The following topics are dealt with: mobile computing; Internet of Things; telecommunication traffic; learning (artificial intelligence); wireless channels; quality of service; wireless sensor networks; health care; radio networks; radiofrequency interference.

ABSTRACT 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) IEEE 802.16m. 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 © 2012 John Wiley & Sons, Ltd.

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/operatorcustomizable 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.

Mobile backhaul has moved to the forefront of wireless industry hot topics. The progressive deployment of spectrally efficient radio access technologies (e.g. HSPA, LTE, WiMAX) in mobile broadband is turning into stringent capacity requirements on the backhaul network. This makes backhaul capacity to become a potential network bottleneck in some deployment scenarios. While more cost-efficient transmission technologies are needed to increase the capacity of mobile backhaul, optimization solutions to get the most out of the backhaul capacity are also necessary. This paper analyses the possibility to exploit load balancing among base stations to improve backhaul capacity utilization. Load balancing is realized through cell selection algorithms accounting for both radio interface and backhaul conditions. An analytical model aimed at evaluating the performance of cell selection strategies for mobile networks with backhaul capacity constraints is developed. The analytical model is used to evaluate the performance of a novel backhaul-aware cell selection algorithm and compare it with classical schemes based exclusively on radio information. Obtained results show that the proposed algorithm can achieve a utilization of backhaul resources higher than the traditional cell selection schemes while providing the same radio interface performance. Analytical results have been verified by means of simulation.

Intercell Interference is the main issue limiting the capacity of modern OFDMA-based cellular networks. Recently, extensive research work has been focused on intercell interference coordination since it has been recognized as a key concept to achieve seamless levels of quality of service. Nevertheless, very often this problematic is addressed as a standalone issue. In this work, a novel channel state information feedback scheme is proposed aiming at improving the overall system performance when both channel state information and static interference coordination are jointly considered. By means of the proposed scheme, gains in terms of users throughput, cell edge performance and energy efficiency are achieved with respect to existing aperiodic LTE-based mechanisms without additional complexity.

Nowadays mobile operators are planning and designing their mid/long term strategies based on new OFDMA-based cellular technologies such as LTE and WiMAX. Co-siting and re-utilization of existing facilities are within their roadmap in order to keep CAPEX as low as possible. Therefore, the optimization of OFDMA networks subject to fixed/previous (and usually suboptimal) coverage is mandatory. In addition, recently there is a great interest in reducing OPEX mainly by means of energy savings. This paper presents a novel multiobjective formulation aiming at improving the performance of OFDMA networks where full frequency reuse is employed. The proposed framework is flexible and results indicate that it is also effective as it improves both spectral efficiency and cell edge performance while it simultaneously reduces energy consumption.

The provision of Quality of Service (QoS) to users of LTE networks depends to a large degree on the choice of an appropriate scheduling algorithm able to meet the requirements of mobile operators. Dynamic packet scheduling has been recognized as a key approach to maximize the utility of OFDMA-based systems due to its inherent ability to exploit the frequency selectiveness of wideband channels both in time and frequency domain. However, one of the main issues associated to dynamic scheduling is the high amount of signaling overhead required to provide users with resource allocation information. While the impact of control channel limitations on LTE VoIP capacity has been widely studied yet, tradeoffs associated to control channel usage and the provision of QoS for Non-Real Time (NRT) services has been basically omitted in current literature. In this paper, such tradeoffs have been addressed from several perspectives. Results show that the relationship between scheduling policies, offered levels of QoS (expressed in terms of guaranteed bit rates) and control channels capacity is not trivial and requires careful planning.

This paper presents a joint study of several intercell interference coordination strategies considering both static and dynamic approaches, and with different adjustments in their basic parameters. A wide evaluation is presented with special emphasis on the efficiency vs. fairness tradeoff. Besides, additional performance metrics have been considered as enablers of a full understanding of the strengths and weaknesses of each method. Results show that, although spectral efficiency can achieve similar values with proper tuning, certain schemas outperform others in important parameters such as the effectiveness in the utilization of resources. Dynamic semi-centralized approaches appear as an attractive option with an acceptable level of adaptability, moderate complexity and good performance.

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.

3GPP LTE is the evolution of UMTS which will make possible to deliver next generation high quality multimedia services according to the users' expectations. The flexibility of the downlink OFDM radio interface with Adaptive Modulation and Coding (AMC), MIMO and H-ARQ plays a crucial role in achieving the low latency and high spectral efficiency promised by the new radio access standard. This paper presents a LTE DL link level simulator whose main purpose is to generate suitable look-up tables to interface with a system level simulator. In this context, the Exponential Effective SIR (EESIR) metric is a link abstraction model that is used to properly characterize multistate channels. The reference BLER curves in AWGN channel and the parameters of the EESIR model are given for the complete list of CQI's specified for LTE DL. The obtained results also include curves of mean link level throughput for different AMC formats and MIMO configurations.

In mobile access networks, base station (BS) assignment mechanisms are mainly driven by radio conditions since it is generally assumed that the limiting factor is the air interface. This assumption has been proven to be very reasonable when circuit voice was the dominant service and backhaul capacity provisioning accounting for the peak rate at the BSs was an economically feasible option. However, as more efficient air interface technologies are introduced along with higher data rate services, a growing concern is that the transport part of the mobile network can also represent a bottleneck. In this paper we analyze a BS assignment strategy that simultaneously exploits load balancing in both the radio interface and the transport backhaul links. The BS assignment problem is solved by means of simulated annealing heuristics under different deployment scenarios comprising partially-limited backhaul radio access networks (RANs) and the presence of traffic hotspots. Results achieved for the proposed BS assignment strategy are compared to those obtained by common strategies such as minimum path loss (MPL) and load balancing radio (LBR).

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.

Growing number of subscribers and deployments of high speed air interfaces (e.g. HSDPA) are imposing stringent requirements for mobile backhaul. In this paper we perform a comparative study of the transport capacity requirements in an IP-based UTRAN when using either release'99 (i.e. DCH) or high speed channels (i.e. HSDPA) in the air interface. The analysis is focused in the interface between base stations and radio network controllers, referred to in the 3GPP as Iub interface. For both scenarios, the minimum bandwidth to be provisioned in the Iub interface is calculated for voice and data services, under different levels of traffic aggregation and delay requirements. Over such a basis, the influence of the protocol overhead within the bandwidth requirements is identified and a sensitivity analysis to factors such as the network size, traffic model parameters and channel rates is conducted.

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.

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.

This paper develops common radio resource management (CRRM) concepts, which allow exploiting trunking gains of heterogeneous cellular 3GPP-based networks through smart radio access technology selection mechanisms. The presented framework covers the complete development cycle: firstly the theoretical conception of the algorithmic solution also supported by means of an analytical approach, secondly the performance assessment and finally, the algorithm implementation definition on real systems.

This work presents an exhaustive analysis of the main parameters used for radio resource management algorithms as call admission, congestion control and system monitoring, for a multilayer and multiservice UMTS environment. Macrocell and microcell scenarios have been studied both separately and jointly, and the variations on load factor, throughput and UL/DL transmitted powers when considering the jointly mixed scenario, have been carefully analyzed.

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.

This paper studies the influence of the active set main parameters in different UTRA-FDD scenarios by evaluating the system capacity, as well as BS and UE transmitted power levels. Some of the parameters obtained as outputs of the proposed power control algorithm (PC) can be also easily used to optimise the admission procedure and scenario capacity, while avoiding cell congestion.

The specifications of UMTS Terrestrial Radio Access (UTRA) for the physical layer of the downlink make use of orthogonal variable spreading factor (OVSF) codes to preserve the orthogonality between downlink channels of different rates and spreading factors. This technique minimises the downlink intra-cell interference. In order to control the inter-cell interference, every base station multiplies the global downlink signal with a cell specific Gold code (scrambling code). Then, while the inter-cell interference may be modelled using the Gaussian hypothesis (that is: replacing the real interference with a Gaussian noise of the same power), the intra-cell interference requires detailed chip level simulations. In this paper we present results of a chip level simulation of the downlink UTRA physical layer. The objective is to evaluate the raw (uncoded) mean bit error rate (BER) of the system in a realistic environment and conditions. Then, by knowing the BER requirements of the different services, one can easily obtain the maximum capacity in terms of simultaneous connections at any combination of bit rates.

The throughput performance of a mobile S-ALOHA network can be improved considering the capture phenomenon, which also depends on the spatial distribution of the mobiles within the cell. We have studied the capture probabilities that arise in a mobile radio scenario in the presence of fading and shadowing, and considering both, uniform and non-uniform spatial distribution models. In particular we were interested in the limit behaviour of these models, which has been shown to be directly related to the capture probability. This analysis allows a quantitative comparison of three spatial distribution models for mobile users under real mobile channels. The use of an exponential backoff retransmission algorithm is considered. With these assumptions the performance of the anarchic ALOHA is improved considerably obtaining higher throughput values with stabilised behaviour and lower delays values.

An overview of the main characteristics of the real time emulator (RTE) to be implemented in the context of the Rainbow project is presented. First of all, the RTE functional description is shown in order to justify the rationality of the envisaged approach. Next, a description of the emulation and simulation models used in the RTE for CoDiT is provided. Off-line simulation models are used to estimate the parameters to be employed in the emulation of the different scenarios, while the use of emulation models allows for a reduction of the RTE complexity.

This paper presents a comparative study of 16-QAM, 32QAM, 64-QAM, and 128-QAM 140 Mbit/s digital radio in the presence of multipath fading. ConventionalT-spaced and fractional tapspaced equalizers have been considered to compensate for the ISI-induced symbols. The performance measure used is the bit error ratio (BER); thus, upper and lower bounds on BER have been developed. Based on this calculation procedure, results showing the net fade margin versus the gross fade margin have been obtained in a variety of cases that include the presence of both nonlinear and linear equalizer structures.