A Multiple-Copy Scheme for Multi-Channel Stop-and-Wait HARQ

HARQ (Hybrid Automatic Repeat Request) combines ARQ (Automatic Repeat Request) with FEC (Forward Error Correction) to provide a reliable way to ensure that data are received correctly and in sequence. A multiple-copy HARQ scheme is proposed for WiMAX (Worldwide Interoperability for Microwave Access) to reduce the waiting time of erroneously received data in the receivers’ buffer. In this project, the performances of WiMAX multi-channel stop-and-wait HARQ scheme are compared with that of the proposed multiple-copy HARQ scheme. The multiple-copy HARQ can send the same copy of a data burst on contiguous channels during noisy channel conditions so that the required time for an unsuccessfully received data burst to recover is shortened. It is beneficial for time sensitive data to have a shorter waiting time in a SS’s (Subscriber Station) buffer. The simulation results show that the multiple-copy HARQ scheme requires only 56% of the time that the original WiMAX HARQ needs to successfully deliver erroneous data bursts in the SS’s buffer. The throughput of the multiple-copy HARQ scheme can still reach more than 73% of the original WiMAX HARQ scheme’s throughput

A transparent ARQ scheme for broadband wireless access

In this paper, we propose an Automatic Repeat reQuest (ARQ) technique for enhancing the reliability anti throughput of broadband wireless Internet access applications, and provide examples of its performance. ARQ is a method for making a link anti How more robust to errors. Other than enhancing link quality ARQ provides early error recovery, so that the transport layer does not lower the data throughput. T he cost of these enhancements is additional overhead. In this work, we have extensively analyzed our proposed ARQ scheme along with realistic wireless channel anti protocol stack models. We have quantified the performance gains of our ARQ scheme as reduced end-to-end delay, increased throughput, SNR gain anti fade margin, also providing the overhead costs. We have proposed anti analyzed enhanced features, namely Segmentation anti Reassembly (SAR) anti Bitmap Compression. We showed that these features reduce the overhead, the extent of which depends on the nature of the errors