Multi-carrier OFDM-CDMA has a range of advantages that make it ideal for high data rate wireless access system. In this paper, a cross-layer multi-service random access and channel assignment approach is proposed for the uplink communication of the mm wavelength multi-carrier OFDM-CDMA BWA system. The OFDM-CDMA solution and the iterative interference cancellation and detection are applied at the system's physical layer to support multi-user multi-service capabilities and to improve the robustness against the flat and frequency selective fading. The proposed scheme grants the uplink random access connections and allocates the radio resources to the active multiservice subscriber stations by using the cooperation between base station and subscriber stations, as well as the diversities in spreading codes, subcarriers, time in OFDM symbols, and time division multiplex. A MAC protocol and its connection and channel assignment procedures are described. Numeric simulations of the uplink BWA system with the proposed random access and channel assignment scheme are carried out to evaluate the system's performance.

Multi-carrier OFDM-CDMA has a range of advantages that make ideal for high data rate wireless access system. A two-layer carrier interferometry (CI) phase coding approach is proposed for enhancing multi-user detection of the mm wavelength multi-carrier OFDM-CDMA based uplink broadband wireless access system (BWA). The proposed OFDM-CDMA scheme uses a two-layer CI phase coding structure, which comprises outer and inner CI modulations and is combined with the iterative interference cancellation and detection to boost the system capability in the high radio fading and strong multiple access interference environment. The orthogonal property of the CI signals is exploited to enhance diversities in time, frequency and spreading code domains, as well as to simplify signal processing. No pilot signal is needed. The proposed two-layer CI OFDM-CDMA scheme for the uplink BWA is mathematically analyzed, and its numeric simulations are carried out to evaluate the system performance. The simulation results show the superior characteristics of the proposed two-layer CI phase coding scheme for the uplink BWA system compared to other schemes.

Huge popularity of mobile devices and Internet open new application field of wireless positioning and navigation systems, and this integration also brings new research issues. Currently the positioning and navigation systems are mostly based on satellite positioning systems, such as GPS. One serious drawback of these satellite based positioning and navigation systems is that they can only operate in outdoor environment. There are several approaches for wireless positioning, e.g. cell ID, DOA (directions of arrivals) or signal strength measurements, but these approaches can not meet requirements of wireless positioning, including latency, availability and accuracy. In this paper, we propose a new approach for Bluetooth positioning, which is based on the time offset acquisition of signals propagating over radio channel, and the forward-backward ranging. Through simulations and experiments, it shows that the new Bluetooth ranging approach could give high ranging accuracy with modest modifications of current Bluetooth technology.

The huge popularity of mobile devices and the Internet opens new application fields of wireless positioning and navigation systems and this integration also brings new research issues. Current positioning and navigation systems, which are based on GPS, Mobile Cell ID, or signal strength measurements, can not meet requirements of wireless positioning, including inter-network operations, latency, availability and accuracy. In this paper, we propose the SIP (Session Initiation Protocol) system architecture and network signalling protocol design for wireless positioning systems, which can have seamless inter-network operation capability, and meet specifications of wireless positioning systems. The performance of the proposed system is evaluated by analysis and simulations