Keith Holt

Wireless LAN: Past, Present, and Future

This paper retraces the historical development of wireless LAN technology in the context of the pursuit of ever higher data rate, describes the significant technical breakthroughs that are now occurring, and speculates on future directions that the technology may take over the remainder of the decade. The challenges that these developments have created for low power operation are considered, as well as some of the opportunities that are presented to mitigate them. The importance of MIMO as an emerging technology for IEEE 802.11 is specifically highlighted, both in terms of the significant increase in data rate and range that it enables as well as the considerable challenge that it presents for the development of low power wireless LAN products.

Space-time-frequency coding for OFDM-based WLANs

We study the impact of space-time-frequency processing techniques on the physical layer performance of an orthogonal frequency division multiplexing (OFDM) based wireless LAN (IEEE 802.11a/g). A space frequency code (SFC) with two different soft-input soft-output multiple antenna receivers is compared with an orthogonal space time block code (OSTBC) and a single antenna system. We find that the multiple antenna schemes outperform the single antenna scheme as expected with the OSTBC-OFDM scheme providing a diversity improvement and the SFC-OFDM scheme simultaneously improving the diversity and the achievable rate of the system. Throughput curves are used to benchmark the performance of the schemes for specific packet error rates (PERs) and demonstrate the value of switching between architectures/multi-antenna schemes in practical systems.

Low Complexity BICM-OFDM-based MIMO Receiver using Successive Interference Cancelation

This paper proposes a low complexity receiver for the next generation BICM-OFDM-based WLAN systems. It uses the multiple transmitting antennas in a spatial multiplexing (SM) mode. After successfully decoding one data stream, the proposed scheme regenerates the transmitted signal and removes its interference to other streams. Each stream independently employs bit interleaving in the frequency domain and uses convolutional codes to mitigate the effect of channel fading. The better stream is decoded first to reduce the error propagation problem. As packet error rate (PER) is used as a comparison metric, simulation results show that the proposed scheme outperforms a simple minimum-mean-squared-error (MMSE) receiver without successive interference cancellation (SIC) by about 2 dB in a 2times2 system