Coordinated multipoint or cooperative MIMO is one of the promising concepts to improve cell edge user data rate and spectral efficiency beyond what is possible with MIMOOFDM in the first versions of LTE or WiMAX. Interference can be exploited or mitigated by cooperation between sectors or different sites. Significant gains can be shown for both the uplink and downlink. A range of technical challenges were identified and partially addressed, such as backhaul traffic, synchronization and feedback design. This article also shows the principal feasibility of COMP in two field testbeds with multiple sites and different backhaul solutions between the sites. These activities have been carried out by a powerful consortium consisting of universities, chip manufacturers, equipment vendors, and network operators.

https://mediatum.ub.tum.de/doc/1189369/file.pdf

Coordinated multipoint: Concepts, performance, and field trial results

Motivated by the ongoing discussion on coordinated multipoint in wireless cellular standard bodies, this paper considers the problem of base station cooperation in the downlink of heterogeneous cellular networks. The focus of this paper is the joint transmission scenario, where an ideal backhaul network allows a set of randomly located base stations, possibly belonging to different network tiers, to jointly transmit data, to mitigate intercell interference and hence improve coverage and spectral efficiency. Using tools from stochastic geometry, an integral expression for the network coverage probability is derived in the scenario where the typical user located at an arbitrary location, i.e., the general user, receives data from a pool of base stations that are selected based on their average received power levels. An expression for the coverage probability is also derived for the typical user located at the point equidistant from three base stations, which we refer to as the worst case user. In the special case where cooperation is limited to two base stations, numerical evaluations illustrate absolute gains in coverage probability of up to 17% for the general user and 24% for the worst case user compared with the noncooperative case. It is also shown that no diversity gain is achieved using noncoherent joint transmission, whereas full diversity gain can be achieved at the receiver if the transmitting base stations have channel state information.

/pdf/coordinated-multipoint-joint-transmission-in-heterogeneous-181bmjvmsf.pdf

Coordinated Multipoint Joint Transmission in Heterogeneous Networks

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.

LTE-advanced: an operator perspective

The choice of OFDM-based multi-carrier access techniques for LTE marked a fundamental and farsighted parting from preceding 3GPP networks. With OFDMA in the downlink and SC-FDMA in the uplink, LTE possesses a robust and adaptive multiple access scheme that facilitates many physical layer enhancements. Despite this flexibility, scheduling in LTE is a challenging functionality to design, especially in the uplink. Resource allocation in LTE is made complex, especially when considering its target packet-based services and mobility profiles, both current and emerging, in addition to the use of several physical layer enhancements. In this paper, we offer a tutorial on scheduling in LTE and its successor LTE-Advanced. We also survey representative schemes in the literature that have addressed the scheduling problem, and offer an evaluation methodology to be used as a basis for comparison between scheduling proposals in the literature.

Uplink Scheduling in LTE and LTE-Advanced: Tutorial, Survey and Evaluation Framework

This paper provides a holistic overview of multi-cell scheduling strategies in emerging wireless systems. Towards this objective, the evolution of interference management techniques is thoroughly investigated from simple inter-cell interference coordination (ICIC) techniques towards more advanced coordinated multipoint transmissions (CoMP), while comparing and contrasting their common features and differences. Finally CoMP is explored in detail as an advanced and challenging mechanism to fully cooperate between adjacent cells in order to have an efficient resource allocation and inter-cell interference mitigation in multi-cell environments.

On the Evolution of Multi-Cell Scheduling in 3GPP LTE / LTE-A

Coordinated multi-point transmission/reception is considered for LTE-Advanced as a tool to improve the coverage of high data rates, the cell-edge throughput and/or to increase the system throughput [1]. Joint transmission schemes are mentioned in [1] as an example of coordinated transmission between cells for the downlink. Here, data are transmitted simultaneously either coherently or non-coherently from multiple cells to a single mobile station. In this paper, a centralized MAC scheduling approach for joint transmission coordinated multi-point (JT CoMP) is proposed. Since several base stations transmit jointly to a single mobile station, the base stations are grouped together in so-called clusters. Several cluster strategies are investigated as well. The focus is on schemes that add only low complexity to the existing 3GPP LTE Release 8 system. Simulation results are provided for non-coherent transmission for full buffer and bursty traffic models with various system loads for different static cell clustering approaches.

Centralized scheduling for joint transmission coordinated multi-point in LTE-Advanced

Methods, apparatus and computer program products are provided to improve the efficiency of resource allocation in wireless communication networks. In one provided embodiment, a wireless communication device determines a received signal strength of each of a number of signals received from a number of transmission sectors, provides first channel information for first signals including a signal having a highest received signal strength and signals having a received signal strength above a specified level relative to the highest received signal strength, provides second channel information for second signals including signals having a received signal strength below the specified level, and receives an allocation of one or more resource blocks from assigned transmission sectors based on a ranking of the first channel information, whereby the one or more resource blocks are reallocated to another wireless communication device, from another transmission sector, based on the second channel information. This Abstract is provided for the sole purpose of complying with the Abstract requirement rules that allow a reader to quickly ascertain the disclosed subject matter. Therefore, it is to be understood that it should not be used to interpret or limit the scope or the meaning of the claims.

Resource block reuse for coordinated multi-point transmission

Certain aspects of the present disclosure relate to a hybrid approach for Physical Downlink Shared Channel (PDSCH) Interference Cancellation (IC). In certain aspects, if the PDSCH information is known for a serving cell but not be known for interfering cell(s), a hybrid approach that involves using Codeword-level IC (CWIC) for the serving cell and using Symbol-level IC (SLIC) for the interfering cells may be used for better IC performance. The hybrid IC approach may start with a UE attempting to decode the serving cell PDSCH. If the decode is unsuccessful, the UE may perform CWIC for the serving cell followed by SLIC using the results of the CWIC stage. After the SLIC stage, the UE may attempt to decode the serving cell PDSCH again. The UE may perform multiple operations of this method until the serving cell PDSCH is successfully decoded or a maximum number of iterations is reached.

Hybrid Approach for Physical Downlink Shared Channel (PDSCH) Interference Cancellation

Methods, systems, and devices are described for generating a hybrid waveform for data transmission between a transmitting device and a receiving device. The transmitting device may employ an OFDM processing technique to periodically transmit known first pilot symbols mapped from a signal constellation where each signal has equal energy during a first time period and a cyclic prefix based single-carrier (CP-SC) processing technique to transmit data packets and second known pilot symbols during a second time period. Channel estimation is based on first pilot symbols, which are inserted into all subcarriers of OFDM symbol blocks within a specific period. Channel estimation tracking is based on the second pilot symbols interleaved within data packets. The receiving device may be configured to estimate CSI based in part on first pilot symbols and to track the channel estimation based in part on the second pilot symbols in order to provide reliable data detection.

Hybrid waveform design combining ofdm and cyclic prefix based single carrier for millimeter-wave wireless communication

A receiver circuit, including a multi-stage QAM de-mapper, for receiving a QAM data signal is disclosed. A first de-mapper circuit recovers a set of encoded data bits from the QAM data signal by calculating a plurality of distances between a received QAM symbol and each of a plurality of possible constellation points. A second de-mapper circuit then generates a set of unencoded data bits for the received QAM symbol based, at least in part, on the plurality of distances calculated by the first de-mapper circuit. The receiver circuit may further include a decoder circuit to decode the set of encoded data bits recovered by the first de-mapper circuit. The second de-mapper circuit may identify a subset of the plurality of possible constellation points based on a result of the decoding and select a constellation point that is associated with the shortest distance of the plurality of distances.

Lu Zhao

Papers

Centralized scheduling for joint transmission coordinated multi-point in LTE-Advanced

Resource block reuse for coordinated multi-point transmission

Hybrid Approach for Physical Downlink Shared Channel (PDSCH) Interference Cancellation

Hybrid waveform design combining ofdm and cyclic prefix based single carrier for millimeter-wave wireless communication

Enhanced decoding and demapping method and apparatus for qam data signals