As software systems grow in size they will also grow in complexity. If the increased complexity is not managed the system will be increasingly difficult to maintain. The effect of unmaintainable software is even more distinct when using a agile development process. By increasing the maintainability of the system these problems will be dealt with and the system can be extended with sustained efficiency. This thesis will evaluate the development process of a modern, agile company in order to find changes that will promote increased maintainability. The result is an modified process that will increase the maintainability with the smallest possible overhead for the development organisation. The result is based on earlier studies of development technologies that have proven to increase the maintainability. The implementation of these technologies are adjusted to fit the development team, and some of the technologies that are not suitable for the team are rejected.

In a study involving two languages: French and Arabic, this thesis examines the patterns and meanings of Arabic religious expressions as a code alternation practice in Algerian television interviews. It is concerned with investigating what participants may accomplish by selecting Arabic over French in some points of interaction to deploy religious expressions in their utterances. It also aims at exploring what the function is that these expressions may achieve for the organization of talk-in-interaction. Based on their manifestation in the participants’ utterances, the current study identifies four categories of the use of religious expressions in Algerian media talk where they appear as: transition words to switch to Arabic to keep going on in interaction; in adjacency pairs as a result of a reciprocal invocation between participants; devices to hold the floor and continue turns in interaction; and finally, signals for closing turns and shifting topics where a speakership change or a move to a new topic is possible.

The Orthogonal frequency division multiplexing (OFDM) technique has been intensively used in many wireless communication systems to achieve higher data rate transmissions. Due to the fact that the OFDM technique entails redundant block transmissions; the transmitted blocks suffer from the inter-symbol interference (ISI) and inter-block interference (IBI). To compensate this serious effect, in many literatures redundant symbols (or guard interval) with adequate length are inserted in the transmitted symbols to prevent the IBI. Also, in the receiver the equalizer can be employed to deal with ISI. In this thesis, we present a new pseudo random cyclic-postfix (PRCP-) OFDM associated with the multiple-input multiple-output (MIMO) antenna system configuration to further improve the system performance. In fact, the MIMO system can enhance channel capacity and achieve high data-rate. The above-mentioned PRCP-OFDM technique combines with the MIMO antennas system, through the appropriate model design can be used to combat the multi-path effect or the inter-block interference. As evident from the simulation results, the proposed ST-BC MIMO PRCP-OFDM system can avoid the interference of transmitted signals during the estimation of channel impulse response (CIR) with proposed cyclic-postfix sequences. In addition, to further improve and eliminate the residual IBI and ICI, the equalizer with the framework of the generalized sidelobe canceller (GSC) is considered. Specifically, when SNR grows, the proposed ST-BC MIMO PRCP-OFDM system can perform successfully in terms of symbol-error rate and semi-blind channel estimation. This is verified via the computer simulations.

In wireless communication system, convolution code has been one of the most popular error-correcting code. To prevent from the interference of noise during transmission, the transmitter usually applies convolution encode to code the processed information, and the receiver will use Viterbi decoder to decode and correct the error bit to decrease the bit error rate. In 3G mobile communication, such decoder is often applied between the base station and the communication device as a decoding mechanism. Since traditional decoders of communication devices consume more than one third power of the whole receiver, the present study focuses on the way effectively reducing the power consumption of Viterbi decoder. Traditional convolution coders use zero-tail, which make decoder be able to resist the interference of noise; however, this method would increase extra tail bits, which would decrease the code rate and affect the efficiency of transmission, especially for those information with short length, such as the header of packet. Tail-biting convolution code is another error-correcting code, which maintains the code rate, and it has been used in the control channel of LTE. Tail-biting convolution code is more complex than traditional decoder. Therefore, this thesis modifies the Wrap-Around Viterbi Algorithm (WAVA) to enormously decrease the power consuming while maintaining the bit error rate and the correctness of decoding. The aim of the present study is achieved by decreasing iteration number of WAVA algorithm to reduce one fourth of the whole power consumption. On the other hand, if the received information is not interfered by noise, it¡¦s unnecessary to turn on Tail-biting Convolution Decoder. As a result, the present study introduces the error detection circuit so that the received information can be simply decode and detected with the error detection circuit. If there is no noise interference, it can directly be outputted; if there is noise interference, however, it should be decoded by Tail-biting Convolution Decoder. The experimental results show that the survivor memory unit saves more than 60% power than traditional decoders, moreover, it will save 55%~88% power consumption when it goes with the error detection circuit. Consequently, the proposed method is indeed able to reduce the power consumption of Tail-biting Convolution Decoder. Keyword¡Gwireless communication, tail-biting convolution code, code rate, Viterbi decoder, power consumption

With the enormous growing applications of mobile communications, how to reduce the power dissipation of wireless communication has become an important issue that attracts much attention. One of the key techniques to achieve low power transmission is to develop a powerful channel coding scheme which can perform good error correcting capability even at low signal-to-noise ratio. In recent years, the trend of the error control code development is based on the iterative decoding algorithm which can lead to higher coding gain. Especially, the rediscovery of the low-density parity-check code ¡]LDPC¡^has become the most famous code after the introduction of Turbo code since it is the code closest to the well-know Shannon limit. However, since the block size used in LDPC is usually very large, and the parity matrix used in LDPC is quite random, the hardware implementation of LDPC has become very difficult. It may require a significant number of arithmetic units as well as very complex routing topology. Therefore, this thesis will address several design issues of LDPC decoder. First, under no SNR estimation condition, some simulation results of several LDPC architectures are provided and have shown that some architectures can achieve close performance to those with SNR estimation. Secondly, a novel message quantization method is proposed and applied in the design LDPC to reduce to the memory and table sizes as well as routing complexity. Finally, several early termination schemes for LDPC are considered, and it is found that up to 42% of bit node operation can be saved.

Orthogonal frequency division multiplexing (OFDM) due to the robustness to the effect of multipath fading and having high spectral efficiency, it has become a good candidate of wireless communications systems. The block transmission of signal-blocks through the channel will suffer from the inter-block interference (IBI) and inter-symbol interference (ISI). Usually in the transmitter of the OFDM systems, redundancy (or guard interval), such cyclic prefix (CP) or zero padding (ZP), with sufficient length, is inserted in the transmitted block to avoid the IBI. In this thesis, we propose a novel pseudo random cyclic postfix (PRCP-) OFDM system configuration, which adopts the PRCP as redundancy and combines with multiple antennas. In fact, the multiple transmit antenna and multiple receive antenna, which exploits the spatial diversity, can be used to further enhance the channel capacity and achieve high data-rate. The main property of PRCP-OFDM modulation is that it exploits the cyclic-postfix sequences to estimate channel information with a low complexity method. Compared with CP-OFDM, it overcomes the channel null problem. For ZP-OFDM, it uses the additional information to estimate channel which is replaced by zero samples in ZP-OFDM. Moreover, PRCP-OFDM avoids the interference of signals to the desired postfix when we estimate channel impulse response (CIR) and which is different from pseudo random postfix (PRP-) OFDM [8]. Thus, as SNR grows, PRCP-OFDM can have better performance than PRP-OFDM. With the help of [9], [12] and [13], we extend the PRCP-OFDM to the MIMO case with space-time block coding. Via computer simulation, we verify that the performance is improved, in terms of the accuracy of channel estimation and symbol error rate (SER).

The Orthogonal frequency division multiplexing (OFDM) modulator with redundancy has been adopted in many wireless communication systems for higher data rate transmissions .The block transmission of signal-blocks through the channel will suffer from the inter-block interference (IBI) and inter-symbol interference (ISI). In the traditional transmitter of the OFDM systems, redundancy (or guard interval), such cyclic prefix (CP) or zero padding (ZP), with sufficient length, is inserted in the transmitted block to avoid the IBI. In this thesis, we propose a novel pseudo random cyclic postfix (PRCP-) OFDM system configuration and joint a blind channel shortening algorithm which named MERRY algorithm [18], which adopts the PRCP as redundancy and combines with multiple antennas. In fact, the multiple input and multiple output (MIMO) system, which exploits the spatial diversity, it can be used to further enhance the channel capacity and achieve high data-rate, and we extend the PRCP-OFDM to the MIMO case with space-time block coding. In redundancy insufficient case, the blind channel shortening algorithm be adopted for suppressing the IBI. The main property of PRCP-OFDM modulation is that it exploits the cyclic-postfix sequences to estimate channel information with a low complexity method. For CP-OFDM, it overcomes the channel null problem. Compared with ZP-OFDM, it uses the additional information to estimate channel which is replaced by zero samples in ZP-OFDM. Moreover, PRCP-OFDM avoids the interference of signals to the desired postfix when we estimate channel impulse response (CIR) and which is different from pseudo random postfix (PRP-) OFDM [8]. Thus, when SNR grows, PRCP-OFDM can have better performance than PRP-OFDM. With the help of [9], [12] and [13]. Via computer simulation, we verify that the performance is improved.

To effectively combat MAI and MI in wireless networks, we exploit complementary code technique in this thesis. Terminals in cooperative communication system are not only doing the transmission or relaying, but also involve a novel strategy "network coding" which has been investigated widely. In our work, we aim to combine network coding into the conventional cooperative communication system, but we face certain problems in it. Cooperative system has diversity at the destination, but when network coding operation involved, theoretically, it violate the rules of diversity, since the new signals transmitted by relay are no longer as same as the signals from sources. However, we discover a method to solve this problem, which is using the multiplier in relay nodes to replace the conventional network coding operation- XOR. After creating the network coding-based system, our goal is to achieve diversity in cooperative communication system. In this work, we use MRC (maximum ratio combining) for the performance analysis, which is the optimal strategy. Many math works will be shown in the following chapters.

The study of architectural parameterization has long neglected other parameterizations in favour of code selector descriptions. In this dissertation, we are concerned with providing linguistic notations for modelling architectures with special emphasis on translation. We focus on high level descriptions to aid code selection and storage allocation. The view taken in the thesis is that a description specializes a framework with a particular architecture. Independently, the framework must support other translation algorithms without constraining their freedom or forcing them towards architecture-specific idioms. The first contribution is an architectural description language with features tuned towards better parameterizability. Emphasis is laid on addressing site (compile time) parameterizability. Within the notation, the type system of the machine is decoupled from that of the language with the mapping being left to the user as a compile-time parameterization. This gives one more degree of freedom for the user to decide on the precision required based on the available realizations. We also give adequate representation to addressing modes. They are considered to be almost equivalent to operations in complexity. This makes the specification simpler for operations. From the framework's perspective, as a second contribution, we propose an algorithm for maintaining registers during allocation. Register allocation algorithms depend on the framework to inform them when registers are exhausted. In such a situation, we pro- pose an adaptation of bipartite graph matching to keep track of register usage during translation in the presence of architec- tural constraints. The research also aims at structuring both the specification and software to prevent the closed-syntax bottle- neck of a lot of specification languages. We also describe the architecture of the implementation in terms of a very flexible model called the blackboard model.

published_or_final_version / Language Studies / Master / Master of Arts