This chapter contains sections titled: Introduction System Overview Iterative Decoding System Parameter Designand Results Conclusion

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 .

In this contribution we show how Shannon's coding theory could be realized for multiple-input multiple-output (MIMO) channels with the aid of Extrinsic Information Transfer (EXIT) charts and the Maximum-Aposteriori Probability (MAP) algorithm. We review the relationship between the channel capacity, EXIT charts and the MAP algorithm, outlining the principles of designing near MIMO-channel capacity coding schemes. Both serial and parallel concatenated coding schemes are designed based on these principles and near MIMO-channel capacity performance is achieved.

Based on extrinsic information transfer (EXIT) charts, the convergence behavior of a three-stage serially concatenated multiuser beamforming receiver is presented. This system uses a linear minimum bit error rate (BER) multiuser detector as the inner module. Due to the nonrecursive nature of this inner module, a unity-rate memory-1 recursive precoder is placed in front of the channel to provide the required recursive structure. Irregular convolutional codes (IRCCs) are constructed to be used as the outer code to achieve near-capacity performance. Our simulations show that this system outperforms the traditional two-component iterative structure and is capable of significantly reducing the error floor.

Iteratively decoded near-capacity Space-Time Block Coding (STBC) schemes are designed. Recursive unity-rate codes and IRregular Convolutional Codes (IRCCs) are employed for assisting the conventional non-recursive STBC schemes in achieving decoding convergence to an infinitesimally low bit error ratio at near-capacity signal-to-noise ratios. IRregular Convolutional Codes (IRCCs) are used as the outer codes for achieving a near-capacity performance. It was shown that the resultant iteratively decoded STBC schemes are capable of approaching the corresponding channel capacity within 0.4 dB, when communicating over uncorrelated, flat Rayleigh fading channels.

An Irregular Bit-Interleaved Coded Modulation based Iterative Decoding (Ir-BICM-ID) aided scheme is proposed.The irregularity of the scheme pervades the three basic components of BICM-ID, namely the encoder, the unity-rate precoder and the bit-to-symbol mapper.As a result, adaptive BICM-ID schemes constituted by irregular components are created, which are capable of approaching the capacity of coded modulation.This is achieved by creating a narrow EXtrinsic Information Transfer (EXIT) chart, using a novel EXIT curve matching algorithm.The proposed Ir-BICM-ID scheme employs Irregular Convolutional Codes (IrCC), Irregular Unity-Rate Codes (IrURC) and Irregular Mappers (IrMapper).

We analyze a precoded and iteratively detected downhink multiuser system employing imperfect Spatio-Temporal Channel Impulse Response at the Transmitters (ST-GIRT) with the aid of Extrinsic Information Transfer (EXIT) charts. A Precoded Iterative DownLink Space Division Multiple Access (PI-DL-SDMA) system proposed in our previous research is further improved and shown to be capable of maintaining an infinites-imally low BER, despite using imperfect ST-CIRT. A further novel feature of the VPI-DL-SDMA system is that we designl an IrRegular Convolutional Code (IRCC) with the aid of EXIT chart analysis for creating an open EXIT tunnel between the inner decoder's and outer decoder's EXIT curve at a reduced Eb/N0 value and hence maintain an infinitesimally low BER.

In this contribution an iterative (turbo) channel equalization and source decoding scheme is considered. In our investigations the source is modelled as a Gaussian-Markov source, which is compressed with the aid of vector quantization. The communications channel is modelled as a time-invariant channel contaminated by intersymbol interference (ISI). Since the ISI channel can be viewed as a rate-1 encoder and since the redundancy of the source cannot be perfectly removed by source encoding, a joint channel equalization and source decoding scheme may be employed for enhancing the achievable performance. In our study the channel equalization and the source decoding are operated iteratively on a bit-by-bit basis under the maximum a-posteriori (MAP) criterion. The channel equalizer accepts the a priori information provided by the source decoding and also extracts extrinsic information, which in turn acts as a priori information for improving the source decoding performance. Simulation results are presented for characterizing the achievable performance of the iterative channel equalization and source decoding scheme. Our results show that iterative channel equalization and source decoding is capable of achieving an improved performance by efficiently exploiting the residual redundancy of the vector quantization assisted source coding

We propose a Vector-Quantized (VQ) Video codec that induces deliberately-introduced code constraints. The complete set of these code constraints are unambiguously described by a novel block-based modification of a symbol-based variable length coding trellis structure. This trellis is employed during VQ encoding to represent video information with a Minimum Mean Squared Error (MMSE) reconstruction. Additionally, the proposed trellis structure is employed in the video decoder to obtain a posteriori probability based MMSE estimates of the transmitted VQ tiles. Since the trellis structure unambiguously describes the code constraints induced by the video codec, its employment guarantees the automatic recovery of valid sets of VQ tiles. The proposed video codec is serially concatenated with a trellis-coded modulation scheme for transmission over a fast-fading Rayleigh fading channel. In the receiver, iterative-decoding convergence that eliminates all perceivable channel-induced video distortion is shown to be supported within 1.29 dB of the system's 2 bit/s/Hz channel-capacity limit of 3.96 dB.

Joint video-coding, channel-coding and modulation schemes based on a Constant Bit Rate (CBR) video codec, Variable Length Codes (VLCs) as well as Trellis Coded Modulation (TCM) and Turbo TCM (TTCM) schemes are proposed. These arrangements have a latency of a single video frame duration. A significant coding gain is achieved without bandwidth expansion with the advent of iterative decoding exchanging extrinsic information between the VLC and the TCM or TTCM decoders. The performance of the proposed schemes was evaluated for transmission over uncorrelated Rayleigh fading channels and the best scheme was found to be about 3 dB from the Rayleigh channel's capacity limit.