Osamah Alamri

Near-Capacity Wireless Transceivers and Cooperative Communications in the MIMO Era: Evolution of Standards, Waveform Design, and Future Perspectives

Classic Shannon theory suggests that the achievable channel capacity increases logarithmically with the transmit power. By contrast, the MIMO capacity increases linearly with the number of transmit antennas, provided that the number of receive antennas is equal to the number of transmit antennas. With the further proviso that the total transmit power is increased proportionately to the number of transmit antennas, a linear capacity increase is achieved upon increasing the transmit power, which justifies the spectacular success of MIMOs. Hence we may argue that MIMO-aided transceivers and their cooperation-assisted distributed or virtual MIMO counterparts constitute power-efficient solutions. In a nutshell, since the conception of GSM in excess of three orders of magnitude bit-rate improvements were achieved in three decades, which corresponds to about a factor ten for each decade, because GSM had a data rate of 9.6 Kb/s, while HSDPA is capable of communicating at 13.7 Mb/s. However, the possible transmit power reductions remained more limited, even when using the most advanced multistage iterative detectors, since the required received signal power has not been reduced by as much as 30 dB. This plausible observation motivates the further research of advanced cooperation-aided wireless MIMO transceivers, as detailed in this treatise.

Near-capacity turbo trellis coded modulation design based on EXIT charts and union bounds - [transactions papers]

Bandwidth efficient parallel-concatenated Turbo Trellis Coded Modulation (TTCM) schemes were designed for communicating over uncorrelated Rayleigh fading channels. A symbol-based union bound was derived for analysing the error floor of the proposed TTCM schemes. A pair of In-phase (I) and Quadrature-phase (Q) interleavers were employed for interleaving the I and Q components of the TTCM coded symbols, in order to attain an increased diversity gain. The decoding convergence of the IQ-TTCM schemes was analysed using symbol-based EXtrinsic Information Transfer (EXIT) charts. The best TTCM component codes were selected with the aid of both the symbolbased union bound and non-binary EXIT charts, for designing capacity-approaching IQ-TTCM schemes in the context of 8 PSK, 16 QAM, 32 QAM and 64 QAM modulation schemes.

Turbo Detection of Precoded Sphere Packing Modulation Using Four Transmit Antennas for Differential Space-Time Spreading

This paper presents a novel turbo-detected multidimensional sphere packing (SP) modulation scheme using four transmit antennas combined with differentially encoded space-time spreading (DSTS). The DSTS scheme can be readily combined with PSK, QAM as well as SP modulation schemes. The SP-aided DSTS system advocated has low-complexity encoding and decoding algorithms that require no channel knowledge and it is capable of outperforming the DSTS system dispensing with sphere packing. Further system performance improvements can be attained by serially concatenated convolutional encoding combined with a unity-rate code (URC) referred to as a precoder. Then, at the receiver side, iterative decoding is invoked by exchanging extrinsic information between the precoders decoder as well as the outer recursive systematic convolutional (RSC) codes decoder. Moreover, the convergence behaviour of the proposed system is evaluated with the aid of extrinsic information transfer (EXIT) charts. Explicitly, the turbo-detected precoded DSTS-SP system performs within 1.6 dB of the achievable multiple-input multiple output (MIMO) capacity. Finally, in contrast to an equivalent 0.5 bit/symbol throughput turbo- detected DSTS-SP scheme using no preceding, the turbo-detected precoded DSTS-SP scheme exhibits no error floor.

Turbo detection of channel-coded space-time signals using sphere packing modulation

A recently proposed space-time signal construction method that combines orthogonal design with sphere packing, referred to as (STBC-SP), has shown useful performance improvements over Alamoutis conventional orthogonal design. In recent years, iterative decoding algorithms have attained substantial performance improvements in the context of wireless communication systems. We demonstrate that the performance of STBC-SP systems can be further improved by concatenating sphere packing aided modulation with channel coding and performing demapping as well as channel decoding iteratively. The sphere packing demapper is modified for the sake of accepting a priori information that is obtained from the channel decoder. Bit-wise mutual information measures are also employed for the sake of searching for the optimum bits-to-symbol mapping. We present simulation results for the proposed scheme communicating over a correlated Rayleigh fading channel. At a BER of 10/sup -5/, the proposed turbo-detected STBC-SP scheme employing optimum mapping, is capable of achieving a coding gain of approximately 19 dB over the identical-throughput 1 bit/symbol uncoded STBC-SP benchmarker scheme. The proposed scheme also achieved a coding gain of approximately 2 dB over the 1 bit/symbol channel-coded STBC-SP benchmarker scheme that employed Gray mapping.

Layered steered space-time codes using multi-dimensional sphere packing modulation

We present a novel multi-functional multiple-input multiple-output (MIMO) scheme, that combines the benefits of space-time codes (STC), of vertical Bell Labs layered space-time (V-BLAST) scheme as well as of beamforming. To further enhance the attainable system performance and to maximise the coding advantage of the proposed transmission scheme, the system is also combined with multi-dimensional sphere packing (SP) modulation. Additionally, we quantify the capacity of the proposed multi-functional MIMO aided multi-dimensional SP arrangement and propose a novel technique of computing an upper limit on the achievable bandwidth efficiency of the system based on extrinsic information transfer (EXIT) charts. Further system performance improvements can be attained by serially concatenating our proposed scheme with an outer code together with a unity-rate code (URC), where three different receiver structures are created by varying the iterative detection configuration of the constituent decoders/demappers. Moreover, the convergence behaviour of the proposed schemes is evaluated with the aid of EXIT charts. Explicitly, the three proposed systems are capable of operating within 0.9 dB, 0.6 dB and 0.4 dB of the maximum achievable rate limit. Additionally, the three stage assisted SP aided scheme is capable of outperforming its counterpart employing QPSK by 1 dB at a BER of 10-6.

Differential space-time spreading using iteratively detected sphere packing modulation and two transmit antennas

A novel differentially encoded space-time spreading (DSTS) scheme using two transmit antennas and Sphere Packing (SP) is proposed, which we refer to as the DSTS-SP arrangement. The advocated SP-aided system outperforms DSTS dispensing with SP and requires no channel knowledge. We also demonstrate that the performance of DSTS-SP systems can be further improved by serially concatenated convolutional coding and by performing SP-symbol-to-bit demapping as well as channel decoding iteratively. Explicitly, the proposed turbo-detected DSTS-SP scheme exhibits an Eb/No gain of 17.0 dB at a bit error rate (BER) of 10-5 over an uncoded identical-throughput system and an Eb/No gain of 1.9 dB over the equivalent 2 bits/symbol effective throughput QPSK-modulated turbo-detected DSTS scheme

Soft-Bit Assisted Iterative AMR-WB Source-Decoding and Turbo-Detection of Channel-Coded Differential Space-Time Spreading Using Sphere Packing Modulation

Jointly optimised iterative source- and channel-decoding is invoked for enhancing the error resilience of the adaptive multi rate wideband (AMR-WB) speech codec. The resultant AMR-WB coded speech signal is protected by recursive systematic convolutional (RSC) codes and transmitted using a sphere packing (SP) aided differential space-time spreading-/(DSTS) assisted transceiver. The performance of the proposed scheme is evaluated when communicating over correlated non-dispersive Rayleigh fading channels. The proposed system exhibits an Eb/N0 gain of about 1 dB in comparison to the benchmark scheme carrying out joint channel decoding and DSTS aided SP-demodulation, but separate AMR-WB decoding, when using Iout = 4 external iterations.

Iterative AMR-WB Source and Channel Decoding Using Differential Space–Time Spreading-Assisted Sphere-Packing Modulation

In this paper, we present a novel system that invokes jointly optimized iterative source and channel decoding for enhancing the error resilience of the adaptive multirate wideband (AMR-WB) speech codec. The resultant AMR-WB-coded speech signal is protected by a recursive systematic convolutional (RSC) code and transmitted using a noncoherently detected multiple-input-multiple-output (MIMO) differential space-time spreading (DSTS) scheme. To further enhance the attainable system performance and to maximize the coding advantage of the proposed transmission scheme, the system is also combined with multidimensional sphere-packing (SP) modulation. Furthermore, the convergence behavior of the proposed scheme is evaluated with the aid of extrinsic information transfer (EXIT) charts. The proposed system exhibits an Eb/N 0 gain of about 1 dB, as compared with the benchmark scheme carrying out joint channel decoding and DSTS-aided SP demodulation in conjunction with separate AMR-WB decoding, when using only I system = 2 system iterations and when communicating over narrow-band correlated Rayleigh fading channels.

Layered Steered Space–Time-Spreading-Aided Generalized MC DS-CDMA

We present a novel trifunctional multiple-input-multiple-output (MIMO) scheme that intrinsically amalgamates space-time spreading (STS) to achieve a diversity gain and a Vertical Bell Labs layered space-time (V-BLAST) scheme to attain a multiplexing gain in the context of generalized multicarrier direct-sequence code-division multiple access (MC DS-CDMA), as well as beamforming. Furthermore, the proposed system employs both time- and frequency-domain spreading to increase the number of users, which is also combined with a user-grouping technique to reduce the effects of multiuser interference. Further system performance improvements can be attained by serially concatenating our proposed scheme with an outer code that is amalgamated with a unity-rate code for the sake of improving the achievable decoding convergence behavior of the proposed system, which is evaluated with the aid of extrinsic information transfer charts. We also propose a novel logarithmic likelihood ratio (LLR) postprocessing technique to improve the iteratively detected systems performance. Explicitly, the proposed system can attain a second-order spatial diversity gain and a frequency diversity gain of order V, where V is the number of subcarriers. Additionally, the proposed system attains a beamforming gain and a multiplexing gain that is twice that of a single-input-single-output system. Furthermore, after I = 10 decoding iterations and employing an interleaver depth of Dint = 160 000 bits, a time-domain spreading factor of Ne = 4, and V = 4 subcarriers, the overloaded system supporting K = 8 users requires an Eb/N0 that is only about 0.45 dB higher than the single-user system.

Near-Capacity Three-Stage Turbo Detection of Irregular Convolutional Coded Joint Sphere-Packing Modulation and Space-Time Coding

Conventional two-stage turbo-detected schemes typically suffer from a Bit Error Rate (BER) floor, preventing them from achieving infinitesimally low BER values, especially, when the inner coding stage is of non-recursive nature. We circumvent this deficiency by proposing a three-stage turbo-detected Sphere Packing (SP) aided Space-Time Block Coding (STBC) STBC-SP scheme, where a rate-1 recursive inner precoder is employed to avoid having a BER floor. The convergence behaviour of this serially concatenated scheme is investigated with the aid of 3D Extrinsic Information Transfer (EXIT) Charts. Furthermore, the capacity of the STBC-SP scheme is determined and an algorithm is proposed for calculating a tighter upper bound on the maximum achievable bandwidth efficiency, based on the EXIT charts of the STBC-SP demapper. The proposed three-stage turbo-detected scheme operates within about 1.0 dB of the capacity and within 0.5 dB of the maximum achievable bandwidth efficiency limit.