Joan Olmos

UMTS optimum cell load balancing for inhomogeneous traffic patterns

The paper addresses the problem of adjusting simultaneously the electrical downtilt of base station antennas and the transmitted power assigned to common pilot channel (CPICH) signals in the framework of a UTRA-FDD system. The proposed optimization procedure is not based on an isolated cell by cell analysis, but on a global scenario by means of simulated annealing. Results show the convergence of the algorithm towards configurations that imply optimal system performance. Interference levels are minimized, effective cell load is reduced and therefore capacity can be increased.

On the need for dynamic downlink intercell interference coordination for realistic Long Term Evolution deployments

Intercell interference is the main issue limiting the capacity of modern orthogonal frequency-division multiple access based cellular networks. Recently, extensive research work has been carried out in this field, and intercell interference coordination techniques have been recognized as key enablers of current and future cellular technologies. In this article, i a comprehensive survey of the most representative contributions is provided together with ii a generic methodology to measure their actual merit. The performance of several interference avoidance strategies has been evaluated both from system and user point of view in the context of a Long Term Evolution LTE-based network considering not only synthetic cellular scenarios but also realistic deployments. Our literature review indicates that there is a need for adaptive/operator-customizable low-complex intercell interference coordination ICIC schemes suitable for realistic LTE deployments. Results obtained by means of a comprehensive set of simulations corroborate and support this premise. In this article, it is shown that simultaneous gains in terms of spectral/energy efficiency and fairness can be achieved through dynamic mechanisms with respect to both classic hard reuse schemes and static ICIC techniques. Besides numerical results, a novel merit assessment methodology based on several weighted performance metrics is proposed. Our findings show that dynamic schemes outperform static techniques by around 20-35% in realistic deployments. Copyright

Evaluation of a Cell Selection Framework for Radio Access Networks considering Backhaul Resource Limitations

Cell selection in mobile radio access networks is mainly driven by efficient resource usage of the air interface. In this paper we add a new dimension to the cell selection problem by considering also the current occupancy of transport resources in the backhaul part of the network since, it is believed that, with the introduction of high speed services, this backhaul network can be a limiting factor. In such cases, we demonstrate that a cell selection algorithm using transport status information provides significant benefits over traditional schemes exclusively based on radio criteria, even under those scenarios where the selection of a cell other than the best radio server can be thought as not adequate in terms of radio resource management (e.g. single-layer/single-RAT deployments). The cell selection problem is analytically formulated and developed by means of a multidimensional Markov chain.

Transport block error rates for UTRA-FDD downlink with transmission diversity and turbo coding

The transport block error rate (BLER) is an important indicator of the link quality in UTRA. For every kind of service in UTRA a BER or BLER threshold, that still satisfies the desired quality, can be specified. Then, the target E/sub b//N/sub 0/ for that service is the mean E/sub b//N/sub 0/ necessary to guarantee the specified BER or BLER threshold. The knowledge of the target E/sub b//N/sub 0/ for different services and propagation environments is fundamental for setting the outer loop in the power control algorithms, for system capacity calculations, for system planning and for radio resource management (RRM) in general. This paper presents simulation results of the downlink BER and BLER versus E/sub b//N/sub 0/ for different services and propagation environments. UTRA services are characterized by means of the radio access bearer (RAB) tables as specified by 3GPP. Results focus on several relevant RAB, which make use of turbo coding techniques.

Static inter-cell interference coordination techniques for LTE networks: a fair performance assessment

This paper focuses in the analysis of 100% static and distributed inter-cell interference coordination techniques in the context of LTE networks. Several methods have been modeled and studied with the aim of deriving practical radio planning rules based on the joint effect of operational parameters and thresholds. The investigation places special emphasis on the efficiency vs. fairness tradeoff through a set of metrics that allow not only to evaluate the measurements from different points of view, but also to look at the effectiveness in radio resources usage. Results show that similar levels of spectral efficiency can be achieved by means of a proper and accurate network tuning. Moreover, interesting second order differences appear due to inherent features of each approach. These can be exploited depending on the particular network operator needs.

A Functional End-to-End QoS Architecture Enabling Radio and IP Transport Coordination

This paper presents a novel end-to-end quality of service (QoS) architecture for wireless networks. The focus is placed in the coordination of QoS management between common radio resource management (CRRM), for heterogeneous radio access technologies, and the QoS enabled IP-based network segments. A functional reference QoS framework is introduced and the envisaged QoS management functions are described. The innovations proposed in the presented QoS framework arise mainly from the study of cross effects between the radio and fixed transport resources management. The proposed QoS framework has been designed considering the current 3GPP R6 networks as well as their long-term evolution (LTE) scenario. Some illustrative results for a coordinated admission control algorithm are given as a proof of concept, to show the advantages of CRRM and IP QoS management coordination.

Comparison of multicast/broadcast services in Long Term Evolution Advanced and IEEE802.16m networks

This paper performs a comparison of multicast/broadcast services MBS support in Long Term Evolution Advanced LTE-A and Worldwide Interoperability for Microwave Access WiMAX IEEE802.16m. Firstly, the main technical features of both standards concerning MBS operation are presented. It is shown that WiMAX offers higher unicast/MBS multiplexing flexibility as it supports both frequency and time multiplexing schemes, whereas LTE-A only includes time multiplexing. Besides, only WiMAX supports multi-antenna transmission. Next, the results of two simulation-based assessments are presented. In the former, it is considered a scenario with all cells transmitting the same MBS service. The effect of inter-site distance ISD on the maximum MBS data rate is evaluated. Results show that WiMAX configurations outperform LTE-A for small ISD. This is because WiMAX provides a higher number of resources dedicated to data transmission for the same bandwidth. Furthermore, some WiMAX configurations support two spatially multiplexed data streams. With higher ISDs, LTE-A outperforms single-stream WiMAX configurations. In the second assessment, a MBSFN area surrounded by interfering cells is considered to compare unicast/MBS multiplexing performance. The higher maximum MBS data rate is achieved in WiMAX with time division multiplexing, which is precisely the only alternative included in LTE-A. Copyright

System level evaluation of LTE networks with semidistributed intercell interference coordination

3GPP LTE is the evolution of UMTS which will make possible to deliver high quality multimedia services with an improved user experience. Since Radio Resource Management (RRM) has been recognized as a key point to successfully accomplish this target, the performance evaluation of a multi-cell resource allocation scheme applied to LTE downlink (DL) is presented in this paper. A semi-distributed RRM framework is discussed and evaluated from a system level viewpoint. Detailed link level simulations have also been carried out to properly back up the results.

An efficient type-II hybrid-ARQ protocol using punctured R-S codes for wireless ATM networks

A type-II hybrid-ARQ protocol, based on punctured Reed-Solomon (R-S) codes for the W-LLC layer of a W-ATM system, is presented. In this protocol a shortened (n,k) R-S code is decomposed into a pair of (n/2, k) punctured R-S codes which are used to protect transmissions. R-S codes are the most commonly used maximum distance separable (MDS) codes and the proposed protocol makes use of the properties of the MDS codes. The objective of the protocol is to use a low number of retransmissions in order to guarantee minimum delay, while keeping maximum throughput and low cell error rate (CER). The performance of the proposed protocol in a realistic indoor environment, taking into consideration the QoS requirements for real time applications is analysed. The analysis was carried out for a multicarrier modulation scheme (OFDM) with QPSK modulation on each carrier. The hidden Markov model (HMM) is used for modelling the physical layer of the system.

Transport Capacity Estimations for Over-Provisioned UTRAN IP-Based Networks

Within the context of beyond 3G (B3G) networks, the usage of IP-based transport to support specific radio access networks (RANs) deployments is becoming a feasible solution as an alternative to ATM or TDM networks. In this paper we address the impact, in terms of the required transport bandwidth, of using dedicated and high speed air interface channels on an IP-based UTRAN. In particular, we estimate the transport capacity requirements, for different mean traffic loads, over the Iub interface so that delay bounds imposed to the transport network layer (TNL) are satisfied. We claim that the provided results can be an useful estimation of an over-provisioning solution for the transport capacity required in an IP-based UTRAN.