SUMMARYIn this paper, we search for a better chip waveform based on orthogonal wavelets for direct sequence-code division multiple access (DS-CDMA) signals to improve the probability of error ðP e Þ performance with minimal signal bandwidth variations. First, we derive the P e expression over a quasi-synchronous additive white Gaussian noise channel for DS-CDMA signals, which use various pulse shaping waveforms including orthogonal wavelets as chip waveforms. It is observed that this expression depends on the chip waveform. Then, we design an optimum wavelet by using the relationship between wavelets and filter coefficients to reduce the probability of error. The DS-CDMA system using the optimum wavelet waveform results in a lower probability of error than those using the conventional chip waveforms such as raised cosine, half-sine and rectangular waveforms. Especially, the P e of the optimum wavelet-based scheme becomes significantly better than those of the conventional chip waveforms-based schemes under the heavy loading that is the case for commercial wireless systems. When the systems work with full load (i.e. the number of users equals the processing gain), the optimum wavelet-based system results in 0.5, 2.1 and 4 dB better SNR values than those of the raised cosine, half-sine and rectangular-based systems, respectively, for a P e value of 10 À3 :

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The role of extended lymphatic dissection on the prognosis and outcome of thoracic esophageal carcinoma is still controversial. The aim of this study was to determine the impact of three-field lymphatic dissection on the survival and recurrence rates of patients with thoracic carcinoma of the esophagus. Forty-six patients with primary squamous cell carcinoma of the thoracic esophagus underwent esophagectomy with three-field lymphatic dissection between 1992 and 2003. Recurrence and survival rates were examined as well as complications. Overall survival for the patients was 45.6 months and 5-year survival rate was 56%. Five-year survival rates for patients with Stage 2A, 2B, 3 and 4 were 68%, 0%, 53% and 33%, respectively. There was no Stage 1 patient. Mean disease-free survival was 41.4 months. Sixty three percent of patients had node-negative disease (5-year survival rate, 68.9%) and 37% had nodal metastases (5-year survival rate, 33.7%) (P = 0.002). Surgical morbidity was seen in 35 patients (76.1%). Conclusively, lymph node involvement in patients with thoracic esophageal carcinoma is the major determinant of prognosis and survival. Extended lymphatic dissection provides higher disease-free and overall survival rates and our study revealed the highest survival rate for thoracic esophageal carcinoma, to best of our knowledge.

Using genetic algorithm (GA), optimal wavelets are obtained to reduce ISI and ICI powers of a wavelet-based orthogonal frequency division multiplexing (OFDM) system over a practical two path low-voltage powerline channel or two path fading channel by relaxing the perfect quadrate mirror filter (QMF) orthogonality. Optimum wavelet-based OFDM system experiences less interference compared to conventional and Daubechies (Db) wavelet-based OFDM systems.

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