Improving the Performance of Viterbi Decoder using Window System

An efficient Viterbi decoder is introduced in this paper; it is called Viterbi decoder with window system. The simulation results, over Gaussian channels, are performed from rate 1/2, 1/3 and 2/3 joined to TCM encoder with memory in order of 2, 3. These results show that the proposed scheme outperforms the classical Viterbi by a gain of 1 dB. On the other hand, we propose a function called RSCPOLY2TRELLIS, for recursive systematic convolutional (RSC) encoder which creates the trellis structure of a recursive systematic convolutional encoder from the matrix “H”. Moreover, we present a comparison between the decoding algorithms of the TCM encoder like Viterbi soft and hard, and the variants of the MAP decoder known as BCJR or forward-backward algorithm which is very performant in decoding TCM, but depends on the size of the code, the memory, and the CPU requirements of the application

Combined source-channel coding for a power and bandwidth constrained noisy channel

This thesis proposes a framework for combined source-channel coding under power and bandwidth constrained noisy channel. The framework is then applied to progressive image coding transmission using constant envelope M-ary Phase Shift Key (MPSK) signaling over an Additive White Gaussian Channel (AWGN) channel. First the framework for uncoded MPSK signaling is developed. Then, its extended to include coded modulation using Trellis Coded Modulation (TCM) for MPSK signaling. Simulation results show that coded MPSK signaling performs 3.1 to 5.2 dB better than uncoded MPSK signaling depending on the constellation size. Finally, an adaptive TCM system is presented for practical implementation of the proposed scheme, which outperforms uncoded MPSK system over all signal to noise ratio (Es/No) ranges for various MPSK modulation formats. In the second part of this thesis, the performance of the scheme is investigated from the channel capacity point of view. Using powerful channel codes like Turbo and Low Density Parity Check (LDPC) codes, the combined source-channel coding scheme is shown to be within 1 dB of the performance limit with MPSK channel signaling

Error control techniques for satellite and space communications

Shannon's capacity bound shows that coding can achieve large reductions in the required signal to noise ratio per information bit (E sub b/N sub 0 where E sub b is the energy per bit and (N sub 0)/2 is the double sided noise density) in comparison to uncoded schemes. For bandwidth efficiencies of 2 bit/sym or greater, these improvements were obtained through the use of Trellis Coded Modulation and Block Coded Modulation. A method of obtaining these high efficiencies using multidimensional Multiple Phase Shift Keying (MPSK) and Quadrature Amplitude Modulation (QAM) signal sets with trellis coding is described. These schemes have advantages in decoding speed, phase transparency, and coding gain in comparison to other trellis coding schemes. Finally, a general parity check equation for rotationally invariant trellis codes is introduced from which non-linear codes for two dimensional MPSK and QAM signal sets are found. These codes are fully transparent to all rotations of the signal set

Capacity-achieving CPM schemes

The pragmatic approach to coded continuous-phase modulation (CPM) is proposed as a capacity-achieving low-complexity alternative to the serially-concatenated CPM (SC-CPM) coding scheme. In this paper, we first perform a selection of the best spectrally-efficient CPM modulations to be embedded into SC-CPM schemes. Then, we consider the pragmatic capacity (a.k.a. BICM capacity) of CPM modulations and optimize it through a careful design of the mapping between input bits and CPM waveforms. The so obtained schemes are cascaded with an outer serially-concatenated convolutional code to form a pragmatic coded-modulation system. The resulting schemes exhibit performance very close to the CPM capacity without requiring iterations between the outer decoder and the CPM demodulator. As a result, the receiver exhibits reduced complexity and increased flexibility due to the separation of the demodulation and decoding functions.Comment: Submitted to IEEE Transactions on Information Theor

The use of multiple antenna techniques for uwb wireless personal area networks (UWB-MIMO WPANS)

The research activities over the three years were presented in this thesis. The work centred on the use of multiple spatial elements for Ultra wide band wireless system in order to increase the throughput, and for wireless range requirement applications, increases the coverage area. The challenges and problems of this type of implementation are identified and analysed when considered at the physical layer. The study presents a model design that integrates the multiple antenna configurations on the short range wireless communication systems. As the demand for capacity increases in Wireless Personal Area Networks (WPAN); to address this issue, the framework of the Wi-Media Ultra Wide Band (UWB) standard has been implemented in many WPAN systems. However, challenging issues still remain in terms of increasing throughput, as well as extending cellular coverage range. Multiple Input Multiple Output (MIMO) technology is a well-established antenna technology that can increase system capacity and extend the link coverage area for wireless communication systems. The work started by carrying out an investigation into integrated MIMO technology for WPANs based on the Wi-Media framework using Multi-band Orthogonal Frequency Division Multiplexing (MB-OFDM). It considered an extensive review of applicable research, the potential problems posed by some approaches and some novel approaches to resolve these issues. The proposed ECMA-368 standard was considered, and a UWB system with a multiple antenna configuration was undertaken as a basis for the analysis. A novel scheme incorporating Dual Circular 32 - QAM was proposed for MB-OFDM based systems in order to enhance overall throughput, and could be modified to increase the coverage area at compromise of the data rate. The scheme was incorporated into a spatial multiplexing model with measured computational complexity and practical design issues. This way the capacity could be increased to twice the theoretical levels, which could pay the way to high speed multi-media wireless indoor communication between devices. Furthermore, the range of the indoor wireless network could be increased in practical wireless sensor networks. The inherent presence of spatial and frequency diversity that is associated with this multiple radiators configuration enlarge the signal space, by introducing additional degrees of freedom that provide a linear increase in the system capacity, for the same available spectrum. By incorporating the spatial elements with a Dual Circular modulation that is specified within the standard, it can be shown that a substantial gain in spectral efficiency could be possible. A performance analysis of this system and the use of spatial multiplexing for potential data rates above Gigabit per second transmission were considered. In this work, a model design was constructed that increases the throughput of indoor wireless network systems with the use of dual radiating elements at the both transmitter and receiver. A simulation model had been developed that encapsulate the proposed design. Tests were carried out which investigate the performance characteristics of various spatial and modulation proposals and identifies the challenges surrounding their deployments. Results analysis based on various simulation tests including the IEEE802.15.3a UWB channel model had shown a lower error rate performance in the implementation of the model. The proposed model can be integrated in commercial indoor wireless networks and devices with relatively low implementation cost. Further, the design used in future work to address the current challenges in this field and provides a framework for future systems development

Applications of satellite technology to broadband ISDN networks

Two satellite architectures for delivering broadband integrated services digital network (B-ISDN) service are evaluated. The first is assumed integral to an existing terrestrial network, and provides complementary services such as interconnects to remote nodes as well as high-rate multicast and broadcast service. The interconnects are at a 155 Mbs rate and are shown as being met with a nonregenerative multibeam satellite having 10-1.5 degree spots. The second satellite architecture focuses on providing private B-ISDN networks as well as acting as a gateway to the public network. This is conceived as being provided by a regenerative multibeam satellite with on-board ATM (asynchronous transfer mode) processing payload. With up to 800 Mbs offered, higher satellite EIRP is required. This is accomplished with 12-0.4 degree hopping beams, covering a total of 110 dwell positions. It is estimated the space segment capital cost for architecture one would be about $190M whereas the second architecture would be about$250M. The net user cost is given for a variety of scenarios, but the cost for 155 Mbs services is shown to be about $15-22/minute for 25 percent system utilization

Trellis- and network-coded modulation for decode-and-forward two-way relaying over time-varying channels

We present a bandwidth-efficient joint channel coding-modulation scheme conceived for the broadcast channel (BC) of Decode-and-forward Two-way Relaying (DF-TWR), where Trellis-coded modulation (TCM) is intrinsically amalgamated with network-coded modulation (NCM) for achieving both a channel coding gain and a high throughput. We conceive a low-complexity receiver algorithm for our joint Trellis- and Network-coded modulation (TC-NCM) scheme, which applies decoding and demodulation simultaneously, without the need to first demodulate the signal before decoding, as in the traditional solutions. As a further contribution, the TC-NCM scheme is intrinsically amalgamated with adaptive transceiver techniques. We then further investigate the performance of our near-instantaneously adaptive discrete-rate TC-NC-QAM/PSK scheme. Both simulation results and numerical analysis are presented, which are compared to the performance of traditional NCM schemes. The results show that our scheme not only increases the achievable transmission rate, but also improves the reliability, yet it is of modest complexity

Source-channel coding for robust image transmission and for dirty-paper coding

In this dissertation, we studied two seemingly uncorrelated, but conceptually related problems in terms of source-channel coding: 1) wireless image transmission and 2) Costa ("dirty-paper") code design. In the first part of the dissertation, we consider progressive image transmission over a wireless system employing space-time coded OFDM. The space-time coded OFDM system based on a newly built broadband MIMO fading model is theoretically evaluated by assuming perfect channel state information (CSI) at the receiver for coherent detection. Then an adaptive modulation scheme is proposed to pick the constellation size that offers the best reconstructed image quality for each average signal-to-noise ratio (SNR). A more practical scenario is also considered without the assumption of perfect CSI. We employ low-complexity decision-feedback decoding for differentially space- time coded OFDM systems to exploit transmitter diversity. For JSCC, we adopt a product channel code structure that is proven to provide powerful error protection and bursty error correction. To further improve the system performance, we also apply the powerful iterative (turbo) coding techniques and propose the iterative decoding of differentially space-time coded multiple descriptions of images. The second part of the dissertation deals with practical dirty-paper code designs. We first invoke an information-theoretical interpretation of algebraic binning and motivate the code design guidelines in terms of source-channel coding. Then two dirty-paper code designs are proposed. The first is a nested turbo construction based on soft-output trellis-coded quantization (SOTCQ) for source coding and turbo trellis- coded modulation (TTCM) for channel coding. A novel procedure is devised to balance the dimensionalities of the equivalent lattice codes corresponding to SOTCQ and TTCM. The second dirty-paper code design employs TCQ and IRA codes for near-capacity performance. This is done by synergistically combining TCQ with IRA codes so that they work together as well as they do individually. Our TCQ/IRA design approaches the dirty-paper capacity limit at the low rate regime (e.g., < 1:0 bit/sample), while our nested SOTCQ/TTCM scheme provides the best performs so far at medium-to-high rates (e.g., >= 1:0 bit/sample). Thus the two proposed practical code designs are complementary to each other

Advanced Modulation and Coding Technology Conference

The objectives, approach, and status of all current LeRC-sponsored industry contracts and university grants are presented. The following topics are covered: (1) the LeRC Space Communications Program, and Advanced Modulation and Coding Projects; (2) the status of four contracts for development of proof-of-concept modems; (3) modulation and coding work done under three university grants, two small business innovation research contracts, and two demonstration model hardware development contracts; and (4) technology needs and opportunities for future missions