Multiple Unicast Transmissions Research Articles

Energy efficient broadcast protocols for asynchronous duty-cycled wireless sensor networks

In asynchronous duty-cycled wireless sensor networks (WSNs), each node has its own sleep schedule that is independent of the schedules of neighboring nodes. Since each node follows its own independent sleep schedule, the probability that a node’s neighbors will wake up concurrently is quite low. For this reason, each single hop broadcast must be completed through multiple unicast transmissions, and the sender node must remain awake until all of its neighboring nodes have received the broadcast packet. In this paper, we present two energy efficient broadcast protocols, namely Broadcast Progress-based Efficient Multihop Broadcast (BPEMB) protocol and Tree-based Efficient Multihop Broadcast (TEMB) protocol, for asynchronous duty-cycled WSNs. In both of the proposed protocols, the decision of whether to transmit the broadcast packet is based on the link quality information and without any forwarder’s guidance list. The redundant transmissions and collisions are avoided effectively with cooperation among the neighbors, so that the node with the best link quality to the receiver node takes responsibility to forward the packet to the receiver node. With this approach, nodes that are not involved in transmitting the broadcast packet can go to sleep and save their energy. In the BPEMB protocol, the forwarding decision of transmitting the broadcast packet is also influenced by the broadcast progress information, which is piggybacked in the broadcast packet. Through extensive simulations, we demonstrate that the proposed protocols can significantly improve the broadcast efficiency through reducing the energy consumption and minimizing the broadcast latency. The evaluation results also show that both the BPEMB and TEMB protocols can substantially reduce the collisions and redundant transmissions in asynchronous duty-cycled WSNs.

An Energy-Efficient Network-Wide Broadcast Protocol for Asynchronous Wireless Sensor Networks

It is very challenging to design an efficient network-wide broadcast protocol for asynchronous wireless sensor networks (AWSNs). Since the neighbors adopt sleep schedule independently and the probability that they wake up concurrently is very low, each single-hop broadcast has to be substituted by multiple unicast transmissions. Moreover, without the schedule knowledge of designated neighbors, a sender has to keep active until all these nodes are covered, which consumes a large amount of energy. In this letter, we propose an energy-efficient network-wide broadcast protocol (EENWB) for AWSNs. By introducing more aggressive cooperations among the neighboring senders, some senders can go to sleep much earlier, only at the cost of increasing the active periods of their cooperators slightly. Extensive simulation results show that EENWB can reduce the total energy consumption greatly.

Towards overhead mitigation in state-free geographic forwarding protocols for wireless sensor networks

Routing has been the most consumptive of all processes engaged in the Wireless Sensor Network communications, thus improving this consumptive process by minimizing the number of overhead bits transmitted is vital. This paper investigates the State-free Geographic Forwarding (SGF) protocols, which employ the cross-layering concept that combines the tasks of the routing and Medium Access Control (MAC) layer to minimize energy consumption. Unfortunately, the numerous SGF protocols proposed in the past utilize a modified variant of the basic 802.11 Distributed Coordinated Function MAC protocol for their routing operations due to its ability to mitigate the hidden terminal problem using the four-way handshake mechanism. The mechanism, however, incurs a substantial amount of overhead, which subsequently affects the end-to-end delay and energy consumption of the network. In line with these, a Directional Compact Geographic Forwarding (DCGF) approach is proposed to mitigate the excessive overhead generated due to the repeated subjection of a multi-hop network to the four-way handshake mechanism. The proposed DCGF utilizes a smart antenna and Quality of Service (QoS) aware aggregation approach to mitigate the spread in a broadcast received and multiple unicast transmissions, respectively. The simulation results show that the proposed DCGF significantly outperforms its base protocol (Dynamic Window Secure Implicit Geographic Forwarding) in terms of message overhead, energy consumed and end-to-end delay.

Multicast-Aware High-Performance Wireless Network-on-Chip Architectures

Today's multiprocessor platforms employ the network-on-chip (NoC) architecture as the preferable communication backbone. Conventional NoCs are designed predominantly for unicast data exchanges. In such NoCs, the multicast traffic is generally handled by converting each multicast message to multiple unicast transmissions. Hence, applications dominated by multicast traffic experience high queuing latencies and significant performance penalties when running on systems designed with unicast-based NoC architectures. Various multicast mechanisms such as XY-tree multicast and path multicast have already been proposed to enhance the performance of the traditional wireline mesh NoC incorporating multicast traffic. However, even with such added features, the multihop nature of the wireline mesh NoC leads to high network latencies and thus limits the achievable system performance. In this paper, to sustain the high-bandwidth and high-throughput requirements of emerging applications, we propose the design of a wireless NoC (WiNoC) architecture incorporating necessary multicast support. By integrating congestion-aware multicast routing with network coding, the WiNoC is able to efficiently handle heavy multicast injections. For applications running with a broadcast-heavy Hammer cache coherence protocol, the proposed multicast-aware WiNoC achieves an average of 47% reduction in message latency compared with the XY-tree-based multicast-aware mesh NoC. This network level improvement translates into a 26% saving in full-system energy delay product.

Complex field network-coded cooperation based on multi-user detection in wireless networks

Cooperative communication can achieve spatial diversity gains, and consequently combats signal fading due to multipath propagation in wireless networks powerfully. A novel complex field network-coded cooperation (CFNCC) scheme based on multi-user detection for the multiple unicast transmission is proposed. Theoretic analysis and simulation results demonstrate that, compared with the conventional cooperation (CC) scheme and network-coded cooperation (NCC) scheme, CFNCC would obtain higher network throughput and consumes less time slots. More-over, a further investigation is made for the symbol error probability (SEP) performance of CFNCC scheme, and SEPs of CFNCC scheme are compared with those of NCC scheme in various scenarios for different signal to noise ratio (SNR) values.

Practical Methods for Wireless Network Coding With Multiple Unicast Transmissions

We propose a simple yet effective wireless network coding and decoding technique for a multiple unicast network. It utilizes spatial diversity through cooperation between nodes which carry out distributed encoding operations dictated by generator matrices of linear block codes. In order to exemplify the technique, we make use of greedy codes over the binary field and show that the arbitrary diversity orders can be flexibly assigned to nodes. Furthermore, we present the optimal detection rule for the given model that accounts for intermediate node errors and suggest a low-complexity network decoder using the sum-product (SP) algorithm. The proposed SP detector exhibits near optimal performance. We also show asymptotic superiority of network coding over a method that utilizes the wireless channel in a repetitive manner without network coding (NC) and give related rate-diversity trade-off curves. Finally, we extend the given encoding method through selective encoding in order to obtain extra coding gains.

Compressed Video Streaming in Cooperative Wireless Networks with Interfering Transmissions

In this paper, we present a video streaming system for wireless networks that employs utility optimization of pre-compressed video at the application layer, together with a novel cooperative wireless physical layer (PHY) that allows interfering transmissions. Our system model considers multiple and independent unicast or multicast transmissions between network nodes while a number of them serve as relays. For this new PHY the average transmission rate that each sender-destination pair can achieve is estimated first. Next, we show that the utility optimization problem can be simplified due to the features of the proposed PHY. Subsequently, we devise a utility optimization algorithm that is executed independently at each sender and it derives the optimal video packets that should be sent in the wireless link given the calculated rate constraint. Simulation results demonstrate that for unicast video streaming scenarios and with the utility optimization framework, allowing packets to interfere is a better choice than employing a typical cooperative PHY. For the case of multicast video delivery the performance of the proposed scheme is significantly improved for good channel conditions while the improvement is minimized in the low channel SNR regime when compared to the unicast scenario.

Scalable and QoS-Aware Dynamic Slot Assignment and Piconet Partitioning to Enhance the Performance of Bluetooth Ad Hoc Networks

Bluetooth is a radio technology for wireless personal area networks in the 2.4 GHz ISM frequency band and allows short-range devices to be connected in the form of ad hoc networks. The Bluetooth medium access control protocol is based on a strict master/slave concept wherein any communication between slave devices has to go through the master. While this model is simple, the use of such a nonoptimal packet forwarding scheme incurs much longer delays between any two slave-devices as double the bandwidth is used by the master. In addition, if two or more devices want to communicate as a group, this can only be achieved by either multiple unicast transmissions or a piconet-wide broadcast from the master. To handle these issues efficiently, we propose a novel combination of dynamic slot assignment (DSA) and piconet partitioning. With DSA, the piconet master dynamically assigns slots to slaves so as to allow them to communicate directly with each other without any intervention from the master. Our proposed communication architecture provides for enhanced quality of service (QoS), better admission control, and multidevice conversation, which make a multicast-like communication feasible within the piconet. To widen the scope of DSA, we propose a QoS-aware enhanced DSA (EDSA) version where dynamic piconet partitioning and scatternet support are exploited by grouping devices into piconets as per their connection endpoints, enabling it to be employed over a scatternet. We have performed extensive simulations and observe that these schemes drastically enhance Bluetooth performance in terms of the delay and the throughput, while significantly reducing the network power consumption

A Broadcast Engagement ACK Mechanism for Reliable Broadcast Transmission in Mobile Ad Hoc Networks

How to safely or reliably flood a packet via broadcast scheme to all nodes in computer networks is an important issue. However, it is a big challenge and critical problem to broadcast data packets over mobile ad hoc networks reliably due to the unsettled wireless links, high mobility, and the lack of the acknowledgment (ACK) scheme. Many solutions deal with this problem by adopting multiple unicast transmissions to achieve reliable broadcast transmission in network layer. Unfortunately, it will cause severe duplicate transmissions and thus rapidly consume the limited network bandwidth. One simplest way to solve this drawback is to broadcast data packets in data link layer. But a serious problem will be arisen that replied ACK frames will collide at the sending node if we enforce each mobile node to reply an ACK after receiving the broadcast data frame. Therefore, in order to overcome the thorny problem, we proposed a broadcast engagement ACK mechanism (BEAM), which is completely compatible with the IEEE 802.11 protocol, for reliable broadcast transmission in the data link layer. We also show that the overhead of raising the reliability of broadcast transmission in network layer would be significantly reduced in data link layer. Simulation results show that the proposed BEAM can reach approximate 100% reliability even in heavy traffic load. We also indicate that the BEAM could be combined with other network layer broadcast schemes to approach higher flooding ratio as well as reduce bandwidth consumption effectively.

An enhanced and energy efficient communication architecture for Bluetooth wireless PANs

Bluetooth is a radio technology for Wireless Personal Area Networking (WPAN) operating in the 2.4 GHz ISM frequency band, and allows devices to be connected into short-range ad hoc networks. The Bluetooth medium access control protocol is based on the Master/Slave paradigm wherein any communication between slave devices has to go through the Master. While this model provides for simplicity, it incurs a longer delay between any two slave devices due to far from optimal packet forwarding, the use of double the bandwidth, and also additional energy wastage at the Master. Moreover, if more than two devices want to communicate as a group, this can only be achieved by either multiple unicast transmissions or a piconet-wide broadcast, clearly resulting in inefficiency. In this paper, we propose a novel Dynamic Slot Assignment (DSA) scheme whereby the Master device dynamically assigns slots to Slaves so as to allow them to communicate directly with each other without any Master intervention. This proposed communication architecture also provides for Quality of Service (QoS) requests, admission control, and multi-device conversation by which a multicast-like communication is implemented within a piconet. Through extensive simulation, we observe that DSA drastically enhances Bluetooth performance in terms of delay and throughput, while significantly reducing power consumption at the master and the overall piconet.

Reducing power consumption and enhancing performance by direct slave-to-slave and group communication in Bluetooth WPANs

Bluetooth is a promising wireless technology aiming at supporting electronic devices to be instantly interconnected into short-range ad hoc networks. The Bluetooth medium access control protocol is based on the Master/Slave concept wherein any communication between slave devices has to go through the Master. While this model provides for simplicity, it incurs longer delay between any two slaves devices due to far from optimal packet forwarding, the use of double the bandwidth, and also wastes additional energy at the Master. Moreover, if more than two devices want to communicate as a group, this can only be achieved by either multiple unicast transmissions or a piconet-wide broadcast, clearly resulting in inefficiency. In this paper, we propose a novel Dynamic Slot Assignment (DSA) scheme whereby the Master device dynamically assigns slots to Slaves so as to allow them to communicate directly with each other without any Master intervention. This proposed communication architecture also provides for Quality of Service (QoS) requests, admission control, and multi-device conversation by which a multicast-like communication is implemented within a piconet. Through extensive simulation, we observe that DSA drastically enhances Bluetooth performance in terms of delay and throughput, while significantly reducing power consumption at the master and also of the overall piconet.

Minimizing the Number of Multicast Transmissions in Single-Hop WDM Networks

The problem of minimizing the number of transmissions for a multicast transmission under the condition that the packet delay is minimum in single-hop wavelength division multiplexing (WDM) networks is studied in this paper. This problem is proved to be NP-complete. A heuristic multicast scheduling algorithm is proposed for this problem. Extensive simulations are performed to compare the performance of the proposed heuristic algorithm with two other multicast scheduling algorithms, namely, the greedy and no-partition scheduling algorithms. The greedy algorithm schedules as many destination nodes as possible in the earliest data slot. The no-partition algorithm schedules the destination nodes of a multicast packet to receive the packet in the same data slot without partitioning the multicast transmission into multiple unicast or multicast transmissions. Our simulation results show that (i) an algorithm which partitions a multicast transmission into multiple unicast or multicast transmissions may not always produce lower mean packet delay than the no-partition algorithm when the number of data channels in the system is limited and (ii) the proposed heuristic algorithm always produces lower mean packet delay than the greedy and the no-partition algorithms because this algorithm not only partitions a multicast transmission into multiple unicast or multicast transmissions to keep the packet delay low but also reduces the number of transmissions to conserve resources.

In single-hop WDM networks, a data packet can be transmitted from one node to another only when one of the transmitters of the source node and one of the receivers of the destination node are tuned to the same wavelength, i.e., a data packet is transmitted from one node to another without going through intermediate nodes. A hybrid multicast scheduling

This paper shows that, for single-hop wavelength division multiplexing (WDM) networks, a multicast scheduling algorithm which always tries to partition a multicast transmission into multiple unicast or multicast transmissions may not always produce lower mean packet delay than a multicast scheduling algorithm that does not partition multicast transmissions. The performance of a multicast scheduling algorithm may depend on the traffic conditions and the availability of the channel resource in the network. A hybrid multicast scheduling algorithm that can be used in single-hop WDM networks.