Showing papers by "Geoffrey G. Messier published in 2005"
TL;DR: A new technique for performing space-time coding by using a phase shifting antenna feed network to manipulate the transmitted signal at RF frequencies and results indicate a performance improvement equivalent to conventional space- time codes.
Abstract: We introduce a new technique for performing space-time coding by using a phase shifting antenna feed network to manipulate the transmitted signal at RF frequencies. The advantage of this scheme is that it allows space-time coding to be implemented with only one transmit chain and amplifier. A code-division multiple-access (CDMA) system that can use this method of space-time coding is described. The antenna feed network is presented along with a modified version of the Alamouti code that is suitable for this application. Imperfections in the antenna phase shifting are quantified using an error vector magnitude (EVM) measure. System level CDMA simulations are also used to evaluate the overall performance of this "RF space-time coding" technique. The results indicate a performance improvement equivalent to conventional space-time codes.
7 citations
TL;DR: This work improves channel decoder performance on the code-division multiple-access (CDMA) forward link through more accurate calculation of the channel code trellis path metrics used to decode convolutional and turbo codes.
Abstract: This work improves channel decoder performance on the code-division multiple-access (CDMA) forward link through more accurate calculation of the channel code trellis path metrics used to decode convolutional and turbo codes. This is achieved by performing the metric calculations with better channel state estimates. Channel state estimation involves determining desired signal amplitude and interference plus noise variance at the channel decoder input. Two options are presented for performing this estimation. Standard estimation is a simple scheme that results from assuming all CDMA forward link interference and noise can be lumped into a single additive white Gaussian noise process. Improved estimation is a new and more accurate technique that separately accounts for the intracell interference and intercell interference plus thermal noise processes. Simulations show that the decoding of convolutional and turbo codes is significantly improved by the more accurate channel state information provided by improved estimation.
5 citations
28 Sep 2005
TL;DR: In this paper, a new CDMA system architecture for combining space time block coding and adaptive sectorization using an electronically tunable reflectarray is introduced, which enables adaptive beam patterns to be synthesized from a single RF signal.
Abstract: We introduce a new CDMA system architecture for combining space time block coding and adaptive sectorization using an electronically tunable reflectarray. The advantage of this architecture is that it allows both adaptive sectorization and space time coding to be implemented with only one base station transmit chain and amplifier. Tunable reflectarrays enable adaptive beam patterns to be synthesized from a single RF signal. It is shown that space time block codes can be implemented with these arrays though a combination of baseband processing and manipulation of the reflectarray phase response. Simulations illustrate that space time coding implemented using reflectarrays will significantly improve CDMA forward link performance, even when reflectarray imperfections are taken into account.
1 citations
01 Jan 2005
TL;DR: Simulations show that the decoding of convolutional and turbo codes is significantly proved by the more accurate channel state information provided by improved estimation, which separately accounts for the intracell interference and intercell interference plus thermal noise processes.
Abstract: This work improves channel decoder performance on the code-division multiple-access (CDMA) forward link through more accurate calculation of the channel code trellis path metrics used to decode convolutional and turbo codes. This is achieved by performing the metric calculations with better channel state estimates. Channel state estimation involves determining desired signal amplitude and interference plus noise variance at the channel decoder input. Two options are presented for performing this estimation. Standard estimation is a simple scheme that results from assuming all CDMA forward link interference and noise can be lumped into a single additive white Gaussian noise process. Improved estimation is a new and more accurate technique that separately accounts for the intracell interference and intercell interference plus thermal noise processes. Simulations show that the decoding of convolutional and turbo codes is significantly im- proved by the more accurate channel state information provided by improved estimation. Index Terms—Code-division multiple-access (CDMA), electro- magnetic radiative interference, error correction coding, estima- tion, Gaussian processes, land mobile radio cellular systems, mul- tipath channels, sequences, turbo coding, Viterbi decoding, Walsh sequences.