Showing papers on "Telecommunications link published in 2010"

Multiuser MIMO Achievable Rates With Downlink Training and Channel State Feedback

Abstract: In this paper, we consider a multiple-input-multiple-output (MIMO) fading broadcast channel and compute achievable ergodic rates when channel state information (CSI) is acquired at the receivers via downlink training and it is provided to the transmitter by channel state feedback. Unquantized (analog) and quantized (digital) channel state feedback schemes are analyzed and compared under various assumptions. Digital feedback is shown to be potentially superior when the feedback channel uses per channel state coefficient is larger than 1. Also, we show that by proper design of the digital feedback link, errors in the feedback have a minor effect even if simple uncoded modulation is used on the feedback channel. We discuss first the case of an unfaded additive white Gaussian noise (AWGN) feedback channel with orthogonal access and then the case of fading MIMO multiple access (MIMO-MAC). We show that by exploiting the MIMO-MAC nature of the uplink channel, a much better scaling of the feedback channel resource with the number of base station (BS) antennas can be achieved. Finally, for the case of delayed feedback, we show that in the realistic case where the fading process has (normalized) maximum Doppler frequency shift 0 ? F < 1/2, a fraction 1 - 2F of the optimal multiplexing gain is achievable. The general conclusion of this work is that very significant downlink throughput is achievable with simple and efficient channel state feedback, provided that the feedback link is properly designed.

System Level Simulation of LTE Networks

Abstract: In order to evaluate the performance of new mobile network technologies, system level simulations are crucial. They aim at determining whether, and at which level predicted link level gains impact network performance. In this paper we present a MATLAB computationally efficient LTE system level simulator. The simulator is offered for free under an academic, noncommercial use license, a first to the authors' knowledge. The simulator is capable of evaluating the performance of the Downlink Shared Channel of LTE SISO and MIMO networks using Open Loop Spatial Multiplexing and Transmission Diversity transmit modes. The physical layer model is based on the postequalization SINR and provides the simulation pre-calculated "fading parameters" representing each of the individual interference terms. This structure allows the fading parameters to be pregenerated offline, vastly reducing computational complexity at run-time.

Mobile communication method and radio base station

Abstract: In a mobile communication method by which a mobile station (UE) transmits a control signal to a radio base station (eNB) in an uplink by using an uplink dedicated resource, different methods for determining whether or not a synchronization state is established in the uplink, are used depending on whether or not the uplink dedicated resource is set up.

Efficient resource allocation for device-to-device communication underlaying LTE network

Abstract: Device-to-device (D2D) communication as an underlaying cellular network empowers user-driven rich multimedia applications and also has proven to be network efficient offloading eNodeB traffic. However, D2D transmitters may cause significant amount of interference to the primary cellular network when radio resources are shared between them. During the downlink (DL) phase, primary cell UE (user equipment) may suffer from interference by the D2D transmitter. On the other hand, the immobile eNodeB is the victim of interference by the D2D transmitter during the uplink (UL) phase when radio resources are allocated randomly. Such interference can be avoided otherwise diminish if radio resource allocated intelligently with the coordination from the eNodeB. In this paper, we formulate the problem of radio resource allocation to the D2D communications as a mixed integer nonlinear programming (MINLP). Such an optimization problem is notoriously hard to solve within fast scheduling period of the Long Term Evolution (LTE) network. We therefore propose an alternative greedy heuristic algorithm that can lessen interference to the primary cellular network utilizing channel gain information. We also perform extensive simulation to prove the efficacy of the proposed algorithm.

MIMO techniques in WiMAX and LTE: a feature overview

Abstract: IEEE 802.16m and 3GPP LTE-Advanced are the two evolving standards targeting 4G wireless systems. In both standards, multiple-input multiple-output antenna technologies play an essential role in meeting the 4G requirements. The application of MIMO technologies is one of the most crucial distinctions between 3G and 4G. It not only enhances the conventional point-to-point link, but also enables new types of links such as downlink multiuser MIMO. A large family of MIMO techniques has been developed for various links and with various amounts of available channel state information in both IEEE 802.16e/m and 3GPP LTE/LTE-Advanced. In this article we provide a survey of the MIMO techniques in the two standards. The MIMO features of the two are compared, and the engineering considerations are depicted.

Uplink control data transmission

Abstract: Methods and systems for transmitting uplink control information and feedback are disclosed for carrier aggregation systems. A user equipment device may be configured to transmit uplink control information and other feedback for several downlink component carriers using one or more uplink component carriers. The user equipment device may be configured to transmit such data using a physical uplink control channel rather than a physical uplink shared channel. The user equipment device may be configured to determine the uplink control information and feedback data that is to be transmitted, the physical uplink control channel resources to be used to transmit the uplink control information and feedback data, and how the uplink control information and feedback data may be transmitted over the physical uplink control channel.

Capacity of the Gaussian Two-Way Relay Channel to Within ${1\over 2}$ Bit

Abstract: In this paper, a Gaussian two-way relay channel, where two source nodes exchange messages with each other through a relay, is considered. We assume that all nodes operate in full-duplex mode and there is no direct channel between the source nodes. We propose an achievable scheme composed of nested lattice codes for the uplink and structured binning for the downlink. Unlike conventional nested lattice codes, our codes utilize two different shaping lattices for source nodes based on a three-stage lattice partition chain, which is a key ingredient for producing the best gap-to-capacity results to date. Specifically, for all channel parameters, the achievable rate region of our scheme is within 1/2 bit from the capacity region for each user and its sum rate is within log3/2 bit from the sum capacity.

Cooperative Interference Management With MISO Beamforming

Abstract: In this correspondence, we study the downlink transmission in a multi-cell system, where multiple base stations (BSs) each with multiple antennas cooperatively design their respective transmit beamforming vectors to optimize the overall system performance. For simplicity, it is assumed that all mobile stations (MSs) are equipped with a single antenna each, and there is one active MS in each cell at one time. Accordingly, the system of interests can be modeled by a multiple-input single-output (MISO) Gaussian interference channel (IC), termed as MISO-IC, with interference treated as noise. We propose a new method to characterize different rate-tuples for active MSs on the Pareto boundary of the achievable rate region for the MISO-IC, by exploring the relationship between the MISO-IC and the cognitive radio (CR) MISO channel. We show that each Pareto-boundary rate-tuple of the MISO-IC can be achieved in a decentralized manner when each of the BSs attains its own channel capacity subject to a certain set of interference-power constraints (also known as interference-temperature constraints in the CR system) at the other MS receivers. Furthermore, we show that this result leads to a new decentralized algorithm for implementing the multi-cell cooperative downlink beamforming.

Method and apparatus for random access in multicarrier wireless communications

Abstract: Methods and apparatus for random access in multicarrier wireless communications are disclosed. Methods and apparatus are provided for physical random access channel (PRACH) resource signaling, PRACH resource handling, preamble and PRACH resource selection, random access response (RAR) reception, preamble retransmission, and transmission and reception of subsequent messages. A method for maintaining an allowed multicarrier uplink (UL) random access channel (RACH) configuration set by adding an UL carrier to the allowed RACH configuration set provided that a triggering event occurs and performing a random access (RA) procedure using the allowed RACH configuration set. A method for sending data in multicarrier wireless communications by determining a set of available UL carriers and selecting an UL carrier from the set of available UL carriers.

Logical channel prioritization procedure for generating multiple uplink transport blocks

Abstract: The invention relates to methods for scheduling of uplink transmission and generating transport blocks according to multiple received uplink assignments. Furthermore, the invention is also related to the implementation of these methods in hardware and software. To propose strategies for generating plural transport blocks within a given time constraint, the invention introduces prioritization of the uplink assignments, so that multiple uplink assignments can be ranked in the mobile terminal in a priority order. The prioritization of the uplink assignments is used to determine the order in which the individual transport blocks corresponding to the uplink assignments are filled, respectively how the data of different logical channels is multiplexed to the transport blocks for transmission in the uplink. Another aspect of the invention is to suggest joint logical channel procedures that operate on virtual transport blocks accumulated from the received uplink assignments. One or more such joint logical channel procedure can be performed in parallel.

Downlink Interference Alignment

Abstract: We develop an interference alignment (IA) technique for a downlink cellular system. In the uplink, IA schemes need channel-state-information exchange across base-stations of different cells, but our downlink IA technique requires feedback only within a cell. As a result, the proposed scheme can be implemented with a few changes to an existing cellular system where the feedback mechanism (within a cell) is already being considered for supporting multi-user MIMO. Not only is our proposed scheme implementable with little effort, it can in fact provide substantial gain especially when interference from a dominant interferer is significantly stronger than the remaining interference: it is shown that in the two-isolated cell layout, our scheme provides four-fold gain in throughput performance over a standard multi-user MIMO technique. We show through simulations that our technique provides respectable gain under a more realistic scenario: it gives approximately 20% gain for a 19 hexagonal wrap-around-cell layout. Furthermore, we show that our scheme has the potential to provide substantial gain for macro-pico cellular networks where pico-users can be significantly interfered with by the nearby macro-BS.

Apparatus and method for uplink power control for a wireless transmitter/receiver unit utilizing multiple carriers

Abstract: A method and apparatus for determining uplink power in a wireless transmit receive unit (WTRU). The WTRU operates in a carrier aggregated system. The WTRU is configured to receive a plurality of uplink power parameters indexed to one of a plurality of uplink carriers and receive a transmit power control command indexed to the one of the plurality of uplink carriers. The WTRU is configured to determine a pathloss of the one of the plurality of uplink carriers and determine a transmit power for the one of the plurality of uplink carriers based on the plurality of power parameters, the transmit power control command, and the pathloss.

Coordinated linear beamforming in downlink multi-cell wireless networks

Abstract: We consider a multi-cell wireless network with universal frequency reuse and treat the problem of co-channel interference mitigation in the downlink channel. Assuming that each base station serves multiple single-antenna mobiles via space-division multiple-access, we jointly optimize the linear beam-vectors across a set of coordinated cells and resource slots: the objective function to be maximized is the instantaneous weighted sum-rate subject to per-base-station power constraints. After deriving the general structure of the optimal beam-vectors, a novel iterative algorithm is presented which attempts to solve the Karush-Kuhn-Tucker conditions of the non-convex problem at hand. The proposed algorithm admits a distributed implementation which we illustrate. Also, various approaches to choose the initial beam-vectors are considered, one of which maximizes the signal-to-leakage-plus-noise ratio. Finally, simulation results are provided to assess the performance of the proposed algorithm.

A method and apparatus for mimo repeater chains in a wireless communication network

Abstract: In one or more embodiments taught herein, a multi-band MIMO repeater is configured to translate normal wireless mobile bands into other frequency bands in the physical layer. An advantageous, multi-hop repeater chain includes two or more such repeaters, for propagating downlink signals from a base station, and for propagating uplink signals to the base station. Each such repeater may use paralleled homodyne structure transceivers for better SNR, spectrum combiners for uplink signal aggregation, spectrum separators for downlink signal de-aggregation, water mark signal inserters for optimization, and, among other things, spectrum analyzers for frequency band selection. In at least one such embodiment, a multi-hop repeater chain is configured for MIMO operation in an LTE Advanced or other MIMO network, to deliver high data rate over larger distances — e.g., further away from cell base stations.

Effective Interference Cancellation Scheme for Device-to-Device Communication Underlaying Cellular Networks

Abstract: It is expected that Device-to-Device (D2D) communication is allowed to underlay future cellular networks such as IMT-Advanced for spectrum efficiency. However, by reusing the uplink spectrums with the cellular system, the interference to D2D users has to be addressed to maximize the overall system performance. In this paper, a novel method to deal with the resource allocation and interference avoidance issues by utilizing the network peculiarity of a hybrid network to share the uplink resource is proposed and the implementation details are described in a real cellular system. Simulation results prove that satisfying performance can be achieved by using the proposed mechanism.

Downlink Interference Alignment

Abstract: We develop an interference alignment (IA) technique for a downlink cellular system. In the uplink, IA schemes need channel-state-information exchange across base-stations of different cells, but our downlink IA technique requires feedback only within a cell. As a result, the proposed scheme can be implemented with minimal changes to an existing cellular system where the feedback mechanism (within a cell) is already being considered for supporting multi-user MIMO. Not only is our proposed scheme implementable with little effort, it can in fact provide substantial gain especially when interference from a dominant interferer is significantly stronger than the remaining interference: it is shown that in the two-isolated cell layout, our scheme provides four-fold gain in throughput performance over a standard multi-user MIMO technique. We show through simulations that our technique provides respectable gain under a more realistic scenario: it gives approximately 20% gain for a 19 hexagonal wrap-around-cell layout.

Power Control and Channel Allocation in Cognitive Radio Networks with Primary Users' Cooperation

Abstract: We consider a point-to-multipoint cognitive radio network that shares a set of channels with a primary network. Within the cognitive radio network, a base station controls and supports a set of fixed-location wireless subscribers. The objective is to maximize the throughput of the cognitive network while not affecting the performance of primary users. Both downlink and uplink transmission scenarios in the cognitive network are considered. For both scenarios, we propose two-phase mixed distributed/centralized control algorithms that require minimal cooperation between cognitive and primary devices. In the first phase, a distributed power updating process is employed at the cognitive and primary nodes to maximize the coverage of the cognitive network while always maintaining the constrained signal to interference plus noise ratio of primary transmissions. In the second phase, centralized channel assignment is carried out within the cognitive network to maximize its throughput. Numerical results are obtained for the behaviors and performance of our proposed algorithms.

High-Speed OQPSK and Efficient Power Transfer Through Inductive Link for Biomedical Implants

Abstract: Biomedical implants require wireless power and bidirectional data transfer. We pursue our previous work on a novel topology for a multiple carrier inductive link by presenting the fabricated coils. We show that the coplanar geometry approach is better suited for displacement tolerance. We provide a theoretical analysis of the efficiency of power transfer and phase-shift-keying communications through an inductive link. An efficiency of up to 61% has been achieved experimentally for power transfer and a data rate of 4.16 Mb/s with a bit-error rate of less than 2 × 10-6 has been obtained with our fabricated offset quadrature phase-shift keying modules due to the inductive link optimization presented in this paper.

Signaling uplink control information in lte-a

Abstract: Methods and systems for transmitting uplink control information in an LTE Advanced system are disclosed. A user device may determine whether uplink control information and/or available channels meet certain criteria and determine whether the uplink control information should be transmitted on a physical uplink control channel, a physical uplink shared channel, or both, based on the criteria. Criteria may include the size of the uplink control information (absolute size or relative to space available on a channel or a threshold value), the type of control information bits, the number of available (i.e., active or configured) component carriers, and the amount of power that may be required to transmit the uplink control information on more than one channel.

Pilot Contamination Reduction in Multi-User TDD Systems

Abstract: This paper considers the problem of interference mitigation in multi-cell multi-antenna time division duplex (TDD) wireless systems for downlink transmission. An efficient way to obtain channel state information (CSI) at the base station is by using uplink pilots and reciprocity of the downlink channel. At the same time, it has been shown that pilots from different cells contaminate each other, resulting in corruption of precoding matrices used by base stations, and high inter-cell interference. This paper studies the effects of shifting the location of pilots in time frames used in neighboring cells, and its effectiveness in obtaining better channel estimates, and, thereby, inter-cell interference reduction.

Optimum and suboptimum channel estimation for the uplink of CDMA mobile radio systems with joint detection

Abstract: In the present paper, channel estimation in the uplink of CDMA mobile radio systems with burst transmission applying joint detection is considered. The different radio channels are estimated at the receiver using known midamble codes. Either maximum-likelihood, i.e. optimum, or suboptimum channel estimation can be realized at the receiver. Several methods for constructing code sets for the simultaneously active users are proposed. It is shown that the structure of the channel estimator for a multi-user synchronous CDMA mobile radio system is the same as for a single-user system when the mid amble codes of the users are segments derived from a single basic code. Furthermore, it is shown that the channel estimator can be implemented as a correlator when the midamble codes are constructed from a periodic basic code. Finally, the effect of noisy channel estimation, i.e. the presence of channel estimation errors, on the detected data is examined.

Method and apparatus for contention-based uplink data transmission

Abstract: A method and apparatus for a wireless transmit receive unit (WTRU) to use a contention-based uplink communications channel, applies a rule-based restriction of access to the contention-based uplink channel that attempts to use at least one contention-free uplink channel allocation for uplink transmissions on a condition that at least one contention-free uplink channel allocation has been granted.

Method and apparatus for transmitting uplink control information for carrier aggregated spectrums

Abstract: Methods and apparatus for transmitting uplink control information (UCI) in carrier aggregated spectrums are disclosed. UCI may include, but is not limited to, Precoding Matrix Indicator (PMI), Rank Indication (RI), Channel Quality Indicator (CQI), Acknowledge/Not Acknowledge (ACK/NACK) and Scheduling Request (SR). For symmetric carrier aggregation, uplink (UL) and downlink (DL) component carriers may be paired and use physical uplink control channel (PUCCH) in each UL component carrier to send UCI for the corresponding DL component carrier. For asymmetric carrier aggregation, methods are provided for UCI transmission and resource allocation depending on component carrier configuration or assignment. Methods are provided for multiple and single component carrier configurations that may further provide backward compatibility.

LDS-OFDM an Efficient Multiple Access Technique

Abstract: In this paper LDS-OFDM is introduced as an uplink multicarrier multiple access scheme. LDS-OFDM uses Low Density Signature (LDS) structure for spreading the symbols in frequency domain. This technique benefits from frequency diversity besides its ability of supporting parallel data streams up to 400% more than the number of subcarriers (overloaded condition). The performance of LDS-OFDM is evaluated and compared with conventional OFDMA systems over multipath fading channel. Monte Carlo based simulations for various loading conditions indicate significant performance improvement over OFDMA system.

Calculation of the spatial preprocessing and link adaption feedback for 3GPP UMTS/LTE

Abstract: This paper presents an efficient method for calculating the Precoding Matrix Indicator (PMI), Rank Indicator (RI) and Channel Quality Indicator (CQI) at a Long Term Evolution (LTE) User Equipment (UE). The indicators are required for spatial preprocessing and link adaption in the downlink of a 3GPP UMTS/LTE system. To reduce the computational burden for the UE, our method decomposes the problem into two separate steps, one of jointly evaluating the PMI and RI based on a mutual information metric and one of choosing the CQI value to achieve a given target Block Error Ratio (BLER) constraint. The performance of the method is evaluated utilizing an LTE downlink physical layer simulator. The influence of estimated channel knowledge on the feedback choice is investigated for Least Squares (LS) and Linear Minimum Mean Squared Error (LMMSE) channel estimators.

Fairness-aware radio resource management in downlink OFDMA cellular relay networks

Abstract: Relaying and orthogonal frequency division multiple access (OFDMA) are the accepted technologies for emerging wireless communications standards. The activities in many wireless standardization bodies and forums, for example IEEE 802.16 j/m and LTE-Advanced, attest to this fact. The availability or lack thereof of efficient radio resource management (RRM) could make or mar the opportunities in these networks. Although distributed schemes are more attractive, it is essential to seek outstanding performance benchmarks to which various decentralized schemes can be compared. Therefore, this paper provides a comprehensive centralized RRM algorithm for downlink OFDMA cellular fixed relay networks in a way to ensure user fairness with minimal impact on network throughput. In contrast, it has been observed that pure opportunistic schemes and fairness-aware schemes relying solely on achievable and allocated capacities may not attain the desired fairness, e.g., proportional fair scheduling. The proposed scheme is queue-aware and performs three functions jointly; dynamic routing, fair scheduling, and load balancing among cell nodes. We show that the proposed centralized scheme is different from the traditional centralized schemes in terms of the substantial savings in complexity and feedback overhead.

Transmitting uplink control information over a data channel or over a control channel

Abstract: Methods and apparatus are described for a User Equipment (UE) to concurrently transmit Uplink Control Information (UCI) and data information to a Node B. The Node B can configure the UE whether to transmit UCI together with data information in a Physical Uplink Shared CHannel (PUSCH) or, separate from data information, in a Physical Uplink Control CHannel (PUCCH). The UE may also determine whether to transmit UCI together with data information in the PUSCH or, separate from data information, in the PUCCH based on criteria involving either a ratio of PUSCH resources for UCI transmission over the total PUSCH resources, a Modulation and Coding Scheme (MCS) for the data information, an absolute power difference between PUCCH and PUSCH transmissions, whether the PUSCH transmission uses frequency hopping, or whether spatial multiplexing is used for the data transmission.

Control and data signaling in heterogeneous wireless communication networks

Abstract: A method in a wireless communication device including receiving control signaling from a base station in a control region of a downlink carrier spanning a first bandwidth, receiving a signaling message from the base station indicating a second bandwidth, receiving a first control message within the control region using a first Downlink Control Information (DCI) format size, the first DCI format size based on the first bandwidth, and receiving a second control message within the control region using a second DCI format size, the second DCI format size based on the second bandwidth, wherein the second bandwidth is distinct from the first bandwidth and the first and second control messages indicate downlink resource assignments for the downlink carrier.

Method and system for transmitting downlink control information

Abstract: The present invention discloses a method and a system for transmitting downlink control information, wherein when a base station is not configured with a carrier indicator field, the base station transmits a physical downlink control channel bearing the corresponding downlink control information on each downlink component carrier in a user equipment's physical downlink shared channel (PDSCH) carrier set, and the user equipment detects the corresponding downlink control information on each downlink component carrier in the configured PDSCH carrier set. When a base station is configured with a carrier indicator field, the base station transmits the physical downlink control channel bearing the corresponding downlink control information on each downlink component carrier in the configured physical downlink control channel (PDCCH) carrier set, and the user equipment detects the corresponding downlink control information on each downlink component carrier in the PDCCH carrier set.

Joint power allocation and relay selection for multiuser cooperative communication

Abstract: User cooperation, whereby multiple users share their antennas and transmit to a common destination in a collaborative manner, has been shown to be an effective way to achieve spatial diversity. We propose in this paper, a strategy to minimize the total transmit power in a decode-and-forward (DF) multi-user, multi-relay cooperative uplink, such that each user satisfies its quality-of-service (QoS) data rate. Each user in the proposed system transmits its own data towards the base station and also serves as a relay for other users. The base station assigns one or more relays to each user in order to minimize total power in the uplink. The relay selection is based upon the instantaneous user to base station channels, inter-user channels and also the target rates of the users. The simulation results indicate significant power savings over a non-cooperative uplink, under proposed joint relay selection and power minimization algorithm in a DF cooperative uplink when using a space-time coded cooperative diversity.