Hitachi, Ltd.

Long Gao

Joydeep Acharya

Sudhanshu Gaur

A communications system includes a macro base station, a plurality of UEs (user equipment), a plurality of small cells, and a network through which the macro base station, the UEs, and the small cells communicate with each other, the small cells within a macro coverage area of the macro base station. The macro base station comprises a processor, a memory, and a small cell on/off module which is operable, for each small cell of the plurality of small cells, to: determine an interference metric for the small cell; if the determined interference metric meets a preset condition for the small cell, then determine a loss in signal strength to the UEs associated with the small cell caused by switching off the small cell; and judge whether to switch off the small cell based on at least one of the determined interference metric or the determined loss in signal strength.

Dual connectivity of user equipment to macro and small cell in long term evolution system

Example implementations are directed to systems and methods based on physical broadcast channel (PBCH) muting are utilized to avoid frequent cell selection/reselection and handover in a LTE-advanced heterogeneous network. In the example implementations, a pico eNB that is fully covered by a macro eNB or other pico eNBs transmits blank PBCH such that it is inaccessible to the UEs who perform cell selection/reselection. Furthermore, a macro eNB may handover a UE to the inaccessible pico eNB by signalling the necessary information to the UE to detect the inaccessible pico eNB. Frequent cell selection/reselection and handover may therefore be avoided in a dense deployment situation.

Method and apparatus for cell selection and handover in LTE-advanced heterogeneous networks

Embodiments described herein are directed to a power control scheme for Long Term Evolution Advanced (LTE-A) heterogeneous networks to reduce the interference from macro base stations (BS) to pico user equipment (UE). The embodiments described herein may be used to develop LTE-A heterogeneous networks to balance the achievable throughput between macro and pico UEs and may thereby improve the overall system performance.

Power control in LTE-advanced heterogeneous networks

The Long Term Evolution Advanced (LTE-A) network, is a heterogeneous network, where macro and pico base stations (BSs) coexist to improve spectral efficiency per unit area. Systems and methods described herein attempt to provide a solution to the interference coordination problem between macro BSs and pico user equipments (UEs). Specifically, the systems and methods conduct interference coordination based on the concept of almost blank subframe (ABS), which is supported by the LTE-A standard. The macro BSs choose their ABS configurations in a cooperative way such that the overall system throughput is optimized.

ABS-based method for inter cell interference coordination in LTE-advanced networks

Example embodiments described herein are directed to systems and methods by which a group of base stations (BS) can configure pilot signals in time and time-frequency, using interference management resources (IMR) and/or channel state information reference signal (CSI-RS) resources, so that the user equipment (UE) such as mobiles and laptops can measure certain possible channel quality indicators (CQI) that correspond to specific channel and interference conditions that can arise during actual data submission. Using these values, example embodiments utilize an interpolation algorithm by which the group of base stations can estimate other possible CQI corresponding to a different set of channel and interference conditions.

Configuration of pilot signals by network for enabling comp

Example embodiments described herein are directed to systems and methods by which a group of base stations (BS) can configure pilot signals in time and time-frequency, called channel state information reference signal (CSI-RS) resources, so that the user equipment (UE) such as mobiles and laptops can measure certain possible channel quality indicators (CQI) that correspond to specific channel and interference conditions that can arise during actual data submission. Using these values, example embodiments utilize an interpolation algorithm by which the group of base stations can estimate other possible CQI corresponding to a different set of channel and interference conditions.

Configuration of CSI-RS resources by network for enabling CoMP

A base station (BS) comprises: an interface to receive radio resource management (RRM) measurement from user equipment on received reference signal (RS) strength for each BS of one or more other BSs in a surrounding area of the user equipment; an X2 interface to receive transmission information of almost blank subframes and corresponding cell-specific reference signal (CRS) resource element (RE) locations from the one or more other BSs; and a controller to manage bit-level PDSCH (Physical Downlink Shared Channel) muting information, which includes identifying PDSCH resource elements (REs) that suffer the most from CRS interference arising from other BSs and that are to be subjected to bit-level muting, and allocating to the identified REs a number of bits less than the number of bits allocated to normal REs, and to transfer data with the two levels of bit allocations to various PDSCH REs to the user equipment.

Method and apparatus for bit-level PDSCH muting and/or receiver puncturing in LTE-advanced heterogeneous networks

A communications system employing CoMP transmission to suppress interference comprises: a CoMP user equipment; and a plurality of base stations, one of the base stations being an associated base station of the CoMP user equipment to transmit data to the CoMP user equipment, the plurality of base stations including multiple CoMP base stations for the CoMP user equipment. The CoMP base stations for the CoMP user equipment transmit CoMP downlink data, including subframes which comprise physical resource blocks having a plurality of resource elements (REs) and cell-specific reference signal (CRS) resource element (RE) locations. PDSCH bit-level muting or puncturing information is determined, based on radio resource management measurement and the subframes sent from the multiple CoMP base stations, to identify PDSCH REs that suffer strong CRS interference transmission from within the multiple CoMP base stations and are to be subjected to one of bit-level muting or bit-level puncturing.

Method and apparatus for handling downlink reference signal interference to PDSCH in long term evolution coordinated multipoint transmission

In a distributed antenna system (DAS), the number of physical antennas is usually larger than that of the antenna ports supported by LTE/LTE-A RS pattern in each cell. Systems and methods are directed to a RS transmission scheme in which the RRHs (or RRH groups) are dynamically scheduled and mapped to the antenna ports for RS transmission based on user density distribution such that the accuracy of the channel state information (CSI) estimation in the DAS is optimized.

Reference signal design for distributed antenna systems

Systems and methods are directed to deciding the number of subframes in a frame to use for uplink transmission, with the remaining frames used for downlink transmission for a Base Station (BS) in a Time Division Duplexing Long Term Evolution (TDD-LTE). Systems and methods are based on the number of User Equipment (UEs) that the BS has to serve in the uplink and in the downlink, as well as the uplink (UL) and downlink (DL) traffic loads per user. Systems and methods are directed to allowing a TDD LTE BS to partition the subframes in a frame for its UL and DL traffic.

Allocation of subframes for uplink and downlink transmission in TDD-LTE

A distributed antenna system comprises users; remote radio heads which are to be divided into clusters; and a central base station (CBS) including a CBS processor, a CBS memory, a user ordering module, and a user scheduling and cluster formation module. The user ordering module is configured to order the users in decreasing values of proportional fair scheduling metrics to provide a set of ordered users. The user scheduling and cluster formation module is configured to schedule the users according to the order of the users in decreasing values of proportional fair scheduling metrics; and for each user being scheduled according to the order of the users, pick up first N number of remote radio heads, in decreasing order of signal strength to the user being scheduled, which have not been picked up previously, to form a cluster of size N for the user being scheduled.

Joint user equipment scheduling and cluster formation for distributed antenna systems

A central base station for interference management in a distributed antenna system comprises a processor; a memory; and a frequency partition module configured to divide the remote radio heads into clusters and allocate a frequency band to each cluster. Multiple clusters use the same frequency band and groups of clusters are formed. A joint scheduler is configured, for each group, to activate at most two clusters at any given time and deactivate remaining clusters in the group, one of the at most two activated clusters being a serving cluster of the group, and to associate one or more users with the serving cluster in the group. An interference alignment module is configured to apply downlink interference alignment between the at most two activated clusters in each group to align transmit directions of all interferences between the at most two activated clusters.

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Santa Clara, CA, United States of America

Long Gao