# US 10,374,680 B2 · Mobility reference signal allocation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,374,680 B2 - Document ID: US10374680B2 - Status: Granted - Kind: B2 - Application number: 14/775,709 - Filed: 2015-08-17 - Published: 2017-02-23 - Granted: 2019-08-06 - Earliest claimed: 2015-08-17 - Assignees: Telefonaktiebolaget LM Ericsson (publ) - Applicants: Telefonaktiebolaget L M Ericsson (publ) - Inventors: Andres Reial; Andreas Cedergren; Claes Tidestav - Web page: https://patentgrep.com/patent/US10374680B2 ## CPC - H04L 27/2613: {Structure of the reference signals} - H04B 7/0617: {for beam forming} - H04B 7/0634: {Antenna weights or vector/matrix coefficients} - H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)} - H04L 5/0069: {Allocation based on distance or geographical location} - H04W 24/10: Scheduling measurement reports {; Arrangements for measurement reports} - H04W 72/23: in the downlink direction of a wireless link, i.e. towards a terminal - H04B 7/10: Polarisation diversity; Directional diversity - H04L 5/0007: {the frequencies being orthogonal, e.g. OFDM(A) or DMT} - H04W 16/28: using beam steering - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract There is provided a method and a network node for allocating and transmitting Mobility Reference Signals, MRS, for a communication device to measure beam signal quality in a wireless communication network. The network node obtains information on one or more of a frequency diversity, a time diversity of a channel between the network node and the communication device, an antenna spatial diversity of the communication device. The network node selects an MRS pattern out of a set of candidate patterns based on the received information, signals the selected MRS pattern to the communication device and transmits the MRS according to the selected MRS pattern. ## Claims ### Claim 1 A method performed in a network node for allocating and transmitting Mobility Reference Signals (MRS) for a wireless communication device to measure beam signal quality in a wireless communication network, the method comprising: obtaining information on one or more of a frequency diversity, a time diversity of a channel between the network node and the wireless communication device, and an antenna spatial diversity of the wireless communication device; selecting an MRS pattern out of a set of candidate patterns based on the obtained information, wherein the candidate patterns are characterized by one or more of their density in time and density in frequency, and by one or more of their temporal duration and frequency range, and wherein each of the candidate patterns differs from each other one of the candidate patterns by at least their densities in time; signalling the selected MRS pattern to the wireless communication device; and transmitting the MRS according to the selected MRS pattern, wherein selecting an MRS pattern out of a set of candidate patterns based on the received information comprises: evaluating a number of independent measurement symbols M for different sets of candidate patterns which comprise different numbers of subcarriers Nf with different spacing Df in frequency dimension and different numbers of symbols Nt with different spacing Dt in time dimension; selecting an MRS pattern which has a minimum number of resource elements in frequency and time dimension, wherein selecting the MRS pattern is based on one or more of a maximum frequency span limit (Fmax), a maximum mobility measurement session length limit (Tmax), and a minimum number of measurement symbols (Lmin). ### Claim 2 (depends on 1) The method according to claim 1, wherein the information on one or more of a frequency diversity, a time diversity and an antenna spatial diversity comprises channel dispersion or coherence bandwidth of the channel, Doppler spread of the channel or channel coherence time, a number of antenna elements and antenna element correlation of the wireless communication device. ### Claim 3 (depends on 1) The method according to claim 1, wherein each MRS pattern comprises a certain number of subframes per second. ### Claim 4 (depends on 1) The method according to claim 1, wherein each MRS pattern comprises the number, Nf, of subcarriers with the spacing, Df, in frequency dimension and the number, Nt, of symbols with the spacing, Dt, in time dimension during one mobility measurement session. ### Claim 5 (depends on 4) The method according to claim 4, wherein a total number of measurement symbols, L, is defined by a number of antennas, A, at the wireless communication device, the number of subcarriers Nf in frequency dimension and the number of symbols Nt in time dimension. ### Claim 6 (depends on 5) The method according to claim 5, wherein the number of independent measurement symbols, M, out of the total number of measurement symbols L is defined by a number of independent antennas, Ai, at the communication device, the number of subcarriers Nf, a ratio of the spacing Df in frequency dimension and channel coherence bandwidth Cf, the number of symbols Nt, a ratio of the spacing Dt in time dimension and channel coherence time Ct. ### Claim 7 (depends on 1) The method according to claim 1, wherein selecting the MRS pattern is based on a maximum frequency span limit, Fmax, a maximum mobility measurement session length limit Tmax, and a minimum number of measurement symbols, Lmin. ### Claim 8 (depends on 7) The method according to claim 7, wherein the number of independent measurement symbols M is larger than a predetermined number of independent measurement symbols, Mmin. ### Claim 9 (depends on 7) The method according to claim 7, wherein the number of resource elements in frequency and time dimension is minimized during one mobility measurement session. ### Claim 10 (depends on 9) The method according to claim 9, wherein one measurement session comprises several subframes. ### Claim 11 A network node for allocating and transmitting Mobility Reference Signals (MRS) for a wireless communication device to measure beam signal quality in a wireless communication network, the network node is configured to: obtain information on one or more of frequency diversity, a time diversity of a channel between the network node and the wireless communication device, an antenna spatial diversity of the wireless communication device; select an MRS pattern out of a set of candidate patterns based on the obtained information, wherein the candidate patterns are characterized by one or more of their density in time and density in frequency, and by one or more of their temporal duration and frequency range, and wherein each of the candidate patterns differs from each other one of the candidate patterns by at least their densities in time; signal the selected MRS pattern to the wireless communication device; and transmit the MRS according to the selected MRS pattern, wherein the network node is further configured to: evaluate a number of independent measurement symbols M for different sets of candidate patterns which comprise different numbers of subcarriers Nf with different spacing Df in frequency dimension and different numbers of symbols Nt with different spacing Dt in time dimension; and select an MRS pattern which has a minimum number of resource elements in frequency and time dimension, wherein the MRS pattern is selected based on one or more of a maximum frequency span limit Fmax, a maximum mobility measurement session length limit Tmax, and a minimum number of measurement symbols Lmin. ### Claim 12 (depends on 11) The network node according to claim 11, wherein the information on one or more of a frequency diversity, a time diversity and an antenna spatial diversity comprises channel dispersion or coherence bandwidth of the channel, Doppler spread of the channel or channel coherence time, a number of antenna elements and antenna element correlation of the communication device. ### Claim 13 (depends on 11) The network node according to claim 11, wherein each MRS pattern comprises certain number of subframes per second. ### Claim 14 (depends on 11) The network node according to claim 11, wherein each MRS pattern comprises the number of subcarriers Nf with the spacing Df in frequency dimension and the number of symbols Nt with the spacing Dt in time dimension during one mobility measurement session. ### Claim 15 (depends on 14) The network node according to claim 14, wherein a total number of measurement symbols, L, is defined by a number of antennas, A, at the wireless communication device, the number of subcarriers Nf in frequency dimension and the number of symbols Nt in time dimension. ### Claim 16 (depends on 15) The network node according to claim 15, wherein the number of independent measurement symbols M out of the total number of measurement symbols L is defined by a number of independent antennas Ai at the wireless communication device, the number of subcarriers Nf, a ratio of the spacing Df in frequency dimension and channel coherence bandwidth Cf, the number of symbols Nt, a ratio of the spacing Dt in time dimension and channel coherence time Ct. ### Claim 17 (depends on 11) The network node according to claim 11, wherein the MRS pattern is selected based on a maximum frequency span limit Fmax, a maximum mobility measurement session length limit Tmax, and a minimum number of measurement symbols Lmin. ### Claim 18 (depends on 17) The network node according to claim 17, wherein the number of independent measurement symbols M is larger than a predetermined number of independent measurement symbols Mmin. ### Claim 19 (depends on 17) The network node according to claim 17, wherein the number of resource elements in frequency and time dimension is minimized during one mobility measurement session. ### Claim 20 (depends on 19) The network node according to claim 19, wherein one measurement session comprises several subframes. ### Claim 21 A nontransitory computer readable storage medium comprising instructions which, when executed on at least one processor in a network node, cause the network node to carry out a method in a network node for allocating and transmitting Mobility Reference Signals (MRS) for a wireless communication device to measure beam signal quality in a wireless communication network, the method comprising: obtaining information on one or more of a frequency diversity, a time diversity of a channel between the network node and the wireless communication device, an antenna spatial diversity of the wireless communication device; selecting an MRS pattern out of a set of candidate patterns based on the obtained information, wherein the candidate patterns are characterized by one or more of their density in time and density in frequency, and by one or more of their temporal duration and frequency range, and wherein each of the candidate patterns differs from each other one of the candidate patterns by at least their densities in time; signalling the selected MRS pattern to the wireless communication device; and transmitting the MRS according to the selected MRS pattern, wherein selecting an MRS pattern out of a set of candidate patterns based on the received information comprises: evaluating a number of independent measurement symbols M for different sets of candidate patterns which comprise different numbers of subcarriers Nf with different spacing Df in frequency dimension and different numbers of symbols Nt with different spacing Dt in time dimension; selecting an MRS pattern which has a minimum number of resource elements in frequency and time dimension, wherein selecting the MRS pattern is based on one or more of a maximum frequency span limit (Fmax), a maximum mobility measurement session length limit (Tmax), and a minimum number of measurement symbols (Lmin).