# US 9,439,138 B2 · Methods and apparatus for cell selection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,439,138 B2 - Document ID: US9439138B2 - Status: Granted - Kind: B2 - Application number: 14/384,882 - Filed: 2012-03-14 - Published: 2015-01-22 - Granted: 2016-09-06 - Earliest claimed: 2012-03-14 - Assignees: Telefonaktiebolaget L M Ericsson (publ) - Applicants: Jinhua Liu; Xinyu Gu; Qingyu Miao; Stephen Grant - Inventors: Jinhua Liu; Xinyu Gu; Qingyu Miao; Stephen Grant - Web page: https://patentgrep.com/patent/US9439138B2 ## CPC - H04W 48/20: Selecting an access point - H04W 36/00692: {using simultaneous multiple data streams, e.g. cooperative multipoint [CoMP], carrier aggregation [CA] or multiple input multiple output [MIMO] (allocation of physical resources in CoMP or in CA H04L5/0035)} - H04W 36/08: Reselecting an access point - H04W 74/0833: Random access procedures, e.g. with 4-step access - H04L 5/0035: {Resource allocation in a cooperative multipoint environment} - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract The present disclosure relates to a cell selection scheme. In one embodiment, there provides a method for performing a cell selection for a UE at a primary serving cell of the UE in a CoMP cluster including the primary serving cell and one or more candidate cells, the method comprising the steps of: receiving PRACH measurements for the UE from the candidate cells; and selecting from the candidate cells one or more cells for the UE as its secondary serving cells based on the received PRACH measurements. ## Claims ### Claim 1 A method for performing a cell selection for a user equipment (UE), the method comprising: detecting, by a primary serving cell of the UE in a Coordinated Multi-Point (CoMP) cluster including the primary serving cell and one or more candidate cells, a Physical Random Access Channel (PRACH) preamble signal of the UE to obtain PRACH information of the UE; transmitting, by the primary serving cell, the PRACH information to the candidate cells for obtaining PRACH measurements; receiving, by the primary serving cell, the PRACH measurements for the UE from the candidate cells, wherein the PRACH measurements are obtained by the candidate cells based on the PRACH information; and selecting, by the primary serving cell, from the candidate cells one or more cells for the UE as the UE's secondary serving cells based on the received PRACH measurements. ### Claim 2 (depends on 1) The method according to claim 1, wherein the PRACH measurements are strengths of a PRACH preamble signal from the UE, the strengths being obtained by the candidate cells. ### Claim 3 (depends on 1) The method according to claim 1, wherein the PRACH measurements are based on all PRACH preambles belonging to all cells in the CoMP cluster. ### Claim 4 (depends on 1) The method according to claim 1, wherein the PRACH information comprises at least one of the UE's scrambling code, PRACH preamble sequence, PRACH timing, and direction of angle (DoA). ### Claim 5 (depends on 1) The method according to claim 1, wherein each of the PRACH measurements is based on the PRACH information and a PRACH preamble signal, which is previously received by a corresponding candidate cell from the UE. ### Claim 6 (depends on 1) The method according to claim 1, further comprising: instructing each of the candidate cells to perform path searching for the UE based on the PRACH information. ### Claim 7 (depends on 6) The method according to claim 6, wherein the path searching is performed on antennas at each of the candidate cells to obtain path strengths as the PRACH measurements. ### Claim 8 (depends on 1) The method according to claim 1, wherein the candidate cells are neighbor cells to the primary serving cell within the CoMP cluster. ### Claim 9 (depends on 1) The method according to claim 1, wherein the candidate cells are all cells in the CoMP cluster other than the primary serving cell. ### Claim 10 (depends on 1) The method according to claim 1, further comprising: after receiving the PRACH measurements for the UE from the candidate cells, terminating the cell selection when all of the received PRACH measurements are lower than a first threshold. ### Claim 11 (depends on 1) The method according to claim 1, further comprising: before receiving the PRACH measurements for the UE from the candidate cells, obtaining the primary serving cell's PRACH measurement for the UE and comparing the obtained PRACH measurement with a second threshold. ### Claim 12 (depends on 11) The method according to claim 11, further comprising: terminating the cell selection when the primary serving cell's PRACH measurement for the UE is higher than the second threshold. ### Claim 13 A non-transitory computer-readable storage medium having computer-readable instructions to facilitate cell selection for a user equipment (UE), the instructions being executable by a computing device, the instructions comprising: detecting, by the computing device serving as a primary serving cell of the UE in a Coordinated Multi-Point (CoMP) cluster including the primary serving cell and one or more candidate cells, a Physical Random Access Channel (PRACH) preamble signal of the UE to obtain PRACH information of the UE; transmitting, by the computing device, the PRACH information to the candidate cells for obtaining PRACH measurements; receiving, by the computing device, the PRACH measurements for the UE from the candidate cells, wherein the PRACH measurements are obtained by the candidate cells based on the PRACH information; and selecting, by the computing device, from the candidate cells one or more cells for the UE as the UE's secondary serving cells based on the received PRACH measurements. ### Claim 14 An apparatus for performing a cell selection for a user equipment (UE), the apparatus comprising: a processor and computer-readable storage medium coupled to the processor, the computer-readable storage medium including: a detecting unit configured to detect a Physical Random Access Channel (PRACH) preamble signal of the UE in a Coordinated Multi-Point (CoMP) cluster including the apparatus serving as a primary serving cell and on or more candidate cells to obtain PRACH information of the UE; a transmitting unit configured to transmit the PRACH information to the candidate cells for obtaining the PRACH measurements; a receiving unit configured to receive PRACH measurements for the UE from the candidate cells, wherein the PRACH measurements are to be obtained by the candidate cells based on the PRACH information; and a selecting unit configured to select from the candidate cells one or more cells for the UE as its secondary serving cells based on the received PRACH measurements. ### Claim 15 (depends on 14) The apparatus according to claim 14, wherein the PRACH measurements are strengths of a PRACH preamble signal from the UE, the strengths being obtained by the candidate cells. ### Claim 16 (depends on 14) The apparatus according to claim 14, wherein the PRACH measurements are based on all PRACH preambles belonging to all cells in the CoMP cluster. ### Claim 17 (depends on 14) The apparatus according to claim 14, wherein the PRACH information comprises at least one of the UE's scrambling code, PRACH preamble sequence, PRACH timing, and direction of angle (DoA). ### Claim 18 (depends on 14) The apparatus according to claim 14, wherein each of the PRACH measurements is based on the PRACH information and a PRACH preamble signal, which is previously received by a corresponding candidate cell from the UE. ### Claim 19 (depends on 14) The apparatus according to claim 14, further comprising: an instructing unit configured to instruct each of the candidate cells to perform path searching for the UE based on the PRACH information. ### Claim 20 (depends on 19) The apparatus according to claim 19, wherein the path searching is to be performed on antennas at each of the candidate cells to obtain path strengths as the PRACH measurements. ### Claim 21 An apparatus for use in a cell selection for a user equipment (UE), the apparatus comprising: a processor and computer-readable storage medium coupled to the processor, the computer-readable storage medium including: a receiving unit configured to receive a PRACH preamble signal from the UE and to receive PRACH information of the UE from a primary serving cell of the UE in a Coordinated Multi-Point (CoMP) cluster including the primary serving cell and one or more candidate cells, wherein the apparatus serves as one included candidate cell; a Physical Random Access Channel (PRACH) measurement obtaining unit configured to obtain a PRACH measurement for the UE based on the PRACH information; and a transmitting unit configured to transmit the PRACH measurement to the primary serving cell for use in the cell selection. ### Claim 22 (depends on 21) The apparatus according to claim 21, wherein the PRACH measurement obtaining unit is configured to obtain the PRACH measurement based on all PRACH preambles belonging to all cells in the CoMP cluster. ### Claim 23 (depends on 21) The apparatus according to claim 21, wherein the PRACH information comprises at least one of the UE's scrambling code, PRACH preamble sequence, PRACH timing, and direction of angle (DoA). ### Claim 24 (depends on 21) The apparatus according to claim 21, wherein the PRACH measurement obtaining unit is configured to obtain the PRACH measurement based on the PRACH information and the PRACH preamble signal. ### Claim 25 (depends on 21) The apparatus according to claim 21, further comprising: a path searching unit configured to perform path searching on an antenna the one of the candidate cells, which is served by the apparatus, based on the PRACH information to obtain a path strength as the PRACH measurement.