Showing papers on "Media access control published in 2013"

Directional Cooperative MAC Protocol Design and Performance Analysis for IEEE 802.11ad WLANs

Abstract: In this paper, we consider the directional multigigabit (DMG) transmission problem in IEEE 802.11ad wireless local area networks (WLANs) and design a random-access-based medium access control (MAC) layer protocol incorporated with a directional antenna and cooperative communication techniques. A directional cooperative MAC protocol, namely, D-CoopMAC, is proposed to coordinate the uplink channel access among DMG stations (STAs) that operate in an IEEE 802.11ad WLAN. Using a 3-D Markov chain model with consideration of the directional hidden terminal problem, we develop a framework to analyze the performance of the D-CoopMAC protocol and derive a closed-form expression of saturated system throughput. Performance evaluations validate the accuracy of the theoretical analysis and show that the performance of D-CoopMAC varies with the number of DMG STAs or beam sectors. In addition, the D-CoopMAC protocol can significantly improve system performance, as compared with the traditional IEEE 802.11ad MAC protocol.

802.1aq support over ietf evpn

Abstract: A method is implemented in a multiprotocol label swapping (MPLS) edge switch (PE) for interworking the 802.1aq control plane with an Ethernet Virtual Private Network (EVPN) Border Gateway Protocol (BGP) control plane. The method and system elect designated forwarders (DFs) for a given Backbone-Virtual Local Area Network Identifier (B-VID) in a local Provider Backbone Bridged Network (PBBN) and thereby determine which PE uniquely transfers specific I-Component Source Identifier (I-SID) and Media Access Control (MAC) information for the B-VID from an Intermediate System-Intermediate System (IS-IS) database into a BGP database and transfers I-SID and MAC information in the BGP database into the IS-IS database of the PE.

Proximity-Based Security Techniques for Mobile Users in Wireless Networks

Abstract: In this paper, we propose a privacy-preserving proximity-based security system for location-based services in wireless networks, without requiring any pre-shared secret, trusted authority, or public key infrastructure. In this system, the proximity-based authentication and session key establishment are implemented based on spatial temporal location tags. Incorporating the unique physical features of the signals sent from multiple ambient radio sources, the location tags cannot be easily forged by attackers. More specifically, each radio client builds a public location tag according to the received signal strength indicators, sequence numbers, and media access control (MAC) addresses of the ambient packets. Each client also keeps a secret location tag that consists of the packet arrival time information to generate the session keys. As clients never disclose their secret location tags, this system is robust against eavesdroppers and spoofers outside the proximity range. The system improves the authentication accuracy by introducing a nonparametric Bayesian method called infinite Gaussian mixture model in the proximity test and provides flexible proximity range control by taking into account multiple physical-layer features of various ambient radio sources. Moreover, the session key establishment strategy significantly increases the key generation rate by exploiting the packet arrival time of the ambient signals. The authentication accuracy and key generation rate are evaluated via experiments using laptops in typical indoor environments.

Credit-based flow control in lossless ethernet networks

Abstract: In one embodiment, a system includes a hardware processor and logic integrated with and/or executable by the processor or media access control (MAC) functionality of a network port, the logic being adapted to initialize a link between a receiving endpoint and a sending endpoint, the receiving and sending endpoints being connected in a network fabric, wherein at least one virtual link is created within the link, receive an amount of available flow credits from the receiving endpoint, wherein the amount of available flow credits are used to determine a capacity to process packets at the receiving endpoint, and transmit one or more packets to the receiving endpoint until all packets are sent or the amount of available flow credits is insufficient to process additional packets, wherein exchange of flow credits is performed on a per virtual link basis.

A scalable Hybrid MAC protocol for massive M2M networks

Abstract: In Machine to Machine (M2M) networks, a robust Medium Access Control (MAC) protocol is crucial to enable numerous machine-type devices to concurrently access the channel. Most literatures focus on developing simplex (reservation or contention based) MAC protocols which cannot provide a scalable solution for M2M networks with large number of devices. In this paper, a frame-based Hybrid MAC scheme, which consists of a contention period and a transmission period, is proposed for M2M networks. In the proposed scheme, the devices firstly contend the transmission opportunities during the contention period, only the successful devices will be assigned a time slot for transmission during the transmission period. To balance the tradeoff between the contention and transmission period in each frame, an optimization problem is formulated to maximize the system throughput by finding the optimal contending probability during contention period and optimal number of devices that can transmit during transmission period. A practical hybrid MAC protocol is designed to implement the proposed scheme. The analytical and simulation results demonstrate the effectiveness of the proposed Hybrid MAC protocol.

Full Duplex Media Access Control for Wireless Multi-Hop Networks

Abstract: Wireless full-duplexing enables a transmission and a reception on the same frequency channel at the same time, and has the potential to improve the end-to-end throughput of wireless multi-hop networks. In the present paper, we propose a media access control (MAC) protocol for wireless full- duplex and multi-hop networks called Relay Full- Duplex MAC (RFD-MAC). The RFD-MAC is an asynchronous full-duplex MAC protocol, which consists of a primary transmission and a secondary transmission. The RFD-MAC increases the full-duplex links by overhearing frames, which include 1-bit information concerning the existence of a successive frame, and selecting a secondary transmission node using the gathered information. The gathered information is also used to avoid a collision between the primary and secondary transmission. Simulation results reveal that the proposed RFD-MAC improves up to 68%, 49% and 56% of end-to-end throughput compared to CSMA/CA, FD-MAC and MFD-MAC, respectively.

Scalable network overlay virtualization using conventional virtual switches

Abstract: In one embodiment, a system includes a server running a virtualization platform, the virtualization platform including logic adapted for creating one or more virtual machines (VMs) and logic adapted for managing a virtual switch (vSwitch), a controller in communication with the server, the controller including logic adapted for assigning a media access control (MAC) address and a virtual local area network (VLAN) identifier (ID) to each of the one or more VMs, wherein a specific tenant to which the one or more VMs belongs is indicated using a tenant ID derived from the VLAN ID, the MAC address, or a combination thereof. Other systems, methods, and computer program products are also described according to more embodiments.

An Intelligent Hybrid MAC With Traffic-Differentiation-Based QoS for Wireless Sensor Networks

Abstract: In this paper, we present the Intelligent Hybrid MAC (IH-MAC), a novel low power with quality of service guaranteed medium access control protocol for wireless sensor networks (WSNs). The IH-MAC achieves high energy efficiency under wide range of traffic load. It ensures shorter latency to critical and delay-sensitive packets. The IH-MAC protocol achieves high channel utilization during high traffic load without compromising energy efficiency. The IH-MAC does it by using the strength of CSMA and TDMA approach with intelligence. The novel idea behind the IH-MAC is that it uses both the broadcast scheduling and link scheduling. Depending on the network loads, the IH-MAC protocol dynamically switches from broadcast scheduling to link scheduling and vice versa in order to achieve better efficiency. The scheduling is done in the IH-MAC with a novel decentralized approach where the nodes locally use the clock arithmetic to find the time slot, allocated for it. Furthermore, the IH-MAC uses Request-To-Send, Clear-To-send handshakes with methods for adapting the transmit power to the minimum level necessary to reach the intended neighbor. Thus, the IH-MAC reduces energy consumption by suitably varying the transmit power. The IH-MAC also uses the concept of parallel transmission that further reduces delay. The analytical and simulation results corroborate the theoretical idea, and show the efficiency of our proposed protocol.

A Bidirectional-Concurrent MAC Protocol With Packet Bursting for Underwater Acoustic Networks

Abstract: The underwater acoustic channel is fundamentally different from the terrestrial wireless channel. Its unique characteristics, such as slow propagation speed and small bit rate distance product, present both challenges and opportunities for media access control (MAC) protocol design. In existing handshaking-based MAC protocols, each successful handshake only allows an initiating sender to transmit a single or multiple consecutive data packets to its intended receiver. In a long propagation delay environment, this unidirectional data transmission often results in extremely poor channel utilization due to the long waiting time for the handshake to complete. By exploiting the channel's unique characteristics, we present a novel approach based on concurrent, bidirectional data packet exchange to improve the data transmission efficiency. To further amortize the high latency overhead, we adopt a packet bursting idea, where a sender-receiver pair can exchange multiple rounds of bidirectional packet transmissions. Based on these strategies, we propose an asynchronous handshaking-based MAC protocol, which we call bidirectional-concurrent MAC with packet bursting (BiC-MAC). Via extensive simulations, we compare BiC-MAC against two representative unidirectional handshaking-based protocols, as well as several existing MAC protocols. We demonstrate that BiC-MAC can significantly increase channel utilization and offer performance gains in terms of both throughput and delay, while achieving a stable saturation throughput. Our study highlights the value of adopting bidirectional, concurrent transmission in underwater networks.

Congestion-Controlled-Coordinator-Based MAC for Safety-Critical Message Transmission in VANETs

Abstract: Vehicular ad hoc networks (VANETs) provide the communication framework for the dissemination of safety-critical messages such as beacons and emergency messages. The communication channel witnesses significant network load generated by frequently exchanged beacons. Under high-density situations, it leads to a serious scalability problem in VANETs. Moreover, contention-based medium access control (MAC) protocols suffer from a great number of packet collisions, and as a result, the reliability and latency of safety messages are severely affected. Because of the periodic nature of beacons, time-division multiple access (TDMA) can be a good choice over contention-based MAC. In this paper, we propose congestion-controlled-coordinator-based MAC (CCC-MAC), which is a time-slot-based medium access protocol that addresses beacons and emergency messages. Basically, the network is virtually partitioned into a number of segments. Within a segment, medium access is accomplished by using a time-slot-scheduling mechanism supervised by a local coordinator vehicle. A significant number of vehicles can be supported under the proposed configuration. In fact, the proposed scheduling mitigates channel congestion by reducing the transmission time of beacons through the use of multiple data rates. Bandwidth utilization is also improved by reusing the unoccupied time slots. Finally, CCC-MAC ensures fast and reliable propagation of emergency messages by employing a pulse-based reservation mechanism. In the simulations, we demonstrate the ability of CCC-MAC to scale well in different vehicular density scenarios. Moreover, it outperforms existing MAC-layer protocols with respect to packet reception probability and latency of safety messages.

Fine-grained channel access in wireless LAN

Abstract: With the increasing of physical-layer (PHY) data rate in modern wireless local area networks (WLANs) (e.g., 802.11n), the overhead of media access control (MAC) progressively degrades data throughput efficiency. This trend reflects a fundamental aspect of the current MAC protocol, which allocates the channel as a single resource at a time. This paper argues that, in a high data rate WLAN, the channel should be divided into separate subchannels whose width is commensurate with the PHY data rate and typical frame size. Multiple stations can then contend for and use subchannels simultaneously according to their traffic demands, thereby increasing overall efficiency. We introduce FICA, a fine-grained channel access method that embodies this approach to media access using two novel techniques. First, it proposes a new PHY architecture based on orthogonal frequency division multiplexing (OFDM) that retains orthogonality among subchannels while relying solely on the coordination mechanisms in existing WLAN, carrier sensing and broadcasting. Second, FICA employs a frequency-domain contention method that uses physical-layer Request to Send/Clear to Send (RTS/CTS) signaling and frequency domain backoff to efficiently coordinate subchannel access. We have implemented FICA, both MAC and PHY layers, using a software radio platform, and our experiments demonstrate the feasibility of the FICA design. Furthermore, our simulation results show FICA can improve the efficiency of WLANs from a few percent to 600% compared to existing 802.11.

MAC Protocol Design and Performance Analysis for Random Access Cognitive Radio Networks

Abstract: In this paper, we consider the medium access control (MAC) protocol design for random access cognitive radio network (CRN). Based on asynchronous spectrum sensing technique and RTS/CTS mechanism, a new MAC protocol, namely, cognitive-radio-based carrier sense medium access with collision avoidance (CR-CSMA/CA) is proposed to coordinate the channel access of secondary network as well as protect the operation of primary network, which applies to both single and multiple channel models. Using the G/G/1 queuing model with consideration of unsaturated and saturated network condition, we develop a framework to analyze the proposed MAC protocol and also derive closed-form expressions of specific performance metrics such as normalized throughput, average packet service time, etc. Performance evaluations illustrate and validate that the performance of CR-CSMA/CA varies with the offered traffic load of secondary network and the spectrum utilization rate of primary network, respectively, and also show that CR-CSMA/CA outperforms other relevant MAC protocols.

Survey on cooperative medium access control protocols

Abstract: In the past decade, there has been ever-increasing research attention to user cooperation in the wireless communication networks. The unique challenges of wireless networks such as channel fading and variation can be addressed well by taking advantage of relaying among cooperating mobile terminals. There are many studies on cooperative communications at the physical layer to exploit spatial diversity for improving channel capacity. In recent years, user cooperation from the perspective of the medium access control (MAC) layer becomes a promising new research area. In this study, the authors present a comprehensive survey on the mainstream cooperative MAC protocols in the literature. Focusing on the contention-based solutions, the authors classify the well-known proposals according to how they address two fundamental questions for user cooperation, that is, when to cooperation and whom to cooperate with. In addition to analysing the essential features of classic cooperative MAC protocols, the authors also discuss the major research challenges and project future research directions for MAC-layer cooperation.

Overview of Wireless Access in Vehicular Environment (WAVE) protocols and standards

Abstract: Institute of Electrical and Electronics Engineers (IEEE) series of standards for Wireless Access in Vehicular Environment (WAVE) is currently considered as the most promising technology for vehicular networks. It aims to support interoperability and robust safety communications in a vehicular environment. The first trial version of WAVE standard was released in 2006, Most of the published review studies were done on the old trail versions. This study reviews the latest released version of the IEEE WAVE standard, reflects the state of art in WAVE technology, and presents the status of each standard in the IEEE 1609 series of standards. IEEE 1609 series contains four standards that are under development, three are published and one is already withdrawn. Then the study discusses the technical details of IEEE 1609.4 for multi-channel operation and highlights the new features of WAVE Media Access Control (MAC) layer. The study also describes the services and protocols that are provided by IEEE 1609.3 as a network service standard. Frame format that is used in standards are also exposed.

Method and system for uniform gateway access in a virtualized layer-2 network domain

Abstract: The disclosure herein describes a system, which provides uniform access to a gateway in an extended virtualized layer-2 network. During operation, the system identifies a media access control (MAC) address, which is associated with a respective gateway in the extended virtualized layer-2 network, in a layer-2 header of a data frame. This MAC address is specific to the extended virtualized layer-2 network (e.g., for a different extended virtualized layer-2 network, a different MAC address is associated with a respective gateway). The system modifies the layer-2 header by swapping the MAC address with another MAC address, which uniquely identifies a gateway in the extended virtualized layer-2 network, in the layer-2 header and forwards the frame with the modified header to the gateway.

Game Theory Applications in CSMA Methods

Abstract: As a mathematical tool, game theory has been used for the analysis of multi-agent systems. Wireless networks are typical examples of such systems, in which communicating nodes access the channel through the CSMA method influencing the other neighboring nodes' access. Different games were examined to model such an environment and investigate its challenging issues. This research reviews different CSMA games presented for wireless MAC and classifies them. Advantages and shortcomings of these games will be recounted and some open research directions for future research, supported.

Virtual mac address, mask-based, packet forwarding

Abstract: A destination Media Access Control (MAC) address of a packet is determined. In response to determining that the destination MAC address is a virtual MAC address and belongs to an access device, mask-based, virtual MAC address, the packet is encapsulated with a Very Large Layer 2 (VLL2) network protocol header, and sent to an access device associated with the access device, mask-based virtual MAC address.

TC-BAC: A trust and centrality degree based access control model in wireless sensor networks

Abstract: Access control is one of the major security concerns for wireless sensor networks. However, applying conventional access control models that rely on the central Certificate Authority and sophisticated cryptographic algorithms to wireless sensor networks poses new challenges as wireless sensor networks are highly distributed and resource-constrained. In this paper, a distributed and fine-grained access control model based on the trust and centrality degree is proposed (TC-BAC). Our design uses the combination of trust and risk to grant access control. To meet the security requirements of an access control system with the absence of Certificate Authority, a distributed trust mechanism is developed to allow access of a trusted node to a network. Then, centrality degree is used to assess the risk factor of a node and award the access, which can reduce the risk ratio of the access control scheme and provide a certain protection level. Finally, our design also takes multi-domain access control into account and solves this problem by utilizing a mapping mechanism and group access policies. We show with simulation that TC-BAC can achieve both the intended level of security and high efficiency suitable for wireless sensor networks.

Performance analysis of opportunistic spectrum access protocol for multi-channel cognitive radio networks

Abstract: Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the single-channel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution. We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.

Media Access Control and Resource Allocation: For Next Generation Passive Optical Networks

Abstract: This book focuses on various Passive optical networks (PONs) types, including currently deployed Ethernet PON (EPON) and Gigabit PON (GPON) as well as next generation WDM PON and OFDM PON. Also this book examines the integrated optical and wireless access networks. Concentrating on two issues in these networks: media access control (MAC) and resource allocation. These two problems can greatly affect performances of PONs such as network resource utilization and QoS of end users. Finally this book will discuss various solutions to address the MAC and resource allocation issues in various PON networks.

FMAC: A fair MAC protocol for coexisting cognitive radio networks

Abstract: Cognitive radio is viewed as a disruptive technology innovation to improve spectrum efficiency. The deployment of coexisting cognitive radio networks, however, raises a great challenge to the medium access control (MAC) protocol design. While there have been many MAC protocols developed for cognitive radio networks, most of them have not considered the coexistence of cognitive radio networks, and thus do not provide a mechanism to ensure fair and efficient coexistence of cognitive radio networks. In this paper, we introduce a novel MAC protocol, termed fairness-oriented media access control (FMAC), to address the dynamic availability of channels and achieve fair and efficient coexistence of cognitive radio networks. Different from the existing MACs, FMAC utilizes a three-state spectrum sensing model to distinguish whether a busy channel is being used by a primary user or a secondary user from an adjacent cognitive radio network. As a result, secondary users from coexisting cognitive radio networks are able to share the channel together, and hence to achieve fair and efficient coexistence. We develop an analytical model using two-level Markov chain to analyze the performance of FMAC including throughput and fairness. Numerical results verify that FMAC is able to significantly improve the fairness of coexisting cognitive radio networks while maintaining a high throughput.

Flow control method for process of sharing WiFi (wireless fidelity) hot spot for mobile terminals

Abstract: The invention discloses a flow control method for a process of sharing WiFi (wireless fidelity) hot spot for mobile terminals. In the flow control method, a mobile terminal starting a WiFi hot spot shared network serves as a host, and a mobile terminal which is connected with the host through WiFi to access to the network serves as a slave. The flow control method includes that the host starts the WiFi hot spot share network functions to receive network access request information of the slave, and replies the network access request of the slave and then acquires terminal identification information of the slave; after the slave accesses to the network, the host monitors flow of the slave and displays the terminal identification information of the slave; further, the host provides a flow control interface capable of controlling flow according to the terminal identification information to control flow of the slave according to corresponding arrangements. By the flow control method, flow of the mobile terminals accessing to the WiFi hot spot network can be monitored in real time conveniently, and flow of mobile terminals at specific MAC (media access control) address or IP (protocol) address can be limited.

Method and Apparatus

Abstract: A method is provided The method comprises performing a media access control reset The media access control reset is provided without performing at least one of a radio link control reset and a packet data convergence protocol reset

A hybrid reservation-based MAC protocol for underwater acoustic sensor networks

Abstract: Due to the characteristics of underwater acoustic channel, such as long propagation delay and low available bandwidth, media access control (MAC) protocol designed for the underwater acoustic sensor network (UWASN) is quite different from that for the terrestrial wireless sensor network. However, for the contention-based MAC protocols, the packet transmission time is long because of the long preamble in real acoustic modems, which increase the packet collisions. And the competition phase lasts for long time when many nodes are competing for the channel to access. For the schedule-based MAC protocols, the delay is too long, especially in a UWASN with low traffic load. In order to resolve these problems, a hybrid reservation-based MAC (HRMAC) protocol is proposed for UWASNs in this paper. In the proposed HRMAC protocol, the nodes reserve the channel by declaring and spectrum spreading technology is used to reduce the collision of the control packets. Many nodes with data packets to be transmitted can reserve the channel simultaneously, and nodes with reserved channel transmit their data in a given order. The performance analysis shows that the proposed HRMAC protocol can improve the channel efficiency greatly. Simulation results also show that the proposed HRMAC protocol achieves better performance, namely higher network throughput, lower packet drop ratio, smaller end-to-end delay, less overhead of control packets and lower energy overhead, compared to existing typical MAC protocols for the UWASNs.

Performance analysis of grouping strategy for dense IEEE 802.11 networks

Abstract: In IEEE 802.11 networks, how to improve the efficiency of contention-based media access is an important, challenging issue. Recently, the grouping strategy is introduced in the IEEE 802.11ah standard to alleviate the channel contention. In IEEE 802.11ah networks, stations can be divided into groups and each group is only allowed to access wireless channel during the designated channel access period. By limiting the number of stations participating in the channel contention, it is anticipated that such a grouping strategy could substantially improve the communication efficiency. However, how to allocate the channel among different groups and how to adjust the number and sizes of groups are still open issues. In this paper, we first study the impact of the grouping strategy on the network performance, and then propose an analytical model to track the performance under saturated traffic. The accuracy of our model has been validated by simulation results. Our analytical model and results also provide important guidelines in optimizing grouping parameters.

Versatile lane configuration using a pcie pie-8 interface

Abstract: Each PCIe device may include a media access control (MAC) interface and a physical (PHY) interface that support a plurality of different lane configurations These interfaces may include hardware modules that support 1×32, 2×16, 4×8, 8×4, 16×2, and 32×1 communication Instead of physically connecting each of the hardware modules in the MAC interface to respective hardware modules in the PHY interface using dedicated traces, the device may include two bus controllers that arbitrate which hardware modules are connected to a internal bus coupling the two interfaces When a different lane configuration is desired, the bus controller couples the corresponding hardware module to the internal bus In this manner, the different lane configurations share the same lanes (and wires) of the bus as the other lane configurations Accordingly, the shared bus only needs to include enough lanes (and wires) necessary to accommodate the widest lane configuration

Group-Based Signaling and Access Control for Cellular Machine-to-Machine Communication

Abstract: Global connectivity and broad coverage of cellular networks constitute a platform for ubiquitous machine-to-machine (M2M) service provisioning on a large scale. However, the access attempt to the radio access network from a massive number of devices demands new cellular access mechanism and signaling design to avoid congestion of control channels. We propose group-based access and signaling policies through a two-level device partitioning, namely, paging groups and access groups. Group paging enables the base station to coordinate access to the network and hence control the random access channel (RACH) overload. However, unlike the conventional scheme where each individual device attempts access to the network, our proposed group-based access mechanism delegates the random access procedure of the devices in an access group to a designated device, referred to as group delegate. In addition, we develop signaling schemes that enable resource allocation at the level of access groups for direct data report as well as a group-based connection via group delegate. Numerical results show that the group access procedure achieves significantly smaller access delay than the conventional access scheme. It is also shown that the group-based signaling policies require signaling overhead proportional to the number of group delegates instead of the number of devices. The proposed group-based schemes enable scaling the number of devices paged simultaneously while controlling the access signaling congestion, access delay, and overhead. Furthermore, the group-based connection enables more resource re- use and hence more efficient resource usage for data transmission.

Modeling and stability analysis of hybrid multiple access in the IEEE 802.15.4 protocol

Abstract: To offer flexible quality of service to several classes of applications, the medium access control (MAC) protocol of IEEE 802.15.4 wireless sensor networks (WSNs) combines the advantages of a random access with contention with a time division multiple access (TDMA) without contention. Understanding reliability, delay, and throughput is essential to characterizing the fundamental limitations of the MAC and optimizing its parameters. Nevertheless, there is not yet a clear investigation of the achievable performance of hybrid MAC. In this article, an analytical framework for modeling the behavior of the hybrid MAC protocol of the IEEE 802.15.4 standard is proposed. The main challenge for an accurate analysis is the coexistence of the stochastic behavior of the random access and the deterministic behavior of the TDMA scheme. The analysis is done in three steps. First, the contention access scheme of the IEEE 802.15.4 exponential back-off process is modeled through an extended Markov chain that takes into account channel, retry limits, acknowledgements, unsaturated traffic, and superframe period. Second, the behavior of the TDMA access scheme is modeled by another Markov chain. Finally, the two chains are coupled to obtain a complete model of the hybrid MAC. By using this model, the network performance in terms of reliability, average packet delay, average queuing delay, and throughput is evaluated through both theoretical analysis and experiments. The protocol has been implemented and evaluated on a testbed with off-the-shelf wireless sensor devices to demonstrate the utility of the analysis in a practical setup. It is established that the probability density function of the number of received packets per superframe follows a Poisson distribution. It is determined under which conditions the guaranteed time slot allocation mechanism of IEEE 802.15.4 is stable. It is shown that the mutual effect between throughput of the random access and the TDMA scheme for a fixed superframe length is critical to maximizing the overall throughput of the hybrid MAC. In high traffic load, the throughput of the random access mechanism dominates over TDMA due to the constrained use of TDMA in the standard. Furthermore, it is shown that the effect of imperfect channels and carrier sensing on system performance heavily depends on the traffic load and limited range of the protocol parameters. Finally, it is argued that the traffic generation model established in this article may be used to design an activation timer mechanism in a modified version of the CSMA/CA algorithm that guarantees a stable network performance.

Method and apparatus for performing backoff in wireless communication system

Abstract: A method and apparatus for performing backoff in a wireless communication system is provided. A user equipment (UE) identifies a prioritized access, receives a backoff parameter from a network, and determines whether or not to apply the received backoff parameter according to the prioritized access. The prioritized access corresponds to one of emergency access, high priority access, control element/information in media access control (MAC), radio link control (RLC) or packet data convergence protocol (PDCP), data radio bearer (DRB) for voice/video service, signaling radio bearer (SRB) 0, SRB 1, SRB 2, multimedia telephony service (MMTEL)-voice, MMTEL-video, and voice over long-term evolution (VoLTE).