Throughput Of Wireless Mesh Networks Research Articles

A new medium access control scheme at relay nodes for throughput improvement in wireless mesh networks

The wireless mesh networks have been a very promising solution for providing last few miles wireless connectivity in the metropolitan area networks. A new medium access control scheme is proposed to improve throughput in wireless mesh networks. The proposed scheme is to adjust the minimum size of contention window of mesh clients according to the information of transmission queue at relay nodes. The relay node carries the load information on an ACK frame by using the reserved subtype fields. The proposed scheme gives a priority to the relay node for transmitting packets when the relay node becomes a bottleneck. The simulation results show much better performance from the proposed scheme in comparison with that from original CSMA/CA scheme.

Priority-Based STDMA Scheduling Algorithm to Enhance Throughput and Fairness in Wireless Mesh Networks

The aggregate throughput of wireless mesh networks (WMNs) can be significantly improved by equipping the mesh routers with multiple radios tuned to orthogonal channels. Not only the links using orthogonal channels can be activated at a time, but some links in the same channel also can be activated concurrently if the Signal-to-Interference-and-Noise Ratio (SINR) at their receivers is not lower than the threshold, which is the spatial-reuse characteristic. STDMA is considered as one of the medium access schemes that can exploit spatial reuse to improve network throughput. Past studies have shown that optimizing the performance of STDMA is NP-Hard. Therefore, we propose a STDMA-based scheduling algorithm that operates in a greedy fashion for WMNs. We show that the proposed algorithm enhances not only the throughput but also the fairness by capturing the essence of spatial-reuse approach of STDMA and giving medium access opportunities to each network element based on its priority. We furthermore validate our algorithm through theoretical analysis and extensive simulations and the results show that our algorithm can outperform state-of-the-art alternatives.

Destination-oriented Routing and Maximum Capacity Scheduling Algorithms in Cayley Graph Model for Wireless Mesh Network

Routing and scheduling act important roles in improving capacity and throughput in wireless mesh networks. In this paper, Cayley graph model is suggested for wireless Mesh Networks (WMN) with MIMO channels for efficient routing and fair scheduling. The model is based on the multiple interfaces, directional antennas, single channel mesh model. And the link edges or active edges can be viewed as connections between node pairs. A node can have as many links as its interface permits, but links are limited not conflicting with the interference model in wireless network. By placing edges into different channel plane virtually, the Cayley graph model allows a node to use maximum active edges under orthogonal channels. The model is helpful for WMN routing and scheduling schemes with the symmetry coding character in WMN. Consequently, layered active edge group scheduling algorithm and destination oriented routing schemes are proposed for maximum capacity and throughput. Furthermore, efficient transformations are used to take advantage of previous maximum active edge group scheduling for fairness.

Capacity and interference aware link scheduling with channel assignment in wireless mesh networks

Wireless mesh networks (WMNs) are receiving lot of attention in recent years due to the unique features such as low cost and easy deployment. The optimal routing in these networks depends on the link capacities determined by link scheduling. To increase the throughput and network capacity, use of multiple channels and interfaces has been introduced in these networks. But the presence of interference limits the use of link and channel assignment in these types of networks. In this paper, we present a novel approach for link scheduling and channel assignment (CA) to improve the overall capacity and throughput of WMNs. The problem of link scheduling and CA is formulated as a Linear Programming (LP) problem with associated constraints. Links are sorted and placed in a particular group based upon link cost metric (LCM). The LCM value is used to group the links together and placed in appropriate group for CA. As the links are sorted and placed in appropriate groups the corresponding entries are made in Link Assignment Matrix (LAM). Once the links are grouped using LCM, then CA for these links is done and corresponding entries are made in Channel Assignment Matrix (CAM). Two algorithms, one for link scheduling and other for CA, are proposed. Simulation results show that proposed scheme outperforms the earlier approaches with respect to packet delivery fraction, end-to-end delay, aggregate throughput, fairness index and packet loss rate.

Design of Node Locations for Indoor Wireless Mesh Network

In literatures, the performance of Wireless Mesh Network (WMN) has been analyzed by assuming the same quality for each hop. However, this assumption is hardly true in practice due to the physical obstructions of wireless link, especially for an indoor environment. Therefore, this paper revisits the analysis of WMN performance by taking the effect of physical obstructions into account instead of assuming an equally deterministic property for each hop. These obstructions cause the degradation of signal strength which relatively decrease the success rate oftransmission between hop to hop. This paper examines these physical concerns through the measured results and then the design of node locations can be achieved. Moreover, it is well known that the analysis of throughput in WMN has indicated the impact of near-far mesh locations. However, these examinations have neglected the quantity of user accessibility. Therefore, this paper presents the effect of user accessibility in terms of traffic intensity on WMN throughput. The simulations provide a substantial remark to realize the effect of physical obstruction and traffic intensity on designing WMN node locations.

On Optimizing Gateway Placement for Throughput in Wireless Mesh Networks

An innovative gateway placement scheme is proposed for wireless mesh networks (WMNs) in this paper. It determines the location of a gateway based on a new performance metric called multihop traffic-flow weight (MTW). The MTW computation takes into account many factors that impact the throughput of WMNs, that is, the number of mesh routers, the number of mesh clients, the number of gateways, traffic demand from mesh clients, locations of gateways, and possible interference among gateways. Thus, the proposed gateway placement scheme provides a framework of significantly improving throughput of WMNs through proper placement of gateways. To evaluate the performance of the new gateway placement scheme, a nonasymptotic throughput of WMNs is derived by considering TDMA scheduling. The derivations also provide a guideline for designing scheduling schemes of WMNs. Numeric results show that the proposed gateway placement scheme constantly outperforms other schemes by a large margin.

Exploiting multiple rates to maximize the throughput of wireless mesh networks

Current works on the joint routing and channel assignment (JRC) problem in wireless mesh networks (WMNs) assume that all links operate at the base rate. In other words, they do not consider the presence of multiple bit-rates. However, in multi-rate WMNs, the achievable throughput of a link operating at higher rates could be much less than its bit-rate when it has to contend with low-rate links. This is also known as the multirate sharing problem. To address the problem, we first present a numerical formulation for estimating the dynamic link capacity, which can indicate the degree of the multi-rate sharing problem. Next, we propose an optimization model called MR2C, which solves the JRC problem by considering the dynamic link capacity in order to maximize the throughput in multi-rate, multi-radio, multi-channel WMNs. We then reformulate the primal problem as a Lagrangian dual problem, and apply the subgradient method to approach the dual. Finally, since each subproblem in the dual problem is also a non-linear problem, we design a polynomialtime algorithm to solve it. Our experiment results demonstrate that the proposed capacity formulation can approximate the actual link throughput. We compare MR2C with the base-rate JRC model via simulations. The results show that MR2C achieves throughput gains of 3-4 times and recover from network failure efficiently.

Symbol-level network coding for wireless mesh networks

This paper describes MIXIT, a system that improves the throughput of wireless mesh networks. MIXIT exploits a basic property of mesh networks: even when no node receives a packet correctly, any given bit is likely to be received by some node correctly. Instead of insisting on forwarding only correct packets, MIXIT routers use physical layer hints to make their best guess about which bits in a corrupted packet are likely to be correct and forward them to the destination. Even though this approach inevitably lets erroneous bits through, we find that it can achieve high throughput without compromising end-to-end reliability. The core component of MIXIT is a novel network code that operates on small groups of bits, called symbols. It allows the nodes to opportunistically route groups of bits to their destination with low overhead. MIXIT's network code also incorporates an end-to-end error correction component that the destination uses to correct any errors that might seep through. We have implemented MIXIT on a software radio platform running the Zigbee radio protocol. Our experiments on a 25-node indoor testbed show that MIXIT has a throughput gain of 2.8x over MORE, a state-of-the-art opportunistic routing scheme, and about 3.9x over traditional routing using the ETX metric.

DMesh: Incorporating Practical Directional Antennas in Multichannel Wireless Mesh Networks

Wireless mesh networks (WMNs) have been proposed as an effective solution for ubiquitous last-mile broadband access. Three key factors that affect the usability of WMNs are high throughput, cost-effectiveness, and ease of deployability. In this paper, we propose DMesh, a WMN architecture that combines spatial separation from directional antennas with frequency separation from orthogonal channels to improve the throughput of WMNs. DMesh achieves this improvement without inhibiting cost-effectiveness and ease of deployability by utilizing practical directional antennas that are widely and cheaply available (e.g., patch and yagi) in contrast to costly and bulky smart beamforming directional antennas. Thus, the key challenge in DMesh is to exploit spatial separation from such practical directional antennas despite their lack of electronic steerability and interference nulling, as well as the presence of significant sidelobes and backlobes. In this paper, we study how such practical directional antennas can improve the throughput of a WMN. Central to our architecture is a distributed, directional channel assignment algorithm for mesh routers that effectively exploits the spatial and frequency separation opportunities in a DMesh network. Simulation results show that DMesh improves the throughput of WMNs by up to 231% and reduces packet delay drastically compared to a multiradio multichannel omni antenna network. A DMesh implementation in our 16-node 802.11b WMN testbed using commercially available practical directional antennas provides transmission control protocol throughput gains ranging from 31% to 57%