Semi-Unauthorized Random Access Method Based on Grouping of Machine Type Communication Devices

Abstract

The invention discloses a semi-Grant-Free random access method based on MTC equipment grouping. It aims to solve the unbalanced load of resource blocks and low utilization of transmission resources caused by severe access request collisions in the mMTC scenario, too long pilots in the Grant‑Free random access scheme, low utilization of access resources, and lack of scheduling The problem. Implementation steps: Active MTC devices send access request information on designated resource blocks according to the grouping scheme; base station performs joint device detection and channel estimation, and calculates the receiving SINR of active MTC devices on access resource blocks; base station executes to maximize success Decode the access scheduling with the number of users as the target, and broadcast the scheduling information to the MTC device; the active MTC device transmits data on the designated resource block according to the scheduling result; the base station performs data recovery and results feedback. The invention effectively improves the access efficiency and transmission reliability of the mMTC system, reduces the power consumption and access delay of MTC equipment, supports massive connections, and is suitable for mMTC scenarios.

Description

technical field [0001] The present invention belongs to the field of communication technology, and mainly relates to a wireless communication technology that supports the access of massive equipment, in particular, semi-unauthorized random access (Grouped Semi-Grant FreeRandom Access, GSGF-RA) based on grouping of machine-type communication equipment The method is suitable for massive machine-type communication (mMTC) scenarios. Background technique [0002] Massive machine type communication is one of the three application scenarios of the fifth generation mobile communication system (5G) defined by 3GPP. The main future evolution directions of mMTC scenarios include connection density, terminal power consumption, and coverage enhancement, among which connection density is the most important design enhancement goal of mMTC. In the current LTE-A (Long Term Evolution Advanced) system, the user's random access process generally includes four steps: [0003] (1) The user rand...

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Problems solved by technology

[0007] In the mMTC scenario, using the above-mentioned random access process will inevitably face three challenging problems: (1) Compared with the small data packets transmitted by the MTC device, the interactive transmission between the MTC device and the base station during the random access process Too much header information (overhead) will make data transmission inefficient; (2) The number of MTC devices is far more than the number of resources and preambles that the system can provide, and the serious mismatch between them will lead to random access. The phenomenon of access collision is serious, so that some MTC devices keep trying to access requests, resulting in increased energy consumption and increased access delay; (3) Under the 5G framework, the access capacity that the system can support is limited. with clear theoretical support

[0013] 1. The loss of access performance due to the limitation of pilot sequences: the pilots used in the Grant-free random access scheme include both orthogonal pilot sequences and non-orthogonal pilot sequences

Limited by the coherence time in the system and the multi-transmission of small data packets by MTC devices, the orthogonal pilot sequences used in the mMTC scenario cannot be too long, that is, the number of available orthogonal pilot sequences is limited, and therefore unavoidable MTC devices. Collision between pilots limits the access success rate of MTC devices

The use of non-orthogonal pilot sequences will lead to large channel estimation errors, which limits the success rate of data transmission of MTC devices

[0014] 2. Due to the unbalanced number of MTC devices sharing different resource blocks, the physical layer coding design is difficult: in Grant-free access, MTC devices randomly select pilots, which means that the number of users accessing each time-frequency resource block is different. Fixed, and the number of other MTC devices sharing resources cannot be estimated when each MTC device accesses

This will make the load on different resource blocks unbalanced, making the physical layer coding design more difficult

[0015] 3. MTC devices occupy too many time slot resources due to and rate limitation: With the AMP algorithm, the error probability of active MTC device detection can approach zero asymptotically

However, limited by the limited length of the orthogonal pilot, the probability of access collision is high, resulting in a long access delay; if the limited length of the non-orthogonal pilot sequence is used, the channel estimation error is large, resulting in the system Asymptotically, the reachability and rate are limited, which will lead to an increase in the time slot resources occupied by MTC devices

At the same time, random pilot sequences lead to unbalanced loads on different resource blocks, making physical layer coding design more difficult

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