This article proposes a method that can calculate the blocking probability of multi-service cellular systems with Wideband Code Division Multiple Access radio interface. The method considers a finite and an infinite source population and takes into account the interdependency of calls service processes in neighboring cells and in both the uplink and the downlink directions. The basis of the proposed method is the fixed-point methodology. A comparison of the results of analytical calculations to those of simulations confirms the accuracy of the proposed method. The proposed scheme can realize cost-effective radio resource management in 3G mobile networks and can be easily applied to network capacity calculations.

In this paper, we propose and analyze a multi-level acknowledgement scheme for hybrid ARQ (H-ARQ) systems, which modifies the general ACK/NAK signals to represent multilevel information. For instance, the other signals except the ACK/NAK signals may be used for scheduling of retransmission in the H-ARQ scheme, which results in increasing the resolution of the uplink channel estimation signals. Simulation results demonstrate that when the retransmission interval is set to the optimal length, the proposed H-ARQ scheme shows a 0.5-2 dB gain with properly selected parameters.

In UMTS (universal mobile telecommunications system) networks upgraded with HSPA (high speed packet access) technology, the high access bandwidth and advanced mobile devices make it applicable to share large files among mobile users by peer-to-peer applications. To receive files quickly is essential for mobile users in file sharing applications, mainly because they are subject to unstable signal strength and battery failures. While many researches present peer-to-peer file sharing architectures in mobile environments, few works focus on decreasing the time spent in disseminating files among users. In this paper, we present an efficient peer-to-peer file sharing design for HSPA networks called AFAM -- Adaptive efficient File shAring for uMts networks. AFAM can decrease the dissemination time by efficiently utilizing the upload-bandwidth of mobile nodes. It uses an adaptive rearrangement of a node's concurrent uploads, which causes the count of the node's concurrent uploads to lower while ensuring that the node's upload-bandwidth can be efficiently utilized. AFAM also uses URF -- Upload Rarest First policy for the block selection and receiver selection, which achieves real rarest-first for the spread of blocks and effectively avoids the "last-block" problem in file sharing applications. Our simulations show that, AFAM achieves much less dissemination time than other protocols including BulletPrime and a direct implementation of BitTorrent for mobile environments.

The linearity and noise required by GSM and UMTS receivers make the design of a CMOS mixer for these applications so challenging. A new technique for IP2 improvement in Zero-IF active mixers is presented in this paper. This inductor-less technique is based on canceling the parasitic capacitor of common source node of the switching transistors and synthesizing resistive impedance. Using this technique, a reconfigurable down converter mixer works from 900 MHz to 2.4 GHz is designed supporting GSM, DCS, PCS, UMTS and IEEE802.11 b-g standards. The mixer IIP2 is higher than 71 dBm in GSM and UMTS bands. The mixer conversion gain is higher that 12 dB in all frequency bands. The design is done in 65 nm CMOS technology and consumes 10 mA from a 1.2 V supply. The design meets the performance required for all mentioned standards, while its area and power is comparable with high performance single band mixers.

This paper proposes two types of network architectures using UMTS Release 5 architecture and wireless LAN suitable for context-aware information delivery and personal communication services, and it reports on preliminary evaluations of their performance. The first type of network architecture is the NCA (network-centric architecture) and the second is the ECA (end-user-centric architecture). The two architectures are modeled with a queuing network and their response times are compared through theoretical analysis and simulation. The results indicate that with low-performance servers, the response times of the ECA are generally shorter or almost the same as those of the NCA. However with high-performance servers, the response times of the NCA are generally shorter except during high server utilization.

The UMTS macrocell downlink capacity is evaluated for macrocells that operate at the same frequency of the Deep Space Network (DSN) and that are nearby the DSN installations. It has been found that the cell capacity is not affected when the distance between the DSN installations and the macrocell is more than 25 km. For lower distance, the effect is high and the downlink vanishes at a distance less than 1 km.

An ultra-low power 4.3 GHz Synchronous Oscillator (SO) is presented, integrated in a 0.25 µm BiCMOS SiGe technology, to act as the RF loop of an UMTS double-loop synthesizer. This SO is tunable in order to counteract technology discrepancies. Hence, the synchronization range is smaller, reducing unwanted synchronization and improving the frequency generation accuracy. This 1.8 V SO provides a -115 dBc/Hz phase noise at 100 kHz offset, consuming only 3.6 mW.

We propose an enhanced packet access scheme for IMT-2000/UMTS random access channel (RACH). In the proposed scheme, 2-level preamble detection threshold and 2-level message transmission power are used to mitigate the power imbalance in RACH. Simulation results demonstrate that the proposed scheme improves the interference characteristics of the conventional RACH and makes wider range of the detection threshold available.

Adaptive beamforming, using the Conjugate Gradient Normal Equation Residual problem, is applied to a base station array, in the UTRA-TDD up-link. A Wideband Directional Channel Model is used, characterising specific micro-cell, street-type scenarios. These differ in the number of mobile terminals, grouped and placed along the street axis, and on their distances to the base station. Time- and angle-of-arrival spreads, and on-the-air interference content are the main parameters inherently varied and analysed. The average beamforming gain and signal-to-noise ratio are evaluated, also varying the number of array elements. The high number of arriving correlated and closely correlated signals, together with the composed nature of the correlation matrix in the algorithm's cost function, result in that other than the MMSE solutions may lead to the best interference suppression, for the tested scenarios. Among the several weighted interfering power components, the most relevant is due to the delayed signals from all the other links. The combination of the number of arriving orthogonal codes, time-of-arrival and angle-of-arrival spreads condition beamforming performance: the number of array elements affect performance, depending on the mobile terminal distance to the base station, and on the number of active links; for short distances and large number of users, larger time-of-arrival spread degrades beamformer performance, over the opposing effect of angle-of-arrival spread; the number of active users affects beamforming gain especially in the case that delay spreads are larger, i.e., for shorter mobile terminal distances to the base station.

This paper presents an efficient public-key protocol for mutual authentication and key exchange designed for mobile information services in UMTS. Certain modifications to the ASPeCT registration protocol is proposed to introduce Temporary Mobile User Certificate in UMTS environments. Proposed Temporary Mobile User Certificate, digitally-signed by the private signing key of the TTP located in the user's visiting domain, will be issued to the user during the registration protocol. ASPeCT AIP protocol can be modified to reduce communication overhead and speed up verification process using Temporary Mobile User Certificate between the user and the Value-Added Service Provider (VASP) located in the user's visiting domain. Furthermore, Temporary Mobile User Certificate can provide anonymity for a mobile user during the ASPeCT AIP protocol.

Mobile telecommunication is a rapidly growing market. Second generation systems such as GSM, DECT and ERMES, which are actually in an evolving status will be replaced by the third generation UMTS from the beginning of the next century on. While UMTS will allow data communication with up to 2Mbit/s, the fourth generation system MBS will provide up to 155Mbit/s. In several European R & D projects of the ESPRIT, DRIVE, COST and RACE programmes investigations concerning network planning, network operation, signalling, access techniques, security, terminal development and image and voice compression are carried out in order to create the scientific and technological bases for future UMTS and MBS. Some of these projects are described in more detail and an outlook toward future R & D activities is given. Finally some considerations are made concerning expectations of future services and questions concerning the development of wide band versus narrow band solutions are put.

The paper deals with the evaluation of channel allotment criteria in a mixed cellular environment composed by a regular grid of macrocells, plus a number of microcells deployed in the most congested areas. The optimum allotment of the resources between microcells and macrocells, which is a key issue for future personal communication systems, has to be tailored on the basis of their different functionalities. The approach is quite innovative since the analysis is carried out considering real traffic statistics, which are characterised by peaks and fluctuations resulting in uneven traffic loads on different cells. Different propagation models for macrocells and microcells have been adopted. Finally, the impact of the allotment of frequency resources to microcells and macrocells is analysed.