Wireless Cellular Networks, Local Area Network Positioning Technology And Multiple Access System

With the development of wireless cellular networks, telecommunication industry grows up to be the backbone of the industry and consequently more and more competitions take place as a result in this field. Especially with the 3G standard, almost all the developers and carriers are involved for the sake of its tremendous profits. Those developers focus on the R&D of all possible services specified by 3GPP, while all the carriers try to provide services both specified and extended to meet the requirements of the telecom market. Therefore Location based services become the hotspot because both the standard and the extended services are enrolled in this field. The benefit of LCS in U.S.A is as high as 360 million USD in 2004.Location based services are defined as the provision of information and applications based on the acknowledgement of the accurate positions of users. The 2G wireless networks provide some simple LCS at present. In 1996, the Federal Communication Committee (FCC) of U.S.A publicized the Enhance-911 requirement which requires that before October, 2004, all the wireless cellular networks should provide the location services to those subscribers who make E-911 emergency call, with the accuracy that is not below 100 meters in the 67% time period and 150 meters in the 95% time period. The E-911 requirement also specified that the location techniques should be based on the wireless cellular networks and no modification is wanted in the user terminals. Furthermore, a better accuracy and three-dimensional information should be available after 2001. Nowadays with the commercialization of 3G wireless cellular networks, the LCS is sure to be more attractive because of the wide band and high speed of 3G networks.There are four categories of location techniques in cellular networks: traditional GPS, network-aided GPS or A-GPS for short, techniques based on the network itself, such as Cell-ID and Enhanced-Observed Time Difference (E-OTD)and hybrid techniques like gpsOne of Quantum Co.Ltd.However, without the assistance of GPS, the present systems cannot provide the location accuracy to meet the E-911 requirement when non-light-of-sight (NLOS) propagations are taken into account. In practice, NLOS propagation is a very common issue in wireless cellular networks. Therefore further research should be focused on it.On the other aspects, great progress has been made in the field of mobile networks. IEEE 802.11b standard, or "Wi-Fi"(Wireless Fidelity) for commerce, is widely known to support the wireless Ethernet. Wi-Fi is featured to consist of a number of Access Points (AP) that are placed within the coverage of the certain wireless network and connected to the wired LAN. Each AP owns the coverage about 300 meters and occupies an exclusive wireless physical channel with the multiplex format TDMA, DS-CDMA or OFDM. CSMA/CA protocol is deployed in its MAC. A certain Wi-Fi card to the AP who receives the maximum power from the wireless terminal connects it.Currently, IP-based cellular networks are the trend of wireless networks and IP-based Multimedia Service (IMS) has received tremendous attention for the sake of next generation wireless networks. It is predictable that, in the next generation wireless networks, a single terminal can be connected to the wireless core network through both Node B and AP. It is not only convenient for the users but also the object of the providers and carriers.Similar to the cellular networks, network carriers also take the indoor location services as a profitable increment. By means of accurate position measurement, the networks are capable to provide users with various location-related information to cater for the market. On the other aspects, accurate location information benefits the network planning, load balancing, radio resource management and some other functionality greatly. What is more, indoor location method with high accuracy is very important to public safety, such as military, police and firework. Especially to the Ad-hoc network, the accuracy ofindoor location services routing efficiency directly.Compared to the location techniques in cellular networks, the indoor location is a relatively new area. But it is greatly important and urgent since the 911 event in U.S.A. Different from that in the outdoor environment, refraction and diffraction are serious and overwhelming indoor and there are a great number of propagation paths which are so close to each other that it is impossible to figure them out by the resolution of present devices and techniques. Therefore, TO A, TDOA and AOA do not work in this field. Thoroughly new methods should be established.As the above demonstrations, the research of location techniques in both the outdoor cellular networks and indoor WLAN is of realistic value and importance. That is the reason why it attracts so many attentions and why I take it as my doctoral project.The first part of this dissertation introduces three original location algorithms for wireless cellular networks, along with two relatively new existing methods for the purpose of comparison. In these three original algorithms, NLOS propagations are the main issue to deal with. Some virtual concepts are included in this part, which maybe results in some difficulty in understanding these methods. However the simulations and comparisons show that these algorithms do work well in the NLOS propagation scenario.In the second part, several indoor location algorithms are explicated based on IEEE 802.11 standard. Because of the convenience in signal strength measurement, devices based on IEEE 802.11b are deployed to fulfill the indoor location functionality. However, the measured strengths are absolutely inaccurate and unreliable. The bias of the measured strength is then described as the shadowing factor. All the indoor location algorithms in this part are proposed to deal with the shadowing factor reasonably and sufficiently. Based on the statistical characteristic of the shadowing factor, the indoor location methods provide satisfactory performances.The third part is an extended part of the research on location methods. In this part, some new multi-user detection methods are introduced. As a key technique for 3G, multi-user detection affects the performance of the location function. In the 3 G standard, all user terminals are required to measure the TO As from several nearby Node Bs simultaneously and by dedicated uplink channels, the measured results are sent back to the serving Node B. Therefore correct detection of multiple users are critical. With the development of wireless networks, more and more users are involved which demands the system to raise its capacity and support more terminals. Traditional MUDs are complicated and impractical up till now. Also, limited to the present modulation method CDMA, a further improvement of capacity is impossible. Therefore some new MUDs are being expected as well as the novel modulation methods. In the paper, Interleaver Multiple Division Access, IDMA for short, is proposed to overcome those shortcomings of traditional CDMA. But the present research of IDMA is still fundamental and does not cover the high-speed transfer. In this part, a QAM-IDMA system is proposed with its demodulation and decoding module. Moreover, a channel estimation approach is developed based on the characteristic of the received noise in IDMA and QAM-IDMA systems. Therefore, blind multi-user detection can be handled in IDMA-based systems.However, IDMA faces some challenges. Firstly, it is impractical for the base station or Node B to allocate a certain long-code interleaver to a user terminal by the air interface. Secondly, IDMA cannot be proved mathematically. Thirdly, no existing systems can support such technique because of the unaffordable delay caused by interleaving. Therefore, a thoroughly new system is proposed to handle the issues related to IDMA systems. That is called Random-coded Multiple Division Access, R-CDMA for short. It shares the identical physical layer as the present UMTS. But its iterative decoder is completely different which provides far better performance. R-CDMA systems provide the performance and capacity as good as IDMA system, because of the same essence where it overcomes some...