Method for randomly accessing super large cell and user equipment

Abstract

The invention discloses a method for being randomly access to an ultra-large type cell and UE. The method comprises the steps that the UE stores the PRACH time slot parameter of the ultra-large type cell, wherein the PRACH time slot parameter of the ultra-large type cell is calculated out according to the cell radius and the maximum time delay spread value of the ultra-large type cell; when the UE is switched to a target ultra-large type cell from a source cell, the subframe position of a PRACH time slot of a target eNodeB is acquired from a source eNodeB, and random access is conducted on the target eNodeB at the corresponding subframe position according to the subframe position information of the PRACH time slot and a self-configured PRACH time slot parameter. The method for being randomly access to the ultra-large type cell and the UE enable the UE in an LTE system to be access to the ultra-large type cell.

Description

Technical field [0001] The present invention relates to the field of wireless technology, in particular to a method for randomly accessing a super large cell and user equipment (UE, User Equipment). Background technique [0002] In the Long Term Evolution (LTE, Long Term Evolution) system, for Frequency Division Duplexing (FDD) cells, the theoretical upper limit of the cell radius is determined by the cycles in the time slots of the Physical Random Access Channel (PRACH) Prefix (CP, Cyclic Prefix) or guard interval (GP, GuardPeriod) is determined. The specific calculation formula is as follows: [0003] [0004] Where R upper_limit Represents the theoretical upper limit of the cell radius; C represents the speed of light; T CP Represents the duration of CP in the PRACH time slot; DS max Indicates the maximum delay spread value of the cell, usually 5.2 microseconds (μs), for relatively large or very large cells, 16.67μs; T GP Represents the duration of the GP in the PRACH time s...

AI Technical Summary

Problems solved by technology

[0007] For cells with a radius exceeding 100.16Km, if the current PRACH time slot parameters are still used, there is no guarantee that the random access preamble sequence (Preamble sequence) sent by the UE will completely fall into the observation of the evolved base station (eNodeB, evolved Node Base) window, which leads to random access failure

For example: the distance from UE1 to eNodeB does not exceed the currently supported upper limit of 100.16Km, so the round-trip time (RTT, Round-Trip Time) 1 corresponding to UE1 will not exceed the CP duration, and eNodeB can receive the complete random access preamble of UE1 within the observation window Sequence; if UE2 is more than 100.16Km away from eNodeB, then the situation is different, UE2's RTT2 will exceed the CP duration, so UE2's random access preamble cannot be completely received by eNodeB, which will cause UE2 to fail to access normally the district

[0008] For ultra-large cells, how to redesign PARCH time slot parameters so that UE can normally access the target cell, there is no solution yet

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