Turbo Packet Combining for Broadband Space-Time BICM Hybrid-ARQ Systems with Co-Channel Interference

In this paper, efficient turbo packet combining for single carrier (SC) broadband multiple-input--multiple-output (MIMO) hybrid--automatic repeat request (ARQ) transmission with unknown co-channel interference (CCI) is studied. We propose a new frequency domain soft minimum mean square error (MMSE)-based signal level combining technique where received signals and channel frequency responses (CFR)s corresponding to all retransmissions are used to decode the data packet. We provide a recursive implementation algorithm for the introduced scheme, and show that both its computational complexity and memory requirements are quite insensitive to the ARQ delay, i.e., maximum number of ARQ rounds. Furthermore, we analyze the asymptotic performance, and show that under a sum-rank condition on the CCI MIMO ARQ channel, the proposed packet combining scheme is not interference-limited. Simulation results are provided to demonstrate the gains offered by the proposed technique.Comment: 12 pages, 7 figures, and 2 table

Frequency Domain Hybrid-ARQ Chase Combining for Broadband MIMO CDMA Systems

In this paper, we consider high-speed wireless packet access using code division multiple access (CDMA) and multiple-input multiple-output (MIMO). Current wireless standards, such as high speed packet access (HSPA), have adopted multi-code transmission and hybrid-automatic repeat request (ARQ) as major technologies for delivering high data rates. The key technique in hybrid-ARQ, is that erroneous data packets are kept in the receiver to detect/decode retransmitted ones. This strategy is refereed to as packet combining. In CDMA MIMO-based wireless packet access, multi-code transmission suffers from severe performance degradation due to the loss of code orthogonality caused by both interchip interference (ICI) and co-antenna interference (CAI). This limitation results in large transmission delays when an ARQ mechanism is used in the link layer. In this paper, we investigate efficient minimum mean square error (MMSE) frequency domain equalization (FDE)-based iterative (turbo) packet combining for cyclic prefix (CP)-CDMA MIMO with Chase-type ARQ. We introduce two turbo packet combining schemes: i) In the first scheme, namely "chip-level turbo packet combining", MMSE FDE and packet combining are jointly performed at the chip-level. ii) In the second scheme, namely "symbol-level turbo packet combining", chip-level MMSE FDE and despreading are separately carried out for each transmission, then packet combining is performed at the level of the soft demapper. The computational complexity and memory requirements of both techniques are quite insensitive to the ARQ delay, i.e., maximum number of ARQ rounds. The throughput is evaluated for some representative antenna configurations and load factors to show the gains offered by the proposed techniques.Comment: Submitted to IEEE Transactions on Vehicular Technology (Apr 2009

Frequency domain packet combining with integrated MMSE block turbo equalization for broadband MIMO communication

International audienceThis paper introduces a new packet combining technique with integrated minimum mean square error (MMSE) turbo equalization for single carrier broadband multi-antenna coded transmission. The proposed scheme considers each trans- mission as an additional set of virtual receive antennas and combines multiple transmissions in the frequency domain with very low computational complexity. Block error rate (BLER) curves, obtained via computer simulations, indicate that the technique has near optimal performance

Packet combining with chip level frequency domain turbo equalization for multi-code transmission over multi-antenna broadband channel

International audienceIn this paper, we introduce two packet combining schemes with low complexity minimum mean square error (MMSE) turbo equalization for single user multi-code CDMA transmission over a broadband multiple input multiple output (MIMO) channel. The first scheme considers each transmission as an additional set of virtual receive antennas and combines multiple transmissions using a frequency domain chip level turbo equalizer. The second scheme performs frequency domain turbo equalization separately for each transmission then combines filter outputs. A comparative study in terms of performance and complexity is conducted to show the great potential of packet combining with integrated turbo equalization

Joint hybrid ARQ and iterative space-time equalization for coded transmission over MIMO-ISI channel

International audienceThis paper focuses on the problem of efficient packet combining techniques for coded systems with hybrid automatic repeat request (ARQ) protocols operating over the frequency selective fading multiple input multiple output (MIMO) channel. We introduce a receiver scheme where space-time soft equalization is integrated into the packet combiner. This allows to create at each transmission an additional set of virtual receive antennas, thereby increasing the diversity order of the system. We also propose a second packet combining scheme where equalization is performed separately for each transmission. Iterative channel estimation is also investigated, and a training scheme where the pilot symbols are not retransmitted is introduced. Block error rate (BLER) performance is investigated via computer simulations for both perfect and imprecise channel state information (CSI) at the receiver side for demonstrating the potential of integrated soft equalization-based packet combining for transmission over multipath MIMO channels