Differential space-time shift-keying aided successive-relaying-assisted decode-and-forward cooperative multiuser CDMA

A Differential Space-Time Shift Keying (DSTSK) aided and successive relaying assisted multi-user Decode-and-Forward (DF) cooperative system is proposed. We employ low-complexity non-coherent detection, which does not require any channel state information, neither at the Relay Nodes (RNs) nor at the Destination Node (DN). More explicitly, the source nodes employ differentially encoded phase-shift-keying modulation, while the RNs perform Soft-Input Soft-Output Multiple-Symbol Differential Sphere Decoding (SISO-MSDSD) based DF relaying during the relaying phase. Similarly, DSTSK transmission is employed at the RNs, which is detected with the aid of SISO-MSDSD at the DN. More explicitly, three-stage serial-concatenated turbo encoding/decoding is employed throughout the system in order to enhance the attainable performance. Additionally, a maximum minimum-determinant based configuration selection algorithm is proposed to select the optimal DSTSK configuration for supporting a specific number of users. Moreover, we adopt a successive relaying architecture for recovering the conventional 50% half-duplex relaying induced throughput loss, at the cost of supporting less users

Norm-based joint transmit/receive antenna selection aided and two-tier channel estimation assisted STSK systems

We propose a simple yet effective norm-based joint transmit and receive antenna selection (NBJTRAS) assisted and two-tier channel estimation (TTCE) aided space-time shift keying (STSK) system, which is capable of significantly outperforming the conventional STSK system, while efficiently utilising available radio frequency (RF) chains. Specifically, the NBJTRAS carries out antenna selection based on the channel estimation (CE) generated using a low-complexity training based least square channel estimator by reusing RF chains. The selected sub-channel matrix is further refined by an efficient semi-blind CE and data detection scheme. Our simulation results show that only a few iterations are sufficient for the TTCE scheme to approach the optimal maximum-likelihood detection performance associated with perfectly channel state information

Coherent versus differential multiple-input multiple-output systems

In recent years, Multiple-Input-Multiple-Output (MIMO) techniques have attracted substantial attention due to their capability of providing spatial diversity and/or multiplexing gains. Inspired by the concept of Spatial Modulation (SM), the novel concept of Space-Time-Shift-Keying (STSK) was recently proposed, which is considered to have the following advantages: 1) STSK constitutes a generalized shift keying architecture, which is capable of striking the required trade-off between the required spatial and time diversity as well as multiplexing gain and includes SM and Space Shift Keying (SSK) as its special cases. 2) Its high degree of design-freedom, the above-mentioned flexible diversity versus multiplexing gain trade-off can be achieved by optimizing both the number and size of the dispersion matrices, as well as the number of transmit and receive antennas. 3) Similar to the SM/SSK schemes, the Inter-Antenna-Interference (IAI) may be eliminated and consequently, the adoption of single-antenna-based Maximum Likelihood (ML) detection becomes realistic in STSK schemes.In this report, our investigation can be classified into two major categories, Coherent STSK (CSTSK) and Differential STSK (DSTSK) schemes. For CSTSK, since Channel State Information (CSI) is required for data detection, Channel Estimation (CE) techniques become necessary. To be more explicit, we first briefly review the conventional Training Based CE (TBCE) and Semi-Blind CE (SBCE) schemes for the CSTSK MIMO schemes. In addition, we develop a Blockof-Bits Selection Based CE (BBSBCE) algorithm for CSTSK schemes for increasing the overall system’s throughput, while improving the accuracy of the CE. Additionally, it has been widely recognised that MIMO schemes are capable of achieving a diversity and/or multiplexing gain by employing multiple Antenna Elements (AEs) at the transmitter and/or the receiver. However, it should also noted that since MIMO systems utilize multiple RF chains, their power consumption and hardware costs become substantial. Against this background, we introduce the concept of (Antenna Selection) AS and propose a simple yet efficient AS algorithm, namely the Norm-Based Joint Transmit and Receive AS (NBJTRAS) for assisting MIMO systems.For DSTSK, since no CSI is required for differential detection schemes, it also draws our attention. However, in the absence of CE, the Conventional Differential Detection (CDD) schemes usually suffer from a 3 dB performance degradation and may exhibit an error-flow when Doppler frequency is excessive. In order to mitigate this problem, we investigate Multiple-Symbol Differential Sphere Detection (MSDSD) scheme and adopt it in our DSTSK scheme to improve the system performance, while reducing the detection complexity. Furthermore, based on our MSDSD detected DSTSK scheme, we propose a DSTSK aided Multi-User Successive Relaying aided Cooperative System (MUSRC), which is capable of supporting various number of users flexibly, while covering the conventional 50% throughput loss due to the half-duplex transmit and receive constraint of practical transceivers

Near-capacity joint channel estimation and three-stage turbo detection for MIMO systems

We propose a novel joint channel estimation and three-stage iterative detection/decoding scheme for near-capacity MIMO systems. In our scheme, as usual, the detected soft information is first exchanged a number of times within the inner turbo loop between the unity-rate-code (URC) decoder and the MIMO soft-demapper, and the information gleaned from the inner URC decoder is then iteratively exchanged with the outer decoder in the outer turbo loop. Our channel estimator however exploits the a posteriori information produced by the MIMO soft-demapper to select a sufficient blocks of high-quality detected soft bits, and it is naturally embedded into the original iterative three-stage detection/decoding process, without introducing the costly iterative loop between the decision-directed channel estimator and the three-stage turbo detector/decoder. Hence, the computational complexity of our joint channel estimation and three-stage turbo detection is similar to that of the three-stage turbo detection/decoding scheme associated with the perfect CSI. Moreover, our reduced-complexity semi-blind scheme is capable of achieving the optimal maximum-likelihood turbo detection performance attained under the perfect CSI, with the same number of turbo iterations