![]() In contrast, the Direct RDRAM memory system is architected for high bandwidth throughput, and a single Direct RDRAM device provides full bandwidth for a given channel of Direct RDRAM devices. Consequently, the on-chip and in-system data movements associated with any given command issued by the memory controller are always distributed across multiple DRAM devices in a single rank and also typically across different ranks in standard 64- or 72-bit-wide SDRAM and DDRx SDRAM memory systems. Moreover, high data rate DDR2 and DDR3 SDRAM devices do not contain enough banks in parallel in a single rank configuration to fully saturate the memory channel. Finally, testbeds, industrial practice, and current standard activities related to WMNs are highlighted.In the classical mesh topology of SDRAM and DDRx SDRAM memory systems, multiple DRAM devices are connected in parallel to form a given rank of memory. Theoretical network capacity and the state-of-the-art protocols for WMNs are explored with an objective to point out a number of open research issues. System architectures and applications of WMNs are described, followed by discussing the critical factors influencing protocol design. ![]() This paper presents a detailed study on recent advances and open research issues in WMNs. Despite recent advances in wireless mesh networking, many research challenges remain in all protocol layers. WMNs will deliver wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. They are undergoing rapid progress and inspiring numerous deployments. WMNs are anticipated to resolve the limitations and to significantly improve the performance of ad hoc networks, wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WMANs). Mesh clients can be either stationary or mobile, and can form a client mesh network among themselves and with mesh routers. The integration of WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be accomplished through the gateway and bridging functions in the mesh routers. ![]() They provide network access for both mesh and conventional clients. Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. 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% 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. 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. ![]() In this paper, we study how such practical directional antennas can improve the throughput of a WMN. 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. 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. 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. Three key factors that affect the usability of WMNs are high throughput, cost-effectiveness, and ease of deployability. Wireless mesh networks (WMNs) have been proposed as an effective solution for ubiquitous last-mile broadband access.
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