In this paper the application of a linear-quadratic processor is proposed for detection of each user's signal in a direct sequence code division multiple access scheme and, in particular, for W-CDMA systems. In this method, the knowledge of the user of interest, and some statistical knowledge of interfering transmitters' signals are used to detect the desired user's signal without needing exact "a priori" knowledge of the interfering signal parameters such as spreading sequences and signal powers. Parameters of the proposed processor, which are derived so as to maximise the signal-to-interference-plus-noise ratio (SINR), can generally be obtained by solving a system of linear equations for which many effective techniques exist. A model for this detection procedure is developed and shown--through analytical and numerical results--to offer a good compromise between complexity and quality of performance.

Power control error is well known for its negative effects on CDMA system capacity. In this Letter, an analytical model is developed to estimate the uplink capacity for a SIR-based power controlled CDMA cellular system. The voice capacity reduction due to power control error is numerically examined with this model.

In this letter we investigated the packet transmission control in downlink CDMA cellular systems. The downlink packet transmission control scheme based on the soft handoff status was proposed to enhance the system performance. The proposed scheme controls the downlink packet transmissions by employing a transmission window which is individually resolved to each mobile station according to its propagation condition and soft handoff status. Computer simulation shows that compared with the conventional scheme the proposed scheme improved the delay performance and fairness of service in packet reception.

The traffic with asymmetry between uplink and downlink has recently been getting remarkable on mobile communication systems providing multimedia communication services. In the future mobile communications, the accommodation of asymmetric traffic is essential to realize efficient multimedia mobile communication systems. This paper discusses asymmetric traffic accommodation in CDMA/FDD cellular packet communication systems and proposes its efficient scheme using an adaptive cell sizing technique. In the proposed scheme, each base station autonomously controls its coverage area so that almost the same communication quality can be achieved across the service area under the asymmetric traffic conditions. We present some numerical examples to demonstrate the effectiveness of the proposed scheme by using computer simulation. The simulation results show that, under asymmetric traffic conditions, the proposed scheme can provide fair communication quality across the service area in both links and can improve total transmission capacity in the uplink.

In this paper the coexistence issue between the DS-UWB systems and Wi-Max/IEEE-802.16 based Fixed Broadband Wireless Access (FBWA) systems has been investigated. The aim is to evaluate the impact that the interference resulting from a realistic UWB hot spot scenario may have on the performance of a FBWA receiver. A mathematical model is developed through which the interference power produced by the UWB hot spot can be calculated. The benchmarks against which the UWB interference is assessed are also developed using the specifications of Wi-Max/IEEE-802.16 systems. Several simulations have been done to both validate the analytical results and calculate the UWB interference. In doing so, the effects of parameters like victim receiver bandwidth, carrier frequency, activity factor, the number of users and the distance from victim receiver in a realistic hot spot scenario have been studied.

Access selection in future multiple radio access environments is considered in this paper from a new perspective, that of the consumer. A model is proposed for the automatic acquisition of user preferences to assist in access selection decision making. The proposed approach uses a two-level Bayesian C-Metanetwork that models individual user preferences in terms of affordable cost, acceptable level of quality of service and reputation of the access networks. User preferences under different contexts, such as leisure and business, are also considered. The model also adapts to the change of user preferences over time. A simulator has been developed to evaluate the proposed model and the simulation results are promising in terms of the proportion of correct preference predictions after a small number of training samples.

This paper proposes wavelet packets for use in ultra wideband communications. The pulse shapes that are generated are quasi orthogonal and have almost identical time duration. After normalization, an M-ary signaling set can be constructed allowing higher data rate. Finally, the performance of such a system when multipath propagation occurs is investigated by computer simulations. In order to combat multipath fading, a Rake receiver using coherent channel estimation is designed. This channel estimation is carried out using adaptive algorithms such as least-mean square (LMS), normalized least-mean square (NLMS), or recursive least square (RLS) algorithms which adapt the received signal given a reference signal.

We have already proposed a carrier power control scheme of OFDM that makes it possible to improve the bit error rate characteristic. However, the data on the lost carriers by the severe fading or large additive noise can't be recovered by only this power control scheme. In this paper, a method of transmission power control of OFDM carriers combined with data spreading scheme in the frequency domain is proposed. In the proposed system, transmission power of each carrier is controlled so as to maximize the average signal to noise ratio of the data symbols after de-spreading the signals from DFT. As the results of computer simulations, it is confirmed that the proposed system can improve the bit error rate characteristics under multi-path channel.

An improved movement-based registration scheme reduces location update cost on conventional movement-based location update scheme but increases uncertainty of the position of a mobile terminal (MT). The effect of this uncertainty of the MT position on the paging cost of the improved movement-based registration scheme is analyzed. We show that the paging cost of the improved movement-based registration scheme in [2] is underestimated, especially for large values of movement threshold. The result shows that the underestimation cannot be ignored.

The forward link capacity plane of a hierarchically structured cellular CDMA system, in which a single frequency band is used for both macrocell and microcell layers, is obtained for isolated microcells (hotspots). The impact of each neighbour microcell and macrocell on the capacity plane, for a reference mobile station as the worst case, is also investigated. The results for the case of three microcells in each macrocell show that 69% of macrocell interference to microcell mobile stations comes from the closest macrocell. It is also found that 80% of macrocell interference to the reference macrocell mobile station comes from the central cell and the first cell tier around it.

This letter addresses the issue of RSVP path management in IP micro-mobility networks. We describe efficient RSVP QoS paths with a minimal impact to the existing protocol and underlying routing infrastructure. The goal of this letter is to reduce RSVP path reservation restoration latency and unnecessary control traffic caused by mobility events. We thus propose a RSVP branch-path rerouting scheme at a crossover router (CR) under IP micro-mobility networks. We show that this scheme could give a good tradeoff between the resource reservation cost and the link usage during the lifetime of a RSVP connection.

This letter addresses the QoS issue of a RSVP flow during handoff events. For the QoS guarantee of real-time applications with RSVP reservation in All-IP wireless networks, mechanisms are required to minimize the resource reservation path changes and the packet loss resulting from handoff events. If the new RSVP reservation is made along the path via a new base station (BS) in advance for soft handoff, on-going RSVP flow session can be kept with the guaranteed QoS. Therefore, we propose a seamless switching scheme of RSVP branch path for soft handoff. We also show that this scheme could provide the QoS guarantee by adaptively adjusting the pilot signal threshold values for soft handoff.