Jacques Antoine

Efficient evaluation of voice quality in GERAN (GSM EDGE Radio Access Network)

The transport of multimedia application is now a key feature of the future radio access networks. The evolution of GSM networks is also able in principle to take benefit from end-to-end transfer of such applications. However, careful attention has to be taken regarding the quality perceived by the end user. Indeed, for voice services, mobile subscribers are familiar with a given quality. The introduction of IP services should not decrease this quality. Besides, the introduction of such feature on the radio links should also enable the operators to increase their network capacity. In this context, this paper analyses the perceived voice quality when voice frames are transported on existing packet radio bearers of GSM/EDGE Radio Access Networks. In this situation, the benefit for the operator should be maximal. The quality is evaluated with an objective method that relies on comparison of reference speech sequence with the same sequence that is passed through GERAN radio links. This methodology of evaluation if by far more consistent than simply considering radio link level performance like the bit error rate.

Performance of a distributed coverage SFH-TDMA system with mobility management in a high density traffic network

Low probability of blocking (Pb) at call set-up and very low probability of forced call termination (Pf), are important design criteria for micro and pico-cell networks deployed for very high traffic density areas like dense urban and indoors. In conventional cellular networks with fixed channel allocation (FCA), fine tuning of radio resource management (RRM) algorithms like channel selection (CS), channel change (CC) and handover (HO) is thus a difficult task. The difficulty is further increased because a higher number of handovers per call has to be handled. A new network architecture based on the concept of distributed radio coverage has been found to manage mobility and interference in high density traffic areas for TDMA systems like GSM/DCS, IS-54/IS-136. This paper focuses on RRM algorithms for such an approach whereby the coverage of a single cell is realised with synchronised relays using the same broadcast channel. The conventional HO is replaced by progressive channel activation on predicted best server relays. Five different strategies for channel selection/activation, ranging from channel activation on one best server antenna to simultaneous channel activation on all the antennas of a cell, have been evaluated. A mix of information of subscriber mobility and the existing traffic load on the cell is shown to have a determining influence on the channel selection/activation strategies offering maximum traffic throughput and minimum Pf.

Deployment of multi-layer TDMA cellular network with distributed coverage for traffic capacity enhancement

In second generation TDMA cellular systems, traffic increase is achieved via cell size reduction. But, to handle moving mobile stations (MS) and ensure coverage on the whole served area, a 2-layer network has to be deployed and radio resource management techniques such as directed retry (DR) are implemented for spectrum efficiency. Optimally, fast (respectively, slow) moving MS should be served by the macrocell (respectively microcell) layer. So, in such network organization, traffic performance is sensitive to both coverage quality and accuracy of estimation of MS speed. Conventional microcell layer deployment suffers from coverage holes and uncertainty of speed estimate (making it impossible to exploit the full capacity of such networks). This paper proposes to replace the usual layer of microcells by a distributed coverage. Strategies for serving base transceiver station (BTS) selection and channel allocation dependent on MS position over the service area, are implemented. Both the communication quality and the accuracy of estimation of MS speed are improved. This makes DR more efficient and enhances the overall traffic performance.

Impact of adaptive modulation on MC-CDMA receiver in beyond 3G systems

The study presented in this paper underlines the capacity increase resulting from the joint use of multicarrier (MC) adaptive modulation techniques and MC-CDMA receiver in the context of beyond 3G systems. The performance enhancement due to such near optimal rate and power adaptation decreases with diversity order. Moreover, results obtained through two different kinds of wireless channels (ETSI BRAN A and C) highlight convergence phenomena, independent of initial channel diversity order. Finally, complete single user detection (SUD) techniques are compared in tit is context of adaptive modulation.

Sensitivity of interfering power estimation to combining strategies in MC-CDMA systems

In this paper, the problem of accuracy in noise/interfering power estimate for an MC-CDMA receiver is considered. This quality parameter is a key feature in the link control for next generation wireless systems. It is used for bit loading, power control, dynamic frequency selection, or even handover. Adaptation of physical layer can also be based on this quality estimate. Therefore, its accuracy is of paramount importance when designing such adaptive systems. The sensitivity of the noise/interfering power estimate are compared and discussed for different diversity combining schemes viz: maximal ratio combining (MRC), equal gain combining (EGC), and selective combining (SC).

Accuracy of interfering power estimation in MC-CDMA systems

In this paper, we present an analytical approach to study the power estimate of the interference in a MC-CDMA transmission scheme. The receiver is implementing a simple RAKE architecture that is not near-far resistant. The regenerated signal (RS) technique is applied on a symbol basis for power estimation of the jamming signal. An exact equation of this estimate is obtained for L uncorrelated diversity branches, and the impact of diversity order is discussed.