Cooperation without synchronization practical cooperative relaying for wireless networks
- 1. Cooperation without Synchronization: Practical Cooperative Relaying for Wireless Networks Abstract: Cooperative relay aims to realize the capacity of multi-antenna arrays in a distributed manner. However, the symbol-level synchronization requirement among distributed relays limits its use in practice. We propose to circumvent this barrier with a cross-layer protocol called Distributed Asynchronous Cooperation (DAC). With DAC, multiple relays can schedule concurrent transmissions with packet-level (hence coarse) synchronization. The receiver then extracts multiple versions of each relayed packet via a collision-resolution algorithm, thus realizing the diversity gain of cooperative communication. We demonstrate the feasibility of DAC by prototyping and testing it on the GNURadio/USRP software radio platform. To explore its relevance at the network level, we introduce a DAC-based medium access control (MAC) protocol, and a generic approach to integration of the DAC MAC/PHY layer into a typical routing algorithm. Considering the use of DAC for multiple network flows, we analyze the fundamental tradeoff between the improvement in diversity gain and the reduction in multiplexing opportunities. DAC is shown to improve the throughput and delay performance of lossy
- 2. networks with intermediate link quality. Our analytical results have also been confirmed via network-level simulation with ns-2. Existing System: A typical cooperative communication protocol allows a relay to overhear the source’s transmission, and then forward the data to the desired receiver in case the direct delivery attempt fails. Such a two-stage cooperative relay protocol establishes a virtual antenna array among multiple distributed transmitters, each with a single antenna, in order to boost the capacity of the link from the source to the destination. Proposed System: We also introduce a generic approach that can use the DAC MAC/PHY to improve existing routing protocols. In applying this approach to multiple network flows, we identify an important tradeoff between the diversity gain provided by concurrent relays, and the multiplexing loss due to the expanded interference region. Our analysis shows that DAC improves network throughput when the link loss rate is below a certain threshold, which can be accurately profiled for simplified topologies. Therefore, DAC is best applicable to lossy wireless networks (such as unplanned mesh networks), where it can enhance the network throughput by improving the reliability of bottleneck links with a low reception rate.
- 3. Hardware Requirements: • System : Pentium IV 2.4 GHz. • Hard Disk : 40 GB. • Floppy Drive : 1.44 Mb. • Monitor : 15 VGA Colour. • Mouse : Logitech. • RAM : 256 Mb. Software Requirements: • Operating system : - Windows XP. • Front End : - JSP • Back End : - SQL Server Software Requirements: • Operating system : - Windows XP. • Front End : - .Net • Back End : - SQL Server