas for directional MAC in MANET environments

The development of Directional Medium Access Control (DMAC) strategies that allow to enhance the limitations due to the use of omnidirectional antennas in Mobile ad Hoc Networks (MANET), introduces several issues that need to be properly addressed such as the Deafness problem. The use of Smart Antenna Systems (SAS) along with Directional Request To Send (DRTS) and Directional Clear To Send (DCTS) could be not sufficient to mitigate the Deafness. In this regard, a sectorized antenna approach together with a frame scheduling mechanism can improve the overall MAC performance while limiting the Deafness; however, the employment of scheduling algorithms without priority such as the Round Robin could limit the network performance especially in terms of Packet Delivery Ratio (PDR) and fairness. For this reason, we propose two approaches: the A-MSDU (Aggregation MAC Service Data Unit) MAC and a WRR (Weighted Round Robin) MAC that could allow to overcome the limitations of the Round Robin scheme applied at MAC layer in order to have an high efficiency in the overall resource allocation. More specifically, obtained results show that, through the use of frame aggregation, it is possible to considerably reduce issues implied by Round Robin such as time slice and network overhead; WRR approach, instead, is able to enhance the overall network fairness by reducing the number of collisions provided by a directional MAC based on Round Robin scheduling; this aspect translates into higher PDR performance compared to Round Robin approach.

Throughput Characteristics of WiMAX Video Surveillance Systems

This paper presents the throughput characteristics for an All-WiMAX (AW) and a Hybrid Wi-Fi –WiMAX (HWW) video surveillance system with varying number of nodes, frame rate and MAC Service Data Unit (MSDU) size. An AW video surveillance system consists of WiMAX IP cameras connected directly to the Base stations while the HWW system consists of Wi-Fi IP cameras linked to the Customer Premises Equipment (CPE) which is equally linked to the base station. Local viewing PCs are connected at the CPE while remote viewing can be done via the internet. WiMAX and Wi-Fi IP cameras capture the video images; convert them to an appropriate digital signal and transmit them via Ethernet cables or wireless interface links. The investigation of the performance of the AW and HWW systems has been done by simulation of the systems using the OPNET modeler.Results show that, under similar conditions, the HWW video surveillance system outperforms the AW system in terms of throughput by a factor of 1.75. The results further show that throughput increases with increase in MSDU size and/or video resolutions, frame rate, number of nodes and decrease with increase in frame time, the reverse being true as well.

A Bi-Scheduler Algorithm for Frame Aggregation In IEEE 802.11N

IEEE 802.11n mainly aims to provide high throughput, reliability and good security over its other previous standards. The performance of 802.11n is very effective on the saturated traffic through the use of frame aggregation. But this frame aggregation will not effectively function in all scenarios. The main objective of this paper is to improve the throughput of the wireless LAN through effective frame aggregation using scheduler mechanism. The Bi-Scheduler algorithm proposed in this article aims to segregate frames based on their access categories. The outer scheduler separates delay sensitive applications from the incoming burst of multi-part data and also decides whether to apply Aggregated - MAC Service Data Unit (AMSDU) aggregation technique or to send the data without any aggregation. The inner scheduler schedules the remaining (delay-insensitive, background and best-effort) packets using Aggregated-MAC Protocol Data unit (A-MPDU) aggregation technique.

End-to-End QoS Improvement using IPv6 Header Reduction over MPLS

standards, PHS suppresses redundant parts of payload header in MAC service data unit. This paper proposes Label Switched Path-Payload Header Suppression (LSP- PHS), in which an MPLS-enabled backbone route compresses packets over an MPLS LSP without compression or decompression cycles at each router. It has two main contributions for MPLS-IPv6 header compression. First, LSP- PHS adds a new facility (MPLS/PHS) to the existing MPLS facilities. Second, it provides an analysis of the effect of implementing LSP-PHS on real-time and non-real-time IPv6 traffic in terms of QoS metrics. The implementation results using NS 2.34 show QoS improvement for real-time and non- real-time traffic.

New adaptive frame aggregation call admission control (AFA‐CAC) for high throughput WLANs

AbstractThe major enhancements introduced by the very high throughput wireless local area network, cannot provide quality of service (QoS) satisfaction for real time and multimedia applications. The recent standard IEEE 802.11n introduced new Medium Access Control (MAC) mechanisms based on aggregation scheme to enhance throughput. Besides that, functional modules for QoS provisioning such as call admission control and bandwidth management should be implemented in the access point. Hence, an efficient call admission control (CAC) algorithm is required for 802.11n network to satisfy QoS requirements of strict multimedia services. In this paper, we propose a new model‐based call admission control algorithm, called adaptation of frame aggregation AFA‐CAC to be implemented within the QoS access point in IEEE 802.11n standard in a way to provide QoS satisfaction to real time services. We first propose an accurate analytical model to estimate the achieved QoS metrics of a new flow entering in the network. Then, we detailed the AFA‐CAC algorithm that supports IEEE 802.11n aggregation schemes aggregated MAC service data unit and aggregated MAC protocol data unit and consider the IEEE 802.11e enhanced distributed channel access. AFA‐CAC is based on both predicting the QoS constraints of the already active flows and the new flow, and adjusting the number of aggregated subframes of each flow. Conducted simulations illustrate the performance of our proposed AFA‐CAC in terms of satisfying QoS throughput and end‐to‐end delay requirements of voice and video traffics. Copyright © 2013 John Wiley & Sons, Ltd.

SRA-MSDU: Enhanced A-MSDU frame aggregation with selective retransmission in 802.11n wireless networks

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. One of the MAC enhancements is the frame aggregation in which multiple frames are concatenated into a single large frame before being transmitted. The 802.11n MAC layer defines two types of aggregation, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). The A-MPDU outperforms A-MSDU due to its large aggregation size and the subframes retransmission in erroneous channels. However, in error free channels and under the same aggregation size the A-MSDU performs better than the A-MPDU due to its smaller headers. Thus, adding a selective retransmission capability to the A-MSDU would improve the system performance. In this paper, we have proposed an MSDU frame aggregation scheme that enables selective retransmission at the MSDU level without altering the original MAC header. In this proposed scheme an implicit sequence control mechanism has been introduced in order to keep the frames in sequence and preserve their correct order at the receiver side. The results show that the proposed scheme improves the system performance in terms of throughput and delay even under highly erroneous channels.

FER Performance in the IEEE 802.11 a/g/n Wireless LAN over Fading Channel

This paper explores and compares FER (Frame Error Rate) of a MAC (Medium Access Control) layer in the IEEE 802.11 a/g/n wireless LAN. It is evaluated under the fading wireless channel, using theoretical analysis method. It is analyzed by using the number of stations with both variable payload size and mobile speed on the condition that fading margin and transmission probability are fixed. Especially, in the IEEE 802.11n, A-MSDU (MAC Service Data Unit Aggregation) scheme is considered and the number of subframe is used as the variable parameter. In the IEEE802.11a/g wireless LAN, fixed wireless channel is assumed to be Rayleigh fading channel. Mobile wireless channel is assumed to be flat fading Rayleigh channel with Jake spectrum. The channel is in fading states or inter-fading states by evaluating a certain threshold value of received signal power level. If and only if the whole frame is in inter-fading state, there is the successful frame transmission. If any part of frame is in fading duration, the frame is received in error.

A Reliable A-MSDU Frame Aggregation Scheme in 802.11n Wireless Networks

IEEE 802.11n standard is introduced to enhance the throughput to more than 100Mbps at the MAC service access point. This high throughput is achieved through several enhancements at the physical and MAC layers. Frame aggregation is a key enhancement at the MAC later in which multiple frames are concatenated and then sent in one channel access. In error free channels the 802.11n MAC service data unit aggregation (A-MSDU) performs better than the MAC protocol data unit aggregation (A-MPDU)due to its smaller headers. However, the performance of A-MSDU at erroneous channels is poor due to lack of sub-frames integrity check. In this paper, we proposed an A-MSDU frame aggregation with sub-frame integrity check and retransmission at the MSDU level without altering the original MAC frames header structure. The results show that the proposed scheme improves the system performance in terms of throughput and delay even under highly erroneous channels.

Performance evaluation and optimisation guidelines for the Type II power-saving class of mobile World Interoperability for Microwave Access

In Mobile World Interoperability for Microwave Access (also known as IEEE802.16e), a standard power-saving mechanism (PSM) that alternates between sleep and wake modes is adopted to extend the lifetime of mobile stations (MSs), but it simultaneously induces a medium access control (MAC) service data unit (SDU) response delay. The standard PSM defines three power-saving classes (PSCs), among which Type I is based on a binary-exponential increase in the sleep window, and Type II is based on a constant sleep window. Over the years, most studies have mainly focused on PSC Type I, while only a few have considered Type II. This study derives several analytical models of PSC Type II and evaluates the power consumption and MAC SDU response delay performance. Based on the derived models, an optimised power under delay-bound mechanism (OPDBM) is proposed to find the optimal initial sleep window parameter that minimises the power consumption of an MS while satisfying a given MAC SDU response delay constraint. Both numerical analysis and simulation experiments show that the OPDBM effectively minimises the power consumption of an MS while guaranteeing any imposed/required MAC SDU response delay constraint in a wide variety of environments.

An Optimized A-MSDU Frame Aggregation with Subframe Retransmission in IEEE 802.11n Wireless Networks

The IEEE 802.11n standard is defined to achieve a high throughput at the MAC layer. This high throughput is accomplished via many enhancements in both the physical and MAC layers. A key enhancement introduced in the 802.11n standard is frame aggregation. Two types of aggregation defined by the 802.11n standard, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). Frame aggregation reduces both the headers and timing overheads at the MAC layer by aggregating multiple frames into a single large frame before being transmitted. The aggregation headers themselves still have a negative impact on the network performance especially when aggregating frames of small payload. Moreover, the lack of partial retransmission in the A-MSDU aggregation is behind its poor performance in error-prone channels. In this paper we proposed an optimized header A-MSDU frame aggregation (OHA-MSDU) with subframes retransmission capability at the MSDU level. The simulation results show the significance of the proposed scheme, especially for applications that have a small frame size such as VoIP.

DCF Throughput Analysis of IEEE 802.11a/g/n-based Mobile LAN over Correlated Fading Channel

This paper explores a MAC (Medium Access Control) layer throughput with DCF (Distributed Coordination Function) protocol in the IEEE 802.11a/g/n-based mobile LAN. It is evaluated in Rayleigh fading wireless channel, using theoretical analysis method. The DCF throughput performance is analyzed by using the number of stations with both variable payload size and mobile speed on the condition that fading margin and transmission probability are fixed. In the IEEE 802.11n, A-MSDU (MAC Service Data Unit Aggregation) scheme is considered and number of subframe is used as the variable parameter. It is identified that MAC efficiency of IEEE 802.11n is the best out of four schemes.

Power-saving mechanism with delay bound for Mobile WiMAX systems

In Mobile World Interoperability for Microwave Access (WiMAX), the power-saving mechanism (PSM), which operates alternately in sleep and awake modes, works to extend the lifetime of mobile stations (MSs), although it concurrently induces a medium access control (MAC) service data unit (SDU) response delay. In this study, the authors derive the analytical models for two of the most important performance metrics: the average power consumption and the average MAC SDU response delay of an MS in sleep mode. These metrics are given as a function of the sleep mode system parameters: initial sleep window Tmin and final sleep window Tmax. Based on these models, the authors show that a tradeoff relationship exists between them. The authors then propose an optimised power-saving mechanism (OPSM) that jointly determines the optimal Tmin and Tmax to minimise the power consumption under a given MAC SDU response delay constraint. Through both numerical analyses and subsequent simulations, the authors show that the OPSM effectively minimises the power consumption of an MS in its sleep mode while guaranteeing the MAC SDU response delay constraint.

IEEE 802.11n 무선 네트워크에서의 협력적 프레임 집약 기법

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.

Time allocation scheme in IEEE 802.15.3 TDMA mechanism

In network with a shared channel in TDMA mechanism, it is a core issue to effectively allocate channel time to provide service guarantees for flows with QoS requirements. This paper proposes a simple and efficient time allocation scheme called MES-ESRPT (MCTA at the End of Superframe-Enhanced Shortest Remaining Processing Time) for delay-sensitive VBR traffic in accordance with IEEE 802.15.3 standard. In this algorithm, PNC (piconet coordinator) allocates one MCTA (Manage- ment Channel Time Allocation) for each stream which is the process of communication at the end of superframe. During the MCTA period, each transmitter should report current fragments number of the first MSDU (MAC Service Data Unit) and the fragments number of the remainder MSDUs to PNC. In the next superframe, PNC firstly allocates part CTAs (Channel Time Allocation) for each stream based on the remainder fragments number of the first MSDU by SRPT rule, then allocates remainder CTAs for each stream based on all fragments number of remainder MSDUs by the same SRPT rule. Simulation results showed that our proposed MES-ESRPT method achieves significantly better performance in QoS for multimedia streams compared to the existing schemes.