Recently, tight network coordination in cellular systems has been demonstrated to improve the spectrum efficiency by means of signal processing methods. However, the performance of signal processing based multi-cell coordination is sensitive to backhaul delays, channel estimation errors and imperfections in fast link control. In this paper we consider tight network coordination for fast radio resource management (RRM) including packet scheduling, power control and modulation and coding scheme selection. We use a system level simulator to analyze the uplink performance of a multi-cell coordinated system that is built around a fast backhaul transport infrastructure for the purpose of enabling coordinated RRM rather than coordinated signal processing. We find that coordinated RRM alone can provide significant performance gains, up to 50% for cell edge and cell capacity as compared to traditional single-cell configurations and that multi-cell fast power control and modulation and coding scheme selection can significantly improve the accuracy of link adaptation in terms of signal-to-interference-and-noise (SINR) distribution, while imposing lower demands on the capacities of backhaul links compared to coordinated signal processing. Therefore RRM coordination can be an efficient complement to coordinated signal processing in multi-cell coordinated clusters.

While intercell interference coordination (ICIC) for the downlink of multi-cell systems in general and orthogonal frequency division multiple access (OFDMA) networks in particular has been extensively studied, the uplink has received less attention. For the uplink, the impact of ICIC on the overall system throughput ("the ICIC gain") must be analyzed in a system model that captures specific constraints such as power limitation and the behavior of other radio resource management functions including scheduling, fast packet retransmissions by means of hybrid automatic repeat requests (HARQ), power control and adaptive modulation and code rate selection. In this paper we investigate the ICIC gain for the uplink of the 3GPP long term evolution (LTE) system and find that this gain much depends on the employed traffic model. Specifically, for non greedy (sometimes termed "non full buffer") traffic sources, HARQ and link adaptation are able to compensate the effect of intercell collisions and therefore the real ICIC gains are typically smaller than those reported based on full buffer models assuming greedy traffic. We expect that our findings provide useful insights for the system design of ICIC schemes.

The emergence of Bluetooth as a default radio interface allows handheld devices to be rapidly interconnected into ad hoc networks. Bluetooth allows large numbers of piconets to form a scatternet using designated nodes that participate in multiple piconets. A unit that participates in multiple piconets can serve as a bridge and forwards traffic between neighbouring piconets. Since a Bluetooth unit can transmit or receive in only one piconet at a time, a bridging unit has to share its time among the different piconets. To schedule communication with bridging nodes one must take into account their availability in the different piconets, which represents a difficult, scatternet wide coordination problem and can be an important performance bottleneck in buillding scatternets. In this paper we propose the Pseudo-Random Coordinated Scatternet Scheduling (PCSS) algorithm to perform the scheduling of both intra- and inter-piconet communication. In this algorithm Bluetooth nodes assign meeting points with their peers such that the sequence of meeting points follows a pseudo random process that is different for each pair of nodes. The uniqueness of the pseudo random sequence guarantees that the meeting points with different peers the node will collide only occasionally. This removes the need for explicit information exchange between peer devices, which is a major advantage of the algorithm. The lack of explicit signaling between Bluetooth nodes makes it easy to deploy the PCSS algorithm in Bluetooth devices, while conformance to the current Bluetooth specification is also maintained. To assess the performance of the algorithm we define two reference case schedulers and perform simulations in a number of scenarios where we compare the performance of PCSS to the performance of the reference schedulers

The emergence of Bluetooth as a default radio interface allows handheld electronic devices to be rapidly interconnected into ad hoc networks. Bluetooth allows large numbers of piconets to form a scatternet using designated nodes that participate in multiple piconets. We study the performance implications of forming scatternets from piconets. The contribution of our work is twofold. First, we establish a network model and define performance metrics for Bluetooth scatternets. Our model is derived from constraints specific to the Bluetooth technology, but is sufficiently abstract to relate to the more general field of ad hoc networking. Second, using a number of simulation studies, we relate scatternet parameters to performance metrics and discover correlations between scatternet formation rules and performance. These results reveal some important performance implications of scatternet design decisions and can serve as guidelines for future scatternet formation algorithms.

In this paper we consider an output port of an ATM switch, where cell streams belonging to different TCP and UDP sessions arrive. During congestion the switch applies early packet discard (EDP) in order to reduce bandwidth waste. In order to guarantee fairness in the sense that only misbehaving sources get affected by the packet drop mechanism and to ensure high server utilization we propose an algorithm which also features simplicity. A salient feature of this algorithm is that it allows a predefined share /spl alpha//sub i/ to be associated with stream i. The algorithm (which we call the weighted fair EPD, WFEPD) attempts to provide this weighted share of the bandwidth for the streams in the long time average. A sliding window implementation of WFEPD allows us to demonstrate its efficiency in terms of fairness and bandwidth utilization.

While several papers and standards promote ATM in combination with the ATM Adaptation Layer Type 2 (AAL2) as the basic switching and multiplexing technology for 3/sup rd/ generation mobile access networks, very little work addresses the issue of AAL2 call admission control (CAC). The hardship of AAL2 CAC comes from the fact that AAL2, unlike ATM, supports variable packet size traffic. In addition, when applied in the cellular environment, the AAL2 CAC needs to co-operate with the radio interface (RI) resource management. In this paper we develop and compare AAL2 CAC algorithms that operate on the AAL2 traffic parameters currently considered by the ITU-T. Based on this comparison we find that one of these algorithms, employing the well-known Hoeffding inequality provides a reasonable trade-off between complexity and precision.

We analyze voice quality and system performance in third-generation mobile communication systems. We argue that in these networks that are expected to integrate voice, data, and multimedia services, the transport network can no longer be considered as a lossless transparent traffic channel. Rather, proper dimensioning is needed even for plain voice services. Furthermore, the efficient utilization of the network resources shared by voice and data traffic requires sophisticated traffic management in the statistical multiplexing environment. The contribution of the paper is twofold: first, voice quality in the cellular transport network is analyzed and network dimensioning criteria are derived. Second, building on advances reported in the literature and taking into consideration current standardization activities, a joint performance model is established for the air interface (AI) and the transmission network (TN) allowing for the analysis of end-to-end service performance within a uniform framework. To demonstrate the applicability of this model, we point to some performance problems in the multiservice environment and suggest and evaluate traffic management actions to overcome these.