Ronghui Hou

Hop-by-Hop Routing in Wireless Mesh Networks with Bandwidth Guarantees

Wireless Mesh Network (WMN) has become an important edge network to provide Internet access to remote areas and wireless connections in a metropolitan scale. In this paper, we study the problem of identifying the maximum available bandwidth path, a fundamental issue in supporting quality-of-service in WMNs. Due to interference among links, bandwidth, a well-known bottleneck metric in wired networks, is neither concave nor additive in wireless networks. We propose a new path weight which captures the available path bandwidth information. We formally prove that our hop-by-hop routing protocol based on the new path weight satisfies the consistency and loop-freeness requirements. The consistency property guarantees that each node makes a proper packet forwarding decision, so that a data packet does traverse over the intended path. Our extensive simulation experiments also show that our proposed path weight outperforms existing path metrics in identifying high-throughput paths.

Routing in multi-hop wireless mesh networks with bandwidth guarantees

This paper presents a distributed polynomial algorithm for finding the maximum bandwidth path in Wireless Mesh Networks (WMNs). Our proposed algorithm can be applied for designing the proactive hop-by-hop routing protocol with bandwidth guarantee. To the best of our knowledge, our work is the first distributed path calculation algorithm in WMNs.

Approximation Algorithm for QoS Routing with Multiple Additive Constraints

In this paper, we study the problem of computing the supported QoS from a source to a destination with multiple additive constraints. The problem has been shown to be NP-complete and many approximation algorithms have been developed. We propose a new approximation algorithm called multi-dimensional relaxation algorithm. We formally prove that our algorithm produces smaller approximation error than the existing algorithms. We further verify the performance by extensive simulations.

An approximation algorithm for QoS routing with two additive constraints

The problem of finding a path that satisfies two additive constraints, such as delay and cost, has been proved to be NP-complete. Many heuristic and approximation algorithms have been developed to identify a path given a certain QoS request. Unfortunately, these algorithms cannot be applied directly in the Internet because routing in the Internet is based on table lookups and routing tables are computed before a request arrives. In this paper, we develop an approximation algorithm for computing the supported QoS going across a domain. We analyze the approximation error of our algorithm and formally prove that the approximation error of our proposed algorithm is smaller than those of the existing approaches. We further verify our performance using extensive simulations.

Network selection policy based on effective capacity in heterogeneous wireless communication systems

A great deal of previous research was based on the concept of Shannon theory without considering the delay characteristic. However, in reality, different services have different delay constraints. In this paper, two new network selection policies are proposed for heterogeneous wireless communication systems using effective capacity, which incorporate delay in the transmission rate. Users can access the proper network after considering the delay demands of different services. Our proposed policies aim to maximize the entire throughput with different delay constraints. Both the mathematical analysis and simulations show that the proposed network selection policies can improve network throughput while providing quality-of-service guarantees.

Joint Congestion Control and Scheduling in Wireless Networks With Network Coding

This paper studies how to perform joint congestion control and scheduling with network coding in wireless networks. Under network coding, a node may need to buffer a sent packet for decoding a packet to be received later. If sent packets are not forgotten smartly, much buffer space will be taken up, leading to dropping of new incoming packets. This unexpected packet dropping harms the final throughput obtained, although optimal scheduling has been used. To solve the problem, we introduce a new node model incorporating a transmission-mode preassignment procedure and a scheduling procedure. The introduced transmission-mode preassignment avoids memorizing several sent packets to reduce buffer overhead. We develop a new scheduling policy based on our node model and analyze formally the stability property of a network system using the proposed policy. We finally evaluate the efficiency of our algorithm through simulations from the perspectives of throughput and packet loss ratio.

Coding- and interference-aware routing protocol in wireless networks

Network coding is considered as a promising technique to increase the bandwidth available in a wireless network. Many studies show that network coding can improve flow throughput only if an appropriate routing algorithm is used to identify paths with coding opportunities. Nevertheless, a good routing mechanism is very difficult to develop. Existing solutions either do not estimate the path bandwidth precisely enough or cannot identify the best path in some situations. In this paper, we describe our coding-aware routing protocol that provides a better path bandwidth estimate and is able to identify high throughput paths. Extensive NS2 simulations show that our protocol outperforms existing mechanisms.

Routing with QoS information aggregation in hierarchical networks

In this paper, we consider the problem of routing with two additive constraints in the hierarchical networks, such as the Internet. In order for scalability, the supported QoS information in the hierarchical networks has to be aggregated. We propose a novel method for aggregating the QoS information. To the best of our knowledge, our approach is the first study to use the area-minimization optimization, the de facto optimization problem of the QoS information aggregation. We use a set of real numbers to approximate the supported QoS between different domains. The size of the set is predefined so that advertisement overhead and the space requirement will not grow exponentially as the network size grows. The simulation results show that the proposed method outperforms the existing methods.

A Novel Interference Management Scheme in Underlay D2D Communication

This paper studies the interference management of D2D communications in cellular networks. We consider the underlay D2D communication, such that the signal quality of cellular user would be affected by D2D users. We explore the application of network coding to mitigate interference. In our proposed interference management scheme, the helper nodes overhears the signals from cellular users, and then, code the received packets and sends to the base station. We design the transmission policy for the helper node, and also describe how to select the helper nodes. Our simulation results show that the proposed interference management can effectively improve the spectrum efficiency and increase system throughput.

Capacity analysis of hybrid wireless networks with long-range social contacts behavior

Hybrid wireless networks are networks that are composed of both ad hoc transmissions and cellular transmissions. Many existing works have analyzed the capacity of hybrid wireless networks. By assuming the uniform traffic model that a source node would select a random node as the destination, the network capacity is a function of number of nodes and number of base stations. Nevertheless, the real network traffic pattern is related to the social behaviors of users. In this work, we study the capacity of hybrid wireless networks with the social traffic model under the L-maximum-hop routing policy. If two nodes are within L hops away, packets will be transmitted in the ad hoc mode; otherwise, packets are transmitted through the base stations. To our best knowledge, we are the first to study this problem and develop the capacity as a function of number of nodes, number of stations, traffic model parameters, and L.