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

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.     

Efficient Patient Care Through Wireless Body Area Networks—Enhanced Technique for Handling Emergency Situations with Better Quality of Service

Wireless body area networks (WBAN) is a wireless network of sensors placed in and around the human body for monitoring the patient conditions remotely. The goal of WBAN networks is to report the patient condition to the monitoring system with maximum reliability and minimum delay and deliver the life critical data in the emergency situation with utmost priority. The proposed MAC protocol is aimed at delivery of emergency packets with maximum reliability and minimum delay through the introduction of mini slots in the beacon enabled superframe for exclusive transmission of the same. To improve the packet delivery ratio of the normal packets and decrease the energy consumption of the low data rate nodes, a packet rate based scheduled slot allocation is added to this protocol. Extensive simulations show that the proposed protocol is able to achieve nearly 98% packet delivery ratio and less than 100 ms delay for emergency packets. By varying the number of allocated scheduled slots based on the packet rate of the nodes, the proposed protocol has shown improved performance in the packet delivery ratio (93%) of normal packets as compared to IEEE 802.15.6 (85%), also the energy consumption of low data rate nodes has decreased by 64%. The results show that the proposed protocol is successful in realizing much better delay and packet delivery values for emergency and normal packets.     

Contention-based MAC protocols with erasure coding for wireless data networks

Contention-based medium access control (MAC) protocol is a key component for the success of wireless data networks. Conventional random access protocols like ALOHA and Carrier Sense Multiple Access (CSMA) suffer from packet collision which leads to low throughput. Aimed at improving the throughput performance, we propose to integrate erasure coding with contention-based MAC protocols for recovering collided packets. To demonstrate the effectiveness of this approach, we focus on combining erasure coding with slotted ALOHA and slotted non-persistent CSMA in this paper. The performances of the resulting protocols are evaluated by both analytical model and simulation. Simulation results match very well with analytical results and show that the system throughput is increased for low to medium traffic loading. Packet loss ratio is also improved considerably with our scheme when the maximum number of packet retransmission times is limited. However, the delay for our scheme is higher due to the longer waiting time in our scheme for recovering collided packets. It is also shown that delay can be significantly reduced if we choose appropriate coding parameters though throughput will be sacrificed.     

Modified Distributed Laxity Based Priority Scheduling Scheme

This paper proposes a medium access control (MAC) protocol for mobile Adhoc networks (MANET). The MAC layer is responsible for selecting the next packet to be transmitted and the timing of its transmission. Various new factors are introduced to determine the priority of the flow. The back-off mechanism devised by us grants node access to the channel based on the rank of its highest priority packets. It is clear that the proposed algorithm works better than the existing distributed laxity based priority-scheduling scheme and the same is proven using the simulation results using Glomosim.     

移动Ad Hoc网络中的一种功率控制MAC协议

本文提出了一种应用于移动Ad Hoc网络中的功率控制MAC（medium access contr01）协议，通过两个通信节点之间的控制包中的信息交换来决定数据包的发送功率以及其它邻节点下一次发送RTS控制包的功率。通过仿真与IEEE 802．11 MAC协议进行比较，由仿真结果可以看出，该协议能大大减少移动节点消耗的功率，提高节点的能量利用效率，并保持系统的吞吐量性能。     

A distributed laxity-based priority scheduling scheme for time-sensitive traffic in mobile ad hoc networks

Characteristics of Mobile Ad hoc Networks such as shared broadcast channel, bandwidth and battery power limitations, highly dynamic topology, and location dependent errors, make provisioning of quality of service (QoS) in such networks very difficult. The Medium Access Control (MAC) layer plays a very important role as far as QoS is concerned. The MAC layer is responsible for selecting the next packet to be transmitted and the timing of its transmission. We have proposed a new MAC layer protocol that includes a laxity-based priority scheduling scheme and an associated back-off scheme, for supporting time-sensitive traffic. In the proposed scheduling scheme, we select the next packet to be transmitted, based on its priority value which takes into consideration the uniform laxity budget of the packet, the current packet delivery ratio of the flow to which the packet belongs, and the packet delivery ratio desired by the user. The back-off mechanism devised by us grants a node access to the channel, based on the rank of its highest priority packet in comparison to other such packets queued at nodes in the neighborhood of the current node. We have studied the performance of our protocol that combines a packet scheduling scheme and a channel access scheme through simulation experiments, and the simulation results show that our protocol exhibits a significant improvement in packet delivery ratio under bounded end-to-end delay requirements, compared to the existing 802.11 DCF and the Distributed Priority Scheduling scheme proposed recently in [ACM Wireless Networks Journal 8 (5) (2002) 455–466; Proceedings of ACM MOBICOM '01, July 2001, pp. 200–209].     

A study of CDPD forward channel performance with coherent and differential detection

The media access control (MAC)-layer performance of the cellular digital packet data (CDPD) forward channel is studied and a new technique to improve the performance is proposed. The study is based on a computer simulation model wherein a CDPD base station continuously transmits a sequence of packets to a CDPD mobile station. We consider a Rayleigh fading channel and demonstrate how the performance metrics are affected by the channel characteristics. At the reception stage, we consider both coherent and differential reception. We argue that the throughput at the MAC layer is affected not only by the error performance of the physical layer, but also by several design characteristics of the MAC layer, including the block length and the alignment between blocks and packets. We illustrate the block error rate, packet error rate, and throughput performance by simulation results, and we show how the receiver may discard data, which is correctly received but nevertheless useless. Our main conclusion is that the CDPD forward-channel performance could be significantly improved should the identified deficiencies are eliminated. For this purpose, we propose a new automatic repeat request (ARQ) protocol that operates in the MAC layer to correct the erroneous blocks by means of retransmissions, and we study its performance. In addition, we discuss an adaptive scheme that maximizes the forward-channel performance by automatically enabling and disabling the ARQ protocol according to the channel conditions.     

Performance analysis of adaptive MAC protocol in VANETs considering the potential impact on throughput and transmission delays

The existing adaptive multichannel medium access control (MAC) protocols in vehicular ad hoc networks can adjust themselves according to different vehicular traffic densities. These protocols can increase throughput and guarantee a bounded transmission delay for real‐time safety applications. However, the optimized control channel interval is computed based on the maximum throughput while ignoring the strict safety packet transmission delay requirements. In this paper, we analyze the effects of the throughput and strict safety packet transmission delay with adaptive multichannel MAC protocols, such as connectivity‐aware MAC (CA MAC), adaptive multi‐priority distributed MAC (APDM), multi‐priority supported p‐persistent MAC (MP MAC), and variable control channel interval MAC (VCI) protocols. The performance and analysis results show that: (a) under a low data rate condition, CA MAC does not guarantee a strict safety packet transmission delay; (b) APDM not only satisfies the safety packet transmission requirement, but also provides the lowest safety packet transmission delay; (c) under a high data rate condition, we suggest APDM for use as an adaptive MAC protocol because it allows for high throughput for nonsafety packets and preserves low safety packet transmission delay; (d) under a low data rate condition with various data packet sizes, we suggest MP MAC for high throughput, which satisfies the safety packet transmission requirement; and (e) under low vehicle density and low data rate conditions, VCI can support high throughput. A balance between transmission delay and throughput must be considered to improve the optimal efficiency, reliability, and adaptability.     

POWMAC: a single-channel power-control protocol for throughput enhancement in wireless ad hoc networks

Transmission power control (TPC) has great potential to increase the throughput of a mobile ad hoc network (MANET). Existing TPC schemes achieve this goal by using additional hardware (e.g., multiple transceivers), by compromising the collision avoidance property of the channel access scheme, by making impractical assumptions on the operation of the medium access control (MAC) protocol, or by overlooking the protection of link-layer acknowledgment packets. In this paper, we present a novel power controlled MAC protocol called POWMAC, which enjoys the same single-channel, single-transceiver design of the IEEE 802.11 ad hoc MAC protocol but which achieves a significant throughput improvement over the 802.11 protocol. Instead of alternating between the transmission of control (RTS/CTS) and data packets, as done in the 802.11 scheme, POWMAC uses an access window (AW) to allow for a series of request-to-send/clear-to-send (RTS/CTS) exchanges to take place before several concurrent data packet transmissions can commence. The length of the AW is dynamically adjusted based on localized information to allow for multiple interference-limited concurrent transmissions to take place in the same vicinity of a receiving terminal. Collision avoidance information is inserted into the CTS packet and is used to bound/ the transmission power of potentially interfering terminals in the vicinity of the receiver, rather than silencing such terminals. Simulation results are used to demonstrate the significant throughput and energy gains that can be obtained under the POWMAC protocol.     

Distributed and Energy-Aware MAC for Differentiated Services Wireless Packet Networks: A General Queuing Analytical Framework

We present a novel queuing analytical framework for the performance evaluation of a distributed and energy-aware medium access control (MAC) protocol for wireless packet data networks with service differentiation. Specifically, we consider a node (both buffer-limited and energy-limited) in the network with two different types of traffic, namely, high-priority and low-priority traffic, and model the node as a MAP (Markovian arrival process)/PH (phase-type)/1/K nonpreemptive priority queue. The MAC layer in the node is modeled as a server and a vacation queuing model is used to model the sleep and wakeup mechanism of the server. We study standard exhaustive and number-limited exhaustive vacation models both in multiple vacation case. A setup time for the head-of-line packet in the queue is considered, which abstracts the contention and the back-off mechanism of the MAC protocol in the node. A nonideal wireless channel model is also considered, which enables us to investigate the effects of packet transmission errors on the performance behavior of the system. After obtaining the stationary distribution of the system using the matrix-geometric method, we study the performance indices, such as packet dropping probability, access delay, and queue length distribution, for high-priority packets as well as the energy saving factor at the node. Taking into account the bursty traffic arrival (modeled as MAP) and, therefore, the nonsaturation case for the queuing analysis of the MAC protocol, using phase-type distribution for both the service and the vacation processes, and combining the priority queuing model with the vacation queuing model make the analysis very general and comprehensive. Typical numerical results obtained from the analytical model are presented and validated by extensive simulations. Also, we show how the optimal MAC parameters can be obtained by using numerical optimization     

C-PRMA: a centralized packet reservation multiple access for localwireless communications

Packet-switched technology has been demonstrated as effective in cellular radio systems with short propagation delay, not only for data, but also for voice transmission. In fact, packet voice can efficiently exploit speech on-off activity to improve bandwidth utilization over time division multiple access (TDMA). Such an approach has been first suggested in the packet reservation multiple-access (PRMA) technique, an adaptation of the reservation ALOHA protocol to the cellular environment. However, being PRMA-based on a fixed frame scheme, it cannot thoroughly take advantage of the very short propagation delays encountered in microcellular systems that allow, for instance, the immediate retransmission of packets lost because of the interference noise from adjacent cells. We present the centralized PRMA, a natural enhancement of PRMA, in which the base station (BS) plays a central role in scheduling the transmissions of mobile stations (MSs). As a consequence, the transmission scheduling is very flexible and can account for the different traffic rate and delay constraints that emerge from voice and data integration. A packet retransmission policy to recover corrupted packets can be implemented and operated efficiently to provide an acceptable grade of service, even in a very noisy environment. The simulation results presented show the quantitative improvements of the centralized packet reservation multiple-access (C-PRMA) performance with respect to PRMA     

Queuing analysis of cooperative GBN-ARQ in wireless networks with peers contending for a common helper

This paper presents a new queuing model for performance analysis of go-back-N automatic repeat request (GBN-ARQ) protocol in cooperative wireless networks. In the model, cooperative medium access control (CoopMAC) protocol and dynamic radio link adaptation are taken into consideration. We analyze the probability distribution of the total delay witnessed by packets at the source side. Multi-rate transmissions are considered for all links with link adaptation. An enhanced Markov model is introduced in our model, which encompasses the following aspects: CoopMAC protocol at the MAC sub-layer; GBN-ARQ protocol at the logical link control sub-layer and the transmission using decode-and-forward cooperative diversity at the physical layer. The stochastic process of random feedback delay because of peers contending for a common helper is analyzed. The queuing system is modeled as a GI/M/1 Markov chain to acquire statistics of the exact queue length and the total delay. We analyze the effects of Doppler frequency shift and packet arrival rate on the total delay. The analysis is validated by simulation.     

Using Chain of Mobile Access Gateway to Reduce Delay for PMIPv6 Protocol Applied in WLAN

Wireless LAN controller (WLC) is used to manage and control Access points (APs) in Wireless local area network (WLAN).Proxy mobile IPv6 (PMIPv6) protocol supports network-layer mobility in WLC based WLAN.However,it introduces extra delay in delivering packets from the APs to the WLC.We use Mobile access gateway (MAG) chain to reduce packet delay.The handoff delay and packet delivery delay under the proposed scheme are derived,based on which we formulate the delay minimization problem whose solution leads to the optimal MAG chain length.Numerical analysis results indicate that the proposed scheme outperforms the existing scheme in terms of delay in the case when the delay between Local mobility anchor (LMA) and WLC is relatively greater than the delay between two neighboring WLCs.The proposed scheme is able to reduce packet loss resulting from the traditional handoff procedure introduced in the PMIPv6 protocol and that due to delay limitation.     

Small‐block interleaving for low‐delay cross‐packet forward error correction over burst‐loss channels

By adding the redundant packets into source packet block, cross‐packet forward error correction (FEC) scheme performs error correction across packets and can recover both congestion packet loss and wireless bit errors accordingly. Because cross‐packet FEC typically trades the additional latency to combat burst losses in the wireless channel, this paper presents a FEC enhancement scheme using the small‐block interleaving technique to enhance cross‐packet FEC with the decreased delay and improved good‐put. Specifically, adopting short block size is effective in reducing FEC processing delay, whereas the corresponding effect of lower burst‐error correction capacity can be compensated by deliberately controlling the interleaving degree. The main features include (i) the proposed scheme that operates in the post‐processing manner to be compatible with the existing FEC control schemes and (ii) to maximize the data good‐put in lossy networks; an analytical FEC model is built on the interleaved Gilbert‐Elliott channel to determine the optimal FEC parameters. The simulation results show that the small‐block interleaved FEC scheme significantly improves the video streaming quality in lossy channels for delay‐sensitive video. Copyright © 2013 John Wiley & Sons, Ltd.     

A hotspot mitigation protocol for ad hoc networks

Hotspots represent transient but highly congested regions in wireless ad hoc networks that result in increased packet loss, end-to-end delay, and out-of-order packets delivery. We present a simple, effective, and scalable hotspot mitigation protocol (HMP) where mobile nodes independently monitor local buffer occupancy, packet loss, and MAC contention and delay conditions, and take local actions in response to the emergence of hotspots, such as, suppressing new route requests and rate controlling TCP flows. We use analysis, simulation, and experimental results from a wireless testbed to demonstrate the effectiveness of HMP in mobile ad hoc networks. HMP balances resource consumption among neighboring nodes, and improves end-to-end throughput, delay, and packet loss. Our results indicate that HMP can also improve the network connectivity preventing premature network partitions. We present analysis of hotspots, and the detailed design of HMP. We evaluate the protocol’s ability to effectively mitigate hotspots in mobile ad hoc networks that are based on on-demand and proactive routing protocols.     

Highly Efficient Voice—Data Integration over Medium and High Capacity Wireless TDMA Channels

A new medium access control (MAC) protocol for mobile wireless communications is presented and investigated. We explore, via an extensive simulation study, the performance of the protocol when integrating voice and data traffic over two wireless channels, one of medium capacity (referring mostly to outdoor microcellular environments) and one of high capacity (referring to an indoor microcellular environment). Data message arrivals are assumed to occur according to a Poisson process and to vary in length according to a geometric distribution. We evaluate the voice packet dropping probability and access delay, as well as the data packet access and data message transmission delays for various voice and data load conditions. By combining two novel ideas of ours with two useful ideas which have been proposed in other MAC schemes, we are able to remarkably improve the efficiency of a previously proposed MAC scheme [5], and obtain very high voice sources multiplexing results along with most satisfactory voice and data performance and quality of service (QoS) requirements servicing. Our two novel ideas are the sharing of certain request slots among voice and data terminals with priority given to voice, and the use of a fully dynamic low-voice-load mechanism.     

移动自组网中基于部分网络编码的机会主义路由

完全网络编码可用以解决机会主义路由中空间重用及重复报文问题,但增大了报文平均延迟,且报文数据流表现出突发性特征,不利于目标节点解码.本文针对移动自组网提出基于部分网络编码的机会主义路由OR-PNC,采用任意长度部分网络编码方式对报文编码.实验表明OR-PNC可有效降低报文平均延迟达26%,目标节点应用层原始报文到达流更均衡.     

A channel reuse strategy with adaptive channel allocation for all-optical WDM networks

The fundamental problems of WDM networks are: (1) high rate of control packet loss and (2) high propagation delay for each (re)transmission. In this paper, we minimize the station randomness to access the control architecture introducing a collisions-free access scheme. We propose a synchronous protocol according which at the end of the propagation delay each station applies a distributed algorithm for packet transmission following the data channel collisions and the receiver collisions avoidance algorithms. We introduce two data transmission stages. The time difference between them is one packet transmission time. At the end of the first stage all data channels are free and can be reused by the remaining data packets during the second stage. The proposed protocol ensures a totally collisions-free performance. The main advantage is that the data channels reuse strategy applied during the second stage provides enhanced transmission probability to the rejected packets during the first stage. This allows the data packets to try retransmission in the same cycle without requiring control packets re-coordination that increases propagation delay. Thus, we achieve large number of data packets transmission, even more than the data channels number, providing throughput improvement and delay reduction, comparing with other studies.     

Performance analysis of prioritized parallel transmission MAC protocol in all‐IP wireless WAN

Prioritized parallel transmission MAC (PPTM) protocol is proposed for all‐IP wireless wide area network (WAN). In this paper, we analyse its performance and compare it with modified channel load sensing protocol (MCLSP). We model PPTM as a non‐preemptive priority queueing system and obtain a close form of transmission time delay for each priority class, throughput of the scheme, and number of packets in the queue in the Poisson arrival case. We find that PPTM achieves less transmission time delay than MCLSP does for high priority data. Hence, the overall performance of the system using PPTM is significantly improved. We verify the conclusions with simulation via a simplified all‐IP wireless WAN. Copyright © 2006 John Wiley & Sons, Ltd.     

IEEE 802.11 WLAN支持语音与数据业务的自适应传输方案研究

IEEE 802.11标准中的MAC协议当采用DCF和PCF时是一种随机竞争接入与轮询相结合的协议。该文通过仿真在分析研究此MAC协议对语音、数据业务综合传输性能的基础上,提出了一种支持语音与数据业务的自适应传输方案。仿真结果表明,在满足语音业务最大允许时延的前提下,自适应传输方案通过动态、合理地调整协议参数,可以提高数据业务的传输性能,从而增加网络容量。特别地,本方案不需要改动协议本身,易于实现。