The Study and Implementation of Core Technologies in Wireless Network

• Main Authors: Meng-Hong Chen, 陳孟宏
• Other Authors: Yang-Han Lee
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/71764671382133208718

碩士 === 淡江大學 === 電機工程學系 === 88 === In the thesis, we investigate and implement some core technologies in the wireless network. The documents can be classified into two parts. In the first partition, we study some problems in the IEEE 802.11 or 802.11b wireless LAN. In another partition, we investigate the research topic about how to provide the real-time service in the general wireless network. Besides, in aid of the future study, we do some pilot study in the appendix. The first one is designing novel codec architectures for the turbo code. Besides, we do some researches in the Fiber-Optical Code Division Multiple Access (FO-CDMA) network and Hybrid Fiber Coaxial (HFC) network. In the first part of my thesis, we study some problem in the wireless LAN. First, we study the standard of IEEE 802.11b. In the standard, the IEEE 802.11b working group adapt the new modulation scheme, “Complementary Code Keying” (CCK), proposed by the Harris and Lucent companies,which technology can improve the data rate of wireless LAN to 1/2/5.5/11 Mbps. However, the allowable transmission distance between hosts is contra-proportional with the data rate. Therefore, we investigate the multi-transmission rate network in IEEE 802.11b wireless LAN with considering the fairness problem. In the second partition, we study the effect of microwave oven to the IEEE 802.11 frequency hopping wireless LAN card. In this section, we compare the FER (Frame Error Rate) of Medium Access Control Sublayer to the PER (Packet Error Rate) of Transport Layer when microwave oven operates. In order to improve the transmission performance, we design a fuzzy controller to adapt the transmitted packet length in order to resist the interference from the microwave oven. Finally, some practical applications are implemented. The first one is writing a program, which uses the genetic algorithm to decide the location where the access points should be located. By this program, least number of access points are required and all of the stations can be covered in the safe area. The second one is designing and writing the Linux driver of IEEE 802.11 frequency hopping wireless LAN card. In the other part of my thesis, we design a bandwidth allocation fuzzy controller to support the real-time transmission in the wireless network. The designed controller can be used in the general TDMA wireless network. For example, it is a good application to use the controller in the gatekeeper of the H.323 standard. In the appendix, the popular topic of “turbo code” is studied. Because the decoding process of turbo code requires the SNR (signal to noise ratio) of channel, I design a new method to obtain this value from the Preamble Signal of the received packet. Besides, I propose a new architecture of the turbo code decoder, which is used in the error control method of ARQ (Automatic-Repeat-Request). In this architecture, the estimated signal of previous disrupted packet would be memorized and used in the decoding process of retransmission for improving the validity of estimation. In the second partition, we proposed an algorithm to find out the exact code of the maximal simultaneous users in the FO-CDMA network. In the third partition, a new network architecture of HFC network is proposed in order to improve the network performance of the traditional network.