Showing papers on "Telecommunications link published in 2012"

Modeling and Analysis of K-Tier Downlink Heterogeneous Cellular Networks

Abstract: Cellular networks are in a major transition from a carefully planned set of large tower-mounted base-stations (BSs) to an irregular deployment of heterogeneous infrastructure elements that often additionally includes micro, pico, and femtocells, as well as distributed antennas. In this paper, we develop a tractable, flexible, and accurate model for a downlink heterogeneous cellular network (HCN) consisting of K tiers of randomly located BSs, where each tier may differ in terms of average transmit power, supported data rate and BS density. Assuming a mobile user connects to the strongest candidate BS, the resulting Signal-to-Interference-plus-Noise-Ratio (SINR) is greater than 1 when in coverage, Rayleigh fading, we derive an expression for the probability of coverage (equivalently outage) over the entire network under both open and closed access, which assumes a strikingly simple closed-form in the high SINR regime and is accurate down to -4 dB even under weaker assumptions. For external validation, we compare against an actual LTE network (for tier 1) with the other K-1 tiers being modeled as independent Poisson Point Processes. In this case as well, our model is accurate to within 1-2 dB. We also derive the average rate achieved by a randomly located mobile and the average load on each tier of BSs. One interesting observation for interference-limited open access networks is that at a given \sinr, adding more tiers and/or BSs neither increases nor decreases the probability of coverage or outage when all the tiers have the same target-SINR.

Achieving "Massive MIMO" Spectral Efficiency with a Not-so-Large Number of Antennas

Abstract: Time-Division Duplexing (TDD) allows to estimate the downlink channels for an arbitrarily large number of base station antennas from a finite number of orthogonal uplink pilot signals, by exploiting channel reciprocity. Based on this observation, a recently proposed "Massive MIMO" scheme was shown to achieve unprecedented spectral efficiency in realistic conditions of distance-dependent pathloss and channel coherence time and bandwidth. The main focus and contribution of this paper is an improved Network-MIMO TDD architecture achieving spectral efficiencies comparable with "Massive MIMO", with one order of magnitude fewer antennas per active user per cell (roughly, from 500 to 50 antennas). The proposed architecture is based on a family of Network-MIMO schemes defined by small clusters of cooperating base stations, zero-forcing multiuser MIMO precoding with suitable inter-cluster interference mitigation constraints, uplink pilot signals allocation and frequency reuse across cells. The key idea consists of partitioning the users into equivalence classes, optimizing the Network-MIMO scheme for each equivalence class, and letting a scheduler allocate the channel time-frequency dimensions to the different classes in order to maximize a suitable network utility function that captures a desired notion of fairness. This results in a mixed-mode Network-MIMO architecture, where different schemes, each of which is optimized for the served user equivalence class, are multiplexed in time-frequency. In order to carry out the performance analysis and the optimization of the proposed architecture in a systematic and computationally efficient way, we consider the large-system regime where the number of users, the number of antennas, and the channel coherence block length go to infinity with fixed ratios.

Device communication using a reduced channel bandwidth

Abstract: Systems and/or methods for supporting communications at a reduced bandwidth with a full bandwidth network such as a long-term evolution (LTE) network may be disclosed. For example, inband assignments such as downlink assignments and/or uplink grants may be provided and/or received and transmissions may be monitored and/or decoded based on the inband assignment. Additionally, information (e.g. a definition or configuration) associated with an ePDCCH may be provided and/or received and ePDCCH resources may be monitored and/or decoded based on such information. An indication for support of a reduced bandwidth by the full bandwidth network may also be provided and/or received and control channels in the reduced or narrow bandwidth may be monitored and/or decoded based on the indication. A PRACH preamble and/or a multi-type subframe definition may also be provided and/or used for support of such a reduced bandwidth.

Systems and methods for an enhanced control channel

Abstract: Methods and systems for sending and receiving an enhanced downlink control channel are disclosed. The method may include receiving control channel information via an enhanced control channel. The method may also include using the control channel information to receive a shared channel. The method may include detecting the presence of the enhanced control channel in a given subframe. The enhanced control channel may be transmitted over multiple antenna ports. For example, code divisional multiplexing and de-multiplexing and the use of common and UE-specific reference signals may be utilized. New control channel elements may be defined, and enhanced control channel state information (CSI) feedback may be utilized. The presence or absence of legacy control channels may affect the demodulation and or decoding methods. The method may be implemented at a WTRU.

Distribution of Downlink SINR in Heterogeneous Cellular Networks

Abstract: The Signal to Interference Plus Noise Ratio (SINR) on a wireless link is an important basis for consideration of outage, capacity, and throughput in a cellular network. It is therefore important to understand the SINR distribution within such networks, and in particular heterogeneous cellular networks, since these are expected to dominate future network deployments . Until recently the distribution of SINR in heterogeneous networks was studied almost exclusively via simulation, for selected scenarios representing pre-defined arrangements of users and the elements of the heterogeneous network such as macro-cells, femto-cells, etc. However, the dynamic nature of heterogeneous networks makes it difficult to design a few representative simulation scenarios from which general inferences can be drawn that apply to all deployments. In this paper, we examine the downlink of a heterogeneous cellular network made up of multiple tiers of transmitters (e.g., macro-, micro-, pico-, and femto-cells) and provide a general theoretical analysis of the distribution of the SINR at an arbitrarily-located user. Using physically realistic stochastic models for the locations of the base stations (BSs) in the tiers, we can compute the general SINR distribution in closed form. We illustrate a use of this approach for a three-tier network by calculating the probability of the user being able to camp on a macro-cell or an open-access (OA) femto-cell in the presence of Closed Subscriber Group (CSG) femto-cells. We show that this probability depends only on the relative densities and transmit powers of the macro- and femto-cells, the fraction of femto-cells operating in OA vs. Closed Subscriber Group (CSG) mode, and on the parameters of the wireless channel model. For an operator considering a femto overlay on a macro network, the parameters of the femto deployment can be selected from a set of universal curves.

Network MIMO With Linear Zero-Forcing Beamforming: Large System Analysis, Impact of Channel Estimation, and Reduced-Complexity Scheduling

Abstract: We consider the downlink of a multicell system with multiantenna base stations and single-antenna user terminals, arbitrary base station cooperation clusters, distance-dependent propagation pathloss, and general “fairness” requirements. Base stations in the same cooperation cluster employ joint transmission with linear zero-forcing beamforming, subject to sum or per-base station power constraints. Intercluster interference is treated as noise at the user terminals. Analytic expressions for the system spectral efficiency are found in the large-system limit where both the numbers of users and antennas per base station tend to infinity with a given ratio. In particular, for the per-base station power constraint, we find new results in random matrix theory, yielding the squared Frobenius norm of submatrices of the Moore-Penrose pseudo-inverse for the structured non-i.i.d. channel matrix resulting from the cooperation cluster, user distribution, and path-loss coefficients. The analysis is extended to the case of nonideal Channel State Information at the Transmitters obtained through explicit downlink channel training and uplink feedback. Specifically, our results illuminate the trade-off between the benefit of a larger number of cooperating antennas and the cost of estimating higher-dimensional channel vectors. Furthermore, our analysis leads to a new simplified downlink scheduling scheme that preselects the users according to probabilities obtained from the large-system results, depending on the desired fairness criterion. The proposed scheme performs close to the optimal (finite-dimensional) opportunistic user selection while requiring significantly less channel state feedback, since only a small fraction of preselected users must feed back their channel state information.

Downlink MIMO in LTE-advanced: SU-MIMO vs. MU-MIMO

Abstract: Single-user multi-antenna technologies are well upported in current standard specifications like LTE Release 8/9. Further development of the specification (LTE-Advanced) is expected to conform to the requirements for IMT-Advanced systems. One of the key enabling features of LTE-Advanced to meet IMT-Advanced downlink performance requirements is multi-user MIMO, where a transmitter serves multiple users simultaneously on the same frequency resource, primarily relying on spatial separation. In general, multi-user MIMO is beneficial for improving average user spectral efficiency. However, cell edge user spectral efficiency may be reduced if multi-user MIMO is used exclusively, due to residual inter-user interference arising from practical multi-user beamforming and reduced transmit power allocated to each user. Therefore, it should be possible to configure the UE-specific transmission mode to support dynamic switching between single-user MIMO and multi-user MIMO to balance the cell edge user spectral efficiency as well as the average cell user spectral efficiency. In this article, we study various aspects of multi-user MIMO including design philosophy, multi-user precoding, and control signaling. The associated feedback schemes, including those that facilitate dynamic switching, are discussed. Performance evaluation is conducted to demonstrate the gain of dynamically switched single-user and multiuser MIMO as opposed to traditional single-user MIMO.

Optimization of UAV Heading for the Ground-to-Air Uplink

Abstract: We consider a collection of single-antenna ground nodes communicating with a multi-antenna unmanned aerial vehicle (UAV) over a multiple-access ground-to-air communications link The UAV uses beamforming to mitigate inter-user interference and achieve spatial division multiple access (SDMA) First, we consider a simple scenario with two static ground nodes and analytically investigate the effect of the UAV's heading on the system sum rate We then study a more general setting with multiple mobile ground-based terminals, and develop an algorithm for dynamically adjusting the UAV heading to maximize the approximate ergodic sum rate of the uplink channel, using a prediction filter to track the positions of the mobile ground nodes For the common scenario where a strong line-of-sight (LOS) channel exists between the ground nodes and UAV, we use an asymptotic analysis to find simplified versions of the algorithm for low and high SNR We present simulation results that demonstrate the benefits of adapting the UAV heading in order to optimize the uplink communications performance The simulation results also show that the simplified algorithms provide near-optimal performance

Dynamic uplink-downlink configuration and interference management in TD-LTE

Abstract: Transmissions in different cells of a time-division duplex system are typically synchronous in order to eliminate the base station-to-base station and terminal-to-terminal interference. The synchronous operation limits dynamic resource configuration for downlink and uplink transmissions. Today, as a large percentage of mobile traffic is generated in hotspots and indoor environments, heterogeneous networks comprising high-power/wide-area and low-power/local-area network nodes are becoming a reality. Such heterogeneous networks provide opportunities to exploit dynamic uplink-downlink configuration in TDD systems, adapting to the individual traffic needs of a specific cell area. This article presents a tutorial overview of dynamic uplink-downlink configuration and interference management in time-division Long Term Evolution, including motivations, target deployment scenarios, opportunities and challenges, system requirements, design aspects, and performance evaluations.

Energy-Efficient Resource Allocation in OFDMA Networks

Abstract: The widespread application of multimedia wireless services and requirements of ubiquitous access have triggered rapidly booming energy consumption at both the base station side and the user equipment (UE) side. Hence, energy-efficient design in wireless networks is very important and is becoming an inevitable trend. In this paper, we study the energy-efficient resource allocation in both downlink and uplink cellular networks with orthogonal frequency division multiple access (OFDMA). For the downlink transmission, the generalized energy efficiency (EE) is maximized while for the uplink case the minimum individual EE is maximized, both under certain prescribed per-UE quality-of-service (QoS) requirements. For both transmission scenarios, we first provide the optimal solution and then develop a suboptimal but low-complexity approach by exploring the inherent structure and property of the energy-efficient design. For the downlink case, by modifying the original problem, we also find a computationally efficient and numerically tractable upper bound on the EE, which indicates the performance limit and is demonstrated to be quite tight if the number of subcarriers is larger than that of UEs and motivates us to find a near-optimal approach relying on the quasiconcave relation between the modified EE and transmit power. Simulation results show that the energy-efficient design greatly improves EE compared with the conventional spectral-efficient design and the low-complexity suboptimal approaches can achieve a promising tradeoff between performance and complexity.

Methods and systems for wireless networks with relays

Abstract: Methods and systems are provided for use with wireless networks having one or more cell in which each cell includes a base station (BS), at least one relay station (RS) and at least one mobile station (MS). The at least one relay station can be used as an intermediate station for providing communication between the BS and MS. Methods are provided for allocating OFDM resources for communicating between the BS, RS and/or MS for example dividing transmission resources into uplink and downlink transmissions and methods of inserting pilot symbols into transmission resources used by the RS. In some embodiments on the invention, the methods are consistent and/or can be used in conjunction with existing standards such as 802.16e.

LTE-advanced: an operator perspective

Abstract: LTE-Advanced extends the capabilities originally developed in LTE within the 3GPP. Carrier aggregationis the most significant, albeit complex, improvement provided by LTE-Advanced. Bandwidths from various portions of the spectrum are logically concatenated resulting in a virtual block of a much larger band, enabling increased data throughput. Additionally, enhancements to MIMO antenna techniques in the uplink and downlink further increase the data throughput. Cell coverage is improved by means of relay nodes, which connect to donor eNode-Bs. To cope with the many varieties of cell types and sizes (macro, pico, femto), intercell interference control is enhanced to handle these heterogeneous networks. Operators hope to leverage LTE-Advanced to offer their mobile wireless customers a vastly superior user experience.

Method and Wi-Fi device for setting communications mode

Abstract: An embodiment of the present invention discloses a Wi-Fi device, including a radio frequency circuit, a signal processor, an application processor, and a Wi-Fi chip. The application processor is configured to preset the work mode of the Wi-Fi chip to a single input single output SISO mode, and is further configured to acquire a value of a parameter of an uplink wireless network, and when the value of the parameter of the uplink wireless network is determined to be greater than or equal to a preset value, set the work mode of the Wi-Fi chip to a multiple-input multiple-output MIMO mode. An embodiment of the present invention further discloses a method for setting a communications mode.

Inter-device communication in wireless communication systems

Abstract: Systems, methods, and apparatuses for inter-device communication in wireless communication systems are provided. A user equipment (UE) may communicate directly with another UE over a direct inter-device communication link when they are located in proximity. The UE may simultaneously maintain an active communication link with its serving base station while communicating with other UEs over the inter-device communication link. Long term evolution (LTE) downlink or uplink radio resources may be used for communications over the inter-device communication link. Further, radio link parameters may be chosen specifically for the inter-device communication link.

Estimation of Sparse MIMO Channels with Common Support

Abstract: We consider the problem of estimating sparse communication channels in the MIMO context. In small to medium bandwidth communications, as in the current standards for OFDM and CDMA communication systems (with bandwidth up to 20 MHz), such channels are individually sparse and at the same time share a common support set. Since the underlying physical channels are inherently continuous-time, we propose a parametric sparse estimation technique based on finite rate of innovation (FRI) principles. Parametric estimation is especially relevant to MIMO communications as it allows for a robust estimation and concise description of the channels. The core of the algorithm is a generalization of conventional spectral estimation methods to multiple input signals with common support. We show the application of our technique for channel estimation in OFDM (uniformly/contiguous DFT pilots) and CDMA downlink (Walsh-Hadamard coded schemes). In the presence of additive white Gaussian noise, theoretical lower bounds on the estimation of sparse common support (SCS) channel parameters in Rayleigh fading conditions are derived. Finally, an analytical spatial channel model is derived, and simulations on this model in the OFDM setting show the symbol error rate (SER) is reduced by a factor 2 (0 dB of SNR) to 5 (high SNR) compared to standard non-parametric methods - e.g. lowpass interpolation.

Iterative receivers with channel estimation for multi-user MIMO-OFDM: complexity and performance

Abstract: A family of iterative receivers is evaluated in terms of complexity and performance for the case of an uplink multi-user (MU) multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system. The transmission over block fading channels is considered. The analyzed class of receivers is performing channel estimation inside the iterative detection loop, which has been shown to improve estimation performance. As part of our results we illustrate the ability of this type of receiver to reduce the required amount of pilot symbols. A remaining question to ask is which combinations of estimation and detection algorithms that provide the best trade-off between performance and complexity. We address this issue by considering MU detectors and channel estimators, with varying algorithm complexity. For MU detection, two algorithms based on parallel interference cancellation (PIC) are considered and compared with the optimal symbol-wise maximum a-posteriori probability (MAP) detector. For channel estimation, an algorithm performing joint minimum-mean-square-error (MMSE) estimation is considered along with a low complexity replica making use of a Krylov subspace method. An estimator based on the space alternating generalized expectation-maximization (SAGE) algorithm is also considered. Our results show that low-complexity algorithms provide the best tradeoff, even though more receiver iterations are needed to reach a desired performance.

Method for transmitting control information and apparatus for same

Abstract: The present invention pertains to a wireless communication system. Particularly, the present invention relates to a method for transmitting uplink control information and an apparatus for the same, wherein the method comprises the steps of: selecting one uplink control channel resource corresponding to a plurality of HARQ-ACKs, from a plurality of uplink control channel resources; and transmitting a bit value corresponding to the plurality of HARQ-ACKs through the use of the selected uplink control channel resource.

Interference Measurement in Wireless Networks

Abstract: Embodiments contemplate methods, systems, and apparatuses for interference measurement in a wireless communication network, including wireless communication networks the employ MIMO in uplink and/or downlink communication. Embodiments contemplate identifying one or more interference measurement resource elements that may be received from one or more transmission points. Embodiments also contemplate performing interference measurement estimation based at least in part on the identified one or more interference measurement resource elements. Channel state information (CSI) perhaps in the form of reports may be generated based at least in part on the one or more interference measurement estimation. Embodiments also contemplate that the CSI report may be transmitted to one or more nodes. In some embodiments, the one or more interference measurement resource elements may be received as part of a set of resource elements.

A Survey on Uplink Resource Allocation in OFDMA Wireless Networks

Abstract: OFDMA has been selected as the multiple access scheme for state-of-the-art wireless communication systems. Efficient resource allocation in OFDMA wireless networks is essential in order to meet the quality of service requirements of emerging services. In this paper, a survey of resource allocation and scheduling schemes in OFDMA wireless networks is presented. The focus is on the uplink direction. Resource allocation is surveyed in various scenarios: centralized and distributed, instantaneous and ergodic, optimal and suboptimal, single cell and multicell, cooperative and non-cooperative, in addition to different combinations of these variants. Directions for future research are outlined.

Joint spatial division and multiplexing: Realizing massive MIMO gains with limited channel state information

Abstract: We propose Joint Spatial Division and Multiplexing (JSDM), an approach to multiuser MIMO downlink that exploits the structure of the channel vectors correlation in order to allow for a large number of base station antennas while requiring a considerably reduced channel state information (CSI) feedback from the users. Thanks to the reduced CSI requirement, JSDM allows the use of a large number of base station antennas also in FDD systems. This work presents the correlated channel model, the main idea of JSDM precoding, and the design of JSDM precoding, formed by the concatenation of a pre-beamforming matrix based only on the structure of the channel covariance, with suitable multiuser precoding based on the CSI of the reduced dimensional transformed channels. We show that in some cases JSDM incurs no loss of optimality with respect to the MIMO broadcast channel with full CSI.

Low-Complexity Energy-Efficient Scheduling for Uplink OFDMA

Abstract: Energy-efficient wireless communication is very important for battery-constrained mobile devices. For mobile devices in a cellular system, uplink power consumption dominates the wireless power budget because of RF power requirements for reliable transmission over long distances. Our previous work in this area focused on optimizing energy efficiency by maximizing the instantaneous bits-per-Joule metric through iterative approaches, which resulted in significant energy savings for uplink cellular OFDMA transmissions. In this paper, we develop energy efficient schemes with significantly lower complexity when compared to iterative approaches, by considering time-averaged bits-per-Joule metrics. We consider an uplink OFDMA system where multiple users communicate to a central scheduler over frequency-selective channels with high energy efficiency. The scheduler allocates the system bandwidth among all users to optimize energy efficiency across the whole network. Using time-averaged metrics, we derive energy optimal techniques in "closed forms" for per-user link adaptation and resource scheduling across users. Simulation results show that the proposed schemes not only have low complexity but also perform close to the globally optimum solutions obtained through exhaustive search.

Method, system and apparatus for downlink shared channel reception in cooperative multipoint transmissions

Abstract: A method and apparatus may be used to enable reception of a downlink (DL) shared channel in a cooperative multipoint transmission (CoMP). The method and apparatus may determine whether CoMP is applied to a transmission. The method and apparatus may acquire other CoMP related information. The method and apparatus may apply to non-transparent CoMP scenarios.

PAR-Aware Large-Scale Multi-User MIMO-OFDM Downlink

Abstract: We investigate an orthogonal frequency-division multiplexing (OFDM)-based downlink transmission scheme for large-scale multi-user (MU) multiple-input multiple-output (MIMO) wireless systems. The use of OFDM causes a high peak-to-average (power) ratio (PAR), which necessitates expensive and power-inefficient radio-frequency (RF) components at the base station. In this paper, we present a novel downlink transmission scheme, which exploits the massive degrees-of-freedom available in large-scale MU-MIMO-OFDM systems to achieve low PAR. Specifically, we propose to jointly perform MU precoding, OFDM modulation, and PAR reduction by solving a convex optimization problem. We develop a corresponding fast iterative truncation algorithm (FITRA) and show numerical results to demonstrate tremendous PAR-reduction capabilities. The significantly reduced linearity requirements eventually enable the use of low-cost RF components for the large-scale MU-MIMO-OFDM downlink.

Transmit Diversity and Relay Selection Algorithms for Multirelay Cooperative MIMO Systems

Abstract: In this paper, we propose a set of joint transmit diversity selection (TDS) and relay selection (RS) algorithms based on discrete iterative stochastic optimization for the uplink of cooperative multiple-input-multiple-output (MIMO) systems. Decode-and-forward (DF) and amplify-and-forward (AF) multirelay systems with linear minimum mean square error (MSE), successive interference cancelation, and adaptive reception are considered. The problems of TDS and RS are expressed as MSE and mutual information (MI) joint discrete optimization problems and solved using iterative discrete stochastic algorithms. Such an approach circumvents the need for exhaustive searching and results in a range of procedures with low complexity and increased speed of convergence that can track the optimal selection over an estimated channel. The proposed schemes are analyzed in terms of their complexity, convergence, and diversity benefits and are shown to be both stable and computationally efficient. Their performance is then evaluated via MSE, MI, and bit error rate comparisons and shown to outperform conventional cooperative transmission and, in the majority of scenarios, match that of the optimal exhaustive solution.

On Capacity of Large-Scale MIMO Multiple Access Channels with Distributed Sets of Correlated Antennas

Abstract: In this paper, a deterministic equivalent of ergodic sum rate and an algorithm for evaluating the capacity-achieving input covariance matrices for the uplink large-scale multiple-input multiple-output (MIMO) antenna channels are proposed. We consider a large-scale MIMO system consisting of multiple users and one base station with several distributed antenna sets. Each link between a user and an antenna set forms a two-sided spatially correlated MIMO channel with line-of-sight (LOS) components. Our derivations are based on novel techniques from large dimensional random matrix theory (RMT) under the assumption that the numbers of antennas at the terminals approach to infinity with a fixed ratio. The deterministic equivalent results (the deterministic equivalent of ergodic sum rate and the capacity-achieving input covariance matrices) are easy to compute and shown to be accurate for realistic system dimensions. In addition, they are shown to be invariant to several types of fading distribution.

Method for transmitting uplink control information, user equipment, method for receiving uplink control information, and base station

Abstract: In the present invention, a user equipment-specific offset information for indicating first physical uplink control channel (PUCCH) resources, which can be used for transmitting ACK/NACK related to a physical downlink control channel (PDCCH) that is transmitted from a data region of a downlink subframe, is provided to a user equipment by means of a base station. The user equipment, which receives the PDCCH from the data region of the downlink subframe, decides the PUCCH resource, based on offset information and an index of the resource that is included in the PDCCH, and transmits ACK/NACK information that corresponds to the PDCCH to the base station using the PUCCH resource.

Method and apparatus for transmitting control information in wireless communication system

Abstract: The present invention relates to a method for receiving a downlink control signal in a TDD-based wireless communication system, and to an apparatus therefor. The method comprises receiving a downlink signal via a downlink interval in a specific frame including the downlink interval, a guard interval and an uplink interval. A combination of the downlink interval, the guard interval and the uplink interval is given using configuration information on the specific subframe. When the configuration information is given such that the length of the downlink interval is larger than a specific value, detecting a first type of PDCCH is performed in the specific subframe. When the configuration information is given such that the length of the downlink interval is equal to or smaller than the specific value, detecting the first type of PDCCH is skipped in the specific subframe.

Multiuser Detection via Compressive Sensing

Abstract: In this paper, we consider a multiuser detection technique when the signal sparsity is changing over time. The key ingredient of our method is a clever switching between the CS reconstruction algorithm and classical detection depending on the sparsity level of the signals being detected. Since none of these approaches is uniformly better in a situation where the sparsity level is varying, proposed switching algorithm can effectively combine the merits of both. We show that the proposed switching algorithm provides substantial performance gain over individual algorithms in the multiuser detection of CDMA downlink.

Multi-Hop Connectivity Probability in Infrastructure-Based Vehicular Networks

Abstract: Infrastructure-based vehicular networks (consisting of a group of Base Stations (BSs) along the road) will be widely deployed to support Wireless Access in Vehicular Environment (WAVE) and a series of safety and non-safety related applications and services for vehicles on the road. As an important measure of user satisfaction level, uplink connectivity probability is defined as the probability that messages from vehicles can be received by the infrastructure (i.e., BSs) through multi-hop paths. While on the system side, downlink connectivity probability is defined as the probability that messages can be broadcasted from BSs to all vehicles through multi-hop paths, which indicates service coverage performance of a vehicular network. This paper proposes an analytical model to predict both uplink and downlink connectivity probabilities. Our analytical results, validated by simulations and experiments, reveal the trade-off between these two key performance metrics and the important system parameters, such as BS and vehicle densities, radio coverage (or transmission power), and maximum number of hops. This insightful knowledge enables vehicular network engineers and operators to effectively achieve high user satisfaction and good service coverage, with necessary deployment of BSs along the road according to traffic density, user requirements and service types.

Downlink SNR to CQI Mapping for Different Multiple Antenna Techniques in LTE

Abstract: Long Term Evolution (LTE) is a step towards the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile wireless access. In Release 8, LTE was standardized by 3GPP as the successor of the Universal Mobile Telecommunication System (UMTS).Before full commercial deployment of LTE, downlink SNR to CQI mapping for different multiple antenna techniques can be of enormous significance for the operators. Such vital RF parameters should be tuned before full-fledged commercial launch. In LTE, Adaptive Modulation and Coding (AMC) has to ensure a BLER value smaller than 10%. The SNR-to-CQI mapping is required to achieve this goal. In this paper, Downlink SNR to CQI Mapping for LTE has been performed for Flat Rayleigh channel in fast fading in different transmission modes considering HARQ.