# US 10,771,298 B2 · Mobile communications network > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,771,298 B2 - Document ID: US10771298B2 - Status: Granted - Kind: B2 - Application number: 16/318,533 - Filed: 2017-06-19 - Published: 2019-08-29 - Granted: 2020-09-08 - Earliest claimed: 2016-08-04 - Assignees: British Telecommunications public limited company - Applicants: British Telecommunications Public Limited Company - Inventors: Zaid Al-Daher; Richard Mackenzie; Michael Fitch - Web page: https://patentgrep.com/patent/US10771298B2 ## CPC - H04L 27/2607: {Cyclic extensions} - H04L 5/0037: {Inter-user or inter-terminal allocation} - H04L 5/0053: {Allocation of signalling, i.e. of overhead other than pilot signals} - H04L 5/0058: {Allocation criteria} - H04W 4/06: Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract At a mobile terminal: communicating with a serving base station over multicast; receiving a first multicast signal from the serving base station and a second signal from a second base station; determining an indication of the length of a first cyclic prefix of the first multicast signal and an indication of the length of a second cyclic prefix of the second signal; and where the mobile terminal determines that the lengths of the first and second cyclic prefixes are different, initiating a switch in communication between the mobile terminal and the serving base station to unicast. In complementary fashion, at a base station serving a mobile terminal over multicast; sending to the mobile terminal a multicast signal comprising a first cyclic prefix with a first length; receiving from the mobile terminal an indication that the mobile terminal has detected a second cyclic prefix with a second length and switching communicating with the mobile terminal from multicast to unicast. ## Claims ### Claim 1 A method comprising, at a mobile terminal: communicating with a serving base station over broadcast or multicast; receiving a first broadcast or multicast signal from the serving base station and a second signal from a second base station; determining an indication of a length of a first cyclic prefix of the first broadcast or multicast signal and an indication of a length of a second cyclic prefix of the second signal; and where the mobile terminal determines that the lengths of the first and second cyclic prefixes are different, initiating a switch in communication between the mobile terminal and the serving base station to unicast. ### Claim 2 (depends on 1) A method as claimed in claim 1, wherein determining that the lengths of the first and second cyclic prefixes are different comprises determining that a number of symbols in a time slot of the first broadcast or multicast signal is different from a number of symbols in a time slot of the second signal. ### Claim 3 (depends on 1) A method as claimed in claim 1, wherein initiating a switch in communication between the mobile terminal and the serving base station to unicast comprises sending to the serving base station a request to switch communications between the mobile terminal and the serving base station to unicast. ### Claim 4 (depends on 1) A method as claimed in claim 1, wherein initiating a switch in communication between the mobile terminal and the serving base station to unicast comprises notifying the serving base station of detection of different-length cyclic prefixes. ### Claim 5 A mobile terminal for operation in a communications network, wherein the mobile terminal comprises: a first transceiver for exchanging signals with a serving base station; a second transceiver for exchanging signals with a second base station; and a processor configured to: receive a first broadcast or multicast signal from the serving base station and a second signal from a second base station; determine an indication of a length of a first cyclic prefix of the first broadcast or multicast signal and an indication of a length of a second cyclic prefix of the second signal; and where the mobile terminal determines that the lengths of the first and second cyclic prefixes are different, initiate a switch in communication between the mobile terminal and the serving base station to unicast. ### Claim 6 (depends on 5) The mobile terminal as claimed in claim 5, wherein the serving base station is comprised in a first multicast-broadcast single-frequency network (MBSFN). ### Claim 7 (depends on 6) The mobile terminal as claimed in claim 6, wherein the second base station is comprised in a second MBSFN. ### Claim 8 (depends on 5) The mobile terminal as claimed in claim 5, wherein the first transceiver and the second transceiver are the same. ### Claim 9 A method comprising, at a base station: serving a mobile terminal over broadcast or multicast; sending to the mobile terminal a broadcast or multicast signal comprising a first cyclic prefix with a first length; receiving from the mobile terminal an indication that the mobile terminal has detected a second cyclic prefix with a second length; and switching communicating with the mobile terminal from broadcast or multicast to unicast. ### Claim 10 (depends on 9) A method as claimed in claim 9, wherein the received indication comprises a request to switch communications between the mobile terminal and the serving base station to unicast. ### Claim 11 (depends on 9) The method of claim 9, wherein the second cyclic prefix is received by the mobile terminal in a signal from a second base station. ### Claim 12 (depends on 1) A non-transitory computer-readable computer program element comprising computer program code to, when loaded into a computer system and executed thereon, cause the computer system to perform the method as claimed in claim 1. ### Claim 13 A base station for a mobile communications network, wherein the base station comprises: a transmitter configured to serve a mobile terminal using broadcast or multicast and to transmit a broadcast or multicast signal to the mobile terminal, wherein the transmitted broadcast or multicast signal comprises a first cyclic prefix with a first length; a receiver configured to receive signals from the mobile terminal; and a processor configured to: receive from the mobile terminal an indication that the mobile terminal has detected a second cyclic prefix with a second length; and switch communication with the mobile terminal from broadcast or multicast to unicast.