Hybrid wireless networks combining the advantages of both mobile ad-hoc networks and infrastructure wireless networks have been receiving increased attention due to their ultra-high performance. An efficient data routing protocol is important in such networks for high network capacity and scalability. However, most routing protocols for these networks simply combine the ad-hoc transmission mode with the cellular transmission mode, which inherits the drawbacks of ad-hoc transmission.
This paper presents a Distributed Three-hop Routing protocol (DTR) for hybrid wireless networks. To take full advantage of the widespread base stations, DTR divides a message data stream into segments and transmits the segments in a distributed manner. It makes full spatial reuse of a system via its high speed ad-hoc interface and alleviates mobile gateway congestion via its cellular interface. Furthermore, sending segments to a number of base stations simultaneously increases throughput and makes full use of widespread base stations.
DTR significantly reduces overhead due to short path lengths and the elimination of route discovery and maintenance. DTR also has a congestion control algorithm to avoid overloading base stations. Theoretical analysis and simulation results show the superiority of DTR in comparison with other routing protocols in terms of throughput capacity, scalability, and mobility resilience. The results also show the effectiveness of the congestion control algorithm in balancing the load between base stations.
Wireless networks including infrastructure wireless networks and mobile ad-hoc networks (MANETs) have attracted significant research interest. The growing desire to increase wireless network capacity for high performance applications has stimulated the development of hybrid wireless networks. A hybrid wireless network consists of both an infrastructure wireless network and a mobile ad-hoc network. Wireless devices such as smart-phones, tablets and laptops, have both an infrastructure interface and an ad-hoc interface. As the number of such devices has been increasing sharply in recent years, a hybrid transmission structure will be widely used in the near future. Such a structure synergistically combines the inherent advantages and overcome the disadvantages of the infrastructure wireless networks and mobile ad-hoc networks. In a mobile ad-hoc network, with the absence of a central control infrastructure, data is routed to its destination through the intermediate nodes in a multi-hop manner. The multi-hop routing needs on-demand route discovery or route maintenance.
Since the messages are transmitted in wireless channels and through dynamic routing paths, mobile ad-hoc networks are not as reliable as infrastructure wireless networks. Furthermore, because of the multi-hop transmission feature, mobile ad-hoc networks are only suitable for local area data transmission. The infrastructure wireless network (e.g., cellular network) is the major means of wireless communication in our daily lives. It excels at inter-cell communication (i.e., communication between nodes in different cells) and Internet access. It makes possible the support of universal network connectivity and ubiquitous computing by integrating all kinds of wireless devices into the network. In an infrastructure network, nodes communicate with each other through base stations (BSes).
A hybrid wireless network synergistically combines an infrastructure wireless network and a mobile ad-hoc network to leverage their advantages and overcome their shortcomings, and finally increases the throughput capacity of a wide-area wireless network. A routing protocol is a critical component that affects the throughput capacity of a wireless network in data transmission. Most current routing protocols in hybrid wireless networks simply combine the cellular transmission mode (i.e., BS transmission mode) in infrastructure wireless networks and the ad-hoc transmission mode in mobile ad-hoc networks. That is, as shown in Fig. 1a, the protocols use the multi-hop routing to forward a message to the mobile gateway nodes that are closest to the BSes or have the highest bandwidth to the BSes. The bandwidth of a channel is the maximum throughput (i.e., transmission rate in bits/s) that can be achieved. The mobile gateway nodes then forward the messages to the BSes, functioning as bridges to connect the ad-hoc network and the infrastructure network.
Since BSes are connected with a wired backbone, we assume that there are no bandwidth and power constraints on transmissions between BSes. We use intermediate nodes to denote relay nodes that function as gateways connecting an infrastructure wireless network and a mobile ad-hoc network. We assume every mobile node is dual-mode; that is, it has ad-hoc network interface such as a WLAN radio interface and infrastructure network interface such as a 3G cellular interface. DTR aims to shift the routing burden from the ad-hoc network to the infrastructure network by taking advantage of widespread base stations in a hybrid wireless network. Rather than using one multi-hop path to forward a message to one BS, DTR uses at most two hops to relay the segments of a message to different BSes in a distributed manner, and relies on BSes to combine the segments.
We simplify the routings in the infrastructure network for clarity. As shown in the figure, when a source node wants to transmit a message stream to a destination node, it divides the message stream into a number of partial streams called segments and transmits each segment to a neighbor node. Upon receiving a segment from the source node, a neighbor node locally decides between direct transmission and relay transmission based on the QoS requirement of the application. The neighbor nodes forward these segments in a distributed manner to nearby BSes. Relying on the infrastructure network routing, the BSes further transmit the segments to the BS where the destination node resides. The final BS rearranges the segments into the original order and forwards the segments to the destination. It uses the cellular IP transmission method  to send segments to the destination if the destination moves to another BS during segment transmission.
OPTIMAL MULTI-HOP CELLULAR ARCHITECTURE FOR WIRELESS COMMUNICATIONS
AUTOHRS: Y. H. Tam, H. S. Hassanein, S. G. Akl, and R. Benkoczi
PUBLISH: Proc. Local Comput. Netw., 2006, pp. 738–745.
Multi-hop relaying is an important concept in future generation wireless networks. It can address the inherent problems of limited capacity and coverage in cellular networks. However, most multi-hop relaying architectures are designed based on a small fixed-cell-size and a dense network. In a sparse network, the throughput and call acceptance ratio degrades because distant mobile nodes cannot reach the base station to use the available capacity. In addition, a fixed-cell-size cannot adapt to the dynamic changes of traffic pattern and network topology. In this paper, we propose a novel multi-hop relaying architecture called the adaptive multi-hop cellular architecture (AMC). AMC adapts the cell size to an optimal value that maximizes throughput by taking into account the dynamic changes of network density, traffic patterns, and network topology. To the best of our knowledge, this is the first time that adaptive (or optimal) cell size is accounted for in a multi-hop cellular environment. AMC also achieves the design goals of a good multi-hop relaying architecture. Simulation results show that AMC outperforms a fixed-cell-size multi-hop cellular architecture and a single-hop case in terms of data throughput, and call acceptance ratio.
COOPERATIVE PACKET DELIVERY IN HYBRID WIRELESS MOBILE NETWORKS: A COALITIONAL GAME APPROACH
AUTOHRS: K. Akkarajitsakul, E. Hossain, and D. Niyato
PUBLISH: IEEE Trans. Mobile Comput., vol. 12, no. 5, pp. 840–854, May 2013
We consider the problem of cooperative packet delivery to mobile nodes in a hybrid wireless mobile network, where both infrastructure-based and infrastructure-less (i.e., ad hoc mode or peer-to-peer mode) communications are used. We propose a solution based on a coalition formation among mobile nodes to cooperatively deliver packets among these mobile nodes in the same coalition. A coalitional game is developed to analyze the behavior of the rational mobile nodes for cooperative packet delivery. A group of mobile nodes makes a decision to join or to leave a coalition based on their individual payoffs. The individual payoff of each mobile node is a function of the average delivery delay for packets transmitted to the mobile node from a base station and the cost incurred by this mobile node for relaying packets to other mobile nodes. To find the payoff of each mobile node, a Markov chain model is formulated and the expected cost and packet delivery delay are obtained when the mobile node is in a coalition. Since both the expected cost and packet delivery delay depend on the probability that each mobile node will help other mobile nodes in the same coalition to forward packets to the destination mobile node in the same coalition, a bargaining game is used to find the optimal helping probabilities. After the payoff of each mobile node is obtained, we find the solutions of the coalitional game which are the stable coalitions. A distributed algorithm is presented to obtain the stable coalitions and a Markov-chain-based analysis is used to evaluate the stable coalitional structures obtained from the distributed algorithm. Performance evaluation results show that when the stable coalitions are formed, the mobile nodes achieve a nonzero payoff (i.e., utility is higher than the cost). With a coalition formation, the mobile nodes achieve higher payoff than that when each mobile node acts alone.
EFFICIENT RESOURCE ALLOCATION IN HYBRID WIRELESS NETWORKS
AUTOHRS: B. Bengfort, W. Zhang, and X. Du
PUBLISH: Proc. Wireless Commun. Netw. Conf., 2011, pp. 820–825.
n this paper, we study an emerging type of wireless network – Hybrid Wireless Networks (HWNs). A HWN consists of an infrastructure wireless network (e.g., a cellular network) and several ad hoc nodes (such as a Mobile ad hoc network). Forming a HWN is a very cost-effective way to improve wireless coverage and the available bandwidth to users. Specifically, in this work we investigate the issue of bandwidth allocation in multi-hop HWNs. We propose three efficient bandwidth allocation schemes for HWNs: top-down, bottom-up, and auction-based allocation schemes. In order to evaluate the bandwidth allocation schemes, we develop a simulated HWN environment. Our simulation results show that the proposed schemes achieve good performance: the schemes can achieve maximum revenue/utility in many cases, while also providing fairness. We also show that each of the schemes has merit in different application scenarios.
Existing methods in the Two-hop transmission protocol in terms of the elimination of route maintenance and the limited number of hops in routing. In two-hop, when a node’s bandwidth to a BS is larger than that of each neighbor, it directly sends a message to the BS. Otherwise, it chooses a neighbor with a higher channel and sends a message to it, which further forwards the message to the BS uses distributed transmission involving multiple cells, which makes full use of system resources and dynamically balances the traffic load between neighboring cells. In contrast, Two-hop employs single-path transmission.
Direct combination of the two transmission modes inherits the following problems that are rooted in the ad-hoc transmission mode.
High overhead: Route discovery and maintenance incur high overhead. The wireless random access medium access control (MAC) required in mobile ad-hoc networks, which utilizes control handshaking and a back-off mechanism, further increases overhead.
Hot spots: The mobile gateway nodes can easily become hot spots. The RTS-CTS random access, in which most traffic goes through the same gateway, and the flooding employed in mobile ad-hoc routing to discover routes may exacerbate the hot spot problem. In addition, mobile nodes only use the channel resources in their route direction, which may generate hot spots while leave resources in other directions under-utilized. Hot spots lead to low transmission rates, severe network congestion, and high data dropping rates.
Low reliability: Dynamic and long routing paths lead to unreliable routing. Noise interference and neighbor interference during the multi-hop transmission process because a high data drop rate. Long routing paths increase the probability of the occurrence of path breakdown due to the highly dynamic nature of wireless ad-hoc networks.
- Route discovery and maintenance incur high overhead.
- The mobile gateway nodes can easily become hot spots.
- Dynamic and long routing paths lead to unreliable routing.
- Noise interference and neighbor interference during the multi-hop transmission process because a high data drop rate.
- Long routing paths increase the probability of the occurrence of path breakdown due to the highly dynamic nature of wireless ad-hoc networks.
We propose a Distributed Three-hop Data Routing protocol (DTR). In DTR, as shown in Fig. 1b, a source node divides a message stream into a number of segments. Each segment is sent to a neighbor mobile node. Based on the QoS requirement, these mobile relay nodes choose between direct transmissions or relay transmission to the BS. In relay transmission, a segment is forwarded to another mobile node with higher capacity to a BS than the current node. In direct transmission, a segment is directly forwarded to a BS. In the infrastructure, the segments are rearranged in their original order and sent to the destination. The number of routing hops in DTR is confined to three, including at most two hops in the ad-hoc transmission mode and one hop in the cellular transmission mode. To overcome the aforementioned shortcomings, DTR tries to limit the number of hops. The first hop forwarding distributes the segments of a message in different directions to fully utilize the resources, and the possible second hop forwarding ensures the high capacity of the forwarder.
DTR also has a congestion control algorithm to balance the traffic load between the nearby BSes in order to avoid traffic congestion at BSes. Using self-adaptive and distributed routing with high speed and short-path ad-hoc transmission, DTR significantly increases the throughput capacity and scalability of hybrid wireless networks by overcoming the three shortcomings of the previous routing algorithms.
It has the following features:
- Low overhead: It eliminates overhead caused by route discovery and maintenance in the ad-hoc transmission mode, especially in a dynamic environment.
- Hot spot reduction: It alleviates traffic congestion at mobile gateway nodes while makes full use of channel resources through a distributed multi-path relay.
- High reliability: Because of its small hop path length with a short physical distance in each step, it alleviates noise and neighbor interference and avoids the adverse effect of route breakdown during data transmission. Thus, it reduces the packet drop rate and makes full use of special reuse, in which several source and destination nodes can communicate simultaneously without interference.
- DTR eliminates overhead caused by route discovery and maintenance in the ad-hoc transmission mode, especially in a dynamic environment.
- DTR should alleviate traffic congestion at mobile gateway nodes while makes full use of channel resources through a distributed multi-path relay.
- Because of its small hop path length with a short physical distance in each step, it alleviates noise and neighbor interference and avoids the adverse effect of route breakdown during data transmission.
- DTR reduces the packet drop rate and makes full use of spacial reuse, in which several source and destination nodes can communicate simultaneously without interference.
- Network with High Throughput Performance.
HARDWARE & SOFTWARE REQUIREMENTS:
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