A phase feedback based extended space-time block code for enhancement of diversity

In this paper we propose a generalization of extended orthogonal space-time block codes (EO-STBCs) for MIMO (multi-input/multi-output) channels using four transmit antennas for quasi-static flat fading channels. Since full rate and complex orthogonal space-time block codes (STBCs) do not exist for more than two transmit antennas, we propose a feedback based STBC scheme. In this scheme, phases of certain symbols are rotated according to the feedback from the receiver which is equivalent to rotating the phases of the corresponding channel coefficients. Simulation results show that this rotation phase feedback method achieves a satisfactory performance and outperforms the previous closed-loop space-time block codes, even when the feedback is quantized

A two-hop amplify-and-forward scheme for extended orthogonal space time coding in cooperative networks

We investigate and propose a new amplify-and- forward cooperative relay networks scheme in which a full-rate and full-diversity extended- orthogonal space-time block coding (EOSTBC) scheme is used. Utilizing a feedback channel, a simple phase rotation is applied at the relay nodes to extract full diversity and array gain. A feedback quantization approach which reduces the overhead in the feedback channel for prac- tical systems is also proposed. The performance of the proposed scheme, with and without opti- mum power allocation strategy, is investigated. Average bit error rate simulations confirm the utility of the scheme. The results also confirm the improvement in bit error rate (BER) perfor- mance over quasi-orthogonal space time block codes (QOSTBC)

Closed-loop extended orthogonal space frequency block coding techniques for OFDM based broadband wireless access systems

A simple extended orthogonal space-frequency coded multiple input single output (MISO) orthogonal frequency division multiplexing (OFDM) transmitter diversity technique for wireless communications over frequency selective fading channels is presented. The proposed technique utilizes OFDM to transform frequency selective fading channels into multiple flat fading sub-channels on which space-frequency coding is applied. A four-branch transmitter diversity system is implemented without bandwidth expansion and with only one receive antenna. The associated simulations verify that the four-branch transmitter diversity scheme achieves a significant improvement in average bit-error rate (BER) performance. The proposed scheme also outperforms the previously reported scheme due to Yu, Keroueden, and Yuan with only single phase feedback, and that improvement is retained with quantized feedback. Since the angle feedback is on a per tone basis, the feedback information would be too large for any practical OFDM system. However, we adopt a method which exploits the correlation among the feedback terms for the subcarriers, i.e. a group based quantization technique to reduce the feedback overhead significantly, rendering this scheme attractive to broadband wireless access systems. The performance improvement of convolutionally concatenated space-frequency block coding (CCSBC) schemes is also investigated

An Enhanced Feedback Scheme for Extended Orthogonal Space-Frequency Block Coded MISO-OFDM Systems

A simple extended orthogonal space-frequency coded multiple input single output (MISO) orthogonal frequency division multiplexing (OFDM) transmitter diversity technique for wireless communications over frequency selective fading channels is presented. The proposed technique utilizes OFDM to transform frequency selective fading channels into multiple flat fading sub-channels on which space-frequency coding is applied. A four-branch transmitter diversity system is implemented without bandwidth expansion and with only one receive antenna. The associated simulations verify that the four-branch transmitter diversity scheme achieves a significant improvement in average bit-error rate (BER) performance. The proposed scheme also outperforms the previously reported scheme due to Yu et. al. with only single phase feedback, and that improvement is retained with quantized feedback. Since the angle feedback is on a per tone basis, the feedback information would be too large for any practical OFDM system. However, we adopt a method which exploits the correlation among the feedback terms for the subcarriers, i.e. a group based quantization technique to reduce the feedback overhead significantly, rendering this scheme attractive to broadband wireless access systems

Resource allocation and block coding within a three-stage collaborative broadband relay network

In this work we propose a power control algorithm for a multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) multi-hop collaborative relaying network. Using orthogonal and quasi-orthogonal block codes with three stage processing our algorithm optimally distributes available transmission power based on the architecture and the channel condition at each stage so as to minimize the end-to-end bit error rate (HER) of the entire relay network. For high data rate applications with maximum throughput (as expected for future OFDM systems), we employ a regenerative relaying process, where the relays at each stage decode and through collaborative processing, re-encode the received data before onward transmission to the next stage and then to the destination. We provide simulation results 1 that confirm the performance improvement in the end-to-end bit error rate (HER) of the network using our explicit power allocation algorithm as compared with equal power distribution technique

Adaptive resource allocation within three-stage OFDM relay networks

In this work we consider OFDM transmission, due to its potential for meeting the stringent quality of service (QoS) targets of next-generation broadband distributed wireless networks, over three-stage relay networks. In particular, we examine distributed adaptive space-frequency coding for generally asynchronous links composed of four transmit and/or receive antennas, i.e. exploiting quasi-orthogonal and extended-orthogonal coding schemes. The successful deployment of these closed-loop methods is dependent upon channel state information (CSI) being available for each stage of the network. Taking the maximum end-to-end data rate as the optimal criterion, an adaptive resource allocation (RA) scheme suitable for a wide range of signal-to-noise-ratios (SNRs) and a prescribed transmit power budget is proposed to distribute appropriate resources to each stage based on the channel state information (CSI) and knowledge of the network topology

Exploitation of quasi-orthogonal space time block codes in virtual antenna arrays: part II Monte Carlo-based throughput evaluation

A full rate and full diversity closed-loop quasi-orthogonal space time block coding scheme due to Toker, Lambotharan and Chambers is proposed for application in virtual antenna arrays. The performance gain is achieved through closed-loop operation involving feedback of phase rotation angle(s) calculated from channel state information (CSI) to the transmitter array. Throughput performance of the proposed scheme, with and without power optimisation, is investigated through Monte Carlo simulation with QPSK constellation signals. The results confirm the improvement in throughput performance over orthogonal space time block codes

A two-hop amplify-and-forward scheme for extended orthogonal space time coding in cooperative networks

We investigate and propose a new amplify-and- forward cooperative relay networks scheme in which a full-rate and full-diversity extended- orthogonal space-time block coding (EOSTBC) scheme is used. Utilizing a feedback channel, a simple phase rotation is applied at the relay nodes to extract full diversity and array gain. A feedback quantization approach which reduces the overhead in the feedback channel for prac- tical systems is also proposed. The performance of the proposed scheme, with and without opti- mum power allocation strategy, is investigated. Average bit error rate simulations confirm the utility of the scheme. The results also confirm the improvement in bit error rate (BER) perfor- mance over quasi-orthogonal space time block codes (QOSTBC)